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Sample records for al ba pb

  1. The Effect of Nanosized Pb Liquid Phase on the Damping Behavior in Aluminum Matrix Composite Based on the 2024Al-BaPbO3 System

    NASA Astrophysics Data System (ADS)

    Fan, G. H.; Geng, L.; Wu, H.; Zheng, Z. Z.; Meng, Q. C.

    2016-03-01

    An aluminum matrix composite containing nanosized Pb particles was fabricated by a powder metallurgy technique based on the 2024Al-BaPbO3 system. The composite exhibited a high and broad damping peak at the melting temperature range of nanosized Pb particles. The increase in value and breadth of the damping peak was attributed to the dislocation damping of the interfacial matrix close to the nanosized Pb liquid phase. The damping peak is expected to be enhanced by further refining the Pb particle size.

  2. Pedogeochemical mapping of Al, Ba, Pb, Ti and V in soils of the Barcelona Province (Catalonia, NE Spain): relationships with soil physico-chemical properties.

    NASA Astrophysics Data System (ADS)

    Bech, J.; Reverter, F.; Tume, P.; Sokolowska, M.; Sanchez, P.; Longan, L.; Bech, J.; Zhiyanski, M.; Lansac, A.; Oliver, M. T.

    2009-04-01

    Pedogeochemical mapping is a useful tool for estimating the local background of potentially toxic elements (PTE), wich is essential for environmental regulation. The aim of this study is to estimate the levels and distribution of Al, Ba, Pb, Ti and V in surface soils of the Barcelona province (Catalonia, NE Spain) and their relationships with administrative-geographic districts, texture, pH, organic carbon and CaCO3. The studied region has a surface area of 7731 Km2. The geology is varied: granites and Paleozoic shales predominate in SE-E. and Mesozoic and Cenozoic limestones, dolomites, marlstones, gypsum and sandstones in the remainder of the studied area. 319 top soil samples (0-20 cm) were collected at 5 km intervals on a regular grid, dried and sieved (2mm). General soil properties were analysed by standard methods. Aqua regia digests (DIN 38414-S7) of Al, Ba, Pb, Ti and V were determined by Inductively Coupled Plasma Spectrometry. Statistical data treatment was carried out using SPSS 12.0 and Statgraphics Plus 5.1. We applied Exploratory Data Analysis (EDA) techniques to statistically describe the data. The software used for mapping was ESRI's Arc Wiew 9.0, Desktop version. Analytical data is represented using growing dot maps. The values of every mapped variable were grouped into a few cartographic classes in order to produce limited legends. The limits for the cartographic classes were chosen by the percentile method (5th, 25th, 50th, 75th, 90th, and 98th). Some results are: Al mg kg-1min 4410.0, max 194786.0, mean 18145.6, sd 12112.1, med 16273.3 ; Ba mgkg-1min 7.32, max 1709.0, mean 128.4, sd 149.2, med 91.7; Pb mg kg-1min 2.76, max 485.7, mean 52.2, sd 46.3, med 46.0; Ti mg kg-1min 11.6, max 3540.0, mean 268.0, sd 421.6, med 132.2, and V mg kg-1min 2.15, max 289.2, mean 31.4, sd 25.7, med 26.0. . The highest mean value of Ba (328mkg-1), Pb (139.6 mgkg-1) and V (54.7 mgkg-1) corresponds to the Barcelonés district with mainly urban soils. The Al contents

  3. Ferroelectric Properties of Ba2Bi4Ti5O18 Doped with Pb2+, Al3+, Ga3+, In3+, Ta5+ Aurivillius Phases

    NASA Astrophysics Data System (ADS)

    Rosyidah, A.; Onggo, D.; Khairurrijal, Ismunandar

    2008-03-01

    In recent years, bismuth layer structured ferroelectrics (BLSFs) have been given much attention because some materials, such as Ba2Bi4Ti5O18, are excellent candidate materials for nonvolatile ferroelectric random access memory (FRAM) applications. BLSFs are also better candidates because of their higher Curie points. Recently, we have carried out computer simulation in atomic scale in order to predict the energies associated with the accommodation of aliovalent and isovalent dopants (Pb2+, Al3+, Ga3+, In3+, Ta5+) in the Aurivillius structure of Ba2Bi4Ti5O18. In this work, the predicted stable phases were synthesized using solid state reactions and their products then were characterized using powder X-ray diffraction method. The cell parameters were determined using Rietveld refinement in orthorhombic system with space group of B2cb. The cell parameters for Ba2Bi4Ti5O18 doped with Pb2+, Al3+, Ga3+, In3+, Ta5+ were a = 5.5006(6) b = 5.4990(5) c = 50.5440(7) Å; a = 5.5012(4) b = 5.4986(8) c = 50.5449(7) Å; a = 5.5006(3) b = 5.4999(3) c = 50.5437(9) Å; a = 5.5007(4) b = 5.4989(7) c = 50.5446(6) Å; and a = 5.5000(5) b = 5.4995(8) c = 50.5436(6) Å. Results from the ferroelectric properties measurement for Ba2Bi4Ti5O18 doped with Pb2+, Al3+, Ga3+, In3+, Ta5+ were Pr = 16.7 μC/cm2, Ec = 35.1 kV/cm; Pr = 15.9 μC/cm2, Ec = 33.8 kV/cm; Pr = 15.6 μC/cm2, Ec = 34.2 kV/cm; Pr = 15.3 μC/cm2, Ec = 34.0 kV/cm; Pr = 16.9 μC/cm2, Ec = 35.6 kV/cm.

  4. Trace element proxies (Sr/Ca, Ba/Ca and Pb/Ca) in Bivalve shells: environmental signals or not?

    NASA Astrophysics Data System (ADS)

    Gillikin, D. P.; Dehairs, F.; Steenmans, D.; Meng, L.; Haifeng, T.; Navez, J.; Andre, L.; Baeyens, W.; Keppens, E.; Calmars Group,.

    2004-12-01

    Coral and sclerosponge skeletons have both been used as recorders of their environment. Sr/Ca, Ba/Ca and Pb/Ca have all shown to be useful in these substrates, giving insight into the past environment in which the skeleton grew (e.g., Lea et al., 1989, Nature 340, 373-376; Beck et al., 1992, Science 257, 644-647; Lazareth et al., 2000, Geology 28, 515-518; Rosenheim et al., 2004, Geology 32, 145-148). Although bivalves have not been studied as extensively as corals, these proxies are apparently not as reliable in bivalves (e.g., Vander Putten et al., 2000, GCA 64, 997-1011). We therefore investigate Sr/Ca and Pb/Ca in two species of aragonitic clams (Mercenaria mercenaria and Saxidomus giganteus) and Ba/Ca in the calcite layer of the mussel Mytilus edulis. Results indicate that Sr/Ca is primarily controlled by growth rate in S. giganteus whereas there was no relationship between these parameters in M. mercenaria. Pb/Ca is somewhat reproducible between specimens of S. giganteus, however long-term Pb/Ca records (1949-2003) in the shell of M. mercenaria did not show the expected curve of anthropogenically introduced lead, indicating that they are not recording environmental Pb concentrations. Therefore, Sr/Ca and Pb/Ca incorporation seem to be regulated by biological processes and not directly by environmental parameters. Ba/Ca in M. edulis shells on the other hand, does seem to be directly linked to the environment. Shells grown under laboratory and natural conditions both show the same linear relationship between dissolved Ba/Ca and shell Ba/Ca. Experiments involving manipulations of dissolved and particulate (i.e. food) Ba/Ca, suggest that the dominant pathway of barium into the shell is from the dissolved phase via the hemolymph. We were unable to explain the large peaks noted in the Ba/Ca profiles, however, they did not seem linked to phytoplankton blooms as has been previously suggested (Stecher et al., 1996, GCA 60, 3445-3456; Vander Putten et al., 2000

  5. Incorporation of Ba in Al and Fe pollucite

    NASA Astrophysics Data System (ADS)

    Vance, Eric R.; Gregg, Daniel J.; Griffiths, Grant J.; Gaugliardo, Paul R.; Grant, Charmaine

    2016-09-01

    Ba, the transmutation product of radioactive Cs, can be incorporated at levels of up to ∼0.07 formula units in Cs(1-2x)BaxAlSi2O6 aluminium pollucite formed by sol-gel methods and sintering at 1400 °C, with more Ba forming BaAl2Si2O8 phases. The effect of Ba substitution in pollucite-structured CsFeSi2O6 was also studied and no evidence of Ba substitution in the pollucite structure via cation vacancies or Fe2+ formation was obtained. The Ba entered a Fe-silicate glass structure. Charge compensation was also attempted with a Cs+ + Fe3+ ↔ Ba2+ + Ni2+ scheme but again the Ba formed a glass and NiO was evident. PCT leaching data showed CsFeSi2O6 to be very leach resistant.

  6. First principles investigations of structural, elastic, dielectric and piezoelectric properties of { Ba,Sr,Pb } TiO3, { Ba,Sr,Pb } ZrO3 and { Ba,Sr,Pb } { Zr,Ti } O3 ceramics

    NASA Astrophysics Data System (ADS)

    Akgenc, Berna; Tasseven, Cetin; Cagin, Tahir

    2015-03-01

    We use first-principle density-functional study of structural, anisotropic mechanical, dielectric and piezoelectric properties of {Ba,Sr,Pb}TiO3, {Ba,Sr,Pb}ZrO3 and {Ba,Sr,Pb}{Zr,Ti}O3 alloys in cubic perovskite structures at zero temperature. Because there is significant interest in finding new piezoelectrics that do not contain toxic elements such as lead. In this study, we compare piezoelectric response of those alloys to synthesize outstanding piezoelectric materials. In perovskite structures, the spontaneous polarization is due to enormous values of Born effective charges computed by linear response within density functional perturbation theory, which are much larger than predicted nominal charge. We deeply investigated the effects of composition, order and site defects structure on piezoelectric constants.

  7. Effects of Ba loading and calcination temperature on BaAl2O4 formation for BaO/Al2O3 NOx Storage and Reduction Catalysts

    SciTech Connect

    Szailer, Tamas; Kwak, Ja Hun; Kim, Do Heui; Szanyi, Janos; Wang, Chong M.; Peden, Charles HF

    2006-04-30

    The effect of thermal treatment on the structure and chemical properties of Ba-oxide-based NOx storage/reduction catalysts with different Ba loadings was investigated using BET, TEM, EDS, TPD and FTIR techniques. On the basis of the present and previously reported results, we propose that moderate (< ~873 K) temperature calcinations result in a single monolayer (ML) ‘coating’ of BaO on the alumina surface. At high Ba loading in excess of that required for a full monolayer ‘coating’ (> 8 wt.% BaO), small (~5 nm) particles of ‘bulk’ BaO are present on top of the 1 ML BaO/Al2O3 surface. We did not observe any detectable morphological changes upon higher temperature thermal treatment of 2 and 8 wt% BaO/Al2O3 samples, while dramatic changes occurred for the 20 wt% sample. In this latter case, the transformations included BaAl2O4 formation at the expense of the bulk BaO phase. In particular, we conclude that the surface (ML) BaO phase is quite stable against thermal treatment, while the bulk phase provides the source of Ba for BaAl2O4 formation.

  8. New insights into the application of the valence rules in Zintl phases-Crystal and electronic structures of Ba7Ga4P9, Ba7Ga4As9, Ba7Al4Sb9, Ba6CaAl4Sb9, and Ba6CaGa4Sb9

    NASA Astrophysics Data System (ADS)

    He, Hua; Stoyko, Stanislav; Bobev, Svilen

    2016-04-01

    Crystals of three new ternary pnictides-Ba7Al4Sb9, Ba7Ga4P9, and Ba7Ga4As9 have been prepared by reactions of the respective elements in molten Al or Pb fluxes. Single-crystal X-ray diffraction studies reveal that the three phases are isotypic, crystallizing in the orthorhombic Ba7Ga4Sb9-type structure (space group Pmmn, Pearson symbol oP40, Z=2), for which only the prototype is known. The structure is based on TrPn4 tetrahedra (Tr=Al, Ga; Pn=P, As, Sb), connected in an intricate scheme into 1D-ribbons. Long interchain Pn-Pn bonds (dP-P>3.0 Å; dAs-As>3.1 Å; dSb-Sb>3.3 Å) account for the realization of 2D-layers, separated by Ba2+ cations. Applying the classic valance rules to rationalize the bonding apparently fails, and Ba7Ga4Sb9 has long been known as a metallic Zintl phase. Earlier theoretical calculations, both empirical and ab-initio, suggest that the possible metallic properties originate from filled anti-bonding Pn-Pn states, and the special roles of the "cations" in this crystal structure. To experimentally probe this hypothesis, we sought to synthesize the ordered quaternary phases Ba6CaTr4Sb9 (Tr=Al, Ga). Single-crystal X-ray diffraction work confirms Ba6.145(3)Ca0.855Al4Sb9 and Ba6.235(3)Ca0.765Ga4Sb9, with Ca atoms preferably substituting Ba on one of the three available sites. The nuances of the five crystal structures are discussed, and the chemical bonding in Ba7Ga4As9 is interrogated by tight-binding linear muffin-tin orbital calculations.

  9. Study of PbTe p-Type Doping With BaF{sub 2}

    SciTech Connect

    Mengui, U. A.; Rappl, P. H. O.; Diaz, B.; Closs, H.; Ueta, A. Y.; Abramof, E.

    2010-01-04

    We investigate here the electrical and structural properties of PbTe layers doped with BaF{sub 2}. The layers were grown on (111)BaF{sub 2} substrates by molecular beam epitaxy. The nominal doping level, defined as the beam flux ratio between BaF{sub 2} and PbTe, was varied from 0.02 to 1%. The hole concentration increases monotonously from 5x10{sup 17} to 1x10{sup 19} cm{sup -3} as the doping level is raised from 0.02 to 0.4%, and saturates at p approx10{sup 19} cm{sup -3} for higher doping levels. This result demonstrates that PbTe can be effectively p-type doped with BaF{sub 2}. Even for the highest doping levels, the PbTe layers remained with a good structural quality, as evidenced by the (222) x-ray rocking curves.

  10. Structure refinement and dielectric relaxation of M-type Ba, Sr, Ba-Sr, and Ba-Pb hexaferrites

    NASA Astrophysics Data System (ADS)

    Ashima; Sanghi, Sujata; Agarwal, Ashish; Reetu; Ahlawat, Neetu; Monica

    2012-07-01

    M-type hexaferrites with compositions BaFe12O19 (BFO), SrFe12O19 (SFO), Ba0.5Sr0.5Fe12O19 (BSFO), and Ba0.5Pb0.5Fe12O19 (BPFO) were synthesized by commercial solid state reaction method. The Rietveld refinement of x-ray powder diffraction revealed a single hexagonal phase with space group P63/mmc for BFO, SFO, and BSFO samples, whereas BPFO sample contains hematite (α-Fe2O3) phase with space group R3c along with the M-type main phase. All the samples show dispersion in dielectric constant (ɛ') and dielectric loss (tan δ) values with frequency. The values of ɛ' and tan δ increase with increase in temperature due to increase in the number of charge carriers and their mobilities, which are thermally activated. The reciprocal temperature dependence of conductivity (σac) and the most probable relaxation time (τM″) satisfies the Arrhenius relation. A perfect overlapping of the normalized plots of modulus isotherms on a single "super curve" for all the studied temperatures reveals a temperature independence of dynamic processes involved in conduction and for relaxation. Further, the complex plots of M* (M″ vs M') indicate that dc conductivity dominates in the region below the M″max point. Above M″max, the variations follow Jonscher power law (σ = Aωs) implying that ac conductivity is dominating in this region. Among the prepared samples, SFO hexaferrite has lowest values of σac, ɛ', and tan δ making it suitable for use in microwave devices.

  11. Size evolution of ion beam synthesized Pb nanoparticles in Al

    NASA Astrophysics Data System (ADS)

    Wang, Huan; Zhu, Hongzhi

    2014-07-01

    The size evolution of Pb nanoparticles (NPs) synthesized by ion implantation in an epitaxial Al film has been experimentally investigated. The average radius R of Pb NPs was determined as a function of implantation fluence f. The R( f) data were analyzed using various growth models. Our observations suggest that the size evolution of Pb NPs is controlled by the diffusion-limited growth kinetics ( R 2∝ f). With increasing implantation current density, the diffusion coefficient of Pb atoms in Al is evident to be enhanced. By a comparative analysis of the R( f) data, values of the diffusion coefficient of Pb in Al were obtained.

  12. Calculation of NMR lineshapes for Ba-Al-Ge clathrates

    NASA Astrophysics Data System (ADS)

    Rodriguez, Sergio; Gou, Weiping; Ross, Joseph

    2008-10-01

    Clathrates consist of Si, Ge, or Sn cages in a crystalline framework, with guest atoms inside the cages. They have gained interest due to thermoelectric properties suitable for potential device application. To understand Al substitutional configurations, we calculated Al NMR line shapes for several structures with compositions Ba8Ge46-x-yAlxy for x=3,8,11,12,16,24; y=2,3; where represents a vacancy. The results were obtained by calculating Electric Field Gradients (EFG) for Al sites of type-I clathrates assuming an ordered superstructure of vacancies and framework occupation. We used ab initio methods in the Generalized Gradient Approximation as implemented by the WIEN2k program, and used the results to simulate NMR lineshapes numerically. These were compared to our previously reported NMR lineshapes. In the case of Ba8Ge31Al123 four Al sites in the superstructure include two sites with small EFG where the vacancy is far away and two sites with large EFG with a vacancy adjacent to Al. Assuming a larger Knight shift for sites next to vacancies, we obtain good agreement with NMR experimental results for reduced-Al Ba8Ge34Al12, while for the Zintl phase Ba8Ge30Al16 we obtain good agreement with no spontaneous vacancies. We infer that Al prefers locations close to vacancies rather than random occupation. This work was supported by Robert A. Welch Foundation (Grant A-1526).

  13. Matrix effects in the detection of Pb and Ba in soils using a laser plasma

    SciTech Connect

    Eppler, A.S.; Cremers, D.A.; Hickmott, D.D.

    1994-12-31

    Laser-Induced Breakdown Spectroscopy (LIBS) has been used for the semi-quantitative determination of Ba and Pb in sand and soil matrices. The detection limits in a sand matrix were 76 ppm (w/w) for Ba and 17 ppm for Pb with analytical precision better than 7% RSD. In soil, the detection limits were 63 ppm for Ba and 112 ppm for Pb with 10% RSD precision. In this study, three factors were found to influence Ba and Pb emissions: (1) compound speciation, where Ba emissions decreased in the order of sulfate > hydroxide > oxide > chloride > nitrate and where Pb emissions decreased in the order of oxide > carbonate > chloride > sulfide > nitrate, (2) bulk matrix composition (e.g. sample absorptivity at the laser wavelength, chemical composition), and (3) the presence of equimolar concentrations of Na, K, Cs (chloride salts), and Fe (elemental powder) in the sample. The analytical capabilities of the LIBS method determined here indicate that a field-based instrument would be useful for the environmental site characterization.

  14. Distribution of Pb, Cd and Ba in soils and plants of two contaminated sites.

    PubMed

    Pichtel, J; Kuroiwa, K; Sawyerr, H T

    2000-10-01

    Evaluation of metal accumulation in soils and plants is of environmental importance due to their health effects on humans and other biota. Soil material and plant tissue were collected along transects in two heavily contaminated facilities, a Superfund site and a lead-acid battery dump, and analyzed for metal content. Soil lead (Pb), cadmium (Cd) and barium (Ba) concentrations for the Superfund site averaged 55,480, 8.5 and 132.3 mg/kg, respectively. Soil Pb occurred primarily in the carbonate, sulfide/residual and organic chemical fractions (41.6, 28.6 and 16.7%, respectively). Soil Pb, Cd and Ba concentrations for the dump site averaged 29,400, 3.9 and 1130 mg/kg, respectively. Soil Pb occurred mostly in the organic and carbonate fractions as 48.5 and 42.5%, respectively. Pb uptake in the two sites ranged from non-detectable (Agrostemma githago, Plantago rugelii, Alliaria officinalis shoots), to 1800 mg/kg (Agrostemma githago root). Cd uptake was maximal in Taraxacum officinale at 15.4 mg/kg (Superfund site). In the majority > or =65%) of the plants studied, root Pb and Cd content was higher than that for the shoots. Tissue Pb correlated slightly with exchangeable and soluble soil Pb; however, tissue Cd was poorly correlated with soil Cd species. None of the sampled plants accumulated measurable amounts of Ba. Those plants that removed most Pb and Cd were predominantly herbaceous species, some of which produce sufficient biomass to be practical for phytoremediation technologies. Growth chamber studies demonstrated the ability of T. officinale and Ambrosia artemisiifolia to successfully remove soil Pb and Cd during repeated croppings. Tissue Pb was correlated with exchangeable soil Pb at r(2)=0.68 in Ambrosia artemisiifolia. PMID:15092867

  15. Cu/Ba/bauxite: an Inexpensive and Efficient Alternative for Pt/Ba/Al2O3 in NOx Removal

    PubMed Central

    Wang, Xiuyun; Chen, Zhilin; Luo, Yongjin; Jiang, Lilong; Wang, Ruihu

    2013-01-01

    Cu/Ba/bauxite possesses superior NOx storage and reduction (NSR) performances, high thermal stability, strong resistance against SO2 poisoning and outstanding regeneration ability in comparison with Pt/Ba/Al2O3. It can serve as a cheap and promising alternative for traditional Pt/Ba/Al2O3 in NOx removal from lean-burn engines. PMID:23536149

  16. Pb-Al relationships in waterfowl feces discriminate between sources of Pb exposure.

    PubMed

    Martínez-Haro, M; Taggart, M A; Mateo, R

    2010-07-01

    Hunted mallards (n = 56) were collected in the Ebro Delta (Spain) in 2007-08 to evaluate the use of feces as a non-invasive monitoring method to study lead shot ingestion. The prevalence of Pb shot ingestion in these birds was 28.6%, and similar to that reported before a ban on Pb shot use in 2003. Lead concentrations in terminal intestinal contents were higher in mallards with Pb shot in their gizzard. Feces Pb concentrations >34 microg/g d.w were indicative of Pb shot ingestion, and background Pb levels were <12.5 microg/g d.w. To discriminate between birds ingesting soil Pb, and those ingesting Pb shot, we correlated Al and Pb levels and showed that mallards with ingested Pb shot in the gizzard stood out as outliers within the regression. Feces Pb-Al relationships can be used as a simple non-invasive tool in monitoring programs regarding Pb shot ingestion in birds. PMID:20398987

  17. Structural and electrical transport properties of proficient Ba-Pb nanoferrites

    NASA Astrophysics Data System (ADS)

    Haq, A.; Anis-ur-Rehman, M.; Malik, Muhammad Ali

    2012-03-01

    The excellent combination of magnetic and dielectric properties of hexaferrites makes these materials suitable for use in high-frequency applications. Ba-Pb nanocrystalline ferrites having the general formula Ba1-xPbxFe12O19 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared by the co-precipitation method. X-ray powder diffraction (XRD) patterns of all prepared samples indicated the formation of the required phase. The crystallite size, lattice parameters and porosities of samples were measured from XRD data. Scanning electron microscopy was carried out to observe the morphology of the synthesized Ba-Pb ferrites. Temperature-dependent dc electrical resistivity, dielectric constant, dielectric loss tangent and the ac electrical conductivity of nanocrystalline Ba ferrites were investigated as a function of frequency and Pb concentration. The effect of Pb doping on dielectric and electric properties of Ba nanoferrites was explained on the basis of cation distribution in the crystal structure.

  18. Room temperature persistent photoconductivity in p-PbTe and p-PbTe:BaF2

    NASA Astrophysics Data System (ADS)

    de Castro, S.; Soares, D. A. W.; Peres, M. L.; Rappl, P. H. O.; Abramof, E.

    2014-10-01

    We investigated the persistent photoconductivity effect observed in p-PbTe:BaF2 and undoped p-PbTe films in the temperature range of T = 100-300 K. It was observed that the PPC effect scales with temperature and that there is a transition in the relaxation time behavior around ˜150 K. We found that the transition is caused by the particular dynamics of the hole carries between the energy barriers that characterize the traps originated from disorder present in the samples. The analysis was performed by comparing the theory of the random potential with the experimental data and revealed the presence of both random local potential fluctuations and localized states, which can be attributed to the presence of disorder due BaF2 doping and Te vacancies.

  19. Electrical properties of PbTe doped with BaF{sub 2}

    SciTech Connect

    Mengui, U. A.; Abramof, E.; Rappl, P. H. O.; Diaz, B.; Closs, H.; Senna, J. R.; Ueta, A. Y.

    2009-02-15

    We study here the p-type doping of PbTe with BaF{sub 2}. For the investigation, PbTe layers were grown on (111) BaF{sub 2} substrates by molecular beam epitaxy. The beam flux ratio between BaF{sub 2} and PbTe, defined as the nominal doping level, was varied from 0.02% to 1%. The hole density increases from 5x10{sup 17} to 1x10{sup 19} cm{sup -3} as the doping level rises from 0.02% to 0.4% and saturates at p{approx}10{sup 19} cm{sup -3} for higher levels. The saturation effect was attributed to self-compensation. The carrier concentration of all samples remained almost constant as the temperature was varied from 10 to 350 K, indicating that no thermal activation is present in the whole doping range. It suggests that the impurity level in PbTe doped with BaF{sub 2} remains resonant with the valence band, similar to the native defects behavior. The low-temperature mobility showed a pronounced reduction from 50 000 to 2 000 cm{sup 2}/V s as the doping level rises from 0.02% to 1%, mainly due to the substantial increase in the hole concentration. For temperatures higher than 80 K, the mobility was essentially limited by phonon scattering. Our results demonstrate that a controlled p-type doping of PbTe with BaF{sub 2} can be obtained up to 10{sup 19} cm{sup -3}.

  20. Bioaccessibility of Ba, Cu, Pb, and Zn in urban garden and orchard soils.

    PubMed

    Cai, Meifang; McBride, Murray B; Li, Kaiming

    2016-01-01

    Exposure of young children to toxic metals in urban environments is largely due to soil and dust ingestion. Soil particle size distribution and concentrations of toxic metals in different particle sizes are important risk factors in addition to bioaccessibility of these metals in the particles. Analysis of particle size distribution and metals concentrations for 13 soils, 12 sampled from urban gardens and 1 from orchard found that fine particles (<105 μm) comprised from 22 to 66% by weight of the tested soils, with Ba, Cu, Pb and Zn generally at higher concentrations in the finer particles. However, metal bioaccessibility was generally lower in finer particles, a trend most pronounced for Ba and Pb. Gastric was higher than gastrointestinal bioaccessibility for all metals except Cu. The lower bioaccessibility of Pb in urban garden soils compared to orchard soil is attributable to the higher organic matter content of the garden soils. PMID:26477581

  1. Raman Scattering Study of PbSe Grown on (111) BaF2 Substrate

    NASA Astrophysics Data System (ADS)

    Yang, Ai-Ling; Wu, Hui-Zhen; Li, Zhi-Feng; Qiu, Dong-Jiang; Chang, Yong; Li, Jian-Feng; P, McCann J.; X, Fang M.

    2000-08-01

    PbSe films were grown on (111)-oriented BaF2 substrates by using molecular beam epitaxy. High resolution x-ray diffraction characterization showed good crystalline quality of PbSe films. Both longitudinal optical phonon at 135 cm-1 and transverse optical phonon at 47.6 cm-1 were observed by Raman scattering measurements. The Raman tensor calculation demonstrates that both transverse-optical and longitudinal-optical (LO) phonons in PbSe crystal are Raman active on (111)-oriented surface. Furthermore, 2LO phonon at about 270 cm-1 and polaron at about 800 cm-1 in PbSe, were also observed. The observed Raman frequencies are in good agreement with theoretical calculations using point ion model.

  2. Matrix effects in the detection of Pb and Ba in soils using laser-induced breakdown spectroscopy

    SciTech Connect

    Eppler, A.S.; Cremers, D.A.; Hickmott, D.D.; Ferris, M.J.; Koskelo, A.C.

    1996-09-01

    With the use of laser-induced breakdown spectroscopy (LIBS), the effects of chemical speciation and matrix composition on Pb and Ba measurements have been investigated by using sand and soil matrices. A cylindrical lens was used to focus the laser pulses on the samples because it yielded higher measurement precision than a spherical lens for the experimental conditions used here. The detection limits for Pb and Ba spiked in a sand matrix were 17 and 76 ppm (w/w), respectively. In spiked soil, the detection limits were 57 and 42 ppm (w/w) for Pb and Ba, respectively. Measurement precision for five replicate measurements was typically 10{percent} RSD or less. Two factors were found to influence emissions from Pb and Ba present in sand and soil matrices as crystalline compounds: (1) compound speciation, where Ba emission intensities varied in the order carbonate{gt}oxide{gt}sulfate{gt}chloride{gt}nitrate, and where Pb emission intensities varied in the order oxide{gt}carbonate{gt}chloride{gt}sulfate{gt}nitrate; and (2) the composition of the bulk sample matrix. Emissions from Ba(II) correlated inversely with the plasma electron density, which in turn was dependent upon the percent sand in a sand/soil mixture. The analytical results obtained here show that a field-screening instrument based on LIBS would be useful for the initial screening of soils contaminated with Pb and Ba. {copyright} {ital 1996 Society for Applied Spectroscopy.}

  3. Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    NASA Astrophysics Data System (ADS)

    Rogge, J.; Hetaba, W.; Schmalhorst, J.; Bouchikhaoui, H.; Stender, P.; Baither, D.; Schmitz, G.; Hütten, A.

    2015-07-01

    We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co2FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  4. Radiation-induced changes in electrical conductivity and structure of BaPbO3 after γ-irradiation

    NASA Astrophysics Data System (ADS)

    Shan, Qing; Cai, Pingkun; Zhang, Xinlei; Li, Jiatong; Chu, Shengnan; Jia, Wenbao

    2015-11-01

    Several barium plumbate (BaPbO3) solid samples, made from PbO and BaCO3 powder by chemistry liquid-phase coprecipitation, were investigated before and after γ-irradiation. The solid samples were irradiated by a 60Co γ-irradiation source whose dose rate is about 0.7 kGy per hour. The irradiation times were 0, 72, 144, 216, 288 and 360 h. Then, the four-probe method, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to indicate the changes in electrical conductivity and microstructure of BaPbO3 after γ-irradiation. The XRD results indicated that the content of PbO was reduced as the irradiation dose was increased and eventually vanished from the surface of samples. However, there was no new obvious substance phase found from the XRD atlas. It seems that the PbO transformed into nearly amorphous Pb5O8. The conjecture could be proved by the results of annealing experiment and SEM. The XPS results seem to show that the microstructure of BaPbO3 was slightly changed.

  5. Preparation and Electrochemical Characterization of Aluminium Liquid Battery Cells With Two Different Electrolytes (NaCl-BaCl2-AlF3-NaF and LiF-AlF3-BaF2).

    PubMed

    Napast, Viktor; Moškon, Jože; Homšak, Marko; Petek, Aljana; Gaberšček, Miran

    2015-01-01

    The possibility of preparation of operating rechargeable liquid battery cells based on aluminium and its alloys is systematically checked. In all cases we started from aluminium as the negative electrode whereas as the positive electrode three different metals were tested: Pb, Bi and Sn. Two types of electrolytes were selected: Na(3)AlF(6) -AlF(3) - BaCl(2) - NaCl and Li(3)AlF(3) - BaF(2). We show that some of these combinations allowed efficient separation of individual liquid layers. The cells exhibited expected voltages, relatively high current densities and could be charged and discharged several times. The capacities were relatively low (120 mAh in the case of Al-Pb system), mostly due to unoptimised cell construction. Improvements in various directions are possible, especially by hermetically sealing the cells thus preventing salt evaporation. Similarly, solubility of aluminium in alloys can be increased by optimising the composition of positive electrode. PMID:26680707

  6. Melting behaviour of In and Pb particles embedded in an Al matrix

    SciTech Connect

    Zhang, D.L.; Cantor, B. )

    1991-07-01

    Microstructures of melt spun hypomonotectic Al-7wt%In, hypermonotectic Al-5wt%Pb and near monotectic Al-2wt%Pb alloys have been examined by transmission electron microscopy and consist of 10-150 nm diameter faceted In particles and 5-150 nm faceted Pb particles homogeneously distributed in an Al matrix. As-melt spun In and Pb particles exhibit bear cube-cube and cube-cube orientation relationships with the Al matrix respectively, and truncated octahedral shapes bounded by [111] and [100] facets. In this paper the melting behavior of In and Pb particles in as-melt spun Al-7wt%In, Al-5wt%Pb and Al-2wt%Pb alloys is investigated by heating and cooling experiments in a differential scanning calorimeter and in situ heating experiments in a transmission electron microscope.

  7. Pb2Ba3(BO3)3Cl: A Material with Large SHG Enhancement Activated by Pb-Chelated BO3 Groups.

    PubMed

    Dong, Xiaoyu; Jing, Qun; Shi, Yunjing; Yang, Zhihua; Pan, Shilie; Poeppelmeier, Kenneth R; Young, Joshua; Rondinelli, James M

    2015-07-29

    Pb(II) has long been associated with lone pair activity and is often substituted in alkali earth metal borates to create new nonlinear optical (NLO) materials with enhanced second harmonic generation (SHG) capabilities. However, large enhancement in isomorphic Pb-free analogues is rare. Here we report a new NLO material Pb2Ba3(BO3)3Cl with a phase-matching SHG response approximately 3.2× that of KDP and 6× higher than its isomorphic compound Ba5(BO3)3Cl. We show that the enhanced SHG response originates from a unique edge-sharing connection between lead-oxygen polyhedra and boron-oxygen groups, making the dielectric susceptibility more easily affected by the external electric field of an incident photon. This understanding provides a route to identify systems that would benefit from SHG-active cation substitution in isomorphic structures that exhibit weak or null SHG responses. PMID:26147880

  8. Structural, optical and electrical properties of GdAlO3:Eu3+Ba2+

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, T.; Tamilarasi, S.; Bose, A. Chandra

    2015-06-01

    Effect of Ba2+ ions concentration on the photoluminescence of GdAlO3:Eu3+ Ba2+ phosphor is investigated. The phosphors are synthesized by citrate-based sol-gel method and the formation of orthorhombic phase GdAlO3 is confirmed by XRD analysis. Kubelka-Munk function is used to estimate the band gap and the value varies with concentration of Ba2+ is observed. Photoluminescence spectra show a strong red emission peak at 616 nm corresponding to5D0→7F2 transition and its intensity increase with the addition of Ba2+ ions. The presence of Eu3+ and Ba2+ ions in GdAlO3 strongly influences the dielectric property of GdAlO3.

  9. Barium aluminides Ba{sub x}Al{sub 5}(x=3,3.5,4)

    SciTech Connect

    Jehle, Michael; Scherer, Harald; Wendorff, Marco; Roehr, Caroline

    2009-05-15

    Three aluminides of the series Ba{sub x}Al{sub 5}(x=3,3.5,4) were synthesized from stoichiometric ratios of the elements in Ta crucibles. The crystal structure of the new compound Ba{sub 7}Al{sub 10} was determined using single crystal X-ray data (space group R3-barm, a=604.23(9), c=4879.0(12)pm, Z=3, R1=0.0325). The compound exhibits Al Kagome (3.6.3.6.) nets in which half of the triangles form the basis of trigonal bipyramids Al{sub 5}. The apical Al are thus three-bonded assuming a charge of -2 ({sup 27}Al-NMR chemical shift delta=660pm), whereas the Al atoms of the basal triangle (i.e. of the Kagome net) are four-bonded and thus of formal charge -1(delta=490ppm). The total charge of the anion is thus exactly compensated by the Ba cations, i.e. the compound can be interpreted as an electron precise Zintl phase, exhibiting a distinct pseudo-band gap at the Fermi level of the calculated tDOS. According to the total formula, the structure displays a combination the stacking sequences of Ba{sub 3}Al{sub 5} and Ba{sub 4}Al{sub 5}, the structures of which have been redetermined with current methods (both hexagonal with space group P6{sub 3}/mmc; Ba{sub 3}Al{sub 5}: a=606.55(7), c=1461.8(2)pm, Z=2, R1=0.0239; Ba{sub 4}Al{sub 5}: a=609.21(7), c=1775.8(3)pm, Z=2, R1=0.0300). These three compounds with slightly different electron counts but similar polyanions allow to compare the bond lengths, the electronic structures and the overall bonding situation in dependence of positive or negative deviation of the electron count in relation to the novel formally electron precise Zintl compound Ba{sub 7}Al{sub 10}. - Al{sub 5} layers of Kagome nets in the new binary electron precise Zintl compound Ba{sub 3.5}Al{sub 5}, also found in Ba{sub 3}Al{sub 5} and Ba{sub 4}Al{sub 5}.

  10. Superconducting properties of Ba(Pb, Bi)O 3 single crystals and melt-processed (Ba, K)BiO 3

    NASA Astrophysics Data System (ADS)

    Grumann, M.; Balakrishnan, G.; Tomy, C. V.; Paul, D. McK.

    1994-06-01

    Single crystals of the superconductors BaPb 1- xBi xO 3 with nominal compositions of x=0.25, were grown by cooling from the melt using an excess of PbO. The superconducting transitions have been measured on the grown crystals as a function of oxygen annealing and sharp transitions with Tconset at 12 K have been observed. The related perovskite Ba 1- xK xBiO 3 superconductor ( x=0.4) has been synthesized by a new melt-processing technique using an infra-red image furnace. The melt-processed material on post annealing, is superconducting with Tconset∼25 K. The superconducting properties of these two families of superconductors are presented.

  11. Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae=Ca,Sr,Ba, as thermoelectric materials

    SciTech Connect

    Parker, David S; Singh, David J

    2013-01-01

    We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2 Sn, Sr2 Sn and Ba2 Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli - roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  12. Current and potential distributions on positive plates with conductive Pb 3O 4 and BaPbO 3 in their formation and discharge

    NASA Astrophysics Data System (ADS)

    Guo, Yonglang; Liu, Huan

    The positive plates with conductive materials, Pb 3O 4 and BaPbO 3, in automotive lead-acid batteries were investigated by measuring their current and potential distributions in the course of formation and discharge. It is found that these two conductive materials, especially Pb 3O 4, enhance the formation in the initial stage greatly and that they make the current and potential distributions more uniform. In the discharge, the addition of Pb 3O 4 increases the capacity of the positive plate, but it is unfavorable to the paste curing and causes poor contact between active mass (AM) particles so that the polarization increases greatly at 3 C discharge rate. The BaPbO 3 additive improves not only the formation but also the discharge performance because of its stability in acidic media and at high polarization. The violent charge at high polarization around the plates in the initial formation can lead to poor AM contact and high polarization resistance.

  13. Synchronizing the Absolute and Relative Clocks: Pb-Pb and Al-Mg Systematics in CAIs from the Allende and NWA 2364 CV3 Chondrites

    NASA Astrophysics Data System (ADS)

    Bouvier, A.; Wadhwa, M.

    2009-03-01

    A Pb-Pb internal isochron of a type-B CAI from the NWA 2364 CV3 chondrite gives an absolute age of 4568.6 ± 0.2 Ma which contrasts with previous internal Pb-Pb ages of CAIs from Allende and Efremovka. Al-Mg systematics are also reported for CV3 CAIs.

  14. Anomalous dielectric and thermal properties of Ba-doped PbZrO3 ceramics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Rožič, B.; Koruza, J.; Cordoyiannis, G.; Malič, B.; Kutnjak, Z.

    2015-11-01

    The dielectric and thermal properties of an antiferroelectric (AFE) material characterised by an intermediate ferroelectric (FE) phase between the AFE and paraelectric phase in zero field are studied by means of a generalised Landau-Kittel model of AFEs. A temperature-dependent coupling of the two sublattices is introduced in accordance with the Rae-Dove (RD) model of re-entrant phase transitions. The sublattice polarisation components are calculated as functions of temperature and the applied electric field by minimising numerically the free energy. The calculated dielectric susceptibility shows anomalies at the boundaries of the intermediate FE phase, characteristic for first-order phase transitions. It is shown that this behaviour is in qualitative agreement with the measured dielectric constant in Ba-doped PbZrO3 ceramics. The model also predicts a negative adiabatic electrocaloric temperature change Δ T in a broad temperature range in the AFE phase, in qualitative agreement with experiments. The dipolar heat capacity is also predicted to be negative in the intermediate phase in zero field, in analogy with the results of the RD model.

  15. Dielectric and Electrical Properties of the Double Perovskite PbBaBiNbO6

    NASA Astrophysics Data System (ADS)

    Panda, Niranjan; Parida, B. N.; Padhee, R.; Choudhary, R. N. P.

    2015-11-01

    The double perovskite PbBaBiNbO6 was synthesized by high-temperature solid-state reaction. Room-temperature x-ray data, energy-dispersive x-ray spectroscopy, and scanning electron microscopy of the sample confirmed formation of a single-phase compound and uniform distribution of grains of high density. Detailed studies of the dependence of the dielectric properties of the material on temperature and frequency confirmed its ferroelectric nature. The electrical transport properties of the material were indicative of non-exponential conductivity relaxation. We suggest this B-site Bi5+-doped ferroelectric perovskite material is a suitable candidate for the bulk photovoltaic effect and related solar applications. The low-lying 6s empty states of the electronegative Bi atom produce empty bands in the energy gap of the parent materials, effectively reducing the activation energy by ˜1 eV, depending on the composition of the ferroelectric end member and the concentration of Bi5+ in the solid solution.

  16. Determination of space group of BaPb 0.75Bi 0.25O 3 by convergent-beam electron diffraction

    NASA Astrophysics Data System (ADS)

    Hashimoto, Takuya; Tsuda, Kenji; Shiono, Junichiro; Mizusaki, Junichiro; Tanaka, Michiyoshi

    2002-11-01

    The space group of BaPb 0.75Bi 0.25O 3 with distorted perovskite structure was investigated by convergent-beam electron diffraction (CBED) and selected area electron diffraction (SAD). The symmetry of observed CBED patterns was either 1 or m and no CBED pattern with fourfold nor sixfold symmetry was observed, indicating that the crystal system of BaPb 0.75Bi 0.25O 3 is either orthorhombic or monoclinic. The ± G dark field disk of CBED patterns indicated that no inversion center existed in BaPb 0.75Bi 0.25O 3 and that the point group of BaPb 0.75Bi 0.25O 3 was either m or mm2. It was concluded that the point group of BaPb 0.75Bi 0.25O 3 was not mm2 but m because CBED patterns with symmetry of not only m but also 1 were taken at [1 1 1] incidence with pseudo-cubic perovskite notation. From CBED patterns taken at [1 1 1] azimuth, unique axis of monoclinic BaPb 0.75Bi 0.25O 3 with point group of m was also determined. The lattice type of BaPb 0.75Bi 0.25O 3 was determined to be a body centered one from the extinction rule of SAD pattern. No Gjønnes-Moodie lines, which indicated existence of glide plane or screw axis, were observed in all of the CBED patterns, leading to the conclusion that the space group of BaPb 0.75Bi 0.25O 3 is Im (No. 8).

  17. Nonlinear-optical susceptibility of hilgardite-like borates MBOX(M=Pb,Ca,Sr,Ba; X=Cl,Br)

    NASA Astrophysics Data System (ADS)

    Plachinda, Paul A.; Dolgikh, Valery A.; Stefanovich, Sergey Yu.; Berdonosov, Petr S.

    2005-10-01

    Usage of non-centrosymmetric boron oxide derivative crystals as nonlinear elements may be a key solution of pressing problem of obtaining powerful radiation at shorter wavelengths via frequency multiplication of solid state laser radiations. It is shown that Pb 2B 5O 9Br and some other members of hilgardite-like borohalogenides demonstrate in powder form, high non-linear optical activity in the SHG experiments. An attempt is made using the Philips-Van Vechten-Levine-Xue bond theory to calculate second-order nonlinear coefficients for isostructural to mineral hilhardite noncentrosymmetric crystals MBOX with M=Pb, Sr, Ba, Eu, Ca and X=Cl, Br. Theoretically obtained values of nonlinear optical coefficients d only partly correlate with the results of SHG measurements. In particular, the experiments distinctively show sharp increase of nonlinear activity along the series Ca < Sr < Ba < Pb and Cl < Br of metal boro-halogenides, while theoretical estimations give substantially more slack composition dependences. Analysis of contribution of different boron-oxygen bonds to optical nonlinearities of the compounds reveals important role of planar BO 3 triangles, though this factor is yet unable to explain enormously high SHG output from Pb 2B 5O 9Br.

  18. Crystallographic Study of Mixture CeBa1.8Pb0.2Cu3Oy in the Range of 860 deg. C to 940 deg. C

    SciTech Connect

    Stergiou, A.; Yilmaz, S.; Stergiou, C.

    2007-04-23

    A powder mixture with chemical formula CeBa1.8Pb0.2Cu3Oy was prepared. The mixture was heated in free atmosphere, at temperatures 860 deg. C to 940 deg. C, for 24 to 72h. The samples were measured by X-Ray powder diffraction with CuKa radiation. Each sample was characterized with the help of the PDF and refined, using the Rietveld's ''Powder Profile Analysis''. The first sample (860 deg. C) was identified with the phases: Ba2CeBiO6, CuO and BaCuO2, while all the remaining samples (870 deg. C-940 deg. C) with the phases Ba2CePbO6, CuO and CeO2. The phases Ba2CeBiO6 and Ba2CePbO6 are the main phases with analogous chemical types, but different symmetry. The phase CuO is common in all the samples, while from the remaining phases the BaCuO2 appears only in the first sample and the CeO2 in all, except the first one. The quantity 0.2 of Pb is distributed in the Ba positions, substituting a part of these. The percentages of phases are about 82%, 10% and 8% for the first sample and for all the remaining about 85%, 8% and 7%, respectively with above serious.

  19. Melting of Pb Nanocrystals Embedded in Al, Si, and Cu Matrices

    NASA Astrophysics Data System (ADS)

    Wang, Huan; Zhu, Hongzhi

    2015-12-01

    Dispersions of nanoscale Pb particles embedded in Si, Al, and Cu matrices have been synthesized by ion implantation and subsequent annealing. The melting transitions of the embedded Pb nanocrystals with epitaxial particle/matrix interfaces were investigated by means of in situ high-temperature X-ray diffraction. Due to different levels of lattice mismatch, the Pb nanoprecipitates experience a different elastic strain in different matrices. Further analysis on the lattice constants of the embedded Pb nanocrystals gives unambiguous evidence of the strain-related pressure effect, which is particle size and matrix dependent, on tuning of the melting behavior of the embedded Pb nanoparticles.

  20. Characterization of highly (110)- and (111)-oriented Pb(Zr,Ti)O{sub 3} films on BaPbO{sub 3} electrode using Ru conducting barrier

    SciTech Connect

    Liang, C.-S.; Wu, J.-M.

    2005-07-11

    Highly non-(001)-oriented Pb(Zr,Ti)O{sub 3} (PZT) films have been fabricated by rf-magnetron sputtering. The preferential (110)-oriented BaPbO{sub 3} (BPO) deposited on Ru buffer layer induces the growth of (110)-oriented PZT film. With the aid of self-organized growth of PZT, the orientation of the film deposited on random-oriented BPO/Pt(111)/Ru(002) is (111)-preferred. The insertion of Pt layer between BPO and Ru changes the orientation of PZT from (110) to (111) and prevents the oxygen diffusion. These non-(001)-oriented PZT films possess more superior ferroelectric, fatigue, and retention properties than those of (001)-oriented PZT films.

  1. Characterization of highly (110)- and (111)-oriented Pb(Zr ,Ti)O3 films on BaPbO3 electrode using Ru conducting barrier

    NASA Astrophysics Data System (ADS)

    Liang, Chun-Sheng; Wu, Jenn-Ming

    2005-07-01

    Highly non-(001)-oriented Pb(Zr ,Ti)O3 (PZT) films have been fabricated by rf-magnetron sputtering. The preferential (110)-oriented BaPbO3 (BPO) deposited on Ru buffer layer induces the growth of (110)-oriented PZT film. With the aid of self-organized growth of PZT, the orientation of the film deposited on random-oriented BPO /Pt(111)/Ru(002) is (111)-preferred. The insertion of Pt layer between BPO and Ru changes the orientation of PZT from (110) to (111) and prevents the oxygen diffusion. These non-(001)-oriented PZT films possess more superior ferroelectric, fatigue, and retention properties than those of (001)-oriented PZT films.

  2. Tunneling spectroscopy of Al/AlO{sub x}/Pb subjected to hydrostatic pressure

    SciTech Connect

    Zhu, Jun; Hou, Xing-Yuan; Guan, Tong; Zhang, Qin-Tong; Li, Yong-Qing; Han, Xiu-Feng; Li, Chun-Hong; Ren, Cong; Yang, Zheng-Xin; Zhang, Jin; Shan, Lei; Chen, Gen-Fu

    2015-05-18

    We develop an experimental tool to investigate high-pressure electronic density of state by combining electron tunneling spectroscopy measurements with high-pressure technique. It is demonstrated that tunneling spectroscopy measurement on Al/AlO{sub x}/Pb junction is systematically subjected to hydrostatic pressure up to 2.2 GPa. Under such high pressure, the normal state junction resistance is sensitive to the applied pressure, reflecting the variation of band structure of the barrier material upon pressures. In superconducting state, the pressure dependence of the energy gap Δ{sub 0}, the gap ratio 2Δ{sub 0}/k{sub B}T{sub c}, and the phonon spectral energy is extracted and compared with those obtained in the limited pressure range. Our experimental results show the accessibility and validity of high pressure tunneling spectroscopy, offering wealthy information about high pressure superconductivity.

  3. The LO-BaFL method and ALS microarray expression analysis

    PubMed Central

    2012-01-01

    Background Sporadic Amyotrophic Lateral Sclerosis (sALS) is a devastating, complex disease of unknown etiology. We studied this disease with microarray technology to capture as much biological complexity as possible. The Affymetrix-focused BaFL pipeline takes into account problems with probes that arise from physical and biological properties, so we adapted it to handle the long-oligonucleotide probes on our arrays (hence LO-BaFL). The revised method was tested against a validated array experiment and then used in a meta-analysis of peripheral white blood cells from healthy control samples in two experiments. We predicted differentially expressed (DE) genes in our sALS data, combining the results obtained using the TM4 suite of tools with those from the LO-BaFL method. Those predictions were tested using qRT-PCR assays. Results LO-BaFL filtering and DE testing accurately predicted previously validated DE genes in a published experiment on coronary artery disease (CAD). Filtering healthy control data from the sALS and CAD studies with LO-BaFL resulted in highly correlated expression levels across many genes. After bioinformatics analysis, twelve genes from the sALS DE gene list were selected for independent testing using qRT-PCR assays. High-quality RNA from six healthy Control and six sALS samples yielded the predicted differential expression for 7 genes: TARDBP, SKIV2L2, C12orf35, DYNLT1, ACTG1, B2M, and ILKAP. Four of the seven have been previously described in sALS studies, while ACTG1, B2M and ILKAP appear in the context of this disease for the first time. Supplementary material can be accessed at: http://webpages.uncc.edu/~cbaciu/LO-BaFL/supplementary_data.html. Conclusion LO-BaFL predicts DE results that are broadly similar to those of other methods. The small healthy control cohort in the sALS study is a reasonable foundation for predicting DE genes. Modifying the BaFL pipeline allowed us to remove noise and systematic errors, improving the power of this

  4. Magnetic field penetration depth of superconducting aluminum-substituted Ba8Si42Al4 clathrate

    NASA Astrophysics Data System (ADS)

    Li, Yang; Garcia, Jose; Franco, Giogiovanni

    2014-03-01

    During past years, efforts have been made to explore the superconductivity of Group IV clathrates with particular attention to the sp3 hybridized networks. In the study, we report on the superconductivity of Al-substituted type-I silicon clathrates. Pure phase samples of the general formula Ba8Si46-xAlx with different values of x were synthesized. The magnetic susceptibility measurements show that Ba8Si42Al4 is a bulk superconductor, with an onset at Tc =6 K. Al substitution results in a large decrease of the electronic density of states at the Fermi level, which explains the decreased superconducting critical temperature within the BCS framework. To further characterize the superconducting state, we carried out magnetic measurements showing Ba8Si42Al4 to be a type II superconductor. The critical magnetic fields were measured to be Hc1 = 77 Oe and Hc2 = 40 kOe. We deduce the London penetration depth 2900 Å and the coherence length 90 Å. Our estimate of the electron-phonon coupling reveals that Ba8Si42Al4 is a moderate phonon-mediated BCS superconductor. NASA PRSG IDEAS-ER Program(Granted No. NNX10AM80H).

  5. Co{sub 2}FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    SciTech Connect

    Rogge, J.; Schmalhorst, J.; Hütten, A.; Hetaba, W.

    2015-07-15

    We succeed to integrate BaO as a tunneling barrier into Co{sub 2}FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co{sub 2}FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  6. Pb nanowire formation on Al/lead zirconate titanate surfaces in high-pressure hydrogen

    SciTech Connect

    Alvine, Kyle J.; Shutthanandan, V.; Arey, Bruce W.; Wang, Chong M.; Bennett, Wendy D.; Pitman, Stan G.

    2012-07-12

    Thin films of Al on lead zirconate titanate (PZT) annealed in high-pressure hydrogen at 100C exhibit surface Pb nanowire growth. Wire diameter is approximately 80 nm and length can exceed 100 microns. Based on microstructural analysis using electron microscopy and ion scattering, a vapor-solid scheme with hydrogen as a carrier gas was proposed as a growth mechanism. We expect that these observations may lead to controlled Pb nanowires growth through pattering of the Al film.

  7. Effective atomic number and mass attenuation coefficient of PbO-BaO-B2O3 glass system

    NASA Astrophysics Data System (ADS)

    Issa, Shams A. M.

    2016-03-01

    Gamma-rays attenuation coefficient, half-value layer, mean free path, effective atomic number and electron density have been measured in glass system of xPbO-(50-x) BaO-50B2O3 (where 5≤x≤45 mol%) for gamma ray photon energies of 0.356, 0.662, 1.173 and 1.33 MeV. The emitted gamma ray was detected by 3×3 in. NaI(Tl) scintillation gamma ray spectrometers. The results were found in good agreement with the theoretical values which calculated from WinXcom.

  8. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure

    PubMed Central

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Do Kim, Keum; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization. PMID:26742878

  9. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    PubMed

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization. PMID:26742878

  10. Transformation of Ba-Al-Si precursors to celsian by high-temperature oxidation and annealing

    NASA Astrophysics Data System (ADS)

    Schmutzler, Hans J.; Sandhage, Kenneth H.

    1995-02-01

    Celsian (monoclinic BaO · A12O3 · 2SiO2) is being considered as a matrix material for ceramic composites used in high-temperature structural applications. The present article describes the synthesis of celsian by the oxidation and annealing of solid, malleable, metallic Ba-Al-Si precursors. The phase and microstructural evolution after various stages of oxidation at 300 °C to 1260 °C in pure oxygen at 1 atm pressure have been examined by X-ray diffraction (XRD) and electron microprobe analyses (EPMA). Barium peroxide, BaO2, formed rapidly during oxidation at 300 °C, with aluminum and silicon remaining largely as unoxidized particles in a BaO2 matrix. Between 300 °C and 500 °C, barium orthosilicate, Ba2Si04, formed by a solid-state reaction between barium peroxide and unoxidized silicon. Further exposure to temperatures between 500 °C and 1200 °C resulted in the oxidation of aluminum and of residual silicon. The oxidized silicon reacted with the barium orthosilicate matrix to yield higher silica-containing barium silicates that, in turn, reacted with alumina or mullite to form metastable hexacelsian (hexagonal BaO-A12O3 · 2SiO2). Celsian was then obtained by further exposure to peak temperatures ≤1260°C.

  11. Corrosion behavior of Al-surface-treated steels in liquid Pb?Bi in a pot

    NASA Astrophysics Data System (ADS)

    Kurata, Y.; Futakawa, M.; Saito, S.

    2004-12-01

    Corrosion tests were performed in oxygen-saturated liquid Pb-Bi at 450 °C and 550 °C in a pot for 3000 h for Al-surface-treated steels containing various levels of Cr contents. The Al surface treatments were achieved using a gas diffusion method and a melt dipping method. Al2O3, FeAl2 and AlCr2 produced by the gas diffusion method exhibited corrosion resistance to liquid Pb-Bi, while the surface layer produced by the melt dipping method suffered a severe corrosion attack. Fe4Al13 and Fe2Al5 produced by the melt dipping method disappeared during the corrosion test at 550 °C and only FeAl remained.

  12. Study on borate glass system containing with Bi 2O 3 and BaO for gamma-rays shielding materials: Comparison with PbO

    NASA Astrophysics Data System (ADS)

    Kaewkhao, J.; Pokaipisit, A.; Limsuwan, P.

    2010-04-01

    In this work, the mass attenuation coefficients and shielding parameters of borate glass matrices containing with Bi 2O 3 and BaO have been investigated at 662 keV, and compare with PbO in same glass structure. The theoretical values were calculated by WinXCom software and compare with experiential data. The results found that the mass attenuation coefficients were increased with increasing of Bi 2O 3, BaO and PbO concentration, due to increase photoelectric absorption of all glass samples. However, Compton scattering gives dominant contribution to the total mass attenuation coefficients for studied glass samples. Moreover the half value layers (HVL) of glass samples were also better than ordinary concretes and commercial window glass. These results reflecting that the Bi-based glass can use replace Pb in radiation shielding glass. In the case of Ba, may be can use at appropriate energy such as X-rays or lower.

  13. Relaxor behavior of (Ba,Bi)(Ti,Al)O3 ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Cui, Lei; Hou, Yu-Dong; Wang, Sai; Wang, Chao; Zhu, Man-Kang

    2010-03-01

    Perovskite type (Ba0.9Bi0.1)(Ti0.9Al0.1)O3 (BBTA) ceramics have been prepared through solid state reaction route. The room temperature x-ray diffraction study suggests that BBTA ceramics have single phase tetragonal symmetry with space group P4mm. In contrast to the sharp dielectric transition of pure BaTiO3, a broad dielectric anomaly coupled with the shift in dielectric maxima toward a higher temperature with increasing frequency has been observed in BBTA. The quantitative characterization based on empirical parameters (ΔTm, γ, ΔTrelax, and ΔTdiffuse(1 kHz)) confirms its relaxor nature. The dielectric relaxation which follows the Vogel-Fulcher relationship with Eα=0.011 eV, Tf=356 K, and f0=1.38×1010 Hz, further supports spin-glass-like characteristics. In this system, the relaxor behavior can be attributed to the dynamic response of the polar clusters induced by the combined substitutions of Bi3+ and Al3+ on the Ba2+ and Ti4+ site. Moreover, the curie temperature of BBTA shows the decreasing trend compared to that of pure BaTiO3, which doesn't follow the normal Vegard's law, confirming that no BiAlO3 sublattice formed in BBTA. All these features indicate that BBTA is a promising candidate for lead-free relaxors.

  14. Pb6Ba2(BO3)5X (X = Cl, Br): new borate halides with strong predicted optical anisotropies derived from Pb(2+) and (BO3)(3.).

    PubMed

    Liu, Lu; Zhang, Bingbing; Zhang, Fangfang; Pan, Shilie; Zhang, Fangyuan; Zhang, Xingwen; Dong, Xiaoyu; Yang, Zhihua

    2015-04-21

    Two new borate halides, Pb6Ba2(BO3)5X (X = Cl, Br), have been synthesized by solid-state reactions and their structures determined by single-crystal X-ray diffraction. They are isostructural and feature 3D frameworks composed of alternate stacking of [PbBO] and [PbBOX] layers which are connected by 10-coordinated Ba atoms along the c direction. First-principles calculations show that both compounds have a large birefringence of 0.1582 and 0.1810 at 532 nm, respectively. The large birefringence originates from the strong optical anisotropies of the Pb(2+) cations and (BO3)(3-) groups based on the real-space atom-cutting analysis. The IR and UV-Vis-NIR diffuse reflectance spectroscopy, as well as thermal stability analyses of both compounds, were performed. PMID:25785911

  15. Light-Emitting Characteristics of Organic Light-Emitting Diodes with Ba/Al Cathode and Effect of Ba Thickness by Measuring their Built-in Potential

    NASA Astrophysics Data System (ADS)

    Lim, Jong Tae; Yeom, Geun Young

    2009-12-01

    The electronic nature of metal-organic semiconductor contacts is a fundamental issue in the field of organic semiconductor device physics, because these contacts control the charge injection. The built-in potential in organic light-emitting diodes (OLEDs) with a Ba/Al cathode was investigated by using the modulated photocurrent technique. To measure the built-in potential, a device with a glass/tin-doped indium oxide (ITO)/tris(8-quinolinolato)aluminum (III) (Alq3, 150 nm)/Ba (x nm, x=3, 2, 1, and 0)/Al (150 nm) structure was fabricated and encapsulated in a nitrogen atmosphere. The device with Ba/Al cathode showed a higher built-in potential, compared with the Al-only device, which reduced the barrier height for electron injection from the Ba/Al cathode to Alq3. For the device with a Ba thickness of 3 nm, the barrier height for electron injection showed a low value of 0.1 eV. On the basis of the built-in potential data, the device with the ITO/4,4',4''-tris(2-naphthylphenyl-1-phenylamino)triphenylamine (2-TNATA, 30 nm)/4,4'-bis(N-(1-napthyl)-N-phenyl-amino)-biphenyl (NPB, 18 nm)/Alq3 (62 nm)/Ba (3 nm)/Al (100 nm) structure showed the best characteristics with the highest luminance of 54,000 cd/m2 and the highest efficiency of 2.7 lm/W, as compared to the other devices with Ba thicknesses of less than 3 nm.

  16. Crystallization kinetics of BaO-Al2O3-SiO2 glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.

    1988-01-01

    Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

  17. Crystallization kinetics of BaO-Al2O3-SiO2 glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.

    1989-01-01

    Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

  18. Phase composition and structure of aluminum Al-Cu-Si-Sn-Pb alloys

    NASA Astrophysics Data System (ADS)

    Belov, N. A.; Stolyarova, O. O.; Murav'eva, T. I.; Zagorskii, D. L.

    2016-06-01

    The structure and phase composition of cast and heat treated Al-Cu-Si-Sn-Pb alloys containing 6 wt % Sn, 2 wt % Pb, 0-4 wt % Cu, 0-10 wt % Si have been studied using calculations and experimental methods. Polythermal and isothermal sections are reported, which indicate the existence of two liquid phases. It was found that the low-melting phase is inhomogeneous and consists of individual leadand tin-based particles.

  19. Enhanced piezoelectric and ferroelectric properties in the BaZrO3 substituted BiFeO3-PbTiO3

    NASA Astrophysics Data System (ADS)

    Fan, Longlong; Chen, Jun; Li, Sha; Kang, Huajun; Liu, Laijun; Fang, Liang; Xing, Xianran

    2013-01-01

    BiFeO3-PbTiO3 (BF-PT) compounds possess very high Curie temperature and tetragonality compared to other PbTiO3-based piezoceramics. The BaZrO3 (BZ), with weakly ferroelectric active cations, was introduced into the BiFeO3-PbTiO3 to reduce the tetragonality (c/a) and improve the piezoelectric property. For the (0.8-x)BiFeO3-0.2BaZrO3-xPbTiO3, the BaZrO3 substitution can effectively decrease the tetragonality (c/a) from 1.18 to 1.02 for those compositions near the morphotropic phase boundary. The piezoelectric property of BiFeO3-PbTiO3 can be much enhanced with an optimal piezoelectric constant ˜270 pC/N with a reduced TC of 270 °C. Both the temperature dependent dielectric properties and polarization loops verified the existence of antiferroelectric relaxor, which was not observed in previous reported BiFeO3-PbTiO3 based materials.

  20. Measurement of the mass attenuation coefficient from 81 keV to 1333 keV for elemental materials Al, Cu and Pb

    NASA Astrophysics Data System (ADS)

    Gjorgieva, Slavica; Barandovski, Lambe

    2016-03-01

    The mass attenuation coefficients (μ/ρ) for 3 high purity elemental materials Al, Cu and Pb were measured in the γ-ray energy range from 81 keV up to 1333 keV using 22Na, 60Co 133Ba and 133Cs as sources of gamma radiation. Well shielded detector (NaI (Tl) semiconductor detector) was used to measure the intensity of the transmitted beam. The measurements were made under condition of good geometry, assuring that any photon absorbed or deflected appreciably does not reach the detector. The measured values are compared with the theoretical ones obtained by Seltzer (1993).

  1. On the microstructure and symmetry of apparently hexagonal BaAl 2O 4

    NASA Astrophysics Data System (ADS)

    Larsson, A.-K.; Withers, R. L.; Perez-Mato, J. M.; Fitz Gerald, J. D.; Saines, P. J.; Kennedy, B. J.; Liu, Y.

    2008-08-01

    The P6 3 ( a=2 ap, b=2 bp, c= cp) crystal structure reported for BaAl 2O 4 at room temperature has been carefully re-investigated by a combined transmission electron microscopy and neutron powder diffraction study. It is shown that the poor fit of this P6 3 ( a=2 ap, b=2 bp, c= cp) structure model for BaAl 2O 4 to neutron powder diffraction data is primarily due to the failure to take into account coherent scattering between different domains related by enantiomorphic twinning of the P6 322 parent sub-structure. Fast Fourier transformation of [0 0 1] lattice images from small localized real space regions (˜10 nm in diameter) are used to show that the P6 3 ( a=2 ap, b=2 bp, c= cp) crystal structure reported for BaAl 2O 4 is not correct on the local scale. The correct local symmetry of the very small nano-domains is most likely orthorhombic or monoclinic.

  2. Energy transfer between Eu-Mn and photoluminescence properties of Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ solid solution

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Wang, Yuhua; Liu, Bitao; Li, Feng

    2010-08-01

    In order to evaluate the energy transfer between Eu-Mn in Ba0.75Al11O17.25-BaMgAl10O17 solid solution, Ba0.75Al11O17.25-BaMgAl10O17:Eu2+,Mn2+ phosphors were prepared by flux method. The crystal structure and the morphology of the solid solution were demonstrated by x-ray dirrfactometer and scanning electron microscopy. The photoluminescence mechanisms were explained by the energy transfer of Eu2+ to Mn2+ and the Dexter theory. A redshift of green emission peak and a decrease in decay time with the increase in Mn2+ concentration were observed. These phenomena are attributed to the formation of Mn2+ paired centers after analysis by a method of Pade approximations.

  3. Stripe-like nanoscale structural phase separation in superconducting BaPb1−xBixO3

    PubMed Central

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H.C.; Beasley, M.R.; Geballe, T.H.; Kramer, M.J.; Fisher, I.R.

    2015-01-01

    The phase diagram of BaPb1−xBixO3 exhibits a superconducting dome in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high-resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare with the Ginzburg–Landau coherence length. We find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome. PMID:26373890

  4. Annealing effects on the structural and electrical properties of pulsed laser deposited BaPbO3 thin films

    NASA Astrophysics Data System (ADS)

    Satish, B.; Jayaraj, M. K.

    2014-01-01

    Conductive pervoskite BaPbO3 (BPO) films as potential electrodes for ferroelectric / tuneable applications were prepared by pulsed laser deposition technique at 600°C and at 0.1 mbar oxygen partial pressure on fused silica substrates. The structural and electrical properties of the films showed a dependence on annealing temperatures and the high oxygen ambient. XRD and standard four probe method with Hall setup were employed to investigate the dependence of growth conditions on crystal structure, resistivity and the carrier concentration on annealing the BPO thin films. The surface topography was analysed by AFM. The unannealed as deposited films showed the least resistivity of 1.6 × 10-2 ohm cm and a bandgap of 4.1eV.

  5. Piezoelectric Enhancement of (PbTiO3)m/(BaTiO3)n Ferroelectric Superlattices through Domain Engineering

    SciTech Connect

    Hong, Liang; Wu, Pingping; Li, Yulan; Gopalan, Venkatraman; Eom, C.B.; Schlom, Darrell G.; Chen, Long-Qing

    2014-11-20

    The phase diagram of (PbTiO3)m/(BaTiO3)n ferroelectric superlattices was computed using the phase-field approach as a function of layer volume fraction and biaxial strain to tune ferroelectric properties through domain engineering. Two interesting domain structures are found: one with mixed Bloch-Néel-Ising domain wall structures and the other with stabilized monoclinic phases. The polarization of the monoclinic phase is able to rotate from out-of-plane to in-plane or vice versa under an electric field, and thus facilitates the domain reversal of rhombohedral domains. This contributes significantly to both reduced coercive fields and enhanced piezoelectric responses.

  6. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3

    DOE PAGESBeta

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3 exhibits a superconducting “dome” in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare to the Ginzburg-Landau coherence length. Thus, we find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying amore » connection between the structural phase separation and the shape of the superconducting dome.« less

  7. The electrical, thermal conductivity, microstructure and mechanical properties of Al-Sn-Pb ternary alloys

    NASA Astrophysics Data System (ADS)

    Alper Billur, C.; Gerçekcioglu, E.; Bozoklu, M.; Saatçi, B.; Ari, M.; Nair, F.

    2015-08-01

    The structural, thermal, electrical and mechanical properties and micro-hardness of four different samples of Al-Sn-Pb ternary alloys (Al-[x] wt. % Sn-10 wt. % Pb) (x = 40, 30, 20 and 10) with constant lead concentrations were investigated for four different samples. Electrical resistivity and conductivity were measured by using (four-point probe measurement techniques) 4PPT techniques. The variations of thermal conductivity were determined by Wiedemann-Franz law (W-F) and Smith-Palmer (S-P) equation using the data obtained from electrical properties. The mechanical properties of the same alloys were obtained by the tensile test and the Vickers micro-hardness test.

  8. Properties of a new type Al/Pb-0.3%Ag alloy composite anode for zinc electrowinning

    NASA Astrophysics Data System (ADS)

    Yang, Hai-tao; Liu, Huan-rong; Zhang, Yong-chun; Chen, Bu-ming; Guo, Zhong-cheng; Xu, Rui-dong

    2013-10-01

    An Al/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corrosion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) displays a more compact interfacial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of Al/Pb-0.3%Ag alloy (hard anodizing) and Al/Pb-0.3%Ag alloy (plating tin) at 500 A·m-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, Al/Pb-0.3%Ag alloy (hard anodizing), and Al/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 g·m-2·h-1, respectively, in accelerated corrosion test for 8 h at 2000 A·m-2. The anodic oxidation layer of Al/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and Al/Pb-0.3%Ag alloy (plating tin) after the test.

  9. Enhanced high temperature performance of MgAl2O4-supported Pt-BaO lean NOx trap catalysts

    SciTech Connect

    Kwak, Ja Hun; Kim, Do Heui; Szanyi, Janos; Cho, Sung June; Peden, Charles HF

    2012-03-05

    The structural and chemical characteristics of Pt/BaO lean-NO{sub x} trap (LNT) catalysts supported on {gamma}-Al{sub 2}O{sub 3} and MgAl{sub 2}O{sub 4} are compared in this study. The Pt-BaO/MgAl{sub 2}O{sub 4} sample shows relatively low NO{sub x} uptake at temperatures below 300 C, and the temperature of maximum NO{sub x} uptake (T{sub max}) is shifted to 350 C in comparison to that of Pt-BaO/Al{sub 2}O{sub 3} (T{sub max} {approx}250 C). More importantly, the NO{sub x} uptake over the MgAl{sub 2}O{sub 4}-supported catalyst at 350 C is twice that of the alumina-based one. The shift toward the higher temperature NO{sub x} uptake is explained by the larger interfacial area between Pt and BaO, due to smaller Pt clusters as evidenced by TEM and Pt L3 EXAFS. In situ TR-XRD results demonstrate that the formation of a BaAl{sub 2}O{sub 4} phase in the BaO/MgAl{sub 2}O{sub 4} LNT catalyst occurs at a temperature about 100 C higher than on BaO/Al{sub 2}O{sub 3}, which may also represent a beneficial attribute of the BaO/MgAl{sub 2}O{sub 4} LNT with respect to catalyst stability.

  10. The effect of Al-substitution on superconducting type-I clathrate Ba8Si46

    NASA Astrophysics Data System (ADS)

    Liu, Lihua; Bi, Shanli; Chen, Ning; Li, Feng; Liu, Yang; Cao, Guohui; Li, Yang

    2014-11-01

    A series of samples with the chemical formula Ba8Si46-xAlx (x = 2, 3, 5, 6, 7 and 8) were prepared by arc melting, ball milling and washing with diluted HCl. The lattice parameter of Ba8Si46-xAlx increases linearly with the increase of nominal Al content x. The composition analysis by energy-dispersive X-ray spectroscopy (EDS) shown that the actual Al contents in clathrates are lager than the nominal compositions because the dilute Al-contained impurity phases were washed out. The experimental results show that the minimum incorporation of Al into clathrate structure is expected to be about 3 at ambient pressure, which is in agreement with a first-principle simulation. The Al substitution for Si results in the decrease of superconducting transition temperature TC, which can be explained on the BCS theoretical frame. The electron density of state at Fermi level N(EF) decreases with the increment of x except for an abnormal increase for the sample x = 6. Such sample has a higher spatial symmetry of the structure in which all the six Si atoms at 6c sites were substituted by Al atoms. Its higher N(EF) causes to a higher TC. In addition, we calculated the phonon-dispersion relations and vibrational density of states for Al-doped silicon clathrates. The high frequency acoustic branch has a red shift from 430 cm-1 to 420 cm-1 with the doping of Al. The decreased frequency of bond-stretching vibration modes is another reason for the suppression of TC induced by Al substitution.

  11. Ordered BaAl4- Type Variants in the BaAuxSn4-x System: A Unified View on Their Phase Stabilities versus Valence Electron Counts

    SciTech Connect

    Lin, Qisheng; Miller, Gordon J.; Corbett, John D.

    2014-05-28

    Three ordered structures of the tetragonal BaAl4 type were identified in the Ba–Au–Sn system, from which a unified view of the interplay between the valence electron counts (VECs) and phase stabilities of these three types of derivatives can be developed. The BaNiSn3 (I4mm), ThCr2Si2 (I4/mmm), and CaBe2Ge2 (P4/nmm) type BaAuxSn4–x phases occurred respectively at x = 0.78(1)–1, 1.38(1)–1.47(1), and 1.52(1)–2.17(1), consistent with theoretical atomic “coloring” analyses that reveal an optimal VEC of 14 for the ThCr2Si2 type but larger and smaller values respectively for the BaNiSn3- and CaBe2Ge2-type structures.

  12. EFFECTS OF AQUEOUS AL, CD, CU, FE(II), NI, AND ZN ON PB IMMOBILIZATION BY HYDROXYAPATITE

    EPA Science Inventory

    The effects of aqueous Al, Cd, Cu, Fe(II), Ni, or Zn on Pb immobilization by hydroxyapatite (Ca10(PO4),(OH)2) were studied. ead was removed mainly via hydroxyapatite dissolution and hydroxypyromorphite (Pb10(PO4)6(OH)2) precipitation in the presence of these metals with a Pb remo...

  13. Al/Pb lightweight grids prepared by molten salt electroless plating for application in lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Hong, Bo; Jiang, Liangxing; Hao, Ketao; Liu, Fangyang; Yu, Xiaoying; Xue, Haitao; Li, Jie; Liu, Yexiang

    2014-06-01

    In this paper, a lightweight Pb plated Al (Al/Pb) grid was prepared by molten salt electroless plating. The SEM and bonding strength test show that the lead coating is deposited with a smooth surface and firm combination. CV test shows that the electrochemical properties of Al/Pb electrodes are stable. 2.0 V single-cell flooded lead-acid batteries with Al/Pb grids as negative collectors are assembled and the performances including 20 h capacity, rate capacity, cycle life, internal resistance are investigated. The results show that the cycle life of Al/Pb-grid cells is about 475 cycles and can meet the requirement of lead-acid batteries. Al/Pb grids are conducive to the refinement of PbSO4 grain, and thereby reduce the internal resistance of battery and advance the utilization of active mass. Moreover, weight of Al/Pb grid is only 55.4% of the conventional-grid. In this way, mass specific capacity of Al/Pb-grid negatives is 17.8% higher and the utilization of active mass is 6.5% higher than conventional-grid negatives.

  14. Electron density distribution in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides studied by double nuclear magnetic resonance methods

    SciTech Connect

    Piskunov, Yu. V. Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-11-15

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of {sup 17}O are measured systematically, and the contributions from {sup 17}O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of {sup 17}O-{sup 207}Pb and {sup 17}O-{sup 121}Sb are measured in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin {sup 17}O-{sup 207}Pb interaction are determined as functions of the local Knight shift {sub 207}Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of {sup 17}O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides.

  15. Electron density distribution in BaPb1 - x Sb x O3 superconducting oxides studied by double nuclear magnetic resonance methods

    NASA Astrophysics Data System (ADS)

    Piskunov, Yu. V.; Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-11-01

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb1 - x Sb x O3 superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of 17O are measured systematically, and the contributions from 17O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of 17O-207Pb and 17O-121Sb are measured in the metal phase of BaPb1 - x Sb x O3 oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin 17O-207Pb interaction are determined as functions of the local Knight shift 207 Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of 17O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb1 - x Sb x O3 oxides.

  16. U-Pb and Al-Mg systematics of the ungrouped achondrite Northwest Africa 7325

    NASA Astrophysics Data System (ADS)

    Koefoed, Piers; Amelin, Yuri; Yin, Qing-Zhu; Wimpenny, Josh; Sanborn, Matthew E.; Iizuka, Tsuyoshi; Irving, Anthony J.

    2016-06-01

    Northwest Africa (NWA) 7325 is a unique ungrouped gabbroic achondrite which has characteristics consistent with a possible link to the planet Mercury. In order to understand the origin of this meteorite and the nature of its parent body, we have determined its crystallisation age using the long-lived U-Pb and short-lived Al-Mg chronometers. An internal Pb-Pb isochron defined by six acid leached pyroxene fractions yields an age of 4563.4 ± 2.6 Ma, assuming that the 238U/235U ratio for NWA 7325 is identical to the bulk Earth and Solar System value of 137.794. The Al-Mg isotope analyses of seven fractions (four plagioclase, one pyroxene, one olivine and one whole rock) define a regression line corresponding to 26Al/27Al0 = (3.03 ± 0.14) × 10-7 and an initial δ26Mg∗ of 0.093 ± 0.004‰. When anchored to the D'Orbigny angrite, this initial 26Al/27Al yields an age of 4563.09 ± 0.26 Ma. The Pb-Pb age of 4563.4 ± 2.6 Ma and Al-Mg age of 4563.09 ± 0.26 Ma are in complete agreement, but the low U concentrations of NWA 7325 resulted in a relatively low precision Pb-Pb age. The observed excess in initial δ26Mg∗ can be explained by 27Al/24Mg fractionation and subsequent Mg isotopic evolution after planetary differentiation. Furthermore, the parental magma of NWA 7325 most likely formed within 1.72 Ma after calcium-aluminium rich inclusion (CAI) formation. NWA 7325 formed near simultaneously with quenched angrites and a number of ungrouped achondrites at ∼4563 Ma, suggesting that a multitude of planetary bodies had formed and differentiated by ∼4-5 Myr after CAI formation. This ancient age may be interpreted as an argument against NWA 7325 originating from Mercury, however it does not completely rule it out.

  17. Morphological Evolution of Ba(NO3)2 Supported on -Al2O3(0001): An In-Situ TEM Study

    SciTech Connect

    Wang, Chong M; Kwak, Ja Hun; Kim, Do Heui; Szanyi, Janos; Sharma, R; Thevuthasan, Suntharampillai; Peden, Charles HF

    2006-06-22

    One of the key questions for the BaO-based NOx catalyst system is the morphological evolution of Ba(NO3)2 to BaO upon heating for releasing of NOx or vice versa from BaO to Ba(NO3)2 upon uptaking of NOx. However, associated with the small crystallite size of high-surface area Al2O3, it can be difficult to extract structural and morphological features of Ba(NO3)2 supported on -Al2O3 by any direct imaging method including transmission electron microscopy. In this work, by choosing a model system of Ba(NO3)2 particles supported on single crystal -Al2O3, we have investigated the structural and morphological features of Ba(NO3)2 as well as the formation of BaO from Ba(NO3)2 during the release of NOx using ex-situ and in-situ TEM imaging, electron diffraction, energy dispersive spectroscopy (EDS), and Wulff shape construction. We find that Ba(NO3)2 supported on -Al2O3 possesses a platelet morphology, with the interface and facets being invariably the 8 {111} planes. Formation of the platelet structure leads to an enlarged interface area between Ba(NO3)2 and -Al2O3, indicating that the interfacial energy is lower than the Ba(NO3)2 surface free energy. In fact, Wulff shape constructions indicate that the interfacial energy is ~1/4 of the {111} surface free energy of Ba(NO3)2. The orientation relationship between Ba(NO3)2 and the -Al2O3 is: -Al2O3[0001]//Ba(NO3)2[111] and -Al2O3(1-2 10)//Ba(NO3)2(110).

  18. Effect of local elastic strain on the structure of Pb-based relaxors: A comparative study of pure and Ba- and Bi-doped PbSc0.5Nb0.5O3

    NASA Astrophysics Data System (ADS)

    Maier, B.; Mihailova, B.; Paulmann, C.; Ihringer, J.; Gospodinov, M.; Stosch, R.; Güttler, B.; Bismayer, U.

    2009-06-01

    The temperature evolution of the nanoscale structure of PbSc0.5Nb0.5O3 (PSN) and (Pb,A″)Sc0.5Nb0.5O3 , (A″=Ba,Bi) is analyzed by applying synchrotron single-crystal and high-resolution powder x-ray diffraction as well as polarized Raman spectroscopy. The study compares the effect of incorporation of two-valent cations with isotropic electron structure (Ba2+) and three-valent cations with stereochemically active lone pairs (Bi3+) on the structure of Pb-based perovskite-type relaxor ferroelectrics. The results reveal that the violation of the host system of cations with lone-pair electrons (Pb2+) , i.e., the reduction in ferroic species with coherent off-centered Pb atoms, is the major factor for the suppression of long-range ferroelectric ordering at low temperatures. The local charge imbalance associated with A site chemical disorder has negligible impact on the development of ferroelectric order if the second type of A -positioned cations also forms lone-pair electrons. The substitution of Bi3+ for Pb2+ even enhances the cubic-to-ferroelectric transformation processes in PSN and results in a structural state consisting of abundant ferroelectric domains, which are large enough to be identified by polarized Raman spectroscopy as crystalline, but with an average size close to the intrinsic detection limit of synchrotron single-crystal x-ray diffraction.

  19. Lead, Ba and Bi in Antarctic Law Dome ice corresponding to the 1815 AD Tambora eruption: an assessment of emission sources using Pb isotopes

    NASA Astrophysics Data System (ADS)

    Vallelonga, P.; Candelone, J.-P.; Van de Velde, K.; Curran, M. A. J.; Morgan, V. I.; Rosman, K. J. R.

    2003-06-01

    Lead, Ba and Bi concentrations and Pb isotopic compositions have been measured in Antarctic Law Dome (66.8°S, 112.4°E) ice dated from 1814 AD to 1819 AD by thermal ionisation mass spectrometry to investigate the possible deposition of heavy metals from the 1815 AD eruption of Tambora volcano (8.5°S, 117.4°E) in Indonesia. Although volcanic S emissions from Tambora (observed as SO 42-) are present in the Antarctic ice core record, there are grounds to question the origin of the Pb and Bi also deposited at Law Dome from late 1817, as the Pb isotope data suggest this Pb originated from Mount Erebus (77.5°S, 167.2°E) on Ross Island, Antarctica. It is shown that at least 97% of any Pb and Bi emitted from Tambora was removed from the atmosphere within the 1.6 year period required to transport aerosols from Indonesia to Antarctica. Consequently, increased Pb and Bi concentrations observed in Law Dome ice about 1818 AD are attributed to either increased heavy metal emissions from Mount Erebus, or increased fluxes of heavy metals to the Antarctic ice sheet resulting from climate and meteorological modifications following the Tambora eruption. Elevated Ba concentrations, observed from mid-1816 to mid-1818, indicate increased atmospheric loading of rock and soil dust also occurred at the time.

  20. Origin of a carbonate-hosted Fe-Mn-(Ba-As-Pb-Sb-W) deposit of Långban-type in central Sweden

    NASA Astrophysics Data System (ADS)

    Holtstam, D.; Mansfeld, J.

    2001-10-01

    The Sjögruvan deposit is one of the Långban-type Fe-Mn oxide deposits hosted by marble interbeds within Svecofennian metavolcanic rocks in the Bergslagen region, central Sweden. Mineralogical and geochemical studies have been carried out to clarify the premetamorphic origin of this type of deposit, which is set apart from most other Mn mineralizations by a significant enrichment in Ba, As, Sb, Pb, W and Be contained by various oxyminerals. The principal ore types at Sjögruvan are (1) hematite+quartz±magnetite, (2) hausmannite+calcite+tephroite and (3) braunite+celsian+phlogopite. The Mn ores are compositionally akin to modern Mn deposits formed by submarine hydrothermal processes (with a high Mn/Fe ratio and low contents of Co, Ni, Th, U and REE) and likely owe their existence to similar mechanisms of formation. Pb isotope data indicate that the metal source and timing of deposition is similar to the major stratabound base-metal and iron deposits in Bergslagen. All the key elements have been leached from the local felsic volcanic units and were deposited on the sea floor; the excellent Mn-Fe separation occurred in an Eh-pH gradient that essentially corresponded to the mixing zone of hydrothermal solutions and seawater. The braunite ore is chemically distinct from the hausmannite ore, with a high concentration of refractory elements (Al, Ti, Zr) and a positive Ce anomaly, which indicate a detrital/hydrogenetic contribution to its protolith. Carbon isotope (δ13C) values around 0‰ (relative PDB) suggest that carbonates in the deposit formed directly from seawater.

  1. Facile controlled synthesis of micro/nanostructure MCrO 4 (M = Ba, Pb) by using Gemini surfactant C 12-PEG-C 12 as a soft template

    NASA Astrophysics Data System (ADS)

    Chang, Wengui; Shen, Yuhua; Xie, Anjian; Liu, Xue

    2010-04-01

    Gemini surfactants, double sodium α-sulfonic polyethylene glycol laurate (abbreviated C 12-PEG-C 12), were prepared and applied as soft templates in the controlled synthesis of BaCrO 4 and PbCrO 4 micro/nanocrystals. The template effects were investigated by adjusting the length of the spacer, using PEG400 and PEG4000, of the Gemini surfactant. The results indicated that the size and morphology of BaCrO 4 and PbCrO 4 micro/nanocrystals varied with the change in spacer length of C 12-PEG-C 12, suggesting that the different lengths of the polyethylene glycol group spacers in the Gemini surfactants played a key role in determining the size and shape of the MCrO 4 micro/nanoparticles. The dynamic process of the formation of the novel morphology BaCrO 4 crystals showed that the morphology grew from a round-bar polyhedron, to regular polyhedron, to approximate octahedron to a uniform pistachio nut shape. The growth mechanism of the BaCrO 4 micro/nanocrystals was explained that C 12-PEG-C 12 had a greater interfacial adsorption and would effectively control the shape evolution during the crystal growth, while PbCrO 4 could be explained that the Gemini surfactants can undergo liquid-crystalline phase transitions with long channels providing a soft template effect and derived the nanorods formation. Room temperature fluorescence spectra were studied and these showed that the pistachio-shaped BaCrO 4 microcrystals and PbCrO 4 nanorods possess photoactive luminescence properties with emission peaks at 470 and 549 nm, respectively.

  2. Low-temperature specific heat in ferroelectric (Pb,Ba)5Ge3O11 crystals

    NASA Astrophysics Data System (ADS)

    Gmelin, E.; Burns, Gerald

    1988-07-01

    We report specific-heat measurements in ferroelectric (Pb1-xBax)5Ge3O11 single crystals for x=0 and 0.02, from 2-80 K. We consider the data in terms of a classical Debye model, and allow for the possibility of an extra low-temperature term CLT and an extra high-temperature Einstein term CE (to account for extra oscillators). The data are accounted for with just the Debye model; CLT and CE terms are not needed, and the implications of these results are discussed.

  3. Electrochemical properties and microstructure of Al/Pb-Sn anodes during copper electrowinning

    NASA Astrophysics Data System (ADS)

    Zhang, Y. C.; Qin, S. J.

    2016-07-01

    Al/Pb-Sn composite anodes used in copper electrowinning are prepared by electro-deposition onto the aluminum Substrates in lead methanesulfonate electrolyte. Using potentiodynamic investigations, the information about corrosion resistance and oxygen reaction (OER) potential of these anodes in the lead dioxide region have been measured. The results show that with an increase of Sn content the OER potential and corrosion rate decrease. The SEM observations show that with an increase of Sn content the lead grain size increases. The X-ray diffraction (XRD) analysis show that with an increase of Sn content the phase of β-PbO2 with lower corrosion rate and OER potential increases.

  4. Geochemical modeling of leaching of Ca, Mg, Al, and Pb from cementitious waste forms

    SciTech Connect

    Martens, E.; Jacques, D.; Van Gerven, T.; Wang, L.; Mallants, D.

    2010-08-15

    Results from extraction tests on cement-waste samples were simulated with a thermodynamic equilibrium model using a consistent database, to which lead data were added. Subsequent diffusion tests were modeled by means of a 3D diffusive transport model combined with the geochemical model derived from the extraction tests. Modeling results of the leached major element concentrations for both uncarbonated and (partially) carbonated samples agreed well with the extraction test using the set of pure minerals and solid solutions present in the database. The observed decrease in Ca leaching with increasing carbonation level was qualitatively predicted. Simulations also revealed that Pb leaching is not controlled by dissolution/precipitation only. The addition of the calcite-cerrusite solid solution and adsorption reactions on amorphous Fe- and Al-oxides improved the predictions and are considered to control the Pb leaching during the extractions tests. The dynamic diffusive leaching tests were appropriately modeled for Na, K, Ca and Pb.

  5. Preparation, photoluminescent properties and luminescent dynamics of BaAlF{sub 5}:Eu{sup 2+} nanophosphors

    SciTech Connect

    Zhang, Wei; Hua, Ruinian; Liu, Tianqing; Zhao, Jun; Na, Liyan; Chen, Baojiu

    2014-12-15

    Graphical abstract: Rice-shaped BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via one-pot hydrothermal process. The as-prepared BaAlF{sub 5}:Eu{sup 2+} are composed of many particles with an average diameter of 40 nm. When excited at 260 nm, the sharp line emission located at 361 nm of Eu{sup 2+} was observed. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The strong ultraviolet emission of Eu{sup 2+} ions in BaAlF{sub 5}:Eu{sup 2+} nanoparticles suggests that these nanoparticles may have potential applications for sensing, solid-state lasers and spectrometer calibration. - Highlights: • BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via a mild hydrothermal process. • The Van and Huang models were used to research the mechanism of concentration quenching. • The optimum doping concentration of Eu2+ was confirmed to be 5 mol%. - Abstract: Eu{sup 2+}-doped BaAlF{sub 5} nanophosphors were synthesized via a facile one-pot hydrothermal method. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. XRD results showed that the prepared samples are single-phase. The FE-SEM and TEM images indicated that the prepared BaAlF{sub 5}:Eu{sup 2+} nanophosphors are composed of many rice-shaped particles with an average diameter of 40 nm. When excited at 260 nm, BaAlF{sub 5}:Eu{sup 2+} nanophosphors exhibit the sharp line emissions of Eu{sup 2+} at room temperature. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The Van and Huang models were used to study the mechanism of concentration quenching and the electric dipole–dipole interaction between Eu{sup 2+} can be deduced to be a dominant for quenching fluorescence in BaAlF{sub 5}:Eu{sup 2+} nanophosphors. The strong ultraviolet emission of Eu{sup 2+} in BaAlF{sub 5}:Eu{sup 2+} nanophosphors suggests that

  6. Suppression of structural phase transition by Sr substitution in the improper ferroelectric BaAl2O4

    NASA Astrophysics Data System (ADS)

    Mori, Shigeo; Ishii, Yui; Tanaka, Eri; Tsukasaki, Hirofumi; Kawaguchi, Shogo

    2015-10-01

    To clarify lattice fluctuations and precursor phenomena accompanied by structural phase transition in stuffed tridymite compounds, changes in diffuse scattering as a function of temperature in Ba0.6Sr0.4Al2O4 have been carefully investigated by powder X-ray diffraction using synchrotron radiation, electron diffraction and transmission electron microscopy (TEM) experiments. In situ electron diffraction experiments revealed that Ba0.6Sr0.4Al2O4 exhibits lattice fluctuation manifested as a unique honeycomb-shaped diffuse scattering in the wide temperature range between 298 and 100 K. Unlike in the case of BaAl2O4, Ba0.6Sr0.4Al2O4 shows no structural phase transition to the ferroelectric structure with the hexagonal P63 space group in the temperature range. In contrast, it is revealed that the electron beam irradiation to the Ba0.6Sr0.4Al2O4 sample inside the transmission electron microscope induced structural change from the hexagonal P6322 structure to the modulated structure with double periodicity in the three equivalent <110> directions in the low-temperature region. This implies that the total energy difference between these two structures is small. The hexagonal P6322 structure transforms into the modulated one with short correlation length owing to some small external perturbations.

  7. Luminescent Characteristics of Ba(1--x)Al2Si2O8:xTb3+ Green Phosphors.

    PubMed

    Hakeem, D A; Kim, Y; Park, K

    2016-02-01

    Ba(1--x)Al2Si2O8:xTb3+ (0.03 < or = x < or = 0.12) green phosphors are prepared by solution combustion method. The photoluminescence properties of the Ba(1--x)Al2Si2O8:xTb3+ phosphors are studied as a function of Tb3+ concentration. The Ba(1--x)Al2Si2O8:xTb3+ phosphors crystallize in a hexagonal crystal structure. The excitation spectra consist of two broad bands with maxima at 238 nm and 265 nm and several weak peaks in the range of 310-500 nm. Strong emission peaks are observed at 484, 540, 589, and 612 nm due to the (5)D4 --> (7)F6, (5)D4 --> (7)F5, (5)D4 --> (7)F4, and (5)D4 --> (7)F3 tran- sitions of the Tb3+, respectively. The emission peak (540 nm) from the (5)D4 --> (7)F3 transition is dominant, indicating green light emission. Ba(1--x)Al2Si2O8:xTb3+ phosphor shows the strongest green emission intensity. The Ba(1--x)Al2Si2O8:xTb3+ can be considered a promising green phosphor for white LEDs applications. PMID:27433666

  8. Behavior of Zn2+, Cd2+, Ba2+ and Pb2+ cations in ferromanganese crusts from the Marcus Wake seamount (Pacific Ocean) in aqueous solutions of metal salts

    NASA Astrophysics Data System (ADS)

    Novikov, G. V.; Bogdanova, O. Yu.; Melnikov, M. E.; Lobus, N. V.; Drozdova, A. N.; Shulga, N. A.

    2016-01-01

    The behavior of heavy-metal cations in ore minerals of cobalt-rich ferromanganese crusts from the Marcus Wake seamount in aqueous solutions of metal salts was studied in experiments. The Zn2+ and Cd2+ cations showed high reactivity and Ba2+ and Pb2+ showed low reactivity. It was found that Zn2+ and Cd2+ cations within the ore mineral composition are mainly absorbed (up to 66%) whereas Pb2+ and Ba2+ are chemically bound (up to 70%). Ore minerals in the crusts are characterized by sorption properties and high ionexchange capacity by these cations (1.94-2.62 mg-equiv/g). The capacity values by heavy-metal cations for ore minerals of the crusts from different areas of the Marcus Wake seamount are close to each other.

  9. Mechanisms of wear in single- and two-phase materials: Final report. [Cu, Pb, Al/sub 2/O/sub 3/, Pb borosilicate glass, SiC (Pb-Cu), (Pb-Al/sub 2/O/sub 3/), (glass-Cu), (glass-Al/sub 2/O/sub 3/)

    SciTech Connect

    Macmillan, N.H.

    1987-11-01

    A comparative study has been made of the rolling-tumbling-sliding wear and solid particle erosion behavior of four single-phase materials (Cu, Pb, Al/sub 2/O/sub 3/, and a lead borosilicate glass and of series of ductile-ductile (Pb-Cu), ductile-brittle (Pb-Al/sub 2/O/sub 3/), brittle-ductile (glass-Cu), and brittle-brittle (glass-Al/sub 2/O/sub 3/) composites prepared from them. The same irregularly shaped 600 ..mu..m WC-8 wt.% Co abrasive particles were used throughout this work. Additional erosion measurements have been made on Danto Koruntz, Abresist, and sintered ..cap alpha..-SiC, using similar particles. Some subtle influences of erosive particle wear are documented for the first time, and the inadequacy of the currently available theoretical models to describe the influence of microstructure on erosion is exposed. 77 refs., 154 figs.

  10. Mechanism of particle growth of a BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphor by firing with AlF{sub 3}

    SciTech Connect

    Oshio, Shozo; Matsuoka, Tomizo; Tanaka, Shosaku; Kobayashi, Hiroshi

    1998-11-01

    The mechanism of particle growth of the blue emitting BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphor by firing with AlF{sub 3} has been clarified. It was found that the reaction between BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} and AlF{sub 3} during firing, on the basis of the following chemical equation, results in recreation of BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} with particle growth BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} + (4/3)AlF{sub 3} {l_reversible} BaMgF{sub 4}:Eu{sup 2+} + (17/3)Al{sub 2}O{sub 3}, the firing of Ba/MgAl{sub 10}O{sub 17}:Eu{sup 2+} with AlF{sub 3} first converts the phosphor into a mixture of the two compounds, BaMgF{sub 4}:Eu{sup 2+} and Al{sub 2}O{sub 3}, at around 1200 C. The BaMgF{sub 4}:Eu{sup 2+} melts at temperatures over 1000 C, then reacts with Al{sub 2}O{sub 3}, and participates in the recreation of both BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} and AlF{sub 3} through a chemical reaction between the two compounds at 1200 C in BaMgF{sub 4}:Eu{sup 2+} solutions. Recreated AlF{sub 3} appears to sublime immediately because it is a material which sublimates with heating. This paper proposes a mechanism for the growth of particle of recreated BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} by the melting of BaMgF{sub 4}:Eu{sup 2+}.

  11. Thick c-axis textured (Tl,Pb)(Ba,Sr)2Ca2Cu3O9/Ag0.37 superconducting tapes by an ink spray pyrolysis method using a Tl-free precursor

    NASA Astrophysics Data System (ADS)

    Schulz, Douglas L.; Parilla, Philip A.; Ginley, David S.; Voigt, James A.; Roth, E. Peter

    1994-11-01

    In this letter we demonstrate a synthetic route to thick (5-20 μm) highly c-axis textured, nearly phase-pure superconducting (Tl,Pb)(Ba,Sr)2Ca2Cu3O9/Ag0.37 tapes. First, a Tl-free ink consisting of Pb0.5Ba0.4Sr1.6Ca2.0Cu3.0O9/Ag0.37 precursor powder in an ethanolic ethyl cellulose binder is sprayed onto a heated LaAlO3 substrate. After an intermediate oxygen anneal to remove the carbonaceous binder, a static 2-zone thallination anneal is performed to promote superconducting phase formation. Films exhibit excellent c-axis texturing as evidenced by x-ray diffraction θ/2θ and rocking curve characterization with morphological evidence for partial melting by scanning electron microscopy. Electrical characterization of these films give Tc onset values of 106-115 K with Tc zero reached by 99-101 K and transport Jc(77 K) up to 2.9×104 A/cm2. A mixed strong/weak-linked magnetic field dependence is observed for these films at 77 K and 0.4 T.

  12. Low temperature synthesis of potassium doped barium lead perovskites K{sub x}Ba{sub 1{minus}x}PbO{sub 3{minus}y} from hydroxide melts

    SciTech Connect

    Bezzenberger, R.; Schoellhorn, R.

    1995-12-01

    Perovskite type barium oxoplumbates can be grown at low temperatures via chemical synthesis from alkali hydroxide melts. Strongly oxidizing conditions and low K/Ba ratio lead to the formation of the ternary phase BaPbO{sub 3} whereas less oxidizing conditions and high K/Ba ratio favor the formation of the quaternary solid solution K{sub x}Ba{sub 1{minus}x}PbO{sub 3{minus}y} with tetragonal symmetry. Mixed valence PbII/PbIV quaternary phases can similarly be prepared by anodic deposition from hydroxide melts in closed systems; partial substitution by rare earth ions is possible. Ternary and quaternary oxoplumbates can be reduced electrochemically in aqueous electrolytes at ambient temperature under formation of lead metal.

  13. Ba3Pt4Al4-Structure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units.

    PubMed

    Stegemann, Frank; Benndorf, Christopher; Bartsch, Timo; Touzani, Rachid St; Bartsch, Manfred; Zacharias, Helmut; Fokwa, Boniface P T; Eckert, Hellmut; Janka, Oliver

    2015-11-16

    Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations. PMID:26536164

  14. Influence of simultaneous doping of Sb and Pb on phase formation, superconducting and microstructural characteristics of HgBa 2Ca 2Cu 3O 8+ δ

    NASA Astrophysics Data System (ADS)

    Giri, Rajiv; Tiwari, R. S.; Srivastava, O. N.

    2007-01-01

    We report systematic studies of structural, microstructural and transport properties of (Hg 0.80Sb 0.2- xPb x)Ba 2Ca 2Cu 3O 8+ δ (where x = 0.0, 0.05, 0.1, 0.15, 0.2) compounds. Bulk polycrystalline samples have been prepared by two-step solid-state reaction route at ambient pressure. It has been observed that simultaneous substitution of Sb and Pb at Hg site in oxygen deficient HgO δ layer of HgBa 2Ca 2Cu 3O 8+ δ cuprate high- Tc superconductor leads to the formation of Hg-1223 as the dominant phase. Microstructural investigations of the as grown samples employing scanning electron microscopy reveal single crystal like large grains embodying spiral like features. Superconducting properties particularly transport current density ( Jct) have been found to be sensitive to these microstructural features. As for example (Hg 0.80Sb 0.05Pb 0.15)Ba 2Ca 2Cu 3O 8+ δ compound which exhibits single crystal like large grains (∼50 μm) and appears to result through spiral growth mechanism, shows highest Jct (∼1.85 × 10 3 A/cm 2) at 77 K. A possible mechanism for the generation of spiral like features and correlation between microstructural features and superconducting properties have been put forward.

  15. Studies on Structural and Dielectric Properties of ABi{sub 4}Ti{sub 4}O{sub 15} (A Ba, Sr and Pb) Ceramics

    SciTech Connect

    Reddy, T. Gopal; Kumar, B. Rajesh; Rao, T. Subba

    2010-12-01

    Bismuth Titanate based electroceramics of layered perovskite structures are technologically important materials for high temperature piezoelectric and ferroelectric applications, due to their high Curie temperature (675 deg. C), Stable piezoelectric response and excellent dielectric properties. The compounds ABi{sub 4}Ti{sub 4}O{sub 15} (A = Ba, Sr and Pb) belongs to Aurivillius family (n = 4) in which BaBi{sub 4}Ti{sub 4}O{sub 15} crystallizes in tetragonal I4/mmm space group, Sr Bi{sub 4}Ti{sub 4}O{sub 15} and PbBi{sub 4}Ti{sub 4}O{sub 15} crystallizes in orthorhombic space group A2{sub 1}am. In the present work ABi{sub 4}Ti{sub 4}O{sub 15} (A = Ba, Sr and Pb) ceramic samples are prepared through the solid state reaction by conventional mixed oxides by calcination at high temperature. Dielectric constant ({epsilon}'{sub r}) and Dielectric Loss (D) for all the compositions as a function of temperature measured from frequencies 100 Hz to 100 KHz using a HIOKI 3532-50 LCR meter. The dielectric constant increases gradually with an increase in temperature up to transition temperature (T{sub c,} K) and then decreases.

  16. Ultrafine BaPb/sub 1-x/Bi/sub x/O/sub 3/ powders prepared by the spray-ICP technique

    SciTech Connect

    Ono, T.; Kagawa, M.; Syono, Y.; Ikebe, M.; Muto, Y.

    1987-06-01

    Ultrafine powders of a ternary oxide system, Ba-Pb-Bi-O, were prepared by spraying aqueous mixed solutions of Ba(NO/sub 3/)/sub 2/, Pb(NO/sub 3/)/sub 2/, and Bi(NO/sub 3/)/sub 3/ into an argon inductively coupled plasma of ultrahigh temperature above 5000 K (the spray-ICP technique). Phases of the powders were largely dependent on the powder collectors enclosing the tail flame and its successive gas flow. In the water-cooled collector, mixtures of amorphous and crystalline materials were formed. In the collector where the gas flow was spontaneously maintained at about 550/sup 0/C by ICP itself, ultrafine BaPb/sub 1-x/Bi/sub x/O/sub 3/ (BPBO) 10-40 nm in particle diameter was obtained. The BPBO thus obtained had a few wt.% of water and carbonate. They were lost by heat treatment up to 550/sup 0/C, and a single-phase BPBO was formed. The as-prepared BPBO (x = 0.25) showed no superconducting transition down to 1.5 K, but the one having a particle diameter of approx. 1 ..mu..m formed by heating the as-prepared BPBO up to 1000/sup 0/C had a superconducting transition temperature at 11.3 K.

  17. Conductor-backed coplanar waveguide resonators of Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O on LaAlO3

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Bhasin, K. B.; Stan, M. A.; Kong, K. S.; Itoh, T.

    1992-01-01

    Conductor-backed coplanar waveguide (CBCPW) resonators operating at 10.8 GHz have been fabricated from Tl-Ba-Ca-O (TBCCO) and Y-Ba-Cu-O (YBCO) thin films on LaAlO3. The resonators consist of a coplanar waveguide (CPW) patterned on the superconducting film side of the LaAlO3 substrate with a gold ground plane coated on the opposite side. These resonators were tested in the temperature range from 14 to 106 K. At 77 K, the best of our TBCCO and YBCO resonators have an unloaded quality factor (Qo) 7 and 4 times, respectively, larger than that of a similar all-gold resonator. In this study, the Qo's of the TBCCO resonators were larger than those of their YBCO counterparts throughout the aforementioned temperature range.

  18. Elastic moduli of nanocrystalline binary Al alloys with Fe, Co, Ti, Mg and Pb alloying elements

    NASA Astrophysics Data System (ADS)

    Babicheva, Rita I.; Bachurin, Dmitry V.; Dmitriev, Sergey V.; Zhang, Ying; Kok, Shaw Wei; Bai, Lichun; Zhou, Kun

    2016-05-01

    The paper studies the elastic moduli of nanocrystalline (NC) Al and NC binary Al-X alloys (X is Fe, Co, Ti, Mg or Pb) by using molecular dynamics simulations. X atoms in the alloys are either segregated to grain boundaries (GBs) or distributed randomly as in disordered solid solution. At 0 K, the rigidity of the alloys increases with decrease in atomic radii of the alloying elements. An addition of Fe, Co or Ti to the NC Al leads to increase in the Young's E and shear μ moduli, while an alloying with Pb decreases them. The elastic moduli of the alloys depend on a distribution of the alloying elements. The alloys with the random distribution of Fe or Ti demonstrate larger E and μ than those for the corresponding alloys with GB segregations, while the rigidity of the Al-Co alloy is higher for the case of the GB segregations. The moduli E and μ for polycrystalline aggregates of Al and Al-X alloys with randomly distributed X atoms are estimated based on the elastic constants of corresponding single-crystals according to the Voigt-Reuss-Hill approximation, which neglects the contribution of GBs to the rigidity. The results show that GBs in NC materials noticeably reduce their rigidity. Furthermore, the temperature dependence of μ for the NC Al-X alloys is analyzed. Only the Al-Co alloy with GB segregations shows the decrease in μ to the lowest extent in the temperature range of 0-600 K in comparison with the NC pure Al.

  19. Solidification Pathways of Alloys in the Mg-Rich Corner of the Mg-Al-Ba Ternary System

    NASA Astrophysics Data System (ADS)

    Bryan, Zachary L.; Hooper, Ryan J.; Henderson, Hunter B.; Manuel, Michele V.

    2015-04-01

    An experimental investigation of the solidification reactions and microstructures of alloys in the Mg-rich corner of the Mg-Al-Ba ternary system has been conducted. Four distinct exothermic reactions involving the formation of α-Mg, Mg17Ba2, Mg17Al12, and a fourth phase designated as τ were observed and their onset temperatures were recorded as functions of composition. Using compositional and microstructural analysis, the Mg17Ba2 intermetallic was found to have significant solubility of Al, up to 20 at. pct. The solidification pathways of the investigated alloys involved both a Class I and Class II equilibrium reaction. A flow block diagram that outlines the observed solidification reactions is presented and discussed in reference to cast microstructures.

  20. Structural changes and microstructures in stuffed tridymite-type compounds Ba1-xSrxAl2O4

    NASA Astrophysics Data System (ADS)

    Tanaka, Eri; Ishii, Yui; Tsukasaki, Hirofumi; Taniguchi, Hiroki; Mori, Shigeo

    2014-09-01

    Crystal structures and microstructures in Ba1-xSrxAl2O4 solid solutions between the end members of BaAl2O4 and SrAl2O4 have been carefully investigated by powder X-ray diffraction, electron diffraction and transmission electron microscopy (TEM) imaging experiments. With the help of fast Fourier transform (FFT) calculation, high-resolution TEM images suggested that diffuse streaks along three equivalent <110> directions in the (001) plane, which appear in the P63 structure of Ba1-xSrxAl2O4 for x = 0.4, originate from the large structural fluctuation of the AlO4 tetrahedral network. On the other hand, the monoclinic P21 structure in Ba1-xSrxAl2O4 with x = 0.7 was found to consist of a modulated structure with \\boldsymbol{{q}} = 0,1/2,0. The present experimental results reveal that a structural phase boundary exists at approximately x = 0.6 between the P63 structure with a large structural fluctuation and a monoclinic P21 phase with the single-q modulated structure.

  1. [Synthesis and properties of nanorod-long afterglow BaAl2O4:Eu2+, Dy3+ phosphor].

    PubMed

    He, Chun-hui; Zheng, Shu-hui; Xiao, Yong; Liu, Ying-liang

    2010-01-01

    The present paper mainly reports a new method to synthesize long afterglow photoluminescent material BaAl2O4:Eu2+, Dy3+. Al(NO3)3.9H2O, Ba(NO3)2, urea, RE(NO3) 3(RE==Eu, Dy) were employed as raw materials, the admixture of H2O/n-butanol and H2O/n-butanol/SBS were used as medium, then BaAl2O4:Eu2+, Dy3+ phosphor was achieved by calcining the precursor, which was synthesized by hydrothermal method, at 130 degrees C under reduction atmosphere. The TEM and SEM were used to analyse the morphology and BaAl2O4:Eu2+, Dy3+ synthesized by annealing at 1300 degrees C are all nanorods. The excitation and emission spectra of the phosphor indicated that all of them are broad band, and the main emission peak is around 498 nm, which is due to 5d-->4f transition of Eu2+. The state-solid synthesis of the long afterglow phosphor BaAl2O4:Eu2+, Dy3+ generally requires a high calcination temperature, so the products are easily agglomerated, and in this paper the hydrothermal solvothermal synthesis was used, so the synthesized products calcined at 130 degrees degrees C still present well-dispersed rod structure, need not milling, and display well luminescence performance. The authors compared the two different conditions of experiment, and found that under the condition without surfactant the authors can still get well-dispersed rod structure of BaAl2O4:Eu2+, Dy3+. The method is hopeful to be used in synthesizing other alkali-earth aluminate and silicate and other luminescent materials. PMID:20302073

  2. Mechanism of X-ray excited optical luminescence (XEOL) in europium doped BaAl2O4 phosphor.

    PubMed

    Rezende, Marcos V Dos S; Montes, Paulo J R; Andrade, Adriano B; Macedo, Zelia S; Valerio, Mário E G

    2016-06-29

    This paper reports a luminescence mechanism in Eu-doped BaAl2O4 excited with monochromatic X-rays (also known as X-ray excited optical luminescence - XEOL) from synchrotron radiation. The material was prepared via a proteic sol-gel methodology. The X-ray absorption near edge structures (XANES) at the Ba LIII- and Eu LIII-edges exhibit typical absorption spectra. XEOL spectra recorded in energy ranges, either around the Ba LIII- or Eu LIII-edges, showed important differences concerning the intensity of the Eu(2+) or Eu(3+) emission bands. Nevertheless, the total area under the XEOL spectra increases as the energy of the X-ray photons increases in both ranges (Ba LIII- and Eu LIII-edges). PMID:27306425

  3. Nonlinear optical properties ofBaAlBO3F2 crystal.

    PubMed

    Zhou, Yong; Yue, Yinchao; Wang, Jianuo; Yang, Feng; Cheng, Xiankun; Cui, Dafu; Peng, Qinjun; Hu, Zhanggui; Xu, Zuyan

    2009-10-26

    We investigated the nonlinear optical properties of new BaAlBO(3)F(2)(BABF) crystal. The high quality BABF is nonhygroscopic and possesses a moderate birefringence suitable for UV light generation. On the basis of its refractive index dispersion curves, it is inferred that BABF has great potential applications nonlinear optical material, notably for UV light generation at 355 nm. In order to characterize its nonlinear optical properties, BABF samples were cut an oriented in phase matching conditions The optical conversion efficiency from 1064 nm to 532 nm was investigated for the first time: up to 49.0% were achieved. The external angular acceptance bandwidth of SHG and THG for 1064 nm pump light was measured. PMID:19997227

  4. The unusual chemical bonding and thermoelectric properties of a new type Zintl phase compounds Ba3Al2As4

    NASA Astrophysics Data System (ADS)

    Yang, Gui; Zhang, Guangbiao; Wang, Chao; Wang, Yuanxu

    2016-07-01

    Ba3Al2As4 exhibits an unusual anisotropic electrical conductivity, that is, the electrical conductivity along the chain is smaller than those along other two directions. The results is conflict with previous conclusion for Ca5M2Pn6. Earlier studies on Ca5M2Pn6 showed that a higher electrical conductivity could be obtained along the chain. The band decomposed charge density is used to explain such unusual behavior. Our calculations indicate the existence of a conductive pathway near the Fermi level is responsible for the electrons transport. Further, the Ba-As bonding of Ba3Al2As4 has some degree covalency which is novel for the Zintl compounds.

  5. Research and analysis on the thin films sputtered by the Ba-Al-S:Eu target fabricated by powder sintering

    NASA Astrophysics Data System (ADS)

    Zhang, Dongpu; Xu, Fang; Yu, Zhinong; Xue, Wei

    2014-11-01

    Europium-doped barium thioaluminate (BaAl2S4:Eu) is currently the most efficient blue phosphor for inorganic thin film electroluminescent (iEL) device. To produce the full-color EL device, several kinds of blue-emitting layer were attempted and tested. As a key point of blue-emitting layer fabrication, single target sputtering deposition is an effective method. In this work, new structural target is introduced and the fabricated process is expatiated. The PL spectra of as fabricated targets show that both of two, 3mol% and 5mol% europium-doped, have blue emitting property. According to the PL spectra excited by 290nm, 300nm and 320nm ultraviolet, emission peaks located in the region near 470nm. So the as-fabricated targets can be used in single target sputtering deposition on thin film of BaAl2S4:Eu. XRD pattern indicates that there are 4 different phases, barium tetraaluminum sulfide (BaAl4S7), barium sulfide (BaS), europium sulfide (EuS) and barium aluminum oxide (BaAl2O4), in target 1. Besides these four compounds, other two phases, aluminum sulfide (Al2S3) and barium thioaluminate (BaAl2S4), are detected in target 2. Considering the analysis results, especially the hydrolyzation of Al2S3, target 1 is more suitable for sputtering deposition of BaAl2S4:Eu thin film. XPS and X-ray Fluorescence patterns describe the precise molar ratio of each element. In target 1 the relative atom concentration of barium, aluminum, sulfur and oxygen can be calculated from the pattern and molar ratio is about 9:33:41:17. Molar ratio of barium and europium is about 1:0.03. In short, the barium thioaluminate doped by europium sputtering target 1 is better to be applied in the fabrication of blue-emitting layer in inorganic electro-luminescent devices.

  6. Photoluminescence Properties of CaAlBO4:M (M: Pb2+, Dy3+, and Sm3+)

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.; Pekgözlü, İ.

    2014-07-01

    Pb2+, Dy3+, and Sm3+ doped CaAlBO4 materials were synthesized by the conventional solid state reaction. The synthesized phosphors were characterized by X-Ray powder diffraction. The emission and excitation spectra of these phosphors were measured at room temperature. The emission band of CaAlBO4:Pb2+ appeared as a broad band at 339 nm upon excitation with 272 nm. The second phosphor, CaAlBO4: Dy3+, emits at 477, 570, and 670 nm upon 347 nm excitation. The third phosphor, CaAlBO4:Sm3+, emits at 563, 594, 643, and 705 nm upon 236 nm excitation.

  7. Laser soldering of sapphire substrates using a BaTiAl6O12 thin-film glass sealant

    NASA Astrophysics Data System (ADS)

    de Pablos-Martin, A.; Tismer, S.; Benndorf, G.; Mittag, M.; Lorenz, M.; Grundmann, M.; Höche, Th.

    2016-07-01

    Two sapphire substrates are tightly bonded through a BaTiAl6O12-glass thin film, by irradiation with a nanosecond laser. After the laser process, the composition of the glass sealant changes, due to incorporation of Al2O3 from the upper substrate. After annealing of the bonded samples (950 °C for 30 minutes) crystalline structures are observed by TEM which are attributed to crystalline BaTiAl6O12. These crystals together with Al2O3:Ti centers are the responsible of the observed strong blue luminescence of the laser irradiated region upon UV excitation. The structural and optical characterizations of the bonded samples clarify the laser soldering procedure as well as the origin of the luminescence. Bond quality and bond strength were evaluated by scanning acoustic microscopy (SAM) and tensile tests, which results in a tensile stress of nearly 13 MPa, which is an acceptable value for glass sealants.

  8. Combustion Synthesized Cr3+-doped-BaMgAl10O17 Phosphor: An Electron Paramagnetic Resonance and Optical Study

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Sivaramaiah, G.; Rao, J. L.; Srivastava, Anoop K.; Ravikumar, R. V. S. S. N.; Dhoble, S. J.; Singh, P. K.; Mohapatra, Manoj

    2016-01-01

    BaMgAl10O17 phosphors doped with Cr3+ ions were prepared by a combustion route at a furnace temperature of 773 K. The X-ray diffraction pattern revealed that the BaMgAl10O17 phosphor was in a hexagonal phase. Energy-dispersive X-ray mapping images demonstrated the presence of the dopant ion in the BaMgAl10O17 matrix. The bands observed in the optical absorption spectrum were characteristic of Cr3+ ions in octahedral geometry. Upon 555-nm excitation, an intense narrow red emission line centred at 690 nm due to the 2Eg → 4A2g transition of Cr3+ ions was observed. The electron paramagnetic resonance (EPR) spectrum of Cr3+ ions in BaMgAl10O17 phosphor showed multiple absorption bands having at least 6 g values. Based on the EPR data, various parameters such as the absolute number of spins, Gibbs potential, magnetic susceptibility and magnetic moments, Curie constant, etc., for the system were evaluated.

  9. [Influence of Eu2+ content on the spectral characteristics of BaMgAl10O17 : Eu2+ phosphors].

    PubMed

    Chen, Zhe; Xie, Hong; Yan, You-Wei

    2007-04-01

    Nanocrsytalline Ba(1-x)MgAl10O17 : xEu2+ (0.05 < or = x < or = 0.4) blue-emitting phosphor was successfully prepared by low-temperature combustion synthesis. The influence of different Eu content on the spectral characteristics of Ba(1-x) MgAl10O17 : xEu2+ was mainly investigated. The results of XRD and SEM analysis show that the sample is single phase and its average grain size is about 30 nm. The luminescence property of Ba(1-x)MgAl10O17 : xEu2+ phosphor is considerably influenced by Eu2+ concentration. In an appropriate Eu2+ doping concentration range, the intensity of the fluorescence of Ba(1-x)MgAl10O17 : xEu2+ was increased obviously with increasing the Eu2+ doping concentration, owing to adding the number of luminescent centers and enhancing the energy transfer between Eu2+ ions. The optimum emission intensity was reached at x = 0.2. However, as the Eu2+ doping concentration was higher than 0.2, the intensity of the fluorescence was reduced, due to the concentration quenching occurrence. PMID:17608168

  10. Microstructure basis for strong piezoelectricity in Pb-free Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Gao, Jinghui; Xue, Dezhen; Wang, Yu; Wang, Dong; Zhang, Lixue; Wu, Haijun; Guo, Shengwu; Bao, Huixin; Zhou, Chao; Liu, Wenfeng; Hou, Sen; Xiao, Ge; Ren, Xiaobing

    2011-08-01

    In this letter, we use transmission electron microscopy to study the microstructure feature of recently reported Pb-free piezoceramic Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 across its piezoelectricity-optimal morphotropic phase boundary (MPB) by varying composition and temperature, respectively. The domain structure evolutions during such processes show that in MPB regime, the domains become miniaturized down to nanometer size with a domain hierarchy, which coincides with the d33-maximum region. Further convergent beam electron diffraction measurement shows that rhombohedral and tetragonal crystal symmetries coexist among the miniaturized domains. Strong piezoelectricity reported in such a system is due to easy polarization rotation between the coexisting nano-scale tetragonal and rhombohedral domains.

  11. Phase transitions and phase diagram of Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 Pb-free system by anelastic measurement

    NASA Astrophysics Data System (ADS)

    Xue, Dezhen; Gao, Jinghui; Zhou, Yumei; Ding, Xiangdong; Sun, Jun; Lookman, Turab; Ren, Xiaobing

    2015-03-01

    The internal friction and storage modulus of Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) Pb-free ceramics have been measured by dynamic mechanical analysis. The anelastic properties show clear anomalies with regard to the transformations between cubic (C), tetragonal (T), orthorhombic (O), and rhombohedral (R) phases, which are all of ferroelastic in nature. The previous reported T-R transition region in the BZT-xBCT system can be divided into the T-O and O-R transitions, consistent with recent studies on the appearance of an intermediate O phase. Based on the internal friction and storage modulus results, a revisited version of BZT-xBCT phase diagram is proposed.

  12. Corrosion barriers processed by Al electroplating and their resistance against flowing Pb-15.7Li

    NASA Astrophysics Data System (ADS)

    Krauss, Wolfgang; Konys, Jürgen; Wulf, Sven-Erik

    2014-12-01

    In the HCLL blanket design, ferritic-martensitic steels are in direct contact with the flowing liquid breeder Pb-15.7Li and have to withstand severe corrosion attack. Beyond corrosion, T-permeation from the breeder into the RAFM-steels is also an important issue and has to be reduced significantly. Earlier work showed that Al-based coatings can act as barriers for both, however, applied processes e.g. HDA or VPS exhibited strong drawbacks in the past. Meanwhile new industrial relevant coating processes, using electroplating technology are under development and called ECA (electrochemical aluminization) and ECX (electrochemical deposition from ionic liquids) process. In this study electrochemically Al-coated and heat-treated Eurofer samples were tested in PICOLO loop for exposure times up to 12,000 h (ECA) and 2000 h (first results ECX) respectively to determine corrosion properties in flowing Pb-15.7Li (550 °C, 0.1 m/s). Cross section analysis afterward corrosion testing proved the ability of thin Al-based barriers made by electrochemical techniques to protect the bare Eurofer from corrosion attack even at exposure times of 12,000 h. Determined radial corrosion rates lay between 10 and 20 μm/a. First results for ECX coated samples (2000 h) revealed more homogeneous corrosion behavior of the barrier layer itself compared to ECA.

  13. Average and local structure of the Pb-free ferroelectric perovskites (Sr,Sn)TiO3 and (Ba,Ca,Sn)TiO3

    DOE PAGESBeta

    Laurita, Geneva; Page, Katharine; Suzuki, Shoichiro; Seshadri, Ram

    2015-12-16

    The characteristic structural off -centering of Pb2+ in oxides, associated with its 6s2 lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds Sr0.9Sn0.1TiO3 and Ba0.79Ca0.16Sn0.05TiO3 using neutron total scattering techniques with data acquired at di erent temperatures. In these compounds, previously reported as ferroelectrics, Sn2+ appears to display some of the characteristics of Pb2+. We compare the local and long-range structures of the Sn2+-substituted compositions to the unsubstituted parent compounds SrTiO3 and BaTiO3. Lastly, we find that even at these smallmore » substitution levels, the Sn2+ lone pairs drive the local ordering behavior, with the local structure of both compounds more similar to the structure of PbTiO3 rather than the parent compounds.« less

  14. A Fluctuating State in the Framework Compounds (Ba,Sr)Al2O4

    PubMed Central

    Ishii, Yui; Tsukasaki, Hirofumi; Tanaka, Eri; Mori, Shigeo

    2016-01-01

    The structural fluctuation in hexagonal Ba1−xSrxAl2O4 with a corner-sharing AlO4 tetrahedral network was characterized at various temperatures using transmission electron microscopy experiments. For x ≤ 0.05, soft modes of q ~ (1/2, 1/2, 0) and equivalent wave vectors condense at a transition temperature (TC) and form a superstructure with a cell volume of 2a × 2b × c. However, TC is largely suppressed by Sr-substitution, and disappears for x ≥ 0.1. Furthermore, the q ~ (1/2, 1/2, 0) soft mode deviates from the commensurate value as temperature decreases and survives in nanoscaled regions below ~200 K. These results strongly suggest the presence of a new quantum criticality induced by the soft mode. Two distinct soft modes were observed as honeycomb-type diffuse scatterings in the high-temperature region up to 800 K. This intrinsic structural instability is a unique characteristic of the framework compound and is responsible for this unusually fluctuating state. PMID:26758625

  15. A Fluctuating State in the Framework Compounds (Ba,Sr)Al2O4

    NASA Astrophysics Data System (ADS)

    Ishii, Yui; Tsukasaki, Hirofumi; Tanaka, Eri; Mori, Shigeo

    2016-01-01

    The structural fluctuation in hexagonal Ba1-xSrxAl2O4 with a corner-sharing AlO4 tetrahedral network was characterized at various temperatures using transmission electron microscopy experiments. For x ≤ 0.05, soft modes of q ~ (1/2, 1/2, 0) and equivalent wave vectors condense at a transition temperature (TC) and form a superstructure with a cell volume of 2a × 2b × c. However, TC is largely suppressed by Sr-substitution, and disappears for x ≥ 0.1. Furthermore, the q ~ (1/2, 1/2, 0) soft mode deviates from the commensurate value as temperature decreases and survives in nanoscaled regions below ~200 K. These results strongly suggest the presence of a new quantum criticality induced by the soft mode. Two distinct soft modes were observed as honeycomb-type diffuse scatterings in the high-temperature region up to 800 K. This intrinsic structural instability is a unique characteristic of the framework compound and is responsible for this unusually fluctuating state.

  16. Synthesis, Crystal and Electronic Structures of the Pnictides AE3TrPn3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

    DOE PAGESBeta

    Stoyko, Stanislav; Voss, Leonard; He, Hua; Bobev, Svilen

    2015-09-24

    New ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. Likewise, the compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e.,more » P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3-]3, or rather [AE2+]6[Tr2Pn6]12-, i.e., as Zintl phases.« less

  17. Multifunctional effect of Al2O3, SiO2 and CaO on the volatilization of PbO and PbCl2 during waste thermal treatment.

    PubMed

    Wang, Si-Jia; He, Pin-Jing; Shao, Li-Ming; Zhang, Hua

    2016-10-01

    Minerals including Al2O3, SiO2 and CaO are predominant matrixes in waste, and are thought to facilitate lead (Pb) emission control. This study distinguished the inhibition of each mineral on common stable Pb-containing compounds, including highly volatile PbCl2 and less volatile PbO. Al2O3 can lower the volatilization temperature of Pb by 29 °C due to the generation of a eutectic compound and play a minor but non-negligible role in reducing Pb volatilization. The most conspicuous inhibition effect was exerted by SiO2 and a mixture of Al2O3 and SiO2, which completely integrated PbO into the glass phase at 690 °C and prohibited its migration. In contrast, SiO2 had no significant inhibition on volatile PbCl2. CaO inhibited PbO volatilization in the absence of oxygen by controlling its diffusion, while it converted PbO to Ca2PbO4 in the presence of oxygen, thus controlling Pb diffusion and decreasing the Pb volatilization ratio and rate. The influence of CaO on PbCl2 was complex because CaO can convert PbCl2 to PbO with formation of CaCl2, and CaCl2 can also be a Cl-donor for PbO. The roles of mineral matrixes in Pb conversion were shown to be important for Pb emission control. PMID:27434254

  18. Disorder Driven Metal-Insulator Transition in BaPb1-xBixO3 and Inference of Disorder-Free Critical Temperature

    NASA Astrophysics Data System (ADS)

    Luna, Katherine; Giraldo-Gallo, Paula; Geballe, Theodore; Fisher, Ian; Beasley, Malcolm

    2014-10-01

    We performed point-contact spectroscopy tunneling measurements on single crystal BaPb1-xBixO3 for 0≤x ≤0.28 at temperatures T =2-40 K and find a suppression in the density of states at low bias voltages that is characteristic of disordered metals. Both the correlation gap and the zero-temperature conductivity are zero at a critical concentration xc=0.30. Not only does this suggests that a disorder driven metal-insulator transition occurs before the onset of the charge disproportionated charge density wave insulator, but we also explore whether a scaling theory is applicable. In addition, we estimate the disorder-free critical temperature and compare these results to Ba1-xKxBiO3.

  19. Partitioning of Nb, Mo, Ba, Ce, Pb, Th and U between immiscible carbonate and silicate liquids: Evaluating the effects of P2O5,F, and carbonate composition

    NASA Technical Reports Server (NTRS)

    Jones, J. H.; Walker, D.

    1993-01-01

    Previously we have reported carbonate liq./silicate liq. partition coefficients (D) for a standard suite of trace elements (Nb, Mo, Ba, Ce, Pb, Th, and U) and Ra and Pa as well. In brief, we have found that immiscible liquid partitioning is a strong function of temperature. As the critical temperature of the carbonate-silicate solvus is approached, all partition coefficients approach unity. Additionally, for the overwhelming majority of the partitioning elements, InD is a linear function of 'ionic field strength,' z/r, where z is the charge of the partitioned cation and r is its ionic radius.

  20. Investigation on photoluminescence properties and defect chemistry of GdAlO3:Dy3+ Ba2+ phosphors

    NASA Astrophysics Data System (ADS)

    Selvalakshmi, Thangaraj; Sellaiyan, Selvakumar; Uedono, Akira; Semba, Takaaki; Bose, Arumugam Chandra

    2016-08-01

    GdAlO3:Dy3+ Ba2+ phosphors are synthesized by citrate-based sol-gel method. Photoluminescence and positron annihilation studies are used to investigate the emission and defect chemistry of the phosphors respectively. The strong yellow (Dy3+) emission properties of phosphors are discussed for various concentrations of Dy3+ ions. Upon the addition of Ba2+ ion, an enhancement in emission intensity is observed due to the lattice distortions around Dy3+ ion. The positron studies indicate the presence of defects at crystallite boundaries, vacancy clusters and large voids in the materials. The influence of Ba2+ ion on the photoluminescence and lattice distortion around Dy3+ is also explored.

  1. Effect of Al3+ on Photoluminescence Properties of Eu3+-Doped BaZr(BO3)2 Phosphors

    NASA Astrophysics Data System (ADS)

    Li, Guang-Min; Li-Lan; Wang, Da-Jian; Zhang, Xiao-Song; Tao, Yi

    2006-08-01

    We discuss the influence of Al3+ on the charge transfer state (CTS) and the photoluminescence properties of BaZr(BO3)2:Eu. The results reveal that there is a red shift which is about 20 nm for the charge transfer state when doping with Al3+ and indicate the formation of `free' electrons due to the change of microstructures. In addition, the influence of Al3+ doping on the PPR is analysed and a new explanation is raised based on the photo luminescent mechanism. It is the CTS intensity rather than the CTS energy that influences the peak-peak ratio.

  2. Luminescence properties of undoped LiBaAlF6 single crystals.

    PubMed

    Omelkov, S I; Kirm, M; Feldbach, E; Pustovarov, V A; Cholakh, S O; Isaenko, L I

    2010-07-28

    This paper presents the results of the study of electronic excitations in undoped LiBaAlF(6) single crystals by means of luminescence spectroscopy and complimentary optical methods. The intrinsic emission at 4.2 eV due to self-trapped excitons was identified. The fast nanosecond defect-related luminescence was revealed at 3.0 eV. Both emissions degrade under electron beam irradiation, the most probable reason of which is defect creation introducing an additional non-radiative relaxation channel prohibiting energy transfer to luminescence centers. These defects can be recovered and luminescence intensity restored at higher temperatures (>200 K). The permanent damage by electron beam irradiation results only in overall growth of the absorption coefficient in the whole 1.5-6.5 eV spectral region studied. The analysis of thermally stimulated luminescence glow curves in the temperature range of 5-410 K revealed two shallow charge carrier traps with the activation energies of 0.22 and 0.33 eV, respectively. The luminescence of an impurity peaked at 2.5 eV was found and tentatively assigned to an oxygen-related emission center. PMID:21399311

  3. On synthesis of BaFe12O19, SrFe12O19, and PbFe12O19 hexagonal ferrite ceramics with multiferroid properties

    NASA Astrophysics Data System (ADS)

    Kostishin, V. G.; Panina, L. V.; Kozhitov, L. V.; Timofeev, A. V.; Zyuzin, A. K.; Kovalev, A. N.

    2015-08-01

    We analyze the possibility of obtaining M-type hexagonal ferrites of barium, strontium, and lead with multiferroid properties with the help of ceramic technology. Using the modified ceramic technology (especially pure initial raw materials, admixture of B2O3, and sintering in the oxygen atmosphere), we obtained for the first time the BaFe12O19 and SrFe12O19 samples with intense multiferroid properties at room temperature. At the same time, the employed technology does not make it possible to obtain PbFe12O19 samples exhibiting ferroelectricity. The multiferroid characteristics of experimental samples are compared with the characteristics of classical high-temperature multiferroic BiFeO3 and with the characteristics of BaFe12O19, SrFe12O19, and PbFe12O19 ferrite ceramics obtained in accordance with polymer precursor technology. We propose a mechanism explaining multiferroid properties of the hexagonal ferrite ceramic samples and note the importance of our results for applications.

  4. X-ray crystal structures of Al-doped (Y,Ca)Ba2Cu3O(7-y) whiskers.

    PubMed

    Bertolotti, Federica; Calore, Leandro; Gervasio, Giuliana; Agostino, Angelo; Truccato, Marco; Operti, Lorenza

    2014-04-01

    Al(+3)-doped (Y,Ca)Ba2Cu3O(7-y) (YBCO) whiskers have been synthesized using a solid-state reaction technique. These materials are promising candidates for solid-state THz applications based on sequences of Josephson Junctions (IJJs). Alumina addition was systematically varied and the effect of aluminium incorporation on the structure has been investigated using single-crystal X-ray diffraction. Aluminium only replaces Cu atoms in the O-Cu-O-Cu chains and a gradual transition from orthorhombic to tetragonal space group occurs, thus increasing the Al content. A gradual modification of the coordination sphere of the copper site has also been observed. The Ca(2+) ion substitutes mainly the Y(3+) ion and also, to a small extent, the Ba(2+) ion. PMID:24675593

  5. Comparison Study of Transition Temperature between the Superconducting Compounds Tl0.9 Pb0.1 Ba2Ca2Cu3O9-δ, Tl0.9Sb0.1Ba2Ca2Cu3O9-δ and Tl0.9Cr0.1Ba2Ca2Cu3O9-δ

    NASA Astrophysics Data System (ADS)

    Jasim, Kareem Ali; Makki, Sameer Atta; Almohsin, Alia abud

    Three high temperature superconductors namely Tl0.9Pb0.1Ba2Ca2Cu3O9-δ, Tl0.9Sb0.1Ba2Ca2Cu3O9-δ and Tl0.9Cr0.1Ba2Ca2Cu3O9-δ have been successfully prepared by three-step solid state reaction method. The sintering was within (1128-1133) K. Electrical resistively, using four probe techniques, is used to find the transition temperature Tc. The transition temperature at zero resistivity Tc(offset) were 110, 115 and 118K, onset superconducting transition temperature Tc(onset) were 128, 131 and 132 K for Tl0.9Cr0.1Ba2Ca2Cu3O9-δ, Tl0.9Sb0.1Ba2Ca2Cu3O9-δ and Tl0.9Cr0.1Ba2Ca2Cu3O9-δ respectively. All samples preparation with O2 flow. X-ray diffraction (XRD) analysis showed a pesudotetragonal structure with changes of lattice parameters for these samples.

  6. Catalyst Size and Morphological Effects on the Interaction of NO2 with BaO/γ-Al2O3 Materials

    SciTech Connect

    Mei, Donghai; Kwak, Ja Hun; Szanyi, Janos; Ge, Qingfeng; Peden, Charles HF

    2010-06-19

    The capability of NOx storage on the supported BaO catalyst largely depends on the Ba loading. With different Ba loadings, the supported BaO component exposes various phases ranging from well-dispersed nanoclusters to large crystalline particles on the oxide support materials. In order to better understand size and morphological effects on NOx storage over -Al2O3 supported BaO materials, the adsorption structures and energetics of single NO2 molecule, as well as NOx+NOy (NO2+NO2, NO+NO3 and NO2+NO3) pairs on the BaO/-Al2O3(100), (BaO)2/-Al2O3(100), and (BaO)5/-Al2O3(100) surfaces were investigated using first-principles density functional theory calculations. A single NO2 molecule prefers to adsorb at basic OBa site forming anionic nitrate species. Upon adsorption, a charge redistribution in the supported (BaO)n clusters occurs. Synergistic effects due to the interaction of NO2 with both the (BaO)n clusters and the  Al2O3(100) support enhances the stability of adsorbed NO2. The interaction between NO2 and the (BaO)n/ Al2O3(100) catalysts was found to be markedly affected by the sizes and morphologies of the supported (BaO)n clusters. The adsorption energy of NO2 increases from 0.98 eV on the BaO/-Al2O3(100) surface to 3.01 eV on (BaO)5/ Al2O3(100). NO2 adsorption on (BaO)2 clusters in a parallel configuration on the -Al2O3(100) surface is more stable than on dimers oriented in a perpendicular fashion. Similar to the bulk BaO(100) surface, a supported (BaO)n cluster-mediated electron transfer induces cooperative effects that dramatically increase the total adsorption energy of NOx+NOy pairs on the (BaO)n/-Al2O3(100) surfaces. Following the widely accepted NO2 storage mechanism of , our thermodynamic analysis indicates that the largest energy gain for this overall process of NOx uptake is obtained on the amorphous monolayer-like (BaO)5/-Al2O3(100) surface. This suggests that -Al2O3-supported BaO materials with ~ 6  12 wt

  7. ABiO2X (A = Cd, Ca, Sr, Ba, Pb; X = halogen) Sillen X1 Series: Polymorphism Versus Optical Properties.

    PubMed

    Olchowka, Jacob; Kabbour, Houria; Colmont, Marie; Adlung, Matthias; Wickleder, Claudia; Mentré, Olivier

    2016-08-01

    The Sillen X1 series of Bi(3+)A(2+)O2X (A = Cd, Ca, Sr, Ba, Pb; X = Cl, Br, I) compounds is composed of three main crystallographic types, namely, the tetragonal form (space group (S.G.) I4/mmm), the orthorhombic form (S.G. Cmcm), and the monoclinic form (S.G. P21/m). Because of Bi(3+)/A(2+) disorder the Bi(3+) based photoluminescence (PL) of the tetragonal polytypes is quenched at room temperature (RT). In the two other ordered forms, the Bi-O-Bi connectivity is different but limited, such that bluish/greenish emission occurs at RT in the monoclinic CdBiO2Cl and CaBiO2Cl and orthorhombic SrBiO2Cl and BaBiO2Cl phases. The crystal structure of BaBiO2Br was refined in the orthorhombic Cmcm space group and also shows RT emission. Focusing on the RT luminescent activity as a key parameter, the PL active compounds were investigated by means of density functional theory calculations and UV-visible reflectance spectroscopy. The influence of A and X ions on the excitation energy is discussed by analyzing the A-O-Bi and Bi-X bonding schemes and gives some insights for rational tuning of both the excitation and emission energies. PMID:27414069

  8. On the microstructure and symmetry of apparently hexagonal BaAl{sub 2}O{sub 4}

    SciTech Connect

    Larsson, A.-K. Withers, R.L.; Perez-Mato, J.M.; Fitz Gerald, J.D.; Saines, P.J.; Kennedy, B.J.; Liu, Y.

    2008-08-15

    The P6{sub 3} (a=2a{sub p}, b=2b{sub p}, c=c{sub p}) crystal structure reported for BaAl{sub 2}O{sub 4} at room temperature has been carefully re-investigated by a combined transmission electron microscopy and neutron powder diffraction study. It is shown that the poor fit of this P6{sub 3} (a=2a{sub p}, b=2b{sub p}, c=c{sub p}) structure model for BaAl{sub 2}O{sub 4} to neutron powder diffraction data is primarily due to the failure to take into account coherent scattering between different domains related by enantiomorphic twinning of the P6{sub 3}22 parent sub-structure. Fast Fourier transformation of [0 0 1] lattice images from small localized real space regions ({approx}10 nm in diameter) are used to show that the P6{sub 3} (a=2a{sub p}, b=2b{sub p}, c=c{sub p}) crystal structure reported for BaAl{sub 2}O{sub 4} is not correct on the local scale. The correct local symmetry of the very small nano-domains is most likely orthorhombic or monoclinic. - Graphical abstract: The electron diffraction pattern of BaAl{sub 2}O{sub 4} (left) is compatible with the 3-q superstructure corresponding to the conventional P6{sub 3}, a=2a{sub p} structure (p refers to the tridymite-related parent P6{sub 3}22 structure). Fast Fourier transforms (right) of small domains of lattice images, however, show that the local structure in fact is single q, and that true symmetry is monoclinic or orthorhombic.

  9. Photoluminescence properties of AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors

    SciTech Connect

    Wang, Yong; Tang, Jianfeng; Ouyang, Xicheng; Liu, Buqiong; Lin, Rong Han

    2013-06-01

    Highlights: ► Ideal hexagonal shape particle size in 5 μm and 2.5–3 μm in thickness are obtained. ► The growth mechanism is studied by a computer simulation. ► The influence of introduced AlN on the sites of Eu{sup 2+} and photoluminescence properties was investigated. - Abstract: The AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors were synthesized by conventional solid-state reaction. Powder X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum (PL) were used for characterization. The growth mechanism was carried out by computer simulation with CASTEP application, and revealed that an ideal hexagonal shape, particle size in 5 μm and 2.5–3 μm in thickness, could be obtained by AlN doping. Additionally, due to the low electronegativity of N{sup 3−}, the AlN-doped sample showed 35% increase in PL intensity and improvement of thermal stability. These fine particle size and better photoluminescence properties are expected to be applicable to industrial production of BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors.

  10. Comparative ab initio calculations of SrTiO3/BaTiO3 and SrZrO3/PbZrO3 (0 0 1) heterostructures

    NASA Astrophysics Data System (ADS)

    Piskunov, Sergei; Eglitis, Roberts I.

    2016-05-01

    Using a B3PW hybrid exchange-correlation functional within the density functional theory (DFT) we calculated from the first principles the electronic structure of BaTiO3/SrTiO3 and PbZrO3/SrZrO3 (0 0 1) interfaces. The optical band gap of both BaTiO3/SrTiO3 and PbZrO3/SrZrO3 (0 0 1) interfaces depends mostly from BaO or TiO2 and SrO or ZrO2 termination of the upper layer, respectively. Based on the results of our calculations we predict increase of the Ti-O and Zr-O chemical bond covalency near the SrTiO3/BaTiO3 and SrZrO3/PbZrO3 (0 0 1) interfaces as compared to the BaTiO3 and PbZrO3 bulk.

  11. Temperature dependence of Zr and Ti K-edge XANES spectra for para- and ferro-electric perovskite-type PbZrO3, PbTiO3 and BaTiO3

    NASA Astrophysics Data System (ADS)

    Yoshiasa, A.; Nakatani, T.; Hiratoko, T.; Tobase, T.; Nakatsuka, A.; Okube, M.; Arima, H.; Sugiyama, K.

    2016-05-01

    Zr and Ti K-edge XANES spectra of PbZrO3, PbTiO3 and BaTiO3 perovskite-type compounds were measured in the temperature range from 10K to 850K. Quantitative comparisons for the near-edge spectra were performed in a wide temperature range using the absorption intensity invariant point (AIIP) standardization. Clear temperature dependence for pre-edge shoulder is identified by the calculating the temperature difference of the XANES spectrum intensity. Decrease of pre-edge shoulder and peak intensity is observed only in the para- and ferro-electric phases and draw curves, not straight lines. The gradients for shoulder and pre-edge peak intensity are rich in a variety. The decrease in absorption of pre-edge peak and shoulder is speculated due to the shift from the off-centre position of the Zr atom with respect to the oxygen octahedron to center position. The Zr ion in the PbZrO3 para-electric phase has same temperature behaviors of Ti ions in the ferroelectric perovskite.

  12. First principles study of magnetoelectric coupling in Co2FeAl/BaTiO3 tunnel junctions.

    PubMed

    Yu, Li; Gao, Guoying; Zhu, Lin; Deng, Lei; Yang, Zhizong; Yao, Kailun

    2015-06-14

    Critical thickness for ferroelectricity and the magnetoelectric effect of Co2FeAl/BaTiO3 multiferroic tunnel junctions (MFTJs) are investigated using first-principles calculations. The ferroelectric polarization of the barriers can be maintained upto a critical thickness of 1.7 nm for both the Co2/TiO2 and FeAl/TiO2 interfaces. The magnetoelectric effect is derived from the difference in the magnetic moments on interfacial atoms, which is sensitive to the reversal of electric polarization. The magnetoelectric coupling is found to be dependent on the interfacial electronic hybridizations. Compared with the Co2/TiO2 interface, more net magnetization change is achieved at the FeAl/TiO2 interface. In addition, the in-plane strain effect shows that in-plane compressive strain can lead to the enhancement of ferroelectric polarization stability and intensity of magnetoelectric coupling. These findings suggest that Co2FeAl/BaTiO3 MFTJs could be utilized in the area of electrically controlled magnetism, especially the MFTJ with loaded in-plane compressive strain with the FeAl/TiO2 interface. PMID:25987345

  13. Mössbauer spectroscopy study of Al distribution in BaAl{sub x}Fe{sub 12−x}O{sub 19} thin films

    SciTech Connect

    Przybylski, M. Żukrowski, J.; Harward, I.; Celiński, Z.

    2015-05-07

    Barium hexagonal ferrite (BaM) films grown on Si are a good candidate material for new-generations of on-wafer microwave devices operating at frequencies above 40 GHz. Doping BaM with Al increases the value of anisotropy field even more, and in combination with a large value of remanence, would allow one to create a self-biasing material/structure that would eliminate the need for permanent bias magnets in millimeter wave devices. To examine the occupation of Fe sublattices by Al ions, we carried out Conversion Electron Mössbauer Spectroscopy (CEMS) measurements at room temperature and zero magnetic field (after magnetizing the samples in a strong magnetic field). The spectra can be reasonably fitted with three components (sub-spectra) corresponding to different Fe sublattices. There are significant changes in the spectra with the addition of Al: The magnetic hyperfine field decreases for all three components, and their relative contributions also change remarkably. These observations are in agreement with the fact that the Al substitutes Fe, thus lowering the component contributions and the value of the hyperfine field. In addition, our previous XRD analysis indicates increasing grain misalignment with Al content, further supporting the CEMS data.

  14. Crystal Growth and Photoluminescence Properties of Truncated Cubic BaMgAl10O17:Eu2+ Phosphors for Three-Dimensional Plasma Display Panels.

    PubMed

    Liu, Bitao; Chen, Yuan; Peng, Lingling; Han, Tao; Yu, Hong; Tian, Liangliang; Tu, Mingjing

    2016-04-01

    Monodispersed, truncated cube BaMgAl10O17:Eu2+ phosphors were synthesized by the sol-gel process. Scanning electron microscope (SEM), photoluminescence spectrum, powder X-ray diffraction and decay curves were used to evaluate the truncated cubic BaMgAl10O17:Eu2+ phosphors. The crystal growth process and photoluminescence properties were discussed in detail. The results showed that this truncated cubic morphology can be achieved via a simple sinter process. These truncated cubic BaMgAl10O17:Eu2+ phosphors showed acceptable emission intensity and better thermal properties. This result indicates truncated cubic BaMgAl10O17:Eu2+ phosphors would meet the requirements of plasma display panels (PDPs). PMID:27451727

  15. Nanocomposite dielectrics in PbO-BaO-Na2O-Nb2O5-SiO2 system with high breakdown strength for high voltage capacitor applications.

    PubMed

    Zhang, Qingmeng; Luo, Jun; Tang, Qun; Han, Dongfang; Zhou, Yi; Du, Jun

    2012-11-01

    Nanocomposite dielectrics in 6PbO-4BaO-20Na2O-40Nb2O5-30SiO2 system were prepared via melt-quenching followed by controlled crystallization. X-ray diffraction studies reveal that Pb2Nb2O7, Ba,NaNb5O15, NaNbO3 and PbNb2O6 phases are formed from the as-quenched glass annealed in temperature range from 700 degrees C to 850 degrees C. Ba2NaNb5O15, Pb2Nb2O7 crystallizes at 700 degrees C and then Pb2Nb2O7 disappears at 850 degrees C, while PbNb2O6 and NaNbO3 are formed at 850 degrees C. Microstructural observation shows that the crystallized particles are nanometer-sized and randomly distributed with glass matrix being often found at grain boundaries. The dielectric constant of the nanocomposites formed at different crystallization temperatures shows good frequency and electric field stability. The breakdown strength is slightly decreased when the glass-ceramics thickness is varied from 1 mm to 4 mm. The corresponding energy density could reach 2.96 J/cm3 with a breakdown strength of 58 kV/mm for thickness of 1 mm. PMID:23421296

  16. Design and Syntheses of Three Novel Carbonate Halides: Cs3 Pb2 (CO3 )3 I, KBa2 (CO3 )2 F, and RbBa2 (CO3 )2 F.

    PubMed

    Liu, Lili; Yang, Yun; Dong, Xiaoyu; Zhang, Bingbing; Wang, Ying; Yang, Zhihua; Pan, Shilie

    2016-02-24

    Three new carbonate halides, Cs3 Pb2 (CO3 )3 I, KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F have been synthesized with hydrothermal and solid-state methods. Cs3 Pb2 (CO3 )3 I is the first product in the lead carbonate iodides family; KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F are the first two centrosymmetric compounds found in the alkaline-alkaline earth carbonate fluorides family. Cs3 Pb2 (CO3 )3 I crystallizes in a centrosymmetric space group C2/m, and exhibits a two- dimensional layered structure which is formed by [Cs4 Pb4 (CO3 )6 I2 ]∞ double-layers consisting of [Pb2 (CO3 )3 I]∞ single-layers bridged by the Cs atoms. KBa2 (CO3 )2 F and RbBa2 (CO3 )2 F, which are isostructural, crystallize in a trigonal crystal system with a centric space group of R3‾ featuring a honeycomb-like framework. First principle calculations indicate that Cs3 Pb2 (CO3 )3 I has a moderate birefringence and explain the difference between the band gaps of the title compounds from electron structures. The effects of cations and halogens on the structures and properties of the title compounds are also discussed. PMID:26822173

  17. Influence of gravity level and interfacial energies on dispersion-forming tendencies in hypermonotectic Cu-Pb-Al alloys

    NASA Technical Reports Server (NTRS)

    Andrews, J. B.; Curreri, P. A.; Sandlin, A. C.

    1988-01-01

    Results on the nondirectional solidification of several hypermonotectic Cu-Pb-Al alloys were obtained aboard NASA's KC-135 zero-gravity aircraft in order to determine the influence of interfacial energies and gravity levels on dispersion-forming tendencies. The Al content was systematially varied in the alloys. The dispersion-forming ability is correlated with gravity level during solidification, the interfacial energy between the immiscible phases, and the tendency for the minority immiscible phase to wet the walls of the crucible.

  18. Self-organized homo-epitaxial growth in nonlinear optical BaAlBO3F2 crystal crossing lines patterned by laser in glass

    NASA Astrophysics Data System (ADS)

    Shinozaki, K.; Abe, S.; Honma, T.; Komatsu, T.

    2015-11-01

    Crystallization processing of glasses is important as a novel technique for the development of new optical materials, and laser-induced crystallization provides a new challenge in science and technology of materials. Nonlinear optical BaAlBO3F2 crystal lines with crossing, bending, and spiral shapes were patterned at the surface of 2NiO-49BaF2-24.5Al2O3-24.5B2O3 (mol%) and 2.9NiO-48.5BaF2-24.3Al2O3-24.3B2O3 (mol%) glasses by laser irradiation (Yb:YVO4 laser with a wavelength of 1080 nm) and the orientation state of BaAlBO3F2 crystals was examined from birefringence image observations. The birefringence images indicate that the growth of highly c-axis oriented BaAlBO3F2 crystals follows along the laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of BaAlBO3F2 crystals changes gradually at the crossing and bending points. The model of "self-organized homo-epitaxial growth" is proposed for the crystal orientation at the crossing and bending points, as a new crystal growth science and engineering beyond the wise providence of nature.

  19. Atomic layer deposition effect on the electrical properties of Al{sub 2}O{sub 3}-passivated PbS quantum dot field-effect transistors

    SciTech Connect

    So, Hye-Mi; Shim, Hyung Cheoul; Choi, Hyekyoung; Lee, Seung-Mo; Jeong, Sohee; Chang, Won Seok

    2015-03-02

    We have investigated the effect of atomic layer deposition (ALD) on the electrical properties of colloidal PbS quantum dot field-effect transistors (PbS QD-FETs). Low-temperature Al{sub 2}O{sub 3} ALD process was used to fill up the pore spaces of PbS QD films containing 1, 2-ethanedithiol ligands. Upon deposition of Al{sub 2}O{sub 3} on PbS film, the PbS QD-FETs showed ambipolar behavior. The treated film retained this property for over 2 months, despite of exposure to air. This change in the electrical properties of the PbS QD-FETs is attributed to the formation of electron channels in the Al{sub 2}O{sub 3}-passivated PbS film. We conclude that these electron transport channels in the Al{sub x}O{sub y}-PbS film are formed due to substitution of the Pb sites by Al metal and chemical reduction of Pb{sup 2+} ions, as determined by an analysis of the depth profile of the film using secondary ion mass spectrometry and X-ray photoelectron spectroscopy.

  20. Synthesis, Crystal and Electronic Structures of the Pnictides AE3TrPn3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

    SciTech Connect

    Stoyko, Stanislav; Voss, Leonard; He, Hua; Bobev, Svilen

    2015-09-24

    New ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. Likewise, the compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3-]3, or rather [AE2+]6[Tr2Pn6]12-, i.e., as Zintl phases.

  1. Origin and evolution of the Nakhla meteorite inferred from the Sm-Nd and U-Pb systematics and REE, Ba, Sr, Rb and K abundances

    USGS Publications Warehouse

    Nakamura, N.; Unruh, D.M.; Tatsumoto, M.; Hutchison, R.

    1982-01-01

    Analyses of Sm-Nd and U-Th-Pb systematics, REE, Ba, Sr, Rb and K concentrations were carried out for whole rock and mineral separates from the Nakhla meteorite. The 1.26 ??.07 b.y. Sm-Nd age obtained in this work is in good agreement with those previously obtained by the Rb-Sr and Ar-Ar methods. The high initial ??{lunate}Nd value of +16 suggests that Nakhla was derived from a light REE-depleted, old planetary mantle source. U-Th-Pb data, after correction for pre-analytical terrestrial Pb contamination assuming an age of 1.26 b.y., suggest that the age of the Nakhla source is ???4.33 b.y. The agreement in the age determined by three independent radiometric methods and the high initial ??{lunate}Nd value strongly suggest that the 1.3 b.y. age dates one thorough igneous event in the parent body which not only reset these isotopic systems but also established the chemical and petrologic characteristics observed for the Nakhla meteorite. Using a three-stage Sm-Nd evolution model in combination with LIL element data and estimated partition coefficients, we have tested partial melting and fractional crystallization models to estimate LIL element abundances in a possible Nakhla source. Our model calculations suggest that partial melting of the light REE-depleted source followed by extensive fractional crystallization (???50%) of the partial melt could account for the REE abundances in the Nakhla constituent minerals. The estimated source is depleted in the light REE, Ba, Rb and K and therefore may resemble the MORB source in the earth's upper mantle or the upper 60-300 km of the moon. The significantly younger age of Nakhla than the youngest lunar rock; the young differentiation age inferred from the U-Th-Pb data, and the estimated LIL element abundances (including those of K, U and Th) in the source suggest that the Nakhla meteorite may have been derived from a relatively large, well-differentiated planetary body such as Mars. ?? 1982.

  2. Paleontological, mineralogical and chemical studies of syngenetic and epigenetic Pb-Zn-Ba-P mineralizations at the stratotype of the K/P boundary (El Kef area, Tunisia)

    NASA Astrophysics Data System (ADS)

    Dill, H. G.; Weiss, W.; Botz, R.; Dohrmann, R.

    2011-06-01

    The El Kef area, Tunisia, is host of the official stratotype of the K/P boundary and of a complex metallic and non-metallic mineralization at Djebel Sekarna, encompassing syn(dia)genetic shale- and carbonate-hosted Zn-P and epigenetic Pb-Zn-Ba ore mineralizations. Micropaleontological, geological, mineralogical, and chemical studies (major and minor elements, C- and O-isotopes) of Upper Santonian to Lower Eocene calcareous-siliciclastic sediments resulted in a subdivision of this mineralization into eight mineralizing stages. Stages 1 and 2 (late Cretaceous-early Paleogene) are representative of syn(diagenetic) shale- and carbonate-hosted sulfidic and siliceous (Fe)-Zn-P mineralization deposited in shallow marine to slightly brackish sediments. Stages 3-5 (early Eocene respectively—pre- and post- Nummulites involutus-exilis zones) are representatives of epigenetic sulfidic and sulfatic (Fe)-Zn-Pb-Ba mineralizations at temperatures as high as 170/200°C and stages 6 and 7 (early Eocene respectively—post- Alveolina oblonga zone) cover the non-sulfidic Zn-(Pb) mineralization at temperatures as high as 60°C which is transitional from hypogene into supergene mineralization ("epithermal calamine deposits"). Stage 8 represents alteration of the pre-existing mineral assemblages in course of the Holocene weathering. The Cretaceous through Paleogene aquatic system is characterized by a poisoning of the sea with base metals, mainly Zn, and the atmosphere was chocked with clouds of fine-grained volcanic ejecta. Both processes contributed to the build-up of Zn-(Pb) deposits and vast, but uneconomic bentonitic clay deposits around the K/P boundary. Ore mineralization in the El Kef area is a multiple-phase process which reached its climax during the early Eocene as indicated by the large foram zones. These inorganic concentration processes resulting in the formation of mineral deposits had obviously also a negative effect on the long-term course of regional Earth

  3. Band alignment at epitaxial BaSnO3/SrTiO3(001) and BaSnO3/LaAlO3(001) heterojunctions

    NASA Astrophysics Data System (ADS)

    Chambers, Scott A.; Kaspar, Tiffany C.; Prakash, Abhinav; Haugstad, Greg; Jalan, Bharat

    2016-04-01

    We have spectroscopically determined the optical bandgaps and band offsets at epitaxial interfaces of BaSnO3 with SrTiO3(001) and LaAlO3(001). 28 u.c. BaSnO3 epitaxial films exhibit direct and indirect bandgaps of 3.56 ± 0.05 eV and 2.93 ± 0.05 eV, respectively. The lack of a significant Burstein-Moss shift corroborates the highly insulating, defect-free nature of the BaSnO3 films. The conduction band minimum is lower in electron energy in 5 u.c. films of BaSnO3 than in SrTiO3 and LaAlO3 by 0.4 ± 0.2 eV and 3.7 ± 0.2 eV, respectively. This result bodes well for the realization of oxide-based, high-mobility, two-dimensional electron systems that can operate at ambient temperature, since electrons generated in the SrTiO3 by modulation doping, or at the BaSnO3/LaAlO3 interface by polarization doping, can be transferred to and at least partially confined in the BaSnO3 film.

  4. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3

    SciTech Connect

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3 exhibits a superconducting “dome” in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare to the Ginzburg-Landau coherence length. Thus, we find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.

  5. Improvement of the phase diagram for the pseudobinary PbNb{sub 2}O{sub 6}-BaNb{sub 2}O{sub 6} system

    SciTech Connect

    Venet, M.; Zabotto, F. L.; Eiras, J. A.; Garcia, D.

    2009-06-15

    Characteristics of phase transitions of lead barium niobate compositions around the morphotropic phase boundary were investigated. Using structural characterizations, it was found that the morphotropic phase boundary extends toward a wide composition range, in which both tetragonal (4mm) and orthorhombic (m2m) tungsten bronze phases coexist. In addition, on heating, two phase transitions were observed for all the studied compositions. First, the fraction with m2m symmetry phase transforms into the 4mm symmetry one and, second, the 4mm symmetry phase, which represents the whole material, transforms into the paraelectric phase (4/mmm symmetry). The phase transition temperatures were determined from dielectric characterizations. These results helped to improve the phase diagram of the pseudobinary PbNb{sub 2}O{sub 6}-BaNb{sub 2}O{sub 6} system around the morphotropic phase boundary region.

  6. Stripe-like nanoscale structural phase separation in superconducting BaPb1-xBixO3

    SciTech Connect

    Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; Manoharan, H. C.; Beasley, M. R.; Geballe, T. H.; Kramer, M. J.; Fisher, I. R.

    2015-09-16

    The phase diagram of BaPb1-xBixO3 exhibits a superconducting dome in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high-resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare with the Ginzburg–Landau coherence length. We find that the maximum Tc occurs when the superconducting coherence length matches the width of the partially disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.

  7. Structural and luminescence studies on Eu3+: B2O3-Li2O-MO-LiF (M=Ba, Bi, Pb and Zn) glasses

    NASA Astrophysics Data System (ADS)

    Arunkumar, S.; Marimuthu, K.

    2012-06-01

    The present work reports structural and luminescence studies on 54B2O3+25Li2O+15MO+ 5LiF+1Eu2O3 (where M= Ba, Pb, Bi and Zn) glasses prepared by following melt quenching technique. The influence of the metal ions in the host matrix have been studied by measuring FTIR, absorption and luminescence spectra. The presence of the functional units in the prepared glasses have been explored through FTIR studies. The Judd-Ofelt (JO) intensity parameters have been determined from the luminescence spectra. The JO parameters have been used to calculate stimulated emission cross-section (σEP), branching ratios (βR) and radiative lifetime (τR) for the 5D0 →7FJ (J= 1, 2, 3 and 4) transitions of the Eu3+ ions in the prepared glasses.

  8. Large electrical manipulation of permittivity in BaTiO{sub 3} and Pb(Zr,Ti)O{sub 3} bimorph heterostructure

    SciTech Connect

    Ci, Penghong; Liu, Guoxi; Dong, Shuxiang; Zhang, Li

    2014-08-18

    We report a strain-mediated electric field manipulation of permittivity in BaTiO{sub 3} (barium titanate, BT) ceramic by a Pb(Zr,Ti)O{sub 3} (PZT) bimorph. This BT/PZT heterostructure exhibited a relatively large permittivity tunability of BT up to ±10% in a wide frequency range under an electric field of ±4 kV/cm applied to the PZT bimorph. The permittivity tunability is attributed to the strain in BT produced by the PZT bimorph. Calculations of the relationship between permittivity and applied electric field were developed, and corresponded well with measurements. The BT/PZT heterostructure has potential for applications in broadband field tunable smart electronic devices.

  9. Effect of diamagnetic Ca, Sr, Pb, and Ba substitution on the crystal structure and multiferroic properties of the BiFeO3 perovskite

    NASA Astrophysics Data System (ADS)

    Khomchenko, V. A.; Kiselev, D. A.; Vieira, J. M.; Jian, Li; Kholkin, A. L.; Lopes, A. M. L.; Pogorelov, Y. G.; Araujo, J. P.; Maglione, M.

    2008-01-01

    In this work, we studied the effect of heterovalent Ca, Sr, Pb, and Ba substitution on the crystal structure, dielectric, local ferroelectric, and magnetic properties of the BiFeO3 multiferroic perovskite. Ceramic solid solutions with the general formula Bi0.7A0.3FeO3 (A is a doping element) were prepared and characterized by x-ray diffraction, dielectric, piezoresponse force microscopy (PFM), and magnetic measurements. It is shown that the crystal structure of the compounds is described within the space group R3c, permitting the spontaneous polarization, whose existence was confirmed by the PFM data. Magnetic properties of the solid solutions are determined by the ionic radius of the substituting element. Experimental results suggest that the increase in the radius of the A-site ion leads to the effective suppression of the spiral spin structure of BiFeO3, resulting in the appearance of net magnetization.

  10. Highly sensitive photodetection using a microwave-coupled BaPb/sub 0. 7/Bi/sub 0. 3/O/sub 3/ Josephson junction array

    SciTech Connect

    Ito, M.; Enomoto, Y.; Murakami, T.

    1983-08-01

    The BaPb/sub 0.7/Bi/sub 0.3/O/sub 3/ sputtered film possesses tunnel Josephson junctions at boundary layers (boundary Josephson junction (BJJ)) normal to the film plane in a homogeneous junction array. The film has high efficiency for optical irradiation of the junctions because of the high optical transparency. The letter presents the optical effect on the current-voltage characteristics for this Josephson junction array locked to a microwave field. The microwave-induced hysteresis loop caused by voltage locking among junctions in a microwave field is highly sensitive to optical illumination with as low an incident power as a few nanowatts. This probably can be exploited in a future, highly sensitive photodetector.

  11. Highly sensitive photodetection using a microwave-coupled BaPb0.7Bi0.3O3 Josephson junction array

    NASA Astrophysics Data System (ADS)

    Ito, Minoru; Enomoto, Youichi; Murakami, Toshiaki

    1983-08-01

    The BaPb0.7Bi0.3O3 sputtered film possesses tunnel Josephson junctions at boundary layers [boundary Josephson junction (BJJ)] normal to the film plane in a homogeneous junction array. The film has high efficiency for optical irradiation of the junctions because of the high optical transparency. The letter presents the optical effect on the current-voltage characteristics for this Josephson junction array locked to a microwave field. The microwave-induced hysteresis loop caused by voltage locking among junctions in a microwave field is highly sensitive to optical illumination with as low an incident power as a few nanowatts. This probably can be exploited in a future, highly sensitive photodetector.

  12. Fluid inclusion and stable isotope studies of the Mesloula Pb-Zn-Ba ore deposit, NE Algeria: Characteristics and origin of the mineralizing fluids

    NASA Astrophysics Data System (ADS)

    Laouar, Rabah; Salmi-Laouar, Sihem; Sami, Lounis; Boyce, Adrian J.; Kolli, Omar; Boutaleb, Abdelhak; Fallick, Anthony E.

    2016-09-01

    In the Saharan Atlas (NE Algeria), the Triassic evaporitic formation was brought to the surface through the thick Cretaceous and Tertiary sedimentary cover as diapirs due to the effect of Atlasic tectonic events. The diapir piercing began in the Jurassic and has continued through present day. Many outcrops of several square kilometres are distributed in a large area (approximately 80 km wide) that extends northeasterly over 300 km towards Tunisia. The diapiric evaporitic formation is often accompanied by the emplacement of Pb-Zn-Ba-F mineralization. The Mesloula massif is an example of these deposits. Fluid inclusion and sulphur, carbon and oxygen isotope studies were carried out on Pb-Zn-Ba mineralization and associated gangue carbonates. Gypsum of the Triassic formation was also analysed for its sulphur isotope composition to show the role of evaporates in the generation of this typical peridiapiric deposit. Gypsum from the Triassic formation showed a narrow range of δ34SVCDT values, ranging from +14.6 to +15.5‰ (n = 8). This range is comparable to that of Triassic seawater sulphates. Sulphide minerals yielded δ34SVCDT values between 0 and + 11.7‰ (n = 15), indicating that sulphide sulphur was likely derived from Triassic sulphates through thermochemical sulphate reduction (TSR) because fluid inclusion microthermometric measurements yielded a mean temperature of 150 °C. Residual sulphate in such a system would have been enriched in 34S; this is reflected in the barite δ34SVCDT values, which range from +21.1 to +33.5‰ (n = 5). The δ13CVPDB values of calcite minerals, ranging from +2.1 to +6.3‰ (n = 4), indicate an inorganic carbon origin, likely from the host carbonate rocks. δ18OVSMOW values were between +21.9 and + 24.9‰, indicating that the most likely source of mineralizing fluids was formation water.

  13. Inelastic neutron scattering studies of phonon spectra, and simulations of pressure-induced amorphization in tungstates A W O4 (A =Ba ,Sr ,Ca , and Pb )

    NASA Astrophysics Data System (ADS)

    Goel, Prabhatasree; Gupta, M. K.; Mittal, R.; Rols, S.; Achary, S. N.; Tyagi, A. K.; Chaplot, S. L.

    2015-03-01

    Lattice dynamics and high-pressure phase transitions in A W O4 (A =Ba ,Sr ,Ca , and Pb ) have been investigated using inelastic neutron scattering experiments, ab initio density functional theory calculations, and extensive molecular dynamics simulations. The vibrational modes that are internal to W O4 tetrahedra occur at the highest energies consistent with the relative stability of W O4 tetrahedra. The neutron data and the ab initio calculations are found to be in excellent agreement. The neutron and structural data are used to develop and validate an interatomic potential model. The model is used for classical molecular dynamics simulations to study their response to high pressure. We have calculated the enthalpies of the scheelite and fergusonite phases as a function of pressure, which confirms that the scheelite to fergusonite transition is second order in nature. With increase in pressure, there is a gradual change in the A O8 polyhedra, while there is no apparent change in the W O4 tetrahedra. We found that all the four tungstates amorphize at high pressure. This is in good agreement with available experimental observations which show amorphization at around 45 GPa in BaW O4 and 40 GPa in CaW O4 . Further molecular dynamics simulations at high pressure and high temperature indicate that application of pressure at higher temperature hastens the process of amorphization. On amorphization, there is an abrupt increase in the coordination of the W atom while the bisdisphenoids around the A atom are considerably distorted. The pair-correlation functions of the various atom pairs corroborate these observations. Our observations aid in predicting the pressure of amorphization in SrW O4 and PbW O4 .

  14. Al doped Ba hexaferrite (BaAlxFe12-xO19) thin films on Pt using metallo-organic decomposition

    NASA Astrophysics Data System (ADS)

    Harward, I.; Nie, Yan; Gardner, A.; Reisman, L.; Celinski, Z.

    2012-04-01

    We grew a series of aluminum-substituted M-type barium hexaferrite (BaAlxFe12-xO19) thin films on a Pt (111) template and Si wafer using metallo-organic decomposition technique. We varied the composition from x = 0 to x = 2 with 0.25 step increments. X-ray diffraction patterns confirm highly textured c-axis polycrystalline films while atomic force microscope measurements allow us to estimate the lateral grain sizes which range from 0.2-1 micron depending on Al content. The microwave properties of these films were studied using a broadband ferromagnetic resonance spectrometer from 35 to 70 GHz. The measured out of plane effective anisotropy field increases in a nearly linear fashion with increasing Al concentration, between 12.8 kOe for x = 0 and 25 kOe for x = 2. The measured ferromagnetic resonance linewidths were relatively low, on the order of 150-300 Oe for compositions below x = 1, increasing significantly up to 800 Oe for x = 2. The easy axis magnetic hysteresis loops exhibit high squareness.

  15. EFFECT OF Sn AND Pb ADDITIONS ON MICROSTRUCTURE OF Mg-6Al-1Zn AS-CAST MAGNESIUM ALLOYS

    NASA Astrophysics Data System (ADS)

    Hou, Haibo; Zhu, Tianping; Wang, Yuxin; Gao, Wei

    2013-07-01

    Much attention has been paid to Mg alloys given that Mg alloys are the most promising lightweight metallic material. They have found applications in automobile and other fields where weight saving is of great significance. Mg-Al-Zn alloy system (AZ series), including AZ91 and AZ61 Mg alloys, is widely used in industry. We have studied the enhancement of mechanical properties by adding alloying elements Sn and Pb. This paper reports our study on the microstructure and element distribution of the alloys with small amounts of tin (Sn) and lead (Pb) additions.

  16. Frequency upconversion luminescence in Yb3+-sensitized Er3+- and Pr3+-codoped PbGeO3:PbF2:xF2 (x = Mg, Ba) glass

    NASA Astrophysics Data System (ADS)

    Silva, Alexandre O.; Gouveia-Neto, Artur; Bueno, Luciano A.

    2016-01-01

    The optical properties and energy-transfer upconversion luminescence of Er3+- and Pr3+/Yb3+-codoped PbGeO3-PbF2-xF2 (x=Mg, Ba) glass and glass-ceramic under infrared excitation at 975 nm is investigated. In Er3+/Yb3+-codoped samples, green (525 and 550 nm) and red (662 nm) luminescence corresponding to the H2→I4, S4→I4 e F4→I4, respectively, was readily observed. In the Pr3+/Yb3+-codoped system, emission peaks around 485, 530, 610, and 645, which were ascribed to the P03-HJ3 (J=4,5,6) and P03-FJ3 (J=2,3,4) transitions, respectively, were observed. The population of the praseodymium P03 emitting level was accomplished through a combination of ground-state absorption of Yb ions at F2, energy-transfer Yb3+(F2)-Pr3+(H43), and excited-state absorption of Pr ions provoking the G41-P03 transition. The dependence of the upconversion emission on glass composition, pump power, and doping contents was also examined. Glassy and glass-ceramic samples were compared in order to determine the system with better luminescence efficiency.

  17. Coupled heat and fluid flow modeling of the Carboniferous Kuna Basin, Alaska: Implications for the genesis of the Red Dog Pb-Zn-Ag-Ba ore district

    USGS Publications Warehouse

    Garven, G.; Raffensperger, J.P.; Dumoulin, J.A.; Bradley, D.A.; Young, L.E.; Kelley, K.D.; Leach, D.L.

    2003-01-01

    The Red Dog deposit is a giant 175 Mton (16% Zn, 5% Pb), shale-hosted Pb-Zn-Ag-Ba ore district situated in the Carboniferous Kuna Basin, Western Brooks Range, Alaska. These SEDEX-type ores are thought to have formed in calcareous turbidites and black mudstone at elevated sub-seafloor temperatures (120-150??C) within a hydrogeologic framework of submarine convection that was structurally organized by large normal faults. The theory for modeling brine migration and heat transport in the Kuna Basin is discussed with application to evaluating flow patterns and heat transport in faulted rift basins and the effects of buoyancy-driven free convection on reactive flow and ore genesis. Finite element simulations show that hydrothermal fluid was discharged into the Red Dog subbasin during a period of basin-wide crustal heat flow of 150-160 mW/m2. Basinal brines circulated to depths as great as 1-3 km along multiple normal faults flowed laterally through thick clastic aquifers acquiring metals and heat, and then rapidly ascended a single discharge fault zone at rates ??? 5 m/year to mix with seafloor sulfur and precipitate massive sulfide ores. ?? 2003 Elsevier Science B.V. All rights reserved.

  18. Co-Dopant Influence on the Persistent Luminescence of BaAl2O4:Eu2+,R3+

    NASA Astrophysics Data System (ADS)

    Rodrigues, Lucas C. V.; Hölsä, Jorma; Carvalho, José M.; Pedroso, Cássio C. S.; Lastusaari, Mika; Felinto, Maria C. F. C.; Watanabe, Shigeo; Brito, Hermi F.

    2014-04-01

    The R3+ (rare earth) co-dopants may have a surprisingly important role in persistent luminescence - enhancement of up to 1-3 orders of magnitude may be obtained in the performance of these phosphor materials - depending strongly on the R3+ ion, of course. In this work, the effects of the R3+ co-dopants in the BaAl2O4:Eu2+,R3+ materials were studied using mainly thermoluminescence (TL) and synchrotron radiation XANES methods. In BaAl2O4, the conventional and persistent luminescence both arise from the 4f7→4f65d1 transition of Eu2+, yielding blue-green emission color. The former, in the presence of humidity, turns to more bluish because of creation of an additional Eu2+ luminescence centre which is not, however, visible in persistent luminescence. The trap structure in the non-co-doped BaAl2O4:Eu2+ is rather complex with 4-5 TL bands above room temperature. With R3+ co-doping, this basic structure is modified though no drastic change can be observed. This underlines the fact that even very small changes in the trap depths can produce significant modifications in the persistent luminescence efficiency. It should be remembered that basically the persistent luminescence performance is controlled by the Boltzmann population law depending exponentially on both the temperature and trap depth. Some mechanisms for persistent luminescence have suggested the presence of either divalent R2+ or tetravalent RIV during the charging of the Eu2+ doped materials. The present XANES measurements on BaAl2O4:Eu2+,R3+ confirmed the presence of only the trivalent form of the R3+ co-dopants excluding both of these pathways. It must thus be concluded, that the energy is stored in intrinsic and extrinsic defects created by the synthesis conditions and charge compensation due to R3+ co-doping. Even though the effect of the R3+ co-dopants was carefully exploited and characterized, the differences in the effect of different R3+ ions with very similar chemical and spectroscopic properties could

  19. Effect of A-site La and Ba doping on threshold field and characteristic temperatures of PbSc0.5Ta0.5O3 relaxor studied by acoustic emission

    NASA Astrophysics Data System (ADS)

    Dul'kin, E.; Mihailova, B.; Gospodinov, M.; Roth, M.

    2012-09-01

    The structural transitions in Pb1-xLaxSc(1+x)/2Ta(1-x)/2O3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) [E. Dul'kin et al., EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at Tn = 276 K, lying in the vicinity of dielectric temperature maximum (Tm). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of Tn previously observed for both the PST and PBST, namely, Tn initially decreases with the increase of E, attains a minimum at a threshold field Eth = 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate Ṅ = 12 s-1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to Tn, Eth, and Ṅ are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb2+ by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of Tn and Eth, whereas the latter is shown to affect the normalized Ṅ, indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.

  20. Effect of coexisting Al(III) ions on Pb(II) sorption on biochars: Role of pH buffer and competition.

    PubMed

    Yang, Yuxi; Zhang, Weihua; Qiu, Hao; Tsang, Daniel C W; Morel, Jean-Louis; Qiu, Rongliang

    2016-10-01

    Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III). PMID:27454898

  1. The crystal structure of bøgvadite (Na2SrBa2Al4F20)

    NASA Astrophysics Data System (ADS)

    Balić-Žunić, Tonči

    2014-08-01

    The crystal structure of bøgvadite, Na2SrBa2Al4F20, has been solved and refined to a R1 factor of 4.4 % from single-crystal data (Mo Kα X-ray diffraction, CCD area detector) on a sample from the cryolite deposit at Ivittuut, SW Greenland. Bøgvadite is monoclinic, P21/ n space group, with unit cell parameters a = 7.134(1), b = 19.996(3) and c = 5.3440(8) Å, β = 90.02(1)o. A close proximity of the crystal structure to an orthorhombic symmetry and the presence of the two twin components in a nearly 1:1 ratio suggest that the investigated bøgvadite crystal has originally formed as a high-temperature orthorhombic polymorph which on cooling transformed to the stable low temperature monoclinic structure. The bøgvadite crystal structure has groupings of cation-fluoride coordination polyhedra similar to those found in the crystal structures of the genetically closely associated minerals jarlite and jørgensenite. However, its structure type is different from the latter two. The fluoridoaluminate framework of bøgvadite consists of infinite zig-zag chains of cis-connected AlF6 coordination octahedra. The 1 ∞[AlF5] chains are interconnected by infinite chains of Na-F coordination polyhedra which extend in the same direction. Na is coordinated by nine F atoms if its full surrounding is taken in consideration, but makes significant chemical bonds only to closest five. The chains of AlF6 and NaF9 coordination polyhedra form double layers. In the centre of layers, relatively large voids in the form of pentagonal antiprisms are occupied by Sr atoms which make chemical bonds with the closest six F atoms. Between the SrF10 coordinations in the centre of layers run empty channels. The double layers are interconnected by Ba atoms which are coordinated by eight F atoms and fill the spaces between the layers. Bøgvadite belongs to the group of fluoridoaluminates with infinite chains of cis-connected AlF6 coordination octahedra, alike those found in the crystal structures of Ba-fluoridoaluminates.

  2. Soot oxidation and NO{sub x} reduction over BaAl{sub 2}O{sub 4} catalyst

    SciTech Connect

    Lin, He; Li, Yingjie; Shangguan, Wenfeng; Huang, Zhen

    2009-11-15

    This study addresses soot oxidation and NO{sub x} reduction over a BaAl{sub 2}O{sub 4} catalyst. By XRD analysis, the catalyst was shown to be of spinel structure. Temperature Programmed Oxidation (TPO) and Constant Temperature Oxidation (CTO) at 673 K show that the presence of O{sub 2} decreases the ignition temperature of soot, and it enhances the conversion of NO{sub x} to N{sub 2} and N{sub 2}O. The kinetic features of soot oxidation in the TPO test are similar to that in the TG-DTA analysis. Analysis by Diffuse Reflectance Fourier Infrared Transform Spectroscopy (DRIFTS) indicates that the nitrates formed from NO{sub x} adsorption and the C(O) intermediates from soot oxidation are the key precursors of the redox process between soot and NO{sub x} over surfaces of the BaAl{sub 2}O{sub 4} catalyst. Moreover, DRIFTS tests suggest that nitrates act as the principal oxidants for C(O) oxidation, through which nitrates are reduced to N{sub 2} and N{sub 2}O. The O{sub 2} in the gas mixture presents a positive effect on the conversion of NO{sub x} to N{sub 2} and N{sub 2}O by promoting the oxidation of nitrites into nitrates species. (author)

  3. Evolution of structure and physical properties in Al-substituted Ba-hexaferrites

    NASA Astrophysics Data System (ADS)

    Alex, Trukhanov; Larisa, Panina; Sergei, Trukhanov; Vitalii, Turchenko; Mohamed, Salem

    2016-01-01

    The investigations of the crystal and magnetic structures of the BaFe12-xAlxO19 (x = 0.1-1.2) solid solutions have been performed with powder neutron diffractometry. Magnetic properties of the BaFe12-xAlxO19 (x = 0.1-1.2) solid solutions have been measured by vibration sample magnetometry at different temperatures under different magnetic fields. The atomic coordinates and lattice parameters have been Rietveld refined. The invar effect is observed in low temperature range (from 4.2 K to 150 K). It is explained by the thermal oscillation anharmonicity of atoms. The increase of microstress with decreasing temperature is found from Rietveld refinement. The Curie temperature and the change of total magnetic moment per formula unit are found for all compositions of the BaFe12-xAlxO19 (x = 0.1-1.2) solid solutions. The magnetic structure model is proposed. The most likely reasons and the mechanism of magnetic structure formation are discussed. Project supported by the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST “MISiS” (Grant No. K4-2015-040). L. Panina acknowledges support under the Russian Federation State contract for organizing a scientific work.

  4. Structural and photoluminescent properties of nanosized BaMgAl10O17:Eu2+ blue-emitting phosphors prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Van Bui, Hao; Nguyen, Tu; Nguyen, Manh Cuong; Tran, Trong An; Le Tien, Ha; Tam Tong, Hao; Nguyen, Thi Kim Lien; Pham, Thanh Huy

    2015-09-01

    We report on the photoluminescent properties of Ba0.9Eu0.1MgAl10O17 (BAM) phosphors in correlation with the host crystalline structures. The phosphors were synthesized by citrate sol-gel process, followed by a sintering and a reduction step, both at elevated temperatures. We found that the phosphors were amorphous when sintered at temperatures below 900 °C. At 1000 °C, the crystalline structure was mainly that of BaAl2O4 phase. The BaMgAl10O17 phase appeared at 1100 °C, and became dominant with increasing temperature. At 1300 °C, the BaAl2O4 phase almost disappeared, and only BaMgAl10O17 features were found. The luminescent characteristics of the phosphors were closely related to the structures of the host lattice. Under the same reduction conditions, the phosphors sintered at 1000 °C showed the emission of both Eu3+ and Eu2+. For the phosphors sintered at higher temperatures, the main features were originated from the emission of Eu2+. We additionally observed the increase of emission intensity and the broadening of emission spectra with increasing reduction temperature.

  5. Structure, infrared and Raman spectroscopic studies of newly synthetic AII(SbV0.50FeIII0.50)(PO4)2 (Adbnd Ba, Sr, Pb) phosphates with yavapaiite structure

    NASA Astrophysics Data System (ADS)

    Aatiq, Abderrahim; Tigha, My Rachid; Fakhreddine, Rachid; Bregiroux, Damien; Wallez, Gilles

    2016-08-01

    The synthesis and structural study of three new AII(SbV0.5FeIII0.5)(PO4)2 (Adbnd Ba, Sr, Pb) phosphates belonging to the Asbnd Sbsbnd Fesbnd Psbnd O system were reported here for the first time. Structures of [Ba], [Sr] and [Pb] compounds, obtained by solid state reaction in air atmosphere, were determined at room temperature from X-ray powder diffraction using the Rietveld method. BaII(SbV0.5FeIII0.5)(PO4)2 features the yavapaiite-type structure, with space group C2/m, Z = 2 and a = 8.1568(4) Å; b = 5.1996(3) Å c = 7.8290(4) Å; β = 94.53(1)°. AII(SbV0.5FeIII0.5)(PO4)2 (Adbnd Sr, Pb) compounds have a distorted yavapaiite structure with space group C2/c, Z = 4 and a = 16.5215(2) Å; b = 5.1891(1) Å c = 8.0489(1) Å; β = 115.70(1)° for [Sr]; a = 16.6925(2) Å; b = 5.1832(1) Å c = 8.1215(1) Å; β = 115.03(1)° for [Pb]. Raman and Infrared spectroscopic study was used to obtain further structural information about the nature of bonding in selected compositions.

  6. Li {sub x}Pb{sup II} {sub 1-2x}M{sup III} {sub x}O (M = Al, Fe): A new solid solution series related to yellow PbO

    SciTech Connect

    Tripathy, Mamata; Mani, Rohini; Gopalakrishnan, J. . E-mail: gopal@sscu.iisc.ernet.in

    2006-12-14

    New series of oxides, Li {sub x}Pb{sub 1-2x}M {sub x}O (M = Al, Fe), for 0PbO structure have been synthesized by solid state reaction of Li{sub 2}CO{sub 3}, Pb(NO{sub 3}){sub 2} and Al{sub 2}O{sub 3}/FeC{sub 2}O{sub 4}.2H{sub 2}O in air at 650-680 deg. C. Optical absorption spectra reveal systematic increase/decrease of electronic band gap E {sub g} for the Al/Fe members as compared to the parent yellow PbO. Partial deintercalation of lithium occurs under oxidative conditions (Br{sub 2}/CH{sub 3}CN) with both the series.

  7. Mineralogy and fluid inclusions study of carbonate-hosted Mississippi valley-type Ain Allega Pb-Zn-Sr-Ba ore deposit, Northern Tunisia

    NASA Astrophysics Data System (ADS)

    Abidi, R.; Slim-Shimi, N.; Somarin, A.; Henchiri, M.

    2010-05-01

    The Ain Allega Pb-Zn-Sr-Ba ore deposit is located in the flysch zone on the Eastern edge of the Triassic diapir of Jebel Hamra. It is part of the extrusive Triassic evaporate formation along the Ghardimaou-Cape Serrat faults. The ore body consists of argilic-dolomite breccias surrounded by argilo-gypsum Triassic formation, which forms the hanging wall of the deposit, and rimmed by the Paleocene marls. The ore minerals show a cap-rock type mineralization with different styles particularly impregnation in dolomite, cement of breccias, replacement ore and open space filling in the dissolution cavities and fractures. Ore minerals include sphalerite, galena, marcasite and pyrite. Principal gangue minerals are composed of barite, celestite, calcite, dolomite and quartz. The ore minerals are hosted by the Triassic carbonate rocks which show hydrothermal alteration, dissolution and brecciation. X-ray - crystallographic study of barite-celestite mineral series shows that pure barite and celestite are the abundant species, whereas strontianiferous barite (85-96.5% BaSO 4) and barian-celestite (95% SrSO 4) are minor. Primary and secondary mono-phase (liquid only) fluid inclusions are common in celestite. Microthermometric analyses in two-phases (liquid and vapour) fluid inclusions suggest that gangue and ore minerals were precipitated by a low-temperature (180 °C) saline (16.37 wt.% NaCl equivalent) solution originated possibly from a basinal brine with some input from magmatic or metamorphic fluid. Based on geology, mineralogy, texture and fluid characteristics, the Ain Allega deposit is classified as a carbonate-hosted Mississippi valley-type deposit.

  8. Synthesis of PbS-Al2O3 nanocomposites by sol-gel process and studies on their optical properties

    NASA Astrophysics Data System (ADS)

    Yadav, Sudheer Kumar; Jeevanandam, P.

    2015-08-01

    PbS-Al2O3 nanocomposites were prepared by a single step sol-gel method starting from lead acetate, thiourea and aluminium isopropoxide. The crystallinity, shape of crystallites and optical properties of the nanocomposites were examined by various analytical techniques. X-ray diffraction indicates that the PbS-Al2O3 nanocomposites consist of small PbS crystallites (18.2-40.5 nm). Transmission electron microscopy images show cube-like and flake-like morphology for pure PbS and Al2O3, respectively and TEM images of the nanocomposites indicate uniform distribution of PbS nanoparticles on the Al2O3 matrix. Diffuse reflectance spectral (DRS) studies on the nanocomposites indicate near infrared (NIR) absorption and the nanocomposites exhibit blue shift of the band gap of PbS compared to pure PbS nanoparticles. Photoluminescence studies show characteristic peak due to excitonic emission of PbS nanoparticles in the nanocomposites.

  9. Synthesis of (Hg,Pb)(Sr,Ba) 2Ca 2Cu 3O z superconducting films via MOCVD and PLD

    NASA Astrophysics Data System (ADS)

    Klimonsky, S. O.; Samoilenkov, S. V.; Gorbenko, O. Yu.; Emelianov, D. A.; Lyashenko, A. V.; Lee, S. R.; Kaul, A. R.; Tretyakov, Yu. D.; Andrianov, D. G.; Kalinov, A. V.; Voloshin, I. F.

    2002-12-01

    (0 0 1)-oriented Sr-containing (Hg,Pb)-1223 films have been synthesised for the first time using the two-step procedure. Hg-free precursor films with the thickness up to 1 μm have been deposited by metalorganic chemical vapor deposition (MOCVD) or pulsed infra-red laser ablation (PLD) and then the films were annealed in a mercury-containing atmosphere in sealed quartz ampoules. No post-annealing in oxygen was used. The phase composition of the PLD-derived films depended crucially on the deposition temperature of the precursor films. MOCVD-derived films contained only very small amounts of non-superconducting phases according to XRD. The Tc=118 K and j c(77 K,0.01 T)=2.5×10 6A/cm 2 have been measured for the MOCVD-derived samples.

  10. Effect of Eu substitution on superconductivity in Ba{sub 8−x}Eu{sub x}Al{sub 6}Si{sub 40} clathrates

    SciTech Connect

    Liu, Lihua; Bi, Shanli; Peng, Bailu; Li, Yang

    2015-05-07

    The silicon clathrate superconductor is uncommon as its structure is dominated by strong Si-Si covalent bonds, rather than the metallic bond, that are more typical of traditional superconductors. To understand the influence of large magnetic moment of Eu on superconductivity for type-I clathrates, a series of samples with the chemical formula Ba{sub 8−x}Eu{sub x}Al{sub 6}Si{sub 40} (x = 0, 0.5, 1, and 2) were synthesised in which Eu occupied Ba sites in cage center. With the increase of Eu content, the cubic lattice parameter decreases monotonically signifying continuous shrinkage of the constituting (Ba/Eu)@Si{sub 20} and (Ba/Eu)@Si{sub 24} cages. The temperature dependence of magnetization at low temperature revealed that Ba{sub 8}Al{sub 6}Si{sub 40} is superconductive with transition temperature at T{sub C} = 5.6 K. The substitution of Eu for Ba results in a strong superconductivity suppression; Eu-doping largely decreases the superconducting volume and transition temperature T{sub C}. Eu atoms enter the clathrate lattice and their magnetic moments break paired electrons. The Curie-Weiss temperatures were observed at 3.9, 6.6, and 10.9 K, respectively, for samples with x = 0.5, 1.0, and 2.0. Such ferromagnetic interaction of Eu can destroy superconductivity.

  11. Measurement of gamma-ray production cross sections in neutron-induced reactions for Al and Pb

    SciTech Connect

    Pavlik, A.; Vonach, H.; Hitzenberger, H.; Nelson, R.O.; Haight, R.C.; Wender, S.A.; Young, P.G.; Chadwick, M.B.

    1995-02-01

    The prompt gamma-radiation from the interaction of fast neutrons with aluminum and lead was measured using the white neutron beam of the WNR facility at the Los Alamos National Laboratory. The samples (Al and isotopically enriched {sup 207}Pb and {sup 208}Pb) were positioned at about 20 m or 41 m distance from the neutron production target. The spectra of the emitted gamma-rays were measured with a high-resolution HPGe detector. The incident neutron energy was determined by the time-of-flight method and the neutron fluence was measured with a U fission chamber. From the aluminum gamma-ray spectra excitation functions for prominent gamma-transitions in various residual nuclei (in the range from O to Al) were derived for neutron energies from 3 MeV to 400 MeV. For lead (n,xn{gamma}) reactions were studied for neutron energies up to 200 MeV by analyzing prominent gamma-transitions in the residual nuclei {sup 200,202,204,206,207,208}Pb. The experimental results were compared with nuclear model calculations using the code GNASH. A good overall agreement was obtained without special parameter adjustments.

  12. Crystal structure of the solid solution (Sr1.65Pb0.35)Al6O11

    PubMed Central

    Weil, Matthias

    2014-01-01

    The title compound, di(strontium/lead) hexa­aluminate, is a member of the solid solution series (Sr2-xPbx)Al6O11. It contains two statistically occupied M 2+ (M = Sr, Pb) sites [both with site symmetries ..m; Sr:Pb occupancy ratios = 0.756 (2):0.244 (2) and 0.8968 (19):0.1032 (19)] that are located in the voids of an aluminate framework. The M 2+ sites are surrounded by six and seven O atoms, respectively, if a cut-off M—O distance of 3 Å is chosen, resulting in considerably distorted MOx polyhedra. The aluminate framework consists of three AlO6 octa­hedra (two with point-group symmetries ..2/m and one with ..2) sharing edges to form partially filled layers extending parallel to (100) and located at x = 0, 0.5. Adjacent AlO6 layers are linked by a network made up from two crystallographically different AlO4 tetra­hedra by sharing corners. PMID:25309169

  13. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    NASA Astrophysics Data System (ADS)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-08-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  14. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    NASA Astrophysics Data System (ADS)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-08-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  15. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    NASA Astrophysics Data System (ADS)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-01-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  16. Conventional and Spark Plasma Sintered Ba0.8Pb0.2TiO3 Nano Ceramics: Structural, Dielectric, and Ferroelectric Properties

    NASA Astrophysics Data System (ADS)

    Mudinepalli, Venkata Ramana; Leng, Feng; Lin, W. C.; Murty, B. S.

    2016-06-01

    Ba0.8Pb0.2TiO3 nanocrystalline ferroelectric ceramics were prepared by high-energy ball mill followed by spark plasma sintering and conventional sintering techniques. Sintering behavior, microstructure, dielectric properties, and ferroelectric properties were investigated by XRD, SEM, dielectric spectrometer, and ferroelectric P-E loop tracer. It was found that the densification process was greatly enhanced during SPS. The sintering temperature was 673 K (400 °C) lower and the microstructure was much finer than that of conventionally sintered ceramics, and dense compacts with a higher density of over 99 pct were obtained. The average grain size in the conventionally sintered samples is up to about 200 nm, while that in the spark plasma sintered prepared sample is only about 100 nm. The room temperature and transition temperature dielectric constant of spark plasma-sintered samples is higher than that of the conventionally sintered sample. There is a noticeable difference in processing time between conventional sintering and spark plasma sintering, and the latter offers potential advantage in time saving also.

  17. Metastable antiparallel polarization configurations in BaTiO3/PbZr0.2Ti0.8O3 epitaxial bilayer

    NASA Astrophysics Data System (ADS)

    Salev, Pavel; Grigoriev, Alexei

    A combination of LGD and semiconductor theories predicts the electrostatic screening of a large polarization mismatch between BaTiO3 (BTO) and Pb(Zr,Ti)O3 (PZT) ferroelectric layers. The source of this screening is in an increased concentration of interfacial free charge carriers due to the strong bending of electronic bands inside the layers. The enhanced concentration of free charges at the interface can allow for independent polarization reversal in each ferroelectric layer suggesting possible antiparallel polarization configurations in BTO/PZT bilayer. We confirmed these theoretical predictions of layer-by-layer switching by demonstrating double polarization switching in epitaxial BTO/PZT thin films. The layer-by-layer switching leads to formation of head-to-head (H-H) and tail-to-tail (T-T) polarization configurations, which have an enhanced dielectric permittivity when compared to parallel polarization domain configurations. While both H-H and T-T states are unstable at a zero electric field, we found that antiparallel polarization configurations can be stabilized by applying a small bias. Our findings provide a pathway to engineer new multilayer systems with switchable multistate polarizations and dielectric responses.

  18. Enhancement of the Electrical Properties in BaTiO3/PbZr0.52Ti0.48O3 Ferroelectric Superlattices.

    PubMed

    He, Bin; Wang, Zhanjie

    2016-03-01

    In this study, BaTiO3/Pb(Zr0.52Ti0.48)O3 (BTO/PZT) ferroelectric superlattices have been grown on the Nb-doped SrTiO3 (NSTO) single-crystal substrate by pulsed laser deposition, and their electrical properties were investigated in detail. The leakage current was reduced significantly in the BTO/PZT superlattices, and the conduction mechanism could be interpreted as the bulk-limited mechanism. In addition, a more symmetric hysteresis loop was observed in the BTO/PZT superlattices compared with the pure PZT and BTO films. The BTO/PZT superlattices with the modulation thickness of 9.8 nm showed remarkably improved dielectric properties with dielectric constant and loss of 684 and 0.02, respectively, measured at the frequency of 10 kHz. Based on these experimental results, it can be considered that the BTO/PZT interfaces play a very important role for the enhanced electrical properties of the BTO/PZT superlattices. PMID:26913563

  19. Effect of Heat Treatment in Air on Thermoelectric Properties of Polycrystalline Type-I Silicon-Based Clathrate: Ba8Al15Si31

    NASA Astrophysics Data System (ADS)

    Anno, Hiroaki; Shirataki, Ritsuko

    2015-06-01

    The effect of heat treatment in air on the thermoelectric properties was investigated for polycrystalline Ba8Al15Si31, where the Al content is almost at the maximum in the Ba8Al x Si46- x system, to evaluate the thermal stability in air at high temperatures, which is indispensable for practical use in thermoelectric applications. Samples were prepared by combining arc melting and spark plasma sintering techniques. Heat treatments were performed in air at 873 K for 10 days and 20 days. The Seebeck coefficient, electrical conductivity, and thermal conductivity were measured before and after the heat treatments. The microstructure and chemical composition were also analyzed before and after the heat treatments, using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Although an oxidation layer was formed on the surface by the heat treatment in air, the chemical composition of the interior of Ba8Al15Si31 was found to be stable in air at 873 K for 10 days and 20 days. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity were found to be almost unchanged after the heat treatment, indicating that Ba8Al15Si31 clathrate is promising as a thermoelectric material with high thermal stability for use in air at 873 K.

  20. Ferroelectricity driven magnetism at domain walls in LaAlO3/PbTiO3 superlattices

    PubMed Central

    Zhou, P. X.; Dong, S.; Liu, H. M.; Ma, C. Y.; Yan, Z. B.; Zhong, C. G.; Liu, J. -M.

    2015-01-01

    Charge dipole moment and spin moment rarely coexist in single-phase bulk materials except in some multiferroics. Despite the progress in the past decade, for most multiferroics their magnetoelectric performance remains poor due to the intrinsic exclusion between charge dipole and spin moment. As an alternative approach, the oxide heterostructures may evade the intrinsic limits in bulk materials and provide more attractive potential to realize the magnetoelectric functions. Here we perform a first-principles study on LaAlO3/PbTiO3 superlattices. Although neither of the components is magnetic, magnetic moments emerge at the ferroelectric domain walls of PbTiO3 in these superlattices. Such a twist between ferroelectric domain and local magnetic moment, not only manifests an interesting type of multiferroicity, but also is possible useful to pursuit the electrical-control of magnetism in nanoscale heterostructures. PMID:26269322

  1. Ferroelectricity driven magnetism at domain walls in LaAlO3/PbTiO3 superlattices.

    PubMed

    Zhou, P X; Dong, S; Liu, H M; Ma, C Y; Yan, Z B; Zhong, C G; Liu, J-M

    2015-01-01

    Charge dipole moment and spin moment rarely coexist in single-phase bulk materials except in some multiferroics. Despite the progress in the past decade, for most multiferroics their magnetoelectric performance remains poor due to the intrinsic exclusion between charge dipole and spin moment. As an alternative approach, the oxide heterostructures may evade the intrinsic limits in bulk materials and provide more attractive potential to realize the magnetoelectric functions. Here we perform a first-principles study on LaAlO3/PbTiO3 superlattices. Although neither of the components is magnetic, magnetic moments emerge at the ferroelectric domain walls of PbTiO3 in these superlattices. Such a twist between ferroelectric domain and local magnetic moment, not only manifests an interesting type of multiferroicity, but also is possible useful to pursuit the electrical-control of magnetism in nanoscale heterostructures. PMID:26269322

  2. Nanocomposite bulk of mechanically milled Al-Pb samples consolidated pore-free by the high-energy rate forming technique.

    PubMed

    Csanády, Agnes; Sajó, István; Lábár, János L; Szalay, András; Papp, Katalin; Balaton, Géza; Kálmán, Erika

    2005-06-01

    It is shown that pore-free bulk samples were produced by the high-energy rate forming axis-symmetrical powder compaction method for different application purposes in case of the very different, immiscible Al and Pb metal pair. The starting Al-Pb nanocomposites were made by mechanical milling of atomized Al and Pb powders either in a SPEX 9000 or a Fritsch Pulverisette 4 mill. Due to the conditions that milling was carried out in air, the PbO layer, originally existing at the surface of the atomized Pb powder, ruptured and was also dispersed in the composite. The presence of the nano PbO particles was proven by XRD and TEM (BF, DF, SAED). When the energy of milling was high, the PbO crystallites became so small that they could hardly be seen by XRD technique. Local distribution of the PbO nanoparticles was still visible in a TEM, using the process diffraction method. Both XRD and SAED proved to be useful for the evaluation of the results of the milling process and compaction. PMID:16060145

  3. Interfacial Reactions Between BaAl2Si2O8 and Molten Al Alloy at 1423 K and 1523 K (1150 °C and 1250 °C)

    NASA Astrophysics Data System (ADS)

    Adabifiroozjaei, E.; Koshy, P.; Pardehkhorram, R.; Rastkerdar, E.; Hart, J.; Sorrell, C. C.

    2016-06-01

    This work investigates the interfacial interactions of Al7075 alloy with BaAl2Si2O8 at high temperatures [1423 K and 1523 K (1150 °C and 1250 °C)]. X-ray diffraction, electron probe microanalysis, and scanning electron microscopy coupled with energy dispersive spectroscopy were used to identify the mineralogical and microstructural changes at the interfaces. The vaporization, migration, and subsequent oxidation of alloying constituents (Mg and Zn) in contact with BaAl2Si2O8 caused intense interfacial phase transformations, forming spinel solid solution, magnesia solid solution, celsian-based solid solution, and barium magnesium silicate solid solution. The driving force for these phase transformations at the reaction front is the interdiffusion processes between Al (or Mg/Zn)-Si and Mg (or Zn)-Ba that occurs owing to the relative elemental gradients. The rate-limiting step of corrosion kinetics was identified to be Ba substitution in the MgO structure. The corrosion mechanism (extensive phase transformation of Ba-celsian by interdiffusion processes) at high temperatures was found to be different from that observed at lower temperatures [1123 K (850 °C)].

  4. Blue, yellow and orange color emitting rare earth doped BaCa2Al8O15 phosphors prepared by combustion method

    NASA Astrophysics Data System (ADS)

    Yerpude, A. N.; Dhoble, S. J.; Reddy, B. Sudhakar

    2014-12-01

    Eu2+, Dy3+, Sm3+ activated BaCa2Al8O15 phosphors were prepared by the combustion method. The phosphor powders were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectrophotometer. Photoluminescence spectra of BaCa2Al8O15:Eu2+ phosphors show emission wavelength at 435 nm that corresponds to 4f65d1→4f7 transition of Eu2+ ion by keeping excitation wavelength extending broad-band from 270 to 400 nm centered at 334 nm. The Dy3+ doped BaCa2Al8O15 phosphors shows blue emission (485 nm) and yellow emission (566 nm) under the excitation of 347 nm, corresponding to the 4F9/2→6H15/2 transition and 4F9/2→6H13/2 transition of Dy3+ ions, respectively. The Sm3+ doped BaCa2Al8O15 phosphors have shown strong orange emission at 604 nm corresponding to the 4G5/2→6H7/2 transition of Sm3+ with intense excitation wavelength at 406 nm. Scanning electron microscopy has been used for exploring the size and morphological properties of the prepared phosphors. The obtained results show that the phosphors have potential application in the field of solid state lighting.

  5. Tunable full-color emitting BaMg2Al6Si9O30:Eu2+, Tb3+, Mn2+ phosphors based on energy transfer.

    PubMed

    Lü, Wei; Hao, Zhendong; Zhang, Xia; Luo, Yongshi; Wang, Xiaojun; Zhang, Jiahua

    2011-08-15

    A series of single-phase full-color emitting BaMg(2)Al(6)Si(9)O(30):Eu(2+), Tb(3+), Mn(2+) phosphors has been synthesized by solid-state reaction. Energy transfer from Eu(2+) to Tb(3+) and Eu(2+) to Mn(2+) in BaMg(2)Al(6)Si(9)O(30) host matrix is studied by luminescence spectra and energy-transfer efficiency and lifetimes. The wavelength-tunable white light can be realized by coupling the emission bands centered at 450, 542, and 610 nm ascribed to the contribution from Eu(2+) and Tb(3+) and Mn(2+), respectively. By properly tuning the relative composition of Tb(3+)/Mn(2+), chromaticity coordinates of (0.31, 0.30), high color rendering index R(a) = 90, and correlated color temperature (CCT) = 5374 K can be achieved upon excitation of UV light. Thermal quenching properties reveal that BaMg(2)Al(6)Si(9)O(30): Eu(2+), Tb(3+), Mn(2+) exhibits excellent characteristics even better than that of YAG:Ce. Our results indicate our white BaMg(2)Al(6)Si(9)O(30):Eu(2+), Tb(3+), Mn(2+) can serve as a key material for phosphor-converted light-emitting diode and fluorescent lamps. PMID:21766885

  6. New oxyfluoride glass with high fluorine content and laser patterning of nonlinear optical BaAlBO{sub 3}F{sub 2} single crystal line

    SciTech Connect

    Shionozaki, K.; Honma, T.; Komatsu, T.

    2012-11-01

    A new oxyfluoride glass of 50BaF{sub 2}-25Al{sub 2}O{sub 3}-25B{sub 2}O{sub 3} (mol. %) with a large fraction of fluorine, i.e., F/(F + O) = 0.4, was prepared using a conventional melt-quenching method in order to synthesize new glass-ceramics containing nonlinear optical oxyfluoride crystals. The refractive index at 632.8 nm and ultra-violet cutoff wavelength of the glass were 1.564 and {approx}200 nm, respectively. Eu{sup 3+} ions in the glass showed a high quantum yield of 88% in the photoluminescence spectrum in the visible region. BaAlBO{sub 3}F{sub 2} crystals (size: 50-100 nm) showing second harmonic generations were formed through the crystallization of the glass. Lines consisting of BaAlBO{sub 3}F{sub 2} crystals were patterned successfully on the glass surface by laser irradiations (Yb:YVO{sub 4} laser with a wavelength of 1080 nm, laser power of 1.1 W, scanning speed of 8 {mu}m/s). High resolution transmission electron microscope observations combined with a focused ion beam technique indicate that BaAlBO{sub 3}F{sub 2} crystals are highly oriented just like a single crystal. The present study proposes that the new oxyfluoride glass and glass-ceramics prepared have a high potential for optical device applications.

  7. Water-Induced Morphology Changes in BaO/gamma-Al2O3 NOx Storage Materials: an FTIR, TPD, and Time-Resolved Synchrotron XRD Study

    SciTech Connect

    Szanyi,J.; Kwak, J.; Kim, D.; Wang, X.; Chimentao, R.; Hanson, J.; Epling, W.; Peden, C.

    2007-01-01

    The effect of water on the morphology of BaO/Al{sub 2}O{sub 3}-based NO{sub x} storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO{sub 3}){sub 2} particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO{sub 2} exposure of a H{sub 2}O-containing (wet) BaO/Al{sub 2}O{sub 3} sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO{sub 2}, the nitrites completely convert to bulk nitrates. The amount of NO{sub x} taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO{sub 2} exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NO{sub x} uptake on similar storage materials.

  8. Novel Magnetic and Charge Orders in Dimer-Chain Iridate Ba5AlIr2O11

    NASA Astrophysics Data System (ADS)

    Ye, Feng; Terzic, J.; Wang, J. C.; Song, W. H.; Yuan, S. J.; Aswartham, S.; Cao, G.

    2015-03-01

    We report a novel magnetic state coexisting with a charge ordering state in a dimer-chain system Ba5AlIr2O11. This newly synthesized single-crystal iridate features both tetravalent Ir4+ and pentavalent Ir5+ ions in each of dimers that are only linked via AlO4-tetrahedra along the b-axis. Despite the evident one-dimensional characteristic, the dimer-chains undergo an unexpected long-rang order at TM = 4.5 K with a large magnetic anisotropy. The magnetic transition is unusually resilient to magnetic field up to 14 T but more susceptible to even modest hydrostatic pressure up to 10 kbar. Furthermore, a subtle structural change discerned at TS = 200 K marks a charge ordering that accompanies a huge enhancement in the dielectric constant and changes in the electrical resistivity. It is evident that the strong SOC imposes a j =1/2 (Ir4+) and singlet j =0 (Ir5+) states in each dimer, which critically hinges on the orbital and lattice degrees of freedom. This work was supported by NSF via Grant DMR 1265162.

  9. Crystal structure and luminescence properties of a novel red-emitting phosphor BaAlBO{sub 3}F{sub 2}:Eu{sup 3+}

    SciTech Connect

    Chen, Wanping Zhou, Ahong; Liu, Yan; Dai, Xiaoyan; Yang, Xin

    2014-12-15

    A series of novel red-emitting phosphors BaAlBO{sub 3}F{sub 2}:xEu{sup 3+} (0.001≤x≤0.08) were first synthesized via a high temperature solid-state reaction. X-ray diffraction and photoluminescence spectroscopy were used to characterize the crystal structure and photoluminescence properties of the phosphor, respectively. The phosphor can be effectively excited with a 395 nm light, and shows a dominant {sup 5}D{sub 0}−{sup 7}F{sub 2} emission with chromatic coordination of 0.628 and 0.372. The optimal doping concentration is about 0.04. Rietveld refinement results and the luminescence behavior of Eu{sup 3+} indicate that the Eu{sup 3+} ion occupies a C{sub 3} symmetry site, and the host BaAlBO{sub 3}F{sub 2} has a hexagonal structure with P-6 space group. In addition, the phosphor could be a potential candidate as red-emitting phosphor for application in white light-emitting diode. - Graphical abstract: The luminescence behavior and Rietveld refinement of BaAlBO{sub 3}F{sub 2}:Eu{sup 3+} indicate that the red-emitting phosphor has potential application in white LED and the host has a hexagonal structure with P-6 space group. - Highlights: • A novel red-emitting phosphor BaAlBO{sub 3}F{sub 2}:Eu{sup 3+} is first synthesized. • The crystal structure of BaAlBO{sub 3}F{sub 2} is confirmed. • The phosphor shows potential application in white LED.

  10. The crystal structure of tin sulphate, SnSO[subscript 4], and comparison with isostructural SrSO[subscript 4], PbSO[subscript 4], and BaSO[subscript 4

    SciTech Connect

    Antao, Sytle M.

    2012-10-23

    The crystal structure of tin (II) sulphate, SnSO{sub 4}, was obtained by Rietveld refinement using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. The structure was refined in space group Pbnm. The unit-cell parameters for SnSO{sub 4} are a = 7.12322(1), b = 8.81041(1), c = 5.32809(1) {angstrom}, and V = 334.383(1) {angstrom}{sup 3}. The average [12] distance is 2.9391(4) {angstrom}. However, the Sn{sup 2+} cation has a pyramidal [3]-coordination to O atoms and the average [3] = 2.271(1) {angstrom}. If Sn is considered as [12]-coordinated, SnSO{sub 4} has a structure similar to barite, BaSO{sub 4}, and its structural parameters are intermediate between those of BaSO{sub 4} and PbSO{sub 4}. The tetrahedral SO{sub 4} group has an average [4] = 1.472(1) {angstrom} in SnSO{sub 4}. Comparing SnSO{sub 4} with the isostructural SrSO{sub 4}, PbSO{sub 4}, and BaSO{sub 4}, several well-defined trends are observed. The radii, rM, of the M{sup 2+}(=Sr, Pb, Sn, and Ba) cations and average distances vary linearly with V because of the effective size of the M{sup 2+} cation. Based on the trend for the isostructural sulphates, the average [12] distance is slightly longer than expected because of the lone pair of electrons on the Sn{sup 2+} cation.

  11. Structural, Thermal and Electrical Study of Multiferroic BiFeO3 Ceramic with Al3+ and Ba2+ Co-substitution

    NASA Astrophysics Data System (ADS)

    Wang, GeMing; Kothari, Deepti; Reddy, V. Raghavendra; Gupta, Ajay

    BiFe1-xAlxO3(x=0.05, 0.1) and BixBa1-xFe0.95Al0.05O3 (x=0.05, 0.07) ceramics were synthesized and their crystal structure, thermal and ferroelectric properties were investigated. X-ray diffraction and Raman data of the ceramics showed all the samples were rhombohedral with small crystal structure distortion. DSC results revealed the evolution of Neel Temperature (TN) by Al and Ba co-doping. The substitution of Al3+ at Fe site changes the TN significantly. Doping effects in terms of crystal structure, electrical property variation are discussed in this paper.

  12. Synthesis, structural characterization and properties of SrAl{sub 4−x}Ge{sub x}, BaAl{sub 4−x}Ge{sub x}, and EuAl{sub 4−x}Ge{sub x} (x≈0.3–0.4)—Rare examples of electron-rich phases with the BaAl{sub 4} structure type

    SciTech Connect

    Zhang, Jiliang; Bobev, Svilen

    2013-09-15

    Three solid solutions with the general formula AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)) have been synthesized via the aluminum self-flux method, and their crystal structures have been established from powder and single-crystal X-ray diffraction. They are isotypic and crystallize with the well-known BaAl{sub 4} structure type, adopted by the three AEAl{sub 4} end members. In all structures, Ge substitutes Al only at the 4e Wyckoff site. Results from X-rays photoelectron spectroscopy on EuAl{sub 4−x}Ge{sub x} and EuAl{sub 4} indicate that the interactions between the Eu{sup 2+} cations and the polyanionic framework are enhanced in the Ge-doped structure, despite the slightly elevated Fermi level. Magnetic susceptibility measurements confirm the local moment magnetism, expected for the [Xe]4f{sup 7} electronic configuration of Eu{sup 2+} and suggest strong ferromagnetic interactions at cryogenic temperatures. Resistivity data from single-crystalline samples show differences between the title compounds, implying different bonding characteristics despite the close Debye temperatures. A brief discussion on the observed electron count and homogeneity ranges for AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba) is also presented. - Graphical abstract: AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)), three “electron-rich” phases with BaAl{sub 4} structure type have been synthesized and characterized. Display Omitted - Highlights: • Three BaAl{sub 4}-type ternary aluminum germanides have been synthesized with Eu, Sr and Ba. • Eu, Sr and Ba cations have no apparent influence on the solubility of Ge. • The Ge atoms substitute Al on one of two framework sites, thereby strengthening the interactions between the cations and the polyanionic framework.

  13. Optically stimulated luminescence (OSL) response of Al2O3:C, BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors.

    PubMed

    Kumar, Pratik; Bahl, Shaila; Sahare, P D; Kumar, Surender; Singh, Manveer

    2015-12-01

    This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors for different doses and bleaching durations. The results have also been compared with the commercially available Landauer Al2O3:C (Luxel®) dosemeter. Nanocrystalline K2Ca2(SO4)3:Eu is known to be a sensitive thermoluminescent phosphor, but its OSL response is hardly reported. At first, pellets of nanocrystalline K2Ca2(SO4)3:Eu powder were prepared by adding Teflon as a binder. Their OSL signal was compared with that of the material in pure form, i.e. without adding the binder (in 100:1 ratio). It was observed that adding the binder does not appreciably affect the OSL intensity. On comparison with the commercially available Al2O3:C from Landauer, it was found that K2Ca2(SO4)3:Eu is around 15 times less sensitive than Al2O3:C. 'Homemade' BaFCl:Eu phosphor has also been studied. The intensity of BaFCl:Eu was ∼20 times more than the standard Al2O3:C dosemeter and ∼200 times more sensitive than K2Ca2(SO4)3:Eu in the dose range of 13-200 cGy. OSL dosemeters are believed to give luminescence signal even if they are read before, i.e. multiple reading may be possible under suitable conditions after single exposure. This was also checked for all the prepared dosemeters and it was found that Al2O3:C showed the least decrease of <2 %, followed by BaFCl:Eu of 15 % and K2Ca2(SO4)3:Eu with 20 %. Finally, Al2O3:C and BaFCl:Eu phosphors were also studied for their optical bleaching durations to which the respective signals get completely removed so that the phosphor can be re-used. It was observed that BaFCl:Eu is bleached faster and more easily than Al2O3:C. PMID:25646524

  14. A salt diapir-related Mississippi Valley-type deposit: The Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: Fluid inclusion and isotope study

    USGS Publications Warehouse

    Bouhlel, Salah; Leach, David; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-01-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian–Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ∼110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained

  15. Synthesis and structural characterization of the ternary Zintl phases AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As)

    SciTech Connect

    He, Hua; Tyson, Chauntae; Saito, Maia; Bobev, Svilen

    2012-04-15

    Ten new ternary phosphides and arsenides with empirical formulae AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) have been synthesized using molten Ga, Al, and Pb fluxes. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4} crystallize with the Ca{sub 3}Al{sub 2}As{sub 4} structure type (space group C2/c, Z=4); Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt the Na{sub 3}Fe{sub 2}S{sub 4} structure type (space group Pnma, Z=4). The polyanions in both structures are made up of TrPn{sub 4} tetrahedra, which share common corners and edges to form {sup 2}{sub {infinity}}[TrPn{sub 2}]{sub 3-} layers in the phases with the Ca{sub 3}Al{sub 2}As{sub 4} structure, and {sup 1}{sub {infinity}}[TrPn{sub 2}]{sub 3-} chains in Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} with the Na{sub 3}Fe{sub 2}S{sub 4} structure type. The valence electron count for all of these compounds follows the Zintl-Klemm rules. Electronic band structure calculations confirm them to be semiconductors. - Graphical abstract: AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) crystallize in two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4}, are isotypic with the previously reported Ca{sub 3}Al{sub 2}As{sub 4} (space group C2/c (No. 15)), while Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt a different structure known for Na{sub 3}Fe{sub 2}S{sub 4} (space group Pnma (No. 62

  16. Crystallization behavior and properties of BaO-Al2O3-2SiO2 glass matrices

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III; Bansal, Narottam P.

    1990-01-01

    Glass of stoichiometric celsian composition, BaO-Al2O3-SiO2, has a density of 3.39 g/cu cm, a thermal expansion coefficient of 6.6 x 10 to the -6th/C, a glass-transition temperature of 910 C, and a dilatometric softening point of 925 C. On heat treatment, only hexacelsian crystallized out on the surface, but both celsian and hexacelsian were present in the bulk. Effects of cold isostatic pressing (CIP), sintering, and hot-pressing, in the presence and absence of an additive, on the formation of the celsian phase in the glass have been studied. CIP'd samples, after appropriate heat treatments, always crystallized out as celsian, whereas presence of 5-10 wt pct of an additive was necessary for formation of celsian in sintered as well as hot-pressed specimens. Green density increased with CIP'ing pressure but had no effect on sintered density. Hot-pressing resulted in fully dense samples.

  17. Morphology control and luminescence properties of BaMgAl 10O 17:Eu 2+ phosphors prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Zhou, Yonghui; Lin, Jun

    2005-02-01

    Starting from the aqueous solutions of metal nitrates with citric acid and polyethylene glycol (PEG) as additives, BaMgAl 10O 17:Eu 2+ (BAM:Eu 2+) phosphors were prepared by a two-step spray pyrolysis (SP) method. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulted BAM:Eu 2+ phosphors. The obtained BAM:Eu 2+ phosphor particles have spherical shape, submicron size (0.5-3 μm). The effects of process conditions of the spray pyrolysis, such as molecular weight and concentration of PEG, on the morphology and luminescence properties of phosphor particles were investigated. Adequate amount of PEG was necessary for obtaining spherical particles, and the optimum emission intensity could be obtained when the concentration of PEG was 0.03 g/ml in the precursor solution. Moreover, the emission intensity of the phosphors increased with increasing of metal ion concentration in the solution. Compared with the BAM:Eu 2+ phosphor prepared by citrate-gel method, spherical BAM:Eu 2+ phosphor particles showed a higher emission intensity.

  18. Crystallization behavior and properties of BaO-Al2O3-2SiO2 glass matrices

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III; Bansal, Narottam P.

    1990-01-01

    Glass of stoichiometric celsian composition, BaO-Al2O3-2SiO2, is a potential glass-ceramic matrix for high-temperature composites. The glass has a density of 3.39 g/cu cm, thermal expansion coefficient of 6.6 x 10(exp -6)/deg C glass transition temperature of 910 C, and dilatometric softening point of 925 C. On heat treatment, only hexacelsian crystallized out on the surface, but both celsian and hexacelsian were present in the bulk. Effects of cold isostatic pressing (CIP), sintering, and hot pressing, in the presence and absence of an additive, on the formation of the celsian phase in the glass were studied. CIP'ed samples, after appropriate heat treatments, always crystallized out as celsian whereas the presence of 5 to 10 weight percent of an additive was necessary for formation of celsian in sintered as well as hot pressed specimens. Green density increased with CIP'ing pressure but had no effect on sintered density. Hot pressing resulted in fully dense samples.

  19. Time-Dependent Negative Capacitance Effects in Al2O3/BaTiO3 Bilayers.

    PubMed

    Kim, Yu Jin; Yamada, Hiroyuki; Moon, Taehwan; Kwon, Young Jae; An, Cheol Hyun; Kim, Han Joon; Kim, Keum Do; Lee, Young Hwan; Hyun, Seung Dam; Park, Min Hyuk; Hwang, Cheol Seong

    2016-07-13

    The negative capacitance (NC) effects in ferroelectric materials have emerged as the possible solution to low-power transistor devices and high-charge-density capacitors. Although the steep switching characteristic (subthreshold swing < sub-60 mV/dec) has been demonstrated in various devices combining the conventional transistors with ferroelectric gates, the actual applications of the NC effects are still some way off owing to the inherent hysteresis problem. This work reinterpreted the hysteretic properties of the NC effects within the time domain and demonstrated that capacitance (charge) boosting could be achieved without the hysteresis from the Al2O3/BaTiO3 bilayer capacitors through short-pulse charging. This work revealed that the hysteresis phenomenon in NC devices originated from the dielectric leakage of the dielectric layer. The suppression of charge injection via the dielectric leakage, which usually takes time, inhibits complete ferroelectric polarization switching during a short pulse time. It was demonstrated that a nonhysteretic NC effect can be achieved only within certain limited time and voltage ranges, but that these are sufficient for critical device applications. PMID:27231754

  20. High-pressure modifications of CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2}: Implications for Laves phase structural trends

    SciTech Connect

    Kal, Subhadeep; Stoyanov, Emil; Belieres, Jean-Philippe; Groy, Thomas L.; Norrestam, Rolf; Haeussermann, Ulrich

    2008-11-15

    High-pressure forms of intermetallic compounds with the composition CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2} were synthesized from CeCu{sub 2}-type precursors (CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}) and Ba{sub 21}Al{sub 40} by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl{sub 2} and BaAl{sub 2}), X-ray single-crystal diffraction (CaZn{sub 2}), and electron microscopy (SrZn{sub 2}). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu{sub 2} (C15) structure, the dizincides adopt the hexagonal MgZn{sub 2} (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions. - Graphical abstract: CeCu{sub 2}-type polar intermetallics can be transformed to Laves phases upon simultaneous application of pressure and temperature. The observed structures are controlled by the valence electron concentration.

  1. Two competing soft modes and an unusual phase transition in the stuffed tridymite-type oxide BaAl2O4

    NASA Astrophysics Data System (ADS)

    Ishii, Y.; Mori, S.; Nakahira, Y.; Moriyoshi, C.; Park, J.; Kim, B. G.; Moriwake, H.; Taniguchi, H.; Kuroiwa, Y.

    2016-04-01

    We investigated the structural phase transition of BaAl2O4 , which has a network structure with corner-sharing AlO4 tetrahedra, via synchrotron x-ray thermal diffuse scattering measurements and first-principles calculations. BaAl2O4 shows the structural phase transition at TC=451.4 K from the P 6322 parent crystal structure to the low-temperature superstructure with a cell volume of 2 a ×2 b ×c . This phase transition is unusual, in which two energetically competing phonon modes at M and K points soften simultaneously. When approaching TC from above, the K -point mode appears first. However, this K -point mode is overcome by the later-developed M -point mode. The thermal diffuse scattering intensities from both modes increase sharply at TC; therefore, both modes soften simultaneously. The first-principles calculations demonstrate that the M -point mode is electrostatically more preferable than the K -point mode and determines the eventual low-temperature structure, although these two modes are competing energetically. This competition is characteristic of BaAl2O4 , which is ascribed to the structurally flexible network structure of this compound.

  2. Effect of Sr 2+-doping on structure and luminescence properties of BaAl 2Si 2O 8:Eu 2+ phosphors

    NASA Astrophysics Data System (ADS)

    Ma, Mingxing; Zhu, Dachuan; Zhao, Cong; Han, Tao; Cao, Shixiu; Tu, Mingjing

    2012-03-01

    Sr 2+ doped BaAl 2Si 2O 8:Eu 2+ phosphor was synthesized by chemical co-precipitation method. With the increase of Sr 2+ concentration, the phase structure of (Ba 0.965 - x Sr xEu 0.035)Al 2Si 2O 8 changes from hexagonal phase to monoclinic phase owing to large activation energy in SrAl 2Si 2O 8 system. (Ba 0.965 - x Sr xEu 0.035)Al 2Si 2O 8 phosphor exhibits a broad blue band peaking at 425 nm due to the 4f 65d-4f 7( 8S 7/2) transition of Eu 2+ ions. The emission intensity increases, accompanied by the blue shift of emission maximum from 459 to 417 nm with the Sr 2+ doping concentration increasing. The optimal concentration of Sr 2+ ion is 40%, and the phosphor shows high color stability in CIE chromaticity diagram. The result indicates that Sr 2+ doped phosphor not only can enhance the relative intensity but also can adjust the chromaticity coordinate.

  3. Water-induced morphology changes in BaO/γ-Al2O3 NOx storage materials: an FTIR, TPD, and time-resolved synchrotron XRD study

    SciTech Connect

    Szanyi, Janos; Kwak, Ja Hun; Kim, Do Heui; Wang, Xianqin; Chimentao, Ricardo J.; Hanson, Jonathan; Epling, William S.; Peden, Charles HF

    2007-03-29

    The effect of water on the morphology of BaO/Al2O3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multi-spectroscopy study reveal that, in the presence of water, surface Ba-nitrates convert to bulk nitrates, and water facilitates the formation of large Ba(NO3)2 particles. This process is completely reversible, i.e. after the removal of water from the storage material a significant fraction of the bulk nitrates re-convert to surface nitrates. NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively, i.e. no surface nitrates form. After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material is, however, essentially unaffected by the presence of water, regardless of whether the water was dosed prior to or after NO2 exposure. Based on the results of this study we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.

  4. Microstructure of screen-printed (Tl 0.5,Pb 0.5)(Sr 0.8,Ba 0.2) 2Ca 2Cu 3O y superconducting films on untextured silver substrate

    NASA Astrophysics Data System (ADS)

    Kim, Bong-Jun; Kim, Hyun-Tak; Matsui, Yoshio; Jeong, Dae-Yong; Deinhofer, Christian; Gritzner, Gerhard

    2007-09-01

    Highly c-axis oriented (Tl 0.5,Pb 0.5)(Sr 0.8,Ba 0.2) 2Ca 2Cu 3O y films with a thickness of ∼1.5 μm and ∼4 μm were prepared by screen printing method on untextured silver substrates. Tl-1223 films have the critical temperatures around 116 K with transition widths, Δ T, of 2 K, The microstructures have been investigated by high-resolution transmission electron microscopy. Tl-1223 film deposited on well-polished Ag substrate shows large single domains in the lateral direction including secondary phases and intergrowth of Tl-1212, 2201 and 1234. From selected area electron diffraction (SAED) pattern, secondary phase is determined as BaCuO 2, which plays an important role in flux pinning to improve magnetic properties. And the relationships between the domain size, alignment and the surface roughness are studied.

  5. Effect of Slag Composition on the Distribution Behavior of Pb between FetO-SiO2 (-CaO, Al2O3) Slag and Molten Copper

    NASA Astrophysics Data System (ADS)

    Heo, Jung Ho; Park, Soo-Sang; Park, Joo Hyun

    2012-10-01

    The distribution behavior of Pb between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K (1200 °C) and p_{{{{O}}2 }} = 10^{ - 10} {{atm}} in view of the reaction mechanism of Pb dissolution into the slag. Furthermore, the lead capacity of the slag was estimated from the experimental results. The distribution ratio of Pb ( L Pb) decreases with increasing CaO content ( 6 mass pct) irrespective of Fe/SiO2 ratio (1.4 to 1.7). However, the addition of alumina into a slag with Fe/SiO2 = 1.5 linearly decreases the L Pb, whereas a minimum value is observed at about 4 mass pct Al2O3 at Fe/SiO2 = 1.3. The log L Pb continuously decreases with increasing Fe/SiO2 ratio, and the addition of Al2O3 (5 to 15 mass pct) into the silica-saturated iron silicate slag (Fe/SiO2 < 1.0) yields the highest Pb distribution ratio. This is mainly due to a decrease in the FeO activity even at silica saturation. The log L Pb linearly decreases by increasing the log (Fe3+/Fe2+) value. The Pb distribution ratio increases and the excess free energy of PbO decreases with increasing Cu2O content in the slag. However, from the viewpoint of copper loss into the slag, the silica-saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in the slag phase at a low Cu2O content. The lead capacity was defined in the current study and shows a linear correlation with the activity of FeO in a logarithmic scale, indicating that the concept of lead capacity is a good measure of absorption ability of Pb in iron silicate slags, and the activity of FeO can be a good basicity index in iron silicate slag.

  6. {110}-Layered B-cation ordering in the anion-deficient perovskite Pb2.4Ba2.6Fe2Sc2TiO13 with the crystallographic shear structure.

    PubMed

    Tyablikov, O A; Batuk, D; Tsirlin, A A; Batuk, M; Verchenko, V Yu; Filimonov, D S; Pokholok, K V; Sheptyakov, D V; Rozova, M G; Hadermann, J; Antipov, E V; Abakumov, A M

    2015-06-21

    A novel anion-deficient perovskite-based compound, Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13), was synthesized via the citrate-based route. This compound is an n = 5 member of the AnBnO(3n-2) homologous series with unit-cell parameters related to the perovskite subcell a(p)≈ 4.0 Å as a(p)√2 ×a(p)× 5a(p)√2. The crystal structure of Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) consists of quasi-2D perovskite blocks with a thickness of three octahedral layers separated by the 1/2[110](1[combining macron]01)(p) crystallographic shear (CS) planes, which are parallel to the {110} plane of the perovskite subcell. The CS planes transform the corner-sharing octahedra into chains of edge-sharing distorted tetragonal pyramids. Using a combination of neutron powder diffraction, (57)Fe Mössbauer spectroscopy and atomic resolution electron energy-loss spectroscopy we demonstrate that the B-cations in Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) are ordered along the {110} perovskite layers with Fe(3+) in distorted tetragonal pyramids along the CS planes, Ti(4+) preferentially in the central octahedra of the perovskite blocks and Sc(3+) in the outer octahedra of the perovskite blocks. Magnetic susceptibility and Mössbauer spectroscopy indicate a broadened magnetic transition around T(N)∼ 45 K and the onset of local magnetic fields at low temperatures. The magnetic order is probably reminiscent of that in other AnBnO(3n-2) homologues, where G-type AFM order within the perovskite blocks has been observed. PMID:25695142

  7. Fermi surface study of ScAu{sub 2}(Al, In) and ScPd{sub 2}(Sn, Pb) compounds

    SciTech Connect

    Reddy, P. V. Sreenivasa; Kanchana, V.; Vaitheeswaran, G.

    2015-06-24

    A detailed study on the electronic structure and Fermi surface (FS) of superconducting Heusler compounds ScAu{sub 2}(Al, In) and ScPd{sub 2}(Sn, Pb) has been carried out using first principles electronic structure calculations. The spin orbit coupling is found to play a major role in understanding the band structure and FS. Analysis of the data shows the importance of spin orbit coupling effect in the above compounds. The bands which cross Fermi level (EF) are found to be dominated by the Sc d{sub t2g}-states. The calculated total density of states are in good agreement with the experimentally reported value for ScPd{sub 2}Sn. Under compression we find a change in the Fermi surface topology of ScPd{sub 2}Sn at V/V{sub 0} = 0.95 (pressure of≈15 GPa), which is explained using the band structure calculations.

  8. A-SITE-AND/OR B-SITE-MODIFIED PBZRTIO3 MATERIALS AND (PB, SR, CA, BA, MG) (ZR, TI,NB, TA)O3 FILMS HAVING UTILITY IN FERROELECTRIC RANDOM ACCESS MEMORIES AND HIGH PERFORMANCE THIN FILM MICROACTUATORS

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2004-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  9. Eu2+ and Mn2+ Co-doped BaMgAl10O17 Blue- and Green-Emitting Phosphor: A Luminescence and EPR Study

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Sivaramaiah, G.; Rao, J. L.; Singh, N.; Srivastava, Anoop K.; Jirimali, H. D.; Li, J.; Gao, H.; Kumaran, R. Senthil; Singh, Pramod K.; Dhoble, S. J.

    2016-06-01

    Eu2+ and Mn2+ co-doped BaMgAl10O17 phosphor has been prepared by a solution combustion method. The structural, morphological and compositional analysis of the BaMgAl10O17:Eu2+ and Mn2+ powders have been studied by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The electron paramagnetic resonance (EPR) spectrum exhibited resonance signals with the effective g values of g ≈ 4.88 and g ≈ 1.98. The resonance signal with the effective g value of g ≈ 4.88 is characteristic of Eu2+ ions whereas g ≈ 1.98 is due to Mn2+ ions. The number of spins participating in resonance, Gibbs free energy, magnetic susceptibility, Curie constant, effective magnetic moment, zero-field splitting parameter and hyperfine splitting constant have been evaluated. From optical and EPR correlation, it is inferred that Eu2+ and Mn2+ are present in the BaMgAl10O17 matrix.

  10. High mobility field effect transistor based on BaSnO{sub 3} with Al{sub 2}O{sub 3} gate oxide

    SciTech Connect

    Park, Chulkwon; Kim, Useong; Ju, Chan Jong; Park, Ji Sung; Kim, Young Mo; Char, Kookrin

    2014-11-17

    We fabricated an n-type accumulation-mode field effect transistor based on BaSnO{sub 3} transparent perovskite semiconductor, taking advantage of its high mobility and oxygen stability. We used the conventional metal-insulator-semiconductor structures: (In,Sn){sub 2}O{sub 3} as the source, drain, and gate electrodes, Al{sub 2}O{sub 3} as the gate insulator, and La-doped BaSnO{sub 3} as the semiconducting channel. The Al{sub 2}O{sub 3} gate oxide was deposited by atomic layer deposition technique. At room temperature, we achieved the field effect mobility value of 17.8 cm{sup 2}/Vs and the I{sub on}/I{sub off} ratio value higher than 10{sup 5} for V{sub DS} = 1 V. These values are higher than those previously reported on other perovskite oxides, in spite of the large density of threading dislocations in the BaSnO{sub 3} on SrTiO{sub 3} substrates. However, a relatively large subthreshold swing value was found, which we attribute to the large density of charge traps in the Al{sub 2}O{sub 3} as well as the threading dislocations.

  11. Glass structure and NIR emission of Er3+ at 1.5 μm in oxyfluoride BaF2-Al2O3-B2O3 glasses

    NASA Astrophysics Data System (ADS)

    Shinozaki, Kenji; Pisarski, Wojciech; Affatigato, Mario; Honma, Tsuyoshi; Komatsu, Takayuki

    2015-12-01

    The glass structure, photoluminescence properties of Eu3+, Judd-Ofelt analysis, and near infrared emissions of Er3+ at 1.5 μm in the oxyfluoride glasses and glass-ceramics of 1Eu2O3- or 1Er2O3-doped 50BaF2-xAl2O3-(50 - x)B2O3 (x = 0-25 mol%) were investigated. It was clarified on the ground of Raman scattering spectroscopy and F1s and O1s XPS measurements that the glass with no Al2O3 (1Er2O3-50BaF2-50B2O3) is composed of BO3, BO2F and BO3F units with F-Ba bonds. The glasses with 25Al2O3 (1Er2O3-50BaF2-25Al2O3-25B2O3) is mainly composed of BO3- and Al(O,F)x units. Existence of non-bridging oxygen was not detected by O1s-XPS spectra. It was proposed that these structures are largely affected on crystallization behavior, e.g., the glass with no Al2O3 forms BaF2 and β-BaB2O4 due to Ba-F bonds and the glass with 25Al2O3 forms BaAlBO3F2 because the glass structure composed of BO3 and Al(O,F) units is similar to the BaAlBO3F2 crystal structure. Judd-Ofelt parameters of Er3+ and Eu3+ in the glasses showed almost the same values in Ω4 and Ω6 for each glass, on the other hand Ω2 decreased with addition of Al2O3. The emission spectra of Er3+ at 1.5 μm in the glasses and glass-ceramics with BaAlBO3F2 crystals showed broad peaks. It is proposed that oxyfluoride glasses and glass-ceramics based on the BaF2-Al2O3-B2O3 system have a high potential for optical device applications such as broadband optical amplifiers.

  12. Influence of electric field on local phase transformations in relaxor ferroelectrics PbSc0.5Ta0.5O3 and Pb0.78Ba0.22Sc0.5Ta0.5O3

    NASA Astrophysics Data System (ADS)

    Maier, B. J.; Steilmann, T.; Gospodinov, M.; Bismayer, U.; Mihailova, B.

    2012-12-01

    In situ temperature-dependent Raman-scattering experiments under an external dc electric field E have been performed on PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba) in order to give further insights into the atomistic mechanism of polar coupling in perovskite-type (ABO3) relaxor ferroelectrics near the intermediate characteristic temperature T⋆. The polarized Raman spectra collected under an electric field E applied along the cubic [100], [110], or [111] crystallographic direction were analyzed in terms of hard-mode spectroscopy. The T⋆(E) dependence was derived from the behavior of the phonon mode near 230 cm-1 localized in off-centered B-site cations. In the case of stoichiometric PST, the increase of T⋆ with E is much stronger when the field is applied along [111] than when E is along [100] or [110]. This indicates that the actual polar B-cation shifts are along the cubic body diagonals, implying a rhombohedral structure of the polar nanoregions. The T⋆(E)-dependence reveals that the local structural distortions associated with locally coupled polar displacements of B-site cations reach saturation near 0.5 kV/cm. When Pb2+ is partially replaced by Ba2+, the strong increase of T⋆ with E occurs if the electric field is applied along the [110] direction. This indicates that the substitution disorder on the A-site lowers the symmetry of the polar nanoregions to orthorhombic or monoclinic. The T⋆(E) dependence determined from the B-cation localized mode shows saturation near 2.0 kV/cm, indicating that the zero-field structural state of PST-Ba exhibits less coupled polar shifts of B-site cations as compared to that of PST. According to the E-dependence of the Raman scattering near 55 cm-1, for both compounds the overall response of the Pb system to the external electric field in the vicinity of T⋆(E) resembles antiferroelectric behavior, which along with the fact that the coupling between the B-site cations is ferroelectric, suggests that

  13. Multilevel Resistance Switching Memory in La2/3Ba1/3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (011) Heterostructure by Combined Straintronics-Spintronics.

    PubMed

    Zhou, Weiping; Xiong, Yuanqiang; Zhang, Zhengming; Wang, Dunhui; Tan, Weishi; Cao, Qingqi; Qian, Zhenghong; Du, Youwei

    2016-03-01

    We demonstrate a memory device with multifield switchable multilevel states at room temperature based on the integration of straintronics and spintronics in a La2/3Ba1/3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) (011) heterostructure. By precisely controlling the electric field applied on the PMN-PT substrate, multiple nonvolatile resistance states can be generated in La2/3Ba1/3MnO3 films, which can be ascribed to the strain-modulated metal-insulator transition and phase separation of Manganite. Furthermore, because of the strong coupling between spin and charge degrees of freedom, the resistance of the La2/3Ba1/3MnO3 film can be readily modulated by magnetic field over a broad temperature range. Therefore, by combining electroresistance and magnetoresistance effects, multilevel resistance states with excellent retention and endurance properties can be achieved at room temperature with the coactions of electric and magnetic fields. The incorporation of ferroelastic strain and magnetic and resistive properties in memory cells suggests a promising approach for multistate, high-density, and low-power consumption electronic memory devices. PMID:26846130

  14. Structure-property correlation over five phases and four transitions in Pb5Al3F19.

    PubMed

    Abrahams, S C; Ravez, J; Ritter, H; Ihringer, J

    2003-10-01

    The calorimetric and dielectric properties of Pb(5)Al(3)F(19) in the five phases stable under ambient pressure are correlated with structure for fuller characterization of each phase. The first-order transition between ferroelectric phase V and antiferroelectric phase IV at T(V,IV) = 260 (5) K exhibits a thermal hysteresis of 135 (5) K on heating, with a maximum atomic displacement Delta(xyz)(max) = 1.21 (6) A; the transition from phase IV to ferroelastic phase III at 315 (5) K is also first order but with a thermal hysteresis of 10 (5) K and Delta(xyz)(max) = 0.92 (7) A; that from phase III to paraelastic phase II at 360 (5) K is second order without hysteresis and has Delta(xyz)(max) = 0.69 (4) A; and the transition from phase II to paraelectric phase I at 670 (5) K is second or higher order, with Delta(xyz)(max) = 0.7 (4) A. The measured entropy change DeltaS at T(V,IV) agrees well with DeltaS as derived from the increased configurational energy by Stirling's approximation. For all other phase transitions, 0.5 > or = DeltaS > 0 J mol(-1) K(-1) is consistent with an entropy change caused primarily by the changes in the vibrational energy. The structure of phase III is determined both by group theoretical/normal mode analysis and by consideration of the structures of phases II, IV and V reported previously; refinement is by simultaneous Rietveld analysis of the X-ray and neutron diffraction powder profiles. The structure of prototypic phase I is predicted on the basis of the atomic arrangement in phases II, III, IV and V. The introduction of 3d electrons into the Pb(5)Al(3)F(19) lattice disturbs the structural equilibrium, the addition of 0.04% Cr(3+) causing significant changes in atomic positions and increasing T(IV,III) by approximately 15 K. Substitution of Al(3+) by 20% or more Cr(3+) eliminates the potential minima that otherwise stabilize phases IV, III and II. PMID:14586075

  15. Thermoluminescence and synchrotron radiation studies on the persistent luminescence of BaAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+}

    SciTech Connect

    Rodrigues, L.C.V.; Stefani, R.; Brito, H.F.; Felinto, M.C.F.C.; Hoelsae, J.; Lastusaari, M.; Laamanen, T.; Malkamaeki, M.

    2010-10-15

    The persistent luminescence materials, barium aluminates doped with Eu{sup 2+} and Dy{sup 3+} (BaAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+}), were prepared with the combustion synthesis at temperatures between 400 and 600 {sup o}C as well as with the solid state reaction at 1500 {sup o}C. The concentrations of Eu{sup 2+}/Dy{sup 3+} (in mol% of the Ba amount) ranged from 0.1/0.1 to 1.0/3.0. The electronic and defect energy level structures were studied with thermoluminescence (TL) and synchrotron radiation (SR) spectroscopies: UV-VUV excitation and emission, as well as with X-ray absorption near-edge structure (XANES) methods. Theoretical calculations using the density functional theory (DFT) were carried out in order to compare with the experimental data. - Graphical abstract: BaAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+} phosphors: Thermoluminescence glow curve and synchrotron radiation spectra. Persistent luminescence photographs obtained after ceased UV irradiation.

  16. Pb(II) sorption onto gamma-Al2O3 surfaces at the oxide-water interface: a novel approach using planar oxides.

    PubMed

    Conrad, Christine F; Chisholm-Brause, Catherine J; Kelley, Michael J

    2002-04-15

    A novel technique for examining metal-ion interactions at the solid-water interface is introduced. Planar oxides, flat, thin coatings of uniform thickness created on a metal support, have been constructed as useful analogs for investigating metal-solid interactions under a variety of conditions. XPS and ToF/SIMS results from sorption studies at pH 6.0 show that the sorption behavior of Pb on each phase is similar with Pb binding preferentially to the bulk gamma-Al(2)O(3). This may be due to the presence of defect sites on the bulk oxides, the preferential exposure of a specific crystallographic plane in the planar oxides, or it may be an artifact of instrumental analysis. A second study examining Pb sorption to planar gamma-Al(2)O(3) under a series of increasingly complex conditions shows that our methods are able to successfully characterize sorption complexes formed in the presence of environmentally derived complexants. Results suggest that Pb is more strongly complexed by aqueous phase organic matter than sediment-bound organic material, indicating a possible control on Pb sorption in natural environments. Overall, the use of planar oxides combined with a powerful suite of spectroscopic tools provides a promising approach to better understanding metal ion sorption to natural sediment surfaces in aquatic environments. PMID:16290532

  17. Characterization of ZrO2 buffer layers for sequentially evaporated Y-Ba-CuO on Si and Al2O3 substrates

    NASA Technical Reports Server (NTRS)

    Valco, George J.; Rohrer, Norman J.; Pouch, John J.; Warner, Joseph D.; Bhasin, Kul B.

    1988-01-01

    Thin film high temperature superconductors have the potential to change the microwave technology for space communications systems. For such applications it is desirable that the films be formed on substrates such as Al2O3 which have good microwave properties. The use of ZrO2 buffer layers between Y-Ba-Cu-O and the substrate has been investigated. These superconducting films have been formed by multilayer sequential electron beam evaporation of Cu, BaF2 and Y with subsequent annealing. The three layer sequence of Y/BaF2/Cu is repeated four times for a total of twelve layers. Such a multilayer film, approximately 1 micron thick, deposited directly on SrTiO3 and annealed at 900 C for 45 min produces a film with a superconducting onset of 93 K and critical temperature of 85 K. Auger electron spectroscopy in conjunction with argon ion sputtering was used to obtain the distribution of each element as a function of depth for an unannealed film, the annealed film on SrTiO3 and annealed films on ZrO2 buffer layers. The individual layers were apparent. After annealing, the bulk of the film on SrTiO3 is observed to be fairly uniform while films on the substrates with buffer layers are less uniform. The Y-Ba-Cu-O/ZrO2 interface is broad with a long Ba tail into the ZrO2, suggesting interaction between the film and the buffer layer. The underlying ZrO2/Si interface is sharper. The detailed Auger results are presented and compared with samples annealed at different temperatures and durations.

  18. A-site- and/or B-site-modified PbZrTiO3 materials and (Pb, Sr, Ca, Ba, Mg) (Zr, Ti, Nb, Ta)O3 films having utility in ferroelectric random access memories and high performance thin film microactuators

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2001-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  19. Nd3+-doped TeO2-PbF2-AlF3 glasses for laser applications

    NASA Astrophysics Data System (ADS)

    Lalla, E. A.; Rodríguez-Mendoza, U. R.; Lozano-Gorrín, A. D.; Sanz-Arranz, A.; Rull, F.; Lavín, V.

    2016-01-01

    A study of the optical properties of Nd3+ ion in TeO2-PbF2-AlF3 glasses has been carried out for different Nd3+ concentrations. Based on the Judd-Ofelt theory, intensity parameters and radiative properties were determined from the absorption spectra. Focusing on the suitability of this host for laser applications, the spectroscopic quality factor χ was obtained with a value of 1.07, a value of the order of other compositions proposed as laser hosts. For the most intense emission corresponding with the 4F3/2 → 4I11/2 transition (1.06 μm), the absorption and emission and have been calculated with values of 1.20 × 10-20 cm2, 2.08 × 10-20 cm2. A positive value for the gain cross-sections has been found for a population inversion factor γ of 0.4 in the spectral range from 1060 to 1110 nm. All these results suggest the potentially use of this system as a laser host.

  20. Interfacial charge-induced polarization switching in Al2O3/Pb(Zr,Ti)O3 bi-layer

    NASA Astrophysics Data System (ADS)

    Kim, Yu Jin; Park, Min Hyuk; Jeon, Woojin; Kim, Han Joon; Moon, Taehwan; Lee, Young Hwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong

    2015-12-01

    Detailed polarization switching behavior of an Al2O3/Pb(Zr,Ti)O3 (AO/PZT) structure is examined by comparing the phenomenological thermodynamic model to the experimental polarization-voltage (P-V) results. Amorphous AO films with various thicknesses (2-10 nm) were deposited on the polycrystalline 150-nm-thick PZT film. The thermodynamic calculation showed that the transition from the ferroelectric-like state to the paraelectric-like state with increasing AO thickness occurs at ˜3 nm thickness. This paraelectric-like state should have exhibited a negative capacitance effect without permanent polarization switching if no other adverse effects are involved. However, experiments showed typical ferroelectric-like hysteresis loops where the coercive voltage increased with the increasing AO thickness, which could be explained by the carrier injection through the thin AO layer and trapping of the carriers at the AO/PZT interface. The fitting of the experimental P-V loops using the thermodynamic model considering the depolarization energy effect showed that trapped charge density was ˜±0.1 Cm-2 and critical electric field at the Pt electrode/AO interface, at which the carrier transport occurs, was ˜±10 MV/cm irrespective of the AO thickness. Energy band model at each electrostatic state along the P-V loop was provided to elucidate correlation between macroscopic polarization and internal charge state of the stacked films.

  1. NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on γ-Al2O3

    SciTech Connect

    Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

    2008-07-15

    NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on γ-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the γ-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/γ-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

  2. Critical magnetic fields of superconducting aluminum-substituted Ba{sub 8}Si{sub 42}Al{sub 4} clathrate

    SciTech Connect

    Li, Yang Garcia, Jose; Lu, Kejie; Shafiq, Basir; Franco, Giovanni; Lu, Junqiang; Rong, Bo; Chen, Ning; Liu, Yang; Liu, Lihua; Song, Bensheng; Wei, Yuping; Johnson, Shardai S.; Luo, Zhiping; Feng, Zhaosheng

    2015-06-07

    In recent years, efforts have been made to explore the superconductivity of clathrates containing crystalline frameworks of group-IV elements. The superconducting silicon clathrate is unusual in that the structure is dominated by strong sp{sup 3} covalent bonds between silicon atoms, rather than the metallic bonding that is more typical of traditional superconductors. This paper reports on critical magnetic fields of superconducting Al-substituted silicon clathrates, which were investigated by transport, ac susceptibility, and dc magnetization measurements in magnetic fields up to 90 kOe. For the sample Ba{sub 8}Si{sub 42}Al{sub 4}, the critical magnetic fields were measured to be H{sub C1} = 40.2 Oe and H{sub C2} = 66.4 kOe. The London penetration depth of 4360 Å and the coherence length 70 Å were obtained, whereas the estimated Ginzburg–Landau parameter of κ = 62 revealed that Ba{sub 8}Si{sub 42}Al{sub 4} is a strong type-II superconductor.

  3. Photoluminescence properties of Si-N-doped BaAl{sub 12}O{sub 19}:Mn{sup 2+} phosphors for three-dimensional plasma display panels

    SciTech Connect

    Liu, Bitao; Han, Boyu; Zhang, Feng; Wen, Yan; Zhu, Ge; Zhang, Jia; Wang, Yuhua

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer The brightness of Si-N-doped BHA phosphor is 119.9% of the un-doped BHA. Black-Right-Pointing-Pointer The decay time of Si-N-doped BHA phosphor is shorter than the un-doped sample. Black-Right-Pointing-Pointer The Si-N doping BHA is expected to be potentially applicable to 3D PDPs. -- Abstract: Si-N-doped BaAl{sub 12}O{sub 19}:Mn{sup 2+} phosphors were synthesized by a conventional solid-state reaction. It reveals that an efficiently host absorption in the vacuum ultraviolet region, which could be ascribed to the restricted Reidinger defects and oxygen vacancies by the Si-N doping. A fortified energy transfer from host to the activators was observed because of the newly formed defect energy levels which generated from the un-equivalence substitution of Si-N for Al-O. The shorter decay time of 4.05 ms was obtained which due to the increased defect concentration. This result indicates that Si-N doping BaAl{sub 12}O{sub 19}:Mn{sup 2+} phosphors would meet the requirements of 3D PDPs.

  4. 266  nm ultraviolet light generation in Ga-doped BaAlBO3F2 crystals.

    PubMed

    Yang, Lei; Yue, Yinchao; Yang, Feng; Hu, Zhanggui; Xu, Zuyan

    2016-04-01

    BaAlBO3F2 (BABF) crystals are a recently developed and promising nonlinear optical material, notably for the third harmonic generation of ultraviolet (UV) light at 355 nm. However, the fourth harmonic generation of UV light at 266 nm has never been obtained by using a BABF crystal due to its relatively small birefringence. We demonstrate that the birefringence of BABF can be effectively increased by doping it with Ga3+. The fourth harmonic generation of UV light at 266 nm was achieved for the first time in a Ga-doped BABF crystal. PMID:27192296

  5. Synthesis, characterization and TL response of Ce{sup 3+} activated BaMgAl{sub 10}O{sub 17} phosphor

    SciTech Connect

    Selot, Anupam; Aynyas, Mahendra; Tiwari, Manoj; Dev, Kapil

    2015-06-24

    Phosphor material BaMgAl{sub 10}O{sub 17} with varying concentration of rare earth Ce{sup 3+} synthesis by combustion method at 500°C. The synthesized phosphor material characterized for their crystallinity and nature by XRD measurements. The thermoluminescecne response of phosphor exhibit TL spectra at 204°c and detailed analysis of kinetic parameter by de convoluted curve. These results show that concentration quenching occur at 5mol% of Ce dopant. The results suggest the possibility of utilizing as a phosphor may be in UV dosimeter and solid state lighting.

  6. Accumulation of Al, Mn, Fe, Cu, Zn, Cd and Pb by the bryophyte Scapania undulata in three upland waters of different pH.

    PubMed

    Vincent, C D; Lawlor, A J; Tipping, E

    2001-01-01

    Measurements were made of the contents of Al, Mn, Fe, Cu, Zn, Cd and Pb in Scapania undulata in three streams (D2, D5, D11) in the English Lake District. The stream waters had average pH values of 5.35 (D2), 5.81 (D5) and 7.26 (D11), the main differences in other major chemical components being in Mg, Al, Ca and alkalinity. There was generally more metal accumulation in the older parts of the plants, but this was not significant in all cases. Extents of accumulation varied with stream pH and dissolved metal concentration. For Al, accumulation was greatest in streams D2 and D5. Mn accumulated most in D5 and Fe was without preference. Cu, Zn and Cd accumulated mostly in the plants in stream D11 and Pb accumulated more in D5 and D11. In terms of enrichment factors (amount of metal in the plants divided by stream water concentration) the sequence was Zn < Cd < Cu < Mn < Pb < Al < Fe. Laboratory experiments supported the findings of the field data, providing evidence that uptake increases with pH at constant total metal concentration. The results are interpreted qualitatively in terms of the chemical speciation of the metals in the stream water and competition between metal ions and protons at the plant-water interface. It is suggested that Al, Cu, Zn, Cd and Pb behave according to chemical complexation, whereas redox processes and/or colloidal interactions may be significant for Mn and Fe. PMID:11444010

  7. Neutron diffraction study of the type I clathrate Ba8Al(x)Si(46-x): site occupancies, cage volumes, and the interaction between the guest and the host framework.

    PubMed

    Roudebush, John H; de la Cruz, Clarina; Chakoumakos, Bryan C; Kauzlarich, Susan M

    2012-02-01

    Samples with the type I clathrate structure and composition Ba(8)Al(x)Si(46-x), where x = 8, 10, 12, 14, and 15, were examined by neutron powder diffraction at 35 K. The clathrate type I structure contains Ba cations as guests in a framework derived from tetrahedrally coordinated Al/Si atoms. The framework is made up of five- and six-membered rings that form dodecahedral and tetrakaidecahedral cages. The change in distances between tetrahedral sites across the series is used to develop a model for the mixed Al/Si occupancy observed in the framework. The calculated volumes of the cages that contain the Ba atoms display a linear increase with increasing Al composition. In the smaller dodecahedral cages, the Ba atomic displacement parameter is symmetry constrained to be isotropic for all compositions. In the larger tetrakaidecahedral cages, the anisotropic atomic displacement of the Ba atom depends upon the composition: the displacement is perpendicular (x = 8) and parallel (x = 15) to the six-membered ring. This difference in direction of the displacement parameter is attributed to interaction with the Al in the framework and not to the size of the cage volume as x increases from 8 to 15. The influence of the site occupation of Al in the framework on displacement of the cation at the 6d site is demonstrated. PMID:22191511

  8. Hexagonal Ba-ferrite: a good model for the crystal structure of a new high-pressure phase CaAl 4Si 2O 11?

    NASA Astrophysics Data System (ADS)

    Gautron, Laurent; Gerald, John D. Fitz; Kesson, Sue E.; Eggleton, R. Anthony; Irifune, Tetsuo

    1997-07-01

    A new calcium aluminosilicate phase of composition CaAl 4Si 2O 11 has been encountered amongst the transformation products of CaAl 2Si 2O 8 (anorthite composition) at 14 GPa (Gautron et al., 1996). X-ray diffraction (XRD) confirms that its crystal structure is essentially the same as that of a new complex CaAl-silicate (abbreviated CAS phase) first reported by Irifune et al. (1994). The crystal structure of the CAS phase has been investigated by transmission electron microscopy (TEM). It has a hexagonal unit cell with lattice parameters a = 5.4Å and c = 12.7Å, and its space group is either P6 3mc , P overline62c or P6 3/mmc. It is proposed that this CAS phase has a six-layer, close-packed structure so that Z = 2 and density is 3.94 g cm -3, reasonable for a phase stable at transition-zone pressures. The most plausible model for the structure of this phase arises from published refinements of hexagonal Ba-ferrites. This postulated P6 3/mmc structure consists of octahedral layers, 3/4 occupied, separated by 12-coordinate Ca atoms, and by Al and Si in face-shared octahedra and in complex trigonal bipyramidal polyhedra, i.e. some Si would be five-fold coordinated. Observed TEM and XRD data are compared with calculated reflection intensities for this CAS model.

  9. Spectroscopic, Elemental and Thermal Analysis, and Positron Annihilation Studies on Ca(II), Sr(II), Ba(II), Pb(II), and Fe(III) Penicillin G Potassium Complexes

    NASA Astrophysics Data System (ADS)

    Refat, M. S.; Sharshara, T.

    2015-11-01

    The [Pb(Pin)2] · 3H2O, [M(Pin)(H2O)2(Cl)] · nH2O (M = SrII, CaII or BaII; n = 0-1), and [Fe(Pin)2(Cl)(H2O)] · H2O penicillin G potassium (Pin) complexes were synthesized and characterized using elemental analyses, molar conductivity, thermal analysis and electronic spectroscopy techniques. The positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques have been employed to probe the defects and structural changes of Pin ligand and its complexes. The PAL and DB line-shape parameters were discussed in terms of the structure, molecular weight, ligand-metal molar ratio, and other properties of the Pin complexes.

  10. Trace element (Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V) distribution and seasonality in compartments of the seagrass Cymodocea nodosa.

    PubMed

    Malea, Paraskevi; Kevrekidis, Theodoros

    2013-10-01

    Novel information on the biological fate of trace elements in seagrass ecosystems is provided. Al, As, B, Ba, Cr, Mo, Ni, Se, Sr, Tl, U and V concentrations in five compartments (blades, sheaths, vertical rhizomes, main axis plus additional branches, roots) of the seagrass Cymodocea nodosa, as well as in seawater and sediments from the Thessaloniki Gulf, Greece were determined monthly. Uni- and multivariate data analyses were applied. Leaf compartments and roots displayed higher Al, Mo, Ni and Se annual mean concentrations than rhizomes, B was highly accumulated in blades and Cr in sheaths; As, Ba, Sr and Tl contents did not significantly vary among plant compartments. A review summarizing reported element concentrations in seagrasses has revealed that C. nodosa sheaths display a high Cr accumulation capacity. Most element concentrations in blades increased in early mid-summer and early autumn with blade size and age, while those in sheaths peaked in late spring-early summer and autumn when sheath size was the lowest; elevated element concentrations in seawater in late spring and early-mid autumn, possibly as a result of elevated rainfall and associated run-off from the land, may have also contributed to the observed variability. Element concentrations in rhizomes and roots generally displayed a temporary increase in late autumn, which was concurrent with high rainfall, low wind speed associated with reduced hydrodynamism, and elevated sediment element levels. The bioaccumulation factor based on element concentrations in seagrass compartments and sediments was lower than 1 except for B, Ba, Mo, Se and Sr in all compartments, Cr in sheaths and U in roots. Blade V concentration positively correlated with sediment V concentration, suggesting that C. nodosa could be regarded as a bioindicator for V. Our findings can contribute to the design of biomonitoring programs and the development of predictive models for rational management of seagrass meadows. PMID:23838054

  11. Analytical and quantitative concentration of gunshot residues (Pb, Sb, Ba) to estimate entrance hole and shooting-distance using confocal laser microscopy and inductively coupled plasma atomic emission spectrometer analysis: an experimental study.

    PubMed

    Turillazzi, Emanuela; Di Peri, Giovanni Paolo; Nieddu, Antonio; Bello, Stefania; Monaci, Fabrizio; Neri, Margherita; Pomara, Cristoforo; Rabozzi, Roberto; Riezzo, Irene; Fineschi, Vittorio

    2013-09-10

    The identification of gunshot residues (GSRs) on human body in firearm related fatalities may be essential for the evaluation of gunshot wounds and for the analysis of the shooting distance. The present study introduces the elemental analysis of the GSRs by inductively coupled plasma atomic emission spectrometer analysis (ICP-AES) performed on skin samples. ICP-AES was used to increase the accuracy of the analysis in gunshots fired from long and medium distance. In this experimental study, a series of 50 test shots have been performed in an open space with lateral wind protection. As target we used pig skin cut into 20 cm × 20 cm squares. The firing distances were 0.2, 5, 50, 100 and 150 cm. To exclude environmental contamination, each skin sample was carefully washed with deionized water and dried at room temperature in a closed box before the shooting test. We choose 9×21 and the 7.65 mm calibers handguns, loaded with different ammunitions. At ICP-AES analysis a clearly decreasing trend in the quantity and the concentration of the different elements of GSR by increasing the firing distance for both the guns used in the test was evident for every portion of skin samples analyzed. The analytical results obtained by ICP-AES confirmed very high concentrations of Pb, Sb, and Ba in the close-range shots and low concentrations of these particles in the intermediate and distant shots. In particular, the concentration of Sb, Ba, and Pb was significantly different from loose values when the firing distance was 100-150 cm for both the 9×21 and the 7.65 mm calibers. PMID:23890629

  12. On BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphor degradation mechanism by vacuum-ultraviolet excitation

    SciTech Connect

    Bizarri, G.; Moine, B.

    2005-12-01

    Additional to a correct color and a high efficiency, phosphors for plasma display panels must maintain their light output for thousands of hours. Often the degradation is the restricting factor in using phosphors. In this article, the mechanism of luminance decrease in blue-emitting BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphor during the operation of the PDPs has been studied. It is shown experimentally that the aging process is mainly due to the vacuum-ultraviolet excitation (VUV). It is demonstrated that the degradation mechanism can be accelerated by using a 193 nm laser excitation. Based on excitation, reflectance, thermoluminescence spectra, and aging or annealing processes by laser excitation, the main causes of the degradation are demonstrated. The aging process can be separated in two different processes according to the temperature: a first one, at low temperature, corresponding to the autoionization of luminescent centers (Eu{sup 2+}{yields}Eu{sup 3+}); and a second one, at high temperature, linked to the formation of traps in the phosphor. These traps induce a perturbation of the energy migration in the phosphor. In addition, the relevant parameters of trap formation are highlighted: density of the VUV excitation, temperature, and atmosphere/pressure surrounding the phosphor. A model of BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphor degradation mechanism is proposed.

  13. Study of Eu{sup 3+} → Eu{sup 2+} reduction in BaAl{sub 2}O{sub 4}:Eu prepared in different gas atmospheres

    SciTech Connect

    Rezende, Marcos V. dos S.; Valerio, Mário E.G.; Jackson, Robert A.

    2015-01-15

    Highlights: • The effect of different gas atmospheres on the Eu reduction process was studied. • The Eu reduction was monitored analyzing XANES region at the Eu L{sub III}-edge. • Hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization. • Only a part of the Eu ions can be stabilized in the divalent state. • A model of Eu reduction process is proposed. - Abstract: The effect of different gas atmospheres such as H{sub 2}(g), synthetic air, carbon monoxide (CO) and nitrogen (N{sub 2}) on the Eu{sup 3+} → Eu{sup 2+} reduction process during the synthesis of Eu-doped BaAl{sub 2}O{sub 4} was studied using synchrotron radiation. The Eu{sup 3+} → Eu{sup 2+} reduction was monitored analyzing XANES region when the sample are excited at the Eu L{sub III}-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization in BaAl{sub 2}O{sub 4} and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.

  14. Tm3+/Er3+/Yb3+ tri-doped TeO2-PbF2-AlF3 glass for white-light-emitting diode

    NASA Astrophysics Data System (ADS)

    Ming, Chengguo; Song, Feng; Ren, Xiaobin; An, Liqun; Qin, Yueting

    2013-09-01

    By the high temperature melting method, Er3+/Yb3+, Tm3+/Yb3+, and Tm3+/Er3+/Yb3+ co-doped oxyfluoride telluride glasses with the compositions of (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3), (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.5Tm2O3), and (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3-0.5Tm2O3) (mol%) were prepared. The emission spectra of the samples were measured under 975 nm excitation. The emission color of Tm3+/Er3+/Yb3+ tri-doped glass is white to the naked eye. The International Commission on Illumination (CIE) coordinates (0.353,0.308) of the sample are close to the equal energy white-light illumination standard (x=0.333,y=0.333) and the color temperature is 4381 K. Our research will be helpful in developing luminescent materials for white light-emitting-diodes (LEDs).

  15. Low dietary levels of Al, Pb and Cd may affect the non-enzymatic antioxidant capacity in caged honey bees (Apis mellifera).

    PubMed

    Gauthier, Maxime; Aras, Philippe; Jumarie, Catherine; Boily, Monique

    2016-02-01

    Several hypotheses have been proposed to explain the abnormally high mortality rate observed in bee populations in Europe and North America. While studies based on the effects of pesticides are paramount, the metals present in agroecosystems are often overlooked. Sources of metals are linked to the nature of soils and to agricultural practices, namely the use of natural or chemical nutrients as well as residual materials from waste-water treatment sludge. The aim of this study was to investigate the effects of metals on honey bees exposed for 10 days to environmentally realistic concentrations of Al, Pb and Cd (dissolved in syrup). The monitoring of syrup consumption combined with the quantification of metals in bees revealed the following order for metal bioconcentration ratios: Cd > Pb > Al. Alpha-tocopherol, metallothionein-like proteins (MTLPs) and lipid peroxidation were quantified. When bees were exposed to increasing amounts of Cd, a marked augmentation of MTLPs levels was found. Lead (Pb) and Cd caused an increase in α-tocopherol content, while alteration of lipid peroxidation was observed only with Al exposure. These findings raise concerns about the bioavailability and the additional threat posed by metals for pollinators in agricultural areas while providing new insights for potential use of the honey bee as a sentinel species for metal exposure. PMID:26421624

  16. Ferroelectric, and piezoelectric properties of BaTi{sub 1−x}Al{sub x}O{sub 3}, 0 ≤ x ≤ 0.015

    SciTech Connect

    Ali, Ahmed I.; Hassen, A.; Khang, Nguyen Cao; Kim, Y. S.

    2015-09-15

    Single phase polycrystalline samples of BaTi{sub 1−x}Al{sub x}O{sub 3}, 0 ≤ x ≤ 0.015, have been prepared by a conventional powder processing method. The Rietveld refinements of X- ray powder diffraction patterns at room temperature indicate that the samples crystallize in tetragonal structure with group symmetry P4mm. Because of the oxygen vacancies, the volume of the unit cell increases with increasing x. Field emission scanning electron microscopy revealed that the particle size of pure BTO ceramics was affected by the Al content. Dielectric, ferroelectric and piezoelectric properties of pure BTO as well as Al-doped BTO were studied. It was found that the dielectric permittivity (ε′) increases significantly with increasing x while the transition from ferroelectric phase to a paraelectric phase changes slightly. The Curie-Weiss law is verified over a wide temperature range. Both ferroelectric and piezoelectric properties of BTO are enhanced by the substitution of Ti{sup 4+} by Al{sup 3+} ions. Piezoelectric strains of Al-doped BTO showed a suitable behavior for application compared with that of pure BTO compound. Finally, the results obtained in this work are discussed and compared with those for similar materials.

  17. U-Pb zircon dating, geochemical and Sr-Nd-Hf isotopic compositions of Motuo quartz-monzonite: Implication for the genesis and diversity of the high Ba-Sr granitoids in orogenic belt

    NASA Astrophysics Data System (ADS)

    Pan, Fa-Bin; Zhang, Hong-Fei; Xu, Wang-Chun; Guo, Liang; Luo, Bi-Ji; Wang, Shuai

    2016-02-01

    Early Paleogene granitoids in Southern Lhasa subterrane have been widely investigated and many petrogenesis and geodynamic models have been proposed in the past few years. However, contemporaneous granitoids in the Motuo tectono-magmatic belt, southeast Lhasa terrane, are still limitedly studied. Here we present the petrology, zircon U-Pb geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotope data of the Damu and 52 K quartz-monzonite in the Motuo area. LA-ICP-MS U-Pb zircon dating shows that they have magma crystallization ages of 49 and 69 Ma, respectively. The Damu quartz-monzonite (SiO2 = 63.76-68.33 wt.%) is high-K calc-alkaline (K2O = 2.54-4.02 wt.% with K2O/Na2O = 0.59-1.09) and metaluminous to weakly peraluminous (A/CNK = 0.99-1.07). The 52 K quartz-monzonite (SiO2 = 61.12-66.12 wt.%) shows slightly higher K2O contents (3.80-5.28 wt.% with K2O/Na2O = 1.03-1.45) and metaluminous series (A/CNK = 0.96-1.00). The analyzed samples are characterized by high Ba (850-2573 ppm), Sr (534-986 ppm) contents, and fractionated REE patterns ((La/Yb)N = 22-72 and (Sm/Yb)N = 4.55-8.24). These geochemical features are comparable with those of high Ba-Sr granite. They display weakly evolved Sr-Nd-Hf compositions (whole-rock (87Sr/86Sr)0 = 0.7068 to 0.7086, εNd(t) = - 4.20 to - 3.41, and zircon εHf(t) = - 5.2 to - 0.9). Geochemical and Sr-Nd-Hf isotopic data reflect that the Damu and 52 K quartz-monzonite represent residual magma from AFC processes of lithospheric mantle-derived mafic melts. The over-thickened lower crust in the eastern Lhasa terrane had been delaminated during ca. 83-70 Ma, which led to the replacement of ancient lithospheric mantle by the juvenile lithospheric mantle. The juvenile mantle wedge in the study area was suspected to be metasomatized by melts that were derived from the foundering arc root, rather than the subducted sediments. Thus, the early Paleogene high Ba-Sr magmas from the SE Lhasa terrane may provide evidence for recycling of

  18. Fabrication and thermoelectric characteristics of [(Bi,Pb)2Ba2O4+/-w]0.5CoO2 bulks with highly aligned grain structure

    NASA Astrophysics Data System (ADS)

    Motohashi, T.; Nonaka, Y.; Sakai, K.; Karppinen, M.; Yamauchi, H.

    2008-02-01

    Here, we report fabrication and thermoelectric characteristics of polycrystalline bulks with aligned grains of the misfit-layered cobalt oxides, [(Bi1-xPbx)2Ba2O4±w]0.5CoO2. High-quality precursor powder was prepared with a spray-drying technique. The precursor was then sintered under a uniaxial pressure to yield dense bulk samples consisting of highly aligned grains. The electrical conductivity of such samples was four times higher than that of conventionally sintered bulks. Accordingly, the thermoelectric characteristics of the grain-aligned specimens were enhanced.

  19. Comparative study of gamma ray shielding and some properties of PbO-SiO2-Al2O3 and Bi2O3-SiO2-Al2O3 glass systems

    NASA Astrophysics Data System (ADS)

    Singh, K. J.; Kaur, Sandeep; Kaundal, R. S.

    2014-03-01

    Gamma-ray shielding properties have been estimated in terms of mass attenuation coefficient, half value layer and mean free path values, whereas, structural studies have been performed in terms of density, optical band gap, glass transition temperature and longitudinal ultrasonic velocity parameters. X-ray diffraction, UV-visible, DSC and ultrasonic techniques have been used to explore the structural properties of PbO-SiO2-Al2O3 and Bi2O3-SiO2-Al2O3 glass systems.

  20. Conduction phenomenon of Al3+ modified lead free (Na0.5Bi0.5)0.92Ba0.08TiO3 electroceramics

    NASA Astrophysics Data System (ADS)

    Borkar, Hitesh; Kumar, Ashok

    2016-05-01

    Choice of proper dopants at A or B-site of ABO3 perovskite structure can modify the morphotropic phase boundary (MPB), and hence functional properties of polar systems. The chemical nature of donor or acceptor will significantly influence the fundamental properties. Lead-free ferroelectrics have vast potential to replace the lead-based ceramics. The (Na0.5Bi0.5)1-xBaxTiO3 (NBT-BT) (at x=0.08) near MPB with small substitution of trivalent cations (Al3+) has been synthesized by solid state reaction route. The aim to choose the trivalent cations (Al3+) was its relatively smaller radii than that of Bi3+ cations to develop the antipolar phases in the ferroelectric ceramic. Structural, morphological and elemental compositional analyses were studied by X-ray diffraction (XRD), Secondary electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDAX), respectively. Ferroelectric studies were carried out on various compositions of (Na0.46Bi0.46-xAlxBa0.08)TiO3 (NBAT-BT) (x=0, 0.05, 0.07, 0.10) electroceramics. It was observed that with increase in concentration of Al the ferroelectricity state changes from soft to hard. Temperature dependent dielectric spectroscopy shows broad dielectric dispersion. The Al doping diminishes the relaxor behavior of NBT-BT ceramics. Impedance spectroscopy shows that electrical resistivity and relaxation frequency decreases with increase in Al-concentration. Modulus spectra indicate that Al significantly change the bulk capacitance of NBT-BT.

  1. Systematic investigation of chemical substitution in BaSnO3 using the combinatorial approach

    NASA Astrophysics Data System (ADS)

    Takeuchi, Ichiro; Shin, Jongmoon; Lee, Seunghun; Zhang, Xiaohang; Jaim, H. M. Iftekhar; Jeong, Se-Young

    BaSnO3 has been regarded as a possible material for photo-catalysis, dielectric capacitors, and transparent conductors. We are systematically investigating the effect of chemical substitution for A and B sites in BaSnO3 using a high-throughput methodology. We have thus far investigated the effect of substituting La and Sr for the Ba-site and Pb and Bi for the Sn-site. The composition spread films were prepared on MgO, SrTiO3 and LaAlO3 using combinatorial pulsed laser deposition. The lattice parameters and band-gap energies were found to continually change as a function of the concentration of each substitutional dopant. We find that the band gap can be tuned from 2.8 eV for BaSn0.05Pb0.95O3 to 4.5 eV for Ba0.05La0.95SnO3. Especially for Ba1-xLaxSnO3 with x in the range of 0.05

  2. Sol-gel synthesis of micro and nanocrystalline BaAl2O4:Eu3+ powders and their luminescence properties

    NASA Astrophysics Data System (ADS)

    Wiglusz, R. J.; Grzyb, T.

    2013-12-01

    In this paper, we report the obtention of barium aluminate (BaAl2O4) powders doped with Eu3+ ions by the sol-gel method heat-treated at 900 and 1000 °C for 3 h. XRD patterns indicated that the powders have orthorhombic structure with a high crystallite dispersion. The powders have size at submicron scale. They are a strong red emitting materials when are irradiated by ultraviolet light (250 nm). Measured emission and excitation luminescence spectra demonstrated characteristic spectroscopic properties of Eu3+ ions. Recorded luminescence decays and emission spectra were base for calculation of Judd-Ofelt intensity parameters. A detailed analysis of calculated parameters in connection with observed structural and spectroscopic measurements has been done and described.

  3. Vibrational spectroscopic characterization of the phosphate mineral kulanite Ba(Fe2+,Mn2+,Mg)2(Al,Fe3+)2(PO4)3(OH)3

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Xi, Yunfei; Granja, Amanda; Scholz, Ricardo

    2013-11-01

    The mineral kulanite BaFe2Al2(PO4)3(OH)3, a barium iron aluminum phosphate, has been studied by using a combination of electron microscopy and vibrational spectroscopy. Scanning electron microscopy with EDX shows the mineral is homogenous with no other phases present. The Raman spectrum is dominated by an intense band at 1022 cm-1 assigned to the PO43-ν1 symmetric stretching mode. Low intensity Raman bands at 1076, 1110, 1146, 1182 cm-1 are attributed to the PO43-ν3 antisymmetric stretching vibrations. The infrared spectrum shows a complex spectral profile with overlapping bands. Multiple phosphate bending vibrations supports the concept of a reduction in symmetry of the phosphate anion. Raman spectrum at 3211, 3513 and 3533 cm-1 are assigned to the stretching vibrations of the OH units. Vibrational spectroscopy enables aspects on the molecular structure of kulanite to be assessed.

  4. An analysis of temperature-dependent absorption and photocurrent spectra in BaAl{sub 2}Se{sub 4} layers

    SciTech Connect

    Hong, K. J.; Jeong, T. S.; Youn, C. J.; Moon, J. D.

    2015-04-28

    The temperature-dependent photoresponse behavior of BaAl{sub 2}Se{sub 4} layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by E{sub g}(T) = E{sub g}(0) − 4.39 × 10{sup −4}T{sup 2}/(T + 250), where E{sub g}(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C) to the conduction band state of Γ{sub 1}, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log J{sub ph} versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl{sub 2}Se{sub 4} layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

  5. The Jahn-Teller effect in the excitation and emission spectra of Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/:Sn/sup 2+/ and Ba/sub 2/YAlO/sub 5/:Sn/sup 2+/

    SciTech Connect

    Smets, B.M.J.; Verlijsdonk, J.G.; Rutten, J. )

    1989-04-01

    Luminescence measurements are presented for Sn/sup 2+/ doped Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/ and Ba/sub 2/YAlO/sub 5/. In these compounds several crystallographic sites are available for Sn/sup 2+/. The luminescence properties of Sn/sup 2+/ in one of these sites can be accounted for by assuming that the Jahn-Teller effect is acting on the /sup 3/P/sub 1/ excited state of the Sn/sup 2+/ ion. The vibronic interaction results in the occurrence of two emission bands in the case of Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/:Sn/sup 2+/.

  6. Cation-Poor Complex Metallic Alloys in Ba(Eu)-Au-Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level.

    PubMed

    Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J; Mudring, Anja-Verena

    2015-11-01

    Four complex intermetallic compounds BaAu(6±x)Ga(6±y) (x = 1, y = 0.9) (I), BaAu(6±x)Al(6±y) (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104-112, Fm3̅c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution ("coloring scheme"). Chemical bonding analyses for two different "EuAu6Tr6" models reveal maximization of the number of heteroatomic Au-Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the "EuAu6Tr6" models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. The effective moments of 8.3 μB/f.u., determined from Curie-Weiss fits, point to divalent oxidation states for europium in both III and IV. PMID:26479308

  7. Properties of B4C-PbO-Al(OH)3-epoxy nanocomposite prepared by ultrasonic dispersion approach for high temperature neutron shields

    NASA Astrophysics Data System (ADS)

    Lee, M. K.; Lee, J. K.; Kim, J. W.; Lee, G. J.

    2014-02-01

    High functional epoxy nanocomposites with three different filler materials, i.e., B4C, PbO, and Al(OH)3, were fabricated using an effective fabrication method consisting of an ultrasonic dispersion of nanoparticles in low-viscosity hardener and a subsequent mixing of a hardener-nanoparticle colloid with epoxy resins. It was confirmed that this approach provided not only an uniform dispersion but also an excellent wetting with enhanced interfacial adhesion of nano-particulate fillers within the matrix. By incorporating those three fillers, a synergistic effect was verified in multiple properties such as mechanical strength properties, thermal degradation, flame retardancy, and radiation shielding performance.

  8. A Comparison of MOCLD With PLD Ba(x)Sr(1-x)TiO3 Thin Films on LaAlO3 for Tunable Microwave Applications

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Mueller, C. H.; Romanofsky, R. R.; Warner, J. D.; Miranda, F. A.; Jiang, H.

    2002-01-01

    Historically, tunable dielectric devices using thin crystalline Ba(x)Sr(1-x)TiO3 (BST) films deposited on lattice-matched substrates, such as LaAlO3, have generally been grown using pulsed laser deposition (PLD). Highly oriented BST films can be grown by PLD but large projects are hampered by constraints of deposition area, deposition time and expense. The Metal-Organic Chemical Liquid Deposition (MOCLD) process allows for larger areas, faster turnover and lower cost. Several BST films deposited on LaAlO3 by MOCLD have been tested in 16 GHz coupled microstrip phase shifters. They can be compared with many PLD BST films tested in the same circuit design. The MOCLD phase shifter performance of 293 deg. phase shift with 53 V/micron dc bias and a figure of merit of 47 deg./dB is comparable to the most highly oriented PLD BST films. The PLD BST films used here have measured XRD full-width-at-half-maxima (FWHM) as low as 0.047 deg.. The best FWHM of these MOCLD BST films has been measured to be 0.058 deg.

  9. The molecular structure of the multianion mineral hidalgoite PbAl 3(AsO 4)(SO 4)(OH) 6 - Implications for arsenic removal from soils

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Palmer, Sara J.; Xi, Yunfei

    2011-11-01

    The objective of this research is to determine the molecular structure of the mineral hidalgoite PbAl 3(AsO 4)(SO 4)(OH) 6 using vibrational spectroscopy. The mineral is found in old mine sites. Observed bands are assigned to the stretching and bending vibrations of (SO 4) 2- and (AsO 4) 3- units, stretching and bending vibrations of hydrogen bonded (OH) - ions and Al 3+-(O,OH) units. The approximate range of O-H⋯O hydrogen bond lengths is inferred from the Raman and infrared spectra. Values of 2.6989 Å, 2.7682 Å, 2.8659 Å were obtained. The formation of hidalgoite may offer a mechanism for the removal of arsenic from the environment.

  10. Performance of LaBaCo 2O 5+ δ-Ag with B 2O 3-Bi 2O 3-PbO frit composite cathodes for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Ruifeng; Gao, Lei; Ge, Lin; Zheng, Yifeng; Zhou, Ming; Chen, Han; Guo, Lucun

    The composite cathodes LaBaCo 2O 5+ δ- x wt.% Ag (LBCO- xAg, x = 20, 30, 40, 50) were prepared by mechanical mixing method for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The experiment results indicated that the addition of a small amount of B 2O 3-Bi 2O 3-PbO (BBP) frit to LBCO- xAg can effectively improve the adhesion and strength of cathode membrane without damaging its porous structure. The BBP frit was proved effective for lowering the sintering temperature of LBCO- xAg to 900 °C. According to the electrochemical impedance spectroscopy and cathodic polarization analysis, the LBCO-30Ag exhibited the best performance and the optimal BBP frit content was 2.5 wt.%. For LBCO-30Ag with 2.5 wt.% BBP frit, the area-specific resistance based on Sm 0.2Ce 0.8O 1.9 (SDC) electrolyte decreased by about 57.6% at 700 °C, 60.5% at 750 °C and 75.9% at 800 °C compared to LBCO, and its cathodic overpotential was 10.7 mV at a current density of 0.2 A cm -2 at 700 °C, while the corresponding value for LBCO was 51.0 mV. The addition of Ag and BBP frit to LBCO had no significant effect on the thermal expansion.

  11. Thickness-dependent electrocaloric effect in mixed-phase Pb0.87Ba0.1 La0.02(Zr0.6Sn0.33Ti0.07)O3 thin films.

    PubMed

    Correia, T M; Zhang, Q

    2016-08-13

    Full-perovskite Pb0.87Ba0.1La0.02(Zr0.6Sn0.33Ti0.07)O3 (PBLZST) thin films were fabricated by a sol-gel method. These revealed both rhombohedral and tetragonal phases, as opposed to the full-tetragonal phase previously reported in ceramics. The fractions of tetragonal and rhombohedral phases are found to be strongly dependent on film thickness. The fraction of tetragonal grains increases with increasing film thickness, as the substrate constraint throughout the film decreases with film thickness. The maximum of the dielectric constant (εm) and the corresponding temperature (Tm) are thickness-dependent and dictated by the fraction of rhombohedral and tetragonal phase, with εm reaching a minimum at 400 nm and Tm shifting to higher temperature with increasing thickness. With the thickness increase, the breakdown field decreases, but field-induced antiferroelectric-ferroelectric (EAFE-FE) and ferroelectric-antiferroelectric (EFE-AFE) switch fields increase. The electrocaloric effect increases with increasing film thickness.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402937

  12. Elastic properties of perovskite ATiO{sub 3} (A = Be, Mg, Ca, Sr, and Ba) and PbBO{sub 3} (B = Ti, Zr, and Hf): First principles calculations

    SciTech Connect

    Pandech, Narasak; Limpijumnong, Sukit; Sarasamak, Kanoknan

    2015-05-07

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO{sub 3} for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO{sub 3} for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C{sub 11} elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C{sub 12} elastic constant is sensitive to B-site cations while C{sub 44} elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed.

  13. Thermal, dielectric and ferroelectric properties of 0.925BaTiO3-0.075Pb(Zn1/3Nb2/3)O3 ceramic

    NASA Astrophysics Data System (ADS)

    Suchanicz, J.; Nogas-Ćwikiel, E.; Sitko, D.; Handke, B.; Jelen, P.; Klimczyk, P.

    2015-08-01

    New low-lead content 0.925BaTiO3-0.075PbZn1/3Nb2/3O3 (0.925BT-0.075PZN) ceramic was fabricated by the spark-plasma-sintering method. X-ray diffraction measurements showed that the obtained specimen possesses a pure perovskite structure. The microstructure investigation indicated a dense ceramic structure with 95% relative density determined by the Archimedes method. Composition undergoes a sequence of phase transitions as pure barium titanate (BT). Dielectric study revealed that the electric permittivity decreases at its maximum and the phase transition shifts to a higher temperature after lead zinc niobate doping of BT. Besides, the dielectric dispersion and polarization increases and decreases, respectively. Obtained results were discussed in term of the difference between ionic size and its mass and local elastic and electric fields. The results show that investigated ceramic is one of the promising low-lead materials for electronic applications.

  14. Thickness-dependent electrocaloric effect in mixed-phase Pb0.87Ba0.1 La0.02(Zr0.6Sn0.33Ti0.07)O3 thin films

    PubMed Central

    Correia, T. M.

    2016-01-01

    Full-perovskite Pb0.87Ba0.1La0.02(Zr0.6Sn0.33Ti0.07)O3 (PBLZST) thin films were fabricated by a sol–gel method. These revealed both rhombohedral and tetragonal phases, as opposed to the full-tetragonal phase previously reported in ceramics. The fractions of tetragonal and rhombohedral phases are found to be strongly dependent on film thickness. The fraction of tetragonal grains increases with increasing film thickness, as the substrate constraint throughout the film decreases with film thickness. The maximum of the dielectric constant (εm) and the corresponding temperature (Tm) are thickness-dependent and dictated by the fraction of rhombohedral and tetragonal phase, with εm reaching a minimum at 400 nm and Tm shifting to higher temperature with increasing thickness. With the thickness increase, the breakdown field decreases, but field-induced antiferroelectric–ferroelectric (EAFE−FE) and ferroelectric–antiferroelectric (EFE−AFE) switch fields increase. The electrocaloric effect increases with increasing film thickness. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’. PMID:27402937

  15. PbZr0.4Ti0.6O3 and Ba0.9Sr0.1TiO3 reflectors derived from chemical solutions containing polymers.

    PubMed

    Hu, G J; Shang, J L; Sun, Y; Zhang, T; Wu, J; Xie, J

    2008-09-15

    Ba(0.9)Sr(0.1)TiO3 (BST)-based and PbZr(0.4)Ti(0.6)O(3)-based quasi-periodic multilayers consisting of dense and porous ferroelectric layers have been fabricated by solgel technique using chemical solutions containing polyethylene glycol (PEG) or polyvinylpyrrolidone k30 (PVP). All multilayers exhibit good performance as dielectric mirrors. For each multilayer, the maximum peak reflectivity is over 90% and the photonic stopband width is no less than 30 nm at room temperature. The reflection-band position can be easily tuned by varying the thickness of the bilayer. With the same processing conditions and number of periods, the Bragg reflection performance is almost the same for quasi-periodic PZT multilayers derived from two precursors containing different polymers. The BST multilayers deposited by using a PVP-containing precursor are superior in optical properties, including peak reflectivities and stop-band width, to those deposited by using the PEG-containing solution. PMID:18794931

  16. Eye-safe actively Q-switched diode-pumped lasers with intracavity Raman conversion in YVO4, KGd(WO4)2, PbWO4, and Ba(NO3)2 crystals

    NASA Astrophysics Data System (ADS)

    Dashkevich, V. I.; Shpak, P. V.; Voitikov, S. V.; Chulkov, R. V.; Grabtchikov, A. S.; Cheshev, E. A.; El-Desouki, M.; Orlovich, V. A.

    2015-09-01

    We have investigated the self-Raman and intracavity Raman frequency conversion of the end-diode-pumped acoustooptic Q-switched Nd:YVO4 laser radiation to eye-safe radiation. The 1st Stokes oscillation in YVO4 (Nd:YVO4), KGd(WO4)2, PbWO4, and Ba(NO3)2 crystals excited by the laser radiation at a wavelength of 1342 nm permits obtaining oscillations at 1524, 1496 or 1527, 1527, and 1562 nm wavelengths, respectively. We have obtained pulsed lasing with a repetition rate of 2-20 kHz, an output energy of 37-95 μJ, and a duration of 6-8 ns. We propose a model of the actively Q-switched intracavity Raman laser taking into account the real switching off/on times of the actively Q-switch and the excited state absorption in the active medium. We used this model to simulate the dynamics of the self-Raman Nd:YVO4 laser. The proposed model gives results that agree fairly well with the experimental data.

  17. Magnetic and magnetocaloric properties of Gd2In0.8X0.2 compounds (X=Al, Ga, Sn, Pb)

    NASA Astrophysics Data System (ADS)

    Tencé, Sophie; Chevalier, Bernard

    2016-02-01

    We show that it is possible to replace in Gd2In some amount of In by X=Al, Ga, Sn and Pb to obtain Gd2In1-xXx samples after melting. The magnetic and magnetocaloric properties of the Gd2In0.8X0.2 intermetallic compounds have been investigated through dc magnetization measurements. We evidence that the substitution of Al and Ga for In barely changes the Curie temperature TC but decreases the second magnetic transition temperature T‧ which corresponds to the transition from a ferromagnetic to an antiferromagnetic state. On the other hand, the substitution of Sn and Pb for In strongly increases TC and changes the nature or even suppresses the transition at lower temperature. This magnetic behavior gives rise to an interesting way to tune the Curie temperature near room temperature without diluting the Gd network and thus to modify the magnetocaloric effect in Gd2In1-xXx compounds.

  18. Giant magnetocaloric effect of Mn{sub 0.92}Ba{sub 0.08}As thin film grown on Al{sub 2}O{sub 3}(0001) substrate

    SciTech Connect

    Dang Duc Dung; Duong Anh Tuan; Duong Van Thiet; Shin, Yooleemi; Cho, Sunglae

    2012-04-01

    The epitaxial Mn{sub 0.92}Ba{sub 0.08}As thin film was grown on Al{sub 2}O{sub 3}(0001) substrate by molecular beam epitaxy. The Curie temperature (T{sub C}) around 350 K was enhanced with the addition of Ba, compared to that of bulk MnAs (T{sub C} {approx} 318 K). We have observed the linear resistivity versus the square of temperature and high negative magnetoresistance near Curie temperature. Moreover, the giant magnetocaloric effect was found with maximum magnetic entropy change, 65 J/kgK, around room temperature at 5 T.

  19. First principle calculation of physical properties of barium based chalcogenides BaM4S7 (M = Ga, Al); a DFT, DFT-D and hybrid functional HSE06 study

    NASA Astrophysics Data System (ADS)

    Benghia, Ali; Dahame, Tahar; Bentria, Bachir

    2016-04-01

    The electronic structure, elastic and optical properties have been calculated for the novel nonlinear optical (NLO) crystals BaQ4S7 (Q = Ga, Al) using plane wave pseudo-potential density functional theory (DFT) method as implemented in CASTEP and ABINIT codes. In this study we used both hybrid HSE06 and DFT-D functionals with GGA approximation. These NLO compounds, which belong to the mm2 point group, are particularly interesting because of their transparency in the mid-infrared region and wide energy band gap. We present results for electronic structure, elastic tensor coefficients, refractive indices and second order nonlinear optical susceptibilities. The calculated energy band gap and frequency dependent refractive indices as well as the NLO coefficients of BaGa4S7 are in good agreement with the experimental values. With no reported theoretical or experimental energy band gap and optical properties of BaAl4S7, we present for the first time its electronic structure and above mentioned optical coefficients. This compound has higher direct band gap with 3.74 eV, better optical birefringence and second-order NLO coefficients than most NLO compounds. The second-order NLO coefficients for BaAl4S7 have been calculated as d31 = 3.15 pm/V, d31 = 2.20 pm/V, d33 = -6.31 pm/V.

  20. Raman Scattering in Tl_0.5Pb_0.5Sr_1.25Ba_0.75 Ca_1Cu_2Ox Thin-Films

    NASA Astrophysics Data System (ADS)

    Subramanyam, G.; Boolchand, P.; Chandrasekhar, M.

    1997-03-01

    RF sputtered c-axis oriented thin-films of the titiled 1212 superconductor have been deposited on LaAlO3 substrates. Films possess a tetragonal structure and a T_c=85K. Raman modes due to A_1g and B_1g vibrations are observed, of which the Cu mode at 124 cm-1, the 0(1) out of phase mode at 294 cm-1 and the 0(2) mode at 543 cm-1 are upshifted in frequency relative to pure T11212.footnote K.F.McCarty, et al. Physica C156, 119 (1988) Two new modes are observed: one at 341 cm-1 corresponding to the 0(1) in-phase vibration calculated( A.D.Kulkarni et al. Phys. Rev. B41, 6409 (1990)) to be at 358 cm-1; and a second at 627 cm-1, which may be due to disallowed 0(3) vibration, observed due to symmetry breaking in the alloyed compound. * Supported by Roy J. Carver Foundation ** Supported by NSF grant DMR-9424556. ***Supported by DOE grant DEFG02-9OER45427 through Midwest Superconductivity Consortium.

  1. High-temperature tribological properties of NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings prepared by plasma spraying

    NASA Astrophysics Data System (ADS)

    Chen, X. H.; Yuan, X. J.; Xia, J.; Yu, Z. H.

    2015-12-01

    In this paper, NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings were produced on a substrate by plasma spray and investigated at the high temperature, such as 500 °C and 800 °C. The structure of the coatings was characterized using XRD pattern and scanning electron microscopy. The TC1 (83wt% NiCoCrAlY) coating has a low friction coefficient at 500C, where the WSe2 is a good solid lubricant. The TC2 (65wt% NiCoCrAlY) coating has the low friction coefficient (0.279) at 800°C, due to the formation of BaCrO4 on the surfaces. As a result, the TC2 coating has the optimal tribological property in the wide temperature.

  2. Heterometallic Alkaline Earth-Lanthanide Ba(II)-La(III) Microporous Metal-Organic Framework as Bifunctional Luminescent Probes of Al(3+) and MnO4(.).

    PubMed

    Ding, Bin; Liu, Shi Xin; Cheng, Yue; Guo, Chao; Wu, Xiang Xia; Guo, Jian Hua; Liu, Yuan Yuan; Li, Yan

    2016-05-01

    In this work a rigid asymmetrical tricarboxylate ligand p-terphenyl-3,4″,5-tricarboxylic acid (H3L) has been employed, and a unique heterometallic alkaline earth-lanthanide microporous luminescent metal-organic framework (MOF) {[Ba3La0.5(μ3-L)2.5(H2O)3(DMF)]·(3DMF)}n (1·3DMF) (DMF = dimethylformamide) has been isolated under solvothermal conditions. Single-crystal X-ray structural analysis demonstrates that 2D inorganic Ba-O-La connectivity can be observed in 1, which are further bridged via rigid terphenyl backbones of L(3-), forming a unique I(2)O(1)-type microporous luminescent framework. A 1D microporous channel with dimensionality of 9.151(3) Å × 10.098(1) Å can be observed along the crystallographic a axis. PXRD patterns have been investigated indicating pure phases of 1. The luminescence explorations demonstrated that 1 exhibits highly selective and sensitive sensing for Al(3+) over other cations with high quenching efficiency Ksv value of 1.445 × 10(4) L·mol(-1) and low detection limit (1.11 μM (S/N = 3)). Meanwhile 1 also exhibits highly selective and sensitive sensing for MnO4(-) over other anions with quenching efficiency Ksv = 7.73 × 10(3) L·mol(-1) and low detection limit (0.28 μM (S/N = 3)). It is noted that, when different concentrations of MnO4(-) solutions (0.5 to 100 μM) were dropped into the suspension of 1, the bright blue luminescence of the suspension observed under UV light can gradually change into pink color, indicating visually luminescent sensing, which makes the detection process of MnO4(-) more convenient in practical. The result also reveals that 1 represents the first example of bifunctional heterometallic alkaline earth-lanthanide MOF-based luminescent probes for selectively detecting Al(3+) and MnO4(-) in the water solutions. PMID:27088966

  3. Raman spectroscopic study of the mineral arsenogorceixite BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Xi, Yunfei; Pogson, Ross E.

    2012-06-01

    Arsenogorceixite BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6 belongs to the crandallite mineral subgroup of the alunite supergroup. Arsenogorceixite forms a continuous series of solid solutions with related minerals including gorceixite, goyazite, arsenogoyazite, plumbogummite and philipsbornite. Two minerals from (a) Germany and (b) from Ashburton Downs, Australia were analysed by Raman spectroscopy. The spectra show some commonality but the intensities of the peaks vary. Sharp intense Raman bands for the German sample, are observed at 972 and 814 cm-1 attributed to the ν1 PO43- and AsO43- symmetric stretching modes. Raman bands at 1014, 1057, 1148 and 1160 cm-1 are attributed to the ν1 PO2 symmetric stretching mode and ν3 PO43- antisymmetric stretching vibrations. Raman bands at 764 and 776 cm-1 and 758 and 756 cm-1 are assigned to the ν3 AsO43- antisymmetric stretching vibrations. For the Australian mineral, the ν1 PO43- band is found at 973 cm-1. The intensity of the arsenate bands observed at 814, 838 and 870 cm-1 is greatly enhanced. Two low intensity Raman bands at 1307 and 1332 cm-1 are assigned to hydroxyl deformation modes. The intense Raman band at 441 cm-1 with a shoulder at 462 cm-1 is assigned to the ν2 PO43- bending mode. Raman bands at 318 and 340 cm-1 are attributed to the (AsO4)3-ν2 bending. The broad band centred at 3301 cm-1 is assigned to water stretching vibrations and the sharper peak at 3473 cm-1 is assigned to the OH stretching vibrations. The observation of strong water stretching vibrations brings into question the actual formula of arsenogorceixite. It is proposed the formula is better written as BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6·xH2O. The observation of both phosphate and arsenate bands provides a clear example of solid solution formation.

  4. Mechanical Properties of Thermoelectric Ba8Al15Si31 Clathrate Prepared by Combining Arc Melting and Spark Plasma Sintering Techniques

    NASA Astrophysics Data System (ADS)

    Anno, Hiroaki; Ueda, Takahiro; Hirata, Shusaku; Kameyama, Tomoki; Iida, Tsutomu; Kogo, Yasuo

    2016-03-01

    The mechanical properties (the elastic moduli, hardness, and fracture toughness) were investigated for polycrystalline Ba8Al15Si31 clathrate as one of useful thermoelectric materials on a phonon glass and electron crystal concept. Samples were prepared by combining arc melting and spark plasma sintering techniques. The Young's modulus E = 96.88 GPa, shear modulus G = 38.61 GPa, bulk modulus K = 65.77 GPa, and Poisson's ratio ν = 0.2545 were calculated from longitudinal sound velocity v L = 6105 m/s and transverse sound velocity v T = 3503 m/s, measured by an ultrasonic test. The elastic constants c 11 = 78.64 GPa, c 12 = 40.03 GPa, and c 44 = 38.61 GPa were calculated from E and G. The Vickers hardness HV and Young's modulus E were simultaneously determined to be 634 and 109.7 GPa, respectively, by a nanoindentation test. The fracture toughness K IC was determined to be 1.1 MPa m1/2, which was comparable to typical values 1.1-1.2 MPa m1/2 for thermoelectric silicide Mg2Si, by a Vickers indentation fracture test.

  5. Enhanced processability of ZrF4-BaF2-LaF3-AlF3-NaF glass in microgravity

    NASA Astrophysics Data System (ADS)

    Torres, Anthony; Ganley, Jeff; Maji, Arup; Tucker, Dennis; Starodubov, Dmitry

    2013-06-01

    Fluorozirconate glasses, such as ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF), have the potential for optical transmission from 0.3 μm in the UV to 7 μm in the IR region. However, crystallites formed during the fiber drawing process prevent this glass from achieving its desired transmission range. The temperature at which the glass can be drawn into a fiber is known as the working range, defined as (Tx - Tg), bounded by the glass transition temperature (Tg) and the crystallization temperature (Tx). In contrast to silica glasses, the working temperature range for ZBLAN glass is extremely narrow. Multiple ZBLAN samples were subject to a heating and quenching test apparatus on the parabolic aircraft, under a controlled 0-g and hyper-g environment and compared with 1-g ground tests. The microgravity duration on board Zero-G Corporation parabolic aircraft is approximately 20 seconds and the hyper-g intervals are approximately 56 seconds. Optical microscopy examination elucidates crystal growth in ZBLAN is suppressed when processed in a microgravity environment. The crystallization temperature, Tx, at which crystals form increased, therefore, significantly broadening the working temperature range for ZBLAN.

  6. Increasing the working temperature range of ZrF-BaF-LaF-AlF-NaF glass through microgravity processing

    NASA Astrophysics Data System (ADS)

    Torres, Anthony; Ganley, Jeff; Maji, Arup; Tucker, Dennis; Starodubov, Dmitry

    2014-03-01

    Fluorozirconate glasses, such as ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF), have the potential for optical transmission from 0.3 μm in the ultraviolet to 7 μm in the infrared regions. However, crystallites formed during the fiber-drawing process prevent this glass from achieving its desired transmission range. The temperature at which the glass can be drawn into a fiber is known as the working range, defined as (Tx-Tg), bounded by the glass transition temperature (Tg) and the crystallization temperature (Tx). In contrast to silica glasses, the working temperature range for ZBLAN glass is extremely narrow. Multiple ZBLAN samples were subjected to a heating and quenching test apparatus on the parabolic aircraft under a controlled μ-g and hyper-g environments and compared with 1-g ground tests. Optical microscopy examination elucidates that crystal growth in ZBLAN is suppressed and initiates at a later temperature when processed in a microgravity environment. Thus, the crystallization temperature, Tx, at which the crystals form has increased. The glass transition temperature, Tg, remains constant, as crystallization does not occur until approximately 360°C for this composition of ZBLAN. Therefore, the working temperature range for ZBLAN has been broadened.

  7. New Insights into the N2O formation mechanism over Pt-BaO/Al2O3 model catalysts using H2 as a reductant.

    PubMed

    Zhu, Jinxin; Wang, Jun; Wang, Jianqiang; Lv, Liangfang; Wang, Xiuting; Shen, Meiqing

    2015-01-01

    The N2O formation mechanism was investigated over a Pt-BaO/Al2O3 catalyst applied on light-duty diesel vehicles using H2 as a reductant in the absence and presence of H2O. In the absence of H2O, N2O forms mainly at the initial phase of lean NOx trapping; while in the presence of H2O, N2O appears mainly at the beginning of the rich reduction phase. In the lean period, N2O is formed via the gaseous NO/O2 reacting with the adsorbed H and NH3 that are formed during the previous rich period. The N2O formation in the rich period is insignificant in the absence of H2O but is greatly enhanced by the presence of H2O. The amount of N2O formed is proportional to the H2O level in the feed, and its formation is favored at low temperatures. Our FTIR data show that H2O enhances the rate of nitrite/nitrate reduction during the rich regeneration, which increases the amount of released NOx, an oxygen source for N2O formation. Our temperature-programmed experiments indicate that H2O competes with NH3 for adsorption sites on Pt surface. This competitive adsorption may increase the NH3 desorption rate at low temperatures in the rich phase and make Pt surface more accessible to NO. PMID:25495837

  8. Effect of water and ammonia on surface species formed during NO(x) storage-reduction cycles over Pt-K/Al2O3 and Pt-Ba/Al2O3 catalysts.

    PubMed

    Morandi, Sara; Prinetto, Federica; Castoldi, Lidia; Lietti, Luca; Forzatti, Pio; Ghiotti, Giovanna

    2013-08-28

    The effect of water, in the temperature range 25-350 °C, and ammonia at RT on two different surface species formed on Pt-K/Al2O3 and Pt-Ba/Al2O3 NSR catalysts during NO(x) storage-reduction cycles was investigated. The surface species involved are nitrates, formed during the NO(x) storage step, and isocyanates, which are found to be intermediates in N2 production during reduction by CO. FT-IR experiments demonstrate that the dissociative chemisorption of water and ammonia causes the transformation of the bidentate nitrates and linearly bonded NCO(-) species into more symmetric species that we call ionic species. In the case of water, the effect on nitrates is observable at all the temperatures studied; however, the extent of the transformation decreases upon increasing temperature, consistent with the decreased extent of dissociatively adsorbed water. It was possible to hypothesize that the dissociative chemisorption of water and ammonia takes place in a competitive way on surface sites able to give bidentate nitrates and linearly bonded NCO(-) that are dislocated, remaining on the surface as ionic species. PMID:23860492

  9. Synthesis of functionalized materials using aryloxo-organometallic compounds toward spinel-like MM'2O4 (M = Ba2+, Sr2+; M' = In3+, Al3+) double oxides.

    PubMed

    John, Łukasz; Kosińska-Klähn, Magdalena; Jerzykiewicz, Lucjan B; Kępiński, Leszek; Sobota, Piotr

    2012-09-17

    The predesigned single-source precursors [Ba{(μ-ddbfo)(2)InMe(2)}(2)] (1), [Me(2)In(μ-ddbfo)](2) (2), [Sr{(μ-ddbfo)(2)AlMe(2)}(2)] (4), and [Me(2)Al(μ-ddbfo)](2) (5) (ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol) for spinel-like double oxides and group 13 oxide materials were prepared via the direct reaction of the homoleptic aryloxide [M(ddbfoH)(4)](ddbfo)(2)·ddbfoH (M = Ba(2+), Sr(2+) (3)) and InMe(3) or AlMe(3) in toluene. In all of the reactions, there was an organometallic-driven abstraction of the OH protons from the 7-benzofuranols in the Ba(2+) and Sr(2+) cation sphere. All compounds were characterized by elemental analysis, (1)H NMR, and FT-IR spectroscopy. In addition, the molecular structures of 1, 2, and 3 were determined by single-crystal X-ray diffraction. The oxide products derived from the compounds mentioned above were studied using elemental analysis, Raman spectroscopy, X-ray powder diffraction, and scanning and transmission electron microscopy equipped with an energy-dispersive spectrometer. Moreover, their specific surface area and mesopore size distribution were evaluated using nitrogen porosimetry. Preliminary investigations of the Eu-doped SrAl(2)O(4) and In(2)O(3) phosphors revealed that the oxides obtained could be considered as matrices for lanthanide ions. PMID:22931100

  10. Cathode Formed by Thermal Evaporation of Ba:Al Alloy and Estimations of Barrier Height in an Organic LED

    NASA Astrophysics Data System (ADS)

    Ding, Lei; Zhang, Fang-Hui

    2011-06-01

    It is demonstrated that barium and aluminum alloy synthesized by melting in a glass tube under low vacuum is applicable for organic laser emitting diodes (LEDs) as a thin film cathode. The alloy film obtained by the thermal evaporation of pre-synthesized alloy is used in a single-boat organic LED device with the structure: indium tin oxide (ITO)/4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(NPB)/tris-(8-hydroxyquinoline) aluminum(Alq3)/barium:aluminum alloy. The experimental results show that devices with this alloy film cathode exhibit better current density-voltage-luminance characteristics than those with a conventional pure Al cathode, and more weight of barium in aluminum leads to better performance of the devices. Characteristics of current density versus voltage for the electron-only devices are fitted by the Richardson—Schottky emission model, indicating that the electron injection barrier has a decrease of about 0.3 eV by this alloy cathode.

  11. Influences of CaO on Crystallization, Microstructures, and Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Bo; Tang, Bo; Xu, Mingjiang

    2015-10-01

    We have developed BaO-CaO-Al2O3-B2O3-SiO2 glass-ceramics with high thermal coefficient of expansion (TCE) to overcome thermal mismatch at board level. The crystalline phases include quartz (major), cristobalite (minor), and bazirite BaZrSi3O9 (minor). Calculations from whole-pattern fitting show that the crystallinity varies slightly within the range of 33.48% to 34.89%, while the mass fraction of the phases changes remarkably with the CaO content. This indicates that CaO cannot promote crystallization of Ba-Al-B-Si glass, but effectively suppresses the phase transformation from quartz to cristobalite, making the thermal expansion curves linear. An empirical equation for the TCE versus the temperature and the amount of CaO is established. Furthermore, the densification mechanism of Ca modifiers is revealed. Due to its higher field strength than Ba, substitution of Ca increases the glass viscosity and inhibits ion diffusion. Excessive CaO is thus harmful to the density, bending strength, and electrical properties. The sample with 10 wt.% CaO sintered at 950°C exhibited high bending strength (154.1 MPa) and high TCE (12.38 ppm/°C) as well as good electrical properties ( ɛ = 6.2, tan δ = 5 × 10-4, ρ = 3.8 × 1012 Ω cm).

  12. Charged particle multiplicity in sup 28 Si+Al, Cu, and Pb reactions at E sub lab =14. 6 GeV/nucleon

    SciTech Connect

    Barrette, J.; Bellwied, R.; Braun-Munzinger, P.; Cleland, W.E.; David, G.; Dietzsch, O.; Duek, E.; Fatyga, M.; Fox, D.; Greene, S.V.; Hall, J.R.; Heifetz, R.; Hemmick, T.K.; Herman, M.; Hermann, N.; Hogue, R.W.; Ingold, G.; Jayananda, K.; Kraus, D.; Kumar, S.; Lacasse, R.; Lissauer, D.; Llope, W.J.; Ludlam, T.; Majka, R.; Makowiecki, D.; Mark, S.K.; McCorkle, S.R.; Mitchell, J.T.; Muthuswamy, M.; O'Brien, E.; Olsen, L.; Polychronakos, V.; Pruneau, C.; Rawool-Sullivan, M.; Rotondo, F.; Sandweiss, J.; Simon-Gillo, J.; Sonnadara, U.; Stachel, J.; Sullivan, J.P.; Sunier, J.; Takagui, E.M.; Takai, H.; Throwe, T.; van Hecke, H.; Waters, L.; Wolf, K.; Wolfe, D.; Woody, C.L.; Xu, N.; Zhang, Z. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 McGill University, Montreal, H3A 2T8 University of New Mexico, Albuquerque, New Mexico 87131 University of Pittsburgh, Pittsburgh,

    1992-07-01

    Collisions of {sup 28}Si+Al, Cu, and Pb at {ital E}{sub lab}=14.6 GeV/nucleon were studied at the Brookhaven National Laboratory Alternating Gradient Synchrotron. Charged particle multiplicity was measured over the pseudorapidity interval 0.875{le}{eta}{le}3.86 with a silicon pad detector. A strong correlation is seen between the multiplicity and the transverse energy measured in the interval {minus}0.5{le}{eta}{le}0.8. Correlation with the energy going forward after the collision and comparison with calculations indicate that rescattering is required to explain the data. The data are compared under the assumption of Koba-Nielson-Olesen scaling. The measured multiplicity scales approximately with the total number of participant nucleons and less well with the available center-of-mass kinetic energy.

  13. Crystal structure, characterization and thermoelectric properties of the type-I clathrate Ba{sub 8-y}Sr{sub y}Al{sub 14}Si{sub 32} (0.6{<=}y{<=}1.3) prepared by aluminum flux

    SciTech Connect

    Roudebush, John H.; Toberer, Eric S.; Hope, Hakon; Jeffrey Snyder, G.; Kauzlarich, Susan M.

    2011-05-15

    The title compound was prepared as single crystals using an aluminum flux technique. Single crystal and powder X-ray diffraction indicate that this composition crystallizes in the clathrate type-I structure, space group Pm3-bar n. Electron microprobe characterization indicates the composition to be Ba{sub 8-y}Sr{sub y}Al{sub 14.2(2)}Si{sub 31.8(2)} (0.77Al content fixed at the microprobe value (12 K data: R{sub 1}=0.0233, wR{sub 2}=0.0441) on a crystal of compositions Ba. The Sr atom preferentially occupies the 2a position; mixed Al/Si occupancy was found on all framework sites. These refinements are consistent with a fully occupied framework and nearly fully occupied cation guest sites as found by microprobe analysis. Temperature dependent electrical resistivity and thermal conductivity have been measured from room temperature to 1200 K on a hot-pressed pellet. Electrical resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers. Thermal conductivity is between 22 and 25 mW/cm K. The sample shows n-type conductivity with a maximum figure of merit, zT of 0.3 at 1200 K. A single parabolic band model predicts a five-fold increase in zT at 800 K if carrier concentration is lowered. -- Graphical abstract: The inorganic type-I clathrate phase with nominal composition Ba{sub 7}Sr{sub 1}Al{sub 14}Si{sub 32} has been prepared by Al flux. Single crystal diffraction at 90 and 12 K reveal that the framework is fully occupied with the cation sites nearly fully occupied. The lattice thermal conductivity is low thereby suggesting further optimization of the carrier concentration will lead to a high zT. Display Omitted Highlights: {yields} Ba{sub 7}Sr{sub 1}Al{sub 14}Si{sub 32} is a light element phase ideal for thermoelectric power generation. {yields} Ba{sub 7}Sr{sub 1}Al{sub 14}Si{sub 32} is a high melting point cubic

  14. Photoemission study of some novel materials: Rare earth/transition metal interface, Ba*0.6*K*0.4*BiO3* and AlPdM

    SciTech Connect

    Wu, X.

    1995-02-10

    Synchrotron radiation photoemission spectroscopy and low energy electron diffraction (LEED) are applied to explore several novel materials: (a) Ce epitaxial growth on W (110) surfaces. (b) Eu epitaxial growth on Ta (110) surfaces. (c) Sm epitaxial growth on Ta (110) surfaces. (d) quasicrystalline AlPdMn, and (e) superconducting Ba{sub 1-x}K{sub x}BiO{sub 3}. In the case of rare earth overlayers on transition metal surface, resonance photoemission spectroscopy is used to enhance the 4f features. The metal surface phase transition is investigated on an atomic-scale. In the case of quasicrystalline AlPdMn and superconducting Ba{sub 1-x}K{sub x}BiO{sub 3} the electronic structures are investigated by angle-resolved photoemission.

  15. Intense violet-blue-emitting Ba(2)AlB(4)O(9)Cl:Eu(2+) phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes.

    PubMed

    Kuo, Te-Wen; Huang, Chien-Hao; Chen, Teng-Ming

    2010-08-01

    We synthesized a violet-blue phosphor Ba(2)AlB(4)O(9)Cl:Eu(2+) with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f(7)-4f(6)d(1) transitions of Eu(2+). The phosphors with different Eu(2+) concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390nm] excitation. The optimum concentration of Eu(2+) in Ba(2)AlB(4)O(9)Cl:Eu(2+) is determined to be 6mol.%. The luminous efficiency was found to be 8.1lm/W for the violet-blue fluorescent lamp and 3.2lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba(2)AlB(4)O(9)Cl:Eu(2+) would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator. PMID:20676174

  16. Primordial Pb, radiogenic Pb and lunar soil maturation

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.

    1978-01-01

    Pb-204 is directly correlated with the reduced Fe measured by ferromagnetic resonance. A similar correlation has been noted for hydrolyzable carbon (Pillinger et al., 1974). An enrichment of these elements appears to have occurred during soil maturation. In contrast to Pb-204, radiogenic Pb is reported to be lost during soil maturation (Church et al., 1976). Radiogenic Pb is present in mineral grains and may be lost by solar wind sputtering (or volatilization) and not resupplied. Pb-204 coating grain surfaces acts as a reservoir to provide the Pb-204 being extracted in the reduced Fe formation process. Venting or some other volatile release mechanism may replenish the surface-related Pb-204.

  17. Low-Al and high-Al trondhjemites in the Huai'an Complex, North China Craton: Geochemistry, zircon U-Pb and Hf isotopes, and implications for Neoarchean crustal growth and remelting

    NASA Astrophysics Data System (ADS)

    Zhang, Hua-Feng; Zhai, Ming-Guo; Santosh, M.; Li, Sheng-Rong

    2012-04-01

    Voluminous tonalite-trondhjemite-granodiorite (TTG) magmas were emplaced in the Huai'an Complex of North China Craton (NCC) during the Neoarchean. Here we present the geochemical characteristics of these rocks and identify low-Al (LAl) and high-Al (HAl) types of trondhjemites within the TTG suite. The LAl group displays high silica (SiO2 = 77-80 wt.%), and low Al2O3 contents (11.06-11.89 wt.%), a strongly peraluminous (A/CNK = 1.16 and 1.19) composition and enrichment in HREE (LaN/YbN = 4 and 5, GdN/YbN = 0.35 and 0.9). Their low Rb (13 and 28 ppm), Th (0.3 and 7.0 ppm), relatively high Na2O/K2O values (3.6 and 4.1) and MgO (0.63 and 0.68 wt.%) with moderately high Mg# (36 and 53), suggest crystallization from a primitive source. The HAl group is characterized by relatively low SiO2 (67.22-71.57 wt.%) and high Al2O3 contents (16.35-16.41 wt.%) with trace element contents and distribution patterns closely comparable to those of Archean high-Al TTGs. Our geochemical data do not favor a direct genetic link between the LAl and HAl trondhjemite groups. The zircon U-Pb data reveal that the LAl and HAl groups represent coeval intrusions at ca. 2.55-2.5 Ga. In situ analysis of Hf isotopes in the zircons (ɛHf = +5.6 to +10, and TDM = 2462-2595 Ma), together with the geochemical features of the low-Al trondhjemites suggest that they were generated under relatively low pressure (<8 kbar), through low degree partial melting of a newly accreted amphibolitic crust. Taking into consideration the contemporaneous (2.55-2.50 Ga) high-Al TTGs widely exposed in the Huai'an Complex, we suggest that the low-Al trondhjemites were formed by intraplating of mantle-derived magmas, and the coeval high-Al TTGs were produced by partial melting of a thickened lower crust, triggered by underplating. Our study attests to a major episode of Neoarchean crustal growth in the NCC, and remelting induced by underplating and intraplating of mantle-derived magmas.

  18. Discovery of a phosphor for light emitting diode applications and its structural determination, Ba(Si,Al)5(O,N)8:Eu2+.

    PubMed

    Park, Woon Bae; Singh, Satendra Pal; Sohn, Kee-Sun

    2014-02-12

    Most of the novel phosphors that appear in the literature are either a variant of well-known materials or a hybrid material consisting of well-known materials. This situation has actually led to intellectual property (IP) complications in industry and several lawsuits have been the result. Therefore, the definition of a novel phosphor for use in light-emitting diodes should be clarified. A recent trend in phosphor-related IP applications has been to focus on the novel crystallographic structure, so that a slight composition variance and/or the hybrid of a well-known material would not qualify from either a scientific or an industrial point of view. In our previous studies, we employed a systematic materials discovery strategy combining heuristics optimization and a high-throughput process to secure the discovery of genuinely novel and brilliant phosphors that would be immediately ready for use in light emitting diodes. Despite such an achievement, this strategy requires further refinement to prove its versatility under any circumstance. To accomplish such demands, we improved our discovery strategy by incorporating an elitism-involved nondominated sorting genetic algorithm (NSGA-II) that would guarantee the discovery of truly novel phosphors in the present investigation. Using the improved discovery strategy, we discovered an Eu(2+)-doped AB5X8 (A = Sr or Ba, B = Si and Al, X = O and N) phosphor in an orthorhombic structure (A21am) with lattice parameters a = 9.48461(3) Å, b = 13.47194(6) Å, c = 5.77323(2) Å, α = β = γ = 90°, which cannot be found in any of the existing inorganic compound databases. PMID:24437942

  19. Effectively simultaneous naked-eye detection of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin extracted from red cabbage as chelating agent

    NASA Astrophysics Data System (ADS)

    Khaodee, Warangkhana; Aeungmaitrepirom, Wanlapa; Tuntulani, Thawatchai

    Simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin as a chelating agent was investigated in terms of both quantitative and qualitative detections. Cyanidin was extracted and purified from red cabbage which is a local plant in Thailand. The selectivity of this method was examined by regulating the pH of cyanidin solution operated together with masking agents. It was found that Cu(II), Pb(II), Al(III) and Fe(III) simultaneously responded with the color change at pH 7, pH 6, pH 5 and pH 4, respectively. KF, DMG and the mixture of KF and DMG were used as masking agents for the determination of Fe(III), Al(III) and Pb(II), respectively. Results from naked-eye detection were evaluated by comparing with those of inductively coupled plasma (ICP), and there was no significant difference noticed. Cyanidin using as a multianalyte reagent could be employed for simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) at the lowest concentration at 50, 80, 50 and 200 μM, respectively, by slightly varying pHs. Moreover, the proposed method could be potentially applied for real water samples with simplicity, rapidity, low cost and environmental safety.

  20. Al2O3 influence on structural, elastic, thermal properties of Yb(3+) doped Ba-La-tellurite glass: evidence of reduction in self-radiation trapping at 1μm emission.

    PubMed

    Balaji, S; Biswas, K; Sontakke, A D; Gupta, G; Ghosh, D; Annapurna, K

    2014-12-10

    Ba-La-tellurite glasses doped with Yb(3+) ions have been prepared through melt quenching technique by modifying their composition with the inclusion of varied concentration of Al2O3 to elucidate its effects on glass structural, elastic, thermal properties and Yb(3+) ion NIR luminescence performance. The FTIR spectral analysis indicates Al2O3 addition is promoting the conversion of BOs from NBOs which have been generated during the process of depolymerisation of main glass forming TeO4 units. The elastic properties of the glass revealed an improved rigidity of the glass network on addition of Al2O3. In concurrence to this, differential thermal analysis showed an increase in glass transition temperature with improved thermal stability factor. Also, Yb(3+) fluorescence dynamics demonstrated that, Al2O3 inclusion helps in restraining the detrimental radiation trapping of ∼1μm emission. PMID:24954756

  1. Structural distortions in Sr{sub 3-x}A{sub x}MO{sub 4}F (A=Ca, Ba; M=Al, Ga, In) anti-Perovskites and corresponding changes in photoluminescence

    SciTech Connect

    Sullivan, Eirin; Avdeev, Maxim; Vogt, Thomas

    2012-10-15

    The ordered oxyfluoride family Sr{sub 3}-{sub x}A{sub x}MO{sub 4}F (A=Ca, Ba and M=Al, Ga) has formed the basis of several new inorganic phosphors, and shows great potential for use in phosphor-conversion LED lamp devices. This study examines the correlation between subtle structural changes and photoluminescent behaviour in some of these materials. In order to ascertain whether cation charge compensation has any influence on structure and subsequent photoluminescent behaviour, a comparison was carried out between phases with the nominal compositions Sr{sub 2.975}Ce{sub 0.025}AlO{sub 4}F and Sr{sub 2.95}Ce{sub 0.025}Na{sub 0.025}AlO{sub 4}F using structural characterisation based upon high-resolution neutron powder diffraction (NPD) data. Additionally, NPD data has been used to elucidate the role of different M cations in these materials, using Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}M{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}} (M=Al, Ga) to determine the effect M cation size has on structure and photoluminescent properties. - Graphical abstract: The structure of Sr3-xAxMO4F (A=Ca, Ba and M=Al, Ga) and excitation and emission spectra for Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}Ga{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}}. Highlights: Black-Right-Pointing-Pointer Correlation between structural changes and photoluminescence in Sr{sub 3-x}A{sub x}MO{sub 4}F (A=Ca, Ba, M=Al, Ga). Black-Right-Pointing-Pointer Comparison of Sr{sub 2.975}Ce{sub 0.025}AlO{sub 4}F and Sr{sub 2.95}Ce{sub 0.025}Na{sub 0.025}AlO{sub 4}F using high-resolution NPD. Black-Right-Pointing-Pointer Study of the effect of cation charge-compensation on structure and photoluminescent behaviour. Black-Right-Pointing-Pointer Examination of high-resolution NPD data for Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}M{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}} (M=Al, Ga). Black-Right-Pointing-Pointer Determination of the effect M cation size has on structure and photoluminescent properties.

  2. Studies of total bremsstrahlung in thick targets of Al, Ti, Sn and Pb for 90Sr beta particles in the photon energy region of 1-100 keV

    NASA Astrophysics Data System (ADS)

    Singh, Amrit; Dhaliwal, A. S.

    2016-02-01

    Total bremsstrahlung (BS) spectra in thick targets of Al, Ti, Sn and Pb produced by beta emitter 90Sr (End point energy=546 keV) are studied in the photon energy range of 1-100 keV. The experimentally measured BS spectra are compared with the theoretical spectral distributions calculated from Elwert corrected (non relativistic) Bethe-Heitler [EBH] theory, modified Elwert factor (relativistic) Bethe-Heitler [Fmod BH] theory for ordinary bremsstrahlung (OB) and the Avdonina and Pratt [Fmod BH+PB] theory, which include the contribution of polarization bremsstrahlung (PB) into OB. The present results are indicating the correctness of Fmod BH+PB theory in the low energy region, where PB dominates into the BS, but at the middle and higher photon energy region of the bremsstrahlung spectrum, the Fmod BH theory is more close to the experimental results. The description of the bremsstrahlung process in stripped atom (SA) approximation, which indicates the suppression of the bremsstrahlung at higher energy ends due to the production of PB in the low energy region, needs further considerations. Hence, the present measurements for BS for different target materials indicates that the considerations of the screening effects along with other secondary effects during the interaction of incident electrons with the target nuclei are important while describing the production of bremsstrahlung, particularly for the higher energy regions.

  3. Engineering oxygen vacancies towards self-activated BaLuAl(x)Zn(4-x)O(7-(1-x)/2) photoluminescent materials: an experimental and theoretical analysis.

    PubMed

    Ma, Lan; Xia, Zhiguo; Atuchin, Victor; Molokeev, Maxim; Auluck, S; Reshak, A H; Liu, Quanlin

    2015-12-14

    Novel self-activated yellow-emitting BaLuAlxZn4-xO7-(1-x)/2 photoluminescent materials were investigated by a combined experimental and theoretical analysis. The effects of Al/Zn composition modulation, calcination atmosphere and temperature on the crystal structure and photoluminescence properties have been studied via engineering oxygen vacancies. Accordingly, BaLuAl0.91Zn3.09O7 prepared in an air atmosphere was found to be the stable crystalline phase with optimal oxygen content and gave a broad yellow emission band with a maximum at 528 nm. The self-activated luminescence mechanism is ascribed to the O-vacancies based on the density functional theory (DFT) calculation. A theoretical model originating from the designed oxygen vacancies has been proposed in order to determine the influence of O-vacancies on the band structure and self-activated luminescence. Therefore, the appearance of a new local energy level in the band gap will cause the wide-band optical transitions in the studied BaLuAlxZn4-xO7-(1-x)/2 materials. PMID:26542229

  4. Acoustic emission during the ferroelectric transition Pm3{sup ¯}m to P4mm in BaTiO{sub 3} and the ferroelastic transition R3{sup ¯}m-C2/c in Pb{sub 3}(PO{sub 4}){sub 2}

    SciTech Connect

    Salje, E. K. H.; Dul'kin, E.; Roth, M.

    2015-04-13

    Acoustic emission (AE) spectroscopy without frequency filtering (∼broadband AE) and moderate time integration is shown to be sensitive enough to allow the investigation of subtle nano-structural changes in ferroelectric BaTiO{sub 3} and ferroelastic Pb{sub 3}(PO{sub 4}){sub 2}. AE signals during weak phase transitions are compatible with avalanche statistics as observed previously in large-strain systems. While the data are too sparse to determine avalanche exponents, they are well suited to determine other thermodynamic parameters such as transition temperatures and critical stresses.

  5. Study of selected off-gases produced during the immobilization of nuclear wastes in the SYNROC process. Final report for year ended December 31, 1981. [Pollucite, CsAlSi/sub 2/O/sub 6/, and barium-cesium hollandite, (Ba,Cs)Al/sub 2/Ti/sub 6/O/sub 16/

    SciTech Connect

    Carpenter, J.H.

    1981-12-31

    Calculation of possible off-gases expected during the fabrication of SYNROC showed that volatilization of cesium would be a significant problem. Samples of the cesium containing minerals pollucite, CsAlSi/sub 2/O/sub 6/, and barium-cesium hollandite, (Ba,Cs)Al/sub 2/Ti/sub 6/O/sub 16/, were prepared for vaporization studies. Fifteen vaporization runs were made with the hollandite samples. With dry air as the carrier gas, the vapor pressure of cesium over Ba/sub 0/ /sub 8/Cs/sub 0/ /sub 4/Al/sub 2/Ti/sub 6/O/sub 16/ was found to be about 1 x 10/sup -7/ atm at 1050/sup 0/C.

  6. Features of crystal and magnetic structures of solid solutions BaFe12-xDxO19 (D=Al3+, In3+; x=0.1) in a wide temperature range

    NASA Astrophysics Data System (ADS)

    Turchenko, Vitalii; Trukhanov, Alexey; Trukhanov, Sergey; Bobrikov, Ivan; Balagurov, Anatoly M.

    2016-04-01

    The study of barium ferrites partially substituted by diamagnetic Al and In ions has been performed by the neutron diffraction method with high resolution. Both samples BaFe11.9 D 0.1O19 ( D=Al and In) preserve a magnetoplumbit structure in a broad temperature range from 4.2K to 730K. The Invar effect was found in the low-temperature region in both samples. This unusual behavior of the unit cell was explained by changes of the regime of mutual rotations and tilts of the oxygen octahedra. The magnetic structure described by the Gorter model is saved up to the ferrimagnetic and paramagnetic phase transition temperature, 705K and 695K, for the Al- and In-substituted ions, respectively. The substitution of iron by aluminum or indium ions decreases the total magnetic moment of the investigated composition from 20 μB (BaFe12O19) to 19 and 16.7 μB, respectively. A higher coercitivity was found Hc˜ 0.1 T, for the In-substituted compositions, differently from Hc˜ 0.007 T of the Al-doped ones because of the frustration of the magnetic structure. The decrease of ambient temperature increases microstresses in crystallites because of the increasing influence of the magnetic subsystem.

  7. Barium-deficient celsian, Ba1-xAl2-2xSi2+2xO8 (x = 0.20 or 0.06).

    PubMed

    Skellern, Matthew G; Howie, R Alan; Lachowski, Eric E; Skakle, Janet M S

    2003-02-01

    Barium-deficient forms of celsian (barium aluminium silicate) with the formula Ba(1-x)Al(2-2x)Si(2+2x)O(8) (x = 0.20 and 0.06) have been identified. In contrast with the celsian-orthoclase solid solutions which have been reported previously, these forms, refined in the space group C2/m, with Ba and one O atom in the 4i sites with m site symmetry, and a further O atom in a 4g site with twofold axial symmetry, suggest a slight solid solution with silica. The serendipitous preparation of the compounds represents a possible hazard associated with solid-state synthesis. PMID:12574637

  8. Microstructure and dielectric properties of (Ba 0.6Sr 0.4)TiO 3 thin films grown on super smooth glazed-Al 2O 3 ceramics substrate

    NASA Astrophysics Data System (ADS)

    Chen, Hongwei; Yang, Chuanren; Zheng, Shanxue; Zhang, Jihua; Zhang, Qiaozhen; Lei, Guanhuan; Lou, Feizhi; Yang, Lijun

    2011-12-01

    Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO-Al2O3-SiO2 (CaAlSi) high temperature glaze with proper additives on the rough-95% Al2O3 ceramics substrates. (Ba0.6Sr0.4)TiO3 (BST) thin films were deposited on modified Al2O3 substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al2O3 substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al2O3 substrates were almost consistent with that of BST thin films grown on LaAlO3 (1 0 0) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al2O3 substrates.

  9. Thermoelectric properties of metallic antiperovskites AXD3 (A=Ge, Sn, Pb, Al, Zn, Ga; X=N, C; D=Ca, Fe, Co)

    NASA Astrophysics Data System (ADS)

    Bilal, Muhammad; Ahmad, Iftikhar; Asadabadi, Saeid Jalali; Ahmad, Rashid; Maqbool, Muhammad

    2015-05-01

    In this paper we communicate the thermoelectric properties of carbon and nitrogen based metallic antiperovskites ANCa3 (A=Ge, Sn, Pb), BCFe3 (B=Al, Zn, Ga) and SnCD3 (D=Co and Fe) using the ab-initio calculations to explore efficient metallic thermoelectric materials. The consistency of the calculated results of SnCCo3 and SnCFe3 with the experimental results confirms the reliability of our theoretical calculations for the other investigated metallic antiperovskites. The results indicate that the thermopower of these materials can be enhanced by changing the chemical potential. The dimensionless figure of merit for the three nitrides approaches 0.96 at room temperature, which proves the usefulness of these materials in thermoelectric generators. Furthermore, the thermal conductivity is minimum at room temperature for chemical potential values between -0.25 μ(eV) and 0.25 μ(eV), and provides the maximum values of dimensionless figure of merit in this range. The striking feature of these studies is identifying a metallic compound, SnNCa3, with the highest value of Seebeck coefficient at room temperature out of all metals. The results anticipate that these materials could be efficient in thermoelectric generators; however, this needs experimental verification.[Figure not available: see fulltext.

  10. U-Pb zircon geochronology and geological evolution of the Halaban- Al Amar region of the eastern Arabian Shield, Kingdom of Saudi Arabia.

    USGS Publications Warehouse

    Stacey, J.S.; Stoeser, D.B.; Greenwood, W.R.; Fischer, L.B.

    1984-01-01

    U/Pb zircon model ages for 11 major units from this region indicate three stages of evolution: 1) plate convergence, 2) plate collision and 3) post-orogenic intracratonic activity. Convergence occurred between the western Afif and eastern Ar Rayn plates that were separated by oceanic crust. Remnants of crust now comprise the ophiolitic complexes of the Urd group; the oldest plutonic unit studied is from one such complex, and gave an age of 694-698 m.y., while detrital zircons from an intercalated sedimentary formation were derived from source rocks with a mean age of 710 m.y. Plate convergence was terminated by collision of the two plates during the Al Amar orogeny which began at -670 m.y.; during collision, the Urd group rocks were deformed and in part obducted on to one or other of the plates. Synorogenic granitic rocks were intruded from 670 to 640 m.y., followed from 640 to 630 m.y. by unfoliated dioritic plutons emplaced in the Ar Rayn block.-R.A.H.

  11. Crystal structure, characterization and thermoelectric properties of the type-I clathrate Ba 8- ySr yAl 14Si 32 (0.6≤ y≤1.3) prepared by aluminum flux

    NASA Astrophysics Data System (ADS)

    Roudebush, John H.; Toberer, Eric S.; Hope, Håkon; Jeffrey Snyder, G.; Kauzlarich, Susan M.

    2011-05-01

    The title compound was prepared as single crystals using an aluminum flux technique. Single crystal and powder X-ray diffraction indicate that this composition crystallizes in the clathrate type-I structure, space group Pm3¯ n. Electron microprobe characterization indicates the composition to be Ba 8- ySr yAl 14.2(2)Si 31.8(2) (0.77< y<1.3). Single-crystal X-ray diffraction data (90 and 12 K) were refined with the Al content fixed at the microprobe value (12 K data: R1=0.0233, wR2=0.0441) on a crystal of compositions Ba. The Sr atom preferentially occupies the 2 a position; mixed Al/Si occupancy was found on all framework sites. These refinements are consistent with a fully occupied framework and nearly fully occupied cation guest sites as found by microprobe analysis. Temperature dependent electrical resistivity and thermal conductivity have been measured from room temperature to 1200 K on a hot-pressed pellet. Electrical resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers. Thermal conductivity is between 22 and 25 mW/cm K. The sample shows n-type conductivity with a maximum figure of merit, zT of 0.3 at 1200 K. A single parabolic band model predicts a five-fold increase in zT at 800 K if carrier concentration is lowered.

  12. 210Pb dating

    USGS Publications Warehouse

    Swarzenski, Peter W.

    2014-01-01

    Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.

  13. Preparation of Tl sub 2 Ba sub 2 CaCu sub 2 O sub 8 superconducting thin films on LaAlO sub 3 substrates from metalorganic-chemical-vapor-deposition-prepared precursor films

    SciTech Connect

    Ladd, J.A.; Collins, B.T.; Matey, J.R. ); Zhao, J.; Norris, P. )

    1991-09-09

    Single phase Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} thin films have been deposited on single-crystal LaAlO{sub 3} substrates, (100) orientation, via a two-step deposition process. First, Ba-Ca-Cu-O precursor films were deposited by metalorganic chemical vapor deposition (MOCVD) using barium, calcium, and copper-tetramethyl-heptanedionate, (tmhd){sub 2}, source materials under reduced pressure in an oxygen/argon atmosphere. Substrate temperatures were between 500 and 600 {degree}C. Thallium was then incorporated by heating the films in a confined surface configuration with an unfired pellet of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub {ital x}} composition at 870 {degree}C for 0.1 h. The resultant films (0.5--1 {mu}m thick) showed a preferred orientation with the {ital c} axis normal to the substrate. The superconducting properties were characterized by resistance and mutual inductance versus temperature and by critical current measurements. Zero resistance temperatures as high as 98 K and {ital J}{sub {ital c}} values close to 1{times}10{sup 4} A/cm{sup 2} at 77 K were observed.

  14. Optical and fluorescence spectroscopy of Eu2O3-doped P2O5-K2O-KF-MO-Al2O3 (M = Mg, Sr and Ba) glasses

    NASA Astrophysics Data System (ADS)

    Kumar, K. Upendra; Babu, S. Surendra; Rao, Ch. Srinivasa; Jayasankar, C. K.

    2011-06-01

    Fluorophosphate glasses of composition, P2O5 + K2O + KF + MO + Al2O3 + xEu2O3 (M = Mg, Sr and Ba; x = 0.01, 0.05, 0.1, 1.0, 2.0, 4.0 and 6.0 mol%) were prepared and characterized their optical properties. Crystal-field (CF) analysis revealed a relatively weak CF strength around Eu3+ ions in the Ba based fluorophosphate glasses. The Judd-Ofelt parameters have been estimated from the oscillator strengths of 7F0 → 5D2, 7F0 → 5D4 and 7F0 → 5L6 absorption transitions of Eu3+ ions and were used to evaluate the radiative properties of the 5D0 → 7FJ (J = 0-4) transitions. Considerable variation has been observed in the relative intensity ratio of 5D0 → 7F2 to 5D0 → 7F1 transitions of Eu3+ ions due to change in the alkaline earth metal ions. The decay of the 5D0 level shows single exponential and less sensitive to Eu3+ ions concentration as well as MgO/SrO/BaO modifiers.

  15. Thermal stability of Ag, Al, Sn, Pb, and Hg films reinforced by 2D (C, Si) crystals and the formation of interfacial fluid states in them upon heating. MD experiment

    NASA Astrophysics Data System (ADS)

    Polukhin, V. A.; Kurbanova, E. D.

    2016-02-01

    Molecular dynamics simulation is used to study the thermal stability of the interfacial states of metallic Al, Ag, Sn, Pb, and Hg films (i.e., the structural elements of superconductor composites and conducting electrodes) reinforced by 2D graphene and silicene crystals upon heating up to disordering and to analyze the formation of nonautonomous fluid pseudophases in interfaces. The effect of perforation defects in reinforcing 2D-C and 2D-Si planes with passivated edge covalent bonds on the atomic dynamics is investigated. As compared to Al and Ag, the diffusion coefficients in Pd and Hg films increase monotonically with temperature during thermally activated disordering processes, the interatomic distances decrease, the sizes decrease, drops form, and their density profile grows along the normal. The coagulation of Pb and Hg drops is accompanied by a decrease in the contact angle, the reduction of the interface contact with graphene, and the enhancement of its corrugation (waviness).

  16. Quarternary oxide phases Ln4- xA4+ xCo 2+ yAl 2- yO 15: The structures of Nd 3.43Ba 4.42Co 2.23Al 1.77O 15 and Y 2Sr 6Co 2.08Al 1.92O 15

    NASA Astrophysics Data System (ADS)

    Lee, J. Y.; Swinnea, J. S.; Steinfink, H.

    1991-12-01

    The crystal structure of two compounds having the generic formula Ln4- xA4+ xCo 2+ yAl 2- yO 15 has been determined. Nd 3.43Ba 4.42(1)Co(Co 1.23(6)Al 1.77)O 15 (compound I), Mr = 1520.96, hexagonal, P6 3mc, a = 11.544(1) Å, c = 6.912(1) Å, V = 797.7(2) Å3, Z = 2, D x = 6.33 g cm-3, MoKα λ = 0.71069 Å, μ 1 = 242.0 cm-1; R = 0.045 for 758 reflections >5 σ( F). Y 2Sr 6Co(Co 1.08(6)Al 1.92)O 15 (compound II), Mr = 1118.00, hexagonal, P6 3mc, a = 11.199(2) Å, c = 6.664(1) Å, V = 723.8(4) Å3, Z = 2, D x = 5.13 g cm-3, MoK α λ = 0.71069 Å, μ 1 = 317.5 cm-1; R = 0.076 for 373 reflections >6 σ( F). The structure consists of clusters formed by a Co-oxygen octahedron that shares three corners of a triangular face with three separate {Co}/{Al}- oxygen tetrahedra leading to a cluster formula [ Co VI( {Co}/{Al}) IV3]O 15. The tetrahedral interstice is randomly occupied by Co 3+ and Al 3+ ions. The octahedral interstice is occupied by Co whose valence is 2+ in compound I and 3 + in II. Two such clusters exist in the unit cell and they are joined by rare earth-alkaline earth cations in 6-fold (octahedral), 8-fold (bisdisphenoid), 10-fold (capped trigonal prism), and 12-fold (cubic close packed) coordination to the oxygen ions. The octahedral cation positions are randomly occupied by about equal amounts of NdBa and YSr, respectively. Phase I forms with Pr and Gd but not with La, Y, or Er, restricting its formation to lanthanide ionic radii between 1.14 and 1.06 Å.

  17. Little Ice Age Recorded in Mn/Fe Precipitates by Pb and Nd Isotopes

    NASA Astrophysics Data System (ADS)

    Liebetrau, V.; Eisenhauer, A.; Frei, R.; Bock, B.; Kronz, A.; Hansen, B. T.; Leipe, T.

    2002-12-01

    Ferromanganese precipitates of the Baltic Sea can be dated by the 226Raexcess/Ba-method (Liebetrau et al., 2002). Recent investigations have shown that these precipitates may represent perfect archives for the postglacial history of the circum Baltic area. In particular, these precipitates offer the possibility to study short term variations of the Scandinavian shield erosion and climate change during the Little Ice Age. The Nd isotope record of a selected Mn/Fe crust from the Mecklenburg Bay of the Baltic Sea shows a significant change of the ɛ Nd-value from around -13 for ages older than 1100 years AD to approx. -18 around 1600 years AD. This shift can be explained by increased erosion and input of Nd from Archean Scandinavian sources and/or a reduced inflow of North Atlantic water (ɛ Nd = -13) to the Baltic Sea. Comparison with a temperature reconstruction for Fennoscandia (Mann, 2001) documents a close relationship of the ɛ Nd record with temperature variations during the Little Ice Age because negative ɛ Nd-value tend to correlate with lower temperature during the last 1000 years. In contrast, the pattern of 207Pb/206Pb record closely correlates with historically known changes of anthropogenic activities during the industrial revolution and times of enhanced Ag and Pb mining. Nd and Pb are correlated before 1100 AD but are decoupled after at about 1100 years AD. We propose that Pb appears to be more sensitive to anthropogenic activities since about 1100 AD. Liebetrau V., Eisenhauer A., Gussone N., W”rner G., Hansen B.T., and Leipe T., 2002, 226Raexcess/Ba growth rates and U-Th-Ra-Ba systematic of Baltic Mn/Fe crusts, Geochim. Cosmochim. Acta, 66, 73-83 Mann M.E., 2001, The Little Ice Age, in: Encyclopedia of Environmental Global Change

  18. Interfacial charge-induced polarization switching in Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} bi-layer

    SciTech Connect

    Kim, Yu Jin; Park, Min Hyuk; Jeon, Woojin; Kim, Han Joon; Moon, Taehwan; Lee, Young Hwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong

    2015-12-14

    Detailed polarization switching behavior of an Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} (AO/PZT) structure is examined by comparing the phenomenological thermodynamic model to the experimental polarization–voltage (P-V) results. Amorphous AO films with various thicknesses (2–10 nm) were deposited on the polycrystalline 150-nm-thick PZT film. The thermodynamic calculation showed that the transition from the ferroelectric-like state to the paraelectric-like state with increasing AO thickness occurs at ∼3 nm thickness. This paraelectric-like state should have exhibited a negative capacitance effect without permanent polarization switching if no other adverse effects are involved. However, experiments showed typical ferroelectric-like hysteresis loops where the coercive voltage increased with the increasing AO thickness, which could be explained by the carrier injection through the thin AO layer and trapping of the carriers at the AO/PZT interface. The fitting of the experimental P-V loops using the thermodynamic model considering the depolarization energy effect showed that trapped charge density was ∼±0.1 Cm{sup −2} and critical electric field at the Pt electrode/AO interface, at which the carrier transport occurs, was ∼±10 MV/cm irrespective of the AO thickness. Energy band model at each electrostatic state along the P-V loop was provided to elucidate correlation between macroscopic polarization and internal charge state of the stacked films.

  19. Relationships Between Pb and 210Pb in Aerosol and Precipitation at a Semiremote Site in Northern Wisconsin

    NASA Astrophysics Data System (ADS)

    Talbot, R. W.; Andren, A. W.

    1983-08-01

    Measurements of Al, Pb, 210Pb, and 210Po in precipitation and aerosol were used to estimate wet and dry components of the atmospheric flux at a semiremote site in northern Wisconsin. Wet deposition was primarily responsible for removing airborne Pb, 210Pb, and 210Po, while dry deposition was also important for Al. Although Pb and 210Pb both exhibited a wet/total ratio of about 0.8, precipitation washout ratios for Pb and 210Pb suggested that 210Pb was washed from the atmosphere with greater efficiency than was Pb. This phenomenon was also illustrated by comparing the weighted mean annual specific activity in precipitation (976 pCi 210Pb mg-1 Pb) and in aerosol (476 pCi 210Pb mg-1 Pb) at this site between June 1979 and June 1980. By consideration of the apparent differential precipitation washout of Pb and 210Pb, a reasonable estimate of the atmospheric flux of Pb was obtained by using the mean Pb/210Pb ratio in aerosol and the 210Pb flux. The atmospheric flux to northern Wisconsin was estimated to be 0.8 μg cm-2 yr-1 for Pb and 0.70 pCi cm-2 yr-1 for 210Pb.

  20. Geogenic and Anthropogenic Moss Responsiveness to Element Distribution Around a Pb-Zn Mine, Toranica, Republic of Macedonia.

    PubMed

    Angelovska, Svetlana; Stafilov, Trajče; Šajn, Robert; Balabanova, Biljana

    2016-04-01

    Moss species (Homalothecium lutescens, Hypnum cupressiforme, Brachythecium glareosum, and Campthotecium lutescens) were used as suitable sampling media for biomonitoring the origin of heavy-metal pollution in the lead-zinc (Pb-Zn) mine "Toranica" near the Kriva Palanka town, Eastern Macedonia. The contents of 20 elements-silver (Ag), aluminum (Al), arsenic (As), barium (Ba), calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), Pb, strontium (Sr), vanadium (V), and (Zn) were determined by atomic emission spectrometry with inductively coupled plasma. Data processing was applied with combinations of multivariate statistical methods: factor analysis, principal component analysis, and cluster analysis. Moss' responsiveness to the atmospheric distribution of the selected elements was investigated in correlation to the specific geology of the region (soil dusting). Lithogenic distribution was characterized with the distribution of three dominant geochemical associations: F1: Al-Li-V-Cr-Ni-Co, F2: Ba-Ca-Sr, and F3: Cd-Zn-Pb-Cu. Spatial distribution was constructed for visualization of the factor deposition. Furthermore, air distribution (passive biomonitoring) versus soil geochemistry of the analyzed elements was examined. Significant correlations were singled out for Pb, Zn, and Cd and for Mg(moss)/Na(soil). Characteristic lithological anomaly characterized the presence of the oldest geological volcanic rocks. Zone 1 (Pb-Zn mine surrounding) presents a unique area with hydrothermal action of Pb-Zn mineralization leading to polymetallic enrichments in soil. This phenomenon strongly affects the environment, which is a natural geochemical imprint in this unique area (described with the strong dominance of the geochemical association Cd-Zn-Pb-Cu). PMID:26888226

  1. Sources of Cu, Zn, Cd and Pb in rainwater at a subtropical islet offshore northern Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, Miao-Ching; You, Chen-Feng; Lin, Fei-Jan; Huang, Kuo-Fang; Chung, Chuan-Hsiung

    2011-02-01

    Pollutants derived from long-range transport and local emission impact significantly of heavy metal compositions in rainwater and aerosols. To identify their sources and relative contributions in rainwater, 47 monthly rainwater samples from January 1998 to December 2001, collected at Peng Chia Yu (PCY), a non-residential islet offshore Taiwan, were analyzed for heavy metals (i.e. Cu, Zn, Cd, and Pb) and Pb isotopic compositions. The dissolved metals concentrations of Al, Mn, Fe, Cu, Zn, Rb, Ba, and Pb in PCY rains are high in spring and winter, but low in summer. This can be understood in terms of pollutant source changes due to wind direction shifted seasonally. The average EF crust and EF seawater values calculated for Cu, Zn, Cd and Pb are far greater than 1500, suggesting their strong anthropogenic sources, also supported by the PCA results. The pollutants derived from long-range transport are the predominated heavy metals sources during the winter monsoon season, whereas local traffic emissions play the most important role during the summer monsoon period. Unique Pb isotopic fingerprints, similar to those of iron ore sinter dusts and oil combustion dusts from Shanghai and the traffic emissions from Taiwan were identified in PCY rainwater. A mixing model based on three typical end-member Pb isotopic compositions derived from Taiwan and China was applied to evaluate the pollutant sources variations.

  2. R3Au(6+x)Al26T (R = Ca, Sr, Eu, Yb; T = early transition metal): a large family of compounds with a stuffed BaHg11 structure type grown from aluminum flux.

    PubMed

    Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

    2009-02-16

    A collection of new quaternary intermetallic compounds with a cubic, stuffed BaHg(11) structure type has been synthesized by the combination of a divalent rare earth or alkaline earth metal R, an early transition metal T, and gold in an excess of molten aluminum. Structural characterization of these R(3)Au(6+x)Al(26)T compounds by powder and single crystal X-ray diffraction indicates that the unit cell varies with the radii of the early transition metal T and the rare earth/alkaline earth R as expected. The element T (where T = group 4, 5, 6, and 7 element) appears to be responsible for the stabilization of up to 43 different members of the R(3)Au(6+x)Al(26)T family of compounds. Varying amounts of disorder and trends in partial occupancies of the Au stuffed site--the site that is vacant in the parent compound BaHg(11)--are also indicated by the diffraction studies of this family of compounds. Magnetic susceptibility data reveals that the transition metal atoms in these materials do not possess local magnetic moments. For the magnetic rare earth containing materials, the europium compounds undergo a ferromagnetic transition at 10 K, and the ytterbium analogues show mixed valent behavior. Band structure calculations also support a mixed valent state for Yb in these compounds. PMID:19146424

  3. Dielectric and ferroelectric properties of highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 thin films grown on LaNiO 3/γ-Al 2O 3/Si substrates by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Guo, Yiping; Akai, Daisuke; Sawada, Kazauki; Ishida, Makoto

    2008-07-01

    A (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 chemical solution was prepared by using barium acetate, nitrate of sodium, nitrate of bismuth, and Ti-isopropoxide as raw materials. A white precipitation appeared during the preparation was analyzed to be Ba(NO 3) 2. We found that ethanolamine is a very effective coordinating ligand of Ba 2+. A transparent and stable (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 precursor chemical solution has been achieved by using ethanolamine as a ligand of Ba 2+. (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were grown on LaNiO 3/γ-Al 2O 3/Si substrates. Highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were obtained in this work due to lattice match growth. The dielectric, ferroelectric and insulative characteristics against applied field were studied. The conduction current shows an Ohmic conduction behavior at lower voltages and space-charge-limited behavior at higher voltages, respectively. These results indicate that, the (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 film is a promising lead-free ferroelectric film.

  4. Biosorption behavior and mechanism of lead (II) from aqueous solution by aerobic granules (AG) and bacterial alginate (BA)

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Li, Yu

    2012-12-01

    Lead (Pb) and its compounds are common pollutants in industrial wastewaters. To develop appropriate Pb2+ treatment technologies, aerobic granules (AG) and bacterial alginates (BA) were studied as alternative biosorbents to remove Pb2+ from aqueous solutions. The biosorption mechanism of AG and BA were further analyzed to determine which functional groups in AG and BA are active in Pb2+ biosorption. In this paper, the Pb2+ biosorption behavior of AG and BA was respectively investigated in batch experiments from the perspectives of the initial pH, contact time, and initial Pb2+ concentration. The results showed that biosorption of Pb2+ by AG and BA occurred within 60min at the initial Pb2+ concentrations (0-150 mg L-1). The actual saturated Pb2+ biosorption capability of AG was 101.97 mg g-1 (dry weight of aerobic granular biomass). When the initial pH was 5, the biosorption capability of AG and BA was highest at the initial Pb2+ concentrations (0-20mg L-1). During the process of Pb2+ biosorption, K+, Ca2+, and Mg2+ were released. The Ion Chromatography (IC) and Fourier Transform Infrared Spectroscopy (FTIR) further highlighted the main role of ion exchange between Ca2+ and Pb2+ and sequestration of Pb2+ with carboxyl (-COO-) of AG and BA. This analogical analysis verifies that BA is responsible for biosorption of Pb2+ by AG. At the same optimal pH, AG cultivated with different carbon source has different Pb2+ biosorption capacity. The Pb2+ biosorption by AG with sodium acetate as the sole carbon source is higher than AG with glucose as carbon source.

  5. Preparation and Characterization of (Ba0.8Sr0.2)TiO3-Al2O3 Composite Oxide for Thin Film Capacitor

    NASA Astrophysics Data System (ADS)

    Jang, Joo-Hee; Kim, Tae-Yoo; Lee, Chang-Hyoung; Zhang, JingJing; Park, Eun-Mi; Park, Chan; Suh, Su-Jeong

    2011-07-01

    Barium strontium titanate-alumina composites were fabricated using a sol-gel and anodizing process for high performance thin film capacitors and the properties of the films were studied. The (Ba0.8Sr0.2)TiO3 (BST) films were formed by spin coating and subsequent annealing at 150-550 °C. The respective annealed films were anodized in a neutral borate solution. The capacitance density increased with increasing annealing temperature up to 450 °C but decreased at 550 °C. The capacitance density was approximately 28.46% higher with the BST coating than without the BST layer.

  6. Large piezoelectricity in Pb-free 0.96(K{sub 0.5}Na{sub 0.5}){sub 0.95}Li{sub 0.05}Nb{sub 0.93}Sb{sub 0.07}O{sub 3}−0.04BaZrO{sub 3} ceramic: A perspective from microstructure

    SciTech Connect

    Gao, Jinghui Li, Huiying; Zhong, Lisheng; Li, Shengtao; Hao, Yanshuang; Ren, Shuai Fang, Minxia; Ren, Xiaobing; Kimoto, Takayoshi; Wang, Yu

    2015-02-28

    We employ transmission electron microscopy to explore the reason for large piezoelectricity (d{sub 33}≈400pC/N) in a Pb-free 0.96(K{sub 0.5}Na{sub 0.5}){sub 0.95}Li{sub 0.05}Nb{sub 0.93}Sb{sub 0.07}O{sub 3} −0.04BaZrO{sub 3} ceramic from microstructure. The result shows that the high piezoelectricity corresponds to a miniaturized nanodomain configuration in a domain hierarchy. The nanodomains disappear on heating accompanied by a reduction in d{sub 33} value. Further convergent beam electron diffraction study reveals a coexistence of tetragonal and orthorhombic phase, which indicates that large piezoelectricity of KNLNS{sub 0.07}-BZ may stem from easy polarization rotation due to low polarization anisotropy on the tetragonal-orthorhombic phase boundary.

  7. Pb isotope record over one century in snow from Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Van de Velde, K.; Vallelonga, P.; Candelone, J.-P.; Rosman, K. J. R.; Gaspari, V.; Cozzi, G.; Barbante, C.; Udisti, R.; Cescon, P.; Boutron, C. F.

    2005-03-01

    Pb and Ba concentrations and Pb isotopic compositions are reported for firn core and snow pit samples from Victoria Land, Antarctica, dating from 1872 AD to 1994 AD. From variations in Pb/Ba ratios and Pb isotopic compositions, two periods of major Pb enhancements were identified, from 1891 to 1908 AD and from 1948 to 1994 AD. The earlier pollution event is attributed to Pb emissions from non-ferrous metal production and coal combustion in the Southern Hemisphere and is in excellent agreement with coincident pollution inputs reported in firn/ice cores from two other regions of Antarctica, at Coats Land and Law Dome. Using Pb isotopic systematics, it was calculated that ˜50% of Pb deposited in Victoria Land in 1897 originated from anthropogenic emission sources. The more recent period of Pb enhancements, from 1948 to 1994 AD, corresponds to the introduction and widespread use of gasoline alkyl Pb additives in automobiles in the Southern Hemisphere, with anthropogenic Pb inputs averaging 60% of total Pb but with large uncertainty. Intra- and inter-annual variations in Pb concentrations and isotopic compositions were evaluated in snow pits samples corresponding to the period 1991-1994. Substantial variations in Pb/Ba and 206Pb/ 207Pb ratios were detected but the absence of a regular seasonal pattern for these parameters suggests that the transport and deposition of aerosols to the Antarctic ice sheet are complex and vary from year to year.

  8. Combined apatite fission track and U-Pb dating by LA-ICPMS

    NASA Astrophysics Data System (ADS)

    Chew, D. M.; Donelick, R. A.

    2012-04-01

    Apatite is a common accessory mineral in igneous, metamorphic and clastic sedimentary rocks. It is a nearly ubiquitous accessory phase in igneous rocks, is common in metamorphic rocks of pelitic, carbonate, basaltic, and ultramafic composition and is virtually ubiquitous in clastic sedimentary rocks. In contrast to the polycyclic behavior of the stable heavy mineral zircon, apatite is unstable in acidic groundwaters and has limited mechanical stability in sedimentary transport systems. Apatite has many potential applications in provenance studies, particularly as it likely represents first-cycle detritus. Fission track and U-Pb dating are very powerful techniques in apatite provenance studies. They yield complementary information, with the apatite fission-track system yielding low-temperature exhumation ages and the U-Pb system yielding high-temperature cooling ages which constrain the timing of apatite crystallization. This study focuses on integrating apatite fission track and U-Pb dating by the LA-ICPMS method. Our approach is intentionally broad in scope, and is applicable to any quadrupole or rapid-scanning magnetic-sector LA-ICPMS system. Calculating uranium concentrations in fission-track dating by LA-ICPMS increases the speed of analysis and sample throughput compared to the conventional external detector method and avoids the need for neutron irradiation (Hasebe et al., 2004). LA-ICPMS-based uranium measurements in apatite are measured relative to an internal concentration standard (typically 43Ca). Ca in apatite is not always stochiometric as minor cations (Mn2+, Sr2+, Ba2+ and Fe2+) and REE can substitute with Ca2+. These substitutions must be quantified by multi-elemental LA-ICPMS analyses. Such data are also useful for discriminating between different apatite populations in sedimentary or volcaniclastic rocks based on their trace-element chemistry. Low U, Th and radiogenic Pb concentrations, elevated common Pb / radiogenic Pb ratios and U-Pb elemental

  9. Dielectric spectroscopy of Pb1- x Ba x (Mg1/3Nb2/3) m (Zn1/3Nb2/3) y (Ni1/3Nb2/3) n Ti z O3 solid solutions in a wide temperature interval

    NASA Astrophysics Data System (ADS)

    Talanov, M. V.; Kubrin, S. P.; Pavelko, A. A.; Reznichenko, L. A.

    2016-06-01

    The dielectric spectra of Pb1- x Ba x (Mg1/3Nb2/3) m (Zn1/3Nb2/3) y (Ni1/3Nb2/3) n Ti z O3 ( x = 0-0.15, m = 0.4541, y = 0.0982, n = 0.1477, and z = 0.3) ceramic samples have been studied in wide intervals of temperature (10-873 K) and frequency of the measurement electric field (0.1-1000 kHz). It has been found that an increase in the Ba2+( x) content leads to a reduction in the phase transition temperature (from 418 K at x = 0 to 256 K at x = 0.15), to the transition from the normal ferroelectric state to the relaxor ferroelectric one (at x ≥ 0.025), and to the disappearance of temperature hysteresis of dependences of the relative dielectric permittivity. It has been hypothesized that a tricritical point is present near x ˜ 0.125 in the x-T phase diagram of the studied solid solutions.

  10. Pressure effects on resistive transition in (Cu,M)Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub y} (M = C,Al,Tl,Mg,Zn) superconductors

    SciTech Connect

    Tokiwa, K.; Kunugi, C.; Kashiwagi, H.

    1999-11-01

    Single phase samples with the composition of (Cu,M)Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub y}(CuM-1234; M = C,Al,Tl,Mg,Zn) have been synthesized using high pressure technique. The authors have measured the pressure dependence of superconducting transition temperature ({Tc}) through in situ resistivity measurements up to 8 GPa for these samples, reproducibly. These samples indicated almost the same {Tc}-enhancement by applied pressure, in spite of their different ambient {Tc} values. The enhancement values of 8--10 K at 8 GPa pressure for these samples are found to be comparable to those of Hg-system and (B,C)-system.

  11. Investigation of the crystal and magnetic structures of BaFe{sub 12-x}Al{sub x}O{sub 19} solid solutions (x = 0.1‒1.2)

    SciTech Connect

    Turchenko, V. A.; Trukhanov, A. V.; Bobrikov, I. A.; Trukhanov, S. V.; Balagurov, A. M.

    2015-09-15

    The structure of barium ferrite BaFe{sub 12-x}Al{sub x}O{sub 19} solid solutions (x = 0.1‒1.2) with iron partially replaced with diamagnetic aluminum ions has been studied by neutron diffraction. Experimental data have been collected at room temperature on a high-resolution diffractometer, which yielded precise information about the changes in the crystal and magnetic structures and data on the behavior of the sample microstructure. Barium hexaferrite retains a magnetoplumbite structure in the entire range of aluminum concentrations under study, and its magnetic structure is described within the Gorter model, with moments orientated along the hexagonal axis. The total magnetic moment per formula unit decreases while diamagnetic aluminum ions substitute for iron ions. Microstrains in crystallites increase with an increase in the diamagnetic ion concentration, which is related to the difference in the ionic radii of iron and aluminum ions.

  12. Epitaxial growth of (111)-oriented BaTiO{sub 3}/SrTiO{sub 3} perovskite superlattices on Pt(111)/Ti/Al{sub 2}O{sub 3}(0001) substrates

    SciTech Connect

    Panomsuwan, Gasidit; Takai, Osamu; Saito, Nagahiro

    2013-09-09

    Symmetric BaTiO{sub 3}/SrTiO{sub 3} (BTO/STO) superlattices (SLs) were epitaxially grown on Pt(111)/Ti/Al{sub 2}O{sub 3}(0001) substrates with various modulation periods (Λ = 4.8 − 48 nm) using double ion beam sputter deposition. The BTO/STO SLs exhibit high (111) orientation with two in-plane orientation variants related by a 180° rotation along the [111]{sub Pt} axis. The BTO layer is under an in-plane compressive state, whereas the STO layer is under an in-plane tensile state due to the effect of lattice mismatch. A remarkable enhancement of dielectric constant is observed for the SL with relatively small modulation period, which is attributed to both the interlayer biaxial strain effect and the Maxwell-Wagner effect.

  13. Experimental demonstration of intracavity solid-state laser cooling of Yb{sup 3+}:ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF glass

    SciTech Connect

    Heeg, B.; Stone, M.D.; Khizhnyak, A.; DeBarber, P.A.; Rumbles, G.; Mills, G.

    2004-08-01

    We report an approach to bulk optical cooling of solid-state materials by placing the cooling medium inside a laser cavity. The laser system is a diode-pumped Yb{sup 3+}:KY(WO{sub 4}){sub 2} (KYW) laser, while the cooling medium is an uncoated sample of 2%-doped Yb{sup 3+}:ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF (ZBLAN) glass. A typical drop of 6 K from ambient temperature was obtained from a noncontact temperature measurement based on the anti-Stokes luminescence profile, using diode pump power at the gain medium of 6 W, a laser wavelength of 1027 nm, and an absorbed power of 1.25 W.

  14. Phase transition sequence in Pb-free 0.96(K{sub 0.5}Na{sub 0.5}){sub 0.95}Li{sub 0.05}Nb{sub 0.93} Sb{sub 0.07}O{sub 3}−0.04BaZrO{sub 3} ceramic with large piezoelectric response

    SciTech Connect

    Gao, Jinghui Zhang, Le; Zhang, Ming; Dai, Ye; Hu, Xinghao; Wang, Dong; Zhong, Lisheng; Li, Shengtao; Ren, Shuai; Hao, Yanshuang Fang, Minxia; Ren, Xiaobing

    2015-07-20

    The piezoceramic 0.96(K{sub 0.5}Na{sub 0.5}){sub 0.95}Li{sub 0.05}Nb{sub 0.93}Sb{sub 0.07}O{sub 3}−0.04BaZrO{sub 3} (KNLNS{sub 0.07}-BZ), which shows large piezoelectric response (d{sub 33} ≈ 425 pC/N), has been considered as one of the promising Pb-free substitutions for Pb(Zr,Ti)O{sub 3}. In this paper, we investigate the phase transition sequence for KNLNS{sub 0.07}-BZ by employing the dielectric measurement, mechanical spectroscopy, as well as Raman spectroscopy. Two ferroelectric-ferroelectric transitions have been detected by inspecting anomalies in the spectra, indicating the existence of three ferroelectric phases. Moreover, in-situ X-ray diffraction study has been further performed on KNLNS{sub 0.07}-BZ to identify the crystal structure for each phase. The result reveals that the phase sequence for KNLNS{sub 0.07}-BZ evolves from tetragonal (T) to rhombohedral (R) via an intermediate orthorhombic (O) phase. And the piezoelectric-optimal region for KNLNS{sub 0.07}-BZ locates on a T-O boundary rather than the previously reported T-R boundary. Strong piezoelectricity may stem from the easier polarization rotation on the T-O boundary with reduced polarization anisotropy.

  15. Ferroelectric properties of (Pb,La)(Zr,Ti)O3 capacitors employing Al-doped ZnO top electrodes prepared by pulsed laser deposition under different oxygen pressures

    NASA Astrophysics Data System (ADS)

    Takada, Yoko; Okamoto, Naoki; Saito, Takeyasu; Kondo, Kazuo; Yoshimura, Takeshi; Fujimura, Norifumi; Higuchi, Koji; Kitajima, Akira

    2016-06-01

    Al-doped ZnO (AZO) top electrodes were deposited under oxygen pressures from 0.02 to 20 Pa using pulsed laser deposition (PLD) to fabricate ferroelectric (Pb,La)(Zr,Ti)O3 capacitors. The oxygen pressure during PLD affected the surface morphology of the AZO top electrodes as well as the ferroelectric properties. In particular, the surface morphologies were dramatically altered by increasing oxygen pressure. We obtained desirable ferroelectric properties with the highest maximum polarization and lowest coercive voltage at around 2.0 Pa. The saturation characteristics, hydrogen degradation resistance, and fatigue resistance were almost unrelated to the oxygen pressure during PLD.

  16. Average and local structure of the Pb-free ferroelectric perovskites (Sr,Sn)TiO3 and (Ba,Ca,Sn)TiO3

    SciTech Connect

    Laurita, Geneva; Page, Katharine; Suzuki, Shoichiro; Seshadri, Ram

    2015-12-16

    The characteristic structural off -centering of Pb2+ in oxides, associated with its 6s2 lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds Sr0.9Sn0.1TiO3 and Ba0.79Ca0.16Sn0.05TiO3 using neutron total scattering techniques with data acquired at di erent temperatures. In these compounds, previously reported as ferroelectrics, Sn2+ appears to display some of the characteristics of Pb2+. We compare the local and long-range structures of the Sn2+-substituted compositions to the unsubstituted parent compounds SrTiO3 and BaTiO3. Lastly, we find that even at these small substitution levels, the Sn2+ lone pairs drive the local ordering behavior, with the local structure of both compounds more similar to the structure of PbTiO3 rather than the parent compounds.

  17. RELATIONSHIPS BETWEEN PB AND 210 PB IN AEROSOL AND PRECIPITATION AT A SEMIREMOTE SITE IN NORTHERN WISCONSIN

    EPA Science Inventory

    Measurements of Al, Pb, (210)Pb, and (210)Po in precipitation and aerosol were used to estimate wet and dry components of the atmospheric flux at a semiremote site in northern Wisconsin. Wet deposition was primarily responsible for removing airborne Pb, (210)Pb, and (210)Po, whil...

  18. Cation-poor complex metallic alloys in Ba(Eu)–Au–Al(Ga) systems: Identifying the keys that control structural arrangements and atom distributions at the atomic level

    DOE PAGESBeta

    Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J.; Mudring, Anja -Verena

    2015-10-19

    Four complex intermetallic compounds BaAu6±xGa6±y (x = 1, y = 0.9) (I), BaAu6±xAl6±y (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104–112, Fm3C), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successivemore » decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution (“coloring scheme”). Chemical bonding analyses for two different “EuAu6Tr6” models reveal maximization of the number of heteroatomic Au–Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the “EuAu6Tr6” models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. As a result, the effective moments of 8.3 μB/f.u., determined from Curie–Weiss fits, point to divalent oxidation states for europium in both III and IV.« less

  19. Effects of Microbial and Phosphate Amendments on the Bioavailability of Lead (Pb) in Shooting Range Soil

    SciTech Connect

    Brigmon, Robin; Wilson, Christina; Knox, Anna; Seaman, John; Smith, Garriet

    2005-06-16

    Heavy metals including lead (Pb) are released continually into the environment as a result of industrial, recreational, and military activities. Lead ranked number two on the CERCLA Priority List of Hazardous Substances and was identified as a major hazardous chemical found on 47% of USEPA's National Priorities List sites (Hettiarachchi and Pierzynski 2004). In-situ remediation of lead (Pb) contaminated soils may be accomplished by changing the soil chemistry and structure with the application of microbial and phosphate amendments. Soil contaminated with lead bullets was collected from the surface of the berm at Savannah River Site (SRS) Small Arms Training Academy (SATA) in Aiken, SC. While uncontaminated soils typically have Pb levels ranging from 2 to 200 mg/kg (Berti et al. 1998), previous analysis show Pb levels of the SATA berm to reach 8,673 mg/kg. Biosurfactants are surface-active compounds naturally produced by soil bacteria that can bind metals. Biosurfactants have a wide variety of chemical structures that reduce interfacial surface tensions (Jennings and Tanner 2000) and have demonstrated efficient metal complexion (Lin 1996). Biosurfactants also have the potential to change the availability of natural organic matter (Strong-Gunderson 1995). Two types of bacteria, Alcaligenes piechaudii and Pseudomonas putida, were employed as amendments based on their ability to produce biosurfactants and survive in metal-contaminated soils. Apatites (calcium phosphate compounds) are important in the formation of Pb phosphates. Pb phosphates form rapidly when phosphate is available and are the most stable environmental form of lead in soil (Ruby et al.1998). Pyromorphites in particular remain insoluble under a wide range of environmental conditions (Zhang et al. 1998). The three apatites evaluated in the current study were North Carolina apatite (NCA), Florida apatite (FA), and biological apatite (BA). BA is ground fish bone that has few impurities such as As, Cr, or U

  20. Stability domain of alumina thermally grown on Fe-Cr-Al-based model alloys and modified surface layers exposed to oxygen-containing molten Pb

    NASA Astrophysics Data System (ADS)

    Jianu, A.; Fetzer, R.; Weisenburger, A.; Doyle, S.; Bruns, M.; Heinzel, A.; Hosemann, P.; Mueller, G.

    2016-03-01

    The paper gives experimental results concerning the morphology, composition, structure and thickness of the oxide scales grown on Fe-Cr-Al-based bulk alloys during exposure to oxygen-containing molten lead. The results are discussed and compared with former results obtained on Al-containing surface layers, modified by melting with intense pulsed electron beam and exposed to similar conditions. The present and previous results provide the alumina stability domain and also the criterion of the Al/Cr ratio for the formation of a highly protective alumina layer on the surface of Fe-Cr-Al-based alloys and on modified surface layers exposed to molten lead with 10-6 wt.% oxygen at 400-600 °C. The protective oxide scales, grown on alumina-forming Fe-Cr-Al alloys under the given experimental conditions, were transient aluminas, namely, kappa-Al2O3 and theta-Al2O3.

  1. Microwave dielectric properties of bismuth-substituted Ba3.75Nd9.5Ti17Al4/3O54 ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Hetuo; Tang, Bin; Xiong, Zhe; Li, Yingxiang; Zhang, Shuren

    2015-10-01

    The impact of bismuth substitution at neodymium (Nd) site in aluminum-replaced Ba3.75Nd9.5Ti18O54 ceramics on dielectric constant ( ɛ r), quality factor ( Qf), and temperature coefficient of resonant frequency ( τ f ) has been determined (0.05 ≤ x ≤ 0.2). With appropriate quality factor values ( Qf > 5000 GHz), the dielectric constant increased from 74.42 to a maximum of 90.8 and the temperature coefficient of resonant frequency was tailored from approximately +20 ppm/°C to the vicinity of 0 ppm/°C. The X-ray diffraction patterns showed a single phase for all compositions, while the scanning electron microscopy and energy-dispersive spectrometer data confirmed XRD results. Factors, such as bulk density, average polarizability, microstructure, and tolerance factor which were caused by the substitution, were taken into consideration to discuss the microwave dielectric properties' variation. Within substituting limit, a series of controllable microwave dielectric properties ( ɛ r = 75.8, Qf = 8994 GHz, τ f = 7.2 ppm/°C; ɛ r = 79.1, Qf = 7282 GHz, τ f = 2.3 ppm/°C; ɛ r = 87.07, Qf = 5548 GHz, τ f = -8.6 ppm/°C) could be obtained when sintered at 1350 °C for 2 h for x = 0.05, 0.1, and 0.15, respectively.

  2. A century long sedimentary record of anthropogenic lead (Pb), Pb isotopes and other trace metals in Singapore.

    PubMed

    Chen, Mengli; Boyle, Edward A; Switzer, Adam D; Gouramanis, Chris

    2016-06-01

    Reconstructing the history of metal deposition in Singapore lake sediments contributes to understanding the anthropogenic and natural metal deposition in the data-sparse Southeast Asia. To this end, we present a sedimentary record of Pb, Pb isotopes and eleven other metals (Ag, As, Ba, Cd, Co, Cr, Cu, Ni, Tl, U and Zn) from a well-dated sediment core collected near the depocenter of MacRitchie Reservoir in central Singapore. Before the 1900s, the sedimentary Pb concentration was less than 2 mg/kg for both soil and sediment, with a corresponding (206)Pb/(207)Pb of ∼1.20. The Pb concentration increased to 55 mg/kg in the 1990s, and correspondingly the (206)Pb/(207)Pb decreased to less than 1.14. The (206)Pb/(207)Pb in the core top sediment is concordant with the (206)Pb/(207)Pb signal of aerosols in Singapore and other Southeast Asian cities, suggesting that Pb in the reservoir sediment was mainly from atmospheric deposition. Using the Pb concentration in the topmost layer of sediment, the estimated atmospheric Pb flux in Singapore today is ∼1.6 × 10(-2) g/m(2) yr. The concentrations of eleven other metals preserved in the sediment were also determined. A principal component analysis showed that most of the metals exhibit an increasing trend towards 1990s with a local concentration peak in the mid-20(th) century. PMID:26967352

  3. Impact of anthropogenic Pb and ocean circulation on the recent distribution of Pb isotopes in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Mi; Boyle, Edward A.; Gamo, Toshitaka; Obata, Hajime; Norisuye, Kazuhiro; Echegoyen, Yolanda

    2015-12-01

    Pb and Pb isotope ratios in the modern ocean have been altered significantly by anthropogenic Pb inputs over the past century. Most studies of anthropogenic Pb in the ocean have focused on the North Atlantic and North Pacific Oceans, and the impact of anthropogenic Pb inputs to the Indian Ocean and processes controlling the distribution of Pb in the Indian Ocean are poorly known. This study presents the Pb and Pb isotopic composition (206Pb/207Pb, 208Pb/207Pb) of 11 deep stations from the Indian Ocean Japanese GEOTRACES cruise (KH-09-5), from the Bay of Bengal and Arabian Sea to the Southern Ocean (62°S). The Pb isotope ratios of the Indian Ocean range 1.140-1.190 for 206Pb/207Pb and 2.417-2.468 for 208Pb/207Pb, with lower ratios appearing in the shallow waters of the northern Indian Ocean and higher ratios appearing in the deep layers of the Southern Ocean. This result agrees with a previous study on Pb concentrations (Echegoyen et al., 2014) showing that the Indian Ocean, particularly its northern part, is largely perturbed by anthropogenic Pb inputs. 206Pb/207Pb and 208Pb/207Pb of the Indian sector Southern Ocean are still lower than natural Pb, showing this region was also affected by anthropogenic Pb. Anomalously low or high 206Pb/207Pb and 208Pb/207Pb were observed in the thermocline and shallow waters of the southern Indian Ocean and the Arabian Sea, which are ascribed to water mass distribution (e.g., Subantarctic Mode Water) and evolving Pb isotope ratios of this region as dominant anthropogenic Pb sources change. 206Pb/207Pb and 208Pb/207Pb in the Bay of Bengal are higher than those in the Arabian Sea, which might be the result of the anthropogenic Pb inputs from different provenance or seawater exchanging Pb isotopes with natural particles derived from rivers and/or sediments at the basin boundaries.

  4. Mafic dykes intrusive into Pre-Cambrian rocks of the São Luís cratonic fragment and Gurupi Belt (Parnaíba Province), north-northeastern Brazil: Geochemistry, Sr-Nd-Pb-O isotopes, 40Ar/39Ar geochronology, and relationships to CAMP magmatism

    NASA Astrophysics Data System (ADS)

    Klein, Evandro L.; Angélica, Rômulo S.; Harris, Chris; Jourdan, Fred; Babinski, Marly

    2013-07-01

    Dykes of diabase and microgabbro intruded into Pre-Cambrian rocks of the São Luís cratonic fragment and Gurupi Belt, which are tectonic and erosive windows of the Parnaíba Basin in north-northeastern Brazil. Ar-Ar ages were determined, and major, trace element, and Nd-Sr-Pb-O isotopic compositions of these dykes were measured to provide insights into their age, and into the nature of their mantle sources and petrogenetic processes. The data have also been used to compare the chemical and isotopic signatures of the dykes with those of the Central Atlantic Magmatic Province (CAMP). Four chemical groups of mafic dykes have been identified. These comprise two subtypes of high-Ti rocks (i) HTi-1 (TiO2 < 2.3 wt.%; SiO2 > 47 wt.%), (ii) HTi-2 (TiO2 > 2.7 wt.%; SiO2 > 47 wt.%), in addition to (iii) evolved high-Ti (TiO2 > 4 wt.%; SiO2 of ~ 46 wt.%) and (iv) low-Si (TiO2 > 2.2 wt.%; SiO2 < 45 wt.%) rocks. 40Ar/39Ar geochronology of plagioclase returned ages of 201 ± 4 Ma and 193 ± 10 Ma for the HTi-2 subtype, and of 201 ± 2 Ma and 207 ± 9 Ma for the evolved high-Ti group. The HTi-1 and low-Si groups presented highly disturbed age spectra, and did not allow the definition of their emplacement ages. The Argon data indicate an age > 200 Ma for the low-Si group and are dubious with respect to the age of theHTi-1 subtype, if coeval with (i.e., ~ 200 Ma), or older than, the HTi-2 and evolved high-Ti types. All groups present δ18O values of pyroxene that are compatible with uncontaminated mantle-derived magmas. The HTi-1 subtype (average 143Nd/144Nd200 = 0.512644; 87Sr/86Sr200 = 0.7035; 206Pb/204Pb of 17.86) shows the less enriched and less fractionated (more primitive) trace element distribution of all groups. The HTi-2 subtype shows enriched trace element pattern and depleted Nd-Sr signature (143Nd/144Nd200 = 0.512610; 87Sr/86Sr200 = 0.7037) and average 206Pb/204Pb ratios of 17.23. The evolved high-Ti chemical group shows average ratios of 143Nd/144Nd200 = 0.512558, 87Sr

  5. A Comparison of MOCLD With PLD Ba(x)Sr(1-x)TiO3 Thin Films on LaAlO3 for Tunable Microwave Applications. Revised

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Mueller, C. H.; Romanofsky, R. R.; Warner, J. D.; Miranda, F. A.; Jiang, H.

    2003-01-01

    Historically, tunable dielectric devices using thin crystalline Ba(x)Sr(1-x),TiO3 (BST) films deposited on lattice-matched substrates, such as LaAlO3 have generally been grown using pulsed laser deposition (PLD). Highly oriented BST films can be grown by PLD but large projects are hampered by constraints of deposition area, deposition time and expense. The Metal-Organic Chemical Liquid Deposition (MOCLD) process allows for larger areas, faster turnover and lower cost. Several BST films deposited on LaAlO, by MOCLD have been tested in 16 GHz coupled microstrip phase shifters. They can be compared with many PLD BST films tested in the same circuit design. The MOCLD phase shifter performance of 293 degree phase shift with 53 V/micron dc bias and a figure of merit of 47 degree/dB is comparable to the most highly oriented PLD BST films. The PLD BST films used here have measured XRD full-width-at-half-maxima (FWHM) as low as 0.047 degrees. The best FWHM of these MOCLD BST films has been measured to be 0.058 degrees.

  6. A Statistical Analysis of Laser Ablated Ba(Sub 0.50)Sr(Sub 0.50)TiO(Sub 3)/LaAlO(Sub 3) Films for Microwave Applications

    NASA Technical Reports Server (NTRS)

    Romanofsky, R. R.; Varaljay, N. C.; Alterovitz, S. A.; Miranda, F. A.; Mueller, C. M.; VanKeuls, F. W.; Kim, J.; Harshavardhan, K. S.

    2002-01-01

    The NASA Glenn Research Center is constructing a 616 element scanning phased array antenna using thin film Ba(sub x)Sr(sub 1-x)TiO(sub 3) based phase shifters. A critical milestone is the production of 616 identical phase shifters at 19 GHz with [asymptotically equal to]4 dB insertion loss and at least 337.5 deg phase shift with 3 percent bandwidth. It is well known that there is a direct relationship between dielectric tuning and loss due to the Kramers-Kronig relationship and that film crystallinity and strain, affected by the substrate template, play an important role. Ba(sub 0.50)Sr(sub 0.50)TiO (sub 3) films, nominally 400 nm thick, were deposited on 48 0.25 mm thick, 5 cm diameter LaAlO(sub 3) wafers. Although previous results suggested that Mn-doped films on MgO were intrinsically superior in terms of phase shift per unit loss, for this application phase shift per unit length was more important. The composition was selected as a compromise between tuning and loss for room temperature operation (e.g. crystallinity progressively degrades for Ba concentrations in excess of 30 percent). As a prelude to fabricating the array, it was necessary to process, screen, and inventory a large number of samples. Variable angle ellipsometry was used to characterize refractive index and film thickness across each wafer. Microstructural properties of the thin films were characterized using high resolution X-ray diffractometry. Finally, prototype phase shifters and resonators were patterned on each wafer and RE probed to measure tuning as a function of dc bias voltage as well as peak (0 field) permittivity and unloaded Q. The relationship among film quality and uniformity and performance is analyzed. This work presents the first statistically relevant study of film quality and microwave performance and represents a milestone towards commercialization of thin ferroelectric films for microwave applications.

  7. Local Structure of amorphous (PbO){sub x}[(B{sub 2}O{sub 3}){sub 1-z}(Al{sub 2}O{sub 3}){sub z}]{sub y} (SiO{sub 2}){sub y} Dielectric Materials by Multinuclear Solid State NMR

    SciTech Connect

    Sawvel, A; Chinn, S; Bourcier, W; Maxwell, R

    2003-09-05

    Structural speciation of glasses in the systems PbO-B{sub 2}O{sub 3}-SiO{sub 2}, PbO-B{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2}, and PbO-Al{sub 2}O{sub 3}-SiO{sub 2} were studied using solid-state {sup 29}Si, {sup 27}Al, {sup 11}B, and {sup 207}Pb nuclear magnetic resonance (NMR) and Raman spectroscopy. Application of these methods provided insight into the role of Al{sub 2}O{sub 3} incorporation in the lead-borosilicate glass networks. The general composition range studied was (PbO){sub x} [(B{sub 2}O{sub 3}){sub 1-z} (Al{sub 2}O{sub 3})z]{sub y}(SiO{sub 2}){sub y} where x = 0.35, 0.5, and 0.65, y = (1-x)/2 and z = 0.0, 0.5 and 1.0. Additional insight was obtained via {sup 27}Al 2D-3QMAS experiments. The {sup 207}Pb spin echo mapping spectra showed a transition from ionic (Pb{sup 2+}) to covalently bound lead species with increased PbO contents in the borosilicate glasses. The addition of aluminum to the glass network further enhanced the lead species transition resulting in a higher relative amount of covalent lead bonding in the high PbO content alumino-borosilicate glass. The number of BO{sub 4} units present in the {sup 11}B MAS NMR decreased with increasing PbO contents for both the borosilicate and the alumino-borosilicate glass systems, with the addition of aluminum further promoting the BO{sub 3} species. A deshielding of the {sup 11}B chemical shifts and the {sup 27}Al chemical shifts with increased lead contents (independent of changes in the quadrupolar coupling) was also observed for both glass systems and was attributed to increasingly homogeneous glass structure. The {sup 29}Si spectra of the borosilicate and alumino-borosilicate glasses showed a downfield shift with increased PbO concentrations representing incorporation of Pb into the silicate and aluminosilicate networks. The Raman spectra were characterized by increased intensities of Si-O-Pb peaks and decreased intensities of Q{sup 3} peaks with increased PbO contents and showed no evidence

  8. Effective hole extraction using MoO{sub x}-Al contact in perovskite CH{sub 3}NH{sub 3}PbI{sub 3} solar cells

    SciTech Connect

    Zhao, Yixin; Nardes, Alexandre M.; Zhu, Kai

    2014-05-26

    We report an 11.4%-efficient perovskite CH{sub 3}NH{sub 3}PbI{sub 3} solar cell using low-cost molybdenum oxide/aluminum (i.e., MoO{sub x}/Al) as an alternative top contact to replace noble/precious metals (e.g., Au or Ag) for extracting photogenerated holes. The device performance of perovskite solar cells using a MoO{sub x}/Al top contact is comparable to that of cells using the standard Ag top contact. Analysis of impedance spectroscopy measurements suggests that using 10-nm-thick MoO{sub x} and Al does not affect charge-recombination properties of perovskite solar cells. Using a thicker (20-nm) MoO{sub x} layer leads to a lower cell performance caused mainly by a reduced fill factor. Our results suggest that MoO{sub x}/Al is promising as a low-cost and effective hole-extraction contact for perovskite solar cells.

  9. Synthesis, crystal structure and photoluminescence of (Ba{sub 0.99}Eu{sub 0.01})Al{sub 3}Si{sub 4}N{sub 9}

    SciTech Connect

    Yamane, Hisanori; Yoshimura, Fumitaka

    2015-08-15

    Crystalline grains of (Ba{sub 0.99}Eu{sub 0.01})Al{sub 3}Si{sub 4}N{sub 9} were obtained from samples synthesized by heating mixtures of binary nitride powders at 2000 °C and 0.85 MPa of N{sub 2} gas. The fundamental reflections of electron diffraction (ED) and X-ray diffraction (XRD) measured for some grains could be indexed with orthorhombic cell parameters: a=10.028(2) Å, b=53.353(9) Å, and c=5.9215(11) Å. Streaks and diffuse lines along the b axis were observed in the ED and XRD photographs, indicating stacking faults. A statistical average structure was analyzed using the intensity data of the fundamental reflections with the space group Fdd2. Local structure models were presented based on the average structure. Similar streaks and diffuse lines with fundamental reflections indexed with monoclinic cell parameters: a=5.8376(4) Å, b=26.6895(12) Å, c=5.8393(3) Å, and β=118.8428(15)° were also observed in the XRD oscillation photographs of another grain. The mixture of the grains having the orthorhombic and monoclinic fundamental structures emitted blue–green light with a peak wavelength of 500 nm and a full width at half-maximum (FWHM) of 65 nm under 400 nm excitation. The emission intensity measured at 300 °C was 67.5% of the intensity measured at 25 °C. A broad excitation band ranged from about 260 nm to 475 nm with maximum intensity at around 290 nm, and 60% of the intensity was obtained by excitation at 400 nm. - Graphical abstract: Crystalline grains of (Ba{sub 0.99}Eu{sub 0.01})Al{sub 3}Si{sub 4}N{sub 9}, having orthorhombic and monoclinic fundamental structures and stacking faults, were obtained from samples synthesized at 2000 °C and 0.85 MPa of N{sub 2}. The grains emitted blue–green light with a peak wavelength of 500 nm and a full width at half-maximum (FWHM) of 65 nm under 400 nm excitation. The emission intensity measured at 300 °C was 67.5% of the intensity measured at 25 °C. - Highlights: • (Ba{sub 0.99}Eu{sub 0.01})Al{sub 3}Si

  10. Structural variety in zinc telluro-phosphates: syntheses, crystal structures and characterizations of Sr2Zn3Te2P2O14, Pb2Zn3Te2P2O14 and Ba2Zn2TeP2O11.

    PubMed

    Xia, Mingjun; Li, R K

    2016-05-01

    Three new zinc telluro-phosphates, Sr2Zn3Te2P2O14 (1), Pb2Zn3Te2P2O14 (2) and Ba2Zn2TeP2O11 (3), were grown by flux method, and their crystal structures were solved by X-ray diffraction method. Although all three crystals crystallize into the same space group P21/c with similar chemical compositions, they exhibit different topology structure types. 1 features a two-dimensional layered structure with the connection of TeO4 and (Zn3TeP2O18)(16-) 12-membered rings (MRs), which are composed of planar square and tetrahedral configuration ZnO4 groups, tetrahedral PO4 and seesaw TeO4. Due to lone-pair Coulomb repulsion of Pb(2+), the structure of 2, which is also composed of unbalanced seesaw TeO4 and ZnO4 groups and distorted PO4 tetrahedra, is slightly different from that of its analog 1. Compound 3 exhibits a complicated three-dimensional network with (Zn2PO9)(9-) 6-MRs and (Zn2Te2O10)(8-) 8-MRs built from distorted tetrahedral ZnO4 and PO4 groups and trigonal pyramidal TeO3 units. According to UV-vis-NIR diffuse reflectance spectra, compounds 1, 2 and 3 are highly transparent in the range of 450 to 2500 nm with a UV cut-off of 275 nm, 330 nm and 278 nm, respectively. In addition, the characterizations, including thermal analyses, XPS measurement and dipole moment calculations, are also reported. PMID:27046132

  11. A New Probe to Change Curie Temperature of PbTiO3 Sensors

    NASA Technical Reports Server (NTRS)

    Katiyar, R. S.; Jinfang, Meng

    1997-01-01

    High temperature Raman spectra of nanocrystalline Pb(0.8)Ba(0.2)TiO3, Pb(0.8)Sr(0.2) TiO3, Pb(0.8)La(0.2)TiO3 and Pb(0.8)Ba(0.2)TiO3, have been measured, as a function of particle size. There appears respectively a distinct temperature-induced soft mode phase transition in every sample whose Curie temperature can be determined from the mean-field theory. The detailed Curie temperature shift in modified PbTi03 ceramics by Ba, Sr, La, and Zr, has also been investigated as a function of particle size. This study will favor preparations of high efficiency PbTi03 sensors with an adjustable Curie temperature.

  12. Petrogenesis and Tectonic Implications for High Ba-Sr Porphyries from South Qinling Oroganic Belt, China

    NASA Astrophysics Data System (ADS)

    Zhang, H. F.; Luo, B. J.; Shen, L. M.; Liu, Y.

    2014-12-01

    The Qinling orgenic belt resulted from collision between the North China plate and the Yangtze blocks during Triassic. In the South Qinling orogenic belt, there are lots of small porphyry bodies with area <0.5 km2. These porphyry bodies consist mainly of granodiorite porphyries in petrography. They are closely related to Cu, Mo, Au and Fe mineralization. In this presentation, we carry out an integrated study of LA-ICP-MS zircon U-Pb dating, geochemical and Sr-Nd-Hf isotopic compositions for the porphyry bodies. U-Pb zircon dating shows that they have magma crystallization ages of 145~150 Ma.They are high-potassium calc-alkaline, characterized by high Sr (up to 1300 ppm) and Ba (up to 5000 ppm). Rear earth element data for the porphyries display moderately fractionated REE patterns with (La/Yb)N=9~26 and Eu/Eu*=0.8~1.0. Geochemical characteristics of the granodiorite porphyries are good consistent with high Ba-Sr granitoids [1,2]. These granodiorite porphyries have whole-rock initial 87Sr/86Sr ratios ranging from 0.7046 to 0.7075, ɛNd (t) values ranging from - 4.6 to - 2.5, and zircon ɛHf(t) values ranging from - 2.2 to +0.8. We suggest that their magma was derived from partial melting of enriched mantle sources. The strong enrichment of Sr and Ba imply that the mantle sources could be metasomatized by fluid or melt released from subducting slab (including sediments) due to previous subduction of the Ma-Lue ocean slab at the south of the South Qinling orogenic belt. Lithospheric delamination at ~150 Ma can account for their magma generation for the porphyries. References [1] Fowler M B, Henney P J, Darbyshire D, et al. Petrogenesis of high Ba-Sr granites: the Rogart pluton, Sutherland. Journal of the Geological Society. 2001, 158: 521-534. [2] Choi S G, Rajesh V J, Seo J, et al. Petrology, geochronology and tectonic implications of Mesozoic high Ba-Sr granites in the Haemi area, Hongseong Belt, South Korea. Island Arc. 2009, 18: 266-281.

  13. Studies of waste-canister compatibility. [Waste forms: Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus SiC

    SciTech Connect

    McCoy, H.E.

    1983-01-01

    Compatibility studies were conducted between 7 waste forms and 15 potential canister structural materials. The waste forms were Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus silicon carbide. The canister materials included carbon steel (bare and with chromium or nickel coatings), copper, Monel, Cu-35% Ni, titanium (grades 2 and 12), several Inconels, aluminum alloy 5052, and two stainless steels. Tests of either 6888 or 8821 h were conducted at 100 and 300/sup 0/C, which bracket the low and high limits expected during storage. Glass and FUETAP evolved sulfur, which reacted preferentially with copper, nickel, and alloys of these metals. The Pb-Sn matrix alloy stuck to all samples and the carbon-coated particles to most samples at 300/sup 0/C, but the extent of chemical reaction was not determined. Testing for 0.5 h at 800/sup 0/C was included because it is representative of a transportation accident and is required of casks containing nuclear materials. During these tests (1) glass and FUETAP evolved sulfur, (2) FUETAP evolved large amounts of gas, (3) Synroc stuck to titanium alloys, (4) glass was molten, and (5) both matrix alloys were molten with considerable chemical interactions with many of the canister samples. If this test condition were imposed on waste canisters, it would be design limiting in many waste storage concepts.

  14. Cation-poor complex metallic alloys in Ba(Eu)–Au–Al(Ga) systems: Identifying the keys that control structural arrangements and atom distributions at the atomic level

    SciTech Connect

    Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J.; Mudring, Anja -Verena

    2015-10-19

    Four complex intermetallic compounds BaAu6±xGa6±y (x = 1, y = 0.9) (I), BaAu6±xAl6±y (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104–112, Fm3C), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution (“coloring scheme”). Chemical bonding analyses for two different “EuAu6Tr6” models reveal maximization of the number of heteroatomic Au–Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the “EuAu6Tr6” models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. As a result, the effective moments

  15. A vibrational spectroscopic study of the silicate mineral harmotome - (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O - A natural zeolite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-01

    The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm-1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm-1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm-1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm-1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm-1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.

  16. A vibrational spectroscopic study of the silicate mineral harmotome--(Ba,Na,K)1-2(Si,Al)8O16⋅6H2O--a natural zeolite.

    PubMed

    Frost, Ray L; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-25

    The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16⋅6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm(-1) are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm(-1) are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm(-1) are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm(-1) spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm(-1) is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome. PMID:25203212

  17. Erratum to “Crystal structure and zinc location in the BaZnFe6O11 Y-type hexagonal ferrite” by Collomb et al. [J. Magn. Magn. Mater. 78(1) (1989) 77-84

    NASA Astrophysics Data System (ADS)

    Wise, Adam; Rocks, Jason; Laughlin, David; McHenry, Michael

    2012-03-01

    In the paper "Crystal structure and zinc location in the BaZnFe6O11 Y-type hexagonal ferrite" by Collomb et al. [1], the detailed list of atomic positions gives the fractional coordinate location of the Me5 atom at the 18h symmetry site as x: 0.50317, y: -0.50317, and z: 0.19073 in a hexagonal cell. We believe this to be a typographical error, and that the fractional coordinate for the z-position should be approximately z: 0.109. The Y-type hexagonal ferrite has the space group symmetry R-3m. When this symmetry is applied to the positions given in the paper, using CrystalMaker software, the center to center distance between the Me5 atoms and the O5 atoms is only 0.27 A, an unrealistic number. In the paper, the closest-approach distance between Me5 and O5 atoms is listed as 2.048 A. Since the R-3m symmetry of the system is well-documented, the issue must lie with either the oxygen or metal atom fractional coordinate.

  18. Heavy ion irradiations on synthetic hollandite-type materials: Ba1.0Cs0.3A2.3Ti5.7O16 (A=Cr, Fe, Al)

    NASA Astrophysics Data System (ADS)

    Tang, Ming; Tumurugoti, Priyatham; Clark, Braeden; Sundaram, S. K.; Amoroso, Jake; Marra, James; Sun, Cheng; Lu, Ping; Wang, Yongqiang; Jiang, Ying.-Bing.

    2016-07-01

    The hollandite supergroup of minerals has received considerable attention as a nuclear waste form for immobilization of Cs. The radiation stability of synthetic hollandite-type compounds described generally as Ba1.0Cs0.3A2.3Ti5.7O16 (A=Cr, Fe, Al) were evaluated by heavy ion (Kr) irradiations on polycrystalline single phase materials and multiphase materials incorporating the hollandite phases. Ion irradiation damage effects on these samples were examined using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). Single phase compounds possess tetragonal structure with space group I4/m. GIXRD and TEM observations revealed that 600 keV Kr irradiation-induced amorphization on single phase hollandites compounds occurred at a fluence between 2.5×1014 Kr/cm2 and 5×1014 Kr/cm2. The critical amorphization fluence of single phase hollandite compounds obtained by in situ 1 MeV Kr ion irradiation was around 3.25×1014 Kr/cm2. The hollandite phase exhibited similar amorphization susceptibility under Kr ion irradiation when incorporated into a multiphase system.

  19. Low-frequency inelastic light scattering in a ZBLAN (ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF) glass

    SciTech Connect

    Adichtchev, S. V.; Malinovsky, V. K.; Surovtsev, N. V.; Ignatieva, L. N.; Merkulov, E. B.

    2014-05-14

    Low-frequency (down to 30 GHz) inelastic light scattering is studied in a multicomponent glass ZBLAN (ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF) in a wide temperature range. The contributions of the THz vibrational spectrum (boson peak) and of the fast relaxation are extracted and analyzed. It is shown that the fast relaxation spectrum is described by a distribution of relaxation times leading to a power-law ν{sup α} dependence in the frequency range 30–300 GHz. Temperature dependence of α(T) is well described by the Gilroy-Phillips model, while the integrated intensity of the fast relaxation increases significantly with the temperature. This feature distinguishes the fast relaxation in ZBLAN from the case of most single-component glasses. Thermodynamic and kinetic fragility indexes are significantly different for the ZBLAN glass. The correlations between the boson peak intensity, elastic moduli, and fragility index, found earlier for single-component glasses, are fulfilled for the thermodynamic fragility index of ZBLAN. In contrast, the correlation between the fast relaxation intensity at T{sub g} and the fragility holds better for the kinetic fragility index of ZBLAN. We propose that thermodynamic and kinetic fragilities reflect different aspects of glassy dynamics in the case of glass formers with the complex chemical composition and structure topology: the former correlates with the elastic properties and the boson peak, the latter with the relaxation.

  20. Levels of Cd, Cu, Pb and V in marine sediments in the vicinity of the Single Buoy Moorings (SBM3) at Mina Al Fahal in the Sultanate of Oman.

    PubMed

    Al-Husaini, Issa; Abdul-Wahab, Sabah; Ahamad, Rahmalan; Chan, Keziah

    2014-06-15

    Recently in the Sultanate of Oman, there has been a rapid surge of coastal developments. These developments cause metal contamination, which may affect the habitats and communities at and near the coastal region. As a result, a study was conducted to assess the level of metal contamination and its impact on the marine sediments in the vicinity of the Single Buoy Moorings 3 (SBM3) at Mina Al Fahal in the Sultanate of Oman. Marine subtidal sediment samples were collected from six different stations of the SBM3 for the period ranging from June 2009 to April 2010. These samples were then analyzed for their level and distribution of the heavy metals of cadmium (Cd), copper (Cu), lead (Pb) and vanadium (V). Overall, low concentrations of all four heavy metals were measured from the marine sediments, indicating that the marine at SBM3 is of good quality. PMID:24775070

  1. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  2. Geoenvironmental weathering/deterioration of landfilled MSWI-BA glass.

    PubMed

    Wei, Yunmei; Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki; Zhao, Chun; Peng, Xuya; Gao, Junmin

    2014-08-15

    Municipal solid waste incineration bottom ash (MSWI-BA) glass serves as a matrix of assorted bottom ash (BA) compounds. Deterioration of the BA glass phases is quite important as they regulate the distribution of a series of toxic elements. This paper studied landfilled MSWI-BA samples from the mineralogical and geochemical viewpoint to understand the deterioration behavior of the BA glass phases as well as mechanisms involved. Bulk analysis by PXRD as well as micro-scale analysis by optical microscopy and SEM/EDX was conducted for such purposes. The results revealed that dissolution of the BA glass phases has resulted in a deterioration layer of 10(0)-10(2)μm thickness after years of disposal. This rapid weathering process is highly relevant to the specific glass characteristics and solution pH. The BA glass phases with more embedded compounds and cracks/fissures tend to be more vulnerable. Moreover, the generally alkaline pH in ash deposit favors a rapid disruption of the glass phase. The weathering products are mainly gel phases (including Al-Si gel, Ca-Al-Si gel, Fe-Al-Si gel etc.) with iron oxide/hydroxide as accessory products. Breakdown of the BA glass phases triggers chemical evolution of the embedded compounds. Based on all the findings above, a model is proposed to illustrate a general evolution trend for the landfilled MSWI-BA glass phases. PMID:25043593

  3. Electron-poor SrAu xIn 4-x (0.5⩽ x⩽1.2) and SrAu xSn 4-x (1.3⩽ x⩽2.2) phases with the BaAl 4-type structure

    NASA Astrophysics Data System (ADS)

    Tkachuk, Andriy V.; Mar, Arthur

    2007-08-01

    Solid solutions SrAu xIn 4-x (0.5⩽ x⩽1.2) and SrAu xSn 4-x (1.3⩽ x⩽2.2) have been prepared at 700 °C and their structures characterized by powder and single-crystal X-ray diffraction. They adopt the tetragonal BaAl 4-type structure (space group I4/ mmm, Z=2; SrAu 1.1(1)In 2.9(1), a=4.5841(2) Å, c=12.3725(5) Å; SrAu 1.4(1)Sn 2.6(1), a=4.6447(7) Å, c=11.403(2) Å), with Au atoms preferentially substituting into the apical over basal sites within the anionic network. The phase width inherent in these solid solutions implies that the BaAl 4-type structure can be stabilized over a range of valence electron counts (vec), 13.0-11.6 for SrAu xIn 4-x and 14.1-11.4 for SrAu xSn 4-x. They represent new examples of electron-poor BaAl 4-type compounds, which generally have a vec of 14. Band structure calculations confirm that substitution of Au, with its smaller size and fewer number of valence electrons, for In or Sn atoms enables the BaAl 4-type structure to be stabilized in the parent binaries SrIn 4 and SrSn 4, which adopt different structure types.

  4. Mechanoluminescence and thermoluminescence of BaFCl:Sm 2+ and BaFBr:Sm 2+ crystals

    NASA Astrophysics Data System (ADS)

    Brahme, Nameeta; Shukla, M.; Choubey, A. K.; Kurrey, U.; Bisen, D. P.; Dhoble, S. J.

    2012-05-01

    The alkaline-earth fluorohalide crystals MFX, where M=Ca, Sr, Ba, Pb and X=Cl, Br, I, form an important class of materials crystallizing in the PbFCl-type tetragonal structure which is also called the matlockite structure. These compounds have long been of interest because of the various defect species which can be detected by spin resonance and associated techniques. The crystals were prepared by slow cooling of the melt of a stoichiometric mixture of BaF 2 and the corresponding chloride or bromide under 0.2 bar of ultrapure argon (5N5), often slightly fluorinated. We have studied the mechanoluminescence (ML) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals. It is seen that after the impact of a moving piston, initially the ML intensity increases with time, attains a maximum value and then it decreases with time up to a particular minimum value, and then it increases again, attaining a peak value and finally disappears. The first peak lies in the deformation region and the second peak lies in the post-deformation region. The ML intensity of the BaFCl:Sm 2+ crystal is much higher than the ML intensity of the BaFBr:Sm 2+ crystal. For different impact velocities, the ML intensity increases with velocity; and the total ML intensity attains a saturation value for higher impact velocities. The total ML intensity increases with the increase in the applied load. It is suggested that the moving dislocation produced during deformation of crystals captures holes from hole-trapped centers (like H centers), and the subsequent radiative recombination of the dislocation holes with electron gives rise to ML. Thermoluminescence (TL) of BaFBr:Sm 2+ and BaFCl:Sm 2+ crystals was studied after exposure to ultraviolet rays with the help of a TLD reader. The peak of TL for the BaFBr:Sm 2+ crystal is found at ∼247°C and for BaFCl:Sm 2+ crystals at 283°C. The TL intensity initially increases with increase in the UV radiation and then it attains saturation for higher values of UV exposure. The

  5. Free carrier absorption in self-activated PbWO4 and Ce-doped Y3(Al0.25Ga0.75)3O12 and Gd3Al2Ga3O12 garnet scintillators

    NASA Astrophysics Data System (ADS)

    Auffray, E.; Korjik, M.; Lucchini, M. T.; Nargelas, S.; Sidletskiy, O.; Tamulaitis, G.; Tratsiak, Y.; Vaitkevičius, A.

    2016-08-01

    Nonequilibrium carrier dynamics in the scintillators prospective for fast timing in high energy physics and medical imaging applications was studied. The time-resolved free carrier absorption investigation was carried out to study the dynamics of nonequilibrium carriers in wide-band-gap scintillation materials: self-activated led tungstate (PbWO4, PWO) ant two garnet crystals, GAGG:Ce and YAGG:Ce. It was shown that free electrons appear in the conduction band of PWO and YAGG:Ce crystals within a sub-picosecond time scale, while the free holes in GAGG:Ce appear due to delocalization from Gd3+ ground states to the valence band within a few picoseconds after short-pulse excitation. The influence of Gd ions on the nonequilibrium carrier dynamics is discussed on the base of comparison the results of the free carrier absorption in GAGG:Ce containing gadolinium and in YAGG without Gd in the host lattice.

  6. Magnetic flux profiles in Bi{sub 1.2}Pb{sub 0.3}Sr{sub 1.5}Ca{sub 2}Cu{sub 3}O{sub y} and NdBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} superconductors and a simulation by critical-state models

    SciTech Connect

    Babu, N.H.; Rajasekharan, T.; Bai, V.S.

    1998-01-01

    The features of the flux profiles recorded for the sintered and press-sintered Bi{sub 1.2}Pb{sub 0.3}Sr{sub 1.5}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO), and sintered and melt-textured NdBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (NdBCO) superconducting samples with widely different microstructures are analyzed. From the slope of the flux profiles (at H{sub ac}{r_arrow}0) recorded for various dc fields, the intergranular J{sub ci} (H{sub dc}) for the BSCCO samples is determined, whose field dependence is found to follow Kim{close_quote}s model. Using the fit parameters thus obtained, the flux profiles for different H{sub dc} could be simulated very well including features like nonlinearity at low fields, the presence of a peak, and the oscillatory behavior. The flux profile of the sintered NdBCO recorded with zero H{sub dc} could also be simulated well using Kim{close_quote}s critical-state model. An analysis of the intragranular flux profile determined from the measured profile at high fields suggests a wide distribution of H{sub g}{sup {asterisk}}, (the full penetration field of the grain) and thereby of the J{sub cg}. This result is in agreement with the broad transition observed in the ac susceptibility of this sample, attributed to the presence of Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub 7{minus}{delta}} precipitates that modify the local J{sub cg} values drastically. All the sintered specimen show nearly 45{percent} of flux penetration (into the sample) at low enough fields (H{sub dc}{lt}40Oe), while the flux entry into the melt-textured NdBCO is {lt}3{percent}. At high dc fields (4{endash}8 KOe) the profile exhibits two distinct slopes that are associated with a flux entry initially into the microcracks and then into the grains, from the microstructural considerations. {copyright} {ital 1997} {ital The American Physical Society}

  7. Critical current density of YBa2Cu3O7-x films with BaZrO3 inclusions on SrTiO3 and Al2O3 substrates

    NASA Astrophysics Data System (ADS)

    Augieri, A.; Galluzzi, V.; Celentano, G.; Fabbri, F.; Mancini, A.; Rufoloni, A.; Vannozzi, A.; Gambardella, U.; Padeletti, G.; Cusmà, A.; Petrisor, T.; Ciontea, L.

    2008-02-01

    Recently, many efforts have been dedicated to the development of a reliable technology for the introduction of artificial pinning sites in YBa2Cu3O7-x (YBCO) films with the aim of improving the in-field Jc performances. One of the most effective technique resulted to be the inclusion of BaZrO3 (BZO) second phase embedded in the YBCO films. In this contribution we present Jc measurements on BZO-added YBCO films deposited on SrTiO3 (STO) and CeO2-buffered-Al2O3 (ALO) substrates. Samples were deposited by pulsed laser ablation technique using a composite YBCO + 5mol.% BZO target at the optimum conditions for fully oxygenated c-axis oriented YBCO films. Despite of a slight Tc reduction, BZO addition in YBCO-STO films resulted in an improvement of in-field performances with the appearance of a Jc plateau in the low field region which extends up to about 2.5 Tesla irrespective of the temperature at least in the investigated range (down to 65K). On the other hand, samples deposited on ALO did not exhibit any remarkable difference neither in the Jc value nor in the magnetic field dependences as compared with pure YBCO. The presence of 0° (magnetic field parallel to the c-axis) peaks in the Jc. angular behaviour revealed a c-axis correlated character of the pinning forces in BZO added YBCO films grown on both STO and ALO substrates. X-ray diffraction measurements and AFM investigations were carried out in order to determine the influence of BZO addition on films crystalline quality and microstructure.

  8. Effects of annealing on the microstructure and mechanical properties of hot pressed BaAl{sub 2}Si{sub 2}O{sub 8} (BAS) and SrAl{sub 2}Si{sub 2}O{sub 8} (SAS) glass-ceramics

    SciTech Connect

    Buzniak, J.J.; Dickerson, R.M.; Lagerlof, K.P.D.

    1994-12-31

    The crystallization behavior, microstructural development during annealing, and the four point bend strength of hot-pressed BaO{center_dot}Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2} (BAS) and SrO{center_dot}Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2} (SAS) glass ceramics have been investigated. Both BAS and SAS show strength loss above the glass transition temperature ({approximately}900{degrees}C), suggesting the presence of residual glass along the grain boundaries in the hot pressed material. Annealing of BAS at temperature above 1000{degrees}C, resulted in an increase of the bend strength when tested above its glass transition temperature. However, increasing porosity during annealing caused a decrease of the fracture strength at temperatures below the glass transition with respect to the as-hot-pressed material. The increased porosity is believed to be associated with the formation of gaseous reaction products during annealing.

  9. Long-Term Performance of Pb Isotopic Analysis by TIMS with 202Pb-205Pb Double Spike

    NASA Astrophysics Data System (ADS)

    Amelin, Y.; Connelly, J. N.

    2008-05-01

    depends mostly on the amount of Pb in the load. The quality of DS Pb analyses is demonstrated by a three-fold improvement in precision of the linear fit for the iron meteorite Cape York [9] compared to the same data reduced with external normalization, and by dates of angrites, eucrites and CAIs with precision between 0.12-0.30 Ma [3-7,9]. [1] Amelin Y. and Davis W.J. (2006) JAAS 21, 1053-1061, [2] Corfu F. and Dahlgren S. (2008) EPSL 265, 256-269, [3] Connelly J.N. et al. (2008) LPS- XXXIX, #2386, [4] Amelin Y. et al. (2006) LPS-XXXVII, #1970 [5] Amelin Y. (2008) GCA 72, 221-232, [7] Connelly J.N. et al. (2008) Astrophys. J., in press, [8] Gerstenberger H. and Haase G. (1997) Chem. Geol. 136, 309-312, [9] Connelly J.N. et al. submitted to GCA.

  10. Crystal Structure and Thermodynamic Stability of Ba/Ti-Substituted Pollucites for Radioactive Cs/Ba Immobilization

    DOE PAGESBeta

    Xu, Hongwu; Chavez, Manuel E.; Mitchell, Jeremy N.; Garino, Terry J.; Schwarz, Haiqing L.; Rodriguez, Mark A.; Rademacher, David X.; Nenoff, Tina Maria

    2015-04-23

    An analogue of the mineral pollucite (CsAlSi2O6), CsTiSi2O6.5 has a potential host phase for radioactive Cs. However, as 137Cs and 135Cs transmute to 137Ba and 135Ba, respectively, through the beta decay, it is essential to study the structure and stability of this phase upon Cs → Ba substitution. In this work, two series of Ba/Ti-substituted samples, CsxBa(1-x)/2TiSi2O6.5 and CsxBa1-xTiSi2O7-0.5x, (x = 0.9 and 0.7), were synthesized by high-temperature crystallization from their respective precursors. Synchrotron X-ray diffraction and Rietveld analysis reveal that while CsxBa(1-x)/2TiSi2O6.5 samples are phase-pure, CsxBa1-xTiSi2O7-0.5x samples contain Cs3x/(2+x)Ba(1-x)/(2+x)TiSi2O6.5 pollucites (i.e., also two-Cs-to-one-Ba substitution) and a secondary phase, fresnoitemore » (Ba2TiSi2O8). Thus, the CsxBa1-xTiSi2O7-0.5x series is energetically less favorable than CsxBa(1-x)/2TiSi2O6.5. To study the stability systematics of CsxBa(1-x)/2TiSi2O6.5 pollucites, high-temperature calorimetric experiments were performed at 973 K with or without the lead borate solvent. Enthalpies of formation from the constituent oxides (and elements) have thus been derived. Our results show that with increasing Ba/(Cs + Ba) ratio, the thermodynamic stability of these phases decreases with respect to their component oxides. Hence, from the energetic viewpoint, continued Cs → Ba transmutation tends to destabilize the parent silicotitanate pollucite structure. However, the Ba-substituted pollucite co-forms with fresnoite (which incorporates the excess Ba), thereby providing viable ceramic waste forms for all the Ba decay products.« less

  11. Pb Isotopic Evolution of Koolau Volcano (Oahu, Hawaii)

    NASA Astrophysics Data System (ADS)

    Fekiacova, Z.; Abouchami, W.

    2003-12-01

    lavas samples a plume component which apparently persisted during the post-erosional stage. The unradiogenic Pb component present in Honolulu lavas has Pb isotope characteristics that are clearly distinct from those of East Pacific Rise MORB [4], suggesting that it may not be derived from the underlying Hawaiian lithosphere. Available isotopic data on the oceanic crust basement near Hawaii [5] are unreliable, making a direct comparison difficult. While the Hawaiian lithosphere hypothesis cannot be entirely ruled out, we suggest that the unradiogenic Honolulu Pb component reflects material thermally entrained by the upwelling plume during its ascent and is essentially sampled during the post-erosional stage of Hawaiian volcanism. 1.Abouchami, W. et al., Eos Trans. AGU, 81 (48), Fall Meet. Suppl., Abstract V21D-03, 2000b 2.Eisele, J. et al., Geochem. Geophys. Geosyst., 4(2), 8710, doi:10.1029/2002GC000339, 2003 3.Tanaka, R. and Nakamura, E., Geophys. Monograph Ser., vol. 128, 311-332, 2002 4.Galer, S.J.G. et al., Eos Trans. AGU, 80 (46), Fall Meet. Suppl., Abstract V11E-08, 1999 5.King et al., Proc. ODP, Sci. Results., 136, 1993, 107-118

  12. Zircon U-Pb dating, geochemistry and Sr-Nd-Pb-Hf isotopes of the Wajilitag alkali mafic dikes, and associated diorite and syenitic rocks: Implications for magmatic evolution of the Tarim large igneous province

    NASA Astrophysics Data System (ADS)

    Zou, Si-Yuan; Li, Zi-Long; Song, Biao; Ernst, Richard E.; Li, Yin-Qi; Ren, Zhong-Yuan; Yang, Shu-Feng; Chen, Han-Lin; Xu, Yi-Gang; Song, Xie-Yan

    2015-01-01

    The Early Permian Tarim large igneous province (Tarim LIP) consists mainly of basaltic lavas, mafic-ultramafic intrusions including dikes and, syenite bodies in the Tarim Basin, NW China. A major unit of the Tarim LIP, the Wajilitag intrusive complex, consists of olivine pyroxenite, clinopyroxenite and gabbro units (from bottom to top), diorite and syenite rocks occurred in the upper part of the complex and alkali mafic dikes intrude the clinopyroxenite phase. Here we report the zircon U-Pb age and Hf isotopes, geochemical characteristics and Sr-Nd-Pb isotopic data of the alkali mafic dikes, and diorite, aegirine-nepheline syenite and syenite porphyry units in the Wajilitag intrusive complex. Zircons from the diorite and alkali mafic rocks yield concordant crystallization ages of 275.2 ± 1.2 Ma and 281.4 ± 1.7 Ma, respectively. The diorite and syenitic rocks in Wajilitag area have a narrow range of SiO2 contents (51.9-57.3 wt.%), and are enriched in total alkalis (Na2O + K2O = 8.3-14.3 wt.%), among which the aegirine-nepheline syenite and syenite porphyry have the geochemical affinity of A-type granites. The alkali mafic rocks and syenitic rocks have high Al2O3 (19.4-21.1 wt.%), Zr, Hf, Ba contents, total rare earth element abundances and LREE/HREE ratios and low Mg# value, K, P and Ti contents. Diorites have lower Al2O3 contents, total REE abundances and LREE/HREE ratios and higher Mg# values than the alkali mafic rocks and syenitic rocks. The diorites and syenitic rocks have low initial 87Sr/86Sr ratios (0.7034-0.7046), and high εNd(t) values (0.1-4.1) and zircon εHf(t) values (- 0.9-4.4). All the diorites and syenitic rocks show the 206Pb/204Pb ratios ranging of 18.0-19.5, 207Pb/204Pb of 15.4-15.6 and 208Pb/204Pb of 38.0-39.9. Sr-Nd isotopic ratios indicate a FOZO-like mantle source for the diorite and syenitic rocks, similar to that of the mafic-ultramafic rocks in the Wajilitag complex. In contrast, zircon Hf isotopes of basalt and syenite elsewhere in the

  13. Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

    NASA Technical Reports Server (NTRS)

    Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

    1990-01-01

    An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

  14. Thermotropic phase transitions in Pb1-xSrx(Al1/3Nb2/3)0.1(Zr0.52Ti0.48)0.9O3 ceramics: Temperature dependent dielectric permittivity and Raman scattering

    NASA Astrophysics Data System (ADS)

    Li, C. Q.; Peng, L.; Wang, P.; Jiang, K.; Liu, A. Y.; Hu, Z. G.; Chu, J. H.

    2015-06-01

    The phase transitions of Pb1-xSrx(Al1/3Nb2/3)0.1(Zr0.52Ti0.48)0.9O3 (Sr-modified PAN-PZT) ceramics with Sr compositions of x = 2%, 5%, 10% and 15% have been investigated using X-ray diffraction (XRD), temperature dependent dielectric permittivity and Raman scattering. The XRD analysis show that the phase transition occurs between Sr composition of 5% and 10%. Based on the broad dielectric peaks at 100 Hz, the diffused phase transition from tetragonal (T) to cubic (C) structure shifts to lower temperature with increasing Sr composition. The dramatic changes of wavenumber and full width at half-maximum (FWHM) for E(TO4)' softing mode can be observed at morphotropic phase boundary (MPB). Moreover, the MPB characteristic shows a wider and lower trend of temperature region with increasing Sr composition. It could be ascribed to the diminishment of the energy barrier and increment of A-cation entropy. Therefore, the Sr-modified PAN-PZT ceramics unambiguously undergo two successive structural transitions (rhombohedral-tetragonal-cubic phase) with temperature from 80 to 750 K. Correspondingly, the phase diagram of Sr-modified PAN-PZT ceramics can be well depicted.

  15. Proton and deuteron double differential cross sections at angles from 10 deg to 60 deg from Be, C, Al, Fe, Cu, Ge, W, and Pb under 558-MeV-proton irradiation

    NASA Technical Reports Server (NTRS)

    Beck, S. M.; Powell, C. A.

    1976-01-01

    The double differential cross sections for the production of protons and deuterons from targets of Be, C, Al, Fe, Cu, Ge, W, and Pb were obtained at laboratory angles of scatter of 10, 20, 30, 40, 50, and 60 degrees for 558-MeV incident protons. The position of the quasi-elastic peak, discernible in the cross sections up to approximately 40 degrees, corresponded closely to the theoretical predictions for proton-proton elastic scattering at 558 MeV. The mean ratio of deuteron to proton energy-integrated cross sections was 0.056 + or - 0.008. The dependence of energy-integrated cross sections for both protons and deuterons on target mass number A varied from A to the 1/3 power at 10 degrees to A to the 2/3 power above approximately 30 degrees. The ratio of energy-integrated deuteron cross sections for quasielastic processes to that for reactions yielding a deuteron-pi-meson pair was approximately 10 percent.

  16. Effect of Cr Addition on Wetting Behavior Between Cu and High-Temperature Zn-25Sn-0.15Al-0.1Ga- xCr Pb-Free Solder

    NASA Astrophysics Data System (ADS)

    Liu, Chin-Wei; Lin, Kwang-Lung

    2014-12-01

    In this study the effect of Cr content (0.02 wt.% to 0.2 wt.%) on the wetting interaction between high-temperature Zn-25Sn-0.15Al-0.1Ga- xCr Pb-free solders and Cu has been investigated using the wetting balance method. Differential scanning calorimetry (DSC) investigation showed that Cr addition reduces the liquidus temperature slightly while raising the solidus temperature. Flux-assisted wetting experiments were carried out at an immersion rate of 15 mm/s at 435°C. The results show that the shortest wetting time of around 0.7 s was achieved when 0.1 wt.% Cr was added, but the wetting force tends to decrease with the Cr content. Cr addition enhances the formation of interfacial Cu5Zn8 intermetallic compound (IMC) during air cooling, but the opposite effect was observed for water cooling. The results suggest that Cr addition depresses the formation of the Cu5Zn8 layer in liquid/solid reaction, but enhances the formation of the Cu5Zn8 layer in solid/solid reaction.

  17. Structural and optical properties of 60B2O3-(20-x)Na2O-10PbO-10Al2O3:xTiO2:yNd2O3 glasses

    NASA Astrophysics Data System (ADS)

    de Souza, N. C. A.; Santos, C. C.; Guedes, I.; Dantas, N. O.; Vermelho, M. V. D.

    2013-10-01

    In this work we investigate the effect of replacing Na2O by TiO2 on the structural and spectroscopic characteristics of the Nd2O3-doped 60B2O3-(20-x)Na2O-10PbO-10Al2O3:xTiO2:yNd2O3 borate glass matrix. Measurements of X-ray patterns, glass temperatures (Tg), vibrational (Raman and infrared (IR)) and optical (absorption and emission) spectra were carried out. The trend of Tg, the Judd-Ofelt parameters and Nephelauxetic ratio as the TiO2 and Nd2O3 concentration increases was interpreted quantitatively and qualitatively in terms of the network bonds and coordination numbers. Measurements of Tg across the Nd-doped glass series for different levels of Ti suggests changes in the rigidity of the matrix due to change of coordination of boron oxide resulting from the BO4-BO3 back conversion effect. The changes observed in the Raman and IR spectra are related to the BO3 → BO4 conversion effect. The variation of the Judd-Ofelt parameters Ω and Ω indicates that the average rare earth-ligand radius decreases establishing an electronic density distribution when Nd3+ concentration increases. This effect is interpreted in terms of Judd-Ofelt parameters and by the bonding parameter b due to Nephelauxetic effect.

  18. Chitosan film loaded with silver nanoparticles-sorbent for solid phase extraction of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II).

    PubMed

    Djerahov, Lubomir; Vasileva, Penka; Karadjova, Irina; Kurakalva, Rama Mohan; Aradhi, Keshav Krishna

    2016-08-20

    The present study describes the ecofriendly method for the preparation of chitosan film loaded with silver nanoparticles (CS-AgNPs) and application of this film as efficient sorbent for separation and enrichment of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II). The stable CS-AgNPs colloid was prepared by dispersing the AgNPs sol in chitosan solution at appropriate ratio and further used to obtain a cast film with very good stability under storage and good mechanical strength for easy handling in aqueous medium. The incorporation of AgNPs in the structure of CS film and interaction between the polymer matrix and nanoparticles were confirmed by UV-vis and FTIR spectroscopy. The homogeneously embedded AgNPs (average diameter 29nm, TEM analysis) were clearly observed throughout the film by SEM. The CS-AgNPs nanocomposite film shows high sorption activity toward trace metals under optimized chemical conditions. The results suggest that the CS-AgNPs nanocomposite film can be feasibly used as a novel sorbent material for solid-phase extraction of metal pollutants from surface waters. PMID:27178907

  19. The Solid Earth Pb Cycle (Invited)

    NASA Astrophysics Data System (ADS)

    Hart, S. R.; Gaetani, G. A.

    2009-12-01

    The geochemical behavior of Pb in the earth is replete with enigmas and paradoxes. There is no satisfactory `balanced budget’ for Pb amongst the various terrestrial reservoirs, and consequently, no consensus understanding of the U-Th-Pb isotope tracer system, or the behavior of Pb during melting processes. Most oceanic mantle melts have Pb isotopic compositions that are more radiogenic than Earth’s Geochron, and have high and relatively constant Ce/Pb ratios compared to `bulk silicate earth’. Most geochemists agree that sulfide phases in the Earth play a major role in controlling the geochemical cycling of Pb. We posit that an understanding of Pb partitioning between sulfide and silicate phases can lead to a reconciliation of the various Pb enigmas and paradoxes. To this end, we have conducted experiments utilizing coexisting immiscible FeS and basaltic melts, over a P-T range from 1 - 3 GPa and 1250° - 1475°C, buffered at either iron-wustite or C-CO-CO2. Sulfide/silicate melt partitioning of Pb varies from 5 - 70, with a dominant (inverse) correlation with the Fe content of the silicate melt. One determination of sulfide melt/clinopyroxene partitioning of Pb is very large, = 3800 at 2 GPa - 1370°C. On a 1650°C mantle adiabat, sulfide will begin melting at ~ 200 km depth. The modal abundance of sulfide melt (for a mantle S content of 250 ppm) will be ~ 0.07%, and will contain 95% of the Pb inventory of that mantle. Silicate melting will start ~ 50 km shallower, and Pb evolution during subsequent decompression will depend largely on the chemical equilibrium and physical coherence between the sulfide and silicate melt phases. If the high density sulfide melt can resist entrainment by the buoyant silicate melt, it may remain as a residual phase. This can lead to similar incompatibilities for Ce and Pb, and thus provide the canonically constant behavior of this pair as championed by Al Hofmann. Thus, the Ce/Pb of the erupted melts will still closely mirror

  20. Pb and Sr isotopic compositions of snowpack from Quebec, Canada: Inferences on the sources and deposition budgets of atmospheric heavy metals

    SciTech Connect

    Simonetti, A.; Gariepy, C.; Carignan, J.

    2000-01-01

    Elemental concentrations of Al, Ba, Cd, Cu, Mg, Mn, Pb, Rb, Sr, and Zn, as well as Pb and Sr isotopic compositions were determined in samples of snowpack obtained along two main transects from the province of Quebec (Canada); one north-south (between 47 N and 55 N; 1994) and the other within the St. Lawrence Valley (1997). Median enrichment factors (relative to upper crustal abundances) for Cd, Cu, Mn, Pb and Zn for all samples range from {approx}300 to {approx}42,000 and are indicative of an anthropogenic origin. Pb isotopes ratios for snow samples retrieved in 1994 are highly variable ({sup 206}Pb/{sup 207}Pb = 1.148 to 1.193) and are characterized by the most radiogenic Sr isotope values ({sup 87}Sr/{sup 86}Sr {ge} 0.710). In contrast, the Pb and Sr isotope results for 1997 snow samples collected along the St. Lawrence Valley (below latitude 47 N), yield the most radiogenic Pb isotope ratios ({sup 206}Pb/{sup 207}Pb = 1.160 to 1.180) for 1997 samples collected north of latitude 47 N indicate input of an additional anthropogenic component, possibly that of Eurasian pollution being transported over the high Arctic during the winter season. A comparison of the Pb isotope results between lichens and snow samples from identical sample locations indicate that these either overlap (along St. Lawrence Valley), or are significantly different (north-south transect). The latter discrepancy may be attributed to either: (1) different time scales for the integration of the atmospheric signal (months for snow vs. years for lichens); (2) recording of the atmospheric signal at substantially different altitudes; or (3) the presence of an important, local point source of atmospheric pollution. Annual depositional budgets have been estimated for Pb, Cd, Zn, Cu, and Mn, and average values (g/km{sup 2} yr) are 1,500, 130, 196,000, 1,900, and 6,400, respectively. Compared to previous depositional fluxes (1993--1994) estimated from adjacent regions in North America, those reported here

  1. Reassortment compatibility between PB1, PB2, and HA genes of the two influenza B virus lineages in mammalian cells.

    PubMed

    Kim, Jin Il; Lee, Ilseob; Park, Sehee; Bae, Joon-Yong; Yoo, Kirim; Lemey, Philippe; Park, Mee Sook; Song, Jin-Won; Kee, Sun-Ho; Song, Ki-Joon; Park, Man-Seong

    2016-01-01

    In addition to influenza A subtypes, two distinct lineages of influenza B virus also cause seasonal epidemics to humans. Recently, Dudas et al. have done evolutionary analyses of reassortment patterns of the virus and suggested genetic lineage relationship between PB1, PB2, and HA genes. Using genetic plasmids and reassortant viruses, we here demonstrate that a homologous lineage PB1-PB2 pair exhibits better compatibility than a heterologous one and that the lineage relationship between PB1 and HA is more important for viral replication than that between PB2 and HA. However, co-adaptation of PB1-PB2-HA genes appears to be affected by complete gene constellation. PMID:27270757

  2. Reassortment compatibility between PB1, PB2, and HA genes of the two influenza B virus lineages in mammalian cells

    PubMed Central

    Kim, Jin Il; Lee, Ilseob; Park, Sehee; Bae, Joon-Yong; Yoo, Kirim; Lemey, Philippe; Park, Mee Sook; Song, Jin-Won; Kee, Sun-Ho; Song, Ki-Joon; Park, Man-Seong

    2016-01-01

    In addition to influenza A subtypes, two distinct lineages of influenza B virus also cause seasonal epidemics to humans. Recently, Dudas et al. have done evolutionary analyses of reassortment patterns of the virus and suggested genetic lineage relationship between PB1, PB2, and HA genes. Using genetic plasmids and reassortant viruses, we here demonstrate that a homologous lineage PB1-PB2 pair exhibits better compatibility than a heterologous one and that the lineage relationship between PB1 and HA is more important for viral replication than that between PB2 and HA. However, co-adaptation of PB1-PB2-HA genes appears to be affected by complete gene constellation. PMID:27270757

  3. cc domains with intrinsic screening and absence of closure domains in atomically ordered BaTiO3 in UHV

    NASA Astrophysics Data System (ADS)

    Watanabe, Y.; Kaku, S.; Nakamura, K.

    2010-03-01

    cc domains have been observed in ordinary environments, where extraneous screening hampers rigorous comparison with theories. Indeed, recent theories predict closure domains in the absence of extraneous screening. Therefore, we performed simultaneous topographic, electrostatic and piezoelectric imaging of atomically clean, free surface of BaTiO3 single crystal by AFM operated in ultra high vacuum (UHV).footnotetextS. Kaku et al., J.Kor.Phys.Soc.55,799(2009) BaTiO3 surface retains stoichiometry in UHV because of the absence of volatile elements (Pb, Bi, Li) and low TC The surface cleanness is confirmed by the detection of chemical bonding. Three imaging methods verified the assignment of ac and cc domains, which is consistent with conventional theory and experiments. These ac and cc domains change reversibly by weak electric field of 2kV/cm at RT. In addition, the temperature dependence of the domains agrees with convention theories. These observations prove the absence of dominating control of defects and impurities on the observed domains. The sole deviation is the reduction of the potential difference to 1/30 of the conventional theories. The described intrinsic nature of the domains indicates an intrinsic screening in cc domains, which is consistent with the intrinsic surface carrier layer on ferroelectrics.footnotetextWatanabe et al. PRL86332(2001), PRB57,789(1998)

  4. Accessing (Ba1-xSrx)Al2Si2O8:Eu Phosphors for Solid State White Lighting via Microwave-assisted Preparation: Tuning Emission Color by Coordination Environment

    SciTech Connect

    Brgoch, Jakoah; Klob, Simon D.; Denault, Kristin A.; Seshadri, Ram

    2014-07-15

    The preparation of Eu2+-substituted barium aluminum silicates is achieved using a rapid microwave-assisted preparation. The phase evolution of two BaAl2Si2O8:Eu2+ polymorphs, the higher temperature hexagonal phase (hexacelsian), and the lower temperature monoclinic phase (celsian), is explored by varying the ramp time and soak time. This preparation method significantly reduces the reaction time needed to form these phases compared to conventional solid state routes. The luminescent properties of the two phases are identified under UV excitation with the hexagonal phase emitting in the UV region (λem = 372 nm) and the monoclinic phase emitting in the blue region (λem = 438 nm). The differences in optical properties of the two polymorphs are correlated to the coordination number and arrangement of the alkali earth site. The optical properties of the monoclinic phase can be further tuned through the substitution of Sr2+, forming the solid solution (Ba1–xSrx)Al2Si2O8:Eu2+. Changes in the crystal structure due to Sr2+ substitution produce a surprising blue-shift in the emission spectrum, which is explained by a greater dispersion of bond lengths in the (Ba/Sr)–O polyhedra. The entire monoclinic solid solution exhibits excellent quantum yields of nearly 90 %, owing to the structural rigidity provided by the highly connected tetrahedral network.

  5. First-Principles Investigations of Pb Anti-Site Defects in PbZrO3 and Pb(Zr, Ti)O3 Perovskites

    NASA Astrophysics Data System (ADS)

    Kagimura, Ricardo; Singh, David J.

    2008-03-01

    Lead zirconate (PZ) and lead zirconate titanate (PZT) have the perovskite type structure, ABO3. Bivalent lead (Pb^+2) ions occupy the A site, while tetravalent titanium and zirconium (Zr^+4, Ti^+4) ions occupy the B site at random of the PZT solid solution. Also, lead can be tetravalent (Pb^+4), such as in PbO2 structure. Recent experimental work has reported that tetravalent Pb ions can locate at the B site of the PZT perovskite forming a lead zirconate-titanate-plumbate solid solution. The experimental results suggest that, based on a PbZrO3-PbTiO3-PbPbO3 ternary solution phase diagram [G. Suchaneck et al., Ferroelectrics 318, 3 (2005)], the substitutional Pb atom prefers to occupy the Zr site instead of the Ti one. In this work, we report density functional supercell calculations for pure PbZrO3 perovskite and for ordered Pb(Zr1/2Ti1/2)O3 solid solution with different configurations for the Zr and Ti atoms. We investigate the anti-site defect energies and the effects on the electronic structure.

  6. New yellow Ba0.93Eu0.07Al2O4 phosphor for warm-white light-emitting diodes through single-emitting-center conversion

    SciTech Connect

    Li, Xufan; Budai, John D.; Liu, Feng; Howe, Jane Y.; Zhang, Jiahua; Wang, Xiao-Jun; Gu, Zhanjun; Sun, Chengjun; Meltzer, Richard S.; Pan, Zhengwei

    2013-01-01

    Phosphor-converted white light-emitting diodes for indoor illumination need to be warm-white (i.e., correlated color temperature <4000 K) with good color rendition (i.e., color rendering index >80). However, no single-phosphor, single-emitting-center-converted white light-emitting diodes can simultaneously satisfy the color temperature and rendition requirements due to the lack of sufficient red spectral component in the phosphors’ emission spectrum. Here, we report a new yellow Ba0.93Eu0.07Al2O4 phosphor that has a new orthorhombic lattice structure and exhibits a broad yellow photoluminescence band with sufficient red spectral component. Warm-white emissions with correlated color temperature <4000 K and color rendering index >80 were readily achieved when combining the Ba0.93Eu0.07Al2O4 phosphor with a blue light-emitting diode (440–470 nm). This study demonstrates that warm-white light-emitting diodes with high color rendition (i.e., color rendering index >80) can be achieved based on single-phosphor, single-emitting-center conversion.

  7. Experimental determination of the partition coefficient for Ba in Neogloboquadrina dutertrei suggests calcification occurs in a Ba-enriched microenvironment

    NASA Astrophysics Data System (ADS)

    Fehrenbacher, J. S.; Russell, A. D.; Davis, C. V.; Spero, H. J.; Chu, E.

    2015-12-01

    The Ba/Ca ratio in several spinose planktic foraminifer species varies as a function of the Ba/Ca concentration of seawater and is not affected by other parameters such as the seawater salinity, temperature and pH (Honisch et al., 2011). Since seawater Ba concentration is linearly related to Ba in nearshore environments, Ba/Ca ratios in spinose species shows promise as an indicator of past changes in monsoon strength and river runoff (e. g. Weldeab et al. 2007). In contrast, the non-spinose foraminifers often have intrashell variability in Ba/Ca, with Ba/Ca ratios much higher than expected for the range of Ba concentrations observed in the ocean. Furthermore, the Ba/Ca ratio can vary by over a factor of 10 within a single specimen. This suggests either 1) the partition coefficient for Ba in non-spinose species differs from that determined for spinose species, or 2) non-spinose species calcify in a micro-environment that is enriched in Ba. We conducted experiments on live specimens to determine the partition coefficient for Ba in the non-spinose foraminifer N. dutertrei. Specimens were collected via plankton net from the Southern California Bight and cultured at the Wrigley Marine Science Center, Santa Catalina Island during the summer of 2013-2015. We use isotopically labeled seawater (87Sr) to identify discrete portions of calcite that grew in culture. We use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for trace element analyses and to identify ocean grown vs. culture grown calcite. We show that the partition coefficient is similar to the spinose species: N. dutertrei incorporates Ba as a function of seawater chemistry. We conclude from these observations that N. dutertrei forms its calcite from fluids enriched in Ba, and hypothesize that this process occurs via attachment to organic-rich particles such as marine snow.

  8. Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

    NASA Astrophysics Data System (ADS)

    Lu, Shengbo; Xu, Zhengkui; Su, Shi; Zuo, Ruzhong

    2014-07-01

    Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

  9. Effects of BiAlO{sub 3}-doping on dielectric and ferroelectric properties of 0.93Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.07BaTiO{sub 3} lead-free ceramics

    SciTech Connect

    Wang, Jian; Chen, Xiao-ming Zhao, Xu-mei; Liang, Xiao-xia; Zhou, Jian-ping; Liu, Peng

    2015-07-15

    Highlights: • BiAlO{sub 3}-doped BNT-based ceramics were synthesized via a conventional solid state reaction method. • T% values are 56%, 32%, 37%, and 37% for the ceramics with x = 0, 0.01, 0.02 and 0.06, respectively. • The mean grain sizes of the ceramics with x = 0, 0.01, 0.02 and 0.06 are about 1.1, 0.9, 0.8 and 0.7 μm, respectively. • Dielectric anomalies in the ϵ{sub r}–T curves are close related to the BiAlO{sub 3} amounts. • The ceramic with x = 0.01 shows the P{sub m} of 32.5 μC/cm{sup 2}, P{sub r} of 24.1 μC/cm{sup 2}, E{sub c} of 20.0 kV/cm and d{sub 33} of 166 pC/N. - Abstract: (1 − x)(0.93Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.07BaTiO{sub 3})–xBiAlO{sub 3} (BNBT-xBA, x = 0, 0.01, 0.02, 0.06) lead-free ceramics were synthesized via a conventional solid state reaction method. Crystallite structure, microstructure, dielectric and ferroelectric properties of the BNBT–xBA ceramics were studied in detail. X-ray diffraction results show that all ceramics exhibit typical diffraction peaks of ABO{sub 3} perovskite structure. Scanning electron microscope images show that all samples have fine microstructures. Both Curie temperature and maximum dielectric constant vary with the change in the BiAlO{sub 3} amounts. The values of hysteresis loop squareness were calculated to be 1.26, 0.81, 0.51 and 0.36 for the ceramics with x = 0, 0.01, 0.02 and 0.06, respectively, indicating a decreased switching behavior of polarization. The changes in dielectric and ferroelectric properties of the ceramics are also discussed.

  10. Pb and Sr isotopic evidence for sources of atmospheric heavy metals and their deposition budgets in northeastern North America

    NASA Astrophysics Data System (ADS)

    Simonetti, Antonio; Gariépy, Clément; Carignan, Jean

    2000-10-01

    Concentrations of Al, Ba, Cd, Cu, Mg, Mn, Pb, Rb, Sr, and Zn, as well as Pb and Sr isotopic compositions were determined in samples of snowpack obtained during the 1998 winter season from northeastern North America. Median enrichment factors, relative to upper crustal abundances, for Cd, Cu, Mn, Pb, and Zn for all samples range from ca. 50 to 36,000 and are indicative of an anthropogenic origin. The Pb isotope ratios correlate with geographic location because snowpack from eastern Ontario and the northeastern USA are characterized by the most radiogenic 206Pb/ 207Pb ratios (ca. 1.18-1.19), and these decrease systematically in an easterly direction towards the Atlantic coast (ca. 1.16). The Pb isotope data for the 1998 samples of snowpack indicate that atmospheric pollution in this region of North America is dominated solely by a mixture of anthropogenic emissions from US ( 206Pb/ 207Pb ca. 1.20) and Canadian ( 206Pb/ 207Pb ca. 1.15) sources. This result contrasts with that obtained for 1997 snowpack from similar geographic regions, because the Pb isotope data for the latter suggest the involvement of an additional anthropogenic component, possibly that of Eurasian pollution transported over the high Arctic. This difference in the distribution pattern of atmospheric pollution over northeastern North America between the 1997 and 1998 winter seasons may be related to the El Niño phenomenon. Sr isotope data for all the 1998 snowpack samples define a large range in 87Sr/ 86Sr values but most are between 0.709 to 0.710, similar to the value of present-day seawater (ca. 0.7092). However, the majority of snowpack samples from eastern Ontario are characterized by lower 87Sr/ 86Sr ratios (<0.709), and these correlate negatively with their enrichment factors of Pb. Such trends suggest the presence of a relatively 'unradiogenic' source of anthropogenic Sr, possibly related to emissions from coal-fired power plants located in the western and midwestern regions of the USA

  11. Structural and Ferroelectric Properties of Epitaxial ultrathin PbZr0.52Ti0.48O3 Films Prepared on La0.67Sr0.33MnO3/(LaAlO3)0.3(Sr2AlTaO6)0.7 Substrates

    NASA Astrophysics Data System (ADS)

    Ortega, Nora; Barrionuevo, Danilo; Kumar, Ashok; Katiyar, Ram

    2012-02-01

    The existence of ferroelectricity in ultrathin films open the possibility to further miniaturize devices based on FE materials, i.e. ferroelectric tunnel junctions take advantage of tunnel electroresistance effect. We have fabricated epitaxial PbZr0.52Ti0.48O3 thin and ultrathin films using pulsed laser deposition on (001) on La2/3Sr1/3MnO3/(LaAlO3)0.3(Sr2AlTaO6)0.7 (LSMO/LSAT) substrates. The film thickness ranged between 3 to 100 nm. X-ray diffraction analysis revealed PZT and LSMO films are (00l) oriented perovskite structure. Atomic force microscopy of the PZT/LSMO(40nm)/LSAT structures show the surface is smoothness, densely packed, and free of cracks. The surface roughness on a 3 x 3 μm^2 area of the 100 nm and 3 nm thick films is ˜2 nm and ˜0.3 nm respectively. Well defined ferroelectric loop was observed in Pt/PZT(100nm)/LSMO(40nm)/LSAT structure with a remanent polarization ˜38 μC/cm^2 and a coercive field ˜80 kV/cm. The ferroelectric nature of the PZT ultrathin films (7--3 nm) was characterized using piezo force microscopy, a clear contrast between up and down ferroelectric domains was observed after writing positive and negative polarized in 2x2 μm^2 and 1x1 μm^2 areas respectively.

  12. Galvanomagnetic and thermomagnetic properties of thallium doped PbSnTe and PbSeTe

    NASA Astrophysics Data System (ADS)

    Jovovic, Vladimir; Heremans, Joseph

    2009-03-01

    Thallium acts as a resonant level in PbTe, so that PbTe:Tl shows a significant improvement of thermoelectric properties due to an increase in thermopower as compared to that of similarly Na-doped PbTe [2]. Further improvements in zT are expected from a reduction of the thermal conductivity by alloy scattering in Pb1-x-y TlySnxTe and Pb1-yTlyTe1-xSex alloys. However, the band structure of PbTe is sensitive to alloying with Sn and Se, and thus the location of the Tl level with respect to the valence band can change with x. In this study, we investigate the effects that band structure modifications have on the enhancement of thermopower. Thermoelectric properties of Pb1-x-y TlySnxTe and Pb1-yTlyTe1-xSex alloys with y=0.01-0.04 and x=0-0.3 are measured in directions longitudinal and transverse to magnetic fields in the range of -1.5 to 1.5T. We report zero field values of electrical resistivity, thermopower, Hall coefficient and adiabatic Nernst-Ettinghausen coefficient as measured in temperature range 80-420K. From these we calculate carrier density and mobility and the density of states effective masses and Fermi energies. [2] J.P. Heremans et al., Science 321, 554 (2008)

  13. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    SciTech Connect

    Fan, Zhaochuan; Vlugt, Thijs J. H.; Koster, Rik S.; Fang, Changming; Huis, Marijn A. van; Wang, Shuaiwei; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.

    2014-12-28

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

  14. BA Degree Handbook, 1978.

    ERIC Educational Resources Information Center

    Open Univ., Walton, Bletchley, Bucks (England).

    This 1978 Open University BA degree Handbook begins with information about the university organization, correspondence materials, assignments and examinations, television and radio broadcasts, audio-cassette loan service, books and libraries, study centers, the computing service, handicapped students, tutor-counselors and course tutors, tuition,…

  15. Phosphor in glasses with Pb-free silicate glass powders as robust color-converting materials for white LED applications.

    PubMed

    Lee, Yl Kwon; Lee, Jin Seok; Heo, Jong; Im, Won Bin; Chung, Woon Jin

    2012-08-01

    Phosphor-in-glass (PiG) typed robust color converters were fabricated using Pb-free silicate glasses for high-power white LED applications. SiO2-B2O3-RO(R=Ba,Zn) glass powder showed good sintering behavior and high visible transparency under the sintering condition of 750 °C for 30 min without noticeable interaction with phosphors. By simply changing the thickness of the PiG plate or mixing ratio of glass to Y3Al5O12:Ce3+ phosphor, CIE chromaticity coordinates of the LED can be easily controlled. Enhanced thermal quenching property of PiG compared to phosphor with conventional silicone resin suggests its prominent feasibility for high-power/high-brightness white LEDs. PMID:22859157

  16. Effect of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film thickness on the dielectric properties of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} in Ag/Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/LaAlO{sub 3} multilayer structures

    SciTech Connect

    Zhu Xiaohong; Peng Wei; Li Jie; Chen Yingfei; Tian Haiyan; Xu Xiaoping; Zheng Dongning

    2005-01-01

    Ferroelectric and superconductor bilayers of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} (BSTO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), with different YBCO film thicknesses, have been fabricated in situ by pulsed-laser deposition on 1.2 deg. vicinal LaAlO{sub 3} substrates. The dielectric properties of BSTO thin films were measured with a parallel-plate capacitor configuration in the temperature range of 77-300 K. We observed a strong dependence of the dielectric properties of BSTO thin films on the thickness of the YBCO layer. As the YBCO-film thickness increases, the temperature of the dielectric permittivity maximum of BSTO thin films shifts to higher values, and the leakage current and dielectric loss increase drastically, while the dielectric constant and dielectric tunability decrease remarkably. The results are explained in terms of the transformation in the growth mode of the YBCO layer from two-dimensional step flow to three-dimensional island that leads to significant deterioration in the dielectric properties of BSTO thin films. We propose that improved dielectric properties could be obtained by reasonably manipulating the growth mode of the YBCO layer in the multilayer structures.

  17. A Single Grain U-Pb and Pb-Pb Dating and D/H Ratios of the Phosphate Mineral in ALH84001

    NASA Astrophysics Data System (ADS)

    Koike, M.; Ota, Y.; Takahata, N.; Sano, Y.; Sugiura, N.

    2012-12-01

    There are many studies that determine U-Pb and Pb-Pb ages of phosphates in Martian meteorites. Phosphate minerals such as an apatite (Ca5(PO4)3[OH, F, Cl]) and a whitlockite (Ca9 [Mg, Fe2+] (PO4)6 PO3OH) contain water in the form of OH, which provides us hydrogen isotopic information. The goal of this study is to obtain a crystallization age and hydrogen isotopic distributions of each grain and to relate them to the surface evolution of Mars. ALH84001 is known to be about 4 billion years old [1]. Its carbonates and maskelynite showed high D/H ratios with large deviations, which indicates large fractionation at early Mars surface [2]. Due to small grain sizes and limited spatial resolutions of measurements, previous studies used several grains for one age or one series of isotopic distributions. Here we determined single grain ages and D/H ratios using NanoSIMS with a high spatial resolution. A thin section of ALH84001 was polished and carbon-coated. The section was then observed by SEM-EDS to locate phosphate minerals. A large phosphate grain (>100μm) was found and analyzed by NanoSIMS. A ~10nA O- primary ion beam (with spot diameter of ~20μm) was used for U-Pb and Pb-Pb measurements and a ~1nA (spot diameter of <10μm) was for D/H ratio measurements. An apatite from a Prairie Lake circular complex, PRAP, with a known age (1156 Ma; [3]) was used as a standard for U-Pb. The D/H ratio and the water content of an apatite from Morocco were measured by conventional methods to use as a D/H standard. 238U-206Pb isochron, 207Pb-206Pb isochron, and total U-Pb isochron age, a regression line in 3-D space (238U/206Pb-207Pb/206Pb-204Pb/206Pb) showed a consistent age ~4 Ga. The ages obtained in this study were also consistent with previous U-Pb dating within experimental errors. D/H ratios in the same grain showed high values and a considerable deviation, which seems to be due to mixing of terrestrial water. References: [1] Terada K. et al. 2003 Meteoritics & Planet. Sci. 38

  18. Computer simulation of the self-assembly of crystal structures of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192O786](H2O) n (tschoertnerite, TSC, V = 31 614 Å3) and Ca2K2[Al6Si6O24](H2O)10 (willhendersonite, cha, V = 804 Å3) from template nanocluster precursors K48 and K12

    NASA Astrophysics Data System (ADS)

    Ilyushin, G. D.; Blatov, V. A.

    2013-07-01

    The self-assembly of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192 O786](H2O) n (tschoertnerite, TSC-type framework, V = 31614 Å3) and Ca2K2[Al6Si6O24] (H2O)10 (willhendersonite, CHA-type framework, V = 804 Å3), which form paragenetic associations, has been simulated using computational methods (TOPOS program package). A new method for analyzing zeolites of any complexity has been used, which is based on the complete expansion of the three-dimensional structural graph (3 D factor graph) in tiles and the selection of nonintersecting tiles forming a packing. The code of self-assembly of 3 D structures from complementary linked nanocluster precursors is reconstructed: primary chain → microlayer → microframework. A supracluster precursor K48 with the symmetry bar 43 m, formed of four K12 clusters corresponding to the t-hpr tile, is established for TSC. The K48 cluster contains Ca template cations, which stabilize its local region in the stages of K12 → K24 → K48 self-assembly. Bifurcations of evolution paths (structural branching points) during the self-assembly of TSC and CHA microframeworks are established in the stage of formation of the K24 supracluster from invariant templated K12 clusters. The models under consideration explain the 100% localization of B = Ca cations, which play the role of templates, and the 50% occupation of the positions of K, Sr, and Ba spacer cations (in TSC) and K spacer cations (in CHA).

  19. Lattice dynamics of crystals with tetragonal BaTiO3 structure

    NASA Astrophysics Data System (ADS)

    Freire, J. D.; Katiyar, R. S.

    1988-02-01

    A lattice-dynamical formalism using the rigid-ion model due to Born and Huang is applied to the ferroelectric crystals PbTiO3 and BaTiO3, in the tetragonal phase. The model includes short-range interactions of axially symmetric type between various ions in the primitive cell and long-range Coulomb interactions. The stability conditions are worked out in the manner described by Katiyar and are used to determine several first-order derivative potential constants for the crystals. The number of potential constants was further reduced by considering the variation of radial force constants with the ion-ion distance, as given by the exponential formalism of Born and Mayer. Zone-center phonons and a few of the low-frequency zone-boundary phonons were used for the nonlinear least-squares fitting. In general, we obtained excellent agreement between the calculated and observed frequencies. The resulting parameters showed that the short-range interaction between the nearest titanium and oxygen is approximately 1 order of magnitude stronger than the interactions between the lead and oxygen or between the oxygens. The calculations showed that the lowest transverse-optic mode of E symmetry in PbTiO3 has eigenvectors similar to those predicted by Last, whereas in BaTiO3 the ionic movement in the lowest optic E mode can be approximated by the description of Slater. The phonon dispersion curves for various directions of the wave vector q were computed. These results are in good agreement with the inelastic neutron measurements by Shirane et al. A calculation of the oblique phonons near the zone center is presented and compared with the available experimental data. These calculations show that the long-range Coulomb forces dominate the anisotropic forces in these crystals. A theoretical approach for computing the elastic, dielectric, and piezoelectric properties is presented and the proposed model applied for calculating these constants. The results are compared with the

  20. Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications

    USGS Publications Warehouse

    Slack, J.F.; Kelley, K.D.; Anderson, V.M.; Clark, J.L.; Ayuso, R.A.

    2004-01-01

    Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqaluk display an antithetic relationship between SiO2/Al2O3 and TiO2/Zr which, together with textural information, suggest preferential silicification of carbonate-bearing sediments. Data for both drill cores also show generally high Tl, Sb, As, and Ge and uniformly positive Eu anomalies (Eu/Eu* > 1.0). Similar high Tl, Sb, As, Ge, and Eu/Eu* values are present in the footwall and shallow hanging wall of Zn-Pb-Ag sulfide intervals at Anarraaq but are not as widely dispersed. Net chemical changes for altered wall rocks in the district, on the basis of average Al-normalized data relative to unaltered black shales of the host Kuna Formation, include large enrichments (>50%) of Fe, Ba, Eu, V, S, Co, Zn, Pb, Tl, As, Sb, and Ge at both Red Dog and Anarraaq, Si at Red Dog, and Sr, U, and Se at Anarraaq. Large depletions (>50%) are evident for Ca at both Red Dog and Anarraaq, for Mg, P, and Y at Red Dog, and for Na at Anarraaq. At both Red Dog and Anarraaq, wall-rock alteration removed calcite and minor dolomite during hydrothermal decarbonation reactions and introduced Si, Eu, and Ge during silicification. Sulfidation reactions deposited Fe, S, Co, Zn, Pb, Tl, As, and Sb; barite mineralization introduced Ba, S, and Sr. Light REE and U were mobilized locally. This alteration and mineralization occurred during Mississippi an hydrothermal events that predated the Middle Jurassic-Cretaceous Brookian orogeny. Early hydrothermal silicification at Red Dog took place prior to or during massive sulfide mineralization, on the basis of the dominantly planar nature of Zn-Pb veins, which suggests

  1. Using grouper fish as bio-indicator of Cd, Cu, Pb and V in the vicinity of a single buoy mooring (SBM3) at Mina Al Fahal in the Sultanate of Oman.

    PubMed

    Abdul-Wahab, S A; Al-Husaini, I S; Rahmalan, A

    2013-12-01

    This paper investigated metal contamination in muscle tissue of the grouper (Epinephelus coioides) in the vicinity of a single buoy mooring (SBM3) at the Sultanate of Oman. The fish samples were analyzed for cadmium (Cd), copper (Cu), lead (Pb) and vanadium (V). The mean concentrations of Cd, Cu, Pb and V in the fish samples were 0.05 ± 0.004, 0.34 ± 0.013, 0.20 ± 0.018 and 0.03 ± 0.006 mg/kg, respectively. The results were compared with the corresponding permissible concentration limits according to the Sultanate of Oman (0.05, 3.28, 0.3 and 1.4 mg/kg for Cd, Cu, Pb and V, respectively) and the European Commission (0.05 mg/kg for Cd and 0.3 mg/kg for Pb). It was found that none of the overall mean metal concentrations exceeded the corresponding Omani legislation or European Commission limits. However, the overall mean concentration of Cd was identical to the maximum permissible limit of 0.05 mg/kg that has been established by both Commissions, and the limits were exceeded for mean Cd levels in fish at two of the six sampling stations at SBM3. In general, this study indicated that the fishes at SBM3 were not highly contaminated with these metals. PMID:24145924

  2. Ba{sub 2}TeO: A new layered oxytelluride

    SciTech Connect

    Besara, T.; Ramirez, D.; Sun, J.; Whalen, J.B.; Tokumoto, T.D.; McGill, S.A.; Singh, D.J.; Siegrist, T.

    2015-02-15

    Single crystals of the new semiconducting oxytelluride phase, Ba{sub 2}TeO, were synthesized from barium oxide powder and elemental tellurium in a molten barium metal flux. Ba{sub 2}TeO crystallizes in tetragonal symmetry with space group P4/nmm (#129), a=5.0337(1) Å, c=9.9437(4) Å, Z=2. The crystals were characterized by single crystal x-ray diffraction, heat capacity and optical measurements. The optical measurements along with electronic band structure calculations indicate semiconductor behavior with a band gap of 2.93 eV. Resistivity measurements show that Ba{sub 2}TeO is highly insulating. - Graphical abstract: Starting from a simple stacking of rocksalt layers, the final structure of Ba{sub 2}TeO can be obtained by accommodation of structural strain via atom displacements. Density of states calculations and optical absorbance measurements show that Ba{sub 2}TeO has a band gap of 2.93 eV, indicative of semiconductor behavior. - Highlights: • Single crystal synthesis of a new layered oxytelluride, Ba{sub 2}TeO. • The structure features inverse PbO-type BaO layers and NaCl-type BaTe layers. • Optical absorbance show Ba{sub 2}TeO to be a semiconductor with a 2.93 eV gap. • Density of states indicate a small hybridization between Te 5p and Ba 5d states. • The BaTe (BaO) layers dominate the heat capacity at low (high) temperatures.

  3. Life-limiting mechanisms in Ba-oxide, Ba-dispenser and Ba-Scandate cathodes

    NASA Astrophysics Data System (ADS)

    Gaertner, G.; Barratt, D.

    2005-09-01

    Ba-oxide, Ba-dispenser and Ba-Scandate cathodes have been continuously improved in their emission performance in the past decades. Ba-oxide and Ba-dispenser cathodes are also the dominant types of thermionic cathodes used in most vacuum tube applications. When improvements in emissive properties are introduced, their impact on cathode life - where several years in a vacuum tube environment are typically required - also needs to be known. Hence, the investigation of cathode life-limiting effects is the basis of accelerated life predictions and of further cathode improvement. In this contribution, the main effects limiting the operating life of Ba/BaO-based thermionic cathodes are discussed, especially related to intrinsic dispensation and resupply to the emissive surface. Emission poisoning induced by adsorption of poisonous gases will not be addressed here. We will stress common points and point out the differences between the three types.

  4. Domain matched epitaxial growth of (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on (0001) Al{sub 2}O{sub 3} with ZnO buffer layer

    SciTech Connect

    Krishnaprasad, P. S. E-mail: mkj@cusat.ac.in; Jayaraj, M. K. E-mail: mkj@cusat.ac.in; Antony, Aldrin; Rojas, Fredy

    2015-03-28

    Epitaxial (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) thin films have been grown by pulsed laser deposition on (0001) Al{sub 2}O{sub 3} substrate with ZnO as buffer layer. The x-ray ω-2θ, Φ-scan and reciprocal space mapping indicate epitaxial nature of BST thin films. The domain matched epitaxial growth of BST thin films over ZnO buffer layer was confirmed using Fourier filtered high resolution transmission electron microscope images of the film-buffer interface. The incorporation of ZnO buffer layer effectively suppressed the lattice mismatch and promoted domain matched epitaxial growth of BST thin films. Coplanar inter digital capacitors fabricated on epitaxial (111) BST thin films show significantly improved tunable performance over polycrystalline thin films.

  5. Melt Processed Single Phase Hollandite Waste Forms For Nuclear Waste Immobilization: Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al

    SciTech Connect

    Brinkman, Kyle; Marra, James; Amoroso, Jake; Conradson, Steven D.; Tang, Ming

    2013-09-23

    Cs is one of the more problematic fission product radionuclides to immobilize due to its high volatility at elevated temperatures, ability to form water soluble compounds, and its mobility in many host materials. The hollandite structure is a promising crystalline host for Cs immobilization and has been traditionally fabricated by solid state sintering methods. This study presents the structure and performance of Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al hollandite fabricated by melt processing. Melt processing is considered advantageous given that melters are currently in use for High Level Waste (HLW) vitrification in several countries. This work details the impact of Cr additions that were demonstrated to i) promote the formation of a Cs containing hollandite phase and ii) maintain the stability of the hollandite phase in reducing conditions anticipated for multiphase waste form processing.

  6. Crystal Structure and Thermodynamic Stability of Ba/Ti-Substituted Pollucites for Radioactive Cs/Ba Immobilization

    SciTech Connect

    Xu, Hongwu; Chavez, Manuel E.; Mitchell, Jeremy N.; Garino, Terry J.; Schwarz, Haiqing L.; Rodriguez, Mark A.; Rademacher, David X.; Nenoff, Tina Maria

    2015-04-23

    An analogue of the mineral pollucite (CsAlSi2O6), CsTiSi2O6.5 has a potential host phase for radioactive Cs. However, as 137Cs and 135Cs transmute to 137Ba and 135Ba, respectively, through the beta decay, it is essential to study the structure and stability of this phase upon Cs → Ba substitution. In this work, two series of Ba/Ti-substituted samples, CsxBa(1-x)/2TiSi2O6.5 and CsxBa1-xTiSi2O7-0.5x, (x = 0.9 and 0.7), were synthesized by high-temperature crystallization from their respective precursors. Synchrotron X-ray diffraction and Rietveld analysis reveal that while CsxBa(1-x)/2TiSi2O6.5 samples are phase-pure, CsxBa1-xTiSi2O7-0.5x samples contain Cs3x/(2+x)Ba(1-x)/(2+x)TiSi2O6.5 pollucites (i.e., also two-Cs-to-one-Ba substitution) and a secondary phase, fresnoite (Ba2TiSi2O8). Thus, the CsxBa1-xTiSi2O7-0.5x series is energetically less favorable than CsxBa(1-x)/2TiSi2O6.5. To study the stability systematics of CsxBa(1-x)/2TiSi2O6.5 pollucites, high-temperature calorimetric experiments were performed at 973 K with or without the lead borate solvent. Enthalpies of formation from the constituent oxides (and elements) have thus been derived. Our results show that with increasing Ba/(Cs + Ba) ratio, the thermodynamic stability of these phases decreases with respect to their component oxides. Hence, from the energetic viewpoint, continued Cs → Ba transmutation tends to destabilize the parent silicotitanate pollucite structure. However, the Ba-substituted pollucite co-forms with fresnoite (which incorporates the excess Ba

  7. Discrimination of the Cigarettes Geographical Origin by DRC-ICP-MS Measurements of Pb Isotope Compositions

    NASA Astrophysics Data System (ADS)

    Guo, W.; Hu, S.; Jin, L.

    2014-12-01

    Trace Pb are taken up with the same isotopic ratios as is present in the source soil, and the isotopic composition of Pb could used to reflect these sources and provide powerful indicators of the geographic origin of agriculture products derived from vegetative matter. We developed a simple and high throughput method, which based on DRC-ICP-MS for determination of Pb isotope ratios for discriminating the geographic origin of cigarettes. After acid digestion procedure, the cigarette digested solutions were directly analyzed by ICP-QMS with a DRC pressurized by the non-reactive gas Ne. In the DRC, Ne molecules collision with Pb ions and improves Pb isotope ratios precision 3-fold, which may be due to the collisional dampling smoothes out the ion beam fluctuations. Under the optimum DRC rejection parameter Q (RPq = 0.45), the main matrix components (K, Na, Ca, Mg, Al, Fe etc.) originating from cigarettes were filtered out. Mass discrimination of 208Pb/206Pb ratio in Ne DRC mode increased 0.3% compared to the standard mode, the mass bias due to the in-cell Ne gas collision can be accurately corrected by NIST 981 Pb isotope standard. This method was verified by a tobacco reference material CTV-OTL-2. Results of 208Pb/206Pb and 207Pb/206Pb were 2.0848 ± 0.0028 (2δ) and 0.8452 ± 0.0011 (2δ) for CTA-VTL-2, which were agreed with the literature values (208Pb/206Pb = 2.0884 ± 0.0090 and 207Pb/206Pb = 0.8442 ± 0.0032). The precision of Pb isotope ratios (208Pb/206Pb and 207Pb/206Pb) for the cigarette samples are ranged from 0.01 to 0.08% (N = 5). It has sufficient precision to discriminate 91 different brand cigarettes originated from four different geographic regions (Shown in Fig).

  8. Pb, Sr, and Nd isotopes in basalts and sulfides from the Juan de Fuca Ridge

    NASA Technical Reports Server (NTRS)

    Hegner, E.; Tatsumoto, M.

    1987-01-01

    Isotopic Pb, Sr, and Nd data were collected by the Alvin submersible from seven basalt glasses in the southern Juan de Fuca Ridge (JFR), giving similar ratios for Pb-206/Pb-204 of about 18.45, for Pb-207/Pb-204 of about 15.47, for Pb-208/Pb-204 of about 37.81, for Sr-87/Sr-86 of about 0.70249, and for Nd-143/Nd-144 of about 0.51315. Data suggest that the basalts are all cogenetic, and that four of the samples are also comagmatic. It is concluded that isotopic data for the JFR and seamount basalts provide additional support for the mantle blob cluster model (Allegre et al., 1984), suggesting the involvement of multiple components in the genesis of ridge basalts, and including an unusual end-member that has nonradiogenic Sr and variable Pb-206/Pb-204 isotopic compositions.

  9. Ancient Pb and Ti mobilization revealed by Scanning Ion Imaging

    NASA Astrophysics Data System (ADS)

    Kusiak, Monika A.; Whitehouse, Martin J.; Wilde, Simon A.

    2014-05-01

    mobilization, which is independent of the degree of metamictisation, oxygen isotope and REE content of the zircons [5]. The Antarctic zircons experienced ancient Ti and Pb mobilization and redistribution, most likely caused by polyphase metamorphism at ~2.8 Ga and ~2.5 Ga, the latter documented as reaching temperatures of >1100ºC [5]. References: [1] Williams et al., 1984, Contr. Min. Petrol. 88, 322-327. [2] Black et al., (1986), Contr. Min. Petrol. 94, 427-437. [3] Harley & Kelly, 2007, Earth's Oldest Rocks: Developments in Precambrian Geology 15, 149-186. [4] Kusiak et al., 2013, Geology 41, 291-294. [5] Kusiak et al., 2013, American J. of Sci. 313, 933-967. [5] Hokada et al., 2004, Contr. Min. Petrol. 147, 1-20.

  10. Redetermination of brackebuschite, Pb2Mn3+(VO4)2(OH)

    PubMed Central

    Lafuente, Barbara; Downs, Robert T.

    2016-01-01

    The crystal structure of brackebuschite, ideally Pb2Mn3+(VO4)2(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula A 2 M(T1O4)(T2O4)(OH, H2O), with A = Pb2+, Ba, Ca, Sr; M = Cu2+, Zn, Fe2+, Fe3+, Mn3+, Al; T1 = As5+, P, V5+; and T2 = As5+, P, V5+, S6+. The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn3+O6] octa­hedra located about inversion centres and decorated by two unique VO4 tetra­hedra (each located on a special position 2e, site symmetry m). One type of VO4 tetra­hedra is linked with the 1 ∞[MnO4/2O2/1] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO4 tetra­hedra link two adjacent octa­hedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn2V ring between the central atoms. The 1 ∞[Mn3+(VO4)2OH] chains run parallel to [010] and are held together by two types of irregular [PbOx] polyhedra (x = 8, 11), both located on special position 2e (site symmetry m). The magnitude of the libration component of the O atoms of the 1 ∞[Mn3+(VO4)2OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hy­droxy group bridges one Pb2+ cation with two Mn3+ cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O⋯O distance of this inter­action determined from the structure refinement agrees well with

  11. Redetermination of brackebuschite, Pb2Mn(3+)(VO4)2(OH).

    PubMed

    Lafuente, Barbara; Downs, Robert T

    2016-03-01

    The crystal structure of brackebuschite, ideally Pb2Mn(3+)(VO4)2(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula A 2 M(T1O4)(T2O4)(OH, H2O), with A = Pb(2+), Ba, Ca, Sr; M = Cu(2+), Zn, Fe(2+), Fe(3+), Mn(3+), Al; T1 = As(5+), P, V(5+); and T2 = As(5+), P, V(5+), S(6+). The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn(3+)O6] octa-hedra located about inversion centres and decorated by two unique VO4 tetra-hedra (each located on a special position 2e, site symmetry m). One type of VO4 tetra-hedra is linked with the (1) ∞[MnO4/2O2/1] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO4 tetra-hedra link two adjacent octa-hedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn2V ring between the central atoms. The (1) ∞[Mn(3+)(VO4)2OH] chains run parallel to [010] and are held together by two types of irregular [PbO x ] polyhedra (x = 8, 11), both located on special position 2e (site symmetry m). The magnitude of the libration component of the O atoms of the (1) ∞[Mn(3+)(VO4)2OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hy-droxy group bridges one Pb(2+) cation with two Mn(3+) cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O⋯O distance of this inter-action determined from the

  12. Characterizing Pb mobilization from upland soils to streams using (206)Pb/(207)Pb isotopic ratios.

    PubMed

    Dawson, Julian J C; Tetzlaff, Doerthe; Carey, Anne-Marie; Raab, Andrea; Soulsby, Chris; Killham, Kenneth; Meharg, Andrew A

    2010-01-01

    Anthropogenically deposited lead (Pb) binds efficiently to soil organic matter, which can be mobilized through hydrologically mediated mechanisms, with implications for ecological and potable quality of receiving waters. Lead isotopic ((206)Pb/(207)Pb) ratios change down peat profiles as a consequence of long-term temporal variation in depositional sources, each with distinctive isotopic signatures. This study characterizes differential Pb transport mechanisms from deposition to streams at two small catchments with contrasting soil types in upland Wales, U.K., by determining Pb concentrations and (206)Pb/(207)Pb ratios from soil core profiles, interstitial pore waters, and stream water. Hydrological characteristics of soils are instrumental in determining the location in soil profiles of exported Pb and hence concentration and (206)Pb/(207)Pb ratios in surface waters. The highest Pb concentrations from near-surface soils are mobilized, concomitant with high dissolved organic carbon (DOC) exports, from hydrologically responsive peat soils with preferential shallow subsurface flows, leading to increased Pb concentrations in stream water and isotopic signatures more closely resembling recently deposited Pb. In more minerogenic soils, percolation of water allows Pb, bound to DOC, to be retained in mineral horizons and combined with other groundwater sources, resulting in Pb being transported from throughout the profile with a more geogenic isotopic signature. This study shows that (206)Pb/(207)Pb ratios can enhance our understanding of the provenances and transport mechanisms of Pb and potentially organic matter within upland soils. PMID:19954181

  13. Improved Properties of Pb Based BLZT Ferroelectric Ceramics

    SciTech Connect

    Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

    2011-11-22

    Present report is concerning with investigation of effect of different sintering profiles on Pb based BLZT ceramics. The material powder of selected composition (Ba{sub 0.795}La{sub 0.005}Pb{sub 0.20}Ti{sub 0.90}Zr{sub 0.10}O{sub 3}) was prepared by solid state reaction route and then powder was compacted in the form of circular discs. The discs were then sintered at different temperatures (1325 deg. C for 4h, 1325 deg. C for 15min+1200 deg. C for 4h). Improved dielectric and ferroelectric properties were observed for samples sintered at 1200 deg. C. Shifting in T{sub c} to higher temperature could be related to enhanced tetragonality, which was further confirmed by X-ray diffraction analysis. All these improvements evidences that there is less Pb loss in case of modified sintering profile.

  14. Alpha decay of {sup 181}Pb

    SciTech Connect

    Davids, C.N.; Henderson, D.J.; Hermann, R.

    1995-08-01

    The {alpha}-decay energy of {sup 181}Pb was measured as 7211(10) keV and 7044(15). In the first study the isotope was produced in {sup 90}Zr bombardments of {sup 94}Mo and, after traversing a velocity filter, implanted in a position-sensitive Si detector; no half life for {sup 181}Pb was reported. In the second study the isotope was produced in {sup 40}Ca bombardments of {sup 144}Sm and transported to a position in front of a Si(Au) surface barrier detector with a fast He-gas-jet capillary system; an estimate of 50 ms was determined for the {sup 181}Pb half life. Recently we investigated {sup 181}Pb {alpha} decay at ATLAS as part of a survey experiment in which a l-pnA beam of 400-MeV {sup 92}Mo was used to irradiate targets of {sup 89}Y, {sup 90,92,94}Zr, and {sup 92}Mo to examine yields for one- and two-nucleon evaporation products from symmetric cold-fusion reactions. Recoiling nuclei of interest were passed through the Fragment Mass Analyzer and implanted in a double-sided silicon strip detector for {alpha}-particle assay. With the {sup 90}Zr target we observed a group at 7065(20) keV which was correlated with A = 181 recoils and had a half life of 45(20) ms. Our new results for {sup 181}Pb therefore agreed with those of the second study. There was no indication in the {sup 90}Zr + {sup 92}Mo data of the 7211(10)-keV {alpha} particles seen by Keller et al. The interested reader is referred to the 1993 atomic mass evaluation wherein the input {alpha}-decay energies and resultant masses of the light Pb isotopes (including {sup 181}Pb) are discussed.

  15. Conventional U-Pb dating versus SHRIMP of the Santa Barbara Granite Massif, Rondonia, Brazil

    USGS Publications Warehouse

    Sparrenberger, I.; Bettencourt, Jorge S.; Tosdal, R.M.; Wooden, J.L.

    2002-01-01

    The Santa Ba??rbara Granite Massif is part of the Younger Granites of Rondo??nia (998 - 974 Ma) and is included in the Rondo??nia Tin Province (SW Amazonian Craton). It comprises three highly fractionated metaluminous to peraluminous within-plate A-type granite units emplaced in older medium-grade metamorphic rocks. Sn-mineralization is closely associated with the late-stage unit. U-Pb monazite conventional dating of the early-stage Serra do Cicero facies and late-stage Serra Azul facies yielded ages of 993 ?? 5 Ma and 989 ?? 13 Ma, respectively. Conventional multigrain U-Pb isotope analyses of zircon demonstrate isotopic disturbance (discordance) and the preservation of inherited older zircons of several different ages and thus yield little about the ages of Sn-granite magmatism. SHRIMP U-Pb ages for the Santa Ba??rbara facies association yielded a 207Pb/206Pb weighted-mean age of 978 ?? 13 Ma. The textural complexity of the zircon crystals of the Santa Ba??rbara facies association, the variable concentrations of U, Th and Pb, as well as the mixed inheritance of zircon populations are major obstacles to using conventional multigrain U-Pb isotopic analyses. Sm-Nd model ages and ??Nd (T) values reveal anomalous isotopic data, attesting to the complex isotopic behaviour within these highly fractionated granites. Thus, SHRIMP U-Pb zircon and conventional U-Pb monazite dating methods are the most appropriate to constrain the crystallization age of the Sn-bearing granite systems in the Rondo??nia Tin Province.

  16. Coherent laser excitation of Ba-137 and Ba-138

    NASA Technical Reports Server (NTRS)

    Lam, Kai-Shue

    1992-01-01

    Computations are carried out for the 1S(6s2)-1P(6s,6p) coherent laser excitation of Ba-137 and Ba-138 in a magnetic field. Results are presented for both the steady-state and time-dependent excited-state populations of the Zeeman-split magnetic sublevels. The quantum-statistical Liouville-equation approach (for the reduced density matrix) is compared to the rate-equations approach. Significant differences are found between these, due to the interference between strongly overlapping lines (especially for Ba-137). The time-evolution profiles indicate that the Ba-137 transient time is much longer than that of Ba-138.

  17. Growth and characterization of PbSe and Pb1-xSnxSe on Si (100)

    NASA Astrophysics Data System (ADS)

    Sachar, H. K.; Chao, I.; McCann, P. J.; Fang, X. M.

    1999-05-01

    PbSe and Pb1-xSnxSe layers, with thicknesses ranging from 1 to 5 μm, were grown by liquid phase epitaxy on Si (100) substrates using PbSe/BaF2/CaF2 buffer layers grown by molecular beam epitaxy. Optical Nomarski characterization revealed excellent surface morphologies and good growth solution wipeoffs. Although most PbSe layers were free of cracks over the entire 8×8 mm2 substrate area, ternary Pb1-xSnxSe layers exhibited varying crack densities ranging from zero in the center of samples to over 30 cracks/cm at the edges. High resolution x-ray diffraction (HRXRD) measurements of crack-free PbSe layers showed a residual in-plane tensile strain of 0.21% indicating that most of the 0.74% thermal expansion mismatch strain was absorbed by plastic deformation. HRXRD full width half maxima values of less than 200 arc sec showed that these layers also had high crystalline quality. Fourier transform infrared transmission measurements at room temperature and 110 K showed absorption edges in the range of 270-80 meV, depending on temperature and tin content. This work shows that these materials should be suitable for fabrication of mid-infrared devices covering the 4.6-16 μm spectral range.

  18. Comparison between LaGaO/sub 3/, LaAlO/sub 3/, KTaO/sub 3/, and SrTiO/sub 3/ substrates for the epitaxial growth of YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/ thin films by a ''BaF/sub 2/ process''

    SciTech Connect

    Feenstra, R.; Budai, J.D.; Galloway, M.D.; Boatner, L.A.

    1989-01-01

    YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/ films with thicknesses in the range 60--320 nm were grown on LaGaO/sub 3/, LaAlO/sub 3/, KTaO/sub 3/, and SrTiO/sub 3/ single-crystal substrates by coevaporation of Y, Cu, and BaF/sub 2/ followed by annealing at 850/degree/C in wet oxygen. Films formed with a thickness of 160 nm or greater on SrTiO/sub 3/, KTaO/sub 3/, and LaGaO/sub 3/ exhibited sharp superconducting transitions near T/sub c/ = 91 K. For films on LaAlO/sub 3/, T/sub c/ was typically reduced by 6--8 K. For films with a thickness less than 120 nm, the superconducting transition broadens for every film-substrate combination investigated, and T/sub c/ shifts to lower temperatures with decreasing film thickness. 6 refs., 1 fig.

  19. High-pressure and high-temperature transformation of Pb(II)-natrolite to Pb(II)-lawsonite.

    PubMed

    Im, Junhyuck; Lee, Yongmoon; Blom, Douglas A; Vogt, Thomas; Lee, Yongjae

    2016-01-28

    We report on high-pressure and high-temperature chemical transformations of Pb(2+)-exchanged natrolite (Pb-NAT, Pb8Al16Si24O80·16H2O) using a combination of in situ synchrotron X-ray powder diffraction and ex situ HAADF-STEM real space imaging. Three high-pressure polymorphs of natrolites (Pb-NAT-I, II, III) are observed via step-wise pressure-induced hydrations (PIH) up to 4.5 GPa, during which the number of H2O molecules located inside the natrolite channel increases from 16 to 40 H2O per unit-cell. At 4.5 GPa after heating the high-pressure Pb-NAT-III phase at 200 °C a reconstructive phase transits into a lawsonite phase (Pb-LAW, Pb4Al8Si8O28(OH)8·4H2O) with an orthorhombic space group Pbnm and a = 5.8216(9), b = 9.114(1) and c = 13.320(1) Å is observed. The structure of the recovered Pb-LAW phase was characterized using Rietveld refinement of the in situ synchrotron X-ray powder diffraction data and HAADF-STEM real space imaging. In the recovered Pb-LAW phase the Pb(2+) content is close to 42 wt% and as bond valence approximations reveal the Pb(2+) cations are more tightly coordinated to the framework oxygen atoms than originally in the natrolite phase. PMID:26692276

  20. U, Th, Pb and REE abundances and Pb 207/Pb 206 ages of individual minerals in returned lunar material by ion microprobe mass analysis.

    NASA Technical Reports Server (NTRS)

    Andersen, C. A.; Hinthorne, J. R.

    1972-01-01

    Results of ion microprobe analyses of Apollo 11, 12 and 14 material, showing that U, Th, Pb and REE are concentrated in accessory minerals such as apatite, whitlockite, zircon, baddeleyite, zirkelite, and tranquillityite. Th/U ratios are found to vary by over a factor of 40 in these minerals. K, Ba, Rb and Sr have been localized in a K rich, U and Th poor glass phase that is commonly associated with the U and Th bearing accessory minerals. Li is observed to be fairly evenly distributed between the various accessory phases. The phosphates have been found to have REE abundance patterns (normalized to the chondrite abundances) that are fairly flat, while the Zr bearing minerals have patterns that rise steeply, by factors of ten or more, from La to Gd. All the accessory minerals have large negative Eu anomalies. Radiometric age dates (Pb 207/Pb 206) of the individual U and Th bearing minerals compare favorably with the Pb 207/Pb 206 age of the bulk rocks.

  1. Structural phase transitions of ionic layered PbFX (X = Cl{sup −}or Br{sup –}) compounds under high pressure

    SciTech Connect

    Sorb, Y.A. Sornadurai, D.

    2015-05-15

    The PbFX (X = Cl{sup –}or Br{sup –}) compounds crystallize in tetragonal structure with space group P4/nmm. High pressure X-ray diffraction studies carried out on PbFCl compound reveals that it undergoes pressure induced structural transitions at ∼18 GPa and ∼38 GPa to orthorhombic and monoclinic (P2{sub 1}/m) phases respectively. Like PbFCl, a similar phase transition from tetragonal to orthorhombic phase is observed in PbFBr at intermediate pressure. These phase transitions seem to be similar to the transitions involving other matlockite structure compounds such as BaFX (X = Cl{sup –}, Br{sup –}or I{sup –}). PbFCl has a larger structural stability range compared to BaFCl and is attributed to the large anisotropic coordination of the Pb{sup 2+} and Cl{sup –}ions.

  2. The interaction of NO2 with BaO: from cooperative adsorption to Ba(NO3)2 formation

    SciTech Connect

    Yi, Cheol-Woo W.; Kwak, Ja Hun; Szanyi, Janos

    2007-10-25

    The effect of water on the morphology of BaO/Al2O3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multi-spectroscopy study reveal that, in the presence of water, surface Ba-nitrates convert to bulk nitrates, and water facilitates the formation of large Ba(NO3)2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible, i.e. after the removal of water from the storage material a significant fraction of the bulk nitrates re-convert to surface nitrates. NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively, i.e. no surface nitrates form. After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material is, however, essentially unaffected by the presence of water, regardless of whether the water was dosed prior to or after NO2 exposure. Based on the results of this study we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.

  3. 207Pb NMR in minium, Pb3O4: Evidence for the [Pb2]4+ ion andpossible relativistic effects in the Pb-Pb bond

    SciTech Connect

    Gabuda, S.P.; Kozlova, S.G.; Terskikh, V.V.; Dybowski, C.; Neue,G.; Perry, D.L.

    1999-07-18

    Solid Pb3O4 has been studied with 207Pb nuclear magnetic resonance (NMR) spectroscopy. The 207Pb NMR chemical-shift tensor of the Pb2+ site has principal values of delta 11=1980+-5 ppm, delta 22=1540+-5ppm, and delta 33=-1108+-10 ppm; delta iso=804+-10 ppm. The chemical-shift tensor of the Pb4+ site is axial, with principal values delta bar bar=-1009+-3 ppm and delta perpendicular=1132+-3 ppm; delta iso=-1091+-3ppm. The Pb4+ Pb2+ scalar coupling constant JPb Pb=2.3+-0.1 kHz. The main contribution to the Pb2+ chemical-shift anisotropy is proposed to arise from an exchange interaction in the Pb2+ Pb2+ pairs, conventionally regarded as molecular [Pb2]4+ ions.

  4. Surface disordering of Pb(110)

    NASA Technical Reports Server (NTRS)

    Tibbits, P.; Karimi, M.; Ila, D.; Dalins, I.; Vidali, G.

    1991-01-01

    A molecular dynamics simulation of Pb(110), using embedded atom method energy functional and two-body potential derived for the purpose, shows that near 400 K the three surface layers begin to disorder well before the bulk (interior) layers. Transfer of atoms from the first subsurface layer to the surface layer occurs. Disordering propagates beyond the top three layers above 550 K, accompanied by formation of an adlayer and vacancies in the top three layers. Behavior of the two-dimensional layer structure factors indicates that disordering is anisotropic. Simulation results are consistent with experimental observations of surface roughening near 400 K and more extensive surface ordering above 525 K. Results are consistent with simulations for Ni and Al.

  5. Contrasted crustal sources as defined by whole-rock and Sr-Nd-Pb isotope geochemistry of neoproterozoic early post-collisional granitic magmatism within the Southern Brazilian Shear Belt, Camboriú, Brazil

    NASA Astrophysics Data System (ADS)

    Florisbal, Luana Moreira; de Assis Janasi, Valdecir; de Fátima Bitencourt, Maria; Stoll Nardi, Lauro Valentim; Heaman, Larry M.

    2012-11-01

    The early phase of post-collisional granitic magmatism in the Camboriú region, south Brazil, is represented by the porphyritic biotite ± hornblende Rio Pequeno Granite (RPG; 630-620 Ma) and the younger (˜610 Ma), equigranular, biotite ± muscovite Serra dos Macacos Granite (SMG). The two granite types share some geochemical characteristics, but the more felsic SMG constitutes a distinctive group not related to RPG by simple fractionation processes, as indicated by its lower FeOt, TiO2, K2O/Na2O and higher Zr Al2O3, Na2O, Ba and Sr when compared to RPG of similar SiO2 range. Sr-Nd-Pb isotopes require different sources. The SMG derives from old crustal sources, possibly related to the Paleoproterozoic protoliths of the Camboriú Complex, as indicated by strongly negative ɛNdt (-23 to -24) and unradiogenic Pb (e.g., 206Pb/204Pb = 16.0-16.3; 207Pb/204Pb = 15.3-15.4) and confirmed by previous LA-MC-ICPMS data showing dominant zircon inheritance of Archean to Paleoproterozoic age. In contrast, the RPG shows less negative ɛNdt (-12 to -15) and a distinctive zircon inheritance pattern with no traces of post-1.6 Ga sources. This is indicative of younger sources whose significance in the regional context is still unclear; some contribution of mantle-derived magmas is indicated by coeval mafic dykes and may account for some of the geochemical and isotopic characteristics of the least differentiated varieties of the RPG. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas despite their emplacement within a low-strain zone. It may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of Paleoproterozoic orthogneisses from the Camboriú Complex.

  6. Archean Pb Isotope Evolution: Implications for the Early Earth.

    NASA Astrophysics Data System (ADS)

    Vervoort, J. D.; Thorpe, R.; Albarede, F.; Blichert-Toft, J.

    2008-12-01

    The U-Pb isotope system provides us with a powerful tool for understanding the chemical evolution of the Earth. Pb isotopes in Archean rocks, however, have not been widely utilized because U mobility makes initial Pb isotope ratios from old silicate rocks difficult, if not impossible, to determine. Galenas in syngenetic volcanogenic massive sulfide (VMS) deposits, however, provide snapshots of initial Pb ratios because their Pb isotopic composition is time invariant at their formation (U/Pb=0). The Pb isotopic record from galenas from rocks of all age have been utilized for over 70 years to answer a wide range of scientific problems beginning with Al Nier's pioneering work analyzing Pb isotopes in the 1930's but are no longer widely used by the isotopic community because they have been produced by older TIMS techniques. We have begun a re-examination of Archean Pb by an extensive analysis of over 100 galena samples from Archean VMS deposits throughout the Superior and Slave Provinces in Canada as well as from other VMS deposits in Finland, South Africa and Western Australia. The goal of this work is to provide modern, high precision measurements and update an old, but venerable, Pb isotopic data set. We feel these data provide important constraints on not only the Pb isotopic evolution of the Earth, but planetary differentiation and recycling processes operating in the first 2 b.y. of Earth's history. Our analytical techniques include dissolving the Pb sulfide minerals, purifying them with ion chromatography, and analyzing them using MC-ICPMS at both Washington State University (Neptune) and Ecole Normale Superieure in Lyon, France (Nu). All Pb solutions are doped with Tl in order to correct for mass fractionation. In this abstract we report preliminary galena Pb isotope data from 6 VMS deposits in the Abitibi greenstone belt: Chibougamu, Matagami, Noranda, Normetal, Timmins, and Val d"Or. These deposits are all approximately 2.7 Ga in age but in detail vary from 2

  7. Pb - Isotopes and Pulses of the Deccan Plume

    NASA Astrophysics Data System (ADS)

    Basu, A. R.; Yannopoulos, A. S.

    2015-12-01

    Mantle plumes are generally implicated for flood basalt generation in both continental and oceanic environments by impact of large plume heads beneath or within the lithosphere. The Deccan and Siberian flood basalt eruptions, synchronous with the Cretaceous-Paleogene and end-Permian extinctions, respectively, continue to fascinate geoscientists in search for the "kill-mechanisms" by impacts, volcanisms or both. Recently, Richards et al. (2015) proposed that bulk of the Deccan eruption was triggered by the Chicxulub impact. We showed (Basu et al., 1993) that early (68.5 Ma) and late (65 Ma) alkalic pulses of the Deccan were before and after the impact event at 66 Ma. Here, we focus on an extensive volcano-stratigraphic study of Pb isotopic systematics of 69 basaltic samples from 3 subgroups and 12 formations of the Deccan, each sampled from bottom to top along the stratigraphic section, covering the 3km thick 12 Deccan formations. Pb is sensitive to crustal contamination of mantle plume-derived magmas as both the upper and lower mantle are low in Pb (0.02 - 0.15 ppm) compared to ~ 4 ppm in continental crust. The lower Deccan formations of Kalsubai and Lonavala have initial 206Pb/204Pb with a widely varying range (16.543 - 22.823) indicating continental crustal contamination. In contrast, the upper formations of the Wai subgroup show a narrow range of 16.883 to 18.956, reflecting the plume signature. In addition, the 206Pb/204Pb and 207Pb/204Pb data of the Kalsubai subgroup lavas give an isochron age of 2603±140 Ma (single-stage, µ = 8). The Wai subgroup shows a narrow and restricted Pb isotopic range plotting closer to the Geochron. We interpret these data to infer that the basement rocks of the Deccan, the Archean Indian craton, were assimilated by the upwelling melt, ultimately clearing the conduit passages for the lavas sourced from direct melting of the plume head.

  8. Pb12 2-: plumbaspherene.

    PubMed

    Cui, Li-Feng; Huang, Xin; Wang, Lei-Ming; Li, Jun; Wang, Lai-Sheng

    2006-08-31

    Although Si or Ge is not known to form empty cage clusters such as the fullerenes, we recently found a unique 12-atom icosahedral tin cluster, Sn12 2- (stannaspherene). Here we report photoelectron spectroscopy and theoretical evidence that Pb12 2- is also a highly stable icosahedral cage cluster and bonded by four delocalized radial pi bonds and nine delocalized on-sphere sigma bonds from the 6p orbitals of the Pb atoms. Following Sn12 2-, we coin a name, plumbaspherene, for the highly stable and nearly spherical Pb12 2- cluster, which is expected to be stable in solution and the solid state. Plumbaspherene has a diameter of approximately 6.3 A with an empty interior volume large enough to host most transition metal atoms, affording a new class of endohedral clusters. PMID:16928103

  9. A new mineral species ferricoronadite, Pb[Mn6 4+(Fe3+, Mn3+)2]O16: mineralogical characterization, crystal chemistry and physical properties

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Aksenov, Sergey M.; Jančev, Simeon; Pekov, Igor V.; Göttlicher, Jörg; Polekhovsky, Yury S.; Rusakov, Vyacheslav S.; Nelyubina, Yuliya V.; Van, Konstantin V.

    2016-04-01

    A new mineral ferricoronadite with the simplified formula Pb(Mn6 4+Fe2 3+)O16 was discovered in the orogenetic zone related to the "Mixed Series" metamorphic complex near the Nežilovo village, Pelagonian massif, Republic of Macedonia. Associated minerals are franklinite, gahnite, hetaerolite, roméite, almeidaite, Mn-analogue of plumboferrite, zincohögbomite analogue with Fe3+ > Al, zincochromite, Zn-bearing talc, Zn-bearing muscovite, baryte, quartz and zircon. Ferricoronadite is a late hydrothermal mineral forming veinlets up to 8 mm thick in granular aggregate predominantly composed by zinc-dominant spinels. The new mineral is opaque, black, with brownish black streak. The luster is strong submetallic to metallic. The micro-indentation hardness is 819 kg/mm2. Distinct cleavage is observed on (100). Ferricoronadite is brittle, with uneven fracture. The density calculated from the empirical formula is 5.538 g/cm3. In reflected light, ferricoronadite is light gray. The reflectance values [R max/R min, % (λ, nm)] are: 28.7/27.8 (470), 27.6/26.6 (546), 27.2/26.1 (589), 26.5/25.5 (650). The IR spectrum shows the absence of H2O and OH groups. According to the Mössbauer spectrum, all iron is trivalent. The Mn K-edge XANES spectroscopy shows that Mn is predominantly tetravalent, with subordinate Mn3+. The chemical composition is (wt%; electron microprobe, Mn apportioned between MnO2 and Mn2O3 based on the charge-balance requirement): BaO 5.16, PbO 24.50, ZnO 0.33, Al2O3 0.50, Mn2O3 9.90, Fe2O3 11.45, TiO2 4.19, MnO2 44.81, total 100.84. The empirical formula based on 8 cations Mn + Fe + Ti + Al + Zn pfu is Pb1.03Ba0.32(Mn{4.85/4+}Fe{1.35/3+}Mn{1.18/3+}Ti0.49Al0.09Zn0.04)Σ8.00O16. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is tetragonal, space group I4/m, a = 9.9043(7), c = 2.8986(9) Å, V = 284.34(9) Å3, Z = 1. In ferricoronadite, double chains of edge-sharing (Mn, Fe, Ti)-centered octahedra are connected via

  10. A new mineral species ferricoronadite, Pb[Mn6 4+(Fe3+, Mn3+)2]O16: mineralogical characterization, crystal chemistry and physical properties

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Aksenov, Sergey M.; Jančev, Simeon; Pekov, Igor V.; Göttlicher, Jörg; Polekhovsky, Yury S.; Rusakov, Vyacheslav S.; Nelyubina, Yuliya V.; Van, Konstantin V.

    2016-07-01

    A new mineral ferricoronadite with the simplified formula Pb(Mn6 4+Fe2 3+)O16 was discovered in the orogenetic zone related to the "Mixed Series" metamorphic complex near the Nežilovo village, Pelagonian massif, Republic of Macedonia. Associated minerals are franklinite, gahnite, hetaerolite, roméite, almeidaite, Mn-analogue of plumboferrite, zincohögbomite analogue with Fe3+ > Al, zincochromite, Zn-bearing talc, Zn-bearing muscovite, baryte, quartz and zircon. Ferricoronadite is a late hydrothermal mineral forming veinlets up to 8 mm thick in granular aggregate predominantly composed by zinc-dominant spinels. The new mineral is opaque, black, with brownish black streak. The luster is strong submetallic to metallic. The micro-indentation hardness is 819 kg/mm2. Distinct cleavage is observed on (100). Ferricoronadite is brittle, with uneven fracture. The density calculated from the empirical formula is 5.538 g/cm3. In reflected light, ferricoronadite is light gray. The reflectance values [ R max/ R min, % ( λ, nm)] are: 28.7/27.8 (470), 27.6/26.6 (546), 27.2/26.1 (589), 26.5/25.5 (650). The IR spectrum shows the absence of H2O and OH groups. According to the Mössbauer spectrum, all iron is trivalent. The Mn K-edge XANES spectroscopy shows that Mn is predominantly tetravalent, with subordinate Mn3+. The chemical composition is (wt%; electron microprobe, Mn apportioned between MnO2 and Mn2O3 based on the charge-balance requirement): BaO 5.16, PbO 24.50, ZnO 0.33, Al2O3 0.50, Mn2O3 9.90, Fe2O3 11.45, TiO2 4.19, MnO2 44.81, total 100.84. The empirical formula based on 8 cations Mn + Fe + Ti + Al + Zn pfu is Pb1.03Ba0.32(Mn 4.85 4+ Fe 1.35 3+ Mn 1.18 3+ Ti0.49Al0.09Zn0.04)Σ8.00O16. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is tetragonal, space group I4/ m, a = 9.9043(7), c = 2.8986(9) Å, V = 284.34(9) Å3, Z = 1. In ferricoronadite, double chains of edge-sharing (Mn, Fe, Ti)-centered octahedra are connected

  11. Systematic study of doping dependence on linear magnetoresistance in p-PbTe

    SciTech Connect

    Schneider, J. M.; Chitta, V. A.; Oliveira, N. F.; Peres, M. L. Castro, S. de; Soares, D. A. W.; Wiedmann, S.; Zeitler, U.; Abramof, E.; Rappl, P. H. O.; Mengui, U. A.

    2014-10-20

    We report on a large linear magnetoresistance effect observed in doped p-PbTe films. While undoped p-PbTe reveals a sublinear magnetoresistance, p-PbTe films doped with BaF{sub 2} exhibit a transition to a nearly perfect linear magnetoresistance behaviour that is persistent up to 30 T. The linear magnetoresistance slope ΔR/ΔB is to a good approximation, independent of temperature. This is in agreement with the theory of Quantum Linear Magnetoresistance. We also performed magnetoresistance simulations using a classical model of linear magnetoresistance. We found that this model fails to explain the experimental data. A systematic study of the doping dependence reveals that the linear magnetoresistance response has a maximum for small BaF{sub 2} doping levels and diminishes rapidly for increasing doping levels. Exploiting the huge impact of doping on the linear magnetoresistance signal could lead to new classes of devices with giant magnetoresistance behavior.

  12. Behavior of BaBr2, BaI2, and BaCl2 at high pressure as analogs to SiO2.

    NASA Astrophysics Data System (ADS)

    Smart, T. J.; Stackhouse, S.; Diamond, M. R.; Godwal, B. K.; Jeanloz, R.

    2015-12-01

    Motivated by the expectation that giant and supergiant planets likely contain rocky components in their cores, we study analogs of the archetypal rock constituent, SiO2. The crystal structures of SiO2 under ultra-high pressures, greater than feasible experimental conditions, are believed to be documented by the high pressure structural sequence of AX2 compounds. Experimental and theoretical work agree on a high pressure transition to the cotunnite (orthorhombic) phase, with first-principles theory predicting that SiO2 transforms to the cotunnite structure at 750 GPa. However, the existence of a postcotunnite (monoclinic) phase as the final high pressure polymorph, suggested by X-ray diffraction (XRD) experiments on ambient pressure cotunnite-structured AX2 compounds (e.g. PbCl2, SnCl2), has been challenged by density-functional theory (DFT) computations. This disagreement could perhaps be due to sensitivity in diamond-anvil cell (DAC) experiments to pressure gradients; conversely, it could perhaps arise from limitations of DFT. This study further explores both the experimental and theoretical sides of this debate, with an aim to resolve this discrepancy. We present synchrotron XRD data on the AX2 compounds BaCl2, BaBr2, and BaI2, compressed up to 70 GPa at room temperature in a DAC. Here we compare our experimentally observed crystallography and equations of state with results from our DFT simulations.

  13. Raman sideband cooling of 138 Ba+ on a Zeeman transition

    NASA Astrophysics Data System (ADS)

    Seck, Christopher; Kokish, Mark; Dietrich, Matthew; Odom, Brian

    2016-05-01

    Here, we report motional ground state preparation of a single 138 Ba+ ion using Raman sideband cooling with the two S1/2 Zeeman sublevels. Owing to the small Zeeman splitting, Raman sideband cooling of 138 Ba+ requires only two AOMs and the Doppler cooling lasers. Additionally, we demonstrate coherent operations using a second, far-off-resonant laser driving Raman π-pulses between the two Zeeman sublevels to characterize our mean motional occupation number, Raman sideband cooling frequency resonance, Raman sideband cooling rate, and ion trap motional heating rate. Motional ground state cooling and molecular internal state preparation, both realized in our group, are important elements for molecular quantum logic spectroscopy (mQLS). We are now working towards motional ground state preparation of a 138 Ba+ and AlH+ ion pair for mQLS. Supported by the AFOSR and the NSF.

  14. Comparison of metals extractability from Al/Fe-based drinking water treatment residuals.

    PubMed

    Wang, Changhui; Bai, Leilei; Pei, Yuansheng; Wendling, Laura A

    2014-12-01

    Recycling of drinking water treatment residuals (WTRs) as environment amendments has attracted substantial interest due to their productive reuse concomitant with waste minimization. In the present study, the extractability of metals within six Al/Fe-hydroxide-comprised WTRs collected throughout China was investigated using fractionation, in vitro digestion and the toxicity characteristic leaching procedure (TCLP). The results suggested that the major components and structure of the WTRs investigated were similar. The WTRs were enriched in Al, Fe, Ca, and Mg, also contained varying quantities of As, Ba, Be, Cd, Co, Cr, Cu, K, Mn, Mo, Na, Ni, Pb, Sr, V, and Zn, but Ag, Hg, Sb, and Se were not detected. Most of the metals within the WTRs were largely non-extractable using the European Community Bureau of Reference (BCR) procedure, but many metals exhibited high bioaccessibility based on in vitro digestion. However, the WTRs could be classified as non-hazardous according to the TCLP assessment method used by the US Environmental Protection Agency (USEPA). Further analysis showed the communication factor, which is calculated as the ratio of total extractable metal by BCR procedure to the total metal, for most metals in the six WTRs, was similar, whereas the factor for Ba, Mn, Sr, and Zn varied substantially. Moreover, metals in the WTRs investigated had different risk assessment code. In summary, recycling of WTRs is subject to regulation based on assessment of risk due to metals prior to practical application. PMID:25023656

  15. Phonon dispersion relation in PbTiO3

    NASA Astrophysics Data System (ADS)

    Tomeno, Izumi; Fernandez-Baca, Jaime; Marty, Karol; Oka, Kunihiko; Tsunoda, Yorihiko

    2013-03-01

    The phonon dispersion relations for cubic PbTiO3 (Tc = 763 K) have been determined along the high symmetry directions at T = 793 K using inelastic neutron scattering. A set of the TO branches drops significantly toward the zone center. This is quite different from the soft mode anomaly in the Pb-based relaxors, named as the waterfall phenomenon. The zone-center TO mode energy softens with decreasing temperature from 1173 to 793 K. The TA branch along [ ξ , ξ , ξ ] shows significant softening around ξ = 0.25 and 0.5. These two anomalies persist up to 1173 K and are weakly temperature dependent. Moreover, the TA branches along [1,0,0] and [1,1,0] soften in the entire q range as the temperature approaches Tc. Although the phonon softening occurs simultaneously, the softening of the zone center TO mode plays an important role in the single phase transition. The phonon dispersion relations for cubic and tetragonal PbTiO3 are discussed in connection with BaTiO3, KTaO3, Pb(Zn1/3Nb2/3)O3, and Pb(Mg1/3Nb2/3)O3. U.S.-Japan cooperative program on neutron scattering

  16. Structure-Curie temperature relationships in BaTiO3-based ferroelectric perovskites: Anomalous behavior of (Ba ,Cd )TiO3 from DFT, statistical inference, and experiments

    NASA Astrophysics Data System (ADS)

    Balachandran, Prasanna V.; Xue, Dezhen; Lookman, Turab

    2016-04-01

    One of the key impediments to the development of BaTiO3-based materials as candidates to replace toxic-Pb-based solid solutions is their relatively low ferroelectric Curie temperature (TC). Among many potential routes that are available to modify TC, ionic substitutions at the Ba and Ti sites remain the most common approach. Here, we perform density functional theory (DFT) calculations on a series of A TiO3 and Ba B O3 perovskites, where A =Ba , Ca, Sr, Pb, Cd, Sn, and Mg and B =Ti , Zr, Hf, and Sn. Our objective is to study the relative role of A and B cations in impacting the TC of the tetragonal (P 4 m m ) and rhombohedral (R 3 m ) ferroelectric phases in BaTiO3-based solid solutions, respectively. Using symmetry-mode analysis, we obtain a quantitative description of the relative contributions of various divalent (A ) and tetravalent (B ) cations to the ferroelectric distortions. Our results show that Ca, Pb, Cd, Sn, and Mg have large mode amplitudes for ferroelectric distortion in the tetragonal phase relative to Ba, whereas Sr suppresses the distortions. On the other hand, Zr, Hf, and Sn tetravalent cations severely suppress the ferroelectric distortion in the rhombohedral phase relative to Ti. In addition to symmetry modes, our calculated unit-cell volume also agrees with the experimental trends. We subsequently utilize the symmetry modes and unit-cell volumes as features within a machine learning approach to learn TC via an inference model and uncover trends that provide insights into the design of new high-TCBaTiO3 -based ferroelectrics. The inference model predicts CdTiO3-BaTiO3 solid solutions to have a higher TC and, therefore, we experimentally synthesized these solid solutions and measured their TC. Although the calculated mode strength for CdTiO3 in the tetragonal phase is even larger than that for PbTiO3, the TC of CdTiO3-BaTiO3 solid solutions in the tetragonal phase does not show any appreciable enhancement. Thus, CdTiO3-BaTiO3 does not follow the

  17. A Structural Molar Volume Model for Oxide Melts Part II: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Ternary and Multicomponent Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2016-04-01

    A structural molar volume model based on the silicate tetrahedral Q-species has been developed to accurately predict the molar volume of molten oxides. In this study, the molar volumes of ternary and multicomponent melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system are reviewed and compared with the predicted molar volumes from the newly developed structural model. The model can accurately predict the molar volumes using binary model parameters without any ternary or multicomponent parameters. The nonlinear behavior in the molar volume of silicate melts is well predicted by the present model.

  18. Raman and Photoluminescence Spectroscopy of Nano-crystalline PbTiO3 Sensor Materials with Different Doping Ions

    NASA Technical Reports Server (NTRS)

    Katiyar, R. S.; Jinfang, Meng

    1998-01-01

    Raman spectra & photoluminescence studies in PbTiO3, have been carried out, as a function of particle size, temperature, pressure and dopants. There appears respectively a distinct temperature-induced soft mode phase transition in each sample whose Curie temperature can be determined from the mean-field theory. The detailed Curie temperature shift in the modified PbTiO3 ceramics by Ba, Sr, La and Zr, has been investigated as a function of particle size. Pressure-induced phase transitions display an obvious diffuse behavior. Room temperature photoluminescence for nanocrystalline Ba(1-x)Pb(x)TiO3 have been observed. These studies favor preparations of high efficiency PbTiO3 sensors.

  19. Preparation of hybrid Josephson junctions on Co-doped Ba-122 single crystals

    NASA Astrophysics Data System (ADS)

    Reifert, D.; Hasan, N.; Döring, S.; Schmidt, S.; Monecke, M.; Feltz, M.; Schmidl, F.; Tympel, V.; Wisniewski, W.; Mönch, I.; Wolf, T.; Seidel, P.

    2014-08-01

    In this paper we present a method for processing a hybrid Josephson junction on Co-doped BaF{{e}_{2}}A{{s}_{2}} (Ba-122) single crystals with a thin film Pb-counter electrode and a barrier layer of Ti{{O}_{x}}. This includes the leveling and polishing of the crystals and structuring them with thin film techniques such as photo lithography, sputtering and ion beam etching. The junctions show hysteretical resistively and capacitively shunted junction-like I-V characteristics with an {{I}_{c}}{{R}_{n}}-product of about 800 \\mu V.

  20. Large Piezoelectric Effect in Pb-Free Ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Wenfeng; Ren, Xiaobing

    2009-12-01

    We report a non-Pb piezoelectric ceramic system Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 which shows a surprisingly high piezoelectric coefficient of d33˜620pC/N at optimal composition. Its phase diagram shows a morphortropic phase boundary (MPB) starting from a tricritical triple point of a cubic paraelectric phase (C), ferroelectric rhombohedral (R), and tetragonal (T) phases. The high piezoelectricity of the MPB compositions stems from the composition proximity of the MPB to the tricritical triple point, which leads to a nearly vanishing polarization anisotropy and thus facilitates polarization rotation between ⟨001⟩T and ⟨111⟩R states. We predict that the single-crystal form of the MPB composition of the present system may reach a giant d33=1500-2000pC/N. Our work may provide a new recipe for designing highly piezoelectric materials (both Pb-free and Pb-containing) by searching MPBs starting from a TCP.

  1. Band-overlap metallization of BaS, BaSe and BaTe

    NASA Technical Reports Server (NTRS)

    Carlsson, A. E.; Wilkins, J. W.

    1983-01-01

    The insulator-metal transition volumes for BaS, BaSe, and BaTe are calculated for the first time, using the self-consistent augmented spherical wave technique. The metallized transition volumes are smaller than those corresponding to the NaCl yields CsCl structural transitions, but, 10 to 15% larger than those obtained by the Herzfeld dielectric theory. The calculated equilibrium energy gaps in the NaCl structure underestimate the measured ones by 50 to 60%.

  2. Decay out of SD Band in ^192Pb

    NASA Astrophysics Data System (ADS)

    McNabb, D. P.; Cizewski, J. A.; Ding, K. Y.; Fotiades, N.; Archer, D. E.; Becker, J. A.; Bernstein, L. A.; Hauschild, K.; Younes, W.; Clark, R. M.; Fallon, P.; Lee, I. Y.; Macchiavelli, A. O.; MacLeod, R. W.

    1997-04-01

    Gamma-ray transitions linking the yrast SD bands to the known (ND) levels have been found in ^194Pb(M. J. Brinkman, et al., Phys. Rev. C53), R1461 (1996), A. Lopez-Martens, et al., Phys. Lett. B380, 18 (1996) and K. Hauschild, et al., submitted to Phys. Rev. C (1996). and ^194Hg.(T. L. Khoo, et al., Phys. Rev. Lett. 76), 1583 (1996). The spin, parity and excitation energy of these SD bands were established. Linking transitions are understood as arising from ND states nearby in excitation energy which are admixed with the SD states.(E. Vigezzi, et al., Phys. Lett. B249), 163 (1990). We anticipate a smaller phase space for quasicontinuous decay of the SD band in ^192Pb because it is predicted to lie lower in excitation than the SD band in ^194Pb.footnote S. J. Krieger, et al. Nucl. Phys. A542, 43 (1992). To search for linking transitions in ^192Pb we used the Gammasphere array at LBNL and the ^24Mg(^173Yb,5n) reaction at 134 MeV. Candidates for linking transitions and general features of the decay will be discussed.

  3. In-situ Pb Isotope Ratio Measurements in Glasses and Melt Inclusions by LA-SF-ICPMS

    NASA Astrophysics Data System (ADS)

    Jochum, K. P.; Stoll, B.; Herwig, K.; Amini, M.; Abouchami, W.

    2004-12-01

    We have developed a technique to determine Pb isotopes in glass fragments and melt inclusions by laser ablation (LA) - sector field (SF) - ICPMS. The measurements were done with a New Wave UP-213 laser system and an ELEMENT2 ICP mass spectrometer using the electrical scan mode. The geological MPI-DING reference glasses (Jochum et al., 2000), for which TIMS and MC-ICPMS Pb triple spike (TS) data are now available, were used to test our technique. Our LA-SF-ICPMS data for 208Pb/206Pb and 207Pb/206Pb agree with the high-precision Pb data within 0.2 %. Polished 150 μ m thick sections were used for the analysis of melt inclusions from samples of the Hawaii Scientific Drilling Project (HSDP). Inclusions were ablated for 10 - 30 s in single spots (40 - 80 μ m diameter). Each analysis consisted of 100 to 300 measurements of 206Pb, 207Pb and 208Pb. Typical in-run precision (1 RSE) ranged from 0.2 - 0.4 %. These values are similar to those obtained by SIMS (Saal et al., 1998). The 208Pb/206Pb (1.91 - 2.13) and 207Pb/206Pb (0.778 - 0.877) in the melt inclusions show large and systematic variations. The range of variability in Pb isotope ratios is similar to that reported in melt inclusions from Mangaia and Tahaa basalts (Saal et al., 1998). The Pb isotope arrays (in 208Pb/206Pb vs 207Pb/206Pb) can be explained by mixing of at least two end members. Groundmass values are uniform and similar to the whole rock data and plot within the melt inclusion fields. LA-SF-ICPMS has also been applied for determining Pb isotope ratios and trace element concentrations in carefully handpicked 200 - 500 μ m large glass fragments from 19 samples of the submarine section of HSDP-2. Precision of the Pb isotope data was about 0.2 - 0.3 %. Most LA-SF-ICPMS data agree with high-precision TIMS data using aliquots of about 50 mg. Both data sets confirm the temporal Pb isotope variations found in the HSDP-2 core based on the whole-rock TS Pb isotope data (Eisele et al., 2003).

  4. Effect of cation substitution at the B site on the oxygen semi-permeation flux in La0.5Ba0.5Fe0.7B0.3O3-δ dense perovskite membranes with B = Al, Co, Cu, Mg, Mn, Ni, Sn, Ti and Zn (part II)

    NASA Astrophysics Data System (ADS)

    Reichmann, M.; Geffroy, P.-M.; Fouletier, J.; Richet, N.; Del Gallo, P.; Chartier, T.

    2015-03-01

    The aim of this paper is to provide insight into the effect of cation substitution at the B site on the oxygen semi-permeation performances. Particular attention is given here to identify the impact of cation substitution at the B site on oxygen diffusion and oxygen surface-exchange kinetics in the La0.5Ba0.5Fe0.7B0.3O3-δ perovskite membrane series with B = Al, Co, Cu, Mg, Mn, Ni, Sn, Ti and Zn. This study clearly shows that the prediction of the oxygen semi-permeation performances of membrane materials from the nature of cation at the A or B sites in perovskite structure is quite complex. The cation substitution at the B-site has a low impact on the nature of rate-determining step and a significant impact on oxygen semi-permeation performances, contrary to the cation substitution at A-site. Unfortunately, it is not possible to establish a relevant trend about the effect of the nature of cation in the A or B sites in perovskite structure on oxygen diffusion and the oxygen surface-exchange kinetics.

  5. A green-yellow emitting oxyfluoride solid solution phosphor Sr[subscript 2]Ba(AlO[subscript 4]F)[subscript 1;#8722;x](SiO[subscript 5])x:Ce[superscript 3+] for thermally stable, high color rendition solid state white lighting

    SciTech Connect

    Denault, Kristin A.; George, Nathan C.; Paden, Sara R.; Brinkley, Stuart; Mikhailovsky, Alexander A.; Neuefeind, Jörg; DenBaars, Steven P.; Seshadri, Ram

    2012-10-23

    A near-UV excited, oxyfluoride phosphor solid solution Sr{sub 1.975}Ce{sub 0.025}Ba(AlO{sub 4}F){sub 1-x}(SiO{sub 5}){sub x} has been developed for solid state white lighting applications. An examination of the host lattice, and the local structure around the Ce{sup 3+} activator ions through a combination of density functional theory, synchrotron X-ray and neutron powder diffraction and total scattering, and electron paramagnetic resonance, points to how chemical substitutions play a crucial role in tuning the optical properties of the phosphor. The maximum emission wavelength can be tuned from green ({lambda}{sub em} = 523 nm) to yellow ({lambda}{sub em} = 552 nm) by tuning the composition, x. Photoluminescent quantum yield is determined to be 70 {+-} 5% for some of the examples in the series. Excellent thermal properties were found for the x = 0.5 sample, with the photoluminescence intensity at 160 C only decreased to 82% of its room temperature value. Phosphor-converted LED devices fabricated using an InGaN LED ({lambda}{sub max} = 400 nm) exhibit high color rendering white light with R{sub a} = 70 and a correlated color temperature near 7000 K. The value of R{sub a} could be raised to 90 by the addition of a red component, and the correlated color temperature lowered to near 4000 K.

  6. Effect of Cr{sub 2}O{sub 3} on solubility and thermo-physical properties of BaO-CaO-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-SiO{sub 2} g

    SciTech Connect

    Goswami, M.; Kumar, Rakesh; Patil, A. S.; Sahu, A. K.; Kothiyal, G. P.

    2012-06-05

    BaO-CaO-Al{sub 2}O{sub 3}-(10-x)B{sub 2}O{sub 3}-xCr{sub 2}O{sub 3} SiO{sub 2} (BCABS), where 1.0 {<=}x {<=} 3.5, (mol%) glasses were prepared by melt-quench technique. Glass samples were characterized for density, microhardness, thermal expansion coefficient and glass transition temperature. Scanning electron microscopy was used to see the homogeneity/solubility of Cr2O3 in this glass system. UV-VIS absorption measurements were carried out to see the Cr speciation in the glass samples. Density values were found to vary from 3.97 to 3.92 g/cc and microhardness values varied from 283 to 503 kg/mm{sup 2}. Glass transition temperature increased from 635 to 671 deg. C while TEC value found to varies from 8.3 to 11.1x10{sup -6}/ deg. C(30-300) with Cr{sub 2}O{sub 3} content. SEM study revealed phase separation in these glasses. From absorption studies we infer the presence of small amount of Cr (VI) along with Cr(III) oxidation state.

  7. Common Pb isotopic compositions of the Lima, Arequipa and Toquepala segments in the Coastal batholith, Peru: Implications for magmagenesis

    NASA Astrophysics Data System (ADS)

    Mukasa, Samuel B.

    1986-05-01

    . Contamination of plutons in the Arequipa and Toquepala segments by unradiogenic Pb from the Precambrian basement, and lack of it in the Lima segment, supports crustal models by Couch et al. (1981) and Jones (1981) which show a thick Precambrian basement layer throughout southern Peru, and an extremely thin layer beneath the Lima segment.

  8. Seven centuries of atmospheric Pb deposition recorded in a floating mire from Central Italy

    NASA Astrophysics Data System (ADS)

    Zaccone, Claudio; Lobianco, Daniela; D'Orazio, Valeria; Miano, Teodoro M.; Shotyk, William

    2016-04-01

    -1650. Lead concentrations were normalized to those of Th, a conservative, lithophile element often used as an indicator of the abundance of mineral particles. Crustal enrichment factor values, calculated by normalizing the Pb/Th ratio in peat samples to the corresponding ratio for the Upper Continental Crust, clearly show that almost all the Pb reaching this floating isle in the last seven centuries is of anthropogenic origin. In particular, while the big peak around 100-115 cm of depth is associated with that of Sb, the band around 300 cm characterized also the trend of several other major and trace elements (i.e., Ag, Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sr, Th, Tl, U, V, Y, Zn) with the exception of Sb. Although γ-spectrometry measurement (210Pb, 137Cs and 241Am) for the first 100 cm of this core is still on-going, at the best of our knowledge, this work may provide the first Pb chronology obtained from a (4 m) deep floating mire. Furthermore, it is to note that a) this floating mire could consist of the southernmost European population of Sphagnum, and b) this core shows a great potential to be used as archive of environmental changes, especially considering its high resolution (1 cm = 0.5 yr in the first 100 cm, and 2-2.5 yrs in the remaining 300 cm of depth). The Authors thank the Municipality of Posta Fibreno, Managing Authority of the Regional Natural Reserve of Lake Posta Fibreno, for allowing peat cores sampling.

  9. Further considerations of the Ce/Yb vs. Ba/Ce plot in volcanology and tectonics

    USGS Publications Warehouse

    Doe, B.R.

    2002-01-01

    and in Ba/Ce (>8) relative to the OIV field. There are some exceptions, also, for IAV that plot outside the IAV field. The values of Ce/Yb in Mariana Islands samples, for example, are exceptionally low for the IAV (Ce/Yb <5 with many samples <2). Examples of two cross-chain Kasuga Islands, however, have average, values of Ce/Yb considerably greater than for any other Mariana Islands data, and individual samples extend from within the IAV field into the OIV field, which may indicate a mixture of IAV and OIV sources (rather than involvement of a hotspot, these island volcanics have been interpreted as magma of OIV entrapped "plums" in an IAV "pudding" by Stern et al., 1993). Not Surprisingly, continental are volcanics, (CAV) are generally similar to IAV, but with somewhat greater dispersion in Ce/Yb, perhaps representing a larger contribution of continental materials to the volcanics. Continental rift volcanics (CRV) are complex. The Antarctic rift data fall in the OIV field, and clearly define a hotspot origin for the rift with little contamination in the continental lithosphere, but most CRV data fall in the IAV field (Rio Grande rift tholeiites, Yellowstone Plateau basalts, Columbia River basalts. East African rift hasalts). The Yellowstone basalt samples judged to be least crustally contaminated from other considerations (e.g., through Pb and Sr isotopes) approach closest to the OIV or hotspot field in the Ce/Yb vs. Ba/Ce plot, compatible with a hotspot origin with variable continental lithosphere interactions. The data from the Rio Grande rift have no such trend in Ce/Yb vs. Ba/Ce. Other trace element and isotopic data are suggestive of a different kind of origin, perhaps melting in the continental lithosphere from pressure release or other causes as suggested in the literature. Carbonatites, kimberlites, and ultrap

  10. Structural phase stability and bonding behavior of BAlH5(B=Mg,Ba) from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Klaveness, A.; Vajeeston, P.; Ravindran, P.; Fjellvåg, H.; Kjekshus, A.

    2006-03-01

    The ground-state structures of MgAlH5 and BaAlH5 have been subjected to full structural optimization considering 50 different potential atomic arrangements as inputs for accurate density-functional total-energy calculations. The experimentally known crystal structure and structural parameters for BaAlH5 are reproduced, and the crystal structure of MgAlH5 is predicted. At 0K and ambient pressures MgAlH5 and BaAlH5 crystallize in monoclinic ( CaFeF5 type, P21/c ) and orthorhombic (prototype, Pna21 ) structures, respectively. In addition to the ground-state MgAlH5 phase (here designated α-MgAlH5 ), it is also predicted a metastable modification (termed β-MgAlH5 , CaCrF5 type, Cc ). The structures comprise isolated, highly distorted AlH6 octahedra, which form one-dimensional chains along the [001] direction. In α - and β-MgAlH5 these chains are fairly linear, while BaAlH5 exhibits distinct zigzag chains. α-MgAlH5 and BaAlH5 are nonmetallic phases with estimated band gaps of 2.48 and 2.73eV , respectively. Analyses of the density of states, charge density, Mulliken population, and Born effective charge indicate that the interaction between Al and H is polar covalent blended with an ionic woof, while Ba and Mg can be considered as virtually divalent ions.

  11. Genesis of the Bangbule Pb-Zn-Cu polymetallic deposit in Tibet, western China: Evidence from zircon U-Pb geochronology and S-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Kan, Tian; Zheng, Youye; Gao, Shunbao

    2016-04-01

    The Banbule Pb-Zn-Cu skarn deposit is located in the Longger-Gongbujiangda volcanic magma arc in the Gangdese-Nyainqentanglha Plate. It is the only lead-zinc polymetallic deposit discovered in the westernmost Nyainqentanglha metallogenic belt. The measured and indicated resources include 0.9 Mt of Pb+Zn (4.77% Pb and 4.74% Zn, respectively), 6499 t of Cu, and 178 t of Ag (18.75g/t Ag). The orebodies mainly occur as lenses, veins and irregular shapes in the contact zone between the quartz-porphyry and limestone of the Upper Permian Xiala Formation, or in the boundaries between limestone and sandstone. Pb-Zn-Cu mineralization in the Banbule deposit is closely associated with skarns. The ore minerals are dominated by galena, sphalerite, chalcopyrite, bornite, and magnetite, with subordinate pyrite, malachite, and azurite. The gangue minerals are mainly garnet, actinolite, diopside, quartz, and calcite. The ore-related quartz-porphyry displays LA-ICP-MS zircon U-Pb age of 77.31±0.74 Ma. The δ34S values of sulfides define a narrow range of -0.8 to 4.7‰ indicating a magmatic source for the ore-forming materials. Lead isotopic systematics yield 206Pb/204Pb of 18.698 to 18.752, 207Pb/204Pb of 15.696 to 15.760, and 208Pb/204Pb of 39.097 to 39.320. The data points are constrained around the growth curves of upper crust and orogenic belt according to the tectonic discrimination diagrams. The calculated Δβ ‑ Δγ values plot within the magmatic field according to the discrimination diagram of Zhu et al. (1995). The S-Pb isotopic data suggest that Bangbule is a typical skarn deposit, and the Pb-Zn-Cu mineralization is genetically related to the quartz-porphyry in the mining district. The discovery of the Bangbule deposit indicates that there is metallogenic potential in the westernmost Nyainqentanglha belt, which is of great importance for the exploration work in this area.

  12. Pb isotope composition in lichens and aerosols from eastern Sicily: Insights into the regional impact of volcanoes on the environment

    SciTech Connect

    Monna, F. ); Aiuppa, A.; Varrica, D. ); Dongarra, G. CNR, Palermo . Istituto Geochimica dei Fluidi)

    1999-08-01

    A total of 25 lichen thalli of Parmelia conspersa (Ehrh), collected at Vulcano island and at Mt. Etna, during a one-year biogeochemical survey, were analyzed for Pb, br, Al, Sc,[sup 206]Pb/[sup 207]Pb, and [sup 208]Pb/[sup 206]Pb ratios. Lead isotope ratios were also measured on aerosol samples from urban areas and industrial sites of Sicily. The observed [sup 206]Pb/[sup 207]Pb range for urban and industrial aerosols matches the anthropogenic signature. Lichens instead, are closer to the compositional field of [sup 206]Pb rich geogenic sources. This natural input is more evident at Vulcano island than at Mt. Etna, where the anthropogenic activities are considerably more effective. On the basis of lead isotope data, Pb/Br ratios and calculated lead enrichment factors, a natural lead pollution from volcanoes is suggested. Volcanic lead contribution ranges from 10 to 30% at Mt. Etna to 10--80% at Vulcano island.

  13. Comment on “Displacement along the Karakoram fault, NW Himalaya, estimated from LA-ICP-MS U-Pb dating of offset geologic markers” published by Shifeng Wang et al. in EPSL, 2012

    NASA Astrophysics Data System (ADS)

    Leloup, P. H.; Weinberg, R. F.; Mukherjee, B. K.; Tapponnier, P.; Lacassin, R.; Boutonnet, E.; Chevalier, M.-L.; Valli, F.; Li, H.; Arnaud, N.; Paquette, J.-L.

    2013-02-01

    Field evidence for syn-deformation migmatization and crystallization along the Karakorum fault contradicts the study of Wang et al. (2012). The ages of such magmatic rocks provide minimum ages for the onset of deformation at ∼23 Ma in North Ayilari and ∼19 Ma in Tangtse. The onset of deformation at 12 Ma in the Ayilari range inferred by Wang et al. (2012) from a muscovite Ar/Ar age is a cooling age, thus only a minimum age. The ∼60 Ma granodiorite bodies, the ophiolitic rocks and the south Kailash thrust that are correlated across the fault to provide a 52±2 km finite offset do not define reliable piercing points. Such observations as well as our previous work concur to show that the Karakorum fault initiated in the Oligo-Miocene, and has a long-term dextral slip-rate between 7.5 and 13 mm/yr, approximately twice that proposed by Wang et al. (2012).

  14. Unraveling the evolution of chondrite parent asteroids by precise U-Pb dating and thermal modeling

    NASA Astrophysics Data System (ADS)

    Amelin, Yuri; Ghosh, Amitabha; Rotenberg, Ethan

    2005-01-01

    U-Th-Pb isotopic data are reported for mineral fractions, individual chondrules and fractions of chondrule fragments from the equilibrated ordinary chondrite Richardton (H5). Chondrules and milligram-sized fractions of pyroxene-rich chondrule fragments contain highly radiogenic Pb and concordant or nearly concordant U-Th-Pb isotopic systems, and are suitable for precise Pb-Pb age determinations. Olivine and sulfide have low U concentrations and contain less radiogenic Pb. The ages of individual chondrules, pyroxene-rich and phosphate fractions are determined using U-Pb and Pb-Pb isochron and model date calculations. The Pb-Pb isochron date of 4562.7 ± 1.7 Ma of the Richardton chondrules and chondrule fragments is resolved from the Pb-Pb isochron date of 4550.7 ± 2.6 Ma obtained from multiple phosphate fractions. Possible biases of the isochron dates due to single-stage approximation of multi-stage evolution, contamination with modern common Pb, and disturbance to the system by reheating, are examined and are found to be insignificant. The chondrule and phosphate dates are interpreted as the timing of cessation of Pb diffusion during cooling following metamorphism in chondrite parent bodies. The difference in estimated closure temperatures, ˜950-1150 K for pyroxenes, and 700-800 K for phosphates (temperature estimates are based on published diffusion rates for Pb in pyroxenes and apatite), allows evaluation of the average cooling rate at 26 ± 13 K/million years for the Richardton parent body over the period of 4563-4551 my. Thermal modeling of the H-chondrite parent body (which is assumed to be asteroid 6 Hebe, heated by decay of 26Al) suggests a scenario in which accretion initiated at 1.7 m.y. after formation of calcium-aluminum-rich inclusions and continued for 3.5 m.y.

  15. Processing-microstructure-property relationships of Al[sub 2]O[sub 3]-fiber-reinforced high-temperature superconducting (Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub y] composite

    SciTech Connect

    Wong, M.S.; Miyase, A.; Yuan, Y.S.; Wang, S.S. )

    1994-11-01

    Monolithic high-temperature superconducting (HTS) materials are recognized to have inherently weak mechanical properties, such as low strength and fracture toughness. These drawbacks usually can be improved by introducing strong continuous fibers into the brittle ceramic materials. In this study, a systematic investigation on the relationships among processing variables, microstructure, and superconducting and mechanical properties of a continuous Al[sub 2]O[sub 3]-fiber-reinforced HTS (Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub y] composite is presented. The Al[sub 2]O[sub 3]/BPSCCO composite is fabricated initially by a slurry method, followed by binder extraction up to 800 C in an 8% O[sub 2] atmosphere, and finally hot pressed at 800 C in an 8% O[sub 2] atmosphere, and finally hot pressed at 800 C in air. Phases present in the HTS composite are identified by XRD, and the microstructure and microchemistry studied by SEM and EPMA. Of particular interest is the fiber/matrix interface; the interfacial reaction is studied for composite specimens which have undergone long heat treatment. The HTS composite is observed to have a good combination of superconducting properties and mechanical properties.

  16. PbCl2-induced hyperpolarization of rat thymocytes: involvement of charybdotoxin-sensitive K+ channels.

    PubMed

    Nishizaki, Yasutaka; Oyama, Yasuo; Sakai, Yoshiro; Hirama, Seigo; Tomita, Kazuyoshi; Nakao, Hiromi; Umebayashi, Chisato; Ishida, Shiro; Okano, Yoshiro; Carpenter, David O

    2003-10-01

    The effect of PbCl2 on membrane potential and intracellular divalent metal cation concentrations of rat thymocytes was examined by flow cytometry. PbCl2 at concentrations of 0.3 microM or higher (up to 10 microM) produced persistent, dose-dependent hyperpolarization (decrease in the intensity of di-BA-C4 fluorescence). Removal of external Ca2+ did not significantly affect the PbCl2-induced hyperpolarization. Charybdotoxin, a specific antagonist of Ca(2+)-dependent K+ conductance, greatly attenuated the PbCl2-induced hyperpolarization. PbCl2 increased the intensity of fluo-3 fluorescence under both normal Ca2+ and nominally Ca(2+)-free conditions. These results suggest that Pb2+ enters thymocytes, causing an increase in fluo-3 fluorescence, and activates Ca(2+)-dependent K+ channels, resulting in hyperpolarization. The persistent activation of K+ channels by Pb2+, leading to persistent hyperpolarization, may be one mechanism whereby Pb2+ alters immune function, as membrane potential changes influence physiological functions of lymphocytes. PMID:14502585

  17. Luminescence in Li2BaP2O7.

    PubMed

    Hatwar, L R; Wankhede, S P; Moharil, S V; Muthal, P L; Dhopte, S M

    2015-09-01

    The photo-, thermo- and optically stimulated luminescence in Li2BaP2O7 activated with Eu(2+) /Cu(+) are reported. Strong thermoluminescence, which is about two times greater than LiF-TLD 100 was observed in the Eu(2+) -activated sample. It also exhibited optically stimulated luminescence sensitivity of ~20% that of commercial Al2O3:C phosphor. PMID:25351563

  18. Dipole and Quadrupole transition strengths in Ba^+ from measurements of K-splittings in high-L Ba Rydberg levels

    NASA Astrophysics Data System (ADS)

    Woods, Shannon L.; Lundeen, Stephen R.; Sturrus, William G.; Snow, Erica L.

    2009-05-01

    Measurements of K-splittings in high-L Rydberg levels of Ba have been used to determine electric dipole (6s-6p) and quadrupole (6s-5d) transition strengths in Ba^+ [1]. In that report, good agreement with calculated values was found for the dipole strength but not for the quadrupole strength. Using the data pattern extended to higher L levels recently [2] and a more complete theoretical model, we find good agreement between the measured K-splittings and the most recent theoretical calculations of relevant transition strengths.[3] [1] E.S. Shuman and T.F. Gallagher, Phys. Rev. A 74, 022502 (2006) [2] E.L. Snow, et. al., Phys. Rev. 71, 022510 (2005) [3] E. Iskrenova-Tchoukova and M. S. Safronova, et. al. Phys. Rev. A 78, 012508 (2008)

  19. S-process Ba, Nd, and SM in presolar SiC from the Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Zinner, Ernst; Amari, Sachiko; Lewis, Roy S.

    1991-11-01

    Ion microprobe isotopic measurements of Ba, Nd, and Sm in the K-series SiC size separates on which noble gas measurements were made by Lewis et al. (1990) are reported. All elements show isotopic abundance patterns characteristic for the s-process. The Ba-134/Ba-136 ratios are distinct from solar, indicating that s-Ba in SiC is different from that in the solar system. Ba-138/Ba-136 ratios decrease with grain size; if interpreted as being due to different neutron exposures, this trend is opposite of that shown by the Kr-86/Kr-82 ratios. Although other isotropic ratios for Ba and those for Nd and Sm differ in detail from theoretical predictions, the disagreements probably being due to uncertainties in the n-capture cross sections and simplifications in the models, the general agreement of the data with models of s-process nucleosynthesis support an AGB star origin for the relatively fine-grain SiC under consideration. Ba-136 in SiC is up to 85 percent pure s-process.

  20. Unradiogenic Pb Anomalies in Historical Lavas of Piton de la Fournaise (Reunion Island)

    NASA Astrophysics Data System (ADS)

    Vlastelic, I.

    2008-12-01

    A detailed investigation (218 samples) of Pb isotope variations in the most recent (1975-2007), well- documented and densely sampled eruptions of Piton de la Fournaise has been undertaken (Vlastelic et al, in press). Lead isotopes exhibit smooth temporal fluctuations (18.87<206Pb/204Pb<18.94) on which superimpose rare (5), but pronounced unradiogenic spikes (206Pb/204Pb down to 17.63). In 208Pb/204Pb vs. 206Pb/204Pb space, normal and anomalous samples plot along a single linear array. In 207Pb/204Pb vs. 206Pb/204Pb space, normal samples define an array whose slope (0.16) is commonly observed in ocean island basalts, whereas anomalous samples define less steep arrays (slopes down to 0.04). It follows that some of the anomalous samples have unusually high 207Pb/204Pb for their 206Pb/204Pb. These latter are enriched in Pb by a factor three. The lack of reproducibility of isotopic analyses suggests that samples are heterogeneous at a sub-millimeter scale. The origin of the unradiogenic anomalies is enigmatic. Leaching experiments rule out anthropogenic contamination. Interaction of plume melts with a contaminant genetically unrelated to the Reunion plume is possible although not supported by trace-element and Sr-Nd isotope signatures indistinguishable from normal lavas. On the other hand, interaction with or entrainment of Pb-rich, most likely unradiogenic sulfides could affect specifically Pb isotope compositions. Inspection of the well-know eruptions history reveals that the isotopic anomalies coincide with transitions from basalts to oceanites (lavas rich in cumulative olivine). Olivine and sulfides, which are both denser than silicate melts, could be entrained with magma pulses, which give rise to high-flux oceanite eruptions. Some sulfides may originate from the oceanic crust. Others may originate from sulfide solidus depth (c.a. 160 km) where sulfides melts are expected to pond (Hart and Gaetani, 2006). These deep sulfides melts could be remnants of past melting

  1. Assessment of the Pb-Pb and U-Pb chronometry of the early solar system

    NASA Astrophysics Data System (ADS)

    Tera, Fouad; Carlson, Richard W.

    1999-06-01

    An evaluation of early solar system chronometry by the Pb-Pb and U-Pb methods is provided. Specifically, three consequential factors are examined: procedure of age calculation, extent of terrestrial Pb contamination, and initial Pb isotopic composition. On a Pb-Pb diagram, high temperature inclusions of the Allende meteorite are tightly organized into a well-defined line (inside a potentially dispersive mixing field), which is consistent with the inclusions containing initial Pb that is more primitive than that of Cañon Diablo troilite (PAT). Consequences of the possible existence of a pre-PAT Pb to the evolution history of the solar nebula are discussed. Phosphates from the ordinary chondrite St. Séverin appear to be contaminated by terrestrial Pb, a condition that renders age calculation based on subtraction of PAT inaccurate. The Pb-Pb mixing line of these phosphates indicates an age of 4.558 Ga. Interestingly, Angra dos Reis phosphate and pyroxene, as well as pyroxene of the other angrite Lewis Cliff 86010 fall precisely on the line defined by St. Séverin phosphates. Whole rocks of ordinary chondrites are pictorially and explicitly shown to be seriously contaminated with terrestrial Pb, thus their single-stage U-Pb ages may not be suitable markers of time. Because their true crystallization ages are often younger than the whole rocks, and because of the possibility of multistage evolution, phosphates of ordinary chondrites may yield single-stage ages older than their true crystallization ages. A hypothetical numerical demonstration is provided. On the basis of revised ages and new observations we provide an "updated" chronometry for the early solar system.

  2. CHARACTERIZATION OF PB2+ UPTAKE AND SEQUESTRATION IN PSEUDOMONAS AERUGINOSA CHL004

    EPA Science Inventory

    In laboratory studies, the soil isolate Pseudomonas aeruginosa CHL004 (Vesper et al 1996) has been found to concentrated Pb2+ in the cytoplasm by formation of particles that contain Pb2+ and phosphorus. Upon examination of the washed lyophilized cells grown in the presence of lea...

  3. Pb isotopes in sediments of Lake Constance, Central Europe constrain the heavy metal pathways and the pollution history of the catchment, the lake and the regional atmosphere

    SciTech Connect

    Kober, B.; Wessels, M.; Bollhoefer, A.; Mangini

    1999-05-01

    Pb isotope ratios and Pb concentrations of well-dated sediments of Lake Constance, Central Europe have been analyzed using thermal ion mass spectrometry. Sequential extraction studies indicated isotope homogeneity of the leachable Pb components within the investigated layers. Since the middle of the 19th century a significant anthropogenic Pb component appeared in the lake sediments, and rapidly approaches concentration levels similar to that of the geogenic Pb background (20 ppm) at the beginning of the 20th century. Anthropogenic Pb was predominantly transferred to the lake sediments via the atmosphere. Pb sources were coal combustion, industrial ore processing and leaded gasoline. The flux of a fluvial Pb component to the lake sediments, additive to atmospheric Pb deposition, peaked in about 1960. This flux is attributed to (re)mobilization of Pb from polluted parts of the lake catchment, and indicates the change of catchment soils from a pollution sink to a heavy metal source. The strong reduction of anthropogenic Pb in the uppermost lake sediments since the 1960s has been caused by advances of environmental protection. The lake sediments record the changing fluxes and the isotope composition of the deposited aeolian Pb pollution. During the 20th century aeolian Pb fluxes to the lake sediments were in the range of 1--4 {micro}g/cm{sup 2}/a. During peak emission periods of gasoline Pb to the atmosphere (1960--1990) the aerosol Pb isotope composition was rather constant ({sup 206}Pb/{sup 207}Pb: 1.12--1.13) and probably a mixture of Canadian and Australian with Russian and Central European Pb types. Aeolian Pb isotope and Pb flux trends in the lake sediments as a whole agree well with the trends found in Alpine glaciers (Doering et al., 1997a,b) and in ombrotrophic peat bogs of Switzerland (Shotyk et al., 1996). However, different industrial Pb components were deposited in the archives of aeolian pollution during the early 20th century.

  4. Microstructure and Characteristics of Ba(Ti,Zr)O3 Ceramics with Addition of Glass Frit

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Huy

    2002-08-01

    Microstructure and characteristics of Ba(Ti,Zr)O3 ceramics are significantly influenced by the addition of 4PbO.B2O3. The melting temperature of 4PbO.B2O3 was approximately 500°C, and thus it provides a liquid phase during sintering. At low sintering temperatures, the grain growth of Ba(Ti,Zr)O3 ceramics is enhanced by capillary rearrangement and solution-reprecipitation from the liquid phase. At high sintering temperatures, exaggerated grain growth of Ba(Ti,Zr)O3 ceramics is restrained by the presence of a liquid phase. The spreading liquid can penetrate the solid-solid interfaces. Penetration leads to disintegration of the solid and the subsequent rearrangement of fragments. With increasing amounts of 4PbO.B2O3, the tetragonal c/a ratio and Curie point temperature increase, but the dielectric loss tangent is depressed. With a suitable amount of glass frit and temperature for sintering, the density is enhanced and the values of the planar coupling factor and the poled dielectric constant are improved.

  5. Trace element and Pb isotope composition of plagioclase from dome samples from the 2004-2005 eruption of Mount St. Helens, Washington: Chapter 35 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    USGS Publications Warehouse

    Kent, Adam J.R.; Rowe, Michael C.; Thornber, Carl R.; Pallister, John S.

    2008-01-01

    Plagioclase crystals from gabbronorite inclusions in three dacite samples have markedly different trace-element and Pbisotope compositions from those of plagioclase phenocrysts, despite having a similar range of anorthite contents. Inclusions show some systematic differences from each other but typically have higher Ti, Ba, LREE, and Pb and lower Sr and have lower 208Pb/206Pb and 207Pb/206Pb ratios than coexisting plagioclase phenocrysts. The compositions of plagioclase from inclusions cannot be related to phenocryst compositions by any reasonable petrologic model. From this we suggest that they are unlikely to represent magmatic cumulates or restite inclusions but instead are samples of mafic Tertiary basement from beneath the volcano.

  6. Noncentrosymmetric selenide Ba4Ga4GeSe12: Synthesis, structure, and optical properties

    NASA Astrophysics Data System (ADS)

    Yin, Wenlong; Iyer, Abishek K.; Li, Chao; Lin, Xinsong; Yao, Jiyong; Mar, Arthur

    2016-09-01

    The selenide Ba4Ga4GeSe12, synthesized by reaction of BaSe, Ga2Se3, and GeSe2 at 1173 K, adopts a noncentrosymmetric tetragonal structure (space group P 4 bar21 c , Z=2, a=13.5468(4) Å, c=6.4915(2) Å) consisting of a three-dimensional network built from two types of corner-sharing MSe4 tetrahedra, with Ba cations occupying the intervening voids. It is isostructural to Pb4Ga4GeS12, Pb4Ga4GeSe12, and Ba4Ga4SnSe12, but differs subtly in site ordering. Structural refinements and bond valence sum analysis suggest partial disorder manifested by mixing of 0.75 Ga and 0.25 Ge within one tetrahedral site, and occupation of exclusively Ga within the other tetrahedral site. The optical band gap of 2.18(2) eV, measured from the UV/VIS/NIR diffuse reflectance spectrum, agrees with a calculated gap of 2.35 eV between valence and conduction bands and is consistent with the orange-yellow color of the crystals. Nonlinear optical measurements on powder samples revealed a weak second harmonic generation signal using 2.09 μm as the fundamental laser wavelength.

  7. What causes Psi suppression in Pb + Pb Collisions?

    SciTech Connect

    Vogt, R.

    1998-01-07

    A reexamination of hadronic comover scattering indicates that this mechanism cannot explain the observed {psi} suppression in Pb+Pb interactions. The possibility of quark-gluon plasma formation is therefore considered. Implications for RHIC and LHC are also discussed. The agreement of the NA50 Pb+Pb data with naive comover models is reassessed. Previous work is reanalyzed and expanded to include feeding of the {psi}' and {chi}{sub c} states to the {psi}. The effect of color screening is also investigated. Only the {psi}/Drell-Yan (DY) ratios are discussed here.

  8. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    NASA Technical Reports Server (NTRS)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1990-01-01

    Since Bednorz and Muller discovered high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides have been synthesized. Here, researchers report the results of search for superconductivity in the compounds based on tin, which has a lone electron pair like Bi, Tl, Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3Ox, Sn1Ba1Ca1Cu3Ox, Sn1Ba1Mg1Cu3Ox, Sn1Sr1Ca1Cu3Ox, Sn1Sr1Mg1Cu3Ox, Sn1Ca1Mg1Cu3Ox. The initial components were oxides and carbonates of the appropriate elements. Standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3Ox showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3Ox was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperatures undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3Ox ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase two-valent cations Ba, Sr were partially substituted by univalent (K) and three-valent ones (Y).

  9. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    NASA Technical Reports Server (NTRS)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1991-01-01

    After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

  10. Trace elements and Pb isotopes in soils and sediments impacted by uranium mining.

    PubMed

    Cuvier, A; Pourcelot, L; Probst, A; Prunier, J; Le Roux, G

    2016-10-01

    The purpose of this study is to evaluate the contamination in As, Ba, Co, Cu, Mn, Ni, Sr, V, Zn and REE, in a high uranium activity (up to 21,000Bq∙kg(-1)) area, downstream of a former uranium mine. Different geochemical proxies like enrichment factor and fractions from a sequential extraction procedure are used to evaluate the level of contamination, the mobility and the availability of the potential contaminants. Pb isotope ratios are determined in the total samples and in the sequential leachates to identify the sources of the contaminants and to determine the mobility of radiogenic Pb in the context of uranium mining. In spite of the large uranium contamination measured in the soils and the sediments (EF≫40), trace element contamination is low to moderate (2Ba (5Pb enrichment is highlighted, the Pb isotopic signature of the contaminated soils is strongly radiogenic. Measurements performed on the sequential leachates reveal inputs of radiogenic Pb in the most mobile fractions of the contaminated soil. Inputs of low-mobile radiogenic Pb from mining activities may also contribute to the Pb signature recorded in the residual phase of the contaminated samples. We demonstrate that Pb isotopes are efficient tools to trace the origin and the mobility of the contaminants in environments affected by uranium mining. PMID:27220101

  11. Modeling the Lead(Pb) concentrations in corals in the Singapore Straits

    NASA Astrophysics Data System (ADS)

    Chen, M.; Lee, J.; Nurhati, I. S.; Switzer, A. D.; Boyle, E. A.

    2012-12-01

    The leaded gasoline has dominated the global Pb emission and has imposed serious health problems in the past 50 years. While countries in North America and Western Europe phased out leaded gasoline in 1970s and early 1980s, many fast developing Asian countries have been using it until recently. In order to monitor anthropogenic Pb variations in marine environments, the history of seawater Pb in the Singapore Strait -- one of the world's busiest shipping lanes has been reconstructed from a 50 year-long coral core (Lee et al., unpublished record). A 50-year-long coral Pb/Ca record from the Singapore Strait was measured using isotope dilution ICPMS (for Pb) and FAAS (for Ca). Here, we propose a statistical model to correlate lead measured in the Singapore coral (Pb/Ca) and the possible Pb sources in the region. The measurement reveals that the Pb in coral is only weakly correlated with Pb the gasoline emission from the neighboring countries (i.e. Singapore, Malaysia, and Batam Indonesia). Such weak correlation implies that either the gasoline may not be a dominating source to Singapore Strait or the transport process of the Pb (either atmospheric or oceanographic) in this region complicates the interpretation. In this case, we tested a number of statistical correlations to understand the possible roles of leaded gasoline emission, rainfall, sediment flux and the residence time of the Pb inferred by the Pb210 data. From our current tests, a relatively high correlation appeared between the Pb in coral and the local annual precipitation, with a lag time of 2 years. The 2 year lag is somewhat surprising and we expect to elaborate further by correlating the Pb in coral with the Pb isotope signatures in an attempt to identify possible sources.;

  12. [Uptake effect of Cd and Pb by rape under single Cd/Pb and Cd-Pb combined stress].

    PubMed

    Wu, Wen-Fei; Nan, Zhong-Ren; Wang, Sheng-Li; Zhao, Zhuan-Jun; Zhou, Ting

    2012-09-01

    This paper investigated the effects of single Cd/Pb and Cd-Pb combined pollution of desert grey soils from the oasis regions on the uptake and translocation of Cd and Pb by rape (Brassica campestris L.), and analyzed the interaction between Cd and Pb. The results of pot experiment showed that the concentration of Cd or Pb was promoted when the concentration of Cd in soil was less than 7.0 mg x kg(-1) and the concentration of Pb in soil was less than 1 500 mg x kg(-1) in single Cd/Pb and Cd-Pb combined pollution. There was an obvious antagonism between Cd and Pb in Cd-Pb combined pollution. As the concentration of Cd in soil increased in single Cd pollution, the enrichment and translocation ability of Cd in rape was firstly improved and then reduced. As the concentration of Pb in soil increased in single Pb pollution, the enrichment and translocation ability of Pb in rape was reduced continuously. The Cd-Pb combined stress reduced the enrichment capacity of Cd and Pb as well as the migration ability of Pb, but improved the migration ability of Cd. The enrichment and translocation ability of Cd was greater than that of Pb. Models of uptake and translocation of Cd and Pb in rape under single Cd/Pb and Cd-Pb combined stress were both well fitted to quadratic equations. PMID:23243889

  13. Toward the Validation of Ba.

    ERIC Educational Resources Information Center

    Burton, Craig L.; Schwen, Thomas M.

    2003-01-01

    The theory of "ba" or "space" offers a prescription for fostering the conversion of particular kinds of knowledge (tacit-to-explicit, tacit-to-tacit, etc.). Three corporate groups were observed as they collaborated to develop instructional, Web-based stories intended to capture their tacit organizational understandings. A comparative case study…

  14. Phase formation in the BaB2O4-BaF2 system

    NASA Astrophysics Data System (ADS)

    Bekker, T. B.; Fedorov, P. P.; Kokh, A. E.

    2012-07-01

    It is shown that the BaB2O4-BaF2 system is quasi-binary with the following eutectics coordinates: 760°C, 59 mol % BaF2, 41 mol % BaB2O4. Due to the intense pyrohydrolysis during the growth of β-BaB2O4 crystals from the 55.6 mol % BaB2O4-44.4 mol % BaF2 composition, the Ba5B4O11 compound is formed in the system. This process leads to the cocrystallization of the β-BaB2O4 and Ba5B4O11 phases and impedes the formation of high-quality crystals.

  15. Observation of sequential Υ suppression in PbPb collisions.

    PubMed

    Chatrchyan, S; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Adam, W; Aguilo, E; Bergauer, T; Dragicevic, M; Erö, J; Fabjan, C; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hörmann, N; Hrubec, J; Jeitler, M; Kiesenhofer, W; Knünz, V; Krammer, M; Krätschmer, I; Liko, D; Mikulec, I; Pernicka, M; Rahbaran, B; Rohringer, C; Rohringer, H; Schöfbeck, R; Strauss, J; Taurok, A; Waltenberger, W; Walzel, G; Widl, E; Wulz, C-E; Mossolov, V; Shumeiko, N; Suarez Gonzalez, J; Bansal, S; Cornelis, T; De Wolf, E A; Janssen, X; Luyckx, S; Mucibello, L; Ochesanu, S; Roland, B; Rougny, R; Selvaggi, M; Staykova, Z; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Van Spilbeeck, A; Blekman, F; Blyweert, S; D'Hondt, J; Gonzalez Suarez, R; Kalogeropoulos, A; Maes, M; Olbrechts, A; Van Doninck, W; Van Mulders, P; Van Onsem, G P; Villella, I; Clerbaux, B; De Lentdecker, G; Dero, V; Gay, A P R; Hreus, T; Léonard, A; Marage, P E; Reis, T; Thomas, L; Vander Velde, C; Vanlaer, P; Wang, J; Adler, V; Beernaert, K; Cimmino, A; Costantini, S; Garcia, G; Grunewald, M; Klein, B; Lellouch, J; Marinov, A; McCartin, J; Ocampo Rios, A A; Ryckbosch, D; Strobbe, N; Thyssen, F; Tytgat, M; Verwilligen, P; Walsh, S; Yazgan, E; Zaganidis, N; Basegmez, S; Bruno, G; Castello, R; Ceard, L; Delaere, C; du Pree, T; Favart, D; Forthomme, L; Giammanco, A; Hollar, J; Lemaitre, V; Liao, J; Militaru, O; Nuttens, C; Pagano, D; Pin, A; Piotrzkowski, K; Schul, N; Vizan Garcia, J M; Beliy, N; Caebergs, T; Daubie, E; Hammad, G H; Alves, G A; Correa Martins, M; De Jesus Damiao, D; Martins, T; Pol, M E; Souza, M H G; Aldá, W L; Carvalho, W; Custódio, A; Da Costa, E M; De Oliveira Martins, C; Fonseca De Souza, S; Matos Figueiredo, D; Mundim, L; Nogima, H; Oguri, V; Prado Da Silva, W L; Santoro, A; Soares Jorge, L; Sznajder, A; Anjos, T S; Bernardes, C A; Dias, F A; Fernandez Perez Tomei, T R; Gregores, E M; Lagana, C; Marinho, F; Mercadante, P G; Novaes, S F; Padula, Sandra S; Genchev, V; Iaydjiev, P; Piperov, S; Rodozov, M; Stoykova, S; Sultanov, G; Tcholakov, V; Trayanov, R; Vutova, M; Dimitrov, A; Hadjiiska, R; Kozhuharov, V; Litov, L; Pavlov, B; Petkov, P; Bian, J G; Chen, G M; Chen, H S; Jiang, C H; Liang, D; Liang, S; Meng, X; Tao, J; Wang, J; Wang, X; Wang, Z; Xiao, H; Xu, M; Zang, J; Zhang, Z; Asawatangtrakuldee, C; Ban, Y; Guo, S; Guo, Y; Li, W; Liu, S; Mao, Y; Qian, S J; Teng, H; Wang, D; Zhang, L; Zhu, B; Zou, W; Avila, C; Gomez, J P; Gomez Moreno, B; Osorio Oliveros, A F; Sanabria, J C; Godinovic, N; Lelas, D; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Kovac, M; Brigljevic, V; Duric, S; Kadija, K; Luetic, J; Morovic, S; Attikis, A; Galanti, M; Mavromanolakis, G; Mousa, J; Nicolaou, C; Ptochos, F; Razis, P A; Finger, M; Finger, M; Assran, Y; Elgammal, S; Ellithi Kamel, A; Khalil, S; Mahmoud, M A; Radi, A; Kadastik, M; Müntel, M; Raidal, M; Rebane, L; Tiko, A; Eerola, P; Fedi, G; Voutilainen, M; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Peltola, T; Tuominen, E; Tuominiemi, J; Tuovinen, E; Ungaro, D; Wendland, L; Banzuzi, K; Karjalainen, A; Korpela, A; Tuuva, T; Besancon, M; Choudhury, S; Dejardin, M; Denegri, D; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Locci, E; Malcles, J; Millischer, L; Nayak, A; Rander, J; Rosowsky, A; Shreyber, I; Titov, M; Baffioni, S; Beaudette, F; Benhabib, L; Bianchini, L; Bluj, M; Broutin, C; Busson, P; Charlot, C; Daci, N; Dahms, T; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Mironov, C; Naranjo, I N; Nguyen, M; Ochando, C; Paganini, P; Sabes, D; Salerno, R; Sirois, Y; Veelken, C; Zabi, A; Agram, J-L; Andrea, J; Bloch, D; Bodin, D; Brom, J-M; Cardaci, M; Chabert, E C; Collard, C; Conte, E; Drouhin, F; Ferro, C; Fontaine, J-C; Gelé, D; Goerlach, U; Juillot, P; Le Bihan, A-C; Van Hove, P; Fassi, F; Mercier, D; Beauceron, S; Beaupere, N; Bondu, O; Boudoul, G; Chasserat, J; Chierici, R; Contardo, D; Depasse, P; El Mamouni, H; Fay, J; Gascon, S; Gouzevitch, M; Ille, B; Kurca, T; Lethuillier, M; Mirabito, L; Perries, S; Sordini, V; Tschudi, Y; Verdier, P; Viret, S; Tsamalaidze, Z; Anagnostou, G; Beranek, S; Edelhoff, M; Feld, L; Heracleous, N; Hindrichs, O; Jussen, R; Klein, K; Merz, J; Ostapchuk, A; Perieanu, A; Raupach, F; Sammet, J; Schael, S; Sprenger, D; Weber, H; Wittmer, B; Zhukov, V; Ata, M; Caudron, J; Dietz-Laursonn, E; Duchardt, D; Erdmann, M; Fischer, R; Güth, A; Hebbeker, T; Heidemann, C; Hoepfner, K; Klingebiel, D; Kreuzer, P; Magass, C; Merschmeyer, M; Meyer, A; Olschewski, M; Papacz, P; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Steggemann, J; Teyssier, D; Weber, M; Bontenackels, M; Cherepanov, V; Flügge, G; Geenen, H; Geisler, M; Haj Ahmad, W; Hoehle, F; Kargoll, B; Kress, T; Kuessel, Y; Nowack, A; Perchalla, L; Pooth, O; Sauerland, P; Stahl, A; Aldaya Martin, M; Behr, J; Behrenhoff, W; Behrens, U; Bergholz, M; Bethani, A; Borras, K; Burgmeier, A; Cakir, A; Calligaris, L; Campbell, A; Castro, E; Costanza, F; Dammann, D; Diez Pardos, C; Eckerlin, G; Eckstein, D; Flucke, G; Geiser, A; Glushkov, I; Gunnellini, P; Habib, S; Hauk, J; Hellwig, G; Jung, H; Kasemann, M; Katsas, P; Kleinwort, C; Kluge, H; Knutsson, A; Krämer, M; Krücker, D; Kuznetsova, E; Lange, W; Lohmann, W; Lutz, B; Mankel, R; Marfin, I; Marienfeld, M; Melzer-Pellmann, I-A; Meyer, A B; Mnich, J; Mussgiller, A; Naumann-Emme, S; Olzem, J; Perrey, H; Petrukhin, A; Pitzl, D; Raspereza, A; Ribeiro Cipriano, P M; Riedl, C; Ron, E; Rosin, M; Salfeld-Nebgen, J; Schmidt, R; Schoerner-Sadenius, T; Sen, N; Spiridonov, A; Stein, M; Walsh, R; Wissing, C; Autermann, C; Blobel, V; Draeger, J; Enderle, H; Erfle, J; Gebbert, U; Görner, M; Hermanns, T; Höing, R S; Kaschube, K; Kaussen, G; Kirschenmann, H; Klanner, R; Lange, J; Mura, B; Nowak, F; Peiffer, T; Pietsch, N; Rathjens, D; Sander, C; Schettler, H; Schleper, P; Schlieckau, E; Schmidt, A; Schröder, M; Schum, T; Seidel, M; Sola, V; Stadie, H; Steinbrück, G; Thomsen, J; Vanelderen, L; Barth, C; Berger, J; Böser, C; Chwalek, T; De Boer, W; Descroix, A; Dierlamm, A; Feindt, M; Guthoff, M; Hackstein, C; Hartmann, F; Hauth, T; Heinrich, M; Held, H; Hoffmann, K H; Honc, S; Katkov, I; Komaragiri, J R; Lobelle Pardo, P; Martschei, D; Mueller, S; Müller, Th; Niegel, M; Nürnberg, A; Oberst, O; Oehler, A; Ott, J; Quast, G; Rabbertz, K; Ratnikov, F; Ratnikova, N; Röcker, S; Scheurer, A; Schilling, F-P; Schott, G; Simonis, H J; Stober, F M; Troendle, D; Ulrich, R; Wagner-Kuhr, J; Wayand, S; Weiler, T; Zeise, M; Daskalakis, G; Geralis, T; Kesisoglou, S; Kyriakis, A; Loukas, D; Manolakos, I; Markou, A; Markou, C; Mavrommatis, C; Ntomari, E; Gouskos, L; Mertzimekis, T J; Panagiotou, A; Saoulidou, N; Evangelou, I; Foudas, C; Kokkas, P; Manthos, N; Papadopoulos, I; Patras, V; Bencze, G; Hajdu, C; Hidas, P; Horvath, D; Sikler, F; Veszpremi, V; Vesztergombi, G; Zsigmond, A; Beni, N; Czellar, S; Molnar, J; Palinkas, J; Szillasi, Z; Karancsi, J; Raics, P; Trocsanyi, Z L; Ujvari, B; Beri, S B; Bhatnagar, V; Dhingra, N; Gupta, R; Jindal, M; Kaur, M; Mehta, M Z; Nishu, N; Saini, L K; Sharma, A; Singh, J; Kumar, Ashok; Kumar, Arun; Ahuja, S; Bhardwaj, A; Choudhary, B C; Malhotra, S; Naimuddin, M; Ranjan, K; Sharma, V; Shivpuri, R K; Banerjee, S; Bhattacharya, S; Dutta, S; Gomber, B; Jain, Sa; Jain, Sh; Khurana, R; Sarkar, S; Sharan, M; Abdulsalam, A; Choudhury, R K; Dutta, D; Kailas, S; Kumar, V; Mehta, P; Mohanty, A K; Pant, L M; Shukla, P; Aziz, T; Ganguly, S; Guchait, M; Maity, M; Majumder, G; Mazumdar, K; Mohanty, G B; Parida, B; Sudhakar, K; Wickramage, N; Banerjee, S; Dugad, S; Arfaei, H; Bakhshiansohi, H; Etesami, S M; Fahim, A; Hashemi, M; Hesari, H; Jafari, A; Khakzad, M; Mohammadi Najafabadi, M; Paktinat Mehdiabadi, S; Safarzadeh, B; Zeinali, M; Abbrescia, M; Barbone, L; Calabria, C; Chhibra, S S; Colaleo, A; Creanza, D; De Filippis, N; De Palma, M; Fiore, L; Iaselli, G; Lusito, L; Maggi, G; Maggi, M; Marangelli, B; My, S; Nuzzo, S; Pacifico, N; Pompili, A; Pugliese, G; Selvaggi, G; Silvestris, L; Singh, G; Venditti, R; Zito, G; Abbiendi, G; Benvenuti, A C; Bonacorsi, D; Braibant-Giacomelli, S; Brigliadori, L; Capiluppi, P; Castro, A; Cavallo, F R; Cuffiani, M; Dallavalle, G M; Fabbri, F; Fanfani, A; Fasanella, D; Giacomelli, P; Grandi, C; Guiducci, L; Marcellini, S; Masetti, G; Meneghelli, M; Montanari, A; Navarria, F L; Odorici, F; Perrotta, A; Primavera, F; Rossi, A M; Rovelli, T; Siroli, G; Travaglini, R; Albergo, S; Cappello, G; Chiorboli, M; Costa, S; Potenza, R; Tricomi, A; Tuve, C; Barbagli, G; Ciulli, V; Civinini, C; D'Alessandro, R; Focardi, E; Frosali, S; Gallo, E; Gonzi, S; Meschini, M; Paoletti, S; Sguazzoni, G; Tropiano, A; Benussi, L; Bianco, S; Colafranceschi, S; Fabbri, F; Piccolo, D; Fabbricatore, P; Musenich, R; Tosi, S; Benaglia, A; De Guio, F; Di Matteo, L; Fiorendi, S; Gennai, S; Ghezzi, A; Malvezzi, S; Manzoni, R A; Martelli, A; Massironi, A; Menasce, D; Moroni, L; Paganoni, M; Pedrini, D; Ragazzi, S; Redaelli, N; Sala, S; Tabarelli de Fatis, T; Buontempo, S; Carrillo Montoya, C A; Cavallo, N; De Cosa, A; Dogangun, O; Fabozzi, F; Iorio, A O M; Lista, L; Meola, S; Merola, M; Paolucci, P; Azzi, P; Bacchetta, N; Biasotto, M; Bisello, D; Branca, A; Checchia, P; Dorigo, T; Gasparini, F; Gonella, F; Gozzelino, A; Gulmini, M; Kanishchev, K; Lacaprara, S; Lazzizzera, I; Margoni, M; Maron, G; Meneguzzo, A T; Montecassiano, F; Pazzini, J; Pozzobon, N; Ronchese, P; Torassa, E; Tosi, M; Vanini, S; Gabusi, M; Ratti, S P; Riccardi, C; Torre, P; Vitulo, P; Biasini, M; Bilei, G M; Fanò, L; Lariccia, P; Lucaroni, A; Mantovani, G; Menichelli, M; Nappi, A; Romeo, F; Saha, A; Santocchia, A; Spiezia, A; Taroni, S; Azzurri, P; Bagliesi, G; Boccali, T; Broccolo, G; Castaldi, R; D'Agnolo, R T; Dell'Orso, R; Fiori, F; Foà, L; Giassi, A; Kraan, A; Ligabue, F; Lomtadze, T; Martini, L; Messineo, A; Palla, F; Rizzi, A; Serban, A T; Spagnolo, P; Squillacioti, P; Tenchini, R; Tonelli, G; Venturi, A; Verdini, P G; Barone, L; Cavallari, F; Del Re, D; Diemoz, M; Fanelli, C; Grassi, M; Longo, E; Meridiani, P; Micheli, F; Nourbakhsh, S; Organtini, G; Paramatti, R; Rahatlou, S; Sigamani, M; Soffi, L; Amapane, N; Arcidiacono, R; Argiro, S; Arneodo, M; Biino, C; Cartiglia, N; Costa, M; Demaria, N; Mariotti, C; Maselli, S; Migliore, E; Monaco, V; Musich, M; Obertino, M M; Pastrone, N; Pelliccioni, M; Potenza, A; Romero, A; Sacchi, R; Solano, A; Staiano, A; Trapani, P P; Vilela Pereira, A; Belforte, S; Candelise, V; Cossutti, F; Della Ricca, G; Gobbo, B; Marone, M; Montanino, D; Penzo, A; Schizzi, A; Heo, S G; Kim, T Y; Nam, S K; Chang, S; Kim, D H; Kim, G N; Kong, D J; Park, H; Ro, S R; Son, D C; Son, T; Kim, J Y; Kim, Zero J; Song, S; Choi, S; Gyun, D; Hong, B; Jo, M; Kim, H; Kim, T J; Lee, K S; Moon, D H; Park, S K; Choi, M; Kim, J H; Park, C; Park, I C; Park, S; Ryu, G; Cho, Y; Choi, Y; Choi, Y K; Goh, J; Kim, M S; Kwon, E; Lee, B; Lee, J; Lee, S; Seo, H; Yu, I; Bilinskas, M J; Grigelionis, I; Janulis, M; Juodagalvis, A; Castilla-Valdez, H; De La Cruz-Burelo, E; Heredia-de La Cruz, I; Lopez-Fernandez, R; Magaña Villalba, R; Martínez-Ortega, J; Sánchez-Hernández, A; Villasenor-Cendejas, L M; Carrillo Moreno, S; Vazquez Valencia, F; Salazar Ibarguen, H A; Casimiro Linares, E; Morelos Pineda, A; Reyes-Santos, M A; Krofcheck, D; Bell, A J; Butler, P H; Doesburg, R; Reucroft, S; Silverwood, H; Ahmad, M; Asghar, M I; Hoorani, H R; Khalid, S; Khan, W A; Khurshid, T; Qazi, S; Shah, M A; Shoaib, M; Bialkowska, H; Boimska, B; Frueboes, T; Gokieli, R; Górski, M; Kazana, M; Nawrocki, K; Romanowska-Rybinska, K; Szleper, M; Wrochna, G; Zalewski, P; Brona, G; Bunkowski, K; Cwiok, M; Dominik, W; Doroba, K; Kalinowski, A; Konecki, M; Krolikowski, J; Almeida, N; Bargassa, P; David, A; Faccioli, P; Ferreira Parracho, P G; Gallinaro, M; Seixas, J; Varela, J; Vischia, P; Afanasiev, S; Belotelov, I; Bunin, P; Gavrilenko, M; Golutvin, I; Kamenev, A; Karjavin, V; Kozlov, G; Lanev, A; Malakhov, A; Moisenz, P; Palichik, V; Perelygin, V; Shmatov, S; Smirnov, V; Volodko, A; Zarubin, A; Evstyukhin, S; Golovtsov, V; Ivanov, Y; Kim, V; Levchenko, P; Murzin, V; Oreshkin, V; Smirnov, I; Sulimov, V; Uvarov, L; Vavilov, S; Vorobyev, A; Vorobyev, An; Andreev, Yu; Dermenev, A; Gninenko, S; Golubev, N; Kirsanov, M; Krasnikov, N; Matveev, V; Pashenkov, A; Tlisov, D; Toropin, A; Epshteyn, V; Erofeeva, M; Gavrilov, V; Kossov, M; Lychkovskaya, N; Popov, V; Safronov, G; Semenov, S; Stolin, V; Vlasov, E; Zhokin, A; Belyaev, A; Boos, E; Ershov, A; Gribushin, A; Klyukhin, V; Kodolova, O; Korotkikh, V; Lokhtin, I; Markina, A; Obraztsov, S; Perfilov, M; Petrushanko, S; Popov, A; Sarycheva, L; Savrin, V; Snigirev, A; Vardanyan, I; Andreev, V; Azarkin, M; Dremin, I; Kirakosyan, M; Leonidov, A; Mesyats, G; Rusakov, S V; Vinogradov, A; Azhgirey, I; Bayshev, I; Bitioukov, S; Grishin, V; Kachanov, V; Konstantinov, D; Korablev, A; Krychkine, V; Petrov, V; Ryutin, R; Sobol, A; Tourtchanovitch, L; Troshin, S; Tyurin, N; Uzunian, A; Volkov, A; Adzic, P; Djordjevic, M; Ekmedzic, M; Krpic, D; Milosevic, J; Aguilar-Benitez, M; Alcaraz Maestre, J; Arce, P; Battilana, C; Calvo, E; Cerrada, M; Chamizo Llatas, M; Colino, N; De La Cruz, B; Delgado Peris, A; Domínguez Vázquez, D; Fernandez Bedoya, C; Fernández Ramos, J P; Ferrando, A; Flix, J; Fouz, M C; Garcia-Abia, P; Gonzalez Lopez, O; Goy Lopez, S; Hernandez, J M; Josa, M I; Merino, G; Puerta Pelayo, J; Quintario Olmeda, A; Redondo, I; Romero, L; Santaolalla, J; Soares, M S; Willmott, C; Albajar, C; Codispoti, G; de Trocóniz, J F; Brun, H; Cuevas, J; Fernandez Menendez, J; Folgueras, S; Gonzalez Caballero, I; Lloret Iglesias, L; Piedra Gomez, J; Brochero Cifuentes, J A; Cabrillo, I J; Calderon, A; Chuang, S H; Duarte Campderros, J; Felcini, M; Fernandez, M; Gomez, G; Gonzalez Sanchez, J; Graziano, A; Jorda, C; Lopez Virto, A; Marco, J; Marco, R; Martinez Rivero, C; Matorras, F; Munoz Sanchez, F J; Rodrigo, T; Rodríguez-Marrero, A Y; Ruiz-Jimeno, A; Scodellaro, L; Sobron Sanudo, M; Vila, I; Vilar Cortabitarte, R; Abbaneo, D; Auffray, E; Auzinger, G; Baillon, P; Ball, A H; Barney, D; Benitez, J F; Bernet, C; Bianchi, G; Bloch, P; Bocci, A; Bonato, A; Botta, C; Breuker, H; Camporesi, T; Cerminara, G; Christiansen, T; Coarasa Perez, J A; D'Enterria, D; Dabrowski, A; De Roeck, A; Di Guida, S; Dobson, M; Dupont-Sagorin, N; Elliott-Peisert, A; Frisch, B; Funk, W; Georgiou, G; Giffels, M; Gigi, D; Gill, K; Giordano, D; Giunta, M; Glege, F; Gomez-Reino Garrido, R; Govoni, P; Gowdy, S; Guida, R; Hansen, M; Harris, P; Hartl, C; Harvey, J; Hegner, B; Hinzmann, A; Innocente, V; Janot, P; Kaadze, K; Karavakis, E; Kousouris, K; Lecoq, P; Lee, Y-J; Lenzi, P; Lourenço, C; Mäki, T; Malberti, M; Malgeri, L; Mannelli, M; Masetti, L; Meijers, F; Mersi, S; Meschi, E; Moser, R; Mozer, M U; Mulders, M; Musella, P; Nesvold, E; Orimoto, T; Orsini, L; Palencia Cortezon, E; Perez, E; Perrozzi, L; Petrilli, A; Pfeiffer, A; Pierini, M; Pimiä, M; Piparo, D; Polese, G; Quertenmont, L; Racz, A; Reece, W; Rodrigues Antunes, J; Rolandi, G; Rommerskirchen, T; Rovelli, C; Rovere, M; Sakulin, H; Santanastasio, F; Schäfer, C; Schwick, C; Segoni, I; Sekmen, S; Sharma, A; Siegrist, P; Silva, P; Simon, M; Sphicas, P; Spiga, D; Tsirou, A; Veres, G I; Vlimant, J R; Wöhri, H K; Worm, S D; Zeuner, W D; Bertl, W; Deiters, K; Erdmann, W; Gabathuler, K; Horisberger, R; Ingram, Q; Kaestli, H C; König, S; Kotlinski, D; Langenegger, U; Meier, F; Renker, D; Rohe, T; Sibille, J; Bäni, L; Bortignon, P; Buchmann, M A; Casal, B; Chanon, N; Deisher, A; Dissertori, G; Dittmar, M; Donegà, M; Dünser, M; Eugster, J; Freudenreich, K; Grab, C; Hits, D; Lecomte, P; Lustermann, W; Marini, A C; Martinez Ruiz del Arbol, P; Mohr, N; Moortgat, F; Nägeli, C; Nef, P; Nessi-Tedaldi, F; Pandolfi, F; Pape, L; Pauss, F; Peruzzi, M; Ronga, F J; Rossini, M; Sala, L; Sanchez, A K; Starodumov, A; Stieger, B; Takahashi, M; Tauscher, L; Thea, A; Theofilatos, K; Treille, D; Urscheler, C; Wallny, R; Weber, H A; Wehrli, L; Amsler, C; Chiochia, V; De Visscher, S; Favaro, C; Ivova Rikova, M; Millan Mejias, B; Otiougova, P; Robmann, P; Snoek, H; Tupputi, S; Verzetti, M; Chang, Y H; Chen, K H; Kuo, C M; Li, S W; Lin, W; Liu, Z K; Lu, Y J; Mekterovic, D; Singh, A P; Volpe, R; Yu, S S; Bartalini, P; Chang, P; Chang, Y H; Chang, Y W; Chao, Y; Chen, K F; Dietz, C; Grundler, U; Hou, W-S; Hsiung, Y; Kao, K Y; Lei, Y J; Lu, R-S; Majumder, D; Petrakou, E; Shi, X; Shiu, J G; Tzeng, Y M; Wan, X; Wang, M; Adiguzel, A; Bakirci, M N; Cerci, S; Dozen, C; Dumanoglu, I; Eskut, E; Girgis, S; Gokbulut, G; Gurpinar, E; Hos, I; Kangal, E E; Karaman, T; Karapinar, G; Kayis Topaksu, A; Onengut, G; Ozdemir, K; Ozturk, S; Polatoz, A; Sogut, K; Sunar Cerci, D; Tali, B; Topakli, H; Vergili, L N; Vergili, M; Akin, I V; Aliev, T; Bilin, B; Bilmis, S; Deniz, M; Gamsizkan, H; Guler, A M; Ocalan, K; Ozpineci, A; Serin, M; Sever, R; Surat, U E; Yalvac, M; Yildirim, E; Zeyrek, M; Gülmez, E; Isildak, B; Kaya, M; Kaya, O; Ozkorucuklu, S; Sonmez, N; Cankocak, K; Levchuk, L; Bostock, F; Brooke, J J; Clement, E; Cussans, D; Flacher, H; Frazier, R; Goldstein, J; Grimes, M; Heath, G P; Heath, H F; Kreczko, L; Metson, S; Newbold, D M; Nirunpong, K; Poll, A; Senkin, S; Smith, V J; Williams, T; Basso, L; Belyaev, A; Brew, C; Brown, R M; Cockerill, D J A; Coughlan, J A; Harder, K; Harper, S; Jackson, J; Kennedy, B W; Olaiya, E; Petyt, D; Radburn-Smith, B C; Shepherd-Themistocleous, C H; Tomalin, I R; Womersley, W J; Bainbridge, R; Ball, G; Beuselinck, R; Buchmuller, O; Colling, D; Cripps, N; Cutajar, M; Dauncey, P; Davies, G; Della Negra, M; Ferguson, W; Fulcher, J; Futyan, D; Gilbert, A; Guneratne Bryer, A; Hall, G; Hatherell, Z; Hays, J; Iles, G; Jarvis, M; Karapostoli, G; Lyons, L; Magnan, A-M; Marrouche, J; Mathias, B; Nandi, R; Nash, J; Nikitenko, A; Papageorgiou, A; Pela, J; Pesaresi, M; Petridis, K; Pioppi, M; Raymond, D M; Rogerson, S; Rose, A; Ryan, M J; Seez, C; Sharp, P; Sparrow, A; Stoye, M; Tapper, A; Vazquez Acosta, M; Virdee, T; Wakefield, S; Wardle, N; Whyntie, T; Chadwick, M; Cole, J E; Hobson, P R; Khan, A; Kyberd, P; Leggat, D; Leslie, D; Martin, W; Reid, I D; Symonds, P; Teodorescu, L; Turner, M; Hatakeyama, K; Liu, H; Scarborough, T; Charaf, O; Henderson, C; Rumerio, P; Avetisyan, A; Bose, T; Fantasia, C; Heister, A; St John, J; Lawson, P; Lazic, D; Rohlf, J; Sperka, D; Sulak, L; Alimena, J; Bhattacharya, S; Cutts, D; Ferapontov, A; Heintz, U; Jabeen, S; Kukartsev, G; Laird, E; Landsberg, G; Luk, M; Narain, M; Nguyen, D; Segala, M; Sinthuprasith, T; Speer, T; Tsang, K V; Breedon, R; Breto, G; Calderon De La Barca Sanchez, M; Chauhan, S; Chertok, M; Conway, J; Conway, R; Cox, P T; Dolen, J; Erbacher, R; Gardner, M; Houtz, R; Ko, W; Kopecky, A; Lander, R; Miceli, T; Pellett, D; Ricci-tam, F; Rutherford, B; Searle, M; Smith, J; Squires, M; Tripathi, M; Vasquez Sierra, R; Andreev, V; Cline, D; Cousins, R; Duris, J; Erhan, S; Everaerts, P; Farrell, C; Hauser, J; Ignatenko, M; Jarvis, C; Plager, C; Rakness, G; Schlein, P; Traczyk, P; Valuev, V; Weber, M; Babb, J; Clare, R; Dinardo, M E; Ellison, J; Gary, J W; Giordano, F; Hanson, G; Jeng, G Y; Liu, H; Long, O R; Luthra, A; Nguyen, H; Paramesvaran, S; Sturdy, J; Sumowidagdo, S; Wilken, R; Wimpenny, S; Andrews, W; Branson, J G; Cerati, G B; Cittolin, S; Evans, D; Golf, F; Holzner, A; Kelley, R; Lebourgeois, M; Letts, J; Macneill, I; Mangano, B; Padhi, S; Palmer, C; Petrucciani, G; Pieri, M; Sani, M; Sharma, V; Simon, S; Sudano, E; Tadel, M; Tu, Y; Vartak, A; Wasserbaech, S; Würthwein, F; Yagil, A; Yoo, J; Barge, D; Bellan, R; Campagnari, C; D'Alfonso, M; Danielson, T; Flowers, K; Geffert, P; Incandela, J; Justus, C; Kalavase, P; Koay, S A; Kovalskyi, D; Krutelyov, V; Lowette, S; McColl, N; Pavlunin, V; Rebassoo, F; Ribnik, J; Richman, J; Rossin, R; Stuart, D; To, W; West, C; Apresyan, A; Bornheim, A; Chen, Y; Di Marco, E; Duarte, J; Gataullin, M; Ma, Y; Mott, A; Newman, H B; Rogan, C; Spiropulu, M; Timciuc, V; Veverka, J; Wilkinson, R; Yang, Y; Zhu, R Y; Akgun, B; Azzolini, V; Carroll, R; Ferguson, T; Iiyama, Y; Jang, D W; Liu, Y F; Paulini, M; Vogel, H; Vorobiev, I; Cumalat, J P; Drell, B R; Edelmaier, C J; Ford, W T; Gaz, A; Heyburn, B; Luiggi Lopez, E; Smith, J G; Stenson, K; Ulmer, K A; Wagner, S R; Alexander, J; Chatterjee, A; Eggert, N; Gibbons, L K; Heltsley, B; Khukhunaishvili, A; Kreis, B; Mirman, N; Nicolas Kaufman, G; Patterson, J R; Ryd, A; Salvati, E; Sun, W; Teo, W D; Thom, J; Thompson, J; Tucker, J; Vaughan, J; Weng, Y; Winstrom, L; Wittich, P; Winn, D; Abdullin, S; Albrow, M; Anderson, J; Bauerdick, L A T; Beretvas, A; Berryhill, J; Bhat, P C; Bloch, I; Burkett, K; Butler, J N; Chetluru, V; Cheung, H W K; Chlebana, F; Elvira, V D; Fisk, I; Freeman, J; Gao, Y; Green, D; Gutsche, O; Hanlon, J; Harris, R M; Hirschauer, J; Hooberman, B; Jindariani, S; Johnson, M; Joshi, U; Kilminster, B; Klima, B; Kunori, S; Kwan, S; Leonidopoulos, C; Linacre, J; Lincoln, D; Lipton, R; Lykken, J; Maeshima, K; Marraffino, J M; Maruyama, S; Mason, D; McBride, P; Mishra, K; Mrenna, S; Musienko, Y; Newman-Holmes, C; O'Dell, V; Prokofyev, O; Sexton-Kennedy, E; Sharma, S; Spalding, W J; Spiegel, L; Tan, P; Taylor, L; Tkaczyk, S; Tran, N V; Uplegger, L; Vaandering, E W; Vidal, R; Whitmore, J; Wu, W; Yang, F; Yumiceva, F; Yun, J C; Acosta, D; Avery, P; Bourilkov, D; Chen, M; Cheng, T; Das, S; De Gruttola, M; Di Giovanni, G P; Dobur, D; Drozdetskiy, A; Field, R D; Fisher, M; Fu, Y; Furic, I K; Gartner, J; Hugon, J; Kim, B; Konigsberg, J; Korytov, A; Kropivnitskaya, A; Kypreos, T; Low, J F; Matchev, K; Milenovic, P; Mitselmakher, G; Muniz, L; Remington, R; Rinkevicius, A; Sellers, P; Skhirtladze, N; Snowball, M; Yelton, J; Zakaria, M; Gaultney, V; Hewamanage, S; Lebolo, L M; Linn, S; Markowitz, P; Martinez, G; Rodriguez, J L; Adams, T; Askew, A; Bochenek, J; Chen, J; Diamond, B; Gleyzer, S V; Haas, J; Hagopian, S; Hagopian, V; Jenkins, M; Johnson, K F; Prosper, H; Veeraraghavan, V; Weinberg, M; Baarmand, M M; Dorney, B; Hohlmann, M; Kalakhety, H; Vodopiyanov, I; Adams, M R; Anghel, I M; Apanasevich, L; Bai, Y; Bazterra, V E; Betts, R R; Bucinskaite, I; Callner, J; Cavanaugh, R; Dragoiu, C; Evdokimov, O; Gauthier, L; Gerber, C E; Hofman, D J; Khalatyan, S; Lacroix, F; Malek, M; O'Brien, C; Silkworth, C; Strom, D; Varelas, N; Akgun, U; Albayrak, E A; Bilki, B; Clarida, W; Duru, F; Griffiths, S; Merlo, J-P; Mermerkaya, H; Mestvirishvili, A; Moeller, A; Nachtman, J; Newsom, C R; Norbeck, E; Onel, Y; Ozok, F; Sen, S; Tiras, E; Wetzel, J; Yetkin, T; Yi, K; Barnett, B A; Blumenfeld, B; Bolognesi, S; Fehling, D; Giurgiu, G; Gritsan, A V; Guo, Z J; Hu, G; Maksimovic, P; Rappoccio, S; Swartz, M; Whitbeck, A; Baringer, P; Bean, A; Benelli, G; Grachov, O; Kenny, R P; Murray, M; Noonan, D; Sanders, S; Stringer, R; Tinti, G; Wood, J S; Zhukova, V; Barfuss, A F; Bolton, T; Chakaberia, I; Ivanov, A; Khalil, S; Makouski, M; Maravin, Y; Shrestha, S; Svintradze, I; Gronberg, J; Lange, D; Wright, D; Baden, A; Boutemeur, M; Calvert, B; Eno, S C; Gomez, J A; Hadley, N J; Kellogg, R G; Kirn, M; Kolberg, T; Lu, Y; Marionneau, M; Mignerey, A C; Pedro, K; Peterman, A; Skuja, A; Temple, J; Tonjes, M B; Tonwar, S C; Twedt, E; Apyan, A; Bauer, G; Bendavid, J; Busza, W; Butz, E; Cali, I A; Chan, M; Dutta, V; Gomez Ceballos, G; Goncharov, M; Hahn, K A; Kim, Y; Klute, M; Krajczar, K; Li, W; Luckey, P D; Ma, T; Nahn, S; Paus, C; Ralph, D; Roland, C; Roland, G; Rudolph, M; Stephans, G S F; Stöckli, F; Sumorok, K; Sung, K; Velicanu, D; Wenger, E A; Wolf, R; Wyslouch, B; Xie, S; Yang, M; Yilmaz, Y; Yoon, A S; Zanetti, M; Cooper, S I; Dahmes, B; De Benedetti, A; Franzoni, G; Gude, A; Kao, S C; Klapoetke, K; Kubota, Y; Mans, J; Pastika, N; Rusack, R; Sasseville, M; Singovsky, A; Tambe, N; Turkewitz, J; Cremaldi, L M; Kroeger, R; Perera, L; Rahmat, R; Sanders, D A; Avdeeva, E; Bloom, K; Bose, S; Butt, J; Claes, D R; Dominguez, A; Eads, M; Keller, J; Kravchenko, I; Lazo-Flores, J; Malbouisson, H; Malik, S; Snow, G R; Baur, U; Godshalk, A; Iashvili, I; Jain, S; Kharchilava, A; Kumar, A; Shipkowski, S P; Smith, K; Alverson, G; Barberis, E; Baumgartel, D; Chasco, M; Haley, J; Nash, D; Trocino, D; Wood, D; Zhang, J; Anastassov, A; Kubik, A; Mucia, N; Odell, N; Ofierzynski, R A; Pollack, B; Pozdnyakov, A; Schmitt, M; Stoynev, S; Velasco, M; Won, S; Antonelli, L; Berry, D; Brinkerhoff, A; Hildreth, M; Jessop, C; Karmgard, D J; Kolb, J; Lannon, K; Luo, W; Lynch, S; Marinelli, N; Morse, D M; Pearson, T; Ruchti, R; Slaunwhite, J; Valls, N; Wayne, M; Wolf, M; Bylsma, B; Durkin, L S; Hill, C; Hughes, R; Hughes, R; Kotov, K; Ling, T Y; Puigh, D; Rodenburg, M; Vuosalo, C; Williams, G; Winer, B L; Adam, N; Berry, E; Elmer, P; Gerbaudo, D; Halyo, V; Hebda, P; Hegeman, J; Hunt, A; Jindal, P; Lopes Pegna, D; Lujan, P; Marlow, D; Medvedeva, T; Mooney, M; Olsen, J; Piroué, P; Quan, X; Raval, A; Safdi, B; Saka, H; Stickland, D; Tully, C; Werner, J S; Zuranski, A; Acosta, J G; Brownson, E; Huang, X T; Lopez, A; Mendez, H; Oliveros, S; Ramirez Vargas, J E; Zatserklyaniy, A; Alagoz, E; Barnes, V E; Benedetti, D; Bolla, G; Bortoletto, D; De Mattia, M; Everett, A; Hu, Z; Jones, M; Koybasi, O; Kress, M; Laasanen, A T; Leonardo, N; Maroussov, V; Merkel, P; Miller, D H; Neumeister, N; Shipsey, I; Silvers, D; Svyatkovskiy, A; Vidal Marono, M; Yoo, H D; Zablocki, J; Zheng, Y; Guragain, S; Parashar, N; Adair, A; Boulahouache, C; Ecklund, K M; Geurts, F J M; Padley, B P; Redjimi, R; Roberts, J; Zabel, J; Betchart, B; Bodek, A; Chung, Y S; Covarelli, R; de Barbaro, P; Demina, R; Eshaq, Y; Garcia-Bellido, A; Goldenzweig, P; Han, J; Harel, A; Miner, D C; Vishnevskiy, D; Zielinski, M; Bhatti, A; Ciesielski, R; Demortier, L; Goulianos, K; Lungu, G; Malik, S; Mesropian, C; Arora, S; Barker, A; Chou, J P; Contreras-Campana, C; Contreras-Campana, E; Duggan, D; Ferencek, D; Gershtein, Y; Gray, R; Halkiadakis, E; Hidas, D; Lath, A; Panwalkar, S; Park, M; Patel, R; Rekovic, V; Robles, J; Rose, K; Salur, S; Schnetzer, S; Seitz, C; Somalwar, S; Stone, R; Thomas, S; Cerizza, G; Hollingsworth, M; Spanier, S; Yang, Z C; York, A; Eusebi, R; Flanagan, W; Gilmore, J; Kamon, T; Khotilovich, V; Montalvo, R; Osipenkov, I; Pakhotin, Y; Perloff, A; Roe, J; Safonov, A; Sakuma, T; Sengupta, S; Suarez, I; Tatarinov, A; Toback, D; Akchurin, N; Damgov, J; Dudero, P R; Jeong, C; Kovitanggoon, K; Lee, S W; Libeiro, T; Roh, Y; Volobouev, I; Appelt, E; Delannoy, A G; Florez, C; Greene, S; Gurrola, A; Johns, W; Johnston, C; Kurt, P; Maguire, C; Melo, A; Sharma, M; Sheldon, P; Snook, B; Tuo, S; Velkovska, J; Arenton, M W; Balazs, M; Boutle, S; Cox, B; Francis, B; Goodell, J; Hirosky, R; Ledovskoy, A; Lin, C; Neu, C; Wood, J; Yohay, R; Gollapinni, S; Harr, R; Karchin, P E; Kottachchi Kankanamge Don, C; Lamichhane, P; Sakharov, A; Anderson, M; Bachtis, M; Belknap, D; Borrello, L; Carlsmith, D; Cepeda, M; Dasu, S; Friis, E; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Herndon, M; Hervé, A; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Mohapatra, A; Ojalvo, I; Palmonari, F; Pierro, G A; Ross, I; Savin, A; Smith, W H; Swanson, J

    2012-11-30

    The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150 μb(-1) and 230 nb(-1), respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, R(AA), is measured as a function of the collision centrality. Integrated over centrality, the R(AA) values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies. PMID:23368113

  16. Optical Properties of PbTe and PbSe

    SciTech Connect

    Ekuma, Chinedu E; Singh, David J; Moreno, Juana; Jarrell, Mark

    2012-01-01

    We report optical properties of PbTe and PbSe as obtained from first-principles calculations with the Tran-Blaha modified Becke-Johnson potential. The results are discussed in relation to existing experimental data, particularly in relation to the temperature dependence of the band gap.

  17. Syntheses, crystal structure and physical properties of new Zintl phases Ba3T2As4 (T=Zn, Cd)

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Xia, Sheng-Qing; Tao, Xu-Tang

    2013-02-01

    Through high temperature Pb-flux reactions, two new arsenide Zintl compounds, Ba3Zn2As4 and Ba3Cd2As4, were successfully obtained and their structures were accurately determined with Single-Crystal X-ray Diffraction. Both compounds are isotypic to Ba3Cd2Sb4 and crystallize in the monoclinic space group C2/m (No=12) with cell parameters of a=16.916(4)/17.089(3) Å, b=4.497(1)/4.6076(7) Å, c=7.225(2)/7.304(1) Å and β=113.147(2)/112.312(1) ° for Ba3Zn2As4 and Ba3Cd2As4, respectively. Electrical resistivity measurement on Ba3Cd2As4 reveals semiconducting behavior between 10 and 100 K, which results in a very small band gap of 0.01 eV. According to TG/DSC analyses, Ba3Cd2As4 exhibits good thermal stability and does not decompose below 950 K.

  18. Prediction and assignment of site occupation and energy levels for Pb 2+ ions in crystal hosts

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Wang, Jing; Shi, Jinsheng

    2010-05-01

    The environmental factor h e of the host was calculated quantitatively in Pb 2+-doped 23 compounds based on the dielectric theory of chemical bond for complex crystals. The relationship between the A band energy E A of Pb 2+ and the environmental factor h e was intensively studied. The results indicate that E A of Pb 2+ decreases linearly with increasing of h e. A linear model was proposed which allows us to correctly predict and assign the site occupations and the position of A band for Pb 2+-doped compounds if the crystal structure and the refraction index were known. Applied to SrGa 2O 4:Pb 2+, CaAl 2B 2O 7:Pb 2+ and SrAl 2B 2O 7:Pb 2+, the theoretical predictions are in very good agreement with the experimental data. In SrGa 2O 4:Pb 2+, the excitation spectrum of Pb 2+ from two different cation sites was identified: the higher energy band of A (265 nm) from the site of Sr2, and the lower ones (280 nm) from the site of Sr1.

  19. Chemical and isotopical characterisation of atmospheric pollution from urban and rural environments of the Rhine Valley (PCBs, trace elements and Sr-, Nd- and Pb- isotope determinations)

    NASA Astrophysics Data System (ADS)

    Guéguen, F.; Stille, P.; Millet, M.; Dietze, V.; Gieré, R.

    2010-05-01

    Atmosheric samples (gas and particulate matter (PM)) have been collected in the urban environment of the cities of Strasbourg and Kehl and in the rural environment of the Vosges mountains. For sampling of gas phase pollutants and particles two different passive sampler devices have been applied (PAS and Sigma-2, respectively). The PAS has been used for gas phase Polychlorinated Biphenyls (PCBs) sampling and is based on the passive adsorption of gas phase pollutants onto XAD-2 resin. The Sigma-2 sampler is based on the sedimentation principle (Stoke's law), collects particles in the size range 2.5-100 μm and allows the calculation of ambient air concentration. The sampler is mainly used for routine air quality measurements in German health and recreation resorts and in this field study the first time for collection of samples for subsequent trace element and isotope analysis. The collection time for the Sigma-2 and PAS are four and two weeks, respectively. Major and trace elements have been analyzed by ICP-MS and the Sr, Nd and Pb isotope ratios by a sector field MC-ICP-MS (Neptune) while PCBs were ASE extracted and analysed by GC-ECD. The aerosol data are compared with those from tree barks which have previously been used successfully as biomonitors of atmospheric pollution (Lahd Geagea et al. 2008)1. The outer 1 mm thick part of the bark has been analyzed corresponding to about 2 to 8 years of accumulation. Some of the trace elements (Cr, Ni and Mo) of the aerosol samples are strongly (up to 1000 times) enriched compared to average 'upper continental crust (UCC)'. Normalization to a « natural » sample with an atmospheric baseline composition allows to identify industrial contributions: transition metals (Cr, Mn, Fe, Co, Ni, Zn, Mo, Cd), Ba and Pb appear to be important elements in steel plant and incinerator (chemical waste) emissions. Similarly enrichment in light rare earth elements (La, Pr, Nd) is observable. The enrichments increase with decreasing distance

  20. A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2016-04-01

    A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

  1. Lead and barium sources in Cambrian siliciclastics and sediment provenance of a sector of the Taconic Orogen, Quebec: a mixing scenario based on Pb-isotopic evidence

    USGS Publications Warehouse

    Schrijver, K.; Zartman, R.E.; Williams-Jones, A. E.

    1994-01-01

    To test the hypothesis that siliciclastic rocks constituted the major source of Pb and Ba in barite-galena deposits of the Taconic Orogen, we determined Pb-isotope ratios in galena, barren rocks and contained minerals, as well as concentrations of Pb, U, Th and Ba in the latter (detrital feldspars, sandstones, mudstones, rock clasts and carbonate cements and clasts). Ranges in 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb of 28 galena samples are 17.96-18.05, 15.56-15.59 and 37.75-37.93, respectively; ranges for 41 barren rocks and minerals are 16.17-23.31, 15.26-15.86 and 35.98-42.51, respectively. The lowest ratios are in feldspar, and the highest in carbonate and mudstone. Values of the mudstones samples overlap those of galena when corrected for in situ decay of U and Th since galena precipitation (???450 Ma). We thus propose that mudstones constituted a source of lead. Corrected ratios for anomalously Pb-rich mudstones are virtually identical to galena-Pb ratios and may be due to contamination by lead-bearing brines. Assuming that burial diagenesis did not disturb the Pb-isotope values of sandstones, these rocks contributed only a minor fraction of lead to the galena, estimated at ???20% for one deposit. The source of barite-Ba was probably perthite. Low Ba and Pb concentrations of sandstone adjacent to this deposit, compared to high concentrations remote from it, support leaching of barium (and minor lead) from feldspar penecontemporaneous with feldspar dissolution. Geological data indicate that the provenance of the siliciclastic rocks was mainly from Grenville terrane. A comparison of our Pb-isotopic data for Taconic perthite with those of Grenville K-feldspar, as well as ratios of trace elements, support this provenance for both sandstones and mudstones. The presence of carbonate platforms peripheral to the orogen, and the Middle Ordovician-Middle Devonian depositional range of the studied and Mississippi Valley type deposits north (Newfoundland) and south (U

  2. Order-disorder transition in clathrate Ba6Ge25 studied by positron annihilation

    NASA Astrophysics Data System (ADS)

    Li, X. F.; Zhao, B.; Zhang, T.; He, H. F.; Zhang, Q.; Yang, D. W.; Chen, Z. Q.; Tang, X. F.

    2015-07-01

    Clathrate Ba6Ge25 is prepared by melt method and spark plasma sintering. Structural transition below room temperature is studied by positron annihilation and X-ray diffraction measurements. There is a pronounced transition in the temperature range of 200-250 K which might be involved with the movement of Ba atoms in Ge cages and result in disordered structure. This transition is further confirmed by the theoretical calculation of positron annihilation states. Thus our results confirm the structural models proposed by Carrillo-Cabrera et al. (2005). The measured specific heat capacity, electric resistivity and magnetic susceptibility all show anomalous transition in the same temperature range, indicating that the movement of Ba atoms in the cage has influence on the thermal, electric as well as magnetic properties of Ba6Ge25.

  3. Ba{sub 2}TeO as an optoelectronic material: First-principles study

    SciTech Connect

    Sun, Jifeng; Shi, Hongliang; Du, Mao-Hua; Singh, David J.; Siegrist, Theo

    2015-05-21

    The band structure, optical, and defects properties of Ba{sub 2}TeO are systematically investigated using density functional theory with a view to understanding its potential as an optoelectronic or transparent conducting material. Ba{sub 2}TeO crystallizes with tetragonal structure (space group P4/nmm) and with a 2.93 eV optical bandgap [Besara et al., J. Solid State Chem. 222, 60 (2015)]. We find relatively modest band masses for both electrons and holes suggesting applications. Optical properties show infrared-red absorption when doped. This could potentially be useful for combining wavelength filtering and transparent conducting functions. Furthermore, our defect calculations show that Ba{sub 2}TeO is intrinsically p-type conducting under Ba-poor condition. However, the spontaneous formation of the donor defects may constrain the p-type transport properties and would need to be addressed to enable applications.

  4. W boson studies in pPb and PbPb collisions with CMS

    NASA Astrophysics Data System (ADS)

    Chapon, Émilien; CMS Collaboration

    2015-05-01

    The electroweak W bosons do not participate in the strong interaction, and thus constitute clean probes of the initial state of nuclear collisions. They provide a unique constraint on the nuclear parton distributions, in particular on the antiquarks from the sea. A first analysis of PbPb data has confirmed the medium-blind characteristic of the electroweak bosons. With the new pPb data collected at the beginning of 2013, nuclear matter without the creation of a hot medium can hence be studied. Being 10 times more prevalent than Z bosons, the yield of W bosons recorded from pPb collisions allows precise comparisons to theoretical predictions. A yield of approximately 20 000 W is observed in pPb collisions in both the muon and electron channels. In this paper the CMS measurements of W bosons in PbPb at nucleon-nucleon center-of-mass energy of \\sqrt{sNN} = 2.76 TeV and from the new pPb data at \\sqrt{sNN} = 5.02 TeV are reported. The charge asymmetry, forward/backward asymmetry and fully corrected yields will be shown.

  5. Microstructure and Cs Behavior of Ba-Doped Aluminosilicate Pollucite Irradiated with F+ Ions

    SciTech Connect

    Jiang, Weilin; Kovarik, Libor; Zhu, Zihua; Varga, Tamas; Engelhard, Mark H.; Bowden, Mark E.; Nenoff, Tina M.; Garino, Terry

    2014-06-24

    Radionuclide 137Cs is one of the major fission products that dominate heat generation in spent fuels over the first 300 hundred years. A durable waste form for 137Cs that decays to 137Ba is needed to minimize its environmental impact. Aluminosilicate pollucite CsAlSi2O6 is selected as a model waste form to study the decay-induced structural effects. While Ba-containing precipitates are not present in charge-balanced Cs0.9Ba0.05AlSi2O6, they are found in Cs0.9Ba0.1AlSi2O6 and identified as monoclinic Ba2Si3O8. Pollucite is susceptible to electron irradiation induced amorphization. The threshold density of the electronic energy deposition for amorphization is determined to be ~235 keV/nm3. Pollucite can be readily amorphized under F+ ion irradiation at 673 K. A significant amount of Cs diffusion and release from the amorphized pollucite is observed during the irradiation. However, cesium is immobile in the crystalline structure under He+ ion irradiation at room temperature. The critical temperature for amorphization is not higher than 873 K under F+ ion irradiation. If kept at or above 873 K all the time, the pollucite structure is unlikely to be amorphized; Cs diffusion and release are improbable. A general discussion regarding pollucite as a potential waste form is provided in this report.

  6. Tuning polarization states and interface properties of BaTiO3/SrTiO3 heterostructure by metal capping layers

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Yang, Ming; Shen, Lei; Wu, Qing Yun; Xu, Lei; Feng, Yuan Ping; Rusydi, Andrivo

    2016-04-01

    How to tune two-dimensional electron gas at interface of heterostructures is becoming an important question for both fundamental physics and electronic applications. Here, using density functional theory calculations, we find that the polarization state of BaTiO3 in metal capped BaTiO3/SrTiO3 heterostructures changes dramatically, depending on the termination of BaTiO3 and the different metal layers (M =Al , Fe, Pt Au). Most interestingly, for Pt on the BaO-terminated BaTiO3/SrTiO3, interface conductivity can be tuned. With a paraelectric state in BaTiO3, Pt_BaTiO 3 /SrTiO3 remains insulating at interface, while when BaTiO3 is ferroelectric, a hole- or electron-conducting BaTiO3/SrTiO3 interface can be realized, depending on its polarization direction in BaTiO3. This conducting interface and the top Pt layer screen the depolarization field, and thus stabilize the ferroelectricity in BaTiO3. Our result provides important clues for the reversibly tunable conductivity at oxide interfaces.

  7. Microstructural properties of (Ba,Sr)TiO3 films fabricated from BaF2/SrF2/TiO2 amorphous multilayers using the combinatorial precursor method

    SciTech Connect

    Takeuchi, I.; Chang, K.; Sharma, R.P.; Bendersky, L.A.; Chang, H.; Xiang, X.-D.; Stach, E.A.; Song, C.-Y.

    2001-01-12

    We have investigated the microstructure of (Ba,Sr)TiO3 films fabricated from BaF2/SrF2/TiO2 amorphous multilayers. Rutherford backscattering spectroscopy and x-ray diffraction studies show that a controlled thermal treatment can interdiffuse the multilayers so as to create predominantly single-phase epitaxial (Ba,Sr)TiO3 films. High resolution cross-sectional transmission electron microscopy investigation of the processed films shows that they consist of large epitaxial grains of (Ba,Sr)TiO3 with atomically sharp interfaces with the LaAlO3 substrates. In addition, we have identified regions where polycrystalline and amorphous phases exist in small pockets in the film matrix. The results here indicate that the combinatorial thin-film synthesis using precursors can produce (Ba,Sr)TiO3 films in combinatorial libraries which exhibit properties similar to those films made by conventional techniques.

  8. Histopathological and ultrastructural perturbations in tilapia liver as potential indicators of pollution in Lake Al-Asfar, Saudi Arabia.

    PubMed

    Abdel-Moneim, Ashraf M

    2014-03-01

    Lake Al-Asfar (Al-Hassa, Saudi Arabia) is under threat from contaminants released through human activities such as agriculture and urban and industrial developments. In the present study, histopathologic and ultrastructural changes in liver of tilapia Oreochromis niloticus were analyzed to monitor the possible impact of pollution in Al-Asfar estuary. Heavy metals such as Ni, Fe, Zn, Co, Ba, Pb, and Cd were predominant in the lake water and far exceeded the international permissible limits. In fish samples, high prevalences of preneoplastic changes (50 %) and one case of cholangiocarcinoma were revealed in liver tissues. Cytological damage in fish hepatocytes included glycogen exhaustion, deformation of nuclear envelope, heterochromatin condensation, mitochondrial degeneration, vesiculation of rough endoplasmic reticulum, augmentation of smooth endoplasmic reticulum, and lysosomal proliferation. In conclusion, the observed biomarker responses were potential indicators of health impairment or disease in field fish populations, although there was no direct proof of a simple cause-effect relationship. This is the first biological effect assessment in Lake Al-Asfar using tilapia as suitable target species. PMID:24323321

  9. Novel reddish-orange-emitting BaLa2Si2S8:Eu(2+) thiosilicate phosphor for LED lighting.

    PubMed

    Lee, Szu-Ping; Chan, Ting-Shan; Chen, Teng-Ming

    2015-01-14

    A novel reddish-orange-emitting BaLa2Si2S8:Eu(2+) thiosilicate was prepared in a sealed fused silica ampule and its crystal structure was refined using Rietveld methods. The BaLa2Si2S8:Eu(2+) phosphor is excitable over a broad range from UV to blue (350-450 nm) and generated a reddish-orange broadband emission peaking at 645 nm with a quantum efficiency of ∼24%. The thermal luminescence quenching of BaLa2Si2S8:Eu(2+) was investigated over the range 25 to 150 °C. This phosphor was utilized to incorporate with two commercially available phosphors, blue BaMgAl10O17:Eu(2+) and green (Ba,Sr)2SiO4:Eu(2+), and a near-UV LED chip (405 nm), a white light with Ra of ∼94 was obtained. PMID:25536279

  10. Pb-12(2-): Plumbaspherene

    SciTech Connect

    Cui, Lifeng; Huang, Xin; Wang, Leiming; Li, Jun; Wang, Lai S.

    2006-08-31

    Photoelectron spectroscopy and theoretical calculations show that Pb122- is a highly stable icosahedral cage cluster, similar to Sn122-. It is bonded by four delocalized radial bonds and nine delocalized on-sphere bonds from the 6p orbitals of the Pb atoms. Following Sn122- (stannaspherene), we coin a name, plumbaspherene, for the highly stable and nearly spherical Pb122- cluster, which has a diameter of ~6.3 Å with an empty interior volume large enough to host most transition metal atoms and afford a new class of stable endohedral plumbaspherenes similar to the endohedral fullerenes.

  11. The chemisorption of H2O, HCOOH and CH3COOH on thin amorphous films of Al2O3

    NASA Technical Reports Server (NTRS)

    Lewis, B. F.; Weinberg, W. H.; Mosesman, M.

    1974-01-01

    Investigation of the irreversible chemisorption of water, formic acid and acetic acid on a thin amorphous aluminum oxide film, using inelastic tunneling spectroscopy. All of the tunnel junctions employed were Al-Al2O3-Pb junctions with the adsorbate on the Al2O3 surface between the Al2O3 and the Pb electrode. The results obtained include the finding that all Al2O3 surfaces prepared by oxidation of Al have free CH groups present on them.

  12. Multiparticle azimuthal correlations in p -Pb and Pb-Pb collisions at the CERN Large Hadron Collider

    NASA Astrophysics Data System (ADS)

    Abelev, B.; Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agostinelli, A.; Agrawal, N.; Ahammed, Z.; Ahmad, N.; Ahmed, I.; Ahn, S. U.; Ahn, S. A.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Awes, T. C.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Baltasar Dos Santos Pedrosa, F.; Baral, R. C.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Baumann, C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Belmont, R.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Berger, M. E.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Bogolyubsky, M.; Böhmer, F. V.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Castillo Castellanos, J.; Casula, E. A. R.; Catanescu, V.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa Del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortese, P.; Cortés Maldonado, I.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dainese, A.; Dang, R.; Danu, A.; Das, D.; Das, I.; Das, K.; Das, S.; Dash, A.; Dash, S.; de, S.; Delagrange, H.; Deloff, A.; Dénes, E.; D'Erasmo, G.; de Caro, A.; de Cataldo, G.; de Cuveland, J.; de Falco, A.; de Gruttola, D.; De Marco, N.; de Pasquale, S.; de Rooij, R.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; di Bari, D.; di Liberto, S.; di Mauro, A.; di Nezza, P.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Dørheim, S.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Dutta Majumdar, A. K.; Hilden, T. E.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erdal, H. A.; Eschweiler, D.; Espagnon, B.; Esposito, M.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fehlker, D.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floratos, E.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Garishvili, I.; Gerhard, J.; Germain, M.; Gheata, A.; Gheata, M.; Ghidini, B.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Graczykowski, L. K.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Guilbaud, M.; Gulbrandsen, K.; Gulkanyan, H.; Gumbo, M.; Gunji, T.; Gupta, A.; Gupta, R.; Khan, K. H.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.

    2014-11-01

    Measurements of multiparticle azimuthal correlations (cumulants) for charged particles in p -Pb at √{sNN}=5.02 TeV and Pb-Pb at √{sNN}=2.76 TeV collisions are presented. They help address the question of whether there is evidence for global, flowlike, azimuthal correlations in the p -Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p -Pb collisions. However, when a |Δ η | gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high multiplicity, indicating the presence of global azimuthal correlations. The Pb-Pb values are higher than the p -Pb values at similar multiplicities. In both systems, the second harmonic four-particle cumulants exhibit a transition from positive to negative values when the multiplicity increases. The negative values allow for a measurement of v2{4 } to be made, which is found to be higher in Pb-Pb collisions at similar multiplicities. The second harmonic six-particle cumulants are also found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find v2{4 } ≃v2{6 } ≠0 which is indicative of a Bessel-Gaussian function for the v2 distribution. For very high-multiplicity Pb-Pb collisions, we observe that the four- and six-particle cumulants become consistent with 0. Finally, third harmonic two-particle cumulants in p -Pb and Pb-Pb are measured. These are found to be similar for overlapping multiplicities, when a |Δ η |>1.4 gap is placed.

  13. Evolution of octupole correlations in 123Ba

    NASA Astrophysics Data System (ADS)

    Chen, X. C.; Zhao, J.; Xu, C.; Hua, H.; Shneidman, T. M.; Zhou, S. G.; Wu, X. G.; Li, X. Q.; Zhang, S. Q.; Li, Z. H.; Liang, W. Y.; Meng, J.; Xu, F. R.; Qi, B.; Ye, Y. L.; Jiang, D. X.; Cheng, Y. Y.; He, C.; Sun, J. J.; Han, R.; Niu, C. Y.; Li, C. G.; Li, P. J.; Wang, C. G.; Wu, H. Y.; Li, Z. H.; Zhou, H.; Hu, S. P.; Zhang, H. Q.; Li, G. S.; He, C. Y.; Zheng, Y.; Li, C. B.; Li, H. W.; Wu, Y. H.; Luo, P. W.; Zhong, J.

    2016-08-01

    High-spin states of 123Ba have been studied via the 108Cd(19F,3 n p )123Ba fusion-evaporation reaction at a beam energy of 90 MeV. Several E 1 transitions linking the positive-parity ν (d5 /2+g7 /2) band and negative-parity ν h11 /2 band are observed in 123Ba for the first time. Evidence for the existence of octupole correlations in 123Ba is presented based on the systematic comparisons of the B (E 1 )/B (E 2 ) branching ratios and the energy displacements in odd-A Ba isotopes. The characteristics of octupole correlation in the odd-A Ba,125123 are explained by the state-of-the-art multidimensionally-constrained relativistic mean-field model and cluster model based on the dinuclear system concept.

  14. Ba{sub 2}phenanthrene is the main component in the Ba-doped phenanthrene superconductor

    SciTech Connect

    Yan, Xun-Wang; Huang, Zhongbing; Lin, Hai-Qing

    2014-12-14

    We have systematically investigated the crystal structure of Ba-doped phenanthrene with various Ba doping levels by the first-principles calculations combined with the X-ray diffraction (XRD) spectra simulations. Although the experimental stoichiometry ratio of Ba atom and phenanthrene molecule is 1.5:1, the simulated XRD spectra, space group symmetry and optimized lattice parameters of Ba{sub 1.5}phenanthrene are not consistent with the experimental ones, while the results for Ba{sub 2}phenanthrene are in good agreement with the measurements. The strength difference of a few XRD peaks can be explained by the existence of pristine phenanthrene. Our findings suggest that instead of uniform Ba{sub 1.5}phenanthrene, there coexist Ba{sub 2}phenanthrene and undoped phenanthrene in the superconducting sample. The electronic calculations indicate that Ba{sub 2}phenanthrene is a semiconductor with a small energy gap less than 0.05 eV.

  15. Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from parton scatterings

    SciTech Connect

    Bzdak, Adam; Ma, Guo-Liang

    2014-12-15

    Using a multiphase transport model (AMPT) we calculate the elliptic v₂ and triangular v₃ Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v₃ are in a good agreement with the CMS data collected at the Large Hadron Collider. The v₂ coefficient is very well described in p-Pb collisions and is underestimated for higher transverse momenta in Pb-Pb interactions. The characteristic mass ordering of v₂ in p-Pb is reproduced, whereas for v₃, this effect is not observed. We further predict the pseudorapidity dependence of v₂ and v₃ in p-Pb and observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher-order Fourier coefficients, v₄ and v₅, in p-Pb are also presented.

  16. Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from parton scatterings

    DOE PAGESBeta

    Bzdak, Adam; Ma, Guo-Liang

    2014-12-15

    Using a multiphase transport model (AMPT) we calculate the elliptic v₂ and triangular v₃ Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v₃ are in a good agreement with the CMS data collected at the Large Hadron Collider. The v₂ coefficient is very well described in p-Pb collisions and is underestimated for higher transverse momenta in Pb-Pb interactions. The characteristic mass ordering of v₂ in p-Pb is reproduced, whereas for v₃, this effect is not observed. We further predict the pseudorapidity dependence of v₂ and v₃ in p-Pb andmore » observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher-order Fourier coefficients, v₄ and v₅, in p-Pb are also presented.« less

  17. Chemical reaction between BaFe2(As,P)2 superconducting thin film and LSAT substrate

    NASA Astrophysics Data System (ADS)

    Adachi, S.; Shimode, T.; Murai, Y.; Chikumoto, N.; Tanabe, K.

    2014-07-01

    BaFe2(As0.67P0.33)2 (Ba122:P) thin films were fabricated on (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) (1 0 0) substrates by a pulsed laser deposition method using a second-harmonic Nd:YAG laser. Superconducting Ba122:P thin films with c-axis orientation and in-plane alignment were successfully obtained. Detailed structural properties on the films were investigated by X-ray diffraction. The X-ray pattern suggested the existence of some apatite-type phase. Transmission electron microscope observation revealed the formation of a reacted layer between the film and the substrate. The reacted layer had a Ba(Sr)-rich and P-rich composition. These analyses indicated the formation of an apatite material at the interface of the film and the substrate.

  18. U-Pb systematics in iron meteorites - Uniformity of primordial lead

    NASA Astrophysics Data System (ADS)

    Gopel, C.; Manhes, G.; Allegre, C. J.

    1985-08-01

    Pb isotopic compositions and U-Pb abundances were determined in the metal phase of six iron meteorites: Canyon Diablo IA, Toluca IA, Odessa IA, Youndegin IA, Deport IA, and Mundrabilla An. Prior to complete dissolution, samples were subjected to a series of leachings and partial dissolutions. Isotopic compositions and abundances of the etched Pb indicate a contamination by terrestrial Pb which is attributable to previous cutting of the meteorite. Pb isotopic compositions measured in the decontaminated samples are identical within 0.2 percent and essentially confirm the primordial Pb value defined by Tatsumoto et al. (1973). These data invalidate more radiogenic Pb isotopic compositions published for iron meteorites, which are the result of terrestrial Pb contamination introduced mainly by analytical procedure. The results of this study support the idea of a solar nebula which was isotopically homogeneous for Pb 4.55 Ga ago. The new upper limit for U-abundance in iron meteorites, 0.001 ppb, is in agreement with its expected thermodynamic solubility in the metal phase.

  19. Reliability of stable Pb isotopes to identify Pb sources and verifying biological fractionation of Pb isotopes in goats and chickens.

    PubMed

    Nakata, Hokuto; Nakayama, Shouta M M; Yabe, John; Liazambi, Allan; Mizukawa, Hazuki; Darwish, Wageh Sobhy; Ikenaka, Yoshinori; Ishizuka, Mayumi

    2016-01-01

    Stable Pb isotope ratios (Pb-IRs) have been recognized as an efficient tool for identifying sources. This study carried out at Kabwe mining area, Zambia, to elucidate the presence or absence of Pb isotope fractionation in goat and chicken, to evaluate the reliability of identifying Pb pollution sources via analysis of Pb-IRs, and to assess whether a threshold for blood Pb levels (Pb-B) for biological fractionation was present. The variation of Pb-IRs in goat decreased with an increase in Pb-B and were fixed at certain values close to those of the dominant source of Pb exposure at Pb-B > 5 μg/dL. However, chickens did not show a clear relationship for Pb-IRs against Pb-B, or a fractionation threshold. Given these, the biological fractionation of Pb isotopes should not occur in chickens but in goats, and the threshold for triggering biological fractionation is at around 5 μg/dL of Pb-B in goats. PMID:26549754

  20. Studies of 27Al NMR in SrAl4

    NASA Astrophysics Data System (ADS)

    Niki, Haruo; Higa, Nonoka; Kuroshima, Hiroko; Toji, Tatsuki; Morishima, Mach; Minei, Motofumi; Yogi, Mamoru; Nakamura, Ai; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika; Harima, Hisatomo

    A charge density wave (CDW) transition at TCDW = 243 K and a structural phase (SP) transition at approximately 100 K occur in SrAl4 with the BaAl4-type body center tetragonal structure, which is the divalent and non-4f electron reference compound of EuAl4. To understand the behaviors of the CDW and SP transitions, the 27Al NMR measurements using a single crystal and a powder sample of SrAl4 have been carried out. The line width below TCDW is modulated by an electrical quadruple interaction between 27Al nucleus and CDW charge modulation. The incommensurate CDW state below TCDW changes into a different structure below TSP. The temperature dependences of Knight shifts of 27Al(I) and 27Al(II) show the different behaviors. The temperature variation of 27Al(I) Knight shift shows anomalies at the CDW and SP transition temperatures, revealing the shift to negative side below TCDW, which is attributable to the core polarization of the d-electrons. However, 27Al(II) Knight shift keeps almost constant except for the small shift due to the SP transition. The 1/T1T of 27Al(I) indicates the obvious changes due to the CDW and SP transitions, while that of 27Al(II) takes a constant value. The density of state at the Fermi level at Al(I) site below 60 K would be about 0.9 times less than that above TCDW.

  1. Petrogenesis of Tertiary continental intra-plate lavas between Siebengebirge and Westerwald, Germany: Constraints from trace element systematics and Nd, Sr and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Schubert, S.; Jung, S.; Pfänder, J. A.; Hauff, F.; Garbe-Schönberg, D.

    2015-10-01

    New 39Ar/40Ar ages and major- and trace-element and radiogenic isotope data are presented for basanites and alkali basalts from the transition area between the Westerwald and Siebengebirge volcanic fields (Germany) that belongs to the Central European Volcanic Province (CEVP). The 39Ar/40Ar ages indicate ages of c. 24 and c. 5 Ma which are fully compatible with previous K/Ar ages indicating that the evolution of this volcanic field belongs to the Westerwald area (28-22 Ma and 5 Ma) rather than to the Siebengebirge area (26-23 Ma). Based on the occurrence of > 30 isolated volcanic plugs with a simple igneous history, this volcanic field can be viewed as a monogenetic volcanic field. Compositions of some basanites are primitive, whereas others and the alkali basalts show decreasing Cr and Ni contents and CaO/Al2O3 ratios. However, increasing TiO2, Al2O3 and incompatible elements (Sr, Zr, Y, Hf, Ta) concentrations with decreasing MgO indicating fractionation of mainly olivine with minor amounts of clinopyroxene and spinel can be noticed. Rare earth element systematics suggest that most of the alkaline rocks are generated by different degrees of melting (5%-10%) of a garnet-bearing peridotite containing some residual amphibole. Negative anomalies of Rb and K in primitive mantle-normalized diagrams and a lack of Ba/Rb fractionation suggest that amphibole was the major OH-bearing mineral phase in the mantle. The alkaline rocks have a restricted range in 87Sr/86Sr and 143Nd/144Nd ratios ranging from 0.7033 to 0.7044 and from 0.51275 to 0.51285, respectively. Lead isotope compositions (206Pb/204Pb: 19.21-19.65; 207Pb/204Pb: 15.62-15.67; 208Pb/204Pb: 39.10-39.46) of the alkaline rocks are within the range of most OIB in which the higher values approach the composition of the European Asthenospheric Reservoir (EAR). The correlation between Sr and Nd isotopes and trace element constraints (Ce/Pb; Nb/U) indicates that for some samples interaction with crustal rocks during

  2. Czochralski growth of the mixed halides BaBrCl and BaBrCl:Eu

    NASA Astrophysics Data System (ADS)

    Yan, Z.; Shalapska, T.; Bourret, E. D.

    2016-02-01

    We present results from the growth of BaBrCl and BaBrCl:Eu single crystals, using the Czochralski method. Cubic inch crack-free crystals of both undoped and 5% Eu doped BaBrCl were obtained. The BaBr2-BaCl2 phase diagram was acquired by differential thermal analysis revealing that the system forms a solid solution at all concentrations with no significant separation between the solidus and liquidus curves. Details of the Czochralski process used to prevent cracking are presented. The scintillation performance of the Czochralski grown crystals is presented.

  3. Effective LA-ICP-MS dating of common-Pb bearing accessory minerals with new data reduction schemes in Iolite

    NASA Astrophysics Data System (ADS)

    Kamber, Balz S.; Chew, David M.; Petrus, Joseph A.

    2014-05-01

    Compared to non-destructive geochemical analyses, LA-ICP-MS consumes ca. 0.1 μm of material per ablation pulse. It is therefore to be expected that the combined analyses of ca. 200 pulses will encounter geochemical and isotopic complexities in all but the most perfect minerals. Experienced LA-ICP-MS analysts spot down-hole complexities and choose signal integration areas accordingly. In U-Pb geochronology, the task of signal integration choice is complex as the analyst wants to avoid areas of common Pb and Pb-loss and separate true (concordant) age complexity. Petrus and Kamber (2012) developed VizualAge as a tool for reducing and visualising, in real time, U-Pb geochronology data obtained by LA-ICP-MS as an add-on for the freely available U-Pb geochronology data reduction scheme of Paton et al. (2010) in Iolite. The most important feature of VizualAge is its ability to display a live concordia diagram, allowing users to inspect the data of a signal on a concordia diagram as the integration area it is being adjusted, thus providing immediate visual feedback regarding discordance, uncertainty, and common lead for different regions of the signal. It can also be used to construct histograms and probability distributions, standard and Tera-Wasserburg style concordia diagrams, as well as 3D U-Th-Pb and total U-Pb concordia diagrams. More recently, Chew et al. (2014) presented a new data reduction scheme (VizualAge_UcomPbine) with much improved common Pb correction functionality. Common Pb is a problem for many U-bearing accessory minerals and an under-appreciated difficulty is the potential presence of (possibly unevenly distributed) common Pb in calibration standards, introducing systematic inaccuracy into entire datasets. One key feature of the new method is that it can correct for variable amounts of common Pb in any U-Pb accessory mineral standard as long as the standard is concordant in the U/Pb (and Th/Pb) systems after common Pb correction. Common Pb correction

  4. Chemically induced renormalization phenomena in Pb-based relaxor ferroelectrics under high pressure

    NASA Astrophysics Data System (ADS)

    Mihailova, B.; Waeselmann, N.; Maier, B. J.; Angel, R. J.; Prüßmann, T.; Paulmann, C.; Gospodinov, M.; Bismayer, U.

    2013-03-01

    The pressure-induced phase transition sequence in PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN) heavily doped with homo- and heterovalent cations on the A- or B-site of the perovskite-type structure (ABO3) was analysed by in situ synchrotron x-ray diffraction and Raman spectroscopy up to pressures of 25 GPa. We focused on the structural phenomena occurring above the first pressure-induced phase transition at pc1 from a relaxor state to a non-polar rhombohedral phase with antiphase tilting of the BO6 octahedra. The samples studied were PST doped with Nb5+ and Sn4+ on the B-site, PST doped with Ba2+ and La3+ on the A-site and PSN doped with Sr2+ and La3+ on the A-site. All of them exhibit a second pressure-induced phase transition at pc2, similar to pure PST and PSN. The second transition involves the development of either order of antiparallel Pb2+ displacements and complementary a+b-b- octahedral tilts, or a-b-b- (0 ≤ a < b) tilting alone. As in pure PST and PSN, the second phase transition is preceded by the occurrence of unequal octahedral tilts on the local scale. The substitution of Nb5+ for Ta5+ as well as the coupled substitution of Sn4+ for Sc3+ + Ta5+ on the octahedral B sites increases the second critical pressure. The doping by Nb5+ also reduces the length of coherence of antipolar Pb2+ order developed at pc2. The isovalent substitution of the larger Ba2+ for Pb2+ on the A-site suppresses the antipolar Pb2+ order due to the induced local elastic stresses and thus significantly increases pc2. The substitution of smaller cations for Pb2+ on the A-site generally favours the development of long-range order of antiparallel Pb2+ displacements because of the chemically enhanced a-a-a- octahedral tilts. However, this ordering is less when the dopant is aliovalent, due to the charge imbalance on the A-site. For all of the relaxors studied here, the dynamic compressibility estimated from the pressure derivative of the wavenumber of the soft mode associated with

  5. Bacteria mediated dissolution of pyromorphite Pb5(PO4)3Cl in presence of Pseudomonas putida bacteria - an effect on Pb remobilization in the environment

    NASA Astrophysics Data System (ADS)

    Flis, Justyna; Manecki, Maciej; Merkel, Broder J.; Latowski, Dariusz

    2010-05-01

    The objective of the study was to determine the mechanisms of microbially enhanced dissolution of lead phosphate-pyromorphite Pb5(PO4)3Cl). Contrary to the current literature, the results of our experiments indicate a great potential for Pb remobilization in the environment by an aerobic microorganism acquiring phosphates. Broad knowledge exists about the role of Pb-apatites in regulating the behavior and the bioavailability of Pb in soils and wastewater. In situ Pb immobilization is one of the methods now routinely applied for the reclamation of Pb-contaminated soils, including shallow unconfined aquifers (Magalhaes & Silva, 2003; Magalhaes, 2002; Ma et al. 1993). This method is based on the principle that aqueous phosphates added to soil pore solutions form a very stable (insoluble) mineral pyromorphite (Pb-apatite) Pb5(PO4)3Cl. Bioavailability of aqueous Pb is thus minimized due to the very low solubility and the high thermodynamic stability of pyromorphite (Flis, 2007; Nriagu, 1974). Several reports have examined the ability of different bacterial species including Pseudomonas to solubilise insoluble inorganic phosphate compounds for example apatites (Welch et al., 2002; Maurice et al., 1999; Rodriguez and Fraga, 1999 ). Various species of Pseudomonas genera are encountered as common inhabitants of soils and wastes in the industrial areas under strong pollution influence. To date, there has not been any published evidence of microbial dissolution of pyromorphite. The major objective of the project was to study Pseudomonas putida growth in the presence of Pb-apatite (Pb5(PO4)3Cl) as the sole source of phosphate. It was to test the hypothesis that in the phosphate deficient environment bacteria are able to actively scavenge for P from the Pb-apatite which results in remobilization of Pb in the environment. The bacteria growth was investigated at 22oC. Commercially available Pseudomonas putida strain was used throughout. The experiment and its controls were run in

  6. On Ba(+) production in the CRIT 2 experiment

    NASA Astrophysics Data System (ADS)

    Liou, K.; Torbert, R. B.

    1995-04-01

    Analysis of partical data from the CRIT 2 experiment, studying Alfven's critical ionization velocity (CIV) effect, shows that the density of newly created ions (presumably Ba(+) from the shaped-charge beam) is consistent with the increase in total plasma density measured by the independent RF plasma probe on board (Swenson et al., 1990) at the most active time period. We model this ion production using the measured electron flux data and the neutral barium model of Stenbaek-Nielsen et al. (1990a). To identify the main source mechanisms which may contribute most to the barium ionization, a simple model for the barium ion density at the payload location is developed based on Liouvilles theorem. We estimate that the electron impact ionization is responsible for 90% of the barium ion production observed by CRIT 2 in the first release and up to 45% in the second release. By employing a two-state approximation calculation (Rapp and Francis, 1962), the Ba-O(+) charge exchange cross section is found to range from about 2.0 X 10(exp -17) sq cm at a velocity of 4 km/s to 2.0 X 10(exp -15) sq cm at a velocity of 20 km/s. This result suggests that the Ba-O(+) charge exchange is probably dominant among all the non-CIV ionization processes. By considering the charge exchange process in our density model, the barrium ion densities are calculated for the two releases on CRIT II. The comparison between the model results and the observed data is found to be resonably consistent if the cross sections, as calculated above, are multiplied by 0.3 for the first release and 1.0 for the second release. Our result suggests that the charge exchange process could be the most important non-CIV ionization mechanism in the CRIT II experiment and it should be considered carefully case by case in CIV experiments.

  7. Processing, electrical and microwave properties of sputtered Tl-Ca-Ba-Cu-O superconducting thin films

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Kapoor, V. J.; Chorey, C. M.; Bhasin, K. B.

    1993-01-01

    A reproducible fabrication process has been established for TlCaBaCuO thin films on LaAlO3 substrates by RF magnetron sputtering and post-deposition processing methods. Electrical transport properties of the thin films were measured on patterned four-probe test devices. Microwave properties of the films were obtained from unloaded Q measurements of all-superconducting ring resonators. This paper describes the processing, electrical and microwave properties of Tl2Ca1Ba2Cu2O(x) 2122-plane phase thin films.

  8. Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments

    NASA Astrophysics Data System (ADS)

    Ning-jing, Hu; Peng, Huang; Hui, Zhang; Ai-mei, Zhu; Ji-hua, Liu; Jun, Zhang; Lian-hua, He

    2015-10-01

    To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (204Pb, 206Pb, 207Pb, and 208