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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. High-Temperature Vaporization Behavior of Oxides II. Oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg

    NASA Astrophysics Data System (ADS)

    Lamoreaux, R. H.; Hildenbrand, D. L.; Brewer, L.

    1987-07-01

    In order to assess the high-temperature vaporization behavior and equilibrium gas phase compositions over the condensed oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Zn, Cd, and Hg, the relevant thermodynamic and molecular constant data have been compiled and critically evaluated. Selected values of the Gibbs energy functions of condensed and vapor phases are given in the form of equations valid over wide temperature ranges, along with the standard entropies and enthalpies of formation. These data were used to generate plots of equilibrium partial pressures of vapor species as functions of temperature for representative environmental conditions ranging from reducing to oxidizing. The calculated partial pressures and compositions agree, for the most part, with experimental results obtained under comparable conditions. Maximum vaporization rates have been calculated using the Hertz-Knudsen equation. Literature references are given.

  4. Superconductivity in Ba(Pb,Bi,Sb)O 3, Ba(Pb,Bi,Te)O 3 and (Ba,La) (Pb,Bi,Tl)O 3 systems

    NASA Astrophysics Data System (ADS)

    Nagarajan, R.; Vasanthacharya, N. Y.; Gopalakrishnan, J.; Rao, C. N. R.

    1991-02-01

    It is possible to substitute Bi in the superconducting BaPb 0.75Bi 0.25O 3 by Sb or Te without destroying the superconductivity. With Sb, a continuous series of solid solutions BaPb 0.75Bi 0.25-ySb yO 3 (0 ⩽ y ⩽ 0.25) exists, while with Te, perovskite BaPb 0.75Bi 0.25-yTe yO 3 exists only upto y = 0.15. With increasing substitution by Sb or Te, T c decreases continously in both the systems. Superconductivity with a maximum T c of 8K is found in Ba 0.9La 0.1Pb 0.9-yBi yTl 0.1O 3 for y = 0.25.

  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. Effect of conductive BaPbO3 electrode on the structural and dielectric properties of (Pb,Ba)ZrO3 films

    NASA Astrophysics Data System (ADS)

    Wu, Lin-Jung; Wu, Jenn-Ming

    2007-08-01

    Highly (1 1 1)-oriented (Pb,Ba)ZrO3 (PBZ) thin films were deposited on BaPbO3(BPO) electrode at different deposition temperatures and different thicknesses. As the deposition temperature increased, the dielectric constant and tunability increased from 150 and 4% to 500 and 56%, respectively. A current transient peak observed prior to dielectric degradation can be related to oxygen vacancy migration (redistribution) with space-charge-limited current transient or modulation of the electric conductivity. We infer that an interfacial layer lying between the PBZ and BPO effectively increases the oxygen vacancy (density ~1020 cm-3) mobility by Pb4+ diffusing into the PBZ films.

  7. Thickness-dependent dielectric properties of nanoscale Pt/(Pb,Ba)ZrO 3/BaPbO 3 capacitors

    NASA Astrophysics Data System (ADS)

    Wu, Lin-Jung; Wu, Jenn-Ming

    2007-10-01

    Lead barium zirconate (PBZ) thin films on BaPbO 3(BPO)/Pt/Ti/SiO 2/Si substrates have been prepared by rf-magnetron sputtering at 500 °C. The orientation of PBZ film changes from random to (1 1 1)-prefer oriented when the thickness increases. The grain size increases with increasing PBZ thickness. The dielectric properties are greatly suppressed when the thickness of dielectrics decreases. The dielectric constant and tunability decrease from 536% and 49.1% to 205% and 22.7%, respectively, when the thickness of PBZ decreases from 323 to 62 nm. The origins of the collapsed dielectric behavior are discussed. The variation of dielectric properties with film thickness can be interpreted by (a) antiferroelectric layer at PBZ/BPO interface, (b) dead layer at Pt/PBZ interface, and (c) grain boundary dead layers.

  8. 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.

  9. 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.

  10. Ferroelectric BaPbO3/PbZr0.53Ti0.47/BaPbO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Liang, Chun-Sheng; Wu, Jenn-Ming; Chang, Ming-Chu

    2002-11-01

    BaPbO3 (BPO)/PbZr0.53Ti0.47 (PZT)/BPO heterostructures were fabricated by combining the sol-gel and rf-magnetron sputtering techniques. Experimental results indicate that the BPO bottom electrodes effectively prevent the formation of the rosette structure of PZT, producing smooth surfaces. Additionally, ferroelectric, fatigue, and leakage current properties were markedly improved when both the top and the bottom electrodes were changed from Pt to BPO. These improvements are due to a superior electrode/ferroelectric interface. BPO is better than Pt and other oxide electrodes for use in PZT ferroelectric capacitors due to its remarkably improved properties and quite low growth temperature.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. Pb, Sr and Ba calix[6]arene hexacarboxylic acid octahedral complexation: a dramatic effect of dealkylation

    PubMed Central

    Adhikari, Birendra Babu; To, Cuong-Alexander; Iwasawa, Tetsuo; Schramm, Michael P.

    2015-01-01

    Calix[6]arene hexacarboxylic acid binds instantly and with low symmetry to Pb, Sr and Ba. Later a highly symmetric up-down alternating conformation emerges. The solution structures are identical to their p-tert-butylcalix[6]arene hexacarboxylic acid counterparts. With either receptor an octahedral cage is formed around the metal. The transformation from low to high symmetry however proceeds at significantly faster rates for the de-t-butylated host. PMID:26752941

  17. Adsorption interaction between Al-5% Pb alloy and water

    NASA Astrophysics Data System (ADS)

    Ryabina, A. V.; Shevchenko, V. G.

    2016-10-01

    The adsorption and structural features of Al-5% Pb alloy powder before and after reacting with water are analyzed. Results from studying the morphology and phase composition of the oxidation products are presented, and the specific surface area and porosity of the powders are calculated. It is shown experimentally that water treatment of Al-5% Pb alloy powder even at room temperature leads to the formation of new phases and affects the powder's morphology. It is established that a major role in the properties of the watertreated powders is played by nanopores that form between crystallites on a particle's surface during waterinduced oxidation and subsequent thermal dehydration.

  18. 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.

  19. RF-Magnetron Sputtered Conductive Perovskite BaPbO3 Films

    NASA Astrophysics Data System (ADS)

    Luo, Yih-Rong; Wu, Jenn-Ming

    2003-01-01

    The crystallinity, chemical bonding, and electrical properties of BaPbO3 (BPO) thin films prepared by rf-magnetron sputtering on SiO2/Si substrates were investigated. The working pressure and the Ar/O2 ratio during sputtering are two of the most important factors that influence the characteristics of the prepared BPO films. Both increasing working pressure and increasing Ar/O2 ratio enhanced the crystallization of the perovskite BPO phase and yielded films with low resistivity. Sputtering in an environment with a working pressure of 80 mTorr and Ar/O2 = 90/10 at 350°C gave deposited BPO films with a low resistivity of 0.9 × 10-3 Ωcm, and a high carrier concentration of 8.3 × 1020 electrons/cm3, which values were almost equal to those of the bulk BaPbO3. X-ray photoelectron spectroscopy (XPS) revealed that Pb4+ ions were formed in the BPO films as the working pressure and the Ar/O2 ratio were increased, enhancing the crystallization of the perovskite BPO phase to yield films of lower resistivity.

  20. 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.

  1. BaPbO3 perovskite electrode for lead zirconate titanate ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Luo, Yih-Rong; Wu, Jenn-Ming

    2001-11-01

    BaPbO3 (BPO) films were prepared by rf-magnetron sputtering at temperatures as low as 350 °C. These films possessed low electrical resistivity of 1.4×10-3 Ω cm, which is appropriate for electrodes. The BPO electrode has an advantage over a Pt electrode in that it lowers the crystallization temperature of Pb(Zr0.53Ti0.47)O3 (PZT) films from 600 to 550 °C. The coercive fields of the PZT films deposited on a BPO/Pt electrode are significantly lower than those deposited on the Pt electrode, but the remanent polarization remained essentially unchanged. The BPO electrode also improved the fatigue resistance and decreased the leakage current of the PZT films deposited.

  2. 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

  3. 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.

  4. 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.

  5. 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}.

  6. Generalized large-scale synthesis of MTiO{sub 3} (M = Ba, Sr, Pb) nanocrystals

    SciTech Connect

    An Changhua Liu Chunying; Wang Shutao; Liu Yunqi

    2008-04-01

    A general hydrothermal synthesis technique has been developed for the large-scale preparation of perovskite oxide nanocrystals of BaTiO{sub 3} (BT), SrTiO{sub 3} (ST) and PbTiO{sub 3} (PT). X-ray diffraction pattern (XRD) and Raman spectrum revealed that tetragonal BT was successfully synthesized. The obtained ST and PT were in cubic and tetragonal phase, respectively. Scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM) images showed that all of the products were on nanometer scale. These nanocrystals should provide an ideal candidate for fundamental studies of nanoscale ferroelectricity, piezoelectricity, and paraelectricity. Meanwhile, the synthetic strategy may be easily extended to prepare other nearly monodispersed nanocrystals of perovskite oxides or solid solutions. The relative studies are in progress and will be reported later.

  7. 26Al- 26Mg and 207Pb- 206Pb systematics of Allende CAIs: Canonical solar initial 26Al/ 27Al ratio reinstated

    NASA Astrophysics Data System (ADS)

    Jacobsen, Benjamin; Yin, Qing-zhu; Moynier, Frederic; Amelin, Yuri; Krot, Alexander N.; Nagashima, Kazuhide; Hutcheon, Ian D.; Palme, Herbert

    2008-07-01

    The precise knowledge of the initial 26Al/ 27Al ratio [( 26Al/ 27Al) 0] is crucial if we are to use the very first solid objects formed in our Solar System, calcium-aluminum-rich inclusions (CAIs) as the "time zero" age-anchor and guide future work with other short-lived radio-chronometers in the early Solar System, as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation. New high-precision multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) measurements of 27Al/ 24Mg ratios and Mg-isotopic compositions of nine whole-rock CAIs (six mineralogically characterized fragments and three micro-drilled inclusions) from the CV carbonaceous chondrite, Allende yield a well-defined 26Al- 26Mg fossil isochron with an ( 26Al/ 27Al) 0 of (5.23 ± 0.13) × 10 - 5 . Internal mineral isochrons obtained for three of these CAIs ( A44A, AJEF, and A43) are consistent with the whole-rock CAI isochron. The mineral isochron of AJEF with ( 26Al/ 27Al) 0 = (4.96 ± 0.25) × 10 - 5 , anchored to our precisely determined absolute 207Pb- 206Pb age of 4567.60 ± 0.36 Ma for the same mineral separates, reinstate the "canonical" ( 26Al/ 27Al) 0 of 5 × 10 - 5 for the early Solar System. The uncertainty in ( 26Al/ 27Al) 0 corresponds to a maximum time span of ± 20 Ka (thousand years), suggesting that the Allende CAI formation events were culminated within this time span. Although all Allende CAIs studied experienced multistage formation history, including melting and evaporation in the solar nebula and post-crystallization alteration likely on the asteroidal parent body, the 26Al- 26Mg and U-Pb-isotopic systematics of the mineral separates and bulk CAIs behaved largely as closed-system since their formation. Our data do not support the "supra-canonical" 26Al/ 27Al ratio of individual minerals or their mixtures in CV CAIs, suggesting that the supra-canonical 26Al/ 27Al ratio in the CV CAIs may have resulted from post

  8. High-resolution neutron powder diffraction study on the phase transitions in BaPbO{sub 3}

    SciTech Connect

    Fu, W.T. Visser, D.; Knight, K.S.; IJdo, D.J.W.

    2007-05-15

    Phase transitions that occurred in perovskite BaPbO{sub 3} have been investigated using high-resolution time-of-flight neutron powder diffraction. The structure at room temperature is orthorhombic (space group Imma), which is derived from the cubic aristotype by tilting the PbO{sub 6} octahedra around the two-fold axis (tilt system a {sup 0} b {sup -} b {sup -}). The orthorhombic structure shows anisotropic line broadening attributed to the presence of micro twins. At above about 573 K, BaPbO{sub 3} undergoes a discontinuous phase transition to a tetragonal structure (space group I4/mcm) with the tilting of the PbO{sub 6} octahedra being about the four-fold axis of the cubic aristotype (tilt system a {sup 0} a {sup 0} c {sup -}). With further increasing the temperature, BaPbO{sub 3} experiences a continuous phase transition to a simple cubic structure (space group Pm3-barm) at above about 673 K. The later phase transition is characterised by a critical exponent of {beta}=0.36, depicted by the three-dimensional Heisenberg universality class. The earlier reported Imma{sup {yields}}I2/m phase transition above room temperature has not been observed. - Graphical abstract: Temperature dependence of the octahedral tilting angles in BaPbO{sub 3}. The continuous line in tetragonal phase region is the fit to the expression: {phi}=A(T {sub c}-T) {sup {beta}} with the fitted values of T {sub c}=658(1) K, {beta}=0.36(2) and A=1.1(1). The shaded area indicates the possible two-phase region.

  9. NOx Uptake Mechanism on Pt/BaO/Al2O3 Catalysts

    SciTech Connect

    Kwak, Ja Hun; Kim, Do Heui; Szailer, Tamas; Peden, Charles HF; Szanyi, Janos

    2006-11-01

    The NOx adsorption mechanism on Pt/BaO/Al2O3 catalysts was investigated by performing NOx storage/reduction cycles, NO2 adsorption and NO + O2 adsorption on 2%Pt/(x)BaO/Al2O3 (x = 2, 8 and 20 wt%) catalysts. NOx uptake profiles on 2%Pt/20%BaO/Al2O3 at 523 K show complete uptake behavior for almost 5 min, and then the NOx level starts gradually increasing with time and it reaches 75% of the inlet NOx concentration after 30 min time-on-stream. Although this catalyst shows fairly high NOx conversion at 523 K, only ~ 2.4 wt% out of 20 wt% BaO is converted to Ba(NO3)2. Adsorption studies by using NO2 and NO + O2 suggest two different NOx adsorption mechanisms. The NO2 uptake profile on 2%Pt/20%BaO/Al2O3 shows the absence of a complete NOx uptake period at the beginning of adsorption and the overall NOx uptake is controlled by the gas-solid equilibrium between NO2 and BaO/Ba(NO3)2 phase. When we use NO + O2, complete initial NOx uptake occurs and the time it takes to convert ~ 4 % of BaO to Ba(NO3)2 is independent of the NO concentration. These NOx uptake characteristics suggest that the NO + O2 reaction on the surface of Pt particles produces NO2 that is subsequently transferred to the neighboring BaO phase by spill over. At the beginning of the NOx uptake, this spill-over process is very fast and so it is able to provide complete NOx storage. However, the NOx uptake by this mechanism slows down as BaO in the vicinity of Pt particles are converted to Ba(NO3)2. The formation of Ba(NO3)2 around the Pt particles results in the development of a diffusion barrier for NO2, and increases the probability of NO2 desorption and consequently, the beginning of NOx slip. As NOx uptake by NO2 spill-over mechanism slows down due to the diffusion barrier formation, the rate and extent of NO2 uptake are determined by the diffusion rate of nitrate ions into the BaO bulk, which, in turn, is determined by the gas phase NO2 concentration.

  10. Characterization of low-temperature-grown epitaxial BaPbO 3 and Pb(Zr,Ti)O 3/BaPbO 3 films on SrTiO 3 substrates

    NASA Astrophysics Data System (ADS)

    Liang, Chun-Sheng; Lee, Yi-Hsien; Wu, Jenn-Ming

    2005-10-01

    The epitaxial BaPbO 3 (BPO) and Pb(Zr,Ti)O 3 (PZT)/BPO films were grown on (0 0 1)- and (1 1 1)-oriented SrTiO 3 (STO) substrates by RF-magnetron sputtering. With the self-template of BPO buffer layer (deposited at 650 °C), BPO main layer and PZT films can be epitaxially grown at temperatures as low as 350 and 475 °C, respectively. The (0 0 1)-oriented BPO film showed a rougher surface and higher work function compared to the (2 2 2)-oriented film. The crystallinity and resistivity of BPO films were independent of their orientation. However, the crystallinity of PZT deposited afterward depends greatly on the orientation of BPO. The crystallinity of PZT deposited on BPO/STO(1 1 1) is significantly higher than that on BPO/STO(0 0 1). The remnant polarization, coercive field, dielectric constant, and resistivity of the PZT/BPO/STO(1 1 1) heterostructure were 35.54 μC/cm 2, 102.67 kV/cm, 242, and 1.1-1.6×10 11 Ω cm, respectively, which are much better than those of the PZT/BPO/STO(0 0 1) heterostructures.

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

    PubMed

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

    2015-11-18

    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 ΔT 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. PMID:26490797

  12. 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.

  13. Studies on Structural and Dielectric Properties of ABi4Ti4O15 (A = Ba, Sr & Pb) Ceramics

    NASA Astrophysics Data System (ADS)

    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° C), Stable piezoelectric response and excellent dielectric properties. The compounds ABi4Ti4O15 (A = Ba, Sr & Pb) belongs to Aurivillius family (n = 4) in which BaBi4Ti4O15 crystallizes in tetragonal I4/mmm space group, Sr Bi4Ti4O15 and PbBi4Ti4O15 crystallizes in orthorhombic space group A21am. In the present work ABi4Ti4O15 (A = Ba, Sr & Pb) ceramic samples are prepared through the solid state reaction by conventional mixed oxides by calcination at high temperature. Dielectric constant (ɛ'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 (Tc, K) and then decreases.

  14. Effect of Pb doping on the structure of HgBa 2CuO 4+δ single crystals

    NASA Astrophysics Data System (ADS)

    Schwer, H.; Kopnin, E.; Molinski, R.; Jun, J.; Meijer, G. I.; Conder, K.; Rossel, C.; Karpinski, J.

    1997-02-01

    X-ray structure analyses were performed with HgBa 2CuO 4+δ and Hg 1- xPb xBa 2CuO 4+δ single crystals. The onset of the superconducting transition of the crystals ranges from 78-92 K. Hg-1201 crystallizes with space group P4/mmm and has lattice pafameters a = 3.8907(2) Å and c = 9.556(1) Å. The structure was refined to R = 0.023 (wR2 = 0.036) in the ideal 1201 type with an excess oxygen content of 6(2)% and an occupancy of 97% at the Hg site. Pb-doping decreases the lattice parameters to a = 3.8836(2) Å and c = 9.553(1) Å, and the refinement converged at R = 0.042 (wR2 = 0.088). Pb atoms are shifted by 0.5 Å to (0.14, 0, 0) and the excess oxygen atom O(3) by 0.45 Å to (0.38, {1}/{2}, 0). It has not a well defined position in the lattice, but is distributed randomly in a ring-like configuration around the ( {1}/{2}, {1}/{2}, 0) site, supporting a Pb clustering model. Rather high anisotropic temperature factors U11 and U22 of Hg and apical O(1) atoms are observed, which are also present in higher members of the Hg(Pb)-12( n - 1) n series. They are discussed in terms of corrugated OHgO bonds. Comparison with other structure refinements of 1201 shows a correlation of the transition temperature with the position of the Ba atom, which seems to be a good indicator for the hole doping evel in 1201.

  15. 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.

  16. 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.

  17. 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.

  18. Thermodynamic stability of radiogenic Ba in CsAlSi2O6 pollucite

    NASA Astrophysics Data System (ADS)

    Jaffe, John; van Ginhoven, Renée; Jiang, Weilin

    2013-03-01

    Pollucite, a zeolite-like nanoporous aluminosilicate structure with nominal composition CsAlSi2O6, has been suggested as a nuclear waste storage form for fission-product radioactive isotopes of cesium, especially 137Cs. One factor affecting the long-term stability of this waste form is the valence change associated with the beta decay that converts Cs into barium. We have used first-principles density functional total energy calculations to evaluate the thermodynamic stability of pollucite with Ba replacing Cs at regular lattice sites with respect to the precipitation of Ba, Cs or their oxides. We included small clusters of substitutional BaCs as well as localized complexes of BaCs with compensating electron donor defects, specifically Cs vacancies and interstitial oxygen. We conclude that Cs-Ba pollucite is thermodynamically stable against precipitation of Cs or its oxide, but that partial precipitation of Ba or BaO may be thermodynamically favored under some conditions. Even this change may be kinetically limited, however. Fuel Cycle Research and Development, U.S. Department of Energy Waste Form Campaign

  19. 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.

  20. 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.

  1. 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

  2. Pb-DOPING Effects in Hg1-xPbxBa2Ca2Cu3O8+δ

    NASA Astrophysics Data System (ADS)

    Xue, Y. Y.; Huang, Z. J.; Qiu, X. D.; Beauvais, L.; Zhang, X. N.; Sun, Y. Y.; Meng, R.; Chu, C. W.

    Samples with a nominal composition of Hg1-xPbxBa2Ca2Cu3O8+δ (x~0.1, 0.2, and 0.3) have been synthesized and characterized. The Pb-doping promotes the formation of the three CuO2-layer compound Hg1-xPbxBa2Ca2Cu3O8+δ, and reduces the release of Hg vapor at the synthesis temperature. The intergrain electric coupling is also significantly enhanced by the doping, resulting in lower normal-state resistivity and higher intergrain critical current density. The carrier concentration of the as-synthesized samples increases with the increase of x, ranging from underdoped (x~0) to overdoped (x≥0.2).

  3. Giant thermal vibrations in the framework compounds Ba1 -xSrxAl2O4

    NASA Astrophysics Data System (ADS)

    Kawaguchi, S.; Ishii, Y.; Tanaka, E.; Tsukasaki, H.; Kubota, Y.; Mori, S.

    2016-08-01

    Synchrotron x-ray diffraction experiments were performed on the network compounds Ba1 -xSrxAl2O4 at temperatures between 15 and 800 K. The ferroelectric phase of the parent BaAl2O4 is largely suppressed by substituting a small amount of Sr for Ba and disappears for x ≥0.1 . Structural refinements reveal that the isotropic atomic displacement parameter Biso in the bridging oxygen atom is largely independent of temperature and retains an anomalously large value in the adjacent paraelectric phase even at the lowest temperature. The Biso systematically increases as x increases, exhibiting an especially large value for x =0.5 . According to previous electron diffraction experiments for Ba1 -xSrxAl2O4 with x ≥0.1 , strong thermal diffuse scattering occurs at two reciprocal points relating to two distinct soft modes at the M and K points over a wide range of temperatures below 800 K [Y. Ishii et al., Sci. Rep. 6, 19154 (2016), 10.1038/srep19154]. Although the latter mode disappears at approximately 200 K, the former does not condense, at least down to 100 K. The anomalously large Biso observed in this study is ascribed to these soft modes existing in a wide temperature range.

  4. Compositional controls on the partitioning of U, Th, Ba, Pb, SR and Zr between clinopyroxene and haplobasaltic melts: Implications for uranium series disequilibria in basalts

    NASA Astrophysics Data System (ADS)

    Lundstrom, C. C.; Shaw, H. F.; Ryerson, F. J.; Phinney, D. L.; Gill, J. B.; Williams, Q.

    1994-12-01

    The partitioning of U, Th, Pb, Sr, Zr and Ba between coexisting chromian diopsides and haplobasaltic liquids at oxygen fugacities between the iron-wustite buffer and air at 1285 C has been characterized using secondary ion mass spectrometry. The partition coefficients for Th, U and Zr show a strong dependence on the Al and Na content of the clinopyroxene. A good correlation between Al-IV and DTh exists for all recent Th partitioning studies, providing a simple explanation for the two order of magnitude variation in DTh observed in this and previous studies. Because mantle clinopyroxenes generally have greater than 5 wt% Al2O3, we suggest that the relevant partition coefficients for U and Th are between 0.01 and 0.02. While variations in Al and Na in clinopyroxene affect the absolute value of the Th and U partition coefficients, they have no effect on their ratio, DTh/DU. Our results reinforce the inference that equilibrium partioning of U and Th between clinopyroxene and melt cannot explain the observed Th-230 excesses in basalts. Indeed, under the oxygen fugacities relevant to mid-ocean ridge basalts (MORB) petrogenesis, clinopyroxene has little ability to fractionate U from Th (DTh/D(sub U less than 2), implying that chemical disequilibrium between melt and wall rock during transport is not required to preserve Th-230 excess generated in the garnet stability field. If the Ba partition coefficient serves as an analog for Ra and the partition coefficient of U(5+) serves as an analog for Pa(5+), then Ra-226 and Pa-231 excesses can be generated by clinopyroxene-melt partitioning. Using compositionally dependent partition coefficients, a melting model is used to show that equilibrium porous flow can explain variation in uranium series activities from the East Pacific Rise by varying the depth of melting.

  5. Ac Impedance Spectroscopic Studies on Li2xPb2xBaP2O7

    NASA Astrophysics Data System (ADS)

    Vijayakumar, M.; Selvasekarapandian, S.

    2002-12-01

    The complex diphosphate (P2O7)4- ions have been used as a building blocks in wide variety of crystal phases for a wide spectrum of physical and chemical properties. Lithium barium diphsophate doped with lead {Li2-xPb2xBaP2O7 (x = 0, 0.2 & 0.4)} has been prepared by solid state reaction method The conductivity is found to be decreasing with the doping of lead. The lithium ion dynamics parameters such as hopping frequency and relaxation frequency were calculated from the frequency dependent conductivity and modulus analysis.

  6. Enhanced Dielectric Properties of [Pb(Mg1/3Nb2/3)O3]0.9-PbTiO3]0.1 Thin Films Grown on BaPbO3 Perovskite Electrode

    NASA Astrophysics Data System (ADS)

    Ho, Sut Kam; Hau, Fei Fei; Wong, Kin Hung

    2004-11-01

    Polycrystalline and epitaxial [Pb(Mg1/3Nb2/3)O3]0.9-[PbTiO3]0.1 (PMN-PT) thin films were prepared by pulsed laser deposition on BaPbO3 (BPO) and La0.7Sr0.3MnO3 (LSMO) oxide electrodes. In comparison, the epitaxial films show higher dielectric constant and the polycrystalline films exhibit lower dielectric loss and smaller leakage current. It is also found that the use of lead based BPO electrodes helps to raise the dielectric constant of the PMN-PT layer by 30%, and to reduce the dielectric leakage by as much as three orders of magnitude. Our results have clearly demonstrated the superiority of using lead based electrodes for growing lead based dielectrics.

  7. Synthesis, crystal and electronic structures of the new Zintl phases Ba3Al3Pn5 (Pn = P, As) and Ba3Ga3P5.

    PubMed

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

    2013-01-01

    The new Zintl compounds Ba(3)Al(3)P(5), Ba(3)Al(3)As(5,) and Ba(3)Ga(3)P(5) have been synthesized using molten metal fluxes. They are isoelectronic and isotypic, crystallizing with a novel rhombohedral structure type in the space group R3c with unit cell constants a = 14.5886(9) Å, c = 28.990(3) Å for Ba(3)Al(3)P(5), a = 14.613(3) Å, c = 28.884(8) Å for Ba(3)Ga(3)P(5), and a = 14.9727(13) Å, c = 29.689(4) Å for Ba(3)Al(3)As(5), respectively. The structures are based on TrPn(4) (Tr = Al, Ga; Pn = P, As) tetrahedra that share both edges and corners, leading to intricate arrangements embodied in the [Tr(4)Pn(9)](15-) and [Tr(3)Pn(6)](9-) strands, interconnected by dimeric [Tr(2)Pn(6)](12-) units. The Ba(2+) cations reside within cylindrical channels within the polyanionic framework and provide the valence electrons needed for Tr-Pn covalent bonding. In spite of the large and complex structure, there are no homoatomic Tr-Tr or Pn-Pn interactions, hence, the structures can be readily rationalized in the context of the Zintl-Klemm formalism as follows [Ba(2+)](3)[Tr(3+)](3)[Pn(3-)](5); calculations on their electronic band-structures confirm this reasoning and reveal about 1.4-1.9 eV energy band gaps, that is, semiconducting behavior. Structural parallels with other known Zintl compounds are also presented.

  8. 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

  9. 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.

  10. 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.

  11. Transformation of Al2O3 to LiAlO2 in Pb-17Li at 800?C

    SciTech Connect

    Pint, Bruce A; More, Karren Leslie

    2008-01-01

    A FeCrAl substrate was pre-oxidized for 2 h at 1000 C to thermally grow an external Al{sub 2}O{sub 3} scale and then isothermally exposed to Pb-17 at.% Li for 1000 h at 800 C to determine if this layer would protect the underlying alloy from dissolution. After exposure, a small mass gain was measured, indicating that the layer did inhibit dissolution. However, characterization of the external layer determined that it had transformed to LiAlO{sub 2} with an increased thickness and a much larger grain size than the original layer. This observation has implications for the use of Al{sub 2}O{sub 3} as a permeation barrier in Pb-Li cooled fusion blanket systems.

  12. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Hoelzer, David T.

    2016-10-01

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb-17Li and He) blanket concept requires improved Pb-17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), (3) Y2O3 + HfO2 (125YH), and (4) Y2O3 + TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb-17Li for 1000 h at 700 °C. Alloys showed promising compatibility with Pb-17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (∼1 at.%) in Al content beneath the oxide scale was observed in all four ODS alloys, which extended 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb-17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

  13. 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.

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

    DOE PAGES

    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

  15. 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.

  16. Preparation and Characterization of BaTiO3-PbZrTiO3 Coating for Pyroelectric Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Raghavendra, R. M.; Praneeth, K. P. S. S.; Dutta, Soma

    2016-08-01

    Harvesting energy from waste heat is a promising field of research as there are significant energy recovery opportunities from various waste thermal energy sources. The present study reports pyroelectric energy harvesting using thick film prepared from a (x)BaTiO3-(1 - x)PbZr0.52Ti0.48O3 (BT-PZT) solid solution. The developed BT-PZT system is engineered to tune the ferro to paraelectric phase transition temperature of it in-between the phase transition temperature of BaTiO3 (393 K) and PbZrTiO3 (573 K) with higher pyroelectric figure-of-merit (FOM). The temperature-dependent dielectric behavior of the material has revealed the ferro- to paraelectric phase transition at 427 K with a maximum dielectric constant of 755. The room-temperature (298 K) pyroelectric coefficient (Pi) of the material was obtained as 738.63 μC/m2K which has yielded a significantly high FOM of 1745.8 J m-3 K-2. The enhancement in pyroelectric property is attributed to the morphotopic phase transition between tetragonal and rhombohedral PZT phases in the BT-PZT system. The developed BT-PZT system is capable of generating a power output of 1.3 mW/m2 near the Curie temperature with a constant rate (0.11 K/s) of heating. A signal conditioning circuit has been developed to rectify the time-varying current and voltage signals obtained from the harvester during heating cycles. The output voltage generated by the pyroelectric harvester has been stored in a capacitor for powering wearable electronics.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Electrical properties of (0 0 1)-textured Pb(Zr,Ti)O 3 thin films with different BaPbO 3 thicknesses

    NASA Astrophysics Data System (ADS)

    Liang, Chun-Sheng; Wu, Jenn-Ming

    2006-05-01

    The microstructure and electrical properties of highly (0 0 1)-textured lead zirconate titanate (PZT) thin films deposited on BaPbO 3 (BPO) at 475 °C by RF-magnetron sputtering were studied. Twenty-three, 65, and 136 nm-thick BPOs were adopted in this study. The dielectric constant is approximately 433 for Pt/PZT/BPO (23 nm), 443 for Pt/PZT/BPO (65 nm), and 466 for Pt/PZT/BPO (136 nm). The remanant polarization values in these three capacitors are 13.5, 14.9, and 10.9 μC/cm 2, and the coercive field values are 76.6, 71.2, and 54.5 kV/cm, respectively. The fatigue endurance of PZT films decreases with the thickness of BPO. The thickness of BPO layer not only influences the crystallinity of PZT films, but also the a-domain populations in PZT films. The variation of resultant electrical properties is attributed partly to the improvement of crystallinity, and partly to the population of a-domain. The effect of the former is remarkable when the BPO is thin while the latter is dominant when the BPO is thick.

  2. 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.

  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. 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

  5. Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

    PubMed

    Jeong, Soyeon; Kim, Do Heui

    2016-05-01

    The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system. PMID:27483765

  6. Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

    PubMed

    Jeong, Soyeon; Kim, Do Heui

    2016-05-01

    The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system.

  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. 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.

  9. Effect of 5. 3-GeV Pb-ion irradiation on irreversible magnetization in Y-Ba-Cu-O crystals

    SciTech Connect

    Konczykowski, M.; Rullier-Albenque, F. ); Yacoby, E.R.; Shaulov, A.; Yeshurun, Y. ); Lejay, P. )

    1991-10-01

    We report a dramatic change in the irreversibility line of Y-Ba-Cu-O crystals after irradiation with Pb ions. Near the transition temperature, following irradiation, the irreversibility temperature increases and the curvature of the irreversibility line changes sign. These changes are accompanied by a strong enhancement of critical current density and a decrease in flux creep rate. Pb irradiation induces damage in the form of amorphous tracks which penetrate throughout the thickness of the sample. We maintain that these defects are most efficient in terms of flux trapping and are responsible for the observed changes in irreversible magnetic features in the irradiated sample.

  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. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Theoretical investigation of superconductivity in Ba(AlSn) under pressure

    NASA Astrophysics Data System (ADS)

    Parlak, Cihan

    2016-10-01

    The compound of Ba(AlSn) from ternary superconductors exhibits the superconductivity behaviour below the temperature 2.9 K. We report the results of an ab initio study based on electronic, and detailed lattice dynamical properties as a function of pressure of superconducting material. The phonon dispersion curves along the high-symmetry directions and phonon frequencies parameters at the Brillouin zone center are computed by using density functional perturbation theory while the elastic constants are calculated in metric-tensor formulation. The Vickers hardness belonging to the compound is also evaluated clearly. The band structure, partial densities of states and Fermi surface topology are also discussed in detail. At the same time we describe the relationship between the properties determined and superconducting characteristic.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

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

    DOE PAGES

    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

  4. 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.

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

    DOE PAGES

    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

  6. 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.

  7. NMR study of glasses in the PbO-B/sub 2/O/sub 3/-PbF/sub 2/-AlF/sub 3/ system

    SciTech Connect

    Vopilov, V.A.; Bogdanov, V.L.; Buznik, V.M.; Karapetyan, A.K.; Matsulev, A.N.

    1986-01-01

    The NMR method has been successfully used in the study of the structure of oxide glasses and in lithium glasses. Using steady-state and pulse methods of B-11 and F-19 NMR, the authors have studied borate glasses in the PbO-B/sub 2/O/sub 3/-PbF/sub 2/-AlF/sub 3/ system. Lead fluoride was added to the composition of the experimental glasses. A small amount of PbF2 has a weak effect on the electrical conductivity, and it is only in the specimen with the maximum values of the PbF/sub 2/ concentration that conductivity becomes significant. In glasses of the PbO X B/sub 2/O/sub 3/ X AlF/sub 3/ compositions, there is an exchange of the oxygen and fluoride modifier anions and as a result the F ions are incorporated into the first coordination sphere of the lead cations.

  8. 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.

  9. Thickness-dependent retention behaviors and ferroelectric properties of BiFeO3 thin films on BaPbO3 electrodes

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Ching; Wu, Jenn-Ming

    2007-09-01

    BiFeO3 (BFO) thin films produced with varied film thicknesses ranging from 100to230nm were fabricated on BaPbO3(BPO )/Pt/Ti/SiOx/Si substrates by rf-magnetron sputtering. Saturated polarization-electrical field hysteresis loops, polarization response by pulse measurement, and retention properties were obtained for BFO films with various thicknesses on BPO. The retention behaviors of BFO demonstrate logarithmic time dependence and stretched exponential law. When the thicknesses of BFO films increase, the contribution of logarithmic time dependence to retention, the stretched exponential law becomes dominant. BFO films with thinner thickness exhibit better retention properties but possess smaller remnant polarization.

  10. 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

  11. 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.

  12. Ferroelectric property of (Ba,Bi)(Ti,M)O3 (M; Cu, Mn, Al, Fe, In, Y, Yb) ceramics

    NASA Astrophysics Data System (ADS)

    Shiroki, K.; Kumada, N.; Ogiso, H.; Yonesaki, Y.; Takei, T.; Kinomura, N.; Wada, S.

    2011-10-01

    Two types of solid solutions, (Ba1-2xBi2x)(CuxTi1-x)O3 (x <= 0.04) and (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb; x <= 0.03) were prepared by conventional high temperature reaction. For the solid solution of (Ba1-2xBi2x)(CuxTi1-x)O3 single phases with the tetragonal cell was obtained in the region of x <= 0.04 and for the solid solutions of (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb) single phases with the tetragonal cell was observed in the region of x <= 0.03 except the sample of M = Al in which a small amount of the second phase was contained. In these solid solutions the Tc increased with the value of x except for M = Al, and was 144.7°C for x = 0.020 of M = Cu, and the highest Tc was observed for x = 0.020 of every M atom and the order of the highest Tc was Cu (144.7°C), Y (141.4°C), Yb (140.8°C), In (138.5°C), Mn (135.5°C) and Fe (131.3°C). The highest apparent piezoelectric constant, (d33 = 258 pm/V) in these solid solutions was observed for x = 0.010 of Al.

  13. 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.

  14. 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.

  15. Coexisting charge and magnetic orders in the dimer-chain iridate Ba5AlIr2O11

    DOE PAGES

    Terzic, J.; Wang, J. C.; Ye, Feng; Song, W. H.; Yuan, S. J.; Aswartham, S.; DeLong, L. E.; Streltsov, S. V.; Khomskii, Daniel I.; Cao, G.

    2015-06-29

    In this paper, we have synthesized and studied single-crystal Ba5AlIr2O11 that features dimer chains of two inequivalent octahedra occupied by tetravalent Ir4+(5d5) and pentavalent Ir5+(5d4) ions, respectively. Ba5AlIr2O11 is a Mott insulator that undergoes a subtle structural phase transition near TS=210K and a magnetic transition at TM=4.5K; the latter transition is surprisingly resistant to applied magnetic fields μoH≤12T but more sensitive to modest applied pressure (dTM/dp ≈ +0.61K/GPa). All results indicate that the phase transition at TS signals an enhanced charge order that induces electrical dipoles and strong dielectric response near TS. It is clear that the strong covalency andmore » spin-orbit interaction (SOI) suppress double exchange in Ir dimers and stabilize a novel magnetic state that is neither S=3/2 nor J=1/2, but rather lies in an “intermediate” regime between these two states. Finally, the novel behavior of Ba5AlIr2O11 therefore provides unique insights into the physics of SOI along with strong covalency in competition with double-exchange interactions of comparable strength.« less

  16. Charge-compensation effect of Al on luminescence properties of M2(Si, Al)5N8:Ce3+ (M = Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Kuramoto, Daiki; Horikawa, Takashi; Hanzawa, Hiromasa; Machida, Ken-ichi

    2013-09-01

    The charge-compensated materials, M2AlxSi5-xN8:Ce3+ (M = Ca, Sr, Ba), were synthesized from appropriate mixtures of MSi, MAlSi, (MSiHy, MAlSiHy), Si3N4 and CeF3 by a direct nitriding process in a N2 gas and the luminescence properties were characterized. The resultant phosphors showed green emission suitable for LED illumination by optimizing the mixing ratio of metal elements. These phosphors were effectively excited by violet or blue light (400-430 nm) and the emission bands were observed at various wavelength regions for Ca: 489-528 nm, Sr: 511-520 nm, and Ba: 508-514 nm. Although the emission intensity of Ca2(Si, Al)5N8:Ce3+ was decreased with increasing amount of Al, those of Sr- and Ba-analogues were maximized at x = 0.5 of Al content in M2Si5-xAlxN8:Ce3+.

  17. 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

  18. 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.

  19. Plasmonics in the ultraviolet with the poor metals Al, Ga, In, Sn, Tl, Pb, and Bi.

    PubMed

    McMahon, Jeffrey M; Schatz, George C; Gray, Stephen K

    2013-04-21

    We discuss how the poor metals Al, Ga, In, Sn, Tl, Pb, and Bi can be used for plasmonics in the near to far ultraviolet (UV) range, similar to the noble metals Ag and Au in the visible (Vis) range. We first discuss the empirical dielectric functions of the poor metals, contrasting them with Ag and Au, and also fitting them to a Drude and multiple Lorentz oscillator form. Using Mie theory, we then compare the optical responses of spherical poor metal nanoparticles to noble metal ones. Finally, nanoparticle dimers are studied using a vectorial finite element method. We show how the poor metals exhibit large electric field enhancements in the UV, comparable to Au in the Vis, which makes them particularly attractive for sensing applications, such as surface enhanced Raman spectroscopy.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. Infrared study of the vibrational behavior of CrO 42- guest ions matrix-isolated in metal (II) sulfates (Me=Ca, Sr, Ba, Pb)

    NASA Astrophysics Data System (ADS)

    Stoilova, D.; Georgiev, M.; Marinova, D.

    2005-03-01

    Infrared spectra of matrix-isolated CrO 42- guest ions in host sulfate matrices - CaSO 4·2H 2O, SrSO 4, BaSO 4 and PbSO 4 are reported and discussed with respect to the Cr-O stretching and O-Cr-O bending modes. An adequate measure for the CrO 42- guest ion distortion is the site group splitting Δ νas and Δ νmax (the difference between the highest and the lowest wavenumbered components of the stretching and bending modes). When the smaller SO 42- ions are replaced by the larger CrO 42- ions the mean frequencies of the asymmetric stretching and bending modes ( ν and ν) as well as the frequencies of ν1 of the CrO 42- guest ions are shifted to higher wavenumbers as compared to those in the respective neat chromates due to the larger repulsion potential at the host lattice sites (smaller values of the unit-cell volumes of the neat sulfates than those of the neat chromates). The CrO 42- guest ions exhibit three bands corresponding to the ν3 modes as deduced from the site group analysis ( C2 site symmetry in CaSO 4·2H 2O and Cs site symmetry in SrSO 4, BaSO 4 and PbSO 4). However, the bending modes ν4 and ν2 of the CrO 42- guest ions in SrSO 4, BaSO 4 and PbSO 4 show an effectively higher local symmetry than the 'rigorous' crystallographic one (two bands for ν4 and one band for ν2 instead of a triplet and a doublet expected, respectively). Such different apparent site symmetries observed in various spectral regions may be attributed to the different influence of energetic and geometrical distortions of the polyatomic entities at particular site on various modes.

  6. 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.

  7. 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.

  8. 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.

  9. Phase transition behaviours near the triple point for Pb-free (1 - x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics

    NASA Astrophysics Data System (ADS)

    Gao, Jinghui; Dai, Ye; Hu, Xinghao; Ke, Xiaoqin; Zhong, Lisheng; Li, Shengtao; Zhang, Lixue; Wang, Yu; Wang, Dong; Wang, Yan; Liu, Yongbin; Xiao, Hu; Ren, Xiaobing

    2016-08-01

    The reason for the large electromechanical response in Pb-free piezoceramic Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) still remains controversial, and a central issue is whether or not the multi-phase-coexisting point (triple point) in the phase diagram is a thermodynamic tricritical point. In this letter, we study the phase transition behaviour for the ferro-para transitions of BZT-BCT specimens in the vicinity of a triple point. Our results show that latent heat and thermal hysteresis approach zero, while the permittivity peak value is maximized close to the triple-point composition, which suggests that the triple point exhibits nearly tricritical transition behaviours in the BZT-BCT system. Further, the TEM result shows that the domain width is minimized with composition approaching the triple point, which indicates a reduction of the domain wall energy possibly relevant to the tricriticality of the triple point. A sixth-order Landau energy modeling shows that the triple tricritical point provides a free-energy state of near-vanishing polarization anisotropy and thus enhances the piezoelectric response for such a material system.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Optical/ferroelectric characterization of BaTiO3 and PbTiO3 colloidal nanoparticles and their applications in hybrid materials technologies.

    PubMed

    Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2013-08-01

    In this paper, we will explore how optical and ferroelectric properties of the stressed ferroelectric nanoparticles prepared through ball milling set a limit on the performance of optical and electro-optical devices based on such materials. It was found that suspensions of BaTiO3 nanoparticles exhibit a blue shift in the optical band gap with a decrease in particle size. The optical band gap of PbTiO3 nanoparticles is not affected by the milling time. Polarization switching is composed of slow and fast components. A slow component is threshold-less and is caused by the particle reorientation while a fast component has a threshold, and its rise time is inversely proportional to the electric field. The absorption edge of these suspensions accounts for the applications in the near UV range, while kinetics of the polarization switching governs the speed of electro-optical devices.

  16. 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.

  17. Improvement of the phase diagram for the pseudobinary PbNb2O6-BaNb2O6 system

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    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 PbNb2O6-BaNb2O6 system around the morphotropic phase boundary region.

  18. 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.

  19. First-principles determination of free energies of ferroelectric phase transitions and domains in BaTiO3 and PbTiO3

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Waghmare, Umesh V.

    2010-03-01

    We present a powerful method based on a combination of (a) constrained polarization molecular dynamics and (b) thermodynamic integration to determine the free energy landscape relevant to structural phase transitions and related phenomena in ferroelectric materials, bridging the gap between first-principles calculations and phenomenological Landau-like theories. We illustrate it using first-principles effective Hamiltonians of BaTiO3 and PbTiO3 to (a) uncover the quantitative features of the free energy function that are responsible for its first-order ferroelectric transitions, and (b) calculate the minimum free energy pathway for the polarization switching and (c) evaluate temperature dependent domain wall free energy and pathways of the formation of domains. Our method can be readily generalized to any classical microscopic Hamiltonian and ensembles characterized with a given constraint. We show that certain terms have to be added to the phenomenological Landau-Devonshire free energy functions to capture the physics of ferroelectric materials.

  20. Highly (110)- and (111)-oriented BiFeO3 films on BaPbO3 electrode with Ru or Pt /Ru barrier layers

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Ching; Wu, Jenn-Ming; Hsiung, Chang-Po

    2007-04-01

    Highly (110)- and (111)-oriented BiFeO3 (BFO) films were fabricated with BaPbO3 (BPO )/Ru and BPO /Pt/Ru as electrode/barrier on Si substrates by rf-magnetron sputtering. The BPO /Ru and BPO /Pt/Ru stacks both induce oriented BFO films and act as diffusion barriers. The (110)- and (111)-oriented BFO films possess excellent ferroelectric properties with only minor leakage. The values of remnant polarization are almost the same, about 42μC/cm2, for (110)- and (111)-oriented BFO films. However, polarization measured under varying pulse widths demonstrates that the switching polarization in (111)-oriented BFO films is higher than in (110)-oriented films. Additionally, (111)-oriented BFO films exhibit better retention properties than (110)-oriented films.

  1. 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.

  2. 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 .

  3. 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.

  4. Monolithic translucent BaMgAl10O17:Eu2+ phosphors for laser-driven solid state lighting

    NASA Astrophysics Data System (ADS)

    Cozzan, Clayton; Brady, Michael J.; O'Dea, Nicholas; Levin, Emily E.; Nakamura, Shuji; DenBaars, Steven P.; Seshadri, Ram

    2016-10-01

    With high power light emitting diodes and laser diodes being explored for white light generation and visible light communication, thermally robust encapsulation schemes for color-converting inorganic phosphors are essential. In the current work, the canonical blue-emitting phosphor, high purity Eu-doped BaMgAl10O17, has been prepared using microwave-assisted heating (25 min) and densified into translucent ceramic phosphor monoliths using spark plasma sintering (30 min). The resulting translucent ceramic monoliths convert UV laser light to blue light with the same efficiency as the starting powder and provide superior thermal management in comparison with silicone encapsulation.

  5. 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

  6. Single-component and white light-emitting phosphor BaAl2Si2O8: Dy3+, Eu3+ synthesis, luminescence, energy transfer, and tunable color

    NASA Astrophysics Data System (ADS)

    Ma, Pingchuan; Song, Yanhua; Sheng, Ye; Yuan, Bo; Guan, Hongxia; Xu, Chengyi; Zou, Haifeng

    2016-10-01

    A series of Dy3+ - Eu3+ co-doped BaAl2Si2O8 phosphors were prepared via the conventional solid-state reaction method. Their crystal structure, luminescent characteristic and lifetime were investigated. The optimum doping concentrations of Dy3+and Eu3+ are both 0.05 for Dy3+ or Eu3+ singly doped BaAl2Si2O8. Furthermore, BaAl2Si2O8: 0.05Dy3+ and BaAl2Si2O8: 0.05Eu3+ emits yellow and red light. The emission color of BaAl2Si2O8: Dy3+, Eu3+ could be tuned from yellow to white due to the energy transfer. This energy transfer from Dy3+ to Eu3+ was confirmed and investigated by photoluminescence spectra and the decay time of energy donor Dy3+ ions. With constantly increasing Eu3+ concentration, the energy transfer efficiency from Dy3+ to Eu3+ in BaAl2Si2O8 host increased gradually and reached as high as 81%, the quantum yield was about 47.43%. BaAl2Si2O8: Dy3+, Eu3+ phosphors can be effectively excited by UV (about 348 nm) light and emit visible light from yellow to white by altering the concentration ratio of Dy3+ and Eu3+, indicating that the phosphors have potential applications as a white light-emitting phosphor for display and lighting.

  7. Synthesis, structural characterization and properties of SrAl4-xGex, BaAl4-xGex, and EuAl4-xGex (x≈0.3-0.4)—Rare examples of electron-rich phases with the BaAl4 structure type

    NASA Astrophysics Data System (ADS)

    Zhang, Jiliang; Bobev, Svilen

    2013-09-01

    Three solid solutions with the general formula AEAl4-xGex (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 BaAl4 structure type, adopted by the three AEAl4 end members. In all structures, Ge substitutes Al only at the 4e Wyckoff site. Results from X-rays photoelectron spectroscopy on EuAl4-xGex and EuAl4 indicate that the interactions between the Eu2+ 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]4f7 electronic configuration of Eu2+ 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 AEAl4-xGex (AE=Eu, Sr, Ba) is also presented.

  8. 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.

  9. 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.

  10. Polarization switching dynamics in thin-film BaTiO3/PbZr0.2Ti0.8O3 bilayer capacitors

    NASA Astrophysics Data System (ADS)

    Salev, Pavel; Grigoriev, Alexei

    2013-03-01

    In this work, we compare polarization switching and dielectric properties of single- (PbZr0.2Ti0.8O3 (PZT)) and bi-layer (BaTiO3/PbZr0.2Ti0.8O3 (BTO/PZT)) ferroelectric thin-film materials. The ferroelectric films were grown by radio-frequency magnetron sputtering on SrRuO3/SrTiO3 (001) substrates. Pt top electrodes ranging in diameter from 50 um to 200 um were fabricated on top of ferroelectric films. Electrical measurements of switching dynamics and dielectric response revealed a significant difference in polarization switching between single- and bi-layer capacitors. Average remnant polarization in the bilayer was reduced to 60 uC/cm2 from 90 uC/cm2 polarization in a single layer capacitor, and the switching speed was reduced significantly. In this presentation, we will discuss effects of interfaces and polarization coupling on polarization dynamics and on the dielectric response in ferroelectric multilayers.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Analyses of whole rock and mineral separates from the Nakhla meteorite are carried out by means of Sm-Nd and U-Tn-Pb systematics and by determining their REE, Ba, Sr, Rb, and K concentrations. Results show that the Sm-Nd age of the meteorite is 1.26 + or - 0.7 b.y., while the high initial epsilon(Nd) value of +16 suggests that Nakhla was derived from a light REE-depleted, old planetary mantle source. A three-stage Sm-Nd evolution model is developed and used in combination with LIL element data and estimated partition coefficients in order to test partial melting and fractional crystallization models and to estimate LIL abundances in a possible Nakhla source. The calculations indicate that partial melting of the source followed by extensive fractional crystallization of the partial melt could account for the REE abundances in the Nakhla constituent minerals. It is concluded that the significantly younger age of Nakhla than the youngest lunar rock, the young differentiation age inferred from U-Th-Pb data, and the estimated LIL abundances suggest that this meteorite may have been derived from a relatively large, well-differentiated planetary body such as Mars.

  12. Optical properties and upconversion emission in Yb3+-sensitized Er3+- and Pr3+-codoped PbGeO3:PbF2:xF2 (x = Mg, Ba) glass

    NASA Astrophysics Data System (ADS)

    Silva, Alexandre O.; Gouveia-Neto, A. S.; Bueno, Luciano A.; Oliveira, Carlos E. N.

    2016-03-01

    In this report the optical properties and energy-transfer upconversion luminescence of Er3+- and Pr3+/Yb3+-codoped PbGeO3-PbF2-xF2(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 2H11/2→4I15/2, 4S3/2→4I15/2 e 4F9/2→4I15/2, respectively, was readily observed. In the Pr3+/Yb3+ co-doped system, emission peaks around 485, 530, 610, and 645 which were ascribed to the 3P0 - 3HJ (J=4,5,6), and 3P0 - 3FJ (J=2,3,4), transitions, respectively, were observed. The population of the praseodymium 3P0 emitting level was accomplished through a combination of ground-state absorption of Yb3+ ions at the 2F7/2, energy-transfer Yb3+(2F5/2) - Pr3+(3H4), and excited-state absorption of Pr3+ ions provoking the 1G4 - 3P0 transition. The dependence of the upconversion emission on glass composition, pump power, and doping contents was also examined. Glassy and glass-ceramic samples was compared in order determine the system with better luminescence efficiency.

  13. Stress analysis and ferroelectric properties of Pb(Zr0.52Ti0.48)0.96Nb0.04O3 thin film grown on different thickness of BaPbO3 electrodes

    NASA Astrophysics Data System (ADS)

    Wen, Xin-Yi; Yu, Jun; Wang, Yun-Bo; Zhou, Wen-Li; Gao, Jun-Xiong

    2010-12-01

    Pb(Zr0.52Ti0.48)0.96Nb0.04O3 (PZTN) thin films were deposited on BaPbO3 (BPO) electrodes by rf-magnetron sputtering. 34, 68, 135, and 270 nm thick BPOs were adopted in this study. The preferred orientation changes from slightly (100)/(001) to slightly (101)/(110) as the BPO thickness increased. The mean grain sizes obtained by Williamson-Hall plots are 81 nm, 120 nm, 146 nm, and 90 nm, respectively. The same tendency was observed by atomic force microscopy method. In residual stress analysis, tensile stress was observed in every film. The stress magnitude is the maximum in the film with 135 nm thick BPO. Through a simple calculation, we suggest that the tensile stress in our films mainly originates from the phase transformation stresses. We also note that the ferroelectric and dielectrics properties are improved with the raise of tensile stresses. A possible reason is that the tensile stress benefits the tetragonal-monoclinic phase transition in the PZTN films with composition near morphotropic phase boundary. The other possible reason is that the raise of the tensile stress is consistent with the increasing of grain size, which decreases the grain boundary density and facilitate domain mobility.

  14. 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.

  15. 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.

  16. 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)

  17. Multiband orange-red photoluminescence of Eu{sup 3+} ions in new '114' LnBaZn{sub 3}GaO{sub 7} and LnBaZn{sub 3}AlO{sub 7} oxides

    SciTech Connect

    Saradhi, M.P.; Raveau, B.; Caignaert, V.; Varadaraju, U.V.

    2010-02-15

    A new series of gallozincates LnBaZn{sub 3}GaO{sub 7} (Ln=La, Nd, Sm, Eu, Gd, Dy, Y) and new aluminozincates LnBaZn{sub 3}AlO{sub 7} (Ln=Y, Eu, Dy) have been synthesized. Their structure refinements show that these phases belong to the '114' series, with hexagonal P6{sub 3}mc space group previously described for SmBaZn{sub 3}AlO{sub 7}. The photoluminescence study of these oxides shows that the Eu{sup 3+} activated LnBaZn{sub 3}MO{sub 7} oxides with Ln=Y, La, Gd; and M=Al, Ga exhibit strong magnetic and electric dipole transitions (multiband emission) which is of interest for white light production. These results also confirm that the site occupied by Eu{sup 3+} is not strictly centrosymmetric. The electric dipole transition intensity is the highest in GdBaZn{sub 3}MO{sub 7} [M=Al, Ga]: 0.05Eu{sup 3+} as compared with other Eu{sup 3+} activated compositions. This is due to the layer distortion around GdO{sub 6} octahedra when compared with YO{sub 6} and LaO{sub 6} octahedra. - Graphical abstract: The projected structure consists of alternate stacked layers of Kagome and Triangular type with statistical distribution of Zn and Ga atoms between two tetrahedral sites. Ba{sup 2+} present in anticuboctahedron coordinating with 12 oxygen atoms. The Eu{sup 3+} present in octahedral coordination with 3-fold rotational symmetry.

  18. 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

  19. 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).

  20. Structural trends for celestite (SrSO[subscript 4]), anglesite (PbSO[subscript 4]), and barite (BaSO[subscript 4]): Confirmation of expected variations within the SO[subscript 4] groups

    SciTech Connect

    Antao, Sytle M.

    2012-05-10

    The crystal structures of the isostructural orthorhombic sulfates celestite (SrSO{sub 4}), anglesite (PbSO{sub 4}), and barite (BaSO{sub 4}) were refined by Rietveld methods using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Their structural model was refined in space group Pbnm. The unit-cell parameters are a = 6.87032(3), b = 8.36030(5), c = 5.34732(1) {angstrom}, and V = 307.139(3) {angstrom}{sup 3} for SrSO{sub 4}; a = 6.95802(1), b = 8.48024(3), c = 5.39754(1) {angstrom}, and V = 318.486(1) {angstrom}{sup 3} for PbSO{sub 4}; and a = 7.15505(1), b = 8.88101(3), c = 5.45447(1) {angstrom}, and V = 346.599(1) {angstrom}{sup 3} for BaSO{sub 4}. The average [12] distances are 2.827(1), 2.865(1), and 2.953(1) {angstrom} for SrSO{sub 4}, PbSO{sub 4}, and BaSO{sub 4}, respectively, and their corresponding average [4] distances are 1.480(1), 1.477(3), and 1.471(1) {angstrom}. The geometrical features of the SO{sub 4} and MO{sub 12} polyhedra become more symmetrical from SrSO{sub 4} to BaSO{sub 4}. Across the series, the a, b, and c parameters vary non-linearly with increasing V. The radii of the M{sup 2+} cations, rM, [12], and [4] distances vary linearly with V. These structural trends arise from the effective size of the M{sup 2+} cation (rM: Sr < Pb < Ba) that is coordinated to 12 O atoms.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. Primary fragmentation pathways of gas phase [M(uracil-H)(uracil)]+ complexes (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd , Mg, Ca, Sr, Ba, and Pb): loss of uracil versus HNCO.

    PubMed

    Ali, Osama Y; Randell, Nicholas M; Fridgen, Travis D

    2012-04-23

    Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive-ion electrospray spectra show that [M(Ura-H)(Ura)](+) (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI-CID experiments show that the main primary decomposition pathway for all [M(Ura-H)(Ura)](+) , except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI-CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura-H)(Ura)](+) are shown to lose a molecule of uracil. Similar results were observed under infrared multiple-photon dissociation excitation conditions, except that [Ca(Ura-H)(Ura)](+) was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura-H)](+) (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic-structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura-H)](+) is ion-dipole complexation and the experimental evidence presented supports this. PMID:22447672

  11. 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)].

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. PbF{sub 2} compared to Al{sub 2}O{sub 3} and AlF{sub 3} to produce an epithermal neutron beam for radiotherapy

    SciTech Connect

    Liu, H.B.

    1996-02-01

    An evaluation of moderating materials is presented for boron neutron captured therapy. PbF{sub 2} was considered and its performance was compared to that of Al{sub 2}O{sub 3} and AlF{sub 3}. PbF{sub 2} is found quite effective as a moderator for medical epithermal neutron beams. (AIP) {copyright} {ital 1996 American Association of Physicists in Medicine.}

  17. 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.

  18. 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

  19. Fluorine sites in glasses and transparent glass-ceramics of the system Na{sub 2}O/K{sub 2}O/Al{sub 2}O{sub 3}/SiO{sub 2}/BaF{sub 2}

    SciTech Connect

    Bocker, Christian; Munoz, Francisco; Duran, Alicia; Ruessel, Christian

    2011-02-15

    The transparent glass-ceramics obtained in the silicate system Na{sub 2}O/K{sub 2}O/SiO{sub 2}/BaF{sub 2} show homogeneously dispersed BaF{sub 2} nano crystals with a narrow size distribution. The X-ray diffraction and the nuclear magnetic resonance spectroscopy were applied to glasses and the respective glass-ceramics in order to clarify the crystallization mechanism and the role of fluorine during crystallization. With an increasing annealing time, the concentration and also the number of crystals remain approximately constant. With an increasing annealing temperature, the crystalline fraction increases until a saturation limit is reached, while the number of crystals decreases and the size of the crystals increases. Fluoride in the glassy network occurs as Al-F-Ba, Al-F-Na and also as Ba-F structures. The latter are transformed into crystalline BaF{sub 2} and fluoride is removed from the Al-F-Ba/Na bonds. However, some fluorine is still present in the glassy phase after the crystallization. -- Graphical abstract: The X-ray diffraction and the nuclear magnetic resonance spectroscopy were applied to glasses in the silicate system Na{sub 2}O/K{sub 2}O/SiO{sub 2}/BaF{sub 2} and the respective glass-ceramics with BaF{sub 2} nano crystals in order to clarify the crystallization mechanism and the role of fluorine during crystallization. Display Omitted Research highlights: {yields} BaF{sub 2} nano crystals are precipitated from a silicate glass system. {yields} Ostwald ripening during the late stage of crystallization does not occur. {yields} Fluorine in the glass is coordinated with Ba as well as Al together with Ba or Na.{yields} In the glass-ceramics, the residual fluorine is coordinated as Al-F-Ba/Na.

  20. 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

  1. 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

  2. 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.

  3. Synthesis and structural investigation of the compounds containing HF 2- anions: Ca(HF 2) 2, Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6)

    NASA Astrophysics Data System (ADS)

    Bunič, Tina; Tramšek, Melita; Goreshnik, Evgeny; Žemva, Boris

    2008-09-01

    Three new compounds Ca(HF 2) 2, Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6) were obtained in the system metal(II) fluoride and anhydrous HF (aHF) acidified with excessive PF 5. The obtained polymeric solids are slightly soluble in aHF and they crystallize out of their aHF solutions. Ca(HF 2) 2 was prepared by simply dissolving CaF 2 in a neutral aHF. It represents the second known compound with homoleptic HF environment of the central atom besides Ba(H 3F 4) 2. The compounds Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6) represent two additional examples of the formation of a polymeric zigzag ladder or ribbon composed of metal cation and fluoride anion (MF +) n besides PbF(AsF 6), the first isolated compound with such zigzag ladder. The obtained new compounds were characterized by X-ray single crystal diffraction method and partly by Raman spectroscopy. Ba 4F 4(HF 2)(PF 6) 3 crystallizes in a triclinic space group P1¯ with a=4.5870(2) Å, b=8.8327(3) Å, c=11.2489(3) Å, α=67.758(9)°, β=84.722(12), γ=78.283(12)°, V=413.00(3) Å 3 at 200 K, Z=1 and R=0.0588. Pb 2F 2(HF 2)(PF 6) at 200 K: space group P1¯, a=4.5722(19) Å, b=4.763(2) Å, c=8.818(4) Å, α=86.967(10)°, β=76.774(10)°, γ=83.230(12)°, V=185.55(14) Å 3, Z=1 and R=0.0937. Pb 2F 2(HF 2)(PF 6) at 293 K: space group P1¯, a=4.586(2) Å, b=4.781(3) Å, c=8.831(5) Å, α=87.106(13)°, β=76.830(13)°, γ=83.531(11)°, V=187.27(18) Å 3, Z=1 and R=0.072. Ca(HF 2) 2 crystallizes in an orthorhombic Fddd space group with a=5.5709(6) Å, b=10.1111(9) Å, c=10.5945(10) Å, V=596.77(10) Å 3 at 200 K, Z=8 and R=0.028.

  4. 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

  5. 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.

  6. 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.

  7. Roles of Pt and BaO in the Sulfation of Pt/BaO/Al2O3 Lean NOx Trap Materials: Sulfur K-edge XANES and Pt LIII XAFS Studies

    SciTech Connect

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

    2008-02-28

    The roles of barium oxide and platinum during the sulfation of Pt-BaO/Al2O3 lean NOx trap catalysts were investigated by S K edge XANES (X-ray absorption near-edge spectroscopy) and Pt LIII XAFS (X-ray absorption fine structure). All of the samples studied (Al2O3, BaO/Al2O3, Pt/Al2O3 and Pt-BaO/Al2O3) were pre-sulfated prior to the X-ray absorption measurements. It was found that barium oxide itself has the ability to directly form barium sulfate even in the absence of Pt and gas phase oxygen. In the platinum-containing samples, the presence of Pt-O species plays an important role in the formation of sulfate species. Even if barium and aluminum sites are available for SO2 to form sulfate, for the case of the BaO(8)/Al2O3 sample, where the barium coverage is about 0.26 ML, S XANES spectroscopy results show that barium sulfates are preferentially produced over aluminum sulfates . When oxygen is absent from the gas phase, the sulfation route that involves Pt-O is eliminated after the initially present Pt-O species are completely consumed. In this case, formation of sulfates is suppressed unless barium oxide is also present. Pt LIII XAFS results show that the first coordination sphere around the Pt atoms in the Pt particles is dependent upon the redox nature of the gas mixture used during the sulfation process. Sulfation under reducing environments (e.g. SO2+H2) leads to formation of Pt-S bonds, while oxidizing conditions (e.g. SO2+O2) continue to show the presence of Pt-O bonds. In addition, the former condition was found to give rise to a higher degree of Pt sintering than the latter one. This result explains why samples sulfated under reducing conditions had lower NOx uptakes than those sulfated under oxidizing conditions. Therefore, our results provide needed information for the development of optimum practical operation conditions (e.g. sulfation or desulfation) for lean NOx trap catalysts that minimize deactivation by sulfur.

  8. 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.

  9. 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.

  10. 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.

  11. Crystal-structure and magnetic phase transformations in solid solutions of BiFeO{sub 3}-AFe{sub 0.5}Nb{sub 0.5}O{sub 3} (A = Ca, Sr, Ba, Pb)

    SciTech Connect

    Troyanchuk, I. O.; Bushinsky, M. V. Chobot, A. N.; Mantytskaya, O. S.; Pushkarev, N. V.; Szymczak, R.

    2008-08-15

    Solid solutions of Bi{sub 1-x}A{sub x}(Fe{sub 1-x/2}Nb{sub x/2})O{sub 3}, where A = Ca, Ba, and Pb, are obtained and their crystal structure and magnetic properties are investigated. It is shown that for A = Ca and x {approx} 0.15, the symmetry of the unit cell changes from rhombohedral (space group R3c) to orthorhombic (Pbnm). The transformation leads to the emergence of spontaneous magnetization due to the Dzyaloshinskii-Moriya interaction. Solid solutions with A = Pb remain rhombohedral up to a concentration of x = 0.3. Spontaneous magnetization sharply increases in the compound with x {approx} 1 at low temperatures and is due to the formation of the spin-glass component.

  12. Synthesis and properties of superconducting (Hg,Re)-Ba-Ca-Cu-O thick films on polycrystalline LaAlO 3 substrate obtained by screen-printing method

    NASA Astrophysics Data System (ADS)

    Przybylski, K.; Brylewski, T.; Bućko, M.; Prażuch, J.; Morawski, A.; Łada, T.

    2003-05-01

    A superconducting Hg 0.7Re 0.3Ba 2Ca 2Cu 3O 8+ δ thick film on a polycrystalline LaAlO 3 (LAO) substrate was obtained by a two-step method by screen-printing a Re 0.3Ba 2Ca 2Cu 3O x precursor coating on the substrate followed by high-pressure gas firing in Hg vapour. Morphological observations have revealed that the adherent to the ceramic substrate film exhibited highly porous microstructure composed of plate-like crystallites characterized by a superconducting transition temperature of about 110 K. The major phases identified were a high- Tc (Hg,Re)-1223 phase and a low- Tc (Hg,Re)-1212 phase. Non-superconducting secondary impurity phases were also identified. Energy dispersion X-ray spectroscopy analyses at the substrate/film boundary showed a thin continuous layer of BaLa 2O 4 compound, the presence of which confirmed chemical interaction between the LAO substrate and (Hg,Re)-Ba-Ca-Cu-O film.

  13. Solubilities of Al, Pb, Cu, and Zn in rain sampled in the marine environment over the North Atlantic Ocean and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Lim, B.; Jickells, T. D.; Colin, J. L.; Losno, R.

    1994-09-01

    Chemical processes controlling the dissolved and particulate phase distribution of crustal (Al) and noncrustal metals (Pb, Cu, and Zn) appear to differ in marine precipitation sampled over the North Atlantic Ocean and Mediterranean Sea. Dissolved Al appears to be in equilibrium with a trivalent Al salt at rainwater pH < 5.1, whereas dissolved Pb, Cu, and Zn concentrations are probably controlled by adsorption/desorption processes in which rainwater particulates provide surface-active sorption sites. In both processes, rainwater pH is a critical parameter. Results suggest that in marine precipitation with pH < 5, > 80% of the total Pb, Cu, and Zn concentrations are delivered to the surface oceans in the dissolved form. For a corresponding pH range, Al solubility varies from <5% to >60%. Over the wider observed pH range (of 3.5 to 6.9), the solubilities of Pb, Cu, Zn, and Al are highly variable. The use of mean trace metal solubilities for the assessment of dissolved atmospheric trace metal wet deposition fluxes, and their effects on surface ocean biogeochemistry should be constrained by taking into account rainwater pH in future estimates in global models.

  14. Characteristics of Y-Ba-Cu-O superconductor films on GaAs with an Al sub 2 O sub 3 or AlGaO sub 3 buffer layer

    SciTech Connect

    Shewchun, J.; Chen, Y.; Hoelder, J.S.; Uher, C. )

    1991-06-10

    By depositing a buffer layer of Al{sub 2}O{sub 3} on GaAs, we have been able to laser ablate a superconducting film of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} overtop. The onset of superconductivity is 92 K and zero resistance is observed at 80 K in a structure with a suitably annealed Al{sub 2}O{sub 3} film which is converted to AlGaO{sub 3}. Both the Al{sub 2}O{sub 3}-GaAs and the Al{sub 2}O{sub 3}-Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} interfaces are remarkably well preserved with virtually no interdiffusion or interaction. The Al{sub 2}O{sub 3} or homolog AlGaO{sub 3} film also prevents decomposition of the GaAs at the deposition temperature of 730 {degree}C.

  15. Electronic structures and magnetism of Rh3Z (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb) with DO3 structures

    NASA Astrophysics Data System (ADS)

    Wang, X. T.; Dai, X. F.; Wang, L. Y.; Liu, X. F.; Wang, W. H.; Wu, G. H.; Tang, C. C.; Liu, G. D.

    2015-03-01

    We investigate the electronic structures and magnetism of Rh3Z (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb) with a DO3 structure using the first-principle calculations. The Rh3Z (Z=Si, Ge, Sn, Pb) alloys have been predicted to be half-metallic ferromagnets at their equilibrium lattice parameters. The half-metallicity of Rh3Z (Z=Si, Ge, Sn, Pb) alloys can be kept in a quite large hydrostatic strain and tetragonal distortion. The magnetic properties are discussed. The Rh3Z (Z=Si, Ge, Sn, Pb) alloys do not follow the Mt=Zt-24 rule but instead of following the Mt=Zt-28 rule (Mt is the total magnetic moment per unit cell and Zt is the valence concentration). Moreover, all the alloys investigated in this paper have a negative formation energy, which implies that they are possible to be synthesized in reality.

  16. Air-stable short-wave infrared PbS colloidal quantum dot photoconductors passivated with Al{sub 2}O{sub 3} atomic layer deposition

    SciTech Connect

    Hu, Chen; Gassenq, Alban; Chen, Hongtao; Roelkens, Günther; Justo, Yolanda; Hens, Zeger; Devloo-Casier, Kilian; Detavernier, Christophe

    2014-10-27

    A PbS colloidal quantum dot photoconductor with Al{sub 2}O{sub 3} atomic layer deposition (ALD) passivation for air-stable operation is presented. Two different types of inorganic ligands for the quantum dots, S{sup 2−} and OH{sup −}, are investigated. PbS/S{sup 2−} photoconductors with a cut-off wavelength up to 2.4 μm are obtained, and a responsivity up to 50 A/W at 1550 nm is reported. The corresponding specific detectivity is ∼3.4 × 10{sup 8} Jones at 230 K. The 3-dB bandwidth of the PbS/S{sup 2−} and PbS/OH{sup −} photodetectors is 40 Hz and 11 Hz, respectively.

  17. 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.

  18. 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

  19. 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.

  20. Symmetry determination on Pb-free piezoceramic 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 using convergent beam electron diffraction method

    NASA Astrophysics Data System (ADS)

    Gao, Jinghui; Zhang, Lixue; Xue, Dezhen; Kimoto, Takayoshi; Song, Minghui; Zhong, Lisheng; Ren, Xiaobing

    2014-02-01

    (1-x)(Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) Pb-free piezoceramic has been reported showing ultrahigh piezoelectric performance in its morphotropic phase boundary (MPB) region. However, the crystal structure characteristic for the MPB composition of BZT-xBCT is still under debate—between single orthorhombic phase and tetragonal + rhombohedral two phase mixture. In the present study, we perform the local symmetry determination on the MPB composition x = 0.5 using convergent beam electron diffraction analysis (CBED). Our CBED results from multiple zone axes suggest that there are two coexisting phases with the point group symmetries of 4 mm (tetragonal) and 3 m (rhombohedral) respectively, which agree with two phase mixture model. The strong piezoelectricity can thus be understood by considering the polarization rotation between tetragonal and rhombohedral phases by external field.

  1. Cation disorder and phase transitions in the four-layer ferroelectric Aurivillius phases ABi{sub 4}Ti{sub 4}O{sub 15} (A=Ca, Sr, Ba, Pb)

    SciTech Connect

    Kennedy, Brendan J. Zhou Qingdi; Ismunandar; Kubota, Yoshika; Kato, Kenichi

    2008-06-15

    Crystal structures of a series of bi-layered compounds ABi{sub 4}Ti{sub 4}O{sub 15} (A=Ca, Sr, Ba, Pb) have been investigated using a combination of synchrotron X-ray and neutron powder diffraction data. All four oxides adopt an orthorhombic structure at room temperature and the structures have been refined in space group A2{sub 1}am. This orthorhombic structure is a consequence of a combination of rotation of the TiO{sub 6}, resulting from the less than optimal size of the A-type cation, and displacement of the Ti atoms towards the Bi{sub 2}O{sub 2} layers. There is partial disorder of the Bi and A-type cations over two of the three available sites, which increases in the order CaPb. - Graphical abstract: Synchrotron X-ray and neutron powder diffraction have been used to establish the temperature dependent structures of Aurivillius-type oxides of the type ABi{sub 4}Ti{sub 4}O{sub 15}.

  2. 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.

  3. Evolution of the magnetic properties during the thermal treatment of nanosize BaMFe 11O 19 (M=Fe, Co, Ni and Al) obtained through aerosol route

    NASA Astrophysics Data System (ADS)

    Singhal, Sonal; Garg, A. N.; Chandra, Kailash

    2005-01-01

    Nanosize pure and metal substituted barium hexaferrites BaMFe11O19 (M=Fe, Co, Ni and Al) were prepared through aerosol route. The particle size of as-obtained samples were found to be ∼15 nm through TEM, which increases up to 100-130 nm after annealing at 1000 °C. The saturation magnetization for all the samples after annealing at 1000 °C lies in the range 45.7-59.8 emu/g. In case of Co substituted barium hexaferrite, the saturation magnetization is maximum and coercivity is minimum. Room temperature Mössbauer spectra of BaFe12O19 exhibited a doublet suggesting super paramagnetic nature, however, after annealing at 1000 °C this doublet gets converted into four magnetic sextets, which are typical of bulk barium hexaferrite.

  4. Sintering aids for producing BaO-Al2O3-2SiO2 and SrO-Al2O3-2SiO2 ceramic materials

    SciTech Connect

    Talmy, I.G.; Zaykoski, J.A.

    1995-07-26

    Accordingly, an object of this invention is to provide a new lower temperature process for preparing dense monoclinic BaO.Al2O3.2SiO2 (BAS; celsian) monoclinic SrO.Al2O3.2SiO2 (SAS), or monoclinic BAS/SAS solid solution ceramic materials. Another object of this invention is to provide new sintering aids suitable for producing high strength, low dielectric ceramic materials from BAS, SAS, or mixtures thereof. These and other objects of this invention are accomplished by providing a sintering aid that is a homogenous glass containing (1) from 14 10 45 mole percent of an alkaline earth oxide that is BaO. SrO. or mixtures of BaO and SrO (2) from 8 to 16 weight percent of Al2O3 and (3) The remainder of the glass being SiO2. The homogeneous glass when mixed as a powder with monoclinic BAS powder, monoclinic SAS powder. or mixture of monoclinic BAS and SAS powders reduces the firing temperature required to produce a fully densified ceramic material.

  5. Distribution of Al atoms in the clathrate-I phase Ba8AlxSi46-x at x = 6.9.

    PubMed

    Bobnar, Matej; Böhme, Bodo; Wedel, Michael; Burkhardt, Ulrich; Ormeci, Alim; Prots, Yurii; Drathen, Christina; Liang, Ying; Nguyen, Hong Duong; Baitinger, Michael; Grin, Yuri

    2015-07-28

    The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy.

  6. Distribution of Al atoms in the clathrate-I phase Ba8AlxSi46-x at x = 6.9.

    PubMed

    Bobnar, Matej; Böhme, Bodo; Wedel, Michael; Burkhardt, Ulrich; Ormeci, Alim; Prots, Yurii; Drathen, Christina; Liang, Ying; Nguyen, Hong Duong; Baitinger, Michael; Grin, Yuri

    2015-07-28

    The clathrate-I phase Ba8AlxSi46-x has been structurally characterized at the composition x = 6.9 (space group Pm3[combining macron]n, no. 223, a = 10.4645(2) Å). A crystal structure model comprising the distribution of aluminium and silicon atoms in the clathrate framework was established: 5.7 Al atoms and 0.3 Si atoms occupy the crystallographic site 6c, while 1.2 Al atoms and 22.8 Si atoms occupy site 24k. The atomic distribution was established based on a combination of (27)Al and (29)Si NMR experiments, X-ray single-crystal diffraction and wavelength-dispersive X-ray spectroscopy. PMID:26085288

  7. 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.

  8. 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.

  9. Coexisting charge and magnetic orders in the dimer-chain iridate Ba5AlIr2O11

    SciTech Connect

    Terzic, J.; Wang, J. C.; Ye, Feng; Song, W. H.; Yuan, S. J.; Aswartham, S.; DeLong, L. E.; Streltsov, S. V.; Khomskii, Daniel I.; Cao, G.

    2015-06-29

    In this paper, we have synthesized and studied single-crystal Ba5AlIr2O11 that features dimer chains of two inequivalent octahedra occupied by tetravalent Ir4+(5d5) and pentavalent Ir5+(5d4) ions, respectively. Ba5AlIr2O11 is a Mott insulator that undergoes a subtle structural phase transition near TS=210K and a magnetic transition at TM=4.5K; the latter transition is surprisingly resistant to applied magnetic fields μoH≤12T but more sensitive to modest applied pressure (dTM/dp ≈ +0.61K/GPa). All results indicate that the phase transition at TS signals an enhanced charge order that induces electrical dipoles and strong dielectric response near TS. It is clear that the strong covalency and spin-orbit interaction (SOI) suppress double exchange in Ir dimers and stabilize a novel magnetic state that is neither S=3/2 nor J=1/2, but rather lies in an “intermediate” regime between these two states. Finally, the novel behavior of Ba5AlIr2O11 therefore provides unique insights into the physics of SOI along with strong covalency in competition with double-exchange interactions of comparable strength.

  10. 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.

  11. Investigation of the degradation mechanisms in BaMgAl10O17:Eu2+ phosphor: on the influence of thermal process on operational durability

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Kang, S.

    2010-02-01

    The thermal and operational degradation in optical property of a europium-doped barium magnesium aluminate (BaMgAl10O17:Eu2+, BAM) phosphor was studied. BAM was heat-treated at 500°C under various conditions to determine the mechanism of thermal degradation. Operational degradation tests were then performed under a discharging Xe/Ne mixed gas to study the influence of thermal history on operational degradation. It was found that the atmosphere during thermal processing was the major factor affecting not only the thermal degradation, but also the operational degradation. The sample heat-treated under a reducing atmosphere showed enhanced stability during operation.

  12. 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.

  13. 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

  14. Misfit Strain Relaxation of Ferroelectric PbTiO3/LaAlO3 (111) Thin Film System

    NASA Astrophysics Data System (ADS)

    Xu, Y. B.; Tang, Y. L.; Zhu, Y. L.; Liu, Y.; Li, S.; Zhang, S. R.; Ma, X. L.

    2016-10-01

    Ferroelectric thin films grown on high index substrates show unusual structural and switching dynamics due to their special strain states. Understanding the misfit relaxation behavior is crucial to facilitate the high index thin film growth with improved quality. In this paper, ferroelectric PbTiO3 thin films were grown on LaAlO3 (111) substrates by pulsed laser deposition technique. The microstructures were investigated by combinations of conventional and aberration-corrected transmission electron microscopy. Diffraction contrast analysis and high resolution imaging reveal that high density interfacial dislocations were distributed at the interfaces. These dislocations have mixed character with Burgers vectors of a <110> and line directions of <112>. The edge components of the dislocations, with the Burgers vectors parallel to the interface, accommodate the lattice mismatch and are the main contributor to the misfit relaxation of this system. The formation mechanism of these dislocations is proposed and discussed to elucidate the novel mismatch relaxation behavior of <111> oriented perovskite films.

  15. Misfit Strain Relaxation of Ferroelectric PbTiO3/LaAlO3 (111) Thin Film System

    PubMed Central

    Xu, Y. B.; Tang, Y. L.; Zhu, Y. L.; Liu, Y.; Li, S.; Zhang, S. R.; Ma, X. L.

    2016-01-01

    Ferroelectric thin films grown on high index substrates show unusual structural and switching dynamics due to their special strain states. Understanding the misfit relaxation behavior is crucial to facilitate the high index thin film growth with improved quality. In this paper, ferroelectric PbTiO3 thin films were grown on LaAlO3 (111) substrates by pulsed laser deposition technique. The microstructures were investigated by combinations of conventional and aberration-corrected transmission electron microscopy. Diffraction contrast analysis and high resolution imaging reveal that high density interfacial dislocations were distributed at the interfaces. These dislocations have mixed character with Burgers vectors of a <110> and line directions of <112>. The edge components of the dislocations, with the Burgers vectors parallel to the interface, accommodate the lattice mismatch and are the main contributor to the misfit relaxation of this system. The formation mechanism of these dislocations is proposed and discussed to elucidate the novel mismatch relaxation behavior of <111> oriented perovskite films. PMID:27725752

  16. Preparation and characterization of Tl sub 2 Ba sub 2 CaCu sub 2 O sub 8 films on (100) LaAlO sub 3

    SciTech Connect

    Holstein, W.L.; Parisi, L.A.; Kountz, D.J.; Wilker, C.; Matthews, A.L. ); Arendt, P.N. ); Taber, R.C. )

    1991-03-01

    A two-step process for the fabrication of 0.12-1.20 {mu}m-thick Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} films on (100) LaAlO{sub 3} has been developed. The process involves the deposition of a BaCaCuO precursor film at low temperature by rf magnetron sputtering, followed by annealing in the presence of Tl{sub 2}O vapor to convert the precursor film into Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}. Over a distance of 4 cm, film composition was Tl:Ba:Ca:Cu = 2.05 {plus minus} 0.09:2.05 {plus minus} 0.06:1.0 {plus minus} 0.3:1.94 {plus minus} 0.6 and thickness was uniform to within 6%. The films contain only trace quantities of secondary phases and are epitaxially oriented, with the c-axis of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} perpendicular to the surface and the two a-axes aligned with the pseudo-cubic a-axes of the underlying LaAlO{sub 3} substrate. Films had a T{sub c} for zero dc resistivity of 106.5 {plus minus} 0.5 K,a transport critical current density for continuous current of 2.9 {times} 10{sup 6} A-cm{sup {minus}2} at 77 K, and a sharp ({lt}0.3{degrees} C) ac inductance transition with an onset temperature of 105 {plus minus} 2 K. Surface resistance at 20 GHz less than 2 m{Omega}, about 10X lower than Cu, was routinely achieved for temperatures below 90 K and, for the best films, at temperatures up to 100 K. Surface resistance at about 10 GHz on one film was 0.067 m{Omega} at 4.2 K, 0.36 m{Omega} at 77 K, and 0.74 m{Omega} at 90 K. Films have been reproducibly fabricated on substrates up to 2.54 cm square.

  17. 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

  18. Structural, morphological and optical investigations on BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} elaborated by a microwave induced solution combustion synthesis

    SciTech Connect

    Pradal, Nathalie; Potdevin, Audrey; Chadeyron, Genevieve; Mahiou, Rachid

    2011-04-15

    Graphical abstract: Graphical abstract (with Research highlights). This is a paragraph for graphical abstract. Research highlights: {yields} Synthesis of BAM:Eu{sup 2+} by MISCS using different fuel to oxidizer molar ratios. {yields} Both blue and red phosphors were obtained. {yields} Majority of blue phosphors was obtained for fuel-rich synthesis. {yields} A specific morphology was observed for each contribution. -- Abstract: Blue-emitting Eu{sup 2+}-doped barium magnesium aluminate (BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}) for advanced displays and lighting devices was prepared by a microwave induced solution combustion synthesis using urea as combustion fuel and nitrates as oxidizer. Purity control of as-synthesized blue phosphor particles was undertaken by modifying the fuel to oxidizer molar ratio. X-ray diffraction, scanning electron microscopy and photoluminescence were used to investigate powders crystallinity, particles size, morphology and luminescent properties, respectively. Fuel-rich urea reactions preferentially lead to pure phases compared to the powders synthesized with a stoichiometric fuel to oxidizer ratio. In both cases, we produce a nearly pure well-crystallized and nanostructured BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}. Photoluminescence measurements exhibit the characteristic blue emission of Eu{sup 2+} under UV light excitation however a weak red emission associated to Eu{sup 3+} is also detected.

  19. 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.

  20. 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.

  1. Comparison of Ba sub 2 YCu sub 3 O sub 7 minus. delta. films on NdGaO sub 3 and LaAlO sub 3

    SciTech Connect

    Phillips, J.M.; Siegal, M.P.; Perry, C.L.; Marshall, J.H. )

    1991-03-01

    This paper studies the properties of 100 nm films of Ba{sub 2}YCu{sub 3}O{sub 7{minus}{delta}} (BYCO) grown on LaAlO{sub 3}(100) and NdGaO{sub 3}(100) by co- evaporation of Cy, Y, and BaF{sub 2} followed by a two-stage anneal ex situ. The authors find that the structural properties of the films on both substrates are optimized when the maximum temperature of the anneal is 900{degrees} C, while the superconducting properties are slightly better if the maximum temperature does not exceed 875{degrees} C. Films on LaAlO{sub 3} can tolerate a longer time at the maximum annealing temperature than can films on NdGaP{sub 3}. The authors postulate that this is due to a reaction between Ga in the NdGaO{sub 3} and at least one of the constituents of the BYCO film (probably Y).

  2. Ferrimagnetic long-range order caused by periodicity of exchange interactions in the spin-1 trimer chain compounds ANi3P4O14 (A=Ca,Sr,Pb,Ba)

    NASA Astrophysics Data System (ADS)

    Hase, Masashi; Kitazawa, Hideaki; Tsujii, Naohito; Ozawa, Kiyoshi; Kohno, Masanori; Kido, Giyuu

    2006-07-01

    We report magnetic properties of ANi3P4O14 (A=Ca,Sr,Pb,Ba) . A spin-1 trimer chain with J1-J1-J2 interactions exists, where J1 and J2 denote two exchange interaction parameters. A magnetic phase transition occurs and a small spontaneous magnetization appears at low temperatures. The temperature dependence of magnetic susceptibility above the transition temperature and the magnetic-field dependence of magnetization in high magnetic fields are consistent with quantum Monte Carlo results for a spin model that consists of trimer chains with antiferromagnetic J1 and ferromagnetic J2 interactions. The small spontaneous magnetization is explainable qualitatively by ferrimagnetic long-range order in the chains and by imperfect cancellation of the net magnetic moments of the chains. To our knowledge, this is the first observation of ferrimagnetic long-range order whose origin is the periodicity of the exchange interactions in chains.

  3. 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.

  4. Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases.

    PubMed

    Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, Haitao

    2015-06-24

    A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range. PMID:25996244

  5. Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases.

    PubMed

    Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, Haitao

    2015-06-24

    A highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm(3) along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range.

  6. 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.

  7. 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

  8. 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.

  9. SIMS and FAB-MS surface studies of Pt-Sn/Al 2O 3 and Pt 3Pb model catalysts

    NASA Astrophysics Data System (ADS)

    Unger, W.; Lietz, G.; Lieske, H.; Völter, J.

    1990-08-01

    SIMS and FAB-MS methods have been applied to study surface complexes in chloride containing Pt-Sn/Al 2O 3 and Pt 3Pb in dependence on the temperature of treatment in oxygen. The existence and the limited (700 to ˜850 K) thermal stability of a (PtO xCl y) surface complex was confirmed. Pt-Sn/Al 2O 3, air treated (calcined) at 770 K, contains already neighbouring Pt and Sn species being precursors of alloy clusters formed during subsequent reduction.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Characteristics of metal-ferroelectric-insulator-silicon structures with ferroelectric (Pb{sub 0.8}Ba{sub 0.2})ZrO{sub 3} thin films and (Ba{sub 0.5}Sr{sub 0.5})TiO{sub 3} buffer layer

    SciTech Connect

    Liu, C.-H.; Wu, J.-M.; Wu, L.-J.

    2006-03-20

    The results of the fabrication and characterization of ferroelectric (Pb{sub 0.8}Ba{sub 0.2})ZrO{sub 3} (PBZ) thin films grown on nitrided silicon substrates with a (Ba{sub 0.5}Sr{sub 0.5})TiO{sub 3} (BST) buffer layer by the rf-magnetron sputtering technique are reported. The PBZ thin films were used as the ferroelectric layer in the ferroelectric field effect transistors. The PBZ thin films were grown with highly (100) preferred orientation on BST buffer layers. The Auger electron spectroscopy depth profiles showed no significant interdiffusion between the PBZ and silicon components. The capacitance-voltage properties of Pt/PBZ (360 nm)/BST (30 nm)/Si structures demonstrated ferroelectric switching effect. The memory windows were about 0.6, 1.25, and 1.76 V, respectively, for sweeping bias of {+-}3, {+-}4, and {+-}5 V. The leakage current density was below 1x10{sup -8} A/cm{sup 2} at {+-}4 V.

  16. Symmetry determination on Pb-free piezoceramic 0.5Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-0.5(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} using convergent beam electron diffraction method

    SciTech Connect

    Gao, Jinghui Zhong, Lisheng; Zhang, Lixue; Xue, Dezhen; Kimoto, Takayoshi; Song, Minghui; Ren, Xiaobing

    2014-02-07

    (1−x)(Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT-xBCT) Pb-free piezoceramic has been reported showing ultrahigh piezoelectric performance in its morphotropic phase boundary (MPB) region. However, the crystal structure characteristic for the MPB composition of BZT-xBCT is still under debate—between single orthorhombic phase and tetragonal + rhombohedral two phase mixture. In the present study, we perform the local symmetry determination on the MPB composition x = 0.5 using convergent beam electron diffraction analysis (CBED). Our CBED results from multiple zone axes suggest that there are two coexisting phases with the point group symmetries of 4 mm (tetragonal) and 3 m (rhombohedral) respectively, which agree with two phase mixture model. The strong piezoelectricity can thus be understood by considering the polarization rotation between tetragonal and rhombohedral phases by external field.

  17. 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+/.

  18. High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

    NASA Astrophysics Data System (ADS)

    Curetti, Nadia; Benna, Piera; Bruno, Emiliano

    2016-10-01

    In situ high-pressure X-ray diffraction study was performed on celsian (Cls97Or3) from Jakobsberg, Sweden. A single crystal of celsian was loaded in an ETH-type diamond anvil cell, and unit-cell parameters were measured at 20 different pressures up to 6.0 GPa at room T. The evolution of the unit-cell parameters and volume as a function of pressure shows a discontinuity at P ~ 5.7 GPa indicating a displacive first-order phase transition. The P-V data were fitted by a second-order Birch-Murnaghan EoS only up to 2.55 GPa, because at higher pressures a slight change in the compressional behavior of the unit-cell volume is observed, indicating a pre-transition volume softening. The resulting EoS coefficients are V 0 = 1461.4(1) Å3 and K T0 = 88.1(6) GPa. A second crystal of celsian was loaded in the DAC cell, and single-crystal in situ HP X-ray diffraction was performed at P = 0.0001, 2.1, 4.2, 5.5, 5.9, 6.5 and 7.8 GPa. The data collections between 0 and 5.5 GPa show only a- and b-type reflections confirming the I2/c space group. The appearance of c and d-type reflections at 5.9, 6.5 and 7.8 GPa, the analysis of the systematic absence and the structural refinements define the HP phase transition as an I2/c-P21/c transition. The most significant changes with compression in celsian are the deformation in the Ba polyhedra and the variation in the T-O-T angles.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Microstructure and evolution of a barium fluorozirconate crystal in a ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF glass

    SciTech Connect

    Lu, G.; Bradley, J.P.

    1986-08-01

    The evolutionary growth of one type of crystal in our ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF glasses is examined. The crystal was found to be a complex structure consisting of five coexisting barium fluorozirconate phases. In the initial very low bi-refringent crystal, the principal phase was ..beta..-ZrF/sub 4/ BaF/sub 2/. Later crystal growth occurred on top of the initial crystal, and was identified as ..beta..-2ZrF/sub 4/ . BaF/sub 2/. A strong scattering center was found at the center of some of the crystals and this was identified as elemental platinum.

  9. Pb-Pb Isotopic and X-ray Tomographic Constraints on the Origin of Chondrules

    NASA Astrophysics Data System (ADS)

    Charles, Christopher R. J.

    207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6+/-1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2+/-1.1Ma, and CAIs in Mokoia are 4567.9+/-5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/ 26Mg ages of CR chondrules. However if a 238U/ 235U<137.88 is used, the age for NWA801 chondrules becomes younger by ˜1Ma and discordant with26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were 'armoured' with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by ash-melting precursors into molten droplets that were vibrating as harmonic oscillators that 'froze-in' their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple ash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)-TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF-4 to suppress the 137Ba isobar during tandem

  10. Spectral behavior of the temperature-dependent photoresponse of BaAl2S4 layers grown by using hot-wall epitaxy

    NASA Astrophysics Data System (ADS)

    Jeong, J. W.; Hong, K. J.; Jeong, T. S.; Youn, C. J.

    2016-08-01

    The characteristic photocurrent (PC) property of BaAl2S4 layers grown by using hot-wall epitaxy was investigated. With decreasing temperature, the PC peaks position shifted toward the short-wavelength region and its intensity decreased dramatically. The energy variation of the PC peaks shift at different temperatures could be matched well by using E g ( T) = E g (0) - 7.556 × 10-4 T 2/( T + 523), where E g (0) was 4.0596, 4.1053, and 4.1094 eV corresponding to Γ4( z), Γ5( y), and Γ5( x) in the valence band in order of increasing energy, respectively. Thus, by the selection rule, the crystal field and the spin-orbit splitting were found to be 47.5 and -5.9 meV, respectively, through PC spectroscopy measurement. From the negative result for the spin-orbit parameter, the middle Γ5( x) and the lowest Γ5( y) levels in the valence band were found to be interchanged. By using the relation between the logarithm of the PC density and the reciprocal temperature, we extracted the dominant trap level as 23.2 in the high-temperature region and 5.4 meV in the low-temperature region. Consequently, we found that the dramatic decrease on the PC intensity was caused by these trapping centers.

  11. Luminous characteristics and thermal stability of BaMgAl 10O 17:Eu 2+ phosphor for white light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Shen, Changyu; Yang, Yi; Jin, Shangzhong; Ming, Jiangzhou

    2010-02-01

    A blue-emitting phosphor, BaMgAl 10O 17:Eu 2+ (BAM) was prepared by the solid-state reaction and X-ray powder diffraction (XRD) analysis confirmed the formation of BAM. Photoluminescence (PL) results showed that the phosphor can be efficiently excited by the light from near ultraviolet (NUV) to visible, and exhibited bright blue emission. The effect of the doped-Eu 2+ in BAM on the PL was investigated. To improve the BAM's thermal stability, BAM doped with additional Mg 2+ was studied. The experiment results showed that additional 0.05 mol Mg 2+-doped BAM had the highest emission intensity and thermal stability. By combining with NUV LED chip (GaN-based 380 nm emitting), a novel intense white LED was fabricated based on the blue phosphor BAM and a red phosphor Ca(La 0.5Eu 0.5) 4Si 3O 13. The white LED has the characteristics of color-rendering index of 87, CIE chromaticity coordinates ( x, y) of (0.3225, 0.3187), color temperature Tc of 5680 K, and light output of 51.7 lm/W under the forward-bias current of 20 mA. As the current increases, the relative intensity increases, the correlated color temperature Tc increases from 4000 to 7900 K and the color-rendering index Ra increases from 83 to 91 simultaneously.

  12. Differences in photoluminescence properties and thermal degradation between nanoparticle and bulk particle BaMgAl10O17:Eu2+ phosphors under UV?VUV irradiation.

    PubMed

    Liu, Bitao; Xin, Shuangyu; Li, Fenghua; Zhang, Jiachi; Wang, Yuhua

    2014-05-01

    BaMgAl10O17:Eu2+ (BAM) phosphors used for plasma display panels and three-band fluorescence lamps are exposed to an oxidizing environment at about 500 degrees C, which is currently unavoidable in actual applications. We investigated the mechanism of the luminance degradation of BAM caused by annealing at 500 degrees C based on the difference in luminance degradation of bulk particle and nanoparticle samples under various excitation source irradiations. When the samples were excited by the different light sources, more than 30% degradation of luminance occurred under 147 nm while less than 10% degradation occurred under 254 nm both for nanoparticle and bulk particle samples. In addition, the luminescence degradation of nanophosphors shows a different tendency compared to the bulk phosphors. With a model based on the particle size and excitation light penetration depth, we demonstrate that the degradation is still mainly ascribed to the oxidized of divalent Eu. The differences in luminescence properties between nanophosphors and bulk phosphors are also illustrated by this model. As a result, the potential industrial applications of nanophosphors are evaluated.

  13. 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.

  14. 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.

  15. 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

  16. 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).

  17. 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

  18. Crystalline orientations of Tl2Ba2Ca2Cu3O(x) grains on MgO, SrTiO3, and LaAlO3 substrates

    NASA Technical Reports Server (NTRS)

    Liou, S. H.; Wu, C. Y.

    1992-01-01

    Crystalline orientations of Tl2Ba2Ca2Cu3O(x) grains in magnetron sputtered films on MgO (001), SrTiO3 (001), and LaAlO3 (001) substrates were investigated by scanning electron microscopy. In contrast to the nearly single crystalline films on the lattice matched substrates SrTiO3 and LaAlO3, films on the MgO (001) substrate, being polycrystalline in nature, exhibit several preferred in-plane grain orientations. These orientations agree well with a simplified theory of near-coincidence site lattices between Tl2Ba2Ca2Cu3O(x) and MgO.

  19. [Determination of Al, Be, Cd, Co, Cr, Mn, Ni, Pb, Se and Tl in whole blood by atomic absorption spectrometry without preliminary sample digestion].

    PubMed

    Ivanenko, N B; Ivanenko, A A; Solov'ev, N D; Navolotskiĭ, D V; Pavlova, O V; Ganeev, A A

    2014-01-01

    Methods of whole blood trace element determination by Graphite furnace atomic absorption spectrometry (in the variant of Zeeman's modulation polarization spectrometry) have been proposed. They do not require preliminary sample digestion. Furnace programs, modifiers and blood dilution factors were optimized. Seronorm™ human whole blood reference materials were used for validation. Dynamic ranges (for undiluted blood samples) were: Al 8 ¸ 210 мg/L; Be 0.3 ¸ 50 мg/L; Cd 0.2 ¸ 75 мg/L; Сo 5 ¸ 350 мg/L; Cr 10 ¸ 100 мg/L; Mn 6 ¸ 250 мg/L; Ni 10 ¸ 350 мg/L; Pb 3 ¸ 240 мg/L; Se 10 ¸ 500 мg/L; Tl 2 ¸ 600 мg/L. Precision (RSD) for the middle of dynamic range ranged from 5% for Mn to 11 for Se.

  20. Tunable deep ultraviolet single-longitudinal-mode laser generated with Ba(1-x)B(2-y-z)O4Si(x)Al(y)Ga(z) crystal.

    PubMed

    Wang, Rui; Teng, Hao; Wang, Nan; Han, Hainian; Wang, Zhaohua; Wei, Zhiyi; Hong, Maochun; Lin, Wenxiong

    2014-04-01

    We report a new nonlinear crystal, Ba(1-x)B(2-y-z)O4Si(x)Al(y)Ga(z), and employ it to a compact 1 kHz single-longitudinal-mode Ti:Sapphire master oscillator power amplifier system for fourth harmonic generation. A maximum output power of 130 mW is obtained in the tunable range of 195-205 nm with linewidth of less than 0.1 pm.

  1. 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.

  2. Interfacial Reaction Between Cu Substrates and Zn-Al Base High-Temperature Pb-Free Solders

    NASA Astrophysics Data System (ADS)

    Takaku, Yoshikazu; Felicia, Lazuardi; Ohnuma, Ikuo; Kainuma, Ryosuke; Ishida, Kiyohito

    2008-03-01

    Chemical reactions between Cu substrates and Zn-Al high-temperature solder alloys, Zn-4Al and Zn-4Al-1Cu (mass%), at temperatures ranging from 420°C to 530°C were experimentally investigated by a scanning electron microscope using backscattered electrons (SEM-BSE) and an electron probe microanalyzer (EPMA). Intermediate phases (IMPs), β(A2) or β'(B2), γ(D82), and ɛ(A3) phases formed and grew during the soldering and aging treatments. The consumption rate of the IMP for Cu substrates is described by the square root of t in both the alloys, while the additional Cu in the molten Zn-Al alloy slightly suppresses the consumption of Cu substrates. The growth of IMPs during soldering treatment is controlled by the volume diffusion of constituent elements, and its activation energy increases in the order of Q ɛ < Q γ < Q β. In view of the aging process, the growth of IMPs is considered to be controlled by the volume diffusion. In particular, the layer thickness of γ rapidly grows over 200°C, although the thickness of the β layer grows very slowly.

  3. 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

  4. Pressure stabilized Se-Se dimer formation in PbSe 2

    NASA Astrophysics Data System (ADS)

    Bremholm, M.; Hor, Y. S.; Cava, R. J.

    2011-01-01

    The preparation of PbSe 2 through the reaction of PbSe with excess Se at 4.5 GPa and 650 °C is reported. The crystal structure, determined from X-ray powder diffraction data (CuAl 2 structure type, I4/mcm (#140), a = 6.42695(11) Å, c = 7.70254(13) Å, Z = 4), consists of layers of [Se 2] 2- dimers with Pb 2+ in square antiprismatic coordination with Se. This is a rare crystal structure for divalent metal chalcogenides, previously only identified for SrS 2 and BaTe 2. Undoped PbSe 2 as well as Bi 3+- and Ag +-doped samples (10% Pb substitution) show semi-metallic resistivity down to 0.4 K. Magnetic susceptibility measurement of PbSe 2 shows no magnetic ordering above 1.8 K. The Seebeck coefficients show nearly linear behavior from 35 to 400 K and the largest numerical values are found in the case of undoped PbSe 2, + 99 μVK -1, and Bi 3+-doped PbSe 2, - 146 μVK -1, at the highest temperature measured, 400 K.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. An Investigation of Armenite, BaCa2Al6Si9O302H2O.H2O Molecules and H Bonding in Microporous Silicates

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Gatta, G.; Xue, X.; McIntyre, G.

    2012-12-01

    The crystal chemistry of armenite, ideally BaCa2Al6Si9O30.2H2O, a double-ring structure belonging to the milarite group, was studied to better understand the nature of extra-framework "Ca-oxygen-anion-H2O-molecule quasi-clusters" and H bonding behavior in microporous silicates. Neutron and X-ray single-crystal diffraction and IR powder and 1H NMR spectroscopic measurements were made. Four crystallographically independent Ca and H2O molecule sites were refined from the diffraction data, whereby both sites appear to have partial occupancies such that locally a Ca atom can have only a single H2O molecule bonded to it through an ion-dipole interaction. The Ca cation is further bonded to six O atoms of the framework forming a quasi cluster around it. The neutron results give the first static description of the protons in armenite, allowing bond distances and angles relating to the H2O molecules and H bonds to be determined. The IR spectrum of armenite is characterized in the OH-stretching region at RT by two broad bands at roughly 3470 and 3410 cm-1 and by a single H2O bending mode at 1654 cm-1. At 10 K four intense OH bands are located at 3479, 3454, 3401 and 3384 cm-1 and two H2O bending modes at 1650 and 1606 cm-1. The 1H MAS NMR spectrum shows a single strong resonance near 5.3 ppm and a smaller one near 2.7 ppm. The former can be assigned to H2O molecules bonded to Ca and the latter to weakly bonded H2O located at a site at the center of the structural double ring and it is partially occupied. The nature of H bonding in the microporous Ca-bearing zeolites scolecite, wairakite and epistilbite are also analyzed. The average OH stretching wavenumber shown by the IR spectra of armenite (~3435 cm-1) and scolecite (~3430 cm-1) are similar, while the average OH wavenumbers for wairakite (~3475 cm-1) and epistilbite (~3500 cm-1) are greater. In all cases the average OH stretching wavenumber is more similar to that of liquid water (~3400 cm-1) than of ice (~3220 cm-1). The

  15. 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.

  16. 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).

  17. Effects of Al substitution and thermal annealing on magnetoelectric Ba0.5Sr1.5Zn2Fe12O22 investigated by the enhancement factor of 57Fe nuclear magnetic resonance.

    PubMed

    Kwon, Sangil; Kang, Byeongki; Kim, Changsoo; Jo, Euna; Lee, Soonchil; Chai, Yi Sheng; Chun, Sae Hwan; Kim, Kee Hoon

    2014-04-01

    The magnetoelectric properties of hexaferrite Ba0.5Sr1.5Zn2Fe12O22 are significantly improved by Al substitution and thermal annealing. Measuring the enhancement factor of 57Fe NMR, we found direct microscopic evidence that the magnetic moments of the L and S blocks are rotated by a magnetic field in such a way as to increase the net magnetic moment of a magnetic unit, even after the field is removed. Al substitution makes magnetoelectric property arise easily by suppressing the easy-plane anisotropy. The effect of thermal annealing is to stabilize the multiferroic state by reducing the number of pinning sites and the electron spin fluctuation. The transverse conic structure gradually changes to the alternating longitudinal conic structure where spins fluctuate more severely.

  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. Formation of nets of corner-shared bicapped gold squares in SrAu3Ge: how a BaAl4-type derivative reconciles fewer valence electrons and the origin of its uniaxial negative thermal expansion.

    PubMed

    Lin, Qisheng; Corbett, John D

    2012-03-14

    SrAu(3)Ge was synthesized by direct fusion of the mixed elements at high temperature followed by annealing treatments, and its structure was determined by single crystal X-ray diffraction means in space group (Pearson symbol: tP10) P4/nmm, a = 6.264(1) Å, c = 5.5082(9) Å, Z = 2 at room temperature. The structure of SrAu(3)Ge, a reapportioned √2 × √2 × 1 superstructure of CeMg(2)Si(2) (P4/mmm), exhibits checkerboard nets of corner-shared bicapped Au squares (or corner-shared Au(Au(4/2))Ge octahedra), in which the apical Au-Ge pairs in adjoining nets are strongly interbonded in the c direction. This motif contrasts with that of the common BaAl(4) (I4/mmm) prototype in which Al squares in comparable layers are alternately monocapped by Al from the top or the bottom. Typical examples show valence electron counts (vec) between 12 and 16 for the BaAl(4) type and that for CeMg(2)Si(2) is similar, 15. The special stability of SrAu3Ge, with vec = 9, derives from significant relativistic contribution of the Au 5d(10) states to the Au-Ge and Au-Au bonding. These factors are also recognized in the marked redistribution of Au and Ge site occupancies from those in CeMg(2)Si(2). SrAu(3)Ge exhibits a pronounced uniaxial negative thermal expansion along c, with a coefficient of -1.57 versus 2.16 × 10(-5) K(-1) in a and b. The reticulated Au(5)Ge octahedral layers expand in the ab plane on heating, whereas the strong, interlayer Au-Ge bonds remain fixed.

  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. Effects of sulfation level on the desulfation behavior of pre-sulfated Pt BaO/Al2O3 lean NOx trap catalysts: a combined H2 Temperature-Programmed Reaction, in-situ sulfur K-edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

    SciTech Connect

    Kim, Do Heui; Szanyi, Janos; Kwak, Ja Hun; Wang, Xianqin; Hanson, Jonathan C.; Engelhard, Mark H.; Peden, Charles HF

    2009-04-03

    Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rather than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.

  2. A new fluorescent chemosensor for Al3+ ion based on schiff base naphthalene derivatives

    NASA Astrophysics Data System (ADS)

    Azadbakht, Reza; Rashidi, Somaye

    2014-06-01

    A new naphthalene derivative receptor (H2L) was synthesized. The chemosensor (H2L) exhibited a strong fluorescence enhancement in the presence of trace amounts of Al3+, attributable to chelation-enhanced fluorescence (CHEF) effect, which also displayed high selectivity over a series of other metal cations (Na+, K+, Cs+, Mg2+, Ba2+, Pb2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) in ethanol.

  3. 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.

  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. Thermally stable green Ba(3)Y(PO(4))3:Ce(3+),Tb(3+) and red Ca(3)Y(AlO)(3)(BO(3))4:Eu(3+) phosphors for white-light fluorescent lamps.

    PubMed

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

    2011-01-01

    A class of thermal stable of green-emitting phosphors Ba(3)Y(PO(4))(3):Ce(3+),Tb(3+) (BYP:Ce(3+),Tb(3+)) and red-emitting phosphors Ca(3)Y(AlO)(3)(BO(3))(4):Eu(3+) (CYAB:Eu(3+)) for white-light fluorescent lamps were synthesized by high temperature solid-state reaction. We observed a decay of only 3% at 150 °C for BYP:0.25Ce3+,0.25Tb3+ (3% for LaPO4:Ce(3+),Tb(3+)), and a decay of 4% for CYAB:0.5Eu(3+) (7% for Y(2)O(3):Eu(3+), 24% for Y(2)O(2)S:Eu(3+)). The emission intensity of composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) is 70% of that of commercial LaPO(4):Ce(3+),Tb(3+) phosphors, and the CIE chromaticity coordinates are found to be (0.323, 0.534). The emission intensity of Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) is 70% and 83% of those of Y(2)O(3):Eu(3+) and Y(2)O(2)S:Eu(3+) phosphors, respectively, and the CIE chromaticity coordinates are redder (0.652, 0.342) than those of Y(2)O(3):Eu(3+) (0.645, 0.347) and Y(2)O(2)S:Eu(3+) (0.647, 0.343). A white-light fluorescent lamp is fabricated using composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) and Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) phosphors and matching blue-emitting phosphors. The results indicate that the quality of the brightness and color reproduction is suitable for application in shortwave UV fluorescent lamps. The white-light fluorescent lamp displays CIE chromaticity coordinates of x = 0.33, y = 0.35, a warm white light with a correlated color temperature of 5646 K, and a color-rendering index of Ra = 70.

  6. Raman spectroscopic study of the hydroxy-phosphate mineral plumbogummite PbAl3(PO4)2(OH,H2O)6

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Palmer, Sara J.; Xi, Yunfei; Čejka, Jiří; Sejkora, Jiří; Plášil, Jakub

    2013-02-01

    Plumbogummite PbAl3(PO4)2(OH,H2O)6 is a mineral of environmental significance and is a member of the alunite-jarosite supergroup. The molecular structure of the mineral has been investigated by Raman spectroscopy. The spectra of different plumbogummite specimens differ although there are many common features. The Raman spectra prove the spectral profile consisting of overlapping bands and shoulders. Raman bands and shoulders observed at 971, 980, 1002 and 1023 cm-1 (China sample) and 913, 981, 996 and 1026 cm-1 (Czech sample) are assigned to the ν1 symmetric stretching modes of the (PO4)3-, at 1002 and 1023 cm-1 (China) and 996 and 1026 cm-1 to the ν1 symmetric stretching vibrations of the (O3POH)2- units, and those at 1057, 1106 and 1182 (China) and at 1102, 1104 and 1179 cm-1 (Czech) to the ν3 (PO4)3- and ν3 (PO3) antisymmetric stretching vibrations. Raman bands and shoulders at 634, 613 and 579 cm-1 (China) and 611 and 596 cm-1 (Czech) are attributed to the ν4 (δ) (PO4)3- bending vibrations and those at 507, 494 and 464 cm-1 (China) and 505 and 464 cm-1 (Czech) to the ν2 (δ) (PO4)3- bending vibrations. The Raman spectrum of the OH stretching region is complex. Raman bands and shoulders are identified at 2824, 3121, 3249, 3372, 3479 and 3602 cm-1 for plumbogummite from China, and at 3077, 3227, 3362, 3480, 3518 and 3601 cm-1 for the Czech Republic sample. These bands are assigned to the ν OH stretching modes of water molecules and hydrogen ions. Approximate O-H⋯O hydrogen bond lengths inferred from the Raman spectra vary in the range >3.2-2.62 Å (China) and >3.2-2.67 Å (Czech). The minority presence of some carbonate ions in the plumbogummite (China sample) is connected with distinctive intensity increasing of the Raman band at 1106 cm-1, in which may participate the ν1 (CO3)2- symmetric stretching vibration overlapped with phosphate stretching vibrations.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Dependences of the density of M{sub 1-x}R{sub x}F{sub 2+x} and R{sub 1-y}M{sub y}F{sub 3-y} single crystals (M = Ca, Sr, Ba, Cd, Pb; R means rare earth elements) on composition

    SciTech Connect

    Sorokin, N. I. Krivandina, E. A.; Zhmurova, Z. I.

    2013-11-15

    The density of single crystals of nonstoichiometric phases Ba{sub 1-x}La{sub x}F{sub 2+x} (0 {<=} x {<=} 0.5) and Sr{sub 0.8}La{sub 0.2-x}Lu{sub x}F{sub 2.2} (0 {<=} x {<=} 0.2) with the fluorite (CaF{sub 2}) structure type and R{sub 1-y}Sr{sub y}F{sub 3-y} (R = Pr, Nd; 0 {<=} y {<=} 0.15) with the tysonite (LaF{sub 3}) structure type has been measured. Single crystals were grown from a melt by the Bridgman method. The measured concentration dependences of single crystal density are linear. The interstitial and vacancy models of defect formation in the fluorite and tysonite phases, respectively, are confirmed. To implement the composition control of single crystals of superionic conductors M{sub 1-x}R{sub x}F{sub 2+x} and R{sub 1-y}M{sub y}F{sub 3-y} in practice, calibration graphs of X-ray density in the MF{sub 2}-RF{sub 3} systems (M = Ca, Sr, Ba, Cd, Pb; R = La-Lu, Y) are plotted.

  13. 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 PAGES

    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

  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. 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

  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. 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.

  18. 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.

  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. Effect of Pb on the Mechanical Properties of Nanocrystalline A1

    SciTech Connect

    Rajulapati, Koteswararao V; Scattergood, Ronald; Murty, K.; Duscher, Gerd J M; Koch, Carl C

    2006-01-01

    Nanocrystalline (nc) Al-Pb two phase mixtures of different Pb concentrations were made by two different routes using high energy ball milling. The microhardness measurements show a softening in nc Al-Pb composites with the increase in Pb content, contradicting the previous results reported in the literature. We conclude that interaction of Pb atoms with nanocrystalline Al grain boundaries is responsible for the softening of the nc Al matrix observed in the current study.

  1. 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

  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.

  3. 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

  4. 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

  5. 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.

  6. Pulsed laser deposition of epitaxial Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7} bilayers on LaAlO{sub 3} substrates

    SciTech Connect

    Harkness, S.D.; Yue, C.F.; Borek, M.A.; Singh, R.K.

    1994-09-01

    YBa{sub 2}Cu{sub 3}O{sub 7}/Ba{sub x}Sr{sub 1{minus}x}TiO{sub 8} bilayers were grown epitaxially on LaAlO{sub 3} substrates using the pulsed laser deposition method. A microstructural investigation revealed that all compositions of Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3} investigated from x = 0 to x = 1 showed (001) orientation and epitaxy across the interface as analyzed by Rutherford backscattering spectroscopy channel yields of <8% for BaTiO{sub 8} on YBa{sub 2}Cu{sub 3}O{sub 7} films. Dielectric properties including the dielectric constant, k, and the loss tangent, tan {delta}, were measured as a function of composition, and it was found that the highest k-values (k = 400) existed for the x = 0.72 composition. 9 refs., 4 figs., 2 tabs.

  7. 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

  8. 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

  9. Isothermal desulfation of pre-sulfated Pt-BaO/γ-Al2O3 lean NOx trap catalysts with H2: the effect of H2 concentration and the roles of CO2 and H2O

    SciTech Connect

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

    2012-01-12

    The desulfation mechanisms of pre-sulfated Pt-BaO/{gamma}-Al{sub 2}O{sub 3} lean NOx trap catalysts were investigated under isothermal conditions (600 C) using H{sub 2} as the reductant. Sulfates were found to be reduced first with H{sub 2} to produce SO{sub 2}, followed by a reaction between SO{sub 2} and H{sub 2} to produce H{sub 2}S. Gas analysis during the rich pulse reveals that the sulfur removal efficiency is initially proportional to the H{sub 2} concentration. At constant H{sub 2} concentration the overall desulfation efficiency decreases in the order of H{sub 2}/CO{sub 2}/H{sub 2}O > H{sub 2}/CO{sub 2} > H{sub 2}/H{sub 2}O > H{sub 2}, as confirmed by XPS analysis of residual sulfur in the desulfated samples. H{sub 2}O limits the evolution of SO{sub 2} at an early stage of the rich pulse and enhances the production of H{sub 2}S in later stages of reduction. CO{sub 2} is involved in both the formation of COS and the production of H{sub 2}O (via the reverse water-gas shift reaction), therefore, resulting in an increased overall efficiency.

  10. 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.

  11. 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.

  12. 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.

  13. Cross sections for the production of residual nuclides by low- and medium-energy protons from the target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au

    NASA Astrophysics Data System (ADS)

    Michel, R.; Bodemann, R.; Busemann, H.; Daunke, R.; Gloris, M.; Lange, H.-J.; Klug, B.; Krins, A.; Leya, I.; Lüpke, M.; Neumann, S.; Reinhardt, H.; Schnatz-Büttgen, M.; Herpers, U.; Schiekel, Th.; Sudbrock, F.; Holmqvist, B.; Condé, H.; Malmborg, P.; Suter, M.; Dittrich-Hannen, B.; Kubik, P.-W.; Synal, H.-A.; Filges, D.

    1997-07-01

    Cross sections for residual nuclide production by p-induced reactions were measured from thresholds up to 2.6 GeV using accelerators at CERN/Geneve, IPN/Orsay, KFA/Jülich, LANL/Los Alamos, LNS/Saclay, PSI/Villigen, TSL/Uppsala, LUC/Louvain La Neuve. The target elements C, N, O, Mg, Al, Si, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Nb, Ba and Au were investigated. Residual nuclides were measured by X- and γ-spectrometry and by Accelerator Mass Spectrometry (AMS). The measured cross sections were corrected for interfering secondary particles in experiments with primary proton energies above 200 MeV. Our consistent database covers presently ca 550 nuclear reactions and contains nearly 15000 individual cross sections of which about 10000 are reported here for the first time. They provide a basis for model calculations of the production of cosmogenic nuclides in extraterrestrial matter by solar and galactic cosmic ray protons. They are of importance for many other applications in which medium energy nuclear reactions have to be considered ranging from astrophysics over space and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification. The experimental data are compared with theoretical ones based on calculations using an INC/E model in form of the HETC/KFA2 code and on the hybrid model of preequilibrium reactions in form of the AREL code.>

  14. Effect of YBa2Cu3O7-δ film thickness on the dielectric properties of Ba0.1Sr0.9TiO3 in Ag /Ba0.1Sr0.9TiO3/YBa2Cu3O7-δ/LaAlO3 multilayer structures

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaohong; Peng, Wei; Li, Jie; Chen, Yingfei; Tian, Haiyan; Xu, Xiaoping; Zheng, Dongning

    2005-01-01

    Ferroelectric and superconductor bilayers of Ba0.1Sr0.9TiO3 (BSTO)/YBa2Cu3O7-δ (YBCO), with different YBCO film thicknesses, have been fabricated in situ by pulsed-laser deposition on 1.2° vicinal LaAlO3 substrates. The dielectric properties of BSTO thin films were measured with a parallel-plate capacitor configuration in the temperature range of 77-300K. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Diffused AFE/RFE/PE phase transitions in (Pb0.88Ba0.1La0.02)(Zr0.6Sn0.4- x Ti x )0.995O3 ceramics obtained from oxides and carbonates

    NASA Astrophysics Data System (ADS)

    Niemiec, Przemysław; Skulski, Ryszard; Bochenek, Dariusz; Wawrzała, Paweł

    2013-02-01

    We present the results of preparation and investigation of antiferroelectric/relaxor/paraelectric (AFE/RFE/PE) phase transitions in ceramics, (Pb0.88Ba0.1La0.02)(Zr0.6Sn0.4- x Ti x )0.995O3 with x = 0.05, 0.055, 0.06, and 0.065, obtained from oxides and carbonates using a conventional ceramic technology. Such compositions can be good candidates for energy storage in pulse capacitors. For such application, the critical field should be appropriate, i.e., neither too high nor too low, since the transition from AFE to FE/RFE properties should take place in fields close to electric breakdown, since in such situation the stored energy is the biggest. We present the results of investigations of the microstructure, dielectric permittivity, and P-E hysteresis loops at various temperatures. It has been stated that some of the investigated materials exhibit field-induced AFE/FE or AFE/RF transition appropriate for application in pulse capacitors.

  19. The role of TiO{sub 2} in the B{sub 2}O{sub 3}-Na{sub 2}O-PbO-Al{sub 2}O{sub 3} glass system

    SciTech Connect

    Sousa, N.C.A. de; Araujo, M.T. de; Jacinto, C.; Vermelho, M.V.D.; Dantas, N.O.; Santos, C.C.; Guedes, I.

    2011-11-15

    Optical and vibrational studies have been carried out on 60B{sub 2}O{sub 3}.(20-x)Na{sub 2}O.10PbO.10Al{sub 2}O{sub 3}:xTiO{sub 2} (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO{sub 2} in the 60B{sub 2}O{sub 3}.20Na{sub 2}O.10PbO.10Al{sub 2}O{sub 3} glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap ({Delta}E{sub opt}) and Urbach's energy (E{sub U}) decreases as TiO{sub 2} content increases. The changes observed in the Raman and IR spectra are related to the BO{sub 4}{yields}BO{sub 3} back conversion effect and the appearance of 'loose' BO{sub 4}{sup -} groups. The data indicate that titanium ions act as a network modifier. - Graphical abstract: Behavior of the relative integrated intensity of the IR bands, Ar=A{sub 4}/A{sub 3}, as TiO{sub 2} content increases. A decrease of 45% of Ar indicates that the number of BO{sub 4} groups is decreasing due to the BO{sub 4}{yields}BO{sub 3} back conversion. Highlights: > The XRD data show the amorphous character of all measured glasses. > The optical absorption results evidenced possible change of the glass structure. > The Raman data have revealed some vibrational modifications. > The overall results indicate that titanium acts as a network modifier.

  20. 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...

  1. 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.

  2. Crystal and electronic structures, luminescence properties of Eu{sup 2+}-doped Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} and M{sub y}Si{sub 6-z}Al{sub z-y}O{sub z+y}N{sub 8-z-y} (M=2Li, Mg, Ca, Sr, Ba)

    SciTech Connect

    Li, Y.Q. Hirosaki, N.; Xie, R.J.; Takeda, T.; Mitomo, M.

    2008-12-15

    The crystal structure, electronic structure, and photoluminescence properties of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} (x=0-0.1, 0Al{sub z-x-y}O{sub z+x+y}N{sub 8-z-x-y} (M=2Li, Mg, Ca, Sr, Ba) have been studied. Single-phase Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} can be obtained in very narrow ranges of x{<=}0.06 (z=0.15) and z<0.5 (x=0.3), indicating that limited Eu{sup 2+} ions can be incorporated into nitrogen-rich Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z}. The Eu{sup 2+} ion is found to occupy the 2b site in a hexagonal unit cell (P6{sub 3}/m) and directly connected by six adjacent nitrogen/oxygen atoms ranging 2.4850-2.5089 A. The calculated host band gaps by the relativistic DV-X{alpha} method are about 5.55 and 5.45 eV (without Eu{sup 2+} 4f5d levels) for x=0 and 0.013 in Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} (z=0.15), in which the top of the 5d orbitals overlap with the Si-3s3p and N-2p orbitals within the bottom of the conduction band of the host. Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} shows a strong green emission with a broad Eu{sup 2+} band centered at about 530 nm under UV to near-UV excitation range. The excitation and emission spectra are hardly modified by Eu concentration and dual-doping ions of Li and other alkaline-earth ions with Eu. Higher Eu concentrations can significantly quench the luminescence of Eu{sup 2+} and decrease the thermal quenching temperature. In addition, the emission spectrum can only be slightly tuned to the longer wavelengths ({approx}529-545 nm) by increasing z within the solid solution range of z<0.5. Furthermore, the luminescence intensity of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} can be improved by increasing z and the dual-doping of Li and Ba. - Graphical abstract: Excitation and emission spectra of Eu{sub x}Si{sub 6-z}Al{sub z-x}O{sub z+x}N{sub 8-z-x} with the project of a 2x2x2 supercell crystal structure

  3. 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.

  4. 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.

  5. Crystal Structure and Thermodynamic Stability of Ba/Ti-Substituted Pollucites for Radioactive Cs/Ba Immobilization

    DOE PAGES

    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

  6. U-Pb ages, geochemistry, C-O-Nd-Sr-Hf isotopes and petrogenesis of the Catalão II carbonatitic complex (Alto Paranaíba Igneous Province, Brazil): implications for regional-scale heterogeneities in the Brazilian carbonatite associations

    NASA Astrophysics Data System (ADS)

    Guarino, Vincenza; Wu, Fu-Yuan; Melluso, Leone; de Barros Gomes, Celso; Tassinari, Colombo Celso Gaeta; Ruberti, Excelso; Brilli, Mauro

    2016-09-01

    The Catalão II carbonatitic complex is part of the Alto Paranaíba Igneous Province (APIP), central Brazil, close to the Catalão I complex. Drill-hole sampling and detailed mineralogical and geochemical study point out the existence of ultramafic lamprophyres (phlogopite-picrites), calciocarbonatites, ferrocarbonatites, magnetitites, apatitites, phlogopitites and fenites, most of them of cumulitic origin. U-Pb data have constrained the age of Catalão I carbonatitic complex between 78 ± 1 and 81 ± 4 Ma. The initial strontium, neodymium and hafnium isotopic data of Catalão II (87Sr/86Sri = 0.70503-0.70599; ɛNdi = -6.8 to -4.7; 176Hf/177Hf = 0.28248-0.28249; ɛHfi = -10.33 to -10.8) are similar to the isotopic composition of the Catalão I complex and fall within the field of APIP kimberlites, kamafugites and phlogopite-picrites, indicating the provenance from an old lithospheric mantle source. Carbon isotopic data for Catalão II carbonatites (δ13C = -6.35 to -5.68 ‰) confirm the mantle origin of the carbon for these rocks. The origin of Catalão II cumulitic rocks is thought to be caused by differential settling of the heavy phases (magnetite, apatite, pyrochlore and sulphides) in a magma chamber repeatedly filled by carbonatitic/ferrocarbonatitic liquids (s.l.). The Sr-Nd isotopic composition of the Catalão II rocks matches those of APIP rocks and is markedly different from the isotopic features of alkaline-carbonatitic complexes in the southernmost Brazil. The differences are also observed in the lithologies and the magmatic affinity of the igneous rocks found in the two areas, thus demonstrating the existence of regional-scale heterogeneity in the mantle sources underneath the Brazilian platform.

  7. 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.

  8. 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

  9. D{sub 3h} [A-CE{sub 3}-A]{sup −} (E = Al and Ga, A = Si, Ge, Sn, and Pb): A new class of hexatomic mono-anionic species with trigonal bipyramidal carbon

    SciTech Connect

    Wu, Yan-Bo E-mail: zxwang@ucas.ac.cn; Li, Yan-Qin; Bai, Hui; Lu, Hai-Gang; Li, Si-Dian; Zhai, Hua-Jin; Wang, Zhi-Xiang E-mail: zxwang@ucas.ac.cn

    2014-03-14

    The non-classical trigonal bipyramidal carbon (TBPC) arrangement generally exists as transition states (TSs) in nucleophilic bimolecular substitution (S{sub N}2) reactions. Nevertheless, chemists have been curious about whether such a carbon bonding could be stable in equilibrium structures for decades. As the TBPC arrangement was normally realized as cationic species theoretically and experimentally, only one anionic example ([At-C(CN){sub 3}-At]{sup −}) was computationally devised. Herein, we report the design of a new class of anionic TBPC species by using the strategy similar to that for stabilizing the non-classical planar hypercoordinate carbon. When electron deficient Al and Ga were used as the equatorial ligands, eight D{sub 3h} [A-CE{sub 3}-A]{sup −} (E = Al and Ga, A = Si, Ge, Sn, and Pb) TBPC structures were found to be the energy minima rather than TSs at both the B3LYP and MP2 levels. Remarkably, the energetic results at the CCSD(T) optimization level further identify [Ge-CAl{sub 3}-Ge]{sup −} and [Sn-CGa{sub 3}-Sn]{sup −} even to be the global minima and [Si-CAl{sub 3}-Si]{sup −} and [Ge-CGa{sub 3}-Ge]{sup −} to be the local minima, only slightly higher than their global minima. The electronic structure analyses reveal that the substantial ionic C–E bonding, the peripheral E–A covalent bonding, and the axial mc-2e (multi center-two electrons) bonding play roles in stabilizing these TBPC structures. The structural simplicity and the high thermodynamic stability suggest that some of these species may be generated and captured in the gas phase. Furthermore, as mono-anionic species, their first vertical detachment energies are differentiable from those of their nearest isomers, which would facilitate their characterization via experiments such as the negative ion photoelectron spectroscopy.

  10. 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.

  11. 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.

  12. Investigation on morphological stability of ultrathin Pb films

    SciTech Connect

    Zhang, L. H.; Sui, M. L.; Zhang, L.; Hu, K. Y.; Li, D. X.

    2001-06-04

    Ultrathin Pb films supported by Al film were made by using cold-rolling and ion-beam thinning techniques. The morphological instability of the Pb film under electron-beam irradiation was investigated by means of in situ transmission electron microscopy observations. It has been found that under electron-beam irradiation, Pb films with an incoherent Pb/Al interface spheroidized into Pb particles, but those with a semicoherent Pb/Al interface were stable in morphology. The morphological stability of thin films depends on the microstructure and the thermodynamic property of the interphase boundary. A critical interfacial energy for the spheroidization of thin films was determined based on a thermodynamics analysis. {copyright} 2001 American Institute of Physics.

  13. Structure-composition-luminescence correlations in Sr{sub 2.5-3x/2}Ba{sub 0.5}Sm{sub x}Al{sub 1-y}In{sub y}O{sub 4}F (0.001{<=}x, y{<=}0.1) oxyfluorides

    SciTech Connect

    Park, Sangmoon

    2012-02-15

    Luminescent materials composed of Sr{sub 2.5-3x/2}Ba{sub 0.5}Sm{sub x}Al{sub 1-y}In{sub y}O{sub 4}F (0.001{<=}x, y{<=}0.1) were prepared by the solid-state reaction method. After the replacement of Sr{sup 2+} and Al{sup 3+} ions by Sm{sup 3+} and In{sup 3+} ions in Sr{sub 2.5}Ba{sub 0.5}AlO{sub 4}F host structure, a novel charge-transfer band centered around 304 nm shifted from 240 nm is monitored; moreover, sharp and well-resolved emission peaks in the {sup 4}G{sub 5/2}{yields}{sup 6}H{sub J} transitions of the Sm{sup 3+} activator are observed. The diverse excitation and emission photoluminescence spectra of Sr{sub 2.5-3x/2}Ba{sub 0.5}Sm{sub x}Al{sub 1-y}In{sub y}O{sub 4}-{alpha}F1-{delta} (0.001{<=}x, y{<=}0.1) phosphors originated by the charge-transfer of the host to the Sm{sup 3+} activator, the f-f transitions in the Sm{sup 3+} ions, and the defect-induced self-activation are also introduced. - Graphical abstract: After the replacement of Sr{sup 2+} and Al{sup 3+} ions by Sm{sup 3+} and In{sup 3+} ions in Sr{sub 2.5}Ba{sub 0.5}AlO{sub 4}F host structure, a novel charge-transfer band centered around 304 nm shifted from 240 nm is monitored; moreover, sharp and well-resolved emission peaks in the {sup 4}G{sub 5/2}{yields}{sup 6}H{sub J} transitions of the Sm{sup 3+} activator are observed (Figure, Left). The diverse excitation and emission photoluminescence spectra of Sr{sub 2.5-3x/2}Ba{sub 0.5}Sm{sub x}Al{sub 1-y}In{sub y}O{sub 4}-{alpha}F1-{delta} (0.001{<=}x, y{<=}0.1) phosphors originated by the charge-transfer of the host to the Sm{sup 3+} activator, the f-f transitions in the Sm{sup 3+} ions, and the defect-induced self-activation are also introduced. Highlights: Black-Right-Pointing-Pointer Strong and well-resolved emitting peaks are monitored in Sm{sup 3+}-doped oxyfluoride phosphors. Black-Right-Pointing-Pointer Diverse excitation and emission spectra of the oxyfluoride phosphors originated from Sm{sup 3+} activator and the defect-induced self

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Performance of two-pole bandpass filters photodefined on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Toncich, S. S.; Bhasin, K. B.

    1993-01-01

    The performance of 7.3-GHz two-pole bandpass filters (5% bandwidth) fabricated on double-sided Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O thin films deposited on LaAlO3 is discussed. At 77 K, the Tl-Ba-Ca-Cu-O and Y-Ba-Cu-O superconducting filters exhibited minimum passband insertion losses of 0.3 and 1.2 dB, respectively. An insertion loss of 3.4 dB was measured for an all-gold filter at 77 K.

  20. 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.

  1. Material Compatibility with Isothermal Pb-Li

    SciTech Connect

    Pint, Bruce A; Walker, Larry R; Unocic, Kinga A

    2012-01-01

    Eutectic Pb-Li is a leading candidate for current fusion blanket concepts as a coolant. However, there is very little data about the compatibility of most materials with Pb-Li above 500 C where the dissolution rate of many conventional alloys increases rapidly. Current work is beginning to assess Pb-Li compatibility from 500 to 800 C using isothermal capsule experiments. Aluminide coatings hold some promise in protecting conventional Fe-base alloys at 600-700 C. However, there is a significant initial Al loss that has not been clearly explained. Furthermore, the reaction product with coated materials is LiAlO{sub 2} rather than Al{sub 2}O{sub 3} at 600 and 700 C. Even when pre-oxidized to form {alpha}-Al{sub 2}O{sub 3}, an alumina layer on FeCrAl transformed to LiAlO{sub 2} at 700 and 800 C. At 500 C, the preformed oxide partially transformed from alumina and some Li was detected in the oxide layer.

  2. Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22}

    SciTech Connect

    Shen, Shipeng; Yan, Liqin; Chai, Yisheng; Cong, Junzhuang; Sun, Young

    2014-01-20

    Low magnetic field reversal of electric polarization has been demonstrated in the multiferroic Y-type hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22} single crystal. The maximum magnetoelectric coefficient at 200 K reaches 1065 ps/m near zero magnetic field. By a systematic investigation of magnetic field dependence of magnetic and dielectric responses at various temperatures, we obtained the magnetoelectric phase diagram describing the detailed evolution of the spin-induced ferroelectric phases with temperature and magnetic field. Below 225 K, the transverse spin cone can be stabilized at zero magnetic field, which is responsible for the reversal behavior of electric polarization. Our study reveals how to eventually achieve magnetic field reversal of electric polarization in hexaferrites at room temperature.

  3. 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.

  4. 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.

  5. 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.

  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. Sr-Pb isotopic studies of primitive and near-primitive basaltic magmas, Garibaldi volcanic belt, northern Cascadia subduction system

    NASA Astrophysics Data System (ADS)

    Green, N. L.; Sinha, A. K.

    2003-12-01

    The northern Cascadia subduction system is intimately associated with aseismic subduction of extremely young and presumably `hot' oceanic lithosphere beneath northwestern Washington and southwestern British Columbia. Sr and Pb isotopic analyses are presented for primitive and near-primitive (>6.0 wt. % MgO) basalts from a southeast-northwest transect along the Garibaldi volcanic belt (GVB), which overlies subducted oceanic lithosphere that decreases in age from ca. 22 m.y. below Glacier Peak at its southern end to about 13 m.y. beneath the northernmost eruptive centers in the Mosaic (Meager Mountain) and Salal Glacier-Bridge River areas. The basaltic rocks have initial 87Sr/86Sr ratios of 0.70317-0.70426, with minimum observed values in individual lava suites decreasing northward. Values of Pb isotopic ratios for GVB basaltic suites range from 18.22 to 18.97 for 206Pb/204Pb, from 15.51 to 15.59 for 207Pb/204Pb, and from 37.73 to 38.49 for 208Pb/204Pb. Sr isotopic compositions, unsupported by lava Rb contents, show positive correlations with Cs/Rb, La/Nb, Ba/La, Ba/Nb, Ba/Ta, B/La, B/Zr, Sr/Nd, and primitive mantle normalized Sr/P; and negative correlations with high field strength elements (HFSE: Nb, and Ta), FeO and other transition metals (Co and Zn), Ce/Pb,Cr/Ni, Sm/Yb, Ta/Yb, Hf/Yb, K/Ba, K/Sr, and La/Yb. Moderate to strong correlations between 87Sr/86Sr and ratios involving fluid-mobile and less-fluid-mobile elements are compatible with decreased slab input northward along the volcanic front as the subducted plate becomes hotter. The Pb isotopic compositions exhibit only limited variations when examined against position along the volcanic arc, but show uniform to extremely weak positive correlations of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb with 87Sr/86Sr, Ba/La, Sr/Nd, Ba/Nb, Zr/Nb, Mg-Number and SiO2; and similarly weak negative correlation of Ce/Pb with 206Pb/204Pb and 207Pb/204Pb. The isotopic data suggest that GVB basaltic magmas have experienced with

  8. 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.

  9. 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

  10. Tunneling studies of compositionally modulated PB/Fe films

    SciTech Connect

    Wawro, A.; Witek, A.; Majewski, J.; Rauluszkiewicz, J.; Nowak, J. )

    1988-01-01

    Preliminary results of preparation and investigation of compositionally modulated Pb/Fe films are reported. These films have been used as electrodes in Al/Al/sub 2/O/sub 3//{kappa}(Pb/Fe) tunnel junctions and the tunnelling characteristics I-V, dV/dI and d/sup 2/V/d/I/sup 2/ vs V have been studied in dependence on the modulation period.

  11. Simultaneous determination of 226Ra and 210Pb in groundwater and soil samples by using the liquid scintillation counter-suspension gel method.

    PubMed

    Kim, Y J; Kim, C K; Lee, J I

    2001-02-01

    A method for the simultaneous determination of 226Ra and 210Pb in groundwater and soil samples by liquid scintillation counting was developed. Radium and lead were separated together from the samples as Ba(Ra) x PbSO4 co-precipitate, which was centrifuged and dissolved with 0.1 M EDTA solution (pH 9.0). Radium was separated as Ba(Ra)SO4 co-precipitate by adding ammonium sulfate and adjusting the pH of the solution to 4.2. Lead remaining in the solution was separated as PbSO4 precipitate by adding 9 M sulfuric acid. These Ba(Ra)SO4 and PbSO4 precipitates were purified with EDTA solution and used for measurement. To save time and to make counting samples simpler, direct counting of Ba(Ra)SO4 and PbSO4 precipitates instead of the phosphoric acid fusion method was attempted. Ba(Ra)SO4 and PbSO4 precipitates were suspended in the scintillation gel, and measured. Two liquid scintillation cocktails, Instagel XF and UltimaGold AB were used to prepare the counting samples. A mixture of water (40%), Instagel XF (40%) and UltimaGold AB (20%) formed a stable gel. Activities of 226Ra and 210Pb were calculated from the alpha spectrum of Ba(Ra)SO4 and beta spectrum of PbSO4, respectively. The long-term stability of the suspension gel was good. The analytical results of 226Ra and 210Pb in spiked groundwater samples were in good agreement with the known concentrations of 226Ra and 210Pb. The analytical values of 226Ra and 210Pb in the soil reference samples were within 11.5 and 1.6% of the relative error from the reference values, respectively.

  12. 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

  13. 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).

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Pb(II) distributions at biofilm-metal oxide interfaces.

    PubMed

    Templeton, A S; Trainor, T P; Traina, S J; Spormann, A M; Brown, G E

    2001-10-01

    The distribution of aqueous Pb(II) sorbed at the interface between Burkholderia cepacia biofilms and hematite (alpha-Fe(2)O(3)) or corundum (alpha-Al(2)O(3)) surfaces has been probed by using an application of the long-period x-ray standing wave technique. Attached bacteria and adsorbed organic matter may interfere with sorption processes on metal oxide surfaces by changing the characteristics of the electrical double layer at the solid-solution interface, blocking surface sites, or providing a variety of new sites for metal binding. In this work, Pb L(alpha) fluorescence yield profiles for samples equilibrated with 10(-7) to 10(-3.8) M Pb(II) were measured and modeled to determine quantitatively the partitioning of Pb(II) at the biofilm-metal oxide interface. Our data show that the reactive sites on the metal oxide surfaces were not passivated by the formation of a monolayer biofilm. Instead, high-energy surface sites on the metal oxides form the dominant sink for Pb(II) at submicromolar concentrations, following the trend alpha-Fe(2)O(3) (0001) > alpha-Al(2)O(3) (1102) > alpha-Al(2)O(3) (0001), despite the greater site density within the overlying biofilms. At [Pb] > 10(-6) M, significant Pb uptake by the biofilms was observed.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Electric-field-induced local structural phenomena in Pb-based ABO3-type relaxor ferroelectrics.

    PubMed

    Mihailova, Boriana; Maier, Bernd J; Steilmann, Thomas; Dul'kin, Evgeniy; Roth, Michael

    2015-01-01

    Lead-based ABO3-type relaxors and related systems have numerous applications in modern technical devices because of their remarkably high dielectric permittivity and piezoelectric/electroelastic and electro-optic coefficients. However, lead is not desired from an environmental point of view, and to switch to alternative alkali-, Ba-, or Bi-based relaxor systems, one must understand in great detail the structural mesoscopic order and coupling processes responsible for the outstanding performance and multifunctionality of the exemplar Pb-based compounds. To elucidate the type of ferroic coupling, three relaxor compounds PbSc0.5Ta0.5O3 (PST), Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba), and PbSc0.5Nb0.5O3 (PSN), were studied by polarized Raman scattering and acoustic emission at different temperatures and under an external electric field. The results reveal the coexistence of mesoscopic-scale ferroelectric and antiferroelectric coupling, which are predominantly related to B-site cations and A-site Pb cations, respectively. This suggests that the polar structural state of relaxors is frustrated ferrielectric. The presence of A-site cations with affinity to off-center is significant for the development of mesoscopic-scale antiferroelectric order coexisting with the mesoscopic-scale ferroelectric order. PMID:25585386

  11. 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%.

  12. 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

  13. 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.

  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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. Compositionally continuously graded cathode layers of (Ba0.5Sr0.5)(Fe0.91Al0.09)O3-δ-Gd0.1Ce0.9O2 by wet powder spraying technique for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Jiang, Taizhi; Wang, Zhenhua; Ren, Baiyu; Qiao, Jinshuo; Sun, Wang; Sun, Kening

    2014-02-01

    Compositionally continuously graded cathode layers (CGCLs) of (Ba0.5Sr0.5)(Fe0.91Al0.09)O3-δ-Gd0.1Ce0.9O2 (BSFA-GDC) have been constructed by a handy and effective technique called wet powder spraying (WPS). CGCLs exhibit similar thermal expansion coefficient (TEC) value between adjacent thin layers. The continuously graded structure and the well-distributed components of BSFA-GDC cathode are confirmed by morphological characterization with scanning electron microscopy (SEM), and by compositional analysis with energy dispersion X-ray spectrometer (EDS), respectively. The polarization resistance (Rp) of CGCLs with three different thicknesses is investigated by electrochemical impedance spectra (EIS). The EIS results show that CGCLs with a moderate thickness of 20 μm achieve the lowest Rp of 0.301 Ω cm2 at 800 °C. In addition, anode-supported single cells with the configuration of NiO-YSZ/YSZ/GDC/BSFA-GDC have been fabricated and tested. The cell with the CGCLs thickness of 20 μm reaches the highest output power density of 848 mW cm-2 at 800 °C.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. Controlled confinement of half-metallic two-dimensional electron gas in BaTiO3/Ba2FeReO6 /BaTiO3 heterostructures: A first-principles study

    NASA Astrophysics Data System (ADS)

    Baidya, Santu; Waghmare, Umesh V.; Paramekanti, Arun; Saha-Dasgupta, Tanusri

    2015-10-01

    Using density functional theory calculations, we establish that the half-metallicity of bulk Ba2FeReO6 survives down to 1 nm thickness in BaTiO3/Ba2FeReO6 /BaTiO3 heterostructures grown along the (001) and (111) directions. The confinement of the two-dimensional (2D) electron gas in this quantum well structure arises from the suppressed hybridization between Re/Fe d states and unoccupied Ti d states, and it is further strengthened by polar fields for the (111) direction. This mechanism, distinct from the polar catastrophe, leads to an order of magnitude stronger confinement of the 2D electron gas than that at the LaAlO3/SrTiO3 interface. We further show low-energy bands of (111) heterostructure display nontrivial topological character. Our work opens up the possibility of realizing ultrathin spintronic devices.

  5. Thermoelectric properties of PbTe/PbSe mesomaterials

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Wang, Yaqi; Xue, Yuyi; Chu, C. W.; Zhang, Jun; Fang, Jiye; Tan, Chunhu; Lin, Zhigang; Liu, Bob

    2008-03-01

    Ball milled PbTe mixed with PbSe nano-wires (PTSW) or with PbSe nano-crystals (PTSC) are sintered under high pressure. Different sintering conditions are tested to preserve the mesostructures. Thermoelectric properties (resistivity, Seebeck coefficient and thermal conductivity) are measured at various temperatures. Pure ball milled PbTe are also sintered and measured for comparison. In this talk, we will present these data and compare with various PbTe data from the literature. Our results show that this mesostructure approach is promising and the sintering condition is the key factor for further improvement.

  6. 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.

  7. 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

  8. Geochemical study (major, trace elements and Pb-Sr-Nd isotopes) of mantle material obducted onto the North African margin (Edough Massif, North Eastern Algeria): Tethys fragments or lost remnants of the Liguro-Provençal basin?

    NASA Astrophysics Data System (ADS)

    Bosch, Delphine; Hammor, Dalila; Mechati, Mehdi; Fernandez, Laure; Bruguier, Olivier; Caby, Renaud; Verdoux, Patrick

    2014-06-01

    The Maghrebides, Betics and some parts of the Calabrian, NE Sicilian and Tuscan allochtons constitute dismembered fragments of the Alpine belt that resulted from the Cenozoic collision between Africa and Eurasia and the opening of the Western Mediterranean basin. Mineral and whole-rock geochemical analyses have been performed on three distinct outcrops of mantle material from the Edough Massif of NE Algeria, namely the Bou Maiza (BM) gabbros, the La Voile Noire (LVN) amphibolites and the Sidi Mohamed (SM) peridotites. In all samples, Sr isotopes are largely affected by seawater alteration (87Sr/86Sract. > 0.70384 and up to 0.70888) and cannot be used to evaluate the nature of the source reservoirs. SM peridotites display variable depleted mantle Nd isotopic signatures (εNdact. from + 7.0 to + 12.2) and geochemical features suggesting no significant chemical depletion as a result of partial melting and melt extraction (Mg# < 90; slightly LREE-depleted patterns with La/YbN = 0.33-0.39). These rocks are interpreted as parts of the subcontinental lithospheric mantle incorporated into the crustal units of the Edough Massif during the early stages of opening of the Algerian basin. BM gabbros and LVN amphibolites show geochemical signatures indicating derivation from a common depleted mantle reservoir (εNd > + 7.9) and are likely cogenetic, but without filiation with the SM peridotites. Pb isotopes indicate a contribution of sediments in the source reservoir, which is attributed to contamination solely by hydrous fluids released from a sedimentary component. This observation, together with a LILE-enrichment, suggests a back-arc basin environment. These results indicate that BM and LVN units were obducted onto the North African margin and subsequently fragmented, probably during doming and exhumation of the lower continental crust of the Edough massif. Doming resulted in opposite movements of the overlying oceanic units, southward for the BM units and northward for LVN

  9. 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.

  10. 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.

  11. Trace-element and Sr, Nd, Pb, and O isotopic composition of Pliocene and Quaternary alkali basalts of the Patagonian Plateau lavas of southernmost South America

    USGS Publications Warehouse

    Stern, C.R.; Frey, F.A.; Futa, K.; Zartman, R.E.; Peng, Z.; Kurtis, Kyser T.

    1990-01-01

    The Pliocene and Quaternary Patagonian alkali basalts of southernmost South America can be divided into two groups. The "cratonic" basalts erupted in areas of Cenozoic plateau volcanism and continental sedimentation and show considerable variation in 87Sr/86Sr (0.70316 to 0.70512), 143Nd/144Nd (e{open}Nd) and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios (18.26 to 19.38, 15.53 to 15.68, and 38.30 to 39.23, respectively). These isotopic values are within the range of oceanic island basalts, as are the Ba/La, Ba/Nb, La/Nb, K/Rb, and Cs/Rb ratios of the "cratonic" basalts. In contrast, the "transitional" basalts, erupted along the western edge of the outcrop belt of the Pliocene and Quaternary plateau lavas in areas that were the locus of earlier Cenozoic Andean orogenic arc colcanism, have a much more restricted range of isotopic composition which can be approximated by 87Sr/86Sr=0.7039??0.0004, e{open}Nd, 206Pb/204Pb=18.60??0.08, 207Pb/204Pb=15.60??0.01, and 208Pb/204Pb=38.50??0.10. These isotopic values are similar to those of Andean orogenic are basalts and, compared to the "cratonic" basalts, are displaced to higher 87Sr/86Sr at a given 143Nd/144Nd and to higher 207Pb/204Pb at a given 208Pb/204Pb. The "transitional" basalts also have Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios higher than the "cratonic" and oceanic island basalts, although not as high as Andean orogenic are basalts. In contrast to the radiogenic isotopes, ??18O values for both groups of the Patagonian alkali basalts are indistinguishable and are more restricted than the range reported for Andean orogenic are basalts. Whole rock ??18O values calculated from mineral separates for both groups range from 5.3 to 6.5, while measured whole rock ??18O values range from 5.1 to 7.8. The trace element and isotopic data suggest that decreasing degrees of partial melting in association with lessened significance of subducted slabderived components are fundamental factors in the west to east transition from arc

  12. Ba isotopic signature for early differentiation between Cs and Ba in natural fission reactors

    NASA Astrophysics Data System (ADS)

    Hidaka, Hiroshi; Gauthier-Lafaye, François

    2008-08-01

    Ba isotopic studies of the Oklo and Bangombé natural fission reactors in east Gabon provide information on the geochemical behavior of radioactive Cs ( 135Cs and 137Cs) in a geological medium. Large isotopic deviations derived from fissiogenic Ba were found in chemical leachates of the reactor uraninites. The fissiogenic Ba isotopic patterns calculated by subtracting the non-fissiogenic component are classified into three types that show different magnifications of chemical fractionation between Cs and Ba. In addition, the isotopic signatures of fissiogenic 135Ba, 137Ba and 138Ba suggest an early differentiation between Cs and Ba of less than 20 years after the production of fissiogenic Cs and Ba. On the other hand, only small excesses of 135Ba ( ɛ < +1.8) and/or 137Ba ( ɛ < +1.3) were identified in some clay samples, which might have resulted from selective adsorption of 135Cs and 137Cs that migrated from the reactors by differentiation.

  13. 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.

  14. 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.

  15. Lead isotope and Pb-Pb model age determinations of ores from Central Europe and their metallogenetic interpretation

    NASA Astrophysics Data System (ADS)

    Bielicki, K.-H.; Tischendorf, G.

    1991-02-01

    The paper presents lead isotope data from 211 samples from Phanerozoic lead-bearing ore occurrences in Central Europe, particularly from the Southern part of the former German Democratic Republic. The data are interpreted in terms of Amov's dynamic model of continuous lead isotope evolution. The relationships between thoro-genic and urano-genic model ages and the source of lead in different regional units are discussed. We observed differences in lead isotope evolution in the Hercynian internides and externides. Within the Moldanubian and Saxothuringian zones we distinguish five main lead-bearing ore associations: (1) Cambrian, stratiform base metal (Hermsdorf-Waldsassen; 206Pb/ 204Pb=17.50 17.70), (2) Devonian, vein type Sb-bearing, metamorphogene (neumühle-Hartmannsdorf; 17.80 18.00), (3) Upper Carboniferous-Permian, polymetallic, including tin, vein type (Kutna hora-Freiberg-Altenberg; 18.00 18.20), (4) Triassic (-Jurassic), Pb-Ba, vein type (Střibro-Halsbrücke; 18.20 18.60), (5) Cenozoic, polymetallic, vein type, riftogene (Roztoky-Banska Štiavnica; 18.80 19.10). Pb isotope characteristics from ores of the Montagne Noire and the Brioude-Massiac district correspond to this subdivision. Ore associations from the Rheno-Hercynian zone display higher 207Pb/204Pb ratios which can be explained by more evolved and less metamorphosed source rocks. Mineralizations of the eastern Harz (Straßberg-Neudorf) belong to the Permian association, those from the western Harz (Clausthal-Bad Grund) to the Triassic-Jurassic. Because of Pb isotope agreement the stratabound Rammelsberg and the vein bound Ramsbeck-I mineralization are presumed to be isogenetic. Pb isotope identity of distinct mineralizations in the basement zone (Halsbrücke-Bad Grund) and in the Triassic sediments (Gorny Slask-Mechernich-Bleiglanzbänke) suggests a strong genetic coherence. Pb isotope conformity between the Upper Carboniferous-Permian-Triassic ore associations and Hercynian postkinematic

  16. 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).

  17. 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).

  18. Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

    NASA Astrophysics Data System (ADS)

    Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

    1990-04-01

    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).

  19. 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.

  20. Electronic and Optical Properties of BaO, BaS, BaSe, BaTe and BaPo Compounds Under Hydrostatic Pressure

    NASA Astrophysics Data System (ADS)

    Drablia, S.; Meradji, H.; Ghemid, S.; Boukhris, N.; Bouhafs, B.; Nouet, G.

    We have performed first-principle full-potential (linear) augmented plane wave plus local orbital calculations (FP-L/APW + l0) with density functional theory (DFT) in local density approximation (LDA) and generalized gradient approximation (GGA), with the aim to determine and predict the electronic and optical properties of rocksalt BaO, BaS, BaSe, BaTe and BaPo compounds. First we present the main features of the electronic properties of these compounds, where the electronic band structure shows that the fundamental energy gap is indirect (Γ-X) for all compounds except for BaO which is direct (X-X). The different interband transitions have been determined from the imaginary part of the dielectric function. The real and imaginary parts of the dielectric function and the reflectivity are calculated. We have presented the assignment of the different optical transitions existing in these compounds from the imaginary part of the dielectric function spectra with respect to their correspondence in the electronic band. We have also calculated the pressure and volume dependence of the optical properties for these compounds.

  1. 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…

  2. 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.

  3. 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.

  4. Major Pb Loss in the Silicate Earth at ~ 4.52 Ga

    NASA Astrophysics Data System (ADS)

    Vervoort, J. D.; Albarede, F.; Blichert-Toft, J.; Thorpe, R.

    2009-12-01

    loss during accretion, and subsequently increased more significantly to the current mean value of ~ 8 for the silicate Earth (e.g., Allegre et al., EPSL, 2008; Wood and Halliday, Nature, 2005; Halliday, Nature, 2004). Our VMS data support this U/Pb evolution in the early Earth. If the Earth evolves with low μ from 4.56 to 4.52 Ga (< 0.7) and then increases to its current high μ at ~4.52 Ga, the VMS Pb trend is nearly coincident with the 2.70 Geochron. With these parameters there is no Pb paradox and no future Pb to the right of the geochron at 2.7 Ga. A large change in μ at 4.52 is unlikely with silicate/melt differentiation and requires a large loss of Pb to either the core or volatile Pb loss during a moon-forming impact (or some combination of the two). Several estimates of the mean Pb isotopic composition of the Earth have been used to determine the Pb age of the Earth. The VMS data may provide a more accurate estimate of the Earth’s Pb age from an Archean vantage point.

  5. Correlations between Pb isotopes and volatile elements in melt inclusions from Sao Miguel, Azores

    NASA Astrophysics Data System (ADS)

    Moreira, M. A.; Rose-Koga, E. F.; Koga, K. T.; Vlastelic, I.; Shimizu, N.; Whitehouse, M.

    2009-12-01

    Sao Miguel is the biggest eastern-most island of the Azores archipelago in the northern Atlantic and is known to have a very peculiar isotopic systematics including Sr, Nd and Pb. We studied 4 lavas of Sao Miguel, one is from the 1563 historical lava flow Queimado peak eruption, one is from Picos Volcanic zone and the two others are Pliocene ankaramites from the Nordest. The olivine phenocrysts of these samples have been documented for helium isotopes and show very radiogenic 3He/4He ratios (<6Ra). We analyzed 9 primitive olivine-hosted melt inclusions for both Pb isotopes and volatile element concentrations (H2O, CO2, F, S, and Cl). The Pb isotope ratios were measured by a multicollection SIMS 1280 (NMNH Stockholm, Sweden) and volatiles by a monocollection SIMS 1280 (WHOI, USA). The repeated 207Pb/206Pb measurements of the GOR132 glass standard (20 ppm Pb) yielded a 0.15% relative variation (1 sigma of the distribution). All the melt inclusions have 207Pb/206Pb (0.782 to 0.797) and 208Pb/206Pb (1.969 to 2.041) lower than MORB value (DMM: 0.857, 2.053), i.e., more radiogenic compositions. We found positive linear correlations between 207Pb/206Pb and CO2, F, S, and Cl. The correlations further improve when Pb isotope ratios are plotted against F/P2O5, and Cl/K2O. The Sao Miguel source is characterized by a mixing between a low 207Pb/206Pb and low 208Pb/206Pb in the Nordest coming from a long time residence of high (U+Th)/Pb recycled material, and a component with higher ratios, more similar to other islands from the central group. The low 3He/4He ratio measured on Nordest samples also suggests a high (U+Th)/3He in its source, which may be due to degassing presumably during an early stage of the recycling. The low 207Pb/206Pb with low volatiles samples could also be explain this early degassing. Samples with the highest 207Pb/206Pb are richer in volatile suggesting the presence of a volatile rich lithology beneath the Azores central group, which was also proposed by

  6. 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...

  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. U-Th-Pb and Rb-Sr systematics of Allende and U-Th-Pb systematics of Orgueil

    USGS Publications Warehouse

    Tatsumoto, M.; Unruh, D.M.; Desborough, G.A.

    1976-01-01

    U-Th-Pb systematics study of Allende inclusions showed that U, Th and Sr concentrations in Ca, Al (pyroxene)-rich chondrules and white and pinkish-white aggregate separates of Allende are five to ten times higher than those of the matrix, whereas Mg (olivine)-rich chondrules have U and Th concentrations about twice as high as the matrix. Th concentrations are extremely high in white aggregates and in pinkish-white (spinel-rich) aggregates while U and Sr concentrations in white aggregates are more than twice as high as those in pinkish-white aggregates. Large enrichment of these refractory elements in the white aggregates indicates that they contain high-temperature condensates from the solar nebula. The Pb concentrations in the inclusions are less than half of those in the whole rock and matrix, indicating that the matrix is a lower-temperature condensate. The isotopic composition of lead in the matrix is less radiogenic than that of the whole meteorite, whereas lead in Ca- and Al-rich chondrules and aggregates is extremely radiogenic. The 206Pb/204Pb ratio reaches as high as 55.9 in a white aggregate separate. The lead of Mg-rich chondrules is moderately radiogenic and the 206Pb/204Pb ratio ranges from 18 to 26. A striking linear relationship exists among leads in the chondrules, aggregates and matrix on the 207Pb/204Pb vs 204Pb/204Pb plot. The slope of the best fit line is 0.6188 ?? 0.0016, yielding an isochron age of 4553 ?? 4 m.y. The regression line passes through primordial lead values obtained from Canyon Diablo troilite. The data, when corrected for Canyon Diablo troilite Pb and plotted on a U-Pb concordia diagram, show that the pink and white aggregates and the Ca-Al-rich and Mg-rich inclusions have excess Pb and define a chord which intersects the concordia curve at 4548 ?? 25 m.y. and 107 ?? 70 m.y. The intercepts might correspond to the agglomeration age of the meteorite and a time of probably later disturbance, respectively. The matrix and some

  9. 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.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    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.

  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.

  11. Evidence for extinct 135Cs from Ba isotopes in Allende CAIs?

    NASA Astrophysics Data System (ADS)

    Bermingham, K. R.; Mezger, K.; Desch, S. J.; Scherer, E. E.; Horstmann, M.

    2014-05-01

    The abundance and distribution of isotopes throughout the Solar System can be used to constrain the number and type of nucleosynthetic events that contributed material to the early nebula. Barium is particularly well suited to quantifying the degree of isotope heterogeneity in the Solar System because it comprises seven stable isotopes that were synthesized by three different nucleosynthetic processes (s-, r-, and p-processes), all of which contributed material to the Solar System. There is also potential contribution to 135Ba from short-lived radioisotope 135Cs, conclusive evidence for which is yet to be reported. Four Allende (CV3) Ca,Al-rich inclusions (CAI 1, CAI 2, CAI 4, CAI 5) and one Allende dark inclusion (DI) were analyzed for Ba isotope variability. Two CAIs (CAI 2 and CAI 5) display 135Ba excesses that are not accompanied by 137Ba anomalies. Calcium-aluminum-rich inclusion 1 displays a 135Ba excess that is possibly coupled with a 137Ba excess, and the remaining refractory inclusions (CAI 2 and DI) have terrestrial Ba isotope compositions. These Ba isotope data are presented in conjunction with published whole rock Ba isotope data from individual Allende CAIs. The enrichment in 135Ba and absence of coupled 137Ba excesses in CAI 2 and CAI 5 is interpreted to indicate that the anomalies are not purely nucleosynthetic in origin but also contain contributions (16-48 ppm) from the decay of short-lived 135Cs. The majority of Allende CAIs studied to date may also have similar contributions from 135Cs on the basis of higher than expected 135Ba excesses if the Ba isotope anomalies were purely nucleosynthetic in origin. The 135Ba anomalies appear not to be coupled with superchondritic Cs/Ba, which may imply that the contribution to 135Ba did not occur via in situ decay of live 135Cs. However, it is feasible that the CAIs had a superchondritic Cs/Ba during decay of 135Cs, but Cs was subsequently removed from the system during aqueous alteration on the parent body

  12. 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.

  13. 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.;

  14. 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.

  15. Ultraperipheral Pb+Pb reactions at LHC energies

    NASA Astrophysics Data System (ADS)

    Norbeck, Edwin; Onel, Yasar

    2011-10-01

    The magnetic field midway between two Pb nuclei passing at 20 fm is 2 × 1020 gauss at LHC energies (1144 TeV in PbPb center of mass). At these energies the Coulomb field of a passing Pb nucleus can be regarded as a cloud of real photons. The cross sections for γγ and γA reactions are huge compared to 7 b for two Pb nuclei actually colliding. The reaction rate is limited by the 323 b cross section for breaking up the Pb nucleus or for the capture by a Pb ion of an e- from the many e+ e- pairs that are formed. These products go down the beam pipe and eventually hit superconducting magnets. The γγ reactions can produce particles with mc2 up to 100 GeV. The γA reactions can produce particles with mc2 more than 900 GeV. These ultraperipheral reactions are particularly clean. In proton-proton reactions, the reaction between two partons to produce something of interest is accompanied by a large background caused by many other parton-parton reactions. When γA breaks up a Pb nucleus, the transverse energy is small so that the fragments continue in the original beam direction. A single neutron in the original beam direction provides a useful flag that shows that an ultraperipheral reaction has occurred.

  16. Observation of sequential Υ suppression in PbPb collisions.

    PubMed

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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.

  17. 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.

  18. 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.

  19. 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.

  20. Thermoluminescence properties of nanophosphors BaSO₄:Dy and BaSO₄:Tb.

    PubMed

    Rezaee Ebrahim Saraee, Kadijeh; Aghay Kharieky, Amin

    2013-12-01

    Nanocrystalline BaSO4:Dy and BaSO4:Tb were prepared by the coprecipitation method. The materials were characterized with X-ray diffractometry, UV-visible spectroscopy, and scanning electron microscopy. The glow curves of the BaSO4:Dy and BaSO4:Tb nanophosphors feature main peaks at 505 K and 480 K, respectively. The responses to the (60)Co dose are linear in the range 0.1-1 kGy for BaSO4:Dy and in the range 0.1-7 kGy for BaSO4:Tb. The energy dependences of the responses were also studied.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Shallow groundwater and cultivated soil suitability assessments with respect to heavy metal content in the Köprübaşi U mineralization area (Manisa, Turkey).

    PubMed

    Kaçmaz, Hülya; Eran Nakoman, M

    2010-07-01

    Shallow groundwater and cultivated soil samples were collected from the area within Köprübaşi U mineralization and analyzed to determine U and selected heavy metals (Fe, Mn, Cu, As, Pb, Zn, Cr, Co and Ba). After this, the suitability of the shallow groundwater and soil samples were evaluated for irrigation, livestock watering and agricultural use, respectively. One groundwater sample (4) showed Mn-concentration of 112.6, exceeding the FAO (Ayers and Westcot 1985) livestock drinking limit (50 microg/l). Nevertheless, the amount of heavy metals including Fe, Cu, As, Pb, Zn, Cr and Co in groundwater is not high for irrigation and livestock drinking water standards cited by the FAO (Ayers and Westcot 1985). On the other hand, all cultivated soil samples have higher uranium concentrations than the typical concentration of natural uranium in soil (ATSDR 1999). The majority of the cultivated soil samples showed higher concentrations than the values for heavy metals (Fe, Mn, Cu, As, Pb, Zn, Cr, Co, Ba) found in normal soils of the world (Connor and Shacklette 1975). However, according to G.L.C guidelines, these soils are classified as uncontaminated with Mn, Cu, Pb, Zn and Cr, slightly contaminated with Ba and As.

  6. Experimental and Theoretical Studies of the Pure Rotational Spectra of Lead Halides: PbF and PbCl

    NASA Astrophysics Data System (ADS)

    Norman, Spencer; Dawes, Richard; Grubbs, G. S., II; Cooke, S. A.; Long, B. E.; Dewberry, Chris

    2014-06-01

    The pure rotational spectrum of lead monochloride, PbCl, has been measured and analyzed using chirped pulse and cavity Fourier transform microwave (CP-FTMW and FTMW) spectrometers equipped with an ablation source. Refined parameters of an effective Hamiltonian including fine and hyperfine interactions similar to those previously reported by Fink et al. [1] were determined. Dynamically-weighted, explicitly-correlated MRCI-F12 calculations [2] were performed for both PbF and the valence isoelectronic PbCl to predict potential energy curves (PEC). Spin-orbit coupling was included in the calculations, which is known to split the X12Π1/2 and X22Π3/2 components of the ground electronic state by roughly 8280 wn in both lead halide systems. Calculated rotational levels were obtained using the PECs and compared with experiment including previously published results for PbF [3]. References: 1- K. Ziebarth, K. D. Setzer, O. Shestakov,1 and E. H. Fink, J. Mol. Spec. 191, 108 (1998). 2- B. J. Barker et al. J. Chem. Phys. 137, 214313 (2012). 3- R. J. Mawhorter et al. Phys. Rev. A 84, 022508 (2011).

  7. ALS Association

    MedlinePlus

    ... toward a world without ALS! Walk to Defeat ALS® Walk to Defeat ALS® draws people of all ... We need your help. I Will Advocate National ALS Registry The National ALS Registry is a congressionally ...

  8. Quarkonium and Bc mesons from Pb + Pb at LHC energies

    NASA Astrophysics Data System (ADS)

    Norbeck, Edwin; Nachtman, Jane; Onel, Yasar

    2013-08-01

    The bbar b(Upsilon) mesons appear to be produced in the initial PbPb collision at 2.76 TeV per nucleon pair followed by partial melting in the hot quark-gluon plasma. In sharp contrast, the cbar c(J/Ψ) mesons seem more likely to be formed by recombination at the hadronization stage. The Bc mesons, with one quark of each kind are seldom seen in pp collisions because a particle-antiparticle pair requires the simultaneous production of four heavy quarks. Although a family of Bc mesons have been predicted, only the ground state has been seen. If the cbar c mesons are produced by recombination, it could be expected that Bc mesons would be abundant with PbPb. Because the quark and antiquark have different flavor, the Bc are relatively long lived, 0.45 ps (to be compared with about 1.5 ps for the lighter B mesons). They would be seen with PbPb reactions by B±c → J/Ψ(μ+μ-)π± looking at muons and pions from displaced vertices.

  9. 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.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hippolyte, B.; Hladky, J.; Hristov, P.; Huang, M.; Humanic, T. J.; Hussain, N.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Innocenti, G. M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Jachołkowski, A.; Jacobs, P. M.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kadyshevskiy, V.; Kalcher, S.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil Svn, M.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, B.; Kim, D. W.; Kim, D. J.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, J.; Klein-Bösing, C.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Köhler, M. K.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Konevskikh, A.; Kovalenko, V.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kravčáková, A.; Krelina, M.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kučera, V.; Kucheriaev, Y.; Kugathasan, T.; Kuhn, C.; Kuijer, P. G.; Kulakov, I.; Kumar, J.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; Ladron de Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; La Pointe, S. L.; La Rocca, P.; Lea, R.; Leardini, L.; Lee, G. R.; Legrand, I.; Lehnert, J.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; Leoncino, M.; León Monzón, I.; Lévai, P.; Li, S.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Lohner, D.; Loizides, C.; Lopez, X.; López Torres, E.; Lu, X.-G.; Luettig, P.; Lunardon, M.; Luparello, G.; Ma, R.; Maevskaya, A.; Mager, M.; Mahapatra, D. P.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Marín, A.; Markert, C.; Marquard, M.; Martashvili, I.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martin Blanco, J.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Meddi, F.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mlynarz, J.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Morando, M.; Moreira de Godoy, D. A.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Müller, H.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nicassio, M.; Niculescu, M.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Nilsen, B. S.; Noferini, F.; Nomokonov, P.; Nooren, G.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Okatan, A.; Olah, L.; Oleniacz, J.; Oliveira da Silva, A. C.; Onderwaater, J.; Oppedisano, C.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Sahoo, P.; Pachmayer, Y.; Pachr, M.; Pagano, P.; Paić, G.; Painke, F.; Pajares, C.; Pal, S. K.; Palmeri, A.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Patalakha, D. I.; Paticchio, V.; Paul, B.; Pawlak, T.; Peitzmann, T.; Pereira da Costa, H.; Pereira de Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Pesci, A.; Peskov, V.; Pestov, Y.; Petráček, V.; Petran, M.; Petris, M.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Pohjoisaho, E. H. O.; Polichtchouk, B.; Poljak, N.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Potukuchi, B.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Rauf, A. W.; Razazi, V.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Rivetti, A.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohni, S.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, R.; Sahu, P. K.; Saini, J.; Sakai, S.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Sánchez Rodríguez, F. J.; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Segato, G.; Seger, J. E.; Sekiguchi, Y.; Selyuzhenkov, I.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabetai, A.; Shabratova, G.; Shahoyan, R.; Shangaraev, A.; Sharma, N.; Sharma, S.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Skjerdal, K.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Soramel, F.; Sorensen, S.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Stolpovskiy, M.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Susa, T.; Symons, T. J. M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tangaro, M. A.; Tapia Takaki, J. D.; Tarantola Peloni, A.; Tarazona Martinez, A.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terrevoli, C.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Vande Vyvre, P.; van der Maarel, J.; van Hoorne, J. W.; van Leeuwen, M.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vechernin, V.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wagner, V.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yang, S.; Yano, S.; Yasnopolskiy, S.; Yi, J.; Yin, Z.; Yoo, I.-K.; Yushmanov, I.; Zaccolo, V.; Zach, C.; Zaman, A.; Zampolli, C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, F.; Zhou, Y.; Zhou, Zhuo; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zoccarato, Y.; Zyzak, M.; Alice Collaboration

    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.

  10. Fabrication and characterization of PbO2 electrode modified with [Fe(CN)6](3-) and its application on electrochemical degradation of alkali lignin.

    PubMed

    Hao, Xu; Quansheng, Yuan; Dan, Shao; Honghui, Yang; Jidong, Liang; Jiangtao, Feng; Wei, Yan

    2015-04-01

    PbO2 electrode modified by [Fe(CN)6](3-) (marked as FeCN-PbO2) was prepared by electro-deposition method and used for the electrochemical degradation of alkali lignin (AL). The surface morphology and the structure of the electrodes were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. The stability and electrochemical activity of FeCN-PbO2 electrode were characterized by accelerated life test, linear sweep voltammetry, electrochemical impedance spectrum (EIS) and AL degradation. The results showed that [Fe(CN)6](3-) increased the average grain size of PbO2 and formed a compact surface coating. The service lifetime of FeCN-PbO2 electrode was 287.25 h, which was longer than that of the unmodified PbO2 electrode (100.5h). The FeCN-PbO2 electrode showed higher active surface area and higher oxygen evolution potential than that of the unmodified PbO2 electrode. In electrochemical degradation tests, the apparent kinetics coefficient of FeCN-PbO2 electrode was 0.00609 min(-1), which was higher than that of unmodified PbO2 electrode (0.00419 min(-1)). The effects of experimental parameters, such as applied current density, initial AL concentration, initial pH value and solution temperature, on electrochemical degradation of AL by FeCN-PbO2 electrode were evaluated.

  11. Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from parton scatterings

    DOE PAGES

    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

  12. 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.

  13. Elliptic and triangular flow in p-Pb and peripheral Pb-Pb collisions from Parton scatterings.

    PubMed

    Bzdak, Adam; Ma, Guo-Liang

    2014-12-19

    Using a multiphase transport model (AMPT) we calculate the elliptic v_{2} and triangular v_{3} Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p-Pb) and peripheral nucleus-nucleus (Pb-Pb) collisions. Our results for v_{3} are in a good agreement with the CMS data collected at the Large Hadron Collider. The v_{2} 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 v_{2} in p-Pb is reproduced, whereas for v_{3}, this effect is not observed. We further predict the pseudorapidity dependence of v_{2} and v_{3} 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, v_{4} and v_{5}, in p-Pb are also presented.

  14. Effects of Simple Leaching of Crushed and Powdered Materials on High-precision Pb Isotope Analyses

    NASA Astrophysics Data System (ADS)

    Todd, E.; Stracke, A.

    2013-12-01

    We present new results of simple leaching experiments on the Pb isotope composition of USGS standard reference material powders and on ocean island basalt whole rock splits and powders. Rock samples were leached with 6N HCl in two steps, first hot and then in an ultrasonic bath, and washed with ultrapure H2O before conventional sample digestion and chromatographic purification of Pb. Pb isotope analyses were determined with Tl-doped MC-ICP-MS. Intra- and inter-session analytical reproducibility of repeated analyses of both synthetic Pb solutions and Pb from single digests of chemically processed natural samples were generally < 100 ppm (2 S.D.). The comparison of leached and unleached samples shows that leaching reliably removes variable amounts of different contaminants for different starting materials. For repeated digests of a single sample, the leached samples reproduce better than the unleached ones, showing that leaching effectively removes heterogeneously distributed extraneous Pb. However, the reproducibility of repeated digests of variably contaminated natural samples is up to an order of magnitude worse than the analytical reproducibility of ca. 100 ppm. More complex leaching methods (e.g., Nobre Silva et al., 2009) yield Pb isotope ratios within error of and with similar reproducibility to our method, showing that the simple leaching method is reliable. The remaining Pb isotope heterogeneity of natural samples, which typically exceeds 100 ppm, is thus attributed to inherent isotopic sample heterogeneity. Tl-doped MC-ICP-MS Pb ratio determination is therefore a sufficiently precise method for Pb isotope analyses in natural rocks. More precise Pb double- or triple-spike methods (e.g., Galer, 1999; Thirlwall, 2000), may exploit their full potential only in cases where natural isotopic sample heterogeneity is demonstrably negligible. References: Galer, S., 1999, Chem. Geol. 157, 255-274. Nobre Silva, et al. 2009, Geochemistry Geophysics Geosystems 10, Q08012

  15. 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.

  16. 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.

  17. On Ba(+) production in the CRIT 2 experiment

    NASA Technical Reports Server (NTRS)

    Liou, K.; Torbert, R. B.

    1995-01-01

    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.

  18. 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.

  19. Non Fermi Liquid behavior and disorder in BaVS3

    NASA Astrophysics Data System (ADS)

    Akrap, Ana; Barisic, Neven; Rullier-Albenque, Florence; Berger, Helmuth; Forro, Laszlo

    2009-03-01

    In strongly correlated BaVS3, the interplay between a wide one-dimensional dz^2 band and the localized eg electrons leads to a wealth of electronic phases. In this work we investigate the high pressure non-Fermi liquid (NFL) phase of BaVS3 by means of transport measurements, focusing on the influence of disorder, introduced by fast electron irradiation and sulfur deficiency. Our results are interpreted within a novel scenario in which quasi-one dimensional 2kF-CDW fluctuations are responsible for the NFL behavior.ootnotetextN. Barisi'c et al., arXiv:0712.3393v1

  20. 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.

  1. The role of BaCO{sub 3} in high temperature synthesis of electronic materials

    SciTech Connect

    Malecki, A.; Oblakowski, J.; Labus, S.

    1995-06-01

    The syntheses of superconducting YBCO powders, prepared by solid state reaction, vacuum pyrolysis of acetates, spray pyrolysis of acetates and calcinated oxalates were performed. All of the powders in a paste form were deposited on the Al{sub 2}O{sub 3} substrate. After sintering and annealing the obtained superconducting YBCO thick layers were examined in different (CO{sub 2}+O{sub 2}) atmospheres. The thermogravimetric as well as IR spectroscopy and SEM study confirm that on the grain boundaries the BaCO{sub 3} phase is formed. The presence of BaCO{sub 3} phase may cause degradation of superconducting materials.

  2. 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

  3. Strangelet search and antinuclei production studies in Pb + Pb collisions

    NASA Astrophysics Data System (ADS)

    Ambrosini, G.; Appelquist, G.; Arsenescu, R.; Baglin, C.; Beringer, J.; Bohm, C.; Borer, K.; Bussière, A.; Dittus, F.; Elsener, K.; Frei, D.; Gorodetzky, Ph.; Guillaud, J. P.; Hess, P.; Hugentobler, E.; Kabana, S.; Klingenberg, R.; Lindén, T.; Lohmann, K. D.; Mommsen, R.; Moser, U.; Pal, T.; Pretzl, K.; Schacher, J.; Selldén, B.; Stoffel, F.; Tuominiemi, J.; Weber, M.; Zhang, Q. P.

    1996-02-01

    We searched for long-lived strange quark matter particles, so-called strangelets, and studied particle and antiparticle production in Pb + Pb collisions at 158 GeV/ c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/ c 2 and lifetimes tlab > 1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

  4. ALS - resources

    MedlinePlus

    Resources - ALS ... The following organizations are good resources for information on amyotrophic lateral sclerosis : Muscular Dystrophy Association -- mda.org/disease/amyotrophic-lateral-sclerosis National Amyotrophic Lateral Sclerosis (ALS) Registry -- ...

  5. Correlated Nd, Sr and Pb isotope variation in Walvis Ridge basalts and implications for the evolution of their mantle source

    NASA Astrophysics Data System (ADS)

    Richardson, S. H.; Erlank, A. J.; Duncan, A. R.; Reid, D. L.

    1982-07-01

    Basement intersected in DSDP holes 525A, 528 and 527 on the Walvis Ridge consists of submarine basalt flows and pillows with minor intercalated sediments. These holes are situated on the crest and mid and lower northwest flank of a NNW-SSE-trending ridge block which would have closely paralleled the paleo mid-ocean ridge [13, 14]. The basalts were erupted approximately 70 m.y. ago, an age equivalent to that of immediately adjacent oceanic crust in the Angola Basin and consistent with formation at the paleo mid-ocean ridge [14]. The basalt types vary from aphyric quartz tholeiites on the ridge crest to highly plagioclase phyric olivine tholeiites on the ridge flank. These show systematic differences in incompatible trace element and isotopic composition. Many element and isotope ratio pairs form systematic trends with the ridge crest basalts at one end and the highly phyric ridge flank basalts at the other. The low 143Nd/ 144Nd (0.51238), 206Pb/ 204Pb (17.54), 208Pb/ 204Pb (15.47), 208Pb/ 204Pb (38.14) and high 87Sr/ 86Sr (0.70512) ratios of the ridge crest basalts suggest derivation from an old Nd/Sm-, Rb/Sr- and Pb/U-enriched mantle source. This isotopic signature is similar to that of alkaline basalts on Tristan de Cunha but offset to significantly lower Nd and Pb isotopic ratios. The isotopic ratio trends may be extrapolated beyond the ridge flank basalts with higher 143Nd/ 144Nd (0.51270), 206Pb/ 204Pb (18.32), 207Pb/ 204Pb (15.52), 208Pb/ 204Pb (38.77) and lower 87Sr/ 86Sr (0.70417) ratios in the direction of increasingly Nd/Sm-, Rb/Sr- and Pb/U-depleted source compositions. These isotopic correlations are equally consistent with mixing od depleted and enriched end member melts or partial melting of an inhomogenous, variably enriched mantle source. However, observe Zr sbnd Ba sbnd Nb sbnd Y interelement relationships are inconsistent with any simple two-component model of magma mixing, as might result from the rise of a lower mantle plume through the upper

  6. Charmonium production at mid-rapidity in Pb-Pb and p-Pb collisions with ALICE

    NASA Astrophysics Data System (ADS)

    Weber, Steffen Georg

    2016-01-01

    We present an overview of the ALICE measurements on the production of J/ψ in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of √SNN = 2.76 TeV and p-Pb collisions at √sNN = 5.02 TeV at mid-rapidity (|ylab| < 0.8) down to zero transverse momentum. The cold nuclear matter effects estimated from the p-Pb measurements and their impact on the interpretation of Pb-Pb results are discussed, based on comparison of data to model calculations.

  7. Magnetoelectric coupling in multiferroic BaTiO3-CoFe2O4 composite nanofibers via electrospinning

    NASA Astrophysics Data System (ADS)

    Fu, Bi; Lu, Ruie; Gao, Kun; Yang, Yaodong; Wang, Yaping

    2015-07-01

    Magnetoelectric (ME) coupling in Pb-based multiferroic composites has been widely investigated due to the excellent piezoelectric property of lead zirconate titanate (PZT). In this letter, we report a strategy to create a hybrid Pb-free ferroelectric and ferromagnetic material and detect its ME coupling at the nanoscale. Hybrid Pb-free multiferroic BaTiO3-CoFe2O4 (BTO-CFO) composite nanofibers (NFs) were generated by sol-gel electrospinning. The perovskite structure of BTO and the spinel structure of CFO nanograins were homogenously distributed in the composite NFs and verified by bright-field transmission electron microscopy observations along the perovskite [111] zone axis. Multiferroicity was confirmed by amplitude-voltage butterfly curves and magnetic hysteresis loops. ME coupling was observed in terms of a singularity on a dM/dT curve at the ferroelectric Curie temperature (TC) of BaTiO3. The lateral ME coefficient was investigated by the evolution of the piezoresponse under an external magnetic field of 1000 Oe and was estimated to be α31 =0.78× 104 \\text{mV cm}-1 \\text{Oe}-1 . These findings could enable the creation of nanoscale Pb-free multiferroic composite devices.

  8. [Effects of adsorbents on partitioning of Cd and Pb in MSW incineration].

    PubMed

    Wu, Rong; Li, Qing-Hai; Meng, Ai-Hong; Zhang, Yan-Guo; Chen, Yong

    2009-07-15

    An incineration experiment using simulated municipal solid waste (MSW) in the tubular furnace was performed to study the effects of SiO2, Al2o3 and CaO on the partitioning of Cd and Pb under different operating conditions which included adsorbents percentage, furnace temperature and residence time. The results indicated that the increasing of SiO2, AL2O3, CaO concentration were favorable for Cd to partition in the bottom ash. And for Pb, SiO2 and Al2O3 had the same effects. However, the condition with CaO showed an opposite tendency of increasing Pb distribution in fly ash. While all of these adsorbents increasing, the effects were also enhanced. When the temperature of the tubular furnace was 850 degrees C, the adsorption efficiencies of these adsorbents for Cd were in the sequence of CaO > Al, O3 > SiO2, and for Pb, Al2O3 > SiO2 > CaO. In addition,with increasing of tubular furnace temperature and residence time, there would be more Cd and Pb compounds moving to the fly ash.

  9. 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

  10. 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

  11. Anomalous magnetic moment at Ba in Au

    NASA Astrophysics Data System (ADS)

    Bhati, A. K.; Kaur, J.; Bansal, N.; Negi, D.; Kumar, R.; Bhowmik, R. K.; Kumar, V.; Dey, C. C.

    2015-04-01

    The Time differential perturbed angular distribution (TDPAD) technique is employed to measure the local susceptibility at the recoil implanted Ba ions in Au following the nuclear reaction 120Sn(12C, 3nγ)129Ba. We have observed first time the local paramagnetic susceptibility of 5.26(18) at Ba ions comparable to 4f-ions in any non-ferromagnetic metal at room temperature which seems to be related to the electronic s-d and s-f transfer at positive lattice pressure.

  12. Mn-Doped BaTiO3 Thin Film Sintered Using Nanocrystals and Its Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Takezawa, Yoko; Kobayashi, Keisuke; Nakasone, Fumi; Suzuki, Toshimasa; Mizuno, Youichi; Imai, Hiroaki

    2009-11-01

    BaTiO3 thin films homogeneously doped with Mn were prepared by a novel powder-sintering thin-film process. Mn-doped BaTiO3 nanocrystals 5-7 nm in diameter were synthesized by a sol-gel method and sintered to form a highly densified microstructure containing columnar grains epitaxially grown on a (111)-oriented Pt/TiO2/Al2O3 substrate at a low temperature of 800 °C. On the basis of the results of various structural analyses, Mn was suggested to act as an acceptor in the perovskite structure of BaTiO3, which was also supported by the experimental finding indicating that the leakage current density was significantly improved compared with that of a nondoped BaTiO3 thin film. Moreover, the dielectric constant of the Mn-doped BaTiO3 thin film, 728 at 10 kHz with a loss tangent of 1.3%, was higher than that of the nondoped BaTiO3 thin film, probably owing to the electrostrictive effect induced by in-plane tensile stress. These results clearly indicate the feasibility of using doped BaTiO3 nanocrystals in the powder-sintering thin-film process for improving dielectric properties.

  13. Syntheses, crystal structure, and electronic properties of the five ABaMQ4 compounds RbBaPS4, CsBaPS4, CsBaVS4, RbBaVSe4, and CsBaVSe4

    NASA Astrophysics Data System (ADS)

    Mesbah, Adel; Prakash, Jai; Rocca, Dario; Lebègue, Sébastien; Beard, Jessica C.; Lewis, Benjamin A.; Ibers, James A.

    2016-01-01

    Five new compounds belonging to the ABaMQ4 family were synthesized by solid-state chemistry at 1123 K. The compounds RbBaPS4, CsBaPS4, CsBaVS4, RbBaVSe4, and CsBaVSe4 are isostructural and have the TlEuPS4 structure type. They crystallize in space group D162h - Pnma of the orthorhombic system. Their structure consists isolated MQ4 tetrahedra separated by A and Ba atoms to form a salt-like structure. Density Functional Theory (DFT) calculations of the electronic structures with the use of the HSE functional suggest that the compounds are semiconductors with calculated band gaps of 3.3 eV (RbBaPS4), 3.4 eV (CsBaPS4), 2.3 eV (CsBaVS4), and 1.6 eV (RbBaVSe4).

  14. Centrality dependence of light (anti)nuclei and (anti)hypertriton production in Pb-Pb collisions at √{s_{NN}} = 2.76 TeV

    NASA Astrophysics Data System (ADS)

    Zhilei, She; Gang, Chen; Hongge, Xu; Tingting, Zeng; Dikai, Li

    2016-04-01

    The centrality dependence of light (anti)nuclei and (anti)hypertriton production in Pb-Pb collisions at √{s_{NN}} = 2.76 TeV are investigated using the dynamically constrained phase-space coalescence (DCPC) model and the parton and hadron cascade (PACIAE) model. We found that the yields of light (anti)nuclei and (anti)hypertriton strongly depend on the centrality, i.e., their yields decrease rapidly with the increase of centrality; but their yield ratios are independent of centrality. The results from our theoretical model are well consistent with ALICE data. Furthermore, we found that the integrated yields of (anti)nuclei per participant nucleon increase from peripheral to central collisions, and a higher mass number corresponds to a more rapid increase of such yields. The coalescence parameters BA of light (anti)nuclei and (anti)hypernuclei are also analyzed.

  15. Materials Data on Ba32Sb7Pb25O96 (SG:65) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Materials Data on Ba2PbO4 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  17. Controlled Confinement of Half-metallic 2D Electron Gas in BaTiO3/Ba2FeReO6/BaTiO3 Heterostructures: A First-principles Study

    NASA Astrophysics Data System (ADS)

    Saha-Dasgupta, Tanusri; Baidya, Santu; Waghmare, Umesh; Paramekanti, Arun

    Using density functional theory calculations, we establish that the half-metallicity of bulk Ba2FeReO6 survives down i to 1 nm thickness in BaTiO3/Ba2FeReO6/BaTiO3 heterostructures grown along the (001) and (111) directions. The confinement of the two-dimensional (2D) electron gas in this quantum well structure arises from the suppressed hybridization between Re/Fe d states and unoccupied Ti d states, and it is further strengthened by polar fields for the (111) direction. This mechanism, distinct from the polar catastrophe, leads to an order of magnitude stronger confinement of the 2D electron gas than that at the LaAlO3/SrTiO3 interface. We further show low-energy bands of (111) heterostructure display nontrivial topological character. Our work opens up the possibility of realizing ultra-thin spintronic devices. Journal Ref: Phys. Rev. B 92, 161106(R) (2015) S.B. and T.S.D thank Department of Science and Technology, India for the support through Thematic Unit of Excellence. AP was supported by NSERC (Canada).

  18. A-type granites from the Pan-African orogenic belt in south-western Chad constrained using geochemistry, Sr-Nd isotopes and U-Pb geochronology

    NASA Astrophysics Data System (ADS)

    Isseini, Moussa; André-Mayer, Anne-Sylvie; Vanderhaeghe, Olivier; Barbey, Pierre; Deloule, Etienne

    2012-11-01

    The Zabili granitic pluton (SW Chad) exposed in the Mayo Kebbi massif is dominated by a coarse-grained hornblende biotite granite grading into a fine-grained biotite granite along its southern margin. Petrologic (micrographic intergrowth of quartz and alkali feldspars, granophyric microstructures, the presence of fluorite and bastnaesite as accessory minerals) and geochemical data (high silica, alkalis and Fe/Mg, depletions in CaO, MgO, TiO2; high Ga, Nb, Zr, Ga/Al, REE, depletions in Ba, Sr, Eu and compatible elements) indicate that this pluton consists of A-type granites crystallized from hot (apatite and zircon saturation temperatures ranging from 744 °C to 923 °C), extremely differentiated magmas. U-Pb zircon geochronology indicates that the magmas crystallized at 567 ± 10 Ma and reveals the presence of older Neoproterozoic xenocrystic zircons at 668 ± 5 Ma in both facies. Within the fine-grained biotite granite, discordant zircons with U-Pb and Pb-Pb ages ranging from Neoproterozoic to Archaean are also reported. The 668 ± 5 Ma old zircons are considered to derive from country-rocks while discordant zircons, characterized by angular shapes, internal fractures and inherited cores, are likely to represent multi-sources detrital crystals that have recorded at least one metamorphic event. Old pre-Neoproterozoic zircons are reported for the first time for rocks of the Mayo Kebbi massif and they attest to the contribution of an old basement (likely to be the Eastern Nigeria basement and/or the Congo craton) involved in a collisional event with a juvenile Neoproterozoic crust prior to the emplacement of the Zabili granitic pluton. Initial ɛNd values calculated for the Zabili pluton range from + 2.6 to + 7.0, the highest value recorded by one sample from the coarse-grained hornblende-biotite granite being close to the one of the depleted mantle at 570 Ma (ɛNd = + 7.4). Combining geochronology, Nd isotopes composition and geochemical modeling, leads us to

  19. Hybrid molecular beam epitaxy for the growth of stoichiometric BaSnO{sub 3}

    SciTech Connect

    Prakash, Abhinav Dewey, John; Yun, Hwanhui; Jeong, Jong Seok; Mkhoyan, K. Andre; Jalan, Bharat

    2015-11-15

    Owing to its high room-temperature electron mobility and wide bandgap, BaSnO{sub 3} has recently become of significant interest for potential room-temperature oxide electronics. A hybrid molecular beam epitaxy (MBE) approach for the growth of high-quality BaSnO{sub 3} films is developed in this work. This approach employs hexamethylditin as a chemical precursor for tin, an effusion cell for barium, and a radio frequency plasma source for oxygen. BaSnO{sub 3} films were thus grown on SrTiO{sub 3} (001) and LaAlO{sub 3} (001) substrates. Growth conditions for stoichiometric BaSnO{sub 3} were identified. Reflection high-energy electron diffraction (RHEED) intensity oscillations, characteristic of a layer-by-layer growth mode were observed. A critical thickness of ∼1 nm for strain relaxation was determined for films grown on SrTiO{sub 3} using in situ RHEED. Scanning transmission electron microscopy combined with electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy confirmed the cube-on-cube epitaxy and composition. The importance of precursor chemistry is discussed in the context of the MBE growth of BaSnO{sub 3}.

  20. Jet production in pp, p-Pb and Pb-Pb collisions measured by ALICE

    NASA Astrophysics Data System (ADS)

    Reed, Rosi; ALICE Collaboration

    2015-08-01

    Particle jets, formed when a hard scattered parton fragments into a jet of hadrons, are an ideal probe of the medium formed in heavy-ion collisions. The hard-scattered partons that produce them come from early in the collision, prior to the medium formation. These partons lose energy as they traverse the medium, and eventually fragment into jets of hadrons, which exhibit a modification when compared to jets produced in pp and p-Pb collisions. At LHC energies, the parton production cross-section is much larger than at RHIC, allowing jets to be reconstructed over a much wider kinematic range. Jet reconstruction allows for a more differential investigation of the parton energy loss than single hadrons, which have been used as jet proxies in the past, as the jets collect a larger percentage of the final state energy, which means their kinematics are more closely correlated to the kinematics of the initial parton. Jets are reconstructed in ALICE either using information from the tracking systems, or by combining this with the ALICE electromagnetic calorimeter (EMCal). In these proceedings, jet spectra from 2.76 TeV Pb-Pb and pp collisions will be presented. In particular, the centrality and event-plane dependence of the measured spectra and the background will be discussed. Jets from different centrality classes and event-plane orientations provide additional information necessary for understanding the path-length and temperature dependence of energy loss mechanisms. The reconstruction and correction procedures for jets will be shown. Results from Pb-Pb events will be compared to the baseline pp and p-Pb results, which allows the initial state and cold nuclear matter effects to be disentangled from hot medium effects. The jet nuclear modification, which quantifies the suppression, will be compared to energy-loss models.

  1. THE DIRC Detector at BaBar

    SciTech Connect

    Ratcliff, Blair N

    1999-10-12

    A dedicated particle identification system based on the Detection of Internally Reflected Cherenkov (DIRC) light will be used in the BaBar detector. We provide an overview of the DIRC concept, design, and expected performance of the production device and a status report on its construction and commissioning. The DIRC is expected to be operating in the BaBar detector on beam line at the PEP-II B Factory in late spring 1999.

  2. AMiBA First SZ Measurements

    NASA Astrophysics Data System (ADS)

    Lin, K.-Y.; Wu, J.-H. P.; Umetsu, K.; Kock, P.; Liu, G.-C.; Nishioka, H.; Huang, C.-W.; Liao, Y.-W.; Wang, F.-C.; Ho, P.

    2008-10-01

    Y.T.Lee Array for Microwave Background Anisotropy (AMiBA) is an array utilizing the 90GHz band to measure the CMB power spectrum and the Sunyaev-Zeldovich effect of galaxy clusters. The first stage with seven antennae has been completed, and the second stage with thirteen antennae is being constructed. Using the seven-element array, AMiBA has performed observations on six massive galaxy clusters at redshifts 0.09 - 0.32 during 2007.

  3. Resonant nature of intrinsic defect energy levels in PbTe revealed by infrared photoreflectance spectroscopy

    SciTech Connect

    Zhang, Bingpo; Cai, Chunfeng; Jin, Shuqiang; Ye, Zhenyu; Wu, Huizhen; Qi, Zhen

    2014-07-14

    Step-scan Fourier-transform infrared photoreflectance and modulated photoluminescence spectroscopy were used to characterize the optical transitions of the epitaxial PbTe thin film grown by molecular beam epitaxy on BaF{sub 2} (111) substrate in the vicinity of energy gap of lead telluride at 77 K. It is found that the intrinsic defect energy levels in the electronic structure are of resonant nature. The Te-vacancy energy level is located above the conduction band minimum by 29.1 meV. Another defect (V{sub X}) energy level situated below valance band maximum by 18.1 meV is also revealed. Whether it is associated with the Pb vacancy is still not clear. It might also be related to the misfit dislocations stemming from the lattice mismatch between PbTe and BaF{sub 2} substrate. The experimental results support the theory prediction (N. J. Parada and G. W. Pratt, Jr., Phys. Rev. Lett. 22, 180 (1969), N. J. Parada, Phys. Rev. B 3, 2042 (1971)) and are consistent with the reported Hall experimental results (G. Bauer, H. Burkhard, H. Heinrich, and A. Lopez-Otero, J. Appl. Phys. 47, 1721 (1976)).

  4. Resonant nature of intrinsic defect energy levels in PbTe revealed by infrared photoreflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Bingpo; Cai, Chunfeng; Jin, Shuqiang; Ye, Zhenyu; Wu, Huizhen; Qi, Zhen

    2014-07-01

    Step-scan Fourier-transform infrared photoreflectance and modulated photoluminescence spectroscopy were used to characterize the optical transitions of the epitaxial PbTe thin film grown by molecular beam epitaxy on BaF2 (111) substrate in the vicinity of energy gap of lead telluride at 77 K. It is found that the intrinsic defect energy levels in the electronic structure are of resonant nature. The Te-vacancy energy level is located above the conduction band minimum by 29.1 meV. Another defect (VX) energy level situated below valance band maximum by 18.1 meV is also revealed. Whether it is associated with the Pb vacancy is still not clear. It might also be related to the misfit dislocations stemming from the lattice mismatch between PbTe and BaF2 substrate. The experimental results support the theory prediction (N. J. Parada and G. W. Pratt, Jr., Phys. Rev. Lett. 22, 180 (1969), N. J. Parada, Phys. Rev. B 3, 2042 (1971)) and are consistent with the reported Hall experimental results (G. Bauer, H. Burkhard, H. Heinrich, and A. Lopez-Otero, J. Appl. Phys. 47, 1721 (1976)).

  5. The mineralization age of the Makeng Fe deposit, South China: implications from U-Pb and Sm-Nd geochronology

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenjie; Zuo, Renguang; Cheng, Qiuming

    2015-04-01

    The Makeng Fe deposit is located in the southwestern Fujian district, South China. The Sm-Nd isochron ages of seven samples of pure garnet and five of pure magnetite separates from the Makeng ores yielded an isochron age of 157 ± 15 Ma. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating of the nearby exposed the Dayang-Juzhou (DJ) porphyritic biotite granite and fine-grained syenogranite yielded 206Pb/238U ages of 140.2 ± 1.1 and 140.1 ± 1.0 Ma, respectively. These results suggest that the intrusion of the DJ granite and the Makeng skarn alterations and Fe mineralization are contemporaneous. The DJ granite exhibits geochemical characteristics of A-type granites, including high values of Na2O + K2O (8.13-8.92 wt%), FeOt/MgO (3.4-21.5), and Ga/Al (2.64-3.45 × 10-4), and low Al2O3 (10.71-13.29 wt%) value. Chondrite-normalized rare earth element patterns are characterized by obviously negative Eu anomalies (δEu = 0.02-0.28) and primitive-mantle normalized spidergrams show the enrichment in high field strength element and depleting in Sr, Ti, Ba, and Eu. The geochemical characteristics of DJ granite suggest that the granite was derived from partial melting of the Paleoproterozoic metasedimentary rocks of the Cathaysia basement. And some underplating of mafic magma in the lower tholeiitic crust and/or depleted mantle might be involved and provide the heat source for the partial melting. The DJ granite also fits the spatiotemporal distribution of the Jurassic-Cretaceous coastward migration of both extensional and arc-related magmatism and fills the A-type granites gap in the early stage of the early Cretaceous (145-125 Ma). Therefore, it is suggested that the late Jurassic and early Cretaceous magmatism in southwestern Fujian district were generated in an extensional environment responding to the slab rollback and concomitant retreating arc system of the paleo-Pacific plate within the South China Block. And the Fe metallogeny

  6. Octahedral tilting in Pb-based relaxor ferroelectrics at high pressure.

    PubMed

    Maier, Bernd J; Angel, Ross J; Marshall, William G; Mihailova, Boriana; Paulmann, Carsten; Engel, Jens M; Gospodinov, Marin; Welsch, Anna-Maria; Petrova, Dimitrina; Bismayer, Ulrich

    2010-06-01

    We have employed a combination of powder neutron diffraction and single-crystal synchrotron X-ray diffraction to characterize the pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc(0.5)Ta(0.5)O(3) (PST) and Pb(0.78)Ba(0.22)Sc(0.5)Ta(0.5)O(3) (PST-Ba). At ambient pressure the symmetry of the average structure for both compounds is Fm3m as a result of partial ordering of the Sc and Ta cations on the octahedral sites. At pressures above the phase transition both the neutron and X-ray diffraction patterns exhibit an increase in the intensities of h,k,l = all odd reflections and no appearance of additional Bragg reflections. Synchrotron single-crystal X-ray diffraction data show that the intensity of hhh peaks, h = 2n + 1, does not change with pressure. This indicates that the structural distortion arising from the phase transition has a glide-plane pseudo-symmetry along the 111 cubic directions. Rietveld refinement to the neutron powder data shows that the high-pressure phase has either R3c or R3 symmetry, depending on whether the presence of 1:1 octahedral cation ordering is neglected or taken into account, and comprises octahedral tilts of the type a(-)a(-)a(-) that continuously evolve with pressure. The cubic-to-rhombohedral transition is also marked by a large increase in the anisotropy of the displacement ellipsoids of the Pb cations, indicating larger displacements of Pb cations along the rhombohedral threefold axis rather than within the perpendicular plane. For PST the anisotropy of the Pb displacement parameters decreases at approximately 3 GPa above the phase-transition pressure. For both PST and PST-Ba the average magnitudes of Pb-cation displacements expressed in terms of isotropic displacement ellipsoids gradually decrease over the entire pressure range from ambient to 7.35 GPa. PMID:20484799

  7. Method for preparing Pb-. beta. ''-alumina ceramic

    DOEpatents

    Hellstrom, E.E.

    1984-08-30

    A process is disclosed for preparing impermeable, polycrystalline samples of Pb-..beta..''-alumina ceramic from Na-..beta..''-alumina ceramic by ion exchange. The process comprises two steps. The first step is a high-temperature vapor phase exchange of Na by K, followed by substitution of Pb for K by immersing the sample in a molten Pb salt bath. The result is a polycrystalline Pb-..beta..''-alumina ceramic that is substantially crack-free.

  8. High-pressure synthesis and X-ray powder structure determination of the nitridophosphate BaP{sub 2}N{sub 4}

    SciTech Connect

    Karau, Friedrich W.; Schnick, Wolfgang . E-mail: wolfgang.schnick@uni-muenchen.de

    2005-01-15

    The novel nitridophosphate BaP{sub 2}N{sub 4} was obtained by means of high-pressure high-temperature synthesis utilizing the multianvil technique (8GPa, 1400 deg. C). The [PN{sub 2}]{sup -} network is isoelectronic with silica. The structure was solved from synchrotron powder data by a combination of direct methods and difference Fourier synthesis and refined using the Rietveld method (BaP{sub 2}N{sub 4},Pa3-bar ,Z=12,a=10.22992(2)A). BaP{sub 2}N{sub 4} is isotypic with BaGa{sub 2}S{sub 4},BaAl{sub 2}S{sub 4} and the high-pressure phase of CaB{sub 2}O{sub 4}. The P31 solid-state NMR yielded a single sharp resonance at 0.4ppm.

  9. Pb uptake and toxicity to Iris halophila tested on Pb mine tailing materials.

    PubMed

    Han, Yulin; Zhang, Lili; Yang, Yongheng; Yuan, Haiyan; Zhao, Jiuzhou; Gu, Jiguang; Huang, Suzhen

    2016-07-01

    Pb tolerant mechanisms, plant physiological response and Pb sub-cellular localization in the root cells of Iris halophila were studied in sand culture and the Pb mine tailings. Results showed that the activities of superoxide dismutase (SOD) and peroxidase (POD) in the underground parts and the activity of catalase (CAT) in the aboveground and underground parts increased as Pb level was enhanced. Glutathione (GSH) and ascorbic acid (AsA) contents increased by Pb treatments. Pb deposits were found in the middle cell walls or along the inner side of epibiotic protoplasm of some cells which accumulated a large quantity of Pb and died. The dry weights (DWs) of aboveground parts under all Pb tailings treatments decreased insignificantly, while the DW of the underground parts growing in the pure Pb tailings decreased significantly. Pb, Cu, Cd, and Zn contents increased significantly as the levels of Pb tailings were enhanced and Pb contents in the aboveground and underground parts reached 64.75 and 751.75 μg/g DW, respectively, at pure Pb tailings treatment. The results indicated that I. halophila is a promising plant in the phytoremediation of Pb contaminated environment. Some antioxidant enzymes, antioxidants and compartmentalization of Pb were played major roles in Pb tolerance of I. halophila. PMID:27131809

  10. Room temperature metastable monoclinic phase in BaTiO3 crystals

    NASA Astrophysics Data System (ADS)

    Lummen, Tom; Wang, Jianjun; Holt, Martin; Kumar, Amit; Vlahos, Eftihia; Denev, Sava; Chen, Long-Qing; Gopalan, Venkatraman

    2011-03-01

    Low-symmetry monoclinic phases in ferroelectric materials are of considerable interest, due to their associated enhanced electromechanical coupling. Such phases have been found in Pb-based perovskite solid solutions such as lead zirconate titanate (PZT), where they form structural bridges between the rhombohedral and tetragonal ground states in compositional space. In this work, we directly image such a monoclinic phase in BaTi O3 crystals at room-temperature, using optical second harmonic generation, Raman, and X-ray microscopic imaging techniques. Phase-field modeling indicates that ferroelectric domain microstructures in BaTi O3 induce local inhomogeneous stresses in the crystals, which can effectively trap the transient intermediate monoclinic structure that occurs across the thermal orthorhombic-tetragonal phase boundary. The induced metastable monoclinic domains are ferroelectrically soft, being easily moved by electric fields as low as 0.5 kV cm-1 . Stabilizing such intermediate low-symmetry phases could very well lead to Pb-free materials with enhanced piezoelectric properties.

  11. Changes in Ba phases in BaO/Al₂O₃ upon thermal aging and H₂O treatment

    SciTech Connect

    Kim, Do Heui; Chin, Ya-Huei; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2005-12-01

    The effects of thermal aging and H₂O treatment on the physicochemical properties of a BaO/Al₂O₃ model catalyst were investigated by means of XRD, BET, TEM/EDX and NO₂ TPD. Thermal aging at 1000 °C for 10 hrs resulted in conversion of dispersed BaCO₃ into low surface area crystalline BaAl₂O₄. It was found that H₂O treatment on a BaO/Al₂O₃ sample at room temperature transformed not only the BaAl₂O₄, but also the dispersed BaCO₃ into highly crystalline BaCO₃ segregated from the Al₂O₃ support, as evidenced in TEM/EDX and XRD analysis. The sample containing dispersed BaCO3 in the initial phase segregated more severely than the BaAl₂O₄ containing one, with the Ba in the BaAl₂O₄ matrix exhibiting higher resistance towards segregation. Contacting the BaO/Al₂O₃ sample with liquid water over a prolong period of time leads to an increase in crystallinity of the segregated BaCO₃. These phenomena imply that special care must be taken during catalyst synthesis and during realistic operation of Pt/BaO/Al₂O₃ NOx trap catalysts since both processes involve potential exposure of the material with liquid H₂O. Based on the results, a model to explain the behavior of Ba containing species upon thermal aging and H₂O treatment is proposed.

  12. Giant topological insulator gap and Rashba splitting in honeycomb Pb

    NASA Astrophysics Data System (ADS)

    He, Haiyan; Hu, Jun; Wu, Ruqian; Ruqian Wu's Group Team

    2014-03-01

    It was predicted that graphene can be a topological insulator (TI) due to its special Dirac states and spin-orbit coupling (SOC). However, the SOC gap of pure graphene is too small for experimental observation. It was found that heavier group IV elements, such as Si and Ge, can also produce the TI state in the tow-dimensional honeycomb lattice, with their SOC gaps a few orders larger than that of graphene. In the present work, we find that the honeycomb Pb is also a TI, with a SOC gap as large as 250 meV. We demonstrate the feasibility of making a honeycomb Pb monolayer on the Al2O3(0001) substrate. Moreover, Pb/Al2O3(0001) has a giant Rashba splitting of 270 meV, useful for spintronics and topotronics applications. This work was supported by DOE-BES(Grant No: DE-FG02-05ER46237) and by NERSC for computing time.

  13. Electrical-transport properties and microwave device performance of sputtered TlCaBaCuO superconducting thin films

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Kapoor, V. J.; Chorey, C. M.; Bhasin, K. B.

    1992-01-01

    The paper describes the processing and electrical transport measurements for achieving reproducible high-Tc and high-Jc sputtered TlCaBaCuO thin films on LaAlO3 substrates, for microelectronic applications. The microwave properties of TlCaBaCuO thin films were investigated by designing, fabricating, and characterizing microstrip ring resonators with a fundamental resonance frequency of 12 GHz on 10-mil-thick LaAlO3 substrates. Typical unloaded quality factors for a ring resonator with a superconducting ground plane of 0.3 micron-thickness and a gold ground plane of 1-micron-thickness were above 1500 at 65 K. Typical values of penetration depth at 0 K in the TlCaBaCuO thin films were between 7000 and 8000 A.

  14. New Horizons in Global Trace Metal Oceanography: the Global Distribution of Pb, Pb Isotope, Fe, and Fe Colloids

    NASA Astrophysics Data System (ADS)

    Boyle, E. A.; Reuer, M. K.

    2001-12-01

    During the most recent epoch of inorganic and isotopic exploration of the global ocean (GEOSECS), trace element oceanography was in its infancy: GEOSECS obtained a global database for Ba, but apart from the analysis of Cd, Cu, Ni, and Mn in some samples from the project, the ocean was left largely unexplored for its trace element secrets. In subsequent decades, trace metal capabilities have advanced enormously, yet no global scale efforts to understand trace metals in the ocean have been mounted. The field has been the purview of small single investigator and limited process-oriented project science. This paucity of global scale trace metal investigation has occurred despite global scale oceanographic surveys (WOCE) and despite increasing recognition of the role of elements such as iron in regulating the global oceanic metabolism. It has also occurred despite increasingly sophisticated analytical and sampling technology progress, where many trace elements can be analyzed shipboard or on very small samples (10 ml or less) with sampling methods that collect large numbers of samples in an economical fashion. We argue that the time is ripe for new global-scale surveys of the trace metal composition of the ocean. It is scandalous that we are forced to model the oceanic behavior of an essential element such as iron lacking an even rudimentary description of its global distribution. The addition of a single profile in the Antarctic or near Hawaii can set the whole field on its head. As examples, we will present data on the distribution of Pb, Pb isotopes ratios, Fe, and Fe colloid distributions obtained in the past few years by plasma mass spectrometry. The utility of Pb as a measure of anthropogenic influence on ocean chemistry and as a tracer of ocean ventilation will be demonstrated, and the prospect for a global Fe database illuminated.

  15. Redetermination of β-Ba(PO3)2.

    PubMed

    Weil, Matthias

    2014-02-01

    In comparison with the previous structure determination of the β-modification of barium catena-polyphosphate that was based on Weissenberg film data [Grenier et al. (1967 ▶). Bull. Soc. Fr. Minéral. Cristallogr. 90, 24-31], the current CCD-data-based redetermination reveals all atoms with anisotropic displacement parameters, standard uncertainties for the atomic coordinates, and the determination of the absolute structure. Moreover, a much higher accuracy in terms of the bond-length distribution for the polyphosphate chain, with two shorter and two longer P-O distances, was achieved. The structure consists of polyphosphate chains extending parallel to [100] with a periodicity of two PO4 tetra-hedra. The Ba(2+) cations are located between the chains and are surrounded by ten O atoms in the form of a distorted coordination polyhedron, with Ba-O distances ranging from 2.765 (3) to 3.143 (3) Å, also reflecting the higher precision of the current redetermination.

  16. Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments

    NASA Astrophysics Data System (ADS)

    Hu, Ningjing; Huang, Peng

    2016-04-01

    Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments Hu Ning-jinga, Huang Pengb,, Liu Ji-huaa, a First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China b Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of surface sediments in this area were determined. The Pb concentration in this bay varied widely from 6.9 to 39.2 μg/g (average: 21.8 ± 7.8 μg/g), and the Pb isotopic compositions ranged from 0.8338 to 0.8864 (average: 2.0997 ± 0.0180) for 208Pb/206Pb and from 2.0797 to 2.1531 (average: 0.8477 ± 0.0135) for 207Pb/206Pb, presenting in three distinct clusters. The Pb isotopic ratios of sediments from the northeastern (NE zone) and northwestern (NW zone) coastal areas were significantly influenced by anthropogenic sources such as coal combustion and automobile emission. In sediments from the central and southern Bohai Bay (C-S zone); however, Pb mainly originated from the Yellow River catchment, as a result of lithogenic sediment (from rock weathering) accumulation. The Pb isotopic ratios further indicate that, apart from riverine inputs, the neighboring large-scale ports and aerosols significantly contributed to the anthropogenic Pb contained in these sediments. Pb contamination in the Haihe and Luanhe river mouths as well as in the regions near ports is also suggested from anthropogenic enrichment factors. As cities and ports continue to develop around Bohai Bay, a long-term extensive sewage monitoring program is highly recommended.

  17. Pb Isotopes Track Asian Pollution in California

    NASA Astrophysics Data System (ADS)

    Ewing, S. A.; Christensen, J. N.; Brown, S. T.; Vancuren, R. A.; Cliff, S. S.; Depaolo, D. J.

    2008-12-01

    The transport of Asian pollution to North America has broad implications for global climate models and regional air quality regulation. In the western US, rising atmospheric Pb levels have been evident since the mid-1990s despite the phase-out of leaded gasoline. We use Pb isotopes to fingerprint the trans-Pacific component of atmospheric pollution in California. We measured Pb isotopes in airborne particles collected at two sites west (Mt. Tamalpais) and east (Chabot Observatory, Oakland Hills) of the San Francisco Bay Area, from winter 2007 through late spring 2008. We also analyzed archived springtime samples from inland sites throughout central California. Wintertime values of 206Pb/207Pb vs. 208Pb/207Pb at Chabot Observatory form a linear array that is consistent with published data for San Francisco Bay waters, whereas published values for Chinese cities and loess fall along a separate and distinct array for that region, consistent with our analysis of samples collected at Hefei, China in 2002. Between March and May 2008, the Tamalpais and Chabot samples diverge from the California regional array toward the Chinese array. About half of the central California samples also show a strong Asian influence. We quantify the divergence of values from the regional California array as Δ208Pb = (208Pb/207Pb)expected - (208Pb/207Pb) )observed, where (208Pb/207Pb)expected is derived from a linear fit to the wintertime samples at Chabot Observatory. These Δ208Pb values increase between winter and spring at both Mt. Tamapais and Chabot Observatory, and are higher at Mt. Tamalpais, despite lower Pb concentrations at that site. They indicate that up to 80% of the Pb in the Tamalpais samples, and up to 40% of the Pb in the Chabot Observatory samples, reflect trans-Pacific transport. The lower proportion in the Chabot samples -- where there is often more Pb -- indicates dilution by local urban sources. Our data provide conclusive evidence of Asian air pollution reaching

  18. The effects of pH and surface composition on Pb adsorption to natural freshwater biofilms.

    PubMed

    Wilson, A R; Lion, L W; Nelson, Y M; Shuler, M L; Ghiorse, W C

    2001-08-01

    Two dominant variables that control the adsorption of toxic trace metals to suspended particulate materials and aquatic surface coatings are surface composition and solution pH. A model for the pH-dependent adsorption of Pbto heterogeneous particulate surface mixtures was derived from experimental evaluation of Pb adsorption to laboratory-derived surrogates. The surrogate materials were selected to represent natural reactive surface components. Pb adsorption to both the laboratory surrogates and natural biofilms was determined in chemically defined solutions under controlled laboratory conditions. Pb adsorption was measured over a pH range of 5-8, with an initial Pb concentration in solution of 2.0 microM. The surface components considered include amorphous Fe oxide, biogenic Mn oxide produced by a Mn(II) oxidizing bacterium (Leptothrix discophora SS-1), Al oxide, the common green alga Chlorella vulgaris, and Leptothrix discophora SS-1 cells. A linearization of Pb adsorption data for each adsorbent was used to quantify the relationship between Pb adsorption and pH. The parameters for individual adsorbents were incorporated into an additive model to predict the total Pb adsorption in multiple-adsorbent natural surface coatings that were collected from Cayuga Lake, NY. Pb adsorption experiments on the natural surface coatings at variable pH were utilized to verify the additive model predictions based on the pH dependent behavior of the experimental laboratory surrogates. Observed Pb adsorption is consistent with the model predictions (within 1-24%) over the range of solution pH values considered. The experimental results indicate that the combination of Fe and biogenic Mn oxides can contribute as much as 90% of Pb adsorbed on Cayuga Lake biofilms, with the dominant adsorbent switching from Mn to Fe oxide with increasing pH. PMID:11505999

  19. Lead (Pb) fluxes and Pb isotopic compositions from Masaya Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Vallelonga, P.; Mather, T. A.

    We report Pb concentrations and isotopic compositions measured in plume aerosol and Pele's hair (lava) samples collected from Masaya volcano, Nicaragua, to provide the first data pertaining to Pb emissions from the Central American volcanic arc. Lead isotopic compositions, determined by Thermal Ionisation Mass Spectrometry, in the Pele's hair samples were found to be 206Pb/ 207Pb˜1.196, 208Pb/ 207Pb˜2.46 and 206Pb/ 204Pb˜18.6. Mean Pb fluxes from Masaya were calculated to be 1.0 ton Pb yr -1 with a mean plume Pb/S (gas) ratio of 1.3×10 -5. Also, it was found that the majority of Pb emitted was present in the fine aerosol (<2.5 μm diameter) fraction but that the percentage of Pb in the fine aerosol fraction decreased from 96% in the dry daytime plume to 61% in the condensed night-time plume. The contribution from the filter blank was usually a substantial fraction of the total amount of Pb measured, requiring the data to be corrected for blank contributions using Pb isotopic systematics.

  20. Monitoring of Pb Exposure in Waterfowl Ten Years after a Mine Spill through the Use of Noninvasive Sampling

    PubMed Central

    Martinez-Haro, Monica; Taggart, Mark A.; Lefranc, Hugues; Martín-Doimeadiós, Rosa C.; Green, Andy J.; Mateo, Rafael

    2013-01-01

    Lead exposure in waterfowl was studied using noninvasive fecal sampling in the Guadalquivir Marshes in Spain, an area affected by the 1998 Aznalcóllar mine disaster. Feces of greylag geese (Anser anser, n = 191) and purple gallinule (Porphyrio porphyrio, n = 91) were collected from three different impacted sites (Entremuros, Caracoles and Cerro de los Ánsares) during the winters of 2004 to 2008. Lead and aluminium (an indicator of sediment ingestion) and Pb isotope signatures (to discriminate between sources of Pb exposure) were analyzed in freeze-dried, acid digested samples. The concentrations of fecal porphyrins and biliverdin were determined as noninvasive biomarkers to study Pb exposure effects. Results showed a decrease in Pb exposure over time in wintering greylag geese. In contrast, for purple gallinule resident in the Entremuros a clear trend was not evident. For both species, sediment ingestion appeared to be the main source of exposure to Pb. In the Entremuros, some samples from purple gallinule were detected with higher Pb levels than expected for simple soil ingestion, and these had Pb isotopic profiles compatible with mining sludge or Pb shot. Whilst fecal Pb isotopic profiles were effective in differentiating between samples from sites with different levels and sources of pollution, the combined use of element ratios (such as Pb/Al) and other non-traditional stable isotope signatures may also prove worthwhile. Overall, the fecal Pb levels detected were below those described in feces for waterfowl from other uncontaminated areas(<10 µg/g d.w.). Despite this, for both species fecal Pb levels were positively correlated with porphyrin excretion, and for purple gallinule, with the coproporphyrin III/I ratio, suggesting some subtle effects on heme synthesis in birds. Ten years after the mine spill, Pb contamination in birds by this pollution source was still detectable and subtlethal effects may persist. PMID:23437364

  1. A new fluorescent chemosensor for Pb²⁺ ions based on naphthalene derivatives.

    PubMed

    Azadbakht, Reza; Vaisi, Hojat; Mohamadvand, Hossain; Khanabadi, Javad

    2015-06-15

    A new naphthalene derivative receptor (L) was synthesized and characterized with common spectroscopic methods. L exhibited a strong fluorescence enhancement in the presence of trace amounts of Pb(2+), attributable to photoinduced electron transfer (PET) effect, which also displayed high selectivity over a series of other metal cations (Na(+), K(+), Cs(+), Mg(2+), Ba(2+), Cr(3+), Mn(2+), Fe(3+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) in acetonitrile/H2O (9:1, v/v) mixture.

  2. Liquidus projection of the Ag-Ba-Ge system and melting points of clathrate type-I compounds

    SciTech Connect

    Zeiringer, I.; Grytsiv, A.; Broz, P.

    2012-12-15

    The liquidus and solidus projection has been constructed for the Ag-Ba-Ge system up to 33.3 at% Ba, using electron micro probe analysis (EPMA), X-ray powder diffraction (XRD) and differential thermal analysis (DSC/DTA). Eight different primary crystallization regions were found: (Ge), Ba{sub 8}Ag{sub x}Ge{sub 46-x-y}{open_square}{sub y} ({kappa}{sub I}) ({open_square} is a vacancy), Ba{sub 6}Ag{sub x}Ge{sub 25-x} ({kappa}{sub Ix}), BaGe{sub 2}, Ba(Ag{sub 1-x}Ge{sub x}){sub 2} ({tau}{sub 1}), BaAg{sub 2-x}Ge{sub 2+x} ({tau}{sub 2}) BaAg{sub 5} and (Ag). The ternary invariant reactions have been determined for the region investigated and are the basis for a Schulz-Scheil diagram. The second part of this work provides a comprehensive compilation of melting points of ternary A{sub 8}T{sub x}M{sub 46-x} and quaternary (A=Sr, Ba, Eu; T=Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga; M=Si, Ge, Sn) clathrate type-I compounds and decomposition temperatures of inverse clathrate type-I Ge{sub 38}{l_brace}P,As,Sb{r_brace}{sub 8}{l_brace}Cl,Br,I{r_brace}{sub 8}, Si{sub 46-x}P{sub x}Te{sub y} and tin based compounds. - Graphical Abstract: Partial liquidus projection of the Ag-Ba-Ge system. Highlights: Black-Right-Pointing-Pointer The liquidus and solidus projection has been constructed for the Ag-Ba-Ge system up to 33.33 at% Ba. Black-Right-Pointing-Pointer Eight different primary crystallization fields have been found. Black-Right-Pointing-Pointer All the ternary compounds form congruently from the melt. Black-Right-Pointing-Pointer The ternary invariant reactions have been determined and are the basis for a Schulz-Scheil diagram.

  3. Synthesis, structural and magnetic characterisation of the fluorinated compound 15R-BaFeO{sub 2}F

    SciTech Connect

    Clemens, Oliver; Berry, Frank J.; Bauer, Jessica; Wright, Adrian J.; Knight, Kevin S.; Slater, Peter R.

    2013-07-15

    The compounds 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.27}F{sub 0.5} have been synthesised by the low temperature fluorination of 15R-BaFeO{sub 3−d}F{sub 0.2} using polyvinylidenedifluoride (PVDF) as a fluorination agent. The materials have been structurally characterised by Rietveld analysis of the X-ray- and HRPD-powder neutron diffraction data. A detailed analysis of bond valence sums suggests that the oxide and fluoride ions order on the different anion sites. A reinvestigation of our recently published structure (Clemens et al., 2013) [34] of 6H-BaFeO{sub 2}F is also reported and incorporation of fluoride in h-type layers is also confirmed in this compound. The magnetic moments for 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.25}F{sub 0.5} align in the a/b-plane with antiferromagnetic alignment of the moments between adjacent layers, and are flipped by 90° as compared to the precursor compound. 15R-BaFeO{sub 2}F exhibits very robust antiferromagnetism with a Néel temperature between 300 and 400 °C. - Graphical abstract: The crystal and magnetic structure of the perovskite phase 15R-BaFeO{sub 2}F. - Highlights: • 15R-BaFeO{sub 2}F and 15R-BaFeO{sub 2.27}F{sub 0.5}were prepared via low temperature fluorination using PVDF. • A structural investigation of the compounds BaFeO{sub 2}F is presented in detail. • This analysis suggests ordering of O{sup 2−} and F{sup −} anions between different layers. • 15R-BaFeO{sub 2}F shows antiferromagnetic ordering at 300 K with T{sub N} ∼300–400 °C. • The magnetic moments align in the a/b-plane.

  4. Local Distortions in PbTe:Tl

    NASA Astrophysics Data System (ADS)

    Keiber, Trevor; Bridges, Frank; Sales, Brian

    2013-03-01

    Lead Telluride (PbTe) is a well characterized thermoelectric material. Tl doping increases the figure of merit with a maximum at 2% Tl. Recent X-ray diffraction and total neutron scattering experiments suggest Pb moves off-center along the 100 axis as T increases. To investigate the local structure we present an Extended X-ray Absorption Fine Structure (EXAFS) analysis for 0-3% Tl concentrations at the Tl and Pb L3 edges and at the Te K edge. At 10K the local structure about Pb is well ordered, the Pb-Te (Te-Pb) pair distribution function (PDF) broadens rapidly with T. Attempts to model the increase in σ2(T) for the Pb-Te pair (σ is the width of the PDF) with a 100 Pb off-center displacement, were not successful. However σ2(T) for the Pb-Te pair is well described by a correlated Debye model with a low correlated Debye temperature. The Te edge shows increased disorder for the the Te-Te pair and later peaks which may be caused by a structural change around the Te atom. For Tl, the environment is distorted even at 10K within the host material. This indicates a large variation of the Tl-Te bond lengths, presumably as a result of the presence of Tl(+1). We discuss possible models for the disorder about Tl, Pb, and Te in PbTe:Tl. Support: NSF DMR 1005568

  5. Epitaxial Ba-Y-Cu-O ceramic superconducting film on perovskite structure substrate

    SciTech Connect

    Chai, B.H.

    1991-07-09

    This patent describes a superconducting structure. It comprises a crystal substrate having a superconducting film epitaxially deposited thereon, wherein the substrate is a crystal selected from the group consisting of LaAlO{sub 3}, LaGaO{sub 3}, PrGaO{sub 3} and NdGaO{sub 3}, and wherein the superconducting film is a Ba- Y- Cu- O superconductor.

  6. Lead (Pb) and other metals in New York City community garden soils: factors influencing contaminant distributions

    PubMed Central

    Mitchell, Rebecca G.; Spliethoff, Henry M.; Ribaudo, Lisa N.; Lopp, Donna M.; Shayler, Hannah A.; Marquez-Bravo, Lydia G.; Lambert, Veronique T.; Ferenz, Gretchen S.; Russell-Anelli, Jonathan M.; Stone, Edie B.; McBride, Murray B.

    2014-01-01

    Urban gardens provide affordable fresh produce to communities with limited access to healthy food but may also increase exposure to lead (Pb) and other soil contaminants. Metals analysis of 564 soil samples from 54 New York City (NYC) community gardens found at least one sample exceeding health-based guidance values in 70% of gardens. However, most samples (78%) did not exceed guidance values, and medians were generally below those reported in NYC soil and other urban gardening studies. Barium (Ba) and Pb most frequently exceeded guidance values and along with cadmium (Cd) were strongly correlated with zinc (Zn), a commonly measured nutrient. Principal component analysis suggested that contaminants varied independently from organic matter and geogenic metals. Contaminants were associated with visible debris and a lack of raised beds; management practices (e.g., importing uncontaminated soil) have likely reduced metals concentrations. Continued exposure reduction efforts would benefit communities already burdened by environmental exposures. PMID:24502997

  7. Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions

    DOE PAGES

    Khachatryan, Vardan

    2015-09-22

    A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pT and η of both particles and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at √sNN=2.76 TeV and pPb collisions at √sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, the magnitude of the factorization breakdown for the secondmore » Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different η. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very-high-multiplicity pPb collisions. The η-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.« less

  8. Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions

    SciTech Connect

    Khachatryan, Vardan

    2015-09-22

    A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pT and η of both particles and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at √sNN=2.76 TeV and pPb collisions at √sNN=5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and η. When measured with particles of different pT, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different η. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very-high-multiplicity pPb collisions. The η-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.

  9. Phase composition identification and microstructure of BaTiO3-containing sodium-aluminoborosilicate glass-ceramics

    NASA Astrophysics Data System (ADS)

    Harizanova, Ruzha; Abrashev, Miroslav; Avramova, Ivalina; Vladislavova, Liliya; Bocker, Christian; Tsutsumanova, Gichka; Avdeev, Georgi; Rüssel, Christian

    2016-02-01

    Bulk glasses with a composition 20.1Na2O/23.1BaO/23.0TiO2/7.6B2O3/17.4SiO2/3Al2O3/5.8Fe2O3 containing less than 30 mol% glass-forming oxides are synthesized. Information on the valency of the glass constituents is obtained by x-ray photoelectron spectroscopy and it is concluded that all species are predominantly present in their oxidized state. Glassy samples are annealed above the glass transition temperature which leads to the crystallization of BaTiO3 for all time-temperature applied schedules. The phase composition of the glass-ceramics is studied by x-ray diffraction and the formation of cubic BaTiO3 is suggested. Temperature-dependent Raman spectroscopy confirms the presence of solely cubic BaTiO3. The microstructures of all annealed samples are similar and consist of globular interconnected particles in which nanosized BaTiO3 crystals grow randomly. The mean size of the spherical formations increases with the increasing annealing time from 200 to 600 nm. Electron microscopy suggests that during the annealing process first phase separation and then crystallization of BaTiO3 occurs.

  10. The Estherville mesosiderite - U-Pb, Rb-Sr, and Sm-Nd isotopic study of a polymict breccia

    NASA Technical Reports Server (NTRS)

    Brouxel, M.; Tatsumoto, M.

    1991-01-01

    The U-Pb, Rb-Sr, and Sm-Nd isotopic systematics of the Estherville mesoderite were studied using analytical procedures and mass spectrometric techniques similar to those reported by Nakamura et al. (1976), Tatsumoto et al. (1987), and Premo et al. (1989) to analyze 21 separates of a 13-g Estherville clast, obtained either by handpicking or by using density and magnetic separation methods. The results on the Pb-Pb and U-Pb ages (about 4555 and about 4560 Ma, respectively) indicate that at least a part of the Estherville silicate fraction was formed early in the history of solar system. Younger Pb-Pb and U-Pb ages (about 4.43 Ga) were also obtained, confirming the heterogeneity of the Estherville mesoderite that is in agreement with the Wasson and Rubin (1985) suggestion of several generations of meteoritic impacts. The Sm-Nd and Rb-Sr ages were found to be close to 4.56 Ga.

  11. Immobilization of Rose Waste Biomass for Uptake of Pb(II) from Aqueous Solutions

    PubMed Central

    Ansari, Tariq Mahmood; Hanif, Muhammad Asif; Mahmood, Abida; Ijaz, Uzma; Khan, Muhammad Aslam; Nadeem, Raziya; Ali, Muhammad

    2011-01-01

    Rosa centifolia and Rosa gruss an teplitz distillation waste biomass was immobilized using sodium alginate for Pb(II) uptake from aqueous solutions under varied experimental conditions. The maximum Pb(II) adsorption occurred at pH 5. Immobilized rose waste biomasses were modified physically and chemically to enhance Pb(II) removal. The Langmuir sorption isotherm and pseudo-second-order kinetic models fitted well to the adsorption data of Pb(II) by immobilized Rosa centifolia and Rosa gruss an teplitz. The adsorbed metal is recovered by treating immobilized biomass with different chemical reagents (H2SO4, HCl and H3PO4) and maximum Pb(II) recovered when treated with sulphuric acid (95.67%). The presence of cometals Na, Ca(II), Al(III), Cr(III), Cr(VI), and Cu(II), reduced Pb(II) adsorption on Rosa centifolia and Rosa gruss an teplitz waste biomass. It can be concluded from the results of the present study that rose waste can be effectively used for the uptake of Pb(II) from aqueous streams. PMID:21350666

  12. Unique accessory Ti-Ba-P mineralization in the Kvalöya ultrapotassic dike, Northern Norway

    NASA Astrophysics Data System (ADS)

    Zozulya, D. R.; Savchenko, E. E.; Kullerud, K.; Ravna, E. K.; Lyalina, L. M.

    2010-12-01

    Unusual ultrapotassic dikes were recently found on the Kvalöya Island in Northern Norway. The dikes crosscutting granites 1.8 Ga in age are 0.1-1.0 m thick and consist of phlogopite phenocrysts in a fine-grained groundmass of K-magnesioarfvedsonite, orthoclase, apatite, and secondary chlorite. According to the composition of the rock-forming minerals (4.5-6.0 wt % K2O and 0.7-3.5 wt % TiO2 in magnesioarfved-sonite, 1.6-3.6 wt % FeO in orthoclase, 9.2-10.7 wt % Al2O3 and 2.1-2.6 wt % TiO2 in phlogopite) and its bulk chemical composition (K/Na = 2.3-2.9, K/Al = 1.0-1.2, (Na + K)/Al = 1.4-1.7, Mg# V = 65-73, (La/Yb) n = 100-140, 3.2-4.0 wt % TiO2, 0.55-1.47 wt % BaO, 2.5-3.0 wt % P2O5, 2650-3000 ppm Zr, 900-1260 ppm REE total, 2300-2500 ppm Sr), the rock corresponds to lamproite of the transitional type. The unique chemical composition of the rock resulted in uncommon Ti-Ba-P accessory mineralization, including baotite Ba4(Ti,Nb)8Si4O28Cl (up to 5 vol %), Sr-apatite (5-7 vol %), and previously unknown Na-Mg-Ba phosphate. Baotite forms anhedral elongated and isometric grains 10-500 μm in size. It is characterized by low Nb (0.03-0.05 f.c.); admixtures of K (0.04-0.12 f.c.) and Sr (0.04-0.07) replacing Ba and Fe (0.01-0.03 f.c.); and Al (0.03-0.04 f.c.) substituting Ti. Euhedral elongated zonal apatite crystals are extremely enriched in SrO (8-12 wt %) and REE2O3 + Y2O3 (6-9 wt %) in the marginal zone. Na-Mg-Ba phosphate occurs as prismatic grains 10-100 μm in size. The atomic ratio of its major cations Na: Mg: Ba: P ˜ 2: 1: 1: 2 corresponds to the conventional formula Na2MgBa(PO4)2; the mineral contains Sr, Mn, Fe, Ca, Si, and Al admixtures.

  13. Quarkonium shadowing in pPb and Pb+Pb collisions

    SciTech Connect

    Vogt, R

    2007-05-21

    The d+Au data from RHIC, including the pA results from the fixed-target CERN SPS pA data, suggest increased importance of initial-state shadowing and decreasing nuclear absorption with increasing energy. This is not surprising since smaller x is probed at higher energy while absorption due to multiple scattering is predicted to decrease with energy. The CERN SPS data suggest a J/{psi} absorption cross section of about 4 mb without shadowing, and a larger absorption cross section if it is included since the SPS x range is in the antishadowing region. The d+Au RHIC data support smaller absorption, {sigma}{sup J/{psi}}{sub abs} {approx} 0-2 mb. Thus our predictions for J/{psi} and {Upsilon} production in pPb and Pb+Pb interactions at the LHC are shown for initial-state shadowing alone with no absorption or dense matter effects. We note that including absorption would only move the calculated ratios down in proportion to the absorption survival probability since, at LHC energies, any rapidity dependence of absorption is at very large |y|, outside the detector acceptance.

  14. Heavy-flavour correlations in pp, p-Pb and Pb-Pb collisions with ALICE

    NASA Astrophysics Data System (ADS)

    Bjelogrlić, S.; ALICE Collaboration

    2015-08-01

    Heavy quarks (charm and beauty) are produced in initial hard scattering processes in heavy-ion collisions, before the formation of a strongly-interacting medium, the Quark-Gluon Plasma (QGP). The measurement of angular correlations between open heavy-flavour hadrons and charged particles can provide insight into the effects of the medium on charm and beauty production. For instance, in Pb-Pb collisions, the azimuthal correlations can provide information on the energy-loss mechanisms of heavy quarks in the QGP. Additionally, azimuthal correlations are sensitive to possible modifications of the heavy-quark parton shower and hadronisation in the presence of the medium. The observed double-ridge long-range correlations between light hadrons in p-Pb collisions could originate from a collective expansion of the system, as well as from gluon saturation in the initial state (color-glass condensate). The same effect can be studied for heavier quarks via the correlation between heavy-flavour hadrons (or their decay electrons) and charged particles. In pp collisions, the azimuthal correlations allow to measure the beauty production cross section as well as they represent a powerful tool to test pQCD models.

  15. Paleoproterozoic crustal evolution in the East Sarmatian Orogen: Petrology, geochemistry, Sr-Nd isotopes and zircon U-Pb geochronology of andesites from the Voronezh massif, Western Russia

    NASA Astrophysics Data System (ADS)

    Terentiev, R. A.; Savko, K. A.; Santosh, M.

    2016-03-01

    Andesites and related plutonic rocks are major contributors to continental growth and provide insights into the interaction between the mantle and crust. Paleoproterozoic volcanic rocks are important components of the East Sarmatian Orogen (ESO) belonging to the East European Craton, although their petrogenesis and tectonic setting remain controversial. Here we present petrology, mineral chemistry, bulk chemistry, Sr-Nd isotopes, and zircon U-Pb geochronological data from andesites and related rocks in the Losevo and Vorontsovka blocks of the ESO. Clinopyroxene phenocrysts in the andesites are depleted in LREE, and enriched in HFSE (Th, Nb, Zr, Hf, Ti) and LILE (Ba, Sr). Based on the chemistry of pyroxenes and whole rocks, as well as Fe-Ti oxides, we estimate a temperature range of 1179 to 1262 °C, pressures of 11.3 to 13.0 kbar, H2O content of 1-5 wt.%, and oxygen fu gacity close to the MH buffer for the melts of the Kalach graben (KG) and the Baygora area (BA) andesites. Our zircon U-Pb geochronological data indicate new zircon growth during the middle Paleoproterozoic as displayed by weighted mean 207Pb/206Pb ages of 2047 ± 17 Ma and 2040 ± 16 Ma for andesite and dacite-porphyry of the BA, and 2050 ± 16 Ma from high-Mg basaltic andesite of the KG. The andesites and related rocks of the KG and BA are characterized by high magnesium contents (Mg # up to 0.68). All these volcanic rocks are depleted in LREE and HFSE, and display negative Nb and Ti anomalies relative to primitive mantle. The high-Mg bulk composition, and the presence of clinopyroxene phenocrysts suggests that the parent melts of the KG and BA suite were in equilibrium with the mantle rocks. The rocks show positive εNd(T) values and low initial 87Sr/86Sr, suggesting that the magmas were mostly derived from metasomatized mantle source. The geochemical differences between the two andesite types are attributed to: the predominance of fractional crystallization, and minor role of contamination in the

  16. [Separation and purification of Al13 by chemical precipitation and metathesis].

    PubMed

    Li, Guo-Hong; Shi, Bao-You; Wang, Dong-Sheng; Cui, Ya-Li

    2007-02-01

    PACls with different concentrations were prepared by adding sodium carbonate powder into AlCl13 solution. Medium concentration and high Al13 content of PACl was chosen to carry out Al13 separation processes. The influences of SO4/Al molar ratio and the initial total Al concentration on the precipitation reactions of sulfate with different Al species were investigated. The factors influencing the metathesis reaction between solid Al13-SO4 and Ba(NO3)2 were evaluated. Results showed that high Al13 PACl could be obtained at the medium high concentration range of 0.4 - 0.6 mol/L, the optimum SO4/Al ratio was 0.6:1 for precipitation- separation of Al13, Al13 -SO4 precipitates were mostly consisted of tetrahedral crystals. During the metathesis reaction, Ba/SO4 molar ratio of 1:1 is the optimal value. Small range temperature variation and ultrasonic action had no marked influence on metathesis reaction rate and final Al13 concentration. Higher initial Ba(NO3)2 concentration could produce higher concentration Al13 accordingly. The purity of Al13 solution could be reached to 92.1% statistically.

  17. Growth of highly textured PbTiO3 films on conductive substrate under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Tang, Haixiong; Zhou, Zhi; Bowland, Christopher C.; Sodano, Henry A.

    2015-08-01

    Perovskite structure (ABO3) thin films have wide applications in electronic devices due to their unique properties, including high dielectric permittivity, ferroelectricity and piezoelectric coupling. Here, we report an approach to grow highly textured thick lead titanate (PbTiO3) films on conductive substrates by a two-step hydrothermal reaction. Initially, vertically aligned TiO2 nanowire arrays are grown on fluorine-doped tin oxide (FTO) coated glass, which act as template crystals for conversion to the perovskite structure. The PbTiO3 films are then converted from TiO2 NW arrays by diffusing Pb2+ ions into the template through a second hydrothermal reaction. The dielectric permittivity and piezoelectric coupling coefficient (d33) of the PbTiO3 films are as high as 795 at 1 kHz and 52 pm V-1, respectively. The reported process can also potentially be expanded for the assembly of other complex perovskite ATiO3 (A = Ba, Ca, Cd, etc) films by using the highly aligned TiO2 NW arrays as templates. Therefore, the approach introduced here opens up a new door to synthesize ferroelectric thin films on conductive substrates for application in sensors, actuators, and ultrasonic transducers that are important in various industrial and scientific areas.

  18. Growth of highly textured PbTiO3 films on conductive substrate under hydrothermal conditions.

    PubMed

    Tang, Haixiong; Zhou, Zhi; Bowland, Christopher C; Sodano, Henry A

    2015-08-28

    Perovskite structure (ABO(3)) thin films have wide applications in electronic devices due to their unique properties, including high dielectric permittivity, ferroelectricity and piezoelectric coupling. Here, we report an approach to grow highly textured thick lead titanate (PbTiO(3)) filmson conductive substrates by a two-step hydrothermal reaction. Initially, vertically aligned TiO(2) nanowire arrays are grown on fluorine-doped tin oxide (FTO) coated glass, which act as template crystals for conversion to the perovskite structure. The PbTiO(3) films are then converted from TiO(2) NW arrays by diffusing Pb(2+) ions into the template through a second hydrothermal reaction. The dielectric permittivity and piezoelectric coupling coefficient (d(33)) of the PbTiO(3) films are as high as 795 at 1 kHz and 52 pm V−1, respectively. The reported process can also potentially be expanded for the assembly of other complex perovskite ATiO(3) (A = Ba, Ca, Cd,etc) films by using the highly aligned TiO(2) NW arrays as templates. Therefore, the approach introduced here opens up a new door to synthesize ferroelectric thin films on conductivesubstrates for application in sensors, actuators, and ultrasonic transducers that are important in various industrial and scientific areas. PMID:26243166

  19. XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning.

    PubMed

    Specht, Aaron J; Lin, Yanfen; Weisskopf, Marc; Yan, Chonghuai; Hu, Howard; Xu, Jian; Nie, Linda H

    2016-01-01

    Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects' bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children. PMID:26856822

  20. XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning

    PubMed Central

    Specht, Aaron J.; Lin, Yanfen; Weisskopf, Marc; Yan, Chonghuai; Hu, Howard; Xu, Jian; Nie, Linda H.

    2016-01-01

    Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects’ bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children. PMID:26856822

  1. XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning.

    PubMed

    Specht, Aaron J; Lin, Yanfen; Weisskopf, Marc; Yan, Chonghuai; Hu, Howard; Xu, Jian; Nie, Linda H

    2016-01-01

    Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects' bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children.

  2. Thermal properties of PbUO4 and Pb3UO6

    NASA Astrophysics Data System (ADS)

    Popa, K.; Beneš, O.; Staicu, D.; Griveau, J.-C.; Colineau, E.; Raison, P. E.; Vigier, J.-F.; Pagliosa, G.; Sierig, M.; Vălu, O. S.; Somers, J.; Konings, R. J. M.

    2016-10-01

    Investigations on the phase relation in the Pb-U-O ternary system have shown the formation of three lead uranium(VI) oxides: PbUO4, Pb3UO6, and Pb3U11O36. We present here the synthesis, thermal expansion, low- and high-temperature heat capacity, and thermal diffusivity of two representative phases (PbUO4 and Pb3UO6 uranates). Combining these results, a value for their thermal conductivity was derived and reported here for the first time.

  3. Ba[Co3(VO4)2(OH)2] with a regular Kagomé lattice.

    PubMed

    Dordević, Tamara; Karanović, Ljiljana

    2013-02-01

    The new layered title compound, barium di-μ-hydroxido-di-μ-vanadato-tricobaltate(II), was prepared under low-temperature hydrothermal conditions. Its crystal structure comprises Co(2+) and O(2-) ions in the Kagomé geometry. The octahedral Co(3)O(6)(OH)(2) Kagomé layers, made up of edge-shared CoO(4)(OH)(2) octahedra with Co on a site of 2/m symmetry, alternate along the c axis with barium vanadate heteropolyhedral layers, in which Ba is on a site of 3m symmetry and V is on a site of 3m symmetry. All three O atoms and the H atom also occupy special positions: two O atoms and the H atom are on sites with 3m symmetry and one O atom is on a site with m symmetry. Ba[Co(3)(VO(4))(2)(OH)(2)] represents the first compound from the four-component BaO-CoO-V(2)O(5)-H(2)O system and its structure is topologically related to the minerals vesignieite, Ba[Cu(3)(VO(4))(2)(OH)(2)], and bayldonite, Pb[Cu(3)(AsO(4))(2)(OH)(2)].

  4. Solution grown PbS/CdS multilayer stacks as selective absorbers

    NASA Astrophysics Data System (ADS)

    Reddy, G. B.; Dutta, V.; Pandya, D. K.; Chopra, K. L.

    1981-08-01

    Theoretical and experimental studies are reported for the design and fabrication of multilayer stacks for selective solar absorbers (25 x 25 sq cm) of PbS and CdSm made on Ni coated Cu and stainless steel, using a solution grown technique. A mathematical model is formulated using the matrix multiplication method to calculate the reflectance of the absorbers. The preparation technique involves dissociating thiourea in an alkaline solution containing Pb or Cb salts, as reported by Sharma et al. (1976) and Kaur et al. (1980). The best values of solar absorptance and thermal emittance obtained are 0.92 and 0.12, respectively, which is in close agreement with the estimated values. Coatings with as many as six alternate layers of PbS and CdS have been made.

  5. Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC

    NASA Astrophysics Data System (ADS)

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