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Sample records for sr ba zn

  1. Magnetoelectric memory effect in the Y-type hexaferrite BaSrZnMgFe12O22

    NASA Astrophysics Data System (ADS)

    Wang, Fen; Shen, Shi-Peng; Sun, Young

    2016-08-01

    We report on the magnetic and magnetoelectric properties of the Y-type hexaferrite BaSrZnMgFe12O22, which undergoes transitions from a collinear ferrimagnetic phase to a proper screw phase at 310 K and to a longitudinal conical phase at 45 K. Magnetic and electric measurements revealed that the magnetic structure with spiral spin order can be modified by applying a magnetic field, resulting in magnetically controllable electric polarization.It was observed that BaSrZnMgFe12O22 exhibits an anomalous magnetoelectric memory effect: the ferroelectric state can be partially recovered from the paraelectric phase with collinear spin structure by reducing magnetic field at 20 K. We ascribe this memory effect to the pinning of multiferroic domain walls, where spin chirality and structure are preserved even in the nonpolar collinear spin state. Project supported by the National Natural Science Foundation of China (Grant Nos. 11534015 and 51371193).

  2. A{sub 2}Zn{sub 3}As{sub 2}O{sub 2} (A Ba, Sr): A rare example of square planar zinc

    SciTech Connect

    Brock, S.L.; Kauzlarich, S.M.

    1994-05-25

    The synthesis and structural characterization of Ba{sub 3}Zn{sub 3}As{sub 2}O{sub 2} and Sr{sub 3}Zn{sub 3}As{sub 2}O{sub 2} is reported. These compounds are novel in that they are the first compounds without Mn that crystallize in the ThCr{sub 2}Si{sub 2} structure type. In addition, Zn is in a rare square planar oxygen coordination mode.

  3. Ba(1-x)Sr(x)Zn2Si2O7--A new family of materials with negative and very high thermal expansion.

    PubMed

    Thieme, Christian; Görls, Helmar; Rüssel, Christian

    2015-01-01

    The compound BaZn2Si2O7 shows a high coefficient of thermal expansion up to a temperature of 280 °C, then a transition to a high temperature phase is observed. This high temperature phase exhibits negative thermal expansion. If Ba(2+) is successively replaced by Sr(2+), a new phase with a structure, similar to that of the high temperature phase of BaZn2Si2O7, forms. At the composition Ba0.8Sr0.2Zn2Si2O7, this new phase is completely stabilized. The crystal structure was determined with single crystal X-ray diffraction using the composition Ba0.6Sr0.4Zn2Si2O7, which crystallizes in the orthorhombic space group Cmcm. The negative thermal expansion is a result of motions and distortions inside the crystal lattice, especially inside the chains of ZnO4 tetrahedra. Dilatometry and high temperature X-ray powder diffraction were used to verify the negative thermal expansion. Coefficients of thermal expansion partially smaller than -10·10(-6) K(-1) were measured. PMID:26667989

  4. Structural and Optoelectronic Properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) Anti-Perovskite Compounds

    NASA Astrophysics Data System (ADS)

    Ullah, Imran; Murtaza, G.; Khenata, R.; Mahmood, Asif; Muzzamil, M.; Amin, N.; Saleh, M.

    2016-06-01

    We employed first-principles calculations to predict the structural and optoelectronic properties of X3ZN (X = Ca, Sr, Ba; Z = As, Sb, Bi) anti-perovskite compounds using an all-electron full-potential linearized augmented plane-wave method. Optimized structural parameters are found to be in good agreement with the available experimental measurements. The electronic band structure is calculated using different exchange-correlation potentials which reveal that the investigated compounds are narrow direct band gap semiconductors. A direct narrow band gap at the center of the Brillouin zone emphasises the optical activity of these compounds. Prediction of the optical properties, such as the real and imaginary parts of the dielectric function and refractive index along with reflectivity and optical conductivity, reveals the importance of these compounds in the visible and near UV optoelectronic devices industry.

  5. Effect of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) metal ions on the antifungal activity of ZnO nanoparticles tested against Candida albicans.

    PubMed

    Haja Hameed, Abdulrahman Syedahamed; Karthikeyan, Chandrasekaran; Senthil Kumar, Venugopal; Kumaresan, Subramanian; Sasikumar, Seemaisamy

    2015-01-01

    The antifungal ability of pure and alkaline metal ion (Mg(2+), Ca(2+), Sr(2+) and Ba(2+)) doped ZnO nanoparticles (NPs) prepared by the co-precipitation method was tested against the pathogenic yeast, Candida albicans (C. albicans), and the results showed that the Mg-doped ZnO NPs possessed greater effect than the other alkaline metal ion doped ZnO NPs. The impact of the concentration of Mg doped ZnO sample on the growth of C. albicans was also studied. The Minimal Fungicidal Concentration (MFC) of the Mg doped ZnO NPs was found to be 2000 μg/ml for which the growth of C. albicans was completely inhibited. The ZnO:Mg sample (1.5mg/ml) with various concentrations of histidine reduced the fungicidal effect of the nanoparticles against C. albicans, which was deliberately explained by the role of ROS. The ZnO:Mg sample added with 5mM of histidine scavenged the ample amount of generated ROS effectively. The binding of the NPs with fungi was observed by their FESEM images and their electrostatic attraction is confirmed by the zeta potential measurement. PMID:25953555

  6. High-resolution of trace elements (Mg, U, Sr, Ba and Zn) in speleothems as Holocene palaeoclimatic proxies: Père Noël cave, Belgium

    NASA Astrophysics Data System (ADS)

    Allan, Mohammed; Verheyden, Sophie; Riotte, Jean; Ghaleb, Bassam; Chmeleff, Jerome; fagel, Nathalie

    2013-04-01

    Speleothems are now regarded as valuable archives of climatic conditions on the continents, offering the advantages of absolute U-series dating relative to other continental climate proxy recorders such as lake sediments and peat cores. High spatial resolution measurements of Mg, U, Sr, Ba and Zn were realized by laser-ablation inductively coupled plasma mass spectrometry in the Belgian Père Noël cave Holocene stalagmite (Verheyden et al., 2000, 2008). The stalagmite of 65 cm long was deposited from ~12000 years to ~2000 years dated by U/Th method. Mg, Sr, Ba, U, and Zn are known as indicators for hydrological conditions (e.g. Ayalon et al., 1999; Fairchild et al., 2000). Mg, Sr, Ba concentrations are positively correlated (r> 0.7) with similar changes in the δ 13C implying similar processes influence their concentration changes. U has an inverse relationship with δ 13C. The study suggests that trace elements in the Père Noël stalagmite have the potential to provide high resolution insights into variability in water recharge during the Holocene. References Ayalon A., Bar-Matthews M. and Kaufman A., 1999. Petrography, strontium, barium and uranium concentrations, and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies: Soreq cave, Israel. The Holocene 9 (6), 715-722. Fairchild I.J., Borsato A., Tooth A.F.,Frisia S., Hawkesworth C.J., Huang Y., Mcdermott F. and Spiro B., 2000. Controls on trace element (Sr-Mg) compositions of carbonate cave waters: implications for speleothem climatic records. Chemical Geology 166, 255-269. Verheyden S., Keppens E. , Fairchild I.J., Mc Dermott F. and D. Weis, 2000. Sr isotope geochemistry of a Belgian Holocene speleothem: implications for paleoclimate reconstructions. Chemical Geology, 169: 131 144. Verheyden S., Genty D., Deflandre G., Quinif Y. and Keppens E., 2008. Monitoring climatological, hydrological and geochemical parameters in the Père Noël cave (Belgium): Implication for the interpretation

  7. Dielectric Properties and AC Conduction of 5 wt % ZnBO Doped (Ba,Sr)TiO3 Ceramics for Low Temperature Co-fired Ceramics Applications

    NASA Astrophysics Data System (ADS)

    Kim, Se-Ho; Koh, Jung-Hyuk

    2009-04-01

    ZnBO doped (Ba0.5Sr0.5)TiO3 (BST) ceramic was synthesized by conventional mixed oxide method. 5 wt % ZnBO addition to the BST has lowered the sintering temperature of BST from 1350 to 1100 °C. From the X-ray diffraction analysis, we found that the 5 wt % ZnBO doped BST has the perovskite structure, and any pryo phase was not observed. The dielectric properties and ac conductivity have been investigated at temperature range from 30 to 130 °C with various frequencies (1-100 kHz). The real part of relative dielectric permittivity ɛr' was decreased with increasing the temperature and the frequency. The activation energy for conduction process was calculated from the slope of ac conductivity at 1 kHz. The activation energy calculated through the Arrhenius law was 0.42 eV. In this paper, we will discuss the low-frequency dielectric relaxation and ac conductivity of 5 wt % ZnBO doped BST ceramics in relation to the electrical conduction.

  8. Thermal Expansion of Sintered Glass Ceramics in the System BaO-SrO-ZnO-SiO2 and Its Dependence on Particle Size.

    PubMed

    Thieme, Christian; Schlesier, Martin; Bocker, Christian; Buzatto de Souza, Gabriel; Rüssel, Christian

    2016-08-10

    The thermal expansion behavior of sintered glass-ceramics containing high concentrations of Ba1-xSrxZn2Si2O7, a phase with very low and highly anisotropic thermal expansion behavior, was investigated. The observed phase has the crystal structure of the high-temperature phase of BaZn2Si2O7, which can be stabilized by the introduction of Sr(2+) into this phase. The high anisotropy leads to microcracking within the volume of the samples, which strongly affects the dilatometric thermal expansion. However, these cracks also have an influence on the nominal thermal expansion of the as-mentioned phase, which decreases if the cracks appear. Below a grain size of approximately 80 μm, the sintered glass-ceramics have almost no cracks and show positive thermal expansion. Hence, coefficients of thermal expansion between -5.6 and 6.5 × 10(-6) K(-1) were measured. In addition to dilatometric studies, the effect of the microstructure on the thermal expansion was also measured using in situ X-ray diffraction at temperatures up to 1000 °C. PMID:27433854

  9. Thermal Expansion of Sintered Glass Ceramics in the System BaO-SrO-ZnO-SiO2 and Its Dependence on Particle Size.

    PubMed

    Thieme, Christian; Schlesier, Martin; Bocker, Christian; Buzatto de Souza, Gabriel; Rüssel, Christian

    2016-08-10

    The thermal expansion behavior of sintered glass-ceramics containing high concentrations of Ba1-xSrxZn2Si2O7, a phase with very low and highly anisotropic thermal expansion behavior, was investigated. The observed phase has the crystal structure of the high-temperature phase of BaZn2Si2O7, which can be stabilized by the introduction of Sr(2+) into this phase. The high anisotropy leads to microcracking within the volume of the samples, which strongly affects the dilatometric thermal expansion. However, these cracks also have an influence on the nominal thermal expansion of the as-mentioned phase, which decreases if the cracks appear. Below a grain size of approximately 80 μm, the sintered glass-ceramics have almost no cracks and show positive thermal expansion. Hence, coefficients of thermal expansion between -5.6 and 6.5 × 10(-6) K(-1) were measured. In addition to dilatometric studies, the effect of the microstructure on the thermal expansion was also measured using in situ X-ray diffraction at temperatures up to 1000 °C.

  10. 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.

  11. 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.

  12. Nonlinear optical properties and glass structure for MO-Nb 2O 5-TeO 2 (M = Zn, Mg, Ca, Sr, Ba) glasses

    NASA Astrophysics Data System (ADS)

    Hayakawa, Tomokatsu; Hayakawa, Masahiko; Nogami, Masayuki; Thomas, Philippe

    2010-01-01

    The third-order nonlinear optical susceptibilities χ(3) of tellurite(TeO 2)-based ternary glasses of MO-Nb 2O 5-TeO 2 (M = Zn, Mg, Ca, Sr, Ba) were investigated by Z-scan measurement using Ti:Sapphire femtosecond laser pulses. The relationship between the nonlinear optical properties and the glass structures estimated by Raman spectroscopy was discussed. The nonlinear susceptibilities χ(3) of these tellurite glasses increased as the stretching Raman band of Te IV-O ax in TeO 4 (trigonal bipyramids (tbp), the roman superscript denotes the coordination number) increased, while the stretching band of Te III-O in TeO 3 (trigonal pyramid (tp)) decreased. This indicates that the amount of TeO 4 (tbp) units was deeply related to the value of χ(3), which was consistent with the theoretical calculation of higher hyperpolarizabilities of TeO 4 than TeO 3 unit. It was also found that higher χ(3) was obtained with decreasing Te IV- eqO ax-Te IV Raman band, indicating that when divalent cations (M 2+) was doped in Nb 2O 5-TeO 2 binary network system the cleavage of Te IV- eqO ax-Te IV chain structure necessarily occurred but the terminations of -Te IV- eqO - M 2+-O-Nb VI-O ax-Te IV-, which importantly stabilized TeO 4 units even in the presence of the network modifier M 2+, were more preferentially induced with an assist of NbO 6 octahedron than -Te IV- eqO - M 2+ O = Te III-O-.

  13. 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

  14. A{sub 2}Zn{sub 3}As{sub 2}O{sub 2}(A = Ba, Sr): a rare example of square planar zinc

    SciTech Connect

    Keane, P.M.; Burdett, J.K.

    1994-06-01

    Purpose of this study was to explore synthesis of novel solid-state compounds that could potentially exhibit interesting or useful physical properties. Goal was to extend the classes of compounds A{sub 2}Mn{sub 3}Pn{sub 2}O{sub 2} (A=Sr,Ba; Pn=P,As,Sb,Bi) to include a transition metal other than Mn. High-temperature fluxes were used to produce these new compounds.

  15. Electronic structure of Ca, Sr, and Ba under pressure.

    NASA Technical Reports Server (NTRS)

    Animalu, A. O. E.; Heine, V.; Vasvari, B.

    1967-01-01

    Electronic band structure calculations phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure

  16. 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

  17. Dielectric properties of (1- x)SrFe1/2Nb1/2O3- xBaZn1/3Ta2/3O3 ceramics

    NASA Astrophysics Data System (ADS)

    Phatungthane, Thanatep; Rujijanagul, Gobwute

    2013-07-01

    In this work, (1- x)SrFe1/2Nb1/2O3- xBaZn1/3Ta2/3O3 ((1- x)SFN- xBZT) ceramics with 0.02 ≤ x ≤ 0.11 were synthesized via a solid state reaction method. A phase formation analysis using the x-ray diffraction technique (XRD) showed that the ceramic samples exhibited a pure phase perovskite for x ≤ 0.10 compositions, indicating that the solubility limit of BZT in SFN is very low. Adding BZT enhanced the dielectric constant and reduced the dielectric loss. Very high dielectric constants (>40,000) were observed for the x = 0.10 samples. The dielectric property investigation also revealed that all samples exhibited dielectric relaxor behavior.

  18. 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.

  19. Proton uptake in the H(+)-SOFC cathode material Ba(0.5)Sr(0.5)Fe(0.8)Zn(0.2)O(3-δ): transition from hydration to hydrogenation with increasing oxygen partial pressure.

    PubMed

    Poetzsch, Daniel; Merkle, Rotraut; Maier, Joachim

    2015-01-01

    Thermogravimetric investigations on the perovskite Ba(0.5)Sr(0.5)Fe(0.8)Zn(0.2)O(3-δ) (BSFZ, with mixed hole, oxygen vacancy and proton conductivity) from water vapor can occur by acid-base reaction (hydration) or redox reaction (hydrogen uptake), depending on the oxygen partial pressure, i.e. on the material's defect concentrations. In parallel, the effective diffusion coefficient of the stoichiometry relaxation kinetics also changes. These striking observations can be rationalized in terms of a defect chemical model and transport equations for materials with three mobile carriers. Implications for the search of cathode materials with mixed electronic and protonic conductivity for application on proton conducting oxide electrolytes are discussed.

  20. Kinetics of Sr/Ba and Sr/Ca ion exchange in synthetic zeolite A

    SciTech Connect

    Gaus, H.; Lutze, W.

    1981-01-08

    The isotopic exchange kinetics of Sr, Ba, and Ca have been measured in zeolites with different compositions and found to be describable as self-diffusion. The self-diffusion coefficients are strongly dependent on the composition. Also the Sr/Ba and Sr/Ca ion exchanges are measured in both directions and described as interdiffusion. While for Sr/Ba tolerable agreement is reached, for Sr/Ca a modification is necessary. The interdiffusion coefficient is multiplied by a factor which takes into account the activity, i.e., the selectivity of the zeolite. As a continuation of an earlier paper the zeolite is described as a mixture of microcells and free water. The above-mentioned factor must be calculated for a nonequilibrium state with respect to the water content in order to get agreement with the measurements.

  1. 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.

  2. 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.

  3. Reaction kinetics and magnetic properties of Ba and Sr ferrites

    NASA Astrophysics Data System (ADS)

    Melzer, K.; Martin, A.; Klink, T.; Wartewig, P.

    1992-04-01

    This Mössbauer study is concerned with the formation mechanism of hexaferrites (n=6) and of monoferrites (n=1) in the systems (1) BaCO3+nFe2O3, (2) SrCO3+nFe2O3 and (3) 0.5BaCO3+0.5SrCO3+nFe2O3. With a molar ratio of 1∶1 for the starting materials one gets final reaction products with different crystalline structures. The experimental results indicate that the thermodynamical final state of the hexaferrite formation is reached on different routes. Various reaction models are discussed.

  4. Magnetic characterization of Ca substituted Ba and Sr hexaferrites

    NASA Astrophysics Data System (ADS)

    Asti, G.; Carbucicchio, M.; Deriu, A.; Lucchini, E.; Slokar, G.

    1980-04-01

    A magnetic characterization has been worked out for the solid solution from Ba and Sr hexaferrites (BaFe 1 2O 1 9, SrFe 1 2O 1 9) towards CaO- xFe 2O 3 (2 ⪕ x ⪕5.5). Measurements of Curie temperature, saturation magnetization, magnetic anisotropy, together with Mössbauer characterization indicate that the intrinsic properties of the studied compounds do not change appreciably with increasing Ca content. These results, together with the X-ray data, are consistent with the formation of an undistorted M-type cell with a low content of iron and oxygen vacancies.

  5. muSR in Ba2CoO4

    NASA Astrophysics Data System (ADS)

    Russo, Peter; Sugiyama, Jun; Ansaldo, Eduardo; Brewer, Jess; Stubbs, Scott; Chow, Kim; Jin, R.; Sha, H.; Zhang, J.

    2008-03-01

    A positive muon spin rotation and relaxation (&+circ;SR) experiment on the single crystal Ba2CoO4 indicates the existence of an antiferromagnetic (AF) transition occurring at TN˜25 K. Weak transverse field measurements (wTF-&+circ;SR) show that the paramagnetic volume fraction of the sample decreases rapidly at the magnetic transition indicating a bulk effect. Zero field measurements (ZF-&+circ;SR) show the presence of a magnetically ordered state below TN. The results are compared to recent magnetic susceptibility and neutron measurements. Although there are two possible AF spin structures proposed by recent neutron experiments, the μSR results clearly exclude AF order along the c-axis while supporting AF order in the ab plane.

  6. Structures and unimolecular chemistry of M(Pro2-H)(+) (M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn) by IRMPD spectroscopy, SORI-CID, and theoretical studies.

    PubMed

    Jami-Alahmadi, Yasaman; Fridgen, Travis D

    2016-01-21

    M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures.

  7. Electric characterization of (Sr, Sr-Ba, Ba) M-type ferrites by AC measurements[Alternating Current

    SciTech Connect

    Huanosta-Tera, A.; Lira-Hueso, R. de; Perez-Orta, O.; Palomares-Sanchez, S.A.; Ponce-Castaneda, S.; Mirabal-Garcia, M.

    2000-02-01

    Considering the electrical conductivity in ceramics, necessary reference should be given to dynamic processes occurring as a function of frequency and temperature. Although the most immediate interest in ferrites lies in their magnetic properties, technological applications require a wider knowledge of general physical properties as well. This is especially applicable when the materials are studied as a function of composition or when adding different modifiers. In this report, the authors present results of the ac and dc electric characteristics of a family of magneto-plumbite-type hexaferrites, where Ba gradually substitutes Sr in the Ba{sub x}Sr{sub 1{minus}x}Fe{sub 12}O{sub 19} compound (0 {le} x {le} 1). The results were determined over a wide range of frequencies and temperatures.

  8. Superstructure formation in SrBa8[BN2]6 and EuBa8[BN2]6.

    PubMed

    Seidel, Stefan; Dierkes, Tobias; Jüstel, Thomas; Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-07-26

    X-ray pure samples of SrBa8[BN2]6 and EuBa8[BN2]6 were synthesized from appropriate amounts of binary nitrides (Sr3N2, Ba3N2 and BN in sealed niobium ampoules and EuN, Ba3N2 and BN in BN crucibles, respectively) at temperatures up to 1370 K. The structure of SrBa8[BN2]6 was refined from single crystal X-ray diffractometer data: Fd3[combining macron]m, a = 1595.1(1) pm, wR(F(2)) = 0.0515, 387 F(2) values and 21 variables. EuBa8[BN2]6 has a lattice parameter of 1595.00(9) pm. Both nitridoborates adopt a new 2 × 2 × 2 superstructure variant of the LiCa4[BN2]3 type, realized through ordering of vacancies and Sr(2+) and Eu(2+) cations, respectively. The structures of SrBa8[BN2]6 and LiCa4[BN2]3 are related by a group-subgroup scheme. The Sr(2+)/vacancy ordering leads to an asymmetric coordination (1 × Sr(2+) and 8 × Ba(2+) in a distorted, mono-capped square prism) for the [BN2](3-) units with B-N distances of 132 and 136 pm. Vibrational spectra of SrBa8[BN2]6 and EuBa8[BN2]6 confirm the discrete linear [BN2](3-) units and (11)B solid state MAS NMR spectra are compatible with single crystallographic sites for the boron atoms. In EuBa8[BN2]6 the spectra are profoundly influenced by interactions of the (11)B nuclei with the unpaired electrons of the paramagnetic Eu(2+) ions. PMID:27397545

  9. Superstructure formation in SrBa8[BN2]6 and EuBa8[BN2]6.

    PubMed

    Seidel, Stefan; Dierkes, Tobias; Jüstel, Thomas; Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-07-26

    X-ray pure samples of SrBa8[BN2]6 and EuBa8[BN2]6 were synthesized from appropriate amounts of binary nitrides (Sr3N2, Ba3N2 and BN in sealed niobium ampoules and EuN, Ba3N2 and BN in BN crucibles, respectively) at temperatures up to 1370 K. The structure of SrBa8[BN2]6 was refined from single crystal X-ray diffractometer data: Fd3[combining macron]m, a = 1595.1(1) pm, wR(F(2)) = 0.0515, 387 F(2) values and 21 variables. EuBa8[BN2]6 has a lattice parameter of 1595.00(9) pm. Both nitridoborates adopt a new 2 × 2 × 2 superstructure variant of the LiCa4[BN2]3 type, realized through ordering of vacancies and Sr(2+) and Eu(2+) cations, respectively. The structures of SrBa8[BN2]6 and LiCa4[BN2]3 are related by a group-subgroup scheme. The Sr(2+)/vacancy ordering leads to an asymmetric coordination (1 × Sr(2+) and 8 × Ba(2+) in a distorted, mono-capped square prism) for the [BN2](3-) units with B-N distances of 132 and 136 pm. Vibrational spectra of SrBa8[BN2]6 and EuBa8[BN2]6 confirm the discrete linear [BN2](3-) units and (11)B solid state MAS NMR spectra are compatible with single crystallographic sites for the boron atoms. In EuBa8[BN2]6 the spectra are profoundly influenced by interactions of the (11)B nuclei with the unpaired electrons of the paramagnetic Eu(2+) ions.

  10. Ca/Ba/Sr-induced conformational changes of ciliary axonemes.

    PubMed

    Tamm, S; Tamm, S

    1990-01-01

    Macrocilia of the ctenophore Beroë undergo Ca/Ba/Sr-dependent activation of ciliary beating and microtubule sliding disintegration [Tamm, J. Comp. Physiol. A163:23-31, 1988a; Tamm, Cell Motil. Cytoskeleton 11:126-138, 1988b; Tamm, Cell Motil. Cytoskeleton 12:104-112, 1989; Tamm and Tamm, Proc. Natl. Acad. Sci. U.S.A. 86:6987-6991, 1989]. Here we report that detergent-extracted macrocilia show an ATP-independent conformational change in response to high concentrations of Ca, Ba, or Sr ions. When applied locally by iontophoresis, these ions induce a rapid planar curvature of the distal end of the macrociliary shaft, followed by a slower relaxation to the rest position. Tip curling occurs in a direction opposite to the physiological Ca/Ba/Sr response. When applied uniformly in the bath, a threshold concentration of 10(-1) M Sr is required to induce curling of the tip, and the distal ends remain curved. Calmodulin antagonists do not inhibit the tip curling response. Previous workers found that Ca induces changes in the helical shape of isolated doublet microtubules [Miki-Noumura and Kamiya, Exp. Cell Res. 97:451-453, 1976; Miki-Noumura and Kamiya, J. Cell Biol. 81:355-360, 1979; Takasaki and Miki-Noumura, J. Mol. Biol. 158:317-324, 1982] and sperm axonemes [Okuno and Brokaw, Cell Motil. 1:349-362, 1981] and suggested that conformational changes in microtubules may play a role in Ca regulation of ciliary motility. We propose that the Ca/Ba/Sr-induced curling of the macrociliary tip is due to similar helical changes of doublet microtubules, some of which in macrocilia are prevented from sliding by permanent connections (compartmenting lamellae) between adjacent axonemes within the shaft. Although the tip curling response does not appear to be directly relevant to the physiological Ca response of macrocilia, it provides a novel system for investigating Ca-induced conformational changes of microtubules independent of dynein-powered active sliding.

  11. 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.

  12. The Structural Disorder and Lattice Stability of (Ba,Sr)(Co,Fe)O3 Complex Perovskites

    SciTech Connect

    S.N.Rashkeev

    2011-05-01

    The structural disorder and lattice stability of complex perovskite (Ba,Sr)(Co,Fe)O3, a promising cathode material for solid oxide fuel cells and oxygen permeation membranes, is explored by means of first principles DFT calculations. It is predicted that Ba and Sr ions easily exchange their lattice positions (A-cation disorder) similarly to Co and Fe ions (B-cation disorder). The cation antisite defects (exchange of A- and B-type cations) have a relatively high formation energy. The BSCF is predicted to exist in an equilibrium mixture of several phases and can decompose exothermically into the Ba- and Co-rich hexagonal (Ba,Sr)CoO3 and Sr- and Fe-rich cubic (Ba,Sr)FeO3 perovskites.

  13. 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.

  14. Ba1-xSrxZn2Si2O7 - A new family of materials with negative and very high thermal expansion

    NASA Astrophysics Data System (ADS)

    Thieme, Christian; Görls, Helmar; Rüssel, Christian

    2015-12-01

    The compound BaZn2Si2O7 shows a high coefficient of thermal expansion up to a temperature of 280 °C, then a transition to a high temperature phase is observed. This high temperature phase exhibits negative thermal expansion. If Ba2+ is successively replaced by Sr2+, a new phase with a structure, similar to that of the high temperature phase of BaZn2Si2O7, forms. At the composition Ba0.8Sr0.2Zn2Si2O7, this new phase is completely stabilized. The crystal structure was determined with single crystal X-ray diffraction using the composition Ba0.6Sr0.4Zn2Si2O7, which crystallizes in the orthorhombic space group Cmcm. The negative thermal expansion is a result of motions and distortions inside the crystal lattice, especially inside the chains of ZnO4 tetrahedra. Dilatometry and high temperature X-ray powder diffraction were used to verify the negative thermal expansion. Coefficients of thermal expansion partially smaller than -10·10-6 K-1 were measured.

  15. Ba1−xSrxZn2Si2O7 - A new family of materials with negative and very high thermal expansion

    PubMed Central

    Thieme, Christian; Görls, Helmar; Rüssel, Christian

    2015-01-01

    The compound BaZn2Si2O7 shows a high coefficient of thermal expansion up to a temperature of 280 °C, then a transition to a high temperature phase is observed. This high temperature phase exhibits negative thermal expansion. If Ba2+ is successively replaced by Sr2+, a new phase with a structure, similar to that of the high temperature phase of BaZn2Si2O7, forms. At the composition Ba0.8Sr0.2Zn2Si2O7, this new phase is completely stabilized. The crystal structure was determined with single crystal X-ray diffraction using the composition Ba0.6Sr0.4Zn2Si2O7, which crystallizes in the orthorhombic space group Cmcm. The negative thermal expansion is a result of motions and distortions inside the crystal lattice, especially inside the chains of ZnO4 tetrahedra. Dilatometry and high temperature X-ray powder diffraction were used to verify the negative thermal expansion. Coefficients of thermal expansion partially smaller than −10·10−6 K−1 were measured. PMID:26667989

  16. Effects of Oxide Additives to (Ba,Sr)TiO3 Ceramics Fired under Reduced Atmosphere

    NASA Astrophysics Data System (ADS)

    Sakai, Y.; Futakuchi, T.; Adachi, M.

    2011-10-01

    Ba0.6Sr0.4TiO3 doped with MgO, CaO, SrO, or BaO thick films with Ni electrodes were prepared by screen printing. The prepared thick films showed a perovskite single phase. TC was changed corresponding to the kinds of doping oxides. The tunability and tanδ value of thick films doping with 2 mol% of BaO or CaO at an electric field of 10 V/μm were approximately 85% and 0.3%, respectively. The leakage current of Ba0.6Sr0.4TiO3 thick films doped with 2 mol% of BaO thick films at 10 V/μm was less than 10-6 A/cm2 and the value was less than that of thick films doped with 2 mol% of CaO.

  17. EPR study of La 2- xM xCuO 4 (M = Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Khan, Shakeel; Singh, Arti; Singh, R. J.

    1998-06-01

    EPR spectra of deoxygenated La 1.81Sr 0.19CuO 4 and La 1.94Ba 0.06CuO 4 have been investigated. In both of them 4 Cu 2+ ions are found to combine ferromagnetically to give S = 2 spectra. At low {Sr}/{Ba} content the spins probably start getting polarised in the ab plane. Spin-Hamiltonian parameters for all the spectra have been determined. Dependence of Tc on the content of Sr or Ba has been attempted to be explained. It seems that holes which are generated on the substitution of La 3+ by Sr 2+ or Ba 2+ and are current carriers first get uniformly distributed over the LaO plane but on increasing Sr 2+ or Ba 2+ content, they may combine together to form O 22- peroxide ions and become unable to carry current. On further increasing the Sr 2+ or Ba 2+ content, the same process is repeated, until the substance becomes metallic or until further amounts of the substituents can bot be dissolved in the parent compound.

  18. 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).

  19. 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).

  20. 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).

  1. SrZn2Sn2 and Ca2Zn3Sn6 — two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    NASA Astrophysics Data System (ADS)

    Stegmaier, Saskia; Fässler, Thomas F.

    2012-08-01

    SrZn2Sn2 and Ca2Zn3Sn6, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn2Sn2 comprises (anti-)PbO-like {ZnSn4/4} and {SnZn4/4} layers. Ca2Zn3Sn6 shows similar {ZnSn4/4} layers and {Sn4Zn} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn2Sn2 adopts the SrPd2Bi2 structure type, and Ca2Zn3Sn6 is isotypic to the R2Zn3Ge6 compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn2Sn2 and Ca2Zn3Sn6 are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {Sn4Zn} layers of Ca2Zn3Sn6.

  2. Magnetic and magnetocaloric properties of Ba and Ti co-doped SrRuO3

    NASA Astrophysics Data System (ADS)

    Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal; De, S. K.

    2014-12-01

    Temperature evolution of magnetic properties in Ba and Ti doped SrRuO3 has been investigated to observe the effects of larger ionic radius Ba at Sr site and isovalent nonmagnetic impurity Ti at Ru site. Ionic radius mismatch and different electronic configuration in comparison with Ru modify Sr(Ba)-O and Ru(Ti)-O bond lengths and Ru-O-Ru bond angle. The apical and basal Ru-O-Ru bond angles vary significantly with Ti doping. Ferromagnetic Curie temperature decreases from 161 K to 149 K monotonically with Ba (10%) and Ti (10%) substitutions at Sr and Ru sites. The zero field cooled (ZFC) magnetization reveals a prominent peak which shifts towards lower temperature with application of magnetic field. The substitution of tetravalent Ti with localized 3d0 orbitals for Ru with more delocalized 4d4 orbitals leads to a broad peak in ZFC magnetization. A spontaneous ZFC magnetization becomes negative below 160 K for all the compositions. The occurrence of both normal and inverse magnetocaloric effects in Ba and Ti co-doped SrRuO3 makes the system more interesting.

  3. Bi3+ Luminescence in ABiO2Cl (A = Sr, Ba) and BaBiO2Br

    SciTech Connect

    Porter-Chapman, Yetta D.; Bourret-Courchesne, Edith E.; Derenzo,Stephen E.

    2007-01-18

    Trivalent bismuth luminescence is reported in three Sillenbismuth oxyhalide phases, SrBiO2Cl, BaBiO2Cl, and BaBiO2Br. Thesecompounds exhibit Bi 6s6->6 s2 emission under UV and X-ray radiation.At room temperature, BaBiO2Cl shows the most intense light emission, withspectral and decay properties similar to those found in Bi4Ge3O12 (BGO).At low temperatures, each phase show an increase in the photoluminescenceintensities and a narrowing of the emission peaks. In contrast to thetemperature dependence of BGO, X-ray excited luminescence intensities ofall three phases remain relatively constant throughout the temperaturerange 10 - 295 K. This result indicates that the Sillen phases undergoless thermal quenching than BGO. The low temperature and room temperatureradio-luminescence decay times were determined from pulsed x-raymeasurements. At room temperature, SrBiO2Cl exhibits faster decays thanBGO, while, BaBiO2Cl and BaBiO2Br have decay times similar toBGO.

  4. EXPLAINING THE Sr AND Ba SCATTER IN EXTREMELY METAL-POOR STARS

    SciTech Connect

    Aoki, W.; Suda, T.; Boyd, R. N.; Kajino, T.; Famiano, M. A. E-mail: takuma.suda@nao.ac.jp E-mail: kajino@nao.ac.jp

    2013-03-20

    Compilations of abundances of strontium and barium in extremely metal-poor stars show that an apparent cutoff is observed for [Sr/Ba] at [Fe/H] < -3.6 and large fluctuations for [Fe/H] > -3.6 with a clear upper bound depending on metallicity. We study the factors that place upper limits on the logarithmic ratio [Sr/Ba]. A model is developed in which the collapses of type II supernovae are found to reproduce many of the features seen in the data. This model is consistent with galactic chemical evolution constraints of light-element enrichment in metal-poor stars. Effects of turbulence in an explosive site have also been simulated, and are found to be important in explaining the large scatter observed in the [Sr/Ba] data.

  5. High-pressure densified solid solutions of alkaline earth hexaborides (Ca/Sr, Ca/Ba, Sr/Ba) and their high-temperature thermoelectric properties

    SciTech Connect

    Gürsoy, M.; Takeda, M.; Albert, B.

    2015-01-15

    Solid solutions of alkaline earth hexaborides were synthesized and densified by spark plasma sintering at 100 MPa. The high-temperature thermoelectric properties (Seebeck coefficients, electrical and thermal diffusivities, heat capacities) were measured between room temperature and 1073 K. CaB{sub 6}, SrB{sub 6}, BaB{sub 6} and the ternary hexaborides Ca{sub x}Sr{sub 1−x}B{sub 6}, Ca{sub x}Ba{sub 1−x}B{sub 6}, Sr{sub x}Ba{sub 1−x}B{sub 6} (x = 0.25, 0.5, 0.75) are n-type conducting compounds over the whole compositional and thermal ranges. The values of the figure of merit ZT for CaB{sub 6} (ca. 0.3 at 1073 K) were found to be significantly increased compared to earlier investigations which is attributed to the densification process. - Highlights: • Solid solutions of alkaline earth hexaborides were synthesized. • High-temperature thermoelectric properties of mixed calcium borides are excellent. • Spark plasma source densification results in high ZT values. • Borides are rare-earth free and refractory materials.

  6. Characterization of novel BaZnSnO thin films by solution process and applications in thin film transistors

    SciTech Connect

    Li, Jun; Huang, Chuan-Xin; Zhang, Jian-Hua; Zhu, Wen-Qing; Jiang, Xue-Yin; Zhang, Zhi-Lin

    2015-08-15

    Graphical abstract: This work reports the Ba content on thin film transistor based on a novel BaZnSnO semiconductor using solution process. - Highlights: • No reports about BaZnSnO thin film using solution process. • BaZnSnO thin film transistor (TFT) was firstly fabricated. • BaZnSnO-TFT shows a acceptable performace. • Influence of Ba content on BaZnSnO-TFT. - Abstract: A novel BaZnSnO semiconductor is fabricated using solution process and the influence of Ba addition on the structure, the chemical state of oxygen and electrical performance of BaZnSnO thin films are investigated. A high performance BaZnSnO-based thin film transistor with 15 mol% Ba is obtained, showing a saturation mobility of 1.94 cm{sup 2}/V s, a threshold voltage of 3.6 V, an on/off current ratio of 6.2 × 10{sup 6}, a subthreshold swing of 0.94 V/decade, and a good bias stability. Transistors with solution processed BaZnSnO films are promising candidates for the development of future large-area, low-cost and high-performance electronic devices.

  7. Synthesis and Structure Determination of Ferromagnetic Semiconductors LaAMnSnO6 (A = Sr Ba)

    SciTech Connect

    T Yang; T Perkisas; J Hadermann; M Croft; A Ignatov; M Greenblatt

    2011-12-31

    LaAMnSnO{sub 6} (A = Sr, Ba) have been synthesized by high temperature solid-state reactions under dynamic 1% H{sub 2}/Ar flow. Rietveld refinements on room temperature powder X-ray diffraction data indicate that LaSrMnSnO{sub 6} crystallizes in the GdFeO{sub 3}-structure, with space group Pnma and, combined with transmission electron microscopy, LaBaMnSnO{sub 6} in Imma. Both space groups are common in disordered double-perovskites. The Mn{sup 3+} and Sn{sup 4+} ions whose valence states were confirmed by X-ray absorption spectroscopy, are completely disordered over the B-sites and the BO{sub 6} octahedra are slightly distorted. LaAMnSnO{sub 6} are ferromagnetic semiconductors with a T{sub C} = 83 K for the Sr- and 66 K for the Ba-compound. The title compounds, together with the previously reported LaCaMnSnO{sub 6} provide an interesting example of progression from Pnma to Imma as the tolerance factor increases. An analysis of the relationship between space group and tolerance factor for the series LaAMnMO{sub 6} (A = Ca, Sr, Ba; M = Sn, Ru) provides a better understanding of the symmetry determination for double perovskites.

  8. 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.

  9. Ca, Sr and Ba stable isotopes reveal the fate of soil nutrients along a tropical climosequence

    USGS Publications Warehouse

    Bullen, Thomas D.; Chadwick, Oliver A.

    2016-01-01

    Nutrient biolifting is an important pedogenic process in which plant roots obtain inorganic nutrients such as phosphorus (P) and calcium (Ca) from minerals at depth and concentrate those nutrients at the surface. Here we use soil chemistry and stable isotopes of the alkaline earth elements Ca, strontium (Sr) and barium (Ba) to test the hypothesis that biolifting of P has been an important pedogenic process across a soil climosequence developed on volcanic deposits at Kohala Mountain, Hawaii. The geochemical linkage between these elements is revealed as generally positive site-specific relationships in soil mass gains and losses, particularly for P, Ba and Ca, using the ratio of immobile elements titanium and niobium (Ti/Nb) to link individual soil samples to a restricted compositional range of the chemically and isotopically diverse volcanic parent materials. At sites where P is enriched in surface soils relative to abundances in deeper soils, the isotope compositions of exchangeable Ca, Sr and Ba in the shallowest soil horizons (< 10 cm depth) are lighter than those of the volcanic parent materials and trend toward those of plants growing on fresh volcanic deposits. In contrast the isotope composition of exchangeable Ba in deeper soil horizons (> 10 cm depth) at those sites is consistently heavier than the volcanic parent materials. The isotope compositions of exchangeable Ca and Sr trend toward heavier compositions with depth more gradually, reflecting increasing leakiness from these soils in the order Ba < Sr < Ca and downward transfer of light biocycled Ca and Sr to deeper exchange sites. Given the long-term stability of ecosystem properties at the sites where P is enriched in surface soils, a simple box model demonstrates that persistence of isotopically light exchangeable Ca, Sr and Ba in the shallowest soil horizons requires that the uptake flux to plants from those near-surface layers is less than the recycling flux returned to the surface as

  10. Clathrate formation in the systems Sr–Cu–Ge and (Ba,Sr)–Cu–Ge

    SciTech Connect

    Zeiringer, I.; Moser, R.; Kneidinger, F.; Podloucky, R.; Royanian, E.; Grytsiv, A.; Bauer, E.; Giester, G.; Falmbigl, M.; Rogl, P.

    2014-09-15

    In the ternary system Sr–Cu–Ge, a novel clathrate type-I phase was detected, Sr{sub 8}Cu{sub x}Ge{sub 46−x} (5.2≤x<5.4), which exists close to the Zintl limit in a small temperature interval. Sr{sub 8}Cu{sub 5.3}Ge{sub 40.7} decomposes eutectoidally on cooling at 730±3 °C into (Ge), SrGe{sub 2} and τ{sub 1}-SrCu{sub 2−x}Ge{sub 2+x}. Phase equilibria at 700 °C have been established for the Ge rich part and are characterized by the appearance of only one ternary compound, τ{sub 1}-SrCu{sub 2−x}Ge{sub 2+x}, which crystallizes with the ThCr{sub 2}Si{sub 2} structure type and forms a homogeneity range up to x=0.4 (a=0.42850(4), c=1.0370(1) nm). Additionally, the extent of the clathrate type-I solid solution Ba{sub 8−y}Sr{sub y}Cu{sub x}Ge{sub 46−x} (0≤y≤∼5.6; 5.2≤x≤5.4, from as cast alloys) has been studied at various temperatures. The clathrate type-I crystal structure (space group Pm3{sup ¯}n) has been proven by X-ray single crystal diffraction on two single crystals with the composition (from refinement): Sr{sub 8}Cu{sub 5.36}Ge{sub 40.64} (a=1.06368(2) nm at 300 K) and Ba{sub 4.86}Sr{sub 3.14}Cu{sub 5.36}Ge{sub 40.64} (a=1.06748(2) nm at 300 K) measured at 300, 200 and 100 K. From the temperature dependence of the lattice parameters and the atomic displacement parameters, thermal expansion coefficients, Debye- and Einstein-temperatures and the speed of sound have been determined. From heat capacity measurements of Sr{sub 8}Cu{sub 5.3}Ge{sub 40.7} at low temperatures the Sommerfeld coefficient (γ=24 mJ/mol K{sup 2}) and the Debye temperature (Θ{sub D}{sup LT}=273 K) have been extracted. From a detailed analysis of these data at higher temperatures, Einstein branches of the phonon dispersion relation have been derived and compared to those obtained from the atomic displacement parameters. Electrical resistivity measurements of Sr{sub 8}Cu{sub 5.3}Ge{sub 40.7} reveal a rather metallic behavior in the low temperature range (<300 K

  11. Pressure driven ferroelectric to paraelectric transition in Sr doped BaTiO{sub 3}

    SciTech Connect

    Basu, Abhisek Jana, Rajesh; Mandal, Guruprasad; Mukherjee, Goutam Dev; Chandra, Amreesh

    2015-02-07

    High pressure Raman spectroscopy, X-ray diffraction, and dielectric measurements have been carried out in Ba{sub 1−x}Sr{sub x}TiO{sub 3} (x = 0.05 and 0.1). Detailed structural analysis revealed a single phase transition from tetragonal P4mm to cubic Pm3m symmetry. Increase in Sr ion concentration resulted in decrease in the phase transition pressure. The dielectric measurements showed considerable lowering of transition pressure which has been attributed to bulk behaviour of the material.

  12. Evaluation of the (Ba,Sr)RuO3 and (Ba,Sr)RuO3/Ru bilayer as an oxygen diffusion barrier

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Hee; Hong, Duck-Hwa; Kim, Young-Bae; Choi, Duck-Kyun

    2002-06-01

    The (Ba,Sr)RuO3 (BSR) oxide electrode which can enhance electrical properties of (Ba,Sr)TiO3 (BST) dielectric film due to structural and chemical matches with BST, was evaluated as an oxygen diffusion barrier. It was possible to restrain the oxidation of TiN layer under BSR to TiO2 by sequential depositions of amorphous BSR and crystalline BSR, in which the amorphous BSR eventually crystallized into crystalline BSR during the deposition of crystalline BSR. When two-step BSR layers on TiN, however, were annealed in oxygen ambient at 700 degC, oxygen atoms diffused and oxidized TiN layer to TiO2. On the other hand, oxygen could be effectively blocked by the BSR/Ru bilayer. In this system, the Ru sublayer plays a role as an oxygen getter and the bilayer tends to block oxygen diffusion. The blocking effect was more obvious when the thickness of BSR in the bilayer increased. The BST/bilayer showed higher dielectric constant due to the suppression of formation of a low dielectric layer between BST and the bilayer. Although the BST/bilayer showed a slightly higher leakage current density, it was possible to reduce the leakage current density to 10-8 order A/cm2 at 1 V by increasing the BSR thickness in the bilayer.

  13. 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

  14. (Ba,Sr)TiO{sub 3} dielectrics: Relationship between bulk and thin film properties

    SciTech Connect

    Kingon, A. I.; Streiffer, S. K.; Parker, C. B.; Stemmer, S.

    1999-12-22

    Thin films of complex perovskites have a number of potentially important applications. Of major scientific and practical concern is the scaling of properties as film dimensions are reduced. This paper describes a satisfactory relationship between bulk and thin film dielectric properties of (Ba,Sr)TiO{sub 3}. Relative contributions of strain, A:B cation stoichiometry, and interface are separated to explain temperature dependent dielectric behavior.

  15. A first principles study on newly proposed (Ca/Sr/Ba)Fe2Bi2 compounds with their parent compounds

    NASA Astrophysics Data System (ADS)

    Sundareswari, M.; Jayalakshmi, D. S.; Viswanathan, E.

    2016-02-01

    The structural, electronic, bonding and magnetic properties of newly proposed iron-based compounds viz., CaFe2Bi2, SrFe2Bi2, BaFe2Bi2 with their Fermi surface topology are reported here for the first time by means of first principles calculation. All these properties of newly proposed compounds are compared and analysed along with their respective parent compounds namely (Ca,Sr,Ba)Fe2As2.

  16. Catalytic behavior of AMoO{sub x} (A = Ba, Sr) in oxidation of 2-propanol

    SciTech Connect

    Kubo, Jun Ueda, Wataru

    2009-04-02

    Perovskite-type oxides, BaMoO{sub 3} and SrMoO{sub 3}, were prepared by reduction of scheelite-type oxides, BaMoO{sub 4} and SrMoO{sub 4}, in H{sub 2} flow at 873 K and characterized by XRD, TG, SEM, TPR, NH{sub 3}-TPD, UV-vis DRS and BET measurement. The catalytic activity of these alkaline-earth molybdenum oxide catalysts was tested for oxidation of 2-propanol with gaseous oxygen under atmospheric pressure. Dehydration to propylene was mainly promoted over the scheelite-type with Mo{sup 6+}, while oxidative dehydrogenation to acetone was mainly promoted over the perovskite-type with Mo{sup 4+}, and selectivity to acetone was much higher over BaMoO{sub 3} than over SrMoO{sub 3}. Both perovskite-type oxide catalysts underwent oxidation to some degree during the catalytic reaction, so that they also contained some Mo{sup 6+}. We concluded that the high selectivity to acetone resulting from oxidative dehydrogenation during 2-propanol conversion is related to the constantly changing oxidation state of the catalyst, resulting in coexistence of Mo{sup 6+} octahedra and Mo{sup 4+} octahedra on the AMoO{sub 3} oxides.

  17. Mechanochemical synthesis of MgF2 - MF2 composite systems (M = Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Scholz, G.; Breitfeld, S.; Krahl, T.; Düvel, A.; Heitjans, P.; Kemnitz, E.

    2015-12-01

    The capability of mechanochemical synthesis for the formation of MgF2-MF2 (M: Ca, Sr, Ba) composites, solid solutions or well-defined compounds was tested applying a fluorination of different fluorine-free metal sources with NH4F directly at milling. No evidence was found for a substitution of Mg2+ with Ca2+ (Sr2+, Ba2+) ions, or vice versa, in rutile or fluorite structure. However, an equimolar ratio of Mg2+ to the second cation allows the mechanochemical synthesis of tetrafluoromagnesates, MMgF4, which is more and more hampered the smaller the radius of the cation M2+ is. BaMgF4 is formed even phase pure from the acetates, SrMgF4 can only be observed in a mixture accompanied by the binary fluorides. In addition, 19F MAS NMR spectra along with calculations of 19F isotropic chemical shift values according to the superposition model point to the formation of a metastable phase of CaMgF4, which disappears at thermal treatment and decomposes into the binary fluorides CaF2 and MgF2.

  18. Crystallization of BaF2-ZnF2-YbF3-ThF4 glass

    NASA Technical Reports Server (NTRS)

    Garcia, Roberto; Doremus, Robert H.; Ko, Sen-Hou; Margraf, Tracey; Bansal, Narottam P.

    1988-01-01

    The phases and the rates of crystallization in a Ba-Zn-Yb-Th fluoride glass were studied using differential scanning calorimetry, XRD, and observational and chemical SEM analyses. The crystallizing phases that were identified included a BaYbTh fluoride, ZnF2, and YbF3. The BaYbTh fluoride crystallized first at about 450 C, and ZnF2, which was excluded from this phase, crystallized at its surfaces. At higher temperatures, the BaYbTh fluoride phase decomposed partially to BaThF6 and YbF3 phases.

  19. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glass transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder X ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structural transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  20. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glasss transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder x ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structure transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  1. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

    PubMed

    Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

    2015-01-01

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

  2. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

    PubMed Central

    Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

    2015-01-01

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

  3. Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

    PubMed

    Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

    2015-05-29

    Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

  4. Determination of Sr and Ba partition coefficients between apatite from fish ( Sparus aurata) and seawater: The influence of temperature

    NASA Astrophysics Data System (ADS)

    Balter, Vincent; Lécuyer, Christophe

    2010-06-01

    The Sr/Ca and Ba/Ca ratios in inorganic apatite are strongly dependent on the temperature of the aqueous medium during precipitation. If valid in biogenic apatite, these thermometers would offer the advantage of being more resistant to diagenesis than those calibrated on biogenic calcite and aragonite. We have reared seabreams ( Sparus aurata) in tanks with controlled conditions during experiments lasting for more than 2 years at 13, 17, 23 and 27 °C, in order to determine the variations in Sr and Ba partitioning relative to Ca ( DSr and DBa, respectively) between seawater and fish apatitic hard tissues (i.e. teeth and bones), as a function of temperature. The sensitivity of the Sr and Ba thermometers (i.e. ∂ DSr/∂ T and ∂ DBa/∂ T, respectively), are similar in bone ( ∂Db-wSr/∂ T = 0.0036 ± 0.0003 and ∂Db-wBa/∂ T = 0.0134 ± 0.0026, respectively) and enamel ( ∂De-wSr/∂ T = 0.0037 ± 0.0005 and ∂De-wBa/∂ T = 0.0107 ± 0.0026, respectively). The positive values of ∂ DSr/∂ T and ∂ DBa/∂ T in bone and enamel indicate that DSr and DBa increase with increasing temperature, a pattern opposite to that observed for inorganic apatite. This distinct thermodependent trace element partitioning between inorganic and organic apatite and water highlights the contradictory effects of the crystal-chemical and biological controls on the partitioning of Ca, Sr and Ba in vertebrate organisms. Taking into account the diet Sr/Ca and Ba/Ca values, it is shown that the bone Ba/Ca signature of fish can be explained by Ca-biopurification and inorganic apatite precipitation, whereas both of these processes fail to predict the bone Sr/Ca values. Therefore, the metabolism of Ca as a function of temperature still needs to be fully understood. However, the biogenic Sr thermometer is used to calculate an average seawater temperature of 30.6 °C using the Sr/Ca compositions of fossil shark teeth at the Cretaceous/Tertiary boundary, and a typical seawater Sr

  5. The low Sr/Ba ratio on some extremely metal-poor stars

    NASA Astrophysics Data System (ADS)

    Spite, M.; Spite, F.; Bonifacio, P.; Caffau, E.; François, P.; Sbordone, L.

    2014-11-01

    Context. It has been noted that, in classical extremely metal-poor (EMP) stars, the abundance ratio of two well-observed neutron-capture elements, Sr and Ba, is always higher than [Sr/Ba] = -0.5, which is the value of the solar r-only process; however, a handful of EMP stars have recently been found with a very low Sr/Ba ratio. Aims: We try to understand the origin of this anomaly by comparing the abundance pattern of the elements in these stars and in the classical EMP stars. Methods: For a rigorous comparison with previous data, four stars with very low Sr/Ba ratios were observed and analyzed in the same way as in the First Stars program: analysis within LTE approximation through 1D (hydrostatic) model atmosphere, providing homogeneous abundances of nine neutron-capture elements. Results: In CS 22950-173, the only turnoff star of the sample, the Sr/Ba ratio is, in fact, found to be higher than the r-only solar ratio, so the star is discarded. The remaining stars (CS 29493-090, CS 30322-023, HE 305-4520) are cool evolved giants. They do not present a clear carbon enrichment, but in evolved giants C is partly burned into N, and owing to their high N abundance, they could still have initially been carbon-rich EMP stars (CEMP). The abundances of Na to Mg present similar anomalies to those in CEMP stars. The abundance patterns of the neutron-capture elements in the three stars are strikingly similar to a theoretical s-process pattern. This pattern could at first be attributed to pollution by a nearby AGB, but none of the stars presents a clear variation in the radial velocity indicating the presence of a companion. The stellar parameters seem to exclude any internal pollution in a TP-AGB phase for at least two of these stars. The possibility that the stars are early-AGB stars polluted during the core He flash does not seem compatible with the theory. Based on observations obtained with the ESO Very Large Telescope at Paranal Observatory, Chile (ID 077.D-0299(A) PI

  6. Microstructural evolution and electrical properties of base-metal electroded BaTi4O9 materials with B-Si-Ba-Zn-O glass system.

    PubMed

    Chou, Chen-Chia; Su, Yu-Hsuan; Liu, Ze-Ming; Utami, Brianti Satrianti; Chen, Cheng-Sao; Chu, Li-Wen

    2012-09-01

    Barium titanate-based microwave dielectrics usually require relatively high temperatures to sinter, which prevents the use of base metals such as copper for electrodes. In this work, BaTi(4)O(9) microwave dielectric ceramics co-fired with copper electrodes are made possible by adding B-Si-Ba- Zn-O glass to induce liquid-phase sintering at sufficiently low temperature and in reduced atmosphere. The microstructures and electric properties of the BaTi(4)O(9) ceramics thus obtained are carefully examined and studied. Proper glass composition may significantly facilitate mass transportation in the low-temperature co-fired ceramic (LTCC) material, resulting in better densification without serious degradation of electric properties. Although the B2O3/SiO2 ratio enhances the glass mobility during sintering, the BaO/ZnO ratio contributes to the chemical affinity of glass to BaTi(4)O(9) ceramics. In addition, various Ba-Ti-O phases with different Ba/Ti ratios may be found in the specimen through the X-ray diffraction patterns when the BaO/ZnO ratio is varied. If the BaO/ZnO ratio is high and the glass flows easily in the material, the Ba(4)Ti(13)O(30) phase is formed. If the BaO/ZnO ratio is low and the glass flows easily in the material, the BaTi(6)O(13) phase appears. We find that glass-induced Ba(4)Ti(13)O(30) transformation may significantly decrease Qxf values in the BT4-BSBZ materials. Therefore, the appropriate glass composition must be selected to ensure the phase stability of dielectrics to achieve the best performance possible.

  7. Investigation of structural, mechanical, electronic, optical, and dynamical properties of cubic BaLiF3, BaLiH3, and SrLiH3

    NASA Astrophysics Data System (ADS)

    Yalcin, Battal G.; Salmankurt, Bahadır; Duman, Sıtkı

    2016-03-01

    The structural, mechanical, electronic, optical, and dynamical properties of BaLiF3, BaLiH3, and SrLiH3 cubic perovskite materials are theoretically investigated by using first principles calculations. Obtained results are in reasonable agreement with other available theoretical and experimental studies. The considered materials are found to be mechanically stable in the cubic structure. We found that all materials are brittle. The modified Becke-Johnson (mBJ) exchange potential has been used here to obtain an accurate band order. The calculated band-gap energy value of BaLiF3 (8.26 eV) within the mBJ potential agrees very well with the experimentally reported value of 8.41 eV. In order to have a deeper understanding of the bonding mechanism and the effect of atomic relaxation on the electronic band structure, the total and partial density of states have also been calculated. We have investigated the fundamental optical properties, such as the real ɛ 1(ω) and imaginary ɛ 2(ω) parts of the dielectric function, absorption coefficient α(ω), reflectivity R(ω), and refractive index n(ω) in the energy range from 0 to 40 eV within the mBJ potential. The band-gap energy obtained from the absorption spectrum is around 8.76, 3.99, and 3.31 eV for BaLiF3, BaLiH3, and SrLiH3 crystals, respectively. It should be noted that BaLiF3 could be a strong potential candidate as a laser material for the development of a vacuum-ultraviolet light emitting diode once direct transition is confirmed by experimental studies. Finally, we have calculated the lattice dynamical properties of BaLiF3, BaLiH3, SrLiH3, and SrLiF3 crystals. The full phonon dispersion curves of these materials are reported for the first time. Our results clearly indicate that the materials are dynamically stable, except for SrLiF3, in the cubic structure. The obtained zone-center phonon frequencies of BaLiF3, BaLiH3, and SrLiH3 accord very well with previous experimental measurements.

  8. Thermoelectric Hexagonal A-Mg-Si with A = Sr and Ba Zintl Phases

    NASA Astrophysics Data System (ADS)

    Kajitani, T.; Takahashi, K.; Saito, M.; Suzuki, H.; Kikuchi, S.; Kubouchi, M.; Hayashi, K.

    2016-10-01

    Hexagonal A-Mg-Si with A = Sr and Ba Zintl phases are promising candidates for p-type magnesium silicides usable with n-Mg2Si under 900 K. We synthesized p-type A-Mg-Si Zintl phases by the spark plasma synthesis procedure. Mg2Si and Mg2A powders were mixed at the ratio of 1- x/ x with x = 0.3-0.4. Two-step synthesis was performed at 850 K for 20 min and 1100 K for 20 min under uniaxial pressure at 30 MPa. Sintered pellets exhibited a stable p-type thermoelectric property. These pellets consisted of several unknown phases. We found two semiconductor phases, namely A2Mg4Si3 and A2Mg12Si7. The crystal structures of the 2/4/3- and 2/12/7-phases were Pbar{6}2m (No. 189)- and P63 /m (No. 176)-types, respectively. Sr0.70Mg2Si, Ba3Mg10Si7 and Sr3Mg10Si7 phases are newly found and characterized by a single crystal diffraction study. Previously found Sr2Mg4Si3 single phase polycrystalline 30φ × 10 mm pellets were successfully synthesized. The thermoelectric performance of the Sr2Mg4Si3 single phase sample was tested. The pellets exhibit p-type behavior from room temperature to 700 K. The thermal conductivity, κ, was almost constant at 1.1 W/mK from 350 K to 700 K.

  9. Thermoelectric Hexagonal A-Mg-Si with A = Sr and Ba Zintl Phases

    NASA Astrophysics Data System (ADS)

    Kajitani, T.; Takahashi, K.; Saito, M.; Suzuki, H.; Kikuchi, S.; Kubouchi, M.; Hayashi, K.

    2016-06-01

    Hexagonal A-Mg-Si with A = Sr and Ba Zintl phases are promising candidates for p-type magnesium silicides usable with n-Mg2Si under 900 K. We synthesized p-type A-Mg-Si Zintl phases by the spark plasma synthesis procedure. Mg2Si and Mg2A powders were mixed at the ratio of 1-x/x with x = 0.3-0.4. Two-step synthesis was performed at 850 K for 20 min and 1100 K for 20 min under uniaxial pressure at 30 MPa. Sintered pellets exhibited a stable p-type thermoelectric property. These pellets consisted of several unknown phases. We found two semiconductor phases, namely A2Mg4Si3 and A2Mg12Si7. The crystal structures of the 2/4/3- and 2/12/7-phases were Pbar{6}2m (No. 189)- and P63 /m (No. 176)-types, respectively. Sr0.70Mg2Si, Ba3Mg10Si7 and Sr3Mg10Si7 phases are newly found and characterized by a single crystal diffraction study. Previously found Sr2Mg4Si3 single phase polycrystalline 30φ × 10 mm pellets were successfully synthesized. The thermoelectric performance of the Sr2Mg4Si3 single phase sample was tested. The pellets exhibit p-type behavior from room temperature to 700 K. The thermal conductivity, κ, was almost constant at 1.1 W/mK from 350 K to 700 K.

  10. Temperature stability of ultra-thin mixed BaSr-oxide layers and their transformation.

    PubMed

    Müller-Sajak, D; Islam, S; Pfnür, H; Hofmann, K R

    2012-08-01

    In the context of investigations of physical, chemical and electrical properties of ultra-thin layers of epitaxial and monocrystalline Sr(0.3)Ba(0.7)O on Si(100), we also investigated their thermal stability with x-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and low energy electron diffraction (LEED). At temperatures above 400 °C, transformation into silicate layers sets in. The stoichiometry after complete transformation was determined to be close to (Ba(0.8)Sr(0.2))(2)SiO(4) except for layers of only a few monolayers, where the silicate is not stoichiometric. There are strong indications that this silicate is stable until it desorbs at temperatures above 750 °C. Crystallinity, as seen with LEED, is lost during this transformation. Although transformation into silicate is coupled with metal desorption and compactification of the layers, they seem to remain closed. In addition, traces of Ba silicide at the Si interface were detected after layer desorption. This silicide cannot be desorbed thermally. The silicate layer has a bandgap of 5.9 ± 0.2 eV already for 3 ML thickness. Upon exposure to air, carbon and oxygen containing species, but no hydroxide, are formed irreversibly.

  11. High temperature crystal structures and superionic properties of SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2}

    SciTech Connect

    Hull, Stephen; Norberg, Stefan T.; Ahmed, Istaq; Eriksson, Sten G.; Mohn, Chris E.

    2011-11-15

    The structural properties of the binary alkaline-earth halides SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2} have been investigated from ambient temperature up to close to their melting points, using the neutron powder diffraction technique. Fluorite-structured SrCl{sub 2} undergoes a gradual transition to a superionic phase at 900-1100 K, characterised by an increasing concentration of anion Frenkel defects. At a temperature of 920(3) K, the tetragonal phase of SrBr{sub 2} undergoes a first-order transition to a cubic fluorite phase. This high temperature phase shows the presence of extensive disorder within the anion sublattice, which differs from that found in superionic SrCl{sub 2}. BaCl{sub 2} and BaBr{sub 2} both adopt the cotunnite crystal structure under ambient conditions. BaCl{sub 2} undergoes a first-order structural transition at 917(5) K to a disordered fluorite-structured phase. The relationship between the (disordered) crystal structures and the ionic conductivity behaviour is discussed and the influence of the size of the mobile anion on the superionic behaviour is explored. - Graphical abstract: Anomalous behaviour of the lattice expansion of SrCl{sub 2} at temperatures of {approx}1000 K is associated with the gradual transition to a superionic phase, whilst SrBr{sub 2} undergoes a first-order structural transition ({beta}{yields}{alpha}) to a fluorite-structured superionic phase at 920(3) K. Highlights: > Anomalous behaviour of the lattice expansion of SrCl{sub 2} occurs at temperatures {approx}1000 K. > Crystal structure of {beta}-SrBr{sub 2} is described in detail. > On heating, SrBr{sub 2} and BaCl{sub 2} transform to a fluorite-structured superionic phase. > Temperature dependence of the BaCl{sub 2} and BaBr{sub 2} structures is presented. > Nature of the superionic phases within the alkaline-earth halides is discussed.

  12. Optical properties of ZnO/BaCO3 nanocomposites in UV and visible regions

    PubMed Central

    2014-01-01

    Pure zinc oxide and zinc oxide/barium carbonate nanoparticles (ZnO-NPs and ZB-NPs) were synthesized by the sol–gel method. The prepared powders were characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis), Auger spectroscopy, and transmission electron microscopy (TEM). The XRD result showed that the ZnO and BaCO3 nanocrystals grow independently. The Auger spectroscopy proved the existence of carbon in the composites besides the Zn, Ba, and O elements. The UV–Vis spectroscopy results showed that the absorption edge of ZnO nanoparticles is redshifted by adding barium carbonate. In addition, the optical parameters including the refractive index and permittivity of the prepared samples were calculated using the UV–Vis spectra. PACS 81.05.Dz; 78.40.Tv; 42.70.-a. PMID:25177218

  13. Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

    PubMed

    Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

    2011-11-01

    Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

  14. Magnetic and magnetocaloric properties of Ba and Ti co-doped SrRuO{sub 3}

    SciTech Connect

    Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal; De, S. K.

    2014-12-28

    Temperature evolution of magnetic properties in Ba and Ti doped SrRuO{sub 3} has been investigated to observe the effects of larger ionic radius Ba at Sr site and isovalent nonmagnetic impurity Ti at Ru site. Ionic radius mismatch and different electronic configuration in comparison with Ru modify Sr(Ba)-O and Ru(Ti)-O bond lengths and Ru-O-Ru bond angle. The apical and basal Ru-O-Ru bond angles vary significantly with Ti doping. Ferromagnetic Curie temperature decreases from 161 K to 149 K monotonically with Ba (10%) and Ti (10%) substitutions at Sr and Ru sites. The zero field cooled (ZFC) magnetization reveals a prominent peak which shifts towards lower temperature with application of magnetic field. The substitution of tetravalent Ti with localized 3d{sup 0} orbitals for Ru with more delocalized 4d{sup 4} orbitals leads to a broad peak in ZFC magnetization. A spontaneous ZFC magnetization becomes negative below 160 K for all the compositions. The occurrence of both normal and inverse magnetocaloric effects in Ba and Ti co-doped SrRuO{sub 3} makes the system more interesting.

  15. Effect of divalent Ba cation substitution with Sr on coupled 'multiglass' state in the magnetoelectric multiferroic compound Ba3NbFe3Si2O14.

    PubMed

    Rathore, Satyapal Singh; Vitta, Satish

    2015-01-01

    (Ba/Sr)3NbFe3Si2O14 is a magneto-electric multiferroic with an incommensurate antiferromagnetic spiral magnetic structure which induces electric polarization at 26 K. Structural studies show that both the compounds have similar crystal structure down to 6 K. They exhibit a transition, TN at 26 K and 25 K respectively, as indicated by heat capacity and magnetization, into an antiferromagnetic state. Although Ba and Sr are isovalent, they exhibit very different static and dynamic magnetic behaviors. The Ba-compound exhibits a glassy behavior with critical slowing dynamics with a freezing temperature of ~35 K and a critical exponent of 3.9, a value close to the 3-D Ising model above TN, in addition to the invariant transition into an antiferromagnetic state. The Sr-compound however does not exhibit any dispersive behavior except for the invariant transition at TN. The dielectric constant reflects magnetic behavior of the two compounds: the Ba-compound has two distinct dispersive peaks while the Sr-compound has a single dispersive peak. Thus the compounds exhibit coupled 'multiglass' behavior. The difference in magnetic properties between the two compounds is found to be due to modifications to super exchange path angle and length as well as anti-site defects which stabilize either ferromagnetic or antiferromagnetic interactions. PMID:25988657

  16. MBiO{sub 2}Cl (M=Sr, Ba) as novel photocatalysts: Synthesis, optical property and photocatalytic activity

    SciTech Connect

    Huang, Hongwei Wang, Shuobo; Zhang, Yihe Han, Xu

    2015-02-15

    Novel quaternary photocatalysts MBiO{sub 2}Cl (M=Sr, Ba) have been successfully developed for efficient photodecomposition of RhB. Their photocatalytic mechanism was also investigated. - Highlights: • Two Bi-based compounds SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were explored as photocatalysts. • They were successfully synthesized by a solid-state reaction. • RhB can be effectively photodecomposed by SrBiO{sub 2}Cl and BaBiO{sub 2}Cl under UV light. • ·OH radicals serving as active species play important roles in degradation process. - Abstract: Two Bi-based compounds SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were successfully synthesized by a solid-state reaction and investigated as new photocatalysts for the first time. Their microstructures and optical properties were characterized by XRD, SEM and DRS. The band gaps of SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were separately determined to be 3.52 and 3.71 eV, and their E{sub CB} and E{sub VB} were also estimated. The photocatalytic activities of the as-prepared samples were evaluated by photodecomposition of rhodamine B (RhB) in aqueous solution. The results revealed that both SrBiO{sub 2}Cl and BaBiO{sub 2}Cl can be used as effective photocatalysts under UV irradiation, and SrBiO{sub 2}Cl exhibits a higher photocatalytic activity than BaBiO{sub 2}Cl, which was also verified by the PL spectra. Terephthalic acid photoluminescence probing technique (TA-PL) demonstrated that ·OH radicals serving as active species play an important role in photooxidative degradation of RhB over SrBiO{sub 2}Cl and BaBiO{sub 2}Cl. Moreover, a larger amount of ·OH radicals generation was observed over SrBiO{sub 2}Cl, which is in agreement with its higher photocatalytic activity.

  17. Crystal structure and polarization hysteresis properties of ferroelectric BaTiO3 thin-film capacitors on (Ba,Sr)TiO3-buffered substrates

    NASA Astrophysics Data System (ADS)

    Maki, Hisashi; Noguchi, Yuji; Kutsuna, Kazutoshi; Matsuo, Hiroki; Kitanaka, Yuuki; Miyayama, Masaru

    2016-10-01

    Ferroelectric BaTiO3 (BT) thin-film capacitors with a buffer layer of (Ba1- x Sr x )TiO3 (BST) have been fabricated on (001) SrTiO3 (STO) single-crystal substrates by a pulsed laser deposition method, and the crystal structure and polarization hysteresis properties have been investigated. X-ray diffraction reciprocal space mapping shows that the BST buffer effectively reduces the misfit strain relaxation of the BT films on SrRuO3 (SRO) electrodes. The BT capacitor with the SRO electrodes on the BST (x = 0.3) buffer exhibits a well-saturated hysteresis loop with a remanent polarization of 29 µC/cm2. The hysteresis loop displays a shift toward a specific field direction, which is suggested to stem from the flexoelectric coupling between the out-of-plane polarization and the strain gradient adjacent to the bottom interface.

  18. Effect of divalent (Sr, Ba) doping on the structural and magnetic properties of BiFeO{sub 3}

    SciTech Connect

    Rangi, Manisha Sanghi, Sujata; Agarwal, Ashish; Jangra, Sandhaya; Singh, Ompal

    2015-06-24

    The effect of divalent substitution on the crystal structure and magnetic properties of BiFeO{sub 3} has been investigated using X-ray diffraction and magnetic measurements technique. Single phase Bi{sub 0.8}A{sub 0.2}FeO{sub 3} (A= Sr, Ba) multiferroics have been synthesized by solid state reaction method. Rietveld analysis of the XRD patterns revealed that the prepared ceramics exhibit rhombohedral structure with space group R3c. M–H hysteresis loops were recorded at 5K revealed that Sr and Ba substitution transformed antiferromagnetic BiFeO3 into weak ferromagnetic. The enhanced magnetization with Sr and Ba addition is confirmed by the MT curve recorded at 1T. It is closely related to intrinsic structural distortion and modification of the antiparallel spin structure.

  19. Theoretical studies of the osmium based perovskites AOsO3 (A=Ca, Sr and Ba)

    NASA Astrophysics Data System (ADS)

    Ali, Zahid; Sattar, Abdul; Asadabadi, S. Jalali; Ahmad, Iftikhar

    2015-11-01

    Osmium based perovskites AOsO3 (A=Ca, Sr and Ba) have been studied theoretically using density functional theory approach. These studies show that CaOsO3 and SrOsO3 are orthorhombic and BaOsO3 is cubic and are consistent with the experiments. The electronic band structures demonstrate that these compounds are metals. The magnetic studies verify the experimental observations at low temperature, where the spin effects are canceled by the orbitals. The stable magnetic phase optimizations and magnetic susceptibilities calculations by the post-DFT treatment confirm that CaOsO3 and SrOsO3 are weak ferromagnetic whereas BaOsO3 is a paramagnetic material. The directional magnetic study shows that these compounds are magnetically anisotropic, and reveals that the easy magnetization axis is [001] direction.

  20. Hybrid improper ferroelectricity in SrZrO3/BaZrO3 superlattice.

    PubMed

    Zhang, Yajun; Wang, Jie; Sahoo, M P K; Wang, Xiaoyuan; Shimada, Takahiro; Kitamura, Takayuki

    2016-08-24

    Incipient ferroelectrics, which show a unique dielectric property, arouse tremendous interests due to their potential application in microwave dielectric devices. However, ferroelectric transition in incipient ferroelectrics is suppressed entirely by quantum fluctuation. Here, by means of first-principles calculations, we demonstrate that there exists hybrid improper ferroelectricity in a layered artificial superlattice composed of the incipient ferroelectrics of SrZrO3 and BaZrO3. The hybrid improper ferroelectric polarization stems from oxygen octahedral rotation and coexists with the strain-induced ferroelectric distortion. The coexistence of oxygen octahedral rotation and ferroelectric distortion results in an enhanced polarization in the superlattice. It is further found that the total polarization in the superlattice is mainly contributed by the oxygen octahedral rotation for zero or small strain, whereas the contribution from strain-induced ferroelectric distortion gradually becomes predominant as the strain increases. The phonon dispersion, energy surface and atomic displacements are calculated to shed light on the underlying mechanism of the hybrid improper ferroelectricity in the SrZrO3/BaZrO3 superlattice.

  1. Hybrid improper ferroelectricity in SrZrO3/BaZrO3 superlattice.

    PubMed

    Zhang, Yajun; Wang, Jie; Sahoo, M P K; Wang, Xiaoyuan; Shimada, Takahiro; Kitamura, Takayuki

    2016-08-24

    Incipient ferroelectrics, which show a unique dielectric property, arouse tremendous interests due to their potential application in microwave dielectric devices. However, ferroelectric transition in incipient ferroelectrics is suppressed entirely by quantum fluctuation. Here, by means of first-principles calculations, we demonstrate that there exists hybrid improper ferroelectricity in a layered artificial superlattice composed of the incipient ferroelectrics of SrZrO3 and BaZrO3. The hybrid improper ferroelectric polarization stems from oxygen octahedral rotation and coexists with the strain-induced ferroelectric distortion. The coexistence of oxygen octahedral rotation and ferroelectric distortion results in an enhanced polarization in the superlattice. It is further found that the total polarization in the superlattice is mainly contributed by the oxygen octahedral rotation for zero or small strain, whereas the contribution from strain-induced ferroelectric distortion gradually becomes predominant as the strain increases. The phonon dispersion, energy surface and atomic displacements are calculated to shed light on the underlying mechanism of the hybrid improper ferroelectricity in the SrZrO3/BaZrO3 superlattice. PMID:27523881

  2. Nd:SrWO 4 and Nd:BaWO 4 Raman lasers

    NASA Astrophysics Data System (ADS)

    Šulc, J.; Jelínková, H.; Basiev, T. T.; Doroschenko, M. E.; Ivleva, L. I.; Osiko, V. V.; Zverev, P. G.

    2007-09-01

    Properties of the laser operation and simultaneously stimulated Raman scattering in the SRS-active neodymium doped SrWO4 and BaWO4 crystals coherently end-pumped at wavelength 752 nm by pulsed free-running alexandrite laser radiation were investigated. The Nd3+ ion emission at wavelength λNd ˜ 1.06 μm was corresponding to 4F3/2 → 4I11/2 transition. To reach the SRS-self-conversion threshold inside Raman crystal the Nd3+ lasers were operating in a Q-switching regime. For Q-switching LiF:F2- crystal as a saturable absorber was used. Raman self-conversion at wavelength ˜1.17 μm was successfully reached with both tungstate crystals. The shortest generated pulse (1.3 ns FWHM) and highest peak power (615 kW) was obtained with Nd:BaWO4 Raman laser Q-switched by LiF:F2- crystal with initial transmission T0 = 60%. Up to 0.8 mJ was registered at the first Stokes wavelength 1169 nm. Using Q-switched Nd:SrWO4 laser higher energy in Raman emission was obtained (1.23 mJ) but generated pulse was longer (2.9 ns FWHM) resulting in lower peak power (430 kW).

  3. Solid solution partitioning of Sr2+, Ba2+, and Cd2+ to calcite

    USGS Publications Warehouse

    Tesoriero, A.J.; Pankow, J.F.

    1996-01-01

    Although solid solutions play important roles in controlling the concentrations of minor metal ions in natural waters, uncertainties regarding their compositions, thermodynamics, and kinetics usually prevent them from being considered. A range of precipitation rates was used here to study the nonequilibrium and equilibrium partitioning behaviors of Sr2+, Ba2+, and Cd2+ to calcite (CaCO3(s)). The distribution coefficient of a divalent metal ion Me2+ for partitioning from an aqueous solution into calcite is given by DMe = (XMeCO3(s)/[Me2+])/(XCaCO3(s)/[Ca 2+]). The X values are solid-phase mole fractions; the bracketed values are the aqueous molal concentrations. In agreement with prior work, at intermediate to high precipitation rates R (nmol/mg-min), DSr, DBa, and DCd were found to depend strongly on R. At low R, the values of DSr, DBa, and DCd became constant with R. At 25??C, the equilibrium values for DSr, DBa, and DCd for dilute solid solutions were estimated to be 0.021 ?? 0.003, 0.012 ?? 0.005, and 1240 ?? 300, respectively. Calculations using these values were made to illustrate the likely importance of partitioning of these ions to calcite in groundwater systems. Due to its large equilibrium DMe value, movement of Cd2+ will be strongly retarded in aquifers containing calcite; Sr2+ and Ba2+ will not be retarded nearly as much.

  4. Magnetic behaviour of the MTbF{sub 6} fluoroterbates (M=Cd, Ca, Sr, ({alpha}/{beta})-Ba)

    SciTech Connect

    Josse, M.; El-Ghozzi, M.; Avignant, D.; Andre, G.; Bouree, F.; Isnard, O.

    2012-01-15

    Neutron powder diffraction has been performed on the MTbF{sub 6} fluorides (M=Cd, Ca, Sr, ({alpha}/{beta})-Ba). Four of these fluorides (Cd, Ca, Sr, {beta}-Ba) are built of a (pseudo-) tetragonal packing of [TbF{sub 6}]{sup 2-} chains and only differs by the chains relative orientations. Thus this series represents a valuable opportunity to evaluate the Tb{sup 4+}-Tb{sup 4+} magnetic interactions. All the compounds displayed antiferromagnetic order (T{sub N}=2.70 K (Cd), 2.15 K (Ca), 2.60 K (Sr), 2.10 K ({beta}-Ba)), except for the {alpha} form of BaTbF{sub 6}. The crystal structure of this latter fluoroterbate has also been investigated by means of high-resolution neutron powder diffraction. From Neutron Powder Diffraction data, CdTbF{sub 6} and {beta}-BaTbF{sub 6} magnetic structures were determined, together with the metamagnetic behaviour of {beta}-BaTbF{sub 6} as a function of an external magnetic field. A tentative phase diagram is then given for {beta}-BaTbF{sub 6}. Advantage was taken of the polymorphism of the BaTbF{sub 6} fluoroterbate to analyse, on the basis of topological parameters such as bond distances and angles, the magnetic behaviour of its {alpha} and {beta} forms. It was shown that superexchange interactions are present in {beta}-BaTbF{sub 6}, and that these interactions may also rule the magnetic behaviour of the other MTbF{sub 6} (M=Ca, Sr, Cd) tetravalent terbium fluorides. - Graphical abstract: Powder neutron diffraction revealed magnetic order in four of the five investigated fluoroterbates, while crystal chemical analyses of {alpha} and {beta} forms of BaTbF{sub 6} evidenced the existence of superexchange interactions. Highlights: Black-Right-Pointing-Pointer Five fluoroterbates are investigated by Powder Neutron Diffraction (PND). Black-Right-Pointing-Pointer Four of them are antiferromagnetically ordered at 1.4 K. Black-Right-Pointing-Pointer Magnetic structures of {beta}-BaTbF{sub 6} and CdTbF{sub 6} are determined. Black

  5. 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.

  6. Synthesis of highly strained mesostructured SrTiO(3)/BaTiO(3) composite films with robust ferroelectricity.

    PubMed

    Suzuki, Norihiro; Zakaria, Mohamed B; Torad, Nagy L; Wu, Kevin C-W; Nemoto, Yoshihiro; Imura, Masataka; Osada, Minoru; Yamauchi, Yusuke

    2013-04-01

    A new class of highly stable ferroelectric material, that is, a mesostructured SrTiO(3)/BaTiO(3) composite film, obtained by a surfactant-templated sol-gel method is reported. Due to the concave surface geometry and abundant hetero-interface between SrTiO(3) (ST) and BaTiO(3) (BT) phases, a large number of strains can be created in the composite film, thereby leading to dramatic enhancement of ferroelectric property (see scheme).

  7. Goosenest Volcano, southern Oregon: High K[sub 2]O, BA and Sr basaltic andesite extrusives

    SciTech Connect

    Mertzman, S.A. . Dept. of Geosciences)

    1992-01-01

    Goosenest Volcano, a cinder cone with coeval lava flows, is located nearly 5 miles WNW of the south entrance into Crater Lake National Park. A summit crater unmodified by glacial erosion but with a blanket of Mazama pumice, suggests the age of latest activity to be between 20,000 and 6850 B.P. The pyroclastics and lavas from Goosenest are augite olivine basaltic andesites, with a strong tendency for these minerals to form 2--5 mm in diameter glomeroporphyritic clumps [+-] plagioclase. Three samples from the cone (2 bombs and 1 spatter agglutinate) and five from lava flows were analyzed for major and trace elements through XRF and ICP techniques. These extrusive are calc-alkaline medium to high K[sub 2]O basaltic andesites; in particular, SiO[sub 2] ranges from 53 to 54 wt. %, K[sub 2]O from 1.39 to 1.94, MgO from 6.3 to 7.3, Ba from 774 to 1,069 ppm and Sr from 1,463 to 1,951 ppm. With increasing K[sub 2]O: P[sub 2]O[sub 5], Ba, Be, Ce, La, Sr, and Zr increase in concentration while Ni, Cr, and Co decrease. All major elements are virtually constant or scatter randomly; Y,V,Sc, and Yb follow the same pattern. The lower Al[sub 2]O[sub 3] content (16 to 17 wt.%) precludes the addition of a large plagioclase component as an explanation of the high Sr content. Batch partial melting of a mineralogically homogeneous source that has been fluxed by variable amounts of an LILE-rich fluid phase whose ultimate origin is tied to the subduction process, is a likely scheme which explains the unusual chemical composition of the Gossenest extrusive rocks.

  8. ABUNDANCES OF C, N, Sr, AND Ba ON THE RED GIANT BRANCH OF {omega} CENTAURI

    SciTech Connect

    Stanford, Laura M.; Da Costa, G. S.; Norris, John E. E-mail: gdc@mso.anu.edu.a

    2010-05-10

    Abundances relative to iron for carbon, nitrogen, strontium, and barium are presented for 33 stars on the red giant branch (RGB) of the globular cluster {omega} Centauri. They are based on intermediate-resolution spectroscopic data covering the blue spectral region analyzed using spectrum synthesis techniques. The data reveal the existence of a broad range in the abundances of these elements, and a comparison with similar data for main-sequence stars enables insight into the evolutionary history of the cluster. The majority of the RGB stars were found to be depleted in carbon, i.e., [C/Fe] < 0, while [N/Fe] for the same stars shows a range of {approx}1 dex, from [N/Fe] {approx} 0.7 to 1.7 dex. The strontium-to-iron abundance ratios varied from solar to mildly enhanced (0.0 {<=} [Sr/Fe] {<=} 0.8), with [Ba/Fe] generally equal to or greater than [Sr/Fe]. The carbon and nitrogen abundance ratios for the one known CH star in the sample, ROA 279, are [C/Fe] = 0.6 and [N/Fe] = 0.5 dex. Evidence for evolutionary mixing on the RGB is found from the fact that the relative carbon abundances on the main sequence are generally higher than those on the RGB. However, comparison of the RGB and main-sequence samples shows that the upper level of nitrogen enhancement is similar in both sets at [N/Fe] {approx} 2.0 dex. This is most likely the result of primordial rather than evolutionary mixing processes. One RGB star, ROA 276, was found to have Sr and Ba abundance ratios similar to the anomalous Sr-rich main-sequence star S2015448. High-resolution spectra of ROA 276 were obtained with the Magellan Telescope/MIKE spectrograph combination to confirm this result, revealing that ROA 276 is indeed an unusual star. For this star, calculations of the depletion effect, the potential change in surface abundance that results from the increased depth of the convective envelope as a star moves from the main sequence to the RGB, strongly suggest that the observed Sr enhancement in ROA 276 is of

  9. New Insulating Antiferromagnetic Quaternary Iridates MLa10Ir4O24 (M = Sr, Ba).

    PubMed

    Zhao, Qingbiao; Han, Fei; Stoumpos, Constantinos C; Han, Tian-Heng; Li, Hao; Mitchell, J F

    2015-01-01

    Recently, oxides of Ir(4+) have received renewed attention in the condensed matter physics community, as it has been reported that certain iridates have a strongly spin-orbital coupled (SOC) electronic state, J eff = ½, that defines the electronic and magnetic properties. The canonical example is the Ruddlesden-Popper compound Sr2IrO4, which has been suggested as a potential route to a new class of high temperature superconductor due to the formal analogy between J eff = ½ and the S = ½ state of the cuprate superconductors. The quest for other iridium oxides that present tests of the underlying SOC physics is underway. In this spirit, here we report the synthesis and physical properties of two new quaternary tetravalent iridates, MLa10Ir4O24 (M = Sr, Ba). The crystal structure of both compounds features isolated IrO6 octahedra in which the electronic configuration of Ir is d(5). Both compounds order antiferromagnetically despite the lack of obvious superexchange pathways, and resistivity measurement shows that SrLa10Ir4O24 is an insulator. PMID:26129886

  10. New insulating antiferromagnetic quaternary iridates MLa10Ir4O24 (M=Sr, Ba)

    DOE PAGESBeta

    Zhao, Qingbiao; Han, Fei; Stoumpos, Constantinos C.; Han, Tian -Heng; Li, Hao; Mitchell, J. F.

    2015-07-01

    Recently, oxides of Ir4+ have received renewed attention in the condensed matter physics community, as it has been reported that certain iridates have a strongly spin-orbital coupled (SOC) electronic state, Jeff = ½, that defines the electronic and magnetic properties. The canonical example is the Ruddlesden-Popper compound Sr2IrO4, which has been suggested as a potential route to a new class of high temperature superconductor due to the formal analogy between Jeff = ½ and the S = ½ state of the cuprate superconductors. The quest for other iridium oxides that present tests of the underlying SOC physics is underway. Inmore » this spirit, here we report the synthesis and physical properties of two new quaternary tetravalent iridates, MLa10Ir4O24 (M = Sr, Ba). The crystal structure of both compounds features isolated IrO6 octahedra in which the electronic configuration of Ir is d5. As a result, both compounds order antiferromagnetically despite the lack of obvious superexchange pathways, and resistivity measurement shows that SrLa10Ir4O24 is an insulator.« less

  11. Measurement of Ca, Zn and Sr in enamel of human teeth by XRF

    SciTech Connect

    Wielopolski, L.; Featherstone, J.D.B.; Cohn, S.H.

    1984-01-01

    Energy dispersive x-ray fluorescence (EDXRF) has been employed to measure Ca, Zn, and Sr in enamel of human teeth. The calibration of the EDXRF system was performed by comparing Sr/Ca ratios with values obtained by atomic absorption analysis of acid etched biopsies of the enamel surface. Two calibration lines were obtained, one line for untreated teeth and the second line for teeth immersed (treated) in solutions containing Sr. A simple analytical model demonstrated that the two calibration lines were the result of the difference in the depth of the enamel sampled by EDXRF and by the acid-etched biopsy. The multi-elemental, non-destructive and quantitative aspects of EDXRF permit the sequential monitoring of the effects of Sr and Zn ions on the mineralization and demineralization processes in human enamel. The portability of the system and adaptability to non-invasive measurements makes it suitable for field studies. 26 references, 4 figures.

  12. The systems Sr-Zn-{l_brace}Si,Ge{r_brace}: Phase equilibria and crystal structure of ternary phases

    SciTech Connect

    Romaka, V.V.; Falmbigl, M.; Grytsiv, A.; Rogl, P.

    2012-02-15

    Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr-Zn-Si at 800 Degree-Sign C and Sr-Zn-Ge at 700 Degree-Sign C. In the Sr-Zn-Si system one new ternary compound SrZn{sub 2+x}Si{sub 2-x} (0{<=}x{<=}0.45) with CeAl{sub 2}Ga{sub 2} structure and a statistical mixture of Zn/Si in the 4e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn{sub 1-x}Si{sub 1+x} with ZrBeSi-type (0.16{<=}x{<=}0.22) and SrZn{sub 1-x}Si{sub 1+x} with AlB{sub 2}-type (0.35{<=}x{<=}0.65) with a random distribution of Zn/Si atoms in the 2c site. For the Sr-Zn-Ge system, the homogeneity regions of the isotypic phases SrZn{sub 1-x}Ge{sub 1+x} with ZrBeSi-type (0{<=}x{<=}0.17) and AlB{sub 2}-type (0.32{<=}x{<=}0.56), respectively, have been determined. Whereas the germanide SrZn{sub 2+x}Ge{sub 2-x} (CeAl{sub 2}Ga{sub 2}-type) is characterized by a homogeneity region (0{<=}x{<=}0.5), the clathrate type-I phase Sr{sub 8}Zn{sub 8}Ge{sub 38} shows a point composition. - Graphical abstract: Phase equilibria of ternary compounds in the Sr-Zn-Si-system at 800 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Si-system are established at 800 Degree-Sign C. Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Ge-system are established at 700 Degree-Sign C. Black-Right-Pointing-Pointer Crystal structures of the ternary compounds were confirmed by X-ray powder diffraction. Black-Right-Pointing-Pointer All ternary compounds except the clathrate-I in the Ge-system are characterized by a homogeneity region.

  13. Band alignment at SrCu2O2/ZnO heterointerface

    NASA Astrophysics Data System (ADS)

    Konovalov, I.; Hesse, R.

    2009-09-01

    SrCu2O2/ZnO interface is interesting for application in blue and UV light emission devices. Measurements of the valence band offset at SrCu2O2/ZnO interface using photoelectron spectroscopy result in an offset of 2.0 eV (cliff), meaning that the interface band gap is reduced to 1.4 eV. Blue and UV light emission observed previously can be attained in this material system presumably by injection of minority carriers involving tunneling through a narrow barrier at the interface. Additional intensive infrared light emission due to interface recombination can be predicted.

  14. Transparent Conducting Properties of SrSnO3 and ZnSnO3

    DOE PAGESBeta

    Ong, Khuong P.; Fan, Xiaofeng; Subedi, Alaska; Sullivan, Michael B.; Singh, David J.

    2015-04-29

    We report optical properties of doped n-type SrSnO3 and ZnSnO3 in relation to potential application as transparent conductors. We find that the orthorhombic distortion of the perovskite structure in SrSnO3 leads to absorption in the visible as the doping level is increased. This arises from interband transitions. We find that strain tuning could modify this absorption, but does not eliminate it. On the other hand, we find that ZnSnO3 although also having a non-cubic structure, can retain excellent transparency when doped, making it a good candidate transparent conductor.

  15. Dependence of the Sr-to-Ba and Sr-to-Eu Ratio on the Nuclear Equation of State in Metal-poor Halo Stars

    NASA Astrophysics Data System (ADS)

    Famiano, M. A.; Kajino, T.; Aoki, W.; Suda, T.

    2016-10-01

    A model is proposed in which the dependence on the equation of state (EOS) of the scatter of [Sr/Ba] in metal-poor stars is studied. Light r-process element enrichment in these stars has been explained via a truncated r-process, or “tr-process.” The truncation of the r-process from a generic core-collapse event followed by a collapse into an accretion-induced black hole is examined in the framework of a galactic chemical evolution model. The constraints on this model imposed by observations of extremely metal-poor stars are explained, and the upper limits in the [Sr/Ba] distributions are found to be related to the nuclear EOS in a collapse scenario. The scatter in [Sr/Ba] and [Sr/Eu] as a function of metallicity has been found to be consistent with turbulent ejection in core-collapse supernovae. Adaptations of this model are evaluated to account for the scatter in isotopic observables. This is done by assuming mixing in ejecta in a supernova event. Stiff EOS are eliminated by this model.

  16. (Ba,Sr)TiO3 tunable capacitors with RF commutation quality factors exceeding 6000

    NASA Astrophysics Data System (ADS)

    Meyers, Cedric J. G.; Freeze, Christopher R.; Stemmer, Susanne; York, Robert A.

    2016-09-01

    The fabrication, measurement, and modeling of radio-frequency (RF), tunable interdigital capacitors (IDCs) are described. High quality factors of 200 in the S/L-bands combined with a 47% tunability are achieved by utilizing epitaxial (Ba,Sr)TiO3 films grown by hybrid molecular beam epitaxy on LaAlO3 substrates. The fabricated devices consisted of one-port and two-port IDCs embedded in ground-signal-ground, coplanar waveguide transmission lines to enable RF probing. Wideband RF scattering parameters under bias were measured from 100 MHz to 40 GHz. A commutation quality factor averaging 6000 across the L band is achieved. These are the highest reported values in this band.

  17. 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.

  18. Fabrication of Multilayer Barrier Layer Capacitors with Semiconducting (Ba, Sr)TiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Itoh, Tatsuhiko; Tashiro, Shinjiro; Igarashi, Hideji

    1993-09-01

    Multilayer barrier layer capacitors were successfully fabricated by utilizing potential barriers at grain boundaries of semiconducting (Ba,Sr)TiO3 ceramics in the temperature region above the Curie point of -140°C. A small amount of Mn improved the dissipation factor and temperature dependence of permittivity in the temperature region from -30°C to 100°C. Multilayer barrier layer capacitors were composed of 10 layers having 80-μm thickness per layer. Resistivity above 1010 Ω\\cdotcm was attained at room temperature, and relative permittivities above 5500 and dissipation factors less than 2% were obtained in the temperature region from -30°C to 100°C.

  19. Ba(Zn1−2xMnxCux)2As2: A Bulk Form Diluted Ferromagnetic Semiconductor with Mn and Cu Codoping at Zn Sites

    PubMed Central

    Man, Huiyuan; Guo, Shengli; Sui, Yu; Guo, Yang; Chen, Bin; Wang, Hangdong; Ding, Cui; Ning, F.L.

    2015-01-01

    We report the synthesis and characterization of a bulk form diluted magnetic semiconductor Ba(Zn1−2xMnxCux)2As2 with the crystal structure identical to that of “122” family iron based superconductors and the antiferromagnet BaMn2As2. No ferromagnetic order occurs with (Zn, Mn) or (Zn, Cu) substitution in the parent compound BaZn2As2. Only when Zn is substituted by both Mn and Cu simultaneously, can the system undergo a ferromagnetic transition below TC ~ 70 K, followed by a magnetic glassy transition at Tf  ~ 35 K. AC susceptibility measurements for Ba(Zn0.75Mn0.125Cu0.125)2As2 reveal that Tf strongly depends on the applied frequency with and a DC magnetic field dependence of , demonstrating that a spin glass transition takes place at Tf. As large as −53% negative magnetoresistance has been observed in Ba(Zn1−2xMnxCux)2As2, enabling its possible application in memory devices. PMID:26492957

  20. Ba(Zn(1-2x)MnxCux)2As2: A Bulk Form Diluted Ferromagnetic Semiconductor with Mn and Cu Codoping at Zn Sites.

    PubMed

    Man, Huiyuan; Guo, Shengli; Sui, Yu; Guo, Yang; Chen, Bin; Wang, Hangdong; Ding, Cui; Ning, F L

    2015-10-23

    We report the synthesis and characterization of a bulk form diluted magnetic semiconductor Ba(Zn(1-2x)MnxCux)2As2 (0.025 ≤ x ≤ 0.2) with the crystal structure identical to that of "122" family iron based superconductors and the antiferromagnet BaMn2As2. No ferromagnetic order occurs with (Zn, Mn) or (Zn, Cu) substitution in the parent compound BaZn2As2. Only when Zn is substituted by both Mn and Cu simultaneously, can the system undergo a ferromagnetic transition below TC ~ 70 K, followed by a magnetic glassy transition at Tf  ~ 35 K. AC susceptibility measurements for Ba(Zn0.75Mn0.125Cu0.125)2As2 reveal that Tf strongly depends on the applied frequency with [formula in text] and a DC magnetic field dependence of [formula in text], demonstrating that a spin glass transition takes place at Tf. As large as -53% negative magnetoresistance has been observed in Ba(Zn(1-2x)MnxCux)2As2, enabling its possible application in memory devices.

  1. Ba(Zn1-2xMnxCux)2As2: A Bulk Form Diluted Ferromagnetic Semiconductor with Mn and Cu Codoping at Zn Sites

    NASA Astrophysics Data System (ADS)

    Man, Huiyuan; Guo, Shengli; Sui, Yu; Guo, Yang; Chen, Bin; Wang, Hangdong; Ding, Cui; Ning, F. L.

    2015-10-01

    We report the synthesis and characterization of a bulk form diluted magnetic semiconductor Ba(Zn1-2xMnxCux)2As2 with the crystal structure identical to that of “122” family iron based superconductors and the antiferromagnet BaMn2As2. No ferromagnetic order occurs with (Zn, Mn) or (Zn, Cu) substitution in the parent compound BaZn2As2. Only when Zn is substituted by both Mn and Cu simultaneously, can the system undergo a ferromagnetic transition below TC ~ 70 K, followed by a magnetic glassy transition at Tf  ~ 35 K. AC susceptibility measurements for Ba(Zn0.75Mn0.125Cu0.125)2As2 reveal that Tf strongly depends on the applied frequency with and a DC magnetic field dependence of , demonstrating that a spin glass transition takes place at Tf. As large as -53% negative magnetoresistance has been observed in Ba(Zn1-2xMnxCux)2As2, enabling its possible application in memory devices.

  2. Magnetic and ferroelectric properties of Zn and Mn co-doped BaTiO3

    NASA Astrophysics Data System (ADS)

    Keshari Das, Sangram; Kumar Roul, Binod

    2015-06-01

    This paper reports an approach to obtaining multiferroic properties in co-doped (Zn:Mn) BaTiO3 near room temperature. Interestingly, an unusual magnetic hysteresis loop is observed in the co-doped compositions in which the central portion of the loop is squeezed. However, in the composition Ba0.9Zn0.1Ti0.9Mn0.1O3, a broad magnetic hysteresis loop is observed. Such a magnetic effect is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system. The observation of the above type of magnetic properties is likely to be due to the presence of exchange interactions between Mn ions. A lossy-type of ferroelectric hysteresis loop is also observed in co-doped ceramic compositions near room temperature. Author S. K. Das supported financially by CSIR, New Delhi (Grant No. 09/750 (0005)/2009-EMR-I).

  3. Luminescence properties of M2Si5N8:Ce3+ (M = Ca, Sr, Ba) mixed nitrides prepared by metal hydrides as starting materials

    NASA Astrophysics Data System (ADS)

    Kuramoto, Daiki; Kim, Hyo Sung; Horikawa, Takashi; Itoh, Masahiro; Machida, Ken-ichi

    2012-08-01

    Mixed metal nitrides, M2Si5N8:Ce3+ (M = Ca, Sr, Ba), were synthesized from M2-yCeySi5 or an appropriate mixture of MSiHx, Si3N4 and CeF3, by a direct nitriding process in N2 gas: 2 MSiHx + Si3N4 + CeF3 → M2Si5N8:Ce3+. Also, charge-compensated materials, M2AlzSi5-zN8:Ce3+ were prepared (from an appropriate mixture of MSiHx, MAlSiHx, Si3N4 and CeF3) and the luminescence properties were characterized. The resultant phosphors showed green emission suitable for LED illumination by optimizing the mixing ratio of metal elements.

  4. ABO3 (A = La, Ba, Sr, K; B = Co, Mn, Fe) perovskites for thermochemical energy storage

    NASA Astrophysics Data System (ADS)

    Babiniec, Sean M.; Coker, Eric N.; Ambrosini, Andrea; Miller, James E.

    2016-05-01

    The use of perovskite oxides as a medium for thermochemical energy storage (TCES) in concentrating solar power systems is reported. The known reduction/oxidation (redox) active perovskites LaxSr1-xCoyMn1-yO3 (LSCM) and LaxSr1-xCoyFe1-yO3 (LSCF) were chosen as a starting point for such research. Materials of the LSCM and LSCF family were previously synthesized, their structure characterized, and thermodynamics reported for TCES operation. Building on this foundation, the reduction onset temperatures are examined for LSCM and LSCF compositions. The reduction extents and onset temperatures are tied to the crystallographic phase and reaction enthalpies. The effect of doping with Ba and K is discussed, and the potential shortcomings of this subset of materials families for TCES are described. The potential for long-term stability of the most promising material is examined through thermogravimetric cycling, scanning electron microscopy, and dilatometry. The stability over 100 cycles (450-1050 °C) of an LSCM composition is demonstrated.

  5. Investigation of the mechanical and degradation properties of Mg-Sr and Mg-Zn-Sr alloys for use as potential biodegradable implant materials.

    PubMed

    Brar, Harpreet S; Wong, Joey; Manuel, Michele V

    2012-03-01

    Magnesium (Mg) has garnered significant interest for its potential use as a biodegradable implant material. Of specific interest in this study is the effect of zinc (Zn) and strontium (Sr) additions on both the mechanical and degradation behaviors in Mg due to their established beneficial effect on strength and microstructural grain refinement while being biocompatible. Three binary Mg-x wt% Sr (x=0.5, 1.0, 1.5) alloys and three ternary Mg-x wt%Zn-0.5 wt% Sr (x=2.0, 4.0, 6.0) were studied to evaluate their mechanical and degradation behavior. Mechanical testing was performed at room temperature on solution-treated and peak aged alloys using microhardness and tensile tests. Degradation was studied using immersion tests in Hanks' solution. Results indicate a decrease in grain size and an increase in strength with increasing Sr and Zn content. When considering degradation behavior Mg-0.5 wt%Sr demonstrated the lowest degradation rate among binary alloys. At constant Sr content at 0.5 wt%, the addition of Zn increased the corrosion rate, with the highest rate for the Mg-6.0 wt%Zn-0.5 wt%Sr. The alloys which best optimized both mechanical and degradation behaviors were Mg-2.0 wt%Zn-0.5 wt%Sr and Mg-4.0 wt%Zn-0.5 wt%Sr. Finally, microstructure and property relationships were evaluated and discussed in reference to each alloy's potential use as a biodegradable implant material.

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

    DOE PAGESBeta

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

    2015-09-24

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

  7. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

    PubMed Central

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

    2016-01-01

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis. PMID:26907515

  8. Addition of Zn to the ternary Mg-Ca-Sr alloys significantly improves their antibacterial property

    PubMed Central

    He, Guanping; Wu, Yuanhao; Zhang, Yu; Zhu, Ye; Liu, Yang; Li, Nan; Li, Mei; Zheng, Guan; He, Baohua; Yin, Qingshui; Zheng, Yufeng; Mao, Chuanbin

    2015-01-01

    Most of the magnesium (Mg) alloys possess excellent biocompatibility, mechanical property and biodegradability in orthopedic applications. However, these alloys may suffer from bacterial infections due to their insufficient antibacterial capability. In order to reduce the post-surgical infections, a series of biocompatible Mg–1Ca-0.5Sr-xZn (x=0, 2, 4, 6) alloys were fabricated with the addition of antibacterial Zn with variable content and evaluated in terms of their biocompatibility and antibacterial property. The in vitro corrosion study showed that Mg-1Ca-0.5Sr-6Zn alloys exhibited a higher hydrogen evolution volume after 100 h immersion and resulted in a higher pH value of the immersion solution. Our work indicated that Zn-containing Mg alloys exhibited good biocompatibility with high cell viability. The antibacterial studies reveal that the number of bacteria adhered on all of these Mg alloy samples diminished remarkably compared to the Ti-6Al-4V control group. We also found that the proliferation of the bacteria was inhibited by these Mg alloys extracts. Among the prepared alloys, Mg-1Ca-0.5Sr-6Zn alloy not only exhibited a strong antibacterial effect, but also promoted the proliferation of MC3T3-E1 osteoblasts, suggesting that it is a promising alloy with both good antibacterial property and good biocompatibility for use as an orthopedic implant. PMID:26693010

  9. Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

    NASA Astrophysics Data System (ADS)

    Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

    2016-02-01

    In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

  10. Sol-gel preparation and luminescent properties of red-emitting phosphor Sr-Ba-Mo-W-O-(Eu(3+),Sm(3+)).

    PubMed

    Li, Fei; Xie, Huidong; Xi, Haihong; Wang, Xiaochang

    2016-02-01

    Two series of red-emitting phosphors Sr-Ba-Mo-W-O:Eu,Sm and Sr-Ba-Mo-W-O:Eu have been synthesized by a sol-gel method. The effects of the chemical composition, concentrations of Sm(3+) and Eu(3+), the Sr(2+)/Ba(2+) ratio, and the W(6+)/Mo(6+) ratio on the luminescent properties were investigated. The as-prepared phosphors were characterized by X-ray diffraction and Raman spectra. Results showed that single phases of the two series were prepared. The compositions of Sr0.6 Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 had the strongest luminescent intensity. The excitation spectra of Sm(3+), Eu(3+) co-doped phosphors were broader and the strongest peak moved to 404 nm when compared with that of Eu(3+) single-doped phosphors. The luminescent intensity of the Sr0.6Ba0.13Mo0.8W0.2O4:Eu0.10 Sm0.08 at 618 nm were 2.8 times greater than that of Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10. The luminescent intensity of Sr0.6Ba0.13Mo0.8 W0.2 O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8W0.2O4:Eu0.10 at 150 °C decreased to 56.8% and 50.3% of the initial value at room temperature, respectively.

  11. Electrophoretic Deposition of Chitosan/45S5 Bioactive Glass Composite Coatings Doped with Zn and Sr

    PubMed Central

    Miola, Marta; Verné, Enrica; Ciraldo, Francesca Elisa; Cordero-Arias, Luis; Boccaccini, Aldo R.

    2015-01-01

    In this research work, the original 45S5 bioactive glass was modified by introducing zinc and/or strontium oxide (6 mol%) in place of calcium oxide. Sr was added for its ability to stimulate bone formation and Zn for its role in bone metabolism, antibacterial properties, and anti-inflammatory effect. The glasses were produced by means of melting and quenching process. SEM and XRD analyses evidenced that Zr and Sr introduction did not modify the glass structure and morphology while compositional analysis (EDS) demonstrated the effective incorporation of these elements in the glass network. Bioactivity test in simulated body fluid (SBF) up to 1 month evidenced a reduced bioactivity kinetics for Zn-doped glasses. Doped glasses were combined with chitosan to produce organic/inorganic composite coatings on stainless steel AISI 316L by electrophoretic deposition (EPD). Two EPD processes were considered for coating development, namely direct current EPD (DC-EPD) and alternating current EPD (AC-EPD). The stability of the suspension was analyzed and the deposition parameters were optimized. Tape and bending tests demonstrated a good coating-substrate adhesion for coatings containing 45S5-Sr and 45S5-ZnSr glasses, whereas the adhesion to the substrate decreased by using 45S5-Zn glass. FTIR analyses demonstrated the composite nature of coatings and SEM observations indicated that glass particles were well integrated in the polymeric matrix, the coatings were fairly homogeneous and free of cracks; moreover, the AC-EPD technique provided better results than DC-EPD in terms of coating quality. SEM, XRD analyses, and Raman spectroscopy, performed after bioactivity test in SBF solution, confirmed the bioactive behavior of 45S5-Sr-containing coating while coatings containing Zn exhibited no hydroxyapatite formation. PMID:26539431

  12. Electrophoretic Deposition of Chitosan/45S5 Bioactive Glass Composite Coatings Doped with Zn and Sr.

    PubMed

    Miola, Marta; Verné, Enrica; Ciraldo, Francesca Elisa; Cordero-Arias, Luis; Boccaccini, Aldo R

    2015-01-01

    In this research work, the original 45S5 bioactive glass was modified by introducing zinc and/or strontium oxide (6 mol%) in place of calcium oxide. Sr was added for its ability to stimulate bone formation and Zn for its role in bone metabolism, antibacterial properties, and anti-inflammatory effect. The glasses were produced by means of melting and quenching process. SEM and XRD analyses evidenced that Zr and Sr introduction did not modify the glass structure and morphology while compositional analysis (EDS) demonstrated the effective incorporation of these elements in the glass network. Bioactivity test in simulated body fluid (SBF) up to 1 month evidenced a reduced bioactivity kinetics for Zn-doped glasses. Doped glasses were combined with chitosan to produce organic/inorganic composite coatings on stainless steel AISI 316L by electrophoretic deposition (EPD). Two EPD processes were considered for coating development, namely direct current EPD (DC-EPD) and alternating current EPD (AC-EPD). The stability of the suspension was analyzed and the deposition parameters were optimized. Tape and bending tests demonstrated a good coating-substrate adhesion for coatings containing 45S5-Sr and 45S5-ZnSr glasses, whereas the adhesion to the substrate decreased by using 45S5-Zn glass. FTIR analyses demonstrated the composite nature of coatings and SEM observations indicated that glass particles were well integrated in the polymeric matrix, the coatings were fairly homogeneous and free of cracks; moreover, the AC-EPD technique provided better results than DC-EPD in terms of coating quality. SEM, XRD analyses, and Raman spectroscopy, performed after bioactivity test in SBF solution, confirmed the bioactive behavior of 45S5-Sr-containing coating while coatings containing Zn exhibited no hydroxyapatite formation. PMID:26539431

  13. Growth, structure and optical properties of nonlinear optical crystal BaZnBO3F

    NASA Astrophysics Data System (ADS)

    Xia, Mingjun; Li, R. K.

    2016-01-01

    Nonlinear optical (NLO) crystal BaZnBO3F (BZBF) with the size of about 20×20×0.5 mm3 is obtained from BaF2-NaF flux, and single crystal X-ray diffraction reveals that it belongs to space group P 6 ̅ with cell parameters of a=5.1045(6) Å, c=4.3116(10) Å and Z=1. In the structure of BZBF, the BO3 planar triangles are interconnected through O atoms from ZnO3F2 trigonal bipyramid to form (Zn3B3O6F6) twelve-membered rings (12-MRs), then the layers which are built with condensation from 12-MRs at ab plane, are further linked by the apical F from ZnO3F2 to form three dimensional framework along the c direction. The title crystal exhibits high transmittance in the range of 300-3000 nm with a UV transmission cutoff at 223 nm according to transmission spectra. Powder SHG tests indicate that the effective NLO coefficient of BZBF crystal is about 2.8 times that of KH2PO4 (KDP) crystal due to perfect alignment of the BO3 groups.

  14. The new barium zinc mercurides Ba{sub 3}ZnHg{sub 10} and BaZn{sub 0.6}Hg{sub 3.4} - Synthesis, crystal and electronic structure

    SciTech Connect

    Schwarz, Michael; Wendorff, Marco; Roehr, Caroline

    2012-12-15

    The title compounds Ba{sub 3}ZnHg{sub 10} and BaZn{sub 0.6}Hg{sub 3.4} were synthesized from stoichiometric ratios of the elements in Ta crucibles. Their crystal structures, which both represent new structure types, have been determined using single crystal X-ray data. The structure of Ba{sub 3}ZnHg{sub 10} (orthorhombic, oP28, space group Pmmn, a=701.2(3), b=1706.9(8), c=627.3(3)pm, Z=2, R1=0.0657) contains folded 4{sup 4} Hg nets, where the meshes form the bases of flat rectangular pyramids resembling the structure of BaAl{sub 4}. The flat pyramids are connected via Hg-Zn/Hg bonds, leaving large channels at the folds, in which Ba(1) and Hg(2) atoms alternate. Whereas the remaining Hg/Zn atoms form a covalent 3D network of three- to five-bonded atoms with short M-M distances (273-301 pm; CN 9-11), the Hg(2) atoms in the channels adopt a comparatively large coordination number of 12 and increased distances (317-348 pm) to their Zn/Hg neighbours. In the structure of BaZn{sub 0.6}Hg{sub 3.4} (cubic, cI320, space group I4{sup Macron }3d, a=2025.50(7) pm, Z=64, R1=0.0440), with a chemical composition not much different from that of Ba{sub 3}ZnHg{sub 10}, the Zn/Hg atoms of the mixed positions M(1/2) are arranged in an slightly distorted primitive cubic lattice with a 4 Multiplication-Sign 4 Multiplication-Sign 4 subcell relation to the unit cell. The 24 of the originating 64 cubes contain planar cis tetramers Hg(5,6){sub 4} with Hg in a nearly trigonal planar or tetrahedral coordination. In another 24 of the small cubes, two opposing faces are decorated by Hg(3,4){sub 2} dumbbells, two by Ba(2) atoms respectively. The third type of small cubes are centered by Ba(1) atoms only. The complex 3D polyanionic Hg/Zn network thus formed is compared with the Hg partial structure in Rb{sub 3}Hg{sub 20} applying a group-subgroup relation. Despite their different overall structures, the connectivity of the negatively charged Hg atoms, the rather metallic Zn bonding characteristic

  15. Halide Free M(BH4)2 (M = Sr, Ba, and Eu) Synthesis, Structure, and Decomposition.

    PubMed

    Sharma, Manish; Didelot, Emilie; Spyratou, Alexandra; Lawson Daku, Latévi Max; Černý, Radovan; Hagemann, Hans

    2016-07-18

    Borohydrides have attained high interest in the past few years due to their high volumetric and gravimetric hydrogen content. Synthesis of di/trimetallic borohydride is a way to alter the thermodynamics of hydrogen release from borohydrides. Previously reported preparations of M(BH4)2 involved chloride containing species such as SrCl2. The presence of residual chloride (or other halide) ions in borohydrides may change their thermodynamic behavior and their decomposition pathway. Pure monometallic borohydrides are needed to study decomposition products without interference from halide impurities. They can also be used as precursors for synthesizing di/trimetallic borohydrides. In this paper we present a way to synthesize halide free alkaline earth metal (Sr, Ba) and europium borohydrides starting with the respective hydrides as precursors. Two novel high temperature polymorphs of Sr and Eu borohydrides and four polymorphs of Ba borohydride have been characterized by synchrotron X-ray powder diffraction, thermal analysis, and Raman and infrared spectroscopy and supported by periodic DFT calculations. The decomposition routes of these borohydrides have also been investigated. In the case of the decomposition of strontium and europium borohydrides, the metal borohydride hydride (M(BH4)H3, M = Sr, Eu) is observed and characterized. Periodic DFT calculations performed on room temperature Ba(BH4)2 revealed the presence of bidentate and tridentate borohydrides. PMID:27351948

  16. Optical anisotropy and dielectric parameters of (Ba0.5Sr0.5)Nb2O6 films on a Pt(111)/Si(001) substrate

    NASA Astrophysics Data System (ADS)

    Kovtun, A. P.; Zinchenko, S. P.; Pavlenko, A. V.; Tolmachev, G. N.

    2016-06-01

    (Ba0.5Sr0.5)Nb2O6 films were synthesized on a Pt(111)/Si(001) substrate by RF gas-discharge sputtering in pure oxygen atmosphere. It was found that the films have a dominant crystallographic orientation in the [001] direction and natural unipolarity, which was revealed through analysis of dielectric and piezoelectric parameters. It was demonstrated that the optical parameters of film material in the Ba0.5Sr0.5, Nb2O6/Pt(111)/Si(001) heterostructure match those typical for a (Ba0.5Sr0.5)Nb2O6 single crystal.

  17. Superconducting and normal-state properties of APd2As2 (A = Ca, Sr, Ba) single crystals

    NASA Astrophysics Data System (ADS)

    Anand, V. K.; Kim, H.; Tanatar, M. A.; Prozorov, R.; Johnston, D. C.

    2013-06-01

    The synthesis and crystallography, magnetic susceptibility χ, magnetization M, specific heat Cp, in-plane electrical resistivity ρ, and in-plane magnetic penetration depth measurements are reported for single crystals of APd2As2 (A = Ca, Sr, Ba) versus temperature T and magnetic field H. The crystals were grown using PdAs self-flux. CaPd2As2 and SrPd2As2 crystallize in a collapsed body-centered tetragonal ThCr2Si2-type structure (I4/mmm), whereas BaPd2As2 crystallizes in the primitive tetragonal CeMg2Si2-type structure (P4/mmm), in agreement with literature data. The ρ(T) data exhibit metallic behavior for all three compounds. Bulk superconductivity is reported for CaPd2As2 and SrPd2As2 below Tc=1.27 and 0.92 K, respectively, whereas only a trace of superconductivity is found in BaPd2As2. No other phase transitions were observed. The χ(T) and M(H) data reveal anisotropic diamagnetism in the normal state, with χc>χab for CaPd2As2 and BaPd2As2, and χc<χab for SrPd2As2. The normal and superconducting state data indicate that CaPd2As2 and SrPd2As2 are conventional type-II nodeless s-wave electron-phonon superconductors. The electronic superconducting state heat capacity data for CaPd2As2, which has an extremely sharp heat capacity jump at Tc, are analyzed using our recent elaboration of the α-model of the BCS theory of superconductivity, which indicates that the s-wave gap in this compound is anisotropic in momentum space.

  18. Microstructural and thermal properties of pure BaFe12O19 and Sr doped barium ferrite (Ba0.9Sr0.1Fe12O19) synthesized by auto combustion method

    NASA Astrophysics Data System (ADS)

    Taufeeq, Saba; Parveen, Azra; Agrawal, Shraddha; Azam, Ameer

    2016-05-01

    Nanoparticles (NPs) of Pure BaFe12O19 and Strontium doped Barium Ferrite (Ba0.9Sr0.1Fe12O19) have been successfully synthesized by Auto combustion method using citric acid as a chelating agent and calcined at 450°C for 3 hrs and 850°C for 4 hrs. Microstructural studies were carried by XRD and SEM techniques. Structural studies suggest that the crystal system remains hexagonal even with the doping of Strontium. The XRD analysis confirms the formation of the structures in the nanometer regime and the peaks are the evidence of the crystalline phase. The SEM images shows the morphology of surface of the samples. The thermal property studied by TGA shows the weight loss which is with varying the temperature and weight loss also varies with Sr doping. The TGA analysis exhibits the loss of weight at different temperatures.

  19. Determining Solute Sources and Water Flowpaths in a Forested Headwater Catchment: Advances With the Ca-Sr-Ba Multi-tracer

    NASA Astrophysics Data System (ADS)

    Bullen, T. D.; Bailey, S. W.; McGuire, K. J.; Zimmer, M. A.; Ross, D. S.

    2011-12-01

    Determining solute sources and water flowpaths in catchments is of critical importance to development of models that effectively describe catchment function. For solutes in soil water and stream water, simple mass balance models that compare precipitation input to catchment outlet compositions can predict average mineral weathering contributions for the catchment as a whole, but fail to provide information about either variability of contributions from different portions of the catchment and different soil depths or processes such as ion exchange and biological cycling. In order to better understand how forested headwater catchments function, we are interpreting concentration and isotope ratios of the alkaline earth elements Ca, Sr and Ba in streamwater, groundwater, the soil ion exchange pool and plants in a hydropedologic context at the 41 hectare hydrologic reference catchment (Watershed 3) at the Hubbard Brook Experimental Forest, New Hampshire, USA. This forested headwater catchment consists of a beech-birch-maple-spruce forest growing on vertically- and laterally-developed Spodosols and Inceptisols formed on granitoid glacial till that mantles Paleozoic metamorphic bedrock. Across the watershed in terms of the soil ion exchange pool, the forest floor has high Sr/Ba and Ca/Sr ratios, mineral soils have intermediate Sr/Ba and low Ca/Sr, and relatively unweathered till in the C horizon has low Sr/Ba and high Ca/Sr. Waters moving through these various compartments will obtain Sr/Ba and Ca/Sr ratios reflecting these characteristics, and thus variations of Sr/Ba and Ca/Sr of streamwater provide evidence of the depth of water flowpaths feeding the streams. 87Sr/86Sr of exchangeable Sr spans a broad range from 0.715 to 0.725, with highest values along the mid-to upper flanks of the catchment and lowest values in a broad zone along the central axis of the catchment associated with numerous groundwater seeps. Thus, variations of 87Sr/86Sr in streamwater provide

  20. Structural and magnetic properties of Ni-Zn doped BaM nanocomposite via citrate precursor

    NASA Astrophysics Data System (ADS)

    Rana, Kush; Thakur, Preeti; Tomar, Monika; Gupta, Vinay; Thakur, Atul

    2016-05-01

    Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi0.5Zn0.5Fe11O19 was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (Ms), coericivity (Hc) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties make this nanocomposite a suitable candidate for magnetic recording and high frequency applications.

  1. Memristive behaviors in Pt/BaTiO{sub 3}/Nb:SrTiO{sub 3} ferroelectric tunnel junctions

    SciTech Connect

    Wen, Zheng; Wu, Di Li, Aidong

    2014-08-04

    We demonstrate memristive behaviors in Pt/BaTiO{sub 3}/Nb:SrTiO{sub 3} metal/ferroelectric/semiconductor ferroelectric tunnel junctions, in which the semiconductor electrode can be switched between the accumulated and the depleted states by polarization reversal in the BaTiO{sub 3} barrier via the ferroelectric field effect. An extra barrier, against electron tunneling, forms in the depleted region of the Nb:SrTiO{sub 3} electrode surface, which together with the ferroelectric barrier itself modulate the tunneling resistance with the change of effective polarization. Continuous resistance modulation over four orders of magnitude is hence achieved by application of programmed voltage pulses with different polarity, amplitude, and repetition numbers, as a result of the development of the extra barrier.

  2. Protonic Conduction of BaCe0.85YO. 1503 Doped with SrTiO3

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.; Sayir, Ali

    2005-01-01

    Reformers based on ceramic membrane technology potentially offer hydrogen production that is comparable to the cost of fossil fuels. Protonic conducting ceramic with the chemical formula AB03 offers the promise of highly selective hydrogen separation at intermediate temperature (400-800 C). Among different perovskite-type oxides, BaCe03 and SrCe03 based compositions show high protonic conductivities but strong resistance to densification. X-ray diffraction studies on sintered specimens of BaCe0.85Y0.1503-6 show multi-phase formation which was found to show dependence upon powder synthesis method. Doping with SrTiO3 suppresses multi-phase formation and enhances grain growth. Conductivity measurements in temperature range of 200 to 1000 C were performed by ac impedance spectroscopy under dry and wet conditions. Sintering behavior, phase formation and conductivity results will be reported.

  3. Migration behaviour of twaite shad Alosa fallax assessed by otolith Sr:Ca and Ba:Ca profiles.

    PubMed

    Magath, V; Marohn, L; Fietzke, J; Frische, M; Thiel, R; Dierking, J

    2013-06-01

    Individual migration behaviour during the juvenile and adult life phase of the anadromous twaite shad Alosa fallax in the Elbe estuary was examined using otolith Sr:Ca and Ba:Ca profiles. Between hatching and the end of the first year of life, juveniles showed two migration patterns. Pattern one exhibited a single downstream migration from fresh water to the sea with no return into fresh water. In contrast, pattern two showed a first migration into the sea, then a return into fresh water and, finally, a second downstream migration into marine water. This first report of migration plasticity for A. fallax points to different exposure times to estuarine threats depending on the migration strategy. In adults, high Sr:Ca and low Ba:Ca in the majority of individuals confirmed prior reports of a primarily marine habitat use. Patterns reflecting spawning migrations were rarely observed on otoliths, possibly due to the short duration of visits to fresh water.

  4. Preparation of Highly Oriented Transparent (Sr,Ba)Nb2O6 Ceramics and Their Ferroelectric Properties

    NASA Astrophysics Data System (ADS)

    Kubota, Teppei; Tanaka, Nobuhiko; Kageyama, Keisuke; Takagi, Hiroshi; Sakabe, Yukio; Suzuki, Tohru S.; Sakka, Yoshio

    2009-03-01

    Highly oriented transparent (Sr,Ba)Nb2O6 (SBN) ceramics were prepared to obtain excellent electrooptic properties and a high spontaneous polarization, such as those observed in a Sr0.75Ba0.25Nb2O6 (SBN75) single crystal. As a result of slip casting at a high magnetic field of 12 T and firing at 1460 °C for 48 h in an oxygen atmosphere, highly oriented ceramics and strong ferroelectric properties were observed. The spontaneous polarization of highly oriented SBN ceramics was above 15 µC/cm2, which was close to that of the SBN75 single crystal (17 µC/cm2).

  5. Ba0.9Sr0.1TiO3-based optical microcavities fabricated by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Hong, X. K.; Hu, G. J.; Shang, J. L.; Bao, J.; Chu, J. H.; Dai, N.

    2007-06-01

    Single or coupled optical microcavities have been prepared by inserting one or two dense Ba0.9Sr0.1TiO3 layers, respectively, in the quasiperiodic Ba0.9Sr0.1TiO3 multilayers fabricated based on phase separation. The single microcavities exhibit well-defined resonant modes in the investigated wavelength range with a quality factor no less than 60. The resonant frequency of the mode can be tuned through varying the spinning rate during the spin-coating process to change the thickness of the inserted layer. The mode properties of the coupled microcavities strongly depend on the mismatch parameter of the inserted defect layers. The approach reported here offers a simple, inexpensive, and flexible route for fabricating high quality microcavities.

  6. DIELECTRIC PROPERTIES OF BA(0.6)SR(0.4)TiO(3) THIN FILMS WITH VARIOUS STRAIN STATES

    SciTech Connect

    B. PARK; E. PETERSON; ET AL

    2001-04-01

    We could systematically control the strain states of a Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} film by depositing a very thin Ba{sub 1{minus}x}Sr{sub x}TiO{sub 3} interlayer between the main layer of the Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} and a MgO(001) substrate. Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} films showed very strong dependence of dielectric properties on the strain states. The strain induced by the MgO substrate was relaxed faster than that induced by an interlayer.

  7. SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} - two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    SciTech Connect

    Stegmaier, Saskia; Faessler, Thomas F.

    2012-08-15

    SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn{sub 2}Sn{sub 2} comprises (anti-)PbO-like {l_brace}ZnSn{sub 4/4}{r_brace} and {l_brace}SnZn{sub 4/4}{r_brace} layers. Ca{sub 2}Zn{sub 3}Sn{sub 6} shows similar {l_brace}ZnSn{sub 4/4}{r_brace} layers and {l_brace}Sn{sub 4}Zn{r_brace} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn{sub 2}Sn{sub 2} adopts the SrPd{sub 2}Bi{sub 2} structure type, and Ca{sub 2}Zn{sub 3}Sn{sub 6} is isotypic to the R{sub 2}Zn{sub 3}Ge{sub 6} compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {l_brace}Sn{sub 4}Zn{r_brace} layers of Ca{sub 2}Zn{sub 3}Sn{sub 6}. - Graphical abstract: Crystal structures of the new Ae-Zn-Sn polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Highlights: Black-Right-Pointing-Pointer New polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Black-Right-Pointing-Pointer Obtained by high temperature reactions of the elements. Black-Right-Pointing-Pointer Single crystal XRD structure determination and DFT electronic structure calculations. Black-Right-Pointing-Pointer Closely related crystal and electronic structures. Black-Right-Pointing-Pointer Metallic conductivity coexisting with lone pairs and covalent bonding

  8. Electric Properties of [(BaO)1.00(XO)x](Ti0.95Zr0.05)O2 (X = Ca, Sr, Ba) Ceramics Fired under Reduced Atmosphere

    NASA Astrophysics Data System (ADS)

    Sakai, Yuichi; Futakuchi, Tomoaki; Adachi, Masatoshi

    2009-09-01

    Ba(Ti0.95Zr0.05)O3 doped with CaO, SrO, or BaO was investigated in order to develop materials suitable for lead-free actuators with resistance to reduction. The grain sizes of [(BaO)1.00(XO)x](Ti0.95Zr0.05)O2 (X = Ca, Sr, Ba; x = 0-0.05) ceramics decreased with increasing amount of dopant concentration x. The grain sizes of the ceramics with a dopant concentration x in the range of 0.005 to 0.05 are approximately 1-2 µm. The crystalline phases of the ceramics with a dopant concentration x = 0.01 or less were perovskite single phases. CaO, SrO, or BaO doping concentrations of x = 0.005 or more were effective for preventing the reduction of Ba(Ti0.95Zr0.05)O3 during firing under 3% H2-N2 atmosphere. The remanent polarizations and dynamic piezoelectric constants of the ceramics decreased with increasing dopant concentration of CaO, SrO, or BaO. The dynamic piezoelectric constant of the ceramics with BaO dopant concentration x of 0.005 was approximately 640 pm/V. The Curie temperature was approximately 109 °C in this composition.

  9. 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

  10. Dielectric properties of Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5)O3 solid solutions.

    PubMed

    Xu, Yebin; Liu, Ting; He, Yanyan; Yuan, Xiao

    2008-11-01

    Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) solid solutions are prepared by a solid-state reaction method, and their dielectric and tunable characteristics are investigated. The solid solutions with cubic perovskite structures are obtained for compositions of 10-50 mol% Sr(Ga(0.5)Ta(0.5))O(3). It is observed that the addition of Sr(Ga(0.5)Ta(0.5))O(3) into Ba(0.6)Sr(0.4)TiO(3) causes a shift in the phase transition peak to a lower temperature. Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) solid solutions exhibit depressed and broadened phase transition peaks, resulting in decreased dielectric constants and dielectric losses at room temperature. With the increase of Sr(Ga(0.5)Ta(0.5))O(3) content, the dielectric constant, loss tangent, and tunability are decreased. 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1Sr(Ga(0.5)Ta(0.5))O(3) has a dielectric constant epsilon = 534 and a tunability of 16% at 100 kHz under 2.63 kV/mm. The dielectric characteristics of Ba(0.6)Sr(0.4)TiO(3)-Sr(Ga(0.5)Ta(0.5))O(3) ceramics at microwave frequencies are also evaluated.

  11. Autocatalytic model of oscillatory zoning in experimentally grown (Ba,Sr)SO4 solid solution.

    PubMed

    Katsev, Sergei; L'Heureux, Ivan

    2002-12-01

    Oscillatory zoning (OZ) is a phenomenon common to many natural minerals whereby the mineral composition varies more or less regularly from the core of the crystal to its rim. Oscillatory zoned barite-celestite (Ba,Sr)SO4 crystals are one of the very few examples of the OZ phenomenon that were obtained under controlled laboratory conditions. It is known that such crystals can be synthesized by precipitation from an aqueous solution during counterdiffusion in a gel column connecting two reservoirs. We present here a model of oscillatory zoning in such a binary solid solution grown from an aqueous solution. By expanding on a previously suggested model, we obtain oscillatory dynamical solutions for two limit cases: the growth of a flat crystal face and the growth of a spherical crystallite. We consider an autocatalytic dependence between the crystal growth rate and the crystal surface composition. The oscillatory patterns then arise as a kinetic effect due to the coupling between the diffusion field around the crystal and the fast crystal growth under far-from-equilibrium conditions. The effects of fluctuations in the aqueous solution concentrations are also considered. It is shown that they may lead to noisy oscillatory patterns.

  12. Autocatalytic model of oscillatory zoning in experimentally grown (Ba,Sr)SO4 solid solution

    NASA Astrophysics Data System (ADS)

    Katsev, Sergei; L'Heureux, Ivan

    2002-12-01

    Oscillatory zoning (OZ) is a phenomenon common to many natural minerals whereby the mineral composition varies more or less regularly from the core of the crystal to its rim. Oscillatory zoned barite-celestite (Ba,Sr)SO4 crystals are one of the very few examples of the OZ phenomenon that were obtained under controlled laboratory conditions. It is known that such crystals can be synthesized by precipitation from an aqueous solution during counterdiffusion in a gel column connecting two reservoirs. We present here a model of oscillatory zoning in such a binary solid solution grown from an aqueous solution. By expanding on a previously suggested model, we obtain oscillatory dynamical solutions for two limit cases: the growth of a flat crystal face and the growth of a spherical crystallite. We consider an autocatalytic dependence between the crystal growth rate and the crystal surface composition. The oscillatory patterns then arise as a kinetic effect due to the coupling between the diffusion field around the crystal and the fast crystal growth under far-from-equilibrium conditions. The effects of fluctuations in the aqueous solution concentrations are also considered. It is shown that they may lead to noisy oscillatory patterns.

  13. 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

  14. Preparation of (Ba,Sr)TiO3 Thick Films with Ni Electrodes by Screen Printing

    NASA Astrophysics Data System (ADS)

    Sakai, Yuichi; Kakuda, Tatsunori; Futakuchi, Tomoaki; Adachi, Masatoshi

    2010-09-01

    The effects of doping MgO into (Ba0.6Sr0.4)TiO3 (BST) fired under a reducing atmosphere were investigated in order to prepare BST thick films with Ni electrodes by the screen-printing method. MgO-doped BST thick films fired under a reducing atmosphere showed insulation resistance. Grain growth in the thick films was advanced by MgO doping. The dielectric constant near TC of the bulk ceramics and thick films increased with increasing MgO concentration up to 2 and 10 mol %, respectively. Mg ion substitution to the B-site was also observed up to these concentrations. The tunability and tan δ of thick films with MgO concentrations of 2 and 4 mol % at an electric field of 10 V/µm were approximately 77 and 0.3%, respectively. It is expected that thick films prepared by screen printing will be applicable to tunable devices with Ni electrodes.

  15. 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.

  16. Ultracold magnetically tunable interactions without radiative-charge-transfer losses between Ca+, Sr+, Ba+, and Yb+ ions and Cr atoms

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2015-12-01

    The Ca+, Sr+, Ba+, and Yb+ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. Ab initio techniques are applied to investigate electronic-ground-state properties of the (CaCr)+, (SrCr)+, (BaCr)+, and (YbCr)+ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin-restricted open-shell coupled-cluster method restricted to single, double, and noniterative triple excitations and the multireference configuration-interaction method restricted to single and double excitations are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction coefficients are also reported. Finally, magnetic Feshbach resonances between the Ca+, Sr+, Ba+, and Yb+ ions interacting with the Cr atoms are analyzed. The present proposal opens the way towards robust quantum simulations and computations with ultracold ion-atom systems free of radiative charge-transfer losses.

  17. Interface engineered BaTiO₃/SrTiO₃ heterostructures with optimized high-frequency dielectric properties.

    PubMed

    Liu, Ming; Ma, Chunrui; Collins, Gregory; Liu, Jian; Chen, Chonglin; Dai, Chao; Lin, Yuan; Shui, Li; Xiang, Feng; Wang, Hong; He, Jie; Jiang, Jiechao; Meletis, Efstathios I; Cole, Melanie W

    2012-11-01

    Interface engineered BaTiO₃/SrTiO₃ heterostructures were epitaxially grown on (001) MgO substrates by pulsed laser deposition. Microstructural characterizations by X-ray diffraction and transmission electron microscopy indicate that the as-grown heterostructures are c-axis oriented with sharp interfaces. The interface relationships between the substrate and multilayered structures were determined to be [001](SrTiO₃)//[001](BaTiO₃)//[001](MgO) and (100)(SrTiO₃)//(100)(BaTiO₃)//(100)(MgO). The high-frequency microwave (∼18 GHz) dielectric measurements reveal that the dielectric constant and dielectric loss of the nanolayered heterostructures are highly dependent upon the stacking period numbers and layer thicknesses. With the increase in the periodic number, or the decrease in each layer thickness, the dielectric constant dramatically increases and the dielectric loss tangent rapidly decreases. The strong interface effect were found when the combination period is larger than 16, or each STO layer is less than 6.0 nm. The optimized dielectric performance was achieved with the best value for the loss tangent (0.02) and the dielectric constant (1320), which suggests that the BTO/STO heterostructures be promising for the development of the room-temperature tunable microwave elements.

  18. Electrical and optical properties of SrTiO3 nanopowders: Effect of different dopants Ba and Ag

    NASA Astrophysics Data System (ADS)

    Ghasemifard, Mahdi; Ghamari, Misagh; Iziy, Meysam

    2016-05-01

    Using strontium-titanium salts precursor, nanopowders (STO-based-NPs) were successfully synthesized by controlled gel-combustion method. Citric and nitric acids in an optimum ratio were used as the fuel and oxidizer agents, respectively. After heat treatment at 850∘C, the crystalline structure of the products was investigated by X-ray diffraction. The effects of Ba and Ag dopants on particle size distribution were discussed by transmission electron microscopy (TEM). The optical and dielectric parameters such as energy band gap (Eg), real and imaginary parts of refractive index, dielectric function and energy loss function of nanopowders have been investigated by UV-Vis and FTIR spectra. The band gap of SrTiO3 increased with increasing Ba, Ag and Ba-Ag. Different atomic radii of dopants are responsible for changing optical and dielectric parameters due to the altered orbital configuration of the lattice structure.

  19. Interfacial dislocations in (111) oriented (Ba0.7Sr0.3)TiO3 films on SrTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di; Xin, Huolin L.; Su, Dong

    2015-10-01

    We have investigated the interfacial structure of epitaxial (Ba,Sr)TiO3 films grown on (111)-oriented SrTiO3 single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a⟨110⟩ comprised of a misfit dislocation along ⟨112⟩, and threading dislocations along ⟨110⟩ or ⟨100⟩. The misfit dislocation with Burgers vector of a⟨110⟩ can dissociate into two ½a⟨110⟩ partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba0.7Sr0.3)TiO3 films.

  20. Structural studies of the rhombohedral and orthorhombic monouranates: CaUO4, α-SrUO4, β-SrUO4 and BaUO4

    NASA Astrophysics Data System (ADS)

    Murphy, Gabriel; Kennedy, Brendan J.; Johannessen, Bernt; Kimpton, Justin A.; Avdeev, Maxim; Griffith, Christopher S.; Thorogood, Gordon J.; Zhang, Zhaoming

    2016-05-01

    The structures of some AUO4 (A=Ca, Sr, or Ba) oxides have been determined using a combination of neutron and synchrotron X-ray diffraction, supported by X-ray absorption spectroscopic measurements at the U L3-edge. The smaller Ca cation favours a rhombohedral AUO4 structure with 8-coordinate UO8 moieties whilst an orthorhombic structure based on UO6 groups is found for BaUO4. Both the rhombohedral and orthorhombic structures can be stabilised for SrUO4. The structural studies suggest that the bonding requirements of the A site cation play a significant role in determining which structure is favoured. In the rhombohedral structure, Bond Valence Sums demonstrate the A site is invariably overbonded, which, in the case of rhombohedral α-SrUO4, is compensated for by the formation of vacancies in the oxygen sub-lattice. The uranium cation, with its flexible oxidation state, is able to accommodate this by inducing vacancies along its equatorial coordination site as demonstrated by neutron powder diffraction.

  1. Interfacial dislocations in (111) oriented (Ba0.7Sr0.3)TiO3 films on SrTiO3 single crystal

    DOE PAGESBeta

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di; Xin, Huolin L.; Su, Dong

    2015-10-08

    In this study, we have investigated the interfacial structure of epitaxial (Ba,Sr)TiO3 films grown on (111)-oriented SrTiO3 single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a<110> comprised of a misfit dislocation along <112>, and threading dislocations along <110> or <100>. The misfit dislocation with Burgers vector of a <110> can dissociate into two ½ a <110> partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrievedmore » the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba0.7Sr0.3)TiO3 films.« less

  2. New Family of Materials with Negative Coefficients of Thermal Expansion: The Effect of MgO, CoO, MnO, NiO, or CuO on the Phase Stability and Thermal Expansion of Solid Solution Phases Derived from BaZn2Si2O7.

    PubMed

    Thieme, Christian; Waurischk, Tina; Heitmann, Stephan; Rüssel, Christian

    2016-05-01

    Recently, a silicate with the composition SrxBa1-xZn2Si2O7 was reported, which exhibits a negative coefficient of thermal expansion. The compound BaZn2Si2O7 shows a highly positive coefficient of thermal expansion up to a temperature of 280 °C and then transfers to a high temperature phase, which exhibits a coefficient of thermal expansion near zero or negative over a limited temperature range up to around 500 °C. This high temperature modification can be stabilized to room temperature if Ba(2+) is replaced by Sr(2+). In the solid solution SrxBa1-xZn2Si2O7, also Zn(2+) can be replaced in a wide concentration range by other cations with the respective valency. In the present study, Zn was partially or completely replaced by Mg, Co, Mn, Ni, or Cu. If the high temperature phase is stable at room temperature, the thermal expansion is negative, and if the partial substitution exceeds a certain concentration threshold, the low temperature phase with the crystal structure of BaZn2Si2O7 and highly positive thermal expansion is formed. The lowest mean coefficients of thermal expansion were measured for the composition Ba0.5Sr0.5Zn1.4Co0.6Si2O7 with a value of -2.9 × 10(-6) K(-1). In general, a lower Zn-concentration leads to a higher anisotropy and a lower mean coefficient of thermal expansion. PMID:27062972

  3. New Family of Materials with Negative Coefficients of Thermal Expansion: The Effect of MgO, CoO, MnO, NiO, or CuO on the Phase Stability and Thermal Expansion of Solid Solution Phases Derived from BaZn2Si2O7.

    PubMed

    Thieme, Christian; Waurischk, Tina; Heitmann, Stephan; Rüssel, Christian

    2016-05-01

    Recently, a silicate with the composition SrxBa1-xZn2Si2O7 was reported, which exhibits a negative coefficient of thermal expansion. The compound BaZn2Si2O7 shows a highly positive coefficient of thermal expansion up to a temperature of 280 °C and then transfers to a high temperature phase, which exhibits a coefficient of thermal expansion near zero or negative over a limited temperature range up to around 500 °C. This high temperature modification can be stabilized to room temperature if Ba(2+) is replaced by Sr(2+). In the solid solution SrxBa1-xZn2Si2O7, also Zn(2+) can be replaced in a wide concentration range by other cations with the respective valency. In the present study, Zn was partially or completely replaced by Mg, Co, Mn, Ni, or Cu. If the high temperature phase is stable at room temperature, the thermal expansion is negative, and if the partial substitution exceeds a certain concentration threshold, the low temperature phase with the crystal structure of BaZn2Si2O7 and highly positive thermal expansion is formed. The lowest mean coefficients of thermal expansion were measured for the composition Ba0.5Sr0.5Zn1.4Co0.6Si2O7 with a value of -2.9 × 10(-6) K(-1). In general, a lower Zn-concentration leads to a higher anisotropy and a lower mean coefficient of thermal expansion.

  4. Preparation and characterisation of nanophase Sr, Mg, and Zn substituted hydroxyapatite by aqueous precipitation.

    PubMed

    Cox, Sophie C; Jamshidi, Parastoo; Grover, Liam M; Mallick, Kajal K

    2014-02-01

    Hydroxyapatite (HA) substituted with 2 mol% Sr, 10 mol% Mg, and 2 mol% Zn were precipitated under identical alkaline conditions (pH 11) at 20°C from an aqueous solution. As-synthesised materials were confirmed to be phase pure by XRD and samples prepared in air contained surface adsorbed CO2 as observed by FTIR. SEM studies revealed a globular morphology and agglomeration behaviour, typical of precipitated nHA. EDS spectra confirmed nominal compositions and substitution of Sr, Mg and Zn. At the levels investigated cationic doping was not found to radically influence particle morphology. An indication of the potential in-vivo bioactivity of samples was achieved by analysing samples immersed in SBF for up to 28 days by interferometry and complementary SEM micrographs. Furthermore, a live/dead assay was used and confirmed the viability of seeded MC3T3 osteoblast precursor cells on HA and substituted HA substrates up to 7 days of culture.

  5. Microstructure and dielectric tunable properties of Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composite.

    PubMed

    He, Yanyan; Xu, Yebin; Liu, Ting; Zeng, Chunlian; Chen, Wanping

    2010-07-01

    Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composite ceramics were prepared by a solid-state reaction method and their dielectric tunable characteristics were investigated for the potential application as microwave tunable materials. The addition of Mg(2)SiO(4)-MgO into Ba(0.6)Sr(0.4)TiO(3) forms ferroelectric (Ba(0.6)Sr(0.4)TiO(3))-dielectric (Mg(2)SiO(4)-MgO) composites and shifts the Curie temperature to a lower temperature. The dielectric constant and loss tangent of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)- MgO composites have been decreased and the overall tunability is maintained at a sufficiently high level. The microwave dielectric properties of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)-MgO composites were evaluated. Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composites have tunability of 9.2 to 10.5% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring a low dielectric constant.

  6. Haldane spin state in Y 2Ba(Ni, Zn or Mg)O 5

    NASA Astrophysics Data System (ADS)

    Batlogg, B.; Cheong, S.-W.; Rupp, L. W.

    1994-02-01

    We have identified Y 2BaNiO 5 as a new Haldane state chain compound with a magnetic excitation gap Δ min/k B of 100±5K and Δ min/|J|≈0.3. Single crystal results of χ(T→0) reveal a splitting of the excited magnetic state. The S=1 chains have been severed in a controlled way by the substitution of Zn or Mg for Ni, and the resulting modifications of χ(T) are presented.

  7. 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.

  8. Epitaxial Stabilization of the Perovskite Phase in (Sr(1-x)Ba(x))MnO3 Thin Films.

    PubMed

    Langenberg, Eric; Guzmán, Roger; Maurel, Laura; Martínez de Baños, Lourdes; Morellón, Luis; Ibarra, M Ricardo; Herrero-Martín, Javier; Blasco, Javier; Magén, César; Algarabel, Pedro A; Pardo, José A

    2015-11-01

    A novel mechanism of ferroelectricity driven by off-centering magnetic Mn(4+) ions was proposed in (Sr1-xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1-xBax)MnO3 thin films, 0.2 ≤ x ≤ 0.5, grown by pulsed laser deposition onto (001)-oriented perovskite substrates. X-ray diffraction measurements and scanning transmission electron microscopy reveal that, under appropriate deposition conditions, the perovskite phase is fully stabilized over the nonferroelectric hexagonal phase, despite the latter being increasingly favored on increasing Ba-content. Moreover, we have managed to grow epitaxial coherent cube-on-cube (Sr1-xBax)MnO3 films upon strains ranging from 0% to 4%. Our results become a milestone in further studying perovskite (Sr1-xBax)MnO3 thin films and pave the way for tailoring ferroic and magnetoelectric properties either by strain engineering or Ba-doping. PMID:26462710

  9. Inclusion property of Cs, Sr, and Ba impurities in LiCl crystal formed by layer-melt crystallization

    SciTech Connect

    Choi, Jung-Hoon; Cho, Yung-Zun; Lee, Tae-Kyo; Eun, Hee-Chul; Kim, Jun-Hong; Park, Hwan-Seo; Kim, In-Tae; Park, Geun-Il

    2013-07-01

    Pyroprocessing is one of the promising technologies enabling the recycling of spent nuclear fuels from a commercial light water reactor (LWR). In general, pyroprocessing uses dry molten salts as electrolytes. In particular, LiCl waste salt after pyroprocessing contains highly radioactive I/II group fission products mainly composed of Cs, Sr, and Ba impurities. Therefore, it is beneficial to reuse LiCl salt in the pyroprocessing as an electrolyte for economic and environmental issues. Herein, to understand the inclusion property of impurities within LiCl crystal, the physical properties such as lattice parameter change, bulk modulus, and substitution enthalpy of a LiCl crystal having 0-6 at% Cs{sup +} or Ba{sup 2+} impurities under existence of 1 at% Sr{sup 2+} impurity were calculated via the first-principles density functional theory. The substitution enthalpy of LiCl crystals having 1 at% Sr{sup 2+} showed slightly decreased value than those without Sr{sup 2+} impurity. Therefore, through the substitution enthalpy calculation, it is expected that impurities will be incorporated within LiCl crystal as co-existed form rather than as a single component form. (authors)

  10. Epitaxial Stabilization of the Perovskite Phase in (Sr(1-x)Ba(x))MnO3 Thin Films.

    PubMed

    Langenberg, Eric; Guzmán, Roger; Maurel, Laura; Martínez de Baños, Lourdes; Morellón, Luis; Ibarra, M Ricardo; Herrero-Martín, Javier; Blasco, Javier; Magén, César; Algarabel, Pedro A; Pardo, José A

    2015-11-01

    A novel mechanism of ferroelectricity driven by off-centering magnetic Mn(4+) ions was proposed in (Sr1-xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1-xBax)MnO3 thin films, 0.2 ≤ x ≤ 0.5, grown by pulsed laser deposition onto (001)-oriented perovskite substrates. X-ray diffraction measurements and scanning transmission electron microscopy reveal that, under appropriate deposition conditions, the perovskite phase is fully stabilized over the nonferroelectric hexagonal phase, despite the latter being increasingly favored on increasing Ba-content. Moreover, we have managed to grow epitaxial coherent cube-on-cube (Sr1-xBax)MnO3 films upon strains ranging from 0% to 4%. Our results become a milestone in further studying perovskite (Sr1-xBax)MnO3 thin films and pave the way for tailoring ferroic and magnetoelectric properties either by strain engineering or Ba-doping.

  11. Is otolith microchemistry (Sr: Ca and Ba:Ca ratios) useful to identify Mugil curema populations in the southeastern Caribbean Sea?

    PubMed

    Avigliano, E; Callicó-Fortunato, R; Buitrago, J; Volpedo, A V

    2015-11-01

    The aim of the present study was to evaluate the potential use of otolith microchemistry (Sr:Ca and Ba:Ca ratios) to identify silver mullet, Mugil curema, populations in Southeastern Caribbean Sea. Fish samples were collected in 7 areas of Nueva Esparta State (Venezuela). The otolith Sr:Ca and Ba:Ca ratios and water Sr:Ca were determined (by ICP-OES and EDTA volumetric method). Otoliths Sr:Ca and Ba:Ca ratios and Sr:Ca partition coefficient of mullets in Cubagua island (south of the State) were significantly different from ratios in La Guardia (north of the State). A discriminant analysis of otolith Sr:Ca and Ba:Ca ratios separated Cubagua Island from La Guardia values. These results suggest the existence of different mullet groups in the Southeastern Caribbean Sea. For this, the simultaneous use of Sr:Ca and Ba:Ca ratios could be a potential tool to identify populations in the study area. PMID:26628220

  12. Is otolith microchemistry (Sr: Ca and Ba:Ca ratios) useful to identify Mugil curema populations in the southeastern Caribbean Sea?

    PubMed

    Avigliano, E; Callicó-Fortunato, R; Buitrago, J; Volpedo, A V

    2015-11-01

    The aim of the present study was to evaluate the potential use of otolith microchemistry (Sr:Ca and Ba:Ca ratios) to identify silver mullet, Mugil curema, populations in Southeastern Caribbean Sea. Fish samples were collected in 7 areas of Nueva Esparta State (Venezuela). The otolith Sr:Ca and Ba:Ca ratios and water Sr:Ca were determined (by ICP-OES and EDTA volumetric method). Otoliths Sr:Ca and Ba:Ca ratios and Sr:Ca partition coefficient of mullets in Cubagua island (south of the State) were significantly different from ratios in La Guardia (north of the State). A discriminant analysis of otolith Sr:Ca and Ba:Ca ratios separated Cubagua Island from La Guardia values. These results suggest the existence of different mullet groups in the Southeastern Caribbean Sea. For this, the simultaneous use of Sr:Ca and Ba:Ca ratios could be a potential tool to identify populations in the study area.

  13. 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.

  14. Thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7} (0{<=}x{<=}2) studied by high-temperature X-ray diffraction and dilatometry

    SciTech Connect

    Kerstan, Marita; Mueller, Matthias; Ruessel, Christian

    2012-04-15

    The thermal expansion behavior of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2}Si{sub 2}O{sub 7} is characterized by both high-temperature X-ray diffraction (HT-XRD) and dilatometry. Ba{sub 2}ZnSi{sub 2}O{sub 7} and BaZnSiO{sub 4} show a thermal expansion (100-800 Degree-Sign C) in the range from 8.9 to 10.4 Multiplication-Sign 10{sup -6} K{sup -1}. By contrast, BaZn{sub 2}Si{sub 2}O{sub 7} has a much higher thermal expansion in the low-temperature modification and shows a phase transition at 280 Degree-Sign C which runs parallel with a steep increase in cell volume. This phase transition is also observed in the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}, but it is shifted to higher temperatures and to a smaller volume change with increasing Mg{sup 2+} concentration. This solid solution series is characterized by dilatometry, X-ray diffraction and differential scanning calorimetry. An adjustment of the MgO/ZnO-ratio enables the preparation of materials with a large variety of thermal expansions. - Graphical abstract: XRD-patterns of Ba{sub 2}ZnSi{sub 2}O{sub 7} were recorded at different temperatures (left). For each XRD-pattern a Rietveld-refinement was performed, the image in the middle shows the XRD-pattern measured at room temperature (circles), the Rietveld calculation (red line) and the difference between them (blue line). The lattice parameters derived hereof were plottet against the temperature and fitted to a polynomial (right picture). From those polynomials the lattice expansion was calculated. Highlights: Black-Right-Pointing-Pointer We examined the thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Thermal expansions were determined by dilatometry and high-temperature X-ray diffraction. Black-Right-Pointing-Pointer High-temperature X-ray diffraction enabled to determine anisotropic thermal expansion. Black-Right-Pointing-Pointer BaZn

  15. Zn and Sr incorporated 64S bioglasses: Material characterization, in-vitro bioactivity and mesenchymal stem cell responses.

    PubMed

    Wu, Xiaoli; Meng, Guolong; Wang, Shanling; Wu, Fang; Huang, Wanxia; Gu, Zhongwei

    2015-01-01

    Essential element like Zn or Sr is known to play an important role in bone remodeling process. In this study, we have used the sol-gel process to synthesize the Zn (2%) and Sr (5%) doped 64S bioglasses (BGs, 64SiO2-5P2O5-31CaO, mol.%), alone and co-doped. The synthesized glasses were characterized by XRD, FTIR and STEM. For biological evaluation, the effects of Zn and Sr incorporation on the in vitro bioactivity of the synthesized BGs were studied using the simulated body fluid (SBF) soaking. The proliferation and differentiation (ALP, OCN) of rat mesenchymal stem cells (MSCs) on these BGs were studied using CCK-8 and ELISA analyses. The results indicated that Zn had been uniformly incorporated into the bioglass, and demonstrated a stimulating effect on apatite-like layer formation, MSC proliferation and differentiation. On the other hand, most of Sr appeared to form a secondary crystal phase with extremely high solubility in SBF, showing an enhancing effect only in MSC differentiation but not in proliferation, as well as an inhibitory effect on apatite-like layer formation. The different dissolution behaviors of Sr and Zn ions seemed to have a strong correlation with the different apatite-like layer formation capabilities and the cellular responses of Zn and Sr containing BGs. PMID:25953564

  16. Trigonal Cu2-II-Sn-VI4 (II = Ba, Sr and VI = S, Se) quaternary compounds for earth-abundant photovoltaics.

    PubMed

    Hong, Feng; Lin, Wenjun; Meng, Weiwei; Yan, Yanfa

    2016-02-14

    We propose trigonal Cu2-II-Sn-VI4 (II = Ba, Sr and VI = S, Se) quaternary compounds for earth-abundant solar cell applications. Through density functional theory calculations, we show that these compounds exhibit similar electronic and optical properties to kesterite Cu2ZnSnS4 (CZTS): high optical absorption with band gaps suitable for efficient single-junction solar cell applications. However, the trigonal Cu2-II-Sn-VI4 compounds exhibit defect properties more suitable for photovoltaic applications than those of CZTS. In CZTS, the dominant defects are the deep acceptors, Cu substitutions on Zn sites, which cause non-radiative recombination and limit the open-circuit voltages of CZTS solar cells. On the contrary, the dominant defects in trigonal Cu2-II-Sn-VI4 are the shallow acceptors, Cu vacancies, similar to those in CuInSe2. Our results suggest that the trigonal Cu2-II-Sn-VI4 quaternary compounds could be promising candidates for efficient earth-abundant thin-film solar cell and photoeletrochemical water-splitting applications. PMID:26804024

  17. High energy storage density performance of Ba, Sr-modified lead lanthanum zirconate titanate stannate antiferroelectric ceramics

    SciTech Connect

    Wang, Jinfei Yang, Tongqing Chen, Shengchen; Li, Gang

    2013-10-15

    Graphical abstract: Polarization hysteresis (P–E) loops of the (Pb{sub 0.85}Ba{sub 0.08}Sr{sub 0.03}La{sub 0.03}) (Zr{sub 0.74}Sn{sub 0.22}Ti{sub 0.04}) samples: (a) measured at different applied electric-field and (b) measured at different temperatures is shown. It is typical antiferroelectrics whose remnant polarization is zero. As the remnant polarization of AFE is small and the ceramics are accompanied by the formation of the anti-parallel domain structure, energy stored in PLZST can be effectively released. Thus we calculated the energy density from the P–E loop and obtained the power density was up to 1.2 J/cm{sup 3} at 55 °C, and at 45 °C the energy density was ∼1.24 J/cm{sup 3}. As usual, for bulk ceramics, the switching between the AFE and FE states occurs at lower field. This value is much higher than that reported previously for the PLZT bulk ceramic (0.4 J/cm{sup 3}). - Highlights: • Ba{sup 2+}, Sr{sup 2+} co-doping caused the T{sub c} of PLZST moved to the lower temperature (T{sub c} ≈ 40 °C). • The ΔE was so smaller, E{sub AF} ≈ 90 kV/cm and E{sub FA} ≈ 85 kV/cm. • Ba, Sr co-doped PLZST ceramic exhibited slanted P–E loops with a large breakdown field (100 kV/cm). • A high energy density was up to 1.2 J/cm{sup 3}. - Abstract: (Pb{sub 0.85}Ba{sub 0.08}Sr{sub 0.03}La{sub 0.03})(Zr{sub 0.74}Sn{sub 0.22}Ti{sub 0.04}) (Ba, Sr co-doped PLZST) co-doping antiferroelectric (AFE) ceramics with orthorhombic perovskite structure were prepared by the traditional solid state reaction process. It was observed that the doping of barium and strontium caused the Curie temperature of PLZST move to the lower temperature (T{sub c} ≈ 40 °C). Ba, Sr co-doped PLZST AFE ceramics exhibited excellent electrical properties, the AFE to ferroelectric (FE) transition occurred at field E{sub AF} ≈ 90 kV/cm, and the transition from FE to AFE occurred at E{sub FA} ≈ 85 kV/cm. The maximum relative permittivity was about 4800, occurring at a field near

  18. Some reduced ternary and quaternary oxides of molybdenum containing strong metal-metal bonds. [Molybdates of ScZn, LiZn, Zn, Ba, and Na

    SciTech Connect

    Torardi, C.C.

    1981-10-01

    ScZnMo/sub 3/O/sub 8/, LiZn/sub 2/Mo/sub 3/O/sub 8/, and Zn/sub 3/Mo/sub 3/O/sub 8/ were synthesized and crystal structures were determined for the latter two. These oxides contain the same type of triangular molybdenum atom clusters found in Zn/sub 2/Mo/sub 3/O/sub 8/, but each of the trimeric clusters has available one or two additional electrons for participation in metal-metal bonding. Another new ternary oxide containing discrete metal atom clusters is Ba/sub 1/ /sub 14/Mo/sub 8/O/sub 16/. The structure of this compound consists of molybdenum-oxide cluster chains extended parallel with the c axis. The new compound NaMo/sub 4/O/sub 6/ contains infinite chains which are comprised of Mo/sub 6/O/sub 12/ clusters fused at opposite edges by removal of two edge-bridging oxygen atoms, and sharing of the metal and remaining oxygen atoms between cluster units. Another new compound, whose structure is closely related to that of NaMo/sub 4/O/sub 6/, is Ba/sub 0/ /sub 62/Mo/sub 4/O/sub 6/. This material also exhibits a sperlattice ordering of barium ions within the channels. Other compounds that have been prepared and also characterized are K/sub 2+x/Mo/sub 12/O/sub 19/, Na/sub 2+x/Mo/sub 12/O/sub 19/, and CaMo/sub 5/O/sub 8/.

  19. Long-range magnetic interaction and frustration in double perovskites Sr2NiIrO6 and Sr2ZnIrO6

    PubMed Central

    Ou, Xuedong; Li, Zhengwei; Fan, Fengren; Wang, Hongbo; Wu, Hua

    2014-01-01

    One often counts the nearest neighbouring (NN) exchange interactions for understanding of a magnetic insulator. Here we present first-principles calculations for the newly synthesized double perovskites Sr2NiIrO6 and Sr2ZnIrO6, and we find that the 2NN Ir-Ir antiferromagnetic coupling is even stronger than the 1NN Ni-Ir ferromagnetic one. Thus, the leading antiferromagnetic interactions in the fcc Ir sublattice give rise to a magnetic frustration. Sr2NiIrO6 and Sr2ZnIrO6 hence appear very similarly as a distorted low-temperature antiferromagnet (probably, of type III). This work highlights the long-range magnetic interactions of the delocalized 5d electrons, and it also addresses why the spin-orbit coupling is ineffective here. PMID:25519762

  20. Photoluminescence and long after glow in Ba2MgSi2O7: Eu2+ and Ba2ZnSi2O7: Eu2+ phosphors

    NASA Astrophysics Data System (ADS)

    Talwar, Gurjeet J.; Moharil, S. V.; Joshi, C. P.

    2016-05-01

    Silicate phosphors doped with Eu2+ find application in solid state lighting, plasma display panel, liquid crystal display and long after glow. In present work long lasting silicate phosphors are prepared by a modified combustion synthesis. The photoluminescence spectra and long lasting decay curves are measured. The Emission wavelength of Ba2MgSi2O7: Eu2+ is observed at 500 nm for excitation 345 nm.The emission wavelength of Ba2ZnSi2O7: Eu2+ is obtained at 496 nm at excitation 350 nm. Decay constants are calculated for both the phosphors.

  1. Intracavity dye laser spectroscopy studies of the Ba + N(2)O, Ca + N(2)O + CO, and Sr + N(2)O + CO reactions.

    PubMed

    Eckstrom, D J; Barker, J R; Hawley, J G; Reilly, J P

    1977-08-01

    A search for gain or absorption on several candidate visible chemical laser transitions has been carried out using the intracavity dye laser probe technique. Absorption was found on the following v'' ? v' bands of the BaO(A(1)Sigma ? X(1)Sigma) bands in the Ba + N(2)O reaction: 0 ? 1; 0 ? 4; 1 ? 1; 1 ? 2, and 5 ? 1. No gain or absorption could be detected on the 7 ? 1, 6 ? 0, and 4 ? 0 bands (sensitivity ~10(-4)/cm). In Ca, Sr + N(2)O + CO flames, absorption was found in the green arc bands of CaO and the red arc bands of SrO. Several new bandhead wavelengths are reported. Our results support assignment of the arc bands to the diatomic metal oxides. Absorptions and enhancements were found on various Sr, Ba, and Ba(+) transitions. PMID:20168881

  2. Transport anomalies in the Zn-substituted La{sub 2{minus}x}Sr{sub x}Cu{sub 1{minus}y}Zn{sub y}O{sub 4} with x{approximately}0.115: Possibility of the pinning of CDW and SDW by Zn

    SciTech Connect

    Adachi, Tadashi; Noji, Takashi; Sato, Hidetaka; Koike, Yoji; Nishizaki, Terukazu; Kobayashi, Norio

    1999-12-01

    Anomalies in the thermoelectric power and the Hall coefficient, which are analogous to those observed in La{sub 2{minus}x}Ba{sub x}CuO{sub 4} with x {approximately} 1/8, have been observed in the Zn-substituted La{sub 2{minus}x}Sr{sub x}Cu{sub 1{minus}y}Zn{sub y}O{sub 4} with x = 0.115 and y = 0 {minus} 0.025 and with x = 0.15 and y {approximately} 0.02. Based on the so-called stripe model, these are explained as being due to the formation of the static order of the stripe-patterned CDW and SDW on account of the pinning by Zn. Accordingly, the long-standing problem on the conspicuous suppression of superconductivity in the Zn-substituted La{sub 2{minus}x}Sr{sub x}Cu{sub 1{minus}y}Zn{sub y}O{sub 4} with x {approximately} 0.115 is likely to be attributed to this static order.

  3. 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.

  4. Electronic and structural properties of low-temperature superconductors and ternary pnictides ANi2Pn2 ( A=Sr,Ba and Pn=P,As )

    NASA Astrophysics Data System (ADS)

    Shein, I. R.; Ivanovskii, A. L.

    2009-02-01

    Based on first-principles full-potential linearized augmented plane wave method (FLAPW)-generalized gradient approximation calculations, we have investigated structural and electronic properties of low-temperature superconductors SrNi2As2 (TC˜0.6K) , BaNi2As2 (TC˜0.7K) , and BaNi2P2 (TC˜3K) , as well as SrNi2P2 . Our results show that the replacement of alkaline-earth metal (Sr↔Ba) and pnictogen (P↔As) types leads to anisotropic deformations of crystal structure caused by strong anisotropy of interatomic bonds. The band structure, density of states, and Fermi-surface features for (Sr,Ba)Ni2(P,As)2 are evaluated and discussed. As distinct from (Ca,Sr,Ba)Fe2As2 —the parent phases for “122” FeAs superconductors—the Fermi level in (Sr,Ba)Ni2(P,As)2 phases is shifted to the bands with higher dispersion E(k) but lower density of states as a result of increased electron concentration. Therefore the Fermi surfaces for (Sr,Ba)Ni2(P,As)2 phases differ essentially from those of the FeAs-based materials and adopt a multisheet three-dimensional type. Our estimations show that (Sr,Ba)Ni2(P,As)2 are within the weak-coupling limit with a small average electron-phonon coupling constant λep˜0.16-0.24 . The bonding in (Sr,Ba)Ni2(P,As)2 is of a complex anisotropic character. Namely, the bonding in [NiP(As)] layers may be described as a mixture of metallic, ionic, and covalent contributions. In turn, between adjacent [NiP(As)] layers and (Sr,Ba) atomic sheets, ionic bonds emerge, whereas between adjacent [NiP(As)]/[NiP(As)] layers covalent bonds occur owing to hybridization of p states of pnictogen atoms.

  5. Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

    SciTech Connect

    Samal, Saroj L.; Gulo, Fakhili; Corbett, John D.

    2013-02-18

    Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.

  6. K, Rb, Sr, Ba, U and Th geochemistry of the Lapland Granulites (Fennoscandia). LILE fractionation controlling factors

    NASA Astrophysics Data System (ADS)

    Barbey, P.; Cuney, M.

    1982-12-01

    The LILE geochemical patterns of the three main lithological units (graywacke-shale metasedimentary sequence, tholeiitic metaigneous rocks and migmatitic rocks) of the Lapland Granulite belt are described. K, Ba, Sr and Th concentrations in metasediments are nearly similar to average continental crust, whereas Rb and U are unevenly impoverished. In particular graphitic metashales and calcsilicate rocks are not significantly depleted in uranium. Tholeiitic metaigneous rocks comprises metavolcanics which present K/Rb ratios similar to metasediments, and metaplutonics with LILE abundances close to those of the low-K-tholeiites. Migmatites show wide range in LILE content. Metatexites and diatexites have higher K, Rb, Th and U concentrations and similar K/Rb ratios with respect to equivalent unmobilized rocks. Potassic pegmatoïds are strongly enriched K, Rb, Ba and Th but moderately in Sr and U. Plagioclasic pegmatoids and ferromagnesian restites are rich in Sr and poor in other LIL elements. A comparative review of the LILE geochemistry between Lapland granulites and equivalent lithological units taken from non metamorphosed to high grade terrains suggest that fractionation processes are not systematic but controlled by original lithology and mineralogy, mineral — fluid equilibria during progressive (or retrogressive) metamorphism and mineral-melt-fluid equilibria during anatexis. Moreover, statistical analysis on K-Rb distribution patterns in these various rock types shows that there is no metamorphic trend characteristic of granulite facies terrains as previously suggested.

  7. μSR investigation of a new diluted magnetic semiconductor Li(Zn,Mn,Cu)As with Mn and Cu codoping at the same Zn sites

    NASA Astrophysics Data System (ADS)

    Guo, S. L.; Zhao, Y.; Man, H. Y.; Ding, C.; Gong, X.; Zhi, G. X.; Fu, L. C.; Gu, Y. L.; Frandsen, B. A.; Liu, L.; Cheung, S. C.; Munsie, T. J.; Wilson, M. N.; Cai, Y. P.; Luke, G. M.; Uemura, Y. J.; Ning, F. L.

    2016-09-01

    We report the successful synthesis and characterization of a new type I–II–V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ∼33 K has been observed with a coercive field  ∼40 Oe for the 12.5% doping level. μSR measurements confirmed that the magnetic volume fraction reaches nearly 100% at 2 K, and the mechanism responsible for the ferromagnetic interaction in this system is the same as other bulk form DMSs.

  8. Pressure-induced superconductivity in Ba0.5Sr0.5Fe2As2

    NASA Astrophysics Data System (ADS)

    Tsoi, Georgiy M.; Malone, Walter; Uhoya, Walter; Mitchell, Jonathan E.; Vohra, Yogesh K.; Wenger, Lowell E.; Sefat, Athena S.; Weir, S. T.

    2012-12-01

    High-pressure electrical resistance measurements have been performed on single crystal Ba0.5Sr0.5Fe2As2 platelets to pressures of 16 GPa and temperatures down to 10 K using designer diamond anvils under quasi-hydrostatic conditions with an insulating steatite pressure medium. The resistance measurements show evidence of pressure-induced superconductivity with an onset transition temperature at ˜31 K and zero resistance at ˜22 K for a pressure of 3.3 GPa. The transition temperature decreases gradually with increasing pressure before completely disappearing for pressures above 12 GPa. The present results provide experimental evidence that a solid solution of two 122-type materials, i.e., Ba1-xSrxFe2As2 (0 < x < 1), can also exhibit superconductivity under high pressure.

  9. (Sr,Ba)(Si,Ge){sub 2} for thin-film solar-cell applications: First-principles study

    SciTech Connect

    Kumar, Mukesh E-mail: mkgarg79@gmail.com; Umezawa, Naoto; Imai, Motoharu

    2014-05-28

    In order to meet the increasing demand for electric power generation from solar energy conversion, the development of efficient light absorber materials has been awaited. To this end, the electronic and optical properties of advanced alkaline-earth-metals disilicides and digermanides (SrSi{sub 2}, BaSi{sub 2}, SrGe{sub 2}, and BaGe{sub 2}) are studied by means of the density functional theory using HSE06 exchange-correlation energy functional. Our calculations show that all these orthorhombic structured compounds have fundamental indirect band gaps in the range E{sub g} ≈ 0.89–1.25 eV, which is suitable for solar cell applications. The estimated lattice parameters and band gaps are in good agreement with experiments. Our calculations show that the electronic band structures of all four compounds are very similar except in the vicinity of the Γ-point. The valence band of these compounds is made up by Si(Ge)-p states, whereas the conduction band is composed of Sr(Ba)-d states. Their band alignments are carefully determined by estimating the work function of each compound using slab model. The optical properties are discussed in terms of the complex dielectric function ε(ω) = ε{sub 1}(ω) + iε{sub 2}(ω). The static and high-frequency dielectric constants are calculated, taking into account the ionic contribution. The absorption coefficient α(ω) demonstrates that a low energy dispersion of the conduction band, which results in a flat conduction band minimum, leads to large optical activity in these compounds. Therefore, alkaline-earth-metals disilicides and digermanides possess great potential as light absorbers for applications in thin-film solar cell technologies.

  10. Characterization and Luminescence Properties of Color-Tunable Dy3+-Doped BaY2ZnO5 Nanophosphors

    NASA Astrophysics Data System (ADS)

    Sonika; Khatkar, S. P.; Khatkar, Avni; Kumar, Rajesh; Taxak, V. B.

    2015-01-01

    Dy3+-doped BaY2ZnO5 nanophosphors were successfully synthesized by use of a solution combustion process. The effects of sintering temperature and dysprosium concentration on the structural and luminescence characteristics of the phosphors were investigated. X-ray diffraction (XRD) analysis confirmed the formation of pure orthorhombic BaY2ZnO5 with the space group Pbnm at 1100°C. Morphological investigation revealed spherical nanoparticles with smooth surfaces. The luminescence features of the nanophosphor were studied by use of photoluminescence excitation (PLE) and photoluminescence emission (PL), with luminescence decay curves and color ( x, y) coordinates. On excitation at 355 nm, BaY2ZnO5 nanophosphor doped with trivalent dysprosium ion emits white light as a mixture of blue (4F9/2 → 6H15/2) and yellow (4F9/2 → 6H13/2) emission. Concentration quenching is explained on the basis of cross-relaxation between intermediate Dy3+ states. Thus, BaY2ZnO5:Dy3+ nanophosphor may be suitable for producing efficient white light for ultraviolet-light-emitting diodes (UV-LEDs), fluorescent lamps, and a variety of optical display panels.

  11. Correlated nucleosynthetic isotopic variability in Cr, Sr, Ba, Sm, Nd and Hf in Murchison and QUE 97008

    NASA Astrophysics Data System (ADS)

    Qin, Liping; Carlson, Richard W.; Alexander, Conel M. O.'D.

    2011-12-01

    Acid leaching of the primitive C-chondrite Murchison and O-chondrite QUE 97008 reveal nucleosynthetic anomalies in Cr, Sr, Ba, Nd, Sm and Hf. The anomalies in all but Cr and Sm are best explained by variable additions of pure s-process nuclides to a background nebular composition slightly enriched in r-process isotopes compared to average Solar System material. Leaching leaves a residue in Murchison that is strongly enriched in s-process nuclides with depletions of over 0.1% in 135Ba and seven parts in 10,000 in 84Sr. If there are p-process anomalies in these two elements, they are lost in the variability caused by different r-, s-process contributions to the normalizing isotopes. The concentration and isotope systematics are consistent with the Ba and Sr isotopic composition in the Murchison residue being strongly influenced by s-process-rich presolar SiC. In general, the nucleosynthetic isotope anomalies are 2- to 5-fold smaller in QUE 97008 than in Murchison. The different magnitudes of isotope anomalies are similar to the difference in matrix abundance between CM and O chondrites consistent with the suggestion that the carriers of nucleosynthetically anomalous material preferentially reside in the matrix and that some of this material has been distributed throughout the O-chondrite minerals as a result of thermal metamorphism. Neodymium, Sm and Hf display variable s-, r-process nuclide abundances as in Ba and Sr, but the anomalies are much smaller (e.g. ɛ 148Nd, ɛ 148Sm = -5.7, 2.1, respectively, in Murchison and -0.43, 0.16, respectively in QUE 97008 residues). After correcting Nd and Sm for s-, r-process variability, Sm in whole rock chondrites shows variable relative abundances of the p-process isotope 144Sm that correlate weakly with 142Nd suggesting that the direct p-process contribution to 142Nd is small (˜7-9%). Nucleosynthetic variability in Nd explains the range in 142Nd/ 144Nd seen between C and O, E-chondrites, but not the difference between

  12. Growth of Sr(0.61)Ba(0.39)Nb2O6 fibers - New results regarding orientation

    NASA Technical Reports Server (NTRS)

    Wilde, Jeffrey P.; Jundt, Dieter H.; Galambos, Ludwig; Hesselink, Lambertus

    1991-01-01

    The paper describes stable growth of Sr(0.61)Ba(0.39)Nb2O6 (SBN) single-crystal optical fibers (grown by the laser-heated pedestal growth method) along the 100-line and 110-line crystallographic axes. The orientation of SBN fibers was investigated using transmission holograms recorded by focusing two separate, but mutually coherent, optical wavefronts into one end of the fiber. Results showed that the crystal quality of 100-line and 110-line SBN fibers grown at a given pull velocity strongly depended on the fiber diameter; generally, the quality improves with decreasing diameter.

  13. Influence of interfacial coherency on ferroelectric switching of superlattice BaTiO3/SrTiO3

    SciTech Connect

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

    2015-04-11

    Switching behavior of (BaTiO3)8/ (SrTiO3)4 heterostructure superlattice grown on SrTiO3 substrate was studied by employing the phase field method. To investigate the constraint effect of the substrate on switching, three types of superlattice/substrate interface mechanical relaxation conditions were considered, i.e. the fully ommensurate, partially relaxed and fully relaxed. Our simulation results demonstrated that the hysteresis loops under the three types of constraints were very different. The interfacial coherency affects dramatically the coercivity and remanence of the superlattice films. The mechanism of the hysteresis loop varying with interfacial coherency was analyzed by the ferroelectric domain configuration and its evolution during the switching process. The hysteresis loop of fully relaxed superlattice shows application potential on ferroelectric energy storage materials.

  14. Elevated silver, barium and strontium in antlers, vegetation and soils sourced from CWD cluster areas: do Ag/Ba/Sr piezoelectric crystals represent the transmissible pathogenic agent in TSEs?

    PubMed

    Purdey, Mark

    2004-01-01

    High levels of Silver (Ag), Barium (Ba) and Strontium (Sr) and low levels of copper (Cu) have been measured in the antlers, soils and pastures of the deer that are thriving in the chronic wasting disease (CWD) cluster zones in North America in relation to the areas where CWD and other transmissible spongiform encephalopathies (TSEs) have not been reported. The elevations of Ag, Ba and Sr were thought to originate from both natural geochemical and artificial pollutant sources--stemming from the common practise of aerial spraying with 'cloud seeding' Ag or Ba crystal nuclei for rain making in these drought prone areas of North America, the atmospheric spraying with Ba based aerosols for enhancing/refracting radar and radio signal communications as well as the spreading of waste Ba drilling mud from the local oil/gas well industry across pastureland. These metals have subsequently bioconcentrated up the foodchain and into the mammals who are dependent upon the local Cu deficient ecosystems. A dual eco-prerequisite theory is proposed on the aetiology of TSEs which is based upon an Ag, Ba, Sr or Mn replacement binding at the vacant Cu/Zn domains on the cellular prion protein (PrP)/sulphated proteoglycan molecules which impairs the capacities of the brain to protect itself against incoming shockbursts of sound and light energy. Ag/Ba/Sr chelation of free sulphur within the biosystem inhibits the viable synthesis of the sulphur dependent proteoglycans, which results in the overall collapse of the Cu mediated conduction of electric signals along the PrP-proteoglycan signalling pathways; ultimately disrupting GABA type inhibitory currents at the synapses/end plates of the auditory/circadian regulated circuitry, as well as disrupting proteoglycan co-regulation of the growth factor signalling systems which maintain the structural integrity of the nervous system. The resulting Ag, Ba, Sr or Mn based compounds seed piezoelectric crystals which incorporate PrP and ferritin into

  15. Elevated silver, barium and strontium in antlers, vegetation and soils sourced from CWD cluster areas: do Ag/Ba/Sr piezoelectric crystals represent the transmissible pathogenic agent in TSEs?

    PubMed

    Purdey, Mark

    2004-01-01

    High levels of Silver (Ag), Barium (Ba) and Strontium (Sr) and low levels of copper (Cu) have been measured in the antlers, soils and pastures of the deer that are thriving in the chronic wasting disease (CWD) cluster zones in North America in relation to the areas where CWD and other transmissible spongiform encephalopathies (TSEs) have not been reported. The elevations of Ag, Ba and Sr were thought to originate from both natural geochemical and artificial pollutant sources--stemming from the common practise of aerial spraying with 'cloud seeding' Ag or Ba crystal nuclei for rain making in these drought prone areas of North America, the atmospheric spraying with Ba based aerosols for enhancing/refracting radar and radio signal communications as well as the spreading of waste Ba drilling mud from the local oil/gas well industry across pastureland. These metals have subsequently bioconcentrated up the foodchain and into the mammals who are dependent upon the local Cu deficient ecosystems. A dual eco-prerequisite theory is proposed on the aetiology of TSEs which is based upon an Ag, Ba, Sr or Mn replacement binding at the vacant Cu/Zn domains on the cellular prion protein (PrP)/sulphated proteoglycan molecules which impairs the capacities of the brain to protect itself against incoming shockbursts of sound and light energy. Ag/Ba/Sr chelation of free sulphur within the biosystem inhibits the viable synthesis of the sulphur dependent proteoglycans, which results in the overall collapse of the Cu mediated conduction of electric signals along the PrP-proteoglycan signalling pathways; ultimately disrupting GABA type inhibitory currents at the synapses/end plates of the auditory/circadian regulated circuitry, as well as disrupting proteoglycan co-regulation of the growth factor signalling systems which maintain the structural integrity of the nervous system. The resulting Ag, Ba, Sr or Mn based compounds seed piezoelectric crystals which incorporate PrP and ferritin into

  16. Investigations of Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics and powders prepared by direct current arc discharge technique

    SciTech Connect

    Li, Shuangbin; Wang, Xiaohan; Yao, Ying Jia, Yongzhong; Xie, Shaolei; Jing, Yan; Yuzyuk, Yu. I.

    2014-09-01

    Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics with x ranging from 0 to 1 were prepared by direct current arc discharge technique and studied by means of x-ray diffraction (XRD) and Raman spectroscopy. The cubic-tetragonal ferroelectric phase transition in Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics was found to occur at x ≈ 0.75. XRD investigation of as-grown BaTiO{sub 3} ceramics revealed co-existence of tetragonal and hexagonal modifications with a small amount of impurity phase BaTi{sub 4}O{sub 9}. No evidences of hexagonal phase were observed in Raman spectra of as-grown BaTiO{sub 3} ceramics, while Raman peaks related to hexagonal phase were clearly observed in the spectrum of fine-grain powders prepared from the same ceramics. A core-shell model for BaTiO{sub 3} ceramics prepared by direct current arc discharge technique is proposed. Absence of the hexagonal phase in any Ba{sub x}Sr{sub 1−x}TiO{sub 3} solid solution with x < 1 is discussed in the frame of specific atomic arrangement.

  17. Microwave dielectric properties of BaTiO3 and Ba0.5Sr0.5TiO3 thin films on (001) MgO

    NASA Astrophysics Data System (ADS)

    Alldredge, L. M. B.; Chang, Wontae; Kirchoefer, Steven W.; Pond, Jeffrey M.

    2009-11-01

    The microwave properties of BaTiO3 and Ba0.5Sr0.5TiO3 films were characterized as a function of in-plane film strain, crystallographic direction, film distortion, and dc bias. The strain dependence of BaTiO3 and Ba0.5Sr0.5TiO3 films showed an opposite pattern at room temperature, going from compression to tension, or vice versa. At zero bias, the dielectric constant and dielectric loss showed little dependence on direction ([100] and [110]). However, the tunability was consistently smaller along the [110] direction than along [100]. These observations agreed well with our previous work on how polarizations (both ionic and spontaneous) form and contribute to the nonlinear dielectric behavior.

  18. Surface composition of BaTiO{sub 3}/SrTiO{sub 3}(001) films grown by atomic oxygen plasma assisted molecular beam epitaxy

    SciTech Connect

    Barbier, A.; Stanescu, D.; Jegou, P.; Magnan, H.; Mocuta, C.; Jedrecy, N.

    2012-12-01

    We have investigated the growth of BaTiO{sub 3} thin films deposited on pure and 1% Nb-doped SrTiO{sub 3}(001) single crystals using atomic oxygen assisted molecular beam epitaxy and dedicated Ba and Ti Knudsen cells. Thicknesses up to 30 nm were investigated for various layer compositions. We demonstrate 2D growth and epitaxial single crystalline BaTiO{sub 3} layers up to 10 nm before additional 3D features appear; lattice parameter relaxation occurs during the first few nanometers and is completed at {approx}10 nm. The presence of a Ba oxide rich top layer that probably favors 2D growth is evidenced for well crystallized layers. We show that the Ba oxide rich top layer can be removed by chemical etching. The present work stresses the importance of stoichiometry and surface composition of BaTiO{sub 3} layers, especially in view of their integration in devices.

  19. Effect of Sr-substitution on the restitution of superconductivity in Pr-substituted at rare earth and Ba-site in EuBa 2Cu 3O z

    NASA Astrophysics Data System (ADS)

    Thampi, R. S.; Rayaprol, S.; Mavani, Krushna; Kuberkar, D. G.; Gonal, M. R.; Prasad, R.; Kulkarni, R. G.

    2001-06-01

    We report the effect of Sr-substitution in restoring the superconductivity of Pr-doped (Eu 1- xPr x)Ba 2Cu 3O z [A] and Eu(Ba 2- xPr x)Cu 3O z [B] samples. The structural and superconducting properties of these A and B samples have been investigated using X-ray diffraction, a.c. susceptibility, electrical resistivity, d.c. magnetization and iodometric measurements. It is observed that the superconductivity gets suppressed at the rate of 1.6 K per at.% of Pr substitution at Eu-site due to the localization of mobile holes, while the sample with 15% Pr at Ba-site [B(0.3)] becomes non-superconducting mainly due to the hole filling and localization of holes. However, the increasing substitution of Sr at Ba-site in both A(0.4) and B(0.3) samples upto 25% resulted in the restoration of superconductivity (T c∼33 K) due to the delocalization of holes. Interestingly, the increasing substitution of Sr at Eu-site in the non-superconducting B(0.4) sample upto 30%, increases Tc from 0 to 52 K mainly due to the hole doping mechanism which is much faster and larger restoration of superconductivity than the Ba-site doping of Sr in the same sample.

  20. Surface modification of MAl2O4:Eu2+,Dy3+ (M = Sr, Ca, Ba) phosphors to enhance water resistance by combustion method

    NASA Astrophysics Data System (ADS)

    Deng, Suqing; Xue, Zhiping; Yang, Qu; Liu, Yingliang; Lei, Bingfu; Xiao, Yong; Zheng, Mingtao

    2013-10-01

    A facile combustion method was introduced into surface modification of MAl2O4:Eu2+,Dy3+ (M = Sr, Ca, Ba) phosphors to improve their water resistance. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), pH measurements and photoluminescence (PL) spectrophotometry were used to characterize the phosphors before and after modification, respectively. Experimental results showed that compact layer of MAl2B2O7 (M = Sr, Ca, Ba) substance was formed on the surface of aluminate phosphors by direct chemical reaction between aluminate and boracic acid. MAl2B2O7 (M = Sr, Ca, Ba) substance is chemically stable in water and could improve water resistance of aluminate phosphors effectively with little influence of luminescence property. It was considered that the versatility of combustion method for surface modification of aluminate phosphors has been confirmed.

  1. Stable BaCe 0.5Zr 0.3Y 0.16Zn 0.04O 3- δ thin membrane prepared by in situ tape casting for proton-conducting solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shangquan; Bi, Lei; Zhang, Lei; Tao, Zetian; Sun, Wenping; Wang, Haiqian; Liu, Wei

    Stable BaCe 0.5Zr 0.3Y 0.16Zn 0.04O 3- δ (BCZYZ) thin membrane was successfully prepared by in situ tape casting/co-firing method for proton-conducting solid oxide fuel cells. The starting powders were BaCO 3, CeO 2, ZrO 2, Y 2O 3, ZnO for electrolyte and BaCO 3, CeO 2, ZrO 2, Y 2O 3, ZnO, NiO, graphite for anode. The anode/electrolyte bi-layers were prepared by a simple multi-layer tape casting/co-firing method. The phase characterizations and microstructures were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anode-electrolyte bi-layers were sintered at 1450 °C. The electrolytes were extremely dense with pure perovskite phase and the thickness was about 25 μm. The anodes were porous and no obvious reaction was found between NiO and BCZYZ. With LaSr 3Co 1.5Fe 1.5O 10- δ (LSCF)/BCZYZ as cathode, the open current voltage and maximum power density respectively, reached 1.00 V and 247 mW cm -2 at 650 °C.

  2. 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.

  3. Acoustoelastic effect of textured (Ba,Sr)TiO{sub 3} thin films under an initial mechanical stress

    SciTech Connect

    Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi; Donner, Wolfgang

    2015-12-14

    Acoustoelastic (AE) analysis of initial stresses plays an important role as a nondestructive tool in current engineering. Two textured BST (Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3}) thin films, with different substrate to target distance, were grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrate by rf-magnetron sputtering deposition techniques. A conventional “sin{sup 2} ψ” method to determine residual stress and strain in BST films by X-ray diffraction is applied. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples. Young's modulus E and Poisson ratio ν of BST films in different propagation directions are derived from the measured dispersion curves. Estimation of effective second-order elastic constants of BST thin films in stressed states is served in SAW study. This paper presents an original investigation of AE effect in prestressed Ba{sub 0.65}Sr{sub 0.35}TiO{sub 3} films, where the effective elastic constants and the effect of texture on second and third order elastic tensor are considered and used. The propagation behavior of Rayleigh and Love waves in BST thin films under residual stress is explored and discussed. The guiding velocities affected by residual stresses, reveal some shifts which do not exceed four percent mainly in the low frequency range.

  4. Acoustoelastic effect of textured (Ba,Sr)TiO3 thin films under an initial mechanical stress

    NASA Astrophysics Data System (ADS)

    Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar; Donner, Wolfgang; Ben Ghozlen, Mohamed Hédi

    2015-12-01

    Acoustoelastic (AE) analysis of initial stresses plays an important role as a nondestructive tool in current engineering. Two textured BST (Ba0.65Sr0.35TiO3) thin films, with different substrate to target distance, were grown on Pt(111)/TiO2/SiO2/Si(001) substrate by rf-magnetron sputtering deposition techniques. A conventional "sin2 ψ" method to determine residual stress and strain in BST films by X-ray diffraction is applied. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples. Young's modulus E and Poisson ratio ν of BST films in different propagation directions are derived from the measured dispersion curves. Estimation of effective second-order elastic constants of BST thin films in stressed states is served in SAW study. This paper presents an original investigation of AE effect in prestressed Ba0.65Sr0.35TiO3 films, where the effective elastic constants and the effect of texture on second and third order elastic tensor are considered and used. The propagation behavior of Rayleigh and Love waves in BST thin films under residual stress is explored and discussed. The guiding velocities affected by residual stresses, reveal some shifts which do not exceed four percent mainly in the low frequency range.

  5. Solvothermal synthesis of well-dispersed MF(2) (M = Ca,Sr,Ba) nanocrystals and their optical properties.

    PubMed

    Zhang, Xiaoming; Quan, Zewei; Yang, Jun; Yang, Piaoping; Lian, Hongzhou; Lin, Jun

    2008-02-20

    MF(2) (M = Ca,Sr,Ba) nanocrystals (NCs) were synthesized via a solvothermal process in the presence of oleic acid and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra, UV/vis absorption spectra, photoluminescence (PL) excitation and emission spectra, and lifetimes, respectively. In the synthetic process, oleic acid as a surfactant played a crucial role in confining the growth and solubility of the MF(2) NCs. The as-prepared CaF(2), SrF(2) and BaF(2) NCs present morphologies of truncated octahedron, cube and sheet in a narrow distribution, respectively. Possible growth mechanisms were proposed to explain these results. The as-prepared NCs are highly crystalline and can be well dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrate strong emission bands centred at 400 nm in photoluminescence (PL) spectra compared with the cyclohexane solvent. The PL properties of the colloidal solutions of the as-prepared NCs can be ascribed to the trap states of surface defects.

  6. Synthesis, structures and photocatalytic activities of microcrystalline ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) powders

    SciTech Connect

    Wu, Weiming; Liang, Shijing; Wang, Xiaowei; Bi, Jinhong; Liu, Ping; Wu, Ling

    2011-01-15

    Microcrystalline ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. The as-prepared samples were characterized by the X-ray diffraction technique, BET surface area analysis, UV-vis diffuse reflectance spectrum, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-atomic emission spectrometry. The results indicated that single-phase orthorhombic SrBi{sub 2}Nb{sub 2}O{sub 9} could be obtained after being calcined above 650 {sup o}C, while BaBi{sub 2}Nb{sub 2}O{sub 9} was tetragonal. Based on the diffuse reflectance spectra, the band gaps of the obtained samples were calculated to be around 3.34-3.54 eV. For the photocatalytic redox reaction of methyl orange under UV-light irradiation, SrBi{sub 2}Nb{sub 2}O{sub 9} exhibited higher photocatalytic activity than that of BaBi{sub 2}Nb{sub 2}O{sub 9}. The effects of the crystallinities, BET surface areas and crystal structures of the samples on the photocatalytic activities were discussed in detail. -- Graphical abstract: Aurivillius-type ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. SrBi{sub 2}Nb{sub 2}O{sub 9} and BaBi{sub 2}Nb{sub 2}O{sub 9} showed different photocatalytic performances in the redox reaction of methyl orange (MO) under UV-light ({lambda}=254 nm), due to the different crystal structures of ABi{sub 2}Nb{sub 2}O{sub 9} (A=Sr, Ba). Display Omitted

  7. Enhanced microwave dielectric properties of Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics doping by metal Fe powders

    SciTech Connect

    Zhang Qiwei; Zhai Jiwei; Yao Xi; Ben Qianqian; Yu Xian

    2012-11-15

    Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics by adding mental Fe powders have been fabricated via the solid-state reaction method. The microstructures and optical properties of samples are systematically studied in order to establish the effects of Fe powder additives on microwave dielectric properties of Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics by x-ray diffraction, x-ray photoelectron spectroscopy, and optical reflective spectrum. The results show the coexistence of Fe{sup 2+} and Fe{sup 3+} in Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics, the decrease of O vacancy concentrations, and their incorporation into the B-site (Ti) of the Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} host lattice give rise to excellent microwave dielectric properties. All samples have a higher Q value above 290 while maintaining relatively high tunability above 16.6%. In particular, the sample with the composition of x = 0.035 mol has the dielectric constant of 889, Q Multiplication-Sign f value of 826 (at 1.370 GHz), and tunability of 24%, which are very promising for high power tunable devices. In comparison, Fe{sub 2}O{sub 3} oxide doped Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ceramics with the same molar ratios of Fe exhibit inferior microwave properties. It indicates that additives of the metal Fe powders can more effectively improve dielectric properties of Ba{sub x}Sr{sub 1-x}TiO{sub 3} system than Fe{sub 2}O{sub 3} oxide.

  8. Preparation and characterisation of nanophase Sr, Mg, and Zn substituted hydroxyapatite by aqueous precipitation.

    PubMed

    Cox, Sophie C; Jamshidi, Parastoo; Grover, Liam M; Mallick, Kajal K

    2014-02-01

    Hydroxyapatite (HA) substituted with 2 mol% Sr, 10 mol% Mg, and 2 mol% Zn were precipitated under identical alkaline conditions (pH 11) at 20°C from an aqueous solution. As-synthesised materials were confirmed to be phase pure by XRD and samples prepared in air contained surface adsorbed CO2 as observed by FTIR. SEM studies revealed a globular morphology and agglomeration behaviour, typical of precipitated nHA. EDS spectra confirmed nominal compositions and substitution of Sr, Mg and Zn. At the levels investigated cationic doping was not found to radically influence particle morphology. An indication of the potential in-vivo bioactivity of samples was achieved by analysing samples immersed in SBF for up to 28 days by interferometry and complementary SEM micrographs. Furthermore, a live/dead assay was used and confirmed the viability of seeded MC3T3 osteoblast precursor cells on HA and substituted HA substrates up to 7 days of culture. PMID:24411358

  9. Metamaterials: A New Ba0.6 Sr0.4 TiO3 -Silicon Hybrid Metamaterial Device in Terahertz Regime (Small 19/2016).

    PubMed

    Wu, Liang; Du, Ting; Xu, Ningning; Ding, Chunfeng; Li, Hui; Sheng, Quan; Liu, Ming; Yao, Jianquan; Wang, Zhiyong; Lou, Xiaojie; Zhang, Weili

    2016-05-01

    A giant terahertz modulation based on a Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial is reported by L. Wu, W. Zhang, and co-workers on page 2610. The proposed nanoscale Ba0.6 Sr0.4 TiO3 (BST) hybrid metamaterial, delivering a transmission contrast of up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate, is promising in developing high-performance real world photonic devices for terahertz technology.

  10. Real Space Imaging of Spin Polarons in Zn-Doped SrCu2(BO3)2

    NASA Astrophysics Data System (ADS)

    Yoshida, M.; Kobayashi, H.; Yamauchi, I.; Takigawa, M.; Capponi, S.; Poilblanc, D.; Mila, F.; Kudo, K.; Koike, Y.; Kobayashi, N.

    2015-02-01

    We report on the real space profile of spin polarons in the quasi-two-dimensional frustrated dimer spin system SrCu2(BO3)2 doped with 0.16% of Zn. The 11B nuclear magnetic resonance spectrum exhibits 15 additional boron sites near nonmagnetic Zn impurities. With the help of exact diagonalizations of finite clusters, we have deduced from the boron spectrum, the distribution of local magnetizations at the Cu sites with fine spatial resolution, providing direct evidence for an extended spin polaron. The results are confronted with those of other experiments performed on doped and undoped samples of SrCu2(BO3)2.

  11. Structural and electrical properties evolution in Ba{sub 1-x}Sr{sub x}RuO{sub 3} synthesized under high pressure

    SciTech Connect

    Zhao Jinggeng; Yang Liuxiang; Yu Yong; Li Fengying; Yu Richeng; Jin Changqing

    2009-06-15

    The 6H and 6M Ba{sub 1-x}Sr{sub x}RuO{sub 3} at x<=0.6 with the normal and distorted hexagonal BaTiO{sub 3} structures were synthesized by using high-pressure and high-temperature method. It is found that the unit cell volume deviates from Vegard's law between 0.3 and 0.4 for the solid solutions due to the increasing distortion degree of crystal structure. With the increasing x, the electrical resistivity at the same temperature is increasing. With the substitution of Sr for Ba ion, the 6H BaRuO{sub 3} transforms to a Fermi-liquid metal at x=0.25 from the primal non-Fermi-liquid metal, and then becomes a semiconductor at low temperature when x is larger than 0.4. - Graphical abstract: The 6H (x<=0.3) and 6M (0.4<=x<=0.6) Ba{sub 1-x}Sr{sub x}RuO{sub 3} solutions synthesized under high pressure adopt the normal and distorted hexagonal BaTiO{sub 3} structures, respectively.

  12. Blue-shift of Eu²⁺ emission in (Ba,Sr)₃Lu(PO₄)₃:Eu²⁺ eulytite solid-solution phosphors resulting from release of neighbouring-cation-induced stress.

    PubMed

    Wang, Ziyuan; Xia, Zhiguo; Molokeev, Maxim S; Atuchin, Victor V; Liu, QuanLin

    2014-11-28

    A series of iso-structural eulytite-type (Ba,Sr)3Lu(PO4)3:Eu(2+) solid-solution phosphors with different Sr/Ba ratios were synthesized by a solid-state reaction. Crystal structures of (Ba,Sr)3Lu(PO4)3:Eu(2+) were resolved by the Rietveld method, which shows an eulytite-type cubic Bi4(SiO4)3 structure with cations disordered in a single C3 site while the oxygen atoms were distributed over two partially occupied sites. The emission peaks of Ba((3-x))Sr(x)Lu(PO4)3:Eu(2+) (0 ≤ x ≤ 3) phosphors were blue-shifted, from 506 to 479 nm, with increasing Sr/Ba ratio upon the same excitation wavelength of 365 nm, and such interesting luminescence behaviours can also be found in other eulytite-type (Ba,Sr)3Ln(PO4)3:Eu(2+) (Ln = Y, Gd) solid-solution phosphors. The blue-shift of the Eu(2+) emission with increasing Sr/Ba ratio was ascribed to the variation of the crystal field strength that the 5d orbital of Eu(2+) ion experiences, and a new model based on the Eu-O bond length and released neighboring-cation stress in disordered Ba(2+)/Sr(2+)/Ln(3+) sites is proposed.

  13. Thermally assisted interlayer magnetic coupling through Ba0.05Sr0.95TiO3 barriers

    NASA Astrophysics Data System (ADS)

    Carreira, Santiago J.; Avilés Félix, Luis; Sirena, Martín; Alejandro, Gabriela; Steren, Laura B.

    2016-08-01

    We report on the interlayer exchange coupling across insulating barriers observed on Ni80Fe20/Ba0.05Sr0.95TiO3/La0.66Sr0.33MnO3 (Py/BST0.05/LSMO) trilayers. The coupling mechanism has been analyzed in terms of the barrier thickness, samples' substrate, and temperature. We examined the effect of MgO (MGO) and SrTiO3 (STO) (001) single-crystalline substrates on the magnetic coupling and also on the magnetic anisotropies of the samples in order to get a deeper understanding of the magnetism of the structures. We measured a weak coupling mediated by spin-dependent tunneling phenomena whose sign and strength depend on barrier thickness and substrate. An antiferromagnetic (AF) exchange prevails for most of the samples and smoothly increases with the barrier thicknesses as a consequence of the screening effects of the BST0.05. The coupling monotonically increases with temperature in all the samples and this behavior is attributed to thermally assisted mechanisms. The magnetic anisotropy of both magnetic components has a cubic symmetry that in the case of permalloy is added to a small uniaxial component.

  14. Dielectric response of Ba0.05Sr0.95TiO3(110) films to variations in temperature and electric field

    NASA Astrophysics Data System (ADS)

    Boikov, Yu. A.; Claeson, T.

    2015-05-01

    Three-layer epitaxial heterostructures, in which a 1000-nm-thick intermediate layer of Ba0.05Sr0.95TiO3 is integrated with strontium ruthenate conducting electrodes, have been grown by laser evaporation. Using photolithography and ion etching, film parallel-plate capacitors SrRuO3/Ba0.05Sr0.95TiO3/SrRuO3 are formed based on the grown heterostructures. A sharp maximum in the temperature dependence of the capacitor capacitance is observed at T ≈ 75 K. At T < 100 K, the capacitance decreases by 50-60% upon applying a bias voltage V b = ±2.5 V to the oxide electrodes. The estimate of the specific capacitance (~2.1 μF/cm2) of the Ba0.05Sr0.95TiO3(110)/SrRuO3(110) interface is obtained. For T > 250 K and the measuring signal frequency of 1 kHz, the dielectric loss tangent of the film capacitors increases exponentially with increasing temperature.

  15. SrAgZn and EuAgZn with KHg{sub 2}-type structure—Structure, magnetic properties, and {sup 151}Eu Mössbauer spectroscopy

    SciTech Connect

    Gerke, Birgit; Rodewald, Ute Ch.; Niehaus, Oliver; Pöttgen, Rainer

    2013-07-15

    Samples of SrAgZn and EuAgZn were synthesized by reaction of the elements in sealed tantalum crucibles. Both structures were refined on the basis of single crystal X-ray diffractometer data: KHg{sub 2}-type, Imma, a=476.7(1), b=780.9(2), c=810.1(2) pm, R{sub 1}/wR{sub 2}=0.0189/0.0119, 381 F² values for SrAg{sub 1.12}Zn{sub 0.88} and a=474.43(9), b=760.8(2), c=799.0(2) pm, R{sub 1}/wR{sub 2}=0.0226/0.0483, 370 F² values for EuAg{sub 1.17}Zn{sub 0.83} with 13 variables per refinement. Silver and zinc are randomly distributed on the Hg position and build up three-dimensional networks. EuAgZn shows ferromagnetic ordering at 29(1) K. In the temperature range from 75 to 300 K the sample shows Curie–Weiss behaviour with μ{sub eff}=7.87(1) μ{sub B}/Eu atom and θ{sub P}=37.1(1) K, indicating divalent europium. {sup 151}Eu Mössbauer spectroscopic measurements confirmed the divalent state with an isomer shift of −9.31 mm/s at 78 K. Temperature dependent {sup 151}Eu data show first magnetic hyperfine field splitting at 25 K and a saturated magnetization of 17 T at 5.2 K. The temperature dependence can be described by an S=7/2 Brillouin function. - Graphical abstract: The near neighbor coordination of the strontium and europium atoms in SrAg{sub 1.12}Zn{sub 0.88}, EuAg{sub 1.17}Zn{sub 0.83}, and EuAuZn. - Highlights: • Synthesis of new intermetallic zinc compounds SrAgZn and EuAgZn. • Ferromagnetic ordering of EuAgZn at 29 K. • Magnetic hyperfine field splitting in the {sup 151}Eu Mössbauer spectrum.

  16. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices--CCSD(T) calculations and atomic site occupancies.

    PubMed

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm(-1)). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications. PMID:26827218

  17. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices--CCSD(T) calculations and atomic site occupancies.

    PubMed

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm(-1)). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.

  18. Enhanced microwave dielectric properties of Ba0.4Sr0.6TiO3 ceramics doping by metal Fe powders

    NASA Astrophysics Data System (ADS)

    Zhang, Qiwei; Zhai, Jiwei; Ben, Qianqian; Yu, Xian; Yao, Xi

    2012-11-01

    Ba0.4Sr0.6TiO3 ceramics by adding mental Fe powders have been fabricated via the solid-state reaction method. The microstructures and optical properties of samples are systematically studied in order to establish the effects of Fe powder additives on microwave dielectric properties of Ba0.4Sr0.6TiO3 ceramics by x-ray diffraction, x-ray photoelectron spectroscopy, and optical reflective spectrum. The results show the coexistence of Fe2+ and Fe3+ in Ba0.4Sr0.6TiO3 ceramics, the decrease of O vacancy concentrations, and their incorporation into the B-site (Ti) of the Ba0.4Sr0.6TiO3 host lattice give rise to excellent microwave dielectric properties. All samples have a higher Q value above 290 while maintaining relatively high tunability above 16.6%. In particular, the sample with the composition of x = 0.035 mol has the dielectric constant of 889, Q × f value of 826 (at 1.370 GHz), and tunability of 24%, which are very promising for high power tunable devices. In comparison, Fe2O3 oxide doped Ba0.4Sr0.6TiO3 ceramics with the same molar ratios of Fe exhibit inferior microwave properties. It indicates that additives of the metal Fe powders can more effectively improve dielectric properties of BaxSr1-xTiO3 system than Fe2O3 oxide.

  19. 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.

  20. Effects of element substitution on the pyroelectric phase transition of stuffed-tridymite-type BaZnGeO4

    NASA Astrophysics Data System (ADS)

    Nagai, Takayuki; Asai, Shinichiro; Okazaki, Ryuji; Terasaki, Ichiro; Taniguchi, Hiroki

    2015-10-01

    Effects of element substitution on the phase transition between different pyroelectric phases of the stuffed-tridymite-type oxide, BaZnGeO4, are examined by dielectric measurements on BaZn1-xMxGeO4 (M=Ni, Co, and Mn) with x=0.05 and 0.10. The Ni2+-substitution is found to suppress strongly the phase transition, in marked contrast to the cases of Co2+ and Mn2+ that have only subtle influences on the transition temperature. Internal distortions of MO4 tetrahedra due to the Jahn-Teller effect might play a major role in the variation of transition temperature induced by the element substitution.

  1. Effect of the [Ba2BO3F]∞ Layer on the Band Gap: Synthesis, Characterization, and Theoretical Studies of BaZn2B2O6·nBa2BO3F (n = 0, 1, 2).

    PubMed

    Wu, Hongping; Su, Xin; Han, Shujuan; Yang, Zhihua; Pan, Shilie

    2016-05-16

    Two new zincoborate fluorides with the common formula BaZn2B2O6·nBa2BO3F (n = 1, 2) have been successfully synthesized for the relationship study between the band gaps and crystal structures in zinc-containing borate fluorides. Ba3Zn2B3O9F with n = 1 in the common formula belongs to the orthorhombic space group Pnma (No. 20), and Ba5Zn2B4O12F2 with n = 2 in the common formula crystallizes in the monoclinic space group C2/c (No. 62). They can both be seen as compounds with the n[Ba2BO3F]∞ (n = 1 or 2) layer inserted in the structure of BaZn2B2O6. UV-vis-near-IR diffuse-reflectance spectra show that the band gaps of BaZn2B2O6·nBa2BO3F (n = 0, 1, 2) gradually increase with more [Ba2BO3F]∞ layers inserted. The first-principles calculation indicates that the inserted n[Ba2BO3F]∞ layers play a positive effect in increasing the band gaps of zincoborate fluorides. Furthermore, the IR spectra, thermal behaviors, and refractive indices of these compounds are also studied. PMID:27119618

  2. Effects of Sr{sup 2+} substitution on photoluminescence characteristics of Ba{sub 1−x−y}Sr{sub y}ZrSi{sub 3}O{sub 9}:xEu{sup 2+} phosphors

    SciTech Connect

    Chiang, Chung-Hao; Gong, Syuan-Jhih; Lin, Han-Yu; Zhan, Ting-Shi; Chu, Sheng-Yuan

    2014-12-14

    In this work, single-phase Ba{sub 1−x−y}Sr{sub y}ZrSi{sub 3}O{sub 9}:xEu{sup 2+} phosphors were synthesized via the solid-state reaction method. The crystal structure and luminescence properties were investigated using X-ray diffraction and photoluminescence measurements, respectively. An increase of the dopant Sr{sup 2+} increased the emission intensity of the phosphors. The peak intensity of the samples was at y = 0.4 under near-ultraviolet light excitation (397 nm). The wavelength of the emission peaks red-shifts slightly from 477 to 483 nm due to the splitting of the 5d energy level. Sr{sup 2+} ions have a smaller ionic radius than that of Ba{sup 2+} ions, and thus the dopant changes the crystal structure, improving the energy transfer efficiency between luminescence centers. More Eu{sup 2+} solid solubility was found in Ba{sub 0.6−x}Sr{sub 0.4}ZrSi{sub 3}O{sub 9}:xEu{sup 2+} phosphors (10 mol. %) than in the host BaZrSi{sub 3}O{sub 9} (6 mol. %), which enhanced the emission intensity. In addition, the thermal reliability of the phosphors was studied.

  3. In vitro synthesis of amorphous Mg-, Ca-, Sr- and Ba-carbonates: What do we learn about intracellular calcification by cyanobacteria?

    NASA Astrophysics Data System (ADS)

    Cam, N.; Georgelin, T.; Jaber, M.; Lambert, J.-F.; Benzerara, K.

    2015-07-01

    Some cyanobacteria, including Candidatus Gloeomargarita lithophora, which was isolated from Lake Alchichica (Mexico), can form intracellular carbonates. This contradicts the common paradigm that cyanobacterial calcification is always extracellular and suggests that calcification might be controlled by these cyanobacterial species. Intracellular carbonates have several peculiar characteristics: they are relatively small (between 60 and 500 nm), they are poorly crystalline, and they have Sr/Ca and Ba/Ca ratios much higher than the solution in which the cells grow. It is therefore crucial to understand whether these unique features may indicate the involvement of specific biological processes. Here, in vitro abiotic syntheses were performed to synthesize Mg-, Ca-, Sr- and Ba-containing carbonates with compositions, crystallinities and sizes close to those observed in intracellularly calcifying cyanobacteria. Precipitates were characterized by scanning and transmission electron microscopies coupled with energy dispersive X-ray spectroscopy, thermogravimetric analysis and X-ray diffraction. The size and the poor crystallinity of cyanobacterial intracellular carbonates could be mimicked under these abiotic conditions. It was shown that similarly to Mg, elements such as Sr and Ba can favor stabilization of poorly crystalline carbonates. In contrast, the differential partitioning of Sr, Ba and Ca between the solution and the solids as observed in cyanobacteria could not be mimicked in vitro. This provides keys to a better understanding of biological processes involved in the formation of intracellular carbonates by some cyanobacteria, including the involvement of membrane transporters.

  4. Synthesis, crystal structures, and magnetic properties of double perovskites SrLaNiOsO6 and BaLaNiOsO6

    NASA Astrophysics Data System (ADS)

    Feng, Hai L.; Schnelle, Walter; Tjeng, Liu Hao; Jansen, Martin

    2016-10-01

    New double perovskite oxides SrLaNiOsO6 and BaLaNiOsO6 were synthesized by solid state reactions from the respective binary metal oxides, and their crystal structures and magnetic properties were characterized. At room temperature SrLaNiOsO6 and BaLaNiOsO6 crystallize in ordered double perovskite structures with space groups of P21/n (monoclinic) and I4/m (tetragonal), respectively. They are electrically semiconducting with an activation energy of ≈0.35 eV. Specific heat and magnetic measurements indicate that SrLaNiOsO6 shows predominantly antiferromagnetic correlations and displays antiferromagnetic transition around 60 K. However, for the isoelectronic BaLaNiOsO6 ferromagnetic correlations are predominant and there is no clear feature of a magnetic transition detectable. The remarkable change in magnetic properties of ALaNiOsO6 (A = Sr and Ba) can be related to the degree of structure distortions, i.e. the bending of the O-B-O (B = Ni,Os) links.

  5. Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

    PubMed

    Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

    2016-04-01

    In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs). PMID:27451689

  6. Relaxation Associated with Oxygen Vacancies at High Temperatures and Leakage Current in Ba x Sr1- x TiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Liu, Qiu-Xiang; Tang, Xin-Gui; Jiang, Yan-Ping; Yue, Jing-Long; Li, Jin-Kai

    2016-06-01

    Ba x Sr1- x TiO3 ( x = 0.7, 0.8, 0.9, 1.0) ceramics were synthesized using traditional solid state reaction methods. The structure, microstructure, ferroelectric and dielectric properties of the ceramics were investigated. X-ray diffraction results show that a pure phase was obtained. For all compositions, a sharp phase transition was observed in the dielectric data and the substitution of Ba2+ by Sr2+ gradually reduced the Curie temperature. A dielectric relaxation phenomenon was observed at high temperatures (300-550°C). From impedance measurements, the activation energy for relaxation and conduction was calculated as approximately 1 eV, which suggests that relaxation in Ba x Sr1- x TiO3 ceramics at high temperatures is associated with the short-range hopping of ions caused by oxygen vacancies. An oxygenation treatment, the variation of dielectric behaviors and activation energy verified that the oxygen vacancies were the origin of the dielectric relaxation. The leakage current of Ba x Sr1- x TiO3 ceramics may be associated with the combined effect of oxygen vacancies and the size of the largest grains.

  7. Optical and spectral studies on pure and europium doped olgite type Na(Sr,Ba)PO4 ceramics.

    PubMed

    Jawaher, K Rackesh; Jagannathan, R; Das, S Jerome; Krishnan, S

    2015-04-01

    Europium ion doped olgite type Na(Sr,Ba)PO4 ceramics, a new generation of light emitting bulb, was prepared by a high temperature solid-state reaction method. The synthesized materials were subjected to various characterizations such as X-ray powder diffraction, Scanning electron microscopy and FT-IR spectra measurements. The EPR spectrum of the sample exhibits a well-resolved hyperfine structure of 151Eu2+ and 153Eu2+ isotopes and the g value has been calculated. Fluorescence spectra revealed that europium ions were present in divalent as well as in the trivalent oxidation states. The critical distance for energy transfer between Eu2+ and Eu2+ ion is calculated as 20Å, which is in good agreement with that of experimental data. The FTIR analysis reveals all the vibrations of PO4(3-) ions.

  8. Heterojunction band offsets and dipole formation at BaTiO{sub 3}/SrTiO{sub 3} interfaces

    SciTech Connect

    Balaz, Snjezana; Zeng, Zhaoquan; Brillson, Leonard J.

    2013-11-14

    We used a complement of photoemission and cathodoluminescence techniques to measure formation of the BaTiO{sub 3} (BTO) on SrTiO{sub 3} (STO) heterojunction band offset grown monolayer by monolayer by molecular beam epitaxy. X-ray photoemission spectroscopy (XPS) provided core level and valence band edge energies to monitor the valence band offset in-situ as the first few crystalline BTO monolayers formed on the STO substrate. Ultraviolet photoemission spectroscopy (UPS) measured Fermi level positions within the band gap, work functions, and ionization potentials of the growing BTO film. Depth-resolved cathodoluminescence spectroscopy measured energies and densities of interface states at the buried heterojunction. Kraut-based XPS heterojunction band offsets provided evidence for STO/BTO heterojunction linearity, i.e., commutativity and transitivity. In contrast, UPS and XPS revealed a large dipole associated either with local charge transfer or strain-induced polarization within the BTO epilayer.

  9. Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi₃ (A = Sr and Ba).

    PubMed

    Shao, D F; Luo, X; Lu, W J; Hu, L; Zhu, X D; Song, W H; Zhu, X B; Sun, Y P

    2016-02-19

    Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

  10. Unconventional Electronic Reconstruction in Undoped (Ba,Sr)Fe2As2 Across the Spin Density Wave Transition

    SciTech Connect

    Yi, M.

    2010-06-02

    Through a systematic high-resolution angle-resolved photoemission study of the iron pnictide compounds (Ba,Sr)Fe{sub 2}As{sub 2}, we show that the electronic structures of these compounds are significantly reconstructed across the spin density wave transition, which cannot be described by a simple folding scenario of conventional density wave ordering. Moreover, we find that LDA calculations with an incorporated suppressed magnetic moment of 0.5{mu}{sub B} can match well the details in the reconstructed electronic structure, suggesting that the nature of magnetism in the pnictides is more itinerant than local, while the origin of suppressed magnetic moment remains an important issue for future investigations.

  11. Relaxor behavior of ferroelectric Ca0.22Sr0.12Ba0.66Nb2O6

    NASA Astrophysics Data System (ADS)

    Shekhar Pandey, Chandra; Schreuer, Jürgen; Burianek, Manfred; Mühlberg, Manfred

    2013-01-01

    The relaxor behavior of tetragonal tungsten bronze uniaxial relaxor ferroelectric calcium strontium barium niobate (Ca0.22Sr0.12Ba0.66Nb2O6 or CSBN-22) single crystal was studied by measuring elastic constants and thermal expansion with the aid of resonant ultrasound spectroscopy and dilatometry, respectively, in the temperature range 300 K-1503 K. Thermal expansion yields evidence of the Burns temperature TB and the intermediate characteristic temperature T*, which was also supported by the temperature evolutions of the elastic constants cij. CSBN-22 was found to be ˜2%-3% elastically stiffer than CBN-28. The presented results open the perspective to understand the relaxor behavior of CSBN.

  12. Multiferroic properties of microwave sintered BaTiO3-SrFe12O19 composites

    NASA Astrophysics Data System (ADS)

    Katlakunta, Sadhana; Raju, Pantagani; Meena, Sher Singh; Srinath, Sanyadanam; Sandhya, Reddigari; Kuruva, Praveena; Murthy, Sarabu Ramana

    2014-09-01

    The composites of xSrFe12O19-(1-x) BaTiO3 where x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1were prepared by Sol-gel method and consequently densified at 1100 °C/90 min using microwave sintering method. The phase formation and diphase microstructure of the composite samples was examined by X-ray diffraction and field emission electron microscope (FESEM), respectively. The effects of constituent phase variation on the ferroelectric, dielectric and magnetic properties were examined. It was observed that with a decrease of x, the Curie temperature shifted towards low temperature side.

  13. Ferroelectric properties of (Ba,Sr)TiO3 thin films grown on YBa2Cu3O7 layers

    NASA Astrophysics Data System (ADS)

    Tao, K.; Hao, Z.; Xu, B.; Chen, B.; Miao, J.; Yang, H.; Zhao, B. R.

    2003-09-01

    Ferroelectric and superconductor bilayers of Ba1-xSrxTiO3(BST)/YBa2Cu3 O7 (YBCO) are grown on (001) SrTiO3 substrates by magnetron sputtering and pulsed laser deposition. The BST thin films exhibit typical ferroelectric behavior in their hysteresis loops. Capacitance-voltage curves are measured. From the capacitance, a dielectric constant of 1250 is obtained. The current-voltage curve is fitted to investigate the mechanism of leakage. The Schottky barrier height at the Ag/BST interface is calculated to be 0.521 eV. The trapped level Et in BST is estimated to be 0.335 eV below the conduction-band edge. An energy band diagram of the Ag/BST/YBCO structure is proposed to explain the experimental results.

  14. Optical and spectral studies on pure and europium doped olgite type Na(Sr,Ba)PO4 ceramics

    NASA Astrophysics Data System (ADS)

    Jawaher, K. Rackesh; Jagannathan, R.; Das, S. Jerome; Krishnan, S.

    2015-04-01

    Europium ion doped olgite type Na(Sr,Ba)PO4 ceramics, a new generation of light emitting bulb, was prepared by a high temperature solid-state reaction method. The synthesized materials were subjected to various characterizations such as X-ray powder diffraction, Scanning electron microscopy and FT-IR spectra measurements. The EPR spectrum of the sample exhibits a well-resolved hyperfine structure of 151Eu2+ and 153Eu2+ isotopes and the g value has been calculated. Fluorescence spectra revealed that europium ions were present in divalent as well as in the trivalent oxidation states. The critical distance for energy transfer between Eu2+ and Eu2+ ion is calculated as 20 Å, which is in good agreement with that of experimental data. The FTIR analysis reveals all the vibrations of PO43- ions.

  15. Synthesis of nanostructured framework of novel ZnBaO2 nanopowder via wet chemical approach and hepatocytotoxicity response

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Alabass, Razzaq; Alqaralosy, Ahmed; Khan, Aleem Ahmed

    2016-08-01

    Wet synthetic process is an effective and facile method at low cost, environmentally benign process for easy scaling-up and then used for fabrication of multi-utility devices. Self-assembling of nanobrick leads to architecture framework with new functional properties which help to make its vast applications as nanodevices with their intrinsic shape, size and functional properties. The bimetallic oxide nanostructure with phase structure was characterized by FTIR, UV-visible electronic absorption, XRD, thermal studies, SEM, TEM, DLS and fluorescence. Nanocrystalline ZnBaO2 powder can be used due to its chemical stability and excellent transmission in the visible region. It was observed that the annealing rate plays an important role to redefine the structural and other physicochemical properties which finally help to change gel into crystalline functional properties with porosity. Wet chemical approach can be used for the synthesis of other metal oxide nanopowders which can be easily scale up for production level. Along with synthesis and characterization, we also assessed biological responses of human hepatocytes exposed to ZnBaO2 nanopowder. Cell membrane permeability and ammonia detoxification were investigated against various concentrations of nanoparticles on in vitro cultured hepatocytes. Our results suggest that low concentrations (<40 μg/ml) of ZnBaO2 nanopowder have no cytotoxic effect on hepatocytes viability, proliferation and detoxification, whereas concentrations above 40 μg/ml depict significant toxicity on cells.

  16. Spectroscopy and structural characteristics of Eu3+-activated perovskite tungstate Ba2La2ZnW2O12

    NASA Astrophysics Data System (ADS)

    Yang, Li; Huang, Yanlin; Cheng, Han; Seo, Hyo Jin

    2015-11-01

    Eu3+-doped tungstate Ba2La2ZnW2O12 was prepared by the high-temperature solid-state reaction method. The x-ray powder diffraction (XRD) patterns indicate that the matrix has a perovskite structure. The samples were characterized by the scanning electron microscope (SEM), by optical diffuse reflection, photoluminescence (PL) spectra and by their decay curves. Eu3+-activated Ba2La2ZnW2O12 shows red luminescence under the excitation of near-ultraviolet and blue light. Laser site-selective excitation and emission spectroscopy technology was applied to investigate the spectroscopic and microstructural properties. The excitation spectra were tested by monitoring the emission from 5D0  →  7F0-4 transitions. Accordingly the emission spectra and decay curves (lifetime) were measured by the excitation in the 5D0  →  7F0 wavelength region using a pulsed, tunable, and narrow-band dye laser. We have detected two Eu3+ sites in Ba2La2ZnW2O12 with the temperature region ranging from 10 K to below 300 K. On the spectra data of the site-selective emission and decay, the Stark energy levels of Eu3+ at two different sites were determined. The lifetimes of Eu3+ ions at the two sites were compared. The energy transfer and crystallographic assignments for the Eu3+ sites were discussed.

  17. Visible to near-infrared luminescence properties of Nd{sup 3+}-doped La{sub 2}BaZnO{sub 5} phosphor

    SciTech Connect

    Cao, Renping Cao, Chunyan; Yu, Xiaoguang; Sun, Xinyuan; Tang, Pengjie; Ao, Hui

    2014-07-01

    La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphors are synthesized by a conventional high temperature solid state reaction method, and its crystal structure and luminescence properties are investigated. Photoluminescence bands peaking at ∼496, 540, 630, 670, 905, 1070, and 1350 nm of La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphors are observed at room temperature due to f–f transition of Nd{sup 3+} ion. The optimum Nd{sup 3+} doped concentration is ∼0.03. Lifetimes of La{sub 1.97}BaZnO{sub 5}:0.03Nd{sup 3+} phosphor with 496 and 1070 nm monitoring wavelengths are ∼280 and 250 µs, respectively. The luminescence mechanism is explained by using simplified energy lever diagram of Nd{sup 3+} ion. La{sub 2}BaZnO{sub 5}:Nd{sup 3+} material can be applied to powerful solid-state lasers as high efficient light sources. - Graphical abstract: PL spectra of La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphor in the visible and near-infrared regions and their corresponding to PLE at room temperature. - Highlights: • La{sub 2}BaZnO{sub 5}:Nd{sup 3+} phosphor is synthesized. • PL spectrum is observed in the visible region. • PL spectrum is observed in the near-infrared region.

  18. Genesis of basalt magmas and their derivatives under the Izu Islands, Japan, inferred from Sr/Ca-Ba/Ca systematics

    NASA Astrophysics Data System (ADS)

    Onuma, Naoki; Hirano, Masataka; Isshiki, Naoki

    1983-10-01

    The Sr/Ca-Ba/Ca systematics defined for a series of volcanic rocks provided by volcanoes of the Izu Islands, Japan, have cast a new light on the origin and evolution of basalt magmas and their derivatives: (1) The mantle material in the source region of primary basalt magmas beneath the Izu Islands shows a chondritic value of Sr/Ca and Ba/Ca ratios. (2) Both the tholeiite magma and the high-alumina/calc-alkali basalt magma are primary with higher degrees (15-20% for the former) and lower degrees (8-11% for the latter) of partial melting of a common mantle material. (3) The primary basalt magmas evolve independently via crystal fractionation process in respective magma chambers at shallower depths each providing a series of andesite and dacite magmas corresponding to respective primary basalt magmas. (4) The crystal fractionation process in magma chamber is controlled mainly by plagioclase and clinopyroxene crystallization in terms of the alkaline earth elements. The plagioclase/clinopyroxene ratio decreases during crystal fractionation process. The chemical environments of magma chambers are similar to each other in the tholeiite series and in the high-alumina basalt/calc-alkali rock series. (5) The end products provided by the crystal fractionation process lie within Bowen's petrogeny's residua system, making a thin, silicic crust under the volcanic islands near the Izu Peninsula. The calc-alkali rhyolites in these islands are derived from the thin silicic crust via melting process by the heat of intruded primary basalt magmas. (6) The regional distribution of degree of partial melting indicates variations from 15 to 20% along the volcanic front and from 8 to 11% in the region behind it. The fact suggests that an interaction between the mantle wedge under the Philippine Sea Plate and the subducting slab of the Pacific Plate beneath the Izu Islands is different from place to place, with respect to temperature distribution and/or water supply from the subducting

  19. Microwave loss mechanisms in Ba0.25Sr0.75TiO3 thin film varactors

    NASA Astrophysics Data System (ADS)

    Vorobiev, A.; Rundqvist, P.; Khamchane, K.; Gevorgian, S.

    2004-10-01

    Parallel-plate Au(Pt )/Ba0.25Sr0.75TiO3/(Pt)Au thin film varactors were fabricated on high resistance Si substrates and characterized at dc, rf, and microwave frequencies. In the frequency range 10-45 GHz the varactors show relatively low losses, with loss tangent less than 0.025 at 45 GHz. Due to the thick and highly conductive Pt/Au electrodes the metal losses are less than 10%. However, the loss tangent of the ferroelectric film is still three to five times higher than that in Ba0.27Sr0.73TiO3 single crystal. The analysis of the dc field dependences of loss tangent and permittivity in a wide frequency range shows that these additional losses are mainly due to the charged defects. Extrapolation of measured low frequency (1 MHz) loss tangents to the microwave region using the power law ω1/3 is in good agreement with experiment. The dc current through the varactor is found to be controlled by Schottky emission and Poole-Frenkel mechanisms depending on the polarity. The Poole-Frenkel mode is associated with field enhanced thermal excitation of charge carriers from internal traps. The trap activation energy (about 0.15 eV) determined from the Poole-Frenkel mode agrees well with the energy level of the oxygen vacancy. We assume that the oxygen vacancies within the grain boundaries of the ferroelectric film act as charged defects and cause additional (extrinsic) microwave losses. The possible correlation between the film's internal strains and density of the oxygen vacancies are discussed. The knowledge of the extrinsic loss mechanism and corresponding microstructure defects is useful in optimization of the varactor design, deposition, annealing process, and further improvement of the varactor performance.

  20. Finite-size effects in the quasi-one-dimensional quantum magnets Sr2CuO3,Sr2Cu 0.99M0.01 O3(M =Ni ,Zn ), and SrCuO2

    NASA Astrophysics Data System (ADS)

    Karmakar, Koushik; Singh, Surjeet

    2015-06-01

    We studied the finite-size effects on the magnetic behavior of the quasi-one-dimensional spin S =1/2 Heisenberg antiferromagnets Sr2CuO3 , Sr2Cu0.99M0.01 O3 (M =Zn and Ni), and SrCuO2. Magnetic susceptibility data were analyzed to estimate the concentration of chain breaks due to extrinsically doped defects and/or due to slight oxygen off-stoichiometry. We show that the susceptibility of Sr2Cu0.99Ni0.01O3 can be described by considering Ni2+ as a scalar defect (Seff=0 ) indicating that the Ni spin is screened. In Sr2Cu0.99Zn0.01O3 susceptibility analysis yields a defect concentration smaller than the nominal value which is in good qualitative agreement with crystal growth experiments. Influence of doping on the low-temperature long-range spin ordered state is studied. In the compound SrCuO2, consisting of zigzag S =1/2 chains, the influence of spin frustration on the magnetic ordering and the defect concentration determined from the susceptibility data is discussed.

  1. Metal-semiconductor-transition observed in Bi{sub 2}Ca(Sr, Ba){sub 2}Co{sub 2}O{sub 8+δ} single crystals

    SciTech Connect

    Dong, Song-Tao; Zhang, Bin-Bin; Zhang, Lun-Yong; Yao, Shu-Hua E-mail: shyao@nju.edu.cn; Zhou, Jian; Zhang, Shan-Tao; Gu, Zheng-Bin; Chen, Yan-Feng; Chen, Y. B. E-mail: shyao@nju.edu.cn

    2014-07-28

    Electrical property evolution of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} single crystals (AE = Ca, Sr and Ba) is systematically explored. When AE changes from Ca to Ba, the electrical property of Bi{sub 2}Ca{sub 2}Co{sub 2}O{sub 8+δ} and Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} demonstrates semiconductor-like properties. But Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} shows the metallic behavior. Analysis of temperature-dependent resistance substantiates that from metallic Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} to semiconductor-like Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} can be attributed to Anderson localization. However the semiconductor behaviour of Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} and Bi{sub 2}Ca{sub 2}Co{sub 2}O{sub 8+δ} is related to electronic correlations effect that is inferred by large negative magnetoresistance (∼70%). The theoretical electronic structures and valence X-ray photoemission spectroscopy substantiate that there is a relative large density of state around Fermi level in Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} compared with other two compounds. It suggests that Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} is more apt to be metal in this material system.

  2. Local structure of Ba(1-x)Sr(x)TiO3 and BaTi(1-y)Zr(y)O3 nanocrystals probed by X-ray absorption and X-ray total scattering.

    PubMed

    Rabuffetti, Federico A; Brutchey, Richard L

    2013-12-23

    The effect of isovalent chemical substitution on the magnitude and coherence length of local ferroelectric distortions present in sub-20 nm Ba(1-x)Sr(x)TiO3 (x = 0.0, 0.30, 0.50, 1.0) and BaTi(1-y)Zr(y)O3 (y = 0.0, 0.15, 0.50, 1.0) nanocrystals synthesized at room temperature is investigated using X-ray absorption near edge structure (XANES) and pair distribution function analysis of X-ray total scattering data (PDF). Although the average crystal structure of the nanocrystals is adequately described by a centrosymmetric, cubic Pm3m space group, local ferroelectric distortions due to the displacement of the titanium atom from the center of the perovskite lattice are observed for all compositions, except BaZrO3. The symmetry of the ferroelectric distortions is adequately described by a tetragonal P4mm space group. The magnitude of the local displacements of the titanium atom in BaTiO3 nanocrystals is comparable to that observed in single crystals and bulk ceramics, but the coherence length of their ferroelectric coupling is much shorter (≤20 Å). Substitution of Sr(2+) for Ba(2+) and of Zr(4+) for Ti(4+) induces a tetragonal-to-cubic transition of the room temperature local crystal structure, analogous to that observed for single crystals and bulk ceramics at similar compositions. This transition is driven by a reduction of the magnitude of the local displacements of the titanium atom and/or of the coherence length of their ferroelectric coupling. Replacing 50% of Ba(2+) with Sr(2+) slightly reduces the magnitude of the titanium displacement, but the coherence length is not affected. In contrast, replacing 15% of the ferroelectrically active Ti(4+) with Zr(4+) leads to a significant reduction of the coherence length. Deviations from the ideal solid solution behavior are observed in BaTi(1-y)Zr(y)O3 nanocrystals and are attributed to an inhomogeneous distribution of the barium atoms in the nanocrystal. Composition-structure relationships derived for Ba(1-x)Sr(x)TiO3

  3. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19.

    PubMed

    Rowley, S E; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A T; Watts, B E; Scott, J F

    2016-05-17

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T(3), in contrast to the 1/T(2) dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T(3), i.e. with a critical exponent γ = 3. In general γ = (d + z - 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T(3).

  4. Geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro basin, Texas

    SciTech Connect

    Langmuir, D.; Melchior, D.

    1985-11-01

    The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin of north Texas, was studied to define geochemical controls on radionuclides such as /sup 90/Sr and /sup 226/Ra. Published solubility data for gypsum, anhydrite, celestite, barite and RaSO/sub 4/ were first reevaluated, in most cases using the ion interaction approach of Pitzer, to determine solubility products of the sulfates as a function of temperature and pressure. Ionic strengths of the brines were from 2.9 to 4.8 m, their temperatures and pressures up to 40/sup 0/C and 130 bars. Saturation indices of the sulfates were computed with the ion-interaction approach in one brine from the arkosic granite wash facies and four from the carbonate Wolfcamp Formation. All five brines are saturated with respect to gypsum, anhydrite and celestite, and three of the five with respect to barite. All are undersaturated by from 5 to 6 orders of magnitude with respect to pure RaSO/sub 4/. /sup 226/Ra concentrations in the brines, which ranged from 10/sup -11.3/ to 10/sup -12.7/ m, are not controlled by RaSO/sub 4/ solubility or adsorption, but possibly by the solubility of trace Ra solid solutions in sulfates including celestite and barite.

  5. The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin, Texas

    NASA Astrophysics Data System (ADS)

    Langmuir, Donald; Melchior, Daniel

    1985-11-01

    The geochemistry of Ca, Sr, Ba and Ra sulfates in some deep brines from the Palo Duro Basin of north Texas, was studied to define geochemical controls on radionuclides such as 90Sr and 226Ra. Published solubility data for gypsum, anhydrite, celestite, barite and RaSO 4 were first reevaluated, in most cases using the ion interaction approach of Pitzer, to determine solubility products of the sulfates as a function of temperature and pressure. Ionic strengths of the brines were from 2.9 to 4.8 m, their temperatures and pressures up to 40°C and 130 bars. Saturation indices of the sulfates were computed with the ion-interaction approach in one brine from the arkosic granite wash fades and four from the carbonate Wolfcamp Formation. All five brines are saturated with respect to gypsum, anhydrite and celestite, and three of the five with respect to barite. All are undersaturated by from 5 to 6 orders of magnitude with respect to pure RaSO 4. 226Ra concentrations in the brines, which ranged from 10 -11.3 to 10 -12.7 m, are not controlled by RaSO 4 solubility or adsorption, but possibly by the solubility of trace Ra solid solutions in sulfates including celestite and barite.

  6. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19

    PubMed Central

    Rowley, S. E.; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A. T.; Watts, B. E.; Scott, J. F.

    2016-01-01

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T3, in contrast to the 1/T2 dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T3, i.e. with a critical exponent γ = 3. In general γ = (d + z – 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T3. PMID:27185343

  7. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19.

    PubMed

    Rowley, S E; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A T; Watts, B E; Scott, J F

    2016-01-01

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T(3), in contrast to the 1/T(2) dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T(3), i.e. with a critical exponent γ = 3. In general γ = (d + z - 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T(3). PMID:27185343

  8. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19

    NASA Astrophysics Data System (ADS)

    Rowley, S. E.; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A. T.; Watts, B. E.; Scott, J. F.

    2016-05-01

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T3, in contrast to the 1/T2 dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T3, i.e. with a critical exponent γ = 3. In general γ = (d + z – 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T3.

  9. Thermoelectric properties of rhodates: Layered β-SrRh2O4 and spinel ZnRh2O4

    NASA Astrophysics Data System (ADS)

    Wilson-Short, G. B.; Singh, D. J.; Fornari, M.; Suewattana, M.

    2007-01-01

    Density functional calculations are used to obtain the electronic structure of β-SrRh2O4 in comparison with spinel ZnRh2O4 . Both materials are band insulators, with substantial crystal field induced band gaps, reflecting strong transition-metal-O hybridization. However, due to the bonding topology in these materials, the valence bands are very narrow. This leads to high thermopowers within standard Boltzmann transport theory, and indicates that they can be the basis of good thermoelectric materials provided that they can be doped into metallic states with reasonable carrier mobility. In the case of β-SrRh2O4 , scattering due to Sr disorder is important. Also, again in β-SrRh2O4 , the band gap may be large enough to be of interest for photoelectrochemical H2 production.

  10. Optical, microstructural, vibrational, and theoretical studies of p-type SrCu2O2 and BaCu2O2 transparent conductive oxides

    NASA Astrophysics Data System (ADS)

    Even, J.; Pedesseau, L.; Modreanu, M.; Huyberechts, G.; Servet, B.; Garry, Guy; Chaix-Pluchery, O.; Durand, O.

    2013-03-01

    Transparent conducting metal oxides (TCO) are unusual semiconducting materials displaying transparency to visible light. TCO materials are used for electrostatic shielding, antistatic screens, transparent heating devices, solar cells and even organic light emitting diodes. However, most TCOs are n-type, while p-type TCOs are scarce. SrCu2O2 is a leading candidate as a p-type transparent conductive oxide. In this paper, we report theoretical calculations and experimental studies on the vibrational, optical and microstructural properties of both bulk and thin films of polycrystalline undoped SrCu2O2 obtained by pulsed laser deposition (PLD). Barium doping of the SrCu2O2 by substitution of Sr atoms is also reported. The simulated crystal structures of both SrCu2O2 and BaCu2O2 materials, obtained through a state-of-the-art implementation of the Density functional theory, are compared with experimental X-ray diffraction data of undoped and Ba-doped SrCu2O2 bulk materials. Raman spectra of both SCO and BCO materials are simulated from the derivatives of the dielectric susceptibility and a symmetry analysis of the optical phonon eigenvectors at the Brillouin zone center is proposed. Good agreement with Raman scattering experimental results is demonstrated.

  11. High ferroelectric polarization in c-oriented BaTiO3 epitaxial thin films on SrTiO3/Si(001)

    DOE PAGESBeta

    Scigaj, M.; Chao, C. H.; Gázquez, J.; Fina, I.; Moalla, R.; Saint-Girons, G.; Chisholm, M. F.; Herranz, G.; Fontcuberta, J.; Bachelet, R.; et al

    2016-09-21

    The integration of epitaxial BaTiO3 films on silicon, combining c-orientation, surface flatness, and high ferroelectric polarization is of main interest towards its use in memory devices. This combination of properties has been only achieved so far by using yttria-stabilized zirconia buffer layers. Here, the all-perovskite BaTiO3/LaNiO3/SrTiO3 heterostructure is grown monolithically on Si(001). The BaTiO3 films are epitaxial and c-oriented and present low surface roughness and high remnant ferroelectric polarization around 6 μC/cm2. Lastly, this result paves the way towards the fabrication of lead-free BaTiO3 ferroelectric memories on silicon platforms.

  12. Large-scale synthesis of Ba{sub x}Sr{sub 1−x}TiO{sub 3} nanowires with controlled stoichiometry

    SciTech Connect

    Tang, Haixiong E-mail: hsodano@ufl.edu; Zhou, Zhi; Sodano, Henry A. E-mail: hsodano@ufl.edu

    2014-04-07

    This study demonstrates a highly efficient method for large-scale synthesis BaTiO{sub 3} nanowires (NWs) using a two-step hydrothermal reaction. This synthesis process provides a facile approach to the growth of BaTiO{sub 3} NWs with high yield and control over the stoichiometry of the Ba{sub x}Sr{sub 1−x}TiO{sub 3} solid solution. The ferroelectricity of the BaTiO{sub 3} NWs is directly characterized using atomic force microscopy with the piezoelectric strain coupling coefficient (d{sub 33}) reaching 31.1 pm/V. This work provide an avenue for high volume manufacturing of ferroelectric NWs, allowing both fundamental investigation of nanoscale ferroelectricity as well as their future application in the electrical devices.

  13. High ferroelectric polarization in c-oriented BaTiO3 epitaxial thin films on SrTiO3/Si(001)

    NASA Astrophysics Data System (ADS)

    Scigaj, M.; Chao, C. H.; Gázquez, J.; Fina, I.; Moalla, R.; Saint-Girons, G.; Chisholm, M. F.; Herranz, G.; Fontcuberta, J.; Bachelet, R.; Sánchez, F.

    2016-09-01

    The integration of epitaxial BaTiO3 films on silicon, combining c-orientation, surface flatness, and high ferroelectric polarization is of main interest towards its use in memory devices. This combination of properties has been only achieved so far by using yttria-stabilized zirconia buffer layers. Here, the all-perovskite BaTiO3/LaNiO3/SrTiO3 heterostructure is grown monolithically on Si(001). The BaTiO3 films are epitaxial and c-oriented and present low surface roughness and high remnant ferroelectric polarization around 6 μC/cm2. This result paves the way towards the fabrication of lead-free BaTiO3 ferroelectric memories on silicon platforms.

  14. In vitro and in vivo studies on biodegradable CaMgZnSrYb high-entropy bulk metallic glass.

    PubMed

    Li, H F; Xie, X H; Zhao, K; Wang, Y B; Zheng, Y F; Wang, W H; Qin, L

    2013-11-01

    In order to enhance the corrosion resistance of the Ca65Mg15Zn20 bulk metallic glass, which has too fast a degradation rate for biomedical applications, we fabricated the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass because of the unique properties of high-entropy alloys. Our results showed that the mechanical properties and corrosion behavior were enhanced. The in vitro tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass could stimulate the proliferation and differentiation of cultured osteoblasts. The in vivo animal tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass did not show any obvious degradation after 4 weeks of implantation, and they can promote osteogenesis and new bone formation after 2 weeks of implantation. The improved mechanical properties and corrosion behavior can be attributed to the different chemical composition as well as the formation of a unique high-entropy atomic structure with a maximum degree of disorder.

  15. Theoretical survey on M@C80 (M = Ca, Sr, and Ba): Behavior of different alkaline earth metal impacting the chemical stability and electronic properties

    NASA Astrophysics Data System (ADS)

    Cui, Jin-Bo; Guo, Yi-Jun; Li, Qiao-Zhi; Zhao, Pei; Zhao, Xiang

    2016-08-01

    Structures of mono-metallofullerenes M@C80 (M = Ca, Sr, and Ba) that separated in early experiment are determined owning the C2v(31920)-C80 cage. The change rule of properties for M@C80 (M = Ca, Sr, and Ba) influenced by different inner metal are discussed. As the trapped metal changes from calcium to barium, performance of thermodynamic stabilities for M@C2v(31920)-C80, M@C2v(31922)-C80, and M@D5h(31923)-C80 are significantly different. Orbital analysis suggests that the lowest unoccupied molecular orbitals (LUMOs) of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 are mostly located on the trapped metal, whereas reduction reactions of Ca@C2v(31920)-C80 and Ca@D5h(31923)-C80 occur on the fullerene cage. Natural electron configuration analyses demonstrates that the decentralized electron back-donation of Ba@C2v(31920)-C80 would take responsible for the instability of itself. Electronic properties such as electron affinities and ionization potentials are significantly affected by encapsulated metal are also found. Computational UV-visible-NIR spectra for M@C2v(31920)-C80 (M = Ca, Sr, Ba) are in perfect accord with the spectra obtained experimentally.

  16. Mechanochemical synthesis, structure, and properties of solid solutions of alkaline earth metal fluorides: Ma1-xMbxF2 (M: Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Heise, M.; Scholz, G.; Düvel, A.; Heitjans, P.; Kemnitz, E.

    2016-10-01

    The capability of mechanochemical synthesis for the formation of solid solutions of alkaline earth metal fluorides Ma1-xMbxF2 (M: Ca, Sr, Ba) was tested by fluorination of metal acetates and metal hydroxides with ammonium fluoride directly at milling. Evidence was found for a mutual substitution of cations on their lattice positions in Ca1-xSrxF2 and Ba1-xSrxF2 samples. For the Ba/Ca-system this synthesis route is only partially successful. X-ray diffraction and 19F MAS NMR spectroscopy were used to characterize all samples concerning their crystal structure and local fluorine coordination. Calculations of 19F chemical shifts with the superposition model along with probability calculations for the intensity of the individual 19F lines, performed in dependence on the molar composition of the samples, perfectly agree with the experimental findings. The fluoride ion conductivity of as-prepared samples, determined by temperature dependent DC conductivity measurements, is significantly higher than those of crystalline binary fluorides. Moreover, a higher F- ion conductivity is observed for samples with higher mixing grade in the Ca/Sr-and the Ba/Sr-systems.

  17. Synthesis and Microwave Dielectric Properties of A16V18O61 (A = Ba, Sr and Ca) Ceramics for LTCC Applications

    NASA Astrophysics Data System (ADS)

    Suresh, E. K.; Prasad, K.; Arun, N. S.; Ratheesh, R.

    2016-06-01

    Low-temperature co-firable A16V18O61 (A = Ba, Sr, Ca) ceramics have been prepared through the solid state ceramic route. The structural features of these ceramics have been studied using the x-ray diffraction (XRD) technique. The existence of the A16V18O61 (A = Ba, Sr, Ca) ceramic phase was confirmed through laser Raman spectroscopic studies. Scanning electron microscopy analysis revealed a dense microstructure for the ceramics with closely packed polygonal grains. Among the samples studied, Ba16V18O61 ceramic was prepared in the ultralow sintering temperature of 620°C for 1 h, which can be co-firable with an aluminium electrode. XRD and electron dispersive spectroscopy analyses showed that the samples under study have excellent compatibility with metal electrodes. The microwave dielectric properties measured using a vector network analyzer revealed that A16V18O61 (A = Ba, Sr, Ca) ceramics have excellent unloaded quality factors.

  18. Les Néandertaliens étaient-ils essentiellement carnivores ? Résultats préliminaires sur les teneurs en Sr et en Ba de la paléobiocénose mammalienne de Saint-CésaireWere Neandertalians essentially carnivores? Sr and Ba preliminary results of the mammalian palaeobiocoenosis of Saint-Césaire

    NASA Astrophysics Data System (ADS)

    Balter, Vincent; Person, Alain; Labourdette, Nathalie; Drucker, Dorothée; Renard, Maurice; Vandermeersch, Bernard

    2001-01-01

    Strontium-calcium (Sr/Ca) and barium-calcium (Ba/Ca) ratios are reduced constantly between diet and bioapatite in mammal organisms. This phenomenon leads to a reduction in the Sr/Ca and Ba/Ca ratios at higher trophic level in predator-prey mammalian communities, and is applied here to the reconstruction of a castelperronian food web, which includes a Neanderthal specimen. Adapted chemical pretreatment allows to isolate bioapatite from diagenetic compounds for analysis of Ca, Sr and Ba. Sr/Ca and Ba/Ca results of the fauna are consistent with trophic predictions. Initial results for the Neandertal suggest that he was mostly carnivorous. Distribution of Ba/Ca values of bones of herbivorous taxa reveals that ruminant animals can be distinguished from non-ruminants. The biosegregation model predicts that the diet of the Neandertal was composed by about 97 % in weight of meat with a weak contribution of vegetable or fish, and that the association of fish and plant is excluded in any proportion.

  19. Concentrations and ratios of Sr, Ba and Ca along an estuarine river to the Gulf of Mexico - implication for sea level rise effects on trace metal distribution

    NASA Astrophysics Data System (ADS)

    He, S.; Xu, Y. J.

    2015-11-01

    Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. As sea level rise continues, many estuarine rivers in the world face saltwater intrusion, which may cause changes in mobility and distribution of these metals upstream. Despite intensive research on metal adsorption and desorption in marine systems, knowledge of the spatiotemporal distribution of these elements along estuarine rivers is still limited. In this study, we conducted an intensive monitoring of Sr and Ba dynamics along an 88 km long estuary, the Calcasieu River in South Louisiana, USA, which has been strongly affected by saltwater intrusion. Over the period from May 2013 to August 2015, we collected monthly water samples and performed in-situ water quality measurements at six sites from the upstream to the river mouth, with a salinity range from 0.02 to 29.50 ppt. Water samples were analyzed for Sr, Ba, and Ca concentrations. In-situ measurements were made on salinity, pH, water temperature, dissolved oxygen concentration, and specific conductance. We found that the Sr and Ca concentrations and the Sr / Ca ratio all increased significantly with increasing salinity. The average Sr concentration at the site closest to the Gulf of Mexico (site 6) was 46.21 μmol L-1, which was about 130 times higher than that of the site furthest upstream (site 1, 0.35 μmol L-1). The average Ca concentration at site 6 was 8.19 mmol L-1, which was about 60 times higher than that of site 1 (0.13 mmol L-1). The average Sr / Ca ratio at site 6 (8.41 mmol mol-1) was about 3 times the average Sr / Ca ratio at site 1 (2.89 mmol mol-1). However, the spatial variation in Ba concentration was marginal, varying from 0.36 μmol L-1 at site 6 to 0.47 at site 5. The average Ba / Ca ratio at site 1 (4.82 mmol mol-1) was about 54 times the average Ba / Ca ratio at site 6 (0.09 mmol mol-1), showing a clear negative relation between the Ba / Ca ratio and increasing

  20. Submerged arc discharge technique to explore novel non-carbon nanotubes: Syntheses of nanotubes from ZnO and BaTiO3

    NASA Astrophysics Data System (ADS)

    Sano, Noriaki; Tamon, Hajime

    2014-04-01

    A unique reaction field using arc discharge in water can create novel nanostructures, where an extreme temperature drop is observed in bubbles around a hot arc plasma zone. Here, a Mo anode had a hole at its tip, into which ZnO or BaTiO3 powder was stuffed. The cathode received film products on its surface. It was revealed that BaTiO3 nanotubes were firstly synthesized as novel nanotubes when BaTiO3 powder was stuffed in the anode hole. When ZnO powder was stuffed in the anode hole, narrow ZnO nanotubes were synthesized. The diameter of the ZnO nanotubes synthesized was the smallest ever reported.

  1. Preferential Eu Site Occupation and Its Consequences in the Ternary Luminescent HalidesAB2I5:Eu2+(A=Li–Cs;B=Sr, Ba)

    DOE PAGESBeta

    Fang, C.  M.; Biswas, Koushik

    2015-07-22

    Several rare-earth-doped, heavy-metal halides have recently been identified as potential next-generation luminescent materials with high efficiency at low cost. AB2I5:Eu2+ (A=Li–Cs; B=Sr, Ba) is one such family of halides. Its members, such as CsBa2I5:Eu2+ and KSr2I5:Eu2+, are currently being investigated as high-performance scintillators with improved sensitivity, light yield, and energy resolution less than 3% at 662 keV. Within the AB2I5 family, our first-principles-based calculations reveal two remarkably different trends in Eu site occupation. The substitutional Eu ions occupy both eightfold-coordinated B1(VIII) and the sevenfold-coordinated B2(VII) sites in the Sr-containing compounds. However, in the Ba-containing crystals, Eu ions strongly prefer themore » B2(VII)sites. This random versus preferential distribution of Eu affects their electronic properties. The calculations also suggest that in the Ba-containing compounds one can expect the formation of Eu-rich domains. These results provide atomistic insight into recent experimental observations about the concentration and temperature effects in Eu-doped CsBa2I5. We discuss the implications of our results with respect to luminescent properties and applications. We also hypothesize Sr, Ba-mixed quaternary iodides ABaVIIISrVIII5:Eu as scintillators having enhanced homogeneity and electronic properties.« less

  2. Explaining the Ba, Y, Sr, and Eu abundance scatter in metal-poor halo stars: constraints to the r-process

    NASA Astrophysics Data System (ADS)

    Cescutti, G.; Chiappini, C.

    2014-05-01

    Context. Thanks to the heroic observational campaigns carried out in recent years we now have large samples of metal-poor stars for which measurements of detailed abundances exist. In particular, large samples of stars with metallicities -5 < [Fe/H] <-1 and measured abundances of Sr, Ba, Y, and Eu are now available. These data hold important clues on the nature of the contribution of the first stellar generations to the enrichment of our Galaxy. Aims: We aim to explain the scatter in Sr, Ba, Y, and Eu abundance ratio diagrams unveiled by the metal-poor halo stars. Methods: We computed inhomogeneous chemical evolution models for the Galactic halo assuming different scenarios for the r-process site: the electron-capture (EC) supernovae and the magnetorotationally driven (MRD) supernovae scenarios. We also considered models with and without the contribution of fast-rotating massive stars (spinstars) to an early enrichment by the s-process. A detailed comparison with the now large sample of stars with measured abundances of Sr, Ba, Y, Eu, and Fe is provided (both in terms of scatter plots and number distributions for several abundance ratios). Results: The scatter observed in these abundance ratios of the very metal-poor stars (with [Fe/H] <-2.5) can be explained by combining the s-process production in spinstars, and the r-process contribution coming from massive stars. For the r-process we have developed models for both the EC and the MRD scenarios that match the observations. Conclusions: With the present observational and theoretical constraints we cannot distinguish between the EC and the MRD scenarios in the Galactic halo. Independently of the r-process scenarios adopted, the production of elements by an s-process in spinstars is needed to reproduce the spread in abundances of the light neutron capture elements (Sr and Y) over heavy neutron capture elements (Ba and Eu). We provide a way to test our suggestions by means of the distribution of the Ba isotopic

  3. Tl 2Ba 2- xSr xCuO 6: A system exhibiting a compositionally controlled superconductor-metal transition

    NASA Astrophysics Data System (ADS)

    Ganguli, A. K.; Subramanian, M. A.

    1991-02-01

    Strontium-substituted thallium cuprates of the type Tl 2Ba 2- xSr xCuO 6 have been synthesized for various values of x. Single phases were obtained for x ≤ 1.2. The compounds crystallize in the tetragonal structure with space group {I4}/{mmm} as the parent Tl 2Ba 2CuO 6 oxide. Both a and c lattice parameter decrease with increase in x. Tc decreases gradually from 92 to 77 K ( x = 0.8). Beyond x = 1.0 superconductivity is lost. The x = 1.2 comparison is metallic down to 4.2 K.

  4. The effect of temperature and surface area on Sr, Ba and REE fractionation during low temperature serpentinization

    NASA Astrophysics Data System (ADS)

    Frisby, C. P.; Bizimis, M.; Foustoukos, D.

    2013-12-01

    Peridotite hosted hydrothermal vent systems are a direct link between the hydrosphere and the Earth's mantle. They promote elemental mass exchange between these two regimes, driven by hydrothermal alteration of peridotite by seawater. Most experimental, theoretical and field studies of peridotite alteration have focused on high temperature (>1800C) conditions where serpentinization is readily observed, but less is known for low-temperature alteration that likely resembles near seafloor processes. Furthermore, while major element exchange during serpentinization has been studied extensively, the behavior of trace elements remains unclear, especially at low temperatures (<1000C). Here we report data from time-series experiments designed to constrain the reaction of Sr, Ba and REE between synthetic seawater and olivine as a function of both temperature (15-900C) and mineral grain size (geometric surface area). Our experimental data shows a clear decoupling of REE from Sr-Ba under all experimental conditions. While Sr and Ba remain quantitatively in solution, the REE are being removed from the solution at rates that increase with increasing temperature and GSA (i.e. decreasing particle size). We also observe the HREE are removed from solution faster than the LREE. The REE removal can be described as a two-stage process, with a fast initial rate followed by a slower rate as the reaction approaches equilibrium. For instance at 900C and GSA of 57.57cm2/g (average grain diameter of 258.7μm), 50% of Nd is removed in 8 hours but only 80% at 120 hours. We quantify the initial reaction rate constant of each element as a function of temperature and grain size, in order to understand the mechanisms of REE removal. The experimentally determined surface-normalized reaction rate constants (0.29-1.84 s-1m-2), constrain the temperature dependence and activation energy for the scavenging of REE driven by olivine hydrolysis. For example, LREE reaction rates have a higher temperature

  5. Epitaxial Ba2IrO4 thin-films grown on SrTiO3 substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Nichols, J.; Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A.

    2014-03-01

    We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metal-insulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting physical properties predicted in layered iridates.

  6. Spontaneous orientation-tuning driven by the strain variation in self-assembled ZnO-SrRuO{sub 3} heteroepitaxy

    SciTech Connect

    Zhu, Yuanmin; Liu, Ruirui; Zhan, Qian; Chang, Wei Sea; Yu, Rong; Wei, Tzu-Chiao; He, Jr-Hau; Chu, Ying-Hao

    2015-11-09

    Heteroepitaxial ZnO and SrRuO{sub 3} were grown on SrTiO{sub 3} (111) substrates and formed a self-assembled wurtzite-perovskite nanostructure. Spontaneous orientation-tuning of the SrRuO{sub 3} pillars was observed, with the growth direction changing from [111]{sub SRO} to [011]{sub SRO} as the film thickness increased, which is attributed to a misfit strain transition from the biaxial strain imposed by the SrTiO{sub 3} substrate to the vertical strain provided by the ZnO matrix. The [011]-SrRuO{sub 3} and [0001]-ZnO combination presents a favorable matching in the nanocomposite films, resulting in higher charge carrier mobility. This vertically integrated configuration and regulation on the crystallographic orientations are expected to be employed in designing multi-functional nanocomposite systems for applications in electronic devices.

  7. Isotopic evidence for the retention of Sr-90 inferred from excess Zr-90 in the Oklo natural fission reactors: Implication for geochemical behaviour of fissiogenic Rb, Sr, Cs and Ba

    NASA Astrophysics Data System (ADS)

    Hidaka, Hiroshi; Sugiyama, Takeshi; Ebihara, Mitsuru; Holliger, Philippe

    1994-03-01

    In order to investigate the mobility of fissiogenic Sr-90 in the geological environment, the Zr isotopic compositions of seven samples from one of the newly formed Oklo natural reactor zones (i.e., reactor core and adjacent rocks (10, SF84)) in the Republic of Gabon were determined with an inductively coupled plasma mass spectrometer (ICP-MS). Zr isotopes in uraninite grains from different reactor zones were also measured by secondary ion mass spectrometry (SIMS). Fissiogenic Zr isotopic abundances of three samples from the reactor core have excess Zr-90, which has never before been formed in previous Oklo samples. In this paper, the geochemical behaviour of Zr-90 is discussed by making use of the relative retentivity inferred from the isotopic abundance of Sr. The excess in Zr-90 suggests dependence on the degree of retention/migration of Sr-90, the precursor of Zr-90 in the fission chain. In the aqueous phase, chemical fractionation between Sr and Zr could have occurred before radioactive Sr-90 decayed. Considering the halflife of Sr-90 (t(sub 1/2) = 29.1 y), considerable amounts of the latter have been produced during criticality. Sr and Zr (including Zr-90) could have been redistributed between the reactor core and its vicinity. The retentivity of fissiogenic Zr-90 in reactor core 10 is not homogeneous. In addition, the distributions of Rb, Cs and Ba is also heterogeneous.

  8. Real space imaging of spin polarons in Zn-doped SrCu(2)(BO(3))(2).

    PubMed

    Yoshida, M; Kobayashi, H; Yamauchi, I; Takigawa, M; Capponi, S; Poilblanc, D; Mila, F; Kudo, K; Koike, Y; Kobayashi, N

    2015-02-01

    We report on the real space profile of spin polarons in the quasi-two-dimensional frustrated dimer spin system SrCu(2)(BO(3))(2) doped with 0.16% of Zn. The (11)B nuclear magnetic resonance spectrum exhibits 15 additional boron sites near nonmagnetic Zn impurities. With the help of exact diagonalizations of finite clusters, we have deduced from the boron spectrum, the distribution of local magnetizations at the Cu sites with fine spatial resolution, providing direct evidence for an extended spin polaron. The results are confronted with those of other experiments performed on doped and undoped samples of SrCu(2)(BO(3))(2). PMID:25699459

  9. Transparent Conducting Properties of SrSnO3 and ZnSnO3

    SciTech Connect

    Ong, Khuong P.; Fan, Xiaofeng; Subedi, Alaska; Sullivan, Michael B.; Singh, David J.

    2015-04-29

    We report optical properties of doped n-type SrSnO3 and ZnSnO3 in relation to potential application as transparent conductors. We find that the orthorhombic distortion of the perovskite structure in SrSnO3 leads to absorption in the visible as the doping level is increased. This arises from interband transitions. We find that strain tuning could modify this absorption, but does not eliminate it. On the other hand, we find that ZnSnO3 although also having a non-cubic structure, can retain excellent transparency when doped, making it a good candidate transparent conductor.

  10. First-Principles Study of the Structural, Optical, Dynamical and Thermodynamic Properties of BaZnO2 Under Pressure

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Xian; Hu, Cui-E.; Chen, Yang-Mei; Cheng, Yan; Ji, Guang-Fu

    2016-11-01

    The structural, optical, dynamical, and thermodynamic properties of BaZnO2 under pressure are studied based on the density functional theory. The calculated structural parameters are consistent with the available experimental data. In the ground state, the electronic band structure and density of states indicate that BaZnO2 is an insulator with a direct gap of 2.2 eV. The Mulliken charges are also analyzed to characterize the bonding property. After the structural relaxation, the optical properties are studied. It is found that the dielectric function of E Vert x and EVert y are isotropic, whereas the EVert x and EVert z are anisotropic. The effect of pressure on the energy-loss function in the ultraviolet region becomes more obvious as the pressure increases. Furthermore, the dynamical properties under different pressures are investigated using the finite displacement method. We find that the P3121 phase of BaZnO2 is dynamically stable under the pressure ranging from 0 GPa to 30 GPa. The phonon dispersion curves, phonon density of states, vibrational modes and atoms that contribute to these vibrations at {{\\varvec{Γ }}} point under different pressures are also reported in this work. Finally, by employing the quasi-harmonic approximation, the thermodynamic properties such as the temperature dependence of the thermal expansion coefficient, specific heat, entropy and Gibbs free energy under different pressures are investigated. It is found that the influences of the temperature on the heat capacity are much more significant than that of the pressure on it.

  11. Luna 16 - Some Li, K, Rb, Sr, Ba, rare-earth, Zr, and Hf concentrations.

    NASA Technical Reports Server (NTRS)

    Philpotts, J. A.; Schnetzler, C. C.; Schuhmann, S.; Thomas , H. H.; Bottino, M. L.

    1972-01-01

    Concentrations of Li, K, Rb, Sr, Na, rare-earths, Zr and Hf have been determined for some Luna 16 core materials by mass-spectrometric isotope-dilution. Two regolith fines samples from different depths in the core, and four rock-chips, including both igneous rocks and breccias, have similar trace-element concentrations. The Luna 16 materials have general lunar trace-element characteristics but differ from other returned lunar samples in a manner that suggests the presence of excess feldspar. Unless the Luna 16 igneous rocks are fused soils, they appear to represent either partial plagioclase cumulates or the least differentiated igneous material yet returned from the moon. The similarity in trace-element concentrations of the igneous rocks and the fines would then suggest largely local derivation of the Luna 16 regolith.

  12. Microwave Dielectric Properties for Ba(Mg1/3Ta2/3)O3 A(Mg1/2W1/2)O3 (A=Ba, Sr, and Ca) Ceramics

    NASA Astrophysics Data System (ADS)

    Furuya, Mitsuru; Ochi, Atsushi

    1994-09-01

    For a high-Q dielectric resonator at microwave frequencies, complex perovskite-structured Ba(Mg1/3Ta2/3)O3 A(Mg1/2W1/2)O3 (A=Ba, Sr, and Ca) ceramics have been developed. A(Mg1/2W1/2)O3 effects on the crystal structure, microstructure, and microwave characteristic of Ba(Mg1/3Ta2/3)O3 (BMT) were investigated. Ba(Mg1/2W1/2)O3 (BMW) decreased the temperature coefficient of resonant frequency ( TCF) for BMT. Sr(Mg1/2W1/2)O3 (SMW) and Ca(Mg1/2W1/2)O3 (CMW) increased it. Zero TCF was obtained for the BMT/BMW=95/5 composition. With 0.5 mol% BMW content, dielectric loss quality, Q d, reached a maximum (40000 at 10 GHz).

  13. Modeling tunable bulk acoustic resonators based on induced piezoelectric effect in BaTiO3 and Ba0.25Sr0.75TiO3 films

    NASA Astrophysics Data System (ADS)

    Vendik, Irina B.; Turalchuk, Pavel A.; Vendik, Orest G.; Berge, John

    2008-01-01

    A model for tunable thin film bulk acoustic resonators (TFBARs) based on ferroelectric films is proposed. The model is based on electromechanical equations taking into account piezoelectric effect and electrostriction effect induced by the dc electric field. The dc field induced shift of the resonant frequency is explained by the high-order nonlinear effects in the ferroelectric material. The main contribution to the tunability of the resonant frequency under dc electric field can be attributed to electrostriction, which is nonlinear with respect to the mechanical deformation. It is shown that the upward or downward shift in the resonant frequency is given by the sign of the nonlinear component of the electrostriction tensor M. The model is verified by comparing the results with the measured microwave input impedance of BaTiO3 and Ba0.25Sr0.75TiO3 based TFBARs. For a positive sign of the nonlinear coefficient of electrostriction M, the model predicts an upward shift of the resonant frequencies (resonance and antiresonance) under dc biasing in case of the TFBAR based on BaTiO3, whereas a negative sign of the nonlinear coefficient of electrostriction M predicts downward shift of the resonant frequencies for TFBAR based on Ba0.25Sr0.75TiO3 films.

  14. MOCVD (Ba{sub x}Sr{sub 1-x})Ti{sub 1+y}O{sub 3+z} (BST) thin films for high frequency tunable devices.

    SciTech Connect

    Baumann, P. K.; Kaufman, D. Y.; Im, J.; Auciello, O.; Streiffer, S. K.; Erck, R. A.; Giumarra, J.

    2001-01-01

    We have investigated the structural and electrical characteristics of (Ba{sub x}Sr{sub 1-x})Ti{sub 1+y}O{sub 3+z} (BST) thin films synthesized at 650{sup o}C on Pt/SiO{sub 2}/Si substrates using a large area, vertical metalorganic chemical vapor deposition (MOCVD) reactor equipped with a liquid delivery system. Films with a Ba/Sr ratio of 70/30 were studied, as determined using X-ray fluorescence spectroscopy (XRF) and Rutherford backscattering spectrometry (RBS). A substantial reduction of the dielectric loss was achieved when annealing the entire capacitor structure in air at 700{sup o}C. Dielectric tunability as high as 2.3:1 was measured for BST capacitors with the currently optimized processing conditions.

  15. Syntheses and characterization of energetic compounds constructed from alkaline earth metal cations (Sr and Ba) and 1,2-bis(tetrazol-5-yl)ethane

    NASA Astrophysics Data System (ADS)

    Xia, Zhengqiang; Chen, Sanping; Wei, Qing; Qiao, Chengfang

    2011-07-01

    Two new energetic compounds, [ M(BTE)(H 2O) 5] n ( M=Sr(1), Ba(2)) [H 2BTE=1,2-bis(tetrazol-5-yl)ethane], have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that they are isomorphous and exhibit 2D (4,4) net framework, generated by 4-connected Sr 2(H 2O) 10/Ba 2(H 2O) 10 SBUs linked up by two independent binding modes of H 2BTE, and the resulting 2D structure is interconnected by hydrogen-bond and strong face to face π- π stacking interactions between two tetrazole rings to lead to a 3D supramolecular architecture. DSC measurements show that they have significant catalytic effects on thermal decomposition of ammonium perchlorate. Moreover, the photoluminescence properties, thermogravimetric analyses, and flame colors of the as-prepared compounds are also investigated in this paper.

  16. Abnormal thermal conductivity in tetragonal tungsten bronze Ba{sub 6−x}Sr{sub x}Nb{sub 10}O{sub 30}

    SciTech Connect

    Kolodiazhnyi, T. Sakurai, H.; Vasylkiv, O.; Borodianska, H.; Mozharivskyj, Y.

    2014-03-17

    Ba{sub 6−x}Sr{sub x}Nb{sub 10}O{sub 30} solid solution with 0 ≤ x ≤ 6 crystallizes in centrosymmetric tetragonal “tungsten bronze” structure (space group P4/mbm). We report on the x dependence of thermal conductivity of polycrystalline samples measured in the 2–400 K temperature interval. Substitution of Sr for Ba brings about a significant decrease in thermal conductivity at x ≥ 3 accompanied by development of a low-temperature (T ≈ 10–30 K) “plateau” region reminiscent of a glass-like compounds. We explain this behaviour based on a size-driven site occupancy and atomic displacement parameters associated with an alkaline earth atomic positions in the title compounds.

  17. Direct approach for flexoelectricity from first-principles calculations: cases for SrTiO3 and BaTiO3.

    PubMed

    Xu, Tao; Wang, Jie; Shimada, Takahiro; Kitamura, Takayuki

    2013-10-16

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO3 and SrTiO3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO3, the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO3, our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects.

  18. Enhance D. C. resistivity of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by acceptor (Mn) doping

    SciTech Connect

    Sharma, Hakikat Arya, G. S.; Pramar, Kusum; Negi, N. S.

    2015-05-15

    In the present work, we prepared Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Mn (2 and 3 at % on Ti site) doped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by sol- gel method. The samples were characterized by X-ray diffraction (XRD). The XRD patterns reveled that Mn ions did not change the perovskite structure of BST (70/30). The dielectric measurements proved that dielectric constant decreased with Mn doping. The dc resistivity was studied by using I-V measurements. The dc resistivity of the BST increased with Mn doping, which suppressed the leakage current.

  19. Comparative studies of dipole polarizabilities in Sr{sup +}, Ba{sup +}, and Ra{sup +} and their applications to optical clocks

    SciTech Connect

    Sahoo, B. K.; Timmermans, R. G. E.; Das, B. P.; Mukherjee, D.

    2009-12-15

    Static dipole polarizabilities are calculated in the ground and metastable states of Sr{sup +}, Ba{sup +} and Ra{sup +} using the relativistic coupled-cluster method. Trends of the electron correlation effects are investigated in these atomic ions. We also estimate the Stark and black-body radiation shifts from these results for these systems for the transitions proposed for the optical frequency standards and compare them with available experimental data.

  20. Structural and photoluminescence properties of Dy3+ co-doped and Eu2+ activated MAl2O4 (M = Ba, Ca, Sr) nanophosphors

    NASA Astrophysics Data System (ADS)

    Dejene, F. B.; Kebede, M. A.; Redi-Abshiro, M.; Kgarebe, B. V.

    2013-09-01

    Long afterglow alkaline earth aluminates MAl2O4:Eu, Dy (M: Ca, Sr, Ba) phosphors are generally synthesized by the solid-state process which is more feasible than other conventional processes in terms of operation and large-scale production. However, the constituents of phosphors synthesized using this process are usually not mixed well, the particles agglomerates and very high temperature requirement to synthesize the final powder make it undesirable. In order to circumvent these problems, MAl2O4:Eu, Dy (Ca, Ba, Sr) phosphors were prepared at low temperatures (500 °C) by the solution-combustion of corresponding metal nitrate-urea solution mixtures, over a time of 5-10 min. In order to elucidate the relationship between the constituent, structure and PL properties product's particle size, morphological and structural properties were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), while the characteristic luminescence properties were investigated using emission spectra. The low temperature monoclinic structure for both CaAl2O4 and SrAl2O4 and the hexagonal structure of BaAl2O4 were observed. The emission spectra of these phosphors indicated that all of them are broad band, and the only emission peaks around 448, 490 and 515 nm of CaAl2O4:Eu, Dy, BaAl2O4:Eu, Dy and SrAl2O4:Eu, Dy, respectively, are due to 5d → 4f transition of Eu2+. The decay curves implied that these phosphors contain fast, medium and slow-decay process. The Dy3+ trap levels may be considered to be responsible for the long afterglow phosphorescence at room temperature.

  1. Syntheses and characterization of energetic compounds constructed from alkaline earth metal cations (Sr and Ba) and 1,2-bis(tetrazol-5-yl)ethane

    SciTech Connect

    Xia Zhengqiang; Chen Sanping; Wei Qing; Qiao Chengfang

    2011-07-15

    Two new energetic compounds, [M(BTE)(H{sub 2}O){sub 5}]{sub n} (M=Sr(1), Ba(2)) [H{sub 2}BTE=1,2-bis(tetrazol-5-yl)ethane], have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that they are isomorphous and exhibit 2D (4,4) net framework, generated by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs linked up by two independent binding modes of H{sub 2}BTE, and the resulting 2D structure is interconnected by hydrogen-bond and strong face to face {pi}-{pi} stacking interactions between two tetrazole rings to lead to a 3D supramolecular architecture. DSC measurements show that they have significant catalytic effects on thermal decomposition of ammonium perchlorate. Moreover, the photoluminescence properties, thermogravimetric analyses, and flame colors of the as-prepared compounds are also investigated in this paper. - Graphical abstract: Two novel 2D isomorphous alkaline earth metal complexes were assembled by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two independent binding modes of H{sub 2}BTE ligands, and the catalytic performances toward thermal decomposition of ammonium perchlorate and photoluminescent properties of them were investigated. Highlights: > Two novel alkaline earth energetic coordination polymers have been prepared.{yields} Both structures are layered based on 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two distinct H{sub 2}BTE coordination modes.{yields} The dehydrated products of the compounds possess good thermostability and significant catalytic effects on thermal decomposition of AP.

  2. Performance Enhancement of the Dielectric Properties of Sn-Doped Ba0.8Sr0.2TiO3 Perovskite

    NASA Astrophysics Data System (ADS)

    Brahem, R.; Farhat, N.; Graça, M. P. F.; Costa, L. C.

    2016-06-01

    The aim of this paper is to study performance enhancement of the dielectric properties of polycrystalline {Ba}_{0.8} {Sr}_{0.2} {Ti}_{(1 - x)} {Sn}x {O}3 , with 0 ≤ x ≤ 0.2 . The material was characterized by x-ray diffraction, scanning electron microscopy (SEM), micro-Raman spectroscopy and impedance spectroscopy technique. The results have been analyzed by studying the effects of substituting Sn4+ for Ti4+. The observed diffraction peaks have been indexed to a cubic structure with space group Pm3m. The calculated lattice parameters increase from 3.9834 Å to 4.0091 Å with increasing Sn concentration. The SEM micrographs show that with increasing Sn an increase of the grain size from x = 0 up to x = 0.15 was observed. The dielectric measurements confirm the relaxor behavior of all the concentrations of {Ba}_{0.8} {Sr}_{0.2} {Ti}_{(1 - x)} {Sn}x {O}3 compounds. The {Ba}_{0.8} {Sr}_{0.2} {Ti}_{0.95} {Sn}_{0.05} {O}3 compound presents the most interesting properties, namely high dielectric constant value (&epsilon^'(T_{m} ) = 5017 ) and a Curie temperature slightly above room temperature (T_{c} = 317 {K}) . An important dielectric constant value persists for a wide range of temperatures around room temperature. This is considered as an advantage of the {Ba}_{0.8} {Sr}_{0.2} {Ti}_{0.95} {Sn}_{0.05} {O}3 relaxor ferroelectrics.

  3. Performance Enhancement of the Dielectric Properties of Sn-Doped Ba0.8Sr0.2TiO3 Perovskite

    NASA Astrophysics Data System (ADS)

    Brahem, R.; Farhat, N.; Graça, M. P. F.; Costa, L. C.

    2016-10-01

    The aim of this paper is to study performance enhancement of the dielectric properties of polycrystalline {Ba}_{0.8} {Sr}_{0.2} {Ti}_{(1 - x)} {Sn}x {O}3, with 0 ≤ x ≤ 0.2. The material was characterized by x-ray diffraction, scanning electron microscopy (SEM), micro-Raman spectroscopy and impedance spectroscopy technique. The results have been analyzed by studying the effects of substituting Sn4+ for Ti4+. The observed diffraction peaks have been indexed to a cubic structure with space group Pm3m. The calculated lattice parameters increase from 3.9834 Å to 4.0091 Å with increasing Sn concentration. The SEM micrographs show that with increasing Sn an increase of the grain size from x = 0 up to x = 0.15 was observed. The dielectric measurements confirm the relaxor behavior of all the concentrations of {Ba}_{0.8} {Sr}_{0.2} {Ti}_{(1 - x)} {Sn}x {O}3 compounds. The {Ba}_{0.8} {Sr}_{0.2} {Ti}_{0.95} {Sn}_{0.05} {O}3 compound presents the most interesting properties, namely high dielectric constant value (ɛ^'(T_{{m}} ) = 5017) and a Curie temperature slightly above room temperature (T_{{c}} = 317 K). An important dielectric constant value persists for a wide range of temperatures around room temperature. This is considered as an advantage of the {Ba}_{0.8} {Sr}_{0.2} {Ti}_{0.95} {Sn}_{0.05} {O}3 relaxor ferroelectrics.

  4. Effect of manganese doping of BaSrTiO{sub 3} on diffusion and domain wall pinning

    SciTech Connect

    Nadaud, Kevin Borderon, Caroline Renoud, Raphaël; Gundel, Hartmut W.

    2015-02-28

    In the present paper, the influence of manganese doping on the dielectric properties of BaSrTiO{sub 3} thin films is presented. The real and imaginary parts of the material's permittivity have been measured in a large frequency range (100 Hz–1 MHz) and as a function of the electric field. The tunability and the figure of merit of the material have been obtained from the measurement of the permittivity under an applied DC bias electric field. For the undoped material, the dielectric losses become important for a large DC bias which leads to breakdown. At a suitable dopant rate, this effect disappears. In order to better understand the origin of the related phenomena, we measure the permittivity as a function of the AC excitation amplitude and we decompose the obtained permittivity with the hyperbolic law. This enables to extract the different contributions of the bulk (low frequency diffusion and high frequency lattice relaxation) and of the domain wall motions (vibration and pinning/unpinning) to the material's dielectric permittivity and to understand the effect of manganese doping on each contribution. Knowledge of the related mechanisms allows us to establish the optimum dopant rate (mainly conditioned by the lattice contribution) and to reduce the domain wall motion, which finally is beneficial for the desired properties of the ferroelectric thin film. A particular attention is paid to low frequency diffusion, an especially harmful effect when a DC biasing is mandatory (tunable electronic component in mobile telecommunication devices for example)

  5. Simulation of the local structure, properties of mixing, and stability of solid solutions Ba x Sr1- x CO3 by the interatomic potential method

    NASA Astrophysics Data System (ADS)

    Dudnikova, V. B.; Eremin, N. N.

    2016-06-01

    The strontianite (SrCO3)-witherite (BaCO3) solid solutions have been simulated using the interatomic potential method. The dependences of the unit cell parameters, the unit cell volume, and the bulk modulus on the composition of the solid solution have been constructed. It has been shown that the unit cell volume and the bulk modulus exhibit negative deviations from the additivity. An analysis of the local structure of the solid solutions has been carried out. It has been found that, for the equimolar composition of the Ba x Sr1- x CO3 solid solution, the relaxations of the barium and strontium positions are equal to 60 and 56%, respectively. It has been established that the enthalpy of mixing is positive and, for the equimolar composition of the solid solution, reaches a maximum value of 3.4 kJ/mol. The obtained results have been compared with the experimental data. The solvus of the Ba x Sr1- x CO3 system has been constructed based on the dependences of the Gibbs free energy on the composition in the temperature range from 300 to 1000 K.

  6. Raman-spectroscopic investigation of Ba{sub 2}InTaO{sub 6} and Sr{sub 2}InTaO{sub 6} perovskites

    SciTech Connect

    Dias, A. Khalam, L.A.; Sebastian, M.T.; Moreira, R.L.

    2007-07-15

    Raman spectroscopy was employed to investigate the structures and phonon modes of Ba{sub 2}InTaO{sub 6} and Sr{sub 2}InTaO{sub 6} ceramics. It was found that Ba-based samples belong to the tetragonal P4/mnc (no. 128 or D{sub 4h}{sup 6}) space group, while Sr-based materials belong to the monoclinic P2{sub 1}/n (no. 14 or C{sub 2h}{sup 5}) space group. Low-temperature measurements did not show any phase transition down to 77K. Lorentzian lines were used to fit the experimental data, which presented 14 phonon modes for Ba{sub 2}InTaO{sub 6} and 24 modes for Sr{sub 2}InTaO{sub 6}, in perfect agreement with the theoretical factor-group analyses for the proposed structures. This paper reports, for the first time, a tetragonal P4/mnc structure for an indium-containing perovskite material.

  7. Synthesis of MSnO{sub 3} (M = Ba, Sr) nanoparticles by reverse micelle method and particle size distribution analysis by whole powder pattern modeling

    SciTech Connect

    Ahmed, Jahangeer; Blakely, Colin K.; Bruno, Shaun R.; Poltavets, Viktor V.

    2012-09-15

    Highlights: ► BaSnO{sub 3} and SrSnO{sub 3} nanoparticles synthesized using the reverse micelle method. ► Particle size and size distribution studied by whole powder pattern modeling. ► Nanoparticles are of optimal size for investigation in dye-sensitized solar cells. -- Abstract: Light-to-electricity conversion efficiency in dye-sensitized solar cells critically depends not only on the dye molecule, semiconducting material and redox shuttle selection but also on the particle size and particle size distribution of the semiconducting photoanode. In this study, nanocrystalline BaSnO{sub 3} and SrSnO{sub 3} particles have been synthesized using the microemulsion method. Particle size distribution was studied by whole powder pattern modeling which confirmed narrow particle size distribution with an average size of 18.4 ± 8.3 nm for SrSnO{sub 3} and 15.8 ± 4.2 nm for BaSnO{sub 3}. These values are in close agreement with results of transmission electron microscopy. The prepared materials have optimal microstructure for successive investigation in dye-sensitized solar cells.

  8. 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+.

  9. Response of Acropora digitifera to ocean acidification: constraints from δ11B, Sr, Mg, and Ba compositions of aragonitic skeletons cultured under variable seawater pH

    NASA Astrophysics Data System (ADS)

    Tanaka, Kentaro; Holcomb, Michael; Takahashi, Asami; Kurihara, Haruko; Asami, Ryuji; Shinjo, Ryuichi; Sowa, Kohki; Rankenburg, Kai; Watanabe, Tsuyoshi; McCulloch, Malcolm

    2015-12-01

    The response of Acropora digitifera to ocean acidification is determined using geochemical proxy measurements of the skeletal composition of A. digitifera cultured under a range of pH levels. We show that the chemical composition (δ11B, Sr/Ca, Mg/Ca, and Ba/Ca) of the coral skeletons can provide quantitative constraints on the effects of seawater pH on the pH in the calcification fluid (pHCF) and the mechanisms controlling the incorporation of trace elements into coral aragonite. With the decline of seawater pH, the skeletal δ11B value decreased, while the Sr/Ca ratio showed an increasing trend. The relationship between Mg/Ca and Ba/Ca versus seawater pH was not significant. Inter-colony variation of δ11B was insignificant, although inter-colony variation was observed for Ba/Ca. The decreasing trend of pHCF calculated from δ11B was from ~8.5, 8.4, and 8.3 for seawater pH of ~8.1, 7.8, and 7.4, respectively. Model calculations based on Sr/Ca and pHCF suggest that upregulation of pHCF occurs via exchange of H+ with Ca2+ with kinetic effects (Rayleigh fractionation), reducing Sr/Ca relative to inorganic deposition of aragonite from seawater. We show that it is possible to constrain the overall carbonate chemistry of the calcifying fluid with estimates of the carbonate saturation of the calcifying fluid ( Ω CF) being derived from skeletal Sr/Ca and pHCF (from δ11B). These estimates suggest that the aragonite saturation state of the calcifying fluid Ω CF is elevated by a factor of 5-10 relative to ambient seawater under all treatment conditions.

  10. Growth and characterization of A1-xKxFe2As2 (A = Ba, Sr) single crystals with x = 0 0.4

    NASA Astrophysics Data System (ADS)

    Luo, Huiqian; Wang, Zhaosheng; Yang, Huan; Cheng, Peng; Zhu, Xiyu; Wen, Hai-Hu

    2008-12-01

    Single crystals of A1-xKxFe2As2 (A = Ba, Sr) with high quality have been grown successfully by an FeAs self-flux method. The samples have sizes up to 4 mm with flat and shiny surfaces. The x-ray diffraction patterns suggest that they have high crystalline quality and c-axis orientation. The non-superconducting crystals show a spin-density-wave (SDW) instability at about 173 and 135 K for the Sr-based and Ba-based compound, respectively. After doping K as the hole dopant into the BaFe2As2 system, the SDW transition is smeared, and superconducting samples of the compound Ba1-xKxFe2As2 (0

  11. Dielectric dispersion of BaSrTiO3 thin film from centimeter to submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Houzet, Gregory; Blary, Karine; Lepilliet, Sylvie; Lippens, Didier; Burgnies, Ludovic; Vélu, Gabriel; Carru, Jean-Claude; Nguéma, Edwin; Mounaix, Patrick

    2011-01-01

    The dielectric dispersion of ferroelectric BaxSr1-xTiO3 (BST) thin film in a paraelectric phase was characterized from centimeter to submillimeter wavelengths. To this aim, interdigitated capacitors were patterned on a micrometer scale onto a BST layer with a barium concentration of 0.5 and were subsequently integrated by using a coplanar waveguide technology. The retrieval of the complex permittivity of BST was performed by vectorial scattering parameter measurements up to 190 GHz for various controlling dc field up to 300 kV/cm. At higher frequency, submillimeter wavelength measurements were performed by time domain spectroscopy under free space condition. On this basis, the dispersion of the real part of the permittivity along with the loss tangent are retrieved in agreement with a distributed interaction of ac-field with soft phonons vibration modes, and overlapping between dipole polarization and ionic polarization is observed, around 700 GHz. It is also shown that dipole polarization can be attributed to the presence of small polar nanoregions in the BST film which act as in ferroelectric material with diffuse phase transition.

  12. Eu(2+)-Activated Alkaline-Earth Halophosphates, M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect.

    PubMed

    Kim, Donghyeon; Kim, Sung-Chul; Bae, Jong-Seong; Kim, Sungyun; Kim, Seung-Joo; Park, Jung-Chul

    2016-09-01

    Eu(2+)-activated M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M5(PO4)3Cl:Eu(2+) (M = Ca, Sr, Ba) compounds were blue-shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr5(PO4)3X:Eu(2+) (X = F, Cl, Br) compounds were red-shifted along the series of halides, F → Cl → Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu(2+)) in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d → 4f transition energies of Eu(2+) using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu(2+) ions preferably enter the fully oxygen-coordinated sites in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field. PMID:27494550

  13. Low temperature preparation of nanocrystalline Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} powders using an aqueous organic gel route

    SciTech Connect

    Li Yao; Zhao Jiupeng; Wang Biao

    2004-03-01

    Nano-sized Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN50) ceramic powders have been synthesized by an aqueous organic gel route. Homogeneous Sr-Ba-Nb precursor gels are prepared with Ba-EDTA, Sr-EDTA, and Nb-citrate complex as source of Sr, Ba, and Nb, respectively. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used as the chelating agents. The structural variation of the SBN powder with annealing temperature was studied by TG-DTA, FT-IR and XRD. The precursor gel on calcination at 800 deg. C for 2 h produces a pure tungsten bronze SBN phase and the corresponding average particle size is 30-50 nm. The influences of the pH and the molar ratio of citric acid:Nb cation on the formation of homogeneous Sr-Ba-Nb precursor gels were also studied. The results show that a homogeneous Sr-Ba-Nb precursor gel with no precipitate is formed at pH 8 and the optimum molar ratio of citric acid and the metal cations is 3:1.

  14. Time-dependent transfer of 137Cs, 85Sr and 65Zn to earthworms in highly contaminated soils.

    PubMed

    Keum, Dong-Kwon; Jun, In; Lim, Kwang-Muk; Choi, Yong-Ho; Howard, Brenda J

    2013-12-01

    The transfer characteristics of (137)Cs, (85)Sr and (65)Zn to earthworms (Eisenia andrei) in soils with different amounts of the radionuclides have been investigated. The time-dependent whole-body concentration ratios (CR) were derived for worms in artificially contaminated soils with three different activity concentrations. Two parameters of a first order kinetic model, the equilibrium concentration ratio (CR(eq)) and the effective loss rate constant (k), were estimated by a comparison of experimental CR results with model predictions. The estimated CR(eq) (Bq/kg fresh worm per Bq/kg dry soil) ranged from 3.9 × 10(-4) to 4.1 × 10(-3) for (137)Cs, 1.39 × 10(-3) to 2.94 × 10(-2) for (85)Sr, and 1.39 × 10(-3) to 5.0 × 10(-2) for (65)Zn, and consistently decreased with increasing soil activity concentration but the trend was not statistically significant. The CR(eq) for (137)Cs was one to two orders of magnitude lower than previously reported CR(wo-soil) values (based on field data with much less contaminated soil), that for (85)Sr was comparable with other reported values and for (65)Zn was less two to three orders of magnitude lower than CR(wo-soil) values for stable zinc. The estimated k (d(-1)) values ranged from 9 × 10(-2) to 1.4 × 10(-1) for (137)Cs, 7 × 10(-2) to 2 × 10(-1) for (85)Sr, and 6 × 10(-2) to 1.8 × 10(-1) for (65)Zn, and did not show a relationship with soil activity concentration. The effect of CR(eq) on the total dose rate was insignificant for (137)Cs or (65)Zn because external dose rates to the soil dwelling earthworms due to these radionuclides were much greater than the internal dose rate. In contrast, the total dose from (90)Sr was determined by the internal dose rate and therefore proportional to the CR(eq). PMID:22948029

  15. Crystal Structures and Reference Powder Patterns of BaR2ZnO5 (R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, and Tm)

    PubMed Central

    Kaduk, J. A.; Wong-Ng, W.; Greenwood, W.; Dillingham, J.; Toby, B. H.

    1999-01-01

    Reference x-ray powder patterns and the crystal structures of the lanthanide compounds, BaR2ZnO5, in which R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, or Tm, were determined by the x-ray Rietveld refinement technique. A structural trend was confirmed for this series of compounds. The compounds with smaller ionic radii (R = Sm, Eu, Gd, Dy, Ho, Y, Er, or Tm) are isostructural to the orthorhombic “green phase” (BaY2CuO5). The lattice parameters for compounds with R = Tm to Sm range from a = 7.01855(9) Å to 7.20452(14) Å, b = 12.25445 (17) Å to 12.5882(2) Å, and c = 5.6786(14) Å to 5.81218(11) Å, respectively. R is sevenfold coordinated inside a monocapped trigonal prism. These prisms share edges to form wave-like chains parallel to the long b-axis. The BaR2ZnO5 compounds which contain larger size R (La and Nd) crystallize in the tetragonal space group I4/mcm. The lattice parameters are a = 6.90982(10) and c = 11.5977(2) Å for BaLa2ZnO5, and a = 6.75979(5) Å and c = 11.54560(12) Å for BaNd2ZnO5. The structure consists of ZnO4 tetrahedra (instead of planar CuO4 groups as found in BaR2CuO5) with 10-fold coordinated bicapped square prismatic Ba and 8-fold coordinated bicapped trigonal prismatic R ions between them. The reference x-ray powder patterns will be submitted to the Powder Diffraction File (PDF).

  16. 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

  17. Microstructural and dielectric properties of Ba0.6Sr0.4Ti1-xZrxO3 based combinatorial thin film capacitors library

    NASA Astrophysics Data System (ADS)

    Liu, Guozhen; Wolfman, Jérôme; Autret-Lambert, Cécile; Sakai, Joe; Roger, Sylvain; Gervais, Monique; Gervais, François

    2010-12-01

    Epitaxial growth of Ba0.6Sr0.4Ti1-xZrxO3 (0≤x≤0.3) composition spread thin film library on SrRuO3/SrTiO3 layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties.

  18. Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba{sub 3}BSb{sub 2}O{sub 9}, B=Mg, Ca, Sr, Ba

    SciTech Connect

    Ling, Chris D. Rowda, Budwy; Avdeev, Maxim; Pullar, Robert

    2009-03-15

    We present a complete temperature-composition phase diagram for Ba{sub 3}BSb{sub 2}O{sub 9}, B=Mg, Ca, Sr, Ba, along with their electrical behavior as a function of B. These compounds have long been recognized as 6H-type perovskites, but (with the exception of B=Mg) their exact structures and properties were unknown due to their low symmetries, temperature-dependent phase transitions, and difficulties in synthesizing pure samples. The full range of possible space group symmetries is observed, from ideal hexagonal P6{sub 3}/mmc to monoclinic C2/c to triclinic P1-bar. Direct second-order transitions between these phases are plausible according to group theory, and no evidence was seen for any further intermediate phases. The phase diagram with respect to temperature and the effective ionic radius of B is remarkably symmetrical for B=Mg, Ca, and Sr. For B=Ba, a first-order phase transition to a locally distorted phase allows a metastable hexagonal phase to persist to lower temperatures than expected before decomposing around 600 K. Electrical measurements revealed that dielectric permittivity corrected for porosity does not change significantly as a function of B and is in a good agreement with the values predicted by the Clausius-Mossotti equation. - Graphical abstract: Thermodynamic phase diagram for Ba{sub 3}BSb{sub 2}O{sub 9}, B=Mg, Ca, and Sr, as a function of temperature T and effective ionic radius (IR) of the B{sup 2+} cation.

  19. One-dimensional SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers and enhancement magnetic property.

    PubMed

    Song, Fuzhan; Shen, Xiangqian; Liu, Mingquan; Xiang, Jun

    2011-08-01

    SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite. PMID:22103109

  20. Magnetic properties of the overdoped superconductor La{sub 2-x}Sr{sub x}CuO{sub 4} with and without Zn impurities

    SciTech Connect

    Wakimoto, S.; Birgeneau, R.J.; Kagedan, A.; Kim, Hyunkyung; Zhang, H.; Swainson, I.; Yamada, K.

    2005-08-01

    The magnetic properties of the Zn-substituted overdoped high-T{sub c} superconductor La{sub 2-x}Sr{sub x}Cu{sub 1-y}Zn{sub y}O{sub 4} have been studied by magnetization measurements and neutron scattering. Magnetization measurements reveal that for Zn-free samples with x{>=}0.22 a Curie term is induced in the temperature dependence of the magnetic susceptibility implying the existence of local paramagnetic moments. The induced Curie constant corresponds to a moment of 0.5 {mu}{sub B} per additional Sr{sup 2+} ion that exceeds x=0.22. Zn substitution in the overdoped La{sub 2-x}Sr{sub x}CuO{sub 4} also induces a Curie term that corresponds to 1.2 {mu}{sub B} per Zn{sup 2+} ion, simultaneously suppressing T{sub c}. The relationship between T{sub c} and the magnitude of the Curie term for Zn-free La{sub 2-x}Sr{sub x}CuO{sub 4} with x{>=}0.22 and for Zn-substituted La{sub 2-x}Sr{sub x}CuO{sub 4} with x=0.22 are closely similar. This signifies a general competitive relationship between the superconductivity and the induced paramagnetic moment. Neutron scattering measurements show that Zn substitution in overdoped La{sub 2-x}Sr{sub x}CuO{sub 4} anomalously enhances the inelastic magnetic scattering spectra around the ({pi},{pi}) position, peaking at {omega}{approx}7 meV. These facts are discussed on the basis of a 'swiss-cheese' model of Zn-substituted systems as well as a microscopic phase separation scenario in the overdoped region indicated by muon-spin-relaxation measurements.

  1. Microwave Loss in the High-Performance Dielectric Ba(Zn1/3Ta2/3)O3 at 4.2 K

    NASA Astrophysics Data System (ADS)

    Liu, Lingtao; Flores, Marco; Newman, Nathan

    2012-12-01

    Temperature- and magnetic-field-dependent measurements of the loss tangent in Ba(Zn1/3Ta2/3)O3 doped with transition metals (Mn, Ni) are compared to those from samples doped with other impurities (Cd, Ga, Mg, and Zr). These results, combined with pulsed electron paramagnetic resonance measurements, show conclusively that microwave loss in transition-metal-doped Ba(Zn1/3Ta2/3)O3 at cryogenic temperatures is attributable to resonant spin excitations of unpaired transition-metal d electrons in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping), a mechanism that differs from the usual suspects.

  2. Hexagonal-diamond-like gold lattices, Ba and (Au,T)3 interstitials, and delocalized bonding in a family of intermetallic phases Ba2Au6(Au,T)3 (T = Zn, Cd, Ga, In, or Sn).

    PubMed

    Lin, Qisheng; Mishra, Trinath; Corbett, John D

    2013-07-31

    Au-rich polar intermetallics exhibit a wide variety of structural motifs, and this hexagonal-diamond-like gold host is unprecedented. The series Ba2Au6(Au,T)3 (T = Zn, Cd, Ga, In, or Sn), synthesized through fusion of the elements at 700-800 °C followed by annealing at 400-500 °C, occur in space group R3[overline]c (a ≈ 8.6-8.9 Å, c ≈ 21.9-22.6 Å, and Z = 6). Their remarkable structure, generated by just three independent atoms, features a hexagonal-diamond-like gold superstructure in which tunnels along the 3-fold axes are systematically filled by interstitial Ba atoms (blue) and triangles of disordered (Au,T)3 atoms (green) in 2:1 proportions. The Au/Zn mixing in the latter spans ~34 to 87% Zn, whereas the Au/Sn result is virtually invariant compositionally. Complementary bonding between the gold lattice and the disordered (Au,T)3 units is substantial and very regular. Bonding and charge density analyses indicate delocalized bonding within the gold host and the (Au,T)3 triangular units, and moderately polarized bonding between Ba and the electronegative framework. The new structure can also be viewed empirically as the result of an atom-by-triad [i.e., Ba by (Au,T)3 triangle] topological substitution in a BaAu2 (AlB2-type) superstructure.

  3. Spectroscopic studies of the ferroelectric and magnetic phase transitions in multiferroic Sr1-x Ba x MnO3

    NASA Astrophysics Data System (ADS)

    Goian, V.; Kadlec, F.; Kadlec, C.; Dabrowski, B.; Kolesnik, S.; Chmaissem, O.; Nuzhnyy, D.; Kempa, M.; Bovtun, V.; Savinov, M.; Hejtmánek, J.; Prokleška, J.; Kamba, S.

    2016-05-01

    Dielectric response of perovskite Sr1-x Ba x MnO3 (x  =  0.43 and 0.45) ceramics was investigated using microwave, THz and infrared spectroscopic techniques in order to study the ferroelectric and antiferromagnetic phase transitions with critical temperatures T C  ≈  350 K and T N  ≈  200 K, respectively. The two lowest-frequency polar phonons are overdamped above T N and they exhibit pronounced softening on heating towards T C. Nevertheless, permittivity ɛ‧ in the THz range shows only a small anomaly at T C because the phonon contribution to ɛ‧ is rather small. The phonons are coupled with a central mode which provides the main contribution to the dielectric anomaly at T C. Thus, the ferroelectric phase transition has characteristics of a crossover from displacive to order-disorder type. At the same time, the intrinsic THz central peak is partially screened by conductivity and related Maxwell-Wagner relaxation, which dominates the microwave and lower-frequency spectra. Below T N, the ferroelectric distortion markedly decreases, which has an influence on the frequencies of both the central and soft modes. Therefore, ɛ‧ in the THz range increases at T N on cooling. In spite of the strong spin-phonon coupling near T N, surprisingly no magnetodielectric effect was observed in the THz spectra upon applying magnetic field of up to 7 T, which is in contradiction with the theoretically expected huge magnetoelectric coupling. We explain this fact as due to the insensitivity of T N to magnetic field.

  4. Structural and optical study of γ –BIMEVOX; ME: Ba{sup 2+} and Sr{sup 2+}

    SciTech Connect

    Gupta, Sakshi Singh, K.

    2015-05-15

    Bismuth oxide based compounds, such as Bi{sub 4}V{sub 2}O{sub 11-δ} (BIVOX), exhibit Aurivillus type of interleaving arrangement of (Bi{sub 2}O{sub 2}){sup 2+} and (VO{sub 3}□{sub 0.5}){sup 2-} (□: oxygen vacancies). Bi{sub 4}V{sub 2}O{sub 11-δ,} is known to have three kinds of temperature dependent interconvertible polymorphs α (monoclinic), β (orthorhombic) and γ (tetragonal). Out of all the three phases, the γ – phase is highly disordered and hence, is the most conductive one which can be stabilized by proper lower valence cation (ME) doping at V site. Bi{sub 4}V{sub 1.90}ME{sub 0.20}O{sub 11-δ} (ME: Ba{sup 2+} and Sr{sup 2+}) were prepared via splat quenching technique. The required compositions were melted at 1250 °C in an electric furnace. The as quenched samples were sintered at 800 °C for 12 hours (h). The formed phases were analyzed using X-ray diffraction on quenched and sintered samples, the peak at 32{sup °} is found to be singlet in all the samples which confirms the presence of γ-phase. Hence, the stabilization of γ-phase with tetragonal structure was found to have taken place with doping and quenching. These samples are also studied by FT-IR and UV/vis spectroscopy to investigate the effect of dopants on structure and band gaps respectively.

  5. Dual ferroic properties of hexagonal ferrite ceramics BaFe12O19 and SrFe12O19

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Dual ferroic properties of a strong magnetism and large ferroelectricity have been observed in barium BaFe12O19 and strontium SrFe12O19 hexaferrite ceramics. The samples were fabricated by a modified ceramic technique from highly purified raw materials with addition of boron oxide allowing the control of grain size and enhancement of bulk resistivity. Whereas the samples of PbFe12O19 fabricated by the same technological method did not have sufficient electric resistivity to support an electric field and did not exhibit the ferroelectric properties. The structure of the samples examined by X-ray diffraction is consistent with a single hexagonal phase. The grains are randomly oriented with the average grain size of 300-400 nm coated with boron oxide. The magnetic properties are characterised by standard ferrimagnetic behavior with the Neel temperature of about 450 °C. Large spontaneous polarization was observed with the maximal values of 45-50 μC/cm2 under an applied electric field of 100-300 kV/m. A strong coupling between magnetic and electric ordering was confirmed by measuring the magnetoelectric (ME) parameter and magnetodielectric ratio. These ME characteristics are more advanced than those for well-known room temperature multiferroic BiFeO3. Furthermore, by applying an electric field, the manipulation of magnetization in the range of up to 9% was observed, which is even greater than in some substituted hexaferrites with a non-collinear magnetic structure. The obtained results on electrical polarization are similar to the values reported for the corresponding hexaferrites sintered by polymer precursor technique. This suggests a promising potential of M-type hexaferrite ceramics in devices utilizing magnetoelectric coupling.

  6. A first-principles study on structural stability and mechanical properties of polar intermetallic phases CaZn2 and SrZn2

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Cheng; Liu, Yong; Li, De-Jiang; Li, Ke; Jin, Hua-Lan; Xu, Ying-Xuan; Xu, Chun-Shui; Zeng, Xiao-Qin

    2014-12-01

    Structural stability and electronic properties of polar intermetallic CaZn2 and SrZn2 in both CeCu2-type and MgZn2-type structures have been investigated using first-principles method. The calculated equilibrium lattice parameters agree closely with the available experimental and other theoretical results. In terms of formation enthalpy, it is discovered that the present compounds with CeCu2-type structure are energetically more stable than that with MgZn2-type. They are all mechanically stable according to the criteria of elastic stability. In particular, we have investigated the pressure effect on the compressive behaviour and structural stability of each compound. Subsequently, the bulk modulus, shear modulus, Young's modulus, theoretical hardness, Poisson's ratio and Debye temperature in the ground state can be estimated using Voigt-Reuss-Hill homogenization method. Mechanical anisotropy is characterized by the anisotropic factors and direction-dependent Young's modulus. Finally, the electronic structures are determined to reveal the bonding characteristics of considered phases.

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

    PubMed

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

    2016-08-01

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

  8. Synthesis of high intensity green emitting (Ba,Sr)SiO4:Eu2+ phosphors through cellulose assisted liquid phase precursor process

    NASA Astrophysics Data System (ADS)

    Humayoun, Usama Bin; Song, Young-Hyun; Lee, MinJi; Masato, Kakihana; Abe, Hiroshi; Toda, Kenji; Sato, Yasushi; Masaki, Takaki; Yoon, Dae-Ho

    2016-01-01

    Green emitting phosphor (Ba1-x,Sr1-x)SiO4:2xEu2+, x = 0.03, 0.05, 0.1, and 0.15 were synthesized through a Liquid Phase Precursor Process (LPP). Liquid phase precursor method is reported to result in phosphors with markedly increased emission intensities compared to other synthesis methods. Here microcrystalline cellulose (MCC) and hydroxypropyl cellulose (HPC) templates were studied to achieve high efficiency green phosphors. The phase formation was investigated by XRD analysis which showed the conformation of the Ba2SiO4 (JCPDS card number 761631) phase. The obtained samples exhibited broad excitation spectra with maximum at 430 nm and a green emission centered around 520 nm. An optimized dopant concentration was selected and the effect of two different types of cellulose, i.e. MCC and HPC templates on the emission properties was considered. It was found that the samples synthesized using HPC and fired at 1050 °C under a reducing atmosphere, showed a high intensity of almost 2 times that of the MCC sample. Further experiments were conducted by varying viscosity, particle weight, and molecular weight of the HPC template. It was found that the green emission from the (Ba,Sr)SiO4:Eu2+ increased with the increase in viscosity and molecular weight of the template.

  9. Internal electrical and strain fields influence on the electrical tunability of epitaxial Ba0.7Sr0.3TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Bagdzevicius, S.; Mackeviciute, R.; Ivanov, M.; Fraygola, B.; Sandu, C. S.; Setter, N.; Banys, J.

    2016-03-01

    Perpetual demand for higher transfer speed and ever increasing miniaturization of radio and microwave telecommunication devices demands new materials with high electrical tunability. We have investigated built in electrical and strain fields' influence on the electrical tunability in Ba0.7Sr0.3TiO3 thin film hetero-system grown by pulsed laser deposition technique. We observed the built in electrical field by local piezo-force microscopy (as deflected hysteresis loops) and macroscopic impedance analysis (as asymmetric tunability curves), with the calculated 88 kV/cm built in field at room temperature. Negative -1.4% misfit strain (due to clamping by the substrate) enhanced ferroelectric phase transition temperature in Ba0.7Sr0.3TiO3 thin film by more than 300 K. Built in fields do not deteriorate functional film properties—dielectric permittivity and tunability are comparable to the best to date values observed in Ba1-xSrxTiO3 thin films.

  10. Interfacial dislocations in (111) oriented (Ba0.7Sr0.3)TiO3 films on SrTiO3 single crystal

    SciTech Connect

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di; Xin, Huolin L.; Su, Dong

    2015-10-08

    In this study, we have investigated the interfacial structure of epitaxial (Ba,Sr)TiO3 films grown on (111)-oriented SrTiO3 single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a<110> comprised of a misfit dislocation along <112>, and threading dislocations along <110> or <100>. The misfit dislocation with Burgers vector of a <110> can dissociate into two ½ a <110> partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba0.7Sr0.3)TiO3 films.

  11. Interfacial dislocations in (111) oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films on SrTiO{sub 3} single crystal

    SciTech Connect

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Xin, Huolin L.; Su, Dong; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di

    2015-10-05

    We have investigated the interfacial structure of epitaxial (Ba,Sr)TiO{sub 3} films grown on (111)-oriented SrTiO{sub 3} single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a〈110〉 comprised of a misfit dislocation along 〈112〉, and threading dislocations along 〈110〉 or 〈100〉. The misfit dislocation with Burgers vector of a〈110〉 can dissociate into two ½a〈110〉 partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films.

  12. The structural and in-plane dielectric/ferroelectric properties of the epitaxial (Ba, Sr)(Zr, Ti)O{sub 3} thin films

    SciTech Connect

    Chan, N. Y. Wang, Y.; Chan, H. L. W.; Wang, D. Y.; Dai, J. Y.

    2014-06-21

    Epitaxial (Ba{sub 1-x}Sr{sub x})(Zr{sub 0.1}Ti{sub 0.9})O{sub 3} (BSZT, x = 0 – 0.45) thin films were deposited on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} (LSAT) substrates by pulsed laser deposition. The experimental results demonstrate that the structural, dielectric, and ferroelectric properties of the BSZT thin films were greatly dependent on the strontium content. The BSZT thin films transformed from tetragonal to cubic phase when x ≥ 0.35 at room temperature. The Curie temperature and room-temperature remnant polarization decrease with increasing strontium concentration. The optimal dielectric properties were found in (Ba{sub 0.55}Sr{sub 0.45})(Zr{sub 0.1}Ti{sub 0.9})O{sub 3} thin films which is in paraelectric state, having tunability of 47% and loss tangent of 0.0338 under an electric field of 20 MV/m at 1 MHz. This suggests that BSZT thin film is a promising candidate for tunable microwave device applications.

  13. Isovalent Ca and Ba substitutions in thermoelectric layer-structured oxyselenide Sr2CoO2Cu2Se2

    NASA Astrophysics Data System (ADS)

    Chou, T. L.; Mustonen, O.; Tripathi, T. S.; Karppinen, M.

    2016-01-01

    Multilayered compounds typically present exotic functionalities, and some of them have been suggested as potential materials for thermoelectric conversion owing to their unique capability to decouple electronic and heat transport. Here we report new [CoO2] and [Cu2Se2] layered A 2CoO2Cu2Se2 compounds in which Sr at the intervening alkaline-earth A site is partially replaced with Ca or Ba. The parent Sr2CoO2Cu2Se2 phase is a direct gap p-type semiconductor, and density functional theory (DFT) calculations indicate its topmost valence band consists of Cu 3d-Se 4p states. Upon the isovalent cation substitution the lattice modification in the ab plane is constrained by the stiff [CoO2] layer such that the lattice shrinkage/expansion mainly happens along the c axis. Substitution of Sr with the heavier and larger Ba significantly enhances the thermopower but more hole states would be required to optimize the thermoelectric performance. Thermal stability is related to the inter-oxide-selenide-layer interaction, and our thermogravimetric measurement data reveal that the A 2CoO2Cu2Se2 materials could operate in the intermediate temperature region.

  14. Structural and dielectric properties of Sr3(MgTa2)O9 and Sr3(ZnTa2)O9

    NASA Astrophysics Data System (ADS)

    Hoque, Md. M.; Dutta, Alo; Kumar, S.; Sinha, T. P.

    2015-07-01

    Herein, we report the crystal structures and morphological properties of Sr3(MgTa2)O9 (SMT) and Sr3(ZnTa2)O9 (SZT) synthesized by solid state ceramic method along with the results of alternating current impedance spectroscopic (ACIS) study in a frequency range from 50 Hz to 1 MHz at selective temperatures between 393 and 573 K. The crystal structures of SMT and SZT have been determined by Rietveld refinement of powder X-ray diffraction pattern using an initial structural model developed on the basis of literature survey. The results indicate that both the samples possess hexagonal structure of trigonal P 3 bar m 1 space group. The lattice parameters of SMT are a=b=5.65162 Å, c=6.94440 Å, α=β=90° and γ=120° and those of SZT are a=b=5.65832 Å, c=6.95911 Å and α=β=90° and γ=120°. SMT and SZT are isostructural and they exhibit 2:1 B site ordering with the staking sequence of {-Ta-Ta-Mg (Zn)-} (Mg for SMT and Zn for SZT) layer repeat on (111) plane of the pseudocells. The characteristic vibrational bands due to Ta-O, Mg-O and Zn-O bonds have been observed in the FTIR spectra of the samples. The FESEM micrographs of the samples show that the grains size ranges between 0.40 and 3.65 μm and 0.9 to 4.2 μm for SMT and SZT, respectively. To account for the polydispersive nature of the dielectric relaxation mechanism along with the effects of dc conductivity and localized space charges the variation of real (ε‧) and imaginary (ε″) parts of dielectric constant with frequency has been analytically interpreted in the framework of modified Cole-Cole model. SMT and SZT having the activation energies of 0.35 eV and 0.33 eV, respectively (obtained from the Arrhenius plot of dc conductivity), are semiconducting in nature. The electrical current conduction in the samples occurs by polaron hopping process. Further, we have shown that chemical property of A site cations has significant role in determining the dielectric properties of A3B‧B″2O9 type perovskites

  15. Sputter deposition of ZnS:Mn/SrS:Ce multilayer stacks for use as white phosphor thin film electroluminscent panels

    SciTech Connect

    Ruffner, J.A.; Tuenge, R.T.; Sun, Sey-Shing

    1995-07-01

    Sputter deposition of ZnS:Mn/SrS:Ce multilayered broad-band ``white`` emission thin film electroluminescent (TFEL) stacks has been investigated. To date, deposition of these multilayers has been limited to vacuum evaporation techniques and atomic layer epitaxy, both of which require two different substrate temperatures for growth of high quality ZnS and SrS. This repeated thermal cycling during multilayer deposition can induce stress, defects, and interdiffusion with adversely affect EL performance. Sputter deposition of ZnS and SrS produces high quality TFELs for a wider range of substrate temperatures. Both materials can be sputter deposited at a common temperature (300-350{degrees}C) which eliminates the need for thermal cycling and increases manufacturability. Luminance outputs from sputter deposited ZnS and SrS thin films are comparable to those from evaporated films, making sputtering an attractive alternative deposition technique for these materials. We report on the effects of sputter deposition parameters including chamber pressure, substrate temperature, and H2S process gas partial pressure on the resultant composition and morphology of ZnS:Mn and SrS:Ce thin films and multilayers. Their EL performance was evaluated and correlated to composition and morphology.

  16. Effects of ZnO Content on Piezoelectric, Dielectric, and Magnetic Properties of Sr-Modified PZT-PMW-PNN/(Ni-Co-Cu) ME Composites

    NASA Astrophysics Data System (ADS)

    Chao, Xiaolian; Wang, Juanjuan; Kang, Chao; Dong, Mingyuan; Yang, Zupei

    2015-10-01

    SrCO3/ZnO-codoped 0.9Pb1- y Sr y [(Zr0.23Ti0.36)-(Mg1/2W1/2)-(Ni1/3Nb2/3)]O3-0.10 Ni0.8Co0.1Cu0.1Fe2O4 + xZnO ceramics have been prepared via a solid-state reaction method. The effects of the SrCO3 and ZnO contents on the phase structure, microstructure, and electrical properties of the ceramics were investigated. The SrCO3 and ZnO contents had a significant effect on the electrical properties of the specimens. The composite with 0.2 mol.% SrCO3 and 0.2 wt.% ZnO content sintered at 1170°C exhibited good performance with d 33 = 332 pC/N, ɛ r = 2433 (1 kHz), ɛ m = 23,787 (1 kHz), T c = 196°C, and d E/d H = 424 μV/cm Oe. The results indicate that this system has potential as a magnetoelectric material for multifunctional applications.

  17. Efficient upconversion luminescence from Ba5Gd8Zn4O21:Yb3+, Er3+ based on a demonstrated cross-relaxation process

    PubMed Central

    Mi, Chao; Wu, Jianhong; Yang, Yanmin; Han, Boning; Wei, Jun

    2016-01-01

    Under 971 nm excitation, bright green and red emissions from Yb3+/Er3+ co-doped Ba5Gd8Zn4O21 phosphor can be observed, especially the intense red emission in highly doped samples. The experimental results indicate that Ba5Gd8Zn4O21:Yb3+, Er3+ emits stronger upconversion luminescence than NaYF4:Yb3+, Er3+ under a low excitation power, and a maximum upconversion power efficiency of 2.7% for Ba5Gd8Zn4O21:Yb3+, Er3+ was achieved. More significantly, to explain the red emission enhanced with the dopant concentration, this paper presents a possible cross-relaxation process and demonstrates it based on the rate equation description and temporal evolution. In view of the strong upconversion luminescence, colour tunable ability and stable chemical nature, Yb3+/Er3+ co-doped Ba5Gd8Zn4O21 phosphor could be an excellent candidate for efficient upconversion luminescence generation. PMID:26931554

  18. Sol–gel synthesis, structure and luminescence properties of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors

    SciTech Connect

    Li, Yuntong; Liu, Xiaohua

    2015-04-15

    Graphical abstract: The phosphor powders of Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} were prepared by sol–gel method. The dependence of luminescence intensity on the Eu{sup 3+} concentration was investigated. - Highlights: • We synthesize Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors by the sol–gel method. • The effect of temperature on the crystallinity and morphology is investigated. • The phosphor presents an intense CT band in near UV range (370–410 nm). • The concentration quenching mechanism is the exchange interaction. - Abstract: Double-perovskite Ba{sub 2}Zn{sub 1−x}MoO{sub 6}:xEu{sup 3+} (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) orange–red emitting phosphors were synthesized by using the sol–gel method. The crystalline structure and photoluminescence properties of the phosphors were investigated. The X-ray diffraction (XRD) patterns indicate that the structure of matrix Ba{sub 2}ZnMoO{sub 6} is cubic double-perovskite with space group Fm-3m. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors present an intense broad charge transfer (CT) band absorption in near UV range (370–410 nm), which attributes to the charge transfer state of MoO{sub 6}, and performs orange–red emission of Eu{sup 3+} ({sup 5}D{sub 0} → {sup 7}F{sub 1} transition) at around 596 nm. A low concentration quenching occurs in Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} and the optimal doping concentration is about 6 mol%. The Ba{sub 2}ZnMoO{sub 6}:Eu{sup 3+} phosphors are considered to be a promising orange–red emitting phosphor for near ultraviolet GaN-based white light emitting diode.

  19. Anisotropic Exchange within Decoupled Tetrahedra in the Quantum Breathing Pyrochlore Ba_{3}Yb_{2}Zn_{5}O_{11}.

    PubMed

    Rau, J G; Wu, L S; May, A F; Poudel, L; Winn, B; Garlea, V O; Huq, A; Whitfield, P; Taylor, A E; Lumsden, M D; Gingras, M J P; Christianson, A D

    2016-06-24

    The low energy spin excitation spectrum of the breathing pyrochlore Ba_{3}Yb_{2}Zn_{5}O_{11} has been investigated with inelastic neutron scattering. Several nearly resolution limited modes with no observable dispersion are observed at 250 mK while, at elevated temperatures, transitions between excited levels become visible. To gain deeper insight, a theoretical model of isolated Yb^{3+} tetrahedra parametrized by four anisotropic exchange constants is constructed. The model reproduces the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity. The fitted exchange parameters reveal a Heisenberg antiferromagnet with a very large Dzyaloshinskii-Moriya interaction. Using this model, we predict the appearance of an unusual octupolar paramagnet at low temperatures and speculate on the development of intertetrahedron correlations. PMID:27391749

  20. Anisotropic Exchange within Decoupled Tetrahedra in the Quantum Breathing Pyrochlore Ba3Yb2Zn5O11

    NASA Astrophysics Data System (ADS)

    Rau, J. G.; Wu, L. S.; May, A. F.; Poudel, L.; Winn, B.; Garlea, V. O.; Huq, A.; Whitfield, P.; Taylor, A. E.; Lumsden, M. D.; Gingras, M. J. P.; Christianson, A. D.

    2016-06-01

    The low energy spin excitation spectrum of the breathing pyrochlore Ba3Yb2Zn5O11 has been investigated with inelastic neutron scattering. Several nearly resolution limited modes with no observable dispersion are observed at 250 mK while, at elevated temperatures, transitions between excited levels become visible. To gain deeper insight, a theoretical model of isolated Yb3 + tetrahedra parametrized by four anisotropic exchange constants is constructed. The model reproduces the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity. The fitted exchange parameters reveal a Heisenberg antiferromagnet with a very large Dzyaloshinskii-Moriya interaction. Using this model, we predict the appearance of an unusual octupolar paramagnet at low temperatures and speculate on the development of intertetrahedron correlations.

  1. Local atomic and magnetic structure of dilute magnetic semiconductor (Ba ,K ) (Zn,Mn ) 2As2

    NASA Astrophysics Data System (ADS)

    Frandsen, Benjamin A.; Gong, Zizhou; Terban, Maxwell W.; Banerjee, Soham; Chen, Bijuan; Jin, Changqing; Feygenson, Mikhail; Uemura, Yasutomo J.; Billinge, Simon J. L.

    2016-09-01

    We have studied the atomic and magnetic structure of the dilute ferromagnetic semiconductor system (Ba ,K )(Zn ,Mn )2As2 through atomic and magnetic pair distribution function analysis of temperature-dependent x-ray and neutron total scattering data. We detected a change in curvature of the temperature-dependent unit cell volume of the average tetragonal crystallographic structure at a temperature coinciding with the onset of ferromagnetic order. We also observed the existence of a well-defined local orthorhombic structure on a short length scale of ≲5 Å , resulting in a rather asymmetrical local environment of the Mn and As ions. Finally, the magnetic PDF revealed ferromagnetic alignment of Mn spins along the crystallographic c axis, with robust nearest-neighbor ferromagnetic correlations that exist even above the ferromagnetic ordering temperature. We discuss these results in the context of other experiments and theoretical studies on this system.

  2. Anisotropic Exchange within Decoupled Tetrahedra in the Quantum Breathing Pyrochlore Ba3Yb2Zn5O11

    DOE PAGESBeta

    Rau, J. G.; Wu, L. S.; May, A. F.; Poudel, L.; Winn, B.; Garlea, V. O.; Huq, A.; Whitfield, P.; Taylor, A. E.; Lumsden, M. D.; et al

    2016-06-24

    Tmore » he low energy spin excitation spectrum of the breathing pyrochlore Ba3Yb2Zn5O11 has been investigated with inelastic neutron scattering. Several nearly resolution limited modes with no observable dispersion are observed at 250 mK while, at elevated temperatures, transitions between excited levels become visible. o gain deeper insight, a theoretical model of isolated Yb3+ tetrahedra parametrized by four anisotropic exchange constants is constructed. he model reproduces the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity. he fitted exchange parameters reveal a Heisenberg antiferromagnet with a very large Dzyaloshinskii-Moriya interaction. Ultimately, using this model, we predict the appearance of an unusual octupolar paramagnet at low temperatures and speculate on the development of inter-tetrahedron correlations.« less

  3. Four-wave-mixing generation of SRS components in BaWO{sub 4} and SrWO{sub 4} crystals under picosecond excitation

    SciTech Connect

    Basiev, Tasoltan T; Doroshenko, Maxim E; Ivleva, Lyudmila I; Smetanin, Sergei N; Jelinek, M; Kubecek, V; Jelinkova, H

    2013-07-31

    Four-wave-mixing stimulated Raman scattering (SRS) generation of Stokes and anti-Stokes components in BaWO{sub 4} and SrWO{sub 4} crystals excited by a 1064-nm pulsed laser with a pulse duration of 18 ps has been investigated. It is shown that, due to the four-wave mixings of SRS components in short ({approx}1 cm) crystals, the generation thresholds of the second and third Stokes components are much lower than the values determined by the cascade SRS mechanism. If the crystal length is increased by a factor of more than four, the mechanism of multiwave SRS becomes similar to the cascade mechanism (without four-wave mixings). Rotation of BaWO{sub 4} crystal makes it possible to control the competition of the processes of four-wave-mixing SRS generation of anti-Stokes and second Stokes components. (nonlinear optical phenomena)

  4. First-Principles Studies of Pressure-Induced Structural and Insulator-To Transitions in Alkaline-Earth Dicarbides MC2 (M = Ca, Sr and Ba)

    NASA Astrophysics Data System (ADS)

    Jiang, Li-Na

    2013-12-01

    Pressure-induced phase transitions in MC2 (M = Ca, Sr and Ba) are investigated by using the first-principles plane wave pseudopotential method within the generalized gradient approximation. The first-order phase transition from tetragonal phase (CaC2-type, space group I4/mmm) to rhombohedral (CsCl-type, space group R/line{3}m) structure is predicted to occur at 22.2, 10.0 and 3.6 GPa, respectively, and transition pressure point of BaC2 agrees well with recent theoretical works. Based on the electronic analysis, the ionic Ca-C bond character becomes stronger with increasing pressure in both I4/mmm and R/line{3}m phases. In particular, there will occur a transition from insulator to metal with increasing pressure due to the reason that the calculated band gap gets narrower and finally closes at some high pressure.

  5. Ba2LnSbO6 and Sr2LnSbO6 (Ln = Dy, Ho, Gd) double perovskites: Lanthanides in the geometrically frustrating fcc lattice

    PubMed Central

    Karunadasa, H.; Huang, Q.; Ueland, B. G.; Schiffer, P.; Cava, R. J.

    2003-01-01

    Magnetic ground states in solids often arise as a result of a delicate balance between competing factors. One currently active area of research in magnetic materials involves compounds in which long-range magnetic ordering at low temperatures is frustrated by the geometry of the crystalline lattice, a situation known as geometrical magnetic frustration. The number of systems known to display the effects of such frustration is growing, but those that are sufficiently simple from theoretical, chemical, and physical perspectives to allow for detailed understanding remain very few. A search for model compounds in this family has led us to the double perovskites Ba2LnSbO6 and Sr2LnSbO6 (Ln = Dy, Ho, and Gd) reported here. Ba2DySbO6,Ba2HoSbO6,Sr2DySbO6, and Sr2HoSbO6 are structurally characterized by powder neutron diffraction at ambient temperature. The trivalent lanthanides and pentavalent antimony are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygens. In such a structure, the lanthanide sublattice displays a classical fcc arrangement, an edge-shared network of tetrahedra known to result in geometric magnetic frustration. No magnetic ordering is observed in any of these compounds down to temperatures of 2 K, and in the case of the Dy-based compounds in particular, frustration of the magnetic ordering is clearly present. Lanthanide-based double perovskites are proposed to be excellent model systems for the detailed study of geometric magnetic frustration. PMID:12824460

  6. 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

  7. Extraordinary role of Ce-Ni elements on the electrical and magnetic properties of Sr-Ba M-type hexaferrites

    SciTech Connect

    Iqbal, Muhammad Javed; Farooq, Saima

    2009-11-15

    The structural, electrical and magnetic behavior of Sr{sub 0.5}Ba{sub 0.5-x}Ce{sub x}Fe{sub 12-y}Ni{sub y}O{sub 19} (where x = 0.00-0.10; y = 0.00-1.00) hexaferrite nanomaterials are reported in this paper. The structural analysis indicates that the Ce-Ni doped Sr-Ba M-type hexaferrite samples synthesized by the co-precipitation method are stoichiometric, single magnetoplumbite phase with crystallite sizes in the range of 35-48 nm. The dc-electrical resistivity of the pure Sr-Ba hexaferrite is enhanced to almost 10{sup 2} times by doping with Ce-Ni contents of x = 0.06; y = 0.60. The dielectric constant and dielectric loss tangent decrease to values {approx}14 and <0.2, respectively, by increasing the frequency up to 1 MHz. Small relaxation peaks at frequencies >10{sup 5} Hz are observed for the samples with Ce content of x > 0.06. The values of saturation magnetization increase from 66.32 to 84.33 emu/g and remanance magnetization from 42.64 to 56.01 emu/g but coercivity decreases from 2.85 to 1.59 kOe by substitution of Ce-Ni. Sharp ferri-paramagnetic transition is observed in the samples, which is confirmed by DSC results. Ce-Ni substitution acts to reduce the electron-hopping between Fe{sup 2+}/Fe{sup 3+} ions and also improves the magnetic properties. These characteristics are desirable for their possible use in microwave and chip devices.

  8. Interfacial charge-mediated non-volatile magnetoelectric coupling in Co0.3Fe0.7/Ba0.6Sr0.4TiO3/Nb:SrTiO3 multiferroic heterostructures

    PubMed Central

    Zhou, Ziyao; Howe, Brandon M.; Liu, Ming; Nan, Tianxiang; Chen, Xing; Mahalingam, Krishnamurthy; Sun, Nian X.; Brown, Gail J.

    2015-01-01

    The central challenge in realizing non-volatile, E-field manipulation of magnetism lies in finding an energy efficient means to switch between the distinct magnetic states in a stable and reversible manner. In this work, we demonstrate using electrical polarization-induced charge screening to change the ground state of magnetic ordering in order to non-volatilely tune magnetic properties in ultra-thin Co0.3Fe0.7/Ba0.6Sr0.4TiO3/Nb:SrTiO3 (001) multiferroic heterostructures. A robust, voltage-induced, non-volatile manipulation of out-of-plane magnetic anisotropy up to 40 Oe is demonstrated and confirmed by ferromagnetic resonance measurements. This discovery provides a framework for realizing charge-sensitive order parameter tuning in ultra-thin multiferroic heterostructures, demonstrating great potential for delivering compact, lightweight, reconfigurable, and energy-efficient electronic devices. PMID:25582090

  9. An ERDA study of proton migration induced by electric potential in SrZrO{sub 3}, SrCeO{sub 3} and BaCeO{sub 3}

    SciTech Connect

    Kunimatsu, A.; Arai, T.; Takahiro, K.; Nagata, S.; Yamaguchi, S.; Akiyama, Y.; Sata, N.; Ishigame, M.

    1998-12-31

    Migration of protons dissolved in acceptor doped SrZrO{sub 3}, SrCeO{sub 3} and BaCeO{sub 3} oxides has been examined under an applied electric potential over a range of temperature from 25 to 220 C. Protons which dissolved in these oxides migrated to the cathode, and they were trapped there when the cathode material had a good ability to getter the migrating hydrogen. The amount of hydrogen accumulated in the cathode could be measured by the ERDA method using a high-energy {sup 4}He beam. The authors measured the amount of hydrogen in the cathode while monitoring the dc current passed through the oxide specimen. The proton transport number was determined from the ratio of the number of hydrogen in the cathode to the total numbers of charge through the specimen. The diffusion coefficient of proton was evaluated using the proton transport number and proton concentration in the specimen.

  10. Dipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted hysteresis loops

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the constricted loop show a similar mechanism to the exchange coupling effect in magnetic multilayers.

  11. Characterization of (Ba(0.5)Sr(0.5)) TiO3 Thin Films for Ku-Band Phase Shifters

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; VanKeuls, Fredrick W.; Romanofsky, Robert R.; Miranda, Felix A.; Warner, Joseph D.; Canedy, Chadwick L.; Ramesh, Rammamoorthy

    1999-01-01

    The microstructural properties of (Ba(0.5)Sr(0.5)TiO3) (BSTO) thin films (300, 700, and 1400 nm thick) deposited on LaAlO3 (LAO) substrates were characterized using high-resolution x-ray diffractometry. Film crystallinity was the parameter that most directly influenced tunability, and we observed that a) the crystalline quality was highest in the thinnest film and progressively degraded with increasing film thickness; and b) strain at the film/substrate interface was completely relieved via dislocation formation. Paraelectric films such as BSTO offer an attractive means of incorporating low-cost phase shifter circuitry into beam-steerable reflectarray antennas.

  12. Observation of an anomalous correlation between permittivity and tunability of a doped (Ba,Sr)TiO3 ferroelectric ceramic developed for microwave applications

    NASA Astrophysics Data System (ADS)

    Kozyrev, Andrey B.; Kanareykin, Alexei D.; Nenasheva, Elizaveta A.; Osadchy, Vitaly N.; Kosmin, Dmitry M.

    2009-07-01

    Anomalous dependencies of the dynamic (pulse) and static tunability [k(U )=C(0)/C(U)] as a function of permittivity (ɛ) were observed in ferroelectric varactors based on doped paraelectric state (Ba,Sr)TiO3 ceramics. The reduction of the relatively high permittivity value from ɛ ≅810 down to ɛ ≅260 by introducing various proportions of a Mg2TiO4 additive resulted in a 20% increase in tunability. Furthermore, ceramics with this additive have demonstrated dynamic tunability noticeably higher than the static tunability, also unexpected for this type of material.

  13. μSR study on multi-layered HgBa 2Ca 4Cu 5O y (Hg-1245) superconductor

    NASA Astrophysics Data System (ADS)

    Tokiwa, K.; Ito, S.; Okumoto, H.; Higemoto, W.; Nishiyama, K.; Iyo, A.; Tanaka, Y.; Watanabe, T.

    2003-05-01

    We have carried out zero-field muon spin relaxation (ZF-μSR) measurements in multi-layered HgBa2Ca4Cu5Oy (Hg-1245) superconductor with Tc of 108 K. The variation of ZF-μSR time spectra from Gaussian-type to exponential-type behavior was observed with decreasing temperature below 60 K and the muon precessions were also observed below 45 K. These results indicate the appearance of a static magnetic order of Cu moments at muon sites below Tc. Compared with the results of NMR measurements, they suggest that this magnetic order is caused in three under-doped inner planes of five CuO2 planes in Hg-1245.

  14. Epitaxial Ba{sub 2}IrO{sub 4} thin-films grown on SrTiO{sub 3} substrates by pulsed laser deposition

    SciTech Connect

    Nichols, J. Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A.

    2014-03-24

    We have synthesized epitaxial Ba{sub 2}IrO{sub 4} (BIO) thin-films on SrTiO{sub 3} (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metal-insulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr{sub 2}IrO{sub 4}. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting physical properties predicted in layered iridates.

  15. Structure refinement of Ba0.5Sr0.5Co0.8Fe0.2O3-d as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

    NASA Astrophysics Data System (ADS)

    Zakaria, Nurhamidah; Osman, Rozana A. M.; Idris, Mohd Sobri

    2016-07-01

    Ba0.5Sr0.5Co0.8Fe0.2O3-δ was successfully prepared using modified solid-state synthesis routes. The lowest temperature to obtained single phase of Ba0.5Sr0.5Co0.8Fe0.2O3-δ is about 900°C for 15 hours. Longer period of time are required compared to only 5 hours at 950°C as established in literatures. The X-ray Diffraction (XRD) data confirmed that Ba0.5Sr0.5Co0.8Fe0.2O3-δ is formed a cubic perovskite with the space group of Pm-3m. The lattice parameters of Ba0.5Sr0.5Co0.8Fe0.2O3-δ are a = 3.990 (1) Å and unit cell volume is V = 63.5 (1) Å3. The Rietveld refinement of XRD data revealed that the crystal structure of Ba0.5Sr0.5Co0.8Fe0.2O3-δ slightly changes as a function of temperature.

  16. Method of forming a dielectric thin film having low loss composition of Ba.sub.x Sr.sub.y Ca.sub.1-x-y TiO.sub.3 : Ba.sub.0.12-0.25 Sr.sub.0.35-0.47 Ca.sub.0.32-0.53 TiO.sub.3

    DOEpatents

    Xiang, Xiao-Dong; Chang, Hauyee; Takeuchi, Ichiro

    2000-01-01

    A dielectric thin-film material for microwave applications, including use as a capacitor, the thin-film comprising a composition of barium strontium calcium and titanium of perovskite type (Ba.sub.x Sr.sub.y Ca.sub.1-x-y)TiO.sub.3. Also provided is a method for making a dielectric thin film of that formula over a wide compositional range through a single deposition process.

  17. Low Loss Composition of BA{sub X}SR{sub Y}CA{sub 1-X-Y}TIO{sub 3}:BA{sub 0.12-0.25}SR{sub 0.35-0.47}CA{sub 0.32-0.53}TIO{sub 3}

    SciTech Connect

    Xiang, Xiao-Dong; Chang, Hauyee; Takeuchi, Ichiro

    1999-10-19

    A dielectric thin-film material for microwave applications, including use as a capacitor, the thin-film comprising a composition of barium strontium calcium and titanium of perovskite type (Ba{sub x}Sr{sub y}Ca{sub 1-x-y})TiO{sub 3}. Also provided is a method for making a dielectric thin film of that formula over a wide compositional range through a single deposition process.

  18. Correlation between upconversion photoluminescence and dielectric response in Ba-substituted (Sr{sub 1−x}Ba{sub x}){sub 4}(La{sub 0.85}Ho{sub 0.025}Yb{sub 0.125}){sub 2}Ti{sub 4}Nb{sub 6}O{sub 30}

    SciTech Connect

    Wei, T.; Wang, X. D.; Zhao, C. Z.; Liu, M. F.; Liu, J. M.

    2014-06-30

    The filled tetragonal tungsten bronze (Sr{sub 1−x}Ba{sub x}){sub 4}(La{sub 0.85}Ho{sub 0.025}Yb{sub 0.125}){sub 2}Ti{sub 4}Nb{sub 6}O{sub 30} (SBLTNx: Ho-Yb) ceramics with different Ba substitution levels (x) are prepared. The upconversion photoluminescence (UC-PL) and dielectric permittivity are investigated. The substitution of Sr{sup 2+} ions at the A{sub 2}-sites by larger Ba{sup 2+} ions results in substantial variation of the UC-PL intensity as a function of substitution level x. Furthermore, the dielectric response to the substitution of Sr{sup 2+} by Ba{sup 2+} suggests a close correlation between the UC-PL intensity and dielectric permittivity. The origin for this correlation is discussed based on the random stress field (RSF) model.

  19. Crystal structure of Ba9La2W4O24 and Sr9Gd2W4O24: A new B-site vacancy ordered 4×4×4 cubic perovskite

    NASA Astrophysics Data System (ADS)

    IJdo, D. J. W.; Fu, W. T.; Akerboom, S.

    2016-06-01

    The crystal structure of Ba9La2W4O24 and the high-temperature modification Sr9Gd2W4O24 has been investigated by the Rietveld method using X-ray powder diffraction data. They crystalize in a 4×4×4 cubic superstructure of the simple cubic perovskite ABO3 with the space group Fm 3 bar and lattice parameter a≈4ap, where ap denotes the lattice constant of the primitive cubic perovskite. The structure consists of the ordered B-site vacancies (☐) and the structure formula can be written as Ba2(Ba1/4La1/2)☐1/4WO6 and (Sr/Gd)2((Sr/Gd)3/4)☐1/4WO6 due to a partial disorder between one of the Sr at A-site and the Gd at B-site. The three crystallographically different W and the randomly distributed Ba/La or (Sr/Gd) ions occupy the B-sites. Two W ions are coordinated with 6 oxygens and arranged as octahedra, but the third one is surrounded by 12 partially occupied (50%) oxygens, which can be viewed as a combination of four tetrahedra. The coordination geometry of the larger B-cations (Ba/La and Sr/Gd) is not octahedral; they coordinate with seven oxygens instead. In addition, the Ba/LaO7 or (Sr/GdO7) polyhedron shares some oxygen atoms with four neighbours. The B-site vacancies form a primitive cube with a≈2ap, and are surrounded by six equal but differently orientated WO6 octahedra being caused by a rotation about a twofold axis.

  20. Effect of sintering optimization on the electrical properties of bulk Ba xSr 1-xTiO 3 ceramics

    NASA Astrophysics Data System (ADS)

    Mohan, C. R. K.; Bajpai, P. K.

    2008-07-01

    Ba xSr 1-xTiO 3 ( x=0.6, 0.75, 0.80, 0.85 and 0.9) compositions are prepared by solid-state reaction route using controlled heating and cooling. Density optimization by varying sintering temperature was achieved. X-ray diffraction (XRD) analysis shows the phase pure materials. The lattice constant decreases from 3.9868 Å ( x=0.90) to 3.9449 Å ( x=0.60) with increasing Sr 2+; the tetragonal distortion also decreases. Dielectric constant show sharp peaks for samples having low strontium content (0.10, 0.15) and gets smeared out as the strontium content is increased (0.20, 0.25). For further higher Sr 2+ composition (0.40), the dielectric peak could not be observed in the measured temperature range. The peak broadening in Sr 2+ rich compositions indicates that diffused transitions and is attributed to the disorder in the arrangement of cations at A-site. A modified Curie-Weiss law using exponent γ and diffuseness parameter δ fits temperature dependence of dielectric constant in paraelectric phase. Both the parameters increase with increasing Sr 2+ content showing that with strontium substitution, the material becomes disordered and may be correlated with the compositional fluctuation in solid solution. Frequency dependence of dielectric behavior is analyzed in terms of Debye formalism and nature of dielectric relaxation processes is explored using Cole-Cole formalism. Ferroelectric hysterisis loops reveal spontaneous polarization and coercive field increases with deceasing Sr content.

  1. Strong growth orientation dependence of strain relaxation in epitaxial (Ba,Sr)TiO{sub 3} films and the resulting dielectric properties

    SciTech Connect

    Yamada, Tomoaki; Kamo, Takafumi; Funakubo, Hiroshi; Su Dong; Iijima, Takashi

    2011-05-01

    The growth orientation dependence of strain relaxation and the dielectric properties were investigated for (001)- and (111)-epitaxial (Ba,Sr)TiO{sub 3} films. The films were deposited on SrRuO{sub 3}/SrTiO{sub 3} and SrTiO{sub 3} substrates using rf magnetron sputtering. The residual strain was found to be remarkably different between the two orientations, although these lattice mismatches are identical; the strain relaxation of the (001)-epitaxial films is significantly slower than that of the (111)-epitaxial films and is promoted only when the growth rate is very low ({<=}5 nm/h). The observed orientation dependence is discussed with the surface energy for both growth orientations, which influences the growth mode of the films. Due to the large contrast of the strain in the (001)- and (111)-epitaxial films, the paraelectric to ferroelectric phase transition temperature of the (001)-epitaxial films is much higher than that of unstrained bulks, while the (111)-epitaxial films show a phase transition temperature corresponding to that of unstrained bulks regardless of the growth rates.

  2. Ba(Zn1/3Ta2/3)O ceramics for microwave and millimeter-wave applications.

    PubMed

    Alexandru, H V; Ioachim, A; Toacsan, M I; Nedelcu, L; Banciu, M G; Berbecaru, C; Voicu, G; Jinga, S; Andronescu, E

    2009-04-01

    The Ba(Zn(1/3)Ta(2/3))O(3) (BZT) ceramic samples were prepared by solid-state reaction and sintered in the range 1550-1650 degrees C for 2 h. Several methods--X-ray diffraction (XRD) and scanning electron microscopy (SEM)--were used for structural and morphological characterization. The unit cell distortion and the presence of the secondary phase content were studied by XRD. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was noticed with the increase of the sintering temperature. SEM investigations revealed polyhedral well-faceted grains and large grain size distribution. The dielectric properties in the microwave range were measured at room temperature and at 1 kHz on a large temperature interval (+/-150 degrees C). The dielectric parameters were correlated with morphological and structural properties. Ceramic samples were annealed at 1410 degrees C for 30 h to improve the microwave properties. The dielectric constant of BZT samples measured at 6 GHz and at 1 kHz was between 27 and 28 on the whole temperature range, that is, typical values for BZT material. The temperature coefficient of the resonance frequency at 6 GHz exhibits positive values less than 6 ppm/degrees C.

  3. Semiconductivity in Ba 2Ni 2- xZn xFe 12O 22 Y-type hexaferrites

    NASA Astrophysics Data System (ADS)

    El Hiti, M. A.; Abo El Ata, A. M.

    1999-06-01

    The electric, thermoelectric and magnetic properties were studied as a function of temperature and composition for a series of Ba 2Ni 2- xZn xFe 12O 22 Y-type hexaferrite samples (with x=0, 0.4, 0.8, 1.2, 1.6 and 2) prepared using the usual ceramic technique. The experimental results indicated that the DC electrical conductivity σDC, thermoelectric power α, diff mobility μd, carrier concentration n and initial magnetic permeability μi increase whereas the Fermi energy EF decreases as the temperature increases. α has a negative sign for all samples indicating that the majority of electric charge carriers are electrons. The study of initial magnetic permeability showed two peaks on μi- T curves. The first peak nearly appears at Curie temperature Tc for all samples except for the sample with x=2 while the second peak Ts appears below room temperature for all samples. Tc decreases due to the replacement of non-magnetic Zn 2+ ions to magnetic Ni 2+ ions. μi, activation energies for hopping EH, for carrier generation Eg and for electric conduction ( E 1, E 2 and E3 in regions I, II and III) decreases to reach minimum at x=1.2 and start to increase for x>1.2. Each of σDC, α, n, μd and energy at donor level ED increase as the substitution of non-magnetic Zn 2+ ions to magnetic Ni 2+ ions increase reaching maximum at x=1.2 and start to decreases for x>1.2. The small values of μd and its strong temperature-dependence (exponential relation) indicate that the hopping conduction mechanism is predominant at high temperatures in region III. In region II, the band conduction mechanism shares in electric conduction process beside the hopping conduction mechanism. The band conduction mechanism is predominant in region I.

  4. High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications.

    PubMed

    Raengthon, Natthaphon; Cann, David P

    2011-09-01

    Solid solutions of BaTiO(3)-Bi(Zn(1/2)Ti(1/2))O(3) were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO(3)-0.2Bi(Zn(1/2)Ti(1/2))O(3) revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba(0.8)-xBi(0.2))(Zn(0.1)Ti(0.9)) O(3) ceramics where 0 ≤ X ≤ 0.08, as well as ZrO2- and Mn(2)O(3)-doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ < 0.05) that persisted up to a temperature of 460δC. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity ((τ)K) and the RC time constant were also investigated.

  5. Octonary resistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions

    DOE PAGESBeta

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; Liu, Yu -Kuai; Yang, Sheng -Wei; Dong, Si -Ning; Zhu, Yi -Mei; Li, Qi; Li, Xiao -Guang

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45°more » and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.« less

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

    DOE PAGESBeta

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

    2015-12-16

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

  7. Epitaxial Ferroelectric Ba(0.5)Sr(0.5)TiO3 Thin Films for Room-Temperature High-Frequency Tunable Element Applications

    NASA Technical Reports Server (NTRS)

    Chen, C. L.; Feng, H. H.; Zhang, Z.; Brazdeikis, A.; Miranda, F. A.; VanKeuls, F. W.; Romanofsky, R. R.; Huang, Z. J.; Liou, Y.; Chu, W. K.; Chu, C. W.

    1999-01-01

    Perovskite Ba(0.5)SR(0.5)TiO3 thin films have been synthesized on (001) LaAl03 substrates by pulsed laser ablation. Extensive X-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of <100>(sub BSTO)//<100>(sub LAO). Rutherford Backscattering Spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield chi(sub min) Of only 2.6 %. The dielectric property measurements by the interdigital technique at 1 MHz show room temperature values of the relative dielectric constant, epsilon(sub r), and loss tangent, tan(sub delta), of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba(0.5)SR(0.5)TiO3 films can be used for development of room-temperature high-frequency tunable elements.

  8. High-pressure phase transitions and compressibilities of aragonite-structure carbonates: SrCO3 and BaCO3

    NASA Astrophysics Data System (ADS)

    Wang, Meili; Liu, Qiong; Nie, Shufang; Li, Baosheng; Wu, Ye; Gao, Jing; Wei, Xiaozhuo; Wu, Xiang

    2015-06-01

    The aragonite-structure carbonates—strontianite (SrCO3) and witherite (BaCO3)—were investigated by synchrotron X-ray diffraction combined with diamond anvil cells up to 30 and 15 GPa at room temperature, respectively. Phase transitions in SrCO3 ( Pmcn to P21212) and BaCO3 ( Pmcn to Pmmn) were observed at 22.2-26.9 and 9.8-11.2 GPa, respectively. Both strontianite and witherite display anisotropic linear compression under pressure, with the c-axis 2-3 times more compressible than the a-axis and b-axis. The obtained second-order Birch-Murnaghan equation of state parameters for strontianite and witherite are V 0 = 258.4(3) Å3, K 0 = 62(1) GPa; and V 0 = 304.8(3) Å3, K 0 = 48(1) GPa, respectively. Based on the current results for strontianite and witherite and previous data for aragonite (CaCO3) and cerussite (PbCO3), the bulk moduli of the aragonite-structure carbonates exhibit a linear correlation with ambient molar volume [ K T0 (GPa) = 138 (5) - 2.0 (3) × V 0], with V 0 in cm3/mol, and the aragonite-structure to post-aragonite-structure phase transition pressures increase with decreasing ionic radius of the cations.

  9. A systematic study of ideal and double layer reconstructions of ABO3(001) surfaces (A = Sr, Ba; B = Ti, Zr) from first principles.

    PubMed

    Iles, N; Finocchi, F; Khodja, K Driss

    2010-08-01

    We conducted a comparative study of various reconstructions for the (001) surfaces of SrTiO(3), BaTiO(3), SrZrO(3) and BaZrO(3) perovskites through calculations within the density functional theory. The atomic structure, the thermodynamic stability and the charge distribution of ideal AO or BO(2) terminations, as well as the so-called AO or BO(2) double layer reconstructions were analysed, and it was found that of all the BO(2) double layer reconstructions the most stable are the (2 × 2) and the (√2 × √2) ones. This is mainly due to stress release through the formation of long B-chains. On Ti-based perovskites, these double layer reconstructions were found to be thermodynamically stable, which was not the case for Zr-based perovskites, for which AO terminations dominated most of the stability domain. We also found that the BO(2) double layer reconstructions are accompanied by a substantial charge redistribution, with an almost neutral surface plane. This charge redistribution has important consequences for the reactivity and the behaviour of the electric field close to the surface.

  10. The first-principle study of the electronic, optical and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) compounds

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A.

    2016-07-01

    The FP-LAPW method is utilized to investigate the elastic, optoelectronic and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) within the GGA. The calculated lattice constants and bulk modulus are found in agreement with previous studies. The present oxide-perovskite compounds are characterized as elastically stable and anisotropic. CaTiO3 and SrTiO3 are categorized as ductile compounds, whereas the BaTiO3 compound is in the critical region between ductile and brittle. The DOS and the band structure calculations reveal indirect (M-Γ) energy bandgap for the present compounds. The hydrostatic pressure increases the energy bandgap and the width of the valence band. The character of the band structure does not change due to this pressure. The optical parameters are calculated in different radiation regions. Beneficial optics applications are predicted as revealed from the optical spectra. The transport properties are applied as a function of the variable temperatures or carrier concentration. It is found that the compounds under study are classified as a p-type semiconductor. The majority charge carriers responsible for conduction in these calculated compounds are holes rather than electrons.

  11. Synthesis, spectroscopic characterization, thermal analysis and electrical conductivity studies of Mg(II), Ca(II), Sr(II) and Ba(II) vitamin B2 complexes

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.; Moussa, Mohamed A. A.; Mohamed, Soha F.

    2011-05-01

    Riboflavin (RF) complexes of Mg(II), Ca(II), Sr(II) and Ba(II) were successfully synthesized. Structures of metal complexes obtained were confirmed and characterized by elemental analysis, molar conductance, and infrared spectra. DC electrical conductivity measurements indicated that the alkaline earth metal (II) complexes of RF ligand are non-electrolytes. Elemental analysis of chelates suggest that the metal(II) ligand ratio is 1:2 with structure formula as [M(RF) 2( X) 2]· nH 2O. Infrared assignments clearly show that RF ligand coordinated as a bidentate feature through azomethine nitrogen of pyrazine ring and C dbnd O of pyrimidine-2,4-dione. Thermal analyses of Mg(II), Ca(II), Sr(II) and Ba(II) complexes were investigated using (TG/DSC) under atmospheric nitrogen between 30 and 800 °C. The surface morphology of the complexes was studied by SEM. The electrical conductivities of RF and its metal complexes were also measured with DC electrical conductivity in the temperature range from room to 483 K.

  12. Step Coverage and Electrical Properties of (Ba, Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition Using TiO(DPM)2

    NASA Astrophysics Data System (ADS)

    Kawahara, Takaaki; Yamamuka, Mikio; Makita, Tetsuro; Naka, Jiro; Yuuki, Akimasa; Mikami, Noboru; Ono, Kouichi

    1994-09-01

    Thin films of (Ba, Sr)TiO3 (BST) with high dielectric constant were prepared on Pt/ SiO2/Si substrates of 6-inch-diameter by liquid source chemical vapor deposition using Ba(DPM)2, Sr(DPM)2 and TiO(DPM)2 (DPM=dipivaloylmethanato; C11H19O2) dissolved in tetrahydrofuran (THF). The reproducibility of ±3 % for the film composition was achieved by optimizing the deposition procedures. It was found that the coverage of 72%, obtained at the substrate temperature T s=753 K, was better than those obtained using other Ti sources such as Ti(O-i-Pr)4 (TTIP) and Ti(O-i-Pr)2(DPM)2. The electrical properties of the 480-Å-thick BST film, deposited at T s=753 K using TiO(DPM)2, were as follows: dielectric constant ɛ=230, equivalent SiO2 thickness t eq=7.8 Å, leakage current density J L=6.7×10-6 A/cm2 at 1.65 V and dielectric loss tan δ=0.013.

  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. Transformation of AeIn4 Indides (Ae = Ba, Sr) into an AeAu2In2 Structure Type Through Gold Substitution

    SciTech Connect

    Dai, Jing-Cao; Corbett, John D.

    2007-04-17

    The title compounds were prepared from the elements by high-temperature solid-state synthesis techniques. X-ray structural analyses shows that BaAu{sub 2}In{sub 2} (1) and SrAu{sub 2}In{sub 2} (2) crystallize in a new orthorhombic structure, Pnma, Z = 4 (a = 8.755(2), 8.530(2) {angstrom}; b = 4.712(1), 4.598(1) {angstrom}; c = 12.368(3), 12.283(4) {angstrom}, respectively). Gold substitutes for 50% of the indium atoms in the tetragonal BaIn{sub 4} and monoclinic SrIn{sub 4} parents to give this new and more flexible orthorhombic structure. The Ae atoms in this structure are contained within chains of hexagonal prisms built of alternating In and Au that have additional augmenting atoms around their waists from further condensation of parallel displaced chains. The driving forces for these structural changes are in part the shorter Au-In distances (2.72 and 2.69 {angstrom}) relative to d(In-In) in the parents, presumably because of relativistic contractions with Au. Generalities about such centered prismatic building blocks and their condensation modes in these and related phases are described. Band structure calculations (EHTB) demonstrate that the two compounds are metallic, which is confirmed by measurements of the resistivity of 1 and the magnetic susceptibilities of both.

  15. Overcoming the Fundamental Barrier Thickness Limits of Ferroelectric Tunnel Junctions through BaTiO3/SrTiO3 Composite Barriers.

    PubMed

    Wang, Lingfei; Cho, Myung Rae; Shin, Yeong Jae; Kim, Jeong Rae; Das, Saikat; Yoon, Jong-Gul; Chung, Jin-Seok; Noh, Tae Won

    2016-06-01

    Ferroelectric tunnel junctions (FTJs) have attracted increasing research interest as a promising candidate for nonvolatile memories. Recently, significant enhancements of tunneling electroresistance (TER) have been realized through modifications of electrode materials. However, direct control of the FTJ performance through modifying the tunneling barrier has not been adequately explored. Here, adding a new direction to FTJ research, we fabricated FTJs with BaTiO3 single barriers (SB-FTJs) and BaTiO3/SrTiO3 composite barriers (CB-FTJs) and reported a systematic study of FTJ performances by varying the barrier thicknesses and compositions. For the SB-FTJs, the TER is limited by pronounced leakage current for ultrathin barriers and extremely small tunneling current for thick barriers. For the CB-FTJs, the extra SrTiO3 barrier provides an additional degree of freedom to modulate the barrier potential and tunneling behavior. The resultant high tunability can be utilized to overcome the barrier thickness limits and enhance the overall CB-FTJ performances beyond those of SB-FTJ. Our results reveal a new paradigm to manipulate the FTJs through designing multilayer tunneling barriers with hybrid functionalities.

  16. Nonlinear Composition-Dependent Optical Spectroscopy of Ba2xSr2-2xV2O7.

    PubMed

    Fang, Hongwei; Wei, Xiantao; Zhou, Shaoshuai; Chen, Yonghu; Duan, Changkui; Yin, Min

    2016-09-19

    In general, adjusting the composition of a fluorescent material is an effective way to tune its luminescent properties such as peak energy and bandwidth. In most solid-solutions, the emission peak shifts linearly with the materials' composition, which is referred to as Vegard's Law. However, we found extraordinary variations in our samples Ba2xSr2-2xV2O7, that is, both the excitation and emission peaks show nonlinear dependence on the composition x, and the same is true for the spectral bandwidths. The nonlinearities are not due to structural anomaly, as all the samples are confirmed to be solid-solutions by X-ray diffraction measurements. To explain these phenomena, we proposed a model by considering the disorder of Ba(2+) and Sr(2+) distributions in solid-solutions and the changes of configurations between the ground and excited electronic states. This novel phenomenon could be applied to further exploit new fluorescent materials. PMID:27584044

  17. Preparation of Ba0.09Sr0.91TiO3/YBa2Cu3O7-x bilayers and investigation of their dielectric properties

    NASA Astrophysics Data System (ADS)

    Jia, Jiqiang; Zhao, Gaoyang; Shi, Xiaoxue; Lei, Li

    2016-08-01

    YBa2Cu3O7-x (YBCO) films of 110 nm thickness were prepared on LaAlO3 (LAO) substrates via the sol-gel method. Subsequently, about 400 nm thick Ba0.09Sr0.91TiO3 (BST) films were epitaxially grown on the YBCO and LNO films surface; the BST films exhibited a strong c-axis orientation. The dielectric adjustability and relative dielectric constant was investigated in the range of 300-83 K. Results indicate that the tunability of the Ba0.09Sr0.91TiO3/YBa2Cu3O7-x (BST/YBCO) displayed an increase relative to c-axis-oriented BST on LaNiO3 (LNO). The tunability was further enhanced as the operating temperature decreased, yet the loss tangent (tanδ) decreased. The tunability and the tanδ at 100 kHz and 83 K were 58% and 0.029, respectively.

  18. Electronic structure and x-ray magnetic circular dichroism in A2FeReO6 (A =Ca ,Sr ,andBa ) oxides

    NASA Astrophysics Data System (ADS)

    Antonov, V. N.; Bekenov, L. V.; Ernst, A.

    2016-07-01

    A systematic electronic structure study of A2FeReO6 (A =Ba ,Sr ,andCa ) has been performed by employing the local-spin-density approximation (LSDA) and LSDA +U methods using the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. We investigated the effects of the subtle interplay between spin-orbit coupling, electron correlations, and lattice distortion on the electronic structure of double perovskites. Ca2FeReO6 has a large distortion in the Fe-O-Re bond, and the electronic structure is mainly determined by electron correlations and lattice distortion. In the Ba -Sr -Ca row, the correlation effects at the Fe site are increased. The correlations at the Re site are small in the Ba- and Sr-based compounds but significant in Ca2FeReO6 . Ca2FeReO6 behaves like an insulator only if considered with a relatively large value of Coulomb repulsion Ueff=2.3 eV at the Re site in addition to Ueff=3.1 eV at the Fe site. Ca2FeReO6 possesses a phase transition at 140 K where the metal-insulator transition (MIT) occurs between metallic high-temperature and insulating low-temperature phases. The spin and orbital magnetic moments are linear functions of temperature before and after the MIT but change abruptly at the point of the phase transition. From theoretically calculated magnetocrystalline anisotropy energy (MAE), we found that the easy axis of magnetization for the low-temperature phase is along the b direction, in agreement with experimental data. We found that the major contribution to the MAE is due to the orbital magnetic anisotropy at the Re site. X-ray-absorption spectra and x-ray magnetic circular dichroism at the Re, Fe, and Ba L2 ,3 and Fe, Ca, and O K edges were investigated theoretically in the frame of the LSDA +U method. A qualitative explanation of the x-ray magnetic circular dichroism spectra shape is provided by an analysis of the corresponding selection rules, orbital character, and occupation numbers of individual orbitals

  19. Ethylene production by ODHE in catalytically modified Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) membrane reactors.

    PubMed

    Lobera, M Pilar; Escolástico, Sonia; Garcia-Fayos, Julio; Serra, José M

    2012-08-01

    Process intensification by the integration of membranes and high-temperature reactors offers several advantages with regard to conventional process schemes, that is, energy saving, safe operation, reduced plant/unit size, and higher process performance, for example, higher productivity, catalytic activity, selectivity, or stability. We present the study of oxidative dehydrogenation of ethane at 850 °C on a catalytic membrane reactor based on a mixed ionic-electronic conducting membrane. The surface of the membrane made of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) has been activated by using different porous catalytic layers based on perovskites. The layer was deposited by screen printing, and the porosity and thickness was studied for the catalyst composition. The different catalyst formulations are based on partial substitution of A- and B-site atoms of doped strontium ferrite/cobaltites (A(0.6)Sr(0.4)Co(0.5)Fe(0.5)O(3-δ) and Ba(0.6)Sr(0.4)BO(3-δ)) and were synthesized by an ethylenediaminetetraacetic acid-citrate complexation route. The use of a disk-shaped membrane in the reactor enabled the direct contact of gaseous oxygen and hydrocarbons to be avoided, and thus, the ethylene content increased. High ethylene yields (up to ≈81 %) were obtained by using a catalytic coating based on Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ), which included macropores produced by the addition of graphite platelets into the screen-printing ink. The promising catalytic results obtained with this catalytically modified membrane reactor are attributed to the combination of 1) the high activity, as a result of the high temperature and oxygen species diffusing through the membrane; 2) the control of oxygen dosing and the low concentration of molecules in the gas phase; and 3) suitable fluid dynamics, which enables appropriate feed contact with the membrane and the rapid removal of products.

  20. Ethylene production by ODHE in catalytically modified Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) membrane reactors.

    PubMed

    Lobera, M Pilar; Escolástico, Sonia; Garcia-Fayos, Julio; Serra, José M

    2012-08-01

    Process intensification by the integration of membranes and high-temperature reactors offers several advantages with regard to conventional process schemes, that is, energy saving, safe operation, reduced plant/unit size, and higher process performance, for example, higher productivity, catalytic activity, selectivity, or stability. We present the study of oxidative dehydrogenation of ethane at 850 °C on a catalytic membrane reactor based on a mixed ionic-electronic conducting membrane. The surface of the membrane made of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) has been activated by using different porous catalytic layers based on perovskites. The layer was deposited by screen printing, and the porosity and thickness was studied for the catalyst composition. The different catalyst formulations are based on partial substitution of A- and B-site atoms of doped strontium ferrite/cobaltites (A(0.6)Sr(0.4)Co(0.5)Fe(0.5)O(3-δ) and Ba(0.6)Sr(0.4)BO(3-δ)) and were synthesized by an ethylenediaminetetraacetic acid-citrate complexation route. The use of a disk-shaped membrane in the reactor enabled the direct contact of gaseous oxygen and hydrocarbons to be avoided, and thus, the ethylene content increased. High ethylene yields (up to ≈81 %) were obtained by using a catalytic coating based on Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ), which included macropores produced by the addition of graphite platelets into the screen-printing ink. The promising catalytic results obtained with this catalytically modified membrane reactor are attributed to the combination of 1) the high activity, as a result of the high temperature and oxygen species diffusing through the membrane; 2) the control of oxygen dosing and the low concentration of molecules in the gas phase; and 3) suitable fluid dynamics, which enables appropriate feed contact with the membrane and the rapid removal of products. PMID:22791570

  1. Direct observation of oxygen-vacancy-enhanced polarization in a SrTiO3-buffered ferroelectric BaTiO3 film on GaAs

    DOE PAGESBeta

    Qiao, Q.; Zhang, Y.; Contreras-Guerrero, Rocio; Droopad, Ravi; Pantelides, S. T.; Pennycook, Stephen J.; Ogut, Serdar; Klie, Robert F.

    2015-11-16

    The integration of functional oxide thin-films on compound semiconductors can lead to a class of reconfigurable spin-based optoelectronic devices if defect-free, fully reversible active layers are stabilized. However, previous first-principles calculations predicted that SrTiO3 thin filmsgrown on Si exhibit pinned ferroelectric behavior that is not switchable, due to the presence of interfacial vacancies. Meanwhile, piezoresponse force microscopy measurements have demonstrated ferroelectricity in BaTiO3 grown on semiconductor substrates. The presence of interfacial oxygen vacancies in such complex-oxide/semiconductor systems remains unexplored, and their effect on ferroelectricity is controversial. We also use a combination of aberration-corrected scanning transmission electron microscopy and first-principles densitymore » functional theory modeling to examine the role of interfacial oxygen vacancies on the ferroelectricpolarization of a BaTiO3 thin filmgrown on GaAs. Moreover, we demonstrate that interfacial oxygen vacancies enhance the polar discontinuity (and thus the single domain, out-of-plane polarization pinning in BaTiO3), and propose that the presence of surface charge screening allows the formation of switchable domains.« less

  2. Interfacial dominated ferromagnetism in nanograined ZnO: a μSR and DFT study

    PubMed Central

    Tietze, Thomas; Audehm, Patrick; Chen, Yu–Chun; Schütz, Gisela; Straumal, Boris B.; Protasova, Svetlana G.; Mazilkin, Andrey A.; Straumal, Petr B.; Prokscha, Thomas; Luetkens, Hubertus; Salman, Zaher; Suter, Andreas; Baretzky, Brigitte; Fink, Karin; Wenzel, Wolfgang; Danilov, Denis; Goering, Eberhard

    2015-01-01

    Diamagnetic oxides can, under certain conditions, become ferromagnetic at room temperature and therefore are promising candidates for future material in spintronic devices. Contrary to early predictions, doping ZnO with uniformly distributed magnetic ions is not essential to obtain ferromagnetic samples. Instead, the nanostructure seems to play the key role, as room temperature ferromagnetism was also found in nanograined, undoped ZnO. However, the origin of room temperature ferromagnetism in primarily non–magnetic oxides like ZnO is still unexplained and a controversial subject within the scientific community. Using low energy muon spin relaxation in combination with SQUID and TEM techniques, we demonstrate that the magnetic volume fraction is strongly related to the sample volume fraction occupied by grain boundaries. With molecular dynamics and density functional theory we find ferromagnetic coupled electron states in ZnO grain boundaries. Our results provide evidence and a microscopic model for room temperature ferromagnetism in oxides. PMID:25747456

  3. Interfacial dominated ferromagnetism in nanograined ZnO: a μSR and DFT study.

    PubMed

    Tietze, Thomas; Audehm, Patrick; Chen, Yu-Chun; Schütz, Gisela; Straumal, Boris B; Protasova, Svetlana G; Mazilkin, Andrey A; Straumal, Petr B; Prokscha, Thomas; Luetkens, Hubertus; Salman, Zaher; Suter, Andreas; Baretzky, Brigitte; Fink, Karin; Wenzel, Wolfgang; Danilov, Denis; Goering, Eberhard

    2015-01-01

    Diamagnetic oxides can, under certain conditions, become ferromagnetic at room temperature and therefore are promising candidates for future material in spintronic devices. Contrary to early predictions, doping ZnO with uniformly distributed magnetic ions is not essential to obtain ferromagnetic samples. Instead, the nanostructure seems to play the key role, as room temperature ferromagnetism was also found in nanograined, undoped ZnO. However, the origin of room temperature ferromagnetism in primarily non-magnetic oxides like ZnO is still unexplained and a controversial subject within the scientific community. Using low energy muon spin relaxation in combination with SQUID and TEM techniques, we demonstrate that the magnetic volume fraction is strongly related to the sample volume fraction occupied by grain boundaries. With molecular dynamics and density functional theory we find ferromagnetic coupled electron states in ZnO grain boundaries. Our results provide evidence and a microscopic model for room temperature ferromagnetism in oxides. PMID:25747456

  4. Interfacial dominated ferromagnetism in nanograined ZnO: a μSR and DFT study

    NASA Astrophysics Data System (ADS)

    Tietze, Thomas; Audehm, Patrick; Chen, Yu–Chun; Schütz, Gisela; Straumal, Boris B.; Protasova, Svetlana G.; Mazilkin, Andrey A.; Straumal, Petr B.; Prokscha, Thomas; Luetkens, Hubertus; Salman, Zaher; Suter, Andreas; Baretzky, Brigitte; Fink, Karin; Wenzel, Wolfgang; Danilov, Denis; Goering, Eberhard

    2015-03-01

    Diamagnetic oxides can, under certain conditions, become ferromagnetic at room temperature and therefore are promising candidates for future material in spintronic devices. Contrary to early predictions, doping ZnO with uniformly distributed magnetic ions is not essential to obtain ferromagnetic samples. Instead, the nanostructure seems to play the key role, as room temperature ferromagnetism was also found in nanograined, undoped ZnO. However, the origin of room temperature ferromagnetism in primarily non-magnetic oxides like ZnO is still unexplained and a controversial subject within the scientific community. Using low energy muon spin relaxation in combination with SQUID and TEM techniques, we demonstrate that the magnetic volume fraction is strongly related to the sample volume fraction occupied by grain boundaries. With molecular dynamics and density functional theory we find ferromagnetic coupled electron states in ZnO grain boundaries. Our results provide evidence and a microscopic model for room temperature ferromagnetism in oxides.

  5. Enhanced luminescence properties in (Sr{sub 1−x}Ba{sub x}){sub 2.97}SiO{sub 3}N{sub 4/3}:0.03Eu{sup 2+} oxynitride phosphor

    SciTech Connect

    He, Xia; Qiu, Kehui; Lu, Xueguang; Zhao, Kun; Jiang, Zixu

    2014-12-15

    An oxynitride phosphor (Sr{sub 1−x}Ba{sub x}){sub 2.97}SiO{sub 3}N{sub 4/3}:0.03Eu{sup 2+} (SBSON) was synthesized by the solid-state reaction at 1550 °C for 4 h. XRD results show that the major phase of the synthesized phosphors is isostructural with Sr{sub 3}SiO{sub 5} when the content of Ba{sup 2+} is not greater than 0.5. Through the doping of Ba{sup 2+} ions, the particle morphology, luminescence intensities and thermal stability are all improved obviously. When the x equals 0.5 the luminescence intensity reaches maximum which is about 1.48 times as that of the phosphor free of Ba{sup 2+}. The emission peaks can be tuned from 583 nm to 601 nm by adjusting Ba{sup 2+} content. The doping of Ba{sup 2+} can also prolong the average lifetime from 1482 to 2122 ns. With high emission intensity and thermal stability, this novel oxynitride phosphor SBSON shows potential application in white LEDs. - Graphical abstract: Through the change of micro-structure by doping Ba{sup 2+} ions proved by the XRD patterns, (Sr{sub 1−x}Ba{sub x}){sub 2.97}SiO{sub 3}N{sub 4/3}:0.03Eu{sup 2+}phosphor eventually achieves the extension of lifetime and the improvement of luminescence properties and thermal stability. - Highlights: • (Sr{sub 1−x}Ba{sub x}){sub 2.97}SiO{sub 3}N{sub 4/3}:0.03Eu phosphors were prepared by the solid-state reaction. • The synthesized phosphor (x≤0.5) is isostructural with Sr{sub 3}SiO{sub 5}. • The emission peaks red shift to 601 nm then slightly blue shift by adding Ba{sup 2+}. • The emission intensity and thermal stability are both enhanced. • Fluorescent lifetime can be prolonged by doping Ba{sup 2+}.

  6. New insulating antiferromagnetic quaternary iridates MLa10Ir4O24 (M=Sr, Ba)

    SciTech Connect

    Zhao, Qingbiao; Han, Fei; Stoumpos, Constantinos C.; Han, Tian -Heng; Li, Hao; Mitchell, J. F.

    2015-07-01

    Recently, oxides of Ir4+ have received renewed attention in the condensed matter physics community, as it has been reported that certain iridates have a strongly spin-orbital coupled (SOC) electronic state, Jeff = ½, that defines the electronic and magnetic properties. The canonical example is the Ruddlesden-Popper compound Sr2IrO4, which has been suggested as a potential route to a new class of high temperature superconductor due to the formal analogy between Jeff = ½ and the S = ½ state of the cuprate superconductors. The quest for other iridium oxides that present tests of the underlying SOC physics is underway. In this spirit, here we report the synthesis and physical properties of two new quaternary tetravalent iridates, MLa10Ir4O24 (M = Sr, Ba). The crystal structure of both compounds features isolated IrO6 octahedra in which the electronic configuration of Ir is d5. As a result, both compounds order antiferromagnetically despite the lack of obvious superexchange pathways, and resistivity measurement shows that SrLa10Ir4O24 is an insulator.

  7. A promising novel orange-red emitting SrZnV2O7:Sm3+ nanophosphor for phosphor-converted white LEDs with near-ultraviolet excitation

    NASA Astrophysics Data System (ADS)

    Dalal, Mandeep; Taxak, V. B.; Chahar, Sangeeta; Khatkar, Avni; Khatkar, S. P.

    2016-02-01

    A novel trivalent samarium doped SrZnV2O7 nanophosphors was developed via urea assisted solution combustion method using metal nitrates as initial raw materials. The qualitative and quantitative phase analysis was carried out using Rietveld refinement technique. It was found to crystallize in monoclinic lattice with the P121/n1 (14) space group. The photoluminescent spectral study of SrZnV2O7:Sm3+ revealed that the excitation of 405 nm yields the characteristic emission peaks at 569, 599, 640 and 702 nm due to 4G5/2→6H5/2, 4G5/2→6H7/2, 4G5/2→6H9/2 and 4G5/2→6H11/2 respectively. The optimum concentration of Sm3+ ion in SrZnV2O7 for best luminescence was found to be 2 mol%. The luminescence intensity was further enhanced by incorporating compensator charge R+ (R=Li, Na, and K) into the SrZnV2O7:0.02Sm3+ nanophosphor. The critical distance for non-radiative energy transfer was calculated to be 26.64 Å. Dipole-dipole (d-d) interactions were ascribed as the major factor responsible for concentration quenching arising from the over-doping of the activator ions. The results indicate that these nanophosphors are suitable candidate for PC-WLEDs using near UV excitation.

  8. Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba_{3}ZnIr_{2}O_{9}.

    PubMed

    Nag, Abhishek; Middey, S; Bhowal, Sayantika; Panda, S K; Mathieu, Roland; Orain, J C; Bert, F; Mendels, P; Freeman, P G; Mansson, M; Ronnow, H M; Telling, M; Biswas, P K; Sheptyakov, D; Kaushik, S D; Siruguri, Vasudeva; Meneghini, Carlo; Sarma, D D; Dasgupta, Indra; Ray, Sugata

    2016-03-01

    We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba_{3}ZnIr_{2}O_{9} is a realization of a novel spin-orbital liquid state. Our results reveal that Ba_{3}ZnIr_{2}O_{9} with Ir^{5+} (5d^{4}) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J=0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir_{2}O_{9} dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK. PMID:26991199

  9. 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.

  10. Ultrafast dynamics of the dielectric functions of ZnO and BaTiO{sub 3} thin films after intense femtosecond laser excitation

    SciTech Connect

    Acharya, S.; Seifert, G.; Chouthe, S.; Graener, H.; Böntgen, T.; Sturm, C.; Schmidt-Grund, R.; Grundmann, M.

    2014-02-07

    The ultrafast carrier dynamics of epitaxial ZnO and BaTiO{sub 3} thin films after intense excitation at 3.10 eV and 4.66 eV photon energy has been studied by femtosecond absorption spectroscopy. Modelling the transient transmission changes on the basis of spectroscopic ellipsometry data and pertinent equilibrium model dielectric functions extended by additional terms for the effects at high carrier density (P-band luminescence and stimulated emission from electron-hole-plasma), a self-consistent parameterized description was obtained for both materials. Excited carrier lifetimes in the range of ≈2 to ≈60 ps and long-lived thermal effects after several hundred ps have been identified in both materials. These findings form a reliable basis to quantitatively describe future femtosecond studies on ZnO/BaTiO{sub 3} heterolayer systems.

  11. Origin of the Spin-Orbital Liquid State in a Nearly J =0 Iridate Ba3ZnIr2O9

    NASA Astrophysics Data System (ADS)

    Nag, Abhishek; Middey, S.; Bhowal, Sayantika; Panda, S. K.; Mathieu, Roland; Orain, J. C.; Bert, F.; Mendels, P.; Freeman, P. G.; Mansson, M.; Ronnow, H. M.; Telling, M.; Biswas, P. K.; Sheptyakov, D.; Kaushik, S. D.; Siruguri, Vasudeva; Meneghini, Carlo; Sarma, D. D.; Dasgupta, Indra; Ray, Sugata

    2016-03-01

    We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5 + (5 d4) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J =0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK.

  12. Formation and structural characterization of 1:1 ordered perovskites in the Ba(Zn{sub 1/3}Ta{sub 2/3})O{sub 3}-BaZrO{sub 3} system

    SciTech Connect

    Chai, L.; Davies, P.K.

    1997-12-01

    The phase stabilities in the (1{minus}x)Ba(Zn{sub 1/3}Ta{sub 2/3})O{sub 3} (BZT)-xBaZrO{sub 3} (BZ) system have been investigated using samples prepared by the mixed-oxide method. The substitution of Zr{sup 4+} destabilizes the 1:2 cation ordering in BZT and promotes the formation of a cubic, 1:1 ordered structure with a doubled perovskite repeat. The homogeneity range of the 1:1 phase extends from x = 0.04 to approximately x = 0.25; substitutions beyond this range stabilize a disordered perovskite. The limits of stability of the 1:1 ordering coincide with compositions previously found to exhibit anomalies in their dielectric loss. The range of homogeneity is consistent with a random layer model for the 1:1 ordered Ba{l_brace}{beta}{prime}{sub 1/2}{beta}{double_prime}{sub 1/2}{r_brace}O{sub 3} structure. In this model the {beta}{double_prime} positions are assumed to be occupied exclusively by Ta{sup 5+}, and the {beta}{prime} sites by a random distribution of Zn{sup 2+}, Zr{sup 4+}, and the remaining Ta{sup 5+} cations. The validity of the model, where the ordered solid solutions can be represented by Ba{l_brace}[Zn{sub (2{minus}y)/3}Ta{sub (1{minus}2y)/3}Zr{sub y}]{sub 1/2}[Ta]{sub 1/2}{r_brace}O{sub 3} (y = 2x) was confirmed by Rietveld refinements conducted using data collected with a synchrotron X-ray source.

  13. Preparation and magnetic properties of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Huang, Ying; Wang, Qiufen

    2012-09-01

    Nanocomposite of hard (BaFe12O19)/soft ferrite (Ni0.8Zn0.2Fe2O4) have been prepared by the sol-gel process. The nanocomposite ferrite are formed when the calcining temperature is above 800 °C. It is found that the magnetic properties strongly depend on the presintering treatment and calcining temperature. The “bee waist” type hysteresis loops for samples disappear when the presintering temperature is 400 °C and the calcination temperature reaches 1100 °C owing to the exchange-coupling interaction. The remanence of BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite with the mass ratio of 5:1 is higher than a single phase ferrite. The specific saturation magnetization, remanence magnetization and coercivity are 63 emu/g, 36 emu/g and 2750 G, respectively. The exchange-coupling interaction in the BaFe12O19/Ni0.8Zn0.2Fe2O4 nanocomposite ferrite is discussed.

  14. Co-existence of diamagnetism and ferromagnetism and possible superconductivity in Y{sub 8}Ba{sub 5}Zn{sub 4}O{sub 21}

    SciTech Connect

    Topal, Ugur

    2011-02-15

    In the present study, we investigate structural and magnetic properties of the Y{sub 8}Ba{sub 5}Zn{sub 4}O{sub 21} structure, which was recently included in the catalog of the International Centre for Diffraction Data (ICDD) as a prototype structure. It was found that the Y{sub 8}Ba{sub 5}Zn{sub 4}O{sub 21} bulk sample seems to be electrically insulating at temperatures of liquid nitrogen and the room temperature. On the other hand, it has quite interesting magnetic properties. Diamagnetic phase transition was observed at {approx} 90 K, which resembles that of the superconducting materials. The studied composition repels permanent magnets at the liquid nitrogen temperature. Ferromagnetism also co-exists with diamagnetism in the temperature range between 50 K and 90 K. Possible reasons for these behaviors are discussed. - Research Highlights: {yields}Y{sub 8}Ba{sub 5}Zn{sub 4}O{sub 21} possesses both ferromagnetic and diamagnetic properties. {yields}A superconducting-like diamagnetic transition takes place at {approx} 90 K. {yields}Ferromagnetism and diamagnetism coexist between temperatures of 50 K and 90 K. {yields}At 10 K, only ferromagnetism exists and no traces of diamagnetism are detected. {yields}The studied samples repel permanent magnets in liquid nitrogen.

  15. Superconductivity in Zn-doped tetragonal LaBaCaCu{sub 3}O{sub 7{minus}{delta}} systems

    SciTech Connect

    Singh, R.; Lal, R.; Upreti, U.C.; Suri, D.K.; Narlikar, A.V.; Awana, V.P.; Albino Aguiar, J.; Shahabuddin, M.

    1997-01-01

    Resistivity and ac susceptibility of Zn-doped samples of the LaBaCaCu{sub 3}O{sub 7{minus}{delta}} (LBCCO) system have been measured for Zn content of 0.5{percent}, 1.0{percent}, 1.5{percent}, 2.0{percent}, 2.5{percent}, and 3.0{percent} at.wt. X-ray diffraction has been used to find the lattice parameters of the samples. The samples remain tetragonal for all the considered concentrations of Zn. Idometry and thermogravimetric analyses have been done to estimate the oxygen content of different samples. Analyzing the resistivity and ac susceptibility data, the following conclusions are drawn about the role of Zn in the LBCCO samples. (1) The conduction mechanism of electrons appears to follow a crossover from the purely metallic regime to the localization regime due to either weak localization or electron-electron interaction effects after about 1.5{percent} Zn. (2) The superconducting transition as revealed by the resistivity vs temperature curves or susceptibility vs temperature curves becomes sharper with Zn increasing content of Zn up to 1.0{percent}. After 1.5{percent} the resistive and ac susceptibility transitions become broader with increasing Zn. (3) T{sub c} depression up to Zn content of 1.0{percent} seems due to direct suppression of the effective pairing interaction, while at and above 2.5{percent} Zn T{sub c} depression is expected to be due to disorder effects such as reduction of density of states at the Fermi energy. {copyright} {ital 1997} {ital The American Physical Society}

  16. Line patterning of (Sr,Ba)Nb{sub 2}O{sub 6} crystals in borate glasses by transition metal atom heat processing

    SciTech Connect

    Sato, M.; Honma, T.; Benino, Y.; Komatsu, T.

    2007-09-15

    Some NiO-doped Bi{sub 2}O{sub 3},La{sub 2}O{sub 3}-SrO-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} glasses giving the formation of strontium barium niobate Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN) crystals with a tetragonal tungsten-bronze structure through conventional crystallization in an electric furnace have been developed, and SBN crystal lines have been patterned on the glass surface by heat-assisted (250-300 deg. C) laser irradiation and scanning of continuous-wave Nd:YAG laser (wavelength: 1064 nm). The surface morphology and the quality of SBN crystal lines are examined from measurements of confocal scanning laser micrographs and polarized micro-Raman scattering spectra. The surface morphology of SBN crystal lines changes from periodic bump structures to homogeneous structures, depending on laser scanning conditions. It is suggested that the line patterned at the laser irradiation condition of laser power P=1 W and of laser scanning speed S=1 {mu}m/s in 2NiO-4La{sub 2}O{sub 3}-16SrO-16BaO-32Nb{sub 2}O{sub 5}-30B{sub 2}O{sub 3} glass has a possibility of the orientation of SBN crystals along the laser scanning direction. The present study demonstrates that the transition metal atom heat processing (i.e., a combination of cw Nd:YAG laser and Ni{sup 2+} ions) is a novel technique for spatially selected crystallization of SBN crystals in glass. - Graphical abstract: This figure shows the polarization optical (a) and confocal scanning laser (b) micrographs for the sample obtained by heat-assisted (300 deg. C) Nd:YAG laser irradiation with a laser power of P=1 W and laser scanning speed of S=1 {mu}m/s in Glass C. The figure demonstrates that the transition metal atom heat processing (i.e., a combination of cw Nd:YAG laser and Ni{sup 2+} ions) is a novel technique for spatially selected crystallization of SBN crystals in glass.

  17. 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.

  18. Experimental study of REE, Ba, Sr, Mo and W partitioning between carbonatitic melt and aqueous fluid with implications for rare metal mineralization

    NASA Astrophysics Data System (ADS)

    Song, WenLei; Xu, Cheng; Veksler, Ilya V.; Kynicky, Jindrich

    2016-01-01

    Carbonatites host some unique ore deposits, especially rare earth elements (REE). Hydrothermal fluids have been proposed to play a significant role in the concentration and transport of REE and other rare metals in carbonatites, but experimental constraints on fluid-melt equilibria in carbonatitic systems are sparse. Here we present an experimental study of trace element (REE, Ba, Sr, Mo and W) partitioning between hydrous fluids and carbonatitic melts, bearing on potential hydrothermal activity associated with carbonatite ore-forming systems. The experiments were performed on mixtures of synthetic carbonate melts and aqueous fluids at 700-800 °C and 100-200 MPa using rapid-quench cold-seal pressure vessels and double-capsule assemblages with diamond traps for analyzing fluid precipitates in the outer capsule. Starting mixtures were composed of Ca, Mg and Na carbonates spiked with trace elements. Small amounts of F or Cl were added to some of the mixtures to study the effects of halogens on the element distribution. The results show that REE, Ba, Sr, Mo and W all preferentially partition into carbonatite melt and have fluid-melt distribution coefficients ( D f/m) below unity. The REE partitioning is slightly dependent on the major element (Ca, Mg and Na) composition of the starting mixtures, and it is influenced by temperature, pressure, and the presence of halogens. The fluid-melt D values of individual REE vary from 0.02 to 0.15 with D_{Lu}^{f} / {fm}{m} being larger than D_{La}^{f} / {fm}{m} by a factor of 1.1-2. The halogens F and Cl have strong and opposite effects on the REE partitioning. Fluid-melt D REE are about three times higher in F-bearing compositions and ten times lower in Cl-bearing compositions than in halogen-free systems. D_{W}^{f} / {fm}{m} and D_{Mo}^{f} / {fm}{m} are the highest among the studied elements and vary between 0.6 and 0.7; D_{Ba}^{f} / {fm}{m} is between 0.05 and 0.09, whereas D_{Sr}^{f} / {fm}{m} is at about 0.01-0.02. The

  19. Up-converted ultraviolet luminescence of Er3+:BaGd2ZnO5 phosphors for healthy illumination

    NASA Astrophysics Data System (ADS)

    Zhang, Ya; Cui, Qingzhi; Wang, Zhanyong; Liu, Gan; Tian, Tian; Xu, Jiayue

    2016-09-01

    Moderate level of exposure to the solar irradiation containing UV component is essential for health care. To incorporate the UV-emitting phosphors into the commercial YAG-based white light-emitting diode introduces the possibilities of healthy illumination to individuals' daily lives. 1 mol.% Er3+-doped BaGd2ZnO5 (BGZ) particles were synthesized via sol-gel method and efficient up-converted luminescence peaked at 380 nm was detected under 480 nm excitation. The mixed phosphors with varied mass ratio of Er3+:BGZ and Ce3+:YAG particles were encapsulated to form LEDs. The study of the LEDs indicated that the introduction of BGZ component favored the enhancement of color-rendering index and the neutralization of the white light emitting. The WLED with the BGZ/YAG ratio of 8:2 was recommendable for its excellent overall white light luminous performances and UV intensity of 84.55 mW/cm2. The UV illumination dose of the WLEDs with mixed YAG and BGZ was controllable by adjusting the ratio, the illumination distance and the illumination time. Er3+:BGZ phosphors are promising UVemitting phosphors for healthy indoor illumination.

  20. Study of barrier layer capacitance effect in lead free Ba0.95Sr0.05(Fe0.5Nb0.5)O3-BaZr0.1Ti0.9O3 ceramics

    NASA Astrophysics Data System (ADS)

    Kumar Patel, Piyush; Yadav, K. L.

    2014-11-01

    Lead-free Ba0.95Sr0.05(Fe0.5Nb0.5)O3-BaZr0.1Ti0.9O3 (50/50) ceramic, a material with potential applications for energy storage, are investigated. X-ray diffraction patterns show a single phase perovskite structure in all the samples. Sintering temperature affects the microstructural and dielectric properties of the ceramics. Microstructural analysis showed the uniformly distributed and highly packed grains in all the samples. We obtained high dielectric constant with low dielectric loss due to the controlled sintering. Giant dielectric constant (~19496) with low dielectric loss (~0.32) was obtained for 1250 °C sintered sample at room temperature and 1 kHz frequency. Complex impedance analysis confirms that the grain boundary effect (barrier layer formation) is responsible for such a high value of dielectric constant. Another interesting feature of this ceramic is the appearance of room temperature magnetodielectric response (1.9%, 8 kOe) at 100 Hz frequency.

  1. Fluorescence and phosphorescence properties of the low temperature forms of the MAl{sub 2}Si{sub 2}O{sub 8}:Eu{sup 2+} (M=Ca, Sr, Ba) compounds

    SciTech Connect

    Clabau, Frederic; Garcia, Alain; Bonville, Pierre; Gonbeau, Danielle; Le Mercier, Thierry; Deniard, Philippe; Jobic, Stephane

    2008-06-15

    The fluorescence and phosphorescence properties of Europium-doped MAl{sub 2}Si{sub 2}O{sub 8} (M=Ca, Sr, Ba) are reinvestigated and discussed on the basis of the propensity of an activator to agglomerate with an oxygen vacancy. Due to a stronger attraction of the anion vacancy towards Eu{sup 2+} cations going from BaAl{sub 2}Si{sub 2}O{sub 8} to SrAl{sub 2}Si{sub 2}O{sub 8} and CaAl{sub 2}Si{sub 2}O{sub 8} host lattices, the interpretation of the fluorescence spectra turns out to be less trivial in the Ca and Sr host lattices than in the Ba one and requests the account for Eu{sup 2+} cations lying at alkaline-earth sites with or without vacancy in their neighborhood. Phosphorescence in these compounds is highlighted. - Graphical abstract: The Eu{sup 2+}-doped MAl{sub 2}Si{sub 2}O{sub 8} (M=Ca, Sr, and Ba) aluminosilicates exhibit a bluish white luminescence, which can last several minutes after the removal of the excitation. The account for Eu{sup 2+} cations coupled with defects is required to explain fluorescence spectra.

  2. BaZn{sub 2}Si{sub 2}O{sub 7} and the solid solution series BaZn{sub 2−x}Co{sub x}Si{sub 2}O{sub 7} (0

    SciTech Connect

    Kerstan, Marita; Thieme, Christian; Grosch, Matthias; Müller, Matthias; Rüssel, Christian

    2013-11-15

    For sealing of solid oxide fuel cells, glasses from which crystalline phases with high coefficient of thermal expansion (CTE) can be crystallized are required. In this paper, a new solid solution series BaZn{sub 2−x}Co{sub x}Si{sub 2}O{sub 7} (0BaZn{sub 2}Si{sub 2}O{sub 7}). Sintered specimens were characterized by dilatometry. The introduction of Co{sup 2+} does not lead to a change in the space group. All compounds show a transition of a low to a high temperature modification. The attributed temperature increases from 300 °C for BaZn{sub 2}Si{sub 2}O{sub 7} to 850 °C for BaCo{sub 2}Si{sub 2}O{sub 7}. The volume expansion which runs parallel to the phase transition decreases with increasing cobalt concentration. The phase BaZn{sub 2}Si{sub 2}O{sub 7} shows the largest CTE and a steep volume effect during phase transition. For the compound BaZn{sub 0.25}Co{sub 1.75}Si{sub 2}O{sub 7} the CTE is minimum (8.6×10{sup −6} K{sup −1} (50–900 °C)) and increases again until for the compound BaCo{sub 2}Si{sub 2}O{sub 7} a CTE of 16.6×10{sup −6} K{sup −1} (50–900 °C) is reached. In the cobalt rich composition range, the CTEs are in the right range for high temperature fuel cells and can be adjusted by the composition. - Graphical abstract: The composition of the solid solution BaZn{sub 2−x}Co{sub x}Si{sub 2}O{sub 7} strongly affects the thermal expansion. Display Omitted - Highlights: • We examined the thermal expansion of solid solutions BaZn{sub 2−x}Co{sub x}Si{sub 2}O{sub 7} (0BaZn{sub 2}Si{sub 2}O{sub 7} exhibits the highest thermal expansion due to a phase transition. • Substitution of small amounts of Zn{sup 2+} against Co{sup 2+} lead to decreasing thermal expansion. • The thermal expansions re-increased with further increasing Co{sup 2+} concentrations. • Seals based on

  3. Dipole spring ferroelectrics in superlattice SrTiO3/BaTiO3 thin films exhibiting constricted hysteresis loops

    SciTech Connect

    Wu, Pingping; Ma, Xingqiao; Li, Yulan; Gopalan, Venkatraman; Chen , L.Q.

    2012-03-01

    Ferroelectric superlattice heterostructures have recently been explored for potential applications in electronic devices. In this letter we employed the phase-field approach to simulate the domain structure and switching of a (BaTiO3)8/(SrTiO3)3 superlattice film constrained by a GdScO3 substrate. A constricted ferroelectric hysteresis loop was observed with a high saturation polarization but a small coercive field. The shape of the hysteresis loop is understood by analyzing the ferroelectric polarization distributions during switching. It is demonstrated that the multilayers stack behave as dipole spring ferroelectric, named in analogy to exchange spring magnets in magnetic multilayers that show similar loops.

  4. Controllable-permittivity and high-tunability of Ba0.5Sr0.5TiO3/MgO based ceramics by composite configuration

    NASA Astrophysics Data System (ADS)

    Tang, Linjiang; Wang, Jinwen; Zhai, Jiwei; Bing Kong, Ling; Yao, Xi

    2013-04-01

    Ba0.5Sr0.5TiO3 (BST50)/MgO composites, with 2-2-type configurations, consisting of BST layers and MgO layers, were fabricated by using tape-casting and laminating technique. Microstructure, dielectric response, and tunable properties of the 2-2-type composites were investigated. An important feature of the 2-2 type composites is that DC fields can be effectively applied to the high-permittivity ferroelectric phase when the fields are applied in parallel direction to the inter-phase boundaries. As a result, with increasing volume fraction (q) of MgO, tunability of the composites remained almost unchanged, whereas their permittivity value could be reduced significantly. This behavior has not been observed in the conventional 3-0 type composites.

  5. Induced Ti magnetization at La0.7Sr0.3MnO3 and BaTiO3 interfaces

    DOE PAGESBeta

    Liu, Yaohua; Tornos, J.; te Velthuis, S. G. E.; Freeland, J. W.; Zhou, H.; Steadman, P.; Bencok, P.; Leon, C.; Santamaria, J.

    2016-04-01

    In artificial multiferroics hybrids consisting of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric BaTiO3 epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. Moreover, the Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. But, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

  6. Measurements of heat capacity associated with the magnetic transition in La_0.7A_0.3MnO3 (A = Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Jeong, Yoon Hee; Moon, I. K.; Ju, H. L.

    2001-03-01

    It is well known that the transition temperature of the paramagnetic insulator-magnetic metal transition in the perovskite manganites La_1-xA_xMnO3 (x = 0.3, A = divalent metal) depends sensitively on the average size of A-site cations. In order to elucidate the physical reason for this behavior, we have carried out high-resolution measurements of heat capacity of samples with A = Ca, Sr, Ba. By critically comparing these results as well as magnetization measurements, we were able to draw a conclusion: as the average size of the A-site cation gets smaller than a certain value, the two-phase coexistence sets in and the transition temperature abruptly decreases.

  7. Giant elastocaloric effect in ferroelectric Ba0.5Sr0.5TiO3 alloys from first-principles

    NASA Astrophysics Data System (ADS)

    Lisenkov, S.; Ponomareva, I.

    2012-09-01

    As the need for efficient energy converting devices has been rapidly increasing, the materials that exhibit large or even giant caloric responses have emerged as promising candidates for solid-state refrigeration, which is an energy-efficient and environmentally friendly alternative to the conventional refrigeration technology. However, despite recent ground breaking discoveries of giant caloric responses in some materials, they appear to remain one of nature's rarities. Here we predict the existence of giant elastocaloric effect in ferroelectric Ba0.5Sr0.5TiO3 alloys, which adds one more member to this exclusive collection. Moreover, this computational finding reveals the multicaloric nature of such alloys, which could lead to new paradigms for cooling devices.

  8. Improvement of critical current density in thallium-based (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) superconductors

    NASA Technical Reports Server (NTRS)

    Ren, Z. F.; Wang, C. A.; Wang, J. H.; Miller, D. J.; Goretta, K. C.

    1995-01-01

    Epitaxial (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) ((Tl,Bi)-1223) thin films on (100) single crystal LaAlO3 substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field cooled magnetization, and transport critical current density (J(sub c)) were measured. The zero-resistance temperature was 105-111 K. J(sub c) at 77 K and zero field was greater than 2 x 10(exp 6) A/sq cm. The films exhibited good flux pinning properties.

  9. Structural and dielectric properties of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} thin films grown by PLD

    SciTech Connect

    James, K. K.; Satish, B.; Jayaraj, M. K.

    2014-01-28

    Ferroelectric thin films of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} (BST) were deposited on Si/SiO{sub 2}/TiO{sub 2}/Pt (PtSi) substrate by pulsed laser deposition (PLD). Crystalline films with perovskite structure were obtained without post-deposition annealing. Phase purity of the deposited films was confirmed by x-ray diffraction. The lowest value of FWHM obtained for the film deposited at oxygen pressure 5.4×10{sup −4} mbar and substrate temperature 600°C, indicates the high crystallinity of the film. The room temperature dielectric constant at 100 kHz was 85. Butterfly loop, which is the characteristic of ferroelectric materials, was obtained in the regime of −4 to +4V. The leakage current density was nearly 9×10{sup −13} Acm{sup −2}.

  10. Real-time observation of pulse reshaping using Sr0.61Ba0.39Nb2O6 single crystal fiber in a microwave cavity

    NASA Astrophysics Data System (ADS)

    Huang, Chuanyong; Guo, Ruyan; Bhalla, Amar S.

    2005-03-01

    Ferroelectric single crystal fiber Sr0.61Ba0.39Nb2O6 (SBN) is evaluated for optical pulse engineering in terms of wavelength shifting and pulse compression/expansion through nonlinear optical (Pockels) effect at microwave frequencies. The microwave-photonic interaction was investigated experimentally in a TE103 microwave cavity at 10GHz. It is shown that the frequency component of an optical pulse can be controlled effectively using the SBN single crystal in a microwave cavity without the need of contact electrodes or any interruption to the optical system. The technique may be utilized in several aspects of optical communications such as channel definition and security encoding of the signal, and shows potential for a range of optoelectronic applications.

  11. Formation of nanodomain ensembles during polarization reversal in Sr0.61Ba0.39Nb2O6: Ce single crystals

    NASA Astrophysics Data System (ADS)

    Shur, V. Ya.; Shikhova, V. A.; Pelegov, D. V.; Ievlev, A. V.; Ivleva, L. I.

    2011-11-01

    The results of the study of nano- and microdomain structure evolution in single crystals of relaxor ferroelectric strontium barium niobate Sr0.61Ba0.39Nb2O6 doped by cerium are presented. It was shown that the initial nanodomain structure represents a self-similar three-dimensional maze. The fractal dimension and average period were revealed. It was demonstrated that application of series of alternating electric field pulses makes it possible to produce a single-domain state in the surface layer. The features of the growth and "merging," as well as the shape of ensembles of isolated nanodomains formed during switching from the single-domain state, were investigated. The formation of the nanodomain ensembles was considered as a result of the self-organized discrete switching controlled by determined nucleation.

  12. Surface functionalized Ba0.6Sr0.4TiO3 /poly(vinylidene fluoride) nanocomposites with significantly enhanced dielectric properties

    NASA Astrophysics Data System (ADS)

    Li, Kecheng; Wang, Hong; Xiang, Feng; Liu, Weihong; Yang, Haibo

    2009-11-01

    A nanocomposite was prepared by embedding Ba0.6Sr0.4TiO3 (BST)/silver core/shell nanoparticles (BST@Ag) into polyvinylidene-fluoride (PVDF). Through functionalizing the surface of BST nanoparticles by silver coating, the relative permittivity of composites was significantly increased to 153 at 100 Hz which is 73% higher than that of the composite making of untreated BST nanoparticals. The loss tangent was still low (less than 0.2) when the filler content of BST@Ag was 0.55. Increasing the conductivity of the interlayer between BST and PVDF by silver enhances the space charge polarization and forms a nanocapacitance network through the interparticle junctions connecting the electrodes of sample.

  13. One dimensional Ba x Sr1 - xEr y Fe12 - yO19 fibers with magnetic crystalline nanoparticles

    NASA Astrophysics Data System (ADS)

    Meng, Xianfeng; Mi, Jianli; Li, Qiang; Bortolini, Christian; Dong, Mingdong

    2014-09-01

    Hexagonal ferrites, also known as hexaferrites, are a very interesting class of materials with peculiar magnetic and electrical properties. Recently, several applications, both commercial and technological, have been developed by employing such materials, such as in magnetic recording and separation, storage devices, and catalysts. In particular, one dimensional magnetic nanostructured materials are very promising since they exhibit physical properties that cannot be found in the bulk. In this work, nanocrystalline Sr1 - xBa x Er y Fe12 - yO19 (x = y ⩽ 0.4) ferrite fibers are successfully fabricated by sol-gel spinning, followed by calcination. By varying the calcination temperature and content of substituted ions, different ferrite fibers have been obtained, which exhibit different magnetic properties and structural characteristics. Our capacity to effectively tune the magnetic properties of one dimensional hexagonal ferrite materials opens new scenarios towards the design and optimization of a multitude of devices that are based on the magnetic properties of hexaferrites.

  14. The features of structural transformations in lanthanum manganites La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba)

    SciTech Connect

    Sedykh, Vera D.

    2014-10-27

    In this work, the effect of the ionic radius and concentration of a doping element on the features of the structural transformations in polycrystalline lanthanum manganites, La{sub 1−x}A{sub x}MnO{sub 3+δ} (A = Ca, Sr, Ba), has been studied by Mössbauer spectroscopy and X-ray diffraction analysis. For Mössbauer investigations, a small amount of {sup 57}Fe (2 at%) Mössbauer isotope was introduced into the samples. It follows from the analysis of the obtained data that both common features of the structural transformations and differences between them exist in lanthanum manganites depending on ionic radius and concentration of a doping element.

  15. Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: early results for Gale crater from Bradbury Landing Site to Rocknest

    USGS Publications Warehouse

    Ollila, Ann M.; Newsom, Horton E.; Clark, Benton; Wiens, Roger C.; Cousin, Agnes; Blank, Jen G.; Mangold, Nicolas; Sautter, Violaine; Maurice, Sylvestre; Clegg, Samuel M.; Gasnault, Olivier; Forni, Olivier; Tokar, Robert; Lewin, Eric; Dyar, M. Darby; Lasue, Jeremie; Anderson, Ryan; McLennan, Scott M.; Bridges, John; Vaniman, Dave; Lanza, Nina; Fabre, Cecile; Melikechi, Noureddine; Perett, Glynis M.; Campbell, John L.; King, Penelope L.; Barraclough, Bruce; Delapp, Dorothea; Johnstone, Stephen; Meslin, Pierre-Yves; Rosen-Gooding, Anya; Williams, Josh

    2013-01-01

    The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.

  16. Annealing of RuO 2 and Ru Bottom Electrodes and Its Effects on the Electrical Properties of (Ba,Sr)TiO 3 Thin Films

    NASA Astrophysics Data System (ADS)

    Ahn, Joon-Hyung; Choi, Won-Youl; Lee, Won-Jae; Kim, Ho-Gi

    1998-01-01

    Crystalline structures and surface morphologies of annealed RuO2 and Ru thin films were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The annealing was performed in oxygen and argon ambient and high vacuum in the temperature range of 400 800° C. In oxygen ambient annealing, the surface morphology was drastically changed due to the evaporation of ruthenium dioxides in the form of RuO3 and RuO4. Annealed RuO2 thin film in vacuum was reduced to the Ru metal phase. The actual variation of RuO2 bottom electrodes during the deposition of (Ba,Sr)TiO3 (BST) thin films and the effects of the thermal stability of bottom electrodes on electrical properties of BST thin films deposited on RuO2/SiO2/Si were also investigated.

  17. Close correlation between magnetic properties and the soft phonon mode of the structural transition in BaFe2As2 and SrFe2As2

    DOE PAGESBeta

    Parshall, D.; Pintschovius, L.; Niedziela, Jennifer L.; Castellan, J. -P.; Lamago, D.; Mittal, R.; Wolf, Th.; Reznik, Dmitry

    2015-04-27

    Pmore » arent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of TA phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe2As2 and SrFe2As2. We found that acoustic phonons at small wave vectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuating magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Finally, our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.« less

  18. Application of on-wafer TRL calibration on the measurement of microwave properties of Ba0.5Sr0.5TiO3 thin films.

    PubMed

    Lue, H T; Tseng, T Y

    2001-11-01

    A series of Al/Ba0.5Sr0.5TiO3(BST)/sapphire multi-layered coplanar waveguide (CPW) transmission lines of different geometries and thin-film configurations was fabricated. We employed an accurate on-wafer Through-Line-Reflect (TRL) calibration technique and quasi-TEM analysis to measure the dielectric constant, loss tangent, and tunability of BST thin films using this CPW structure. Experimental results show that the overall insertion loss is less than 3 dB/cm even at frequencies as high as 20 GHz, which is the lowest obtained to date for metal/BST CPW devices. This result indicates that, with optimized impedance matching, normal conductors are also possibly suitable for fabricating low-loss tunable phase-shifter devices.

  19. 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 .

  20. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    PubMed

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology. PMID:26891039

  1. Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

    SciTech Connect

    Du, Peng; Yu, Jae Su

    2015-10-15

    Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patterns were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.

  2. Luminescent properties of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} and its luminescence improvement by incorporating A{sup +} (A=Li, Na, and K)

    SciTech Connect

    Li, Panlai Wang, Zhijun Yang, Zhiping; Guo, Qinglin

    2014-12-15

    A novel green phosphor SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is synthesized by a high temperature solid-state method, and its luminescent property is investigated. X-ray diffraction patterns of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} indicate a similarity crystalline phase to SrZn{sub 2}(PO{sub 4}){sub 2}. SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} shows green emission under 369 nm excitation, and the prominent luminescence in green (544 nm) due to {sup 5}D{sub 4}–{sup 7}F{sub 5} transition of Tb{sup 3+}. For the 544 nm emission, excitation spectrum has several excitation band from 200 nm to 400 nm. Emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is influenced by Tb{sup 3+} concentration, and concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is also observed. With incorporating A{sup +} (A=Li, Na, and K) as compensator charge, the emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can be obviously enhanced. CIE color coordinates of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} locate in the green region. The results indicate this phosphor may be a potential application in white LEDs. - Graphical abstract: SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation, and its luminescent properties can be improved by incorporating A{sup +} (A=Li, Na, and K). - Highlights: • SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation. • Concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is observed. • Emission intensities of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} are enhanced by codoped A{sup +} (A=Li, Na, K)

  3. Investigation of site preference of Zn doped Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} by Mössbauer spectroscopy

    SciTech Connect

    Lim, Jung Tae; Kim, Chul Sung

    2014-05-07

    The polycrystalline Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were prepared by using solid-state-reaction method. The crystal structures and magnetic properties of samples were investigated with x-ray diffractometer, vibrating sample magnetometer, and Mössbauer spectroscopy. The crystal structure of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples was determined to be a hexagonal structure with P6{sub 3}/mmc space group at 295 K, and the saturation magnetization (M{sub s}) of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were found to be M{sub s} = 50.9, 53.1, 55.0 emu/g, respectively. From the temperature dependence of magnetization curves under 100 Oe between 4.2 and 740 K, we were able to observe the spin transition, and both spin transition temperature (T{sub s}) and Curie temperature (T{sub C}) decrease with increasing Zn concentration. Mössbauer spectra of all samples were obtained and analyzed at various temperatures ranging from 4.2 to 295 K. With ten-sextets for Fe sites corresponding to the Z-type hexagonal crystallographic sites, all spectra below T{sub C} were fitted by least-square method. In addition, from the site occupation numbers of Fe, calculated from the relative areas fitted to the Mössbauer spectra, we find that Zn ions preferentially occupy the tetrahedral sublattices of down sites.

  4. High critical temperature superconductor substrate and buffer layer compounds, A2MeSbO6 (where A=Ba and Sr; and Me=Sc, In and Ga). Technical report, January-December 1995

    SciTech Connect

    Tauber, A.; Tidrow, S.C.; Finnegan, R.D.; Wilber, W.D.

    1996-05-01

    Compounds in the series A2MeSbO6, where A=Ba, Sr, and Me=Sc, In, and Ga, have been used as substrate buffer layers with YBa2Cu3O(7-x) thin films. These materials were prepared by solid-state reaction of the oxides and carbonates. The compounds are ordered perovskites except for Ba2InSbO6. All compounds are cubic except Sr2ScSbO6 and Sr2GaSbO6 which are pseudo-cubic, tetragonal. Dielectric constant and loss tangent are reported for each bulk compound. Herein is described the successful deposition of thin films A2MeSbO6 on (100) MgO and A2MeSbO6/(001) YBCO/(100) MgO by pulsed laser ablation.

  5. 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.

  6. Crystal structures of the four new quaternary copper(I)-selenides A0.5CuZrSe3 and ACuYSe3(A=Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Maier, Stefan; Prakash, Jai; Berthebaud, David; Perez, Olivier; Bobev, Svilen; Gascoin, Franck

    2016-10-01

    The four new quaternary copper(I)-selenides, Sr0.5CuZrSe3 (a=3.8386(7), b=14.197(2), c=10.1577(17) Å), Ba0.5CuZrSe3 (a=3.8386(7), b=14.196(2), c=10.1577(17) Å), SrCuYSe3 (a=10.620(2), b=4.1000(8), c=13.540(3) Å) and BaCuYSe3 (a=4.1800(7), b=13.940(2), c=10.6200(17) Å) were synthesized by high-temperature solid state reactions and their crystal structures were determined using single-crystal X-ray diffraction. A0.5CuZrSe3 (A= Sr, Ba) and BaCuYSe3 crystallize in the KCuZrS3 structure type (Cmcm), while SrCuYSe3 is isostructural to Eu2CuS3 (Pnma). All compounds form layered structures in which the charge of the - ∞ 2[CuZrSe3 and 2 - ∞ 2[CuYSe3 ] layers as well as the site occupancy of the A cations depend on the transition metal. Combining the alkaline earth metals Sr and Ba with tetravalent Zr leads to the formation of cation vacancies between the - ∞ 2[CuZrSe3 ] layers and structure type as well as symmetry are determined by the ratio between the cation and transition metal ionic radii r(A2+)/r(M3+/4+).

  7. 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.

  8. 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

  9. 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

  10. Interfacial charge-mediated non-volatile magnetoelectric coupling in Co0.3Fe0.7/Ba0.6Sr0.4TiO3/Nb:SrTiO3 multiferroic heterostructures

    DOE PAGESBeta

    Zhou, Ziyao; Howe, Brandon M.; Liu, Ming; Nan, Tianxiang; Chen, Xing; Mahalingam, Krishnamurthy; Sun, Nian X.; Brown, Gail J.

    2015-01-13

    The central challenge in realizing non-volatile, E-field manipulation of magnetism lies in finding an energy efficient means to switch between the distinct magnetic states in a stable and reversible manner. In this work, we demonstrate using electrical polarization-induced charge screening to change the ground state of magnetic ordering in order to non-volatilely tune magnetic properties in ultra-thin Co0.3Fe0.7/Ba0.6Sr0.4TiO3/Nb:SrTiO3 (001) multiferroic heterostructures. A robust, voltage-induced, non-volatile manipulation of out-of-plane magnetic anisotropy up to 40 Oe is demonstrated and confirmed by ferromagnetic resonance measurements. This discovery provides a framework for realizing charge-sensitive order parameter tuning in ultra-thin multiferroic heterostructures, demonstrating great potentialmore » for delivering compact, lightweight, reconfigurable, and energy-efficient electronic devices.« less

  11. Structural characterisation of BaTiO{sub 3} thin films deposited on SrRuO{sub 3}/YSZ buffered silicon substrates and silicon microcantilevers

    SciTech Connect

    Colder, H.; Jorel, C. Méchin, L.; Domengès, B.; Marie, P.; Boisserie, M.; Guillon, S.; Nicu, L.; Galdi, A.

    2014-02-07

    We report on the progress towards an all epitaxial oxide layer technology on silicon substrates for epitaxial piezoelectric microelectromechanical systems. (101)-oriented epitaxial tetragonal BaTiO{sub 3} (BTO) thin films were deposited at two different oxygen pressures, 5.10{sup −2} mbar and 5.10{sup −3} mbar, on SrRuO{sub 3}/Yttria-stabilized zirconia (YSZ) buffered silicon substrates by pulsed laser deposition. The YSZ layer full (001) orientation allowed the further growth of a fully (110)-oriented conductive SrRuO{sub 3} electrode as shown by X-ray diffraction. The tetragonal structure of the BTO films, which is a prerequisite for the piezoelectric effect, was identified by Raman spectroscopy. In the BTO film deposited at 5.10{sup −2} mbar strain was mostly localized inside the BTO grains whereas at 5.10{sup −3} mbar, it was localized at the grain boundaries. The BTO/SRO/YSZ layers were finally deposited on Si microcantilevers at an O{sub 2} pressure of 5.10{sup −3} mbar. The strain level was low enough to evaluate the BTO Young modulus. Transmission electron microscopy (TEM) was used to investigate the epitaxial quality of the layers and their epitaxial relationship on plain silicon wafers as well as on released microcantilevers, thanks to Focused-Ion-Beam TEM lamella preparation.

  12. The deposition of Sm1Ba2Cu3O7-δ on SrTiO3 using co-evaporation method

    NASA Astrophysics Data System (ADS)

    Kim, H. S.; Ha, H. S.; Kim, T. H.; Yang, J. S.; Ko, R. K.; Song, K. J.; Ha, D. W.; Lee, N. J.; Oh, S. S.; Youm, D. J.; Park, Chan

    2007-09-01

    The SmBCO(Sm 1Ba 2Cu 3O 7- δ) films were deposited on SrTiO 3 substrates using co-evaporation method. The deposition system was specially designed, that is named evaporation using drum in dual chambers, as the following features. The deposition system consists of reaction chamber and evaporation one. The role of reaction chamber is for the deposited materials to react with oxygen gas, and that of the evaporation chamber is to evaporate the composing elements of SmBCO, respectively. The composition ratio of SmBCO is controlled by the deposition rate of each element. The drum of 50 cm of diameter and 72 cm of length is located between the reaction chamber and the evaporation chamber. By rotating the drum, deposition and reaction process are repeated. In this system, SmBCO films were deposited on SrTiO 3 single crystal substrates. We obtained Ic and Jc results of 83.3 A/cm and 2.1 MA/cm 2 at 77 K in self-field.

  13. Structure and magnetic properties of three-dimensional (La,Sr)MnO{sub 3} nanofilms on ZnO nanorod arrays

    SciTech Connect

    Gao Haiyong; Gao Puxian; Shimpi, Paresh; Guo Yanbing; Cai Wenjie; Lin Huijan; Staruch, M.; Jain, Menka

    2011-03-21

    Three-dimensional (3D) cubic perovskite (La,Sr)MnO{sub 3} (LSMO) nanofilms have been deposited on ZnO nanorod arrays with controlled dimensionality and crystallinity by radio frequency (rf) magnetron sputtering and post thermal annealing. Compared to the two-dimensional (2D) LSMO nanofilm on flat Si, the structure and magnetic properties of 3D LSMO nanofilms on ZnO nanorod arrays have a strong anisotropic morphology and thickness dependence. Ferromagnetic property has been observed in both 2D and 3D LSMO nanofilms while a ferromagnetic-superparamagnetic transition was revaled in 3D LSMO nanofilms on ZnO nanorod array with decreasing nanofilm thickness, due to a large surface dispersion effect. The LSMO/ZnO nanofilm/nanorod structures could open up new avenues for intriguing magnetic properties studies and applications of nanoscale perovskites.

  14. Current injection emission from a transparent p-n junction composed of p-SrCu2O2/n-ZnO

    NASA Astrophysics Data System (ADS)

    Ohta, Hiromichi; Kawamura, Ken-ichi; Orita, Masahiro; Hirano, Masahiro; Sarukura, Nobuhiko; Hosono, Hideo

    2000-07-01

    An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p-n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron-hole plasma of ZnO.

  15. The crystal structure and magnetic properties of Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22}

    SciTech Connect

    Cho, Kwang Lae; Rhee, Chan Hyuk; Kim, Chul Sung

    2014-05-07

    We have synthesized the Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22} samples (x = 0.1, 0.2, 0.3, 0.4, 0.5) by the solid-state reaction method and investigated their crystalline and magnetic properties by X-ray diffractometer (XRD), Mössbauer spectrometer, vibrating sample magnetometer, and network analyzer. XRD patterns show that all samples are rhombohedral with space group R-3m. The lattice constants a{sub 0} and c{sub 0} decrease with Sr substitution due to smaller ion radius of Sr{sup 2+} (1.27 Å) than that of Ba{sup 2+} (1.43 Å). The Mössbauer spectroscopy measurements show that the relative area ratios of Fe ion were maintained constant regardless of the Sr concentration. However, average magnetic hyperfine field slightly increased with the Sr concentration. This observation agrees with the fact that the saturation magnetization (M{sub s}) linearly increases due to the increasing super-exchange interaction, originated from the difference in the ionic radius between Ba{sup 2+} and Sr{sup 2+}. To investigate its properties at high frequency range, all samples were sintered at 1100 °C, and complex permeability and permittivity were measured by network analyzer between 100 MHz and 4 GHz. For x below 0.3, the initial permeability at 100 MHz increases, at higher values of x, its value decreases. Our study shows that magnetic properties of Sr{sup 2+} substitution for Ba{sup 2+} in Y-type hexaferrite as well as low magnetic loss less than 0.1 in 1 GHz band, indicating the potential application of Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22} samples for RF and antenna devices in ultra high frequency band.

  16. Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) with remarkably enhanced upconversion luminescence.

    PubMed

    Su, Yue; Liu, Xiuling; Lei, Pengpeng; Xu, Xia; Dong, Lile; Guo, Xianmin; Yan, Xingxu; Wang, Peng; Song, Shuyan; Feng, Jing; Zhang, Hongjie

    2016-07-01

    Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) have been successfully fabricated via the thermal decomposition method. Upconversion nanoparticles (UCNPs) were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), upconversion luminescence (UCL) spectroscopy, etc. Under 980 nm excitation, the emission intensities of the UCNPs are remarkably enhanced after coating the MF2 (M = Ca, Sr, and Ba) shell. Among these samples, CaF2 coated UCNPs show the strongest overall emission, while BaF2 coated UCNPs exhibit the longest lifetime. These results demonstrate that alkaline earth metal fluorides are ideal materials to improve the UCL properties. Meanwhile, although the lattice mismatch between the ternary NaREF4 core and the binary MF2 (M = Sr and Ba) shell is relatively large, the successfully synthesized NaLuF4:Yb/Er@NaLuF4:Yb@MF2 indicates a new outlook on the fabrication of heterostructural core-shell UCNPs. PMID:27327414

  17. On the photo-luminescence properties of sol–gel derived undoped and Dy{sup 3+} ion doped nanocrystalline Scheelite type AMoO{sub 4} (A = Ca, Sr and Ba)

    SciTech Connect

    Jena, Paramananda; Gupta, Santosh K.; Natarajan, V.; Padmaraj, O.; Satyanarayana, N.; Venkateswarlu, M.

    2015-04-15

    Nanocrystalline Scheelite type Dy doped AMoO{sub 4} [where A = Ba, Sr and Ca] samples were prepared by acrylamide assisted sol–gel process and characterized by XRD, FT-Raman, FTIR, SEM and photoluminescence (PL). PL of undoped sample shows blue/green emission in CaMoO{sub 4} and SrMoO{sub 4} but multicolour visible emission leading to near white light in BaMoO{sub 4} nanoparticles; the origin of which is explained. It was observed that on doping 0.5 mol% of Dy{sup 3+} in molybdate samples complete energy transfer takes place in case of SrMoO{sub 4} and BaMoO{sub 4}, but host contributed substantially in Dy doped BaMoO{sub 4} sample, resulting in biexponential decay. It was also observed that symmetry around Dy{sup 3+} decreases as the size of alkaline earth ion increases. Due to combined blue, yellow and red colour emission in dysprosium doped sample; all samples showed near white light emission under UV and near UV excitation.

  18. La(0.4)Ba(0.6)Fe(0.8)Zn(0.2)O(3-delta) as cathode in solid oxide fuel cells for simultaneous NO reduction and electricity generation.

    PubMed

    Zhou, Renjie; Bu, Yunfei; Xu, Dandan; Zhong, Qin

    2014-01-01

    A perovskite-type oxide La(0.4)Ba(0.6)Fe(0.8)Zn(0.2)O(3-delta) (LBFZ) was investigated as the cathode material for simultaneous NO reduction and electricity generation in solid oxide fuel cells (SOFCs). The microstructure of LBFZ was demonstrated by X-ray diffraction and scanning electron microscopy. The results showed that a single cubic perovskite LBFZ was formed after calcined at 1100 degrees C. Meanwhile, the solid-state reaction between LBFZ and Ce(0.8)Sm(0.2)O(1.9) (SDC) at 900 degrees C was negligible. To measure the electrochemical properties, SOFC units were constructed with Sm(0.9)Sr(0.1)Cr(0.5)Fe(0.5)O3 as the anode, SDC as the electrolyte and LBFZ as the cathode. The maximum power density increased with the increasing NO concentration and temperature. The cell resistance is mainly due to the cathodic polarization resistance.

  19. 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.

  20. 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

  1. 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

  2. Fabrication and characterization of ultraviolet-emitting diodes composed of transparent p-n heterojunction, p-SrCu2O2 and n-ZnO

    NASA Astrophysics Data System (ADS)

    Ohta, Hiromichi; Orita, Masahiro; Hirano, Masahiro; Hosono, Hideo

    2001-05-01

    An ultraviolet light-emitting diode (UV-LED) was realized using a p-n heterojunction composed of the transparent oxide semiconductors p-SrCu2O2 and n-ZnO. A Ni/SrCu2O2/ZnO/ITO multilayered film was epitaxially grown on an extremely flat YSZ (111) surface by a pulsed-laser deposition technique. SrCu2O2 (112) was preferentially grown on ZnO (0001) at 350°C, while the preferential plane was changed into the (100) when the temperature was increased to 600 °C. The grown films were processed by conventional photolithography followed by reactive ion etching to fabricate heterojunction diodes. The resulting devices exhibited rectifying I-V characteristics inherent to p-n junctions. A relatively sharp electroluminescence band centered at 382 nm, attributed to transitions associated with exciton-exciton collision or electron-hole plasma in ZnO, was generated by applying a forward bias voltage greater than the turn-on voltage of 3 V. UV-LED performance characteristics such as threshold current and conversion efficiency improved with higher SrCu2O2 deposition temperatures. On the other hand, increased laser power density at 600 °C during deposition raised the incidence of insulating layer formation between the p and n layers, probably due to migration of K+ ions doped as an acceptor impurity. The resulting p-i-n diode emits broad luminescence centered at 500 nm for forward voltage greater than 14 V.

  3. [Study on the method for the determination of Fe, Si, Cu, Mg, Mn, Ni, Zn, Ti, Cr, Sr in aluminium alloy by ICP-AES].

    PubMed

    Zhong, Zhi-guang; Bian, Qun-zhou; Zheng, Jian-guo; Chen, Pei-ling; Liu, Chong-hua; Wei, Xian-ying

    2002-02-01

    The method for the determination of Fe, Mn, Cu, Zn, Mg, Ti, Si, Ni, Cr, Sr in aluminum alloy has been developed in this study. The sample was dissolved with sodium hydroxide, the matrix interference and interference among tested elements were studied and then corrected by matrix match and interference coefficient respectively. The method is rapid, simple and accurate, and it is suitable for daily testing of aluminum alloy for import and export.

  4. Zn2+ and Sr2+ Adsorption at the TiO2 (110)-Electrolyte Interface: Influence of Ionic Strength, Coverage, and Anions

    SciTech Connect

    Zhang,Z.; Fenter, P.; Cheng, L.; Sturchio, N.; Bedzyk, M.; Machesky, M.; Anovitz, L.; Wesolowski, D.

    2006-01-01

    The X-ray standing wave technique was used to probe the sensitivity of Zn{sup 2+} and Sr{sup 2+} ion adsorption to changes in both the adsorbed ion coverage and the background electrolyte species and concentrations at the rutile ({alpha}-TiO{sub 2}) (110)-aqueous interface. Measurements were made with various background electrolytes (NaCl, NaTr, RbCl, NaBr) at concentrations as high as 1 m. The results demonstrate that Zn{sub 2+} and Sr{sub 2+} reside primarily in the condensed layer and that the ion heights above the Ti-O surface plane are insensitive to ionic strength and the choice of background electrolyte (with <0.1 Angstroms changes over the full compositional range). The lack of any specific anion coadsorption upon probing with Br{sup -}, coupled with the insensitivity of Zn{sup 2+} and Sr{sup 2+} cation heights to changes in the background electrolyte, implies that anions do not play a significant role in the adsorption of these divalent metal ions to the rutile (110) surface. Absolute ion coverage measurements for Zn{sup 2+} and Sr{sup 2+} show a maximum Stern-layer coverage of {approx}0.5 monolayer, with no significant variation in height as a function of Stern-layer coverage. These observations are discussed in the context of Gouy-Chapman-Stern models of the electrical double layer developed from macroscopic sorption and pH-titration studies of rutile powder suspensions. Direct comparison between these experimental observations and the MUltiSIte Complexation (MUSIC) model predictions of cation surface coverage as a function of ionic strength revealed good agreement between measured and predicted surface coverages with no adjustable parameters.

  5. Heterogeneous distribution of B-site cations in BaZrxTi1-xO3 epitaxial thin films grown on (0 0 1) SrTiO3 by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Ventura, J.; Polo, M. C.; Ferrater, C.; Hernández, S.; Sancho-Parramón, J.; Coy, L. E.; Rodríguez, L.; Canillas, A.; Fábrega, L.; Varela, M.

    2016-09-01

    The isovalent susbstitution of Ti4+ by Zr4+ in BaZrxTi1-xO3 modifies the dielectric character of ferroelectric BaTiO3 yielding different behaviours such as relaxor, polar cluster, etc. The dynamic coupling between BaTiO3 polar nanoregions and BaZrO3 nonpolar ones as well as microstrain between them are thought to be behind such a rich phase diagram. However, these short-range compositonal variations are elusive to detect and this topic is thus rarely addressed. We have grown epitaxial thin films of BaZrxTi1-xO3 on (0 0 1)-oriented SrTiO3 substrates by pulsed laser deposition sweeping the entire composition range between BaTiO3 and BaZrO3 in increments of 0.1 in x. Several characterization techniques (AFM, TEM, XRD, Raman spectroscopy) were used for this research in order to understand the morphological and structural properties of the deposited films. Ellipsometric measurements allowed the calculation of the band gap energy of the films. This work demonstrates the existence of a heterogeneous distribution in the substitution of titanium by zirconium yielding relaxor and polar cluster nanoregions.

  6. Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets

    NASA Astrophysics Data System (ADS)

    Radmanesh, M. A.; Seyyed Ebrahimi, S. A.

    2012-09-01

    Magnetic nanocomposite SrFe12O19/Ni0.7Zn0.3Fe2O4 powders with different weight fractions of the Ni0.7Zn0.3Fe2O4 soft ferrite were synthesized by a combination of the sol-gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe12O19 which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe12O19 and 20 wt% Ni0.7Zn0.3Fe2O4. The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.

  7. Structural, thermal and optical properties of TeO2-ZnO-CdO-BaO glasses doped with VO2+

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, V.; Upender, G.; Chandra Mouli, V.; Prasad, M.

    2015-09-01

    The glasses with composition 64TeO2-15ZnO-(20-x)CdO-xBaO-1V2O5 (0 ⩽ x ⩽ 20 mol%) were prepared by conventional melt quenching technique. X-ray diffraction analysis was used to confirm the amorphous nature of the glasses. The optical absorption studies revealed that the cut-off wavelength (λα) decreases while optical band gap energy (Eopt) and Urbach energy (ΔE) values increase with an increase of BaO content. Refractive index (n) evaluated from Eopt was found to decrease with an increase of BaO content. The physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), optical basicity (Λ), molar refraction (Rm), and metallization criterion (M) evaluated and discussed. FTIR and Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1/TeO3 and ZnO4 units as basic structural units. The glass transition temperature (Tg) of glass sample, onset crystallization temperature (To) and thermal stability ΔT were determined from Differential Scanning Calorimetry (DSC). Using electron paramagnetic resonance (EPR) spectra of vanadium glasses the spin Hamiltonian parameters and dipolar hyperfine coupling parameters of VO2+ ions were calculated. It was found that V4+ ions in these glasses exist as VO2+ in octahedral coordination with a tetragonal distortion and have C4V symmetry with ground state dxy. Tetragonality (Δg∥ / Δg⊥) of vanadium ion sites exhibited non-linear variation with BaO content.

  8. Structural, thermal and optical properties of TeO2-ZnO-CdO-BaO glasses doped with VO(2+).

    PubMed

    Sreenivasulu, V; Upender, G; Chandra Mouli, V; Prasad, M

    2015-09-01

    The glasses with composition 64TeO2-15ZnO-(20-x)CdO-xBaO-1V2O5 (0⩽x⩽20 mol%) were prepared by conventional melt quenching technique. X-ray diffraction analysis was used to confirm the amorphous nature of the glasses. The optical absorption studies revealed that the cut-off wavelength (λα) decreases while optical band gap energy (Eopt) and Urbach energy (ΔE) values increase with an increase of BaO content. Refractive index (n) evaluated from Eopt was found to decrease with an increase of BaO content. The physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), optical basicity (Λ), molar refraction (Rm), and metallization criterion (M) evaluated and discussed. FTIR and Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1/TeO3 and ZnO4 units as basic structural units. The glass transition temperature (Tg) of glass sample, onset crystallization temperature (To) and thermal stability ΔT were determined from Differential Scanning Calorimetry (DSC). Using electron paramagnetic resonance (EPR) spectra of vanadium glasses the spin Hamiltonian parameters and dipolar hyperfine coupling parameters of VO(2+) ions were calculated. It was found that V(4+) ions in these glasses exist as VO(2+) in octahedral coordination with a tetragonal distortion and have C4V symmetry with ground state dxy. Tetragonality (Δg∥/Δg⊥) of vanadium ion sites exhibited non-linear variation with BaO content.

  9. A theoretical study of the extinction of antiferromagnetic order by holes and dilution in LaSrCuZnO

    NASA Astrophysics Data System (ADS)

    Ricardo de Sousa, J.; Pacobahyba, J. T. M.; Singh, M.

    2009-01-01

    We have used the quasi-two-dimensional Heisenberg antiferromagnetic model to explain the extinction of long-range order by holes and dilution in LaSrCuZnO. An analytical expression is obtained for the Néel temperature TN(x,z) by using the Green's-function formalism with random phase approximation (RPA). The expression for the Néel temperature TN(x,z) is a function of concentration of holes x and dilution z. To treat the dilution effect in CuO 2 plane (XY), we use three different approximations for percolation. The frustration effect is induced by interplane coupling which depends linearly on the doping concentration x. We have explained qualitatively the non-monotonic and reentrant behavior of TN(x,z) which was observed experimentally by Hücker [M. Hücker, V. Kataev, J. Pommer, J. Harass, A. Hosni, C. Pflitsch, R. Gross, B. Buchner, Phys. Rev. B 59 (1999) R725].

  10. Impact of hydrogen forming gas annealing on microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric ceramics

    NASA Astrophysics Data System (ADS)

    Sezer, N.; Saka, E.

    2016-03-01

    The effect of H2 forming gas annealing on the microwave properties of Ba(Zn1/3Ta2/3)O3 (BZT) dielectric ceramics has been studied. The structural, microwave, DC electrical and optical properties were analyzed by experiment results. With elevated temperature annealing, the microwave loss of BZT was increased. This trend correlated with high DC conductivity of annealed samples, as well as dampened phonons found in Raman spectra. These evidences, together, prove that the enhancement of oxygen vacancy defects induced by oxygen deficient sintering environment is one of the main extrinsic root causes for the high microwave loss in practical ceramic materials.

  11. 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.

  12. 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

  13. 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.

  14. Structural and dielectric properties of A(Fe{sub 1/2}Ta{sub 1/2})O{sub 3} [A = Ba, Sr, Ca

    SciTech Connect

    Dutta, Alo

    2011-04-15

    Graphical abstract: FTIR spectra of BFT, SFT and CFT at room temperature. Research highlights: {yields} The structural and dielectric properties of BaFe{sub 1/2}Ta{sub 1/2}O{sub 3}, SrFe{sub 1/2}Ta{sub 1/2}O{sub 3} and CaFe{sub 1/2}Ta{sub 1/2}O{sub 3}. {yields} Fourier transform infrared spectra show two primary phonon modes of the samples at around 450 cm{sup -1} and 620 cm{sup -1}. {yields} The compounds show significant frequency dispersion in its dielectric properties. {yields} The relaxation mechanism of the samples is modelled by Cole-Cole equation. -- Abstract: The complex perovskite oxide barium iron tantalate (BFT), BaFe{sub 1/2}Ta{sub 1/2}O{sub 3}, strontium iron tantalate (SFT), SrFe{sub 1/2}Ta{sub 1/2}O{sub 3} and calcium iron tantalate (CFT), CaFe{sub 1/2}Ta{sub 1/2}O{sub 3} are synthesized by a solid-state reaction technique. Rietveld refinement of the X-ray diffraction data of the samples shows that BFT and SFT crystallize in cubic structure, with lattice parameter a = 4.06 A for BFT and 3.959 A for SFT, whereas CFT crystallizes in orthorhombic structure having lattice parameters a = 5.443 A, b = 5.542 A and c = 7.757 A. Fourier transform infrared spectra show two primary phonon modes of the samples at around 450 cm{sup -1} and 620 cm{sup -1}. The compounds show significant frequency dispersion in its dielectric properties. The complex impedance plane plots of the samples show that the relaxation (conduction) mechanism in these materials is purely a bulk effect arising from the semiconductive grains. The relaxation mechanism of the samples is modelled by Cole-Cole equation. The frequency dependent conductivity spectra are found to follow the power law.

  15. Soil-water distribution coefficients and plant transfer factors for (134)Cs, (85)Sr and (65)Zn under field conditions in tropical Australia.

    PubMed

    Twining, J R; Payne, T E; Itakura, T

    2004-01-01

    Measurements of soil-to-plant transfer of (134)Cs, (85)Sr and (65)Zn from two tropical red earth soils ('Blain' and 'Tippera') to sorghum and mung crops have been undertaken in the north of Australia. The aim of the study was to identify factors that control bioaccumulation of these radionuclides in tropical regions, for which few previous data are available. Batch sorption experiments were conducted to determine the distribution coefficient (K(d)) of the selected radionuclides at pH values similar to natural pH values, which ranged from about 5.5 to 6.7. In addition, K(d) values were obtained at one pH unit above and below the soil-water equilibrium pH values to determine the effect of pH. The adsorption of Cs showed no pH dependence, but the K(d) values for the Tippera soils (2300-4100 ml/g) exceeded those for the Blain soils (800-1200 ml/g) at equilibrium pH. This was related to the greater clay content of the Tippera soil. Both Sr and Zn were more strongly adsorbed at higher pH values, but the K(d) values showed less dependence on the soil type. Strontium K(d)s were 30-60 ml/g whilst Zn ranged from 160 to 1630 ml/g for the two soils at equilibrium pH. With the possible exception of Sr, there was no evidence for downward movement of radionuclides through the soils during the course of the growing season. There was some evidence of surface movement of labelled soil particles. Soil-to-plant transfer factors varied slightly between the soils. The average results for sorghum were 0.1-0.3 g/g for Cs, 0.4-0.8 g/g for Sr and 18-26 g/g for Zn (dry weight) with the initial values relating to Blain and the following values to Tippera. Similar values were observed for the mung bean samples. The transfer factors for Cs and Sr were not substantially different from the typical values observed in temperate studies. However, Zn transfer factors for plants grown on both these tropical soils were greater than for soils in temperate climates (by more than an order of magnitude

  16. 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.

  17. Effect of Mn and Ti substitution on the reflection loss characteristic of Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0, 1, 2 and 3)

    NASA Astrophysics Data System (ADS)

    Gunanto, Y. E.; Cahyadi, L.; Adi, W. Ari

    2016-04-01

    The synthesis and characterization of composition Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0; 1; 2 and 3) compound by solid state reaction using mechanical milling have been performed. The raw materials were BaCO3, SrCO3, Fe2O3, MnCO3, and TiO2. The mixed powder was compacted and sintered at 1000°C for 5 hours. X-ray diffraction studies indicate expansion of hexagonal unit cell and compression of atomic density with substitution of Mn2+ and Ti4+ ions. Effect of substitution upon magnetic properties revealed that total magnetization, remanence, and coercivity changed with substitution due to preferential site occupancy of substituted Mn2+ and Ti4+ ions. Since the coercivity and total magnetization may be controlled by substitution while maintaining resistive properties, this material is useful for microwave absorber.

  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. Crystal structure of Na 2MMgP 2O 8 ( M: Ba, Sr, Ca) orthophosphates and their luminescence properties activated by Eu 2+; analogous structural behaviors of glaserite-type phosphates and silicates

    NASA Astrophysics Data System (ADS)

    Yonesaki, Yoshinori; Matsuda, Chihiro

    2011-12-01

    Rietveld refinements of X-ray powder diffraction data and vibrational spectroscopy have confirmed the crystal structure of Na 2MMgP 2O 8 ( M: Ba, Sr, Ca) prepared by a standard solid state reaction. They have glaserite-type layered structure. Na 2MMgP 2O 8 has a trigonal P3¯ form for M=Ba, and monoclinic P2 1/ c forms for M=Sr and Ca. The observed structural transition is analogous to the corresponding layered orthosilicate M3MgSi 2O 8. Eu 2+-doped Na 2MMgP 2O 8 exhibits an intense blue to violet emission under ultraviolet excitation, based on 5 d-4 f electron transition of Eu 2+ ions. The emission character is very sensitive to the structural transition induced by M2+ and the subsequent site symmetry changes.

  20. A basement-interacted fluid in the N81 deposit, Pine Point Pb-Zn District, Canada: Sr isotopic analyses of single dolomite crystals

    NASA Astrophysics Data System (ADS)

    Gromek, Paulina; Gleeson, Sarah A.; Simonetti, Antonio

    2012-10-01

    The Mississippi Valley-type Pb-Zn deposits of the Pine Point district (Northwest Territories, Canada) are located close to the eastern edge of the present day Western Canadian Sedimentary Basin. The deposits are thought to have formed as the result of basin-wide fluid flow in the Presqu'ile Barrier, the host to the ore deposits. A laser ablation multi-collector inductively coupled plasma mass spectrometric study of 87Sr/86Sr ratios of ore-related dolomites from the N81 deposit at Pine Point indicates that at least two sources of Sr were present in the mineralizing system. One fluid has a range in Sr isotopic values from 0.07073 to 0.71200 and is interpreted to be derived from Middle Devonian seawater that interacted with clastic units in the basin. The second fluid has higher Sr isotopic values (up to 0.71520), similar to those found in some Canadian Shield brines, and is interpreted to represent an evaporated seawater-derived brine which has interacted with crystalline basement rocks. Reactivation of old structures in the basement may have provided a pathway for cross-formation fluid flow to the site of mineralization. The data suggest that the stratigraphic location of the Pine Point District, near the interface between the Western Canadian Sedimentary Basin and its basement, may have exerted a fundamental control on the formation of these deposits.

  1. Electronic structure and properties of isoelectronically substituted compounds Y{sub 1}Ba{sub 2-m}M{sub m}Cu{sub 3}O{sub 7} and Y{sub 1}Ba{sub 2-m}M{sub m}Cu{sub 4}O{sub 8} (M = Be, Mg, Ca, Sr, Ba, Ra)

    SciTech Connect

    Ermakov, A.I.; Zharikova, E.A.; Markushin, N.A.

    1994-09-01

    According to cluster calculations, the electronic structures of compounds based on Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} and Y{sub 1}Ba{sub 2}Cu{sub 4}O{sub 8} with isoelectronically substituted barium have some qualitative distinctions. These compounds behave differently upon barium substitution by other elements due to differences in the character of their highest occupied and lowest unoccupied molecular orbitals. Substitution of barium by radium is expected to lead to an increase in oxygen stability without a significant decrease in the critical temperature of superconduction transition T{sub s}. In order to raise T{sub s}, it is of interest to study the systems YBa{sub 2-m}(Be or Mg){sub m}Cu{sub 3}O{sub x} and YBa{sub 2-m}(Ca, Sr){sub m}Cu{sub 3}O{sub x}. On partial substitution of barium by calcium in YBa{sub 2}Cu{sub 4}O{sub 8}, the mechanism of T{sub s} elevation may involve contraction of the forbidden band due to oxygen sublattice distortions in the vicinity of Ba centers.

  2. Blockage of domain growth by nanoscale heterogeneities in a relaxor ferroelectric Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6}

    SciTech Connect

    Pertsev, N. A.; Gainutdinov, R. V.; Bodnarchuk, Ya. V.; Volk, T. R.

    2015-01-21

    The growth of localized subsurface domains in a relaxor ferroelectric Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} is studied using the technique of piezoresponse force microscopy (PFM). Ferroelectric domains are created by applying moderate voltages of 10–50 V to the conductive tip of a scanning force microscope brought into contact with a nonpolar face of a Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} crystal. PFM images of written domains are acquired and analyzed quantitatively to determine the domain length along the polar axis and its width in the transverse direction. The dependences of domain sizes on the applied voltage, pulse duration, and the time passed after completion of the voltage pulse are reported and analyzed theoretically. It is shown that the observed kinetics of domain growth can be explained by the creep of domain boundaries occurring in the presence of random electric fields inherent in Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6}. The comparison of measured domain sizes with their equilibrium values calculated with the aid of the thermodynamic theory demonstrates that the growth of subsurface domains in Sr{sub 0.61}Ba{sub 0.39}Nb{sub 2}O{sub 6} is blocked by nanoscale heterogeneities characteristic of this relaxor ferroelectric. These results may have important implications for the development of nonlinear optical devices based on nanoheterogeneous ferroelectrics.

  3. Low loss composition of BaxSryCa1-x-yTiO3: Ba0.12-0.25Sr0.35-0.47Ca0.32-0.53TiO3

    DOEpatents

    Xiang, Xiao-Dong; Chang, Hauyee; Takeuchi, Ichiro

    2001-01-01

    A dielectric thin-film material for microwave applications, including use as a capacitor, the thin-film comprising a composition of barium strontium calcium and titanium of perovskite type (Ba.sub.x Sr.sub.y Ca.sub.1-x-y)TiO.sub.3. Also provided is a method for making a dielectric thin film of that formula over a wide compositional range through a single deposition process.

  4. Schottky barrier effect on the electrical properties of Fe3O4/ZnO and Fe3O4/Nb : SrTiO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Kiwon; Kim, D. H.; Dho, Joonghoe

    2011-09-01

    The current-voltage (I-V) characteristics of Fe3O4/Nb-doped SrTiO3(Nb : STO) and Fe3O4/ZnO junctions prepared by pulsed laser deposition were investigated as a function of temperature. The rectifying behaviour was more distinctive in Fe3O4/Nb : STO than in the Fe3O4/ZnO. Contrary to Fe3O4/Nb : STO, remarkably, the current flow in Fe3O4/ZnO was slightly larger for negative bias voltages than for positive bias voltages. The threshold voltage in Fe3O4/Nb : STO dramatically shifted to a higher voltage by decreasing the temperature, and hysteresis behaviour with a cyclic voltage sweep appeared below 120 K. Upon cooling, the rectifying behaviour in Fe3O4/ZnO gradually disappeared within the measurement range. The observed difference between Fe3O4/Nb : STO and Fe3O4/ZnO could be explained by the shape and height of the Schottky barrier which was determined by the relative magnitude of the work functions of the two contact materials. The formation of the Schottky barrier presumably resulted from an upward shift of the interface band in Fe3O4/Nb : STO, while a little downward shift of the interface band occurred in Fe3O4/ZnO. In addition, Al-doping into ZnO induced a complete disappearance of the Schottky barrier in the Fe3O4/Al-doped ZnO junction.

  5. Ultraviolet C upconversion fluorescence of trivalent erbium in BaGd2ZnO5 phosphor excited by a visible commercial light-emitting diode.

    PubMed

    Yang, Yanmin; Mi, Chao; Su, Xianyuan; Jiao, Fuyun; Liu, Linlin; Zhang, Jiao; Yu, Fang; Li, Xiaodong; Liu, Yanzhou; Mai, Yaohua

    2014-04-01

    Multiple ultraviolet (UV) emission bands have been obtained in Er3+ doped BaGd2ZnO5 phosphor under the excitation of a 532 nm solid-state laser, and the emission peaks at 217, 254, 278, 296, 314, 348, 374 and 394 nm were determined to stem from the high-energy states 4D(1/2), 4D(7/2), 2H(9/2), 2P(1/2), 2P(3/2), 4G(7/2), 4G(11/2), 4H(9/2) of trivalent erbium, respectively. Some UV emission bands in the UVC region can be observed when the sample was excited by commercial green (529 nm) and blue (460 nm) LED. In view of the small size, low-drive voltage and price of LED, UVC upconversion phosphor BaGd2ZnO5:Er3+ excited by visible LED has potential application in environmental sciences.

  6. Production of Ba(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} ceramic by coprecipitation

    SciTech Connect

    Mergen, A. Sert, D.

    2012-01-15

    A simple coprecipitation technique was successfully applied for the preparation of pure, nanosized, single phase Ba(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} microwave dielectric ceramic powders. Barium, zinc and niobium ions were precipitated as hydroxide under basic conditions using aqueous sodium hydroxide solution and single phase Ba(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} ceramic was produced at 800 Degree-Sign C. TEM revealed an average particle size of around 100 nm for the calcined powders. The samples sintered at 1250 Degree-Sign C for 4 h had a relatively high density and fine grain sizes. While the dielectric constant of ceramics varied between 37.5 and 39.8 the dielectric losses were lower than 4 Multiplication-Sign 10{sup -3} at frequency range of 1 kHz-2 MHz between 20 and 200 Degree-Sign C. - Highlights: Black-Right-Pointing-Pointer Production of BZN by coprecipitation. Black-Right-Pointing-Pointer Nanoscale BZN powder. Black-Right-Pointing-Pointer Dielectric properties of BZN.

  7. Role of Mn doping for obtaining of hexagonal phase in Ba0.98Zn0.02TiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Das, S. K.; Roul, B. K.

    2016-08-01

    This paper reports the observation of hexagonal phase of barium titanate by Mn doping and its effect on dielectric and magnetic properties. Ceramic samples of Ba0.98Zn0.02Ti1-xMnxO3 (where, x= 0.04, 0.06 and 0.08) were prepared by traditional solid-state reaction route. The hexagonal phase is stabilized in the composition Ba0.98Zn0.02Ti0.92Mn0.08O3 and a very feeble M-H loop is also observed in that composition. This induced magnetism is expected due to the exchange interactions between magnetic polarons formed by oxygen vacancies with Mn ions. The dielectric constant as well as the ferroelectric to paraelectric transition temperature is systematically decreased with increasing of Mn doping concentration. Further to that, the temperature dependent dielectric constant curve is also broadened at transition temperature with increasing of Mn concentration. However, the ferroelectric to paraelectric transition temperature is well above room temperature.

  8. Life Cycle Testing of Ba(x)Sr(1-x)TiO3 Ferroelectric Thin Films in a Tunable Microwave Device

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; VanKeuls, Fred W.; Romanofsky, Robert R.; Mueller, Carl H.; Warner, Joseph D.

    2000-01-01

    Thin film ferroelectrics are being studied as candidates for novel tunable microwave components such as tunable filters, tunable oscillators, and phase shifters for applications in phased array antennas. Much work has been done optimizing the ferroelectric material and in producing proof-of-concepts of these components. However, little attention has been given to their reliability. In this study we present our results on the reliability of high quality K-band phase shifters made of Ba(sub x)Sr(sub 1-x)TiO3 (BSTO) ferroelectric thin films (0.5 to 0.75 micrometers thick) on MgO and LAO. The phase shift and insertion loss were measured at 300 K over 104 operation cycles within a 0 to 400 V dc bias range (0 to 40 V/micrometer) at 15, 18, and 22 GHz. Results for these phase shifters indicate that in general there were no appreciable changes in phase shift after 4x10(exp 4) cycles, suggesting that these phase shifters are robust enough to sustain optimal performance under the operating mode typical of fast tracking phased arrays.

  9. Probing the role of encapsulated alkaline earth metal atoms in endohedral metallofullerenes M@C76 (M = Ca, Sr, and Ba) by first-principles calculations.

    PubMed

    Yang, Tao; Zhao, Xiang; Xu, Qian; Zheng, Hong; Wang, Wei-Wei; Li, Sheng-Tao

    2012-05-01

    By means of density functional theory and statistical mechanics, we investigate the geometric and electronic structures, thermodynamic stability and infrared (IR) vibrational frequencies of alkaline earth metal endohedral fullerenes, M@C(76) (M = Ca, Sr, and Ba). The results reveal that M@C(1)(17,459)-C(76) possesses the lowest energy followed by M@C(2v)(19,138)-C(76) with a very small energy difference. Both the structures have a pair of adjacent pentagons and are related by a single Stone-Wales transformation. Equilibrium statistical thermodynamic analyses based on Gibbs energy treatments suggest that M@C(1)(17,459)-C(76) has a prominent thermodynamic stability at higher temperatures, in contrast with M@C(2v)(19,138)-C(76) whose thermodynamic stability is affected by the encapsulated metal atom. The encapsulated metallic atoms as well as cage structures significantly influence the electronic properties of endohedral fullerenes such as electron affinities and ionization potentials. On the other hand, the singlet-triplet splitting energy ΔE(S-T) depends on the cage structures. In addition, IR spectra and chemical shifts of these compounds have been computed to assist further experimental characterization.

  10. Visible light absorption in La, Cr co-doped SrTiO3 and BaTiO3 for ferroelectric photovoltaics

    NASA Astrophysics Data System (ADS)

    Comes, Ryan; McBriarty, Martin; Ong, Phuong-Vu; Heald, Steve; Carroll, Gerard; Gamelin, Daniel; Freedy, Keren; Smolin, Sergey; Baxter, Jason; Kaspar, Tiffany; Bowden, Mark; Sushko, Peter; Chambers, Scott

    Ferroelectric materials offer intriguing possibilities as photovoltaic materials, as their built-in electric field is ideal for separation of optically-excited electron-hole pairs without the need for a p-n junction. However, the majority of ferroelectrics suffer from a wide optical band gap outside the visible range. By co-doping La and Cr into epitaxial SrTiO3 and BaTiO3 (SLTCO/BLTCO) thin films, we show that absorption in the visible light regime can be achieved with a band gap of ~2.3 eV while preserving ideal stoichiometry. Through x-ray photoelectron spectroscopy, spectroscopic ellipsometry, photoconductivity and ultrafast pump-probe transient reflectance measurements, we show that visible light excitation of Cr 3d valence electrons into the Ti 3d conduction band produces optical carriers. Using piezoresponse force microscopy and polarized x-ray absorption fine structure measurements, we measure the ferroelectric polarization of the doped BLTCO films. These results are compared to density functional theory models to understand the optical and structural properties of the materials.

  11. Direct correlation and strong reduction of native point defects and microwave dielectric loss in air-annealed (Ba,Sr)TiO3

    NASA Astrophysics Data System (ADS)

    Zeng, Z. Q.; Podpirka, A.; Kirchoefer, S. W.; Asel, T. J.; Brillson, L. J.

    2015-05-01

    We report on the native defect and microwave properties of 1 μm thick Ba0.50Sr0.50TiO3 (BST) films grown on MgO (100) substrates by molecular beam epitaxy (MBE). Depth-resolved cathodoluminescence spectroscopy (DRCLS) showed high densities of native point defects in as-deposited BST films, causing strong subgap emission between 2.0 eV and 3.0 eV due to mixed cation VC and oxygen Vo vacancies. Post growth air anneals reduce these defects with 2.2, 2.65, and 3.0 eV VO and 2.4 eV VC intensities decreasing with increasing anneal temperature and by nearly two orders of magnitude after 950 °C annealing. These low-defect annealed BST films exhibited high quality microwave properties, including room temperature interdigitated capacitor tunability of 13% under an electric bias of 40 V and tan δ of 0.002 at 10 GHz and 40 V bias. The results provide a feasible route to grow high quality BST films by MBE through post-air annealing guided by DRCLS.

  12. Thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics in different oxygen-reduction conditions

    NASA Astrophysics Data System (ADS)

    Li, Yi; Liu, Jian; Wang, Chun-Lei; Su, Wen-Bin; Zhu, Yuan-Hu; Li, Ji-Chao; Mei, Liang-Mo

    2015-04-01

    The thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics, reduced in different conditions, are investigated in the temperature range from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping in the low temperature range, the Fermi glass behavior in the middle temperature range, and the Anderson localized behavior in the high temperature range. The thermal conductivity presents a plateau at high-temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increase of the degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value is obtained to be ˜0.19 at 1073 K in the heaviest oxygen reduced sample. Project supported by the National Basic Research Program of China (Grant No. 2013CB632506) and the National Natural Science Foundation of China (Grant Nos. 51202132 and 51002087).

  13. Observation of superconductivity at 30~46 K in A(x)Fe₂Se₂(A = Li, Na, Ba, Sr, Ca, Yb, and Eu).

    PubMed

    Ying, T P; Chen, X L; Wang, G; Jin, S F; Zhou, T T; Lai, X F; Zhang, H; Wang, W Y

    2012-01-01

    New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30 K in KFe₂Se₂, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced T(c) = 30∼46 K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a∼3.755-3.831 Å while c∼15.99-20.54 Å. Resistivities show the corresponding sharp transitions at 45 K and 39 K for NaFe₂Se₂ and Ba₀.₈Fe₂Se₂, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well. PMID:22645642

  14. The MBE growth and optical quality of BaTiO{sub 3} and SrTiO{sub 3} thin films on MgO

    SciTech Connect

    McKee, R.A.; Specht, E.D.; Alexander, K.B.; Walker, F.J.

    1994-05-01

    High quality epitaxial BaTiO{sub 3} and SrTiO{sub 3} have been grown on MgO; stabilized at a one unit cell height; and grown to film thicknesses of 0.5--0.7 {mu}m. These relatively thick films remain adherent when thermally cycled between growth temperatures and room temperature, are crack free with high optical quality, and have both in-plane and out-of-plane X-ray rocking curves of 0.3--0.5{degree}. These films have been grown using molecular beam epitaxy (MBE) methods starting with the TiO{sub 2} layer of the perovskite structure. The TiO{sub 2}-layer/MgO interface uniquely satisfies electrostatic requirements for perovskite heteroepitaxy and provides the template structure that leads to the high quality films that are obtained. Wavelength dependence of optical loss has been characterized between 475 nm and 705 nm with loss coefficients < l dB/cm being obtained at the He-Ne wavelength.

  15. Improved Dielectric Properties of Heterostructured Ba2.5Sr0.5TiO3 Thin Film Composites for Microwave Dielectric Devices

    NASA Technical Reports Server (NTRS)

    Jain, M.; Majumder, S. B.; Katiyar, R. S.; Bhalla, A. S.; Agrawal, D. C.; Kulkarni, V. N.; VanKeuls, F. W.; Miranda, F. A.; Romanofsky, R. R.; Mueller, C. H.; Fernandez, F.

    2002-01-01

    In the present work we have deposited MgO and Ba(sub 0.5)Sr(sub 0.5)TiO(sub 3)(BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films. These films were characterized by X-ray diffraction and Rutherford backscattering technique and found to be highly (100) textured. The figure of merit {(C(sub0)-C(sub v)/(C(sub0-tandelta)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm. These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13-15 GHz. The high frequency figure of merit (kappa factor, defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 deg/dB for hetero-structured film as compared to 24.65 deg /dB for pure film). Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.

  16. Ion beam-assisted pulsed laser deposition of (Ba,Sr)(Ti,Zr)O{sub 3} films on Pt-Si substrates

    SciTech Connect

    Sakai, Joe; Vayunandana Reddy, Y. K.; Autret-Lambert, Cecile; Lagrange, Jean-Francois; Motret, Olivier; Roger, Sylvain; Wolfman, Jerome

    2011-05-15

    Ion beam-assisted pulsed laser deposition with an Ar-oxygen ion mixture was used to prepare Ba{sub 0.6}Sr{sub 0.4}Ti{sub 0.7}Zr{sub 0.3}O{sub 3} (BSTZ) thin films on Pt-coated Si substrates. The ion beam with an anode voltage of 600 V was effective to reduce the thermal budget, i.e., to achieve similar crystallinity with approximately 100 deg. C lower deposition temperature compared to the cases without ionization. It was revealed that the dielectric properties (relative dielectric constant {epsilon}{sub r} and its electric field tunability), out-of-plane lattice parameter of (001)-oriented grains (a{sub 001}), and the existence of (110)-oriented grains are correlated with one another. Elongation of a{sub 001} was suppressed, resulting in large {epsilon}{sub r} values comparable with that of a ceramic bulk of the same composition, in the BSTZ films that contain (110)-oriented grains. Less volume of amorphous BSTZ region is supposed to be playing an important role for the bulklike properties of these BSTZ films.

  17. Linear and nonlinear optical properties of rare earth doped of Ba0.7Sr0.3TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Reshmi, R.; Sreeja, R.; Jayaraj, M. K.; James, J.; Sebastian, M. T.

    2009-08-01

    Ba0.7Sr0.3TiO3:Eu ferroelectric films were deposited on quartz substrates by pulsed laser deposition. The linear absorption coefficient and the linear refractive index calculated from the transmission spectrum at 532 nm were found to be 1.67×104 cm-1 and 1.82 respectively. The room temperature photoluminescence shows the characteristic emission of Eu3+ ions. The nonlinear optical properties of the film were investigated by a single beam Z-scan setup. The negative nonlinear refractive index and two photon absorption coefficient was found to be -1.508×10-6 m2/GW and 240 m/GW respectively. The real and imaginary part of the third order susceptibility of the thin films is 2.58×10-17 m2/V2 and 1.16×10-16 m2/V2 respectively. The BST:Eu thin films show good optical limiting property.

  18. Direct correlation and strong reduction of native point defects and microwave dielectric loss in air-annealed (Ba,Sr)TiO{sub 3}

    SciTech Connect

    Zeng, Z. Q.; Podpirka, A.; Kirchoefer, S. W.; Asel, T. J.; Brillson, L. J.

    2015-05-04

    We report on the native defect and microwave properties of 1 μm thick Ba{sub 0.50}Sr{sub 0.50}TiO{sub 3} (BST) films grown on MgO (100) substrates by molecular beam epitaxy (MBE). Depth-resolved cathodoluminescence spectroscopy (DRCLS) showed high densities of native point defects in as-deposited BST films, causing strong subgap emission between 2.0 eV and 3.0 eV due to mixed cation V{sub C} and oxygen Vo vacancies. Post growth air anneals reduce these defects with 2.2, 2.65, and 3.0 eV V{sub O} and 2.4 eV V{sub C} intensities decreasing with increasing anneal temperature and by nearly two orders of magnitude after 950 °C annealing. These low-defect annealed BST films exhibited high quality microwave properties, including room temperature interdigitated capacitor tunability of 13% under an electric bias of 40 V and tan δ of 0.002 at 10 GHz and 40 V bias. The results provide a feasible route to grow high quality BST films by MBE through post-air annealing guided by DRCLS.

  19. Structural, dielectric, electrical and piezoelectric properties of Ba4SrRTi3V7O30 (R=Sm, Dy) ceramics

    NASA Astrophysics Data System (ADS)

    Sahoo, Priyadarshini; Panigrahi, Anuradha; Patri, Sunanda; Choudhary, Ram

    2008-12-01

    Polycrystalline samples of Ba4SrRTi3V7O30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31-500°C) and frequency (1 kHz-1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355°C for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization study.

  20. Structural, dielectric, electrical and piezoelectric properties of Ba4SrRTi3V7O30 (R=Sm, Dy) ceramics

    NASA Astrophysics Data System (ADS)

    Sahoo, Priyadarshini S.; Panigrahi, Anuradha; Patri, Sunanda K.; Choudhary, Ram N. P.

    2008-12-01

    Polycrystalline samples of Ba4SrRTi3V7O30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31 500°C) and frequency (1 kHz-1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355°C for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization study.

  1. Downscaling at submicrometer scale of the gap width of interdigitated Ba0.5Sr0.5TiO3 capacitors.

    PubMed

    Khalfallaoui, Abderrazek; Burgnies, Ludovic; Blary, Karine; Velu, Gabriel; Lippens, Didier; Carru, Jean-Claude

    2015-02-01

    The goal of this work was to study the influence of shrinking the gap width between the fingers of interdigitated tunable capacitors (IDCs). Voltage control of the capacitance was achieved with a 500-nm-thick Ba0.5Sr0.5TiO3 film which is in paraelectric state at room temperature. Eight devices with finger spacing ranging from 3 μm down to 0.25 μm were fabricated by the sol-gel deposition technique, electron beam patterning, and gold evaporation. The equivalent capacitance, quality factor, and tunability of the devices were measured subsequently by vector network analysis from 40 MHz to 40 GHz and for a dc bias voltage varying from -30 V to +30 V. This experimental study mainly shows that a decrease of the gap below 1 μm 1) introduces a frequency dependence of the capacitance caused by resonance effects with the finger inductance; 2) degrades the quality factor above 20 GHz, and 3) optimizes the tunability of the devices by enhancing the local electric field values. As a consequence, some trade-offs are pointed out related to the goal of ultra-thin ferroelectric film which can be voltage controlled by means of finger-shaped electrodes with deep submicrometer spacing.

  2. Polar phase transitions and physical properties in fresnoite A2TiSi2O8 (A= Ba, Sr) by first principles calculations

    NASA Astrophysics Data System (ADS)

    Song, Nayoung; Momida, Hiroyoshi; Oguchi, Tamio; Kim, Bog G.

    2016-10-01

    Polar phase transitions of fresnoites, Ba2TiSi2O8 (BTS) and Sr2TiSi2O8 (STS) have been comparatively analyzed by the first principles calculations. We show that both BTS and STS have a polar structure with the space group P4bm as a ground state, and there is a fictitious phase transition in the tetragonal space group from the nonpolar P4/mbm meta-stable phase to the polar P4bm phase. From the analyses of the two atomic structures, we find that a noticeable issue in the phase transition is bond length changes of Si-O and Ti-O which break the inversion symmetry, resulting that one of vertices in the edge-shared Si-O and Ti-O polyhedron is detached in the polar phase. The structural phase transition between the polar and the nonpolar states are discussed in terms of electronic structures and structural symmetry mode analyses. We evaluate the size of spontaneous polarizations of BTS and STS in the polar P4bm phases, and the correlation analysis shows significant contributions of the detached polyhedrons to the strong polar property. We also show second harmonic generation susceptibilities of BTS and STS as a candidate for second-order nonlinear optics materials. Our quantitative studies can provide full understandings of atomic and electronic mechanisms of their polar phase and nonlinear optical properties.

  3. Direct imaging of the structural domains in the iron pnictides AFe[subscript 2]As[subscript 2] (A=Ca, Sr, Ba)

    SciTech Connect

    Tanatar, M.A.; Kreyssig, A.; Nandi, S.; Ni, N.; Bud'ko, S.L.; Canfield, P.C.; Goldman, A.I.; Prozorov, R.

    2009-06-29

    The parent compounds of recently discovered iron-arsenide superconductors, AFe{sub 2}As{sub 2} with alkaline earth A=Ca,Sr,Ba, undergo simultaneous structural and magnetic phase transitions at a temperature T{sub SM}. Using a combination of polarized light microscopy and spatially resolved high-energy synchrotron x-ray diffraction we show that the orthorhombic distortion leads to the formation of 45{sup o}-type structural domains in all parent compounds. Domains penetrate through the sample thickness in the c direction and are not affected by crystal imperfections such as growth terraces. The domains form regular stripe patterns in the plane with a characteristic dimension of 10--50 {mu}m. The direction of the stripes is fixed with respect to the tetragonal (100) and (010) directions but can change by 90{sup o} on thermal cycling through the transition. This domain pattern may have profound implications for intrinsic disorder and anisotropy of iron arsenides.

  4. Characterization of Fe-doped SrTiO3/BaTiO3 multilayer films and their ethanol sensing applications

    NASA Astrophysics Data System (ADS)

    Supasai, Thidarat; Wisitsoraat, Anurat; Hodak, Satreerat

    2010-03-01

    Fe-doped SrTiO3/BaTiO3 multilayer films have been deposited on alumina substrate using a sol-gel spin coating technique. The field effect scanning electron microscope photographs revealed a mixture of round and facet-shaped crystals in the undoped films. This microstructure disappeared in Fe-doped films which adopted a more porous sponge-like structure. The grain size of the films decreased from 300 nm for undoped films to 100 nm and 70 nm with Fe doping concentrations of 4 and 8 wt%, respectively. The absorption edge energy for X-rays by Fe was found to be about 7121 eV consistent with Fe^2+ oxidation state. Interdigitated electrodes were applied on these films for ethanol gas sensing application. A sensitivity figure of merit based on the relative change in the resistance of the Fe-doped films 8 wt% film was found to be in the 1-3 range for ethanol doses of 100-1000 ppm when operating at 250 C and in the range of 3-10 when the operating temperature was 350 C.

  5. Electric-field influence on the neutron diffuse scattering near the ferroelectric transition of Sr0.61Ba0.39Nb2O6

    NASA Astrophysics Data System (ADS)

    Ondrejkovic, Petr; Kempa, Martin; Savinov, Maxim; Bednyakov, Petr; Kulda, Jiri; Bourges, Philippe; Dec, Jan; Hlinka, Jirka

    2016-08-01

    Uniaxial relaxor ferroelectric Sr0.61Ba0.39Nb2O6 single crystal has been investigated in the vicinity of its phase transition using neutron scattering and dielectric spectroscopy. A global-type thermal hysteresis is evidenced by both techniques in the ferroelectric phase and up to about 15 K above Tc. In addition, a part of the transverse neutron diffuse scattering in the 001 Brillouin zone, presumably related to static nanodomain structure, can be suppressed by prior poling the crystal in electric field of 3 kV/cm. The remaining part of the transverse neutron diffuse scattering and the real part of permittivity show a similar temperature dependence. The temperature position of the maximal scattering intensity Tmax depends significantly on the scattering wave vector. Tmax shifts monotonically to higher temperature with the increasing wave vector in all investigated cooling and heating regimes. It is concluded that the critical fluctuations have space correlations which depend on frequency and wave vector.

  6. X-ray combined analysis of fiber-textured and epitaxial Ba(Sr,Ti)O{sub 3} thin films deposited by radio frequency sputtering

    SciTech Connect

    Remiens, D.; Ponchel, F.; Legier, J. F.; Yang, L.; Chateigner, D.; Wang, G.; Dong, X.

    2011-06-01

    A complete study is given in this paper on the structural properties of Ba(Sr,Ti)O{sub 3} (BST) thin films which present various preferred orientations: (111) and (001) fiber and epitaxial textures. The films are deposited in situ at 800 deg. C by sputtering on Si/SiO{sub 2}/TiO{sub x}/Pt substrates and the orientation is controlled by monitoring the concentration of O{sub 2} in the reactive plasma or by prior deposition of a very thin TiO{sub x} buffer layer between BST films and substrates. The epitaxial films are obtained on (001)-alpha-Al{sub 2}O{sub 3} substrates covered with TiO{sub x} buffer layers. In order to analyze finely the preferred orientations, the texture, the microstructural features, and the anisotropy-related quantities such as residual stresses in the films, the conventional Bragg-Brentano {theta} - 2{theta} x-ray diffraction diagrams is shown not to be sufficient. So, we systematically used x-ray combined analysis, a recently developed methodology which gives access to precise determination of the structure (cell parameters and space group) of the films, their orientation distributions (texture strengths and types) and mean crystallite sizes, their residual stresses. This fine structural analysis shows important modifications between the film qualities which induce differences in BST films electrical behavior, permittivity, loss tangent, and tunability.

  7. 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.

  8. Temperature evolution of the luminescence decay of Sr0.33Ba0.67Nb2O6 : Pr3+.

    PubMed

    Mahlik, S; Lazarowska, A; Speghini, A; Bettinelli, M; Grinberg, M

    2014-04-23

    This article presents a spectroscopic investigation of Sr(0.33)Ba(0.67)(NbO2)3, doped with 1 mol% of Pr(3+). Photoluminescence and luminescence kinetics were measured at different temperatures at ambient (ferroelectric phase) and 76 kbar pressures (paraelectric phase). The photoluminescence spectrum is dominated by (1)D2 → (3)H4 transition of Pr(3+) in both phases. At ambient pressure when the system is excited with UV radiation, the intensity of dominant (1)D2 → (3)H4 emission evidently increases in the 200-293 K temperature range. This effect is attributed to enhancement of the excitation of the (1)D2 state through the praseodymium trapped exciton state, which at higher temperatures does not populate the higher lying (3)P0 state. Additionally, under UV radiation the material exhibits afterglow luminescence activated by temperature that can also have an impact on the increase of the (1)D2 emission. We propose that the afterglow luminescence is related to the existence of electron traps. At a pressure of 76 kbar the depth of the electron traps decreases in comparison to the ones observed at ambient pressure. However, the phase transition does not change the number of electron traps. PMID:24695003

  9. Ultra high energy density nanocomposite capacitors with fast discharge using Ba0.2Sr0.8TiO3 nanowires.

    PubMed

    Tang, Haixiong; Sodano, Henry A

    2013-04-10

    Nanocomposites combining a high breakdown strength polymer and high dielectric permittivity ceramic filler have shown great potential for pulsed power applications. However, while current nanocomposites improve the dielectric permittivity of the capacitor, the gains come at the expense of the breakdown strength, which limits the ultimate performance of the capacitor. Here, we develop a new synthesis method for the growth of barium strontium titanate nanowires and demonstrate their use in ultra high energy density nanocomposites. This new synthesis process provides a facile approach to the growth of high aspect ratio nanowires with high yield and control over the stoichiometry of the solid solution. The nanowires are grown in the cubic phase with a Ba0.2Sr0.8TiO3 composition and have not been demonstrated prior to this report. The poly(vinylidene fluoride) nanocomposites resulting from this approach have high breakdown strength and high dielectric permittivity which results from the use of high aspect ratio fillers rather than equiaxial particles. The nanocomposites are shown to have an ultra high energy density of 14.86 J/cc at 450 MV/m and provide microsecond discharge time quicker than commercial biaxial oriented polypropylene capacitors. The energy density of our nanocomposites exceeds those reported in the literature for ceramic/polymer composites and is 1138% greater than the reported commercial capacitor with energy density of 1.2 J/cc at 640 MV/m for the current state of the art biaxial oriented polypropylene.

  10. Improving Electrical Properties and Thermal Stability of (Ba,Sr)TiO3 Thin Films on Cu(Mg) Bottom Electrodes

    NASA Astrophysics Data System (ADS)

    Tsai, Kou‑Chiang; Wu, Wen‑Fa; Chao, Chuen‑Guang; Lee, Jain‑Tsai; Shen, Shih‑Wen

    2006-06-01

    Cu(Mg) alloy films have replaced pure Cu as bottom electrodes for (Ba,Sr)TiO3 (BST) capacitors used in high-frequency devices. A combined BST/Cu(Mg) structure reduced the leakage current density to 3.0× 10-8 A/cm2 at 1 MV/cm, and increased the breakdown field from 0.4 to 2.4 MV/cm at 10-6 A/cm2, from the corresponding values of the BST/Cu structure. High-quality characteristics probably follow the formation of a self-aligned MgO layer following the deposition of a Cu(Mg) alloy by annealing in an oxygen ambient, yielding an electrode with an excellent diffusion barrier and electrical characteristics, which is therefore effective in a BST thin-film capacitor. Additionally, the bias temperature stress and time-dependent dielectric breakdown in ambient nitrogen at an electric field of up to 2 V at temperatures between 100 and 200 °C were considered to accelerate Cu+ ion drift.

  11. Dielectric microwave properties of Si-integrated pulsed laser deposited (Ba, Sr)TiO3 thin films up to 110 GHz

    NASA Astrophysics Data System (ADS)

    Ning, Xi; Chen, Shuming; Zhang, Jinying; Huang, Hui; Wang, Lei

    2015-08-01

    Ba0.6Sr0.4TiO3 thin films with a thickness of 339 nm are deposited directly on the high resistivity silicon through pulsed laser deposition. Coplanar waveguides with a slot width of 4.5 μm are designed to extract the complex permittivity of ferroelectric thin film in the frequency range from 1 GHz to 110 GHz. A fast three-dimensional (3D) finite element method (FEM) model is proposed to implement the permittivity extraction based on the propagation-constant matching, i.e., narrowing the difference between measured and simulated propagation-constants by adjusting the changeable permittivity in the fast 3D FEM model. In order to reduce the calculation overhead, the quasi transverse electromagnetic mode and conformal mapping analysis are introduced to realize the adjusting. The relative difference between measured and simulated propagation-constants is defined to describe the precision of the result. Experimental results show that the relative difference is less than 1.1%. The relative dielectric permittivity of BST films equals 332.6 at 1 GHz and reduces to 240.1 at 110 GHz. The loss tangent is about 17.5% at 110 GHz.

  12. Order-disorder in In{sup 3+} perovskites: The example of A(In{sub 2/3}B''{sub 1/3})O{sub 3} (A=Ba, Sr; B''=W, U)

    SciTech Connect

    Larregola, S.A. Alonso, J.A.; Pinacca, R.M.; Viola, M.C.; Pedregosa, J.C.

    2008-10-15

    We describe the preparation and structural characterization of four In-containing perovskites from neutron powder diffraction (NPD) and X-ray powder diffraction (XRPD) data. Sr{sub 3}In{sub 2}B''O{sub 9} and Ba(In{sub 2/3}B''{sub 1/3})O{sub 3} (B''=W, U) were synthesized by standard ceramic procedures. The crystal structure of the W-containing perovskites and Ba(In{sub 2/3}U{sub 1/3})O{sub 3} have been revisited based on our high-resolution NPD and XRPD data, while for the new U-containing perovskite Sr{sub 3}In{sub 2}UO{sub 9} the structural refinement was carried out from high-resolution XRPD data. At room temperature, the crystal structure for the two Sr phases is monoclinic, space group P2{sub 1}/n, where the In atoms occupy two different sites Sr{sub 2}[In]{sub 2d}[In{sub 1/3}B''{sub 2/3}]{sub 2c}O{sub 6}, with a=5.7548(2) A, b=5.7706(2) A, c=8.1432(3) A, {beta}=90.01(1){sup o} for B''=W and a=5.861(1) A, b=5.908(1) A, c=8.315(2) A, {beta}=89.98(1){sup o} for B''=U. The two phases with A=Ba should be described in a simple cubic perovskite unit cell (S.G. Pm3-bar m) with In and B'' distributed at random at the octahedral sites, with a=4.16111(1) A and 4.24941(1) A for W and U compounds, respectively. - Graphical abstract: The structure of the new uranium-based double perovskite Sr{sub 3}In{sub 2}UO{sub 9} is described and the true symmetry of the other title compounds are revisited. The presence of long-range ordering in the Sr samples, by contrast with the Ba perovskites, is related with the smaller unit cell and B-B distances in the Sr oxides, promoting the electrostatic repulsions between highly charged W{sup 6+} and U{sup 6+} cations as driving force for the long-range B-site ordering.

  13. 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.

  14. Magnetron sputter-deposited multilayer (Ba{sub x}Sr{sub 1x})Ti{sub 1+y}O{sub 3+z} thin films for passive and active devices.

    SciTech Connect

    Im, J.; Auciello, O.; Baumann, P. K.; Streiffer, S. K.; Kaufman, D. Y.; Krauss, A. R.

    2001-01-01

    High permittivity (Ba{sub x}Sr{sub 1-x})Ti{sub 1+y}O{sub 3+z}(BST) thin films are being investigated for integration into charge storage dielectrics and electric-field tunable elements for high frequency devices. For the latter application, it is desirable to have BST capacitors with high tunability and low losses. Therefore, we investigated the use of multilayer BST thin films consisting of very low dielectric loss BST/electrode interfacial layers ((Ba+Sr)/Ti = 0.73) sandwiching a high tunability, high permittivity primary BST layer ((Ba+Sr)/Ti = 0.9). BST capacitors with multiple layers of controlled composition can be effectively produced insitu by magnetron sputter deposition, using a single stoichiometric target and controlling the layer composition by changing the total process gas (Ar+O<{sub 2}) pressure. The layered BST film capacitors exhibit simultaneous low loss (tan {Delta} = 0.005), high tunability (76%), high charge storage energy density (34 J/cm{sup 3}), low leakage, and high dielectric breakdown (>2.8 MV/cm).

  15. Modification of energy band alignment and electric properties of Pt/Ba0.6Sr0.4TiO3/Pt thin-film ferroelectric varactors by Ag impurities at interfaces

    NASA Astrophysics Data System (ADS)

    Hirsch, S.; Komissinskiy, P.; Flege, S.; Li, S.; Rachut, K.; Klein, A.; Alff, L.

    2014-06-01

    We report on the effects of Ag impurities at interfaces of parallel-plate Pt/Ba0.6Sr0.4TiO3/Pt thin film ferroelectric varactors. Ag impurities occur at the interfaces due to diffusion of Ag from colloidal silver paint used to attach the varactor samples with their back side to the plate heated at 600-750 °C during deposition of Ba0.6Sr0.4TiO3. X-ray photoelectron spectroscopy and secondary ion mass spectrometry suggest that amount and distribution of Ag adsorbed at the interfaces depend strongly on the adsorbent surface layer. In particular, Ag preferentially accumulates on top of the Pt bottom electrode. The presence of Ag significantly reduces the barrier height between Pt and Ba0.6Sr0.4TiO3 leading to an increased leakage current density and, thus, to a severe degradation of the varactor performance.

  16. Preparation of nanofiber polythiophene layered on Ba x Sr1- x Fe12O19/Fe3O4/polyacrylic acid core-shell structure and its microwave absorption investigation

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Hossein; Moloudi, Maryam

    2015-09-01

    Ba x Sr1- x Fe12O19/Fe3O4/polyacrylic acid/polythiophene (Ba x Sr1- x Fe12O19/Fe3O4/PAA/PTh) nanocomposites with multi-core-shell structure were successfully synthesized by four steps. The samples were characterized by FTIR, X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer, and radar absorbing material reflectivity far-field radar cross-section method, respectively. XRD and TEM results indicated that the obtained nanoparticles have multi-core-shell morphology. The magnetic properties and microwave absorption analyses reveal that there are interphase interactions at the interface of Ba x Sr1- x Fe12O19, Fe3O4, PAA, and PTh, which can affect the magnetic properties and microwave absorption properties of the samples. The microwave-absorbing properties of nanocomposites were investigated at 8-14 GHz. A typical layer absorber exhibited an excellent microwave absorption with a -26 dB maximum absorption at 14 GHz. Compared with core material, the coercivity and saturation magnetization of multi-core-shell nanocomposites decrease obviously, but the microwave absorption properties of nanocomposites are improved greatly. The results show that these composite could be used as advancing absorption and shielding materials due to their favorable microwave-absorbing properties.

  17. Modification of energy band alignment and electric properties of Pt/Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}/Pt thin-film ferroelectric varactors by Ag impurities at interfaces

    SciTech Connect

    Hirsch, S.; Komissinskiy, P. Flege, S.; Li, S.; Rachut, K.; Klein, A.; Alff, L.

    2014-06-28

    We report on the effects of Ag impurities at interfaces of parallel-plate Pt/Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}/Pt thin film ferroelectric varactors. Ag impurities occur at the interfaces due to diffusion of Ag from colloidal silver paint used to attach the varactor samples with their back side to the plate heated at 600–750 °C during deposition of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}. X-ray photoelectron spectroscopy and secondary ion mass spectrometry suggest that amount and distribution of Ag adsorbed at the interfaces depend strongly on the adsorbent surface layer. In particular, Ag preferentially accumulates on top of the Pt bottom electrode. The presence of Ag significantly reduces the barrier height between Pt and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} leading to an increased leakage current density and, thus, to a severe degradation of the varactor performance.

  18. MOCVD growth and characterization of (Ba{sub x}Sr{sub 1{minus}x})Ti{sub 1+y}O{sub 3+z} thin films for high frequency devices

    SciTech Connect

    Baumann, P. K.; Streiffer, S. K.; Im, J.; Baldo, P.; McCormick, A.; Auciello, O.; Kaufman, D. Y.; Erck, R. A.; Giumarra, J.; Zebrowski, J.

    2000-01-18

    The authors have investigated the structural and electrical characteristics of (Ba{sub x}Sr{sub 1{minus}x})Ti{sub 1+y}O{sub 3+z} (BST) thin films. The BST thin films were deposited at 650 C on platinized silicon with good thickness and composition uniformity using a large area, vertical liquid-delivery metalorganic chemical vapor deposition (MOCVD) system. The (Ba+Sr)/Ti ratio of the BST films was varied from 0.96 to 1.05 at a fixed Ba/Sr ratio of 70/30, as determined using x-ray fluorescence spectroscopy (XRF) and Rutherford backscattering spectrometry (RBS). Patterned Pt top electrodes were deposited onto the BST films at 350 C through a shadow mask using electron beam evaporation. Annealing the entire capacitor structure in air at 700 C after deposition of top electrodes resulted in a substantial reduction of the dielectric loss. Useful dielectric tunability as high as 2.3:1 was measured.

  19. In-plane strain modulated magnetization and magnetoelectric effect in La0.7Sr0.3MnO3-BaTiO3 and La0.7Sr0.3MnO3-BaTiO3-BiFeO3 multilayer's

    NASA Astrophysics Data System (ADS)

    Kumar, Virendra; Gaur, Anurag; Chaudhury, Ram Janay; Kumar, Dileep

    2016-10-01

    La0.7Sr0.3MnO3-BaTiO3(LSMO/BTO) and La0.7Sr0.3MnO3-BaTiO3-BiFeO3 (LSMO/BTO/BFO) multilayer thin films are deposited on STO (100) substrate by pulsed laser deposition. In-plane lattice mismatch induced strain is thoroughly investigated with the conclusion, that upper BTO layer of bilayer resides in high strained state, while upper BFO layer of trilayer remains under partially relaxed state. Significantly higher value (∼20) of dielectric constant is observed for LSMO/BTO bilayer in compliance with its higher (12.28 μC/cm2) in-plane strain induced interfacial polarization, which exceeds (2.06 μC/cm2), the observed value of polarization for LSMO/BTO/BFO trilayer. In LSMO/BTO bilayer, antiferromagnetic LSMO phase coexists due to the existence of strong tensile strain between the interfaces, which causes the reduction in value of saturation magnetization up to 50.76 emu/cm3 in comparison to 145.01 emu/cm3 for LSMO/BTO/BFO trilayer. The maximum value of linear magnetoelectric coefficient (α31) observed for LSMO/BTO bilayer is 24.77 mV/cm-Oe, which is higher in comparison to 19.54 mV/cm-Oe for LSMO/BTO/BFO trilayer, where the upper layer undergoes less strain in comparison to the bilayer.

  20. The effect of ionic dissolution products of Ca-Sr-Na-Zn-Si bioactive glass on in vitro cytocompatibility.

    PubMed

    Murphy, S; Wren, A W; Towler, M R; Boyd, D

    2010-10-01

    Many commercial bone grafts cannot regenerate healthy bone in place of diseased bone. Bioactive glasses have received much attention in this regard due to the ability of their ionic dissolution products to promote cell proliferation, cell differentiation and activate gene expression. Through the incorporation of certain ions, bioactive glasses can become therapeutic for specific pathological situations. Calcium-strontium-sodium-zinc-silicate glass bone grafts have been shown to release therapeutic levels of zinc and strontium, however the in vitro compatibility of these materials is yet to be reported. In this study, the in vitro cytocompatibility of three different calcium-strontium-sodium-zinc-silicate glasses was examined as a function of their ion release profiles, using Novabone® bioglass as a commercial comparison. Experimental compositions were shown to release Si(4+) ranging from 1 to 81 ppm over 30 days; comparable or enhanced release in comparison to Novabone. The maximum Ca(2+) release detected for experimental compositions was 9.1 ppm, below that reported to stimulate osteoblasts. Sr(2+) release was within known therapeutic ranges, and Zn(2+) release ranged from 0.5 to 1.4 ppm, below reported cytotoxic levels. All examined glass compositions show equivalent or enhanced in vitro compatibility in comparison to Novabone. Cells exposed to BT112 ionic products showed enhanced cell viabilities indicating cell proliferation was induced. The ion release profiles suggest this effect was due to a synergistic interaction between certain combinations and concentrations of ions. Overall, results indicate that the calcium-strontium-sodium-zinc-silicate glass compositions show equivalent or even enhanced in vitro compatibility compared to Novabone®.

  1. Device loss of (Ba,Sr)TiO3 film-based capacitors at 1-20 GHz

    NASA Astrophysics Data System (ADS)

    Chang, Wontae; Alldredge, L. M. B.; Kirchoefer, Steven W.; Pond, Jeffrey M.

    2009-02-01

    Device loss of BaxSr1-xTiO3 (BST, x =0.5 and 0.6) film-based interdigitated capacitors as a function of frequency (1-20 GHz) at room temperature is observed to range broadly from less than 0.01 to larger than 1 while the commonly observed device losses are around 0.05. Frequency dependence of the device loss tends to be larger for the higher device losses (>0.05) and at the higher frequencies (>10 GHz). The various characteristics of the microwave device loss are examined by analyzing the complex power applied in the devices, P =Pactive+jPreactive, where Pactive is the dissipated power and Preactive is the stored power in the devices. The dissipated power at the devices (Pactive), subsequently resulting in the device loss, e.g., device loss=-Pactive/Preactive, is well fitted with the dissipated powers associated with the dielectric resistance and the electrode resistance (including the conduction and radiation resistances) of the devices.

  2. Microstructural and dielectric properties of Ba{sub 0.6}Sr{sub 0.4}Ti{sub 1-x}Zr{sub x}O{sub 3} based combinatorial thin film capacitors library

    SciTech Connect

    Liu Guozhen; Wolfman, Jerome; Autret-Lambert, Cecile; Sakai, Joe; Roger, Sylvain; Gervais, Monique; Gervais, Francois

    2010-12-01

    Epitaxial growth of Ba{sub 0.6}Sr{sub 0.4}Ti{sub 1-x}Zr{sub x}O{sub 3} (0{<=}x{<=}0.3) composition spread thin film library on SrRuO{sub 3}/SrTiO{sub 3} layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties.

  3. Magnetic properties, exchange coupling and novel stripe domains in bulk SrFe12O19/(Ni,Zn)Fe2O4 composites

    NASA Astrophysics Data System (ADS)

    Xia, Ailin; Zuo, Conghua; Zhang, Lijiao; Cao, Chunxiang; Deng, Yong; Xu, Wei; Xie, Mingfu; Ran, Songlin; Jin, Chuangui; Liu, Xianguo

    2014-10-01

    Bulk SrFe12O19/(Ni0.4Zn0.6)Fe2O4 composite ferrites with mass ratios Rm = 2 : 1, 1 : 1 and 1 : 2 were prepared using nanopowders obtained via a hydrothermal method, and their phase composition, magnetic properties, exchange coupling (EC) and magnetic microstructures were systematically investigated. It is found that all the bulk specimens sintered at either 700 or 900 °C are composed of two phases but exhibit typical single-phase magnetic behaviours, indicating the existence of EC between the magnetically hard and soft phases. However, too much (Rm = 2 : 1) or too little (Rm = 1 : 2) soft (Ni0.4Zn0.6)Fe2O4 phase weakens the EC in the composites. It is also proved that except for the EC, the strengthening of chemical polarization of the internal chemical bonds affects saturation magnetization, and the size of nanoscale grains significantly influences the EC and magnetic properties. In addition, novel stripe domains are found in all of the bulk composite specimens, which could be ascribed to the magnetization of the soft (Ni,Zn)Fe2O4 phase induced by the hard SrFe12O19 phase.

  4. 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)} (0.77Ba. 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

  5. Natural speciation of Ni, Zn, Ba, and As in ferromanganese coatings on quartz using X-ray fluorescence, absorption, and diffraction

    NASA Astrophysics Data System (ADS)

    Manceau, Alain; Lanson, Martine; Geoffroy, Nicolas

    2007-01-01

    The mineralogy of natural ferromanganese coatings on quartz grains and the crystal chemistry of associated trace elements Ni, Zn, Ba, and As were characterized by X-ray microfluorescence, X-ray diffraction, and EXAFS spectroscopy. Fe is speciated as ferrihydrite and Mn as vernadite. The two oxides form alternating Fe- and Mn-rich layers that are irregularly distributed and not always continuous. Unlike naturally abundant Fe-vernadite, in which Fe and Mn are mixed at the nanoscale, the ferrihydrite and vernadite are physically segregated and the trace elements clearly partitioned at the microscopic scale. Vernadite consists of two populations of interstratified one-water layer (7 Å phyllomanganate) and two-water layer (10 Å phyllomanganate) crystallites. In one population, 7 Å layers dominate, and in the other 10 Å layers dominate. The three trace metals Ni, Zn, and Ba are associated with vernadite and the metalloid As with ferrihydrite. In vernadite, nickel is both substituted isomorphically for Mn in the manganese layer and sorbed at vacant Mn layer sites in the interlayer. The partitioning of Ni is pH-dependent, with a strong preference for the first site at circumneutral pH and for the second at acidic pH. Thus, the site occupancy of Ni in vernadite may be an indicator of marine vs. continental origin, and in the latter, of the acidity of streams, lakes, or soil pore waters in which the vernadite formed. Zinc is sorbed only in the interlayer at vacant Mn layer sites. It is fully tetrahedral at a Zn/Mn molar ratio of 0.0138, and partly octahedral at a Zn/Mn ratio of 0.1036 consistent with experimental studies showing that the VIZn/ IVZn ratio increases with Zn loading. Barium is sorbed in a slightly offset position above empty tetrahedral cavities in the interlayer. Arsenic tetrahedra are retained at the ferrihydrite surface by a bidentate-binuclear attachment to two adjacent iron octahedra, as commonly observed. Trace elements in ferromanganese precipitates

  6. Growth of transparent Zn1 - xSrxO (0.0 ≤ x ≤ 0.08) films by facile wet chemical method: Effect of Sr doping on the structural, optical and sensing properties

    NASA Astrophysics Data System (ADS)

    Rana, Amit Kumar; Das, Rajasree; Kumar, Yogendra; Sen, Somaditya; Shirage, Parasharam M.

    2016-08-01

    Zn1 - xSrxO (0.0 ≤ x ≤ 0.08) nano-rods thin films are prepared using simple wet chemical technique on transparent flexible substrate. Effect of Sr-doping on structural and optical properties of ZnO is systematically investigated. SEM and TEM confirm the nano-rods like morphology with single crystalline nature of all the samples. Rietveld refinement of XRD shows the samples belongs to P63mc space group, furthermore, a gradual increment in lattice parameters and change in Zn/oxygen occupancy ratio is observed with Sr doping. SIMS and XPS confirm the doping of Sr in the ZnO nanostructures. XPS measurements shows that increase in Sr doping creates more oxygen associated defects, which is further supported by the photoluminescence spectra indicating the gradual change in Zn vacancy (Vzn) and oxygen interstitial (Oin) point defect intensities in the films. Near band edge emission peak shows to shift toward higher wavelength in the doped films. Pure ZnO film shows Raman peaks around 99 (E2low), 333 (E2high - E2low) , 382 (A1 (TO)), 438 (E2high) and 582 (A1 (LO) +E1 (TO)) cm-1, whereas two additional defect driven vibrational modes (at 277 and 663 cm-1) are appeared in the Sr-doped films. The sensing property of the ZnO is enhanced by Sr doping and replicates as a promising material for future toxic and flammable gas sensor applications as well as for opto-electronic devices.

  7. Sintering of BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) with/without SrTiO3 Dopant

    NASA Technical Reports Server (NTRS)

    Dynys, F.; Sayir, A.; Heimann, P. J.

    2004-01-01

    The perovskite composition, BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta), displays excellent protonic conduction at high temperatures making it a desirable candidate for hydrogen separation membranes. This paper reports on the sintering behavior of BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) powders doped with SrTiO3. Two methods were used to synthesize BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) powders: (1) solid state reaction and (2) wet chemical co-precipitation. Co-precipitated powder crystallized into the perovskite phase at 1000 C for 4 hrs. Complete reaction and crystallization of the perovskite phase by solid state was achieved by calcining at 1200 C for 24 hrs. Solid state synthesis produced a coarser powder with an average particle size of 1.3 microns and surface area of 0.74 sq m/g. Co-precipitation produced a finer powder with a average particle size of 65 nm and surface area of 14.9 sq m/g. Powders were doped with 1, 2, 5, and 10 mole % SrTiO3. Samples were sintered at 1450 C, 1550 C and 1650 C. SrTiO3 enhances sintering, optimal dopant level is different for powders synthesized by solid state and co-precipitation. Both powders exhibit similar grain growth behavior. Dopant levels of 5 and 10 mole % SrTiO3 significantly enhances the grain size.

  8. Growth and characterizations of nonpolar [1 1 -2 0] ZnO on [1 0 0] (La,Sr)(Al,Ta)O 3 substrate by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chou, Mitch M. C.; Hang, Da-Ren; Chuan Wang, Shih; Chen, Chenlong; Lee, Chun-Yu

    2010-04-01

    Nonpolar a-plane ZnO film with [1 1 -2 0] orientation was grown on a nearly lattice-matched [1 0 0] (La 0.3,Sr 0.7)(Al 0.65,Ta 0.35)O 3 (LSAT) substrate from a simple chemical vapor deposition method. LSAT single crystal was grown by the Czochralski method. The dependence of growth characteristics on the growth temperatures and reactor's pressures was investigated. The surface morphologies of ZnO films were studied by a scanning electron microscope. The sample orientations were identified by X-ray diffraction pattern and transmission electron microscope. Optical properties examined by room temperature photoluminescence spectra exhibit a strong near-band-edge emission peak at 378.6 nm and a negligible green band.

  9. Fabrication of c-axis Oriented Epitaxial EuBa2Cu3O7-δ and EuBa2Cu4O8 Films on SrTiO3 (100) Substrate by Molten Hydroxide Method at 450°C

    NASA Astrophysics Data System (ADS)

    Miyachi, Y.; Funaki, S.; Yamada, Y.

    EuBa2Cu3O7-δ (Eu123) and EuBa2Cu4O8 (Eu124) films oriented in c-axis were deposited on SrTiO3 (100) substrates with eutectic NaOH-KOH flux at 450 °C. Synthesized phase has changed by using various types of barium source materials. Pure Eu124 films showed superconducting transition at ∼70 K, zero-resistance was not observed for Eu123/124 two-phase films. One of the possible reasons of this is Eu/Ba substitution of Eu123 phase. According to Tc of the Eu124, the molten hydroxide method enables to deposit high-quality Eu124 films.

  10. High-pressure transitions and thermochemistry of MGeO3 ( M=Mg, Zn and Sr) and Sr-silicates: systematics in enthalpies of formation of A2+B4+O3 perovskites

    NASA Astrophysics Data System (ADS)

    Akaogi, M.; Kojitani, H.; Yusa, H.; Yamamoto, R.; Kido, M.; Koyama, K.

    2005-12-01

    Phase transitions in MgGeO3 and ZnGeO3 were examined up to 26 GPa and 2,073 K to determine ilmenite-perovskite transition boundaries. In both systems, the perovskite phases were converted to lithium niobate structure on release of pressure. The ilmenite-perovskite boundaries have negative slopes and are expressed as P(GPa)=38.4-0.0082 T(K) and P(GPa)=27.4-0.0032 T(K), respectively, for MgGeO3 and ZnGeO3. Enthalpies of SrGeO3 polymorphs were measured by high-temperature calorimetry. The enthalpies of SrGeO3 pseudowollasonite-walstromite and walstromite-perovskite transitions at 298 K were determined to be 6.0±8.6 and 48.9±5.8 kJ/mol, respectively. The calculated transition boundaries of SrGeO3, using the measured enthalpy data, were consistent with the boundaries determined by previous high-pressure experiments. Enthalpy of formation (Δ H f°) of SrGeO3 perovskite from the constituent oxides at 298 K was determined to be -73.6±5.6 kJ/mol by calorimetric measurements. Thermodynamic analysis of the ilmenite-perovskite transition boundaries in MgGeO3 and ZnGeO3 and the boundary of formation of SrSiO3 perovskite provided transition enthalpies that were used to estimate enthalpies of formation of the perovskites. The Δ H f° of MgGeO3, ZnGeO3 and SrSiO3 perovskites from constituent oxides were 10.2±4.5, 33.8±7.2 and -3.0±2.2 kJ/mol, respectively. The present data on enthalpies of formation of the above high-pressure perovskites were combined with published data for A2+B4+O3 perovskites stable at both atmospheric and high pressures to explore the relationship between Δ H f° and ionic radii of eightfold coordinated A2+ ( R A) and sixfold coordinated B4+ ( R B) cations. The results show that enthalpy of formation of A2+B4+O3 perovskite increases with decreasing R A and R B. The relationship between the enthalpy of formation and tolerance factor ( t = {left( {R_{{text{A}}} + R_{{text{o}}} } right)}/{sqrt {text{2}} }{left( {R_{{text{B}}} + R_{{text{o}}} } right)}, R

  11. Formation of solar cells based on Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) ferroelectric thick film

    SciTech Connect

    Irzaman, Syafutra, H. Arif, A. Alatas, H.; Hilaluddin, M. N.; Kurniawan, A.; Iskandar, J.; Dahrul, M.; Ismangil, A.; Yosman, D.; Aminullah; Prasetyo, L. B.; Yusuf, A.; Kadri, T. M.

    2014-02-24

    Growth of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) 1 M thick films are conducted with variation of annealing hold time of 8 hours, 15 hours, 22 hours, and 29 hours at a constant temperature of 850 °C on p-type Si (100) substrate using sol-gel method then followed by spin coating process at 3000 rpm for 30 seconds. The BST thick film electrical conductivity is obtained to be 10{sup −5} to 10{sup −4} S/cm indicate that the BST thick film is classified as semiconductor material. The semiconductor energy band gap value of BST thick film based on annealing hold time of 8 hours, 15 hours, 22 hours, and 29 hours are 2.58 eV, 3.15 eV, 3.2 eV and 2.62 eV, respectively. The I-V photovoltaic characterization shows that the BST thick film is potentially solar cell device, and in accordance to annealing hold time of 8 hours, 15 hours, 22 hours and 29 hours have respective solar cell energy conversion efficiencies of 0.343%, 0.399%, 0.469% and 0.374%, respectively. Optical spectroscopy shows that BST thick film solar cells with annealing hold time of 8 hours, 15 hours, and 22 hours absorb effectively light energy at wavelength of ≥ 700 nm. BST film samples with annealing hold time of 29 hours absorb effectively light energy at wavelength of ≤ 700 nm. The BST thick film refraction index is between 1.1 to 1.8 at light wavelength between ±370 to 870 nm.

  12. Scanning Tunneling Microscopy Studies of Charge Density Waves in NbSe2 and muSR studies of Nickel doping in BaFe2As 2

    NASA Astrophysics Data System (ADS)

    Arguello Ortiz, Carlos Jose

    Scanning Tunneling Microscopy is a very powerful technique to study electronic properties of condensed matter systems at the nanoscale. Part I of this thesis describes my work on Charge Density Waves (CDW) in NbSe2. NbSe2 is a layered dichalcogenide that has a CDW phase below 33K. We describe our study of the phase transition from the normal phase to the CDW phase at atomic scales. This is more relevant in light of recent discoveries of charge order in cuprates. Brand new research has shed some light about the relationship between the pseudogap phase, charge order and superconductivity in cuprates. The behavior of the CDW phase in NbSe 2 described in chapter 3 is strongly reminiscent of this physics of cuprates. NbSe2 is an excellent test bed for the study of the effect of impurities in correlated phases. In chapter 4 we revisit the cause of CDW formation in NbSe2. By including a very dilute concentration of impurities, we obtain information of the electronic bands of the material in the CDW phase. Based on this information, we are able to discuss the relationship between nesting, electron-phonon coupling and CDW in NbSe2. We demonstrate that by combining quasiparticle interference data with additional knowledge of the quasiparticle band structure from angle resolved photoemission measurements, one can extract the wavevector and energy dependence of the important electronic scattering processes. Part II focuses on Muon Spin Rotation and its application to the study of high-Tc superconductors. We describe our muSR studies on Nickel doped BaFe 2As2. By analyzing several doping concentrations, we explore the phase diagram in the antiferromagnetic and in the superconducting phases. This discussion also includes a detailed discussion of a doping concentration which falls in-between the AF and the SC phase.

  13. Preparation Process and Dielectric Properties of Ba(0.5)Sr(0.5)TiO3-P(VDF-CTFE) Nanocomposites

    NASA Technical Reports Server (NTRS)

    Zhang, Lin; Wu, Peixuang; Li, Yongtang; Cheng, Z. -Y.; Brewer, Jeffrey C.

    2014-01-01

    Ceramic-polymer 0-3 nanocomposites, in which nanosized Ba(0.5)Sr(0.5)TiO3 (BST) powders were used as ceramic filler and P(VDF-CTFE) 88/12 mol% [poly(vinylidene fluoridechlorotrifluoroethylene)] copolymer was used as matrix, were studied over a concentration range from 0 to 50 vol.% of BST powders. It is found that the solution cast composites are porous and a hot-press process can eliminate the porosity, which results in a dense composite film. Two different configurations used in the hot-press process are studied. Although there is no clear difference in the uniformity and microstructure of the composites prepared using these two configurations, the composite prepared using one configuration exhibit a higher dielectric constant with a lower loss. For the composite with 40 vol. BST, a dielectric constant of 70 with a loss of 0.07 at 1 kHz is obtained at room temperature. The composites exhibit a lower dielectric loss than the polymer matrix at high frequency. However, at low frequency, the composites exhibit a higher loss than the polymer matrix due to a low frequency relaxation process that appears in the composites. It is believed that this relaxation process is related to the interfacial layer formed between BST particle and the polymer matrix. The temperature dependence of the dielectric property of the composites was studied. It is found that the dielectric constant of these composites is almost independent of the temperature over a temperature range from 20 to 120 C. Key words: A. Polymer-matrix composites (PMCs); B. Electrical Properties; E. Casting; E. Heat treatment; Dielectric properties.

  14. Single Variable and Multivariate Analysis of Remote Laser-Induced Breakdown Spectra for Prediction of Rb, Sr, Cr, Ba, and V in Igneous Rocks

    SciTech Connect

    Clegg, Samuel M; Wiens, Roger C.; Speicher, Elly A; Dyar, Melinda D; Carmosino, Marco L

    2010-12-23

    Laser-induced breakdown spectroscopy (LIBS) will be employed by the ChemCam instrument on the Mars Science Laboratory rover Curiosity to obtain UV, VIS, and VNIR atomic emission spectra of surface rocks and soils. LIBS quantitative analysis is complicated by chemical matrix effects related to abundances of neutral and ionized species in the resultant plasma, collisional interactions within plasma, laser-to-sample coupling efficiency, and self-absorption. Atmospheric composition and pressure also influence the intensity of LIBS plasma. These chemical matrix effects influence the ratio of intensity or area of a given emission line to the abundance of the element producing that line. To compensate for these complications, multivariate techniques, specifically partial least-squares regression (PLS), have been utilized to predict major element compositions (>1 wt.% oxide) of rocks, PLS methods regress one or multiple response variables (elemental concentrations) against multiple explanatory variables (intensity at each pixel of the spectrometers). Because PLS utilizes all available explanatory variable and eliminates multicollinearity, it generally performs better than univariate methods for prediction of major elements. However, peaks arising from emissions from trace elements may be masked by peaks of higher intensities from major elements. Thus in PLS regression, wherein a correlation coefficient is determined for each elemental concentration at each spectrometer pixel, trace elements may show high correlation with more intense lines resulting from optical emissions of other elements. This could result in error in predictions of trace element concentrations. Here, results of simple linear regression (SLR) and multivariate PLS-2 regression for determination of trace Rb, Sr, Cr, Ba, and V in igneous rock samples are compared. This study focuses on comparisons using only line intensities rather than peak areas to highlight differences between SLR and PLS.

  15. The impedance spectroscopic study and dielectric relaxation in A(Ni1/3Ta2/3)O3 [A=Ba, Ca and Sr

    NASA Astrophysics Data System (ADS)

    Hoque, Md M.; Dutta, A.; Kumar, S.; Sinha, T. P.

    2012-09-01

    We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni1/3Ta2/3)O3 (BNT), Calcium Nickel Tantalate Ca(Ni1/3Ta2/3)O3 (CNT) and Strontium Nickel Tantalate Sr(Ni1/3Ta2/3)O3 (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 Å and 3.98 Å respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 Å, b=13.45 Å and c=5.47 Å with β=118.3°. The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole-Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan δ/tan δm and M″/M″m versus log ω for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

  16. Tuning the optical, electrical and magnetic properties of Ba(0.5)Sr(0.5)Ti(x)M(1-x)O3 (BST) nanopowders.

    PubMed

    Turky, Ali Omar; Rashad, Mohamed Mohamed; Kandil, Abd El-Hakim Taha; Bechelany, Mikhael

    2015-05-21

    Metal doped barium strontium titanate (BST; Ba0.5Sr0.5TixM1-xO3) nanopowders have been successfully synthesized through the oxalate precursor route based on low cost starting materials. The effect of metal ion substitution, namely Fe(3+), Mn(2+), Co(2+) and Y(3+), on the crystal structure, microstructure and optical, electrical, dielectric and magnetic properties of BST was studied. The results revealed that a crystalline single cubic BST phase was formed for pure and Mn(2+), Co(2+) and Y(3+) ion-substituted BST samples, whereas a tetragonal BST structure was obtained for the Fe(3+) substituted BST sample at an annealing temperature of 1000 °C for 2 h. Furthermore, addition of the metal ions was found to decrease the crystallite size and unit cell volume of the produced BST phase. The microstructure of the produced pure BST phase was metal ion dependent. Most BST particles appeared as a cubic like structure. The transparency of BST was found to increase with metal substitution. Meanwhile, the band gap energy was increased from 3.4 eV for pure BST to 3.8, 4.1, 4.2 and 4.3 eV as the result of substitution by Fe(3+), Mn(2+) and Co(2+) and Y(3+) ions, respectively. The DC resistivity was metal ion dependent. The highest DC resistivity (ρ = 66.60 × 10(5) Ω cm) was accomplished with the Mn(2+) ion. Moreover, the addition of metal ions decreased the dielectric properties of the expected Mn(2+) ion and increased the magnetic properties.

  17. Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-02-07

    We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H2O)n]2+, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M2+(H2O)n-1 + H2O) and the two hydrolysis channels resulting to the loss of hydronium ([MOH(H2O)n-2]+ + H3O+) and Zundel ([MOH(H2O)n-3]+ + H3O+(H2O)) cations. The Potential Energy Curves (PECs) corresponding to those three channels were constructed at the Møller-Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H2O)n]+, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.

  18. La doped Ba{sub 1{minus}x}Sr{sub x}TiO{sub 3} thin films for tunable device applications

    SciTech Connect

    Cole, M. W.; Joshi, P. C.; Ervin, M. H.

    2001-06-01

    Pure and La doped Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} thin (BST) films were fabricated via the metalorganic solution deposition technique using carboxylate-alkoxide precursors on Pt{endash}Si substrates. The La doping concentration, from 0 to 10 mol%, was found to have a strong influence on the 750{degree}C postdeposition annealed films material properties. All films possessed a nontextured polycrystalline microstructure with no evidence of secondary phase formation. The pure and 1 mol% La doped films exhibited a uniform microstructure suggestive of a fully developed film at this annealing temperature. Improved dielectric and insulating properties were achieved for the 1 mol% La doped BST thin films with respect to that of undoped BST films. The 1 mol% La doped BST film exhibited a lower dielectric constant, (283 vs 450) and enhanced resistivity (31.4{times}10{sup 13}{Omega}cm vs 0.04{times}10{sup 13}{Omega}cm) with respect to that of undoped BST films. The loss tangent and tunability (at 100 kHz) of the 1 mol% La doped BST films were 0.019% and 21% (at E=300kV/cm), respectively. Films doped at concentrations between 5 and 10 mol% possessed under developed microstructures suggesting that higher annealing temperatures and/or longer annealing times are required. The single phase structure of the 5{endash}10 mol% La doped BST films, combined with the beneficial influence of the 1 mol% La doping on the BST films dielectric and insulating properties, suggest potential for further enhancement of the films material properties after optimization of the thermal treatments for the 5{endash}10 mol% La doped BST thin films.

  19. Validity and limitations of the superexchange model for the magnetic properties of Sr2IrO4 and Ba2IrO4 mediated by the strong spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Solovyev, I. V.; Mazurenko, V. V.; Katanin, A. A.

    2015-12-01

    Layered perovskites Sr2IrO4 and Ba2IrO4 are regarded as the key materials for understanding the properties of magnetic relativistic insulators, mediated by the strong spin-orbit (SO) coupling. One of the most fundamental issues is to which extent these properties can be described by the superexchange (SE) model, formulated in the limit of the large Coulomb repulsion for some appropriately selected pseudospin states, and whether these materials themselves can be classified as Mott insulators. In this work, we address these issues by deriving the relevant models and extracting parameters of these models from the electronic-structure calculations with the SO coupling, based on the density functional theory. First, we construct the effective Hubbard-type model for the magnetically active t2 g bands, by recasting the problem in the language of localized Wannier orbitals. Then, we map the obtained electron model onto the pseudospin model by applying the theory of SE interactions, which is based on the second-order perturbation theory with respect to the transfer integrals. We discuss the microscopic origin of anisotropic SE interactions, inherent to the compass Heisenberg model, and the appearance of the antisymmetric Dzyaloshinskii-Moriya term, associated with the additional rotation of the IrO6 octahedra in Sr2IrO4 . In order to solve the pseudospin Hamiltonian problem and evaluate the Néel temperature (TN), we employ the nonlinear sigma model. We have found that, while for Sr2IrO4 our value of TN agrees with the experimental data, for Ba2IrO4 it is overestimated by a factor of 2. We argue that this discrepancy is related to limitations of the SE model: while for more localized t2 g states in Sr2IrO4 it works reasonably well, the higher-order terms in the perturbation theory expansion play a more important role in the more "itinerant" Ba2IrO4 , giving rise to the new type of isotropic and anisotropic exchange interactions, which are not captured by the SE model. This

  20. Crystal Structures of the Trifluoromethyl Sulfonates M(SO3CF3)2 (M = Mg, Ca, Ba, Zn, Cu) from Synchrotron X-ray Powder Diffraction Data

    SciTech Connect

    Dinnebier,R.; Sofina, N.; Hildebrandt, L.; Jansen, M.

    2006-01-01

    The crystal structures of divalent metal salts of trifluoromethyl sulfonic acid ('trifluoromethyl sulfonates') M(SO{sub 3}CF{sub 3}){sub 2} (M = Mg, Ca, Ba, Zn, Cu) were determined from high-resolution X-ray powder diffraction data. Magnesium, calcium and zinc trifluoromethyl sulfonate crystallize in the rhombohedral space group R{bar 3}. Barium trifluoromethyl sulfonate crystallizes in the monoclinic space group I2/a(C2/c) and copper trifluoromethyl sulfonate crystallizes in the triclinic group P{bar 1}. Within the crystal structures the trifluoromethyl sulfonate anions are arranged in double layers with the apolar CF{sub 3} groups pointing towards each other. The cations are located next to the SO{sub 3} groups. The symmetry relations between the different crystal structures have been analyzed.

  1. Synthesis, persistent luminescence, and thermoluminescence properties of yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce, Nd, Dy, Ho, Er, Tm, Yb) and orange-red Sr(3-x)Ba(x)SiO5:Eu2+, Dy3+ phosphor.

    PubMed

    Li, Ye; Li, Baohong; Ni, Chenchen; Yuan, Shuxia; Wang, Jing; Tang, Qiang; Su, Qiang

    2014-02-01

    Sunlight-excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange-red Sr3-xBaxSiO5:Eu(2+),Dy(3+) persistent luminescence phosphor was successfully developed by a two-step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non-equivalent trivalent rare earth co-dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu(2+) in Sr3SiO5 was significantly modified. The yellow persistent emission intensity of Eu(2+) was greatly enhanced by a factor of 4.5 in Sr3SiO5:Eu(2+),Nd(3+) compared with the previously reported Sr3SiO5:Eu(2+), Dy(3+). Furthermore, Sr ions were replaced with equivalent Ba to give Sr3-xBaxSiO5 :Eu(2+),Dy(3+) phosphor, which shows yellow-to-orange-red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu(2+) is significantly improved by a factor of 2.7 in Sr3-xBaxSiO5 :Eu(2+),Dy(3+) (x=0.2) compared with Sr3SiO5 :Eu(2+),Dy(3+). A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu(2+) in Sr3-xBaxSiO5:Eu(2+),RE(3+) (RE=rare earth) is also proposed and discussed.

  2. 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.

  3. Theoretical and Experimental Study on Thermoelectric Properties of Ba8TM x Ga y Ge46- x- y (TM = Zn, Cu, Ag) Type I Clathrates

    NASA Astrophysics Data System (ADS)

    Leszczynski, Juliusz; Kolezynski, Andrzej; Juraszek, Jarosław; Wojciechowski, Krzysztof

    2016-10-01

    In the type I clathrates Ba8TM x Ga y Ge46- x- y (TM = group 10 to 12 elements) where some of the Ge framework atoms are substituted by Zn, Cu or Ag, the transition-metal elements prefer to occupy the 6 c site. Preliminary band-structure calculations showed that this substitution implies modification of the electronic bands in the vicinity of the energy gap. By appropriate tailoring of the band structure, improved thermoelectric properties can be obtained. More detailed full-potential linearized augmented plane wave (FP-LAPW) method calculations within density functional theory (DFT) were performed using the WIEN2k package for compositions where the transition element TM fully occupies the 6 c site. Additional analysis of the properties of the electron density topology within Bader's atoms-in-molecules approach was carried out to study the chemical bonding in intermetallic clathrates. To verify the theoretical predictions, polycrystalline samples of the type I clathrates Ba8TM x Ga y Ge46- x- y (TM = Zn, Cu, Ag) modified by transition-metal element substitution for Ge were obtained. The samples were characterized using powder x-ray diffraction analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. The electrical conductivity, Seebeck coefficient, and thermal conductivity were measured in the temperature range from 320 K to 720 K. Several models were used to fit the experimental results for the electronic transport properties and to estimate the energy gap. Vacancies at the Ge site were considered responsible for deviations from the desired properties, and appropriate defect equations correlating the vacancies and TM concentration are presented. Finally, the results of DFT calculations are compared with the experiments, showing good agreement with theoretically predicted cell parameters and general observations of the transport properties.

  4. Theoretical and Experimental Study on Thermoelectric Properties of Ba8TM x Ga y Ge46-x-y (TM = Zn, Cu, Ag) Type I Clathrates

    NASA Astrophysics Data System (ADS)

    Leszczynski, Juliusz; Kolezynski, Andrzej; Juraszek, Jarosław; Wojciechowski, Krzysztof

    2016-06-01

    In the type I clathrates Ba8TM x Ga y Ge46-x-y (TM = group 10 to 12 elements) where some of the Ge framework atoms are substituted by Zn, Cu or Ag, the transition-metal elements prefer to occupy the 6c site. Preliminary band-structure calculations showed that this substitution implies modification of the electronic bands in the vicinity of the energy gap. By appropriate tailoring of the band structure, improved thermoelectric properties can be obtained. More detailed full-potential linearized augmented plane wave (FP-LAPW) method calculations within density functional theory (DFT) were performed using the WIEN2k package for compositions where the transition element TM fully occupies the 6c site. Additional analysis of the properties of the electron density topology within Bader's atoms-in-molecules approach was carried out to study the chemical bonding in intermetallic clathrates. To verify the theoretical predictions, polycrystalline samples of the type I clathrates Ba8TM x Ga y Ge46-x-y (TM = Zn, Cu, Ag) modified by transition-metal element substitution for Ge were obtained. The samples were characterized using powder x-ray diffraction analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. The electrical conductivity, Seebeck coefficient, and thermal conductivity were measured in the temperature range from 320 K to 720 K. Several models were used to fit the experimental results for the electronic transport properties and to estimate the energy gap. Vacancies at the Ge site were considered responsible for deviations from the desired properties, and appropriate defect equations correlating the vacancies and TM concentration are presented. Finally, the results of DFT calculations are compared with the experiments, showing good agreement with theoretically predicted cell parameters and general observations of the transport properties.

  5. Mechanism and stability of spectrally pure green up-conversion emission in Yb(3+)/Ho(3+) co-doped Ba5Gd8Zn4O21 phosphors.

    PubMed

    Suo, Hao; Guo, Chongfeng; Wang, Wenbin; Li, Ting; Duan, Changkui; Yin, Min

    2016-02-14

    A series of green-emitting up-conversion (UC) phosphors Ba5Gd8Zn4O21:Yb(3+),Ho(3+) were prepared by a modified sol-gel method, and X-ray diffraction (XRD) patterns were measured to characterize the crystal structure. The obtained UC samples emit dazzling green light and their spectra are composed of strong green emission peaking at 544 nm and negligible red emission peaking at 666 nm with the excitation of a 980 nm near-infrared (NIR) laser diode, assigned to (5)F4/(5)S2 → (5)I8 and (5)F5 → (5)I8 transitions of Ho(3+), respectively. The dependence of UC spectra on dopant contents, temperature and pumping power was employed to analyze UC emission color stability. The possible UC mechanisms and processes were proposed based on dependence of the UC emission intensity on pump power, and the lifetimes of green emission ((5)F4/(5)S2 → (5)I8) were also investigated to better comprehend the energy transfer (ET) process. The origin of spectrally pure green-emitting was discussed in detail by analyzing UC and down-conversion (DC) spectra in both the visible and NIR region by comparing that of the UC phosphor CaIn2O4:Yb(3+)/Ho(3+) with highly efficient green emission. Results suggest that Ba5Gd8Zn4O21:Yb(3+),Ho(3+) phosphors with intense green emission and high color purity have potential applications in displays and illuminating technology.

  6. Observation of superconductivity ( Tc = 50 K) in a new tetragonal alkaline-earth cuprate Sr 0.8Ba 1.2CuO 3+δ, synthesised at ambient pressure

    NASA Astrophysics Data System (ADS)

    Hodges, J. P.; Slater, P. R.; Edwards, P. P.; Greaves, C.; Slaski, M.; Van Tendeloo, G.; Amelinckx, S.

    1996-02-01

    The ambient-pressure synthesis of a new tetragonal alkaline-earth superconducting cuprate, Sr 0.8Ba 1.2CuO 3+δ, from a cupro-oxycarbonate is reported. Magnetic-susceptibility measurements show the presence of a superconducting transition ˜50 K in a post-annealed sample. The crystal structure, refined from time-of-flight powder neutron-diffraction data was found to have an oxygen-deficient La 2CuO 4-type tetragonal T structure ( a = 3.8988(3) Å and c = 12.815(3) Å) with oxygen vacancies located within the CuO 2 planes. Ordering of these oxygen vacancies is responsible for the observation of a superlattice in both neutron- and electron-diffraction measurements. An interpretation of the electron-diffraction patterns suggests that the superlattice in Sr 0.8Ba 1.2CuO 3+δ and also in the isostructural superconductor Sr 2CuO 3+δ are of an identical nature.

  7. Origin of the Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska: Evidence from regional Pb and Sr isotope sources

    USGS Publications Warehouse

    Ayuso, R.A.; Kelley, K.D.; Leach, D.L.; Young, L.E.; Slack, J.F.; Wandless, G.; Lyon, A.M.; Dillingham, J.L.

    2004-01-01

    Pb and Sr isotope data were obtained on the shale-hosted Zn-Pb-Ag Red Dog deposits (Qanaiyaq, Main, Aqqaluk, and Paalaaq), other shale-hosted deposits near Red Dog, and Zn-Pb-Ag sulfide and barite deposits in the western and central Brooks Range. The Red Dog deposits and other shale-hosted Zn-Pb-Ag deposits near Red Dog are hosted in the Mississippian Kuna Formation, which is underlain by a sequence of marine-deltaic clastic rocks of the Upper Devonian to Lower Mississippian Endicott Group. Ag-Pb-Zn vein-breccias are found in the Endicott Group. Galena formed during the main mineralization stages in the Red Dog deposits and from the Anarraaq and Wulik deposits have overlapping Pb isotope compositions in the range 206Pb/204Pb = 18.364 to 18.428, 207Pb/204Pb = 15.553 to 15.621, and 208Pb/204Pb = 38.083 to 38.323. Galena and sphalerite formed during the main ore-forming stages in the Red Dog deposits define a narrow field on standard uranogenic and thorogenic Pb isotope diagrams. Lead in sulfides of the Red Dog district is less radiogenic (238U/204Pb: ?? = 9.51-9.77) than is indicated by the average crustal lead evolution model (?? = 9.74), a difference consistent with a long history of evolution at low ratios of ?? before the Carboniferous. The homogeneous regional isotopic reservoir of Pb may indicate large-scale transport and leaching of minerals with various ?? ratios and Th/Pb ratios. Younger and genetically unrelated fluids did not significantly disturb the isotopic compositions of galena and sphalerite after the main mineralization event in the Red Dog district. Some pyrite shows evidence of minor Pb remobilization. The overall lead isotope homogeneity in the shale-hosted massive sulfide deposits is consistent with three types of control: a homogeneous regional source, mixing of lead during leaching of a thick sedimentary section and fluid transport, or mixing at the site of deposition. Isotopic variability of the hydrothermal fluids, as represented by galena

  8. Photoluminescence and phosphorescence properties of SrZn(PO):Eux2+,Mny2+ phosphor for UV-based white-LEDs

    NASA Astrophysics Data System (ADS)

    Jeong, Junho; Jayasimhadri, M.; Sueb Lee, Ho; Jang, Kiwan; Soo Yi, Soung; Hyun Jeong, Jung; Kim, Changdae

    2009-07-01

    SrZn(PO)2:Eux2+,Mny2+ (SZP: Eux2+, Mny2+) phosphors ( x=0, 0.01 and y=0, 0.01) were prepared by using a stoichiometric solid-state reaction method and their photoluminescence and phosphorescence decay properties were investigated. The emission spectrum of SrZn 2(PO 4) 2: Eu0.012+, Mn0.012+ measured under 400 nm excitation was composed of the violettish blue and the emerald green emissioins centered at 421 and 547 nm, respectively. The excitation wavelength of the emission peak at 547 nm was about 421 nm in the excitation spectrum of SZP: Mn0.012+. Since, this value is equal to the transition energy of Eu 2+, the energy transfer from Eu 2+ to Mn 2+ in SZP: Eu0.012+, Mn0.012+ phosphor has been demonstrated. The CIE chromaticity coordinates of SZP: Eu0.012+, Mn0.012+ phosphor were (0.330, 0.328) under the excitation wavelength 375 nm at room temperature. The phosphorescence from SZP: Eu0.012+, Mn0.012+ could be seen by naked eyes for few seconds and it has persisted for about 4.4 h while monitoring by using a PMT spectrometer. Therefore, SZP: Eux2+, Mny2+phosphor may be a potential candidate for the UV-based white light-emitting diodes (LEDs).

  9. Magnetic composite ZnFe2O4/SrFe12O19: Preparation, characterization, and photocatalytic activity under visible light

    NASA Astrophysics Data System (ADS)

    Xie, Taiping; Xu, Longjun; Liu, Chenglun; Wang, Yuan

    2013-05-01

    One-step chemical coprecipitation with high-temperature sintering method was employed for preparing magnetic composite ZnFe2O4/SrFe12O19 including a hard-magnetic phase (SrFe12O19) and a soft-magnetic phase (ZnFe2O4). The magnetic composite was characterized by FTIR, XRD, SEM, BET, XPS, VSM, and UV-vis. The testing results showed that the saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) were 34.95 emu/g, 18.31 emu/g, and 2254.54 G, respectively, indicating that the composite possessed excellent magnetic properties and a greater capacity for anti-demagnetize. The properties of the composite were favourable to its separation, recycling, and reuse after reaction. The photocatalytic performance of the composite was studied by the degradation reaction of methylene blue under visible light irradiation. The experimental results revealed that the degradation rate was still more than 70% when the composite was reused for four times. In addition, this research was expected to provide a promising method to prepare various composite materials with multi-functional components.

  10. Synthesis and Characterization of SrFe11.2Zn0.8O19 Nanoparticles for Enhanced Microwave Absorption

    NASA Astrophysics Data System (ADS)

    Tyagi, Sachin; Baskey, Himanshu B.; Agarwala, Ramesh Chandra; Agarwala, Vijaya; Shami, Trilok Chand

    2011-09-01

    SrFe12O19/ZnFe2O4 (SrFe11.2Zn0.8O19) nanoparticles having superparamagnetic nature were synthesized by coprecipitation of chloride salts using 7.5 M sodium hydroxide solution. The resulting precursors were heat-treated at 900°C and 1200°C for 4 h in nitrogen atmosphere. During heat treatment (HT), transformation proceeds through instantaneous nucleation and three-dimensional diffusion-controlled growth with an activation energy of 175.9 kJ/mole. The hysteresis loops showed an increase in saturation magnetization from 1.044 emu/g to 61.227 emu/g with increasing HT temperature. As-synthesized particles had sizes in the range of 20 nm to 25 nm with spherical shape. Further, these spherically shaped nanoparticles tended to change their morphology to hexagonal plate and pyramidal shape with increasing HT temperature. The effects of this systematic morphological transformation of nanoparticles on dielectric (complex permittivity and permeability) and microwave absorption properties were estimated in the X-band (8.2 GHz to 12.2 GHz). The maximum reflection loss of the composite powder reached -29.81 dB at 10.37 GHz, making it suitable for application in radar-absorbing materials.

  11. Timing of the formation of the Changba-Lijiagou Pb-Zn ore deposit, Gansu Province, China: Evidence from Rb-Sr isotopic dating of sulfides

    NASA Astrophysics Data System (ADS)

    Hu, Qiaoqing; Wang, Yitian; Mao, Jingwen; Wei, Ran; Liu, Shengyou; Ye, Dejin; Yuan, Qunhu; Dou, Ping

    2015-05-01

    The giant Changba-Lijiagou Pb-Zn deposit is located in the north of the Xihe-Chengxian (abbreviated as "Xicheng") ore cluster in Gansu Province, China. The orebodies in the deposit are mainly hosted in the marble, dolomitic marble, and biotite-calcite-quartz schist of the Middle Devonian Anjiacha Formation. The genesis of the deposit has previously been argued to be of SEDEX type (sedimentary exhalative type) or of epigenetic hydrothermal type. This paper reports results of Rb-Sr isotopic dating on sphalerite and pyrite taken from the main orebody, which yield an isochron age of 222.3 ± 2.2 Ma for eight sphalerite samples, and 222.0 ± 3.0 Ma for the eight sphalerite samples combined with four pyrite samples, indicating that the deposit formed during the Late Triassic. The (87Sr/86Sri) value of the sphalerite is 0.71370 ± 0.00013, and that of the sphalerite and pyrite is 0.71371 ± 0.00014, which are identical within experimental error, suggesting that the ore metals are derived mainly from the continental crust. By integrating the present results with the regional geology, we propose that the Changba-Lijiagou Pb-Zn deposit is a product of regional hydrothermal mineralization processes, forced by tectono-magmatic activities, which took place in the Xicheng ore cluster during Triassic orogenic processes.

  12. XPS and electroluminescence studies on SrS 1- xSe x and ZnS 1- xSe x thin films deposited by atomic layer deposition technique

    NASA Astrophysics Data System (ADS)

    Ihanus, Jarkko; Lambers, Eric; Holloway, Paul H.; Ritala, Mikko; Leskelä, Markku

    2004-01-01

    SrS 1- xSe x and ZnS 1- xSe x thin films were deposited by the atomic layer deposition (ALD) technique using elemental selenium as the Se source, thus avoiding use of H 2Se or organometallic selenium compounds. X-ray diffraction (XRD) analysis showed that the films were solid solutions and X-ray photoelectron spectroscopy (XPS) data showed that the surface of both ZnS 1- xSe x and SrS 1- xSe x were covered with an oxide and carbon-containing contaminants from exposure to air. The oxidation of SrS 1- xSe x extended into the film and peak shifts from sulfate were found on the surface. Luminance measurements showed that emission intensity of the ZnS 1- xSe x:Mn alternating current thin film electroluminescent (ACTFEL) devices at fixed voltage was almost the same as that of the ZnS:Mn device, while emission intensity of the SrS 1- xSe x:Ce devices decreased markedly as compared to the SrS:Ce device. Emission colors of the devices were altered only slightly due to selenium addition.

  13. Substitution effects of barium and calcium on magnetic properties of AxSr1-x(Fe0.5Ru0.5)O3 double perovskites (x =0.05, A =Ba,Ca)

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Zboril, R.; Tucek, J.; Kosaka, W.; Ohkoshi, S.; Felner, I.

    2007-07-01

    AxSr1-x(Fe0.5Ru0.5)O3 double perovskites (x =0.05 and A =Ba,Ca) were prepared by a sol-gel method and an effect of the cation substitution at the A site of the crystal structure of SrFe0.5Ru0.5O3 on their magnetic properties was monitored by x-ray diffraction (XRD), magnetic measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and temperature-dependent and in-field Fe57 Mössbauer spectroscopy. Both Ca- and Ba-substituted samples reveal the orthorhombic structure similar to the undoped perovskite; however, the cell volume changes with the substituting ion radius. TEM and SEM micrographs manifest agglomerated nanocrystalline samples with particle sizes of about 20-60, 15-50, and 40-70nm for the undoped, Ba-doped, and Ca-doped perovskites, respectively. Generally, the magnetic regime of both substituted and undoped perovskites can be described by a spin-glass behavior caused by a spin frustration. Among other factors, this is manifested by a nonsaturation of the hysteresis loops even at a high field of 50kOe, by a low-temperature divergence of the zero-field-cooled and field-cooled magnetization curves, and by a cusp in the zero-field-cooled magnetization curve. The low-temperature spin-glass state is also supported by the in-field Mössbauer spectra, recorded on these systems. The isomer shift parameters, extracted from the Mössbauer spectra, confirm a high-spin iron(III) state with S =5/2. In contrast to the undoped and Ba-doped samples, the narrower distribution of the hyperfine magnetic fields, observed in the Ca-doped perovskite can be ascribed to the larger particles. Compared to the undoped sample, the field of maximum probability is higher in the Ca-substituted perovskite while it is reduced in the Ba-doped sample because of the effects of the chemical compression and expansion, respectively. In addition, the Ca-doped sample exhibits more negative Weiss temperature (Θ=-105K) than that found for the Ba

  14. Ab initio study of the structural phase transitions of the double perovskites Sr2MWO6 (M=Zn, Ca, Mg)

    NASA Astrophysics Data System (ADS)

    Petralanda, U.; Etxebarria, I.

    2014-02-01

    We study the interplay of structural distortions in double perovskites Sr2MWO6 (M = Zn, Ca, Mg) by means of first-principles calculations and group theoretical analysis. Structure relaxations of the cubic, tetragonal, and monoclinic phases show that the ground states of the three compounds are monoclinic, although the energy difference between the monoclinic and tetragonal structures is very small in the case of Sr2MgWO6. The symmetry analysis of the distortions involved in the experimental and calculated low-temperature structures shows that the amplitude of two primary distortions associated to rigid rotations of the MX6 and WO6 octahedra are dominant, although the amplitude of a third mode related to deformations of the MX6 groups can not be neglected. The energy maps of the space spanned by the three relevant modes are calculated, and the couplings among the modes are evaluated, showing that the role of a hard secondary mode (in the Landau sense) coupled trilinearly to the two primary instabilities is crucial to stabilize the monoclinic ground state. Results suggest that the key role of the trilinear coupling among three modes could be rather common. A phenomenological theory including the effects of the chemical pressure is also developed. We find that the evolution of the stiffness constants in terms of the atomic substitution follows an accurate linear dependence and that the influence of quantum saturation of the order parameters could stabilize the tetragonal phase of Sr2MgWO6.

  15. 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.

  16. Enhanced magnetic response in single-phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) ceramics

    NASA Astrophysics Data System (ADS)

    Sharma, Poorva; Kumar, Ashwini; Varshney, Dinesh

    2015-10-01

    Single phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) dense ceramics were synthesized via solid state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics crystallized in a rhombohedrally (R 3 barC)distorted BiFeO3 structure with compressive lattice distortion induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning electron micrograph of the compounds showed the uniform distribution of grains on the sample surface with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g and remnant magnetization of 2.72 emu/ g at 300 K. Clear ferromagnetic ground state was observed in Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and dielectric loss were found to decrease with increase in frequency for all the compounds. These improved properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability and makes very promising for industrial applications such as new devices in information storage.

  17. Uniform AMoO{sub 4}:Ln (A=Sr{sup 2+}, Ba{sup 2+}; Ln=Eu{sup 3+}, Tb{sup 3+}) submicron particles: Solvothermal synthesis and luminescent properties

    SciTech Connect

    Yang Piaoping; Li Chunxia; Wang Wenxin; Quan Zewei; Gai Shili; Lin Jun

    2009-09-15

    Rare-earth ions (Eu{sup 3+}, Tb{sup 3+}) doped AMoO{sub 4} (A=Sr, Ba) particles with uniform morphologies were successfully prepared through a facile solvothermal process using ethylene glycol (EG) as protecting agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the kinetic decays were performed to characterize these samples. The XRD results reveal that all the doped samples are of high purity and crystallinity and assigned to the tetragonal scheelite-type structure of the AMoO{sub 4} phase. It has been shown that the as-synthesized SrMoO{sub 4}:Ln and BaMoO{sub 4}:Ln samples show respective uniform peanut-like and oval morphologies with narrow size distribution. The possible growth process of the AMoO{sub 4}:Ln has been investigated in detail. The EG/H{sub 2}O volume ratio, reaction temperature and time have obvious effect on the morphologies and sizes of the as-synthesized products. Upon excitation by ultraviolet radiation, the AMoO{sub 4}:Eu{sup 3+} phosphors show the characteristic {sup 5}D{sub 0}-{sup 7}F{sub 1-4} emission lines of Eu{sup 3+}, while the AMoO{sub 4}:Tb{sup 3+} phosphors exhibit the characteristic {sup 5}D{sub 4}-{sup 7}F{sub 3-6} emission lines of Tb{sup 3+}. These phosphors exhibit potential applications in the fields of fluorescent lamps and light emitting diodes (LEDs). - Graphical abstract: Uniform rare-earth ions (Eu{sup 3+}, Tb{sup 3+}) doped AMoO{sub 4} (A=Sr, Ba) submicron phosphors with tetragonal scheelite-type structure have been prepared through a facile solvothermal process using EG as reaction media. Display Omitted

  18. Cobalt-free Ba0.5Sr0.5Fe0.8Cu0.1Ti0.1O3-δ as a bi-functional electrode material for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Guangming; Shen, Jian; Chen, Yubo; Tadé, Moses O.; Shao, Zongping

    2015-12-01

    In this study, we investigate a cobalt-free titanium-doped perovskite oxide with the nominal composition of Ba0.5Sr0.5Fe0.8Cu0.1Ti0.1O3-δ (BSFCuTi) as a potential electrode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). In comparison to Ba0.5Sr0.5Fe0.9Cu0.1O3-δ, BSFCuTi exhibits improved phase stability and a reduced thermal expansion coefficient even though the electrical conductivity decreases. A low area specific resistance of 0.088 Ω cm2 is achieved at 600 °C based on a symmetrical cell test, which is comparable to the result for the benchmark Ba0.5Sr0.5Co0.8Fe0.2O3-δ cobalt-based perovskite electrocatalyst. Stable operation for a period of 200 h is also demonstrated. The I-V test shows a very high power output of 1.16 W cm-2 for a single cell using a BSFCuTi cathode at 600 °C. In addition, the BSFCuTi can be partially reduced under a reducing atmosphere to prepare a suitable anode material. A cell with BSFCuTi as the material for both electrodes and a thick Gd0.2Ce0.8O1.9 electrolyte (300 μm) delivers an attractive power density of 480 mW cm-2 at 800 °C. The high activity, favorable stability and bi-functionality make BSFCuTi a promising electrode material for IT-SOFCs.

  19. Structural, electrochemical and magnetic characterization of the layered-type PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} perovskite

    SciTech Connect

    Azad, Abul K.; Kim, Jung H.; Irvine, John T.S.

    2014-05-01

    Structural, electrical and magnetic properties of the layered cobaltite PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrO{sub δ}] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2a{sub p} and c≈2a{sub p} (a{sub p} is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573 K in air, structural rearrangement takes place and the structure can be defined as a≈a{sub p} and c≈2a{sub p} in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373 K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973 K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573 K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153 Ωcm{sup 2} and 0.286 Ωcm{sup 2} at 973 K and 923 K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order. - Graphical abstract: Structural phase changes in PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at elevated temperatures determined by neutron powder diffraction. Depending on oxygen occupancy it form different phases at different temperatures. This pictures show the schematic 3D diagram of PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at 295 K (a), 373 K (b) and 573 K (c). Co atoms are inside the

  20. Effect of Y doping and composition-dependent elastic strain on the electrical properties of (Ba,Sr)TiO{sub 3} thin films deposited at 520 deg. C

    SciTech Connect

    Wang, R.-V.; McIntyre, Paul C.; Baniecki, John D.; Nomura, Kenji; Shioga, Takeshi; Kurihara, Kazuaki; Ishii, Masatoshi

    2005-11-07

    We demonstrate that large and simultaneous improvements in permittivity, tunability, and leakage current density of (Ba,Sr)TiO{sub 3} (BST)-based thin-film capacitors can be achieved by yttrium doping. We have found that, for a low deposition temperature (520 deg. C) sputtering process, Y-doped BST capacitors exhibit tenfold lower leakage current density (<10{sup -9} A/cm{sup 2} at 100 KV/cm) and 70% higher permittivity than nominally undoped BST-based capacitors. Furthermore, this work suggests an intriguing correlation between dopant concentration-dependent elastic strain in the films and their enhanced dielectric properties.