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Sample records for ba sr ca

  1. Theoretical electric quadrupole transition probabilities for Ca, Sr and Ba

    Science.gov (United States)

    Bauschlicher, C. W., Jr.; Langhoff, S. R.; Jaffe, R. L.; Partridge, H.

    1984-01-01

    The 1D-1S quadrupole transition probabilities for Ca, Sr and Ba have been computed using extended GTO and STO valence basis sets and configuration-interaction wavefunctions that include the important core-valence correlation effects. For Ba and Sr, the relativistic contraction of the core orbitals was accounted for in the GTO calculations by a relativistic effective-core potential. The computed Einstein coefficient for Ca of 39.6/s is in excellent agreement with the recent experimental value of 40 + or - 8/s. The best Einstein coefficients for Sr (44.7/s) and Ba (2.98/s) imply increasing quadrupole line strengths down the column. Relativistic effects substantially increase the quadrupole Einstein coefficient for Ba.

  2. Allometric constraints on Sr/Ca and Ba/Ca partitioning in terrestrial mammalian trophic chains.

    Science.gov (United States)

    Balter, Vincent

    2004-03-01

    In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs ( Rn and R(n -1)) is measured with an observed ratio (OR) expressed by the (Sr/Ca) Rn /(Sr/Ca)( Rn-1) and (Ba/Ca) Rn /(Ba/Ca)( Rn-1) ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for ORSr and ORBa are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated ORSr and ORBa of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give ORSr=0.30+/-0.08 and ORBa=0.16+/-0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation ORBa=ORSr(1.79+/-0.33), where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the

  3. Phase diagrams for systems Cu2S-AIIS (AII=Mg, Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    By the methods of physicochemical analysis phase diagrams of Cu2S-AIIS (AII=Mg, Ca, Sr, Ba) systems are studied. The system Cu2S-SrS is of eutectic type with eutectic coordinates 1095 K and 21.5 mol.% of SrS. Solubility of SrS in Cu2S is 2 mol.% at 1095 K. Regularities of phase diagram changes of Cu2S-AIIS (AII=Mg, Ca, Sr, Ba) system are determined. Thermodynamic analysis is done

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

    Science.gov (United States)

    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 (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 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 litterfall. This observation implicates an uptake flux from an additional source which we attribute to biolifting. We view the heavy exchangeable Ba relative to soil parent values in deeper soils at sites where P is enriched in surface soils, and indeed at all but the wettest site across the climosequence, to represent the complement of an isotopically light Ba fraction removed from these soils by plant

  5. Effect of local environment on crossluminescence kinetics in SrF{sub 2}:Ba and CaF{sub 2}:Ba solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Terekhin, M.A. [P.N. Lebedev Physical Institute, Leninskij Prospekt 53, 119991 Moscow (Russian Federation); Makhov, V.N., E-mail: makhov@sci.lebedev.ru [P.N. Lebedev Physical Institute, Leninskij Prospekt 53, 119991 Moscow (Russian Federation); Lebedev, A.I.; Sluchinskaya, I.A. [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2015-10-15

    Spectral and kinetic properties of extrinsic crossluminescence (CL) in SrF{sub 2}:Ba (1%) and CaF{sub 2}:Ba (1%) are compared with those of intrinsic CL in BaF{sub 2} and are analyzed taking into account EXAFS data obtained at the Ba L{sub III} edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF{sub 2}:Ba and CaF{sub 2}:Ba compared to BaF{sub 2}. This fact contradicts the expected acceleration of luminescence decay which could result from an increased overlap of wave functions in solid solutions due to shortening of the Ba-F distance obtained in both EXAFS measurements and first-principles calculations. This discrepancy is explained by the effect of migration and subsequent non-radiative decay of the Ba (5p) core holes in BaF{sub 2} and by decreasing of the probability of optical transitions between Ba (5p) states and the valence band in SrF{sub 2}:Ba and CaF{sub 2}:Ba predicted by first-principles calculations. - Highlights: • The crossluminescence kinetics in SrF{sub 2}:Ba and CaF{sub 2}:Ba is slower than in BaF{sub 2}. • Ba{sup 2+} ions substitute for host Ca{sup 2+}(Sr{sup 2+}) ions in the on-center positions. • The nearest Ba-F distances in SrF{sub 2}:Ba and CaF{sub 2}:Ba are shorter than in BaF{sub 2}. • EXAFS data and first-principles calculations of the local structure agree well. • First-principles calculations explain slower luminescence decay in solid solutions.

  6. Itinerant electron metamagnetism in AFe4Sb12(A=Ca,Sr,Ba)

    International Nuclear Information System (INIS)

    Magnetic properties of the alkaline earth filled skutterudite AFe4Sb12(A=Ca,Sr,Ba), which are located in a proximity to a ferromagnetic instability, have been investigated by the high-field magnetization measurements in a pulsed magnetic field. At 1.3K, in CaFe4Sb12, a metamagnetic increase of magnetization appears at 13T where M reaches about 0.25μB/Fe. This metamagnetic anomaly weakens and the critical field shifts to a lower field in sequence of A=Ca,Sr,Ba. The temperature variation of the metamagnetism has also been investigated, and the results are discussed in relation to the ferromagnetic instability

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    David Parker and David J Singh

    2013-01-01

    We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead c...

  10. Theoretical studies of the paramagnetic perovskites MTaO{sub 3} (M = Ca, Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Zahid, E-mail: zahidf82@gmail.com [Center for Computational Materials Science, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Khan, Imad; Ahmad, Iftikhar; Khan, M. Salman [Center for Computational Materials Science, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Asadabadi, S. Jalali [Department of Physics, Faculty of Science, University of Isfahan, Hezar Gerib Avenue, Isfahan, 81744 (Iran, Islamic Republic of)

    2015-07-15

    In the present density functional studies, structural, mechanical and magneto-electronic properties of CaTaO{sub 3,} SrTaO{sub 3} and BaTaO{sub 3} perovskites have been investigated. The calculated structural parameters by DFT and analytical methods are found consistent with the experiments. The analytically calculated tolerance factors of these compounds as well as their mechanical properties show that they are stable in the cubic phase. Furthermore elastic properties show that these materials are ductile in nature and confirm that BaTaO{sub 3} is harder than the rest compounds. The calculated spin dependent magneto-electronic properties reveal the paramagnetic metallic nature of these compounds. The electrical conductivity curve demonstrates significant conductivity above room temperature. On the basis of the presented properties it is expected that these compounds could be efficient electrode materials and need experimental investigations. - Highlights: • MTaO{sub 3} (M = Ca, Sr and Ba) perovskites are investigated theoretically in the frame work of density functional theory. • Mechanical properties explain the stability of these compounds and show that BaTaO{sub 3} is more ductile. • The magneto-electronic studies reveal the paramagnetic metallic nature of these compounds. • Significant electrical conductivity is observed above room temperature.

  11. Separation of Sr from Ca, Ba and Ra by means of Ca(OH)2 and Ba(Ra)Cl2 or Ba(Ra)SO4 for the determination of radiostrontium

    DEFF Research Database (Denmark)

    Chen, Q.J.; Hou, Xiaolin; Yu, Y.X.; Dahlgaard, H.; Nielsen, S.P.

    2002-01-01

    A simple procedure is developed to separate Sr from a large amount of Ca, which relies on the insolubility of Ca(OH)(2) in alkaline solution. Calcium is quantitatively separated from Sr and more than 95% of Sr is recovered from a sample with as much as 50 g of Ca and a Ca/Sr mole ratio of 250. A...... new procedure for the separation of Sr from Ba and Ra is also investigated, which is based on the difference in solubility of the chlorides of Sr, Ba and Ra in HCl media. In 9.5 mol 1(-1) HCl or 7.5 mol 1(-1) HCl-10% acetone media, >97% of Ba and Ra can be removed by Ba(Ra)Cl-2 precipitation, and >94...... completed. The new separation procedure has been successfully used for the determination of Sr-90 in samples with high Ca content, such as 451 of seawater and 2001 of drinking water. The analytical quality of the results is comparable to that of the traditional method using fuming nitric acid and BaCrO4...

  12. Trigermanides AEGe{sub 3} (AE = Ca, Sr, Ba). Chemical bonding and superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Castillo, Rodrigo; Schnelle, Walter; Baranov, Alexey I.; Burkhardt, Ulrich; Bobnar, Matej; Cardoso-Gil, Raul; Schwarz, Ulrich; Grin, Yuri [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany)

    2016-08-01

    The crystal structures of the trigermanides AEGe{sub 3}(tI32) (AE = Ca, Sr, Ba; space group I4/mmm, for SrGe{sub 3}: a = 7.7873(1), c = 12.0622(3) Aa) comprise Ge{sub 2} dumbbells forming layered Ge substructures which enclose embedded AE atoms. The chemical bonding analysis by application of the electron localizability approach reveals a substantial charge transfer from the AE atoms to the germanium substructure. The bonding within the dumbbells is of the covalent two-center type. A detailed analysis of SrGe{sub 3} reveals that the interaction on the bond-opposite side of the Ge{sub 2} groups is not lone pair-like - as it would be expected from the Zintl-like interpretation of the crystal structure with anionic Ge layers separated by alkaline-earth cations - but multi-center strongly polar between the Ge{sub 2} dumbbells and the adjacent metal atoms. Similar atomic interactions are present in CaGe{sub 3} and BaGe{sub 3}. The variation of the alkaline-earth metal has a merely insignificant influence on the superconducting transition temperatures in the s,p-electron compounds AEGe{sub 3}.

  13. Luminescence of MFX:Eu/sup 2+/ M=Ca,Sr,Ba; X=Cl,Br, I

    International Nuclear Information System (INIS)

    BaFCl:Eu/sup 2+/ as an excellent x-ray phosphor, has been used successfully in medical x-ray intensifying screens and other x-ray displaying devices. Others have reported the emission spectra of MFCl:Eu (M=Ca, Sr, Ba). In this paper the authors focus the discussion on the characteristics of the emission and the energy level splitting of 4f 5d excited state of Eu/sup 2+/ ion in matrices MFX (M=Ca, Sr or Ba; X=Cl, Br or I)

  14. Dielectric behaviour of hexagonal ferrimagnetic MFe12O19 (M=Ca, Sr and Ba) compounds

    International Nuclear Information System (INIS)

    Ferrimagnetic compounds CaM, SrM and BaM with hexagonal structure related to magnetoplumbite type have been synthesized by ceramic route. The phase purity and unit cell parameters have been confirmed by x-ray powder diffractometric data. The dielectric constant (is an element of) and loss tangent (tanδ) of these pure hexaferrites are measured at 300 K in the frequency range 100 Hz to 1 MHz using a impedance analyser. The plots of dielectric constant (is an element of) versus frequency show normal behaviour which is usually observed for ferrites. Frequency dependence of dielectric loss tangent (tanδ) is also investigated. (author)

  15. Variation of Ca, Sr, Ba and Mg in the Otolith of Mudskipper in West Coast of Peninsular Malaysia

    OpenAIRE

    A.S. Sarimin; M.A. Ghaffar; C.A.R. Mohamed

    2009-01-01

    A study on elemental composition in the otolith of giant mudskipper, Periophthalmodon schlosseri, was done from June to October 2003. Specimens were obtained from the mangrove areas of Kuala Selangor, Sepang and Melaka in the west coast of Peninsular Malaysia. A total of 70 sagitta otoliths were analyzed to detect variation of Sr, Ba and Mg, replacing the natural chemical composition of the otolith, which is the calcium carbonate (CaCO3). The average ratio of Sr:Ca was 0.11x10-4, Ba:Ca...

  16. Structural disorder in AMoO4 (A = Ca, Sr, Ba) scheelite nanocrystals.

    Science.gov (United States)

    Rabuffetti, Federico A; Culver, Sean P; Suescun, Leopoldo; Brutchey, Richard L

    2014-01-21

    The crystal structure of sub-15 nm AMoO4 (A = Ca, Sr, Ba) scheelite nanocrystals has been investigated using a dual-space approach that combines Rietveld and pair distribution function (PDF) analysis of synchrotron X-ray diffraction data. Rietveld analysis yields an average crystal structure in which the Mo-O bond distance exhibits an anomalously large contraction (2.8%) upon chemical substitution of Ba(2+) for Ca(2+). Such a dependence on chemical composition contradicts the well-known rigid character of Mo(VI)-O bonds and the resulting rigidity of MoO4 tetrahedra in scheelites. Unlike Rietveld, PDF analysis yields a local crystal structure in which the Mo-O bond distance shows a negligible contraction (0.4%) upon going from Ba(2+) to Ca(2+) and, therefore, appears independent of the chemical composition. Analysis of the anisotropic displacement parameters of the oxygen atom reveals that the disagreement between the average and local structural models arises from the presence of static orientational disorder of the MoO4 tetrahedra. Rietveld analysis averages the random rotations of the MoO4 tetrahedra across the scheelite lattice yielding an apparent Mo-O bond distance that is shorter than the true bond distance. In contrast, PDF analysis demonstrates that the structural integrity of the MoO4 tetrahedra remains unchanged upon chemical substitution of the alkaline-earth cation, and that their orientational disorder is accommodated through geometric distortions of the AO8 dodecahedra. PMID:24266706

  17. Thermal Diffusivity of Ordered Double Perovskite A2FeMoO6 (A = Ca, Sr and Ba)

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-Jun; HUANG Qiao-Jian; NIU Dong-Lin; XU Sheng; ZHANG Shu-Yi

    2004-01-01

    @@ Thermal diffusivity has been investigated in ordered double perovskite Sr2FeMoO6 by means of transient surface grating technique in the temperature range of 300-450 K. The thermal diffusivity shows an appreciable decrease from 39mm2/s at 300 K to 37mm2/s at 360K in the ferromagnetic phase, and then steeply drops to 10mm2/s with further increasing temperature above the critical temperature Tc ~ 380 K. Such an abrupt decrease of the thermal diffusivity has been ascribed to the structural phase transition at Tc. We further investigate the lattice effect on the thermal diffusivity in A2FeMoO6 (A = Ca, Sr and Ba) by substitution of Ca2+ or Ba2+ ions for Sr2+ions at 300K. We find that the thermal diffusivity increases from 35mm2/s for A = Ca to 41 mm2/s for A = Ba.Considering the change of the Fe-O-Mo bond angle from 152.4° for A = Ca to 180° for A = Ba, the increased thermal diffusivity for Ba compound has been ascribed to the enhanced hybridization between transition-metal d and oxygen p states due to the larger Fe-O-Mo bond angle and hence the wider one-electron bandwidth W.

  18. Study of chromites YbMIICr2O5,5 (MII - Mg, Ca, Sr, Ba by X-ray diffraction

    Directory of Open Access Journals (Sweden)

    B. Kasenov

    2012-03-01

    Full Text Available Compounds of composition YbMeMnFeO5,5 (Me – Mg, Ca, Sr, Ba are synthesized from Yb2O3, , Cr2O3 and MgCO3, CaCO3, SrCO3, BaCO3 by solid phase method. X-ray powder diffraction showed that the compound YbMgCr2O5,5, YbCaCr2O5,5, YbSrCr2O5,5, YbBaCr2O5,5 crystallizes in the tetragonal crystal system.

  19. Structure and Properties of Egyptian Blue Monolayer Family: XCuSi4O10 (X = Ca, Sr, and Ba).

    Science.gov (United States)

    Chen, Yu; Kan, Min; Sun, Qiang; Jena, Puru

    2016-02-01

    Motivated by the recent experimental advances in exfoliating Egyptian blue monolayers, we have carried out extensive calculations using density functional theory to understand their geometry, stability, mechanical properties, electronic structures, and magnetism. Upon exfoliation from the bulk, XCuSi4O10 (X = Ca, Sr, and Ba) monolayers are found to change symmetry from tetragonal to orthorhombic. They all satisfy Born criteria and are mechanically stable. Each Cu site carries a magnetic moment of 1.0 μB but with degenerate ferromagnetic and antiferromagnetic coupling states. From Ca to Sr and Ba, as the atomic number increases, the thickness, elastic constants, Young's moduli, and Poisson's ratios of the monolayers increase, while the band gaps decrease. Applying strain can tune the magnitude of energy band gaps, but the direct gap feature remains. Complementing the widely studied graphene, MXenes, black phosphorus, and dichalcogenide sheets, the Egyptian blue monolayers add additional features to the family of two-dimensional materials. PMID:26763651

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

    Directory of Open Access Journals (Sweden)

    David Parker and David J Singh

    2013-01-01

    Full Text Available We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli—roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  1. Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba3BSb2O9, B=Mg, Ca, Sr, Ba

    International Nuclear Information System (INIS)

    We present a complete temperature-composition phase diagram for Ba3BSb2O9, 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 P63/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 Ba3BSb2O9, B=Mg, Ca, and Sr, as a function of temperature T and effective ionic radius (IR) of the B2+ cation

  2. Comparative study of the ionic exchange of Ca++, Sr++, and Ba++ cations on resins and inorganic exchangers

    International Nuclear Information System (INIS)

    With a view to applying the results to certain problems related to chemical separations in activation analysis, a study has been made, of the possibilities of separating the alkaline-earth elements Ca, Sr and Ba on organic resins and inorganic exchangers using the radioactive indicator method. The partition coefficients of the cations Ca2+, Sr2+ and Ba2+ have been measured on Dowex 50 W (NH4+) x 8 resin in the presence of EDTA - NTA - EGTA and DCTA as complexing agents, and on zirconium phosphate, tungstate and molybdate in the presence of HCl and NH4Cl. Methods have been developed for separating mixtures of alkaline-earth elements using DCTA-NH4+ followed by elution on Dowex 50 W (NH4+) x 8 resin columns and on zirconium phosphate. Amongst the complexing agents used on the ion-exchange resins the most promising appears to be DCTA which leads to partition coefficients Ca, Sr and Ba which are very different. The results of measurements of partition coefficients on zirconium phosphate (NH4+ form) using DCTA-NH4+ show the interesting possibilities of separations on columns. The separation of the alkaline-earth elements on zirconium phosphate seems to be less quantitative than on Dowex 50 resin; it is however much faster in the former case and this can be useful for treating short half-life radioisotopes in activation analysis. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Samal, Saroj L. [Ames Laboratory; Gulo, Fakhili [Ames Laboratory; Corbett, John D. [Ames Laboratory

    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.

  4. Epitaxial thin films of ATiO(3-x)H(x) (A = Ba, Sr, Ca) with metallic conductivity.

    Science.gov (United States)

    Yajima, Takeshi; Kitada, Atsushi; Kobayashi, Yoji; Sakaguchi, Tatsunori; Bouilly, Guillaume; Kasahara, Shigeru; Terashima, Takahito; Takano, Mikio; Kageyama, Hiroshi

    2012-05-30

    Epitaxial thin films of titanium perovskite oxyhydride ATiO(3-x)H(x) (A = Ba, Sr, Ca) were prepared by CaH(2) reduction of epitaxial ATiO(3) thin films deposited on a (LaAlO(3))(0.3)(SrAl(0.5)Ta(0.5)O(3))(0.7) substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO(3)/LSAT thin film hydridized at 530 °C for 1 day had hydride concentration of 4.0 × 10(21) atoms/cm(3) (i.e., SrTiO(2.75)H(0.25)). The electric resistivity of all the ATiO(3-x)H(x) films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO(3-x)H(x) powder, revealing that ATiO(3-x)H(x) are intrinsically metallic, with high conductivity of 10(2)-10(4) S/cm. Treatment with D(2) gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials' inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible. PMID:22563869

  5. Magnetic exchange interactions and antiferromagnetism of ATcO3 (A= Ca, Sr, Ba) studied from first principles

    Science.gov (United States)

    Borisov, V. S.; Maznichenko, I. V.; Böttcher, D.; Ostanin, S.; Ernst, A.; Henk, J.; Mertig, I.

    2012-04-01

    The magnetic properties of ATcO3 (A = Ca, Sr, Ba) perovskites were studied from first principles using multiple-scattering theory. For each system, the most preferable magnetic order is antiferromagnetic where the magnetic moments of the nearest Tc atoms are aligned antiparallel to each other. In the case of CaTcO3 and SrTcO3, their recently observed antiferromagnetism is supported by our calculation of the Tc-Tc exchange coupling parameters. The Néel temperatures TN estimated for CaTcO3 and SrTcO3 are in a good agreement with experiment. For BaTcO3, which is not synthesized so far, we predict a fundamental band gap of 0.3 eV and TN below 900 K. In general, TN increases with volume expansion, whereas the presence of vacancies on both the oxygen and cation sites of ATcO3 should significantly suppress the critical temperature as well as the magnetic moment of Tc. Electronic correlations play a minor role in the formation of the magnetic state, although they may improve the calculated value of TN.

  6. Preparation and characterization of Eu3+ activated CaSiO3, (CaA)SiO3 [A = Ba or Sr] phosphors

    Indian Academy of Sciences (India)

    S J Dhoble; N S Dhoble; R B Pode

    2003-06-01

    Eu3+ activated CaSiO3, (Ca, Ba) SiO3 and (Ca, Sr) SiO3 have been prepared by sol–gel technique. Residual solvent and organic contents in the gel were removed by firing at 100°C for 3–4 h at 300 and 600°C for 2 h. Small exothermic shoulder around 850 to 875°C, as observed in DTA curve, corresponds to crystallization temperature of the doped calcium silicate. Influence of firing temperature on the luminescence of Eu3+ shows the maximum emission intensity in gel fired at 850°C. Photoluminescence emission peak is observed at 614 nm due to ${}^{5}D_{0} \\rightarrow {}^{7}F_{2}$ transition of Eu3+ ion in (Ca, Ba) SiO3 and (Ca, Sr) SiO3 phosphors, when excited by 254 nm. The (Ca, Ba) SiO3 material is proposed as an efficient red phosphor.

  7. Structural, electronic and mechanical properties of alkaline earth metal oxides MO (M=Be, Mg, Ca, Sr, Ba)

    Science.gov (United States)

    Cinthia, A. Jemmy; Priyanga, G. Sudha; Rajeswarapalanichamy, R.; Iyakutti, K.

    2015-04-01

    The structural, electronic and mechanical properties of alkaline earth metal oxides MO (M=Be, Mg, Ca, Sr, Ba) in the cubic (B1, B2 and B3) phases and in the wurtzite (B4) phase are investigated using density functional theory calculations as implemented in VASP code. The lattice constants, cohesive energy, bulk modulus, band structures and the density of states are computed. The calculated lattice parameters are in good agreement with the experimental and the other available theoretical results. Electronic structure reveals that all the five alkaline earth metal oxides exhibit semiconducting behavior at zero pressure. The estimated band gaps for the stable wurtzite phase of BeO is 7.2 eV and for the stable cubic NaCl phases of MgO, CaO, SrO and BaO are 4.436 eV, 4.166 eV, 4.013 eV, and 2.274 eV respectively. A pressure induced structural phase transition occurs from wurtzite (B4) to NaCl (B1) phase in BeO at 112.1 GPa and from NaCl (B1) to CsCl (B2) phase in MgO at 514.9 GPa, in CaO at 61.3 GPa, in SrO at 42 GPa and in BaO at 14.5 GPa. The elastic constants are computed at zero and elevated pressures for the B4 and B1 phases for BeO and for the B1 and B2 phases in the case of the other oxides in order to investigate their mechanical stability, anisotropy and hardness. The sound velocities and the Debye temperatures are calculated for all the oxides using the computed elastic constants.

  8. Electronic structure and photocatalytic properties of ABi2Ta2O9 (A=Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    A new series of layered perovskite photocatalysts, ABi2Ta2O9 (A=Ca, Sr, Ba), were synthesized by the conventional solid-state reaction method and the crystal structures were characterized by powder X-ray diffraction. The results showed that the structure of ABi2Ta2O9 (A=Ca, Sr) is orthorhombic, while that of BaBi2Ta2O9 is tetragonal. First-principles calculations of the electronic band structures and density of states (DOS) revealed that the conduction bands of these photocatalysts are mainly attributable to the Ta 5d+Bi 6p+O 2p orbitals, while their valence bands are composed of hybridization with O 2p+Ta 5d+Bi 6s orbitals. Photocatalytic activities for water splitting were investigated under UV light irradiation and indicated that these photocatalysts are highly active even without co-catalysts. The formation rate of H2 evolution from an aqueous methanol solution is about 2.26 mmol h-1 for the photocatalyst SrBi2Ta2O9, which is much higher than that of CaBi2Ta2O9 and BaBi2Ta2O9. The photocatalytic properties are discussed in close connection with the crystal structure and the electronic structure in details. - Graphical abstract: The valence band of the photocatalysts is consisted of O 2p, Ta 5d and Bi 6s orbitals and the conduction band is from Bi 6p, Ta 5d and O 2p orbitals. Photocatalytic properties of the photocatalyst for H2 evolution without using other co-catalysts from CH3OH/H2O solution and O2 evolution from AgNO3/H2O solution were observed under Hg lamp irradiation

  9. Optical properties of $A$Fe$_\\mathbf{2}$As$_\\mathbf{2}$ ($A=\\,$Ca, Sr, and Ba) single crystals

    OpenAIRE

    Dai, Y. M.; Akrap, A.; Bud'ko, S. L.; Canfield, P. C.; Homes, C. C.

    2016-01-01

    The detailed optical properties have been determined for the iron-based materials $A$Fe$_2$As$_2$, where $A=\\,$Ca, Sr, and Ba, for light polarized in the iron-arsenic ($a-b$) planes over a wide frequency range, above and below the magnetic and structural transitions at $T_N =\\,$138, 195, and 172~K, respectively. The real and imaginary parts of the complex conductivity are fit simultaneously using two Drude terms in combination with a series of oscillators. Above $T_N$, the free-carrier respon...

  10. Chemical, structural and magnetic studies of new mono- and diphosphates appearing in ternary diagrams AO-CuO-(P2O5); A= Mg, Ca, Sr, Ba

    International Nuclear Information System (INIS)

    A systematic study of mixed mono- and diphosphates of AO-CuO-(P2O5) systems (A= Mg, Ca, Sr, Ba) has been carried out. This study showed up, on one hand, continuous and wide ranges in magnesium system and on the other hand, eight new phases in the other systems: Sr sub 18 Cu sub 3 (PO4)14, A2 Cu (PO4)2, (A= Sr, Ba), Sr3 Cu3 (PO4)4, BaCu2 (PO4)2 and ACu(P2O7) (A= Ca, Sr, Ba). The crystalline structures of SrCu(P2O7), BaCu(P2 O7),Sr3 Cu3 (PO4)4 and BaCu2 (PO4)2 phosphates have been described and discussed. The first compound presents a Tunnel structure and the three others have Foliation structures. The magnetic behaviours of some Cu sup 2+ ions phos-phates have been correlated to their crystalline structures. The experimental data have been parametered using the Ising model and/or the Heisenberg model. In this work, three Ising theoretical models have been developed. This magnetic study showed up new chains of antiferro- or ferrimagnetic Cu sup 2+ ions. 59 figs., 32 tabs., 113 refs. (author)

  11. Luminescent Afterglow Behavior in the M2Si5N8: Eu Family (M = Ca, Sr, Ba

    Directory of Open Access Journals (Sweden)

    Koen Van den Eeckhout

    2011-05-01

    Full Text Available Persistent luminescent materials are able to emit light for hours after being excited. The majority of persistent phosphors emit in the blue or green region of the visible spectrum. Orange- or red-emitting phosphors, strongly desired for emergency signage and medical imaging, are scarce. We prepared the nitrido-silicates Ca2Si5N8:Eu (orange, Sr2Si5N8:Eu (reddish, Ba2Si5N8:Eu (yellowish orange, and their rare-earth codoped variants (R = Nd, Dy, Sm, Tm through a solid state reaction, and investigated their luminescence and afterglow properties. In this paper, we describe how the persistent luminescence is affected by the type of codopant and the choice and ratio of the starting products. All the materials exhibit some form of persistent luminescence, but for Sr2Si5N8:Eu,R this is very weak. In Ba2Si5N8:Eu the afterglow remains visible for about 400 s, and Ca2Si5N8:Eu,Tm shows the brightest and longest afterglow, lasting about 2,500 s. For optimal persistent luminescence, the dopant and codopant should be added in their fluoride form, in concentrations below 1 mol%. A Ca3N2 deficiency of about 5% triples the afterglow intensity. Our results show that Ba2Si5N8:Eu(,R and Ca2Si5N8:Eu(,R are promising persistent phosphors for applications requiring orange or red light.

  12. Encapsulating MAl 2O 4:Eu 2+, Dy 3+ (M = Sr, Ca, Ba) phosphors with triethanolamine to enhance water resistance

    Science.gov (United States)

    Ji, Ping Ting; Chen, Xiang Ying; Wu, Ye Qin

    2011-12-01

    Traditional aluminates phosphors with persistent luminescence are chemically unstable to water or moisture. Thus, how to improve the water-resistance of these phosphors is becoming a key issue in their practical applications. In this work, a series of alkaline earth aluminate phosphors including MAl 2O 4:Eu 2+, Dy 3+ (M = Sr, Ca, Ba) have been prepared by a co-precipitation synthesis and postannealing approach, using 8-hydroxyquinoline and sodium oxalate as precipitants. The samples before and after encapsulation were well characterized by means of XRPD, FESEM, FT-IR, TGA-DTG and PL techniques as well as water resistance measurements. The precipitants involved can react with Al 3+ and Sr 2+ (or Ca 2+, Ba 2+) to form complex compounds in aqueous solution, which further convert into porous phosphors by postannealing method under reducing atmosphere. Next, triethanolamine encapsulation at room temperature was conducted onto their surfaces to improve the water resistance. The results reveal that the encapsulation of aluminate phosphors with triethanolamine can effectively enhance the water resistance, and minimally affect on persistent phosphorescence.

  13. 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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  15. Direct imaging of the structural domains in the iron pnictides AFe2As2 (A=Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    The parent compounds of recently discovered iron-arsenide superconductors, AFe2As2 with alkaline earth A=Ca,Sr,Ba, undergo simultaneous structural and magnetic phase transitions at a temperature TSM. 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 45o-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 μm. The direction of the stripes is fixed with respect to the tetragonal (100) and (010) directions but can change by 90o on thermal cycling through the transition. This domain pattern may have profound implications for intrinsic disorder and anisotropy of iron arsenides.

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

    Science.gov (United States)

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

    2016-01-01

    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.

  17. The photo-catalytic activities of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO43-, HPO42-) microparticles

    Science.gov (United States)

    Zhang, Fan; Shi, Yuanji; Zhao, Zongshan; Song, Weijie; Cheng, Yang

    2014-02-01

    For the good performance of apatite-based materials in the removal of dyes and their environment-friendly advantage, five kinds of apatite microparticles of MP (M = Ba, Ca, Cu, Sr, Ag; P = PO43-, HPO42-) were synthesized by a simple precipitation method and their photo-catalytic properties were invested. Better performance in the decolorization of methyl orange (MO) under the assistance of H2O2 than that of TiO2 were obtained for all the MPs. The photo-catalytic activity was mainly affected by surface area, energy band, impurity, crystallinity and crystal structure. The DFT calculation results demonstrated that the 2p of O and 3p of P in PO43- played the main role in the photo-catalytic process. This work would be helpful to design and synthesize low cost apatite materials with good photo-catalytic performance.

  18. Moessbauer study on the CMR double perovskite AFe0.5Mo0.5O3 with A = (Ba,Sr) or (Sr,Ca). Chemical pressure effect

    International Nuclear Information System (INIS)

    The double perovskites, AFe0.5Mo0.5O3 with A = (Ba,Sr) or (Sr,Ca), were prepared by a sol-gel method, and the substitution effect at site A was studied by Moessbauer spectrometry. In the Moessbauer spectra of the double perovskite (Ba, Sr)Fe0.5Mo0.5O3, the isomer shifts decreased from δ = 0.72 mm/s to δ = 0.4 mm/s and the internal magnetic fields increased with the increase of the Sr content. The Ba-rich samples were shown to contain superparamagnetic components under the same preparation conditions. Better crystallinity and larger hyperfine fields were obtained when 5% of the Sr-content of SrFe0.5Mo0.5O3 was substituted by Ca as compared with substitution by Ba. Phonon density of states (DOS) of SrFe0.5Mo0.5O3 substituted with Ca or Ba were obtained by nuclear inelastic scattering. The peaks of phonon DOS were shifted, depending on chemical compression/expansion of the lattice. The chemical pressure effect could be observed in the Moessbauer spectra and the phonon DOS spectra. (author)

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

    Science.gov (United States)

    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

  20. First principle calculations for improving desorption temperature in Mg16H32 doped with Ca, Sr and Ba elements

    Indian Academy of Sciences (India)

    M Bhihi; M Lakhal; S Naji; H Labrim; A Belhaj; A Benyoussef; A Elkenz; M Loulidi; B Khalil; O Mounkachi; M Abdellaoui; E K Hlil

    2014-12-01

    Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as,Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

  1. Synthesis and characterization of M3V2O8 (M = Ca, Sr and Ba) by a solid-state metathesis approach

    Indian Academy of Sciences (India)

    Purnendu Parhi; V Manivannan; Sandeep Kohli; Patrick Mccurdy

    2008-11-01

    A solid-state metathesis approach initiated by microwave energy has been successfully applied for the synthesis of orthovanadates, M3V2O8 (M = Ca, Sr, and Ba). The structural, vibrational, thermal, optical and chemical properties of synthesized powders are determined by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, magnetic property measurements and diffused reflectance spectra in the UV–VIS range. The direct bandgap of the synthesized materials was found to be 3.55 ± 0.2 eV, 3.75 ± 0.2 eV and 3.57 ± 0.2 eV for Ca3V2O8, Sr3V2O8 and Ba3V2O8, respectively.

  2. Improvement in the microwave dielectric properties of SrCa4Nb4TiO17 ceramics by Ba substitution

    Indian Academy of Sciences (India)

    Abdul Manan; Yaseen Iqbal

    2014-10-01

    Microwave dielectric ceramics in the Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) solid solutions within the detection limit of in-house X-ray diffraction (XRD). The sintered microstructure of these ceramics comprised densely packed elongated and plate-like grains. The dielectric properties varied linearly with . Relative permittivity (r) increased from 47.2 to 54.5, unloaded quality factor multiplying the resonant frequency (u o) decreased from 11,984 to 9345 GHz and temperature coefficient of resonant frequency (f) increased from –78.6 to 20 ppm/°C with an increase in x from 0 to 0.75. In the present study, r ≈ 51.6, u o ≈ 10,160 GHz (5.37 GHz) and f ≈ –13.5 ppm/°C were achieved for Sr0.5Ba0.5Ca4Nb4TiO17 ( = 0.5) ceramics.

  3. Theoretical characterization of quaternary iridium based hydrides NaAeIrH{sub 6} (Ae = Ca, Ba and Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Bouras, S. [Laboratory of Studies Surfaces and Interfaces of Solids Materials, Department of Physics, Faculty of Science, University of Setif 1, 19000 (Algeria); Ghebouli, B., E-mail: bghebouli@yahoo.fr [Laboratory of Studies Surfaces and Interfaces of Solids Materials, Department of Physics, Faculty of Science, University of Setif 1, 19000 (Algeria); Benkerri, M. [Laboratory of Studies Surfaces and Interfaces of Solids Materials, Department of Physics, Faculty of Science, University of Setif 1, 19000 (Algeria); Ghebouli, M.A., E-mail: med.amineghebouli@yahoo.fr [Microelectronic Laboratory (LMSE), University of Bachir Ibrahimi, Bordj-Bou-Arreridj 34000 (Algeria); Research Unit on Emerging Materials (RUEM), University of Setif 1, 19000 (Algeria); Choutri, H. [Microelectronic Laboratory (LMSE), University of Bachir Ibrahimi, Bordj-Bou-Arreridj 34000 (Algeria); Louail, L.; Chihi, T.; Fatmi, M. [Research Unit on Emerging Materials (RUEM), University of Setif 1, 19000 (Algeria); Bouhemadou, A. [Laboratory for Developing New Materials and Their Characterization, Department of Physics, Faculty of Science, University of Setif 1, 19000 (Algeria); Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Khenata, R.; Khachai, H. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 (Algeria)

    2015-01-15

    The quaternary iridium based hydrides NaAeIrH{sub 6} (Ae = Ca, Ba and Sr) are promising candidates as hydrogen storage materials. We have studied the structural, elastic, electronic, optical and thermodynamic properties of NaAeIrH{sub 6} (Ae = Ca, Ba and Sr) within the generalized gradient approximation, the local density approximation (LDA) and mBj in the frame of density functional perturbation theory. These alloys have a large indirect Γ–X band gap. The thermodynamic functions were computed using the phonon density of states. The origin of the possible transitions from valence band to conduction band was illustrated. By using the complex dielectric function, the optical properties such as absorption, reflectivity, loss function, refractive index and optical conductivity have been obtained. - Graphical abstract: Real and imaginary parts of the dielectric function, the absorption spectrum α(ω), reflectivity R(ω) and energy-loss spectrum L(ω). - Highlights: • NaAeIrH{sub 6} (Ae = Ca, Ba and Sr) alloys have been investigated. • The elastic moduli, energy gaps are predicted. • The optical and thermal properties were studied.

  4. Half-metallic ferromagnetism in zinc-blende CaC , SrC , and BaC from first principles

    Science.gov (United States)

    Gao, G. Y.; Yao, K. L.; Şaşıoǧlu, E.; Sandratskii, L. M.; Liu, Z. L.; Jiang, J. L.

    2007-05-01

    Using the first-principles full-potential linearized augmented plane-wave method based on density functional theory, we have investigated the electronic structure and magnetism of hypothetical M C ( M=Mg , Ca, Sr, and Ba) compounds with the zinc-blende (ZB) crystal structure. It is shown that ZB CaC , SrC , and BaC are half-metallic ferromagnets with large half-metallic gaps (up to 0.83eV ). The half metallicity is found to be robust with respect to the lattice compression and is maintained up to the lattice-constant contraction of 14%, 13%, and 9% for CaC , SrC , and BaC , respectively. The exchange interactions in these compounds are studied using the augmented spherical wave method in conjunction with the frozen-magnon approach. The Curie temperature is estimated within both the mean field approximation and the random phase approximation. The predicted Curie temperatures of all three half-metallic compounds considerably exceed the room temperature. The large half-metallic gaps, the robustness of the half metallicity with respect to the lattice contraction, and the high Curie temperatures make these systems interesting candidates for applications in spintronic devices. The absence of the transition-metal atoms makes these compounds important model systems for the study of the origin and properties of the half-metallic ferromagnetism of s-p electron systems.

  5. Theoretical characterization of quaternary iridium based hydrides NaAeIrH6 (Ae = Ca, Ba and Sr)

    International Nuclear Information System (INIS)

    The quaternary iridium based hydrides NaAeIrH6 (Ae = Ca, Ba and Sr) are promising candidates as hydrogen storage materials. We have studied the structural, elastic, electronic, optical and thermodynamic properties of NaAeIrH6 (Ae = Ca, Ba and Sr) within the generalized gradient approximation, the local density approximation (LDA) and mBj in the frame of density functional perturbation theory. These alloys have a large indirect Γ–X band gap. The thermodynamic functions were computed using the phonon density of states. The origin of the possible transitions from valence band to conduction band was illustrated. By using the complex dielectric function, the optical properties such as absorption, reflectivity, loss function, refractive index and optical conductivity have been obtained. - Graphical abstract: Real and imaginary parts of the dielectric function, the absorption spectrum α(ω), reflectivity R(ω) and energy-loss spectrum L(ω). - Highlights: • NaAeIrH6 (Ae = Ca, Ba and Sr) alloys have been investigated. • The elastic moduli, energy gaps are predicted. • The optical and thermal properties were studied

  6. Spectroscopy and laser properties of Nd3+-doped CaF2,SrF2, and BaF2

    International Nuclear Information System (INIS)

    This paper reports on the optical properties of Nd3+ in caF2, SrF2, and BaF2 that have been investigated in order to determine if these materials are useful at laser-pumped amplifier media. The CaF2:Nd crystal was found to not be useful because the impurities tend to cluster at very low concentration, leading to the formation of nonluminescent centers. On the other hand, the Nd3+ centers in BaF2 exhibit unacceptably low transition strengths. SrF2:Nd appears to have adequate absorption strength, and, in addition, to have a remarkably long emission lifetime at 1280 μs. A maximum doping of 0.20 atomic % Nd3+ can be tolerated in SrF2 without the occurrence of detrimental clustering. The peak emission cross section of SrF2:Nd is 1.7 x 10-20 cm2 at 1036.5 nm. Direct measurement of the gain spectrum of SrF2:Nd3+ reveals the presence of the 4F3/2 → 2G9/2 excited state absorption lines, although the impact on the emission cross section is minor

  7. Structural and optical analysis on europium doped AZrO3 (A=Ba, Ca, Sr) phosphor for display devices application

    Science.gov (United States)

    Dubey, Vikas; Tiwari, Neha

    2016-05-01

    Behavior displayed by europium doped AZrO3 phosphor which was synthesized by solid state reaction method. For synthesis of BaZrO3, SrZrO3 and CaZrO3 phosphor with fixed concentration of europium ion was calcination at 1000°C and sintered at 1300°C following intermediate grinding. Synthesized sample was characterized by X-ray diffraction analysis and crystallite sized was calculated by Scherer's formula. From PL spectra of prepared phosphors shows intense emission centred at 612nm (red emission) with high intensity for SrZrO3:Eu3+. For europium doped BaZrO3 and CaZrO3 (613nm) phosphor shows less intense PL spectra as compared to SrZrO3:Eu3+. The strong emission peak of AZrO3:Eu3+ phosphor is due to forced electric dipole transition of 5D0 to 7F2 centered at 612 and 613nm. It is characteristic red emission for europium ion. The excitation spectra of AZrO3:Eu3+ phosphor mainly consists of the charge transfer and (CTB) of Eu3+ located in 200-350 nm centred at 254nm. The present phosphors can act as single host for red light emission in display devices. The CIE coordinates were calculated by Spectrophotometric method using the spectral energy distribution of the AZrO3:Eu3+ sample.

  8. Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Du, Peng; Yu, Jae Su, E-mail: jsyu@khu.ac.kr

    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.

  9. Studies on the new superconducting system (RE) Ba2Ca3Sr4Cu5Ox (RE=Gd, Ho & Dy)

    Science.gov (United States)

    Arumugam, S.

    1996-03-01

    Superconducting studies have been carried out in the new high TC (50-65K) system (RE)Ba2Ca3Sr4Cu5OX [(RE) 12345] with RE=Gd, Ho&Dy. The unit cell dimensions are of the order of a=5.44 °A, b=5.46°A and c=14.62°A. The data above the diamagnetic onset and below the upturn temperature due to ordering were analyzed to yield the effective magnetic moments (Peff) of the rare earth ions.

  10. Theoretical study for the reduction of N2O with CO Mediated by alkaline-earth metal oxide cations 2MO+(M=Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    The reaction mechanism of the reaction N2O(0Σ+) + CO (1Σ+)→N2 (1Σg+) + CO2 (1Σg+) mediated by alkaline-earth metal oxide cations 2MO+ (m=Ca, Sr, Ba) have been investigated by using the UB3LYP and CCSD (T) levels of theory. The O-atom affinities (OA) testified that only the 2CaO+ can capture O from N2O and transfer O to CO is thermodynamically allowed in three ions. The processes can be expressed as channels l and 2 for the reaction of N2O and CO mediated by 2MO+ (M=Ca, Sr, Ba). For the former, the main reaction processes in a two-step manner to products, the 2MO+, as a catalyzer, transports an oxygen atom from N2O to CO. For the latter, firstly, the N2O interact with the 2MO+ to form IM1, then IM1 interact with the CO to form IM2', along the reaction pathway the intermediate species convert into products 21MO+, N2 and CO2. From above results, the following conclusion was drawn. The channel 2 is kinetically and thermodynamically feasible. Our calculated results show the title reactions are accord with the experiment. (authors)

  11. Impact of A cation size of double perovskite A2AlTaO6 (A = Ca, Sr, Ba) on dielectric and catalytic properties

    International Nuclear Information System (INIS)

    Highlights: • Synthesis by solid state reaction of the double perovskite A2AlTaO6, where A = Ca, Sr and Ba. • The role of different A-site cations on their synthesis and structures was investigated. • The influence of the divalent A-site cations on the dielectric properties was evaluated by resistivity measurements. • Catalytic properties were evaluated in water splitting process, under gamma-rays irradiation emitted by a 60Co source, for the first time. - Abstract: Double perovskite-type oxide A2AlTaO6 materials, where A = Ca, Sr and Ba, were prepared using conventional solid state reaction. The role of different A-site cations on their synthesis, structures, dielectric and catalytic properties was investigated. Double perovskite oxide structures were evaluated using X-ray diffraction (XRD). As the average cation size decreases, the crystallographic structure at room temperature evolves from cubic to monoclinic. The influence of the nature of the divalent A-site cations on the dielectric properties was evaluated by resistivity measurements in the frequency range of 10–106 Hz. It can be found that relative permittivity and dielectric loss regularly changed with A cation size. Catalytic properties of the obtained compounds were evaluated in water splitting process, under gamma-rays irradiation emitted by a 60Co source for the first time. From experimental data it was noticed that the double perovskite Ca2AlTaO6 had a higher catalytic effect

  12. Analysis of (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8}:Eu{sup 2+}, Mn{sup 2+} phosphors for application in solid state lighting

    Energy Technology Data Exchange (ETDEWEB)

    Han, J.K. [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); Piqutte, A.; Hannah, M.E. [OSRAM SYLVANIA Central Research, 71 Cherry Hill Drive Beverly, MA 01915 (United States); Hirata, G.A. [Centro de Nanociencias y Nanotecnolgía, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana-Ensenada Apdo, Ensenada MX CP 22860 (Mexico); Talbot, J.B. [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); University of California, San Diego, Department of Nanoengineering, La Jolla, CA 92093 (United States); Mishra, K.C. [OSRAM SYLVANIA Central Research, 71 Cherry Hill Drive Beverly, MA 01915 (United States); McKittrick, J., E-mail: jmckittrick@ucsd.edu [University of California, San Diego, Materials Science and Engineering Program, La Jolla, CA 92093 (United States); University of California, San Diego, Department of Mechanical and Aerospace Engineering, La Jolla, CA 92093 (United States)

    2014-04-15

    The luminescence properties of Eu{sup 2+} and Mn{sup 2+} co-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} phosphors prepared by combustion synthesis were studied. Eu{sup 2+}-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} has a broad blue emission band centered at 450–485 nm and Eu{sup 2+}–Mn{sup 2+}-activated (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8} exhibits a red emission around 620–703 nm, depending on the relative concentrations of Ba, Ca and Sr. The particle size of Eu{sup 2+} and Mn{sup 2+} co-activated (Ba,Ca){sub 3}MgSi{sub 2}O{sub 8} ranges from 300 nm to 1 μm depending on the metal ion and are agglomerated due to post-synthesis, high temperature annealing. The green emission of Ba{sub 3}MgSi{sub 2}O{sub 8} originates from secondary phases (Ba{sub 2}SiO{sub 4} and BaMgSiO{sub 4}) confirmed by emission spectra and X-ray diffraction patterns. The secondary phases of Ba{sub 3}MgSi{sub 2}O{sub 8} are removed by the addition of Sr. The quantum efficiencies range from 45% to 70% under 400 nm excitation and the lifetime of red emission of Ba{sub 3}MgSi{sub 2}O{sub 8} decreases significantly with increasing temperature, which is 54% at 400 K of that at 80 K compared to that of blue emission (90% at 400 K of that at 80 K). -- highlights: • (Ba,Ca,Sr){sub 3}MgSi{sub 2}O{sub 8}:Eu{sup 2+}, Mn{sup 2+} phosphors were prepared by a combustion synthesis method. • The emission spectra consist of broad blue-emission band and red-emission band. • The quantum efficiencies range between 45% and 70%, depending on the relative concentrations of Ba, Ca and Sr. • The secondary phases were eliminated by additions of Sr. • Lifetime of the red-emission decreases with increasing temperature, suggesting that these phosphors are not useful for solid state lighting applications.

  13. Transport properties of the superconducting Bi2Sr2Ca2Cu3O10-DyBa2SnO5.5 percolation system

    International Nuclear Information System (INIS)

    Electrical transport properties and percolation behavior of superconducting Bi2Sr2Ca2Cu3O10-DyBa2SnO5.5, a superconductor-insulator composite system, have been studied by x-ray diffraction and temperature-resistivity measurements. Normal-state and superconducting percolation threshold values are found to be ∼20 vol % of Bi(2223) in the composite. The values obtained for critical exponents describing the normal-state transport behavior of the system are matched with theoretically expected values for an idealized metal-insulator composite system. No detectable chemical reactivity was observed between Bi(2223) and the ceramic insulator DyBa2SnO5.5, even under severe heat treatment at 850 degree C. The implications are discussed

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

    Science.gov (United States)

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

    2016-01-27

    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 A2CoO2Cu2Se2 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 A2CoO2Cu2Se2 materials could operate in the intermediate temperature region. PMID:26702873

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

    Science.gov (United States)

    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.

  16. Massive production of A2SiO4:Eu3+ and A2SiO4:Eu2+ (A = Ca, Sr, Ba) microspheres and luminescent properties

    Science.gov (United States)

    Wei, Fengjun; Jia, Qiuli

    2015-06-01

    A2SiO4:Eu3+ and A2SiO4:Eu2+ (A = Ca, Sr, Ba) microspheres with dense structure were synthesized by the modified spray-drying process. The obtained samples were characterized by XRD, SEM, and spectrophotometer. The XRD results reveal that all samples are isostructure. The SEM results show that the obtained samples are microspheres with size in the range of 0.6-2.2 μm. Dextrin plays an important role in the formation of spherical morphology. The excitation and emission spectra of the samples indicate that Eu3+ (or Eu2+) ions doped into different alkaline earth silicates will give different emission bands in different color regions and with different emission intensities. A2SiO4:Eu3+ samples show characteristic emission bands originating from 5D0 → 7Fj transitions of Eu3+ ions. A2SiO4:Eu2+ samples show different emission bands. The two emission bands for Sr2SiO4:Eu2+ relate to the two Eu2+ activator sites locating at two Sr2+ sites in Sr2SiO4 host. The difference of luminescent properties relates to the different sites of Eu3+ (or Eu2+) ions in the A2SiO4 hosts.

  17. Bulk and Surface Nanoscale Hole Density Inhomogeneity in HgBa$_2$CuO$_{4+\\delta}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\\delta}$ Cuprates

    OpenAIRE

    Chen, Wei; Sushkov, Oleg P.; Khaliullin, Giniyat

    2010-01-01

    It is well established that the hole density in the prototypical superconductor La$_{2-x}$Sr$_x$CuO$_4$ is very inhomogeneous due to Sr-dopant induced disorder. On the other hand, until recently it is widely believed that the hole distribution in HgBa$_2$CuO$_{4+\\delta}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\\delta}$ doped by interstitial oxygen is much more uniform. Recent nuclear magnetic resonance measurements indicate, however, that the charge inhomogeneity in HgBa$_2$CuO$_{4+\\delta}$ is close to...

  18. Effect of RO (R=Ca,Sr,Ba,Zn or Pb) component on spectroscopic properties of Eu3+ in RO-B2O3 glasses

    Institute of Scientific and Technical Information of China (English)

    FU Shaobo; CHEN Baojiu; LI Xiangping; ZHANG Jinsu; TIAN Yue; SUN Jiashi; ZHONG Haiyang; CHENG Lihong; WU Zhongli

    2012-01-01

    Eu3+-doped binary borate glasses with different metal oxide components RO (R=Ca,Sr,Ba,Zn or Pb) were prepared by meltquenching technique.The fluorescent spectral properties of Eu3+ in these glasses were experimentally studied.The analysis on the phonon sidebands (PSBs) indicated that RO component did not cause obvious change of the electron-phonon coupling constant (EPC).By inspecting the optical absorption edges it was found that RO could greatly affect the band gap energy,and the glass with PbO component revealed the smallest band gap energy,the glasses with ZnO,BaO and SrO showed similar band gap energy.The optical transition intensity parameters of Eu3+ in all studied glasses were calculated,it was found that for each sample its value of Ω2 was larger than that of Ω4 and Ω6,and the sample with PbO component exhibited the smallest Ω2,but the Ωλ values for ZBE,CBE,BBE and SBE were very similar.These results might be helpful for the design of borate glasses.

  19. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    Science.gov (United States)

    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

  20. Large pyroelectric figure of merits for Sr-modified Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics

    Science.gov (United States)

    Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

    2016-02-01

    In the present work ferroelectric, dielectric and pyroelectric properties of Sr-modified Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics were investigated. A significant increase in polarization has been observed, from 16 μC/cm2 to 25 μC/cm2 for 15% Sr added BCZT compositions. Correspondingly an improvement in dielectric constant, from 2743 to 4040, was observed at room temperature (1 MHz). It was found that Curie-Weiss temperature (TCW) decreases from 357 K to 308 K for 15% Sr containing BCZT ceramics. Simultaneously, it also enhances the order-disorder to displacing phase transition as γ varies from 1.91 to 1.31. Pyroelectric coefficient was found to be 25 μC/cm2K at 308 K. Finally, pyroelectric figures of merit (FOMs) for voltage responsivity (Fv), current responsivity (Fi), detectivity (Fd), energy harvesting (Fe) and new energy harvesting (Fe∗) are calculated. A large improvement in pyroelectric FOMs indicates that it might be a potential material for pyroelectric applications.

  1. Double perovskite oxides A{sub 2}FeMoO{sub 6-{delta}} (A=Ca, Sr and Ba) as catalysts for methane combustion

    Energy Technology Data Exchange (ETDEWEB)

    Falcon, H. [Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Instituto de Investigaciones en Fisicoquimica de Cordoba INFIQC, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Barbero, J.A.; Araujo, G.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, 28049 Madrid (Spain); Casais, M.T.; Martinez-Lope, M.J.; Alonso, J.A. [Instituto de Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid (Spain)

    2004-10-15

    Double perovskites of composition A{sub 2}FeMoO{sub 6-{delta}} (A, alkali earths) have been prepared by soft-chemistry procedures, followed by annealing under reducing conditions (H{sub 2}/N{sub 2} flow). These materials are half metallic ferromagnets, well known for their colossal magnetoresistance properties. The samples have been characterized by X-ray diffraction; temperature-programmed oxidation, specific surface measurements and XPS. The Sr compound, of tetragonal symmetry, exhibits a significant amount of oxygen vacancies, as assessed by TPO. The materials have been tested as catalysts for methane oxidation. At moderate temperatures, a significantly higher catalytic activity is observed for the Sr double perovskite, for which a 80% of conversion is reached at 800K; by contrast the Ca and Ba materials are found to display much poorer characteristics, hardly achieving 50% of conversion rate at 1000K. The much superior characteristics of Sr{sub 2}FeMoO{sub 6-{delta}} are believed to be related to the presence of oxygen vacancies in the crystal structure.

  2. Photocatalytic properties of CoOx-loaded nano-crystalline perovskite oxynitrides ABO2N (A = Ca, Sr, Ba, La; B = Nb, Ta)

    Science.gov (United States)

    Oehler, Florian; Ebbinghaus, Stefan G.

    2016-04-01

    Highly crystalline niobium- and tantalum-based oxynitride perovskite nanoparticles were obtained from hydrothermally synthesized oxide precursors by thermal ammonolysis at different temperatures. The samples were studied with respect to their morphological, optical and thermal properties as well as their photocatalytic activity in the decomposition of methyl orange. Phase pure oxynitrides were obtained at rather low ammonolysis temperatures between 740 °C (CaNbO2N) and 1000 °C (BaTaO2N). Particle sizes were found to be in the range 27 nm-146 nm and large specific surface areas up to 37 m2 g-1 were observed. High photocatalytic activities were found for CaNbO2N and SrNbO2N prepared at low ammonolysis temperatures. CoOx as co-catalyst was loaded on the oxynitride particles resulting in a strong increase of the photocatalytic activities up to 30% methyl orange degradation within 3 h for SrNbO2N:CoOx.

  3. Improvement of critical current density in thallium-based (Tl, Bi)Sr1.6Ba0.4Ca2Cu3O9-δ superconductors

    International Nuclear Information System (INIS)

    Epitaxial (Tl,Bi)Sr1.6Ba0.4Ca2Cu3Ox ((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 (Jc) were measured. The zero-resistance temperature was 105--111 K. Jc at 77 K and zero field was >2 x 106 A/cm2. The films exhibited good flux pinning properties

  4. The red-emitting phosphors of Eu3+-activated MR2(MoO4)4 (M = Ba, Sr, Ca; R = La3+, Gd3+, Y3+) for light emitting diodes

    International Nuclear Information System (INIS)

    Graphical abstract: The luminescence quantum efficiencies of Eu3+-doped MY2−xEux(MoO4)4 show the dependence on the Eu3+ doping (x) for M = Ca (a), Sr (b), Ba (c). Display Omitted Highlights: ► Eu3+-activated MY2(MoO4)4 (M = Ba, Sr, Ca) were firstly prepared. ► Comprehensive investigations of QEs and thermal stabilities of Eu3+-activated MR2(MoO4)4 (M = Ba, Sr, Ca; R = La, Gd). ► BaYEu(MoO4)4, SrY0.6Eu1.4(MoO4)4 and CaEu2(MoO4)4 are the best choice for solid state lighting because of high QEs and thermal stabilities. -- Abstract: A series of red-emitting phosphors of MR2(MoO4)4:Eu3+ (M = Ba, Sr, Ca; R = La3+, Gd3+, Y3+) were prepared by solid-state reaction. The photoluminescence excitation and emission spectra were investigated. The phosphors can be efficiently excited by the near UV light and exhibit a red luminescence corresponding to the electric dipole transition 5D0 → 7F2 at 615 nm. The optimum doping in MY2−xEux(MoO4)4 (M = Ba, Sr, Ca) were investigated by the dependence of luminescence quantum efficiency (QE) on the Eu3+ concentrations. The absolute luminescence quantum efficiencies were measured for all the samples. The luminescence thermal satiability was checked by measuring the temperature-dependent luminescence intensities in temperature region of 10–450 K. The results indicate that the three phosphors of BaYEu(MoO4)4, SrY0.6Eu1.4(MoO4)4 and CaEu2(MoO4)4 are the best choice for white-LEDs to be used for lighting. This was evaluated in details by taking into account of the properties such as the excitation spectra, the luminescence QEs, the red color coordinates, the luminescence quenching of Eu3+-doping concentrations and the thermal stability.

  5. Oxygen vacancies and peroxo groups on regular and low-coordinated sites of MgO, CaO, SrO, and BaO surfaces

    Science.gov (United States)

    Di Valentin, Cristiana; Ferullo, Ricardo; Binda, Riccardo; Pacchioni, Gianfranco

    2006-03-01

    The formation of an oxygen vacancy and the simultaneous re-adsorption of an oxygen atom on regular and low-coordinated (LC) sites (edges and corners) of the surface of alkaline-earth oxides with cubic rock salt structure, MgO, CaO, SrO, and BaO, has been investigated using DFT cluster model calculations. The process corresponds to the formation of a surface Frenkel defect when the vacancy formation energy is partially compensated by the energy gained in the formation of a peroxo group. The structural and electronic properties of vacancies and peroxo groups along the series of alkaline-earth oxides have been analyzed. We found that the role of low-coordinated sites on the surface chemistry of alkaline-earth oxides is of crucial importance for MgO, but decreases for the heavier members. For instance, on BaO the formation of a peroxo group is practically site-insensitive. This is not the case of the vacancy formation, which is always favored on the low-coordinated sites.

  6. One step synthesis of Bi(Pb)-2223 phase in Bi(Pb)-Sr(Ba)-Ca-Cu nitrate freeze dried powder

    International Nuclear Information System (INIS)

    One step synthesis of the superconducting Bi(Pb)-2223 phase during heat treatment for non-equilibrium decomposition of the freeze dried Bi:Pb:Sr:Ba:Ca:Cu=1.8:0.4:1.8:0.2:2.2:3.0 nitrate powder has been studied. The heating rate was ∼ 100 deg. C min-1 and samples were maintained in air at 848 deg. C for 0, 5, 10, 20, 30, 60, 90, 240 and 1080 min. Each batch was investigated by x-ray diffraction analysis and ac magnetic susceptibility χ'(T). Evolution of phases and kinetics of phase formation-decomposition processes were discussed. ∼ 80% of Bi(Pb)-2223 has formed indicating the possibility of lowering the processing time of the freeze dried precursor powders by one order of magnitude comparative to the multistep synthesis route (from hundreds to tens of hours). A 30 min heat treatment step at 840 deg. C performed on the way up to the synthesis temperature is a forthcoming operation in order to block the formation of secondary undesired phases (e.g. Ca1-xSrx)14Cu24O41). (author)

  7. Hall measurements of La0.8A0.2TiO3-δ (A= Ba, Sr, Ca, Li, Mg) perovskites

    International Nuclear Information System (INIS)

    Metal-insulator transitions have been extensively studied in an effort to understand the mechanism essential for the localization of carriers in a wide range of materials. Electron correlation plays an important role in complex oxides, including colossal magnetoresistive materials and high-Tc superconductors. The Mott insulator LaTiO3 has received renewed interest because of its metallicity in (001) superlattices. The effects of chemical doping have been investigated extensively in bulk LaTiO3 in order to study the roles of electronic bandwidth and band filling. Metallicity in LaTiO3 can be induced by cation vacancies, excess oxygen, or alkaline-earth doping of the rare-earth site. In a search to observe the effect of nanosize on its electrical and magnetic properties, A-site doped LaTiO3 (with Ba, Sr, Ca, Li. Mg) were prepared by sol-gel method followed by calcinations. After calcinations these perovskites were deposited as thin films in a glass substrates using chemical deposition method. The structural characteristics of the perovskites were analysed through X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). To know the electrical nature and the majority charge carriers Hall measurements were carried out at room temperature. The normal state resistivity, upper critical field and hall coefficient in the perovskite materials were reported. (author)

  8. Unusual suppression of low energy spin excitations near Fermi level in AFe4Sb12 (A=Ca, Sr, and Ba) probed by Sb-NQR

    International Nuclear Information System (INIS)

    Sb nuclear quadrupole resonances (NQR) have been performed on the alkaline-earth filled skutterudite AFe4Sb12 (A=Ca, Sr, and Ba) being close to ferromagnetic instability. No hyperfine splitting in NQR spectrum even at the lowest temperature (1.5 K) confirms an absence of uniform ferromagnetic order in these compounds. Above about T* - 70 K, the nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, follows an empirical relationship 1/T1T=a+b χspin with respect to the Curie Weiss (CW) like T-dependence of the static spin susceptibility χspin. The correlation between 1/T1T and χspin is consistent with the self-consistent renormalization (SCR) theory for the three-dimensional (3D) nearly ferromagnet despite the relatively large contribution of the first term not correlating to χspin. However, below about T*, 1/T1T exhibits a gap-like suppression with a gap magnitude of about 65 K. This unusual suppression of the low energy spin excitations is contrasting to the case in LaFe4Sb12, and a characteristic feature in the filled skutterudites with divalent filler ion. The pseudo-gap structure near the Fermi level is proposed for the hybridized Fe3d-Sb5p band (mainly partial p state) for the unusual suppression. (author)

  9. Legitional behavior of 5,5-diethylbarbituric acid sodium salt (HL) towards Mg, Ca, Sr, Ba(II), spectral, thermal and biological studies

    Science.gov (United States)

    Refat, Moamen S.; El-Metwaly, Nashwa M.

    2011-03-01

    A new series of sodium barbital complexes with Alkaline earth metals (Mg2+, Ca2+, Sr2+ and Ba2+ ions) was prepared. The molecular formulas for the isolated complexes were suggested basically on the elemental analysis data. The binuclear central were proposed for all investigated complexes. The geometry suggested based on knowing the coordination sits for each complex was built on concerning with the shift observed in IR spectra surround the coordinating groups. The shifts in charge transfer bands appeared in the electronic spectra of the complexes supports the coordination process. The presence of solvent molecules coordinately attached with central metal atoms as well as the conjugated anions was supported based on thermogravimetric analysis. The kinetic parameters were calculated for each complex. The theoretical calculations for the molecular modeling structures reflect an insight about their stability in comparing with the free ligand. The XRD studies were performed and concluding the nanocrystalline feature for all complexes. The biochemical effect of all investigated compounds was performed towards Gram-negative and Gram-positive bacteria as well as their degradation effect on calf Thymus DNA. The biological performance is the major goal in this study especially with such essential metal ions.

  10. Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study

    Indian Academy of Sciences (India)

    Ashim Baishya; V Rao Mundlapati; Sharanappa Nembenna; Himansu S Biswal

    2014-11-01

    A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their -diketiminate, guanidinate and -diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature.

  11. On the photo-luminescence properties of sol–gel derived undoped and Dy3+ ion doped nanocrystalline Scheelite type AMoO4 (A = Ca, Sr and Ba)

    International Nuclear Information System (INIS)

    Nanocrystalline Scheelite type Dy doped AMoO4 [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 CaMoO4 and SrMoO4 but multicolour visible emission leading to near white light in BaMoO4 nanoparticles; the origin of which is explained. It was observed that on doping 0.5 mol% of Dy3+ in molybdate samples complete energy transfer takes place in case of SrMoO4 and BaMoO4, but host contributed substantially in Dy doped BaMoO4 sample, resulting in biexponential decay. It was also observed that symmetry around Dy3+ 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

  12. 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)

    Energy Technology Data Exchange (ETDEWEB)

    Jena, Paramananda [Department of Physics, Pondicherry University, Pondicherry 605014 (India); Gupta, Santosh K., E-mail: santufrnd@gmail.com [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Natarajan, V. [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Padmaraj, O. [Department of Physics, Pondicherry University, Pondicherry 605014 (India); Satyanarayana, N., E-mail: nallanis2011@gmail.com [Department of Physics, Pondicherry University, Pondicherry 605014 (India); Venkateswarlu, M. [R & D Amara Raja Batteries Ltd., Karakambadi 517501, AP (India)

    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.

  13. Temperature and wavelength dependent trap filling in M{sub 2}Si{sub 5}N{sub 8}:Eu (M=Ca, Sr, Ba) persistent phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Smet, Philippe F., E-mail: philippe.smet@ugent.be [LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium); Center for Nano- and Biophotonics (NB-Photonics), Ghent University (Belgium); Van den Eeckhout, Koen [LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium); Center for Nano- and Biophotonics (NB-Photonics), Ghent University (Belgium); Bos, Adrie J.J.; Kolk, Erik van der; Dorenbos, Pieter [Delft University of Technology, Faculty of Applied Sciences, 2629 JB Delft (Netherlands)

    2012-03-15

    The evaluation of persistent phosphors is often focused on the processes right after the excitation, namely on the shape of the afterglow decay curve and the duration of the afterglow, in combination with thermoluminescence glow curve analysis. In this paper we study in detail the trap filling process in europium-doped alkaline earth silicon nitrides (Ca{sub 2}Si{sub 5}N{sub 8}:Eu, Sr{sub 2}Si{sub 5}N{sub 8}:Eu and Ba{sub 2}Si{sub 5}N{sub 8}:Eu), i.e., how the persistent luminescence can be induced. Both the temperature at which the phosphors are excited and the spectral distribution of the excitation light on the ability to store energy in the phosphors' lattices are investigated. We show that for these phosphors this storage process is thermally activated upon excitation in the lower 5d excited states of Eu{sup 2+}, with the lowest thermal barrier for europium doped Ca{sub 2}Si{sub 5}N{sub 8}. Also, the influence of co-doping with thulium on the trap filling and afterglow behavior is studied. Finally there exists a clear relation between the luminescence quenching temperature and the trap filling efficiency. The latter relation can be utilized to select new efficient 5d-4f based afterglow phosphors. - Highlights: Black-Right-Pointing-Pointer Orange afterglow in M{sub 2}Si{sub 5}N{sub 8}:Eu(Tm) studied with thermoluminescence spectroscopy. Black-Right-Pointing-Pointer Strong influences of excitation wavelength and temperature on trap filling. Black-Right-Pointing-Pointer Energy level scheme is presented. Black-Right-Pointing-Pointer Relation between trap filling with visible light and thermal quenching behavior.

  14. Isomorphous miscibility in MEO4 (scheelite) - LnVO4 (zircon) systems, where M=Ca, Sr, Ba, Cd, Pb; E=Mo, W; Ln=Y and lanthanides

    International Nuclear Information System (INIS)

    Method of X-ray phase analysis was used to study phase relations in MEO4 (scheelite) - LnVO4 (zircon) systems, where M=Ca, Sr, Ba, Cd, Pb; E=Mo, W; Ln=Y, Ce, Nd, Eu. Formation of limited solid solutions M1-xVxO4 was established. Evaluation of isomorphous miscibility in scheelite-zircon systems according to the statements of energy theory of isomorphous miscibility was conducted

  15. [Photoluminescence properties of nanocrystalline A3(VO4)2:Eu(A = Mg, Ca, Sr and Ba)].

    Science.gov (United States)

    Fu, Xiao-yan; Niu, Shu-yun; Zhang, Hong-wu; Xin, Qin

    2006-01-01

    A series of europium doped alkali earth orthovanadates were prepared by Pechini-type sol-gel. The powders were characterized by transmission electron microscopy (TEM), infrared spectrum (IR) and photoluminescence (PL). The results of TEM show that high-quality nanopowders with controlled particle size about 50 nm were prepared. The relation between alkali earth ions and luminescence properties was observed from the results of luminescence spectra. Due to the similar ion radius of Ca2+ ions and Eu3+ ions, Ca3 (VO4 )2:Eu powders exhibit the strongest emission intensity among the four kind of phosphors. PMID:16827335

  16. Synthesis of leucite, sanidine and a melt of sanidine at 930-10300C and 2 Kb: partition coefficients of Rb, Ca, Sr and Ba between these phases and hydrothermal solution of KCl. Geological utilizations

    International Nuclear Information System (INIS)

    This work shows the results of hydrothermal experiments to determine the distribution coefficients of alcali and alcaline earth elements in trace concentrations between sanidine and liquids of same composition and between leucite and liquid. At 2 Kb pressure and 9300C for sanidine, 9300 and 10300C for leucite and 10300C for a melt of sanidine composition the concentration of trace elements (TE) in the coexisting potassium bearing aqueous fluid phase was varied between 10-1 to 10-6 mole to one mol of K+. By use of radioactive tracers (Rb86, Ca45, Sr85, Ba133) the concentrations in TE of the aqueous phase, the solids and melts has been determined. This indirect method will give a good aproximation of the behaviour of TE between a melt and crystallising solids. These aprotimations lead to following conclusions: a) during the crystallisation of leucite, this phase incorporates large quantities of Ba and Rb, depleting the residual melt in those elements. Sr and Ca, on the other hand are enriched in the residual melt. b) the crystallisation of sanidine depletes even more the residual melt in Ba, Sr shows similias behaviour, Rb and Ca, however, are enriched in the residual melt phase. (author)

  17. Synthesis of (Hg,Pb)(Sr,Ba)2Ca2Cu3Oz superconducting films via MOCVD and PLD

    International Nuclear Information System (INIS)

    (0 0 1)-oriented Sr-containing (Hg,Pb)-1223 films have been synthesised for the first time using the two-step procedure. Hg-free precursor films with the thickness up to 1 μm have been deposited by metalorganic chemical vapor deposition (MOCVD) or pulsed infra-red laser ablation (PLD) and then the films were annealed in a mercury-containing atmosphere in sealed quartz ampoules. No post-annealing in oxygen was used. The phase composition of the PLD-derived films depended crucially on the deposition temperature of the precursor films. MOCVD-derived films contained only very small amounts of non-superconducting phases according to XRD. The Tc=118 K and jc(77 K,0.01 T)=2.5x106A/cm2 have been measured for the MOCVD-derived samples

  18. Studies of two-powders mixtures in Bi(Pb)-Sr(Ba)-Ca-Cu- oxide/nitrate system obtained by freeze drying used for synthesis of 2223 superconducting ceramic

    International Nuclear Information System (INIS)

    Nitrate freeze dried raw powders Bi:Pb:Sr:Ba:Ca:Cu 1.8:0.4:1.8:0.2:2.2:3.0('2223-nitrate'). Bi:Pb:Sr:Ba:Ca:Cu 1.8:0.4:1.8:0.2:1.2:2.0 ('2212-nitrate') and Ca:Cu = 1:1 ('11-nitrate') have been decomposed at 840 deg. C for 30 min. to obtain '2223-oxide', '2212-oxide' and '11-oxide' powders. From the above powders the following mixtures (mechanically mixed) were prepared: '2212-oxide' + '11-nitrate', '2212-nitrate' + '11-oxide' and '2212-nitrate' + '11-nitrate' and thermally decomposed in the same conditions. The decomposed powders were investigated by XRD analysis. From the indicated decomposed mixtures, '2223-oxide' powder and mixture '2212-oxide' + '11-oxide' superconducting pellets with composition 2223 were sintered. Electrical resistance R(T) measurements on pellets have been performed. The obtained data have shown different phase compositions in the decomposed samples indicating different phase formation reactions. Because of this fact superconducting parameters in sintered pellets are changing. The optimum precursor powder considering R(T) results for the synthesis of 2223 phase is the decomposed sample '2212-nitrate + 11-nitrate', although the best level of mixing is in the '2223-oxide' powder. The most unfavorable mixture for 2212 and 2223-phase formation is the decomposed sample '2212-nitrate + 11-oxide' due to the lack of (Sr,Ca)CuO2 phase. (authors)

  19. CO adsorption on Ni, Pd, Cu and Ag deposited on MgO, CaO, SrO and BaO: Density functional calculations

    International Nuclear Information System (INIS)

    The adsorption properties of CO molecules adsorbed on Ni, Pd, Cu and Ag atoms deposited on O2-, F and F+ sites of MgO, CaO, SrO and BaO terrace surfaces have been studied by means of density functional calculations and embedded cluster model. The examined clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The adsorption properties of CO have been analyzed with reference to the basicity of the oxide support, bond order conservation energy, pairwise and non-pairwise additivity, associative adsorption, electrostatic potentials, and orbital interactions. CO adsorption on an oxide support is drastically enhanced when CO is adsorbed on a metal deposited on this support. A dramatic change is found, and explained, when one compares the CO binding energy to O2- and F sites. The formation of a strong bond at the support-metal interface has a considerable consequence on the metal-CO binding energy. The binding of CO is dominated by the metal-CO pairwise additive term, and the non-additivity term increases with increasing the basicity of the support. While the classical contributions to the electrostatic interactions are quite similar for the deposited metals, they are quite dissimilar when going from defect-free to defect-containing surfaces. The adsorption properties correlate linearly with the basicity and energy gaps of the oxide support where the electrostatic potential generated by the oxide modifies the physical and chemical properties of the adsorbed metal and therefore its reactivity versus the CO adsorbate.

  20. Metal-clad superconducting tapes with high critical current density in the Y-Ba-Cu-O and Bi(Pb)-Sr-Ca-Cu-O systems

    International Nuclear Information System (INIS)

    Superconducting powders representing the Y-Ba-Cy-O (YBCO) and Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) systems were used either alone or combining them with different amounts of silver powder to fabricate metal-clad superconducting tapes by the powder-in-tube method. The metallic tubes used were nickel for the YBCO system and silver for the BPSCCO system. The initial tapes were produced by cold-rolling the tubes to various thicknesses and then processed following rigorous regimens of sintering, annealing and oxygenation schedules. The YBCO tapes were generally processed by a gradientless melt-texturizing process in an oxygen atmosphere, and the BPSCCO tapes were processed by a combination of rolling and sintering operations in air and in low oxygen partial pressure. This paper reports on the effects of various compositional and processing variables on the superconductive properties of the tapes measured by the DC magnetization, AC susceptibility and direct transport current measurements. Transport critical currents greater than 600 A at 4.2K were routinely carried by the YBCO tapes. Also, for the YBCO system, the effects of silver addition to control oxygenation and nickel poisoning of the superconducting phase were studied in detail with the help of magnetization measurements. Addition of silver up to 5 wt% was found to be beneficial for critical current density in YBCO tapes. However, direct contact of the superconductor with oxygen was essential for optimum current density. On the other hand, homogenization of the precursor powder by repeated calcination and the tapes of the lowest thickness offered the most improved critical current density values of the BPSCCO system

  1. Effect of Ag additions on shock wave degradation of superconductivity in Bi-Pb-Sr-Ca-Cu-O and Y-Ba-Cu-O

    International Nuclear Information System (INIS)

    While it has been successfully demonstrated that Bi-Pb-Sr-Ca-Cu-O and YBa2Cu3Ox powders as well as mixtures of these powders along with silver and copper can be shock fabricated in metal or alloy matrices, it has been found that their superconducting properties are degraded by the shock wave. In shock fabricating Bi7Pb3Sr10Ca10Cu15Ox, it has been observed that at peak shock pressures of 4 GPa and above, the as-shocked material behaves as a semiconductor and there is no transition or superconducting onset in the resistance-temperature (R-T) signature. A transition was recently seen for the first time in Bi7Pb3Sr10Ca10Cu15Ox with plane wave shock loading at 1.5 GPa peak shock pressure. However, even at such a low peak pressure, the R-T signature showed signs of residual degradation: the normal state resistivity was semiconducting and it showed a two phase transition with a Tc(R=O) of about 77 K. The R-T signatures of these degraded samples could, however, be completely recovered on proper heat treatment (typically around 860 degrees C in flowing air for 90 hours). The results of the effect of the shock wave on Bi7Pb3Sr10Ca10Ci15Ox and YBa2Cu3Ox at different Ag doping levels is presented in this paper

  2. The magnetic properties of the hole-doped cobaltites R0.5A0.5CoO3 (R=La, rare earth and A=Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    The ac and dc magnetic properties of hole-doped cobaltites with compositions La0.5Sr0.5-xAxCoO3 (A=Ca, Ba) and La0.5-xRxSr0.5CoO3 (R=Nd, Eu) have been studied. The suppression of the cluster glass behaviour of the parent compound, La0.5Sr0.5CoO3, by substitutions for either the lanthanum or the strontium ions is accompanied by an increase in coercive field (HC) and thermomagnetic irreversibility. The results suggest that the large thermomagnetic irreversibility and coercive fields observed in the hole-doped perovskite cobaltites, arising due to the anisotropic nature of their ferromagnetic character, cannot be correlated with the cluster glass freezing observed in them. (author)

  3. Defect chemistry and oxygen transport of (La0.6Sr0.4-xMx)(0.99)Co0.2Fe0.8O3-delta, M = Ca (x=0.05, 0.1), Ba (x=0.1, 0.2), Sr Part I: Defect chemistry

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas; Søgaard, Martin; Bouwmeester, Henry J.M.;

    2009-01-01

    This paper is the first part of a two part series, where the effects of varying the A-site dopant on the defect chemistry, the diffusion coefficient and the surface catalytic properties of the materials (La0.6Sr0.4 − xMx)0.99Co0.2Fe0.8O3 − δ, M = Sr, Ca (x = 0.05, 0.1), Ba (x = 0.1, 0.2) (LSMFC......) have been investigated. In part I, the findings on the defect chemistry are reported, while the transport properties are reported in part II. Substitution of Sr2+ ions with Ca2+ ions (smaller ionic radius) and Ba2+ ions (larger ionic radius) strains the crystal structure differently for each...... oxygen loss was modelled with point defect chemistry models. Measurements at very low pO2 showed several phase transitions....

  4. Formation of compounds in the quasi-binary systems AcX4-MX2 (Ac = Th, U; M = Ca, Sr, Ba, Eu, Ge, Sn, Pb; X = Br, I)

    International Nuclear Information System (INIS)

    T,x-phase diagrams of the systems ThI4-SnI2, ThI4-PbI2, ThI4-CaI2 and ThI4-SrI2 were established using thermoanalysis and X-ray methods. The only ternary compounds have a 1:1 composition. Further AcMX6 compounds (Ac: Th, U; M: Ca, Sr, Ba, Eu, Ge, Sn, Pb; X: Br, I) were synthesized and their structures investigated. Four structure types are found depending on the temperature and the Ac/M combinations. The structures of γ-ThSnI6 and β-ThSnI6 were determined with single crystal methods as representatives of a whole series of isotypic compounds. (orig.)

  5. Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF2, SrF2, and BaF2)

    International Nuclear Information System (INIS)

    The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF2, SrF2, and BaF2 is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF2 crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ∼2 × 103 pA/cm2). In BaF2 samples, the transformation of BaO into Ba(OH)2 was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH)2 into BaO. In the initial stage of irradiation of all MF2 compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF2 matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF2 destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ∼20 nm in the sample.

  6. AFe2As2 (A = Ca, Sr, Ba, Eu) and SrFe2-xTMxAs2 (TM = Mn, Co, Ni): crystal structure, charge doping, magnetism and superconductivity

    International Nuclear Information System (INIS)

    The electronic structure and physical properties of the pnictide compound families REOFeAs (RE=La, Ce, Pr, Nd, Sm), AFe2As2 (A=Ca, Sr, Ba, Eu), LiFeAs and FeSe are quite similar. Here, we focus on the members of the AFe2As2 family whose sample composition, quality and single-crystal growth are more controllable compared with the other systems. Using first-principles band structure calculations, we focus on understanding the relationship between the crystal structure, charge doping and magnetism in AFe2As2 systems. We will elaborate on the tetragonal to orthorhombic structural distortion along with the associated magnetic order and anisotropy, the influence of doping on the A site and the Fe site and the changes in the electronic structure as a function of pressure. Experimentally, we investigate the substitution of Fe in SrFe2-xTMxAs2 by other 3d transition metals, TM=Mn, Co or Ni. In contrast to a partial substitution of Fe by Co or Ni (electron doping), a corresponding Mn partial substitution does not lead to the suppression of the antiferromagnetic order or the appearance of superconductivity. Most of the calculated properties agree well with the measured properties, but several of them are sensitive to the As z position. For a microscopic understanding of the electronic structure of this new family of superconductors, this structural feature related to the Fe-As interaction is crucial, but its correct ab initio treatment still remains an open question.

  7. Luminescent phosphors, based on rare earth substituted oxyfluorides in the A(1){sub 3-x} A(2){sub x}MO{sub 4}F family with A(1)/A(2)=Sr, Ca, Ba and M=Al, Ga

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sangmoon, E-mail: spark@silla.ac.k [Department of Engineering in Energy and Applied Chemistry, Silla University, Busan 617-736 (Korea, Republic of); Vogt, Thomas [NanoCenter and Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, SC (United States)

    2009-09-15

    A new family of UV-activated phosphors made by substituting rare-earth activators such as trivalent Eu, Tb, Tm and Er into A(1){sub 3-x}A(2){sub x}MO{sub 4}F host lattices (A(1)/A(2)=Sr, Ca, Ba; M=Al, Ga) are introduced and their activation and emission spectra as well as their CIE values reported. The Tm-substituted system can be activated using light with a wavelength of 360 nm. Relative intensities of a family of Tb-substituted green phosphors activated at 254 nm and with emissions centered near 548 nm are discussed.

  8. Adsorpsi Dan Desorpsi Karotenoida Dari Minyak Sawit Mentah (Crude Palm Oil/Cpo) Menggunakan Adsorben Garam M-Amberlit Ir 120 Dan Garam M-Polistirena Sulfonat (M=Na, Mg, Ca, Sr Dan Ba)

    OpenAIRE

    Karo Karo, Justaman Arifin

    2016-01-01

    Have performed the synthesis of 2 (two) types of adsorbents M-Amberlite salt (M-Am) and M-polistiril sulfonate salt (M-PSS), M = Na, Mg, Ca, Sr, and Ba. M-Am prepared by reacting Na-Am with chloride salts of magnesium, calcium, strontium and barium. Na-Am was obtained from Dow Rohm and Haas Shanghai Chemical Industry Co.. LTD, China. While the M-PSS salt made from Na-PSS with chloride salts of magnesium, calcium, strontium and barium. Na-PSS was made by neutralizing the sulfonic acid polystyr...

  9. Mixed ligand complexes of alkaline earth metals: Part XII. Mg(II, Ca(II, Sr(II and Ba(II complexes with 5-chlorosalicylaldehyde and salicylaldehyde or hydroxyaromatic ketones

    Directory of Open Access Journals (Sweden)

    MITHLESH AGRAWAL

    2002-04-01

    Full Text Available The reactions of alkaline earth metal chlorides with 5-chlorosalicylaldehyde and salicylaldehyde, 2-hydroxyacetophenone or 2-hydroxypropiophenone have been carried out in 1 : 1 : 1 mole ratio and the mixed ligand complexes of the type MLL’(H2O2 (where M = Mg(II, Ca(II, Sr(II and Ba(II, HL = 5-chlorosalicylaldehyde and HL’ = salicylaldehyde, 2-hydroxyacetophenone or 2-hydroxypropiophenone have been isolated. These complexes were characterized by TLC, conductance measurements, IR and 1H-NMR spectra.

  10. Perovskite oxides MRuO3 (M = Sr, Ca and Ba): Structural distortion, electronic and magnetic properties with GGA and GGA-modified Becke–Johnson approaches

    OpenAIRE

    Labdelli Abbes; Hamdad Noura

    2015-01-01

    Electronic and magnetic properties of transition-metal oxides are a continuing research theme due to the variety of ground states and their technological applications. In the present paper, we present first-principles calculations using the full-potential linear augmented plane-wave methods (FP-LAPW) on the structural, electronic and magnetic properties of tree cubic (Pm–3m space group) perovskite oxides SrRuO3, BaRuO3, and CaRuO3 in comparison with other phases ((4H) four-layered hexagonal (...

  11. Effects of M2+ (M = Ca, Sr, and Ba Addition on Crystallization and Microstructure of SiO2-MgO-Al2O3-B2O3-K2O-F Glass

    Directory of Open Access Journals (Sweden)

    Mrinmoy Garai

    2015-01-01

    Full Text Available In understanding the effect of K+ substitution by M2+ (M = Ca, Sr, and Ba on crystallization and microstructural properties of boroaluminosilicate glass system, the SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glasses were prepared by single-step melt-quenching at 1500°C. Density of base glass (2.64 g·cm−3 is found to be decreased in presence of CaO and SrO. Tg is increased by 5–10°C and Td decreased by 13–20°C on addition of M2+. The variation of Tg, Td and decrease of thermal expansion (CTE from 7.55 to 6.67–6.97 (×10−6/K, at 50–500°C in substituting K+ by M2+ are attributed to the higher field-strength of Ca2+, Sr2+, and Ba2+. Opaque mica glass-ceramics were derived from the transparent boroaluminosilicate glasses by controlled heat treatment at 1050°C (duration = 4 h; and the predominant crystalline phase was identified as fluorophlogopite (KMg3AlSi3O10F2 by XRD and FTIR study. Glass-ceramic microstructure reveals that the platelike mica flake crystals predominate in presence of K2O and CaO but restructured to smaller droplet like spherical shaped mica on addition of SrO and BaO. Wide range of CTE values (9.54–13.38 × 10−6/K at 50–800°C are obtained for such glass-ceramics. Having higher CTE value after crystallization, the CaO containing SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glass can be useful as SOFC sealing material.

  12. 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.

    Science.gov (United States)

    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. PMID:26685890

  13. Photoluminescence and phosphorescence properties of MAl2O4:Eu2+, Dy3+ (M=Ca, Ba, Sr) phosphors prepared at an initiating combustion temperature of 500 deg. C

    International Nuclear Information System (INIS)

    Eu2+ and Dy3+ co-doped calcium aluminate, barium aluminate and strontium aluminate phosphors were synthesized at an initiating combustion temperature of 500 deg. C using urea as an organic fuel. The crystallinity of the phosphors was investigated by using X-ray diffraction (XRD) and the morphology was determined by a scanning electron microscope (SEM). The low temperature monoclinic structure for both CaAl2O4 and SrAl2O4 and the hexagonal structure of BaAl2O4 were observed. The effect of the host materials on the photoluminescence (PL) and phosphorescence properties were investigated by using a He-Cd Laser and a Cary Eclipse fluorescence spectrophotometer, respectively. The broad band emission spectra observed at 449 nm for CaAl2O4:Eu2+, Dy3+, 450 nm (with a shoulder-peak at 500 nm) for BaAl2O4:Eu2+, Dy3+ and 528 nm for SrAl2O4:Eu2+, Dy3+ are attributed to the 4f65d1 to 4f7 transition in the Eu2+ ion in the different hosts.

  14. Photoluminescence and phosphorescence properties of MAl{sub 2}O{sub 4}:Eu{sup 2+}, Dy{sup 3+} (M=Ca, Ba, Sr) phosphors prepared at an initiating combustion temperature of 500 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Mothudi, B.M., E-mail: mothudibm@qwa.uovs.ac.z [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa); Ntwaeaborwa, O.M. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa); Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth, ZA 6031 (South Africa); Swart, H.C., E-mail: swarthc.sci@ufs.ac.z [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa)

    2009-12-01

    Eu{sup 2+} and Dy{sup 3+} co-doped calcium aluminate, barium aluminate and strontium aluminate phosphors were synthesized at an initiating combustion temperature of 500 deg. C using urea as an organic fuel. The crystallinity of the phosphors was investigated by using X-ray diffraction (XRD) and the morphology was determined by a scanning electron microscope (SEM). The low temperature monoclinic structure for both CaAl{sub 2}O{sub 4} and SrAl{sub 2}O{sub 4} and the hexagonal structure of BaAl{sub 2}O{sub 4} were observed. The effect of the host materials on the photoluminescence (PL) and phosphorescence properties were investigated by using a He-Cd Laser and a Cary Eclipse fluorescence spectrophotometer, respectively. The broad band emission spectra observed at 449 nm for CaAl{sub 2}O{sub 4}:Eu{sup 2+}, Dy{sup 3+}, 450 nm (with a shoulder-peak at 500 nm) for BaAl{sub 2}O{sub 4}:Eu{sup 2+}, Dy{sup 3+} and 528 nm for SrAl{sub 2}O{sub 4}:Eu{sup 2+}, Dy{sup 3+} are attributed to the 4f{sup 6}5d{sup 1} to 4f{sup 7} transition in the Eu{sup 2+} ion in the different hosts.

  15. Research on new rare-earth half-metallic ferromagnets X0.75Eu0.25O (X=Ca, Sr and Ba) based on the first-principles calculations

    Science.gov (United States)

    Jun, Liu; Xiao-Lan, Yang; Wei, Kang

    2016-09-01

    New rare-earth half-metallic ferromagnets X0.75Eu0.25O (X=Ca, Sr and Ba) with the NaCl structure are predicted based on the first-principles calculations. These materials only have up-spin subbands at the Fermi level and their net magnetic moments are all 7.00 μB per unit cell, which exhibits the evident half-metallic characteristics. Their energy gaps and half-metallic gaps are both wide so that they all have high Curie temperatures and stable half-metallicity, holding great potential applications in spintronics. From the calculated formation energies, it is possible to prepare Sr0.75Eu0.25O and Ba0.75Eu0.25O experimentally. However, it may be difficult to prepare Ca0.75Eu0.25O in experiments. The magnetic moments and the half-metallicity of X0.75Eu0.25O mainly originate from the spin-polarization of Eu 4f-orbitals, which are caused by the strong octahedral crystal field in the ligand compound ML6 consisting of the Eu-ion and six O-ions around it.

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

    International Nuclear Information System (INIS)

    In this letter we demonstrate a synthetic route to thick (5--20 μm) highly c-axis textured, nearly phase-pure superconducting (Tl,Pb)(Ba,Sr)2Ca2Cu3O9/Ag0.37 tapes. First, a Tl-free ink consisting of Pb0.5Ba0.4Sr1.6Ca2.0Cu3.0O9/Ag0.37 precursor powder in an ethanolic ethyl cellulose binder is sprayed onto a heated LaAlO3 substrate. After an intermediate oxygen anneal to remove the carbonaceous binder, a static 2-zone thallination anneal is performed to promote superconducting phase formation. Films exhibit excellent c-axis texturing as evidenced by x-ray diffraction θ/2θ and rocking curve characterization with morphological evidence for partial melting by scanning electron microscopy. Electrical characterization of these films give Tconset values of 106--115 K with Tczero reached by 99--101 K and transport Jc(77K) up to 2.9x104 A/cm2. A mixed strong/weak-linked magnetic field dependence is observed for these films at 77 K and 0.4 T

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

    Science.gov (United States)

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

    1994-11-01

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

  18. Hydrothermal synthesis and luminescent properties of color-tunable Dy3+ doped and Eu3+/Tb3+ co-doped MMoO4 (M=Ca, Sr, Ba) phosphors

    International Nuclear Information System (INIS)

    Dy3+ doped and Eu3+/Tb3+ co-doped MMoO4 (M=Ca, Sr, Ba) phosphors have been successfully prepared via a simple surfactant-free hydrothermal method. Their crystal structure, morphology, and luminescent characteristics were investigated. The results show that the as-prepared CaMoO4 particles have the cylinder-like shape, SrMoO4 samples present dumbbell-like shape, and the as-prepared BaMoO4 products show micro-rods shape with a length of 5–15 μm. MMoO4:Dy3+ phosphors exhibited the characteristic excitation and emission transitions of Dy3+ and most of the chromaticity coordinates are located in the white-light region. In addition, with increasing Dy3+ ions concentration the color changes gradually from near blue to near yellow. All the characteristic emissions of Eu3+ and Tb3+ can be observed in Eu3+/Tb3+ co-doped MMoO4 phosphors, and the emission color can be easily tuned from red, through yellow or green-yellow, to green by simply adjusting the relative doping concentrations of the Eu3+ and Tb3+ ions. The present work suggests that these phosphors may have potential application for light-emitting diodes (LEDs)

  19. Synthesis, spectroscopic and thermal studies of Mg(II), Ca(II), Sr(II) and Ba(II) diclofenac sodium complexes as anti-inflammatory drug and their protective effects on renal functions impairment and oxidative stress

    Science.gov (United States)

    El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

    2015-01-01

    The main task of our present study is the preparation of newly complexes of Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac which succeeded to great extent in alleviating the side effects of diclofenac alone and ameliorating the kidney function parameters and antioxidant capacities with respect to diclofenac treated group alone. The Mg(II), Ca(II), Sr(II) and Ba(II) with diclofenac have been synthesized and characterized using infrared, electronic and 1H NMR spectral, thermogravimetric and conductivity measurements. The diclofenac ligand has been found to act as bidentate chelating agent. Diclofenac complexes coordinate through the oxygen's of the carboxyl group. The molar ratio chelation is 1:2 (M2+-dic) with general formula [M(dic)2(H2O)2]ṡnH2O. Antibacterial screening of the alkaline earth metal complexes against Escherichia coli (Gram - ve), Bacillus subtilis (Gram + ve) and anti-fungal (Asperagillus oryzae, Asperagillus niger, Asperagillus flavus) were investigated. The kidney functions in male albino rats were ameliorated upon treatment with metal complexes of dic, which are represented by decreasing the levels of urea and uric acid to be located within normal values. The other looks bright spot in this article is the assessment of antioxidant defense system including SOD, CAT and MDA with the help of Sr2+, Mg2+ and Ca2+-dic complexes. The hormones related to kidney functions and stresses have been greatly ameliorated in groups treated with dic complexes in comparable with dic treated group.

  20. Comparison of the photoluminescence properties of Eu{sup 2+}, Mn{sup 2+} co-doped M{sub 5}(PO{sub 4}){sub 3}Cl (M = Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Fengli [National Engineering Research Center for Rare Earth Materials, General Research Institute for Nonferrous Metals, and Grirem Advanced Materials Co., Ltd., Beijing 100088 (China); State Key Laboratory of Rare Earth Materials and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou, Jiangxi 341000 (China); An, Wei [School of Physics, Peking University, Beijing 100871 (China); Wei, Heng-Wei [State Key Laboratory of Rare Earth Materials and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Chen, Guantong [National Engineering Research Center for Rare Earth Materials, General Research Institute for Nonferrous Metals, and Grirem Advanced Materials Co., Ltd., Beijing 100088 (China); Zhuang, Weidong, E-mail: wdzhuang@126.com [National Engineering Research Center for Rare Earth Materials, General Research Institute for Nonferrous Metals, and Grirem Advanced Materials Co., Ltd., Beijing 100088 (China); Jing, Xi-Ping, E-mail: xpjing@pku.edu.cn [State Key Laboratory of Rare Earth Materials and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2014-03-25

    Highlights: • Good size match between the doped and host cations narrows the emission band. • Low phonon energy of the hosts enhances the luminescence intensity. • “Inverse bottleneck effect” related to Eu/Mn lifetime mismatch causes quenching. • “Charge transfer process” in the Eu–Mn clusters causes quenching. -- Abstract: Eu{sup 2+} and Mn{sup 2+} singly doped or co-doped M{sub 5}(PO{sub 4}){sub 3}Cl (M = Ca, Sr and Ba) phosphors were synthesized by conventional solid state reactions and characterized by X-ray diffraction (XRD), photoluminescence (PL) spectra, PL decay curves, energy dispersive spectra (EDS) and Raman spectra. The results show that a better size match between the doped cation and the host cation allows a wider solid solution range (e.g. Ca{sup 2+}/Mn{sup 2+}) and a narrower emission band (e.g. Sr{sup 2+}/Eu{sup 2+} and Ca{sup 2+}/Mn{sup 2+}). A lower phonon energy of the host (e.g. the Sr phase) reduces the non-radiation probability and enhances the PL efficiency. The PL performance of the Ba phase is exceptional possibly because of the large size difference between the doped cations and the host cations. The transfer efficiency (η) and the emission quantum efficiency (Q) were analyzed. In the studied phosphors, superficially Eu{sup 2+} efficiently transferred its absorbed energy to Mn{sup 2+} but the Q of the Mn{sup 2+} emission was not as high as expected. Two loss mechanisms are proposed: an “inverse bottleneck effect” and “charge transfer” between Eu{sup 2+} and Mn{sup 2+}.

  1. Chemical stabilization and high pressure synthesis of Ba-free Hg-based superconductors, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y}(N=1{approximately}3)

    Energy Technology Data Exchange (ETDEWEB)

    Kishio, K. [Univ. of Tokyo (Japan)]|[Kyoto Univ. (Japan); Shimoyama, J.; Hahakura, S. [Univ. of Tokyo (Japan)] [and others

    1994-12-31

    A homologous series of new Hg-based HTSC compounds, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y} with n=1 to 3, have been synthesized. The stabilization of the pure phases have been accomplished by chemical doping of third elements such as M=Cr, Mo and Re. While the Hg1201(n=1) phase was readily obtained in this way, it was necessary to simultaneously dope Y into the Ca site to stabilize the Hg1212(n=2) phase. On the other hand, single-phase Y-free Hg1212(n=2) and Hg1223(n=3) samples were synthesized only under a high pressure of 6 GPa. In sharp contrast to the Ba-containing compounds, all the samples prepared in the present study have been quite stable during the synthesis and no deterioration in air has been observed after the preparation.

  2. Structural, Optical, and Dielectric Properties of A[(Mg0.32Co0.02 Nb0.66]O3 Semiconductor, Where (a = Ba, Sr or Ca

    Directory of Open Access Journals (Sweden)

    R. Kumar

    2011-01-01

    Full Text Available Structural optical and dielectric properties of single phase A[(Mg0.32Co0.02 Nb0.66]O3, where A = Ba, Sr, or Ca, compounds were studied in the temperature range from room temperature (293 K to 458 K. The X-ray diffraction revealed that the Ba[(Mg0.32Co0.02Nb0.66]O3 [BMCN] compounds exhibit hexagonal symmetry whereas Sr[(Mg0.32Co0.02Nb0.66]O3 [SMCN] and Ca[(Mg0.32Co0.02Nb0.66]O3 [CMCN] compounds exhibit monoclinic symmetry. The replacement of Barium (r =1.61 Å by smaller ions like Strontium (r = 1.44 Å or Calcium (r = 1.34 Å in the polar dielectric Ba[(Mg0.32Co0.02 Nb0.66]O3 introduces the relaxation phenomenon and a gradual increase in the transition temperature maximum (Tm. The ac conductivity, as determined from the dielectric data, as a function of temperature and frequency, reveals the crossover from small polaron tunneling (SPT to correlated barrier hopping (CBH type conduction at ≈ 370 K. The activation energy of the non-Debye type process evaluated both from the electric modulus and the conductivity data are nearly identical suggesting similarity in the hopping mechanism. The band gap of these materials lies in the range of narrow to wide band semi conductors.

  3. Luminescent properties and energy transfer process of Sm3+-Eu3+ co-doped MY2(MoO4)4 (M=Ca, Sr and Ba) red-emitting phosphors

    Science.gov (United States)

    Ye, Menglin; Zhou, Gaojian; Zhou, Liqun; Lu, Di; Li, Yue; Xiong, Xing; Yang, Kunzhou; Chen, Menghuan; Pan, Yaxi; Wu, Peng; Wang, Zheng; Liu, Hongying; Xia, Qinghua

    2016-09-01

    MY2(MoO4)4:Sm3+ and MY2(MoO4)4:xSm3+,yEu3+ (M=Ca, Sr and Ba) phosphors were successfully prepared using solid-state reaction route, and their luminescent properties and energy transfer process from Sm3+ to Eu3+ were systematically investigated. The results indicate that MY2(MoO4)4:Sm3+ phosphors can be effectively excited by 407 nm near UV light originating from the 6H5/2 → 4F7/2 transition of Sm3+, and exhibit a satisfactory red emission at 646 nm attributed to the 4G5/2 → 6H9/2 transition of Sm3+, in which the emission intensity of SrY2(MoO4)4:Sm3+ is the strongest among the MY2(MoO4)4:Sm3+ (M=Ca, Sr and Ba) phosphors. For Eu3+ co-doped MY2(MoO4)4:Sm3+ samples, with increasing Eu3+ doping content, the main emission peaks of Sm3+ (approximately 646 nm) are decreased, but the emission peaks and intensity of Eu3+ are increased while the maximum intensity of luminescence at the Eu3+ concentration 0.9. The introduction of Eu3+ in the MY2(MoO4)4:Sm3+ phosphors can remarkably generate a strong emission line at 616 nm, originating from the 5D0→7F2 transition of Eu3+ and Sm3+ (4G5/2) → Eu3+ (5D0) effective energy transfer process. The energy transfer mechanism from Sm3+ to Eu3+ was discussed in detail.

  4. A 170-year Sr/Ca and Ba/Ca coral record from the western Pacific warm pool: 2. A window into variability of the New Ireland Coastal Undercurrent

    Science.gov (United States)

    Alibert, Chantal; Kinsley, Leslie

    2008-06-01

    A Porites coral from New Ireland (2.5°S, 150.5°E), at the heart of the Pacific warm pool, records variations of Ba/Ca back to the early 1820s. The New Ireland Coastal Undercurrent, which flows along the north coast and transports high-nutrient thermocline waters, is thought to be the main source of the Ba enrichment observed in the coral during El Niño. Between the 1850s and the 1960s, frequent large Ba peaks indicate that nutrients were available during both phases of El Niño-Southern Oscillation (ENSO). During La Niña, Ba could be advected along the South Equatorial Current. Also during this period, clusters of Ba/Ca peaks at nearly decadal timescale generally coincide with the return time of a strong El Niño, in accord with the high decadal variance of NINO3 sea surface temperatures. Ba enrichment in this coral primarily reflects the stratification in the thermocline that controls vertical mixing. The coral records long-term changes in those properties affecting nutrients in surface waters, with reduced Ba after the 1960s, and even less between 1823 and 1850. These reductions are tentatively attributed to the high rate of warming at the end of the Dalton Minimum and since the mid-20th century. An ensuing weakening of the trade winds may have produced a more stratified equatorial thermocline, hindering the transport of Ba and nutrients from the undercurrent to the shallow coastal waters north of New Ireland.

  5. Effects of Ca-dopant on the pyroelectric, piezoelectric and dielectric properties of (Sr 0.6Ba 0.4) 4Na 2Nb 10O 30 ceramics

    KAUST Repository

    Yao, Yingbang

    2012-12-01

    Calcium-doped sodium strontium barium niobate (SBNN, (Sr 0.6Ba 0.4) 4-xCa xNa 2Nb 10O 30, 0 ≤ x ≤ 0.5) ceramics were prepared by a conventional solid-state reaction method. SBNN showed \\'filled\\' tetragonal tungsten-bronze structure with fully occupied A-sites. The tetragonal structure, as revealed by X-ray diffraction (XRD) and Raman spectroscopy, was not affected by the Ca-dopant. Effects of Ca-doping concentration on the phase transitions as well as ferroelectric, piezoelectric and pyroelectric properties of the SBNN ceramics were investigated. From the dielectric studies, two anomalies were observed, namely, a sharp normal ferroelectric transition at 260 °C and a broad maximum at round -110 °C. The later was affected by the Ca-doping concentration and its origin was discussed. At x = 0.3, the sample exhibited the highest pyroelectric coefficient of 168 μC/m 2 K and the largest piezoelectric coefficient (d 33) of 63 pC/N at room temperature. On the basis of our results, the pyroelectric properties of the SBNN were improved by Ca-doping. © 2012 Elsevier B.V. All rights reserved.

  6. Effect of the A-site cation on methane oxidation of perovskite-type (La{sub 1-x}M{sub x})CoO{sub 3} (M=Ca, Sr, and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, Hideki, E-mail: htaguchi@cc.okayama-u.ac.jp [Graduate School of Natural Science and Technology (Science), Okayama University, 3-1-1 Tsushima-Naka, Kita-Ku, Okayama 700-8530 (Japan); Matsu-ura, Keiko [Graduate School of Natural Science and Technology (Science), Okayama University, 3-1-1 Tsushima-Naka, Kita-Ku, Okayama 700-8530 (Japan); Takada, Masao; Hirota, Ken [Department of Molecular Chemistry and Biochemistry, Faculty of Science and Engineering, Doshisha University, Kyo-Tanabe 610-0321 (Japan)

    2012-06-15

    Perovskite-type (La{sub 1-x}M{sub x})CoO{sub 3} (M=Ca, Sr, and Ba) synthesized at 700 Degree-Sign C in air using the polymerizable complex method had a rhombohedral perovskite-type structure in the range of x{<=}0.06. The oxygen content of the samples was 2.98-2.99, and the specific surface area was 3.5-8.3 m{sup 2}/g regardless of the M ion or x. The Rietveld method indicated that the Co-O distance was also constant regardless of the M ion or x, and that the Co-O-Co angle between two CoO{sub 6} octahedra increased with an increase in the ionic radius of the M ion. The temperature corresponding to the 50% conversion (T{sub 1/2}) of CH{sub 4} oxidation was almost constant for the samples with x=0.04, while the T{sub 1/2} of the samples with x=0.06 was linearly lowered with increases in the ionic radius of the M ion. - Graphical abstract: The conversion from CH{sub 4} to CO{sub 2} and H{sub 2}O on (La{sub 0.94}M{sub 0.06})CoO{sub 3} (M=Ca, Sr, and Ba). Highlights: Black-Right-Pointing-Pointer (La{sub 1-x}M{sub x})CoO{sub 3} (M=Ca, Sr, and Ba) was synthesized using the polymerizable complex method. Black-Right-Pointing-Pointer The Co-O distance was constant regardless of the M ion or x. Black-Right-Pointing-Pointer The Co-O-Co angle increased with an increase in the ionic radius of the M ion. Black-Right-Pointing-Pointer CH{sub 4} oxidation started above 300 Degree-Sign C and finished at 700 Degree-Sign C. Black-Right-Pointing-Pointer The catalytic activity increased with increases in the ionic radius of the M ion.

  7. Investigations of metastable Ca2IrO4 epitaxial thin-films: systematic comparison with Sr2IrO4 and Ba2IrO4

    Science.gov (United States)

    Souri, M.; Gruenewald, J. H.; Terzic, J.; Brill, J. W.; Cao, G.; Seo, S. S. A.

    2016-05-01

    We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. The epitaxial Ca2IrO4 thin-films are of K2NiF4-type tetragonal structure. Transport and optical spectroscopy measurements indicate that the electronic structure of the Ca2IrO4 thin-films is similar to that of Jeff = 1/2 spin-orbit-coupled Mott insulator Sr2IrO4 and Ba2IrO4, with the exception of an increased gap energy. The gap increase is to be expected in Ca2IrO4 due to its increased octahedral rotation and tilting, which results in enhanced electron-correlation, U/W. Our results suggest that the epitaxial stabilization growth of metastable-phase thin-films can be used effectively for investigating layered iridates and various complex-oxide systems.

  8. Investigations of metastable Ca2IrO4 epitaxial thin-films: systematic comparison with Sr2IrO4 and Ba2IrO4.

    Science.gov (United States)

    Souri, M; Gruenewald, J H; Terzic, J; Brill, J W; Cao, G; Seo, S S A

    2016-01-01

    We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. The epitaxial Ca2IrO4 thin-films are of K2NiF4-type tetragonal structure. Transport and optical spectroscopy measurements indicate that the electronic structure of the Ca2IrO4 thin-films is similar to that of Jeff = 1/2 spin-orbit-coupled Mott insulator Sr2IrO4 and Ba2IrO4, with the exception of an increased gap energy. The gap increase is to be expected in Ca2IrO4 due to its increased octahedral rotation and tilting, which results in enhanced electron-correlation, U/W. Our results suggest that the epitaxial stabilization growth of metastable-phase thin-films can be used effectively for investigating layered iridates and various complex-oxide systems. PMID:27193161

  9. 10-π-Electron arenes à la carte: structure and bonding of the [E-(CnHn)-E](n-6) (E = Ca, Sr, Ba; n = 6-8) complexes.

    Science.gov (United States)

    Mondal, Sukanta; Cabellos, Jose Luis; Pan, Sudip; Osorio, Edison; Torres-Vega, Juan Jose; Tiznado, William; Restrepo, Albeiro; Merino, Gabriel

    2016-04-28

    In this paper, we provide solid evidence to show that among an overwhelming structural diversity, alkaline earth metals (Ca, Sr, Ba) have the ability to form inverted sandwich compounds with C6H6, C7H7(+), and C8H8(2+) of Dnh symmetry and general formula [E-(CnHn)-E](n-6) (n = 6-8) with planar 10-π-electron aromatic cores by virtue of transferring two electrons per metal atom to the ring. However, the origin of the orbital interaction between the metals and the carbon ring is quite different; while [E-(C6H6)-E] complexes are dominated by δ-interactions, both π- and δ-interactions are important in [E-(C7H7)-E](+) and [E-(C8H8)-E](2+) complexes. PMID:26936126

  10. Luminescence characteristics of Eu2+ activated Ca2SiO4, Sr2SiO4 and Ba2SiO4 phosphors for white LEDs

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Jun; Yang Zhi-Ping; Guo Qing-Lin; Li Pan-Lai; Fu Guang-Sheng

    2009-01-01

    This paper investigates the luminescence characteristics of Eu2+ activated Ca2SiO4, Sr2SiO4 and Ba2SiO4 phos-phors. Two emission bands are assigned to the f-d transitions of Eu2+ ions doped into two different cation sites in host lattices, and show different emission colour variation caused by substituting M2+ cations for smaller cations. This be-haviour is discussed in terms of two competing factors of the crystal field strength and covalence. These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes (LEDs) based on ultraviolet chip/phosphor technology.

  11. Improvement of critical current density in thallium-based (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Z.F.; Wang, C.A.; Wang, J.H. [State Univ. of New York at Buffalo, Amherst, NY (United States)] [and others

    1994-12-31

    Epitaxial (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} (Tl,Bi)-1223 thin films on (100) single crystal LaAlO{sub 3} 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 > 2 x 10{sup 6} A/cm{sup 2}. The films exhibited good flux pinning properties.

  12. 4f and 5d energy levels of the divalent and trivalent lanthanide ions in M{sub 2}Si{sub 5}N{sub 8} (M=Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Kate, O.M. ten, E-mail: o.m.tenkate@tudelft.nl [Luminescent Materials Research Group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft (Netherlands); Energy Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, 5600MB Eindhoven (Netherlands); Zhang, Z. [Energy Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, 5600MB Eindhoven (Netherlands); Dorenbos, P. [Luminescent Materials Research Group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft (Netherlands); Hintzen, H.T. [Energy Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, 5600MB Eindhoven (Netherlands); Kolk, E. van der [Luminescent Materials Research Group, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft (Netherlands)

    2013-01-15

    Optical data of Sm, Tb and Yb doped Ca{sub 2}Si{sub 5}N{sub 8} and Sr{sub 2}Si{sub 5}N{sub 8} phosphors that have been prepared by solid-state synthesis, are presented. Together with luminescence data from literature on Ce{sup 3+} and Eu{sup 2+} doping in the M{sub 2}Si{sub 5}N{sub 8} (M=Ca, Sr, Ba) hosts, energy level schemes were constructed showing the energy of the 4f and 5d levels of all divalent and trivalent lanthanide ions relative to the valence and conduction band. The schemes were of great help in interpreting the optical data of the lanthanide doped phosphors and allow commenting on the valence stability of the ions, as well as the stability against thermal quenching of the Eu{sup 2+}d-f emission. Tb{sup 3+} substitutes on both a high energy and a low energy site in Ca{sub 2}Si{sub 5}N{sub 8}, due to which excitation at 4.77 eV led to emission from both the {sup 5}D{sub 3} and {sup 5}D{sub 4} levels, while excitation at 4.34 eV gave rise to mainly {sup 5}D{sub 4} emission. Doping with Sm resulted in typical Sm{sup 3+}f-f line absorption, as well as an absorption band around 4.1 eV in Ca{sub 2}Si{sub 5}N{sub 8} and 3.6 eV in Sr{sub 2}Si{sub 5}N{sub 8} that could be identified as the Sm{sup 3+} charge transfer band. Yb on the other hand was incorporated in both the divalent and the trivalent state in Ca{sub 2}Si{sub 5}N{sub 8}. - Graphical abstract: Energy level schemes showing the 4f ground states of the trivalent ( Black-Down-Pointing-Small-Triangle ) and divalent ( Black-Up-Pointing-Small-Triangle ) lanthanide ions and lowest energy 5d states of the trivalent ({nabla}) and divalent ({Delta}) ions with respect to the valence and conduction bands of Ca{sub 2}Si{sub 5}N{sub 8} (left) and Sr{sub 2}Si{sub 5}N{sub 8} (right). Highlights: Black-Right-Pointing-Pointer Construction of energy level schemes of all lanthanides within the M{sub 2}Si{sub 5}N{sub 8} hosts. Black-Right-Pointing-Pointer Construction was done by analyzing existing as well as new

  13. Defect chemistry and oxygen transport of (La0.6Sr0.4 − xMx)0.99Co0.2Fe0.8O3 − δ, M = Ca (x = 0.05, 0.1), Ba (x = 0.1, 0.2), Sr: Part II: Oxygen transport

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas; Søgaard, Martin; Hendriksen, Peter Vang

    This paper is the second part of a two part series, where the effects of varying the A-site dopant on the defect chemistry and transport properties of the materials (La0.6Sr0.4 − xMx)0.99Co0.2Fe0.8O3 − δ, M = Sr, Ca (x = 0.05, 0.1), Ba (x = 0.1, 0.2) (LSMFC) have been investigated. In part I, the...... electrolyte probe were used to extract the permeability and surface resistance, rs. The highest permeability was found for (La0.6Sr0.3Ca0.1)0.99Co0.2Fe0.8O3 − δ. The apparent activation energy of the permeability was 78 kJ/mol. The inverse surface resistance, rs− 1, also had an activated behavior with an...... activation energy close to 180 kJ/mol for most of the materials. A reversible transition to an abnormally low rs was found in (La0.6Sr0.3Ca0.1)0.99Co0.2Fe0.8O3 − δ at T > 1223 K....

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

    Science.gov (United States)

    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).

  15. Investigation on birefringence property in uniaxial crystal (Ca{sub 0.28}Ba{sub 0.72}){sub 0.75}(Sr{sub 0.60}Ba{sub 0.40})Nb{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Xia, H.R. [School of Physics and Microelectronics of Shandong University, Jinan (China); State Key Laboratory of Crystal Materials, Shandong University, Jinan (China); Xu, J.Q.; Si, S.C. [School of Physics and Microelectronics of Shandong University, Jinan (China); Zhang, H.J.; Wang, J.Y. [Institute of Crystal Materials, Shandong University, Jinan (China); Gao, C.Y.

    2008-04-15

    The birefringence of (Ca{sub 0.28}Ba{sub 0.72}){sub 0.75}(Sr{sub 0.60}Ba{sub 0.40})Nb{sub 2}O{sub 6} crystal is measured basing on polarization- extinction method and conoscopic interference method. Experimental results show that the birefringence in this crystal is up to 10{sup -5}, the natural birefringence in this crystal is (n{sub o}-n{sub e})=5.89 x 10{sup -5} with the He-Ne laser wavelength at 632.8 nm and the birefringence grads with wavelength at 532 nm is 5.68 x 10{sup -5}, which indicate the good optical homogeneity of this crystal. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Crystal structure and magnetic properties of Bi0.8A0.2FeO3 (A = La, Ca, Sr, Ba multiferroics using neutron diffraction and Mossbauer spectroscopy

    Directory of Open Access Journals (Sweden)

    Manisha Rangi

    2014-08-01

    Full Text Available Bi0.8A0.2FeO3 (A = La, Ca, Sr, Ba multiferroics were studied using x-ray, neutron diffraction and magnetization techniques. All the samples crystallized in rhombohedral structure with space group R3c. The compounds exhibit antiferromagnetic (AFM ordering at 300 K and no evidence of further structural or magnetic transition was observed on lowering of temperature below it. The magnetic structure of these substituted compounds are found to be collinear G-type AFM structure as against the non collinear incommensurate magnetic structure reported in the case of parent compound. The moments on Fe at 6 K are aligned along the a-axis in the case of Ca-doped sample. With increase in the ionic radii of dopant, the moments are found to be aligned in the ac plane and the angle of tilt away from the a-axis increases. The observed change in the magnetic structure with substitution is attributed to the intrinsic structural distortion as evidenced by the change in the bond angle (Fe-O-Fe and bond distances (Bi-O, Fe-O. It has been found that heterovalent substitution A2+ results in the formation of oxygen vacancies in the parent lattices as the possibility of Fe4+ ruled out by Mössbauer spectra recorded at room temperature. Higher value of remnant magnetization (0.4187 emu/g and coercivity (4.7554kOe is observed in Bi0.8Ba0.2FeO3 sample in comparison to other substituted samples revealing a strong correlation between ionic radii and magnetization.

  17. Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

    Science.gov (United States)

    Zhu, Xiao Na; Gao, Ting Ting; Xu, Xing; Liang, Wei Zheng; Lin, Yuan; Chen, Chonglin; Chen, Xiang Ming

    2016-08-31

    Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching. PMID:27514235

  18. Physicochemical impact studies of gamma rays on "aspirin" analgesics drug and its metal complexes in solid form: Synthesis, spectroscopic and biological assessment of Ca(II), Mg(II), Sr(II) and Ba(II) aspirinate complexes

    Science.gov (United States)

    Refat, Moamen S.; Sharshar, T.; Elsabawy, Khaled M.; Heiba, Zein K.

    2013-09-01

    Metal aspirinate complexes, M2(Asp)4, where M is Mg(II), Ca(II), Sr(II) or Ba(II) are formed by refluxed of aspirin (Asp) with divalent non-transition metal ions of group (II) and characterized by elemental analysis and spectroscopic measurements (infrared, electronic, 1H NMR, Raman, X-ray powder diffraction and scanning electron microscopy). Elemental analysis of the chelates suggests the stoichiometry is 1:2 (metal:ligand). Infrared spectra of the complexes agree with the coordination to the central metal atom through three donation sites of two oxygen atoms of bridge bidentate carboxylate group and oxygen atom of sbnd Cdbnd O of acetyl group. Infrared spectra coupled with the results of elemental analyzes suggested a distorted octahedral structure for the M(II) aspirinate complexes. Gamma irradiation was tested as a method for stabilization of aspirin as well as their complexes. The effect of gamma irradiation, with dose of 80 Gy, on the properties of aspirinate complexes was studied. The aspirinate chelates have been screened for their in vitro antibacterial activity against four bacteria, gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two strains of fungus (Aspergillus flavus and Candida albicans). The metal chelates were shown to possess more antibacterial activity than the free aspirin chelate.

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

    Energy Technology Data Exchange (ETDEWEB)

    Pandech, Narasak; Limpijumnong, Sukit, E-mail: sukit@sut.ac.th [School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics (ThEP Center), Commission on Higher Education, Bangkok 10400 (Thailand); Sarasamak, Kanoknan [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)

    2015-05-07

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

  20. Elastic properties of perovskite ATiO3 (A = Be, Mg, Ca, Sr, and Ba) and PbBO3 (B = Ti, Zr, and Hf): First principles calculations

    International Nuclear Information System (INIS)

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO3 for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO3 for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C11 elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C12 elastic constant is sensitive to B-site cations while C44 elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed

  1. Formation of phases with the structure of Ca3Ga2Ge4O14 in the AO-BO2-M2O3-SiO2 systems (A = Ca, Sr, Ba; B = Ge, Ti, Sn, Zr; M = Ga, Fe, Al)

    International Nuclear Information System (INIS)

    A search was arranged for phases of the structure Ca3Ga2Ge4O14 (I), featuring promising piezoelectric properties, in the systems AO-BO2-M2O3-SiO2 (A = Ca, Sr, Ba; B = Ge, Ti, Sn, Zr; M = Ga, Fe, Al), using the method of X-ray phase analysis. In 17 systems studied phases of variable composition A3BxM2Si4-xO14 with disordered structure of I have been detected. In joins A3M2B4O14 - A3M2Si4O14 homogeneity regions have been defined, which are localized inside tetrahedron of the compositions in 14 systems with B = Ti, Sn, Zr and emerging on one of the tetrahedron faces in three Ge-systems. Thermal stability is studied and cations distribution over synthesized phases is discussed

  2. The influence of impurities on the dissolution of Ca- and Sr-bearing barite at room temperature

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The reaction path in the (Ba, Sr, Ca)SO4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities "fluorite" and "iron sulfides" admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity "fluorite" affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSO4 component from dissolving into water, and reduce the release rate of SO42 - from the solid solution to the aqueous solution and the removing rate of Ba2+ from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba2 + and Sr2 + concentrations were controlled by the dissolution-precipitation of the end-members BaSO4 and SrSO4, respectively; the aqueous F- , Ca2+ and SO42- concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the ( Ba, Sr, Ca) SO4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO4) , while the aqueous composition shifted towards the more soluble end-members (SrSO4 and CaSO4 ) as equilibrium was approached to.

  3. Energetic prediction on the stability of A{sub 2}Mg{sub 12}Si{sub 7}, A{sub 2}Mg{sub 4}Si{sub 3}, and AMgSi in the A{sub 2}Si–Mg{sub 2}Si system (A = Ca, Sr and Ba) and their calculated electronic structures

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Yoji, E-mail: imai-y@aist.go.jp [National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 5, Higashi 1-1, Tsukuba, Ibaraki 305-8565 (Japan); Mori, Yoshihisa [Okayama University of Science, Ridai-cho 1-1, Kita-ku, Okayama 700-0005 (Japan); Nakamura, Shigeyuki [Tsuyama National College of Technology, Numa 624-1, Tsuyama, Okayama 708-8509 (Japan); Takarabe, Ken-ichi [Okayama University of Science, Ridai-cho 1-1, Kita-ku, Okayama 700-0005 (Japan)

    2014-03-25

    Highlights: • Formation energies of A{sub 2}Mg{sub 4}Si{sub 3}, A{sub 2}Mg{sub 12}Si{sub 7}, and AMgSi (A = Ca,Sr,Ba) were calculated. • All AMgSi are quite stable compared to mixture of A{sub 2}Si and Mg{sub 2}Si. • Ba{sub 2}Mg{sub 4}Si{sub 3} and Sr{sub 2}Mg{sub 4}Si{sub 3} are predicted to be stable, but Ca{sub 2}Mg{sub 4}Si{sub 3} is not. • Ca{sub 2}Mg{sub 12}Si{sub 7} and Sr{sub 2}Mg{sub 12}Si{sub 7} are energetically unstable. • Stability of Ba{sub 2}Mg{sub 12}Si{sub 7} is a tender subject. -- Abstract: In order to evaluate the relative stability of A{sub 2}Mg{sub 4}Si{sub 3}, A{sub 2}Mg{sub 12}Si{sub 7}, and AMgSi (A = Ca, Sr, and Ba) in the A{sub 2}Si–Mg{sub 2}Si system, electronic energy changes in the formation of these compounds were calculated using a density-functional theory with the Perdew–Wang generalized gradient approximations. It was found that (1) AMgSi’s are quite stable compared to equi-molar mixture of A{sub 2}Si and Mg{sub 2}Si, (2) Ba{sub 2}Mg{sub 4}Si{sub 3} and Sr{sub 2}Mg{sub 4}Si{sub 3} are also stable, (3) Ca{sub 2}Mg{sub 4}Si{sub 3} and Ca{sub 2}Mg{sub 12}Si{sub 7} are less stable than the mixture of CaMgSi and Mg{sub 2}Si, and (4) Stability of Ba{sub 2}Mg{sub 12}Si{sub 7} is a tender subject and Sr{sub 2}Mg{sub 12}Si{sub 7} is energetically unstable compared to the mixture of Sr{sub 2}Mg{sub 4}Si{sub 3} (or, SrMgSi) and Mg{sub 2}Si. The presence of Sr{sub 2}Mg{sub 12}Si{sub 7} may be due to the vibrational and/or configurational entropy, which are not treated in the present study. From the calculated electronic densities of state, complex compounds of SrMgSi and Mg{sub 2}Si have both p-type and n-type character, depending on the ratio of SrMgSi and Mg{sub 2}Si in that compound.

  4. Gallium Pnictides of the Alkaline Earth Metals, Synthesized by Means of the Flux Method: Crystal Structures and Properties of CaGa[subscript 2]Pn[subscript 2], SrGa[subscript 2]As[subscript 2], Ba[subscript 2]Ga[subscript 5]As[subscript 5], and Ba[subscript 4]Ga[subscript 5]Pn[subscript 8] (Pn = P or As)

    Energy Technology Data Exchange (ETDEWEB)

    He, Hua; Stearrett, Ryan; Nowak, Edmund R.; Bobev, Svilen (Delaware)

    2014-05-28

    The focus of this paper is on the structural characterization of the new Zintl phases CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, SrGa{sub 2}As{sub 2}, and Ba{sub 2}Ga{sub 5}As{sub 5}, and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2}Ga{sub 5}As{sub 5}, all of which were synthesized from molten metal fluxes.CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, and SrGa{sub 2}As{sub 2} have layered structures with polyanionic layers made of ethane-like Ga{sub 2}P6 and Ga{sub 2}As6 motifs fused through common edges; the polyanionic substructure in Ba{sub 2}Ga{sub 5}As{sub 5} consists of condensed Ga{sub 2}As6 units and GaAs{sub 4} tetrahedra. Ba{sub 4}Ga{sub 5}P{sub 8} and Ba{sub 4}Ga{sub 5}As{sub 8}, another pair of new compounds with channel-like 3D structures, were also synthesized from metal fluxes, and their structures were established from single-crystal X-ray and synchrotron powder diffraction. They are based on GaP{sub 4} and GaAs{sub 4} tetrahedra, with parts of their structures being heavily disordered. The electronic structures computed with the linear muffin-tin orbital (LMTO) method are discussed as well, alongside the thermopower and the electrical conductivity, measured on single crystals of Ba{sub 2}Ga{sub 5}As{sub 5} and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2} Ga{sub 5}As{sub 5}. They demonstrate that such an approach would be an effective way to fine-tune the transport properties.

  5. Zintl phase compounds AM2Sb2 (A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd) and their substitution variants:a class of potential thermoelectric materials

    Institute of Scientific and Technical Information of China (English)

    郭凯; 操齐高; 赵景泰

    2013-01-01

    Zintl phase compounds AM2Sb2 (A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd) is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A2+and anionic slabs (M2Sb2)2-. In addi-tion, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters (carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity) for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title com-pounds AM2Sb2 were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal trans-port were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 (ZT700 K=1.26), EuZn1.8Cd0.2Sb2 (ZT650 K=1.06), and YbCd1.85Mn0.15Sb2 (ZT650 K=1.14).

  6. 120-K Tl-Ca-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    The authors have discovered reproducible and stable bulk superconductivity in the Tl-Ca-Ba-Cu-O system above 130 K, with zero resistance above 120 K. Magnetic and electronic transport properties including thermoelectric power of the new superconductors are presented. The Tl-Ca- Ba-Cu-O system contains the 125-K 2223 (Tl:Ca:Ba:Cu) phase and the 105-K 2122 phase, while the Ca-free Tl-Ba-Cu-O system consists of the 80-K 2021 phase, suggesting that the addition of each Cu and Ca layer increases the transition temperature by about 20 K

  7. Interplay between crystal structure and magnetism in the superconducting AFe2As2 (A = Ca, Sr, Ba and Eu) systems: A First-principles study

    International Nuclear Information System (INIS)

    Although the recently discovered FeAs-based superconducting compounds crystallize in different structures, they have the same Fe-As substructure and display very similar electronic properties including similar patterns of structural and magnetic transitions. However, experimentally important differences are also found between the REOFeAs (RE = rare-earth) and the AFe2As2 families. Because sample composition and quality are easier to control in the latter family, we focus on the AFe2As2 systems. Using all-electron full-potential calculations, we study the relation between the onset of spin-density wave (SDW) and the tetragonal-to-orthorhombic transition. We find that the SDW pattern is necessary for the structural transition to take place. We also explore how electronic structure and magnetic behavior change when all free structural parameters, As-z, c/a and a/b, are optimized at different unit cell volumes (pressures). All four systems are compared with each other based on the calculation results. Most calculated properties agree well with the measured properties, but several of them are rather sensitive to the As z position. For a microscopic understanding of the electronic structure of this new family of superconductors this structural feature is crucial, but its correct ab initio treatment still remains an open question.

  8. Seasonal Sr/Ca, and 44Ca/40Ca co-variation in Arctica islandica

    International Nuclear Information System (INIS)

    Full text: We have studied the Ca isotopic variations and Sr/Ca ratios within an A. islandica shell in relation to temperature fluctuations of the ambient seawater with sub-seasonal resolution. The long-lived bivalve A. islandica dwells at 10-200 m depth throughout much of the North Atlantic continental shelf. Its shells represent a promising SST archive for boreal marine settings. The A. islandica shell used for this study was collected at 60-m depth near the former position of the Nantucket Shoals Lightship. The years 1956-1958 were analyzed for both, Sr/Ca ratios and δ44/40Ca, with 1957 being the best resolved. The δ44/40Ca are highly correlated with Sr/Ca ratios (r= 0.92 for 1957). The positive correlation of Sr/Ca ratios and temperature in A. islandica is in accordance with published data on other bivalves, but contrary to thermodynamic expectations and e.g. coral data. The same inversion is found for Ca isotope fractionation: the δ44/40Ca correlation with temperature of A. islandica is negative, while all δ44/40Ca temperature gradients published so far (inorganic precipitates and foraminifera data) show varying degrees of positive correlation. Thus, as for Sr/Ca, the temperature correlation of δ44/40Ca in A. islandica is not under thermodynamic control. It appears inevitable to conclude that biological effects dominate both, Sr incorporation and Ca isotope fractionation in A. islandica. Growth rates and food supply are parameters that might relate Sr/Ca ratios as well as Ca isotopic compositions to vital activity and thus indirectly to temperature. In any case the high correlation of Sr/Ca ratios and Ca isotope fractionation indicates a common metabolic process for the observed variations. (author)

  9. Understanding the role of A-site and B-site cations on piezoelectric instability in lead--free (1-x) BaTiO3 -- xA(Cu1/3Nb2/3)O3 (A = Sr, Ca, Ba) solid solutions

    Science.gov (United States)

    Maurya, Deepam; Zhou, Yuan; Priya, Shashank

    2013-03-01

    This study provides fundamental understanding of the enhanced piezoelectric instability in lead-free piezoelectric (1-x) BaTiO3-xA(Cu1/3Nb2/3) O3(A: Sr, Ba and Ca and x = 0.0-0.03) solid solutions. These compositions were found to exhibit large longitudinal piezoelectric constant (d33) of ~330 pC/N and electromechanical planar coupling constant (kp) ~ 46% at room temperature. The X-ray diffraction coupled with atomic pair distribution functions (PDF)s indicated increase in local polarization. Raman scattering and electron paramagnetic resonance (EPR) analysis revealed that substitutions on A and B-site both substantially perturbed the local octahedral dynamics and resulted in localized nano polar regions with lower symmetry. The presence of nano domains and local structural distortions smears the Curie peak resulting in diffuse order-disorder type phase transitions. The effect of these distortions on the variations in physical property was modeled and analyzed within the context of nanodomains and phase transitions. *spriya@vt.edu The financial support from National Science Foundation and Office of Basic Energy Science, Department of Energy (Microscopy analysis) is gratefully acknowledged. The authors would also like to acknowledge the support from KIMS (new piezoelectric)

  10. 120-K Tl-Ca-Ba-Cu-O superconducting system

    International Nuclear Information System (INIS)

    The authors have discovered a reproducible and stable bulk superconductivity in the Tl-Ca-Ba-Cu-O system. The Tl-Ca-Ba-Cu-O superconductors can be easily prepared, and have highest Tc (125 K) and high critical current. Some Tl-Ca-Ba-Cu-O samples show an unusual phenomenon of coexistence of diamagnetism and ferromagnetic like behavior. The Tl-based system is rich in new superconducting structures, and has provided insight into mechanisms of high Tc oxide superconductivity

  11. The effect of Ba substitution at Sr site in Bi-2223 high-TC superconductors

    Directory of Open Access Journals (Sweden)

    H Salamati

    2010-09-01

    Full Text Available Bi1.8Pb0.4Sr2-xBaxCa2.2Cu3Oy (x-0, 0.1, 0.2, 0.3 samples were prepared by a conventional solid state reaction method. The effect of Ba substitution at Sr site in Bi-2223 high-TC superconductors have been investigated by the XRD, SEM, dc electrical resistivity and ac susceptibility. XRD and SEM analysis indicated Ba substitution decreased temperature of 2223 phase formation. The highest 2223 phase fraction was obtained for the sample with x=0.1 (A1 sample. This phase decreased by increasing Ba concentration (x>0.1. Ba doping up to x=0.1 decreased impurity phases but doping more than 0.1 increased. Dc electrical resistivity data and ac susceptibility measurements showed the transition temperature of grains and grain boundaries (Tc , Tcj increased and the transition width (ΔTc decreased for A1 sample. This behavior can be described by decreasing impurity phases and increasing 2223 phase. Flux pinning force and intergranular critical current densities (Jcm of A1 sample increased. It was suggested it is because of a small precipitation of Ba in grain boundaries as effective pinning centers. Ba doping more than 0.1 reduced the intergranular coupling and increased weak link behavior by increasing impurity phases. It decreased Tcj , Jcm and flux pinning force.

  12. Bi-Sr-Ca-Cu-O superconducting ceramics

    International Nuclear Information System (INIS)

    BiSrCaCu2Ox ceramic samples with a superconducting phase at 107K have been sinthesized. The critical temperature has been determined by Meissner effect measurements. That same 107K phase has also been detected in the following compounds: Bi2Sr2Ca2Cu3Ox and Bi3.6Sr2.7Ca2.7Cu2.7Cu4Ox. (author)

  13. The thermodynamic properties of Ba2SrUO6

    International Nuclear Information System (INIS)

    Standard formation enthalpy (-2940.0±8.5 kJ/mol) of the crystal Ba2SrUO6 was determined by the method of reaction calorimetry at 298.15 K. Specific heat was studied, and thermodynamic functions were calculated by the method of adiabatic calorimetry in the range of 8-330 K for the given compound. Its standard entropy (-558.6±2.1 J/(mol K)) and Gibbs formation function (-2773.5±9.0 kJ/mol) were calculated at 298.15 K. The reaction of the Ba2SrUO6 synthesis was shown to take place exothermic manner and through enthalpy contribution in the Gibbs function of the reaction

  14. Crystal-structure and magnetic phase transformations in solid solutions of BiFeO3-AFe0.5Nb0.5O3 (A = Ca, Sr, Ba, Pb)

    International Nuclear Information System (INIS)

    Solid solutions of Bi1-xAx(Fe1-x/2Nbx/2)O3, where A = Ca, Ba, and Pb, are obtained and their crystal structure and magnetic properties are investigated. It is shown that for A = Ca and x ∼ 0.15, the symmetry of the unit cell changes from rhombohedral (space group R3c) to orthorhombic (Pbnm). The transformation leads to the emergence of spontaneous magnetization due to the Dzyaloshinskii-Moriya interaction. Solid solutions with A = Pb remain rhombohedral up to a concentration of x = 0.3. Spontaneous magnetization sharply increases in the compound with x ∼ 1 at low temperatures and is due to the formation of the spin-glass component

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Effect of dopants ionic radii on dielectric properties of Bi{sub 4}V{sub 2-x}ME{sub x}O{sub 11-δ} (where x = 0.0 and 0.15; ME = Mg, Ca, Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sakshi; Singh, K. [Thapar University, School of Physics and Materials Science, Patiala, Punjab (India)

    2015-11-15

    Different alkaline earth metals doped Bi{sub 4}V{sub 2-x}ME{sub x}O{sub 11-δ} (where x = 0.0 and 0.15; ME = Mg, Ca, Sr and Ba) samples are synthesized by melt quench technique followed by heat treatment. The γ-phase is stabilized at room temperature in all the doped samples, whereas undoped sample (x = 0.0) exhibits the α-phase at room temperature. These samples are investigated for their dielectric properties with respect to temperature and frequencies. From the scanning electron micrographs, it is clear that liquid-phase sintering has taken place in all the doped samples. The highest dielectric constant is observed in Bi{sub 4}V{sub 1.85}Ca{sub 0.15}O{sub 11-δ} sample ∝10{sup 5}. The minimum loss is observed in Bi{sub 4}V{sub 1.85}Ba{sub 0.15}O{sub 11-δ} sample, i.e., ∝2.58. The highest optical band gap ∝2.42 eV is observed for Bi{sub 4}V{sub 1.85}Ca{sub 0.15}O{sub 11-δ} sample. The obtained results are discussed in the light of ionic radii, oxygen vacancies and disordering in the samples. (orig.)

  17. Effects of c/a Anisotropy and Local Crystal Structure on Superconductivity in AFe2(As1-xPx)2 (A = Ba1-ySry, Sr1-yCay and Eu)

    Science.gov (United States)

    Adachi, Toru; Nakamatsu, Yusuke; Kobayashi, Tatsuya; Miyasaka, Shigeki; Tajima, Setsuko; Ichimiya, Masayoshi; Ashida, Masaaki; Sagayama, Hajime; Nakao, Hironori; Kumai, Reiji; Murakami, Youichi

    2016-06-01

    We investigated the effects of c/a anisotropy and local crystal structure on superconductivity (SC) in As/P solid solution systems, AFe2(As1-xPx)2 (A122P) with various A ions. With decreasing A site atomic size from A = Ba to Eu, the structural anisotropy decreases, and the rate of decreasing with x also increases. The rapid narrowing of the region of antiferromagnetic composition (x) can be considered to be a result of this anisotropy change due mainly to the change in the Fermi surface (FS) nesting condition. By contrast, although the structural anisotropy systematically changes, the maximum Tc values are almost the same in all A122P systems except for Eu122P. These results indicate that the modification of the FS topology via the structural anisotropy does not affect SC. However local structural parameters, such as pnictogen height, are crucial for Tc.

  18. Crystal structure and phase transition studies in perovskite-type oxides using powder-diffraction techniques and symmetry-mode analysis : SrLnMRuO6 (Ln=La,Pr,Nd; M=Zn,Co,Mg,Ni,Fe) and ALn2CuTi2O9 (A=Ca,Ba; Ln=La,Pr,Nd,Sm)

    OpenAIRE

    Iturbe Zabalo, Edurne

    2013-01-01

    La tesis se ha centrado en la síntesis y caracterización estructural de materiales tipo perovskita: SrLnMRuO6 (Ln=La,Pr,Nd; M=Zn,Co,Mg,Ni,Fe) y ALn2CuTi2O9 (A=Ca,Ba; Ln=La,Pr,Nd,Sm). El estudio de las estructuras de los materiales se ha realizado mediante el análisis de los patrones de difracción en polvo de rayos-X, sincrotrón y/o neutrones. En el refinamiento por el método de Rietveld de las estructuras se han sustituido las coordenadas atómicas (el método más común), por coordenadas colect...

  19. 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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Synthesis of TlBaCaCuO superconductive films with Tl diffusion into BaCaCu precursors

    International Nuclear Information System (INIS)

    There exists several techniques to synthesize TlBaCaCuO from precursor films. Recently, a two zone furnace technique was developed by DeLuca. Based on the authors' experience on the two zone furnace technique, they systematically conducted a series of experiments in a tube furnace with a temperature gradient distribution. The BaCaCuO precursor films were fabricated by an ink method, and the Tl diffusion source was Tl2O3. Superconductive films were characterized by SQUID magnetization measurement, X-ray diffraction, SEM, and EDS. Experimental results will be summarized

  2. Mechanical-chemical synthesis Ba0.77Sr0.23TiO3

    OpenAIRE

    Kosanović D.; Obradović N.; Živojinović J.; Filipović S.; Maričić A.; Pavlović V.; Tang Y.; Ristić M.M.

    2012-01-01

    Barium-Strontium-Titanate Ba0.77Sr0.23TiO3 was prepared from starting materials BaCO3, SrCO3 and TiO2 through solid-state reactions. Mixtures of these oxides are mechanically activated in a high-energy planetary ball mill at different time intervals from 0 to 120 minutes. In order to obtain information on phase composition, crystal structure was determent by X-ray diffraction. It was observed that after 80 minutes in process synthesis Ba0.77Sr0.23TiO3 started Thermal analyzes were perfo...

  3. Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca

    Directory of Open Access Journals (Sweden)

    Corinna Kloss

    2014-06-01

    Full Text Available The first observations of the feedstocks, CFC-216ba (1,2-dichlorohexafluoropropane and CFC-216ca (1,3-dichlorohexafluoropropane, as well as the CFC substitute HCFC-225ca (3,3-dichloro-1,1,1,2,2-pentafluoropropane, are reported in air samples collected between 1978 and 2012 at Cape Grim, Tasmania. Present day (2012 mixing ratios are 37.8 ± 0.08 ppq (parts per quadrillion; 1015 and 20.2 ± 0.3 ppq for CFC-216ba and CFC-216ca, respectively. The abundance of CFC-216ba has been approximately constant for the past 20 years, whilst that of CFC-216ca is increasing, at a current rate of 0.2 ppq/year. Upper tropospheric air samples collected in 2013 suggest a further continuation of this trend. Inferred annual emissions peaked 421 at 0.18 Gg/year (CFC-216ba and 0.05 Gg/year (CFC-216ca in the mid-1980s and then decreased sharply as expected from the Montreal Protocol phase-out schedule for CFCs. The atmospheric trend of CFC-216ca and CFC-216ba translates into continuing emissions of around 0.01 Gg/year in 2011, indicating that significant banks still exist or that they are still being used. HCFC-225ca was not detected in air samples collected before 1992. The highest mixing ratio of 52 ± 1 ppq was observed in 2001. Increasing annual emissions were found in the 1990s (i.e., when HCFC-225ca was being introduced as a replacement for CFCs. Emissions peaked around 1999 at about 1.51 Gg/year. In accordance with the Montreal Protocol, restrictions on HCFC consumption and the short lifetime of HCFC-225ca, mixing ratios declined after 2001 to 23.3 ± 0.7 ppq by 2012.

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

    Science.gov (United States)

    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.

  5. New 120 K Tl-Ca-Ba-Cu-O superconductor

    International Nuclear Information System (INIS)

    Electronic and magnetic properties of the new 120 K Tl-Ca-Ba-Cu-O superconductor are presented. Resistance-temperature variations, ac susceptibility, and the (low) magnetic field dependence of the critical current density are reported. The new superconductor can be prepared in a molten state, which should allow processing leading to high critical current density. Preliminary x-ray diffraction data are also presented

  6. TlBaCaCuO High Temperature Superconducting Bolometer

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Meanders of thin films of TlBa2Ca2CuO2 have been used to make radiation bolometers. Using cw-HeNeat 632 nm the peak responsivity of these films is measured to be 0. 560 V/W at the temperature of 106.0 K. Thepresent experimental data agree well with bolometric response of irradiated films, and the calculations are presentedto support this conclusion.

  7. 120 K superconductor TlBaCaCu2Oy

    International Nuclear Information System (INIS)

    The author have prepared 120K superconductor in Tl-Ba-Ca-Cu oxide system. This 120K superconductor has been investigated by x-ray diffraction and EDAX micro-analysis. EDAX analysis shows that the composition of this superconductor is very close to TLBa(Ca1-xCux)CuOy(chi - 0.3). Most of the x-ray powder diffractions including all the strong ones can be indexed according to a tetragonal structure with α = 5.46 A and c = 36.2A which means that the sample is nearly a single phase material

  8. Exoemission during phase transformations in superconducting monocrystal Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Low-temperature exoemission from a superconducting Bi2Sr2CaCu2Ox monocrystal under thermal cycling within 77-300 K interval is investigated. During thermal compression under cooling and subsequent expansion under heating, emission current peaks near 80 K and within the temperature intervals of structural phase transitions (SPT) (130-160, 180-200 and 240-280 K) are detected. Based on comparing the results to the earlier obtained ones for polycrystalline Y-Ba-Cu-O ceramics a conclusion is made that electron processes conductioning exoemission at SPT occur in the cuprate layer of HTSC

  9. Anisotropic electrical and thermal conductivity in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} [AE = Ca, Sr{sub 1−x}Ba{sub x} (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Song-Tao [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Institute of Material Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Zhang, Bin-Bin; Lv, Yang-Yang; Zhou, Jian; Zhang, Shan-Tao [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Xiong, Ye [College of Physical Science and Technology, Nanjing Normal University, Nanjing 210097 (China); Yao, Shu-Hua, E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); State Key laboratory of Crystal Material, Shandong University, Jinan, 250100 (China); Chen, Y. B., E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn [National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China); Chen, Yan-Feng [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-09-28

    Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE represents alkaline earth), constructed by stacking of rock-salt Bi{sub 2}AE{sub 2}O{sub 4} and triangle CoO{sub 2} layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ}, as reported previously, is their electrical conductivity mainly lying along CoO{sub 2} plane, adjusting Bi{sub 2}AE{sub 2}O{sub 4} layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE = Ca, Sr, Ba, Sr{sub 1−x}Ba{sub x}) single crystals. The results substantiate that isovalence replacement in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi{sub 2}AE{sub 2}O{sub 4} layer in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

  10. Experimental determination of partition coefficients for Rb, Sr, and Ba between alkali feldspar and silicate liquid

    International Nuclear Information System (INIS)

    Partitioning of Rb, Sr and Ba between alkali feldspar and a synthetic granitic melt has been determined at 8 kb and 720 to 7800C for a single quaternary granite composition. The results suggest that Henry's Law is obeyed by Rb up to approximately 0.8 wt.%Rb2O in both the liquid and in the alkali feldspar. The measured D values for Rb range from 0.77 to 1.1 For Ba, Henry's Law is obeyed up to approximately 0.6 wt.% BaO in the liquid and approximately 5 wt.% BaO in the alkali feldspar. D values for Ba range from 6.4 to 14. For Sr there is only a crude relationship between concentration in the liquid and concentration in the alkali feldspar at concentrations greater than approximately 0.6wt.%SrO in the liquid and approximately 0.4 wt.% SrO in the alkali feldspar. D values for Sr range from 1.2 to 5.0. Partitioning of Sr is apparently sensitive to the concentration of Ba in the system and this partly explains the failure of Sr to obey Henry's Law. Linear least-squares fits to the partitioning data as a function of temperature suggest inverse correlation between temperature and D values. Rb shows only a slight temperature effect whereas Ba and Sr appear to be rather strongly affected by temperature, but the temperature range examined here is small compared to the scatter in the data making these trends relatively uncertain. Other factors that appear to affect partitioning, especially of Sr, are growth rate, development of sector zoning, and Or content of the alkali feldspar. These factors severely limit the use of partitioning of these elements in alkali feldspar as geothermometers. The technique for measuring growth rates utilized here combined with measurement of trace element depletion in diffusion boundary layers adjacent to the alkali feldspar crystals makes it possible to estimate diffusivities for Ba and Sr. These estimates suggest a difference of 2 orders of magnitude between diffusivities for Ba and Sr in a vapor-saturated melt and those measured for a dry

  11. Muon spin rotation study of magnetism in multilayer HgBa2Ca4Cu5Oy superconductor

    International Nuclear Information System (INIS)

    Zero- and longitudinal-field muon-spin rotation (ZF-μSR and LF-μSR) measurements were carried out on a multi-layered HgBa2Ca4Cu5Oy (Hg-1245) superconductor with Tc of 108 K. With decreasing temperature, the observed ZF-μSR function changed from a Gaussian-type to an exponential-type below 60 K and zero field muon precession was also observed below 45 K. These μSR signals are attributed to the development of the antiferromagnetic ordering in inner CuO2 planes with a low carrier concentration. These results seem to indicate clear evidence that antiferromagnetism microscopically coexists with superconductivity in the Hg-1245 superconductor below 60 K

  12. Hysteresis and relaxation in TlBa2Ca2Cu3Oy superconducting polycrystals

    International Nuclear Information System (INIS)

    We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa2Ca2Cu3Oy (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa2Cu3O7-δ (YBCO), (Hg, Re)Ba2Ca2Cu3O8+δ (HBCCO) and (Bi, Pb)2Sr2Ca2Cu3O10-δ (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model

  13. Effect of Sr2+ addition on electrical properties of BaTiO3 PTCR ceramics

    International Nuclear Information System (INIS)

    Semiconducting PTCR (Positive Temperature Coefficient of Resistivity) ceramics based in BaTiO3, Ba0,8Sr0,2TiO3 e Ba0,6Sr0,4TiO3 compositions with 0.3at% La-doped have been investigated. The substitution of Ba2+ by Sr2+ in the lattice resulted in a decrease of tetragonal to cubic transition temperature (Tc) observed by X-ray diffraction. The results have shown a strong dependence of structure with the resistivity measured in d.c. mode. Using impedance spectroscopy technique was possible to attribute the PTC effect entirely to grain boundary region resistance. AFM and EFM images have shown potential barriers on the grain boundaries of evaluated samples below and above Tc.(author)

  14. Punta Pitt, Galapagos Ba/Ca Data for 1963-1982

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — File contains Ba/Ca data (in mmol/mol) presented by Lea et al. (1989). Samples were measured at the Massachusetts Institute of Technology by D. Lea. Ba...

  15. Search for fission-produced Rb, Sr, Cs and Ba at Oklo

    International Nuclear Information System (INIS)

    Five samples from the 2'P' cross-section, Oklo Mine, Gabon have been analysed to determine the isotopic composition of Rb, Sr, and Ba in order to search for the presence of fission-produced isotopes of these elements, as well as 135Ba and 137Ba which may be enriched due to fission-produced Cs. Three of the samples were powders and the other two U-rich segments of core; all five contain abundant total U (40 to 55%) and are depleted in 235U (0.52 to 0.41% of total U). Further, all samples are mixed to various degrees with silicate plus oxide gangue material. Even on the core samples the gangue is present along grain edges, in cracks, and is virtually impossible to separate from the uraninite. Presumably this gangue material is rich in alkali and alkaline earth elements and thus acts as a diluent for any fission-produced material. Rb, Sr, and Ba were separated by ion-exchange chromatographic techniques following cleansing by leaching with HCl and standard HF:HClO4 dissolution and their isotopic compositions determined by mass spectrometric thermionic emission. The leachate fractions of four of the five samples contain more Rb, Sr, and Ba of normal isotopic composition than the insoluble residues for which three of the five samples indicate the presence of fission-produced Cs (now as Ba isotopes) and Rb; further, increasing (135Ba/137Ba) correlates with decreasing (85Rb/87Rb). All five samples indicate the presence of fission-produced 88Sr as reflected in very low (86Sr/88Sr) ratios; available data suggest correlation between increase in fission 88Sr and depletion in 235U. The collective data suggest that fission-produced Rb, Sr, and Cs (now as Ba isotopes) are present in these samples but highly diluted by large amounts of the normal elements. Enrichment in 138Ba has not been demonstrated; which may be attributed to the high Ba content (i.e. 0.2-0.3%). (author)

  16. ПОИСК НОВЫХ ТЕРМОЛЮМИНОФОРОВ НА ОСНОВЕ БОРАТОВ AB 4O 7:DY (A=MG, SR, CA, CD, BA)

    OpenAIRE

    Субанаков, Алексей; Базаров, Баир; Чимитова, Ольга; Базарова, Баир

    2012-01-01

    Синтезирован и протестирован на эффект термолюминесценции ряд боратов Mg 2B 2O 5:Dy, Mg 3B 2O 6:Dy, LiMg 05B 4O 7:Dy, LiMgBO 3:Dy, AB 4O 7:Dy (A=Sr, Ca, Cd, Ba). Получен высокочувствительный боратный термолюминофор CaB 4O 7:Dy. Проведено сравнение CaB 4O 7:Dy с известным термолюминесцентным материалом MgB 4O 7:Dy. Изучено влияние вторичного допирования одновалентными металлами (Li, Na, Tl) на термолюминесцентные свойства CaB 4O 7:Dy....

  17. Effects of hole doping on the electronic transport properties of PrBa1.8Sr0.2Cu3Oy and PrSr2Cu2.7Mo0.3Oy

    International Nuclear Information System (INIS)

    We investigate the effect of Ca doping on the electronic transport properties and superconductivity of Pr1-xCaxBa1.8Sr0.2Cu3Oy and Pr1-xCaxSr2Cu2.7Mo0.3Oy systems. It is found that when PrBa2Cu3Oy (Pr123) is in a highly localized state, the Ca doping mainly decreases the 4f-2p hybridized states and thus releases the holes into the CuO2 planes. Whereas when Pr123 is in a less localized state, the Ca doping not only introduces holes into the CuO2 planes, but also induces dramatic charge transfer. Our results suggest that only when the hole concentration in both the CuO chain and the CuO2 planes reaches a proper value, can the superconductivity be restored in the Pr123 system

  18. Molecular Dynamics Simulations for Melting Temperatures of SrF2and BaF2

    Institute of Scientific and Technical Information of China (English)

    Xiao-yu Huang; Xin-lu Cheng; Chao-lei Fan; Qiong Chen; Xiao-li Yuan

    2009-01-01

    The shell-model molecular dynamics method was applied to simulate the melting temper-atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state for SrF2 and BaF2 over the pressure range of 0.1 MPa-3 GPa and 0.1 MPa-7 GPa. Compared with previous results for equations of state, the maximum errors are 0.3% and 2.2%, respectively. Considering the pre-melting in the fluorite-type crystals, we made the necessary corrections for the simulated melting temper-atures of SrF2 and BaF2. Consequently, the melting temperatures of SrF2 and BaF2 were obtained for high pressures. The melting temperatures of SrF2 and BaF2 that were obtained by the simulation are in good agreement with available experimental data.

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

    CERN Document Server

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

    2014-01-01

    It has been noted that, in classical extremely metal-poor (EMP) stars, the abundance ratio of Sr and Ba, is always higher than [Sr/Ba] = -0.5, 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. 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. Four stars with very low Sr/Ba ratios were observed and analyzed within LTE approximation through 1D (hydrostatic) model atmosphere, providing homogeneous abundances of nine neutron-capture elements. 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. The abundance patterns of the neutron-capture elements in the three stars are strikingly similar to a theoretical s-pro...

  20. Structure-microwave dielectric property relations in Sr and Ca titanates

    International Nuclear Information System (INIS)

    Tuning the temperature coefficient of resonant frequency (TCF) in microwave dielectrics has been attributed to two main mechanisms: (i) dilution of the average ionic polarisability and (ii) the onset of an octahedral tilt transition above room temperature. The contributions of these mechanisms have been examined using ceramics in the Srn+1TinO3n+1, (SrxCa1-x)3Ti2O7 and SrxCa1-xTiO3 series. In the Srn+1TinO3n+1 series, dielectric constant (εr) and TCF are directly proportional over a broad range of values, 100 - 37 and 800 -140MK-1, n=4 and 1, respectively. No structural phase transitions occur on cooling from the prototype symmetry and the mechanism of tuning TCF is attributed solely to dilution of the average ionic polarisability as the SrO:SrTiO3 ratio (εr 14.5:290) increases. The dilution effect can be quantified by the gradient of the curve which shows a decrease of ∼9-10MK-1 in TCF for each single point reduction in εr. Substituting Ca for Sr in the (SrxCa1-x)3Ti2O7 series resulted in an 80% reduction in TCF from +320 to +50MK-1, but only 20% in dielectric constant (57 to 46). Dilution was therefore eliminated as the main tuning mechanism. However, Ca substitution onto the A-site of Sr based RP phases induces a structural phase transition involving rotations of the O-octahedra. The behaviour of TCε and therefore TCF as a function of tolerance factor was similar in the (SrxCa1-x)3Ti2O7 series to that observed for Ba and Sr based complex perovskites. It was therefore concluded that tilting of the octahedra dominated tuning of TCF. The domain variance associated with structural phase transitions in the solid (SrxCa1-x)TiO3 solid solution series has been investigated using electron diffraction. Only electron diffraction patterns from end member compositions conformed to those simulated using other workers' X-ray diffraction and neutron diffraction refinement data. For compositions where x=0.8, a tetragonal (I4/mcm) antiphase tilt system (a deg a deg c-) is

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

    International Nuclear Information System (INIS)

    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 y1P←a1S 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Barry M.; McCaffrey, John G., E-mail: john.mccaffrey@nuim.ie [Department of Chemistry, Maynooth University, National University of Ireland—Maynooth, County Kildare (Ireland)

    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{sup 1}P←a{sup 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{sup −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 Sr{sub 2} while this transition is quenched in Ba{sub 2}. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba{sub 2} 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.

  3. Tectonic forcing of early to middle jurassic seawater Sr/Ca

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz; Hesselbo, Stephen P.; Korte, Christoph

    2013-01-01

    sections in the UK and Poland demonstrate that the Sr/Ca ratio of seawater varied systematically throughout the Early and Middle Jurassic in parallel with already documented seawater 87Sr/86Sr. The Sr flux from increased mid-ocean ridge activity in the Early Jurassic outbalanced the input of riverine Sr......Sr/86Sr and Sr/Ca suggest a common cause for these long-term variations and are best explained by changes in the balance of continental weathering and hydrothermal fluxes. These findings underline the strong control of global tectonic processes on the evolution of biomineralization and downplay the...

  4. Structure-microwave dielectric property relations in Sr and Ca titanates

    CERN Document Server

    Wise, P L

    2001-01-01

    induces a structural phase transition involving rotations of the O-octahedra. The behaviour of TC epsilon and therefore TCF as a function of tolerance factor was similar in the (Sr sub x Ca sub 1 sub - sub x) sub 3 Ti sub 2 O sub 7 series to that observed for Ba and Sr based complex perovskites. It was therefore concluded that tilting of the octahedra dominated tuning of TCF. The domain variance associated with structural phase transitions in the solid (Sr sub x Ca sub 1 sub - sub x)TiO sub 3 solid solution series has been investigated using electron diffraction. Only electron diffraction patterns from end member compositions conformed to those simulated using other workers' X-ray diffraction and neutron diffraction refinement data. For compositions where x=0.8, a tetragonal (I4/mcm) antiphase tilt system (a deg a deg c sup -) is predicted. However, comparisons of simulated with experimental single domain patterns suggested that this composition has more than one axis tilted in antiphase. Tuning the temperatu...

  5. Investigation of Ba2–SrTiO4: Structural aspects and dielectric properties

    Indian Academy of Sciences (India)

    Vishnu Shanker; Tokeer Ahmad; Ashok K Ganguli

    2004-10-01

    Investigation of solid solution of barium–strontium orthotitanates of the type, Ba2–SrTiO4 (0 ≤ ≤ 2), show that pure phases exist only for the end members, Ba2TiO4 and Sr2TiO4, crystallizing in the -K2SO4 and K2NiF4 structures, respectively. The intermediate compositions (till ≤ 1) lead to a biphasic mixture of two Ba2TiO4-type phases (probably through a spinodal decomposition) with decreasing lattice parameters, indicating Sr-substitution in both the phases. For > 1, Sr2TiO4 along with a secondary phase is obtained. The dielectric constant and dielectric loss were found to decrease with Sr substitution till the nominal composition of = 1. However, pure Sr2TiO4 shows higher dielectric constant compared to the solid solution composition. Sr2TiO4 shows very high temperature stability of the dielectric constant.

  6. Mechanical-chemical synthesis Ba0.77Sr0.23TiO3

    Directory of Open Access Journals (Sweden)

    Kosanović D.

    2012-01-01

    Full Text Available Barium-Strontium-Titanate Ba0.77Sr0.23TiO3 was prepared from starting materials BaCO3, SrCO3 and TiO2 through solid-state reactions. Mixtures of these oxides are mechanically activated in a high-energy planetary ball mill at different time intervals from 0 to 120 minutes. In order to obtain information on phase composition, crystal structure was determent by X-ray diffraction. It was observed that after 80 minutes in process synthesis Ba0.77Sr0.23TiO3 started Thermal analyzes were performed in order to determine the characteristic temperatures of the processes that occur in the solid phase. Particle size distribution, together with electron microscopy scanning has given us very useful information about the morphology of the powder.

  7. Flexibility of EF-hand motifs: structural and thermodynamic studies of Calcium Binding Protein-1 from Entamoeba histolytica with Pb2+, Ba2+, and Sr2+

    Directory of Open Access Journals (Sweden)

    Kumar Shivesh

    2012-08-01

    Full Text Available Abstract Background EF-hand proteins can be activated by the binding of various heavy metals other than calcium, and such complexes can disturb the calcium-signaling pathway and cause toxicity and disease causing state. So far, no comprehensive study has been done to understand different heavy metals binding to calcium signaling proteins. Results In this work, the flexibility of the EF-hand motifs are examined by crystallographic and thermodynamic studies of binding of Pb2+, Ba2+ and Sr2+ to Calcium Binding Protein-1 from Entamoeba histolytica (EhCaBP1. The structures of the EhCaBP1- heavy metal complexes are found to be overall similar, nevertheless specific differences in metal coordination, and small differences in the coordination distances between the metal and the ligands in the metal binding loop. The largest such distances occur for the Ba2+- EhCaBP1 complex, where two bariums are bound with partial occupancy at the EF2 motif. Thermodynamic studies confirm that EhCaBP1 has five binding sites for Ba2+ compared to four binding sites for the other metals. These structures and thermodynamic studies reveal that the EF-hand motifs can accommodate several heavy atoms with similar binding affinities. The binding of Ca2+ to the 1st, 2nd and 4th sites and the binding of Ba2+ to the 1st, 2nd, 4th and 5th sites are both enthalpically and entropically driven, whereas the binding of Sr2+ to the 1st, 2nd and 4th sites are simply enthalpy driven, interestingly in agreement with ITC data, Sr2+ do not coordinate with water in this structure. For all the metals, binding to the 3rd site is only entropy driven. Conclusion Energetically, Ca2+ is preferred in three sites, while in one site Ba2+ has better binding energy. The Sr2+-coordination in the EF hand motifs is similar to that of the native Ca2+ bound structure, except for the lack of water coordination. Sr2+ coordination seems to be a pre-formed in nature since all seven coordinating atoms are from the

  8. Structural and thermodynamic characterization of the perovskite-related BA1+yUO3+x and (BA,SR)1+yUO3+x phases

    International Nuclear Information System (INIS)

    The perovskite-type BaUO3 structure has been investigated by X-ray and neutron diffraction. The Ba/U ratio, the (Ba, Sr)/U ratio, and the oxygen stoichiometry in Ba1+yUO3+x were varied, and the integral enthalpies of formation determined by solution calorimetry. In addition, equilibrium oxygen partial pressures were measured using a reversible EMF cell. The chemical defect mechanism is discussed, and it is shown that a continuous series BaUO3-Ba1+yUO3+x-Ba3UO6 exist in which uranium vacancies are gradually filled up with barium ions, whereas uranium is oxidized via the pentavalent to the hexavalent state in Ba3UO6(=Ba2(Ba, U)O6). (orig.)

  9. Optical Properties of Blue-Light-Emitting (Ca,Sr)Mg2Si3O9:Eu2+ Phosphor

    Science.gov (United States)

    Lee, Hyun Ju; Choi, Sung Hwan; Kim, Kyung Pil; Shin, Hyun Ho; Yoo, Jae Soo

    2010-10-01

    For light-emitting diode (LED) excitation at 400 nm, the optical properties of a Eu2+-activated CaO-SrO-MgO-SiO2 material system were investigated. All the materials were synthesized by solid state reaction. In particular, (Ca,Sr)Mg2Si3O9:Eu2+, which has the same crystal structure as CaMgSi2O6, was found to be promising as a blue-light-emitting phosphor for near UV LED application. The luminance intensity was optimized by controlling the Eu2+ concentration and the composition of the host lattice. The ratio of calcium ions to strontium ions was a convenient parameter for adjusting the maximum excitation peak to 400 nm, which is favorable for near UV LED excitation. The highest luminance intensity of Ca1-x-ySryMg2Si3O9:Eux2+ under 405 nm excitation was achieved at the Eu2+ concentration of x=0.01 and a Sr2+ concentration of y=0.3. The luminance intensity of (Ca,Sr)Mg2Si3O9:Eu2+ was found to be superior to that of a commercial blue-light-emitting BaMgAl10O17:Eu2+ phosphor, which is used for near-UV LED excitation.

  10. Thermophysical and thermochemical properties of Ba0 and Sr0 from 5 to 1000K

    International Nuclear Information System (INIS)

    The low temperature heat capacities from 5 to 350 K by adiabatic calorimetry and the high-temperature enthalpy increments from 470 to 877 K by drop calorimetry of BaO and SrO have been measured. From the results smoothed thermochemical and thermophysical functions have been calculated at selected temperatures up to 1000 K. For the standard entropies of BaO and SrO at 298.15 K the values (70.01±0.10) and (53.63±0.10) 3xmol-1xK-1, respectively, have been found. (orig.)

  11. Temperature-Dependent Structure of Epitaxial (Ba,Sr)TiO3 Films Grown on SrRuO3-Covered SrTiO3 Substrates

    Institute of Scientific and Technical Information of China (English)

    HE Jia-Qing; E. VASCO; R. DITTMANN; WANG Ren-Hui

    2006-01-01

    @@ Growth dynamics of epitaxial (Ba, Sr)TiO3 thin films deposited at different temperatures on SrRuOa/SrTiO3substrates by pulsed laser deposition is investigated by transmission electron microscopy. The films exhibit a layered structure comprising sublayers with distinctive features in regard to the remaining strain, density of misfit dislocations and/or lattice defects, and growth habit. We correlate these temperature-dependent features with the predominant misfit-strain relaxation mechanisms for each one of the detected growth regimes. The thickness dependence of the film structure is discussed within the framework of the predictions for a kinetically modified Stranski-Krastanov growth mode.

  12. Improvement of electron mobility in La:BaSnO3 thin films by insertion of an atomically flat insulating (Sr,Ba)SnO3 buffer layer

    Science.gov (United States)

    Shiogai, Junichi; Nishihara, Kazuki; Sato, Kazuhisa; Tsukazaki, Atsushi

    2016-06-01

    One perovskite oxide, ASnO3 (A = Sr, Ba), is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO3 substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO3 / (Sr,Ba)SnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,Ba)SnO3 bilayer buffer structures reduces the number of dislocations and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO3 buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO3 shows that the highest obtained value of mobility is 78 cm2V-1s-1 because of its fewer dislocations. High electron mobility films based on perovskite BaSnO3 can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.

  13. CaCO3 and SrCO3 bioprecipitation by fungi isolated from calcareous soil.

    Science.gov (United States)

    Li, Qianwei; Csetenyi, Laszlo; Paton, Graeme Iain; Gadd, Geoffrey Michael

    2015-08-01

    The urease-positive fungi Pestalotiopsis sp. and Myrothecium gramineum, isolated from calcareous soil, were examined for their properties of CaCO3 and SrCO3 biomineralization. After incubation in media amended with urea and CaCl2 and/or SrCl2 , calcite (CaCO3 ), strontianite (SrCO3 ), vaterite in different forms [CaCO3 , (Cax Sr1-x )CO3 ] and olekminskite [Sr(Sr,Ca)(CO3 )2 ] were precipitated, and fungal 'footprints' were observed on mineral surfaces. The amorphous precipitate mediated by Pestalotiopsis sp. grown with urea and equivalent concentrations of CaCl2 and SrCl2 was identified as hydrated Ca and Sr carbonates by Fourier transform infrared spectroscopy. Liquid media experiments showed M. gramineum possessed the highest Sr(2+) removal ability, and ∼ 49% of supplied Sr(2+) was removed from solution when grown in media amended with urea and 50 mM SrCl2 . Furthermore, this organism could also precipitate 56% of the available Ca(2+) and 28% of the Sr(2+) in the form of CaCO3 , SrCO3 and (Cax Sr1-x )CO3 when incubated in urea-amended media and equivalent CaCl2 and SrCl2 concentrations. This is the first report of biomineralization of olekminskite and coprecipitation of Sr into vaterite mediated by fungi. These findings suggest that urease-positive fungi could play an important role in the environmental fate, bioremediation or biorecovery of Sr or other metals and radionuclides that form insoluble carbonates. PMID:26119362

  14. Highest temperature (120 K) Tl-Ba-Ca-Cu-O superconducting system

    International Nuclear Information System (INIS)

    The highest temperature (120K) Tl-Ba-Cu-O superconducting system comprises a number of superconducting compounds. The Tl-Ba-Ca-Cu-O superconductors are easily made. The structure, electronic and magnetic properties are presented. An unusual levitation phenomenon, in which the Tl-Ba-Ca-Cu-O superconductor can be suspended above, below, or to the side of a magnet, is discussed. A new Tl2O3-vapor process for fabricating the Tl-Ba-Ca-Cu-O superconductors is described

  15. Thermoluminescence glow curves of Ca2+ and Sr2+ doped LiCl single crystals

    International Nuclear Information System (INIS)

    Effects of Ca2+ and Sr2+ dopants on the thermoluminescence glow curves of LiCl monocrystals have been studied. The crystals containing different amounts of Sr2+ and Ca2+, resp., were irradiated either by 60Co γ-radiation or by 90Sr beta particles

  16. Structure of the new Tl(Ba sub 1.0 Sr sub 1.0) PrCu sub 2 O sub 7-x by Rietveld analysis

    International Nuclear Information System (INIS)

    The crystalline structure of Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x was obtained at room temperature from x-ray powder diffraction with CuK sub α radiation using Rietveld analysis. Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x isomorphous at both room temperature (300 K) and low temperature (100 K) with TlBa sub 2 ca Cu sub 2 O sub 7-x type (1212) structure, crystallized with space group P4/mmm and one formula in the unit cell. At 300 K, cell parameters a=3.8892(2) A, c=12.3099(6) A, the structure was refined with 25 parameters to R sub WP = 6.30%, R sub P = 4.38% for 3551 step intensities and R sub b = 5.01%, R sub f = 4.20% for 156 reflections. The goodness of fitting S=3.18. At 100K, cell parameters a=3.8866(4) A, c= 12.289(1) A, the structure was refined with 26 parameters to R sub WP = 8.42%, R sub P = 6.21% for 2676 step intensities and R sub b = 6.72%, R sub f = 5.28% for 120 reflections. The goodness of fitting S=2.32. Reasonable anisotropic thermal parameters were obtained. The compositions of Ba and Sr atoms were refined to about Ba sub 1.1 Sr sub 0.9 compared with the stoichiometric Ba sub 1.0 Sr sub 1.0

  17. Mechanism of superconductivity in Yb1-xCax(Ba0.8SrO.2)2 Cu3O6+δ

    International Nuclear Information System (INIS)

    EXAFS, X-ray Rietveld refinement and infra-red absorption measurements have been made on Yb1-xCax (Ba0.8Sr0.2)2 Cu3O6+δ in order to understand the effect of Ca doping on the local structure of planar Cu ion. The study indicates that restoration of superconductivity is due to oxidation of copper ions in the CuO2 planes. (author)

  18. Strong biological controls on Sr/Ca ratios in aragonitic marine bivalve shells

    Science.gov (United States)

    Gillikin, David Paul; Lorrain, Anne; Navez, Jacques; Taylor, James W.; André, Luc; Keppens, Eddy; Baeyens, Willy; Dehairs, Frank

    2005-05-01

    It is well known that skeletal remains of carbonate secreting organisms can provide a wealth of information about past environments. Sr/Ca ratios have been successfully used as a temperature proxy in corals and sclerosponges. Previous work on aragonitic bivalve shells has not been conclusive but suggests a major control of growth rate on Sr/Ca ratios. As many studies have used bivalve growth rates to determine temperature, we tested if Sr/Ca ratios could predict temperature through its relationship with growth rate. Shells from the two species of clams from the same family (veneroidea) studied here, Saxidomus giganteus and Mercenaria mercenaria, show vastly different seasonal Sr/Ca profiles. A strong relationship between average annual Sr/Ca ratios and annual growth rate was found in S. giganteus shells from both Washington (R2 = 0.87) and Alaska (R2 = 0.64), USA, but not in M. mercenaria shells from North Carolina, USA. Furthermore, the Sr/Ca-growth rate relationship was also evident upon a more detailed inspection of subannual growth rates in S. giganteus (R2 = 0.73). Although there were significant positive correlations between Sr/Ca ratios and temperature in S. giganteus shells, the correlations were weak (0.09 control in either clam species, since thermodynamics predict a negative correlation between Sr/Ca ratios and temperature in aragonite. This points toward dominance of biological processes in the regulation of Sr2+. This is also reflected by the largely differing Sr/Ca partition coefficients (DSr) in these shells (DSr ≈ 0.25), when compared to inorganic, coral, and sclerosponge studies (DSr ≈ 1), all of which show a negative dependence of Sr/Ca on temperature. We suggest that caution be taken when using Sr/Ca in any biogenic aragonite as a temperature proxy when the DSr greatly deviates from one, as this indicates the dominance of biological controls on Sr/Ca ratios.

  19. 87Sr/ 86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280 kyr ago

    Science.gov (United States)

    Li, Hong-Chun; Ku, Teh-Lung; You, Chen-Feng; Cheng, Hai; Edwards, R. Lawrence; Ma, Zhi-Bang; Tsai, Wang-sheng; Li, Mung-Dar

    2005-08-01

    Limestone cave deposits (speleothems) provide archives for past changes in regional climates over a range of timescales. While δ 18O and δ 13C in speleothem calcite have been commonly used for reconstruction of paleoclimates, we report here further efforts in the use of 87Sr/ 86Sr and Sr/Ca signals in speleothem calcite to deduce paleomonsoon variability near the Loess Plateau of central China. A two end-member mass-balance model of concentration and isotopic composition of strontium in a cave system is used to estimate variation of the 87Sr/ 86Sr ratio in sediments overlying a limestone cave. We show that this ratio reflects climate-driven variations in the provenance and the extent of chemical weathering of the epikarstic sediments. The measurements of 87Sr/ 86Sr made on a well-dated stalagmite, SFL, from Buddha Cave (33 o40N' 109 o05'E) show ratios of 0.71092 to 0.71133 (±0.00001 as 2σ) during relatively cold periods (e.g., Marine Isotope Stage (MIS) 5b, 5d, and 8), lower than ratios of 0.71133 to 0.71194 during relatively warm periods (e.g., MIS 5a, 5c, 5e, and 7). As changes in the Sr/Ca ratio may affect speleothem 87Sr/ 86Sr, we show that the direct use of speleothem 87Sr/ 86Sr is less ideal than our modeled 87Sr/ 86Sr for the exogenic Sr source above the cave as a paleomonsoon proxy. Using the δ 18O, δ 13C, Sr/Ca, and 87Sr/ 86Sr records of the stalagmite, we reconstruct the variability of the East Asian monsoon for the time period between 70 and 280 kyr ago. The results show that summer monsoons were more intense during interglacial periods than during glacial periods.

  20. Crystal structure and phase transitions in the uranium perovskite, Ba2SrUO6

    International Nuclear Information System (INIS)

    The structure of one of the oxides proposed to be present in the grey phase of irradiated mixed oxide fuel, the double perovskite Ba2SrUO6 has been investigated from room temperature to 1300 K using synchrotron X-ray powder diffraction methods. The divalent strontium and hexavalent uranium are found to be fully ordered in the double-perovskite arrangement of alternating octahedra sharing corner oxygen atoms. At room temperature Ba2SrUO6 adopts a monoclinic structure in space group P21/n. Heating to above 900 K induces a first order transition to a rhombohedral structure, and further heating to above 1200 K results in a continuous transition to a cubic structure. The sequence of structures is associated with the progressive loss of cooperative tilting of the corner sharing SrO6 and UO6 octahedra

  1. Ca2+ Alternans in a Cardiac Myocyte Model that Uses Moment Equations to Represent Heterogeneous Junctional SR Ca2+

    OpenAIRE

    Huertas, Marco A; Smith, Gregory D.; Györke, Sándor

    2010-01-01

    Multiscale whole-cell models that accurately represent local control of Ca2+-induced Ca2+ release in cardiac myocytes can reproduce high-gain Ca2+ release that is graded with changes in membrane potential. Using a recently introduced formalism that represents heterogeneous local Ca2+ using moment equations, we present a model of cardiac myocyte Ca2+ cycling that exhibits alternating sarcoplasmic reticulum (SR) Ca2+ release when periodically stimulated by depolarizing voltage pulses. The model...

  2. Crystal structures and phase transitions in Sr doped Ba2InTaO6 perovskites

    International Nuclear Information System (INIS)

    The crystal structures of the double perovskites of the type Ba2−xSrxInTaO6 have been studied by synchrotron X-ray and neutron powder diffraction methods. The structures are based on ordered array of the tilted InO6 and TaO6 octahedra, with the Ba/Sr cations being completely disordered. The structure evolves from cubic to monoclinic Fm3¯m→x∼0.6I4/m→x∼1.2I2/m→x∼1.6P21/n. The changes in the symmetry induced by replacing the Ba with Sr have been identified by a symmetry-mode analysis. Variable temperature S-XRD studies of selected examples have shown that heating the samples induces the same sequence of transitions observed in the composition dependent studies. - Graphical abstract: The evolution of the structure of the B-site ordered perovskites has been determined by high resolution powder diffraction. The nature of the transitions are probed by examination of the symmetry-adapted modes. Display Omitted - Highlights: • Synthesis of Ba2−xSrxInTaO6 cation ordered perovskites. • Synchrotron X-ray and neutron diffraction structural studies of Ba2−xSrxInTaO6. • Phase transitions in Ba2−xSrxInTaO6. • Symmetry-adapted mode analysis of phase transitions

  3. Superconductivity and thermoelectric power in Tl2Ca2Ba2Cu3O10 and TlCa3BaCu3O9

    International Nuclear Information System (INIS)

    The authors report the synthesis and superconducting temperature of the high-Tc compounds Tl2Ca2Ba2Cu3O10 and TlCa3BaCu3O9. The transition to the superconducting state was measured by the magnetic susceptibility changes and by the temperature dependence of the electrical a.c and d.c. resistivity and by thermoelectric power measurements. For Tl2Ca2Cu3O10 a superconducting transition with zero resistance at 114.5Κ have been observed. Higher Tc with zero resistance at 122Κ have been found in TlCa3BaCu3O9

  4. Flexibility of EF-hand motifs: structural and thermodynamic studies of Calcium Binding Protein-1 from Entamoeba histolytica with Pb2+, Ba2+, and Sr2+

    International Nuclear Information System (INIS)

    EF-hand proteins can be activated by the binding of various heavy metals other than calcium, and such complexes can disturb the calcium-signaling pathway and cause toxicity and disease causing state. So far, no comprehensive study has been done to understand different heavy metals binding to calcium signaling proteins. Energetically, Ca2+ is preferred in three sites, while in one site Ba2+ has better binding energy. The Sr2+-coordination in the EF hand motifs is similar to that of the native Ca2+ bound structure, except for the lack of water coordination. Sr2+-coordination seems to be a pre-formed in nature since all seven coordinating atoms are from the protein itself, which also correlates with entropy contributions in Sr2+ binding. These findings improve our understanding of metal association with calcium binding proteins and of metal induced conformational changes.

  5. Synthesis and properties of polycrystalline TlP2Ba2CaCu2Ox and Tl2Ba2Ca2Cu3Ox

    International Nuclear Information System (INIS)

    This paper reports polycrystalline samples of Tl2Ba2CaCu2Ox and Tl2Ba2Ca2Cu3Ox superconductors with high (>95 wt%) phase purity prepared by a solid state reaction of Tl2O3 with a mixture of BaCuO2, Ca2CuO3, and CuO. Starting compositions of Tl1+δBaCaCu2Ox and Tl2+δBa2Ca2Cu3Ox were fired in semi-sealed reaction vessels for durations of 12 to 48 hours in flowing oxygen with low, reproducible thallium losses. Samples fired at temperatures below 870 degree C produced predominately the 2212 phase, while samples above 870 degree C yielded the 2223 phase. While pressed mixed oxides reacted in a single firing step produced low-density (≤50% theoretical) material, samples prepared by a two-step sequence of reactive calcination, intermediate grinding, and sintering yielded higher density material (>70% theoretical). The sintered polycrystalline superconductors were characterized by x-ray diffraction, reflected light and electron microscopy, magnetic susceptibility, and dc transport resistivity. Critical current density measurements by direct transport and magnetic moment hysteresis methods are presented for the denser samples. Transport Jc values up to 300 A/cm2 at 75 K were observed for moderately dense material (5.2 g/cm3, 74% theoretical) in transverse H fields up to 10 kOe

  6. Theory of polarization enhancement in epitaxial BaTiO$_3$/SrTiO$_3$ superlattices

    OpenAIRE

    Neaton, J. B.; Rabe, K. M.

    2002-01-01

    The spontaneous polarization of epitaxial BaTiO$_3$/SrTiO$_3$ superlattices is studied as a function of composition using first-principles density functional theory within the local density approximation. With the in-plane lattice parameter fixed to that of bulk SrTiO$_3$, the computed superlattice polarization is enhanced above that of bulk BaTiO$_3$ for superlattices with BaTiO$_3$ fraction larger than 40%. In contrast to their bulk paraelectric character, the SrTiO$_3$ layers are found to ...

  7. Determination of Sr and Ca sources in small tropical catchments (La Selva, Costa Rica) - A comparison of Sr and Ca isotopes

    Science.gov (United States)

    Wiegand, B. A.; Schwendenmann, L.

    2013-04-01

    SummaryA comparative study of Sr and Ca isotopes was conducted to assess solute sources and effects of biogeochemical processes on surface water and groundwater in four small tropical catchments located at La Selva Biological Station, Costa Rica. Variable concentrations of dissolved Sr2+ and Ca2+ in the catchments are related to mixing of waters from different origin. Three catchments are influenced by high-solute bedrock groundwater, while another catchment is primarily supplied by local recharge. 87Sr/86Sr ratios were employed to discriminate contributions from mineral weathering and atmospheric sources. Solutes in bedrock groundwater have a predominant geogenic origin, whereas local recharge is characterized by low-solute inputs from rainwater and minor in situ weathering releases from nutrient-depleted soils. Bedrock groundwater contributes more than 60% of dissolved Sr2+ to surface discharge in the Salto, Saltito, and Arboleda catchments, whereas the Taconazo catchment receives more than 95% of dissolved Sr2+ from rainwater. δ44/40Ca values of dissolved Ca2+ vary greatly in the catchments, mainly as a result of heterogeneous Ca isotope compositions of the contributing sources. Based on differences in δ44/40Ca values, two distinct bedrock groundwaters discharging at the Salto and the Arboleda catchments are suggested. Effects of biological processes in the plant-soil system on solute generation in the catchments are indicated by variable Ca/Sr ratios. However, these effects cannot clearly be assessed by Ca isotopes due to the strong heterogeneity of δ44/40Ca values of Ca2+ sources and high Ca2+ concentrations in bedrock groundwater.

  8. Growth kinetics of Cu1-xTlxBa2Ca3Cu4O12-y thin films

    International Nuclear Information System (INIS)

    Cu1-xTlxBa2Ca3Cu4O12-y (Cu1-xTlx-1234) thin films have been found to be very attractive candidates in the cuprate family due to their low superconductor anisotropy, long coherence length and, consequently, high Jc. The method of preparation has been reported previously, however the kinetics of their formation has not yet been studied. In this paper, we report on the growth kinetics of superconducting Cu1-xTlxBa2Ca3Cu4O12-y thin films. In the preparation, we use the amorphous phase epitaxy method, which is a thallium treatment of the amorphous phase at elevated temperatures. The amorphous phase was deposited on a SrTiO3 substrate by rf-sputtering from a stoichiometric target with a composition of CuBa2Ca3Cu4Oy. The thallium treatment of the amorphous phase was carried out in a gold capsule for 45 min. The mechanism of the growth kinetics has shown that the formation of Cu1-xTlxBa2Ca3Cu4O12-y thin films was accomplished from Cu1-xTlxBa2Ca1Cu2O8-y (Cu1-xTlx-1212) and Cu1-xTlxBa2Ca2Cu3O10-y (Cu1-xTlx-1223) by the successive introduction of CuO2 planes in these phases. We also studied the effect of the time and temperature of the thallium treatment on the growth of Cu1-xTlx-1234 films. The best synthesis temperature for Cu1-xTlx-1234 films was found to be 910 deg. C, but this phase could also be isolated as a single phase at lower temperatures (∼890 deg. C). However, the low-temperature synthesis results in a higher thallium content in the final compound. From the x-ray diffraction measurements the c-axis length was found to increase with the increase of the thallium content. The pole figure measurements of the (103) reflection of the films have shown a-axis oriented crystals with Δ φ = 0.8 deg. The observed critical temperature (Tc) for Cu1-xTlx-1212, Cu1-xTlx-1223 and Cu1-xTlx-1234 are 78 K, 103 K and 110 K respectively. Current density measurements have shown a maximum Jc∼2x106 A cm-2. (author)

  9. Bonding in Zintl phase hydrides: density functional calculations for SrAlSiH, SrAl2H2, SrGa2H2 and BaGa2H2

    Energy Technology Data Exchange (ETDEWEB)

    Subedi, Alaska P [ORNL; Singh, David J [ORNL

    2008-01-01

    We investigate the bonding characteristics of SrAlSiH, SrAl{sub 2}H{sub 2}, SrGa{sub 2}H{sub 2}, and BaGa{sub 2}H{sub 2} using density functional calculations. The mixed bonding characteristic of other families of Zintl phases is found, with the formation of covalent sp{sup 2} bonds in the Al/Ga/Al-Si planes of the various compounds. On the other hand the Sr and Ba atoms occur as divalent cations, while the H is anionic. The results indicate that insulating SrSiAlH may be a switchable ferroelectric.

  10. Fabrication and properties of BiSrCaO superconductors

    International Nuclear Information System (INIS)

    Fabrication processes for increasing the critical current density Jc in BiSrCaCuO superconductor have been studied. Calcining mixtures of raw material in a reduced oxygen partial pressure or in vacuum after in-air calcination is found to be effective. Intermediate cold work (ICW) i.e. uniaxial pressing, cold flat rolling, etc. incorporated in the sintering Ag-sheathed tape is also effective for raising Jc. From a preliminary experiment on Ag-added tape sample, a combination of both processes appeared to be most effective. The highest Jc obtained is 4.37x104 A/cm2 at 4.2 K and 12 Tesla. Effects of additional element Ag etc. on Jc have also been described. (author). 10 refs., 7 figs., 1 tab

  11. Structural and magnetic study of the cation-ordered perovskites Ba2-x Sr x ErMoO6

    International Nuclear Information System (INIS)

    A series of perovskite phases have been prepared from the appropriate carbonates and oxides by heating under reducing conditions at temperatures up to 1300 deg. C. Complete ordering between ErO6 and MoO6 octahedra and a disordered distribution of Sr2+ and Ba2+ occur in all compounds. Neutron powder diffraction experiments show that the substitution of Sr2+ into Ba2ErMoO6 introduces a progressive reduction in symmetry from Fm3-barm (x=0) to I4/m (x=0.5, 0.8) to P21/n (x=1.25, 1.75, 2.0). Magnetic susceptibility measurements indicate that all of these compounds show Curie-Weiss paramagnetism and that for x0.25Sr1.75ErMoO6 and Sr2ErMoO6, respectively. Ba0.75Sr1.25ErMoO6, Ba0.25Sr1.75ErMoO6 and Sr2ErMoO6 do not undergo structural distortion on cooling from room temperature. - Graphical abstract: Introduction of Sr2+ into the double perovskite Ba2ErMoO6 introduces increasingly large distortions from cubic symmetry and permits antiferromagnetic order at T N≤4 K

  12. Magnetoresistance in Parent Pnictide AFe2As2(A = Sr, Ba)

    International Nuclear Information System (INIS)

    Magnetoresistances of SrFe2As2 and BaFe2As2 in the magnetic ordered state are studied. Positive magnetoresistance is observed in the magnetic fields H applied in the azimuthes of θ = 0° and 30° with respect to the c-axis. The magnetoresistance can reach 20% for SrFe2As2 and 12% for BaFe2As2 at H = 9 T with θ = 0° (H || c). Above the magnetic transition temperature, the magnetoresistance becomes negligible. The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap. The field enhanced spin-density-wave gaps for different types of carriers are different. Temperature dependencies of the fitting parameters are discussed

  13. Magnetoresistance in Parent Pnictide AFe_2As_2(A=Sr, Ba)

    Institute of Scientific and Technical Information of China (English)

    ZHENG Ping; CHEN Gen-Fu; LI Zheng; HU Wan-Zheng; DONG Jing; LI Gang; WANG Nan-Lin; LUO Jian-Lin

    2009-01-01

    Magnetoresistances of SrFe_2 As_2 and BaFe_2 As_2 in the magnetic ordered state are studied.Positive magnetoresis-tance is observed in the magnetic fields H applied in the azimuthes foθ = 0°and 30°with respect to the c-axis.The magnetoresistance can reach 20% for SrFe_2 As_2 and 12% for BaFe_2As_2 at H = 9 T with θ= 0°(H||c).Above the magnetic transition temperature, the magnetoresistance becomes negligible.The data in the magnetic ordered state could be described by a modified two-band galvanomagnetic model including the enhancement effect of the applied magnetic field on the spin-density-wave gap.The field enhanced spin-density-wave gaps for different types of carriers are different.Temperature dependencies of the fitting parameters are discussed.

  14. Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi

    Science.gov (United States)

    Stoll, Heather M.; Rosenthal, Yair; Falkowski, Paul

    2002-03-01

    Continuous culture of the coccolithophorid Emiliania huxleyi reveals that coccolith Sr/Ca ratios depend on temperature and growth rate. At a constant temperature of 18°C, coccolith Sr/Ca ratios increased nearly 15% as growth rate increased from 0.1 to 1.5 divisions per day and calcification rate increased from 1.5 to 50 pg calcite per cell per day. When temperature increased from 7 to 26°C, Sr/Ca ratios increased by more than 25% (i.e., 1%/1°C), although the range in growth and calcification rates was the same as for experiments at constant temperature. The temperature dependence of Sr/Ca ratios in coccoliths is consistent with that observed in planktonic foraminifera and abiogenic calcites, suggesting that it is controlled by thermodynamic processes. However, the positive correlation of coccolith Sr/Ca with temperature contrasts with field studies in the equatorial Pacific, where Sr/Ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures. This paradox may reflect different calcification rate effects between E. huxleyi and the other species dominating assemblages in the equatorial Pacific sediments, which may be resolved by new techniques for separation of monospecific coccolith samples from sediments. Models of crystal growth indicate that kinetic effects on Sr partitioning in calcite due to surface enrichment could explain the Sr/Ca variations observed in constant temperature experiments but not the larger amplitude calcification rate effects observed in equatorial Pacific sediments. Despite the dual influence of temperature and growth rate on coccolith Sr/Ca, coccolith Sr/Ca correlates with "b," the slope of the dependence of carbon isotope fractionation in biomarkers (ɛ p) on CO 2(aq) at a range of growth rates and temperatures. Consequently, using coccolith Sr/Ca in combination with alkenone ɛ p may improve paleo-CO 2 determinations.

  15. STIM1 enhances SR Ca2+ content through binding phospholamban in rat ventricular myocytes.

    Science.gov (United States)

    Zhao, Guiling; Li, Tianyu; Brochet, Didier X P; Rosenberg, Paul B; Lederer, W J

    2015-08-25

    In ventricular myocytes, the physiological function of stromal interaction molecule 1 (STIM1), an endo/sarcoplasmic reticulum (ER/SR) Ca(2+) sensor, is unclear with respect to its cellular localization, its Ca(2+)-dependent mobilization, and its action on Ca(2+) signaling. Confocal microscopy was used to measure Ca(2+) signaling and to track the cellular movement of STIM1 with mCherry and immunofluorescence in freshly isolated adult rat ventricular myocytes and those in short-term primary culture. We found that endogenous STIM1 was expressed at low but measureable levels along the Z-disk, in a pattern of puncta and linear segments consistent with the STIM1 localizing to the junctional SR (jSR). Depleting SR Ca(2+) using thapsigargin (2-10 µM) changed neither the STIM1 distribution pattern nor its mobilization rate, evaluated by diffusion coefficient measurements using fluorescence recovery after photobleaching. Two-dimensional blue native polyacrylamide gel electrophoresis and coimmunoprecipitation showed that STIM1 in the heart exists mainly as a large protein complex, possibly a multimer, which is not altered by SR Ca(2+) depletion. Additionally, we found no store-operated Ca(2+) entry in control or STIM1 overexpressing ventricular myocytes. Nevertheless, STIM1 overexpressing cells show increased SR Ca(2+) content and increased SR Ca(2+) leak. These changes in Ca(2+) signaling in the SR appear to be due to STIM1 binding to phospholamban and thereby indirectly activating SERCA2a (Sarco/endoplasmic reticulum Ca(2+) ATPase). We conclude that STIM1 binding to phospholamban contributes to the regulation of SERCA2a activity in the steady state and rate of SR Ca(2+) leak and that these actions are independent of store-operated Ca(2+) entry, a process that is absent in normal heart cells. PMID:26261328

  16. Ba/Ca Reproducibility and Growth Banding in Gulf of Alaska Bamboo Corals

    Science.gov (United States)

    Serrato Marks, G.; LaVigne, M.; Hill, T. M.; Sauthoff, W.; Guilderson, T. P.; Roark, E. B.; Dunbar, R. B.

    2014-12-01

    Deep-sea bamboo corals have been proposed as deep-ocean paleoceanographic archives because of their longevity and radial growth bands. Previous work has shown that bamboo coral Ba/Ca is a promising proxy for seawater barium, however, validation of Ba/Ca reproducibility is required. In addition, the growth band formation mechanism is uncertain, with some proposing that crystal orientation causes banding visible under light microscopy. The objective of this study was to evaluate Ba/Ca reproducibility and characterize growth band crystal orientation. Visible bands measured with a petrographic microscope were used to align LA-ICP-MS data collected along three replicate radii of the calcitic internodes of two well-dated corals from the Gulf of Alaska (collected live at 720m and 643m; 48°3'N, 132°44'W). Ba/Ca signals smoothed to ~annual resolution were reproducible within each coral (r=0.6-0.7; p<0.0001; n=3 radii/coral), suggesting that Ba/Ca varies in response to the external environment on annual timescales. Ba/Ca in the 720m coral increased from 1977 to 1998, a warm Pacific Decadal Oscillation (PDO) regime, possibly due to increased export production. The shallower coral (634m) revealed the inverse trend, suggesting variability in seawater barium dynamics with depth. Electron backscatter diffraction analysis of visible growth bands showed a preferred crystal orientation that does not correspond to location of visible bands or elemental composition, suggesting that crystal orientation does not cause bamboo coral banding. Overall, results show that regional oceanic signals are recorded as reproducible Ba/Ca variability in these corals. Comparison of these data to other well-dated records from the northeast Pacific would determine whether the relationship between Ba/Ca and PDO is regional. Additional archives of trace element variability will strengthen our understanding of how rapid climate change impacts intermediate ocean biogeochemistry.

  17. Defect analysis of BaSrFBr:Eu irradiated by X-ray

    International Nuclear Information System (INIS)

    The mechanical property of the BaSrFBr:Eu phosphor layer of X-ray image plates was investigated by using image quality (IQ), resolution (LP/mm), and coincidence Doppler broadening (CDB) positron annihilation. The screen samples of BaSrFBr:Eu phosphors were irradiated with hospital X-rays in the course of diagnostic radiography at an average rate of 20,000 times per year and were used for various periods of time. The LP/mm values of the irradiated BaSrFBr:Eu image plates varied between 2.4 and 2.0 for three years while the IQ values varied between 35 and 11 over the same period. CDB positron annihilation spectroscopy was used to analyze the defect structures in the phosphor layer. The S parameter values increased in correlation with increased exposure time, which indicated that more defects were generated. There was a positive relationship between the IQ and S parameters. Measurements of the defects indicate that most of the defects were likely to have been generated by the X-ray radiation.

  18. Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO2

    International Nuclear Information System (INIS)

    The diffusivity of the solid fission products (FP) Zr (Zr4+), Ru (Ru4+, Ru3+), Ce (Ce4+), Y (Y3+), La (La3+), Sr (Sr2+) and Ba (Ba2+) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. For all solid FPs except Y3+, the migration of the FP has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. However, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru3+ and Ru4+ diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO2, and the tendency to form metallic and oxide second phase inclusions

  19. Thermal properties of perovskite RCeO{sub 3} (R = Ba, Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Aarti, E-mail: aarti.phy@gmail.com [Department of Physics, Barkatullah University, Bhopal 462026 (India); Parey, Vanshree; Thakur, Rasna [Department of Physics, Barkatullah University, Bhopal 462026 (India); Srivastava, Archana [Department of Physics, Sri Sathya Sai College for women, Bhopal 462024 (India); Gaur, N.K. [Department of Physics, Barkatullah University, Bhopal 462026 (India)

    2015-08-20

    Highlights: • (Ba,Sr)CeO{sub 3} are high temperature protonic conductor materials. • This makes their thermal properties very interesting. • MRIM has successfully predicted the thermodynamic properties. • The computed results are in good agreement with the available experimental data. • Present results will serve as guide to experimental workers in future. - Abstract: We have investigated the bulk modulus and thermal properties of proton conducting perovskite RCeO{sub 3} (R = Ba, Sr) for the first time by incorporating the effect of lattice distortion in modified rigid ion models (MRIM). The computed bulk modulus, specific heat, thermal expansion coefficient and other thermal properties of BaCeO{sub 3} and SrCeO{sub 3} reproduce well with the available experimental data. In addition the cohesive energy (ϕ), molecular force constant (f), reststrahlen frequency (ν), Debye temperature (θ{sub D}) and Gruneisen parameter (γ) are also reported and discussed. The specific heat results can further be improved by taking into account the spin and the orbital ordering contribution in the specific heat formulae.

  20. Damage in etching of (Ba, Sr)TiO3 thin films using inductively coupled plasma

    International Nuclear Information System (INIS)

    High dielectric (Ba, Sr)TiO3 thin films were etched in an inductively coupled plasma as a function of the Cl2/Ar gas mixing ratio. Under Cl2 (20)/Ar (80), the maximum etch rate of the BST film was 400 Aa/min and the selectivities of BST to Pt and PR obtained were 0.4 and 0.2, respectively. Etching by-products remained on the surface of BST and resulted in varying the stochiometry. Therefore, we investigated the surface of the etched BST using x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and x-ray diffraction (XRD). From the results of XPS analysis, we found that metal (Ba or Sr) chloride compounds remained on the surface of the etched BST for high boiling points. The morphology of the etched surface was evaluated with AFM. The surface roughness decreased as the Cl2 increased in the Cl2/Ar plasma. From the results of XRD analysis, the crystallinity of etched BST films under Ar only and under Cl2 (20)/Ar (80) was similar to that of as-deposited BST. However, the (100) diffraction peak abruptly decreased at the Cl2 only plasma. It was assumed that metal (Ba or Sr) chloride compounds remained on the etched BST surface and changed the stoichiometry, resulting in crystallinity of the BST film during the etch process

  1. Positron annihilation investigation of BaSrFBr:Eu by X-ray irradiation

    Science.gov (United States)

    Lee, C. Y.

    2014-12-01

    The mechanical property of the BaSrFBr:Eu phosphor layer of X-ray image plates was investigated by using resolution (LP/mm) and coincidence Doppler broadening (CDB) positron annihilation as well as positron annihilation lifetime (PAL). The image plate samples of BaSrFBr:Eu phosphors in this experiment were irradiated by using hospital X-rays. The LP/mm values of the irradiated BaSrFBr:Eu image plates varied from 3.35 to 1.25 for up to 20,000 exposures. CDB positron annihilation and lifetime spectroscopy were used to analyze defect structures in the phosphor layer. Even when the LP/mm values were greatly decreased due to exposures, the S parameter and the lifetime ( τ 1, τ 2) values were almost constant with increasing number of exposures. A positive relationship existed between the SEM images and positron annihilation spectroscopy (PAS). According to the SEM images and the positron annihilation spectroscopy (PAS) results, measurements of the defects with PAS indicate that the image-plate phosphor can be safely used for hospital X-rays in the course of diagnostic radiography at an average rate of 20,000 times for one year.

  2. Structure of alkaline-earth pentafluoroantimonates(III), MSbF5(M=Sr, Ba)

    International Nuclear Information System (INIS)

    Strontium pentafluoroantimonate(III), SrSbF5, Mr=304.36, orthorhombic, Pbcm, a=4.378 (1), b=8.853 (3), c=11.233 (4) A, V=435.4 (3) A3, Z=4, Dm=4.60, Dx=4.64 Mg m-3, Mo Kα, λ=0.71069 A, μ=18.9 mm-1, F(000)=536, T=298 K, R=0.028 for 596 independent reflections with I>3α(I). Barium pentafluoroantimonate(III), BaSbF5, Mr=354.08, orthorhombic, Pbcm, a=4.676 (1), b=9.313 (2), c=11.213 (3) A, V=488.3 (2) A3, Z=4, Dm=4.77, Dx=4.82 Mg m-3, Mo Kα, λ=0.71069 A, μ=13.6 mm-1, F(000)=608, T=298 K, R=0.015 for 914 independent reflections with I>3σ(I). SrSbF5 and BaSbF5 are isostructural compounds. The three-dimensional network consists of isolated SbF52- units which are connected by ten-coordinated alkaline-earth ions Sr2+ or Ba2+. The geometry of these pentafluoroantimonate ions is approximately square pyramidal with the Sb atom outside the pyramid, below the four F atoms constituting the basal plane. (orig.)D

  3. Orthorhombic strontium titanate in BaTiO sub 3 -SrTiO sub 3 superlattices

    CERN Document Server

    Rios, S; Jiang, A Q; Scott, J F; Lü, H; Chen, Z

    2003-01-01

    It has been suggested by several authors that SrTiO sub 3 layers in SrTiO sub 3 -BaTiO sub 3 superlattices should be tetragonal and ferroelectric at ambient temperatures, like the BaTiO sub 3 layers, rather than cubic, as in bulk SrTiO sub 3 , and that free-energy minimization requires continuity of the polarization direction. A recent ab initio calculation constrained solutions to this structure. Surprisingly, our x-ray study shows that the SrTiO sub 3 layers are orthorhombic with 0.03% in-plane strain, with the BaTiO sub 3 c-axis matching the SrTiO sub 3 a- and b-axis better than the c-axis; strain energy overcomes the cost in electrostatic energy. (letter to the editor)

  4. Structure and superconductivity of sputtered Bi-Sr-Ca-Cu-O films from various targets

    International Nuclear Information System (INIS)

    Bi-Sr-Ca-Cu-O films were prepared by use of the single-target sputtering method: deposited on [100] MgO substrates and then annealed at 860degC. Targets of three types were used: 1) mixed powder of, 2) calcined powder of, 3) a sintered disk of Bi2O3, SrCO3, CaCO3 and CuO. Films made from the type 1) target almost peeled off from the substrate during the annealing, and small residual films consisted of c-axis-oriented phases of Bi2Sr2Ca1Cu2Ox (2212), Bi2Sr2Ca0Cu1Ox (2201) and a slight amount of Bi2Sr2Ca2Cu3Ox (2223). The films from the type 2) and 3) targets did not peel off and consisted of randomly oriented 2212 and 2201 phases. (author)

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, N.P.; Hyatt, M.J.; Drummond, C.H. III

    1991-08-01

    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. 9 refs.

  7. Electrical properties of resistive switches based on Ba1-χSrχTiO3 thin films prepared by RF co-sputtering

    International Nuclear Information System (INIS)

    In this work, was proposed the use of Ba1-χSrχTiO3(0≤x≤1) thin films for the construction of metal-insulator-metal heterostructures; and their great potential for the development of non-volatile resistance memories (ReRAM) is shown. The deposition of Ba1-χSrχTiO3 thin films was done by the RF co-sputtering technique using two magnetron sputtering cathodes with BaTiO3 and SrTiO3 targets. The chemical composition (x parameter) in the deposited Ba1-χSrχTiO3 thin films was varied through the RF powder applied to the targets. The constructed metal-insulator-metal heterostructures were Al/Ba1-χSrχTiO3/nichrome. The I-V measurements of the heterostructures showed that their hysteretic characteristics change depending on the Ba/Sr ratio of the Ba1-χSrχTiO3 thin films; the Ba/Sr ratio was determined by employing the energy dispersive spectroscopy; Sem micrographs showed that Ba1-χSrχTiO3 thin films were uniform without cracks or pinholes. Additionally, the analysis of the X-ray diffraction results indicated the substitutional incorporation of Sr into the BaTiO3 lattice and the obtainment of crystalline films for the entire range of the x values. (Author)

  8. High Tc superconductivity of Sr-La-Cu-O and Ba-Y-Cu-O thin films

    International Nuclear Information System (INIS)

    In a very short time after it was reported that perovskite-type Ba-La-Cu oxide system could have high temperature superconductivity, many new results were reported. Later, Y was substituted for La to form Ba-Y-Cu oxides and the Tc rose to the liquid nitrogen region. In this report the authors describe the results obtained with the Sr-La-Cu-O and Ba-Y-Cu-O thin films

  9. Solidification of Bi2Sr2Ca1Cu2Oy and Bi2Sr1.75Ca0.25CuOy

    International Nuclear Information System (INIS)

    The solidification processes for the compositions Bi2Sr2CaCu2Oy (2212) and Bi2Sr1.75Ca0.25CuOy (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. In both cases, the solidus is lowered to approximately 750 degree C. Solidification of Bi2Sr1.75Ca0.25CuOy in Ar resulted in a divorced eutectic structure of Bi2Sr2-xCaxOy(22x) and Cu2O while solidification of Bi2Sr2CaCu2Oy in Ar resulted in a divorced eutectic structure of Bi2Sr3-xCaxOy(23x) and Cu2O. Solidification of Bi2Sr1.75Ca0.25CuOy in O2 resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22x and CuO/Cu2O. Solidification of Bi2Sr2CaCu2Oy in partial pressures of 1%, 20%, and 100% oxygen resulted in multiphase samples consisting of 2212, 2201, some alkaline-earth cuprates, and both divorced eutectic structures found during solidification in Ar. For both compositions, these latter structures can be attributed to oxygen deficiencies present in the melt regardless of the overpressure of oxygen. These eutectic structures are unstable and convert into the superconducting phases during subsequent anneals in oxygen. The formation process of the 2212 phase during solidification from the melt was determined to proceed through an intermediate state involving the 2201 phase

  10. Fabrication of Hg(Tl)-Ba-Ca-Cu-O high-Tc thin film RF-SQUID and its operation up to 121 K

    International Nuclear Information System (INIS)

    The development of high-Tc SQUID operating at temperatures higher than 77 K is very much desirable for reducing the cost of cryocoolers so that widespread field application of SQUID may become a reality. YBCO SQUID has been operated up to 87 K where as Bi (Pb) SrCaCuO and TlBaCaCuO high-Tc SQUID have shown SQUID modulation characteristics up to 101 K. The discovery of superconductivity in Hg-based high-Tc with maximum Tc ≅ 133 K at ambient pressure has generated hopes to develop high-Tc SQUID which can be operated at further higher temperatures. This paper reports fabrication of Hg(Tl)-Ba-Ca-Cu-O high-Tc thin film rf- SQUID using natural grain boundary junction and its operation; up to 121 K which is the highest temperature reported so far

  11. Phase diagram study of CaBr2-SrBr2 binary system

    International Nuclear Information System (INIS)

    Hydride ion conducting electrolytes are used in the electrochemical sensors for detecting hydrogen in liquid sodium coolant of fast reactors. In this connection several combinations of alkali/alkaline earth metal halides mixed with alkali/alkaline earth metal hydrides were investigated for using them as hydride ion conducting electrolytes. Currently, a mixture of CaBr2-CaH2 is used as the solid electrolyte in electrochemical sensors. With a view to develop and understand electrolyte characteristics of CaBr2-SrBr2-CaH2, system, the binary phase diagram of CaBr2-SrBr2 is being investigated in this work. Samples were prepared in dry argon atmosphere glove box using purified CaBr2 and SrBr2 salts covering the composition range of 0 to 100 mol% of CaBr2 in SrBr2 in steps of ∼10 mol%. Approximately 30 mg of samples were loaded inside hermetically closed iron capsules and were analysed by DTA under argon+4% hydrogen gas at controlled heating and cooling rates. Results have shown that the system shows appreciable terminal solid solution at both CaBr2 and SrBr2 rich sides. The system exhibits a eutectic reaction involving the terminal solid solutions at 553℃ and at ∼40 mol% CaBr2 in SrBr2. Further investigations are in progress. (author)

  12. Cenozoic Seawater Sr/Ca ratios: Implications for coral reef development through ocean de-acidification

    Science.gov (United States)

    Sosdian, S. M.; Grossman, E. L.; Lear, C. H.; Tao, K.; Rosenthal, Y.

    2010-12-01

    Records of seawater chemistry help constrain the temporal variation in geochemical processes that impact the global carbon cycle and global climate across Earth’s history. To date, various attempts to reconstruct Cenozoic seawater Sr/Ca ratios have produced markedly different results, with estimated Paleogene seawater Sr/Ca ranging from ~50% higher than today to 70% lower. We reconstruct seawater Sr/Ca using Eocene to Pliocene fossil mollusks collected from US Gulf Coast (Mississippi, Alabama, and Florida). We use Conus spp. and Turritella, taxa for which the Sr/Ca distribution coefficients have been determined as a function of temperature in modern specimens [1, 2]. Specimens were serially sampled perpendicular to growth to produce seasonal records of Sr/Ca. Fossil Conus shells show pronounced seasonal Sr/Ca cycles with a strong inverse correlation between Sr/Ca and δ18O, similar to those observed in modern specimens [1]. The fossil Turritella also show similar Sr/Ca cyclicity as modern specimens [2]. We calculate seawater Sr/Ca ratios using our Sr/Ca record, modern Sr/Ca-temperature calibrations for Conus and Turritella [1, 2], and a paleotemperature record based on oxygen isotopes from the same samples [3]. Seawater Sr/Ca increased from ~11.5 to 13.9 mmol/mol between the mid-Eocene (42 Ma) and early Oligocene (33 Ma) and decreased substantially from the mid-Miocene (11 mmol/mol) to the Pliocene (9 mmol/mol) and modern (8.5 mmol/mol). A mass balance model of variations in seawater Sr concentrations suggests a long-term decrease through the Neogene, which we attribute to a significant increase in the proportion of aragonite versus calcite deposition in shallow waters. The largest change is coincident with the proliferation of coral reefs, which occurred after the calcite-aragonite sea transition, and was likely ultimately driven by ocean de-acidification. [1] Sosdian et al. (2006) Geochemistry, Geophysics, Geosystems (G3) 7, Q11023, doi:10.1029/2005GC001233; [2

  13. Na, Ca and Sr retardation on crushed crystalline rock

    Energy Technology Data Exchange (ETDEWEB)

    Hoelttae, P.; Siitari-Kauppi, M. [Univ. of Helsinki, Lab. of Radiochemistry (Finland); Lindberg, A. [Geological Survey of Finland (Finland); Hautojaervi, A. [Posiva Oy (Finland)

    1998-12-31

    Different approaches for measuring the interaction between radionuclides and rock matrix are needed to test the compatibility of transport models and retardation experiments. In this work sorption of sodium ({sup 22}Na), calcium ({sup 45}Ca) and strontium ({sup 85}Sr) was studied on mica gneiss, unaltered, moderately altered and strongly altered tonalite samples taken from hole SY-KR7 drilled in the Syyry area in Sievi in western Finland. The mass distribution ratio values for sieved fractions were determined using static batch and thin section methods as well as crushed rock column method. Sodium, calcium and strontium sorption on mica gneiss and unaltered tonalite was slight and no difference due to fraction size was observed. Higher sorption and fair dependence on fraction size was obtained for altered tonalites owing to the composition of alteration minerals and larger specific surface areas. Difference in the R{sub d} values between unaltered and altered rocks is partly the result of the higher specific surface areas for altered rocks. R{sub d}-values calculated from thin section R{sub d}-values and R{sub d}-values obtained from batch experiments were in good greement. Except for sodium, R{sub d}-values obtained from column experiments were lower but in agreement with R{sub d}-values from batch and thin section experiments. (orig.)

  14. Low temperature synthesis of Ba1–SrSnO3 ( = 0–1) from molten alkali hydroxide flux

    Indian Academy of Sciences (India)

    B Ramdas; R Vijayaraghavan

    2010-02-01

    Perovskite structured stannates (Ba1–SrSnO3, = 0.0–1.0) powders have been synthesized for the first time by molten salt synthesis (MSS) method using KOH as the flux at lower temperature (400°C) compared to other methods. The phase formation was confirmed by FT–IR spectroscopy, powder X-ray diffraction (XRD) and the microstructure was analysed by scanning electron microscopy. XRD patterns reveal the formation of single phasic products for parent and substituted products with good crystallinity throughout the range ( = 0.0–1.0). The morphology of the particles of BaSnO3 and SrSnO3 is spherical and rod shaped, respectively. Effect of soaking periods on the grain growth is observed clearly in SrSnO3. Ba0.5Sr0.5SnO3 (BSS5) crystallizes in flake like morphology.

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

    Science.gov (United States)

    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.

  16. Dielectric behaviour of (Ba,Sr)TiO3 perovskite borosilicate glass ceramics

    International Nuclear Information System (INIS)

    Various perovskite (Ba,Sr)TiO3 borosilicate glasses were prepared by rapid melt-quench technique in the glass system ((Ba1-xSrx).TiO3)-(2SiO2.B2O3)-(K2O)-(La2O3). On the basis of differential thermal analysis results, glasses were converted into glass ceramic samples by regulated heat treatment schedules. The dielectric behaviour of crystallized barium strontium titanate borosilicate glass ceramic samples shows diffuse phase transition. The study depicts the dielectric behaviour of glass ceramic sample BST5K1L0.2S814. The double relaxation was observed in glass ceramic samples corresponding 80/20% Ba/Sr due to change in crystal structure from orthorhombic to tetragonal and tetragonal to cubic with variation of temperature. The highest value of dielectric constant was found to be 48289 for the glass ceramic sample BST5K1L0.2S814. The high value of dielectric constant attributed to space charge polarization between the glassy phase and perovskite phase. Due to very high value of dielectric constant, such glass ceramics are used for high energy storage devices. La2O3 acts as nucleating agent for crystallization of glass to glass ceramics and enhances the dielectric constant and retarded dielectric loss. Such glass ceramics can be used in high energy storage devices such as barrier layer capacitors, multilayer capacitors etc. (author)

  17. Moessbauer studies of the H2 reduction effects on magnetic properties of Ba-Sr hexagonal ferrite

    International Nuclear Information System (INIS)

    The concept of composite magnets with hard materials and soft materials have been applied for increasing specific saturation magnetization (σs) of M-type hexagonal ferrites. We have synthesized Ba0.5Sr0.5Fe10O19 and Ba0.3Sr0.7Fe10CoTiO19 by the sol-gel method. These Ba-Sr ferrite particles were reduced in H2 gas with varying temperature from 250 deg. C to 500 deg. C. As the reduction temperature increases, the patterns of X-ray diffraction show that the peaks of α-Fe appear above 250 deg. C and the pattern corresponding to M-type hexagonal ferrite of Ba0.5Sr0.5Fe10O19 disappears above 450 deg. C. However, that for M-type hexagonal ferrite can be found at 450 deg. C in Ba0.3Sr0.7Fe10CoTiO19. Moessbauer spectra have been analysed with 7 sub-patterns which correspond to the 4fVI, 2b, 12k, 4fIV, 2a, α-Fe and paramagnetic Fe. The Moessbauer results show that Co and Ti substitutions suppress the reduction process. This behavior between Ba0.5Sr0.5Fe10O19 and Ba0.3Sr0.7Fe10CoTiO19 is explicable with the site preference of Co2+ ions and Ti4+ ions. Moessbauer analysis revealed that α-Fe, which influences coercivity and specific saturation magnetization of particles, is introduced from the 12k site mainly, and from 4fVI

  18. Characteristics (Delta44/40Ca, Mg/Ca and Sr/Ca) of Mytilus edulis and Arctica islandica Shells formed in a Temperature-Salinity Matrix

    Science.gov (United States)

    Hiebenthal, C.; Eisenhauer, A.; Wahl, M.

    2008-12-01

    We investigated the influence of temperature (5°C to 15°C (A. islandica) resp. 25°C (M. edulis)) and salinity (15 to 35 psu) regimes on the calcium (Ca) isotope fractionation (Δ44/40Ca) and on Mg/Ca and Sr/Ca in cultured bivalves (Mytilus edulis and Arctica islandica). In an orthogonal 2-factorial (temperature vs. salinity) experiment, the bivalves were allowed to grow for 15 weeks under tightly controlled conditions and then probed and analysed by thermal ionisation mass spectrometry (TIMS) and optical emission spectrometry (ICP-OES). Several interactions between the factors temperature and salinity with respect to their influence on bivalve shell parameters could be found. However, with the exception of Sr/Ca data, the variation of measured shell characteristics between individual bivalves was high. The Sr/Ca - salinity proxy seems to be the most reliable (linear. regression, M. edulis: Sr/Ca = -0.0283*sal + 1.7967, R2 = 0.81, p 0.05, at 10°C: Sr/Ca = - 0.061*sal + 3.13, R2 = 0.93, p edulis shells Mg/Ca ratios related well with seawater temperature (lin. regr.: Mg/Ca = 0.642*t - 0.107, R2 = 0.81, p edulis appear to provide the better element ratio proxies (Mg/Ca for temperature and Sr/Ca for salinity) and the aragonitic shells of A. islandica have the better Ca isotope - temperature proxy.

  19. Mesures conjointes des rapports Sr/Ca et δ 18O effectuées sur Acropora nobilis et Pontes lutea: le paléothermomètre Sr/Ca est-il toujours fiable?

    Science.gov (United States)

    Boiseau, Muriel; Cornu, Hélène; Turpin, Laurent; Juillet-Leclerc, Anne

    1997-11-01

    We measured the Sr/Ca and 18O/ 16O ratios in Acropora nobilis and Porites lutea, from the Mayotte lagoon. As the variations of δ 18O seawater are negligible, coral δ 18O aragonite reflects only seasonal temperature variations. While there is a good agreement between the Sr/Ca ratio and δ 18O for Acropora nobilis, it is not the case for Porites lutea. Coral biological and environmental parameters cannot explain the discrepancies between Sr/Ca ratios and isotopic measurements. However, transport mechanisms of Sr 2+ and Ca 2+ and the presence of two mineralogical structures of strontium may affect the Sr/Ca ratio.

  20. Seawater nutrient and carbonate ion concentrations recorded as P/Ca, Ba/Ca, and U/Ca in the deep-sea coral D. dianthus

    OpenAIRE

    Anagnostou, Eleni; Sherrell, Robert M; Gagnon, Alex; LaVigne, Michele; Field, M Paul; William F. McDonough

    2011-01-01

    As paleoceanographic archives, deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating, but have not been fully investigated for geochemical reconstructions of past ocean conditions. Here we assess the utility of skeletal P/Ca, Ba/Ca and U/Ca in the deep sea coral D. dianthus as proxies of dissolved phosphate (remineralized at shallow depths), dissolved barium (trace element with silicate-type distribution) and carbonate ion concentrations, respec...

  1. Superconducting properties of Cu1-xTlxBa2Ca3Cu4O12-y thin films

    International Nuclear Information System (INIS)

    Superconducting thin films with a predominant single phase of Cu1-xTlxBa2Ca3Cu4O12-y [Cu1-xTlx-1234] have been prepared for the first time by employing a two-step method. In this method the crystalline material was prepared from the sputtered amorphous phase by thallium treatment. This process was carried out at 900 deg. C for 1 h in an Au capsule. The amorphous phase was prepared by sputter deposition onto an SrTiO3 substrate from a stoichiometric target of composition CuBa2Ca3Cu4Ox. The films achieved after thallium treatment were aligned bi-axially along the a- and c-axes. XRD (x-ray diffraction) measurements showed a single-phase material with a c-axis lattice constant of 18.74 A. The c-axis lattice constant of Cu1-xTlx-1234 films is in between that of Cu-1234 (17.99 A) and Tl-1234 (19.11 A) superconductors. The pole figure measurements of 103 reflection of the films showed a-axis-oriented crystals with Δφ=0.8 deg. The composition of the films after EDX (energy dispersive x-ray spectroscopy) measurements was Cu0.3Tl0.7Ba2Ca3Cu4O12-y. From the resistivity measurements Tc was 110 K and Jc measurements showed a current density of 2.0x106 A cm-2 (77 K, 0 T). The preparation of Cu1-xTlx-1234 superconductor films by this method was highly reproducible. (author)

  2. A sol-gel route to prepare Ti-Ca-Ba-Cu-O superconductor with Tc above 120

    International Nuclear Information System (INIS)

    This paper reports on the preparation of Tl-Ca-Ba-Cu-O superconductor with Tc above 120 K from Ca-Ba-Cu-O precursor mixed with thallium oxide. The Ca-Ba-Cu-O precursor was prepared by sol-gel method from the proper complexation and polymerization of the metal nitrates by citric acid and ethylene diamine. The homogeneity and small particle size make the sol-gel precursor a potential candidate for Tl-Ca-Ba-Cu-P film preparation by screen-printing or spin-coating and thallium vapor diffusion

  3. Progress of (Sr, Ba) TiO3 ferroelectric thin film and tunability

    Indian Academy of Sciences (India)

    Fu Xinghua; Shan Lianwei; Ding Biyan; Hou Wenping; Fang Zhou; Fu Zhengyi

    2004-10-01

    The fabrication method, technology route and structure performances of (Sr, Ba) TiO3 (SBT) ferroelectric thin film have been summarized in this paper. The tunability of dielectric constant, dielectric loss and leakage current are the basic parameters of tunable microwave devices. The thin films of SBT with high properties could be fabricated by means of RF magnetron sputtering and sol–gel processing. The electrical performances of thin film material can be improved largely by dopants. Some problems are put forward to pay attention to this material research process.

  4. Competing atomic processes in Ba and Sr injection critical velocity experiments

    Science.gov (United States)

    Newell, P. T.; Torbert, R. B.

    1985-01-01

    The critical ionization velocity effect requires a superthermal electron population to ionize through collisional impact. Such superthermal electrons can however lose energy to competing atomic processes, as well as to ionization, thus limiting the efficiency of the effect. Considering Ba and Sr magnetospheric injection experiments designed to test the CIV theory, it is found that in both cases roughly 60 percent of the superthermal electron energy is lost on exciting line radiation. Moreover, energy loss to background neutral oxygen places a strict limit on the injected cloud densities for which critical velocity effects are possible; a finding which explains the consistently negative results in radial injection experiments.

  5. Spin correlations in amorphous Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Zero and longitudinal field μSR has been used to probe the magnetic state of amorphous Bi2Sr2CaCu2Ox prepared by rapid quenching from the melt. The results suggest quasi-static spin correlations between extremely dilute Cu2+ ions. (orig.)

  6. New perturbed Pb{sup -} aggregate centers in electrolytically colored KBr:Pb{sup 2+}+(Ca, Ba) crystals

    Energy Technology Data Exchange (ETDEWEB)

    Polosan, Silviu [Faculty of Engineering, Kyoto Sangyo University, Kyoto (Japan) and NIMP Bucharest-Magurele, P.O. Box MG-7 (Romania)]. E-mail: polosan@cc.kyoto-su.ac.jp; Topa, Vladimir [Center of Advanced Studies in Physics, Romanian Academy (Romania); Apostol, Elena [NIMP Bucharest-Magurele, P.O. Box MG-7 (Romania); Tsuboi, Taiju [Faculty of Engineering, Kyoto Sangyo University, Kyoto (Japan)

    2007-01-15

    New luminescent centers with a large near-infrared emissions were obtained by unusual electrolytic coloration method (low temperature and high electric field) in the KBr:Pb{sup 2+} crystals co-doped with alkali-earth ions (Ca{sup 2+}, Sr{sup 2+}, Ba{sup 2+}). These so-called Tx centers involve Pb{sup -}-negative metal ions and the presence of at least one alkali-earth ion, which enhances the photoluminescence properties of those centers. The formation of these new centers is due to the presence of F-centers created in the process of electrolytical coloration. The photoluminescence properties, together with the magnetic circular dichroism spectra, prove the existence of at least one paramagnetic luminescent center.

  7. Effect of divalent (Sr, Ba) doping on the structural and magnetic properties of BiFeO3

    International Nuclear Information System (INIS)

    The effect of divalent substitution on the crystal structure and magnetic properties of BiFeO3 has been investigated using X-ray diffraction and magnetic measurements technique. Single phase Bi0.8A0.2FeO3 (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

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

    Energy Technology Data Exchange (ETDEWEB)

    Rangi, Manisha, E-mail: mrangi100@gmail.com; Sanghi, Sujata; Agarwal, Ashish; Jangra, Sandhaya; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar, Haryana- 125001 (India)

    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.

  9. Measurement of the superconducting energy gap in La-Ba-Cu oxide and La-Sr-Cu oxide

    International Nuclear Information System (INIS)

    We report on far-infrared (FIR) reflectivity measurements on sintered pressed powder samples of La-Ba-Cu oxide and La-Sr-Cu oxide. The best samples show fairly sharp transitions to zero measurable resistance with a transition midpoint of 28 K for the Ba alloy and 36 K for the Sr alloy. The FIR measurements reveal an energy gap below T/sub c/ with, depending on the measurement criterion used, values of 2Δ/k/sub B/T/sub c/ of 1.3--1.95 for La-Ba-Cu oxide and 1.6--2.7 for La-Sr-Cu oxide, which are lower than expected for a BCS superconductor

  10. Luminescence properties and energy transfer in Eu2+, Mn2+ codoped Na(Sr,Ba)PO4 phosphor

    International Nuclear Information System (INIS)

    Eu2+ and Mn2+ singly doped and codoped Na(Sr,Ba)PO4 phosphors were synthesized, and their luminescent properties were investigated. A broad blue emission and a broad orange emission band were observed in Na(Sr,Ba)PO4:Eu2+, Mn2+ phosphor. The resonant-type energy transfer from Eu2+ to Mn2+ was demonstrated, and the energy transfer efficiency was also calculated according to their emission spectra. Based on the principle of energy transfer, the emission intensity ration of Eu2+ and Mn2+ could be appropriately tuned by adjusting the contents of activators. Due to the strong absorption in the 250-400 nm range, Na(Sr,Ba)PO4:Eu2+, Mn2+ phosphor could be used as a potential candidate for near-UV white light-emitting diodes (LEDs). (orig.)

  11. Thermodynamic properties of SrMoO3(s) and BaMoO3(s)

    International Nuclear Information System (INIS)

    Enthalpy increment measurements for SrMoO3(s) and BaMoO3(s) have been carried out using a high temperature Calvet drop calorimeter. The data were least squares fitted using the constraints that Cpo(298.15 K) values are from literature and Ho(T)-Ho(298.15 K) at 298.15 K equals zero. The enthalpy increment values for SrMoO3(s) and BaMoO3(s) can be given, respectively, by the following equations: Ho(T) - Ho(298.15 K) (J/mol) 123.2 T(K) + 8.092x10-3 T2(K) + 19.998x105/T(K) - 44162 (426 to 1011 K). Ho(T) - Ho(298.15 K)(J/mol) = 132.72 T(K) + 7.3646x10-3 T2 (K) + 27.696x 105/T(K) - 49539 (478 to 1011 K). The first differential of the above equations with respect to temperature gives Cpo(T). Other thermal properties were then derived. (author). 7 refs., 2 tabs

  12. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

    Indian Academy of Sciences (India)

    P S Sahoo; A Panigrahi; S K Patri; R N P Choudhary

    2010-04-01

    Polycrystalline sample of Ba3Sr2DyTi3V7O30 was prepared at 950°C using a high-temperature solid-state reaction technique. X-ray structural analysis indicated the formation of a single-phase orthorhombic structure with lattice parameters: = 12.2719 (39) Å, = 8.9715(39) Å and = 19.7812(39) Å. Microstructural study showed densely packed uniform distribution of grains over the surface of the sample. The a.c. impedance plots were used as tools to analyse the electrical response of the sample as a function of frequency at different temperatures (30–500°C). These plots revealed the presence of grain boundary effect, from 200°C onwards. Complex impedance analysis showed non-Debye type of dielectric relaxation. The Nyquist plots showed the negative temperature coefficient of resistance character of Ba3Sr2DyTi3V7O30. A hopping mechanism of electrical transport processes in the system is evident from the modulus analysis. The activation energy of the compound (calculated both from loss and modulus spectrum) is the same, and hence the relaxation process may be attributed to the same type of charge carrier.

  13. Scintillation properties of Ba0.20Sr0.80Cl2 single crystal

    International Nuclear Information System (INIS)

    New scintillation crystal of a Ba0.20Sr0.80Cl2 grown by the Czochralski technique is reported. The grown crystal was cut into a size of 10x10x10 mm3. The lattice parameter of the grown crystal is a=b=c=7.041 A and the crystal structure is cubic. The luminescence and scintillation properties of the Ba0.20Sr0.80Cl2 crystal were studied. The luminescent characteristics were measured with ultraviolet (UV) light and X-ray source to study the emission spectra of the crystal. Scintillation properties of the crystal such as pulse height spectra, energy resolution, α/β ratio, light output, proportionality curve, and fluorescence decay time were measured with the various radioactive γ-ray sources and α-source at room temperature. The light output of the crystal was compared with that of the CsI(Tl) crystal and the absolute light output was measured with avalanche photodiode (APD). While the light output of the crystal was less than that of the CsI(Tl), the energy resolution was approximately 6.9% for 137Cs 662 keV γ-ray with PMT which is similar to that of the CsI(Tl) crystal for 137Cs γ-rays. (author)

  14. The isotypic family of the diarsenates MM'As{sub 2}O{sub 7} (M = Sr, Ba; M' = Cd, Hg)

    Energy Technology Data Exchange (ETDEWEB)

    Weil, Matthias [Technische Univ. Wien (Austria). Inst. for Chemical Technologies and Analytics

    2016-08-01

    The diarsenates MM'As{sub 2}O{sub 7} (M = Sr, Ba; M' = Cd, Hg) were prepared under hydrothermal conditions (∝200 C, autogenous pressure), starting from As{sub 2}O{sub 5} and the corresponding metal oxides or precursor compounds thereof in aqueous solutions. Structure analyses on the basis of single crystal X-ray data revealed the four structures to be isotypic. They are the first diarsenates to crystallize in the triclinic BaZnP{sub 2}O{sub 7} structure type (space group P anti 1, Z = 2, a ∼ 5.8 Aa, b ∼ 7.3 Aa, c ∼ 7.6 Aa, α ∼ 101 , β ∼ 91 , γ ∼ 98 ). All related MM'As{sub 2}O{sub 7} diarsenates reported so far (M = Sr, Ba, Pb; M' = Mg, Co, Cu, Zn) crystallize in the monoclinic α-Ca{sub 2}P{sub 2}O{sub 7} structure type (P2{sub 1}/n, Z = 4). Hence, the size of the divalent M' cation determines which of the two structure types is adopted.

  15. Spectroscopic characteristics of Olgite (Ba,Sr)(Na,Sr){sub 2}Na[PO{sub 4}]{sub 2} crystals doped with Sm{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Huang Yanlin [School of Material Engineering, Soochow University, 178 GanJiang East Road, Suzhou 215021 (China)], E-mail: huangyanlin@hotmail.com; Kai Weifang [School of Material Engineering, Soochow University, 178 GanJiang East Road, Suzhou 215021 (China); Lee, Ho Sueb; Cho, Eunjin [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of); Jang, Kiwan [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of)], E-mail: kwjang@changwon.ac.kr; Cao Yonggang; Zhao Wanxue; Ding Haiyan; Wang Xigang [School of Material Engineering, Soochow University, 178 GanJiang East Road, Suzhou 215021 (China)

    2008-10-15

    Sm{sup 3+} ions doped Olgite crystals (Ba,Sr)(Na,Sr){sub 2}Na[PO{sub 4}]{sub 2} were prepared by high temperature solid-state reaction. Sm{sup 2+} ions were obtained by X-ray irradiation reduction. The samples were investigated by X-ray diffraction, SEM, photoluminescence and decay curves measurements. In (Ba,Sr)(Na,Sr){sub 2}Na[PO{sub 4}]{sub 2}, the influence of different mole ratios of Sr to Ba atoms on the crystal structure, reducing efficiencies of Sm{sup 3+} to Sm{sup 2+} and luminescence properties of Sm{sup 2+} ions were discussed. It is found that the conversion of Sm{sup 3+} {yields} Sm{sup 2+} after X-ray irradiation is efficient in this phosphate. The emission of Sm{sup 2+} in this host after excitation into the 4f{sup 5} 5d{sup 1} levels shows {sup 5}D{sub 0} {yields} {sup 7}F{sub J} (J = 0, 1, 2) emission together with a broad emission band. The characteristic of Sm{sup 2+} ions luminescence was discussed.

  16. Spectroscopic characteristics of Olgite (Ba,Sr)(Na,Sr)2Na[PO4]2 crystals doped with Sm2+ ions

    International Nuclear Information System (INIS)

    Sm3+ ions doped Olgite crystals (Ba,Sr)(Na,Sr)2Na[PO4]2 were prepared by high temperature solid-state reaction. Sm2+ ions were obtained by X-ray irradiation reduction. The samples were investigated by X-ray diffraction, SEM, photoluminescence and decay curves measurements. In (Ba,Sr)(Na,Sr)2Na[PO4]2, the influence of different mole ratios of Sr to Ba atoms on the crystal structure, reducing efficiencies of Sm3+ to Sm2+ and luminescence properties of Sm2+ ions were discussed. It is found that the conversion of Sm3+ → Sm2+ after X-ray irradiation is efficient in this phosphate. The emission of Sm2+ in this host after excitation into the 4f5 5d1 levels shows 5D0 → 7FJ (J = 0, 1, 2) emission together with a broad emission band. The characteristic of Sm2+ ions luminescence was discussed

  17. Structure Refinement of (Sr,Ba)Nb2O6 Ceramic Powder from Neutron and X-Rays Diffraction Data

    OpenAIRE

    J.G. Carrio; Y.P. Mascarenhas; Yelon, W.; I. A. Santos; Garcia, D.; J.A. Eiras

    2002-01-01

    The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ~ 64/36 was found from the initial batch composition Sr0.61Ba0.39Nb2O6, corroborating with the quantitative X-ray dispersive spectroscopy (EDS) measurements. The structure is tetragonal with cell parameters a, b = 12.4504(3) Å and c = 3.9325(1) Å and space group P4bm. It was no...

  18. Electrical Properties of Crystalline Ba0.5Sr0.5TiO3 Thin Films

    OpenAIRE

    Irzaman; H. Darmasetiawan; Sukaryo, M. Nur Indro S. G.; Hikam, M; Bo, Na Peng; Barmawi, M.

    2001-01-01

    Thin Ba0.5Sr0.5TiO3 (BST) films on p-type Si (100) using The Chemical Solution Deposition (CSD) method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), C-V meter analysis measurement were employed to characterise the films. The growth condition to obtain enough quality epitaxial of Ba0.5Sr0.5TiO3 carried out by spin coating at 3000 rpm for 30 seconds, and then annealing at 900oC for 15 hours. The structure and crystallinity of thin films were investigated by XRD preffered orienta...

  19. Diffused phase transition of polycrystalline (Ba0.80Sr0.20)TiO3

    OpenAIRE

    C. Kajtoch; W. Bąk; M. Gabryś; K. Mroczka; B. Handke; F. Starzyk

    2009-01-01

    Purpose: The purpose of this work was to determinate the influence of the 20% Sr substitutions (in sublattice A) on changes of the character of phase transition (PT) in comparison with pure barium titanate BaTiO3 (BT).Design/methodology/approach: Polycrystalline samples of (Ba0.80Sr0.20)TiO3 (BS20T) were prepared by calcinations method at temperature 1620 K. X-ray measurements were executed from 10 deg to 120 deg with the 0.008 deg step. Images of the morphology of the samples were taken by m...

  20. Pressure Induced Ferromagnetism in Cubic Perovskite SrFeO3 and BaFeO3

    OpenAIRE

    Li, Zhi; Iitaka, Toshiaki; Tohyama, Takami

    2012-01-01

    The spin order in cubic perovskite SrFeO3 and BaFeO3 under high pressure is studied by density functional theory (DFT) calculation with local spin density approximation plus Hubbard U (LSDA+U). At ambient pressure, A-type and G-type helical spin orders are almost degenerate in BaFeO3 whose lattice constant is 3.97{\\AA} . When the lattice constant is reduced to 3.85 {\\AA} which is same as the lattice constant of SrFeO3 at ambient pressure, G-type helical spin order becomes stable, being consis...

  1. A Preliminary study of Sr/Ca thermometry in Chang Islands, Gulf of Thailand

    Directory of Open Access Journals (Sweden)

    Wararat Sirianansakul

    2014-10-01

    Full Text Available Variations in ratios of strontium-to-calcium (Sr/Ca for two Porites sp. coral specimens collected from Wai (PW and Loa Ya (PLY islands, part of Chang islands, Gulf of Thailand, were determined. Inductively coupled plasma optimal emission spectrometry (ICP-OES was used to analyze this ratio, which demonstrates annual cycles and the data is assumed to reflect the sea surface temperature (SST. Comparing the ratios with SST data, following Sr/Ca–SST relationships were determined PW: Sr/Ca (mmol/mol = 11.56–0.070×SST, PLY: Sr/Ca (mmol/mol = 11.89–0.081×SST. Our correlations are different from those previously reported; a discrepancy that may involve differences in analytical methods employed and abnormally low sea surface salinity (SSS (<30 psu in the Gulf of Thailand.

  2. Seasonal dynamics of 90Sr and Ca distribution between alga Chara tomentosa and hydric environment

    International Nuclear Information System (INIS)

    It has been established, that total water mineralization and 90Sr content in it increase abruptly in a shallow mesodistrophic reservoir of the lake type over a winter period with ice layer accumulation and decrease of subice water layer owing to freezing processes in comparison with a spring-summer period. In this case the ice has a poor content of mineral components and is ''purified'' from the radionuclide. On the contrary, the 90Sr,Ca and total ash contents in alga Chara tomentosa decrease over the winter period increasing in spring and summer. Over all the year seasons the alga accumulates comparatively more Ca from the water medium than 90Sr. The 90Sr and Ca discrimination coefficients in the water-plant system vary from 0.25 to 0.68 during a year

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

    Science.gov (United States)

    He, Hua; Stoyko, Stanislav; Bobev, Svilen

    2016-04-01

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

  4. Dielectric properties of polycrystalline (Ba0.40Sr0.60O3

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2009-11-01

    Full Text Available Purpose: Purpose of this paper is to qualify of the degree and the causes of broadening of the phase transition in the polycrystalline solid solution (Ba0.40Sr0.60TiO3 (BS60T.Design/methodology/approach: Polycrystalline samples of (Ba0.40Sr0.60TiO3 (BS60T were prepared by calcinations method at temperature 1570K. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 Agilent Precision LRC meter HP4824A equipped with WinDETA 5.62 software Novocontrol. Measurements were taken under cooling with 2K/min speed. Measuring electric field frequency was from the range 20 Hz - 1 MHz.Findings: The dielectrometry was applied to measure complex dielectric permittivity and other dielectric functions of ferroelectric (BS60T. It was affirmed, that 60% substitution of Sr ions changed the type of phase transition. Weak dependence of temperature Tm=208 K (temperature of maximum electric permittivity ε’ on frequency of the external electric field testifies about diffused character of the phase transition (DPT. The polar character of this material was also observed in the paraelectric phase (to 360 K. This observation is connected with the occurrence of polar clusters in this phase.Research limitations/implications: Results can be used in order to describe the phase transition modifications in the solid solutions with ferroactive substitutions in sublattice B of the perovskite.Originality/value: Value of this work relies on the experimental examination of the electric properties of BS60T solid solution. The low value of phase angle in the paraelectric phase is connected with the occurrence of the polar regions (clusters.

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

    CERN Document Server

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

    2016-01-01

    A model is proposed in which the light r-process element enrichment in metal-poor stars is explained via enrichment from 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 equation of state 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.

  6. Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7 crystals.

    Science.gov (United States)

    Oh, Yoon Seok; Luo, Xuan; Huang, Fei-Ting; Wang, Yazhong; Cheong, Sang-Wook

    2015-04-01

    On the basis of successful first-principles predictions of new functional ferroelectric materials, a number of new ferroelectrics have been experimentally discovered. Using trilinear coupling of two types of octahedron rotation, hybrid improper ferroelectricity has been theoretically predicted in ordered perovskites and the Ruddlesden-Popper compounds (Ca3Ti2O7, Ca3Mn2O7 and (Ca/Sr/Ba)3(Sn/Zr/Ge)2O7). However, the ferroelectricity of these compounds has never been experimentally confirmed and even their polar nature has been under debate. Here we provide the first experimental demonstration of room-temperature switchable polarization in bulk crystals of Ca3Ti2O7, as well as Sr-doped Ca3Ti2O7. Furthermore, (Ca, Sr)3Ti2O7 is found to exhibit an intriguing ferroelectric domain structure resulting from orthorhombic twins and (switchable) planar polarization. The planar domain structure accompanies abundant charged domain walls with conducting head-to-head and insulating tail-to-tail configurations, which exhibit a conduction difference of two orders of magnitude. These discoveries provide new research opportunities, not only for new stable ferroelectrics of Ruddlesden-Popper compounds, but also for meandering conducting domain walls formed by planar polarization. PMID:25581628

  7. Superconductivity up to 29 K in SrFe2As2 and BaFe2As2 at high pressures

    International Nuclear Information System (INIS)

    We report the discovery of superconductivity at high pressure in SrFe2As2 and BaFe2As2. The superconducting transition temperatures are up to 27 K in SrFe2As2 and 29 K in BaFe2As2, the highest obtained for materials with pressure-induced superconductivity thus far. (fast track communication)

  8. Sr, Ca, and C isotope systematic in small tropical catchments, La Selva, Costa Rica

    Science.gov (United States)

    Wiegand, B. A.; Schwendenmann, L.

    2010-12-01

    Sr, Ca, and C isotopes were analyzed to assess sources and biogeochemical processes affecting surface and groundwater composition of four small catchments located at La Selva Biological Station, Costa Rica. 87Sr/86Sr ratios were employed to quantify inputs from mineral weathering and atmospheric sources. δ13C values of dissolved organic carbon (DOC) and δ44Ca values provide information on biological processes that affect water chemistry. Sr2+ and Ca2+ concentrations of surface and groundwater show large variations due to intermixture of bedrock groundwater with local groundwater [1]. Low 87Sr/86Sr ratios suggest weathering of volcanic rocks as the primary solute source in bedrock groundwater, while atmospheric and in situ weathering contributions are predominant in local groundwater. Contributions of bedrock groundwater constitute > 60 % in the Salto, Saltito and Arboleda catchments, whereas the Taconazo catchment receives atmospheric inputs of > 95 % in addition to local weathering contributions. Surface water and groundwater wells show δ13C-DOC values between -24 ‰ and -30 ‰ due to transfer of organic carbon from the soil zone. δ44Ca values of dissolved Ca2+ in surface and groundwater are considerably fractionated from the input sources rainwater and bedrock groundwater. Light δ44Ca values are preferentially distributed in stream water and shallow groundwater horizons and contrast with heavy Ca isotopes in deeper groundwater wells. Biological processes including plant uptake and decomposition in combination with cation exchange processes in the soils may explain the fractionation of Ca isotopes. [1]Genereux et al., 2009. Water Resour. Res, 45, W08413, doi:10.1029/2008WR007630

  9. Investigation of Adsorption Behavior of Ba and Other Fission Products on the Sr·spc Chromatographic Column by Static Method

    Institute of Scientific and Technical Information of China (English)

    YANG; Lei; MA; Peng; YANG; Su-liang; LIANG; Xiao-hu

    2012-01-01

    <正>Adsorption behavior of Ba, Cs and some other fission products on the Sr·spc resin has been investigated for the purpose of extracting 141Ba from the fission product. Sr·spc resin with the main functional group of 18-crown-6 ether was purchased from US. Eichrom Company. Tracers of Ba, Cs and some other fission products were acquired from an irradiated U target.

  10. Ca-Mg-Sr-Nd Isotopes in Granitic Rocks of the Lhasa Terrane, Southern Tibet

    Science.gov (United States)

    Peterson, B. T.; Simon, J. I.; Depaolo, D. J.; Christensen, J. N.; Harrison, T. M.

    2010-12-01

    Magnesium (Mg) and Calcium (Ca) isotopes are fractionated by aqueous precipitation and incongruent silicate weathering, resulting in sedimentary reservoirs with characteristic isotopic compositions. Limestones and dolomites are isotopically light in both elements, whereas shales/pelites can have heavy Mg and light Ca. The isotopic character of these reservoirs may persist through anatexis (Shen, et al., PNAS 106(49), 2009). Mg and Ca isotopes could therefore be used to gain new insights into the sources of granitic magmas and hence the mechanisms by which the continental crust forms and evolves. Radiogenic 40Ca gives additional information about the K/Ca ratios of magma sources, and Sr and Nd isotopes provide complementary age and lithology information. To evaluate the potential of Ca and Mg isotopes for studying granite petrogenesis we made measurements on a suite of granitic intrusive rocks of Jurassic to Miocene age in southern Tibet that exhibit large variations in Nd (ɛNd = +5 to -12) and Sr isotopes (87Sr/86Sr = 0.704 to 0.722). Our samples represent a transect northward from the Indus-Yalu Suture (IS), west of Lhasa. Rocks close to the IS have mantle-like Nd and Sr isotopic compositions, whereas those farther to the north have low ɛNd and higher 87Sr/86Sr, and include Mesozoic, Paleogene and Neogene peraluminous (2-mica) granites (DePaolo, et al., Goldschmidt, 2008; Kapp, et al., JGR 110, 2005; Hou et al., EPSL 220, 2004). Radiogenic 40Ca is detectable in peraluminous (2-mica) granites and correlates with high 87Sr/86Sr, but does not correlate with Nd isotopes, indicating that 2-mica granite magmas come from both low-K and high-K sources. Stable isotopes of both Ca and Mg show substantial variation. Relative to bulk silicate Earth (BSE, which we define as δ=0 for discussion) δ44Ca values vary from 0 to -0.7, and δ26Mg varies from -0.3 to +0.6. Thus to first order Ca is light and Mg is heavy relative to BSE. For samples with mantle-like Nd and Sr, δ44Ca

  11. Effect of low level substitution of Sr–Ba on transport and magnetic behaviour of La0.67Ca0.33MnO3

    Indian Academy of Sciences (India)

    B Munirathinam; M Krishnaiah; M Manivel Raja; S Arumugam; K Porsezian

    2011-02-01

    In this paper we report the investigation of transition metal oxide compound, La0.67Ca0.25Sr0.04Ba0.04MnO3 (LCSBMO), along with La0.67Ca0.33MnO3 (LCMO), synthesized by sol–gel route under identical conditions. The effect of simultaneous low level substitution of large size ions such as Sr2+ and Ba2+ for Ca2+ ions on the electronic transport and magnetic susceptibility properties are analysed and compared apart from microstructure and lattice parameters. The temperature dependent electrical transport of the polycrystalline pellets of LCSBMO and LCMO when obeying the well studied law, ρ = ρ0 + ρ2 2 for < MI, is observed to differ by more than 50% from the values of ρ0 and ρ2, with the former compound showing enhanced electrical conductivity than the latter. Similarly in fitting the adiabatic small polaron model for resistivity data of both the samples for > MI, the polaron activation energy is found to differ by about 11%. In addition, the temperature dependent a.c. magnetic susceptibility study of the compounds shows a shift of about 6% in the paramagnetic to ferromagnetic transition temperature (285 K for LCSBMO and 270 K for LCMO).

  12. Neutron diffraction studies on Ca1-BaZr4P6O24 solid solutions

    Indian Academy of Sciences (India)

    S N Achary; O D Jayakumar; S J Patwe; A B Shinde; P S R Krishna; S K Kulshreshtha; A K Tyagi

    2008-11-01

    Herein we report the results of detailed crystallographic studies of Ca1-BaZr4P6O24 compositions from combined Rietveld refinements of powder X-ray and neutron diffraction data. All the studied compositions crystallize in rhombohedral lattice (space group R-3 No. 148). A continuous solid solution is concluded from the systematic variation of unit cell parameters. The variation of unit cell parameters with the composition indicates decreasing trend in parameter with increasing Ba2+ concentration contrast to an increasing trend in parameter.

  13. Charge traps in Ce-doped CaF2 and BaF2

    OpenAIRE

    Drozdowski, Winicjusz; Przegi��tka, Krzysztof; Wojtowicz, Andrzej J; Oczkowski, Hubert Lucjan

    1999-01-01

    Thermoluminescence of CaF2:Ce, BaF2, and BaF2:Ce irradiated at room temperature is reported. X-ray induced emission spectra of the samples show that both excitonic (due to e- + VK recombination) and Ce3+ d-f luminescence may contribute to thermoluminescence signal. The simple Randall-Wilkins model is used to deconvolute glow curves into seven to eight first-order peaks. Parameters of all traps are calculated and correlations between peaks in the curves of the examined materials are discussed.

  14. Microstructure and photoluminescence properties of Ho-doped (Ba,Sr)TiO3 thin films

    International Nuclear Information System (INIS)

    Ba0.65Sr0.35TiO3 (BST) thin films doped with Ho3+ were prepared on silicon substrates by a modified sol-gel technique. The microstructure of the BST films was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The results showed that 3 mol% Ho-doped BST has the largest grain size and surface root-mean square roughness. The thickness of the film was about 1.36 μm. The Ho3+ luminescence intensity reached a maximum value in the sample with 3 mol% Ho3+ ions concentration sintered at 700 deg. C. All the results showed that the BST: Ho3+ films may have potential use for photonic devices

  15. Multi-colony calibrations of coral Ba/Ca with a contemporaneous in situ seawater barium record

    Science.gov (United States)

    LaVigne, Michèle; Grottoli, Andréa G.; Palardy, James E.; Sherrell, Robert M.

    2016-04-01

    The coral skeleton barium to calcium ratio (Ba/Cacoral), a proxy for seawater barium concentrations (BaSW), has been interpreted as a tracer of upwelling based on the characteristic "nutrient like" depth profile of BaSW. However, in some tropical regions, such as the Gulf of Panamá, substantial influence of terrestrial runoff inputs and differences between the vertical distribution of BaSW and that of the major nutrients (nitrate and phosphate) in the upper water column can complicate the interpretation of Ba/Cacoral as an upwelled nutrient proxy. In the Gulf of Panamá, contemporaneous Ba/Cacoral records from multiple colonies of Porites lobata, Pavona gigantea, and Pavona clavus corals record a nearly twofold change in surface water BaSW as a 20-70% increase in skeletal Ba/Ca with excellent correlation among Ba/Ca records from co-located colonies (r = 0.86-0.99). These results provide, for the first time, an absolute calibration of the coral Ba proxy with a contemporaneous BaSW record. Compiling the Ba/Cacoral records from three co-located colonies of each species into taxon-specific composite regressions reveals strong statistically significant correlations with the BaSW time-series record (p coefficient, as well as a demonstration of the application of the P. clavus calibration to a previously published Ba/Cacoral record, emphasize the necessity of using taxon-specific calibrations to reconstruct changes in BaSW with accuracy. These results support the application of Ba/Cacoral to reconstruct past changes in absolute BaSW concentrations, adding an important tool to the collection of geochemical proxies for reconstructing surface ocean biogeochemical processes in the past.

  16. Structural studies and c dependence in La2-DyCaBa2Cu4+O type mixed oxide superconductors

    Indian Academy of Sciences (India)

    S Rayaprol; Krushna Mavani; C M Thaker; D S Rana; Keka Chakravorty; S K Paranjape; M Ramanadham; Nilesh A Kulkarni; D G Kuberkar

    2002-05-01

    A new series of mixed oxide superconductors with the stoichiometric composition La2-DyCaBa2Cu4+O ( = 0.0 - 0.5, = 2) has been studied for structural and superconductiong properties. Our earlier studies on La2-(Y/Er)CaBa2Cu4+O series, show a strong dependence of c on hole concentration (sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on = 0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum c is obtained for = 0.5, = 1.0 sample (c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O (La-2125).

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  20. Theory of PbTiO3, BaTiO3, and SrTiO3 Surfaces

    OpenAIRE

    Meyer, B.; Padilla, J.; Vanderbilt, David

    1999-01-01

    First-principles total-energy calculations are carried out for (001) surfaces of the cubic perovskite ATiO3 compounds PbTiO3, BaTiO3, and SrTiO3. Both AO-terminated and TiO2-terminated surfaces are considered, and fully-relaxed atomic configurations are determined. In general, BaTiO3 and SrTiO3 are found to have a rather similar behavior, while PbTiO3 is different in many respects because of the partially covalent character of the Pb-O bonds. PbTiO3 and BaTiO3 are ferroelectrics, and the infl...

  1. A new family of isostructural titanates, MLi2Ti6O14 (M = Sr, Ba, Pb)

    International Nuclear Information System (INIS)

    The existence of isostructural titanates with a composition corresponding to the formula MLi2Ti6O14 has been evidenced in the ternary oxide systems MO-Li2O-TiO2 (M = Sr, Ba, Pb). Single crystals of these compounds have been grown by the flux method using LiBO2 as a high-temperature solvent. The structure, as determined by single crystal X-ray diffraction is orthorhombic (space group Cmca (no. 64), Z = 8) with (i) a = 16.570(5)A, b = 11.150(2)A, c = 11.458(2)A, V = 2116.9(8)A3, R1 = 0.039, wR2 = 0.087 for SrLi2Ti6O14; (ii) a = 16.577(1)A, b = 11.273(1)A, c = 11.581(1)A, V 2164.2(5)A3, R1 = 0.018, wR2 = 0.047 for BaLi2Ti6O14 and (iii) a 16.649(1)A, b = 11.146(1)A, c = 11.494(1)A, V = 2132.9(5)A3, R1 = 0.033, wR2 = 0.078 for PbLi2Ti6O14. A three-dimensional framework of edge and corner sharing TiO6 octahedra sets up the crystal structure. Lithium occupies the tetrahedral vacancies, while M atoms are located at 11-oxygen coordinated sites

  2. Synthesis of star shaped Ba1-xSr xTiO3 (BST) powders

    International Nuclear Information System (INIS)

    Uniform star shaped strontium substituted barium titanyl oxalate Ba1-xSr xTiO(C2O4)2 (BSTO)/strontium substituted barium titanate, Ba1-xSr xTiO3 (BST) powders were prepared via a simple chemical co-precipitation route with x = 0.15, 0.20, and 0.25. The process involved an addition of 0.1 M solution of titanium tetrabutoxide (BTM) in isopropanol (IPA) to 0.1 M oxalic acid in IPA containing 0.2 M of H2O to produce titanyl oxalate precipitate which was further reacted with 0.1 M solution of ammonium oxalate to obtain 0.1 M clear homogeneous solution of ammonium titanyl oxalate (ATO) with pH 4.25 containing titanium in the form of soluble anionic oxalate species [TiO(C2O4)22-]. Stoichiometric quantities of barium hydroxide and strontium nitrate were dissolved in distilled water and its pH was adjusted nearly equal to that of ATO (∼4.15) by drop wise addition of dilute HNO3 solution 1:10 (v/v). The addition of this mixed cation precursor solution to ATO solution resulted in precipitation of strontium substituted barium titanyl oxalate (BSTO) having star shaped morphology. The calcination of BSTO precursors at 730 deg. C for 4 h in air produced cubic BST powders (a 0 ∼4.001, 3.996 and 3.991 A for x = 0.15, 0.20, 0.25, respectively) having star shaped morphology. SEM, XRD and FTIR techniques were used to characterize the BSTO/BST powders

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

    Science.gov (United States)

    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.

  4. Effects of Sr2+ doping on the electrical properties of (Bi0.5Na0.50.94Ba0.06TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Amrita Singh

    2015-03-01

    Full Text Available The influence of SrTiO3 addition on the microstructure and various electrical properties of (Bi0.5Na0.50.94Ba0.06TiO3 (BNTBT6 ceramics, fabricated by a conventional high temperature solid state reaction, was investigated. Analysis of X-ray diffraction patterns revealed the formation of phase pure materials with tetragonal unit cell structure, tetragonality parameter c/a in the interval from 0.9940 to 1.0063 and crystallite sizes ranging from 33–76 nm for addition of 0.2 to 1 wt.% of SrTiO3. SEM studies indicated that Sr2+ doping led to decrease in grain size and non-homogeneity of grain distribution for higher SrTiO3 amount (>0.6 wt.%. Complex impedance, modulus, and conductivity studies indicated the presence of grains and grain boundary contribution, non-Debye type of relaxation and NTCR behaviour of the test ceramic samples. Temperature dependent real part of complex permittivity showed peaks at 475 °C and the dielectric loss tangent showed peaks corresponding to 125 °C and 475 °C for almost all compositions. AC activation energies, computed using Arrhenius relation in the temperature range of 325–500 °C for the BNTBT6 ceramic compositions having SrTiO3 concentration from 0.2 to 1.0 wt.%, were seen to have maximal values at the lowest measurement frequency. Amongst the different chosen doped BNTBT6 ceramic compositions, the composition having 0.6 wt.% of SrTiO3 showed the best ferroelectric and piezoelectric response with maximum value of Pr (8.24 µC/cm2, minimum value of Ec (5.73 kV/mm and maximum d33 value (∼46 pC/N.

  5. Superconducting thin films of Bi-Sr-Ca-Cu-O obtained by laser ablation processing

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.F.; Bohandy, J.; Phillips, T.E.; Green, W.J.; Agostinelli, E.; Adrian, F.J.; Moorjani, K.; Swartzendruber, L.J.; Shull, R.D.; Bennett, L.H.; and others

    1988-07-25

    Thin films of Bi-Sr-Ca-Cu-O, deposited on (100) cubic zirconia by laser ablation from a bulk superconducting target of nominal composition BiSrCaCu/sub 2/ O/sub x/ , have been investigated by dc resistance and magnetically modulated microwave absorption measurements. The latter technique reveals important features regarding the phase purity of superconducting samples that are masked in the dc resistance measurements. The superconducting behavior of the films, as a function of the substrate temperature during deposition and the post-deposition annealing conditions, is discussed.

  6. Superconductivity in the high-Tc Bi-Ca-Sr-Cu-O system - Phase identification

    Science.gov (United States)

    Hazen, R. M.; Prewitt, C. T.; Angel, R. J.; Ross, N. L.; Finger, L. W.

    1988-01-01

    Four phases are observed in superconducting Bi-Ca-Sr-Cu-O samples. The superconducting phase, with onset temperature near 120 K, is a 15.4-A-layered compound with composition near Bi2Ca1Sr2Cu2O9 and an A-centered orthorhombic unit subcell 5.41 x 5.44 x 30.78 A. X-ray diffraction and electron microscopy data are consistent with a structure of alternating perovskite and Bi2O2 layers. High-resolution transmission electron microscopy images reveal a b-axis superstructure of 27.2 A, numerous (001) stacking faults, and other defects.

  7. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  8. Superconducting oxide processing in the Bi-Ca-Sr-Cu-O system

    International Nuclear Information System (INIS)

    This paper reports microstructures of superconducting phase with transitions near 85 K and 110 K studied by analytical electron microscopy (AEM) in samples of the system Bi-Ca-Sr-Cu-O prepared by sintering and liquid mixing methods. The heat treatment was restricted to a temperature range near 860 degrees C to obtain good superconducting behavior. The microchemistry and the crystal structure of the superconducting phase in the Bi-Ca-Sr-Cu-O system were investigated by energy dispersive x-ray spectroscopy and convergent-beam electron diffraction, and were related to the processing routes

  9. Geochemie von Rudistenschalen : Beiträge zur Meerwasserchemie (Sr/Ca, Mg/Ca, δ13C) und Paläoklima der Kreide

    OpenAIRE

    Rauch, Markus

    2005-01-01

    Schalen von 38 Rudisten aus dem Barreme bis Maastricht wurden hinsichtlich der Spurenelemente und stabilen Isotope analysiert. Das Sr/Ca-Verhältnis des Kreide-Meerwassers wurde aus den Sr-Konzentrationen der Schalen rekonstruiert und damit eine Lücke in der phanerozoischen Sr/Ca-Kurve des Meerwassers geschlossen. Die negative Korrelation von Mg und δ18O-Werten in den Rudistenschalen zeigt eine Übereinstimmung mit den Verteilungsmustern rezenter kalzitischer Molluskenschalen. So...

  10. The Pr and Ca substitution in GdBa2Cu3O7-8

    International Nuclear Information System (INIS)

    The granular Gd1-x-zPrxCazBa2Cu3O7-8 (Gd Pr Ca-123) high-temperature cuprate samples with 0.0≤x≤0.3 and 0.0≤z≤0.35 are prepared by standard solid state reaction and characterized by XRD and SEM techniques. The BaCuO2 and impurity phases are less than 1% in the samples having high levels of Pr and Ca concentrations. The electrical resistivity measurements show a nonlinear reduction in Tc(x,z=etc) versus x. Moreover, the Tc(z) curve with x=0 is nonlinear and a plateau appears at z≅0.05-0.015. For Pr-Ca-doped samples with a constant concentration of Pr, Tc increases with the increase of Ca up to an optimum value of Ca doping and then in decreases. Based on these observations, we suggest that hole filling and hole localization the main effects of Pr ion substitution. The magnetic measurements indicate that the value of HC1 is in the order of 10 m T. The magnetoresistance measurements have been measured and analyzed. The superconducting transition region is broadened by the application of magnetic field. The experimental data near the on sen of superconductivity are fitted with the Ambegakor and Halperin (A H) phase-slip model. We observe that the A H parameter, γ(H), depends not only on the temperature and the magnetic field, but also on the Pr and Ca ions concentrations. It is observed that the critical current density increases with Ca substitution and decreases with pr substitution in Gd-123 system. We suggest that the pr ion substitution probably enhances the weak link, but the Ca ion acts as flux pinning center in the Gd Pr Ca-123 system

  11. Measurements of Sr/Ca in bones to evaluate differences in temperature

    Energy Technology Data Exchange (ETDEWEB)

    Santos, P.R. [IFUSP, Travessa R da rua do Matao 187, Cidade Universitaria, CEP 05508-970, Sao Paulo, SP (Brazil); Added, N. [IFUSP, Travessa R da rua do Matao 187, Cidade Universitaria, CEP 05508-970, Sao Paulo, SP (Brazil)], E-mail: nemitala@dfn.if.usp.br; Aburaya, J.H.; Rizzutto, M.A. [IFUSP, Travessa R da rua do Matao 187, Cidade Universitaria, CEP 05508-970, Sao Paulo, SP (Brazil)

    2008-04-15

    Analysis of aragonite from sea shells and coral skeletons showed a clear correlation between the strontium and calcium concentrations for these crystals (Sr/Ca ratio) and seawater temperature obtained by satellites and ship readings. In this work we present the results of a study that correlates Sr/Ca ratio with formation temperature of another calcium crystal, the hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}), main mineral compound of teeth and bones from vertebrates. These animals, independent of its thermoregulation pattern (endothermic or ectothermic) have variations of internal temperature along the body. One interesting application of this work is to differentiate warm-blooded animals from cold-blooded ones just by measuring Sr/Ca ratio in their bones. Bones from a crocodile from Caiman yacare species and two dogs, a poodle and a non defined race, were analyzed using PIXE technique and thick target correction. A 1.78 (18) MeV external proton beam was used in LAMFI-USP with an accumulated charge of about 10 {mu}C for probing the samples. Emitted X-rays were collected using Si-PIN detectors (140 keV for Fe). As in coral skeletons, the Sr/Ca ratio of animals is lower in the body's warmer parts and higher in colder parts.

  12. Measurements of Sr/Ca in bones to evaluate differences in temperature

    International Nuclear Information System (INIS)

    Analysis of aragonite from sea shells and coral skeletons showed a clear correlation between the strontium and calcium concentrations for these crystals (Sr/Ca ratio) and seawater temperature obtained by satellites and ship readings. In this work we present the results of a study that correlates Sr/Ca ratio with formation temperature of another calcium crystal, the hydroxyapatite (Ca10(PO4)6(OH)2), main mineral compound of teeth and bones from vertebrates. These animals, independent of its thermoregulation pattern (endothermic or ectothermic) have variations of internal temperature along the body. One interesting application of this work is to differentiate warm-blooded animals from cold-blooded ones just by measuring Sr/Ca ratio in their bones. Bones from a crocodile from Caiman yacare species and two dogs, a poodle and a non defined race, were analyzed using PIXE technique and thick target correction. A 1.78 (18) MeV external proton beam was used in LAMFI-USP with an accumulated charge of about 10 μC for probing the samples. Emitted X-rays were collected using Si-PIN detectors (140 keV for Fe). As in coral skeletons, the Sr/Ca ratio of animals is lower in the body's warmer parts and higher in colder parts

  13. Structural investigations of (Ca,Sr)ZrO3 and Ca(Sn,Zr)O3 perovskite compounds

    Science.gov (United States)

    Tarrida, Martine; Larguem, H.; Madon, M.

    2009-07-01

    (Ca x ,Sr1- x )ZrO3 and Ca(Sn y ,Zr1- y )O3 solid solutions were synthesized by solid-state reaction at high temperature before to be studied by powder X-ray diffraction and Raman Spectroscopy. Diffraction data allow the distortion of the ABO3 perovskite structure to be investigated according to cations substitution on A and B-sites. It is shown that distortion, characterized by Φ, the tilt angle of BO6 octahedra, slightly increases with decreasing y content in Ca(Sn y ,Zr1- y )O3 compounds and strongly decreases with decreasing x content in (Ca x ,Sr1- x )ZrO3 compounds. Such results are discussed in view of the relative A and B cation sizes. Raman data show that vibrational spectra are strongly affected by the cation substitution on A-site; the frequencies of most vibrational modes increase with increasing x content in (Ca x ,Sr1- x )ZrO3 compounds, i.e. with the decreasing mean size of the A-cation; the upper shift is observed for the 358 cm-1 mode (∂ ν/∂r = -60.1 cm-1/Å). On the other hand, the cation substitution on B-sites, slightly affect the spectra; it is shown that in most cases, the frequency of vibrational modes increases with increasing y content in Ca(Sn y ,Zr1- y )O3 compounds, i.e. with the decreasing mean size of the B-cation, but that two modes (287 and 358 cm-1) behave differently: their frequencies decrease with the decreasing mean size of the B-cation, with a shift respectively equal to +314 and +162 cm-1/Å. Such results could be used to predict the location of different elements such as trivalent cations or radwaste elements on A- or B-site, in the perovskite structure.

  14. Investigation on double perovskite Ba 4Ca 2Ta 2O 11

    Science.gov (United States)

    Baliteau, S.; Mauvy, F.; Fourcade, S.; Grenier, J. C.

    2009-09-01

    The structure, conductivity and water uptake of the oxygen-deficient perovskite-type compound Ba 4Ca 2Ta 2O 11 have been investigated. Ba 4Ca 2Ta 2O 11 crystallizes in the cryolite structure (cubic, Fm3 m SG) with a = 8.4508(2) Å, under dry air. The compound can be partially hydrated up to a maximum water content of approximately 0.52 mol H 2O per mol Ba 4Ca 2Ta 2O 11. In moist air, the structure symmetry becomes monoclinic ( C2/ m) and the temperature dependence of total conductivity shows a different behavior because of changes in transport mechanism. Three regions can be observed as a function of temperature. For the low temperature range 200-400 °C, the protonic conduction is prevailing with an activation energy EA = 0.85 eV. In the intermediate temperature range (400-600 °C), O 2- anionic and protonic conductions are mixed with an activation energy EA = 0.45 eV and in the third region, for temperatures above 600 °C, O 2-conduction is prevailing with an activation energy EA = 0.85 eV.

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

    Science.gov (United States)

    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. The Pr and Ca Substitution in GdBa2Cu3O7- & delta

    Directory of Open Access Journals (Sweden)

    H. S. H.

    2001-12-01

    Full Text Available   The granular Gd1-x-zPrxCazBa2Cu3O7-δ high-temperature cuprate samples with 0.0 ≤ x ≤ 0.3 and 0.0≤ x ≤ 0.35 are prepared by standard solid state reaction and characterized by XRD and SEM techniques. The BaCuO2 and impurity phases are less than 1% in the samples having high levels of pr and Ca concentrations. The electrical resistivity measurements show a nonlinear reduction in Tc(x,z=etc versus x. Moreover, the Tc(z curve with x=0 is nonlinear and aplateau appears at z≈ 0.05-0.015. For Pr-Ca-doped samples with a constant concentration of Pr, Tc increases with the increase of Ca up to an optimum value of Ca doping and then in decreases. Based on these observations, we suggest that hole filling and hole localization the main effects of Pr ion substiution. The magnetic measurements indicate that the value of Hc1 is in the order of 10 mT. The mangetoresistance measurements have been measured and analyzed. The superconducting transition region is broadened by the application of magnetic field. The experimental data near the onsen of superconductivity are fitted with the Ambegakor and Halperin (AH phase-slip model. We observe that the AH parameter,γ (H, depends not only on the temperature and the magnetic field, but also on the Pr and Ca ions concentrations. It is observed that the critical current density increases with Ca substitution and decreases with Pr substitution in Gd-123 system. We suggest that the Pr ion substitution probably enhances the weak link, but the Ca ion acts as flux pinning center in the GdPrCa-123 system.

  17. Synthesis of HgBa2Ca3Cu4O10+δ(Hg-1234) and HgBa2Ca4Cu5O12+δ(Hg-1245) from oxygen controlled precursors under high pressure

    International Nuclear Information System (INIS)

    Effects of oxygen content in the precursor have been investigated on the synthesis of HgBa2Ca4Cu5O12+δ(Hg-1245) under high pressure. The superconducting phases continuously changed from Hg-1234 to Hg-1245 with reducing the oxygen content in the precursor of Ba2Ca4Cu5O11+δ. Samples of Hg- 1245 have been synthesized by optimizing the oxygen content of the precursor with the stoichiometric composition. (author)

  18. Enhanced current density Jc and extended irreversibility in single-crystal Bi2Sr2Ca1Cu2O8 via linear defects from heavy ion irradiation

    International Nuclear Information System (INIS)

    Large enhancements in the critical current density Jc were produced in single crystals of the high-temperature superconductor Bi2Sr2Ca1Cu2O8 by irradiation with high energy Sn ions. In addition, the irreversibility line was moved to considerably higher magnetic fields. In contrast with analogous studies on Y1Ba2Cu3O7, there was little, if any, selective pinning when the magnetizing field was applied parallel to the linear, ion-damage-produced tracks

  19. Observation of a commensurate array of flux chains in tilted flux lattices in Bi-Sr-Ca-Cu-O single crystals

    International Nuclear Information System (INIS)

    We report the observation of a novel flux-lattice structure, a commensurate array of flux-line chains. Our experiments consist of the magnetic decoration of the flux lattices in single crystals of Ba-Sr-Ca-Cu-O where the magnetic field is applied at an angle with respect to the conducting planes. For a narrow range of angles, the equilibrium structure is one with uniformly spaced chains with a higher line density of vortices than the background lattice. Our observations are in qualitative agreement with theories which suggest that, in strongly anisotropic materials the vortices develop an attractive interaction in tilted magnetic fields

  20. NONLINEAR OPTICAL PHENOMENA: Stimulated Raman scattering of picosecond pulses in SrMoO4 and Ca3(VO4)2 crystals

    Science.gov (United States)

    Zverev, Petr G.; Karasik, Aleksandr Ya; Basiev, Tasoltan T.; Ivleva, Lyudmila I.; Osiko, Vyacheslav V.

    2003-04-01

    An express technique is proposed for the study of stimulated Raman scattering (SRS) in crystals excited by long trains of picosecond pulses. SRS was studied in several crystals excited by 15-ps pulses from an Nd3+:CLNGG disordered garnet laser. SRS in SrMoO4 and Ca3(VO4)2 crystals was obtained and investigated for the first time, and compared with SRS in popular SRS-active BaWO4 and KGd(WO4)2 crystals.

  1. Thermal expansion behaviour and phase stability of AFe$_2$As$_2$ (A=Ca, Sr and Eu) using powder diffraction technique

    Indian Academy of Sciences (India)

    MISHRA S K; MITTAL R; KRISHNA P S R; SASTRY P U; CHAPLOT S L; BABU P D; MATSUISHI S; HOSONO H

    2016-06-01

    The thermal expansibilities and phase stabilities of AFe$_2$As$_2$ (A = Ca, Sr and Eu) have been investigated by powder diffraction techniques in the temperature range 5–600 K.We found the anisotropic thermal expansivities with temperature for all the compounds. The lattice parameter in the tetragonal phase (AT) of CaFe$_2$As$_2$ contracts with increasing temperature, whereas CT expands. The rate of contraction in AT is lower than the rate of expansion in CT. Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the a-axis) is found to be the smallest for EuFe$_2$As$_2$ and the highest for BaFe$_2$As$_2$. However, therate of change of thermal expansivities along out-of-plane (i.e., along the c-axis) is higher as we go from Ba, Sr, Eu and Ca, respectively. Above 600 K, we notice the appearance/disappearance of certain reflections which suggest that tetragonal phase is not stable above this temperature for these compounds.

  2. Superconducting Tl-Ca-Ba-Cu-O thin films with zero resistance at temperatures of up to 120 K

    International Nuclear Information System (INIS)

    We have prepared superconducting Tl-Ca-Ba-Cu-O thin films on a variety of substrates with transition temperatures as high as ≅120 K, confirmed by sharp onsets of substantial Meissner and shielding signals at the same temperatures. The properties of the films are found to depend sensitively on the post-annealing conditions. Highly textured c-axis-oriented films comprised mostly of Tl2Ca1Ba2Cu2O/sub x/, Tl1Ca2Ba2Cu3O/sub x/, and Tl2Ca2Ba2Cu3O/sub x/ were synthesized by varying the annealing procedure with corresponding maximum superconducting transition temperatures of ≅100, 110, and 120 K, respectively

  3. Structural properties and superconductivity in the Y1-xPrxBaSrCu3O7-δ system

    International Nuclear Information System (INIS)

    The single phase of Y1-xPrxBaSrCu3O7-δ has been investigated by powder X-ray diffraction and temperature dependence of the resistivity. It is found that the system undergoes an orthorhombic-to-tetragonal transition at x=0.5. Superconductivity still survives until x=0.7. These results have been compared with those of the Y1-xPrxBa2Cu3O7-δ system, which was discussed in terms of the Pr-O covalent bonding effect. ((orig.))

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

    Science.gov (United States)

    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.

  5. Half-metallicity and stability of the rock salt BaC and SrC (111) surfaces: A density functional study

    International Nuclear Information System (INIS)

    The electronic structure and magnetic properties of relaxed (111) surfaces of the alkaline-earth monocarbides BaC and SrC in the stable rock salt structure, are calculated on the basis of first principle density functional theory within the framework of self-consistent field plane wave pseudo-potential method, using the generalized gradient approximation for the exchange-correlation functional. The results of this study reveal that the C-terminated (111) surfaces retain the bulk half-metallic property in both BaC and SrC. The half-metallicity of the C-terminated BaC surface is found to be more robust compared to the bulk BaC due to the larger half-metallic energy gap. In contrast, the half-metallic energy gap of the C-terminated SrC surface is found to be smaller than that of the bulk. The Ba-terminated surface of BaC and the Sr-terminated surface of SrC, however, lose their bulk half-metallicity due to the formation of surface states in the majority spin band gap. The calculations also show that the atomic magnetic moments at the half-metallic C-terminated surfaces in both BaC and SrC increase considerably with respect to the corresponding bulk values, which is explained in terms of an increase in the number of unpaired 2p electrons of the carbon atom at the surface. We also discuss the stability of the surfaces via the calculated bulk formation energies. The bulk formation energies for both BaC and SrC in the rock salt structure are found to be positive, which indicate that the surfaces are not stable at normal pressure and temperature conditions, and non-equilibrium growth techniques may be required for the realization of BaC and SrC thin films

  6. Half-metallicity and stability of the rock salt BaC and SrC (111) surfaces: A density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Tabatabaeifar, A. H.; Davatolhagh, S., E-mail: davatolhagh@susc.ac.ir; Foroughpour, M. [Department of Physics, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2013-12-07

    The electronic structure and magnetic properties of relaxed (111) surfaces of the alkaline-earth monocarbides BaC and SrC in the stable rock salt structure, are calculated on the basis of first principle density functional theory within the framework of self-consistent field plane wave pseudo-potential method, using the generalized gradient approximation for the exchange-correlation functional. The results of this study reveal that the C-terminated (111) surfaces retain the bulk half-metallic property in both BaC and SrC. The half-metallicity of the C-terminated BaC surface is found to be more robust compared to the bulk BaC due to the larger half-metallic energy gap. In contrast, the half-metallic energy gap of the C-terminated SrC surface is found to be smaller than that of the bulk. The Ba-terminated surface of BaC and the Sr-terminated surface of SrC, however, lose their bulk half-metallicity due to the formation of surface states in the majority spin band gap. The calculations also show that the atomic magnetic moments at the half-metallic C-terminated surfaces in both BaC and SrC increase considerably with respect to the corresponding bulk values, which is explained in terms of an increase in the number of unpaired 2p electrons of the carbon atom at the surface. We also discuss the stability of the surfaces via the calculated bulk formation energies. The bulk formation energies for both BaC and SrC in the rock salt structure are found to be positive, which indicate that the surfaces are not stable at normal pressure and temperature conditions, and non-equilibrium growth techniques may be required for the realization of BaC and SrC thin films.

  7. Superconducting glass-ceramics in the Bi-Sr-Ca-Cu-O system

    Science.gov (United States)

    De Guire, Mark R.; Kim, Cheol J.; Bausal, Narottam P.

    1990-01-01

    Differential thermal analysis, XRD, SEM, and resistivity measurements, have been used to study the recrystallization during various heat treatments of a Bi1.5SrCaCu2O(z) glass obtained by rapid quenching from the melt. Heating at 450 C formed the Bi(2+x)Sr(2-x)-CuO(z) solid solution designated 'R'. Between 765 and 845 C, R reacts slowly with the glass to form the 80 K superconductor Bi2(Sr,Ca)3Cu2O(z), together with CuO. Heating for 7 days at the higher temperature, followed by slow cooling, raised the temperature of zero resistance to 77 K.

  8. Comparative kinetics of 47Ca, 85Sr and 226Ra in the freshwater turtle, Trachemys scripta

    International Nuclear Information System (INIS)

    The kinetics of 47Ca, 85Sr and 226Ra were compared in the yellow-bellied slider, a common freshwater turtle of the southeastern USA. The absorption and elimination processes were examined as a function of stable dietary Ca, season, age and sex of the animals. Turtles were gavaged with radionuclides and serial whole-body analyses were performed on the live animals for up to 480 days. Only in the juvenile age class did reduced dietary Ca cause a significant increase in 85Sr absorption. The absorption of 85Sr and 226Ra in the adult male, adult female and hatchling groups was unaffected by dietary Ca. Mean absorption was greater than that which has been reported for other organisms and significantly differed among isotopes. The high absorption values were not restricted to immatures, but continued into maturity. Elimination rates were not affected by the dietary treatment, nor were isotopic differences in elimination observed. Annual mean elimination rate constants pooled among animal groups, were 0.22 ± 0.07 for 85Sr and 0.26 ± 0.18 for 226Ra. Retention was strongly affected by season with the greatest elimination occurring in the summer and declining to levels that were not distinguishable from zero in the winter. Elimination rate constants for hatchlings were greater than for the other age groups. (author)

  9. Inter-and intragranular properties of Bi2CaSr2Cu2Oy superconductors

    International Nuclear Information System (INIS)

    The granular behavior of a sintered bulk Bi2CaSr2Cu2Oy superconductor is investigated by resistivity and χac measurements. The observed temperature and magnetic field dependence is discussed within the framework of a granular model. The frequency dependence of the intragranular losses leads to a flux flow or flux creep picture

  10. A study on the superconducting phases of the Bi-Sr-Ca-Cu-O system

    International Nuclear Information System (INIS)

    In this paper a preparation technique of superconducting Bi-Sr-Ca-Cu-O phases starting from amorphous matrices of composition 1:1:1:2 and 2:2:2:3 is described. DTA, TGA, XRD and Tc resistive measurements are reported. The competitive growth of different superconducting phases is discussed

  11. Current voltage characteristics of tunneling structures based on B1-Sr-Ca-Cu-O:Pb

    International Nuclear Information System (INIS)

    The I (V) and d I(V)/d V contacts in polymers microcracks Bi-Sr-Ca-Cu-O-Pb (2212 phase) microcrystalline in 4,2 K. temperature characteristics are investigated. The revealed negative declination area in voltage-current characteristics is summarized, that this microcracks contact concerns to S 1-I-S 2 kind

  12. Gamma-ray shielding properties of CaO–SrO–B2O3 glasses

    DEFF Research Database (Denmark)

    Singh, K; Singh, H; Sharma, G;

    2005-01-01

    Mass attenuation coefficients, effective atomic numbers and effective electron densities have been determined experimentally for the glass system xCaO . (0.3-x)SrO . 0.7B(2)O(3) at photon energies 511, 662, 1173, and 1332KeV. The results are compared with theoretical calculations. In addition, the...

  13. Positron lifetime studies on the BiSrCaCuO(F) superconductors

    International Nuclear Information System (INIS)

    We have measured the positron lifetime and the transition temperature Tc as a function of doped F content for Bi2Sr2CaCu2Oy-xFx superconductors. The observed results are interpreted in terms of the change of the electron density in the Bi - O layers, which is the region probed by the positron, and the hole concentration in the Cu - O planes, which is correlated with the Tc of the sample. From this point of view, it is suggested that the F atom mainly substitutes the oxygen atom in the Bi - O layers, and it causes the electrons transfer from the Bi - O layers to the Sr - O planes; when x = 0.4, the F atom mainly substitues the oxygen atom in the Sr - O planes, it causes the electrons transfer from the Sr - O planes to the Bi - O layers and the Cu - O planes. (orig.)

  14. Elemental intermixing within an ultrathin SrRuO{sub 3} electrode layer in epitaxial heterostructure BaTiO{sub 3}/SrRuO{sub 3}/SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H. B.; Qi, R. J.; Ding, N. F.; Sun, L. [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062 (China); Huang, R., E-mail: rhuang@ee.ecnu.edu.cn [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062 (China); Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Duan, C. G., E-mail: cgduan@clpm.ecnu.edu.cn; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Fisher, Craig A. J. [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Ikuhara, Y. [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan)

    2016-01-15

    Aberration corrected scanning transmission electron microscopy is used to directly observe atom columns in an epitaxial BaTiO{sub 3} thin film deposited on a 3.6 nm-thick SrRuO{sub 3} electrode layer above an SrTiO{sub 3} (001) substrate. Compositional gradients across the heterointerfaces were examined using electron energy-loss spectroscopy techniques. It was found that a small amount of Ba and Ti had diffused into the SrRuO{sub 3} layer, and that this layer contained a non-negligible concentration of oxygen vacancies. Such point defects are expected to degrade the electrode’s electronic conductivity drastically, resulting in a much longer screening length. This may explain the discrepancy between experimental measurements and theoretical estimates of the ferroelectric critical thickness of a BaTiO{sub 3} ferroelectric barrier sandwiched between metallic SrRuO{sub 3} electrodes, since theoretical calculations generally assume ideal (stoichiometric) perovskite SrRuO{sub 3}.

  15. Elemental intermixing within an ultrathin SrRuO3 electrode layer in epitaxial heterostructure BaTiO3/SrRuO3/SrTiO3

    International Nuclear Information System (INIS)

    Aberration corrected scanning transmission electron microscopy is used to directly observe atom columns in an epitaxial BaTiO3 thin film deposited on a 3.6 nm-thick SrRuO3 electrode layer above an SrTiO3 (001) substrate. Compositional gradients across the heterointerfaces were examined using electron energy-loss spectroscopy techniques. It was found that a small amount of Ba and Ti had diffused into the SrRuO3 layer, and that this layer contained a non-negligible concentration of oxygen vacancies. Such point defects are expected to degrade the electrode’s electronic conductivity drastically, resulting in a much longer screening length. This may explain the discrepancy between experimental measurements and theoretical estimates of the ferroelectric critical thickness of a BaTiO3 ferroelectric barrier sandwiched between metallic SrRuO3 electrodes, since theoretical calculations generally assume ideal (stoichiometric) perovskite SrRuO3

  16. Elemental intermixing within an ultrathin SrRuO3 electrode layer in epitaxial heterostructure BaTiO3/SrRuO3/SrTiO3

    Directory of Open Access Journals (Sweden)

    H. B. Zhang

    2016-01-01

    Full Text Available Aberration corrected scanning transmission electron microscopy is used to directly observe atom columns in an epitaxial BaTiO3 thin film deposited on a 3.6 nm-thick SrRuO3 electrode layer above an SrTiO3 (001 substrate. Compositional gradients across the heterointerfaces were examined using electron energy-loss spectroscopy techniques. It was found that a small amount of Ba and Ti had diffused into the SrRuO3 layer, and that this layer contained a non-negligible concentration of oxygen vacancies. Such point defects are expected to degrade the electrode’s electronic conductivity drastically, resulting in a much longer screening length. This may explain the discrepancy between experimental measurements and theoretical estimates of the ferroelectric critical thickness of a BaTiO3 ferroelectric barrier sandwiched between metallic SrRuO3 electrodes, since theoretical calculations generally assume ideal (stoichiometric perovskite SrRuO3.

  17. Growth of epitaxial (Sr, Ba)n+1RunO3nP+1films

    International Nuclear Information System (INIS)

    We have grown epitaxial (Sr,Ba)n+1RunO3n+1 films, n = 1, 2 and ∞, by pulsed laser deposition (PLD) and controlled their orientation by choosing appropriate substrates. The growth conditions yielding phase-pure films have been mapped out. Resistivity versus temperature measurements show that both a-axis and c-axis films of Sr2RuO4 are metallic, but not superconducting. The latter is probably due to the presence of low-level impurities that are difficult to avoid given the target preparation process involved in growing these films by PLD. (author)

  18. A new oxochromate: SrNi2Cr8O15 of the BaV10O15 type

    International Nuclear Information System (INIS)

    A new quaternary oxochromate(III) was prepared by solid state reaction. Single crystal X-ray investigations of SrNi2Cr8O15 show that this compound belongs to the BaV10O15type. [Space group D2h18-Ccmb, a = 10,042; b = 11,413; c = 9,260A; Z = 4.] Ni2+ and Cr3+ occupy the octahedrally coordinated point positions statistically. The surrounding of Sr2+ is similar to the iso- and heteropolyacids. (Author)

  19. Structural phase transition in early growth of Bi2Sr2CaCu2O8+x films on SrTiO3 substrates

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Onellion, M.; Margaritondo, G.; Pavuna, D.

    2002-02-01

    We used pulsed laser deposition, with a Bi2Sr2CaCu2O8+x target, to grow films ranging from (1/4) to 10 unit cells thick. We studied these films, and reference Bi2Sr2CaCu2O8+x single crystal samples, using angle-integrated photoemission, core level photoemission, and x-ray diffraction. The data indicate that all films exhibit a metallic-like Fermi edge in the photoemission data. More strikingly, a structural phase transition occurs at a nominal Bi2Sr2CaCu2O8+x thickness of approximately one unit cell, converting the precursor Bi2O2.33 highly coherent thin film into a Bi2Sr2CaCu2O8+x structure.

  20. Structure Refinement of (Sr,BaNb2O6 Ceramic Powder from Neutron and X-Rays Diffraction Data

    Directory of Open Access Journals (Sweden)

    Carrio J.G.

    2002-01-01

    Full Text Available The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ~ 64/36 was found from the initial batch composition Sr0.61Ba0.39Nb2O6, corroborating with the quantitative X-ray dispersive spectroscopy (EDS measurements. The structure is tetragonal with cell parameters a, b = 12.4504(3 Å and c = 3.9325(1 Å and space group P4bm. It was not necessary to introduce any positional disorder for the oxygen atoms. Cation Nb+5 displacements not parallel to the c direction are presented, which can influence the behavior of the ferroelectric properties.

  1. Effects of photoassisted O2 annealing on the properties of (Ba,Sr)TiO3 thin films

    International Nuclear Information System (INIS)

    A photoassisted O2 annealing method is proposed to anneal (Ba0.75Sr0.25)TiO3 thin films grown by rf magnetron sputtering. A deuterium lamp, which emits strong ultraviolet and vacuum ultraviolet light, was used as the light source of our photoassisted O2 annealing system. It was found that we could achieve a leakage current density lower than 3x10-8 A/cm2 at 2 V and a dielectric constant, ε, as high as 158.6 by annealing (Ba0.75Sr0.25)TiO3 thin films in this system at 650 deg. C for 2 h

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

    Science.gov (United States)

    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. Charge trapping-detrapping induced resistive switching in Ba0.7Sr0.3TiO3

    Directory of Open Access Journals (Sweden)

    Xi Zou

    2012-09-01

    Full Text Available Intensive research has been devoted to the resistive switching phenomena observed in many transitional metal oxides because of its potential for non-volatile memory application. To clarify the underlying mechanism of resistive switching, a planar device can provide information that is not accessible in conventional vertical sandwich structures. Here we report the observation of resistive switching behavior in a Pt/Ba0.7Sr0.3TiO3/Pt planar device. Using in-situ scanning Kelvin probe microscopy, we demonstrate that charge trapping/detrapping around the Pt/Ba0.7Sr0.3TiO3 interface modulates the Schottky barrier, resulting in the observed resistive switching. The findings are valuable for the understanding of resistive switching in oxide materials.

  4. A coprecipitation technique to prepare Sr0.5Ba0.5Nb2O6

    Indian Academy of Sciences (India)

    A Vadivel Murugan; A B Gaikwad; V Samuel; V Ravi

    2006-06-01

    An aqueous mixture of ammonium oxalate and ammonium hydroxide was used to coprecipitate barium and strontium ions as oxalates and niobium ions as hydroxide under basic conditions. This precursor on calcining at 750°C yielded Sr0.5Ba0.5Nb2O6 phase. This is a much lower temperature than that prepared by traditional solid state method (1000°C) as reported for the formation of Sr0.5Ba0.5Nb2O6 (SBN). Transmission electron microscopic (TEM) investigations revealed that the average particle size was 80 nm for the calcined powders. The room temperature dielectric constant at 1 kHz was found to be 1100. The ferroelectric hysteresis loop parameters of these samples were also studied.

  5. Ba0.8Sr0.2TiO3 films crystallized on glass and platinized substrates by laser-assisted annealing at room temperature

    International Nuclear Information System (INIS)

    In this work, Ba0.8Sr0.2TiO3 (BST) films were grown by pulse laser ablation on bare glass and platinized substrates. The crystalline phase was obtained with the help of laser-assisted annealing (LAA) at room temperature, in air environment. By adjusting LAA conditions, like frequency of the laser and number of shots, we were able to grow crack-free BST thin films with pure perovskite phase on bare glass and platinized substrates. The crystalline layer was found to be the same irrespective of the substrate used, c.a. 250 nm thick. The electric characteristics of the amorphous and LAA crystalline BST films deposited on platinized substrate were further studied and analyzed. While in amorphous films it was found that the oxygen defects are responsible for conduction, in LAA films the amorphous/crystalline interface layer plays an important role in current leakage. (orig.)

  6. Neutron scattering studies of structure, magnetism and superconductivity under pressure in AFe2As2 (A=Ca, Ba) under pressure

    International Nuclear Information System (INIS)

    The interplay between superconductivity, magnetism, and structure has become a major theme of research in the iron arsenide families of superconductors. The strong coupling between magnetism and structure, for example, is illustrated by the parent compounds, AEFe2As2 (AE = Ba, Sr, Ca), which manifest simultaneous transitions from a paramagnetic, tetragonal phase to an antiferromagnetically ordered, orthorhombic phase. The coupling between superconductivity and magnetism has been demonstrated by, for example, the suppression of the antiferromagnetic ordering and orthorhombic distortion below the superconducting transition in some electron doped compounds. The elastic and inelastic neutron scattering measurements, under pressure, that have elucidated the nature of the magnetic order and its relationship to the tetragonal-orthorhombic structural transition at ambient pressure, the quenching of magnetism in the cT phase, and the identification of the superconducting phase in CaFe2As2 under applied uniaxial pressure are discussed

  7. Excited state absorption measurements of Sm2+ in CaF2, SrF2, and SrCl2

    International Nuclear Information System (INIS)

    We measured the pump-probe spectrum of the Sm2+ ion in three materials: CaF2, SrF2, and SrCl2. The onset of the observed prominent excited-state absorption band is consistent with an electrostatic model for impurity levels in a solid-state material. 15 refs., 4 figs., 1 tab

  8. Scintillation properties of LiF–SrF2 and LiF–CaF2 eutectic

    International Nuclear Information System (INIS)

    Dopant free eutectic scintillators 6LiF–SrF2 and 6LiF–CaF2 were developed by the vertical Bridgeman method for the purpose of thermal neutron detection. The molar ratio of LiF and Ca/SrF2 was 4:1 on its eutectic composition. The α-ray induced radioluminescence spectra of the scintillators showed intense emission peak at 300 nm due to the emission from the self-trapped exciton in Ca/SrF2 layers. When the samples were irradiated with 252Cf neutrons, 6LiF–SrF2 and 6LiF–CaF2 exhibited the light yields of 4700 and 9400 ph/n, respectively. Scintillation decay times of 6LiF–SrF2 and 6LiF–CaF2 were accepted for scintillation detectors, 90 and 250 ns, respectively. -- Highlights: • Nondoped LiF–CaF2 and LiF–SrF2 eutectic scinitillators are reported for the first time. • Two sample showed self-trapped exciton emission. • LiF–SrF2 sample exhibited the light yield of 9400 ph/n and this value was comparable to conventional materials doped with rare earth ions. • Scintillation decay times of LiF–CaF2 and LiF–SrF2 were 250 and 90 ns, respectively

  9. Dielectric properties of polycrystalline (Ba0.60Sr0.40Ti0.8O3

    Directory of Open Access Journals (Sweden)

    M. Gabryś

    2008-11-01

    Full Text Available Purpose: The purpose of the work was to determinate the influence of the ferroactive Sr substitutions insublattice A and the nonstoichiometry in sublattice B on changes of physical properties and the character of phasetransition (PT in pure barium titanate BaTiO3 (BT.Design/methodology/approach: The polycrystalline samples of (Ba0.60Sr0.40TiO3 and (Ba0.60Sr0.40Ti0.8O3were obtained by the calcinations method in temperature 1620 K. The dielectric measurements were executed byautomatic device (QUATRO KRIO 4.0 with LCR Agilent 4824A meter and BDS 1100 cryostat. The materials wereinvestigated under cooling conditions with speed of 2 K/min and within frequency range from 20 Hz to 1 MHz.Findings: The dielectrometry was applied to measure complex dielectric permittivity and other dielectricfunctions of ferroelectric (Ba0.60Sr0.40TiO3 (BST-40 and (Ba0.60Sr0.40Ti0.8O3 (BST-40/0.8. It was affirmed, that40% substitution of Sr ions as well as 20% deficiency of Ti ions in solid solution reduced temperature and changedthe type of phase transformation. The transformation stood strongly diffused. The weak dependence of temperatureTm (peak of electric permittivity ε’ from frequency of electric measuring field was observed. It means, that thismaterial should be prescribed to the class of ferroelectrics with diffused phase transformation (DPT. The polarcharacter of this solution was also observed in the paraelectric phase. It is connected with the occurrence of polarclusters in paraelectric phase.Practical implications: Results can be used to construct the model describing changes in the solid solutionswith ferroactive and nonferroactive substitutions in sublattice A or B of the perovskite.Originality/value: Value of this work relies on the experimental examination of the electric properties ofnonstoichiometric BST-40 solid solution. The low value of phase angle in the paraelectric phase was connectedwith the occurrence of the polar regions.

  10. Establishment of strongly overdoped states in the HgBa2Ca2Cu3O8+[delta] superconductor

    OpenAIRE

    Fujinami, K.; Ito, T.; Suematsu, H.; Matsuura, K.; Karppinen, Maarit; Yamauchi, H.

    1997-01-01

    Strongly overdoped HgBa2Ca2Cu3O8+δ (Hg-1223) samples with superconducting transitions as low as 97 K were successfully obtained by using HgO, Ca2CuO3, CuO, and mixtures of highly oxidized BaCuO2+ε (ε≈0.13) and/or BaO2 powders as starting materials for the high-pressure synthesis at 5 GPa and 950 °C. The overdoped state was confirmed by observing negative values for the Seebeck coefficient throughout the temperature range from Tc to 320 K in a thermoelectric power measurement. Also, both of th...

  11. Structural properties and chemical homogeneity of underdoped La2-xMxCuO4 cuprates (M = Sr, Ba)

    International Nuclear Information System (INIS)

    The present work reports a systematic and accurate study on crystal structure and chemical homogeneity of underdoped La2-xMxCuO4 (M = Ba, Sr). Samples' structural characterization performed by Rietveld refinement of XRD powder diffraction profiles provided an accurate working trendline for the dopant concentration determination. Furthermore FT-IR skeletal analysis and SIMS investigations ensured chemical homogeneity even for samples with very low dopant contents

  12. Effect of radiation-induced defects on the (Ba, Sr)TiO3 film electric conductivity

    International Nuclear Information System (INIS)

    The results of experimental study on electroconducting properties of planar MDM structures on the basis of γ-irradiated (Ba0.4Sr0.6)TiO3 film are presented. The obtained experimental results testify to formation of donor-type defects in the films under absorption of γ-radiation up to 109 rad; these defects do not cause noticeable changes in electroconducting properties of the films

  13. The comparative kinetics of Ca, Sr, And Ra in a freshwater turtle, Trachemys scripta

    International Nuclear Information System (INIS)

    The accumulation of 45Ca, 47Ca, 88Sr, and 226Ra was studied in the yellow-bellied slider, a common freshwater turtle of the Southeastern US. The author was particularly interested in testing the hypothesis of competitive inhibition, a concept whereby decreasing the intake of a stable dietary element increases the absorption and retention of chemically similar radionuclides. He established four specific hypotheses and examined the processes of absorption and elimination as a function of stable dietary calcium (2 and 20 mg g-1), season (summer, fall, winter and spring), and age and sex of the animals (hatchlings, juveniles, adult males, adult females, and gravid females). Turtles were gavaged with radionuclides and the gamma-emitting isotopes were detected during serial whole-body counts performed on the live animals for up to 480 d. The analysis of the beta-emitting 45Ca was accomplished by chemical separation procedures. Data were fit to a two-component exponential retention model by nonlinear regression. The 10-fold reduction in dietary Ca did not affect the elimination rate constants, and increased the assimilation of Sr and Ra only within juveniles. For all animals the absorption of Ca was significantly greater than Sr, and likewise, Sr was greater than Ra. Mean absorptions were generally higher than values reported for other organisms. Unlike many other organisms, absorption rates did not decline at maturity. He suspects that high Ca demands in constructing and maintaining the massive shell, necessitated by the turtle's survival strategy, may contribute to the high absorption, as well as the lack of a decline at maturity. Elimination rate constants were greatest in the summer and declined to levels that were generally not distinguishable from zero in the spring, winter, and fall seasons

  14. Bright yellow and green Eu(ii) luminescence and vibronic fine structures in LiSrH3, LiBaH3 and their corresponding deuterides

    NARCIS (Netherlands)

    Kunkel, Nathalie; Meijerink, Andries; Kohlmann, Holger

    2014-01-01

    The luminescence of Eu2+ in hydride and deuteride perovskite hosts LiMH3 and LiMD3 (M = Sr, Ba) is reported. Bright yellow (M = Sr) and green (M = Ba) emission is observed and assigned to 4f 65d-4f7 emission from Eu2+ in the highly symmetric 12-coordinated M2+ site (m3m). The long wavelength of the

  15. Microstructure and photoluminescence properties of Nd-doped (Ba,Sr)TiO3 thin films

    International Nuclear Information System (INIS)

    Ba0.8Sr0.2TiO3(BST) thin films with different Nd-doped concentrations have been frabracated on silicon substrates by modified Sol-gel process. All the samples were annealed at 700 deg. C for 60 min.The structural and morphological properties of the films were examined by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The XRD studies indicated that both pure and doped BST thin films show crystallized perovskite structures, the particle size is about 20 nm. The AFM images displayed that the films have high quality and finegrained polycrystalline structure. The photoluminescence spectra(PL) were carried out using the 808 nm Ar+ laser line as the excitation source at room temperature. The Nd-doped BST thin films show three NIR luminescence peaks corresponding to 4F3/2-4I9/2 transition at 880 nm; 4F3/2-4I11/2 transition at 1066 nm and 4F3/2-4I13/2 transition at 1345 nm; respectively. The influence of Nd3+ concentration on the microstructure and the luminescence properties were discussed. All the results showed that the Nd-doped BST films have great potential uses for novel integrated optic devices.

  16. Synthesis and characterization of nanocomposite of Ba3SrNb2O9 perovskite for dielectric applications

    International Nuclear Information System (INIS)

    Owing to their outstanding electronic dielectric and magnetic properties, metal oxide ceramics with perovskite structure continue to attract considerable scientific and commercial interest resulting in a variety of industrial applications. Perovskite are materials having the general formula ABO3 and a cubic crystal structure where B atoms are octahedrally coordinated with oxygen atoms whereas A atoms have cuboctahedral coordination. It is a flexible material, hence by substituting A and/or B with suitable cations, it can be used for various applications. Ba3SrNb2O9 is found to be one of such perovskite which has enhance dielectric property and should satisfy the following criteria: high dielectric constant, high breakdown field strength, small dielectric loss and good thermal stability. Small crystalline materials with particle diameters of 100 nm or less exhibit many novel physical properties (optical, magnetic, thermal) not found in their bulk. Ba2Sr2Nb2O9 of around 50 nm size is expected to be synthesized by sol-gel method. It is mostly applicable in microelectronic and telecommunication. Precursors used for synthesis of Ba2Sr2Nb2O9 in sol gel method are Barium acetate, Strontium acetate, Niobium chloride and Acetic acid. Transmission Electron Microscope (TEM) for structural analysis such as surface morphology and particle size. Thermal properties were obtained using Thermo Gravimetric Analyzer (TGA), X-ray powder diffraction (XRD) to find the crystallite size. Dielectric constant was calculated using impedance analyser. (author)

  17. Magnetic ordering in spin-orbit Mott insulator Ba2IrO4 probed by μSR

    International Nuclear Information System (INIS)

    Magnetic properties in the novel spin-orbit Mott insulator Ba2IrO4 were studied using muon spin rotation (μSR) technique. Zero-field μSR experiments revealed that Ba2IrO4 shows an antiferromagnetic transition at TN ∼ 240 K without any spontaneous magnetization. The most stable μ+ site was determined by the electrostatic (Madelung) potential calculation. The effective magnetic moment of the iridium ions (|μ|) in the antiferromagnetic ordered state was calculated using a dipolar-field model, with an internal field obtained by μSR experiments. The magnetic moment is significantly reduced (|μ| ∼ 0.34 μB) due to a low-dimensional quantum spin fluctuation with a large intra-plane correlation. The magnetic ground state of the spin-orbit Mott insulator Ba2IrO4 is quite similar to those in parent materials of high-TC cuprate superconductors such as La2CuO4.

  18. Influence of CuO addition on dielectric properties of (Ba,Sr)TiO3 thick films

    International Nuclear Information System (INIS)

    The structural and the dielectric properties of CuO doped (Ba,Sr)TiO3 thick film interdigital capacitors on the alumina substrates have been investigated. Various contents of CuO dopants were added to the (Ba,Sr)TiO3 thick films to lower the sintering temperature of the (Ba,Sr)TiO3 thick films on alumina substrates. Thick films were screen printed on the alumina substrates; then, interdigital capacitors with five pairs of fingers with a finger gap of 50 μm, a width of 100 μm, and a length of 200 μm were fabricated with 1-μm-thick silver electrodes through an e-beam evaporation process. For the analysis of the structural and dielectric properties, X-ray diffraction and dielectric spectroscopy were employed, respectively. Scanning electron microscopy was used to determine the morphologies of the thick films. In this experiment, we found that the lattice parameters as well as the dielectric constant were decreased with increasing CuO dopants. The 3-wt% CuO-doped BST thick film have the lowest loss tangent of 0.21% at 1 MHz and the lowest leakage current density of 10 pA at 20 kV/cm.

  19. Influence of CuO addition on dielectric properties of (Ba,Sr)TiO{sub 3} thick films

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Seok-Woo; Koh, Jung-Hyuk [Kwangwoon University, Seoul (Korea, Republic of)

    2011-03-15

    The structural and the dielectric properties of CuO doped (Ba,Sr)TiO{sub 3} thick film interdigital capacitors on the alumina substrates have been investigated. Various contents of CuO dopants were added to the (Ba,Sr)TiO{sub 3} thick films to lower the sintering temperature of the (Ba,Sr)TiO{sub 3} thick films on alumina substrates. Thick films were screen printed on the alumina substrates; then, interdigital capacitors with five pairs of fingers with a finger gap of 50 {mu}m, a width of 100 {mu}m, and a length of 200 {mu}m were fabricated with 1-{mu}m-thick silver electrodes through an e-beam evaporation process. For the analysis of the structural and dielectric properties, X-ray diffraction and dielectric spectroscopy were employed, respectively. Scanning electron microscopy was used to determine the morphologies of the thick films. In this experiment, we found that the lattice parameters as well as the dielectric constant were decreased with increasing CuO dopants. The 3-wt% CuO-doped BST thick film have the lowest loss tangent of 0.21% at 1 MHz and the lowest leakage current density of 10 pA at 20 kV/cm.

  20. Impedance spectroscopy and structural properties of the perovskite-like Sn(Ba,Sr)O{sub 3} stagnate

    Energy Technology Data Exchange (ETDEWEB)

    Cuervo Farfan, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Ciencias Basicas, Universidad Manuela Beltran, Bogota DC (Colombia); Olaya, J.J. [Departamento de Ingenieria Mecanica y Mecatronica, Universidad Nacional de Colombia, Bogota DC (Colombia); Vera Lopez, E. [Grupo de Superficies, Electroquimica y Corrosion, Universidad Pedagogica y Tecnologica de Colombia, Tunja (Colombia); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia)

    2012-08-15

    An exhaustive study of structural, electrical and transport properties on the perovskite stagnate Sn(Ba,Sr)O{sub 3} was performed. Samples of SnBa{sub 1-x}Sr{sub x}O{sub 3} with 0{<=}x{<=}1.00 were prepared by the solid state reaction method. The crystallographic structure was studied by X-ray diffraction experiments and Rietveld refinement using the GSAS code. Results reveal the material synthesized in a cubic structure (space group Pm3-bar m, no. 221) for 0{<=}x{<=}0.50 and in an orthorhombic (space group Pnma, no. 62) for x>0.50. The approximate grain size was found from experiments' Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0 mHz up to 0,10 MHz. Electric polarization measurements for SnSrO{sub 3} and SnBaO{sub 3} were determined through curves of polarization as a function of applied electric field, which reveal the ferroelectric character of the material. From the saturation polarization the dielectric constants of materials were calculated.

  1. 57Fe hyperfine interaction parameters and selected magnetic properties of high purity MFe12O19 (M = Sr, Ba)

    International Nuclear Information System (INIS)

    Much of the confusion regarding the 57Fe Moessbauer spectroscopic hyperfine parameters of SrFe12O19 and BaFe12O19 at 300 K has been removed by means of an interlaboratory investigation of well-characterized samples prepared from high purity starting materials. In contrast to previous investigations, the contributions of each of the five Fe sublattices to the Moessbauer spectrum are discernible at 300 K and five components are necessary for an adequate fit of the data. The relative magnitudes of the hyperfine fields, Hn, and isomer shifts, δ, are as follows: for SrFe12O19 and BaFe12O19: Hn(2b)n(12k)n(4f1)n(2a)n(4f2), for SrFe12O19 δ(4f1)≤δ(2b)2), and for BaFe12O19 δ(2b)1)2)<δ(2a). The above assignment is based on considerations of both magnetic and crystal/chemical structures. The high purity starting materials seem to have appreciable influences on both hyperfine interaction parameters and bulk magnetic properties as observed by others for spinel and garnet ferrites. (orig.)

  2. Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3

    International Nuclear Information System (INIS)

    The integration of ferromagnetic and ferroelectric materials into hybrid heterostructures leads to systems with improved or even novel functionality. We here discuss the properties of the ferromagnetic double perovskite Sr2CrReO6, deposited as a thin film onto ferroelectric BaTiO3 single crystal substrates via pulsed laser deposition. High resolution X-ray diffraction evidences the high crystalline quality of the epitaxial Sr2CrReO6 layers. Temperature dependent electrical transport and SQUID measurements show abrupt changes both in resistivity and magnetization at the temperatures of the BaTiO3 phase transitions. Furthermore, the coercive field abruptly changes by more than 1.2 T at the BaTiO3 phase transitions. These observations reveal a giant change of the magnetic anisotropy in the Sr2CrReO6 thin film associated with the crystalline phase transitions of the substrate. We attribute these effects to the high sensitivity of the double perovskites to mechanical deformation.

  3. Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Perriot, R., E-mail: rperriot@lanl.gov; Liu, X.-Y.; Stanek, C.R.; Andersson, D.A.

    2015-04-15

    The diffusivity of the solid fission products (FP) Zr (Zr{sup 4+}), Ru (Ru{sup 4+}, Ru{sup 3+}), Ce (Ce{sup 4+}), Y (Y{sup 3+}), La (La{sup 3+}), Sr (Sr{sup 2+}) and Ba (Ba{sup 2+}) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. For all solid FPs except Y{sup 3+}, the migration of the FP has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. However, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru{sup 3+} and Ru{sup 4+} diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO{sub 2}, and the tendency to form metallic and oxide second phase inclusions.

  4. Structural and dielectric properties of polycrystalline (Ba0.9Sr0.1TiO3

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2008-10-01

    Full Text Available Purpose: This work is aimed to determination of the influence of Sr – ferroactive substitution on physical properties and character of phase transitions (PT in barium titanate BaTiO3 (BT.Design/methodology/approach: Polycrystalline samples of BST-10 were prepared by means of calcination method at the ~1600 K. Roentgenogram of BST-10 was made within the angles from 10 deg to 110 deg with the 0.008 deg step. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 and Agilent Precision LCR meter HP4284A equipped with WinDETA 5.62 software Novocontrol. Measurement were taken under cooling with 2 K/min speed. Measuring electric field frequency was from the range 20 Hz-1 MHz.Findings: Dielectric spectroscopy in the frequency domain was applied to measure complex dielectric permittivity and other dielectric functions of ferroelectric polycrystalline (Ba0.9Sr0.1TiO3 (BST-10. It was established that 10% substitution of Sr in BST-10 solid solution did not change the character of the phase transitions. The temperatures of the phase transitions were correlated with low temperature of PT in SrTiO3 (ST. Similar properties of Ba and Sr ions were taken into consideration. The dipolar character of solid solution was also observed in paraelectric phase.Practical implications: Obtained results can be used to model the effects of ferroactive and nonferroactive substitutions in the A and B subnets of perovskite ferroelectrics.Originality/value: An attempt to correlate low phase angle values observed in the paraelectric phase of BTS-10 with high dielectric permittivity and the occurrence of polar regions.

  5. Growth mode mapping and structural properties of controlled perovskite BaTiO3/SrTiO3 heterostructure

    International Nuclear Information System (INIS)

    Perovskite heteroepitaxy was investigated under various conditions using laser molecular beam epitaxy. Well-controlled BaTiO3/SrTiO3 heterostructure was studied with in situ reflective high energy electron diffraction and ex situ atomic force microscopy, x-ray diffraction, and transmission electron microscopy. The growth mode map of BaTiO3 thin films was obtained as a function of substrate temperature under 600 deg. C for various laser repetition rates. The effective activation energy of surface migration was determined to be 0.33 eV. A mechanism of surface migration in BaTiO3 heteroepitaxy was described for a basic understanding of atomic-scale controlled preparation of ferroelectric heterostructures at low temperature

  6. Measurement of Cs, Sr, K and Ca concentrations in total diet and in important food materials consumed by Indian population: application of the data for the evaluation of Sr/Ca and Cs/K ratios

    International Nuclear Information System (INIS)

    The concentrations of Cs, Sr, K and Ca in total diet and in major food components were determined using the sensitive and reliable analytical method involving the neutron activation analysis technique. The mean concentration of the Cs, Sr, K and Ca in diet were found to be 8.5 ng/g, 2.72 μg/g, 3.45mg/g and 0.60 mg/g respectively. In food materials the elemental concentrations varies from 0.39 -30.40 ng/g for Cs, 0.14-3.75 μg/g for Sr, 0.90-6.8 mg/g for K and 0.036-2.40 mg/g for Ca respectively. The mean concentrations of Cs, Sr, K and Ca in diet and in other food samples were employed to obtain their Cs/K and Sr/Ca ratios. These ratios can be of use in predicting the Sr and Cs contents in body organs of interest based on the knowledge Ca and K content in the organs. The mean Cs/K ratio of 1.82 E-06 in the food materials was found to be comparable with that of 2.46E-06 in diet. Whereas the mean Sr/Ca ratio of 6.89E-03 obtained from the food materials was found to be twice that of total diet (3.33E-03).(author)

  7. Interface enhanced functionalities in BaTiO3/CaTiO3 superlattices

    Science.gov (United States)

    Wu, Xifan

    2014-03-01

    Interface engineering of oxide thin films has led to the development of many intriguing physical properties and new functionalities, in which the oxygen rotation and tilting take an crucial role. The oxygen octahedral tilt has been considered to be a coherent motion in the oxide thin-films, based on which the tilt is often neglected in the modeling of ABO3 superlattices. However, combined with state-of-art experimental high-resolution electron microscopic image, our first-principles results clearly show that oxygen octahedral tilt should be more appropriately defined by the tilting angles of two individual pyramids. Each pyramid will tilt rather independently as a function of its local chemical environment. Considering the oxygen octahedral rotation at the same time, the new picture of oxygen octahedral tilting will induce a novel interface effect, in which an unstable structure in bulk CaTiO3 will be stabilized at the interface in BaTiO3/CaTiO3 superlattice. This novel interface effect induces large polarizations both in-plane and out-of-plane with a corresponding enhanced piezoelectricity. The above scenario successfully explains the recent experimental discoveries in BaTiO3/CaTiO3 superlattices by H. Lee's and P. Evan's groups respectively.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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+ or Ba2+ impurities under existence of 1 at% Sr2+ impurity were calculated via the first-principles density functional theory. The substitution enthalpy of LiCl crystals having 1 at% Sr2+ showed slightly decreased value than those without Sr2+ 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. Hysteresis and relaxation in TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} superconducting polycrystals

    Energy Technology Data Exchange (ETDEWEB)

    Batista-Leyva, A J [Physics Department, Engineering Faculty, University of Holguin, Holguin 80100 (Cuba); Cobas, R [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Orlando, M T D [Physics Department, Universidade Federal do Espiritu Santo, Vitoria ES 29060-900 (Brazil); Altshuler, E [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba)

    2003-08-01

    We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), (Hg, Re)Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} (HBCCO) and (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-{delta}} (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model.

  11. Regulation of plant immunity through ubiquitin-mediated modulation of Ca(2+) -calmodulin-AtSR1/CAMTA3 signaling.

    Science.gov (United States)

    Zhang, Lei; Du, Liqun; Shen, Chenjia; Yang, Yanjun; Poovaiah, B W

    2014-04-01

    Transient changes in intracellular Ca(2+) concentration are essential signals for activation of plant immunity. It has also been reported that Ca(2+) signals suppress salicylic acid-mediated plant defense through AtSR1/CAMTA3, a member of the Ca(2+) /calmodulin-regulated transcription factor family that is conserved in multicellular eukaryotes. How plants overcome this negative regulation to mount an effective defense response during a stage of intracellular Ca(2+) surge is unclear. Here we report the identification and functional characterization of an important component of ubiquitin ligase, and the associated AtSR1 turnover. The AtSR1 interaction protein 1 (SR1IP1) was identified by CytoTrap two-hybrid screening. The loss-of-function mutant of SR1IP1 is more susceptible to bacterial pathogens, and over-expression of SR1IP1 confers enhanced resistance, indicating that SR1IP1 acts as a positive regulator of plant defense. SR1IP1 and AtSR1 act in the same signaling pathway to regulate plant immunity. SR1IP1 contains the structural features of a substrate adaptor in cullin 3-based E3 ubiquitin ligase, and was shown to serve as a substrate adaptor that recruits AtSR1 for ubiquitination and degradation when plants are challenged with pathogens. Hence, SR1IP1 positively regulates plant immunity by removing the defense suppressor AtSR1. These findings provide a mechanistic insight into how Ca(2+) -mediated actions are coordinated to achieve effective plant immunity. PMID:24528504

  12. Dielectric Enhancement and Maxwell-Wagner Effect in Polycrystalline BaTiO3/Ba0.2Sr0.8TiO3 Multilayered Thin Films

    Institute of Scientific and Technical Information of China (English)

    葛水兵; 沈明荣; 宁兆元

    2002-01-01

    Polycrystalline BaTiO3/Ba0.2Sr0.sTiO3 multilayer thin films were fabricated by pulsed laser deposition onto Pt/Ti/SiO2/Si substrates with various stacking periodicities. The dielectric constant of the films was obviously enhanced with the decrease of the individual layer thickness, while the dielectric loss was kept at a low level comparable to that of the pure Ba0.6Sr0.4TiO3 thin films. The Maxwell-Wagner model is used to explain the experimental data.

  13. Hydration and proton transport in solid solutions based on Ba2CaWO6

    International Nuclear Information System (INIS)

    Hydrated alkaline earth metal tungstates Ba4Ca2+xW2-xO12-2x with perovskite like structure have been investigated by methods of thermal gravimetric analysis, NMR H1, IR spectroscopy and Raman scattering; measurements of electric conductivity and transfer numbers have been conducted with variations of T, pO2, pH2O. Solid solutions are capable reversibly intercalated water and show high temperature neutron transport. Proton localization at oxygen leads to the appearance of energetically nonequivalent OH-groups, small part of protons are present in the forms H2O and H3O+

  14. Critical currents in Tl2Ca2Ba2Cu3O10 single crystals

    International Nuclear Information System (INIS)

    Tl2Ca2Ba2Cu3O10 single crystals were investigated by SQUID magnetometry and in a Faraday magnetometer up to magnetic fields of 8 T. The transition temperature Tc, the irreversibility line and the magnetization were measured. The critical current densities Jc were determined from the hysteric magnetization loops using an anisotropic Bean model. We find that annealing in oxygen does not rise the superconducting transition to higher temperatures. Jc is high at low temperatures, but drops sharply above 20 K. The irreversibility line is very flat over a wide range of temperatures down to T/Tc∼0.3 and follows an exponential law. (orig.)

  15. High-Tc superconductivity of Tl-Ba-Ca-Cu-O samples

    International Nuclear Information System (INIS)

    A TlBaCaCuO4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the sample exhibits superconductivity with an onset of 121 K and zero resistivity of 106 K and the other part of them shows a sharp drop in resistivity at 130 K which hints at an existence of superconducting grains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of critical magnetic fields. (author). 5 refs, 6 figs

  16. Evaluation of formation enthalpies of compounds with magnetoplumbate structure MFe12O19 (M = Pb, Sr, Ba), as well as barium ferrites

    International Nuclear Information System (INIS)

    Formation enthalpies of ferrites with magnetoplumbate structure MFe12O19 (M = Pb, Sr, Ba), as well as barium ferrites, were calculated by approximate methods with the use of enthalpies of cation coordination change during formation of compounds from simple oxides. For SrFe12O19 ΔHf = -38 kJ/mol

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

    International Nuclear Information System (INIS)

    Graphical abstract: Polarization hysteresis (P–E) loops of the (Pb0.85Ba0.08Sr0.03La0.03) (Zr0.74Sn0.22Ti0.04) 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/cm3 at 55 °C, and at 45 °C the energy density was ∼1.24 J/cm3. 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/cm3). - Highlights: • Ba2+, Sr2+ co-doping caused the Tc of PLZST moved to the lower temperature (Tc ≈ 40 °C). • The ΔE was so smaller, EAF ≈ 90 kV/cm and EFA ≈ 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/cm3. - Abstract: (Pb0.85Ba0.08Sr0.03La0.03)(Zr0.74Sn0.22Ti0.04) (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 (Tc ≈ 40 °C). Ba, Sr co-doped PLZST AFE ceramics exhibited excellent electrical properties, the AFE to ferroelectric (FE) transition occurred at field EAF ≈ 90 kV/cm, and the transition from FE to AFE occurred at EFA ≈ 85 kV/cm. The maximum relative permittivity was about 4800, occurring at a field near the AFE to FE transition point, with a dielectric loss of 0.006. The samples exhibited small ΔE and slanted hysteresis loops with a large breakdown field of 100 k

  18. Provenancing fish in freshwaters of the Alpine Foreland using Sr/Ca and 87Sr/86Sr ratios in otoliths and otolith shape parameters

    Directory of Open Access Journals (Sweden)

    Johannes Oehm

    2015-12-01

    Although the studied freshwaters were located only in a 50 km range around lake Chiemsee on a similar geological background, differences in water chemistry, fish otolith chemistry and shape were identified. Species specific differences in reflection of the Sr/Ca ratio of a specific water body were detected. Microchemical and morphological otoliths analyses complemented each other and allowed assigning fish to specific groups of waters of origin. This information provides an important basis for the further application of otolith chemistry and shape analysis in the Alpine foreland for a diverse range of ecological questions.

  19. Freeze drying of (Bi,Pb)2Sr2Ca2Cu3O10+y

    International Nuclear Information System (INIS)

    It is well known that Bi2Sr2Ca2Cu3O10+y (2223) is difficult to prepare as a single phase; sintering times of the order 102 h are required to equilibrate the starting powders. Co-precipitation is an advantageous processing technique because nearly atomic-scale mixing can be achieved. However, differential rates of precipitation make it difficult to achieve a uniform mixture of precipitated salts. Sol-gel processing is also advantageous but, like co-precipitation, it has the problem of favouring the formation of carbonates (SrCO3 and CaCO3) that are stable during calcining. Freeze drying is a superior technique because the use of flash frozen nitrate solutions avoids the aforementioned problems. The present work compares some of the various procedures for the formation of 2223

  20. Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

    Science.gov (United States)

    Chiang, C. K.; Wong-Ng, W.; Cook, L. P.; Freiman, S. W.; Hwang, N. M.; Vaudin, M.; Hill, M. D.; Shull, R. D.; Shapiro, A. J.; Swartzendruber, L. J.

    1991-01-01

    The bismuth based high T sub c superconductors can be processed via an amorphous Bi-Pb-Sr-Ca-Cu oxide. The amorphous oxides were prepared by melting the constituent powders in an alumina crucible at 1200 C in air followed by pouring the liquid onto an aluminum plate, and rapidly pressing with a second plate. In the amorphous state, no crystalline phase was identified in the powder x ray diffraction pattern of the quenched materials. After heat treatment at high temperature the amorphous materials crystallized into a glass ceramic containing a large fraction of the Bi2Sr2Ca2Cu3O(x) phase T sub c = 110 K. The processing method, crystallization, and results of dc electrical resistivity and ac magnetic susceptibility measurements are discussed.

  1. Magnetic properties of a chemically synthesized Bi(Pb)SrCaCuO superconductor

    International Nuclear Information System (INIS)

    It has been reported that the presence of lead serves to increase the fraction of high temperature phase in the Bi-Sr-Ca-Cu-O system prepared by a solid state reaction. To test if this is also the case for material prepared by a chemical method, a lead containing bismuth superconductor (Bi1.5Pb0.5Sr1.5Ca1.75Cu2Ox) was chemically synthesized and its magnetic properties measured. The material obtained contained a large fraction (≅ 50%) of a phase with a superconducting onset temperature near 110 K. Inspection of the AC susceptibility with a small applied transverse magnetic field indicated the presence of additional superconducting phases with lower onset temperatures. Flux depinning was found to occur at relatively low fields

  2. Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

    International Nuclear Information System (INIS)

    The bismuth based high T sub c superconductors can be processed via an amorphous Bi-Pb-Sr-Ca-Cu oxide. The amorphous oxides were prepared by melting the constituent powders in an alumina crucible at 1200 C in air followed by pouring the liquid onto an aluminum plate, and rapidly pressing with a second plate. In the amorphous state, no crystalline phase was identified in the powder x ray diffraction pattern of the quenched materials. After heat treatment at high temperature the amorphous materials crystallized into a glass ceramic containing a large fraction of the Bi2Sr2Ca2Cu3O(x) phase T sub c = 110 K. The processing method, crystallization, and results of dc electrical resistivity and ac magnetic susceptibility measurements are discussed

  3. Annealing studies of α-irradiated Bi-Sr-Ca-Cu-O superconductors

    International Nuclear Information System (INIS)

    Polycrystalline samples of Bi2Sr2CaCu2O8+x (Bi-2212) and Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06O10+x (Bi-2223) superconductors irradiated with 40 MeV α-particles at various doses have been annealed in oxygen and air. Irradiated Bi-2212 samples have been annealed at 450 deg C and Bi-2223 samples have been annealed at 500 deg C as well as at high temperature (850 deg C). At lower dose of irradiation, Tc of Bi-2212 samples has decreased after annealing. In case of Bi-2223, there has been partial recovery by annealing at low temperature. But, annealing at high temperature has been detrimental. (author). 6 refs., 3 tabs., 3 figs

  4. Processing and microstructural development of Ag-clad Bi-Sr-Ca-Cu-O tapes

    International Nuclear Information System (INIS)

    Ag-clad Bi2Sr2CaCu2Ox (2212) and (Bi,Pb)2Sr2Ca2Cu3Ox (2223) tapes were fabricated by drawing and rolling. Highly textured microstructures and high critical current density values were obtained for each system. However, the heat treatments and phase evolutions for 2212 and 2223 were different. For 2212, nearly phase-pure powder was used, and the heat treatments consisted of partial melting followed by solid-state sintering. For 2223, several compositions, initial phases, and sintering schedules were used. Results are discussed in terms of microstructural evolution as observed by X-ray diffraction and scanning and transmission electron microscopy

  5. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

    Science.gov (United States)

    Naveed-Ul-Haq, M; Shvartsman, Vladimir V; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  6. Structural study of Sr0.3Ba0.7Nb2O6 and La0.030Sr0.255Ba0.700Nb2O6 ceramic systems

    International Nuclear Information System (INIS)

    Sr0.3Ba0.7Nb2O6 (SBN) and La0.030Sr0.255Ba0.700Nb2O6 (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 deg. C) and later sintered both at 1400 deg. C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A1 site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.

  7. Preparation and characterization of glossy and superconducting (Bi, Pb, Sb)-Sr-Ca-Cu-O systems

    International Nuclear Information System (INIS)

    Superconducting compounds with nominal compositions Bisub(1.7)Pbsub(0.3) Srsub(1.6)Ca2Cusub(3.4)Ox and Bisub(1.9)Sbsub(0.1)Sr2Ca2Cu3Oy have been synthesized by ceramic and glass routes and characterized by X-ray diffraction, electrical resistivity and dielectric constant measurements. The zero-electrical resistance temperatures are about 70 K. The dielectric constant of the glasses at room temperature is around 30. (author). 5 refs., 8 figs

  8. Sorption of Ba and Sr on potassium-copper, -nickel, -cobalt, -zinc hexacyanoferrate(II) and DOWEX-50 from hydrochloric and sulfuric acid solutions

    International Nuclear Information System (INIS)

    We have determined sorption coefficients of Ba and Sr on nickel-potassium hexacyanoferrate(II) (NiNF), cobalt-potassium hexacyanoferrate(II) (CoNF), cupric-potassium hexacyanoferrate(II) (CuNF) and on the ion exchange resin (Dowex-50) in the sulfuric and hydrochloric acid solutions. The results indicate that Ba is strongly sorbed on the investigated hexacyanoferrates and Dowex-50 from sulfuric acid while it is sorbed from the hydrochloric acid at the low acid concentrations. The sorption mechanism of Sr from H2SO4 and HCl is similar, at all presented acid concentrations the values of the coefficients for Sr are rather low. (author)

  9. Isomorphous substitutions in SrO-BaO-Al2O3-TiO2-SiO2 system

    International Nuclear Information System (INIS)

    The SrO-BaO-Al2O3-TiO2-SiO2 system is studied. It is shown that in the samples with higher SrO concentration in comparison with BaO and at their equal quantities solid solutions on the base of triclinic strontium anorthite are formed, and at the increased BaO content - on the base of monoclinic celsian. The homogeneity range of the BaAl2Si2O8 celsianic form is relatively narrower in comparison with SrAl2Si2O8. The Al2O3/(SrO + BaO) ratio considerably influence isomorphism in the SrO-BaO-Al2O3-Ti02-SiO2 system: in the studied glasses the increase of this value from 0.5 to 1.25 reduces the temperature of the beginning of solid solution formation from 1470 to 1220 K

  10. On the electronic structure of CaCuO2 and SrCuO2

    OpenAIRE

    Rosner, H.; Divis, M.; Koepernik, K.; Drechsler, S. -L.; Eschrig, H.

    2000-01-01

    Recent electronic structure calculations for the prototypical lowdimensional cuprate compounds CaCuO2 ans SrCuO2 performed by Wu et. al. (J. Phys.: Condens. Matter v. 11 p.4637 (1999))are critically reconsidered, applying high precision full-potential bandstructure methods. It is shown that the bandstructure calculations presented by the authors contain several important inconsistencies, which make their main conclusions highly questionable.

  11. Microstructure of laser floating zone (LFZ) textured (Bi,Pb)-Sr-Ca-Cu-O superconductor composites

    International Nuclear Information System (INIS)

    Directionally solidified high temperature superconducting (Bi,Pb)-Sr-Ca-Cu-O pure ceramics and composites were obtained using a laser floating zone (LFZ) apparatus. The presence of secondary non-superconducting and metallic phases as well as their solidification habit have been analysed. The influence of the LFZ growth conditions and the precursor composition on the microstructure of the final products was studied using optical and electron microscopies. (orig.)

  12. Evaluating the chemical compatibility of potential substrate materials for Bi-Sr-Ca-Cu-O films

    International Nuclear Information System (INIS)

    Potential substrate and buffer layer materials for Bi2Sr2CaCu2Ox (BSCCO) were surveyed using bulk ceramic processing techniques. Of the materials tested, only Ag was inert with respect to BSCCO. MgO slightly degrades the superconducting onset temperature and volume fraction. LaGaO3 may be a feasible ceramic substrate for BSCCO, although some reaction appears to occur

  13. "Quick and dirty" technology for fabrication of a single BiSrCaCuO mesas

    OpenAIRE

    Vopilkin, E. A.; Chiginev, A. V.; Revin, L. S.; Tropanova, A. N.; Shuleshova, I. Yu.; Okhapkin, A. I.; Shovkun, A. D.; Kulakov, A. B.; Pankratov, A. L.

    2014-01-01

    The technology of wet etching allowing fabrication of standalone BiSrCaCuO mesa structures was proposed. The produced mesas can be produced much thicker than ones usually being studied. The time required for the fabrication is much smaller in comparison with the standard method of ion milling. The process used is controllable which provides acceptable precision of mesa fabrication. The current-voltage characteristics of the sample showing Josephson nature were obtained. The qualitative compar...

  14. Nature of the irreversibility line in Bi2Sr2CaCu2O8

    International Nuclear Information System (INIS)

    Local vortex dynamics in Bi2Sr2CaCu2O8 single crystals was studied using novel microscopic GaAs/AlGaAs Hall-sensor arrays. The irreversibility line (IL) is found to exist in the absence of bulk pinning. At high temperatures the IL is due to geometrical barriers whereas at intermediate temperatures the irreversible behavior is determined by surface barriers. Bulk pinning governs the IL only at T < 22 K. (orig.)

  15. Effect of doping Ca on polaron hopping in LaSr2Mn2O7

    Indian Academy of Sciences (India)

    S N Bhatia; Osama A Yassin

    2002-05-01

    From the transport studies in the bilayer manganites LaSr2-CaMn2O7, we have found the variable-range hopping model proposed by Viret et al to be inadequate to describe the transport of charge in these materials. The polarons appear to hop to their nearest neighbors with an activation energy, which in part is dependent on the magnetic interactions in the lattice.

  16. Effect of doping in the Bi-Sr-Ca-Cu-O superconductor

    Science.gov (United States)

    Akbar, S. A.; Wong, M. S.; Botelho, M. J.; Sung, Y. M.; Alauddin, M.; Drummer, C. E.; Fair, M. J.

    1991-01-01

    The results of the effect of doping on the superconducting transition in the Bi-Sr-Ca-Cu-O system are reported. Samples were prepared under identical conditions with varying types (Pb, Sb, Sn, Nb) and amounts of dopants. All samples consisted of multiple phases, and showed stable and reproducible superconducting transitions. Stabilization of the well known 110 K phase depends on both the type and amount of dopant. No trace of superconducting phase of 150 K and above was observed.

  17. Preparation of thermal infrared and microwave absorber using SrTiO3/BaFe12O19/polyaniline nanocomposites

    Science.gov (United States)

    Hosseini, Seyed Hossein; Zamani, Parisa

    2016-01-01

    In this research, first, SrTiO3 was synthesized as thermal infrared (TIR) absorbent and core and then BaFe12O19 as microwave absorbent was prepared on SrTiO3 via co-precipitation method as first shell. Second, polyaniline (PANI) was coated on SrTiO3/BaFe12O19 NPs (NPs) via in situ polymerization by multi core-shell structures (SrTiO3/BaFe12O19/PANI). Nanometer size and structures of samples were measured by TEM, XRD and FTIR. Morphology of nanocomposite was showed by SEM images. The magnetic and electric properties were also performed by VSM and four probe methods. The TIR absorption and microwave reflection loss of nanocomposites were investigated at 10-40 μm and 8-12 GHz, TIR and microwave frequencies, respectively. The results showed that the SrTiO3/BaFe12O19/PANI nanocomposites have good compatible electric and magnetic properties and hence the microwave absorbency show wide bandwidth properties. The infrared thermal image testing showed that the ability of infrared thermal imaging was increased by increasing SrTiO3/BaFe12O19 as core and independent to increasing PANI as final shell.

  18. Electronic and magnetic structure of (Ca,Sr)RuO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Assmann, Andrea; Uebe, Stephan; Wissinger, Markus [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik (Germany); Karlsruhe Institute of Technology, Fakultaet fuer Physik (Germany); Merz, Michael; Fuchs, Dirk; Nagel, Peter; Schuppler, Stefan [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik (Germany); Loehneysen, Hilbert von [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik (Germany); Karlsruhe Institute of Technology, Physikalisches Institut (Germany)

    2011-07-01

    The 4d transition metal oxide (Ca,Sr)RuO{sub 3} exhibits ferromagnetic order in the doping range 0.4 {<=} x {<=}1 while it is a paramagnetic metal for x < 0.4. Since (Ca,Sr)RuO{sub 3} remains essentially isostructural and has a similar electronic configuration throughout the doping series, the differences in the magnetic properties might be attributed to chemical pressure effects. To verify a possible dependence of direction and/or magnitude of the magnetic moments on pressure, (Ca,Sr)RuO{sub 3} films were deposited on different substrates (LSAT, STO, DyScO{sub 3}=DSO). The magnetic and electronic structure of the samples was studied by soft x-ray absorption and magnetic circular dichroism at the Ru M{sub 2,3} and O K edges. In addition, depth-dependent information on element-specific core levels was obtained by varying the photon energy in soft x-ray photoemission spectroscopy. Various implications will be discussed.

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

    Science.gov (United States)

    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.

  20. 110K Bi-Sr-Ca-Cu-O superconductor oxide and method for making same

    International Nuclear Information System (INIS)

    A superconductor is disclosed consisting of a sufficiently pure phase of the oxides of Bi, Sr, Ca, and Cu to exhibit a resistive zero near 110K resulting from the process of forming a mixture of Bi2O3, SrCO3, CaCO3 and CuO into a particulate compact wherein the atom ratios are Bi2, Sr1.2-2.2, Ca1.8-2.4, Cu3. Thereafter, heating the particulate compact rapidly in the presence of oxygen to an elevated temperature near the melting point of the oxides to form a sintered compact, and then maintaining the sintered compact at the elevated temperature for a prolonged period of time. The sintered compact is cooled and reground. Thereafter, the reground particulate material is compacted and heated in the presence of oxygen to an elevated temperature near the melting point of the oxide and maintained at the elevated temperature for a time sufficient to provide a sufficiently pure phase to exhibit a resistive zero near 110K. 7 figs

  1. Preliminary results of Sr:Ca ratios of Coilia nasus in otoliths by micro-PIXE

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, L. [Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai 200433 (China); Guo, H. [Institute of Life Science, Shanghai Fisheries University, Shanghai 200090 (China); Shen, H. [Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai 200433 (China)]. E-mail: haoshen@fudan.edu.cn; Li, X. [Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201800 (China); Tang, W. [Institute of Life Science, Shanghai Fisheries University, Shanghai 200090 (China); Liu, J. [Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201800 (China); Jin, J. [Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai 200433 (China); Mi, Y. [Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai 200433 (China)

    2007-07-15

    Coilia nasus, distributed in Changjiang River as well as northwest Pacific, has a high economic value owing to its delicacy and nutritional value. Recently, the fishing yields in Changjiang River have decreased dramatically due to excessive fishing and changes in the aquatic ecology. In order to prevent excessive fishing effectively, the life history pattern of C. nasus should be known in detail. Ootoliths contain much information about a fish's life history, because elemental concentrations remain unaltered after deposition, and can be analysed. C. nasus collected from Jing Jiang (lower reaches of the Changjiang River) and Jiu Duan Sha (the estuary of the Changjiang River) were studied by measuring Sr:Ca ratios in their otoliths using micro-PIXE. On average, the Sr:Ca ratios of estuarine C. nasus were found to be higher. The Sr:Ca ratios were higher in the core regions and lower in the outermost marginal regions, and shows fluctuations in certain regions. Possible corresponding life history patterns are discussed.

  2. Preliminary results of Sr:Ca ratios of Coilia nasus in otoliths by micro-PIXE

    International Nuclear Information System (INIS)

    Coilia nasus, distributed in Changjiang River as well as northwest Pacific, has a high economic value owing to its delicacy and nutritional value. Recently, the fishing yields in Changjiang River have decreased dramatically due to excessive fishing and changes in the aquatic ecology. In order to prevent excessive fishing effectively, the life history pattern of C. nasus should be known in detail. Ootoliths contain much information about a fish's life history, because elemental concentrations remain unaltered after deposition, and can be analysed. C. nasus collected from Jing Jiang (lower reaches of the Changjiang River) and Jiu Duan Sha (the estuary of the Changjiang River) were studied by measuring Sr:Ca ratios in their otoliths using micro-PIXE. On average, the Sr:Ca ratios of estuarine C. nasus were found to be higher. The Sr:Ca ratios were higher in the core regions and lower in the outermost marginal regions, and shows fluctuations in certain regions. Possible corresponding life history patterns are discussed

  3. New Tl-Ba-Ca-Cu-O (1234 and 1245) superconductors with Tc > 117 K

    International Nuclear Information System (INIS)

    The new TlBa/sub 2/Ca/sub 3/Cu/sub 4/O/sub 11/ (1234) and TlBa/sub 2/Ca/sub 4/Cu/sub 5/O/sub 13/ (1245) superconductors with new composition and new structure have been designed and synthesized for the first time. The compounds have the Tc values of 116 -- 122 K. The highest Tc value was obtained for the 1234 phase. These are single Tl-O layer compounds with less Tl content than a half of that in the previous 2223 phase. The structure of the compounds is a simple tetragonal phase with the lattice constants of a = b = 3.85 A and c = 19.1 A for the 1234 phase and a = b = 3.85 A and c = 22.3 A for the 1245 phase. The electron diffraction patterns and the lattice images from a high resolution TEM have confirmed the oxygen-deficient layered-perovskite structure with the space group of P4/mmm. The c-lattice constant follows the c-axis rule of a linear relation of c = 6.3 + 3.2 n (n = the number of Cu-O layer). The Tc value is strongly related to the valence of Cu ion

  4. Magnetic and electrical properties on possible room temperature hybrid multiferroic BaTiO3/La2/3Sr1/3MnO3

    Science.gov (United States)

    Ordoñez, John Edward; Gómez, María Elena; Lopera Muñoz, Wilson; Prieto, Pedro Antonio; Thin Film Group Team; Center of Excellence on Novel Materials-CENM, Cali, Colombia Team

    2015-03-01

    We addressed to deposit the ferromagnetic phase of the La1-xSrxMnO3 and the ferroelectric BaTiO3 for possible hybrid multiferroic heterostructure. We have optimized the growth parameters for depositing BaTiO3(BTO) / La2/3Ca1/3MnO3(LCMO) / (001) SrTiO3 by sputtering RF and DC, respectively, in pure oxygen atmosphere and a substrate temperature of 830°C. Keeping fixed the magnetic layer thickness (tLSMO = 40 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 40, 80, 100 nm). We want to point out the influence of the thicknesses ratio (tBTO/tLSMO) on electrical and magnetic properties. From x-ray diffraction (XRD) analysis, we found the bragg peaks for LSMO maintain its position but BTO peak shift to lower Bragg angle indicating a strained BTO film. Magnetization and polarization measurements indicate a possible multiferroic behavior in the bilayers. Hysteresis loop measurements of bilayers show ferromagnetic behavior. Authors thank Instituto de Nanociencia de Aragón, Zaragoza, Spain. Work partially supported by COLCIENCIAS-UNIVALLE Project 110656933104 Contract No. 2013-0002, CI 7917 and CI 7978.

  5. Effects of Sr-substitution on the structural and magnetic behavior of Ba-based Y-type hexagonal ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mukhtar, E-mail: mukhtarahmad25@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Ali, Qasim; Ali, Ihsan; Ahmad, Ishtiaq [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Azhar Khan, M. [Department of Physics, The Islamia University of Bahawalpur 63100 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Murtaza, G. [Centre for Advanced Studies in Physics, G.C. University, Lahore (Pakistan); Rana, M.U., E-mail: mazharrana@bzu.edu.pk [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan)

    2013-12-15

    Highlights: •Sr-substituted Y-type hexaferrites synthesized by sol–gel method have been investigated. •Platelet grains with well defined hexagonal shape are suitable for microwave absorbers. •Saturation magnetization values were calculated by the law of approach to saturation. •Coercivity of a few hundred oersteds found for all samples is suitable for EM materials. -- Abstract: Sr-substituted samples of Y-type hexagonal ferrites with chemical formula Ba{sub 2−x}Sr{sub x}Ni{sub 2}Fe{sub 12}O{sub 22} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized using the sol–gel autocombustion method and were sintered at 1150 °C for 3 h. The samples were investigated by differential thermal and thermogravimetry analysis, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry. X-ray diffraction analysis reveals that single phase samples can be achieved by substituting Sr{sup 2+} ions at Ba{sup 2+} sites in Y-type hexagonal ferrites. X-ray density and bulk density were observed to decrease whereas porosity increased with increasing Sr-concentration. All the samples show well defined hexagonal shape which is favorable for microwave absorbing purposes. The saturation magnetization values were calculated from M–H loops by the law of approach to saturation. The loops show low values of coercivity of a few hundred oersteds which is one of the necessary conditions for electromagnetic (EM) materials and is suitable for security, switching, sensing and high frequency applications.

  6. Performance of Ca{sub 1-x}Sr{sub x}TiO{sub 3} as barriers in dielectric barrier discharges with different Sr content

    Energy Technology Data Exchange (ETDEWEB)

    Li Ruixing; Tang Qing; Yin Shu; Sato Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2007-09-07

    Plasma assisted catalytic technology, which uses synergetic technologies between the catalyst and plasma, has attracted much attention over the past several years. Theoretically, permittivity of a dielectric barrier influences the transferred charge of a microdischarge; thus high permittivity can improve the plasma reaction in a dielectric barrier discharge (DBD) plasma reactor. Despite the increased interest in the chemical processes, very little has been reported concerning the influence of materials of a dielectric barrier on DBD plasma reactions, since a high permittivity barrier generally exhibits low fracture strength and low dielectric strength making it break down under strong current pulses. In the present study, Ca{sub 1-x}Sr{sub x}TiO{sub 3} (0.1 {<=} x {<=} 0.4) which possesses a high permittivity and a high fracture strength was prepared by liquid phase sintering and was used as a dielectric barrier for the destruction of carbon dioxide by a DBD plasma reaction. The permittivity of Ca{sub 1-x}Sr{sub x}TiO{sub 3} (0.1 {<=} x {<=} 0.4) increased with increasing SrTiO{sub 3} content; however, the observed CO{sub 2} conversion became greatest using Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} and then decreased with increasing SrTiO{sub 3} content. These results imply that the reactivity of CO{sub 2} destruction does not monotonously increase with increased permittivity of the Ca{sub 1-x}Sr{sub x}TiO{sub 3} barriers. Both amplitude and density of the current pulses ignited by Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} were much greater than that of Ca{sub 0.6}Sr{sub 0.4}TiO{sub 3}. Further, it was confirmed that a plasma reaction uniformly proceeded using the Ca{sub 0.8}Sr{sub 0.2}TiO{sub 3} barrier, but proceeded non-uniformly using the Ca{sub 0.6}Sr{sub 0.4}TiO{sub 3} barrier by observing the carbon deposition profiles on the surfaces of the barriers.

  7. Synchrotron X-ray diffraction study of the Ba1−xSrSnO3 solid solution

    International Nuclear Information System (INIS)

    At room temperature the sequence of phases with increasing amounts of strontium in the stannate perovskite system Ba1−xSrSnO3 has been established from high resolution synchrotron X-ray powder diffraction. The observed sequence orthorhombic (Pbnm), orthorhombic (Ibmm), tetragonal (I4/mcm), and cubic (Pm3-bar m) is a consequence of the sequential introduction of cooperative tilting of the corner sharing SnO6 octahedra. The cell volume changes smoothly across the series with no obvious discontinuities associated with the phase transitions. - Graphical abstract: Portions of the synchrotron X-ray diffraction profiles (λ=0.82453 Å) from selected Ba1−xSrxSnO3 samples together with the results of fitting by the Rietveld method. Highlights: ► Structures of the stannate perovskites Ba1−xSrSnO3 refined from synchrotron XRD. ► The sequence Pm3-bar m→I4/mcm→Ibmm→Pbnm results from tilting of the octahedra. ► The tilting maintains optimal bonding of the cations seen from the BVS analysis

  8. Giant Tc shift in HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ superconductors due to Hg-Tl exchange

    International Nuclear Information System (INIS)

    The irreversibility lines of epitaxial thin films of HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ, whether deduced from field-induced magnetoresistive broadening or onset of nonhysteretic magnetization, were found to coincide when plotted against reduced temperature, showing the same exponential-decay temperature behavior for T/Tcc>0.8 (where Tc is zero-field, zero-resistivity critical temperature). These results indicate that replacing Tl with Hg has no noticeable effect on the anisotropy and suggests that Tc is not determined by anisotropy. copyright 1999 The American Physical Society

  9. Growth of Nucleation Sites on Pd-doped Bi_2Sr_2Ca1 Cu_2O_8+δ

    Science.gov (United States)

    Kouzoudis, D.; Finnemore, D. K.; Xu, Ming; Balachandran

    1996-03-01

    Enviromental Scanning Electron Microscope has shown evidence that during the growth of Bi_2Sr_2Ca_2Cu_3O_10+δ from mixed powders of Pb-doped Bi_2Sr_2Ca_1Cu_2O_8+δ and other oxides, a dense array of hillocks or mesas grow at the interface between an Ag overlay and Pb doped Bi_2Sr_2Ca_1Cu_2O_8+δ grains. These hillocks develop a texture that looks like ''chicken pox'' during the ramp up to the reaction temperature starting at about 700^circ C and they are about 500 to 1000 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurments indicate that the hillocks are re-crystallization of (Bi,Pb)_2Sr_2Ca_1Cu_2O_8+δ and are definetely not a Pb rich phase

  10. Multifunctional dual-tunable multiferroic Ba0.25Sr0.75TiO3-BiFeO3-Ba0.25Sr0.75TiO3 trilayered structure for tunable microwave applications

    International Nuclear Information System (INIS)

    A multiferroic trilayered structure composed of a BiFeO3 (BFO) layer and two Ba0.25Sr0.75TiO3 (BST) layers is grown on a Pt/TiO2/SiO2/Si substrate by pulsed laser deposition. The trilayered BST/BFO/BST thin film structure exhibits a significant tuning response for the dielectric constant with an electric field and a magnetic field, respectively. Microwave devices based on such multifunctional materials can offer dual, i.e. electric and magnetic, tuning possibility and extra flexibility in designing and shaping the device performances.

  11. Development of materials for thermoelectric generators: superlattice Ca3Co4O9-Sr3Co4O9

    International Nuclear Information System (INIS)

    We have prepared multilayered structures composed from misfit layered Ca- and Sr- cobaltates by Metalorganic Aerosol Deposition technique. X-ray and Transmission Electron Microscopy analyzes confirms the forming superlattice along c direction from common CoO2 interlayers and alternating Ca2CoO3 and Sr2CoO3 layers with periodicity of 4-6 unit cell. Our results indicate the possibility to fabricate artificial material on the base of layered cobaltates for thermoelectric applications. (authors)

  12. Growth and superconducting properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} thin films incorporated with iridate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    De Vero, Jeffrey C.; Hwang, Inwoong; Shin, Hyeonseop; Song, Jong Hyun [Department of Physics, Chungnam National University, Daejeon, 305-764 (Korea, Republic of); Santiago, Alvin Carl; Sarmago, Roland V. [National Institute of Physics, University of the Philippines, Diliman, 1101 (Philippines); Lee, Doopyo [Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of); Chang, Jungwon [Department of Display and Semiconductor Physics, Korea University, Sejong Campus, Sejong, 339-700 (Korea, Republic of); Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of); Kim, Jinhee [Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of)

    2014-08-15

    Iridate nanoparticle AIrO{sub 3} (A = Sr, Ba) incorporated Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} (Bi-2212) thin films were successfully grown using pulsed laser deposition with post-growth ex situ heat treatment. Nanosized particles of SrIrO{sub 3} (Sr-iridate) and BaIrO{sub 3} (Ba-iridate) were deposited on top of MgO (100) substrate, followed by Bi-2212 layers to investigate their effects on the physical and superconducting properties of Bi-2212 thin films. The number of laser pulses was changed from 450 to 1800 to control the density of iridates in the Bi-2212 matrix. The composite film is then partial-melted at 890 C for 15 min and annealed at 850 C for 5 h in ambient air. Scanning electron microscopy shows that the surfaces of thin films with iridates are more compact with minimal voids and porosity than those of pure Bi-2212 thin films. Both types of iridate incorporation suppress T{sub c-zero} of Bi-2212 thin films. Incorporating Sr-iridate in the Bi-2212 strongly affects T{sub c-zero} than those with Ba-iridate at low density. However, both iridate incorporations result in the expansion of the c-axis lattice constant and variation of Bi/Sr ratio of Bi-2212 films. On the other hand, we observed improvement of the activation energy, U{sub 0}, as well as the self-field critical current density, J{sub c}(0), of Bi-2212 films with incorporated iridates even with suppressed T{sub c-zero}. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Photoluminescence properties of Ca-doped BaMgAl10O17:Eu2+,Mn2+blue phosphor using BaF2 and CaF2 as co-flux

    Institute of Scientific and Technical Information of China (English)

    冶林琴; 朋兴平; 张水合; 王育华; 常文瑞

    2014-01-01

    Ca-doped BaMgAl10O17:Eu2+,Mn2+(BAM) blue phosphors were synthesized by flux assisted solid-state reaction method using CaF2 and BaF2 as co-flux. Good dispersity and particle size homogenization of hexagonal pure phase BAM were obtained by sintering at 1400 °C. The effects of the Ca2+ions content on the structure, morphology and photoluminescence properties of the phosphors were studied. The results indicated that the incorporation of Ca could decrease the lattice constant, improve the homogene-ity and dispersity and enhance the photoluminescence (PL) intensity of the phosphor effectively. The optimum Ba0.86Ca0.04Mg0.97Al10O17:0.1Eu2+,0.03Mn2+PL intensity was enhanced for about 30%and relative brightness was improved about 4%. Furthermore, the synthesized BAM and commercial BAM phosphors were annealed for 30 min at 600 ºC in air. The Ca-doped phos-phors had stronger emission intensity, higher brightness and better chromaticity stability than that of the commercial phosphor. These results indicated that Ca-doped blue phosphors had good potential applications in the commercial tricolor fluorescent lamps as well as in other display and lamps.

  14. Doping effects on protonic conduction in SrCeO3- and BaCeO3 - based perovskites

    International Nuclear Information System (INIS)

    One studied the electric conductivity of SrCe1-xMxO3 and BaCe1-xMxO3 (M - rare-earth elements) proton conductors with the perovskite structure depending on the doping level. Occurrence of maximums and minimums of the proton conductivity was explained on the basis of the typical conductivity was explained on the basis of the typical structure variations of the lattice under doping. One studied the anomalies of BaCe1-xErxO3 ceramics properties within two-phase range on the basis of the concepts about percolation clusters. It is shown, that mobility percolation types in proton-conducting thin films and ceramics should differ essentially

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

    Science.gov (United States)

    Kumar, Mukesh; Umezawa, Naoto; Imai, Motoharu

    2014-05-01

    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 (SrSi2, BaSi2, SrGe2, and BaGe2) 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 Eg ≈ 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 ɛ(ω) = ɛ1(ω) + iɛ2(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.

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

    International Nuclear Information System (INIS)

    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 (SrSi2, BaSi2, SrGe2, and BaGe2) 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 Eg ≈ 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) = ε1(ω) + iε2(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.

  17. Synthesis and dielectric properties of MXTi7O16 (M = Ba and Sr;X = Mg and Zn) hollandite ceramics

    Indian Academy of Sciences (India)

    V M Manisha; K P Murali; S N Potty; V Priyadarsini; R Ratheesh

    2004-04-01

    MXTi7O16 (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (r), loss tangent (tan ) and temperature variation of dielectric constant ($\\tau_{\\varepsilon r}$) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.

  18. Aerosol deposition of Ba0.8Sr0.2TiO3 thin films

    OpenAIRE

    Branković Zorica; Branković G.; Tucić A.; Radojković A.; Longo E.; Varela J.A.

    2009-01-01

    In this work we optimized conditions for aerosol deposition of homogeneous, nanograined, smooth Ba0.8Sr0.2TiO3 thin films. Investigation involved optimization of deposition parameters, namely deposition time and temperature for different substrates. Solutions were prepared from titanium isopropoxide, strontium acetate and barium acetate. Films were deposited on Si (1 0 0) or Si covered by platinum (Pt (1 1 1) /Ti/SiO2/Si). Investigation showed that the best films were obtained at substrate te...

  19. A correlation between the optimum levels of hole doping in the Sr- and Ba-classes of copper oxide superconductors

    International Nuclear Information System (INIS)

    This paper reports on considerations of the in-plane Cu-O bond distance in a variety of cuprate-based superconducting systems which indicate: that an optimum level of hole doping exists in these systems, and that this optimum value is roughly the same for Sr- and Ba-classes of superconductors when one normalizes for structural effects due to the difference in ionic size. Structural adjustment at the optimum level of doping leads to variations in Tc between structure-types

  20. Enhanced ferroelectric properties of Mg doped (Ba,Sr)TiO3 thick films grown on (001) SrTiO3 substrates

    International Nuclear Information System (INIS)

    Highly (001)-oriented 1 mol% Mg doped (Ba0.67,Sr0.33)TiO3 (BST) films with a thickness of 1.25 μm were grown on (110) SrRuO3/(001) SrTiO3 substrates by pulsed laser deposition. X-ray diffraction measurements reveal that the BST thick films have very high crystalline quality, and have a distorted lattice with a large tetragonality a/c = 1.012. The BST thick films have a remanent polarization (Pr) value as large as 10.1 μC/cm2 and a coercive electric field (Ec) value of 65.0 kV/cm. The films possess dielectric constant and loss values of εr = 385.36 and tgδ = 0.038 at 1 kHz and room temperature. The leakage currents of the films are on the order of 10−5 A/cm2 at ± 150 kV/cm. The mechanism for enhancing electric properties of the Mg doped BST films was also discussed.

  1. Enhanced ferroelectric properties of Mg doped (Ba,Sr)TiO{sub 3} thick films grown on (001) SrTiO{sub 3} substrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hong, E-mail: liuh@scu.edu.cn; Zhu Jianguo; Chen Qiang; Yu Ping; Xiao Dingquan

    2012-02-29

    Highly (001)-oriented 1 mol% Mg doped (Ba{sub 0.67},Sr{sub 0.33})TiO{sub 3} (BST) films with a thickness of 1.25 {mu}m were grown on (110) SrRuO{sub 3}/(001) SrTiO{sub 3} substrates by pulsed laser deposition. X-ray diffraction measurements reveal that the BST thick films have very high crystalline quality, and have a distorted lattice with a large tetragonality a/c = 1.012. The BST thick films have a remanent polarization (P{sub r}) value as large as 10.1 {mu}C/cm{sup 2} and a coercive electric field (E{sub c}) value of 65.0 kV/cm. The films possess dielectric constant and loss values of {epsilon}{sub r} = 385.36 and tg{delta} = 0.038 at 1 kHz and room temperature. The leakage currents of the films are on the order of 10{sup -5} A/cm{sup 2} at {+-} 150 kV/cm. The mechanism for enhancing electric properties of the Mg doped BST films was also discussed.

  2. Scintillation properties of LiF–SrF{sub 2} and LiF–CaF{sub 2} eutectic

    Energy Technology Data Exchange (ETDEWEB)

    Yanagida, Takayuki, E-mail: yanagida@lsse.kyutech.ac.jp [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196 (Japan); Kawaguchi, Noriaki [Tokuyama Corporation, 1-1 Mikage-cho, Shunan-shi, Yamaguchi 745-8648 (Japan); Fujimoto, Yutaka [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196 (Japan); Fukuda, Kentaro [Tokuyama Corporation, 1-1 Mikage-cho, Shunan-shi, Yamaguchi 745-8648 (Japan); Watanabe, Kenichi; Yamazaki, Atsushi; Uritani, Akira [Quantum Science and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2013-12-15

    Dopant free eutectic scintillators {sup 6}LiF–SrF{sub 2} and {sup 6}LiF–CaF{sub 2} were developed by the vertical Bridgeman method for the purpose of thermal neutron detection. The molar ratio of LiF and Ca/SrF{sub 2} was 4:1 on its eutectic composition. The α-ray induced radioluminescence spectra of the scintillators showed intense emission peak at 300 nm due to the emission from the self-trapped exciton in Ca/SrF{sub 2} layers. When the samples were irradiated with {sup 252}Cf neutrons, {sup 6}LiF–SrF{sub 2} and {sup 6}LiF–CaF{sub 2} exhibited the light yields of 4700 and 9400 ph/n, respectively. Scintillation decay times of {sup 6}LiF–SrF{sub 2} and {sup 6}LiF–CaF{sub 2} were accepted for scintillation detectors, 90 and 250 ns, respectively. -- Highlights: • Nondoped LiF–CaF{sub 2} and LiF–SrF{sub 2} eutectic scinitillators are reported for the first time. • Two sample showed self-trapped exciton emission. • LiF–SrF{sub 2} sample exhibited the light yield of 9400 ph/n and this value was comparable to conventional materials doped with rare earth ions. • Scintillation decay times of LiF–CaF{sub 2} and LiF–SrF{sub 2} were 250 and 90 ns, respectively.

  3. Effects of Mg or Sr Doping on the Intrinsic Characteristics and Absorption Properties of Micro-nano BaFe12O19 Hollow Multiphase Ceramic Microspheres

    International Nuclear Information System (INIS)

    Micro-nano BaM hollow multiphase ceramic microspheres (HMCMs) and Mg-doped and Sr-doped BaM HMCMs were prepared by combining the low-temperature self-reactive quenching method with heat treatment. The effects of Mg or Sr doping on the intrinsic characteristics and absorption properties of micro-nano BaM HMCMs were investigated. The results showed that Mg or Sr doping modified the phase compositions and particle size distributions of the HMCMs. The Mg- and Sr-doped BaM HMCMs had large real and imaginary permittivities and large real permeabilities at low frequencies relative to the, undoped HMCM. To maximize the absorption properties of the undoped and Sr- and Mg-doped HMCMs, optimal thicknesses of 8, 10 and 10 mm were used with corresponding reflectivities of −8.2, −31.5 and −26.6 dB, respectively. - Highlights: • Three HMCMs were prepared using the low-temperature self-reactive quenching method. • Changes and mechanisms of intrinsic characteristics of Mg or Sr doping were investigated. • Relationships between the intrinsic characteristics and absorption properties were studied

  4. The (Y sub 1-x Ca sub x )(Ba sub 2-x La sub x )Cu sub 3 O sub 7 system and the pseudo 'CaBaLaCu sub 3 O sub 7 '

    Energy Technology Data Exchange (ETDEWEB)

    Keller-Berest, F.; Collin, G. (Laboratoire Chimie Structurale, 75 - Paris (France)); Megtert, S.; Monod, P.; Ribault, M. (Paris-11 Univ., 91 - Orsay (France). Lab. de Physique des Solides)

    1989-11-01

    The (Y{sub 1-x}{sup 3+}Ca{sub x}{sup 2+})(Ba{sub 2-x}{sup 2+}La{sub x}{sup 3+})Cu{sub 3}O{sub 7} system is investigated by X-ray diffraction on powders and single crystals. The homogeneity range is limited to x{approx equal} 0.5, after which the La substitution occurs on both yttrium and barium sites. The pseudo 'Ca(BaLa)Cu{sub 3}O{sub 7}' (x=1) corresponds to a mixture of (Ca{sub 0.5}La{sub 0.5})(Ba{sub 1.25}La{sub 0.75})Cu{sub 3}O{sub 7.125} and CaCuO{sub 2}. All the materials exhibit a superconductive transition, broadened by disorder, with 90 K > T{sub c} ge 75 K. The Meissner effect is large, {approx equal} 60%, for the ideal materials (x{sub Ca}=x{sub La}) and decreases for the compounds with x{sub Ca}

  5. Relationship between coccolith Sr/Ca ratios and coccolithophore production and export in the Arabian Sea and Sargasso Sea

    Science.gov (United States)

    Stoll, Heather M.; Ziveri, Patrizia; Shimizu, Nobumichi; Conte, Maureen; Theroux, Susanna

    2007-03-01

    Coccolithophore CaCO 3 production can account for 20-80% of biogenic carbonate exported from the photic zone, and coccoliths are a dominant biogenic carbonate in many deep-sea sediments. A new method for picking individual coccoliths from sediment traps and sediments for analysis using Secondary Ion Mass Spectrometry (ion probe) allows us to make precise Sr/Ca and Mg/Ca determinations on coccoliths from single species even in samples where material is limited. There are large biological effects in Sr/Ca partitioning in coccoliths that have been related to variations in coccolithophore productivity. In sediment traps from the Sargasso Sea at Bermuda and Arabian Sea in the Somali Basin, we can identify Sr/Ca variations in several species that are consistent with inferred seasonal variations in coccolithophore productivity in surface waters. In the Arabian Sea, coccolith Sr/Ca ratios in Calcidiscus leptoporus and Helicosphaera carteri are lowest during the nonproductive intermonsoon. They are highest during the upwelling of southwest monsoon and during the nutrient entrainment from strong winds of the northeast monsoon. These Sr/Ca variations match seasonal trends in coccolith export flux. Furthermore, Sr/Ca variations in C. leptoporus are larger, and this species also has the greater variation in export flux between southwest monsoon and intermonsoon seasons. At Bermuda, a 1996 fall bloom, driven by passage of a warm mode water eddy, induced a large increase in Sr/Ca of C. leptoporus coincident with an increase of C. leptoporus export. Over an annual series for 2004, highest Sr/Ca ratios of C. leptoporus in the summer months match the typical summer peak in surface standing stock of this species and the stimulation of its productivity by mesoscale cyclonic eddies and eddy-eddy interactions. High Sr/Ca did not coincide with the highest export of C. leptoporus coccoliths, likely because cyclonic eddies, unlike mode-water eddies, are dominated by small phytoplankton

  6. Effect of Sr/Zr doping and polishing on structure and dielectric properties of BaTiO3 ceramics%Sr/Zr掺杂以及抛光对BaTiO3陶瓷结构和介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    李雪翠; 路大勇

    2010-01-01

    采用冷压陶瓷技术制备了(Ba0.75Sr0.25)TiO3、Ba(Ti0.8Zr0.2)O3、(Ba0.75Sr0.25)(Ti0.8Zr0.2)O3陶瓷.XRD结果表明,Sr和Zr在BaTiO3的Ba位、Ti位、及Ba/Ti双位并入均具有高固溶性,且为没有超结构特征的单相钙钛矿结构.Sr/Zr的双位并入加快介电峰向低温的移动.Sr掺杂对Ba(Ti0.8Zr0.2)O3介电峰移动率的贡献为-1.5℃/mol% Sr.抛光技术对介电温谱的影响研究表明,尽管水抛光导致(Ba0.75Sr0.25)(Ti0.8Zr0.2)O3陶瓷颜色变暗,但晶体结构不变、介电峰值降低.

  7. Liquid Be, Ca and Ba. An orbital-free ab-initio molecular dynamics study

    International Nuclear Information System (INIS)

    Several static and dynamic properties of liquid beryllium (l-Be), liquid calcium (l-Ca) and liquid barium (l-Ba) near their triple point have been evaluated by the orbital-free ab initio molecular dynamics method (OF-AIMD), where the interaction between valence electrons and ions is described by means of local pseudopotentials. These local pseudopotentials used were constructed through a force-matching process with those obtained from a Kohn-Sham ab initio molecular dynamics study (KS-AIMD) of a reduced system with non-local pseudopotentials. The calculated static structures show good agreement with the available experimental data, including an asymmetric second peak in the structure factor which has been linked to the existence of a marked icosahedral short-range order in the liquid. As for the dynamic properties, we obtain collective density excitations whose associated dispersion relations exhibit a positive dispersion

  8. Doubling of the Bands in Overdoped Bi2Sr2CaCu2O

    International Nuclear Information System (INIS)

    We present high resolution angle resolved photoemission data of the bilayer superconductor Bi2Sr 2CaCu2O8+δ (Bi2212) showing a clear doubling of the near EF bands. This splitting approaches zero along the (0,0)→(π,π) nodal line and is not observed in single layer Bi2Sr 2CuO 6+δ (Bi2201), indicating that the splitting is due to the long sought after bilayer splitting effect. The splitting has a magnitude of approximately 75 meV near the middle of the zone, extrapolating to about 110 meV near the (π,0) point. The existence of these two bands also helps to clear up the recent controversy concerning the topology of the Fermi surface

  9. Symmetry of the hole states in BiCaSrCuO high-Tc superconductors

    International Nuclear Information System (INIS)

    Polarized CuL3-edge X-ray absorption spectra (XAS) of oriented film of Bi2Sr2Sr2Ca1Cu2Oy have been measured to determine the symmetry of the orbital of the electronic holes. The states with the configuration 3d9L (L indicates ligand holes) have been detected. The holes d in superconducting materials are found to be in the antiferromagnetic band with b1 symmetry, derived by the Cu 3dchisup 2/-y2/ orbital, but also in a second band wit8h a1 molecular symmetry, derived by Cu 3dzsup 2/-r2/ orbital at the Cu site. The results can be rationalized with the formation of both d (b1) L and ed(a1) L states in the ground state of this high-Tc superconductor

  10. The influences of mole composition of strontium (x) on properties of barium strontium titanate (Ba{sub 1−x}Sr{sub x}TiO{sub 3}) prepared by solid state reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Sandi, Dianisa Khoirum; Supriyanto, Agus; Iriani, Yofentina, E-mail: yopen-2005@yahoo.com [Physics Department, Faculty of Mathematics and Natural Science, Sebelas Maret University (Indonesia); Jamaluddin, Anif [Physics Department, Faculty of Teacher Training and Education, Sebelas Maret University (Indonesia)

    2016-02-08

    Barium Strontium Titanate (Ba{sub 1-x}Sr{sub x}TiO{sub 3}) or BST was prepared by solid state reaction method. Raw materials are BaCO{sub 3}, SrCO{sub 3}, and TiO{sub 2}. Those materials are mixed for 8 h, pressed, and sintered at temperature 1200°C for 2 h. Mole composition of Sr (x) was varied to study its influences on structural, morphological, and electrical properties of BST. Variation of (x) are x = 0; x = 0.1; and x = 0.5. XRD patterns showed a single phase of BST, which mean that mixture of raw materials was homogenous. Crystal structure was influenced by x. BaTiO{sub 3} and Ba{sub 0.9}Ti{sub 0.1}TiO{sub 3} have tetragonal crystal structure, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is cubic. The diffraction angle shifted to right side (angle larger) as the increases of x. Crystalline size of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3}, and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} are 38.13 nm; 38.62 nm; and 37.13 nm, respectively. SEM images showed that there are still of pores which were influenced by x. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface (pores are few and small in size). Sawyer Tower circuit showed that BaTiO{sub 3} and Ba{sub 0.9}Sr{sub 0.1} TiO{sub 3} is ferroelectric, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is paraelectric. The dielectric constants of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} at frequency of 1 KHz are 156; 196; and 83, respectively. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has relatively highest dielectric constant. It is considered that Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface.

  11. Effects of La{sub 2}O{sub 3}-doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Hong Wei; Chang, Chun Rui [College of Science, North China University of Science and Technology, Hebei Province (China); Li, Yuan Liang [Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, North China University of Science and Technology, Hebei Province (China); Yan, Chun Liang [Analysis and Testing Center, North China University of Science and Technology, Hebei Province (China)

    2016-03-15

    Using BaCO{sub 3}, SrCO{sub 3} and TiO{sub 2}, et al as crude materials, La{sub 2}O{sub 3} as dopant, Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) Ceramics of perovskite structure were prepared by solid state reaction method. We investigated the effects of La{sub 2}O{sub 3} -doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics. The experiment results show that: The amount of La{sub 2}O{sub 3} can increase the dielectric constant of the sample, with the doping amount increasing, the dielectric constant increases. The sintering temperature has also significant impact on the dielectric properties. The dielectric constant of the sample reaches its highest point at 1280 °C. (author)

  12. The Solid Solution Sr(1-x)Ba(x)Ga2: Substitutional Disorder and Chemical Bonding Visited by NMR Spectroscopy and Quantum Mechanical Calculations.

    Science.gov (United States)

    Pecher, Oliver; Mausolf, Bernhard; Lamberts, Kevin; Oligschläger, Dirk; Niewieszol, Carina; Englert, Ulli; Haarmann, Frank

    2015-09-28

    Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr(1-x)Ba(x)Ga2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10% cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. PMID:26272697

  13. Effects of La2O3-doping and sintering temperature on the dielectric properties of BaSrTiO3 ceramics

    International Nuclear Information System (INIS)

    Using BaCO3, SrCO3 and TiO2, et al as crude materials, La2O3 as dopant, Ba0.8Sr0.2TiO3 (BST) Ceramics of perovskite structure were prepared by solid state reaction method. We investigated the effects of La2O3 -doping and sintering temperature on the dielectric properties of BaSrTiO3 ceramics. The experiment results show that: The amount of La2O3 can increase the dielectric constant of the sample, with the doping amount increasing, the dielectric constant increases. The sintering temperature has also significant impact on the dielectric properties. The dielectric constant of the sample reaches its highest point at 1280 °C. (author)

  14. Radiochemical analysis of 90Sr, 41Ca, 129I and 36Cl in waste samples

    International Nuclear Information System (INIS)

    Full text: The decommissioning of a nuclear facility requires estimating the total inventory of radioactivity in various materials and its variation with time, which has to be carried out by the determination of the radioactivity of various radionuclides presented in the materials. Of all materials in the nuclear facilities, graphite, concrete, and steel are the main low-medium radioactive waste due to their large volume. Besides the neutron activation products of components and impurity in the materials including 36Cl and 41Ca, some fission products, such as 90Sr, 99Tc, 129I, and 137Cs also exist in the materials due to the contamination of the leaked nuclear fuel. Of these radionuclides, the determination of gamma emitters is easier and can be directly carried out by gamma spectroscopy without any radiochemical separation. But the beta and alpha emitters including 3H, 14C, 36Cl, 41Ca, 55Fe, 63Ni, 90Sr, 9 and 129I and some transuranics, have to be determined by radiochemical analysis including a completely separation of individual radionuclides from matrix and other radionuclides before measurement by beta counting, alpha spectrometry or mass spectrometry. This work presents radiochemical analytical methods developed in our laboratory in the recent years for the determination of 36Cl, 41Ca, 90Sr and 129I in bio-shielding concrete, graphite and metals. for the decommissioning of nuclear facilities. Besides individual procedure for the purification of various radionuclides, a combined procedure is also developed and presented for the simultaneous determination of all four radionuclides from one sample. (author)

  15. Luminescence Properties of SrCaS:Cu Thin Film Phosphors

    Science.gov (United States)

    Mohammed, Edris; Park, Won; Tong, Wusheng; Stock, Stuart; Summers, Chris

    2000-03-01

    Luminescence Properties of SrxCa1-xS:Cu Thin Film Phosphors E. Mohammed, W. Park, W. Tong, S. Stock and C. J. Summers Phosphor Technology Center of Excellence Georgia Institute of Technology, Atlanta, GA 30332-0560 The luminescence properties of MBE grown thin film SrCaS:Cu phosphors are investigated. 10K photoluminescence (PL) results showed a broad emission band of Cu that shifted between 2.98eV and 2.58eV, with a large increase in linewidth ranging from 0.36eV for CaS:Cu to 0.49eV as the Sr composition was increased. The significant increase in linewidth suggested that the broad emission band of Cu was composed of two closely spaced bands suggesting a possible spin-orbit or Jahn-Teller splitting of the emitting level. Curve fitting of the 10K PL showed that the splitting varied from 100meV for x=0 to 240 meV for x=0.98. In the excitation spectra, the optical absorption edge shifted from 5.1eV to 4.7eV while the energies of the two direct excitation bands of Cu shifted from 4.4 to 4.8eV and 4.0 to 4.2eV respectively. The crystal field parameter 10Dq obtained from experiments showed a linear as the composition of Sr was varied between x=0 to x=0.98 and the result was in excellent agreement with crystal field calculations.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kamel, Marwa; Mseddi, Souhir; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, Sfax (Tunisia); Donner, Wolfgang [Institute of Materials Science, University of Technology, Alarich-Weiss-Strasse.2, 64287 Darmstadt (Germany)

    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.

  17. Dielectric dynamics of the polycrystalline Ba0.5Sr0.5TiO3 thin films

    Science.gov (United States)

    Pečnik, Tanja; Eršte, Andreja; Matavž, Aleksander; Bobnar, Vid; Ivanov, Maksim; Banys, Juras; Xiang, Feng; Wang, Hong; Malič, Barbara; Glinšek, Sebastjan

    2016-05-01

    Polycrystalline Ba0.5Sr0.5TiO3 films, with thicknesses between 90 and 600 nm, were prepared on alumina substrates at 900 °C by chemical solution deposition (CSD) and a dielectric spectroscopy investigation of the in-plane properties was performed. The 5-kHz permittivity ε‧ shows a non-monotonic thickness dependence, reaching 1230 at room temperature for the 310-nm-thick film, whose grain size is ∼75 nm. Its 15-GHz-value and losses are 1105 and 0.05, respectively. The temperature of the permittivity maximum T max at 5 kHz decreases with increasing thickness from 277 to 250 K for the 170- and 600-nm-thick films, respectively, which has been linked to the residual biaxial stress. A hysteresis is observed in the permittivity ε‧-electric field E DC characteristics in all the films up to ∼50 K above T max . Frequency dispersion in which permittivity decreases with increasing frequency is present below T max in films thicker than 90 nm. The high permittivity values of the thinnest films, which are among the highest reported in the (Ba,Sr)TiO3 films with grain sizes below 75 nm, are a direct proof of the optimized CSD processing conditions.

  18. Modeling the behavior of Xe, I, Cs, Te, Ba, and Sr in solid and liquefied fuel during severe accidents

    International Nuclear Information System (INIS)

    This paper describes the primary physical/chemical models recently incorporated into a mechanistic code (FASTGRASS) for the estimation of fission product release from fuel, and compares predicted results with test data. The theory of noble gas behavior is discussed in relation to its effect on the release behavior of I, Cs, Te, Ba, and Sr. The behavior of these fission products in the presence of fuel liquefaction/dissolution and grain-growth phenomena is presented, as is the chemistry of Sr, Ba, I, and Cs. Comparison of code predictions with data indicates the following trends. Fission products release behavior from solid fuel strongly depends on fuel microstructure, irradiation history, time at temperature, and internal fuel rod chemistry. Fuel liquefaction/dissolution, fracturing, and oxidation also exert a pronounced effect on release during fuel rod degradation. For low burnup fuel (e.g., TMI-2), appreciable fission product retention in previously liquefied fuel can occur due to the low concentration of fission products, and the limited growth of bubbles in the liquefied material. Many of the calculations described in this paper were made with a version of FASTGRASS developed for use on a personal computer (IBM compatibile). (orig.)

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

    International Nuclear Information System (INIS)

    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

  20. Influence of Ca substitution on the microstructure and magnetic properties of SrLaCo ferrite

    International Nuclear Information System (INIS)

    M-type ferrites Sr(0.55−x)CaxLa0.45Fe11.65Co0.35O19 (x=0, 0.05, 0.15, 0.25 and 0.35) were prepared by the ceramic process. Phase composition, morphology and sublattice occupation of the material were characterized by X-ray diffraction, scanning electron microscopy and Mössbauer spectroscopy, respectively. Magnetic properties of the materials were tested by a vibrating sample magnetometer. The results show that the samples are all composed of single M-type hexagonal ferrite after the Ca substitution, while the lattice constant c decreases and the lattice constant a does not change basically with increase of the substitution amount. In addition, the intrinsic coercive force increases obviously when the Ca substitution amount x3+ sublattice occupations suggested by Mössbauer spectroscopy. - Highlights: ► Ca substitution can increase coercive force without a drop of saturation intensity. ► Lattice constant c decreases while a remains the same after Ca substitution. ► Ca substitutions have an effect on the cation occupation.

  1. Transport and tunneling in Bi2Sr2CaCu2O8-x

    International Nuclear Information System (INIS)

    The authors report their measurement of the resistivity, TEP, Hall coefficient, and tunneling characteristics of single crystals of Bi2Sr2CaCu2O8-x (BSCCO). Simple empirical expressions were found for the normal state transport coefficients that hold true for different crystal directions, oxygen contents, and for different classes of high Tc oxides. Tunneling measurements on BSCCO single crystals suggest an anisotropic or modulated gap below Tc with 2(cgd)ab/kBTc (app) 6-7 and 2(cgd)c/kBTc ∼ 3-4

  2. Structures in the system CaTiO{sub 3}/SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ball, C.J.; Begg, B.D.; Cookson, D.J.; Thorogood, G.J.; Vance, E.R. [ANSTO, Menai, New South Wales (Australia). Materials Div.

    1998-09-01

    At room temperature the sequence of phases with increasing amounts of strontium in the system CaTiO{sub 3}/SrTiO{sub 3} is orthorhombic (Pnma), orthorhombic (Bmmb), tetragonal (I4/mcm), and cubic (Pm3m). All phase boundaries shift toward smaller strontium contents with increase of temperature. Volume changes resulting from phase transformations are small for all compositions. Shape changes are greatest ({approximately}0.3%) for the Bmmb/I4/mcm transition, but would probably be accommodated by microtwinning and so are unlikely to affect the mechanical integrity of a specimen.

  3. Gamma-ray shielding properties of CaO-SrO-B 2O 3 glasses

    Science.gov (United States)

    Singh, Kulwant; Singh, Harvinder; Sharma, Gopi; Gerward, Leif; Khanna, Atul; Kumar, Rajesh; Nathuram, Rohila; Sahota, Hari Singh

    2005-02-01

    Mass attenuation coefficients, effective atomic numbers and effective electron densities have been determined experimentally for the glass system xCaO·(0.3- x)SrO·0.7B 2O 3 at photon energies 511, 662, 1173, and 1332 keV. The results are compared with theoretical calculations. In addition, the molar volume of the glasses has been derived from density measurements, and the excess volume has been determined as a function of composition. The reported data should be useful for potential applications of these glasses in radiation shielding.

  4. Dielectric properties of (CuO,CaO2, and BaO)y/CuTl-1223 composites

    International Nuclear Information System (INIS)

    We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties such as real and imaginary part of dielectric constant, dielectric loss, and ac-conductivity of these composites are studied by capacitance and conductance measurement as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). The x-ray diffraction analysis reveals that the characteristic behavior of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ superconductor phase and its structure is nearly undisturbed by doping of nanoparticles. The scanning electron microscopy images show the improvement in the intergranular links among the superconducting grains with increasing nanoparticles concentration. Microcracks are healed up with the inclusion of these nanoparticles and superconducting volume fraction is also increased. The dielectric properties of these composites strongly depend upon the frequency and temperature. The zero resistivity critical temperature and dielectric properties show opposite trend with the addition of nanoparticles in Cu0.5Tl0.5Ba2Ca2Cu3O10-δ superconductor matrix.

  5. Diffused phase transition of polycrystalline (Ba0.80Sr0.20TiO3

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2009-10-01

    Full Text Available Purpose: The purpose of this work was to determinate the influence of the 20% Sr substitutions (in sublattice A on changes of the character of phase transition (PT in comparison with pure barium titanate BaTiO3 (BT.Design/methodology/approach: Polycrystalline samples of (Ba0.80Sr0.20TiO3 (BS20T were prepared by calcinations method at temperature 1620 K. X-ray measurements were executed from 10 deg to 120 deg with the 0.008 deg step. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 Agilent Precision LRC meter HP4824A equipped with WinDETA 5.62 software Novocontrol. Measurements were taken under cooling with 2 K/min speed. Measuring electric field frequency was from the range 20 Hz - 1 MHz.Findings: The difference between the value of temperature of structural transition (cubic-tetragonal equal 310K and the temperature Tm (the temperature of maximum of real part electric permittivity equal 340 K was affirmed. It was affirmed, that 20% substitution of Sr ions changed the type of phase transition. The transition was strongly diffused (DPT. The polar character of this solid solution was also observed in a broad temperature range (in the paraelectric phase too. It is connected with the occurrence of polar regions (clusters.Research limitations/implications: The results can be used to describe changes of PT in the DPT solid solutions with ferroactive substitutions in sublattice A.Originality/value: Value of this work relies on the experimental examination of the dielectric properties of (Ba0.80Sr0.20TiO3 (BS20T solid solution. The temperature of the DPT was calculated. The low value of phase angle is connected with the existence of the polar regions.

  6. Phytoremediation modelling - phytoextraction of 137Cs, 133Ba, and 90Sr from liquid media and artificially contaminated soil

    International Nuclear Information System (INIS)

    The phytoremediation model based on experiments with plants cultivated in vitro in media supplemented with radionuclide salts was investigated. The plant species Brassica napus, Sinapis alba, Helianthus annuus, Zea mays and Pisum sativum were cultivated on the Murashige-Skoog basal salt mixture enriched with salts of 137Cs, 133Ba, and 90Sr in aseptic conditions. The time-dependent radioactivity decrease in the medium was determined using LSC, and the phytoextraction curves were plotted. Radioactivity in the plant roots and shoots was measured and the efficiency of phytoextraction and the distribution between the roots and shoots as a measure of radionuclide transport in the plant tissues were calculated for each of the plants used. Cultivation experiments were also performed on artificially contaminated soil. Seeds of the plants were placed into contaminated soil and cultivated for 2 months in conditions similar to those of the in vitro experiments. The extracted radioactivity and distribution between roots and shoots were determined. The in vitro experiments simulated extraction of the radionuclide salt from solution analogously to real extraction from the soil solution, while the processes occurring in the rhizosphere were eliminated. The phytoextraction efficiency in terms of the percentage of the starting radioactivity ranged from 12 to 31 % for 90Sr, 8 to 24% for 137 Cs, and 12 to 17 % for 133 Ba in a cultivation cycle. The root/shoot radioactivity ratios demonstrate that the plant species used may be suitable for real phytoremediation. The experiments in which the plants were cultivated from seeds in artificial contaminated substrate showed that the ability of roots to extract radionuclide salts from their environment remains unchanged. The relative efficiency values were lower than for the extraction from solutions (3 to 11.5 % for 90Sr, 1.5 to 4 % for 137Cs, and 1 to 6.2 %, for 133Ba), but in this process, the equilibrium between the soil particles and the

  7. Preparation and characterization of composites from Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} and polystyrene

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Q. [College of Chemistry, Chemical Engineering and Materials Science and Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); Hong, R.Y., E-mail: rhong@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science and Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); School of Chemical Engineering, Fuzhou University, Fuzhou 350108 (China); Feng, W.G. [Suzhou Nanocomp Inc., Suzhou New District, Suzhou 215011 (China)

    2014-10-01

    Highlights: • Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} was synthesized through the method of co-precipitation. • Inexpensive TiOSO{sub 4} was used as raw material. • The molten salt contributes to better crystal morphology. • Composites with modified particles showed good thermal and dielectric properties. - Abstract: Pure perovskite phase Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} powders were synthesized by facile co-precipitation using inexpensive TiOSO{sub 4} as the raw material. The post-calcining treatment was at the low temperature of 950 °C, which was about 200 °C lower than that of the conventional solid-state method. The effects of two types of precipitation agents on the properties of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} powders were investigated, and cubic Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} particles were obtained at the optimal conditions. Afterwards, the obtained Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} ceramics were ground into fine ceramic powders, and modified with oleic acid to improve the compatibility with the polystyrene (PS) matrix. The modified ceramic powders were dispersed in PS via solution co-blending to obtain Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites. The structure and morphology of the Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites were characterized through X-ray diffraction (XRD), and scanning electron microscopy (SEM). The SEM images showed that the modified ceramic powders had good dispersion in the PS resin. Moreover, the dielectric and thermal properties of the Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites were investigated, and the results showed that the modified ceramic powders could enhance the dielectric constants and thermal stability of ceramic–polymer composites.

  8. Photoluminescence properties of X5SiO4Cl6:Tb3+ (X = Sr, Ba) green phosphor prepared via modified solid state method

    Indian Academy of Sciences (India)

    A N Yerpude; S J Dhoble

    2013-08-01

    Luminescence property of a new halo silicate phosphor, X5SiO4Cl6:Tb3+ (X = Sr, Ba) prepared by modified solid state method is reported here. It is characterized by powder X-ray diffraction and studied by photoluminescence excitation and emission spectra. In the emission spectra of X5SiO4Cl6:Tb3+ (X = Sr, Ba) phosphor, characteristic blue and green emission peaks are present corresponding to Tb3+ intra 4 transition. Emission spectrum shows a dominant peak at 544 nm due to the ${}^{5}D_{4} \\rightarrow {}^{7}F_{5}$ transition of Tb3+.

  9. Magnetism of CaAs, CaP, and CaN half-metals

    International Nuclear Information System (INIS)

    First principles calculations indicate that CaAs, CaP, and CaN compounds are ferromagnets. Analysis of these and other II-V compounds that do not contain transition metal atoms shows that their magnetism derives from the spin polarization of the atomic p(anion) orbitals, which persists in the compounds of Ca, Sr, and Ba due to their large atomic radii

  10. Magnetism of CaAs, CaP, and CaN half-metals

    Energy Technology Data Exchange (ETDEWEB)

    Volnianska, O. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)]. E-mail: volnian@ifpan.edu.pl; Jakubas, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Boguslawski, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2006-10-26

    First principles calculations indicate that CaAs, CaP, and CaN compounds are ferromagnets. Analysis of these and other II-V compounds that do not contain transition metal atoms shows that their magnetism derives from the spin polarization of the atomic p(anion) orbitals, which persists in the compounds of Ca, Sr, and Ba due to their large atomic radii.

  11. Structure determination at room temperature and phase transition studies above $T_c$ in ABi4Ti4O15 (A = Ba, Sr or Pb)

    Indian Academy of Sciences (India)

    G Nalini; T N Guru Row

    2002-08-01

    The room temperature structure of three compounds belonging to the Aurivillius family ( = 4), ABi4Ti4O15 (A = Ba, Sr or Pb) has been analysed. BaBi4Ti4O15 crystallizes in a tetragonal 4/ space group whereas SrBi4Ti4O15 and PbBi4Ti4O15 crystallize in the orthorhombic space group $A2_1am$. The starting model for the Sr and Pb analogues was derived from ab initio methods and refined using the Rietveld method. The cations Ba and Sr are disordered over the Bi sites while the Pb cation is found exclusively in the [Bi2O2]2+ layers. The TiO6 octahedra are tilted with the Ti–O bonds forming zigzag chains along the `’ axis. The displacement of Bi atoms along the `’ axis might be responsible for ferroelectricity in these compounds. The high temperature X-ray data above $T_c$ indicate no structural transition for A = Ba and Pb while A = Sr transforms to the tetragonal structure.

  12. Superconducting Bi-Ca-Sr-Cu oxide thin films by spray pyrolysis of metal acetates

    International Nuclear Information System (INIS)

    Superconducting Bi-Ca-Sr-Cu oxide thin films have been prepared on ZrO2-coated silicon (111) wafers by spray pyrolysis of metal acetate precursors followed by rapid annealing to 850 0C in air. Resistivity measurements indicate a broad superconducting transition with T/sub c/ onset near 90 K and zero resistivity below 60 K. The films are highly oriented with the c axis normal to the substrate surface and can be indexed to a tetragonal structure with lattice parameters of a = 3.832(1) A and c = 30.78(5) A. Both x-ray photoelectron spectroscopy and x-ray diffraction measurements indicate the loss of Ca to the ZrO2 buffer layer

  13. Structure-property relations in Sr, Nb, Ba doped lead zirconate titanate

    CERN Document Server

    Zheng, H

    2001-01-01

    rhombohedral or tetragonal forms or as mixture of the two (MPB), depending on Zi:Ti ratio. Zr:Ti ratio strongly affected d sub 3 sub 3 , which was maximised in the tetragonal phase close to, but not at, the MPB. Sr sup 2 sup + substitution on the A-site promoted tetragonality in PZT, greatly reducing T sub C , and broadening the dielectric maximum. As the Sr sup 2 sup + content was increased, Zr:Ti ratio was adjusted to maximise d sub 3 sub 3 and the optimised d sub 3 sub 3 values increased from 410 pC/N (Sr sup 2 sup + = 0) to 640 pC/N (Sr sup 2 sup + = 0.12), commensurate with a decrease in the T sub C. However, for ceramics where Sr sup 2 sup + > 0.12, optimised d sub 3 sub 3 decreased with respect to the values for ceramics where Sr sup 2 sup + = 0.12 even though T sub C was lowered. Electron diffraction patterns revealed superlattice reflections occurring at 1/2 left brace hkl right brace positions associated with rotations of oxygen octahedra in anti-phase. It was suggested that Sr sup 2 sup + substitut...

  14. A coral Sr/Ca calibration and replication study of two massive corals from the Gulf of Mexico

    Science.gov (United States)

    DeLong, Kristine L.; Flannery, Jennifer A.; Maupin, Christopher R.; Poore, Richard Z.; Quinn, Terrence M.

    2011-01-01

    This study examined the variations in the ratio of strontium-to-calcium (Sr/Ca) for two Atlantic corals (Montastraea faveolata and Siderastrea siderea) from the Dry Tortugas National Park (centered on 24.7°N, 82.8°W) in the Gulf of Mexico. Cores from coral colonies in close proximity (10s of meters) and with the same environmental conditions (i.e., depth and water chemistry) were micro-sampled with approximately monthly resolution and the resulting Sr/Ca variations were calibrated with local sea surface temperature (SST) records. Replication tests for coral Sr/Ca variations found high agreement between intra-colony variations and between individual colonies of S. siderea (a single M. faveolata colony was sampled). Regression analysis of monthly variations in coral Sr/Ca and local SST revealed significant correlation on monthly and inter-annual timescales. Verification of the calibration on different timescales found coral Sr/Ca–SST reconstructions in S. siderea were more accurate than those from M. faveolata, especially on inter-annual timescales. Sr/Ca–SST calibration equations for the two species are significantly different (cf., Sr/Ca = -0.042 SST + 10.070, S. siderea; Sr/Ca = -0.027 SST + 9.893, M. faveolata). Mean linear extension for M. faveolata is approximately twice that of S. siderea (4.63, 4.31, and 8.31 mm year−1, A1, F1, and B3, respectively); however, seasonal Sr/Ca variability in M. faveolata is less than S. siderea (0.323, 0.353, and 0.254 mmol mol−1, A1, F1, and B3, respectively). The reduced slope for M. faveolata is attributed to physical sampling issues associated with complex time-skeletal structure of M. faveolata, i.e., a sampling effect, and not a growth effect since the faster growing M. faveolata has the reduced Sr/Ca variability.

  15. Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

    Science.gov (United States)

    Lu, Shengbo; Xu, Zhengkui; Su, Shi; Zuo, Ruzhong

    2014-07-01

    Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

  16. Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

    International Nuclear Information System (INIS)

    Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

  17. Rectification in (La,Sr)MnO3/(Ba,Sr)TiO3/(La,Ce)2CuO4 trilayer p-i-n junctions

    International Nuclear Information System (INIS)

    Oxide trilayer p-i-n junctions, with p-type La0.67Sr0.33MnO3 (LSMO) manganite layer and n-type La1.89Ce0.11CuO4 (LCCO) cuperate layer separated by Ba0.7Sr0.3TiO3 (BST) titanite insulator layer, have been deposited in situ and characterized. With the increment of the insulator layer thickness, the I-V characteristic of such p-i-n junctions changes from symmetric to asymmetric, and then to symmetric again, given the highest rectifying performance at the BST layer of about 25 nm thick. The largest asymmetry, defined as the ratio of dI/dV at +2 V and -2 V, respectively, is found >1000. The insulator layer thickness dependency indicates that the transport properties of the p-i-n junctions are dominated by the interplay between the interior fields at the LSMO/BST and BST/LCCO interfaces

  18. Effect of Ca doping on thermally activated flux flow in the Y3Ba5Cu8O18 superconductor

    Indian Academy of Sciences (India)

    Mustafa Akyol; Ali Osman Ayaş; Gönül Akça; Selda Kiliç Çeti̇n; Ahmet Eki̇ci̇bi̇l

    2015-09-01

    Y3Ba5Cu8O18 (Y-358) and Y3Ba5Ca2Cu8O18 (YCa-358) compounds were prepared by the so-called sol–gel method. The effect of doping Ca atoms into the Y3Ba5Cu8O18 superconductor is studied by employing the electrical resistivity measurements at various magnetic fields. The possible degradation in microstructural and superconducting properties due to the addition of Ca was discussed. The resistivity as a function of temperature measurements shows that the depression in superconducting temperature is more pronounced for both samples. A systematic analysis of the magnetoresistivity of the Y-358 and YCa-358 compounds has been carried out by using the thermally activated flux flow (TAFF) model. The TAFF activation energy, , is field dependent and obeys the power law = –, where increases while decreases with the addition of Ca. Furthermore, and the calculated upper critical field, 2, decrease with the addition of Ca.

  19. Influence of cetyltrimethylammonium bromide on the morphology of AWO4 (A = Ca, Sr) prepared by cyclic microwave irradiation

    International Nuclear Information System (INIS)

    AWO4 (A = Ca, Sr) was prepared from metal salts [Ca(NO3)2.4H2O or Sr(NO3)2], Na2WO4.2H2O and different moles of cetyltrimethylammonium bromide (CTAB) in water by cyclic microwave irradiation. The structure of AWO4 was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the presence of nanoparticles in clusters with different morphologies; spheres, peaches with notches, dumb-bells and bundles, influenced by CTAB. Six Raman vibrational peaks of scheelite structure were detected at 908, 835, 793, 399, 332 and 210 cm-1 for CaWO4 and 917, 833, 795, 372, 336 and 192 cm-1 for SrWO4, which are assigned as ν1(Ag), ν3(Bg), ν3(Eg), ν4(Bg), ν2(Ag) and νf.r.(Ag), respectively. Fourier transform infrared (FTIR) spectra provided the evidence of W-O stretching vibration in [WO4]2- tetrahedrons at 793 cm-1 for CaWO4 and 807 cm-1 for SrWO4. The peaks of photoluminescence (PL) spectra were at 428-434 nm for CaWO4, and 447-451 nm for SrWO4

  20. Measurement of magnetic properties in a melt cast Bi-Ca-Sr-Cu-O superconductor

    International Nuclear Information System (INIS)

    Magnetic measurements were made to examine the superconducting properties of a crystalline chunk, consisting of many small crystals, prepared by casting from the oxide melt with a starting composition of Bi3Ca2Sr2Cu3Ox. AC susceptibility revealed an onset temperature of 82 K and a transition width of ∼ 10 K. Hysteresis loops at 70 K showed a very small hysteresis, indicating a low density of effective flux pinning sites at this temperature, similar to the behavior observed for some superconducting samples of the Bi-Ca-Sr-Cu-O system prepared by other techniques. However, the magnetization at 10 K showed no hysteresis for fields greater than ∼ 3.5 kOe, a much smaller value than we have previously observed for other samples of this material regardless of preparation method, or for any other material with a Tc greater than 70 K. This critical field for flux depinning, Hcp, varies with temperature as Hcp - 4980(1-t)2.5, where t is T/Tc

  1. Electrical conductivity of cobalt-titanium substituted SrCaM hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Eraky, M.R., E-mail: moharamderak@yahoo.com [Physics Department, Faculty of Science, Kafrelsheikh University, 33516 Kafrelsheikh (Egypt)

    2012-03-15

    A series of polycrystalline M-type hexagonal ferrites with the composition Sr{sub 0.5}Ca{sub 0.5}Co{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (where x=0.0-0.8) were prepared by the conventional ceramic technique. The electrical conductivity has been measured from 300 to 590 K. The dc conductivity, {sigma}{sub dc}, exhibited a semiconductor behavior. The negative sign of thermoelectric power coefficient S reveals that all samples are n-type semiconductors. Both {sigma}{sub dc} and mobility, {mu}{sub d}, increases with the substitution of Co{sup 2+} and Ti{sup 4+} ions, reach maximum at x=0.4 and start decreasing at x>0.4. Many conduction mechanisms were discussed to explain the electric conduction in the system. It was found that the hopping conduction is the predominant conduction mechanism. For samples with compositional parameter x=0.0 and 0.8, the band conduction mechanism shares in electric conduction beside the hopping process. - Highlights: Black-Right-Pointing-Pointer SrCaCoTiM hexaferrites have been prepared by conventional ceramic technique. Black-Right-Pointing-Pointer The electrical conductivity exhibited a semiconductor behavior. There is an increase in conductivity up to x=0.4 for Co and Ti substitution. Black-Right-Pointing-Pointer The hopping conduction is the predominant conduction mechanism.

  2. Floating Zone Growth of Bi2Sr2Ca2Cu3Oy Superconductor

    Directory of Open Access Journals (Sweden)

    Andrey Maljuk

    2016-05-01

    Full Text Available The crystal growth of high-temperature oxide superconductors has been hampered by the complexities of these materials and the lack of knowledge of corresponding phase diagrams. The most common crystal growth technique adopted for these materials is the so-called “Flux” method. This method, however, suffers from several drawbacks: (i crystals are often crucible and flux contaminated; (ii crystals are difficult to detach from solidified melt; and (iii crystals are rather small. In most cases, these drawbacks can be overcome by the crucible-free floating zone method. Moreover, this technique is suitable for crystal growth of incongruently melting compounds, and has been thus successfully used to make large single crystals of Bi2Sr2Ca2Cu3Oy superconductor. In this review, the authors summarize the published and their own growth efforts as well as detailed characterization of as-grown and post-growth annealed samples. The optimal growth conditions that allowed one to obtain the large-size, almost single phase and homogeneous in composition Bi2Sr2Ca2Cu3Oy single crystals are presented. The effect of long lasting post-growth heat treatment on both crystal quality and superconducting properties has also been demonstrated.

  3. Ultrasonic study of structural instability of monocrystalline and polycrystalline Bi-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Two internal-friction (attenuation) peaks around 95 and 130 K in the polycrystal and single crystal of Bi-Sr-Ca-Cu-O are found to be related to the superconducting transition at 84 and 107 K, respectively. The jump of lattice parameter and shape-memory effect occurring at the peak temperatures reveal the characteristics of a martensitic transition. The velocity and attenuation versus temperature of ultrasonic longitudinal waves propagating along two directions in the a-b plane at 10 degree to the a and b axes and of [010] shear waves with [100] polarization were measured for the Bi2Sr2CaCu2O8 single crystals. The anisotropic elasticity in the c plane is manifested. Only the longitudinal waves in a direction and the shear waves show an obvious softening minimum of velocity around 250 K, which is associated with an attenuation peak due to a phaselike transition, but other longitudinal waves reveal a monotonic stiffening from room temperature down to Tc. The origin of the overall trend of elastic stiffening that appears in the measurements so far for high-Tc oxides is discussed

  4. Radiation Damage in CaF2 and BaF2 Investigated by the Channeling Technique

    International Nuclear Information System (INIS)

    The radiation damage in single crystals of CaF2 and BaF2 due to room temperature bombardment with 2.0 MeV helium ions has been studied by the channeling technique. Back scattering spectra for the and axial directions were taken after different doses of random irradiation. A slight in crease of the aligned yield with radiation dose has been found for both crystals at doses below 1017 ions/cm2. For CaF2 at a dose of about 1.4x1017 ions/cm2 a steep increase is found, after which the aligned yield saturates at a high value. Analyses of spectra measured along different aligned directions indicate that the structures of defects in CaF2 and BaF2 differ

  5. Experimentally determined Mg/Ca and Sr/Ca ratios in juvenile bivalve calcite for Mytilus edulis: implications for paleotemperature reconstructions

    Science.gov (United States)

    Wanamaker, Alan D., Jr.; Kreutz, Karl J.; Wilson, Tiffany; Borns, Harold W., Jr.; Introne, Douglas S.; Feindel, Scott

    2008-10-01

    To further evaluate the potential use of Mg/Ca and Sr/Ca ratios as a paleothermometer in the shell carbonate of the blue mussel Mytilus edulis, we grew juvenile mussels (˜15 mm shell height; edulis to reconstruct paleotemperatures in estuarine settings (salinity below 24) with a corresponding RMSE (root mean squared error; 95% confidence interval) of ±2.4°C and ±2.8°C, respectively. In order for this methodology to be statistically meaningful, water temperature changes must be rather large, as the errors associated with using Mg/Ca and Sr/Ca ratios from the shell material of M. edulis are substantial. Further work is required to determine if the findings presented here can be duplicated, and if the potential salinity effect is pervasive.

  6. Magnetic behavior of La2/3Ca1/3MnO3 / BaTiO3 bilayers

    Science.gov (United States)

    Ordonez, John E.; Gomez, Maria E.; Lopera, Wilson; Marin, Lorena; Pardo, Jose A.; Morellon, Luis; Algarabel, Pedro; Prieto, Pedro

    2013-03-01

    We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820° C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 Å, and aLCMO=3.804 Å, for each individual layer. In the BTO/LCMO bilayer, (002)-Bragg peak for BTO maintain its position whereas (002) LCMO peak shift to lower Bragg angle indicating a strained LCMO film. Magnetization measurements reveal an increase in the Curie temperature from 170 K to 220 K for the bilayer when LCMO (t = 47 nm) is deposited on BTO (t=52 nm) film, while depositing the BTO (50 nm) above LCMO (48 nm) the Curie temperature remains at values close to that obtained for a LCMO single layer (~175 K), deposited under identical growth parameters This work has been supported by Instituto de Nanociencias de Aragón, Zaragoza, Spain, ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' COLCIENCIAS-CENM Contract RC 275-2011 and Research Project COLCIENCIAS-UNIVALLE.

  7. Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite

    Science.gov (United States)

    Zougrou, I. M.; Katsikini, M.; Brzhezinskaya, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

    2016-08-01

    Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

  8. Environmental and biological controls on the geochemistry (δ18O, δ13C, Mg/Ca, and Sr/Ca) of living ostracods from Lake Geneva

    OpenAIRE

    Decrouy L.

    2009-01-01

    ABSTRACT : Ostracods are benthic microcrustaceans enclosed in low-Mg calcite bivalves. Stable isotope compositions, Mg/Ca, and Sr/Ca ratios of ostracod fossil valves have proven useful to reconstruct past environmental conditions. Yet, several discrepancies persist and the influence of many factors remains unclear. It is the aim of this study to improve the use of ostracod valve geochemistry as palaeoenvironmental proxies by examining the extent of isotope fractionation and trace element part...

  9. Preparation and characterisation of LaBaCaCu3Ox and La1.3Ba1.7Cu3Ox

    International Nuclear Information System (INIS)

    An important subject for understanding the mechanism of high temperature superconductivity is the investigation of the substituted compounds of the 123 system. A new superconductor compounds have been prepared by solid state reaction from the stochiometric amounts of oxide and carbonite materials. crystal structures were found to be tetragonal for both samples, and the electrical resistivity data obtained by the four probe technique. LaCaBaCu3O7.1 sample reached zero resistivity at 83 K, while La1.3Ba1.7Cu3O7.1 sample reached zero resistivity at 33 K and it has almost metalic behaviour. 4 refs., 9 figs., 4 tabs. (author)

  10. BaTiO3和SrTiO3薄膜生长初期化学分子反应机理%Reaction mechanism of chemical molecules in early growth of BaTiO3 and SrTiO3 thin films

    Institute of Scientific and Technical Information of China (English)

    梁晓琴; 张姝; 黄平; 杨春

    2012-01-01

    Density functional theory(DFT) is applied to study microscopic reaction mechanism of the formation of BaTiO3 and Sr-TiOjby BaO,SrO and TiO2 molecules and Ti2O3by two TiO2 molecules. The reaction intermediates,transition states and activation energies have been obtained. NBO is used to analyze bonding process,orbital interactions and atomic charges in intermediates and transition states of the reaction process. The calculated results show activation energies of the formation of BaTiO3 ,SrTiO,and Ti2O4 are respectively 16.3,17. 3 and 9.6 kJ/moL Activation energies of Ti2O4 is relatively lower ,TiO2 dimer observed in the experiment can theoretically be explained. However,the reaction enthalpies of the formation of the first intermediates of BaTiO3 and SrTiO3 are respectively-484.7 and-534.7 kj/mol. Activation energies are low. And strong orbital interactions and static gravitations are found in molecules. These results indicate that BaO and SrO acts as a combining center TiO2in the early growth of BaTiO3and SrTiO3thin films,which should be propitious to form of primary unit cell.%本文采用B3LYP密度泛函方法,研究了BaO、SrO与TiO2形成BaTiO3、SrTiO3及TiO2二聚形成Ti2O4的微观反应机理,获得了相应的中间体、过渡态及反应活化能.采用自然键轨道NBO方法分析了反应过程中各中间体和过渡态的成键情况、轨道间的相互作用以及原子的电荷.计算结果表明,形成BaTiO3、SrTiO3和Ti2O4反应活化能分别为16.3、17.3和9.6 kJ/mol,TiO2形成二聚体活化能相对较小,从理论上解释了实验过程中观测到TiO2二聚体;但SrO、BaO和TiO2形成BaTiO3、SrTiO3的反应过程中,形成最初的稳定中间体时分别放热484.7和534.7 kJ/mol,且活化能较低,轨道间相互作用较强,静电引力作用显著,有利于SrTiO3和BaTiO3薄膜生长初期以TiO2为中心,结合BaO和SrO成核生长,从而有利予单元胞的进一步形成.

  11. Nano structure formation on the surfaces of SrTiO{sub 2} and BaF{sub 2} induced by impact of slow highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Heller, Rene; El-Said, Ayman S.; Wilhelm, Richard A.; Facsko, Stefan [Helmholtz-Zentrum Dresden Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany)

    2011-07-01

    The interaction of slow highly charged ions with solid surfaces with particular interest on the nano structure formation ability was investigated intensively within the last years. The rapid release of the HCI's potential energy as a unique feature of this kind of projectiles can cause local energy densities at the surface which are comparable to those induced by ultra short laser pulses or swift heavy ions. Thus HCI give strong rise to be a promising tool for nano structure formation on solid surfaces. Since the potential energy release is strongly restricted to the surface proximity the amount of damage created in the bulk can be strongly suppressed. In recent time the authors spent much effort in the exploration of the microscopic mechanisms of HCI nanostructure creation on the surfaces of the alkali halide KBr and the earth alkali halide CaF{sub 2}, respectively. Motivated by the promising results and the predictions of the developed models we extended our investigation to the surfaces of SrTiO{sub 2} as well as of BaF{sub 2}. The results of these measurements are presented and discussed in the present contribution.

  12. Investigation of interaction processes in SrCO3-VOsub(1,5) and BaCO3-VOsub(1,5) systems

    International Nuclear Information System (INIS)

    Interaction of sesquioxide of vanadium with strontium and barium carbonates is of redox character. Orthovanadate and carbon oxide are formed at the initial stage of the reaction. Therefore, it seems impossible to obtain stoichiometric vanadites MV2O4 in the systems SrCo3(BaCO3)-VOsub(1.5)

  13. A New Ba0.6 Sr0.4 TiO3 -Silicon Hybrid Metamaterial Device in Terahertz Regime.

    Science.gov (United States)

    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

    Metamaterials, offering unprecedented functionalities to manipulate electromagnetic waves, have become a research hotspot in recent years. Through the incorporation of active media, the exotic electromagnetic behavior of metamaterials can be dramatically empowered by dynamic control. Many ferroelectric materials such as BaSrTiO3 (abbreviated as BST), exhibiting strong response to external electric field, hold great promise in both microwave and terahertz tunable devices. A new active Ba0.6 Sr0.4 TiO3 -silicon hybrid metamaterial device, namely, a SRR (square split-ring resonator)-BaSrTiO3 thin film-silicon three-layer structure is fabricated and intensively studied. The active Ba0.6 Sr0.4 TiO3 thin film hybrid metamaterial, with nanoscale thickness, delivers a transmission contrast up to ≈79% due to electrically enabled carrier transport between the ferroelectric thin film and silicon substrate. This work has significantly increased the low modulation rate of ferroelectric based devices in terahertz range, a major problem in this field remaining unresolved for many years. The proposed BST metamaterial is promising in developing high-performance real world photonic devices for terahertz technology. PMID:27007192

  14. Water oxidation catalysis: an amorphous quaternary Ba-Sr-Co-Fe oxide as a promising electrocatalyst for the oxygen-evolution reaction.

    Science.gov (United States)

    Zhang, Cuijuan; Berlinguette, Curtis P; Trudel, Simon

    2016-01-25

    We present an amorphous quaternary Ba-Sr-Co-Fe oxide (a-BSCF) with a specific stoichiometry, readily fabricated via a photochemical decomposition method. a-BSCF demonstrates high catalytic activity towards the oxygen-evolution reaction (OER). PMID:26659269

  15. Selective removal of Cs-137, Sr-90, Ba-133, Co-60 and Pb-210 radioisotopes with proton-ionizable lariat ethers in the ion flotation process

    International Nuclear Information System (INIS)

    Authors present procedure for the selective removal of Cs-137, Sr-90, Ba-133, Co-60 and Pb-210 radioisotopes with proton-ionizable lariat ethers in the ion flotation process from dilute aqueous solutions in the presence of nonionic foaming agent, which might have a practical meaning for the decontamination of industrial (toxic, radioactive) aqueous solutions

  16. Toward Complete Isotopic Analysis of Individual Presolar Silicon Carbide Grains: C, N, Si, Sr, Zr, Mo, and Ba in Single Grains of Type X

    Science.gov (United States)

    Pellin, M. J.; Calaway, W. F.; Davis, A. M.; Lewis, R. S.; Amari, S.; Clayton, R. N.

    2000-01-01

    The isotopic compositions of Sr, Ba, Zr and Mo in single presolar SiC grains from supernovae are different from those expected from either of the dominant heavy element neutron capture nucleosynthesis mechanisms, the s-process and the r-process.

  17. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Science.gov (United States)

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

    2016-01-01

    The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials. PMID:27580744

  18. Effects of Sr and Sn on microstructure and corrosion resistance of Mg–Zr–Ca magnesium alloy for biomedical applications

    International Nuclear Information System (INIS)

    Highlights: ► Element alloying is one of the effective ways to modify the performance of alloys. ► Sr and Sn were simultaneously used to improve the corrosion resistance of Mg–Zr–Ca. ► Mg2Sn was mainly found within the grain interior. ► Corrosion resistance was improved obviously. -- Abstract: Magnesium based alloy is a biodegradable metal that has significant potential advantages as an implant material. Element alloying is one of the effective methods to modify the performance of the magnesium alloy. In the paper, Sr and Sn as alloy elements were simultaneously added into the Mg–Zr–Ca alloy to improve the corrosion resistance. The differences of Mg–Zr–Ca alloy and Mg–Zr–Ca–Sr–Sn alloy were compared. The X-ray diffractometer (XRD) and the scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to analysis the phases and the microstructure of the alloys. The results indicated that the addition of Sn could form Mg2Sn mainly within the grain interior; Sr phase was mainly detected along the grain boundary. Immersion tests and electrochemical measurements showed that the corrosion resistance was improved obviously with simultaneous addition of Sr and Sn in Mg–Zr–Ca alloy. It suggested that bio-magnesium based alloy can use Sr and Sn as effective alloy elements to modify its performance.

  19. Synthesis and crystal structure of CaAgBi and BaAg1.837Bi2

    International Nuclear Information System (INIS)

    Two ternary alkali earth silver bismuthides, CaAgBi and BaAg1.837Bi2, have been synthesized by solid-state reactions of the corresponding metals in welded Nb tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. CaAgBi crystallizes in the hexagonal space group P63 mc (No.186) with cell parameters of a = b = 4.8113(4) A, c = 7.8273(9) A, V = 156.92(3) A3, and Z = 2. BaAg1.837Bi2 belongs to tetragonal space group P4/nmm (No.129) with cell parameters of a = b = 4.9202(2) A, c = 11.628(1) A, V = 281.50(3) A3, and Z = 2. The structure of CaAgBi is of the LiGaGe type, and features a three-dimensional four-connected (3D4C) anionic network with Ca2+ encapsulated in the channels formed by [Ag3Bi3] six-membered rings. BaAg1.837Bi2 is isostructural with CaBe2Ge2, a variant of the tetragonal ThCr2Si2-type structure. Its structure exhibits a three-dimensional anionic network built of (0 0 1) and (0 0 2) puckered [Ag2Bi2] layers interconnected via additional Ag-Bi bonds along the c-axis. BaAg1.837Bi2 is metallic based on band structure calculations

  20. Raman scattering, magnetization and magnetotransport study of SrFeO3-delta, Sr3Fe2O7-delta and CaFeO3

    OpenAIRE

    Damljanovic, Vladimir

    2008-01-01

    In this thesis we have determined the Raman spectra as well as the magnetization, resistance and magnetoresistance of the compounds SrFeO3-delta, Sr3Fe2O7-delta and CaFeO3 as a function of temperature. These materials are interesting because they contain iron in the unusually high oxidation state +4, which has the same electroncic configuration as the Mn3+ ion in LaMnO3, a material that shows the giant magnetoresistance effect when doped with calcium or strontium. A novel aspect of the work d...

  1. The Luminescence Properties of New FED Phosphor MSi2N2O2: Eu2+ (M = Sr, Ba)%新型FED荧光粉MSi2N2O2∶Eu2+(M=Sr,Ba)的发光性能

    Institute of Scientific and Technical Information of China (English)

    王灵利; 倪海勇; 张秋红

    2011-01-01

    采用高温固相法合成了一系列新型绿色FED(Field Emission Display)荧光粉MSi2N2O2∶Eu2+(M=Sr,Ba),研究了该荧光粉在不同电压和电流密度下的发光特性.在电子束激发下,SrSi2N2O2:Eu2+的发射主峰位于541 nm,属于黄绿光发射;BaSi2N2O2∶Eu2+的发射主峰位于492 nm,属于蓝绿光发射.BaSi2N2O2∶Eu2+的电流饱和性能要比SrSi2N2O2∶Eu2+好.但在相同电流密度的激发下,SrSi2N2O2∶Eu2+的发光强度明显高于BaSi2N2O2∶Eu2+,因此,SrSi2N2O2∶Eu2+更适合应用于FED中.%A series of new FED (Field Emission Display) green phosphors of MSi2N2O2: Eu2+ (M = Sr, Ba) are synthesized by solid state reaction, and their luminescence properties under the excitation of different voltage and current density are studied. Under the excitation of electron beams, SrSi2N2O2: Eu2+ emits yellow green light with the peak at 541 nm, and BaSi2N2O2: Eu + shows a blue-green emission dominates at 492 nm. The current saturation character of BaSi2N2O2: Eu2+ is better than that of SrSi2N2O2: Eu2+ . While, under the excitation of the same current density, the luminescence intensity of SrSi2 N2 02: Eu + is much higher than that of BaSi2N2O2: Eu2+. So, SrSi2N2O2: Eu2+ is more suitable for FED application.

  2. Thermopower of ceramic HgBa2Ca2Cu3O8+x and HgBa2Ca3Cu4O10+x superconductors under pressure

    International Nuclear Information System (INIS)

    The temperature dependence of thermopower α of a sample, contained 75% HgBa2Ca2Cu3O8+x (Hg-1223 phase) and 10% HgBa2Ca3Cu4O10+x (Hg-1234 phase), was studied in a 95-300 K temperature range under hydrostatic pressure up to 10 kbar. Two superconductive transitions were observed at 132 and 118 K, which were thought to be associated with Hg-1223 and Hg-1234 phases, respectively. Pressure increases Tc of both phases with a rate of 0.2 K/kbar. At T=200 K, d ln α/dP ≅ 3,8 centre dot 10-3 kbar-1

  3. Thermal gradient induced flexoelectric effects in bulk Ba0.67Sr0.33TiO3

    Science.gov (United States)

    Kim, Taeyang; Huang, Wenbin; Huang, Shujin; Jiang, Xiaoning

    2016-05-01

    Flexoelectric effect, denoting electric field gradient induced mechanical strain or mechanical strain gradient induced electric polarization, is a universal phenomenon in all dielectrics. Although research on the topic of flexoelectricity under stress fields and electric fields has advanced significantly, information regarding the phenomenon under thermal fields is rather limited. In this letter, the flexoelectricity field of Ba0.67Sr0.33TiO3 (BST) was investigated by generating temperature gradients along the lengths of samples with symmetric geometry. An electric field gradient induced by a thermal gradient was analyzed based on the temperature-dependent dielectric property of BST. The strain was then experimentally verified due to the electric field gradient. Experimental results suggest converse flexoelectric effect of BST samples with symmetric geometry in a thermal field. This result was not only consistent with the theoretical prediction, but it also followed the scaling effect of flexoelectricity.

  4. Effect of different dopants Ba and Ag on the properties of SrTiO3 nanopowders

    Science.gov (United States)

    Ghasemifard, M.; Abrishami, M. E.; Iziy, M.

    Undoped and Ba and Ag-doped SrTiO3-based nanopowders (NPs) were successfully grown by a modified auto-combustion method. An optimum ratio of citric acid and nitric acid was used as the polymerization agent and fuel. The X-ray diffraction (XRD) results revealed that the products were crystalline with cubic and tetragonal structures. The particle aggregation state, nanoparticles size distribution, morphology and electrical properties were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) were studied, respectively. Using the X-ray peak broadening and size-strain plot (SSP) method the crystallite sizes and lattice strain of the samples were investigated. The UV-vis absorption spectra revealed that the band gap of the STO-based has a strong absorption peak which lies in the UV region.

  5. Interfacial characteristics and dielectric properties of Ba0.65Sr0.35TiO3 thin films

    International Nuclear Information System (INIS)

    Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) depth profiling data show that each element component of the BST film possesses a uniform distribution from the outermost surface to subsurface, but obvious Ti-rich is present to BST/Pt interface because Ti4+ cations are partially reduced to form amorphous oxides such as TiOx (x -7 A/cm2 at 1.23 V and lower than 5.66 x 10-6 A/cm2 at 2.05 V as well as breakdown strength is above 3.01 x 105 V/cm

  6. Effect of different dopants Ba and Ag on the properties of SrTiO3 nanopowders

    Directory of Open Access Journals (Sweden)

    M. Ghasemifard

    2015-01-01

    Full Text Available Undoped and Ba and Ag-doped SrTiO3-based nanopowders (NPs were successfully grown by a modified auto-combustion method. An optimum ratio of citric acid and nitric acid was used as the polymerization agent and fuel. The X-ray diffraction (XRD results revealed that the products were crystalline with cubic and tetragonal structures. The particle aggregation state, nanoparticles size distribution, morphology and electrical properties were characterized by transmission electron microscopy (TEM, dynamic light scattering (DLS, atomic force microscopy (AFM and ultraviolet–visible (UV–vis were studied, respectively. Using the X-ray peak broadening and size–strain plot (SSP method the crystallite sizes and lattice strain of the samples were investigated. The UV–vis absorption spectra revealed that the band gap of the STO-based has a strong absorption peak which lies in the UV region.

  7. Synthesis, vacuum ultraviolet and ultraviolet spectroscopy of Ce3+ ion doped olgite Na(Sr, Ba)PO4

    International Nuclear Information System (INIS)

    Ce3+ ion doped olgite mineral samples, Na(Sr, Ba)PO4, were prepared by a high temperature solid-state reaction. The sample was investigated through x-ray powder diffraction, FT-IR and FT-Raman spectra measurements. The optical properties under vacuum ultraviolet (VUV) synchrotron radiation and ultraviolet (UV) irradiation are reported for the first time. The investigated samples show a strong absorption in the VUV and UV ranges. The bands corresponding to the 4f1 → 4f05d1 transitions of Ce3+ ions in the host lattices are identified. The barycentre of Ce3+ ions in the host lattices, the host absorption, the crystal field splitting, the emission and the Stokes shifts are presented and discussed. This Ce3+ ion doped material is a potential candidate for plasma display panel (PDP) application

  8. Photoluminescence properties of Pb{sup 2+} doped M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Mergen, Ayhan [Marmara University, Faculty of Engineering, Department of Metallurgical and Materials Science Engineering, Istanbul 34722 (Turkey); Pekgoezlue, Ilhan, E-mail: ayhan.mergen@marmara.edu.tr [Bartin University, Faculty of Engineering, Department of Environmental Engineering, Bartin 74100 (Turkey)

    2013-02-15

    Pure and Pb{sup 2+} doped M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) materials were synthesized at 900 Degree-Sign C for 12 h in air. The phases of the synthesized materials were determined using the powder XRD. The photoluminescence properties of the synthesized phosphors were investigated using a spectrofluorometer at room temperature. The emission and excitation bands of Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} were observed at 330 and 260 nm, respectively. And, the emission and excitation bands of Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} were observed at 381 and 293 nm, respectively. The dependence of the emission intensity on the Pb{sup 2+} concentration for the M{sub 2-x}Pb{sub x}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) was studied in detail. It was observed that the optimum concentrations of Pb{sup 2+} in Sr{sub 2}Mg(BO{sub 3}){sub 2} and Ba{sub 2}Mg(BO{sub 3}){sub 2} are 0.06 and 0.01 mol, respectively. The Stokes shifts of Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} phosphors were calculated to be 8159 and 7883 cm{sup -1}, respectively. The luminescence behavior of the Pb{sup 2+} ion in M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) is discussed. - Highlights: Black-Right-Pointing-Pointer We have synthesized two novel inorganic borate phosphors for the first time. Black-Right-Pointing-Pointer Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} phosphors emit at 330 and 381 nm, respectively. Black-Right-Pointing-Pointer Consequently, they are promising phosphors for UV lamp phosphors.

  9. Mass spectrometric analysis of laser evaporation products of ceramics of Bi2Sr2CaCu2Ox composition

    International Nuclear Information System (INIS)

    Mass spectrometric analysis is used to study mechanism of laser evaporation of superconducting ceramics of Bi2Sr2CaCu2Ox composition. During evaporation as a result of pulsed laser irradiation of a sample placed in vaccum ions of all metals containing in ceramics and also neutral O2, Ca, Sr, Cu, Bi and metal oxides were detected on yttrium aluminate. Time-of-flight spectra had two peaks corresponding to ion and neutral components. Comparison of neutral components. Comparison of neutral particle rates points to the fact that gas dynamic processes connected with formation of dense gas cloud near the target surface play an important

  10. Magnetic-field-modulated microwave-absorption detection in a Bi-Sr-Ca-Cu-O superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Bohandy, J.; Adrian, F.J.; Kim, B.F.; Moorjani, K.; Shull, R.D.; Swartzendruber, L.J.; Bennett, L.H.; Wallace, J.S.

    1988-06-01

    Superconducting transitions are observed at 110 K, 100 K, and 72 K in a nominally BiSrCaCu/sub 2/O/sub x/ ceramic using the novel technique of magnetic-field-modulated microwave-absorption detection. The response of the BiSrCaCu/sub 2/O/sub x/ ceramic to an external magnetic field differs markedly from that of YBa/sub 2/Cu/sub 3/O and, in particular, -dT/sub c//dH is much greater in the bismuth sample.

  11. Magnetic-field-modulated microwave-absorption detection in a Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Superconducting transitions are observed at 110 K, 100 K, and 72 K in a nominally BiSrCaCu2O/sub x/ ceramic using the novel technique of magnetic-field-modulated microwave-absorption detection. The response of the BiSrCaCu2O/sub x/ ceramic to an external magnetic field differs markedly from that of YBa2Cu3O and, in particular, -dT/sub c//dH is much greater in the bismuth sample

  12. Electric-field modulation of a Bi-Sr-Ca-Cu-O film with a polymer film as an insulator

    International Nuclear Information System (INIS)

    The authors fabricated the multilayered structure with Au gate electrode/polymer film/Bi-Sr-Ca-Cu-O film to study the electric-field control of high Tc superconductor. A Bi-Sr-Ca-Cu-O(BSCOO) film was fabricated using an ion beam sputtering technique. The plasma polymerization using trifluoroethane gas was used to make the gate insulator. The patterning of the BSCCO film was carried out using an ion beam etching technique. The supercurrent of the structure decreased when the gate voltage was applied to the gate electrode

  13. High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

    Science.gov (United States)

    Ginley, David S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.; Martens, Jon S.; Plut, Thomas A.; Tigges, Chris P.; Vawter, Gregory A.; Zipperian, Thomas E.

    1994-10-25

    A process for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO.sub.3 crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O.sub.3, followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry.

  14. Theoretical study of the new zintl phases compounds K{sub 2}ACdSb{sub 2} (A=(Sr, Ba))

    Energy Technology Data Exchange (ETDEWEB)

    Azam, Sikander [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Reshak, A.H., E-mail: maalidph@yahoo.co.uk [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia)

    2015-05-01

    The electronic structure and optical properties of K{sub 2}SrCdSb{sub 2} and K{sub 2}BaCdSb{sub 2} compounds are computed using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2k code. In this perspective, the local density approximation (LDA), generalized gradient approximation (GGA) and Engel and Vosko approximation (EV-GGA) were used for the exchange correlation potential. The calculated band structure shows a direct band gap of about 0.344/0.20 eV (LDA), 0.463/0.285 eV (GGA) and 0.904/0.707 eV (EV-GGA) for K{sub 2}SrCdSb{sub 2}/K{sub 2}BaCdSb{sub 2} compounds. The part of different bands was scrutinized from total and partial density of states curves. There is strong hybridization between Sr-s and Sr-p states and also between Cd-d and Sb-s states in the valence band. The electronic charge density has also been studied in the (200) crystallographic plane. The K, Sr/Ba, Cd and Sb atoms shows ionic bonding. Besides this, the optical properties, including the dielectric function are obtained and analyzed in details.

  15. Magnetic and magnetotransport properties of ultrathin La{}_{0.7}Ba{}_{0.3}MnO3 epitaxial films embedded in SrRuO3

    Science.gov (United States)

    Bern, F.; Ziese, M.; Vrejoiu, I.; Li, X.; van Aken, P. A.

    2016-05-01

    The structural, magnetic and magnetotransport properties of La{}0.7Ba{}0.3MnO3 layers interfaced with SrRuO3 layers were studied. High quality trilayers with coherent interfaces were fabricated by pulsed laser deposition. The thickness of the embedded La{}0.7Ba{}0.3MnO3 layer was varied between one and five unit cells, whereas the embedding SrRuO3 layers were kept at a constant thickness of three unit cells. In this embedded geometry La{}0.7Ba{}0.3MnO3 layers are ferromagnetic, even if only one unit cell thick. Magnetization and anomalous Hall effect curves show an antiferromagnetic coupling of the layers that leads to an intricate magnetic field dependence. When this is disentangled, it can be shown that the magnetic and transport properties are mainly dominated by the corresponding properties of the constituent materials.

  16. Thermoluminescence study of BaMgAl10O17 and SrMgAl10O17 doping with Mn2+ by γ-irradiation

    International Nuclear Information System (INIS)

    The synthesis of Mn2+ doped BaMgAl10O17 and SrMgAl10O17 phosphor by combustion method at 500°C. For the TL study, Mn2+ doped BaMgAl10O17 shows two intensive TL glow peak around at 403.5K and ∼488K respective to BaMgAl10O17: Mn2+ and 650 K for SrMgAl10O17:Mn2+. The trapping parameter were calculated by Chen's peak shape method. The maximum intensity and the glow curve obtained by γ-irradiation at 2Gy/min. These results are supported by corresponding X-ray diffraction measurements which exhibit crystalline nature. Overall results suggest the possibility of utilizing this material in futuristic dosimeter application. (author)

  17. The Effect Of Coupling Agent On Composite Magnet Characteristic Based On Hexa ferrite (Sr M/Ba M) With Polyester And Epoxy Binder

    International Nuclear Information System (INIS)

    Magnetic composites are mixtures of hexa ferrite powder and non magnetic materials such as polymers as binders. These composites have been investigated because they are light, elastic, and cheap. In this study thermoset polymer (epoxy and polyester) were used as binders. Inside study of coupling agent added effect on mechanical properties, hardness and microstructure. The composites were prepared by mixture thermoset polymer epoxy or polyester with hexa ferrite powder Sr M (SrFe12O19) or Ba M (BaFe12O19) with volume fraction of 40,50 and 60 % v/v, coupling agent of the Tetra Isopropyl Titanate in the amount of 5 ml or 10 ml are added before mix turing of the thermoset polymer epoxy or polyester with hexa ferrite powder. The resulting composite were characterized mechanically (tensile strength), hardness and microstructure test. The results showed that the tensile strength and hardness of the composite magnet were increased by increasing the composition of magnetic powder, either Sr M or Ba M, it caused by microstructure of particle Sr M magnetic powder 1.6 μm in the form splinter, where as the Ba M magnetic powder 1,2 μm in nodular form. Thermoset polymer epoxy as binder have tensile strength and hardness is bigger than composite magnet based on polyester, either Sr M or Ba M. The addition of coupling agent is very influenced on the tensile strength and hardness composite magnet, the more coupling magnet addition causes the more tensile strength and hardness of the composite magnet

  18. Decoupling of the CuO2 plane and superconductivity in Cu0.5Tl0.5Ba2(Ca2‑ySry)Cu3O10‑δ(y = 0-0.4) samples

    Science.gov (United States)

    Khan, Nawazish A.; Usman Muzaffar, M.

    2016-05-01

    Cu0.5Tl0.5Ba2(Ca2‑ySry)Cu3O10‑δ(y = 0-0.4) samples have been synthesized at normal pressure at 860∘C. The main objectives of these experiments to study the role of inter-plane decoupling in suppressing the superconductivity of high temperature superconductors (HTSC). These samples have shown orthorhombic crystal structure and the c-axis length increases with increased Sr-doping. All the samples have shown metallic variations of resistivity (ρ) from room temperature down to the onset of superconductivity. The magnitude of the superconductivity is suppressed and the apical oxygen modes are hardened with Sr-doping. These studies have shown that Sr-doping promotes decoupling of conducting CuO2 planes which suppress the superconducting properties of final compound. The excess conductivity analyses have shown increases in the width of two-dimensional (2D) Lawrence-Doniach (LD) regime with Sr-doping. The coherence length along the c-axis ξc(0), the inter-layer coupling J, the phase relaxation time of the carriers τφ and the Fermi velocity vF of superconductor carriers is suppressed. The underlying reason for the suppression of superconductor properties is the decrease in the density of carriers in the superconductor planes. However, the values of Bc0(T), Bc1(T) and Jc(0) have been found to increase with the increased Sr-doping, which is suggested to be originating from the enhancement in the flux pinning character which is induced by Sr-doping. The values of magnetic field penetration depth λp.d and the Ginzburg-Landau (GL) parameter κ decrease with Sr-doping and it is also suggested to be originating from the increase of flux pinning character of the samples with Sr-doping.

  19. Structural phase transition and spontaneous interface reconstruction in La2/3Ca1/3MnO3/BaTiO3 superlattices

    Science.gov (United States)

    Turner, S.; Lebedev, O. I.; Verbeeck, J.; Gehrke, K.; Moshnyaga, V.; Van Tendeloo, G.

    2013-01-01

    (La2/3Ca1/3MnO3)n/(BaTiO3)m (LCMOn/BTOm) superlattices on MgO and SrTiO3 substrates with different layer thicknesses (n = 10, 38, 40 and m = 5, 18, 20) have been grown by metal organic aerosol deposition (MAD) and have been fully characterized down to the atomic scale to study the interface characteristics. Scanning transmission electron microscopy combined with spatially resolved electron energy-loss spectroscopy provides clear evidence for the existence of atomically sharp interfaces in MAD grown films, which exhibit epitaxial growth conditions, a uniform normal strain, and a fully oxidized state. Below a critical layer thickness the LCMO structure is found to change from the bulk Pnma symmetry to a pseudocubic R3¯c symmetry. An atomically flat interface reconstruction consisting of a single Ca-rich atomic layer is observed on the compressively strained BTO on LCMO interface, which is thought to partially neutralize the total charge from the alternating polar atomic layers in LCMO as well as relieving strain at the interface. No interface reconstruction is observed at the tensile strained LCMO on BTO interface.

  20. 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.

    Science.gov (United States)

    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

  1. Spin tunneling in Co/Au/I/BiSrCaCuO tunnel junctions

    International Nuclear Information System (INIS)

    Conductance spectra of Co/Au/I/Bi2Sr2CaCu2Ox+8(BSCCO) tunnel junctions have been measured to investigate the tunneling of spin polarized quasiparticles. BSCCO thin films prepared by molecular beam epitaxy are used for the Co/Au/I/BSCCO tunnel junctions because those have flat surface without any large steps as observed on the cleaved surface of single crystals. The superconducting gap is clearly observed in the conductance spectra at the temperature below the critical temperature Tc. In addition, a splitting of the zero bias conductance peak and the imbalance of the peak heights are observed. This feature is induced by the spin polarization of quasiparticles injected into the superconductors. [copyright] 2001 American Institute of Physics

  2. Optimization of the 120 K superconducting phase in the BiSrCaCuO system

    International Nuclear Information System (INIS)

    The formation of the 120 K superconducting phase in the BiSrCaCu2Oy system has been investigated by microwave absorption. This material is characterized by an intense, low-field microwave absorption (LFMA) below the superconducting transition temperature Tc and a g = 2 electron spin resonance (ESR) signal above Tc. The LFMA is used to follow the formation of the high Tc phases in this compound. The purity of these superconducting phases is also reflected by the intensity of the g = 2 signal. Various stages of sample preparation are studied to optimize the reaction conditions for the formation of the 120 K phase. LFMA and ESR results are also compared and contrasted with resistance measurements

  3. Spin-mixed doubly excited resonances in Ca and Sr spectra

    International Nuclear Information System (INIS)

    We present a joint theoretical and experimental investigation to demonstrate explicitly how the combined spin-dependent interaction and the configuration interaction may affect the mixing of different spin states along various doubly excited autoionization series for Ca and Sr as energy increases across several ionization thresholds. In particular, our study has identified the inversion of energy levels between members of a number of multiplets, i.e., in contrast to the Hund's rules, due to the presence of perturber from other overlapping resonance series. We are also able to demonstrate the beginning of the breakdown of the LS coupling for resonance series corresponding to electron configurations with higher orbital angular momenta and those above the third ionization threshold.

  4. Synthesis and characterization of nanostructured CaZrO{sub 3} and BaZrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ibiapino, Amanda Laura; Figueiredo, Laysa Pires de [Departamento de Quimica, Instituto de Ciencias Exatas e da Terra, Universidade Federal do Mato Grosso, MT (Brazil); Lascalea, Gustavo E. [LISAMEN/CONICET, Ciudad de Mendoza (Argentina); Prado, Rogerio Junqueira, E-mail: rjprado@ufmt.br [Instituto de Fisica, Universidade Federal do Mato Grosso, Cuiaba - MT (Brazil)

    2013-09-01

    In this work, nanostructured samples of barium zirconate (BaZrO{sub 3}) and calcium zirconate (CaZrO{sub 3}) were synthesized by the gel-combustion method, using glycine as fuel. The ceramic powders were calcined at 550 Degree-Sign C for 2 h and subsequently heat treated at 1350 Degree-Sign C for 10 min (fast-firing). The X-ray diffraction technique was employed to identify and characterize the crystalline phases present in the synthesized powders, using the Rietveld method. Monophasic nanostructured samples of BaZrO{sub 3} and CaZrO{sub 3} presenting average crystallite sizes of around 8.5 and 10.3 nm, respectively, were found after fast-firing. (author)

  5. Chemistry of the M (M=Fe, Ca, Ba)-Se-H2O Systems at 25 °C

    OpenAIRE

    Fumihiko Hasegawa; Tadahisa Nishimura; Ryosuke Hata

    2009-01-01

    The chemistry of the M (M=Fe, Ca, Ba)-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H2O, Ca-Se(IV,VI)-H2O and Ba-Se(IV,VI)-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high con...

  6. Chemistry of the M (M=Fe, Ca, Ba-Se-H2O Systems at 25 °C

    Directory of Open Access Journals (Sweden)

    Fumihiko Hasegawa

    2009-09-01

    Full Text Available The chemistry of the M (M=Fe, Ca, Ba-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III-Se(IV-H2O, Ca-Se(IV,VI-H2O and Ba-Se(IV,VI-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L.

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

    Science.gov (United States)

    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

  8. Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

    International Nuclear Information System (INIS)

    The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high Tc, chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO2 laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with Tc(0)'s of 76 K could be deposited using the KrF laser at substrate temperatures of 5 degrees C to 20 degrees C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in Tc(0) was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component

  9. The records and implications of Mg,Sr and Ba in cave water and active speleothems in Jiguan Cave,western Henan Province%豫西鸡冠洞洞穴水及现代沉积物Mg,Sr和Ba记录及其意义

    Institute of Scientific and Technical Information of China (English)

    任小凤; 张志钦; 杨琰; 彭涛; 赵景耀; 张银环; 聂旭东; 刘肖; 李建仓; 凌新有

    2014-01-01

    Speleothems contain a number of suitable proxies reconstructing climate environmental changes, which is a top topic in current research.Due to the variety of sources and complex factors,trace elements are less frequently used than the oxygen isotopes in climate studies.However,they are used to reveal the groundwater runoff in the epikarst overlying the cave with the process and the surface environment.Induc-tively coupled plasma mass spectrometry (ICP-MS)and inductively coupled plasma optical emission spec-trometry(ICP-OES)have been used to analyse the trace elements of Ca、Mg、Sr and Ba in cave water and ac-tive formations in Jiguan Cave during December,2009 and August,2013.Jiguan Cave (33°46′N,111°34′E) is located in Luanchuan county,western Henan Province,which is north of the Qinling ranges-Huaihe River and southeast of Loess Plateau,while at the foot of the northern watershed of the Yangtze River and the Yellow River.It main exposed rocks are Sinian chlorite marbles.Located in the typical east Asian monsoonal zone,the Jiguan Cave area is typically has cold/dry winters and warm/wet summers.More than 50 % of the total annual precipitation occurs in summer.The mean annual temperature and precipitation recorded at a nearby meteorological station are 12.1±0.9 ℃ and 846±181 mm (1957-2009)respectively.In the paper, trace elements such as Ca,Mg,Sr and Ba in cave water and active formations collected in Jiguan Cave were analyzed with ICP-MS and ICP-OES.The Mg/Ca,Sr/Ca and Ba/Ca of cave water varied between 0.2-0.8, (1.2-6.0)×10-3 and (0.3-2.0)×10-3 respectively.Mg/Ca can respond to the environment outside the cave faithfully.The wet-dry condition of the karst system is suggested as the dominant controller of Mg/Ca ratios in cave pool water and underground rivers,whereas the Sr/Ca and Ba/Ca may have nothing to do with precipitation and temperature.The Mg/Ca,Sr/Ca and Ba/Ca ratios in active speleothems varied between (9-50)×10-3 ,(0.1-1.2)×10-3 and (0

  10. Monte Carlo Simulation of Gamma-Ray Response of BaF2 and CaF2

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Fei; Xie, YuLong; Wang, Zhiguo; Kerisit, Sebastien N.; Wu, Dangxin; Campbell, Luke W.; Van Ginhoven, Renee M.; Prange, Micah P.

    2013-12-01

    We have employed a Monte Carlo (MC) method to study intrinsic properties of two alkaline-earth halides, namely BaF2 and CaF2, relevant to their use as radiation detector materials. The MC method follows the fate of individual electron-hole (e-h) pairs and thus allows for a detailed description of the microscopic structure of ionization tracks created by incident γ-ray radiation. The properties of interest include the mean energy required to create an e-h pair, W, Fano factor, F, the maximum theoretical light yield, and the spatial distribution of e-h pairs resulting from γ-ray excitation. Although W and F vary with incident photon energy at low energies, they tend to constant values at energies higher than 1 keV. W is determined to be 18.9 and 19.8 eV for BaF2 and CaF2, respectively, in agreement with published data. The e-h pair spatial distributions exhibit a linear distribution along the fast electron tracks with high e-h pair densities at the end of the tracks. Most e-h pairs are created by interband transition and plasmon excitation in both scintillators, but the e-h pairs along fast electron tracks in BaF2 are slightly clustered, forming nanoscale domains and resulting in the higher e-h pair densities than in CaF2. Combining the maximum theoretical light yields calculated for BaF2 and CaF2 with those obtained for CsI and NaI shows that the theoretical light yield decreases linearly with increasing band gap energy.

  11. Monte Carlo simulation of gamma-ray response of BaF{sub 2} and CaF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gao, F.; Xie, Y. L.; Wang, Z. G.; Kerisit, S.; Wu, D. X.; Campbell, L. W.; Van Ginhoven, R. M.; Prange, M. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)

    2013-11-07

    We have employed a Monte Carlo (MC) method to study intrinsic properties of two alkaline-earth halides, namely, BaF{sub 2} and CaF{sub 2}, relevant to their use as radiation detector materials. The MC method follows the fate of individual electron-hole (e-h) pairs and thus allows for a detailed description of the microscopic structure of ionization tracks created by incident γ-ray radiation. The properties of interest include the mean energy required to create an e-h pair, W, Fano factor, F, the maximum theoretical light yield, and the spatial distribution of e-h pairs resulting from γ-ray excitation. Although W and F vary with incident photon energy at low energies, they tend to constant values at energies higher than 1 keV. W is determined to be 18.9 and 19.8 eV for BaF{sub 2} and CaF{sub 2}, respectively, in agreement with published data. The e-h pair spatial distributions exhibit a linear distribution along the fast electron tracks with high e-h pair densities at the end of the tracks. Most e-h pairs are created by interband transition and plasmon excitation in both scintillators, but the e-h pairs along fast electron tracks in BaF{sub 2} are slightly clustered, forming nanoscale domains and resulting in the higher e-h pair densities than in CaF{sub 2}. Combining the maximum theoretical light yields calculated for BaF{sub 2} and CaF{sub 2} with those obtained for CsI and NaI shows that the theoretical light yield decreases linearly with increasing band gap energy.

  12. Study of gel grown mixed crystals of BaCa(1–)(IO3)4

    Indian Academy of Sciences (India)

    S L Garud; N K Mahajan; K B Saraf

    2009-04-01

    The growth of mixed crystals of BaCa1–(IO3)4 were carried out with simple gel method. The effect of various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants on the growth was studied. Crystals having different morphologies and habits were obtained. The grown crystals were characterized by XRD, FT–IR, EDAX, TGA, DTA and DSC.

  13. Electrochemical properties of mixed conducting (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, J.W.; Armstrong, T.R.; Bates, J.L. [and others

    1996-04-01

    Electrical properties and oxygen permeation properties of solid mixed-conducting electrolytes (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba) have been characterized. These materials are potentially useful as passive membranes to separate high purity oxygen from air and as the cathode in a fuel cell. Dilatometric linear expansion measurements were performed as a function of temperature and oxygen partial pressure to evaluate the stability.

  14. Hole-filling in Tl2Ba2Ca1-xPrxCu2O8+δ system

    International Nuclear Information System (INIS)

    Studies of resistivity and thermoelectric power in Pr doped Tl2Ba2Ca Cu2O8 superconducting system show an increase in the localization of the carriers with the incorporation of Pr in the system. X-ray absorption measurements show the Pr to be present predominantly in the 4+ state. These observations point towards hole-filling to be the dominant mechanism for the suppression of superconductivity in this system. (author)

  15. Performance of Ca1-xSrxTiO3 as barriers in dielectric barrier discharges with different Sr content

    International Nuclear Information System (INIS)

    Plasma assisted catalytic technology, which uses synergetic technologies between the catalyst and plasma, has attracted much attention over the past several years. Theoretically, permittivity of a dielectric barrier influences the transferred charge of a microdischarge; thus high permittivity can improve the plasma reaction in a dielectric barrier discharge (DBD) plasma reactor. Despite the increased interest in the chemical processes, very little has been reported concerning the influence of materials of a dielectric barrier on DBD plasma reactions, since a high permittivity barrier generally exhibits low fracture strength and low dielectric strength making it break down under strong current pulses. In the present study, Ca1-xSrxTiO3 (0.1 ≤ x ≤ 0.4) which possesses a high permittivity and a high fracture strength was prepared by liquid phase sintering and was used as a dielectric barrier for the destruction of carbon dioxide by a DBD plasma reaction. The permittivity of Ca1-xSrxTiO3 (0.1 ≤ x ≤ 0.4) increased with increasing SrTiO3 content; however, the observed CO2 conversion became greatest using Ca0.8Sr0.2TiO3 and then decreased with increasing SrTiO3 content. These results imply that the reactivity of CO2 destruction does not monotonously increase with increased permittivity of the Ca1-xSrxTiO3 barriers. Both amplitude and density of the current pulses ignited by Ca0.8Sr0.2TiO3 were much greater than that of Ca0.6Sr0.4TiO3. Further, it was confirmed that a plasma reaction uniformly proceeded using the Ca0.8Sr0.2TiO3 barrier, but proceeded non-uniformly using the Ca0.6Sr0.4TiO3 barrier by observing the carbon deposition profiles on the surfaces of the barriers

  16. A Comparative Study of Si-BaSO4 and Si-CaSO4 Pyrotechnic Time-Delay Compositions

    Science.gov (United States)

    Tichapondwa, Shepherd M.; Focke, Walter W.; del Fabbro, Olinto; Gisby, John; Kelly, Cheryl

    2016-07-01

    Slow-burning Si-BaSO4 pyrotechnic delay compositions are employed commercially for intermediate to long-time delays. However, there is very little information on this composition available in open literature. The reactivity of this composition was therefore characterized and compared to that of Si-CaSO4. The Si-BaSO4 composition supported combustion in the range of 20-60 wt% Si in the bomb calorimeter. However, burning was only sustained between 20 and 40 wt% Si in rigid aluminum tubes, with burning rates of between 8.4 and 16 mm s-1. These values are comparable to those for the Si-CaSO4 system (6.9-12.5 mm s-1). However, the CaSO4-based formulations tended to have higher energy output and produced more transient pressure compared to the barium sulfate compositions. Both formulations were insensitive to impact, friction, and electrostatic discharge stimuli. The reaction products were a complex mixture that contained crystalline phases in addition to an amorphous phase. Although barium sulfate is insoluble in water and decidedly nontoxic, the reaction products produced by the Si-BaSO4 compositions were found to release soluble barium ions when contacted with water. This ranged from 50 to 140 mg per gram of barium sulfate reacted.

  17. Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2

    International Nuclear Information System (INIS)

    We have performed low-temperature specific heat C and thermal conductivity κ measurements on the Ni-pnictide superconductors BaNi2As2 (Tc = 0.7K) and SrNi2P2 (Tc = 1.4K). The temperature dependences C(T) and κ(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual κ for BaNi2As2 rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba0.6La0.4Ni2As2 shows a mild suppression of Tc and Hc2 relative to BaNi2As2.

  18. Study on Ca8Mg(SiO4)4Cl2:Eu2+ Doped with Sr2+

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Ca8Mg(SiO4)4Cl2:Eu2+ phosphor doped with Sr2+ cation for Ca2+ partially, was synthesized by solid-state reaction at high temperature under reducing atmosphere, and its luminescent properties were investigated. The experimental results indicate that the emission intensity of the phosphor increases after being doped with a few amount of Sr2+ ion. The emission peak of the phosphor blue shift to about 464 nm when the phosphor is doped with large quantity of Sr2+ ions. The excitation spectrum indicates that the phosphor can be well excited by UV and blue light from 300 to 460 nm, and the phosphor was fitted well for the excitation by UV or blue-LED.

  19. Layer-by-layer deposition of superconducting Sr-Ca-Cu-O films by the spray pyrolysis technique

    International Nuclear Information System (INIS)

    Layer-by-layer deposition of Sr-Ca-Cu-O films has been carried out using the spray pyrolysis technique. Reagent-grade nitrates of strontium, calcium and copper were used to prepare starting solutions for spray pyrolysis. A two-step procedure was used for every layer of the constituents in the sequence Sr-Cu-Ca-Cu-Sr: first, deposition onto silver substrate at 350 C, then firing at T≥450 C, both at atmospheric pressure. The films were 2-3 μm thick and showed adequate adhesion to the substrate. The films were then characterised by studying their electron micrographs, X-ray diffraction patterns and electrical resistivity. The films showed superconductivity below 104 K. ((orig.))

  20. Soft X-ray magnetic dichroism of (Ca,Sr)RuO{sub 3}: Evidence for strain-dependent magnetism

    Energy Technology Data Exchange (ETDEWEB)

    Assmann, Andrea; Uebe, Stephan; Wissinger, Markus; Loehneysen, Hilbert von [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik (Germany); Karlsruhe Institute of Technology, Physikalisches Institut (Germany); Merz, Michael; Fuchs, Dirk; Nagel, Peter; Schuppler, Stefan [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik (Germany)

    2010-07-01

    The 4d transition metal oxide Ca{sub 1-x}Sr{sub x}RuO{sub 3} exhibits ferromagnetic order in the doping range 0.4Ca{sub 1-x}Sr{sub x}RuO{sub 3} remains essentially isostructural and has a similar electronic configuration throughout the doping series, the differences in the magnetic properties might be caused by chemical pressure or magnetic dilution. To verify a possible dependence of the magnetic moments on pressure, (Ca,Sr)RuO{sub 3} films were deposited on different substrates (LSAT, STO, DyScO{sub 3}=DSO), with the lattice mismatch imposing a specific strain on the epitaxial films that increases when going from LSAT to STO and DSO. The magnetic and electronic structure of the strained samples was studied by soft x-ray absorption and magnetic circular dichroism at the Ru M{sub 2,3} and O K edges. It turns out that at 20 K, the magnetic moments strongly depend on the strain: while the spin moment of samples on LSAT almost vanishes, a distinct moment is found for (Ca,Sr)RuO{sub 3} films deposited on STO and DSO. Furthermore, a significant magnetic anisotropy is observed, with the spin moments mainly oriented perpendicular to the substrate plane. Implications are discussed.

  1. Growth of nucleation sites on Pb-doped Bi2Sr2Ca1Cu2O8 + delta

    Science.gov (United States)

    Finnemore, D. K.; Xu, Ming; Kouzoudis, D.; Bloomer, T.; Kramer, M. J.; McKernan, Stuart; Balachandran, U.; Haldar, Pradeep

    1996-01-01

    In the growth of Bi2Sr2Ca2Cu3O10+δ from mixed powders of Pb-doped Bi2Sr2Ca1Cu2O8+δ and other oxides, it has been discovered that a dense array of hillocks or mesas grow at the interface between a Ag overlay and Pb-doped Bi2Sr2Ca1Cu2O8+δ grains during the ramp up to the reaction temperature. As viewed in an environmental scanning electron microscope, the Ag coated grains develop a texture that looks like ``chicken pox'' growing on the grains at about 700 °C. These hillocks are about 100 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurements indicate that the hillocks are a recrystallization of (Bi,Pb)2Sr2Ca1Cu2O8+δ, and are definitely not a Pb rich phase.

  2. Synthesis and magnetic properties of the Bi-Sr-Ca-Cu oxide 80- and 110-K superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, J.S.; Ritter, J.J.; Fuller E.R. Jr.; Bennett, L.H.; Shull, R.D.; Swartzendruber, L.J.

    1989-02-01

    We report on the observation of both the 80- and 110-K superconducting transitions in a nominally BiSrCaCu/sub 2/O/sub x/ material produced by a new chemical synthesis procedure as well as by solid-state reaction. We also discuss a method for the confirmation of the presence of superconductivity when only a small amount is present.

  3. Synthesis and magnetic properties of the Bi-Sr-Ca-Cu oxide 80- and 110-K superconductors

    International Nuclear Information System (INIS)

    We report on the observation of both the 80- and 110-K superconducting transitions in a nominally BiSrCaCu2O/sub x/ material produced by a new chemical synthesis procedure as well as by solid-state reaction. We also discuss a method for the confirmation of the presence of superconductivity when only a small amount is present

  4. EPR and optical spectroscopy of Yb3+ ions in CaF2 and SrF2

    International Nuclear Information System (INIS)

    The Yb3+ paramagnetic center of the trigonal symmetry ('oxygen' paramagnetic center T2) in CaF2 and SrF2 single crystals is studied by EPR and optical spectroscopy. The Stark level energies of the Yb3+ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated

  5. STM Studies of Near-Optimal Doped Bi_2Sr_2CaCu_2O_8 delta

    Energy Technology Data Exchange (ETDEWEB)

    Kapitulnik, Aharon

    2010-04-05

    In this paper we summarize our STM studies of the density of electronic states in nearly optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8 + {delta}} in zero field. We report on the inhomogeneity of the gap structure, density of states modulations with four-lattice constant period, and coherence peak modulation.

  6. Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr

    KAUST Repository

    Zhang, J.-Y.

    2013-04-05

    Dispersion coefficients for the long-range interactions of the first four excited states of He, i.e., He(2 1, 3 S) and He(2 1, 3 P), with the low-lying states of the alkaline earth atoms Mg, Ca, and Sr are calculated by summing over the reduced matrix elements of multipole transition operators.

  7. Excitonic emission of scheelite tungstates AWO.sub.4./sub. (A = Pb, Ca, Ba, Sr)

    Czech Academy of Sciences Publication Activity Database

    Nikl, Martin; Boháček, Pavel; Mihóková, Eva; Kobayashi, M.; Ishii, M.; Babin, V.; Stolovich, A.; Zazubovich, S.; Bacci, M.

    Moscow : Faculty of Physics M.V. Lomonosov Moscow State University, 2000 - (Mikhailin, V.), s. 429-434 ISBN 5-8279-0007-9. [International Conference on Inorganic Scintillators and Their Applications - SCINT99 /5./. Moscow (RU), 16.08.1999-20.08.1999] Institutional research plan: CEZ:AV0Z1010914 Subject RIV: BM - Solid Matter Physics ; Magnetism

  8. New perovskite-related oxides having high dielectric constant: Ln2Ba2CaZn2Ti3O14 (Ln = La and Pr)

    Indian Academy of Sciences (India)

    Pika Jha; Ashok K Ganguli

    2003-10-01

    Two new oxides, La2Ba2CaZn2Ti3O14 and Pr2Ba2CaZn2Ti3O14, have been synthesized by the ceramic route at 1100°C. These oxides crystallize in the disordered cubic structure with an `a’ lattice parameter of 3.9728 (2) and 3.9448 (5) respectively. These oxides show high dielectric constant (70 and 57) and low loss (0.003 and 0.013 at 100 kHz) for La2Ba2CaZn2Ti)3O14 and Pr2Ba2CaZn2Ti3O14 respectively. The dielectric constant is highly stable with frequency and temperature.

  9. Studies on structural and thermo-chemical behavior of MFe12O19(s) (M = Sr, Ba and Pb) prepared by citrate-nitrate gel combustion method

    International Nuclear Information System (INIS)

    The citrate-nitrate gel combustion route was used to prepare SrFe12O19(s), BaFe12O19(s) and PbFe12O19(s). The compounds were characterized by Rietveld profile analysis of the X-ray powder diffraction data. The thermal expansion coefficients of MFe12O19 (M = Sr, Ba and Pb) were determined using high temperature powder X-ray diffraction data. The lattice parameters of these compounds were fitted into polynomial expressions as a function of temperature. Melting points of MFe12O19 (M = Sr, Ba and Pb) were determined using high temperature calorimeter and the values are; 1632 K, 1611 K and 1538 K, respectively. Standard molar heat capacities of BaFe12O19(s) and PbFe12O19(s) were determined from 130 K to 850 K using a heat flux type differential scanning calorimeter (DSC) and heat capacity anomalies were observed at 725 K and 718 K, respectively. This heat capacity anomaly is due to the magnetic order-disorder transition from ferrimagnetic state to paramagnetic state

  10. First-principles calculation of defect energetics in cubic-BaTiO3 and a comparison with SrTiO3

    International Nuclear Information System (INIS)

    The structural relaxation and formation energies of intrinsic vacancies in cubic-BaTiO3 were studied by using a first-principles plane-wave-based pseudopotential calculation. The calculated defect formation energies and the atomic relaxations were compared with previously reported data for SrTiO3 [Tanaka T, Matsunaga K, Ikuhara Y, Yamamoto T. Phys Rev B 2003;68:205213]. It was found that the formation energies of the partial Schottky species, VTi2-+VO2+ and VBa2-+VO2+, are the lowest in the oxidized condition. In contrast, as the oxygen chemical potential decreased, namely the reduced condition, the O vacancy becomes dominant in cubic-BaTiO3. Concerning the atomic relaxation, it was found that BaTiO3 and SrTiO3 show a difference in magnitude. It was also found that the overall vacancy formation energy in BaTiO3 is higher than that in SrTiO3

  11. Preparation and characterizations of Ba(Zr,Ti)O{sub 3}/(Ba,Sr)TiO{sub 3} heterostructures grown on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} single crystal substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chan, N.Y.; Gao, G.Y.; Wang, Y. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University (Hong Kong); Chan, H.L.W., E-mail: apahlcha@inet.polyu.edu.h [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University (Hong Kong)

    2010-10-01

    Epitaxial perovskite (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} (BST), Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} (BZT), Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}/(Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3}(BZT/BST) and Ba{sub 0.85}Sr{sub 0.15}Zr{sub 0.1}Ti{sub 0.9}O{sub 3} (BSZT) thin films were grown on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} (LSAT)[001]single crystal substrate coated with conducting oxide LaNiO{sub 3}(LNO) by pulsed laser deposition. X-ray diffraction, atomic force microscopy and electrical measurements were used to characterize the thin films. The {theta}-2{theta} linear scan indicated that the thin films with LNO layer show (001) orientations perpendicular to the substrate. Smooth and dense surface with grain size of 30 nm-80 nm were observed. The relative permittivity of the BST, BZT/BST, BZT and BSZT thin films are 1101, 799, 584 and 1784 respectively at 10 kHz. The tunability of the thin films are 39%, 32%, 44% and 60%. The results show that BSZT film has the highest tunability.

  12. Preparation and characterizations of Ba(Zr,Ti)O3/(Ba,Sr)TiO3 heterostructures grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 single crystal substrates by pulsed laser deposition

    International Nuclear Information System (INIS)

    Epitaxial perovskite (Ba0.7Sr0.3)TiO3 (BST), Ba(Zr0.2Ti0.8)O3 (BZT), Ba(Zr0.2Ti0.8)O3/(Ba0.7Sr0.3)TiO3(BZT/BST) and Ba0.85Sr0.15Zr0.1Ti0.9O3 (BSZT) thin films were grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT)[001]single crystal substrate coated with conducting oxide LaNiO3(LNO) by pulsed laser deposition. X-ray diffraction, atomic force microscopy and electrical measurements were used to characterize the thin films. The θ-2θ linear scan indicated that the thin films with LNO layer show (001) orientations perpendicular to the substrate. Smooth and dense surface with grain size of 30 nm-80 nm were observed. The relative permittivity of the BST, BZT/BST, BZT and BSZT thin films are 1101, 799, 584 and 1784 respectively at 10 kHz. The tunability of the thin films are 39%, 32%, 44% and 60%. The results show that BSZT film has the highest tunability.

  13. Grain anomalous growth in ferroelectric ceramics of the (Sr, Ba)Nb2 O6 system

    International Nuclear Information System (INIS)

    The microstructure behavior of the ceramics of Srx Ba1-x Nb2 O6, with x=0.75, that possess tetragonal tungsten bronze type of structure, was analysed by scanning electron microscope (SEM) from samples obtained by conventional method and hot-pressing. The SEM micrographs of sintered by hot-pressed, showed an unexpected grain growth, mainly for hot-pressed materials. In the conventional sintering, we observed abnormal growth and bimodal distribution of grains. For the hot-pressing the sample structure was formed by many elongated and hollow grains, with, in some cases, a square cross-section shaped. (author)

  14. Full-potential calculation of the structural, elastic, electronic and magnetic properties of XFeO3 (X=Sr and Ba) perovskite

    International Nuclear Information System (INIS)

    First-principles study of the structural, elastic, magnetic and electronic properties of the cubic perovskite SrFeO3 and BaFeO3 has been performed using the full-potential linear muffin-tin orbital (FP-LMTO) method within the local spin density approximation (LSDA). The calculated equilibrium lattice constant of SrFeO3 is in good agreement with the available theoretical results. The independent elastic constants Cij, bulk modulus B and its pressure derivatives B', Shear modulus G, Young's modulus E and Poisson's ratio ν are obtained for both compounds. From the analysis of the ratio of shear to bulk modulus, it is found that SrFO3 (BaFeO3) is ductile (brittle) in nature. Band structures, total and partial densities of states show that the orbitals formed by Fe-O band have a primary importance in the determination of the electronic properties of the studied compounds. The calculated magnetic properties show that the magnetic moment of Fe is much higher and the contribution of the (Sr, Ba) and O elements to the magnetic moment is negligible.

  15. Full-potential calculation of the structural, elastic, electronic and magnetic properties of XFeO{sub 3} (X=Sr and Ba) perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Rached, H. [Laboratoire des Materiaux Magnetiques, Faculte des Sciences, Universite Djillali Liabes de Sidi-Bel-Abbes, Sidi-Bel-Abbes (22000) (Algeria); Rached, D., E-mail: rachdj@yahoo.f [Laboratoire des Materiaux Magnetiques, Faculte des Sciences, Universite Djillali Liabes de Sidi-Bel-Abbes, Sidi-Bel-Abbes (22000) (Algeria); Rabah, M. [Laboratoire des Materiaux Magnetiques, Faculte des Sciences, Universite Djillali Liabes de Sidi-Bel-Abbes, Sidi-Bel-Abbes (22000) (Algeria); Khenata, R., E-mail: Khenata_rabah@yahoo.f [Laboratoire de Physique Quantique et de Modelisation Mathematique de la Matiere (LPQ3M), Universite de Mascara, Mascara 29000 (Algeria); Department of Physics and Astronomy, King Saud University, P.O Box 2455, Riyadh 11451 (Saudi Arabia); Reshak, Ali H. [Institute of Physical Biology, South Bohemia University, Nove Hrady 373 33 (Czech Republic); Institute of Nano Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis (Malaysia)

    2010-09-01

    First-principles study of the structural, elastic, magnetic and electronic properties of the cubic perovskite SrFeO{sub 3} and BaFeO{sub 3} has been performed using the full-potential linear muffin-tin orbital (FP-LMTO) method within the local spin density approximation (LSDA). The calculated equilibrium lattice constant of SrFeO{sub 3} is in good agreement with the available theoretical results. The independent elastic constants C{sub ij}, bulk modulus B and its pressure derivatives B', Shear modulus G, Young's modulus E and Poisson's ratio {nu} are obtained for both compounds. From the analysis of the ratio of shear to bulk modulus, it is found that SrFO{sub 3} (BaFeO{sub 3}) is ductile (brittle) in nature. Band structures, total and partial densities of states show that the orbitals formed by Fe-O band have a primary importance in the determination of the electronic properties of the studied compounds. The calculated magnetic properties show that the magnetic moment of Fe is much higher and the contribution of the (Sr, Ba) and O elements to the magnetic moment is negligible.

  16. 用PLD在不同衬底上制备Ba0.5Sr0.5Ti03薄膜

    Institute of Scientific and Technical Information of China (English)

    马维云

    2011-01-01

    用固相反应法制备了Ba0.5Sr0.5Ti03靶材,采用在LaA103 (100)衬底上PLD法制备Ba0.5Sr0.5Ti03薄膜的最佳条件(村底温度760℃,生长氧压5Pa,脉冲激光能量350mj,频率5Hz,不退火直接降温),利用PLD技术在LaA103 (100),SrTi03 (100),LSAT(1 00)单晶平衬底上制备了Ba0.5Sr0.5Ti03薄膜.通过分析x射线衍射图谱,晶格失配度,单θ摇摆曲线半高宽,表明在三种衬底上薄膜是沿[00I]取向的近外延生长,影响薄膜生长的主要因素并不是村底与品格的失配度,如希望消除失配度对薄膜生长造成的不利影响,我们可以通过优化PLD工艺参数,这在一定程度上是有效的.

  17. Electrical properties of SrBa1−Fe0.6Sn0.4O3− NTC thermistors

    Indian Academy of Sciences (India)

    C L Yuan; X Y Liu; J W Xu; X W Zhang; C R Zhou

    2012-06-01

    Polycrystalline thermistor ceramics with the stoichiometric formula, SrBa1−Fe0.6Sn0.4O3− (0.2 ≤ ≤ 0.8), had been prepared by a standard solid state reaction route. X-ray diffraction analysis indicates that the ceramic system remains cubic perovskite structure with a very small lattice change. The electrical properties of SrBa1−Fe0.6Sn0.4O3− thermistors were studied using a digital thermometer over a wide range of 298–400 K. The thermistors showed an excellent negative temperature coefficient (NTC) thermistor behaviour. The values of resistivity at 298 K (ρ982), thermistor constant (298/358) and activation energy (a) of the SrBa1−Fe0.6Sn0.4O3− thermistors, decreasing with the increase of Sr content, were in the range of 0.37–11.0 k.cm, 2466–3703 K and 0.212–0.319 eV, respectively. For the thermistors with the compositions = 0.2 and 0.4, the fitting equivalent circuit was composed of three RCPE elements corresponding to grain, grain boundary and ceramic–electrode interface, respectively. From the impedance plots, it was found that the fitting data showed good agreement with the experimental data. The extracted grain boundary resistance exhibited a NTC thermistor behaviour.

  18. In situ stress measurements during pulsed laser deposition of BaTiO3 and SrTiO3 atomic layers on Pt(0 0 1)

    Science.gov (United States)

    Premper, J.; Sander, D.; Kirschner, J.

    2015-04-01

    We apply the cantilever deflection technique to measure stress in nm thin BaTiO3 and SrTiO3 films during pulsed laser deposition on a Pt(0 0 1) single crystal cantilever substrate. We find a compressive film stress of -4.2 GPa for BaTiO3 on Pt(0 0 1) (misfit = -2.3%), whereas the deposition of SrTiO3 (misfit = +0.4%) induces a tensile stress of +1.5 GPa. The stress measurements are augmented by in situ low energy electron diffraction experiments which indicate an epitaxial order of the films. We apply continuum elasticity to calculate film stress. We conclude that sign and magnitude of the measured stress are due to the epitaxial misfit between film and substrate, which is -2.3% and +0.4% for BaTiO3 and SrTiO3, respectively. We identify that in addition to misfit also the oxygen partial pressure during PLD film growth influences film stress. PLD growth in an oxygen-free environment leads to factor of two increased tensile stress in SrTiO3 on Pt(0 0 1) as compared to growth at pO2 =10-4 mbar. The role of film stoichiometry for film stress is discussed.

  19. Preparation of Y-Ba-Cu-O superconducting films on SrTiO3 and MgO substrates by chemical vapor deposition

    International Nuclear Information System (INIS)

    Y-Ba-Cu-O superconducting films were prepared at 850 C by chemical vapor deposition using metal β-diketonates as source materials. The films on SrTiO3(100) and MgO (100) substrates showed c-axis orientation. The degree of c-axis orientation estimated from the rocking curve of the (007) reflection for the film on SrTiO3 was higher than that for the film on MgO. Superconducting transition temperature defined by zero resistivity was 92 K for the films on SrTiO3 and 86 K for the films on MgO. Transport critical-current densities of the films on SrTiO3 and MgO at 77.3 K and O T were 6.0x105 and 8.3x103 A/cm2, respectively

  20. Influence of cetyltrimethylammonium bromide on the morphology of AWO{sub 4} (A = Ca, Sr) prepared by cyclic microwave irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Thongtem, Titipun [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)], E-mail: ttpthongtem@yahoo.com; Kaowphong, Sulawan; Thongtem, Somchai [Department of Physics, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2008-09-30

    AWO{sub 4} (A = Ca, Sr) was prepared from metal salts [Ca(NO{sub 3}){sub 2}.4H{sub 2}O or Sr(NO{sub 3}){sub 2}], Na{sub 2}WO{sub 4}.2H{sub 2}O and different moles of cetyltrimethylammonium bromide (CTAB) in water by cyclic microwave irradiation. The structure of AWO{sub 4} was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the presence of nanoparticles in clusters with different morphologies; spheres, peaches with notches, dumb-bells and bundles, influenced by CTAB. Six Raman vibrational peaks of scheelite structure were detected at 908, 835, 793, 399, 332 and 210 cm{sup -1} for CaWO{sub 4} and 917, 833, 795, 372, 336 and 192 cm{sup -1} for SrWO{sub 4}, which are assigned as {nu}{sub 1}(A{sub g}), {nu}{sub 3}(B{sub g}), {nu}{sub 3}(E{sub g}), {nu}{sub 4}(B{sub g}), {nu}{sub 2}(A{sub g}) and {nu}{sub f.r.}(A{sub g}), respectively. Fourier transform infrared (FTIR) spectra provided the evidence of W-O stretching vibration in [WO{sub 4}]{sup 2-} tetrahedrons at 793 cm{sup -1} for CaWO{sub 4} and 807 cm{sup -1} for SrWO{sub 4}. The peaks of photoluminescence (PL) spectra were at 428-434 nm for CaWO{sub 4}, and 447-451 nm for SrWO{sub 4}.