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Sample records for ba sr ca

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

    Science.gov (United States)

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

    1967-01-01

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

  2. Magnetic comparison of BaCa and BaSr substituted hexaferrite powders

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Angeles, A [Alvaro Gonzalez-Angeles, Facultad de IngenierIa, Universidad Autonoma de Baja California, (UABC), Blvd. Benito Juarez s/n, Cp 21280 Mexicali, B. C. (Mexico); Lipka, J; Gruskova, A; Slama, J; Jancarik, V; Slugen, V, E-mail: gangelesa@yahoo.com.m [Faculty of Electrical Engineering and Information Technology, (FEEIT), Slovak University of Technology, (SUT), Ilkovicova 3, 812 19 Bratislava (Slovakia)

    2010-03-01

    Results on magnetic studies of Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12-2x}(ZnTi){sub x}O{sub 19} and Ba{sub 0.75}Ca{sub 0.25}Fe{sub 12-2x}(ZnTi){sub x}O{sub 19}, where x = 0.2 to 0.6, ferromagnetic powders prepared by mechanical alloying are discussed. The structural and magnetic properties of the resulting powders were analyzed by thermo-magnetic analysis, X-ray diffraction, scanning electron microscopy, Moessbauer spectroscopy and magnetic measurements. Curie temperature, T{sub c} decreased dramatically (drop {approx} 39%) for BaCa samples, whilst for BaSr samples remained almost without change (diminution {approx} 2%) at x {<=} 0.2. SEM studies showed that all the particles present nearly hexagonal platelet shape.

  3. (CaA)SiO3 [A = Ba or Sr] phosphors

    Indian Academy of Sciences (India)

    Unknown

    378 terized by photoluminescence (PL), X-ray diffraction. (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) techniques. 2. Experimental. Eu doped CaSiO3, (Ca, Ba) SiO3 and (Ca, Sr) SiO3 pow- ders were prepared by sol–gel technique. Analar grade powder CaCO3, tetra ethyl orthosilicate ...

  4. Substitution site and effects on magnetism in Sr-for-Ca substituted CaBaCo4O7

    Science.gov (United States)

    Aurelio, G.; Curiale, J.; Bardelli, F.; Junqueira Prado, R.; Hennet, L.; Cuello, G.; Campo, J.; Thiaudière, D.

    2015-10-01

    Cationic substitutions in the novel magnetoelectric compound CaBaCo4O7 lead to profound changes in its magnetic and electric behaviors. In this work, we present a structural study of the isovalent substitution Sr-for-Ca in CaBaCo4O7. X-ray diffraction, as well as neutron powder diffraction experiments, are reported for a series of samples Ca1-xSrxBaCo4O7 with 0 ≤ x ≤ 0.10 . Special emphasis is given to the identification of the substitution site, as Sr has also been reported to substitute for Ba in this crystal structure. The solubility limit for Sr at the Ca site is shown to be at x ≃ 0.08 . The variation of lattice constants with Sr-doping firmly supports the Sr-for-Ca substitution. Rietveld refinements of the Sr-substituted samples are presented, and used as starting point to analyse the local structure around Sr by means of X-ray absorption spectroscopy at the Sr K-edge. Both the near-edge absorption and the extended absorption fine-structure confirm the substitution of Sr for Ca, giving definite support to the proposed nominal formula. In addition, macroscopic magnetization measurements are presented which reveal the striking effects of Sr-substitution over the magnetic landscape of this puzzling compound.

  5. [Structure and photoluminescence of ASnO3 (A = Ca, Sr and Ba) : Eu nanocrystalline].

    Science.gov (United States)

    Fu, Xiao-Yan; Niu, Shu-Yun; Zhang, Hong-Wu; Xin, Qin

    2007-09-01

    The present paper reports the photoluminescence properties of nanocrytalline ASnO3 (A = Ca, Sr and Ba) : 1% Eu phosphor synthesized by the Pechini-type sol-gel method. The powder was characterized by X-ray diffraction (XRD), UV-Vis absorption spectra, transmission electron microscopy (TEM) and photoluminescence measurements. The experimental results show that BaSnO3 has the ideal cubic peroskite structure, while SrSnO3 and CaSnO3 are both distorted from cubic symmetry by an octahedral tilting distortion. The difference of structure in induced the different spectral properties of ASnO3 : 1% Eu. On the other hand, when A2+ changes from Ca2+ to Ba2+, the luminescence intensity becomes weak. So CaSnO3 : 1% Eu seems to be a good candidate for new phosphors.

  6. Sequential separation of cs, ca and ba for 90sr assessment

    International Nuclear Information System (INIS)

    Dianu, M.; Bucur, C.

    2015-01-01

    A two-steps chemical treatment technique for strontium assessment from aqueous samples is described in this paper. The method was applied to simulated samples containing stable elements of Ni, Cs, Ca, Ba, Mn, Fe, Co and Eu. The transition elements (Ni, Mn, Fe, Co, Eu) were precipitated as hydroxides, followed by alkaline-earth metals separation (Ca, Ba) as carbonates. Finally, the Sr was purified by extraction chromatography using Triskem International Sr resin. The strength of Sr sorption in nitric acid increases with increasing acid concentration, and the optimal bonding strength is achieved in 8 M HNO3. The combination of successive precipitations with extraction chromatography for complete removal of other interferences from Sr matrix leads to good recovery and decontamination factor values. (authors)

  7. Preparation of MAl 2 O 4 : Eu 2+ , Sm 3+ (M = Ca, Sr, Ba) Phosphors ...

    African Journals Online (AJOL)

    A series of MAl2O4: Eu2+, Sm3+ (M = Ca, Sr, Ba) phosphors was prepared by the combustion method, and the influence of these alkaline earth metals on the structure and luminescent performances for these phosphors was investigated. A relationship was established between their composition, crystallization capacity and ...

  8. 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 (contrast the isotope composition of exchangeable Ba in deeper soil horizons (> 10 cm depth) at those sites is consistently heavier than the volcanic parent materials. The isotope compositions of exchangeable Ca and Sr trend toward heavier compositions with depth more gradually, reflecting increasing leakiness from these soils in the order Ba < Sr < Ca and downward transfer of light biocycled Ca and Sr to deeper exchange sites. Given the long-term stability of ecosystem properties at the sites where P is enriched in surface soils, a simple box model demonstrates that persistence of isotopically light exchangeable Ca, Sr and Ba in the shallowest soil horizons requires that the uptake flux to plants from those near-surface layers is less than the recycling flux returned to the surface as litterfall. This observation implicates an uptake flux from an additional source which we attribute to biolifting. We view the heavy exchangeable Ba

  9. The role of π-bonding on the high temperature structure of the double perovskites Ba2CaUO6 and BaSrCaUO6.

    Science.gov (United States)

    Reynolds, Emily; Thorogood, Gordon J; Avdeev, Maxim; Brand, Helen E A; Gu, Qinfen; Kennedy, Brendan J

    2015-09-28

    The high temperature structural behaviour of the uranium perovskites Ba2CaUO6 and BaSrCaUO6 has been investigated using a combination of synchrotron X-ray and neutron powder diffraction. Ba2CaUO6 undergoes a complex sequence of structures associated with the progressive loss of cooperative octahedral tilting: P21/n → I2/m → I2/m → I4/m → Fm3[combining macron]m. The observation of the intermediate tetragonal structure, I4/m, in this, contrasts with the previously reported rhombohedral R3[combining macron] intermediate formed by the Ba2SrUO6 oxide. The importance of π-bonding in determining the structural sequence is discussed.

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

    Directory of Open Access Journals (Sweden)

    E. Avigliano

    Full Text Available Abstract 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.

  11. 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.

  12. Theoretical studies of the paramagnetic perovskites MTaO3 (M = Ca, Sr and Ba)

    International Nuclear Information System (INIS)

    Ali, Zahid; Khan, Imad; Ahmad, Iftikhar; Khan, M. Salman; Asadabadi, S. Jalali

    2015-01-01

    In the present density functional studies, structural, mechanical and magneto-electronic properties of CaTaO 3, SrTaO 3 and BaTaO 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 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 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 3 is more ductile. • The magneto-electronic studies reveal the paramagnetic metallic nature of these compounds. • Significant electrical conductivity is observed above room temperature

  13. Consideration of the band-gap tunability of BaSi2 by alloying with Ca or Sr based on the electronic structure calculations

    International Nuclear Information System (INIS)

    Imai, Yoji; Watanabe, Akio

    2007-01-01

    The electronic structures and total energies of BaSi 2 -SrSi 2 and BaSi 2 -CaSi 2 systems have been calculated using the first-principle pseudopotential method to clarify the band gap tunability of BaSi 2 by alloying with Sr or Ca. From an energetic consideration of the compounds where all the Ba I sites or all the Ba II sites of the BaSi 2 lattice are preferentially replaced by Sr or Ca, it is expected that the Ba I site will be preferentially replaced by Sr rather than the Ba II sites. Compounds where all the Ba II sites are replaced by Sr or all the Ba II or all the Ba I sites are replaced by Ca are energetically unfavorable compared to the undissolved system of BaSi 2 and SrSi 2 or CaSi 2 . The effect of the addition of Sr or Ca into the BaSi 2 lattice on the gap value is different depending on the replaced sites of Ba. The replacement of Ba I site by Sr will broaden the band gap of BaSi 2 , which is consistent with the observed results

  14. 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}.

  15. MIIGe(PO 4) 2 ( M=Ca, Sr, Ba): Crystal structure, phase transitions and thermal expansion

    Science.gov (United States)

    Popa, Karin; Wallez, Gilles; Bregiroux, Damien; Loiseau, Pascal

    2011-10-01

    Three earth alkali-germanium monophosphates MIIGe(PO 4) 2 ( M=Ca, Sr, Ba) were prepared by solid state reaction and their structures, previously unknown, studied by Rietveld analysis. BaGe(PO 4) 2 and high-temperature β-SrGe(PO 4) 2 (space group C2/ m, Z=2) are fully isotypic with yavapaiite, whereas CaGe(PO 4) 2 and low-temperature α-SrGe(PO 4) 2 ( C2/ c, Z=4) are distorted derivatives. The phase transition between the two forms is observed for the first time. The thermal expansion, resulting from several structural mechanisms, is very anisotropic.

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

    Science.gov (United States)

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

    2013-06-01

    Individual migration behaviour during the juvenile and adult life phase of the anadromous twaite shad Alosa fallax in the Elbe estuary was examined using otolith Sr:Ca and Ba:Ca profiles. Between hatching and the end of the first year of life, juveniles showed two migration patterns. Pattern one exhibited a single downstream migration from fresh water to the sea with no return into fresh water. In contrast, pattern two showed a first migration into the sea, then a return into fresh water and, finally, a second downstream migration into marine water. This first report of migration plasticity for A. fallax points to different exposure times to estuarine threats depending on the migration strategy. In adults, high Sr:Ca and low Ba:Ca in the majority of individuals confirmed prior reports of a primarily marine habitat use. Patterns reflecting spawning migrations were rarely observed on otoliths, possibly due to the short duration of visits to fresh water. © 2013 The Authors. Journal of Fish Biology © 2013 The Fisheries Society of the British Isles.

  17. Synthesis and characterization of ASnO3 (A = Ba, Ca, Sr) perovskites

    International Nuclear Information System (INIS)

    Seethalakshmi, V.; Bradha, M.; Vigneshwaran, J.; Kalaiselvi, V.; Sheeja, C.J.J.; Ashok, Anuradha

    2015-01-01

    Oxide materials with perovskite structure have exhibited excess of interesting physical properties such as superconductivity, ferroelectricity, piezoelectricity, and multiferroicity. Perovskite type oxide materials have the general formula ABO 3 having simple and flexible structures that can easily accommodate suitable dopants to create defects and oxygen non-stoichiometry. This makes the materials suitable for various applications such as catalysis, sensors, electrode materials for fuel cell applications etc. The alkaline earth stannates with chemical formula ASnO 3 (A = Ba, Sr, and Ca) is a perovskite system that has been used in industry for photoelectrochemical energy conversions, stable capacitors, and gas sensors. The transport properties of the stannates vary from insulating to metallic material subjected to temperature. In the present work, nano - sized ASnO 3 perovskite (A = Sa, Ca, Sr) were synthesized using chemical method followed by calcinations. The dried gel was subjected to thermogravimetry/differential scanning calorimetry (TG/DSC) to identify the perovskite phase formation. Phase purity and crystal structural analysis of the calcined samples were examined using powder X-ray diffraction (XRD). In addition, the local crystal structure and the particle morphology of the perovskites were examined by High resolution Transmission Electron Microscopy (HRTEM). The lattice fringes in the high resolution images can be interpreted according to the crystal structure obtained through XRD. The synthesized nanoperovskites can further be used for energy storage applications. (author)

  18. Synthesis and characterization of M3V2O8 (M = Ca, Sr and Ba) by a ...

    Indian Academy of Sciences (India)

    Wintec

    Abstract. 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 ...

  19. Synthesis and thermophysical properties of AMoO4 (A = Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    Maji, Binoy Kumar; Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K.V.

    2013-01-01

    The alkaline earth molybdates AMoO 4 (A=Ca, Sr, Ba) belong to Scheelite type crystal structure with space group 14 1 /a, and are naturally occurring minerals. They are often found as secondary phases in irradiated oxide nuclear fuels as a product of fission product interaction. These compounds can also form as microcrystallites when the high-level nuclear waste is vitrified. As high temperature ceramics, they find applications as sensor materials, oxide ion conductors, etc. The thermophysical properties of these molybdates are essential for understanding their impact on the high temperature properties of the systems and devices containing them. In the present study, these compounds were synthesized by solid state reaction route in air at 823 K, and characterized by powder XRD and TG/DTA. The thermal expansion behavior was investigated by dilatometry in the temperature range of 300-800 K in air. The % thermal expansion of BaMoO 4 was found to be the lowest among the three compounds. The electrical conductivity of the compounds was measured by AC-impedance spectroscopy, and the conductivity was found to be in the range of 10 -4 S.cm -1 at 1073 K in air. The activation energy of electrical conduction was measured to be about 1.3 eV. (author)

  20. 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.

    2002-01-01

    be 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...

  1. Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

    Science.gov (United States)

    Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

    2017-12-01

    Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

  2. Relativistic semiempirical-core-potential calculations in Ca+,Sr+ , and Ba+ ions on Lagrange meshes

    Science.gov (United States)

    Filippin, Livio; Schiffmann, Sacha; Dohet-Eraly, Jérémy; Baye, Daniel; Godefroid, Michel

    2018-01-01

    Relativistic atomic structure calculations are carried out in alkaline-earth-metal ions using a semiempirical-core-potential approach. The systems are partitioned into frozen-core electrons and an active valence electron. The core orbitals are defined by a Dirac-Hartree-Fock calculation using the grasp2k package. The valence electron is described by a Dirac-like Hamiltonian involving a core-polarization potential to simulate the core-valence electron correlation. The associated equation is solved with the Lagrange-mesh method, which is an approximate variational approach having the form of a mesh calculation because of the use of a Gauss quadrature to calculate matrix elements. Properties involving the low-lying metastable D 3 /2 ,5 /2 2 states of Ca+, Sr+, and Ba+ are studied, such as polarizabilities, one- and two-photon decay rates, and lifetimes. Good agreement is found with other theory and observation, which is promising for further applications in alkalilike systems.

  3. 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.

  4. Alkaline earth lead and tin compounds Ae2 Pb, Ae2 Sn, Ae =Ca,Sr,Ba, as thermoelectric materials

    Science.gov (United States)

    Parker, David; Singh, David

    2014-03-01

    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 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.

  5. 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.

  6. First principle prediction of half-metallic ferromagnetism in zinc-blende MBi (M=Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Yao, K.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China) and International Center of Materials Physics, Chinese Academy of Science, Shenyang 110015 (China)]. E-mail: klyao@hust.edu.cn; Jiang, J.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: lianghust@126.com; Liu, Z.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); State Key Lab of Coordination Chemistry, Nanjing University, Nanjing 210093 (China); Gao, G.Y. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2006-11-27

    The first-principle calculations have been performed to investigate the zinc-blende compounds of alkaline elements with the Bi atom to find new half-metallic ferromagnets. It is found that CaBi, SrBi and BaBi are true half-metallic ferromagnets with the magnetic moment of 1{mu}{sub B}/formula unit. Their half-metallicity can be maintained within a wide range of lattice constants.

  7. Luminescence investigations of rare earth doped lead-free borate glasses modified by MO (M = Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Janek, Joanna, E-mail: janek.joanna@gmail.com; Sołtys, Marta; Żur, Lidia; Pietrasik, Ewa; Pisarska, Joanna; Pisarski, Wojciech A.

    2016-09-01

    Series of lead-free borate glasses with different oxide modifiers and lanthanide ions were prepared. The effect of oxide modifiers MO (M = Ca, Sr, Ba) on spectroscopic properties of trivalent Ln{sup 3+} (Ln = Eu, Er, Pr) were systematically investigated. Especially, the luminescence spectra of Ln{sup 3+}-doped lead-free borate glasses are presented and discussed in relation to the impact of selective components (CaO, SrO and BaO). Several spectroscopic parameters, such as the fluorescence intensity ratio R/O (Eu{sup 3+}) and measured luminescence lifetimes for the {sup 5}D{sub 0} (Eu{sup 3+}), {sup 4}I{sub 13/2} (Er{sup 3+}) and {sup 1}D{sub 2} (Pr{sup 3+}) excited states of lanthanide ions were analyzed in details. The research proved that spectroscopic properties of trivalent Ln{sup 3+} depend significantly on kind of presence oxide modifiers MO (M = Ca, Sr, Ba) in glass host matrices. - Highlights: • Luminescence of Ln{sup 3+}-doped borate glasses was presented and discussed. • Effect of glass modifiers on spectroscopic properties of rare earths was studied. • Measured luminescence lifetimes of Ln{sup 3+} (Ln = Eu, Er, Pr) were analyzed. • Luminescence intensity ratios R/O (Eu{sup 3+}) were determined.

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

    International Nuclear Information System (INIS)

    Sanchez Batanero, P.

    1969-03-01

    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 Ca 2+ , Sr 2+ and Ba 2+ have been measured on Dowex 50 W (NH 4 + ) 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 NH 4 Cl. Methods have been developed for separating mixtures of alkaline-earth elements using DCTA-NH 4 + followed by elution on Dowex 50 W (NH 4 + ) 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 (NH 4 + form) using DCTA-NH 4 + 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) [fr

  9. Color Point Tuning for (Sr,Ca,Ba) Si2O2N2:Eu2+ for White Light LEDs

    OpenAIRE

    Bachmann, Volker; Ronda, Cees; Oeckler, Oliver; Schnick, Wolfgang; Meijerink, Andries

    2009-01-01

    Color point tuning is an important challenge for improving white light LEDs. In this paper, the possibilities of color tuning with the efficient LED phosphor Sr1−x−y−zCaxBaySi2O2N2:Euz2+ (0 ≤ x, y ≤ 1; 0.005 ≤ z ≤ 0.16) are investigated. The emission color can be tuned in two ways: by changing Eu2+ concentration and by substitution of the host lattice cation Sr2+ by either Ca2+ or Ba2+. The variation in the Eu2+ concentration shows a red shift of the emission upon increasing the Eu concentrat...

  10. 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.

  11. Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, BaAl2O4:Eu2+, Dy3+ Phosphors

    Directory of Open Access Journals (Sweden)

    Qidi Xie

    2017-10-01

    Full Text Available (Sr, Ca, BaAl2O4:Eu2+, Dy3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, CaAl2O4:Eu2+,Dy3+ phosphors, the different phase formation from monoclinic SrAl2O4 phase to hexagonal SrAl2O4 phase to monoclinic CaAl2O4 phase was observed when the Ca content increased. The emission color of SrAl2O4:Eu2+, Dy3+ phosphors varied from green to blue. For the (Sr, BaAl2O4:Eu2+, Dy3+ phosphors, different phase formation from the monoclinic SrAl2O4 phase to the hexagonal BaAl2O4 phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl2O4:Eu2+, Dy3+changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr2+ with Ba2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED. Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(InN near UV chips.

  12. Cathode characterization system: preliminary results with (Ba,Sr,Ca) O coated cathodes

    International Nuclear Information System (INIS)

    Nono, M.C.A.; Goncalves, J.A.N.; Barroso, J.J.; Dallaqua, R.S.; Spassovsky, I.

    1993-01-01

    The performance of a cathode characterization system for studying the emission parameters of thermal electron emitters is reported. The system consists of vacuum chamber, power supplies and equipment for measuring and control. Measurements have been taken of the emission current as function of cathode temperature and anode voltage. Several (Ba, Sr) O coated cathodes were tested and the results have shown good agreement with Child's and Richardson's laws. The experimental work function is between 1.0 and 2.0 e V. All emission parameters measured are consistent with international literature data. (author)

  13. Structure, magnetization, and resistivity of La1-xMxCoO3 (M=Ca, Sr, and Ba)

    Science.gov (United States)

    Kriener, M.; Zobel, C.; Reichl, A.; Baier, J.; Cwik, M.; Berggold, K.; Kierspel, H.; Zabara, O.; Freimuth, A.; Lorenz, T.

    2004-03-01

    We present an investigation of the influence of structural distortions in charge-carrier doped La1-xMxCoO3 by substituting La3+ with alkaline-earth metals of strongly different ionic sizes, that is, M=Ca2+, Sr2+, and Ba2+, respectively. We find that both the magnetic properties and the resistivity change nonmonotonically as a function of the ionic size of M. Doping La1-xMxCoO3 with M=Sr2+ yields higher transition temperatures to the ferromagnetically ordered states and lower resistivities than doping with either Ca2+ or Ba2+ having a smaller or larger ionic size than Sr2+, respectively. From this observation we conclude that the different transition temperatures and resistivities of La1-xMxCoO3 for different M (of the same concentration x) do not only depend on the varying chemical pressures. The local disorder due to the different ionic sizes of La3+ and M2+ plays an important role, too.

  14. Quasi-2D silicon structures based on ultrathin Me2Si (Me = Mg, Ca, Sr, Ba) films

    Science.gov (United States)

    Migas, D. B.; Bogorodz, V. O.; Filonov, A. B.; Borisenko, V. E.; Skorodumova, N. V.

    2018-04-01

    By means of ab initio calculations with hybrid functionals we show a possibility for quasi-2D silicon structures originated from semiconducting Mg2Si, Ca2Si, Sr2Si and Ba2Si silicides to exist. Such a 2D structure is similar to the one of transition metal chalcogenides where silicon atoms form a layer in between of metal atoms aligned in surface layers. These metal surface atoms act as pseudo passivation species stabilizing crystal structure and providing semiconducting properties. Considered 2D Mg2Si, Ca2Si, Sr2Si and Ba2Si have band gaps of 1.14 eV, 0.69 eV, 0.33 eV and 0.19 eV, respectively, while the former one is also characterized by a direct transition with appreciable oscillator strength. Electronic states of the surface atoms are found to suppress an influence of the quantum confinement on the band gaps. Additionally, we report Sr2Si bulk in the cubic structure to have a direct band gap of 0.85 eV as well as sizable oscillator strength of the first direct transition.

  15. Pressure-driven phase transitions in TiOCl and the family (Ca, Sr, Ba)Fe2As2

    International Nuclear Information System (INIS)

    Zhang YuZhong; Opahle, Ingo; Jeschke, Harald O; ValentI, Roser

    2010-01-01

    Motivated by recent experimental measurements on pressure-driven phase transitions in Mott insulators as well as the new iron pnictide superconductors, we show that first principles Car-Parrinello molecular dynamics calculations are a powerful method to describe the microscopic origin of such transitions. We present results for (i) the pressure-induced insulator to metal phase transition in the prototypical Mott insulator TiOCl as well as (ii) the pressure-induced structural and magnetic phase transitions in the family of correlated metals AFe 2 As 2 (A = Ca, Sr, Ba). Comparison of our predictions with existing experimental results yields very good agreement.

  16. 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.

  17. 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

  18. Systems of Ba(PO3)2-Sr(Pu3)2, Cd(PO3)2-Ca(PO3)2

    International Nuclear Information System (INIS)

    Tokman, I.A.; Bukhalova, G.A.

    1977-01-01

    Phase diagrams of the Ba(PO 3 ) 2 -Sr(PO 3 ) 2 and Cd(PO 3 ) 2 -Ca(PO 3 ) 2 systems have been studied and plotted by the methods of differential-thermal analysis (DTA), visual-polythermal, X-ray phase and infrared spectroscopy. The Ba(PO 3 ) 2 -Sr(PO 3 ) 2 system is of the eutectic type. In the binary system Cd(PO 3 ) 2 -Ca(PO 3 ) 2 the existence of a continuous series of solid solutions with a minimum at 858 deg C and 27.5 mol.% Ca(PO 3 ) 2 has been established

  19. Rapid and efficient visible light photocatalytic dye degradation using AFe2O4 (A = Ba, Ca and Sr) complex oxides

    International Nuclear Information System (INIS)

    Vijayaraghavan, T.; Suriyaraj, S.P.; Selvakumar, R.; Venkateswaran, R.; Ashok, Anuradha

    2016-01-01

    Highlights: • Alkaline earth ferrites AFe 2 O 4 (A = Ba, Ca and Sr) were synthesized by sol–gel method. • Visible light photocatalytic activity of these ferrites were studied using congo red dye degradation. • BaFe 2 O 4 exhibited the best photocatalytic activity under visible light (xenon lamp) irradiation; CaFe 2 O 4 was the best photocatalyst under natural sun light irradiation. - Abstract: Photocatalytic activity of spinel type complex oxides has been investigated in this study. Alkaline earth ferrites AFe 2 O 4 (A = Ba, Ca, Sr) were synthesized by sol–gel method. Structural characterizations reveal that the synthesized ferrites have orthorhombic crystal structures with different space groups and cell dimensions when they have different alkaline earth metals in their A site. All the synthesized ferrites exhibited their bandgap in the range 2.14–2.19 eV. Their photocatalytic activities were studied using congo red dye under sunlight and xenon lamp radiation. The substitution of Ba, Ca and Sr at A site of these ferrites had varying impact on dye degradation process. Under xenon lamp irradiation, BaFe 2 O 4 exhibited the highest percentage of dye degradation (92% after 75 min). However, CaFe 2 O 4 showed the fastest degradation of the dye (70% within 15 min). In the absence of irradiation, SrFe 2 O 4 showed the highest dye adsorption (44% after 75 min).

  20. Dy3+-activated NaM4(VO4)3 (M = Ca, Ba, Sr) phosphor for near-UV solid-state lighting.

    Science.gov (United States)

    Singh, Roshani; Dhoble, S J

    2011-01-01

    We report the photoluminescence characterization of Dy(3+)-activated NaM(4)(VO(4))(3) (M = Ca, Ba, Sr) phosphors prepared by a solid-state method. The synthesis was confirmed by X-ray diffraction (XRD) characterization and photoluminescence (PL) emission results showed sharp blue and yellow bands for NaM(4)(VO(4))(3) (M = Ca, Ba, Sr):Dy(3+) phosphors at the excitation wavelength of 323 nm, which is near-UV excitation. Thus, these phosphors could be applicable for near-UV excited solid-state lighting devices. Copyright © 2011 John Wiley & Sons, Ltd.

  1. High Tc thin film superconductors: preparation, patterning and characterization. [Y-Ba-Cu-O; Bi-Sr-Ca-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, J. (Center for Tech. Education, Holon (Israel) Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv Univ. (Israel))

    1991-12-10

    A conventional oil-pumped vacuum system equipped with resistively heated tungsten boat sources was used for evaporation of bismuth- or yttrium-based cuprates for high Tc thin films superconductors. A well-ground mixture with atomic proportions of bismuth, SrF{sub 2}, CaF{sub 2} and copper for bismuth-based material, and of YF{sub 3}, BaF{sub 2} and copper for yttrium-based material, was inserted into the boat and then resistively evaporated onto different substrates such as MgO, ZrO{sub 2} and SrTiO{sub 3} kept at room temperature. Yttrium-based thin films were found to have a better quality upon reduction of fluorine in the constituents. Thus, films prepared with an yttrium BaF{sub 2} and copper mixture show a metallic-like behaviour, sharper transition and higher zero-resistance temperature as compared with that of films obtained by using a YF{sub 2} constituent instead of yttrium. Bismuth-based thin films were found to lose bismuth during heat treatment unless the copper constituent ended the evaporation process and was subsequently fully oxidized at 400degC. Bismuth-based patterned films were easily obtained by using a lift-off photolithographic method. Typical thickness of the films was measured to be about 0.5 {mu}m after heat treatment. (orig.).

  2. High Q ceramics in the ACe{sub 2}(MoO{sub 4}){sub 4} (A = Ba, Sr and Ca) system for LTCC applications

    Energy Technology Data Exchange (ETDEWEB)

    Surjith, A. [Microwave Materials Division, Centre for Materials for Electronics Technology (C-MET), Department of Information Technology, Government of India, Athani P.O. Thrissur, Kerala 680 771 (India); Ratheesh, R., E-mail: ratheeshr@yahoo.com [Microwave Materials Division, Centre for Materials for Electronics Technology (C-MET), Department of Information Technology, Government of India, Athani P.O. Thrissur, Kerala 680 771 (India)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer Solid state synthesis of phase pure ACe{sub 2}(MoO{sub 4}){sub 4} (A = Ba, Sr and Ca) ceramics. Black-Right-Pointing-Pointer Structural and microstructural evaluation of the synthesized ceramic materials. Black-Right-Pointing-Pointer Microwave dielectric property studies of ACe{sub 2}(MoO{sub 4}){sub 4} (A = Ba, Sr and Ca) ceramics. Black-Right-Pointing-Pointer Structure-property correlation through Laser Raman studies. - Abstract: Novel low temperature sinterable high Q ceramic systems ACe{sub 2}(MoO{sub 4}){sub 4} (A = Ba, Sr and Ca) have been prepared through solid state ceramic method. The effect of ionic radii of alkaline earth cations on the structure, microstructure and microwave dielectric properties of these ceramics were studied using powder X-ray diffraction, Laser Raman spectroscopy, scanning electron microscopy and Vector Network Analyzer. A structural change from monoclinic to tetragonal structure was observed while substituting Sr{sup 2+} and Ca{sup 2+} cations in place of Ba{sup 2+}. The Sr and Ca analogues possess better microwave dielectric properties compared to BaCe{sub 2}(MoO{sub 4}){sub 4}. All the ceramics were well sintered below 840 Degree-Sign C with dielectric constant in the range 10.2-12.3 together with good quality factor. The SrCe{sub 2}(MoO{sub 4}){sub 4} ceramic exhibits an unloaded quality factor of 6762 at 8.080662 GHz with a temperature coefficient of resonant frequency of -46 ppm/ Degree-Sign C while the CaCe{sub 2}(MoO{sub 4}){sub 4} ceramic shows an unloaded quality factor of 7549 at 6.928868 GHz and a temperature coefficient of resonant frequency of -44 ppm/ Degree-Sign C.

  3. Internal oxidation of ag-Y1Ba2Cu3,-Bi2Sr2Ca1Cu2 and -Bi(1. 8)Pb(0. 3)Sr2Ca2Cu3 alloys, and their resulting superconducting properties. Ag-Y1Ba2Cu3, -Bi2Sr2Ca1Cu2, -Bi(1. 8)Pb(0. 3)Sr2Ca2Cu3 gokin no naibu sanka to sono chodendo tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sato, M.; Numazawa, T.; Kimura, H.; Kimura, T.; Fukamachi, M. (National Research Inst. for Metals, Tsukuba, Ibaraki (Japan))

    1994-02-20

    Concerning wire rods for magnets and materials for magnetic shielding, etc. using oxide superconducting substances, studies and development are being made for making the above materials to be composite materials using Ag. In this study, concerning the solute composition of Ag-based alloys, Y1Ba2Cu3, Bi2Sr2Ca1Cu2, and Bi(1.8)Pb(0.3)Sr2Ca2Cu3 have been selected imaging the 123 phase at the Y system, and the 2212 low Tc phase as well as the 2223 high Tc phase at the Bi system. And oxide superconducting substances have been made precipitated in Ag by internal oxidation and thermal treatment of the dissolved alloys compound of Ag-Y1Ba2Cu3, Ag-Bi2Sr2Ca1Cu2, and Ag-Bi(1.8)Pb(0.3)Sr2Ca2Cu3, and its superconducting properties have been studied. Thereby electroconducting paths have been formed by the precipitated oxide superconducting substances and the critical current, though at a low value, has been attained. Also the composition of the above oxide superconducting substances has been image-analyzed from the observation result with an electron beam probe X-ray microanalyzer. With regard to the Ag-Bi(1.8)Pb(0.3)Sr2Ca2Cu3 alloy, precipitation of the single phase of the 2223 phase has not been able to obtain by thermal treatment. 11 refs., 8 figs.

  4. Rapid and efficient visible light photocatalytic dye degradation using AFe{sub 2}O{sub 4} (A = Ba, Ca and Sr) complex oxides

    Energy Technology Data Exchange (ETDEWEB)

    Vijayaraghavan, T. [PSG Institute of Advanced Studies, Coimbatore 641004 (India); Suriyaraj, S.P.; Selvakumar, R. [Nanobiotechnology Laboratory, PSG Institute of Advanced Studies, Coimbatore 641004 (India); Venkateswaran, R. [PSG Institute of Advanced Studies, Coimbatore 641004 (India); Ashok, Anuradha, E-mail: anu@psgias.ac.in [PSG Institute of Advanced Studies, Coimbatore 641004 (India)

    2016-08-15

    Highlights: • Alkaline earth ferrites AFe{sub 2}O{sub 4} (A = Ba, Ca and Sr) were synthesized by sol–gel method. • Visible light photocatalytic activity of these ferrites were studied using congo red dye degradation. • BaFe{sub 2}O{sub 4} exhibited the best photocatalytic activity under visible light (xenon lamp) irradiation; CaFe{sub 2}O{sub 4} was the best photocatalyst under natural sun light irradiation. - Abstract: Photocatalytic activity of spinel type complex oxides has been investigated in this study. Alkaline earth ferrites AFe{sub 2}O{sub 4} (A = Ba, Ca, Sr) were synthesized by sol–gel method. Structural characterizations reveal that the synthesized ferrites have orthorhombic crystal structures with different space groups and cell dimensions when they have different alkaline earth metals in their A site. All the synthesized ferrites exhibited their bandgap in the range 2.14–2.19 eV. Their photocatalytic activities were studied using congo red dye under sunlight and xenon lamp radiation. The substitution of Ba, Ca and Sr at A site of these ferrites had varying impact on dye degradation process. Under xenon lamp irradiation, BaFe{sub 2}O{sub 4} exhibited the highest percentage of dye degradation (92% after 75 min). However, CaFe{sub 2}O{sub 4} showed the fastest degradation of the dye (70% within 15 min). In the absence of irradiation, SrFe{sub 2}O{sub 4} showed the highest dye adsorption (44% after 75 min).

  5. 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).

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

    Science.gov (United States)

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

    2016-06-01

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

  7. The importance of passive smoking in the accumulation of Pb, Be, Ba, Mg, Ca, Sr in the children adenoid

    Directory of Open Access Journals (Sweden)

    Maria Gerycka

    2014-09-01

    Full Text Available Introduction. The quality of our life is determined by the quality of the air that we breathe. Hence the influence of cigarette smoking and secondary exposure of persons within the smoking environment is significant. Previous studies have confirmed the influence of passive smoking to on the accumulation of given elements in the tonsils. The subject of the study is to determine the importance of ETS exposure for the accumulation of Pb, Be, Ba, Ca, Mg and Sr in the pharyngeal tonsils. Material and methods. The study involved 162 adenoids from boys and girls living in Tychy and Chorzów. exposed and not exposed to passive smoking. All biological samples were subjected to mineralization with nitric acid (V from Merck. The chemical composition of the samples was determined by the ICP – AES method. Results. The statistical analysis of the elements in the tonsils of children exposed and not exposed to ETS is performed taking into account as an additional criterion of distribution the place of residence and gender of the children. Conclusions. There was no significant effect of passive smoking on the increase of the examined metals in the adenoid. However the role of gender and place of residence to the process of accumulation of elements in this organ remains significant.

  8. Spectroscopic and thermal degradation behavior of Mg(II, Ca(II, Ba(II and Sr(II complexes with paracetamol drug

    Directory of Open Access Journals (Sweden)

    Moamen S. Refat

    2017-05-01

    Full Text Available Complexes of Mg(II, Ca(II, Ba(II and Sr(II with paracetamol drug were synthesized and characterized by elemental analysis, conductivity, UV–Vis, IR, and 1H NMR spectroscopy and thermal analysis, as well as screened for antimicrobial activity. The IR spectral data suggested that the ligand behaves as paracetamol behaves as a neutral bidentate ligand coordinated to the metal ions via the lone pair of electrons of nitrogen and carbonyl-O atoms of the amide group. From the microanalytical data, the stoichiometry of the complexes reacts with Mg(II, Ca(II, Ba(II and Sr(II by molar ratios (2:1 (paracetamol:metal ion. The thermal behavior (TG/DTG of the complexes was studied. The ligand and their metal complexes were screened against both of antibacterial and fungicidal activities.

  9. Structural, electronic, optical and thermoelectric investigations of antiperovskites A3SnO (A = Ca, Sr, Ba) using density functional theory

    Science.gov (United States)

    Hassan, M.; Shahid, A.; Mahmood, Q.

    2018-02-01

    Density functional theory study of the structural, electrical, optical and thermoelectric behaviors of very less investigated anti-perovskites A3SnO (A = Ca, Sr, Ba) is performed with FP-LAPW technique. The A3SnO exhibit narrow direct band gap, in contrast to the wide indirect band gap of the respective perovskites. Hence, indirect to direct band gap transformation can be realized by the structural transition from perovskite to anti-perovskite. The p-p hybridization between A and O states result in the covalent bonding. The transparency and maximum reflectivity to the certain energies, and the verification of the Penn's model indicate potential optical device applications. Thermoelectric behaviors computed within 200-800 K depict that Ca3SnO exhibits good thermoelectric performance than Ba3SnO and Sr3SnO, and all three operate at their best at 800 K suggesting high temperature thermoelectric device applications.

  10. 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.

  11. Band structure and photocatalytic activities for H{sub 2} production of ABi{sub 2}Nb{sub 2}O{sub 9} (A = Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yingxuan; Chen, Gang; Zhang, Hongjie; Lv, Zushun [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

    2010-04-15

    A new series of layered perovskite photocatalysts, ABi{sub 2}Nb{sub 2}O{sub 9} (A = Ca, Sr, Ba), were synthesized by the conventional solid-state reaction method and characterized by X-ray diffraction (XRD) and UV-visible spectrometer. The results showed that the structure of ABi{sub 2}Nb{sub 2}O{sub 9} (A = Ca, Sr) is orthorhombic, while that of BaBi{sub 2}Nb{sub 2}O{sub 9} is tetragonal. The band gaps of CaBi{sub 2}Nb{sub 2}O{sub 9}, SrBi{sub 2}Nb{sub 2}O{sub 9}, and BaBi{sub 2}Nb{sub 2}O{sub 9} were estimated to be 3.46, 3.43, and 3.30 eV, respectively. It was found from the electronic band structure study, using the density functional theory (DFT) with planewave basis, that the conduction bands of these photocatalysts mainly consist of Nb 4d + Bi 6p + O 2p orbitals and the valence bands are composed of hybridization with O 2p + Nb 4d + Bi 6s orbitals. The photocatalytic activities for water splitting were investigated under UV-light irradiation and indicated that these photocatalysts showed photocatalytic activity for H{sub 2} and O{sub 2} evolution from aqueous solutions containing sacrificial reagents (methanol and Ag{sup +}). (author)

  12. Crystal phase evolution, sintering, and strength of anorthite-based LTCC materials by substitution of M2+ (M=Mg, Sr, Ba) for Ca2+

    Science.gov (United States)

    Gu, Sin Il; Shin, Hyo Soon; Yeo, Dong Hun; Nahn, Sahn

    2013-05-01

    LTCC, composed of Ca-Al-Si-O, is well-known for its high strength and phase stability. However research on the correlation of LTCC substrate composition and phase change to strength characteristics has rarely been reported. In this study, an anorthite glass component, group 2 elements, Mg, Sr, and Ba were substituted for Ca, and the resulting changes in the physical properties of the glass were observed. Then, the effect of varying glass composition on the characteristics of LTCCs was investigated. An increase in the Mg content caused an increase in the T g of glass, sintering temperature of the glass/Al2O3 composite material and synthesis temperature of anorthite. The content of Sr and Ba had almost no correlation with T g . Synthesis of BaAlO4 and increased LTCC sintering temperature were observed with the addition of Ba, and high strength of over 320 MPa was demonstrated when glass, Al2O3 and a small amount of anorthite were formed.

  13. Electronic structure and x-ray magnetic circular dichroism in A2FeReO6 (A =Ca ,Sr ,andBa ) oxides

    Science.gov (United States)

    Antonov, V. N.; Bekenov, L. V.; Ernst, A.

    2016-07-01

    A systematic electronic structure study of A2FeReO6 (A =Ba ,Sr ,andCa ) has been performed by employing the local-spin-density approximation (LSDA) and LSDA +U methods using the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. We investigated the effects of the subtle interplay between spin-orbit coupling, electron correlations, and lattice distortion on the electronic structure of double perovskites. Ca2FeReO6 has a large distortion in the Fe-O-Re bond, and the electronic structure is mainly determined by electron correlations and lattice distortion. In the Ba -Sr -Ca row, the correlation effects at the Fe site are increased. The correlations at the Re site are small in the Ba- and Sr-based compounds but significant in Ca2FeReO6 . Ca2FeReO6 behaves like an insulator only if considered with a relatively large value of Coulomb repulsion Ueff=2.3 eV at the Re site in addition to Ueff=3.1 eV at the Fe site. Ca2FeReO6 possesses a phase transition at 140 K where the metal-insulator transition (MIT) occurs between metallic high-temperature and insulating low-temperature phases. The spin and orbital magnetic moments are linear functions of temperature before and after the MIT but change abruptly at the point of the phase transition. From theoretically calculated magnetocrystalline anisotropy energy (MAE), we found that the easy axis of magnetization for the low-temperature phase is along the b direction, in agreement with experimental data. We found that the major contribution to the MAE is due to the orbital magnetic anisotropy at the Re site. X-ray-absorption spectra and x-ray magnetic circular dichroism at the Re, Fe, and Ba L2 ,3 and Fe, Ca, and O K edges were investigated theoretically in the frame of the LSDA +U method. A qualitative explanation of the x-ray magnetic circular dichroism spectra shape is provided by an analysis of the corresponding selection rules, orbital character, and occupation numbers of individual orbitals

  14. Raman spectroscopy of DNA-metal complexes. I. Interactions and conformational effects of the divalent cations: Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Pd, and Cd.

    OpenAIRE

    Duguid, J.; Bloomfield, V. A.; Benevides, J.; Thomas, G. J.

    1993-01-01

    Interactions of divalent metal cations (Mg2+, Ca2+, Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) with DNA have been investigated by laser Raman spectroscopy. Both genomic calf-thymus DNA (> 23 kilobase pairs) and mononucleosomal fragments (160 base pairs) were employed as targets of metal interaction in solutions containing 5 weight-% DNA and metal:phosphate molar ratios of 0.6:1. Raman difference spectra reveal that transition metal cations (Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) ind...

  15. High conductive and long-term phase stable anode materials for SOFCs: A2FeMoO6 (A = Ca, Sr, Ba)

    Science.gov (United States)

    Huan, Yu; Li, Yining; Yin, Baoyi; Ding, Dong; Wei, Tao

    2017-08-01

    In this work, the mixed oxide-ion/electron conductor (MIEC) double-perovskite compounds A2FeMoO6 (AFMO, A = Ca, Sr, Ba) are investigated as anode materials for O2--ion conducting solid-oxide fuel cells (SOFCs). Several advantages are outlined here; 1) under H2 atmosphere, the conductivities of Ba2FeMoO6 (BFMO), Sr2FeMoO6 (SFMO) and Ca2FeMoO6 (CFMO) reach as high as 243, 302 and 561 S cm-1, respectively, which can be comparable with the commercial NiO-electrolyte anode; 2) excellent structure and phase stability at high temperature and in H2 atmosphere; 3) matched thermodynamic compatibility (such as TECs) with electrolyte materials; 4) fast oxidization for fuel with O2- ions accepted by oxygen vacancies from the electrolyte. Moreover, with H2 as fuel gas, the cell power output, cell's long-term stabilities and the structural parameter are also been examined to evaluate the AFMO anode.

  16. Absolute refractive indices and thermal coefficients of CaF2, SrF2, BaF2, and LiF near 157 nm.

    Science.gov (United States)

    Burnett, John H; Gupta, Rajeev; Griesmann, Ulf

    2002-05-01

    We present high-accuracy measurements for wavelengths near 157 nm of the absolute index of refraction, the index dispersion, and the temperature dependence of the index for the ultraviolet optical materials with cubic symmetry: CaF2, SrF2, BaF2, and LiF. Accurate values of these quantities for these materials are needed for designs of the lens systems for F2 excimer-laser-based exposure tools for 157-nm photolithography. These tools are expected to use CaF2 as the primary optical material and possibly one of the others to correct for chromatic aberrations. These optical properties were measured by the minimum deviation method. Absolute refractive indices were obtained with an absolute accuracy of 5 x 10(-6) to 6 x 10(-6).

  17. 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.

  18. Transport and magnetic properties of R sub 1 sub - sub x A sub x CoO sub 3. (R = La, Pr and Nd; A = Ba, Sr and Ca)

    CERN Document Server

    Masuda, H; Miyashita, T; Soda, M; Yasui, Y; Kobayashi, Y; Sato, M

    2003-01-01

    Transport and magnetic measurements have been carried out on perovskite Co-oxides R sub 1 sub - sub x A sub x CoO sub 3 (R = La, Pr, and Nd; A = Ba, Sr and Ca; 0 <= x <= 0.5: All sets of the R and A species except Nd sub 1 sub - sub x Ba sub x CoO sub 3 have been studied.). With increasing the Sr- or Ba-concentration x, the system becomes metallic ferromagnet with rather large magnetic moments. For R = Pr and Nd and A = Ca, the system approaches the metal-insulator phase boundary but does not become metallic. The magnetic moments of the Ca-doped systems measured with the magnetic field H = 0.1 T are much smaller than those of the Ba- and Sr-doped systems. The thermoelectric powers of the Ba- and Sr-doped systems decrease from large positive values of lightly doped samples to negative ones with increasing doping level, while those of Ca-doped systems remain positive. These results can be understood by considering the relationship between the average ionic radius of R sub 1 sub - sub x A sub x and the ene...

  19. The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid.

    Science.gov (United States)

    Smith, Graham; Wermuth, Urs D

    2017-01-01

    (4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H 2 O) 6 ](C 6 H 7 AsNO 3 )·4H 2 O, (I), catena-poly[[[diaquacalcium]-bis[μ 2 -hydrogen (4-aminophenyl)arsonato-κ 2 O:O']-[diaquacalcium]-bis[μ 2 -hydrogen (4-aminophenyl)arsonato-κ 2 O:O

  20. Electric conductivity of solid solutions the Cs3-2xMxPO4 (M=Ba, Sr, Ca, Mg) systems

    International Nuclear Information System (INIS)

    Burmakin, E.I.; Stroev, S.S.; Shekhtman, G.Sh.; Antonov, B.D.

    2003-01-01

    The solid solutions in the Cs 3-2x M x PO 4 (M=Ba, Sr, Ca, Mg) system are synthesized and their thermal behavior and electric conductivity are studied. The introduction of the alkaline earth metal cations into cesium orthophosphates is accompanied by the shift of the phase transition occurring in the pure Cs 3 PO 4 at 450-620 Deg C into the low-temperature area as well as by increase in the cesium-cation conductivity at low temperatures. The electric conductivity in the area of existence of the Cs 3 PO 4 high-temperature modification slightly depends on the availability and concentration of the modifying additions, which make it possible to suppose the calcium sublattice structural disordering [ru

  1. Calculation of the hyperfine constants of Vk center in CaF2, SrF2 and BaF2

    International Nuclear Information System (INIS)

    Bufaical, R.F.

    1975-03-01

    The magnetic hyperfine constants of the V sub(K) center in CaF 2 , SrF 2 and BaF 2 have been calculated, assuming a phenomenological model, based on the F 2 central molecule, to describe the wave function of the defect. The introduction of covalence, with the ions neighboring the central molecule, have shown that this is a better description for the defect than a simple central molecule model. It was also shown that the results for the hyperfine constants are strongly dependent on the relaxations of these neighboring ions, which have been determined by fitting the experimental data. The present results are compared with other previous calculations where similar and different methods have been used. A better description for the wave function of the defect is suggested

  2. Transport properties and photo electrochemical characterization of oxygen-deficient ASnO3-δ (A=Ca, Sr and Ba)

    International Nuclear Information System (INIS)

    Zidi, N.; Omeiri, S.; Hadjarab, B.; Bouguelia, A.; Akroun, A.; Trari, M.

    2010-01-01

    The deficient stannate BaSnO 3-δ , prepared at 980 deg. C in sealed tube, crystallizes in an ideal perovskite structure. The oxide exhibits a blue color, the bandgap is found to be 2.65 eV and the transition is directly allowed. The non-stoichiometry could not be measured, indicating no appreciable oxygen deficiency. Nevertheless, the transport properties were found to change markedly with the heat treatment. BaSnO 3-δ behaves as degenerate SC with a conductivity σ 300K (=1.63 Ω -1 cm -1 ) and where the level E f drops above mobility edge to delocalized states. The electric balance leads to a simultaneous reduction of Sn 4+ inducing n-type behavior. The thermal variation of the thermopower indicates an electron mobility μ 300K (=0.013 cm 2 V -1 s -1 ) thermally activated. The metal-insulating transition is considered of Anderson type due to the random potential to oxygen vacancies. A predominant variable range hopping is predicted from the non-linearity of Ln σ versus T -1 plot. The capacitance measurement (C -2 -V), measured in KOH media, shows a linear behavior from which a flat band potential V fb (=-0.67V SCE ) and a density N D (=7.59x10 20 cm -3 ) are determined. The deficient stannates CaSnO 3 and SrSnO 3 are reported for a comparative purpose. The decrease of E g is ascribed to the increase of the conduction band width when going from Ba to Ca.

  3. Effect of Ca, Sr and Ba on the structure, morphology and electrical properties of (Co,Sb)-doped SnO{sub 2} varistors

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Martínez, J.A., E-mail: josue.aguilarm@uanl.mx [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Centro de Investigación e Innovación en Ingeniería Aeronáutica (CIIIA), Carretera a Salinas Victoria km. 2.3, C.P. 66600 Apodaca, N.L. (Mexico); Rodríguez, Edén [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Av. Universidad S/N, Cd. Universitaria, C.P. 66451 San Nicolás de los Garza, N.L. (Mexico); García-Villarreal, S.; Falcon-Franco, L. [Universidad Autónoma de Coahuila, Facultad de Metalurgia, Carr. 57, Km 4.5, C.P. 25710 Monclova, Coah. (Mexico); Hernández, M.B. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, Av. Universidad S/N, Cd. Universitaria, C.P. 66451 San Nicolás de los Garza, N.L. (Mexico)

    2015-03-01

    In this work, the effect of calcium (Ca), barium (Ba) and strontium (Sr) additions on the microstructure and electrical properties of SnO{sub 2}-Co{sub 3}O{sub 4}-Sb{sub 2}O{sub 5} ceramic varistors was investigated. It was found that the calcium addition promotes densification and grain growth. Ceramics with calcium addition exhibit the lowest electric field at a fixed current density (10{sup −3} A cm{sup −2}). The addition of strontium shows a similar effect on microstructure and current-voltage characteristics. However, barium addition causes porosity increase, grain size reduction, changes in the grain morphology (from approximately equiaxed to elongated grains) and the electric field at a fixed current density showed almost no change. Consequently, Ba-containing SnO{sub 2}-based ceramics cannot be considered as attractive candidates for low-voltage varistors. - Highlights: • The calcium and Strontium addition promotes densification and grain growth. • Barium addition causes porosity increase, grain size reduction and changes in the grain morphology. • Ceramics with calcium addition exhibit the lowest electric field. • Ceramics with calcium addition can be considered as promising materials for low-voltage varistors.

  4. Dielectric properties of Nb2O5-doped (Ba,Sr,Ca)TiO3 thick films for microwave phase shifters

    International Nuclear Information System (INIS)

    Lee, Sung Gap; Lee, Sang Heon

    2004-01-01

    (Ba,Sr,Ca)TiOi 3 (BSCT) powders, prepared by using the sol-gel method, were mixed with an organic vehicle, and the BSCT thick films were fabricated on alumina substrates by using screen printing techniques. The structural and the dielectric properties were investigated for various composition ratios and Nb 2 O 5 doping contents. All the BSCT thick films, sintered at 1420 .deg. C, showed the typical X-ray diffraction patterns of a perovskite polycrystalline structure. The average grain sizes decreased with increasing amounts of Nb 2 O 5 , and the thickness of thick films deposited by using four-cycle on printing/drying was approximately 110 μm. The Curie temperature and the relative dielectric constant decreased with increasing Ca content and Nb 2 O 5 doping amount. The relative dielectric constant, dielectric loss, and tunability of the BSCT(50/40/10) thick films doped with 1.0 wt% Nb 2 O 5 were 1410, 0.65 %, and 17.29 %, respectively.

  5. Color point tuning for (Sr,Ca,Ba)Si2O2N2:Eu2+ for white light LEDs

    NARCIS (Netherlands)

    Bachmann, V.M.; Ronda, R.C.; Meijerink, A.|info:eu-repo/dai/nl/075044986; Oeckler, O.; Schnick, W.

    2009-01-01

    Color point tuning is an important challenge for improving white light LEDs. In this paper, the possibilities of color tuning with the efficient LED phosphor Sr1-x-y-zCaxBaySi2O2N2:Euz 2+ (0 e x, y e 1; 0.005 e z e 0.16) are investigated. The emission color can be tuned in two ways: by changing Eu2+

  6. Temperature-controlled down-conversion luminescence behavior of Eu3+ -doped transparent MF2 (M = Ba, Ca, Sr) glass ceramics.

    Science.gov (United States)

    Zhou, B; E, C Q; Bu, Y Y; Meng, L; Yan, X H; Wang, X F

    2017-03-01

    Eu 3 + -doped transparent glass ceramics containing MF 2 (M = Ba, Ca, Sr) nanocrystals were fabricated using a melt-quenching method, and the resulting structures were studied using X-ray diffraction. Levels 5 D 1 and 5 D 0 of Eu 3 + ions were verified as thermally coupled levels using the fluorescence intensity ratio method. The fluorescence intensity ratios, optical temperature sensitivity and thermal quenching ratios of the transparent glass ceramics were studied as a function of temperature. With an increase in temperature, the relative sensitivity (S R ) decreased sharply at first, then slowly increased, before finally decreasing. The minimum S R values of GCBaF 2 (GCB), GCCaF 2 (GCC) and GCSrF 2 (GCS) were 2.8 × 10 -4 , 0.8 × 10 -4 and 1.9 × 10 - 4  K -1 at 360, 269 and 319 K, respectively. Glass ceramics with an intense emission intensity can be used to convert the measured spectrum into temperature and may have an important role in temperature detectors. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Mechanochemical synthesis, structure and properties of lead containing alkaline earth metal fluoride solid solutions MxPb1-xF2 (M = Ca, Sr, Ba)

    Science.gov (United States)

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

    2018-03-01

    The paper deals with the mechanochemical synthesis of lead containing alkaline earth metal fluoride solid solutions MxPb1-xF2 (M = Ca, Sr, Ba) by high-energy ball milling. Several metal precursors and fluorinating agents were tested for synthesizing M0.5Pb0.5F2. Metal acetates and ammonium fluoride as precursors show the most promising results and were therefore used for the formation of MxPb1-xF2 with different metal cationic ratios. The characterization of the local fluorine coordination and the crystal structure was performed by 19F MAS NMR spectroscopy and X-ray diffraction. Additional calculations of 19F chemical shifts using the superposition model allow a deeper insight into the local structure of the compounds. The fluoride ion conductivity was followed by temperature dependent DC conductivity measurements. Significantly higher conductivities were found in comparison with those of the corresponding binary fluorides. The highest values were observed for samples with high lead content M0.25Pb0.75F2, bearing in mind the much higher conductivity of PbF2 compared to MF2.

  8. Why are some ML2 molecules (M = Ca, Sr, Ba; L = H, F, Cl, Br) bent while others are linear? Implications of the pseudo Jahn-Teller effect.

    Science.gov (United States)

    Garcia-Fernandez, Pablo; Bersuker, Isaac B; Boggs, James E

    2007-10-18

    The unexpected bent geometries of some alkaline earth dihalides and dihydrides, ML(2) (M = Ca, Sr, Ba; L = H, F, Cl, Br) have been explained in the literature using various models that attribute the effect to different phenomena like covalency, metal core polarization, sd-hybridization, and electron pair repulsion. We employ (based on first principles) the pseudo Jahn-Teller effect, as the only source of instability of high-symmetry configurations in nondegenerate states, to analyze the origin of the geometry of these systems and show that this approach explains all of their main structural features, including the topology of the Laplacian of the electron density and the vibrational frequencies. The main contribution to the distortion of the linear configuration is due to the pseudo Jahn-Teller mixing by bending of the sigma(u) HOMO formed by the ligand orbitals with the unoccupied pig orbitals of the metal (with main d(xz) and d(yz) character), resulting in new covalency which stabilizes the bent configuration. We show that the model approaches to the problem, mentioned above, are either restricted particular cases of the pseudo Jahn-Teller interaction, or they yield very small contributions to the instability that do not explain the origin of the bending. All of our conclusions are supported by high-quality ab initio calculations.

  9. 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.

  10. Raman spectroscopy of DNA-metal complexes. I. Interactions and conformational effects of the divalent cations: Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Pd, and Cd.

    Science.gov (United States)

    Duguid, J; Bloomfield, V A; Benevides, J; Thomas, G J

    1993-11-01

    Interactions of divalent metal cations (Mg2+, Ca2+, Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) with DNA have been investigated by laser Raman spectroscopy. Both genomic calf-thymus DNA (> 23 kilobase pairs) and mononucleosomal fragments (160 base pairs) were employed as targets of metal interaction in solutions containing 5 weight-% DNA and metal:phosphate molar ratios of 0.6:1. Raman difference spectra reveal that transition metal cations (Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) induce the greatest structural changes in B-DNA. The Raman (vibrational) band differences are extensive and indicate partial disordering of the B-form backbone, reduction in base stacking, reduction in base pairing, and specific metal interaction with acceptor sites on the purine (N7) and pyrimidine (N3) rings. Many of the observed spectral changes parallel those accompanying thermal denaturation of B-DNA and suggest that the metals link the bases of denatured DNA. While exocyclic carbonyls of dT, dG, and dC may stabilize metal ligation, correlation plots show that perturbations of the carbonyls are mainly a consequence of metal-induced denaturation of the double helix. Transition metal interactions with the DNA phosphates are weak in comparison to interactions with the bases, except in the case of Cu2+, which strongly perturbs both base and phosphate group vibrations. On the other hand, the Raman signature of B-DNA is largely unperturbed by Mg2+, Ca2+, Sr2+, and Ba2+, suggesting much weaker interactions of the alkaline earth metals with both base and phosphate sites. A notable exception is a moderate perturbation by alkaline earths of purine N7 sites in 160-base pair DNA, with Ca2+ causing the greatest effect. Correlation plots demonstrate a strong interrelationship between perturbations of Raman bands assigned to ring vibrations of the bases and those of bands assigned to exocyclic carbonyls and backbone phosphodiester groups. However, strong correlations do not occur between

  11. 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)

    Moreira, A.H.P.

    1988-01-01

    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 930 0 C for sanidine, 930 0 and 1030 0 C for leucite and 1030 0 C 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 (Rb 86 , Ca 45 , Sr 85 , Ba 133 ) 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) [pt

  12. On ternary intermetallic aurides. CaAu{sub 2}Al{sub 2}, SrAu{sub 2-x}Al{sub 2+x} and Ba{sub 3}Au{sub 5+x}Al{sub 6-x}

    Energy Technology Data Exchange (ETDEWEB)

    Stegemann, Frank [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Benndorf, Christopher [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Mineralogie, Kristallographie und Materialwissenschaften, Universitaet Leipzig (Germany); Zhang, Yuemei; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Bartsch, Manfred; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms-Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP (Brazil); Janka, Oliver [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Chemie, Carl von Ossietzky Universitaet Oldenburg (Germany)

    2017-11-17

    The intermetallic compound CaAu{sub 2}Al{sub 2}, and the members of the solid solutions SrAu{sub 2-x}Al{sub 2+x} (0 ≤ x ≤ 0.33) and Ba{sub 3}Au{sub 5+x}Al{sub 6-x} (x = 0, 0.14, 0.49) were synthesized from the elements in sealed tantalum ampoules. The Ca compound crystallizes with the orthorhombic ThRu{sub 2}P{sub 2} type structure, whereas the targeted SrAu{sub 2}Al{sub 2} was found to form a solid solution according to SrAu{sub 2-x}Al{sub 2+x}. For the Ba system no ''BaAu{sub 2}Al{sub 2}'' was found, however, Ba{sub 3}Au{sub 5+x}Al{sub 6-x} was discovered to crystallize in the monoclinic space group C2/c with its own structure type. The samples were investigated by powder X-ray diffraction and their crystal structures were refined on the basis of single-crystal X-ray diffraction data. All compounds were characterized furthermore by susceptibility measurements. The crystallographic aluminum sites of CaAu{sub 2}Al{sub 2} and Ba{sub 3}Au{sub 5}Al{sub 6} can be differentiated by {sup 27}Al solid state NMR spectra on the basis of their different electric field gradients, in agreement with theoretical calculations. The electron transfer from the alkaline earth metals and the aluminum atoms onto the gold atoms was investigated by X-ray photoelectron spectroscopy (XPS) classifying these intermetallics as aurides, in full agreement with the calculated Bader charges. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Mechanism of superconductivity in Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub O sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta

    CERN Document Server

    Anvekar, T S; Sarode, P R; Kamat-Dalal, V N; Narlikar, Anant V

    2002-01-01

    EXAFS, X-ray Rietveld refinement and infra-red absorption measurements have been made on Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub 0 sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta 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 CuO sub 2 planes. (author)

  14. Structural Phase Transition of BaRu2/3M1/3O3 (M=Ca, Cd, and Sr) Studied by 117In(←117Cd) Time-Differential Perturbed-Angular-Correlation

    Science.gov (United States)

    Yanagida, Yasuo; Nakamura, Jin; Asai, Kichizo; Yamada, Nobuyoshi; Ohkubo, Yoshitaka; Ambe, Shizuko; Okada, Takuya; Ambe, Fumitoshi; Uehara, Shin-ichi; Kawase, Yoichi

    1995-12-01

    Electric field gradients at 117In(←117Cd) nuclei in BaRu2/3(M0.97116Cd0.03)1/3O3 (M=Ca, Cd, and Sr) were measured in the temperature range between 4 and 773 K by time-differential perturbed-angular-correlation of the 90-345 keV cascade γ -rays. For each oxide,the quadrupole interaction frequency markedly increases below a specific temperature; the temperatures are between 4 and 77 K for M=Ca, and about 300 and 600 K for M=Cd and Sr,respectively. Combined with the results of the X-ray powder diffraction measurements, it is concluded that a hexagonal-monoclinic structural phase transition, associated with a deformation of MO6 octahedra, takes place at the temperature.

  15. Crystal structures and thermal decomposition of permanganates AE[MnO{sub 4}]{sub 2} . n H{sub 2}O with the heavy alkaline earth elements (AE=Ca, Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Henning, Harald; Bauchert, Joerg M.; Conrad, Maurice; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

    2017-10-01

    Reexamination of the syntheses and crystal structures as well as studies of the thermal decomposition of the heavy alkaline earth metal permanganates Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O and Ba[MnO{sub 4}]{sub 2} are the focus of this work. As an alternative to the very inelegant Muthmann method, established for the synthesis of Ba[MnO{sub 4}]{sub 2} a long time ago, we employed a cation-exchange column loaded with Ba{sup 2+} cations and passed through an aqueous potassium-permanganate solution. We later used this alternative also with strontium- and calcium-loaded columns and all the compounds synthesized this way were indistinguishable from the products of the established methods. Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O exhibiting [CaO{sub 8}] polyhedra crystallizes in the orthorhombic space group Pccn with the lattice parameters a=1397.15(9), b=554.06(4) and c=1338.97(9) pm with Z=4, whereas Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O with [SrO{sub 10}] polyhedra adopts the cubic space group P2{sub 1}3 with a=964.19(7) pm and Z=4. So the harder the AE{sup 2+} cation, the higher its demand for hydration in aqueous solution. Consequently, the crystal structure of Ba[MnO{sub 4}]{sub 2} in the orthorhombic space group Fddd with a=742.36(5), b=1191.23(7) and c=1477.14(9) pm with Z=8 lacks any crystal water, but contains [BaO{sub 12}] polyhedra. During the thermal decomposition of Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, the compound expels up to two water molecules of hydration, before the crystal structure collapses after the loss of the third H{sub 2}O molecule at 157 C. The crystal structure of Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O breaks down after the expulsion of the third water molecule as well, but this already occurs at 148 C. For both the calcium and the strontium permanganate samples, orthobixbyite-type α-Mn{sub 2}O{sub 3} and the oxomanganates(III,IV) AEMn{sub 3}O{sub 6} (AE=Ca and Sr) remain as final decomposition products at 800 C

  16. Investigation of the structural, electronic and optical properties of the cubic RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr and Ba) using modified Becke-Johnson exchange potential

    Energy Technology Data Exchange (ETDEWEB)

    Sandeep, E-mail: sndp.chettri@gmail.com [Department of Physics, Mizoram University, Aizawl, 796004 (India); Rai, D.P. [Department of Physics, Pachhunga University College, Mizoram University, 796001 (India); Shankar, A. [Department of Physics, University of North Bengal, Darjeeling, 734013 (India); Ghimire, M.P. [Condensed Matter Physics Research Center, Butwal-13, Rupandehi, Lumbini (Nepal); IFW-Dresden, Helmholtzstraße 20, D-01069, Dresden (Germany); Khenata, R. [Laboratoire de Physique Quantique de la Mati´ere et de Modélisation Mathématique LPQ3M, Université de Mascara, Mascara, 29000 (Algeria); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P. O. Box 2455, Riyadh, 11451 (Saudi Arabia); Syrotyuk, S.V. [Semiconductor Electronics Department, Lviv Polytechnic National University, Lviv, 79013 (Ukraine); Thapa, R.K. [Department of Physics, Mizoram University, Aizawl, 796004 (India)

    2017-05-01

    The structural, electronic and optical properties of the cubic RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr, Ba) have been investigated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential was applied using the generalized gradient approximation for calculating the structural properties In addition, the modified Becke-Johnson (TB-mBJ) potential was used for calculating the electronic and optical properties. It was found that the lattice constant increases while the bulk modulus decreases with the change of cation (M) in going from Be to Ba in the RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr, Ba). The reflectivity and absorption properties were also studied using the mBJ method to understand the inter-band transitions and their possible applications in absorption devices in the UV-region. - Highlights: • Closer estimate of the band-gaps of RbMF{sub 3} with experimental results using GGA and mBJ results predicting them to be absorption devices and substrates for thin film growth. • The RbMF{sub 3} were also found to be potential candidate for in absorption devices in UV-region which were correlated to their calculated optical properties. • The materials are transparent, so may be used as substrates for thin film growth, for the optoelectric applications.

  17. Effect of elastic strain on the band gaps, band alignment, and electronic structure of epitaxial ASnO3 (A = Ca, Sr, and Ba) films and heterostructures revealed through in situ photoemission, spectroscopic ellipsometry, and density functional theory

    Science.gov (United States)

    Baniecki, John; Yamazaki, Takashi; Aso, Hiroyuki; Imanaka, Yoshihiko; Ricinschi, Dan

    The alkaline earth stannates ASnO3 (A = Ba, Sr, and Ca) are emerging as important materials. Band gaps in stannates are remarkably dependent on volumetric strain with a decrease in volumetric strain of 3 percent in SrSnO3 resulting in an increase in the band gap of 0.35 eV. However, little understanding of volumetric strain dependence on the valence band (VB) electronic structure and band alignments between stannates and other oxides exits. In this talk we will examine the effect of elastic strain on the band gaps, band alignment, and electronic structure of stannate films and heterostructures through in situ photoemission, spectroscopic ellipsometry, scanning transmission electron microscopy with geometric phase analysis, and density functional theory. CaSnO3 (CSO), SrSnO3 (SSO) and La-doped BaSnO3 (BLSO) thin films were grown by pulsed laser epitaxy with strain control via epitaxial buffer layers. While the VB electronic structure is strain dependent VB offsets do not vary significantly with strain, which resulted in ascribing most of the difference in band alignment to the conduction band (CB) edge. Significantly, strain-induced tuning of CB offset differences are as large as 0.6 eV for SSO and may provide a pathway to enhance stannate-based devices.

  18. 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)

    Sriram, M.A.; Birudavolu, R.; Niou, C.S.; Murr, L.E.

    1991-01-01

    While it has been successfully demonstrated that Bi-Pb-Sr-Ca-Cu-O and YBa 2 Cu 3 O x 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 Bi 7 Pb 3 Sr 10 Ca 10 Cu 15 O x , 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 Bi 7 Pb 3 Sr 10 Ca 10 Cu 15 O x 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 T c (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 Bi 7 Pb 3 Sr 10 Ca 10 Ci 15 O x and YBa 2 Cu 3 O x at different Ag doping levels is presented in this paper

  19. Luminescent phosphors, based on rare earth substituted oxyfluorides in the A(1)3-x A(2)xMO4F family with A(1)/A(2)=Sr, Ca, Ba and M=Al, Ga

    International Nuclear Information System (INIS)

    Park, Sangmoon; Vogt, Thomas

    2009-01-01

    A new family of UV-activated phosphors made by substituting rare-earth activators such as trivalent Eu, Tb, Tm and Er into A(1) 3-x A(2) x MO 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.

  20. 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.

  1. Raman spectroscopy of DNA-metal complexes. II. The thermal denaturation of DNA in the presence of Sr2+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+.

    OpenAIRE

    Duguid, J G; Bloomfield, V A; Benevides, J M; Thomas, G J

    1995-01-01

    Differential scanning calorimetry, laser Raman spectroscopy, optical densitometry, and pH potentiometry have been used to investigate DNA melting profiles in the presence of the chloride salts of Ba2+, Sr2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+. Metal-DNA interactions have been observed for the molar ratio [M2+]/[PO2-] = 0.6 in aqueous solutions containing 5% by weight of 160 bp mononucleosomal calf thymus DNA. All of the alkaline earth metals, plus Mn2+, elevate the melting temperature of ...

  2. Magnetic hyperfine interactions of U2 center in CaF2, SrF2 and BaF2

    International Nuclear Information System (INIS)

    Graf, C.J.F.

    1976-02-01

    The magnetic hyperfine parameters of the U 2 center in CaF 2 , SeF 2 and BaF 2 , using a molecular orbitals scheme have been calculated. The need for the inclusion of mechanisms such as Pauli Repulsion and Covalence in order to describe the electronic structure of the defect has been shown. In the molecular orbitals model a weak covalence parameter has been phenomenologically introduced, mixing the is atomic wavefunction of hydrogen with a properly symmetrized linear combination of 2p F - functions centered on the ions of the first fluorine shell. The results obtained are compared with experimental measurements of EPR and ENDOR. (Author) [pt

  3. 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.

  4. 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)

    Mothudi, B.M.; Ntwaeaborwa, O.M.; Botha, J.R.; Swart, H.C.

    2009-01-01

    Eu 2+ and Dy 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 2 O 4 and SrAl 2 O 4 and the hexagonal structure of BaAl 2 O 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 2 O 4 :Eu 2+ , Dy 3+ , 450 nm (with a shoulder-peak at 500 nm) for BaAl 2 O 4 :Eu 2+ , Dy 3+ and 528 nm for SrAl 2 O 4 :Eu 2+ , Dy 3+ are attributed to the 4f 6 5d 1 to 4f 7 transition in the Eu 2+ ion in the different hosts.

  5. 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.

  6. Chemical stabilization and high pressure synthesis of Ba-free Hg-based superconductors, (Hg,M)Sr2Ca(n-1)Cu(n)O(y)(n=1 to approximately 3)

    Science.gov (United States)

    Kishio, K.; Shimoyama, J.; Hahakura, S.; Kitazawa, K.; Yamaura, K.; Hiroi, Z.; Takano, M.

    1995-01-01

    A homologous series of new Hg-based HTSC compounds, (Hg,M)Sr2Ca(n - 1)Cu(n)P(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 Hgl2O1(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.

  7. Luminescence properties of Sr3−x−3y/2MxCeyAlO4F (M=Ca, Ba, 0≤x≤0.9, 0.001≤y≤0.05) phosphors

    International Nuclear Information System (INIS)

    Choi, Hye-Min; Park, Sangmoon

    2012-01-01

    Luminescent materials composed of Sr 3−x−3y/2 M x Ce y AlO 4 F (M=Ca, Ba, 0≤x≤0.9, 0.001≤y≤0.05) were prepared by the solid-state reaction method. X-ray diffraction (XRD) patterns of the obtained oxyfluorides are exhibited for indexing peak positions. Dynamic excitation and emission spectra of the Ce 3+ -activated oxyfluoride phosphors are clearly monitored. The critical emission quenching as a function of Ce 3+ contents in Sr 2.5−3y/2 M 0.5 Ce y AlO 4 F phosphors is revealed at quite low concentrations of the activator. CIE coordinates of blue and green Sr 2.5−3y/2 M 0.5 Ce y AlO 4 F phosphors are clearly measured. The relative quantum efficiency of Sr 2.4985 Ca 0.5 Ce 0.005 AlO 4 F based on the integrated emission is determined. The Sr 3−x−3y/2 M x Ce y AlO 4 F phosphors excited near 410 nm light could be prominent phosphors in applications of NUV-LED. - Highlights: ► Blue and green emitting oxyfluoride phosphors are excitated near 410 nm ► Ce 3+ -activated oxyfluoride phosphors are quite effective to prepare white light for near-UV LED applications. ► Gradual substitution of Ce 3+ content in the oxyfluoride hosts changes CIE values.

  8. 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.

  9. Studies on up/down-conversion emission of Yb3+ sensitized Er3+ doped MLa2(MoO4)4 (M = Ba, Sr and Ca) phosphors for thermometry and optical heating

    Science.gov (United States)

    Sinha, Shriya; Kumar, Kaushal

    2018-01-01

    The photoluminescence properties of Yb3+ sensitized Er3+ doped BaLa2(MoO4)4, SrLa2(MoO4)4 and CaLa2(MoO4)4 phosphors synthesized via hydrothermal method are investigated upon 980 nm and 380 nm light excitations. The phase, purity, and morphology of the samples are characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Field emission scanning electron microscope. Among these three phosphors, the strongest emission intensity is seen in BaLa2(MoO4)4: Er3+/Yb3+ through both the 980 nm and 380 nm light excitations and is explained by the lifetime measurement of 4S3/2 level of Er3+ ion. Temperature sensing measurements were performed by using the fluorescence intensity ratio (FIR) of green emission bands originated from the two thermally coupled 2H11/2 → 4I15/2 and 4S3//2 → 4I15/2 transitions of Er3+ and maximum temperature sensitivity of 1.05% K-1 at 305 K is found for BLa2(MoO4)4: Er3+/Yb3+ sample. Moreover, the laser induced heating is measured in the samples and the maximum temperature of the sample particles is calculated as 422 K at 76 W/cm2 in BaLa2(MoO4)4: Er3+/Yb3+, pointing out large amount of heat generation in such phosphors. The BaLa2(MoO4)4: Er3+/Yb3+ also exhibits higher photothermal conversion efficiency of 46.7%.

  10. 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

    2009-01-01

    , the findings on the defect chemistry were reported, while the oxygen transport properties are reported here in part II. In the investigated material series, the amount of divalent dopant has been kept constant, while Sr ions have been substituted with Ca ions (smaller ionic radius) or Ba ions (larger ionic...... radius). The size difference induces different strains into the crystal structure in each composition. The possibility of simple relationships between various crystal strain parameters and the transport properties were analyzed. Oxygen pump controlled permeation experiments and a surface sensitive...

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

    Science.gov (United States)

    Rangi, Manisha; Agarwal, Ashish; Sanghi, Sujata; Singh, Ripandeep; Meena, S. S.; Das, A.

    2014-08-01

    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.

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

    International Nuclear Information System (INIS)

    Rangi, Manisha; Agarwal, Ashish; Sanghi, Sujata; Singh, Ripandeep; Meena, S. S.; Das, A.

    2014-01-01

    Bi 0.8 A 0.2 FeO 3 (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 A 2+ results in the formation of oxygen vacancies in the parent lattices as the possibility of Fe 4+ 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 Bi 0.8 Ba 0.2 FeO 3 sample in comparison to other substituted samples revealing a strong correlation between ionic radii and magnetization

  13. Raman spectroscopy of DNA-metal complexes. II. The thermal denaturation of DNA in the presence of Sr2+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+.

    Science.gov (United States)

    Duguid, J G; Bloomfield, V A; Benevides, J M; Thomas, G J

    1995-12-01

    Differential scanning calorimetry, laser Raman spectroscopy, optical densitometry, and pH potentiometry have been used to investigate DNA melting profiles in the presence of the chloride salts of Ba2+, Sr2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+. Metal-DNA interactions have been observed for the molar ratio [M2+]/[PO2-] = 0.6 in aqueous solutions containing 5% by weight of 160 bp mononucleosomal calf thymus DNA. All of the alkaline earth metals, plus Mn2+, elevate the melting temperature of DNA (Tm > 75.5 degrees C), whereas the transition metals Co2+, Ni2+, and Cd2+ lower Tm. Calorimetric (delta Hcal) and van't Hoff (delta HVH) enthalpies of melting range from 6.2-8.7 kcal/mol bp and 75.6-188.6 kcal/mol cooperative unit, respectively, and entropies from 17.5 to 24.7 cal/K mol bp. The average number of base pairs in a cooperative melting unit () varied from 11.3 to 28.1. No dichotomy was observed between alkaline earth and transition DNA-metal complexes for any of the thermodynamic parameters other than their effects on Tm. These results complement Raman difference spectra, which reveal decreases in backbone order, base unstacking, distortion of glycosyl torsion angles, and rupture of hydrogen bonds, which occur after thermal denaturation. Raman difference spectroscopy shows that transition metals interact with the N7 atom of guanine in duplex DNA. A broader range of interaction sites with single-stranded DNA includes ionic phosphates, the N1 and N7 atoms of purines, and the N3 atom of pyrimidines. For alkaline earth metals, very little interaction was observed with duplex DNA, whereas spectra of single-stranded complexes are very similar to those of melted DNA without metal. However, difference spectra reveal some metal-specific perturbations at 1092 cm-1 (nPO2-), 1258 cm-1 (dC, dA), and 1668 cm-1 (nC==O, dNH2 dT, dG, dC). Increased spectral intensity could also be observed near 1335 cm-1 (dA, dG) for CaDNA. Optical densitometry, employed to detect DNA

  14. 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.

  15. 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.

  16. 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)

    Pandech, Narasak; Limpijumnong, Sukit; Sarasamak, Kanoknan

    2015-01-01

    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 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 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 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 12 elastic constant is sensitive to B-site cations while C 44 elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed

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

    Directory of Open Access Journals (Sweden)

    Labdelli Abbes

    2015-01-01

    Full Text Available 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 (P63/mmc space group, (2H two-layered hexagonal (P63/mmc space group and orthorhombic (Pnma space group. The current study is given within the density-functional theory basis DFT. The exchange-correlation potential is introduced by different approaches. We computed the equilibrium lattices, bulk modulus and its pressure derivatives and equilibrium volume. Our obtained results agree successfully with the theoretical and experimental data. The spin magnetic moments of these oxides have been obtained to investigate the magnetic properties. We report a detailed analysis of the different ground states properties for considerable oxides using GGA and GGA-modified Becke–Johnson computational approaches.

  18. Electric-field control of electronic transport properties and enhanced magnetoresistance in La0.7Sr0.3MnO3/0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 lead-free multiferroic structures

    Science.gov (United States)

    Yan, Jian-Min; Gao, Guan-Yin; Liu, Yu-Kuai; Wang, Fei-Fei; Zheng, Ren-Kui

    2017-10-01

    We report the fabrication of lead-free multiferroic structures by depositing ferromagnetic La0.7Sr0.3MnO3 (LSMO) polycrystalline films on polished 0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 (BZT-BCT) piezoelectric ceramic substrates. By applying electric fields to the BZT-BCT along the thickness direction, the resistivity of LSMO films can be effectively manipulated via the piezoelectric strain of the BZT-BCT. Moreover, the LSMO polycrystalline films exhibit almost temperature independent and significantly enhanced magnetoresistance (MR) below TC. At T = 2 K and H = 8 T, the MR of polycrystalline films is approximately two orders of magnitude higher than that of LSMO epitaxial films grown on (LaAlO3)0.3(SrAl1/2Ta1/2O3)0.7 single-crystal substrates. The enhanced MR mainly results from the spin-polarized tunneling of charge carriers across grain boundaries. The LSMO/BZT-BCT structures with electric-field controllable modulation of resistivity and enhanced MR effect may have potential applications in low-energy consumption and environmentally friendly electronic devices.

  19. Novel microwave initiated synthesis of Zn{sub 2}SiO{sub 4} and MCrO{sub 4} (M = Ca, Sr, Ba, Pb)

    Energy Technology Data Exchange (ETDEWEB)

    Parhi, Purnendu [Department of Mechanical Engineering, Colorado State University, Fort Collins 80523 (United States); Manivannan, V. [Department of Mechanical Engineering, Colorado State University, Fort Collins 80523 (United States)], E-mail: mani@engr.colostate.edu

    2009-02-05

    A novel microwave initiated solid-state metathesis synthesis of metal chromates and zinc silicate has been investigated. The high lattice energy of NaCl drives the solid-state metathesis reaction (CaCl{sub 2}.2H{sub 2}O + Na{sub 2}CrO{sub 4}.4H{sub 2}O {yields} NaCl + CaCrO{sub 4} + 6H{sub 2}O{up_arrow}) in the forward direction to obtain the products. The structural, optical, and chemical properties of synthesized compounds are determined by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and diffused reflectance spectroscopy in the UV-vis range.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ashima; Sanghi, Sujata; Agarwal, Ashish; Reetu; Ahlawat, Neetu; Monica [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125001 (India)

    2012-07-01

    M-type hexaferrites with compositions BaFe{sub 12}O{sub 19} (BFO), SrFe{sub 12}O{sub 19} (SFO), Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12}O{sub 19} (BSFO), and Ba{sub 0.5}Pb{sub 0.5}Fe{sub 12}O{sub 19} (BPFO) were synthesized by commercial solid state reaction method. The Rietveld refinement of x-ray powder diffraction revealed a single hexagonal phase with space group P6{sub 3}/mmc for BFO, SFO, and BSFO samples, whereas BPFO sample contains hematite ({alpha}-Fe{sub 2}O{sub 3}) phase with space group R3c along with the M-type main phase. All the samples show dispersion in dielectric constant ({epsilon} Prime ) and dielectric loss (tan {delta}) values with frequency. The values of {epsilon} Prime and tan {delta} increase with increase in temperature due to increase in the number of charge carriers and their mobilities, which are thermally activated. The reciprocal temperature dependence of conductivity ({sigma}{sub ac}) and the most probable relaxation time ({tau}{sub M Double-Prime }) satisfies the Arrhenius relation. A perfect overlapping of the normalized plots of modulus isotherms on a single 'super curve' for all the studied temperatures reveals a temperature independence of dynamic processes involved in conduction and for relaxation. Further, the complex plots of M{sup *} (M Double-Prime vs M Prime ) indicate that dc conductivity dominates in the region below the M Double-Prime {sub max} point. Above M Double-Prime {sub max}, the variations follow Jonscher power law ({sigma} = A{omega}{sup s}) implying that ac conductivity is dominating in this region. Among the prepared samples, SFO hexaferrite has lowest values of {sigma}{sub ac}, {epsilon} Prime , and tan {delta} making it suitable for use in microwave devices.

  1. Gas-Phase Reactions of Hydrated Alkaline Earth Metal Ions, M2+ (H2O)n (M = Mg, Ca, Sr, Ba and n = 4–7), With Benzene

    Science.gov (United States)

    Rodriguez-Cruz, Sandra E.; Williams, Evan R.

    2005-01-01

    Gas-phase reactions of hydrated divalent alkaline earth metal ions and benzene were investigated by electrospray ionization Fourier-transform mass spectrometry. Rate constants for solvent-exchange reactions were determined as a function of hydration extent for Mg2+, Ca2+, Sr2+, and Ba2+ clusters containing four to seven water molecules each. All of the strontium and barium clusters react quickly with benzene. Barium reacts slightly faster than the corresponding strontium cluster with the same number of water molecules attached. For calcium, clusters with four and five water molecules react quickly, whereas those with six and seven water molecules do not. Magnesium with four water molecules reacts quickly, but not when five through seven water molecules are attached. The slow reactivity observed for some of these clusters indicates that the cation–π interaction between the metal ion and benzene is partially screened by the surrounding water molecules. The reactivity of magnesium with seven water molecules is intermediate that of the hexa- and pentahydrate and the tetrahydrate. This result is consistent with the seventh water molecule being in the outer shell and much more weakly bound. The unusual trend in reactivity observed for magnesium may be due to the presence of mixed shell structures observed previously. These results are the first to provide information about the relative importance of cation–π interactions in divalent metal ions as a function of metal hydration extent. Such studies should also provide a model and some insight into the relative binding affinities of divalent metal ions to aromatic residues on peptides and proteins. PMID:11281600

  2. Gas-phase reactions of hydrated alkaline earth metal ions, M2+ (H2O)n (M = Mg, Ca, Sr, Ba and n = 4-7), with benzene.

    Science.gov (United States)

    Rodriguez-Cruz, S E; Williams, E R

    2001-03-01

    Gas-phase reactions of hydrated divalent alkaline earth metal ions and benzene were investigated by electrospray ionization Fourier-transform mass spectrometry. Rate constants for solvent-exchange reactions were determined as a function of hydration extent for Mg2+, Ca2+, Sr2+, and Ba2+ clusters containing four to seven water molecules each. All of the strontium and barium clusters react quickly with benzene. Barium reacts slightly faster than the corresponding strontium cluster with the same number of water molecules attached. For calcium, clusters with four and five water molecules react quickly, whereas those with six and seven water molecules do not. Magnesium with four water molecules reacts quickly, but not when five through seven water molecules are attached. The slow reactivity observed for some of these clusters indicates that the cation-pi interaction between the metal ion and benzene is partially screened by the surrounding water molecules. The reactivity of magnesium with seven water molecules is intermediate that of the hexa- and pentahydrate and the tetrahydrate. This result is consistent with the seventh water molecule being in the outer shell and much more weakly bound. The unusual trend in reactivity observed for magnesium may be due to the presence of mixed shell structures observed previously. These results are the first to provide information about the relative importance of cation-pi interactions in divalent metal ions as a function of metal hydration extent. Such studies should also provide a model and some insight into the relative binding affinities of divalent metal ions to aromatic residues on peptides and proteins.

  3. Isothermal sections of Eu(Ca, Zr, Ba)-Mn-Al ternary phase diagrams at 770 K

    International Nuclear Information System (INIS)

    Manyako, N.B.; Yanson, T.I.; Zarechnyuk, O.S.

    1988-01-01

    Isothermal cross sections of Eu(Ca, Sr, Ba)-Mn-Al state diagrams at 770 K are plotted by means of X-ray structural analysis. EuMn 2.3-3.6 Al 9.7-8.4 (ThMn 12 structure type) and Eu 2 Mn 5 Al 12 (eigenstructure type) two compound are found within Eu-Mn-Al system. Existance of CaMn 0.16- 0 .32 Al 1.84-1.68 compound (MgNi 2 structure type) is proved and CaMn 3.2-2.1 Al 8.8-9.9 compound (ThMn 12 type partially ordered structure) is found within Ca-Mn-Al system. Ternary compounds are not formed within Sr(Ba)-Mn-Al systems. Regions of stratification, occurring within Eu(Ca, Sr, Ba)-Mn systems, penetrate in ternary system

  4. Synthesis and characterisation of alkaline earth bis(diphenylphosphano)metallocene complexes and heterobimetallic alkaline earth metal/platinum(II) complexes [Ae(thf)(x)(η5-C5H4PPh2)2Pt(Me)2] (Ae = Ca, Sr, Ba).

    Science.gov (United States)

    Daniels, Daisy P; Deacon, Glen B; Harakat, Dominique; Jaroschik, Florian; Junk, Peter C

    2012-01-07

    A series of alkaline earth metallocene complexes carrying the diphenylphosphanocyclopentadienyl ligand, [Ae(L)(x)(η(5)-C(5)H(4)PPh(2))(2)] (Ae = Ca, L = thf, x = 1 (6a); Ae = Ca, L = dme, x = 1 (6b); Ae = Sr, L = thf, x = 1 (7); Ae = Ba, L = thf, x = 1 (8a); Ae = Ba, L = dme, x = 2 (8b)), were prepared by redox transmetallation/protolysis from the free metals, diphenylmercury and diphenylphosphanocyclopentadiene. These complexes were characterised using multinuclear NMR spectroscopy and two by single crystal X-ray diffraction. [Ca(dme)(η(5)-C(5)H(4)PPh(2))(2)] (6b) is a discrete neutral monomeric eight coordinate molecule in which the phosphorus atoms are not coordinated to the calcium ion and the larger barium analogue, ten-coordinate [Ba(dme)(2)(η(5)-C(5)H(4)PPh(2))(2)] (8b), has an extremely bent sandwich structure due to the two dme ligands attached to the metal. Bimetallic complexes, [Ae(thf)(x)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].(solv) (Ae = Ca, L = thf, x = 2, solv = 1.5thf (9); Ae = Sr, L = thf, x = 3, solv = 1.5thf (10); Ae = Ba, L = thf, x = 3, solv = thf (11)) were obtained by reaction of the homometallic complexes with [Pt(cod)(Me)(2)]. The crystal structures of [Ca(thf)(2)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].1.5thf (9), [Sr(thf)(3)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].1.5thf (10) and [Ba(thf)(3)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].thf (11) show the eight (calcium) and nine coordinate (strontium and barium) fragments acting as a chelating metalloligand attached to the square planar platinum through the phosphorus donor atoms. The solution chemistry of these bimetallic complexes has been investigated by NMR spectroscopy, electro-spray ionisation mass spectrometry and conductivity experiments which indicate that the bimetallic compounds persist in solution.

  5. Basic properties of Sr{sub 1-x}Ba{sub x}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Motoharu, E-mail: IMAI.Motoharu@nims.go.jp; Sato, Akira; Kimura, Takashi; Aoyagi, Takeshi

    2011-10-03

    Basic properties, such as the phase relationship, crystal structure, and energy gap E{sub g}, have been investigated in Sr-rich Sr{sub 1-x}Ba{sub x}Si{sub 2}. Sr{sub 1-x}Ba{sub x}Si{sub 2} (0 {<=} x {<=} 1.0) has two phases: one with the SrSi{sub 2}-type structure and another with the BaSi{sub 2}-type structure. The SrSi{sub 2} phase exists at x ranging from 0 to 0.13, and the BaSi{sub 2} phase exists at x ranging from 0.24 to 1.0. The volume increases with x in both the SrSi{sub 2} and BaSi{sub 2} phases. A volume jump of 13.7% appears at the structural phase transition from the SrSi{sub 2} phase to the BaSi{sub 2} phase. E{sub g} increases with x in SrSi{sub 2}-phase Sr{sub 1-x}Ba{sub x}Si{sub 2} but E{sub g} decreases with x in the BaSi{sub 2}-phase Sr{sub 1-x}Ba{sub x}Si{sub 2}. In Sr-rich BaSi{sub 2}-phase Sr{sub 1-x}Ba{sub x}Si{sub 2}, Ba atoms at a specific crystallographic site, the A1 site, are preferentially substituted by Sr atoms, as well as in Ba-rich BaSi{sub 2}-phase Sr{sub 1-x}Ba{sub x}Si{sub 2}.

  6. Structural and compositional characterization of synthetic (Ca,Sr)-tremolite and (Ca,Sr)-diopside solid solutions

    Science.gov (United States)

    Gottschalk, M.; Najorka, J.; Andrut, M.

    Tremolite (CaxSr1-x)2Mg5[Si8O22/(OH)2] and diopside (CaxSr1-x)Mg[Si2O6] solid solutions have been synthesized hydrothermally in equilibrium with a 1 molar (Ca,Sr)Cl2 aqueous solution at 750°C and 200 MPa. The solid run products have been investigated by optical, electron scanning and high resolution transmission electron microscopy, electron microprobe, X-ray-powder diffraction and Fourier-transform infrared spectroscopy. The synthesized (Ca,Sr)-tremolites are up to 2000 µm long and 30 µm wide, the (Ca,Sr)-diopsides are up to 150 µm long and 20 µm wide. In most runs the tremolites and diopsides are well ordered and chain multiplicity faults are rare. Nearly pure Sr-tremolite (tr0.02Sr-tr0.98) and Sr-diopside (di0.01Sr-di0.99) have been synthesized. A continuous solid solution series, i.e. complete substitution of Sr2+ for Ca2+ on M4-sites exists for (Ca,Sr)-tremolite. Total substitution of Sr2+ for Ca2+ on M2-sites can be assumed for (Ca,Sr)-diopsides. For (Ca,Sr)-tremolites the lattice parameters a, b and β are linear functions of composition and increase with Sr-content whereas c is constant. For the diopside series all 4 lattice parameters are a linear function of composition; a, b, c increase and β decreases with rising Sr-content. The unit cell volume for tremolite increases 3.47% from 906.68 Å3 for tremolite to 938.21 Å3 for Sr-tremolite. For diopside the unit cell volume increases 4.87 % from 439.91 Å3 for diopside to 461.30 Å3 for Sr-diopside. The observed splitting of the OH stretching band in tremolite is caused by different configurations of the next nearest neighbors (multi mode behavior). Resolved single bands can be attributed to the following configurations on the M4-sites: SrSr, SrCa, CaCa and CaMg. The peak positions of these 4 absorption bands are a linear function of composition. They are shifted to lower wavenumbers with increasing Sr-content. No absorption band due to the SrMg configuration on the M4-site is observed. This indicates

  7. An investigation on the microstructures and magnetic properties of the Sr{sub 0.35−x}Ba{sub x}Ca{sub 0.30}La{sub 0.35}Fe{sub 11.71}Co{sub 0.29}O{sub 19} hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yujie, E-mail: loyalty-yyj@163.com; Liu, Xiansong

    2014-11-15

    M-type hexaferrite Sr{sub 0.35−x}Ba{sub x}Ca{sub 0.30}La{sub 0.35}Fe{sub 11.71}Co{sub 0.29}O{sub 19} (0≤x≤0.35) magnetic powders and magnets were prepared by the solid-state reaction. The phase compositions of the magnetic powders were investigated by X-ray diffraction. X-ray diffraction patterns show that the hexagonal single phase is obtained in all samples. The micrographs of the magnets were observed by a field emission scanning electron microscopy. All magnets have formed hexagonal structures and the particles are distributed evenly. Magnetic properties of the magnets were measured by a magnetic properties test instrument. The remanence, intrinsic coercivity, magnetic induction coercivity and maximum energy product of the magnets continuously decrease with increasing barium content (x). - Highlights: • Hexaferrites Sr{sub 0.35−x}Ba{sub x}Ca{sub 0.30}La{sub 0.35}Fe{sub 11.71}Co{sub 0.29}O{sub 19} were prepared by the solid-state reaction. • The hexagonal single phase is obtained in all magnetic powders. • B{sub r}, H{sub cj}, H{sub cb} and (BH){sub max} of the magnets continuously decrease with increasing barium content.

  8. Syntheses and structural characterization of vanado-tellurites and vanadyl-selenites: SrVTeO5(OH), Cd2V2Te2O11, Ca3VSe4O13·H2O and Ba2VSe3O10

    Science.gov (United States)

    Konatham, Satish; Vidyasagar, Kanamaluru

    2017-05-01

    Four new quaternary vanado-tellurites and vanadyl-selenites, namely, SrVTeO5(OH)(1), Cd2V2Te2O11(2), Ca3VSe4O13·H2O(3) and Ba2VSe3O10(4) have been synthesized and structurally characterized by single crystal X-ray diffraction. The oxidation state of vanadium is +5 in tellurites 1 and 2 and +4 in selenites 3 and 4. The structures of SrVTeO5(OH)(1) and Cd2V2Te2O11(2) compounds consist of (VTeO5(OH))2- and (V2Te2O11)4-anionic chains respectively, which are built from tetrahedral VO4 and disphenoidal TeO4 moieties. Similarly the structures of Ca3VSe4O13·H2O(3) and Ba2VSe3O10(4) respectively contain (VSe2O7)2- and (VSe3O10)4- anionic chains, which are made up of octahedral VO6 and pyramidal SeO3 units. Compounds 1 and 3 have been characterized by thermogravimetric and infrared spectroscopic methods. Compounds 1 and 2 are wide band gap semiconductors.

  9. Syntheses and structural characterization of vanado-tellurites and vanadyl-selenites: SrVTeO_5(OH), Cd_2V_2Te_2O_1_1, Ca_3VSe_4O_1_3·H_2O and Ba_2VSe_3O_1_0

    International Nuclear Information System (INIS)

    Konatham, Satish; Vidyasagar, Kanamaluru

    2017-01-01

    Four new quaternary vanado-tellurites and vanadyl-selenites, namely, SrVTeO_5(OH)(1), Cd_2V_2Te_2O_1_1(2), Ca_3VSe_4O_1_3·H_2O(3) and Ba_2VSe_3O_1_0(4) have been synthesized and structurally characterized by single crystal X-ray diffraction. The oxidation state of vanadium is +5 in tellurites 1 and 2 and +4 in selenites 3 and 4. The structures of SrVTeO_5(OH)(1) and Cd_2V_2Te_2O_1_1(2) compounds consist of (VTeO_5(OH))"2"- and (V_2Te_2O_1_1)"4"-anionic chains respectively, which are built from tetrahedral VO_4 and disphenoidal TeO_4 moieties. Similarly the structures of Ca_3VSe_4O_1_3·H_2O(3) and Ba_2VSe_3O_1_0(4) respectively contain (VSe_2O_7)"2"- and (VSe_3O_1_0)"4"- anionic chains, which are made up of octahedral VO_6 and pyramidal SeO_3 units. Compounds 1 and 3 have been characterized by thermogravimetric and infrared spectroscopic methods. Compounds 1 and 2 are wide band gap semiconductors. - Graphical abstract: Ca_3VSe_4O_1_3·H_2O and Ba_2VSe_3O_1_0 compounds contain (VSe_2O_7)"2"- and (VSe_3O_1_0)"4"- chains. - Highlights: • Four new vanado-tellurites and vanadyl-selenites are synthesized. • Their structural features are different. • The vanado-tellurites are wide band gap semiconductors.

  10. Study on the equilibrium in the MBr2-CH3OH-H2O system (M = Sr2+, Ba2+) at 25 0C

    International Nuclear Information System (INIS)

    Zlateva, I.; Stoev, M.

    1985-01-01

    The dehydration processes in the three-component system MBr 2 -CH 3 OH-H 2 O (M = Sr 2+ , Ba 2+ ) have been studied at 25 0 C by physio-chemical analyses. Crystallization fields for the lower crystal hydrates SrBr 2 x H 2 O and BaBr 2 x H 2 O have been found. The solubility curves exhibit complex-formation processes. The dehydration and solvation processes in three-component system such as MBr 2 -CH 3 OH-H 2 O at 25 0 C with M = Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ have been discussed in general terms. (author)

  11. Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals

    Science.gov (United States)

    Sangeetha, N. S.; Smetana, V.; Mudring, A.-V.; Johnston, D. C.

    2018-01-01

    Crystals of SrMn2Sb2 and BaMn2Sb2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ , heat capacity Cp, and magnetic susceptibility χ measurements versus temperature T , and magnetization versus field M (H ) isotherm measurements. SrMn2Sb2 adopts the trigonal CaAl2Si2 -type structure, whereas BaMn2Sb2 crystallizes in the tetragonal ThCr2Si2 -type structure. The ρ (T ) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn2Sb2 and 0.16 eV for BaMn2Sb2 . The χ (T ) and Cp(T ) data reveal antiferromagnetic (AFM) ordering at TN = 110 K for SrMn2Sb2 and 450 K for BaMn2Sb2 . The anisotropic χ (T ≤TN) data also show that the ordered moments in SrMn2Sb2 are aligned in the hexagonal a b plane, whereas the ordered moments in BaMn2Sb2 are aligned collinearly along the tetragonal c axis. The a b -plane M (H ) data for SrMn2Sb2 exhibit a continuous metamagnetic transition at low fields 0 survey of the literature for Mn pnictides with the CaAl2Si2 and ThCr2Si2 crystal structures show that the TN values for the CaAl2Si2 -type compounds are much smaller than those for the ThCr2Si2 -type materials.

  12. 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.)

  13. Variable dimensionality and new uranium oxide topologies in the alkaline-earth metal uranyl selenites AE[UO2)(SeO3)2] (AE=Ca, Ba) and Sr[UO2)(SeO3)2] · 2H2O

    International Nuclear Information System (INIS)

    Almond, Philip M.; Peper, Shane M.; Bakker, Eric; Albrecht-Schmitt, Thomas E.

    2002-01-01

    Three new alkaline-earth metal uranyl selenites, Ca[UO 2 )(SeO 3 ) 2 ] (1), Sr[UO 2 )(SeO 3 ) 2 ] · 2H 2 O (2), and Ba[UO 2 )(SeO 3 ) 2 ] (3), have been prepared from the reactions of CaCO 3 and Ca(OH) 2 , SrCl 2 and Sr(OH) 2 , or BaCl 2 and Ba(OH) 2 with UO 3 and SeO 2 under mild hydrothermal conditions. Single-crystal X-ray diffraction experiments reveal that the structures of 1-3 differ in both connectivity and dimensionality even though all contain the same fundamental building unit, namely [UO 2 (SeO 3 ) 4 ]. This polyhedron consists of a linear uranyl unit that is bound by one chelating and three bridging selenite anions creating a pentagonal bipyramidal environment around the U(VI) center. The crystal structure of 1 contains one-dimensional ribbons where the edges are terminated by monodentate selenite anions. The interior of the ribbons are constructed from edge-sharing pentagonal bipyramidal UO 7 units. The structure of 2 is also one-dimensional; however, here there are chains of edge-sharing pentagonal bipyramidal UO 7 dimers that are connected by bridging selenite anions. Ba[(UO 2 )(SeO 3 ) 2 ] (3) is two-dimensional, and the highly ruffled anionic sheets present in this structure are formed from both bridging and chelating/bridging selenite anions bound to uranyl moieties. The anionic substructures in 1-3 are separated by Ca 2+ , Sr 2+ , or Ba 2+ cations. Crystallographic data (193 K, MoKα, λ=0.71073): 1, triclinic, space group P1-bar, a=5.5502(6) A, b=6.6415(7) A, c=11.013(1) A, α=104.055(2) deg., β=93.342(2) deg., γ=110.589(2) deg. , Z=2, R(F)=4.56% for 100 parameters with 1530 reflections with I>2σ(I); 2, triclinic, space group P1-bar, a=7.0545(5) A, b=7.4656(5) A, c=10.0484(6) A, α=106.995(1) deg., β=108.028(1) deg., γ=98.875(1) deg., Z=2, R(F)= 2.43% for 128 parameters with 2187 reflections with I>2σ(I); 3, monoclinic, space group P2 1 /c, a=7.3067(6) A, b=8.1239(7) A, c=13.651(1) A, β=100.375(2) deg., Z=4, R(F)=4.31% for 105 parameters

  14. Incorporation of Mg, Sr, Ba, U, and B in High-Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

    Science.gov (United States)

    Not, C.; Thibodeau, B.; Yokoyama, Y.

    2018-01-01

    Measurement of elemental ratios (E/Ca) has been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing preindustrial, modern, and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca, such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U, and B incorporation could be controlled by Rayleigh fractionation. However, more data are needed to validate and quantify the relative importance of this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multielemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca is sensitive to bottom water pCO2 or pH for these species.

  15. High field-effect mobility at the (Sr,Ba)SnO3/BaSnO3 interface

    Science.gov (United States)

    Fujiwara, Kohei; Nishihara, Kazuki; Shiogai, Junichi; Tsukazaki, Atsushi

    2016-08-01

    A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,Ba)SnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,Ba)SnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  16. High field-effect mobility at the (Sr,BaSnO3/BaSnO3 interface

    Directory of Open Access Journals (Sweden)

    Kohei Fujiwara

    2016-08-01

    Full Text Available A perovskite oxide, BaSnO3, has been classified as one of transparent conducting materials with high electron mobility, and its application for field-effect transistors has been the focus of recent research. Here we report transistor operation in BaSnO3-based heterostructures with atomically smooth surfaces, fabricated on SrTiO3 substrates by the (Sr,BaSnO3 buffer technique. Indeed, modulation of band profiles at the channel interfaces with the insertion of wide bandgap (Sr,BaSnO3 as a barrier layer results in a significant improvement of field-effect mobility, implying effective carrier doping at the regulated heterointerface. These results provide an important step towards realization of high-performance BaSnO3-based field-effect transistors.

  17. NaF-CaF2-BaF2-BaMoO4 system

    International Nuclear Information System (INIS)

    Verdiev, N.N.; Gasanaliev, A.M.

    1986-01-01

    Stable tetrahedron NaF-CaF 2 -BaF 2 -BaMoO 4 of a mutual quaternary system Na, Ca, Ba parallel F, MoO 4 was investigated. The investigations were carried on using differential thermal (DTA), X-ray phase (RPA) and visual-polythermal (VPM) analyses. A quaternary eutectic point found as a result of the investigations performed is characterized with relatively low melting temperature and considerable content of barium molybdates which permits to refer it to perspective compositions for electrodeposition of molybdenum

  18. 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.

  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. Structural and magnetic characterization of (Ba,Sr-hexaferrite Powders

    Directory of Open Access Journals (Sweden)

    Palomares-Sánchez, S.

    1999-06-01

    Full Text Available Results on magnetic and structural characterization of ferrimagnetic compounds of BaxSr1-xFe12O19 (x=0.0, 0.25, 0.50, 0.75 and 1.0 prepared by the conventional ceramic method are reported. The samples were systematically examined using atomic force microscopy (AFM, X-ray diffraction and vibrating sample magnetometer. Structural and magnetic differences among the specimens were observed. The relations between structural features and magnetic properties are discussed. The presintering temperatures of the samples were 800°C and 1,000°C. The specimens were sintered at 1,200°C for one hour.

    Se presentan resultados de la caracterización estructural y magnética de compuestos ferrimagnéticos BaxSr1-xFe12O19 (x=0,0, 0,25, 0,50, 0,75 y 1,0 preparados por el método cerámico convencional. Las muestras fueron examinadas por microscopía de fuerza atómica, difracción de rayos X y magnetometría de muestra vibrante. Se observaron diferencias tanto estructurales como magnéticas en las muestras analizadas. Se discuten las relaciones entre los aspectos estructurales y los parámetros magnéticos medidos. Las temperaturas de presinterización de las muestras fueron de 800°C y 1.000°C y fueron sinterizadas a 1.200°C durante una hora.

  1. La{sub x}A{sub 1-x}MnO{sub 3} (A = Sr,Ca)/Y Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} superlattices deposited by the 'eclipse' pulsed laser deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Pang, B S H; Tomov, R I; Blamire, M G [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, CB2 3QZ (United Kingdom)

    2004-04-01

    Multilayered structures of La{sub x}Sr{sub 1-x}MnO{sub 3} (LSMO), La{sub x}Ca{sub 1-x}MnO{sub 3} (LCMO) and Y Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) were successfully grown by 'eclipse' pulsed laser ablation deposition (PLD) on (100) SrTiO{sub 3} and (100) NdGaO{sub 3} substrates. X-ray diffraction and scanning electron microscopy were used to investigate epitaxial growth, interface quality and structural disorder. The composition and the roughness of the films was characterized by energy dispersive x-rays (EDX) and atomic force microscopy (AFM) respectively. The results are discussed in terms of the optimization of PLD parameters and the establishment of its limits. Issues such as interdiffusion and particulate contamination reduction as well as utilizations of the 'eclipse' technique are addressed. The interaction between superconductivity and magnetism was investigated by varying the thicknesses of YBCO layers while the keeping the thicknesses of the ferromagnetic layers constant.

  2. 130-K Superconductivity in the Hg-Ba-Ca-Cu-O System

    Science.gov (United States)

    Salem, A.; Gamal, G. A.; Jakob, G.; Adrian, H.

    2006-09-01

    (Hg0.9Re0.1)Ba2Ca2Cu3 O8+δ(HgRe-1223) HTSC thin films have been prepared by pulsed laser deposition (PLD) of a precursor on (100)-oriented SrTiO3 substrates followed by annealing in a controlled mercury atmosphere. The critical temperature is 129 K determined by the temperature dependence of AC susceptibility. Resistance measurements show a superconducting transition at Tc= 130 K with transition width ΔTc ≈ 3 K.

  3. Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

    OpenAIRE

    Hathorne, Ed C.; Gagnon, Alex; Felis, Thomas; Adkins, Jess; Asami, Ryuji; Boer, Wim; Caillon, Nicolas; Case, David; Cobb, Kim M.; Douville, Eric; deMenocal, Peter; Eisenhauer, Anton; Garbe-Schönberg, Dieter; Geibert, Walter; Goldstein, Steven L.

    2013-01-01

    The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7 degrees C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 m...

  4. Magnetothermopower in A2−xLaxFeMoO6 (A = Sr, Ba

    Directory of Open Access Journals (Sweden)

    G. V. M. Williams

    2017-01-01

    Full Text Available A magnetothermopower has been observed in electronically spin-polarized polycrystalline Sr2-xLaxFeMoO6 and Ba2FeMoO6. The magnetothermopower is linear up to ~50 K for Sr2-xLaxFeMoO6 and linear up to ~270 K for Ba2FeMoO6. We suggest that the magnetothermopower may arise from a spin-tunneling magnetothermopower between the grains.

  5. Isothermal cross-sections of Sr-Al-Ge and Ba-Al-Ge systems at 673 K

    International Nuclear Information System (INIS)

    Kutsenok, N.L.; Yanson, T.I.

    1987-01-01

    X-ray and microstructural analyses are used to study phase equilibria in Sr-Al-Ge and Ba-Al-Ge systems. Existence of SrAl 2 Ge 2 , Sr(Al, Ge) 2 Ba(Al, Ge) 2 , Sr 3 Al 2 Ge 2 , Ba 3 Al 2 Ge 2 ternary compounds is confirmed, a new BaGe 4 binary compound and also new ternary compounds of approximate composition Sr 57 Al 30 Ge 13 and Ba 20 Al 40 Ge 40 , which crystal structure is unknown, are detected. Aluminium solubility in SrAl 4 and BaAl 4 binary compounds (0.05 atomic fraction) is determined. Ba(Al, Ge) 2 compound homogeneity region is defined more exactly (aluminium content varies from 0.27 to 0.51 at. fractions)

  6. Ultrasonic Investigations on Polonides of Ba, Ca, and Pb

    Science.gov (United States)

    Singh, Devraj; Bhalla, Vyoma; Bala, Jyoti; Wadhwa, Shikha

    2017-10-01

    The temperature-dependent mechanical and ultrasonic properties of barium, calcium, and lead polonides (BaPo, CaPo, and PbPo) were investigated in the temperature range 100-300 K. The second- and third-order elastic constants (SOECs and TOECs) were computed using Coulomb and Born-Mayer potential and these in turn have been used to estimate other secondary elastic properties such as strength, anisotropy, microhardness, etc. The theoretical approach followed the prediction that BaPo, CaPo, and PbPo are brittle in nature. PbPo is found to be the hardest amongst the chosen compounds. Further the SOECs and TOECs are applied to determine ultrasonic velocities, Debye temperature, and acoustic coupling constants along , , and orientations at room temperature. Additionally thermal conductivity has been computed using Morelli and Slack's approach along different crystallographic directions at room temperature. Finally ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms has been computed for BaPo, CaPo, and PbPo. The behaviour of these compounds is similar to that of semi-metals with thermal relaxation time of the order 10-11 s. The present computation study is reasonably in agreement with the available theoretical data for the similar type of materials.

  7. Ultrasonic investigations on polonides of Ba, Ca, and Pb

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Devraj; Bhalla, Vyoma [Amity School of Engineering and Technology, New Delhi (India). Dept. of Applied Physics; Bala, Jyoti [Amity School of Engineering and Technology, New Delhi (India). Dept. of Applied Physics; Guru Gobind Singh Indraprastha Univ., New Delhi (India). USICT; Wadhwa, Shikha [Amity Univ., Noida (India). Amity Inst. of Nanotechnology

    2017-07-01

    The temperature-dependent mechanical and ultrasonic properties of barium, calcium, and lead polonides (BaPo, CaPo, and PbPo) were investigated in the temperature range 100-300 K. The second- and third-order elastic constants (SOECs and TOECs) were computed using Coulomb and Born-Mayer potential and these in turn have been used to estimate other secondary elastic properties such as strength, anisotropy, microhardness, etc. The theoretical approach followed the prediction that BaPo, CaPo, and PbPo are brittle in nature. PbPo is found to be the hardest amongst the chosen compounds. Further the SOECs and TOECs are applied to determine ultrasonic velocities, Debye temperature, and acoustic coupling constants along left angle 100 right angle, left angle 110 right angle, and left angle 111 right angle orientations at room temperature. Additionally thermal conductivity has been computed using Morelli and Slack's approach along different crystallographic directions at room temperature. Finally ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms has been computed for BaPo, CaPo, and PbPo. The behaviour of these compounds is similar to that of semi-metals with thermal relaxation time of the order 10{sup -11} s. The present computation study is reasonably in agreement with the available theoretical data for the similar type of materials.

  8. Synthesis of BiPbSrCaCuO superconductor

    Science.gov (United States)

    Hults, William L.; Kubat-Martin, Kimberly A.; Salazar, Kenneth V.; Phillips, David S.; Peterson, Dean E.

    1994-01-01

    A process and a precursor composition for preparing a lead-doped bismuth-strontium-calcium-copper oxide superconductor of the formula Bi.sub.a Pb.sub.b Sr.sub.c Ca.sub.d Cu.sub.e O.sub.f wherein a is from about 1.7 to about 1.9, b is from about 0.3 to about 0.45, c is from about 1.6 to about 2.2, d is from about 1.6 to about 2.2, e is from about 2.97 to about 3.2 and f is 10.+-.z by reacting a mixture of Bi.sub.4 Sr.sub.3 Ca.sub.3 Cu.sub.4 O.sub.16.+-.z, an alkaline earth metal cuprate, e.g., Sr.sub.9 Ca.sub.5 Cu.sub.24 O.sub.41, and an alkaline earth metal plumbate, e.g., Ca.sub.2-x Sr.sub.x PbO.sub.4 wherein x is about 0.5, is disclosed.

  9. Impedance spectroscopy of Li2CO3 doped (Ba,Sr)TiO3 ceramic

    Science.gov (United States)

    Ham, Yong-Su; Koh, Jung-Hyuk

    2013-02-01

    (BaxSr1-x)TiO3-based ceramic has been considered as one of the most important electronic materials widely employed in microwave passive device applications. Many researches have been performed to lower the high sintering temperature, by adding various dopants such as B2O3, La2O3, etc. In our previous study, by adding Li2CO3 to (Ba0.5,Sr0.5)TiO3 ceramics, the sintering temperature of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics decreased from 1350 to 900 °C. This study observed the crystalline structure and electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics. In scanning the crystalline structure of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, no pyro phase was observed by X-ray diffraction analysis. To investigate the electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, real and imaginary parts of the impedances were analyzed. Complex impedance data were measured from 100 Hz to 1 MHz at various temperature ranges.

  10. Electronic structure and properties of BaAIGe and SrAlGe

    Energy Technology Data Exchange (ETDEWEB)

    Youn, S.J., E-mail: ysj@gnu.ac.kr [Department of Physics Education and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701 (Korea, Republic of); Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208-3112 (United States); Freeman, A.J. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208-3112 (United States)

    2012-06-15

    The electronic structures of BaAlGe and SrAlGe which are superconductors with hexagonal honeycomb layers have been studied by using a first principles method. Energy bands, Fermi surfaces, and density of states are presented. The two materials have topologically different Fermi surfaces. BaAlGe has two Fermi surfaces: one has a three dimensional spinning-top-like shape and the other has a cylindrical shape with two dimensional character. SrAlGe has only one connected Fermi surface. Two gap superconductivity for BaAlGe is suggested from the inherently different character of the two Fermi surfaces. The higher T{sub c} of SrAlGe than BaAlGe is related to the difference in both the topology of the Fermi surface and the band dispersions along the z direction.

  11. 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.

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

    Science.gov (United States)

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (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.

  13. Dielectric enhancement of BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals

    International Nuclear Information System (INIS)

    Xiong Zhengwei; Sun Weiguo; Wang Xuemin; Jiang Fan; Wu Weidong

    2012-01-01

    Highlights: ► The BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs were successfully fabricated by L-MBE. ► The influence with the various concentrations of Ni nanocrystals embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. ► The BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss compared with the pure BaTiO 3 /SrTiO 3 superlattices. ► The dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory. - Abstract: The self-organized Ni nanocrystals (NCs) were embedded in BaTiO 3 /SrTiO 3 superlattices using laser molecular beam epitaxy (L-MBE). The stress of the composite films was increased with the increasing concentration of embedded Ni NCs, as investigation in stress calculation. The influence with the various concentrations of Ni NCs embedded in BaTiO 3 /SrTiO 3 superlattices was also discussed. The internal stress of the films was too strong to epitaxial growth of BaTiO 3 /SrTiO 3 superlattices. Compared with the pure BaTiO 3 /SrTiO 3 superlattices, the BaTiO 3 /SrTiO 3 superlattices with lower concentration of embedded Ni NCs had higher permittivity and dielectric loss. Furthermore, the dielectric enhancement of BaTiO 3 /SrTiO 3 superlattices with embedded Ni NCs was proposed to explained by Drude quasi-free-electron theory.

  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. 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.

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

    Directory of Open Access Journals (Sweden)

    Junichi Shiogai

    2016-06-01

    Full Text Available 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,BaSnO3 for buffering this large lattice mismatch between La:BaSnO3 and SrTiO3 substrate. The insertion of 200-nm-thick BaSnO3 on (Sr,BaSnO3 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.

  17. Hysteretic electrical transport in BaTiO{sub 3}/Ba{sub 1−x}Sr{sub x}TiO{sub 3}/Ge heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ngai, J. H.; Kumah, D. P.; Walker, F. J. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, 15 Prospect Street, New Haven, Connecticut 06520-8284 (United States); Ahn, C. H. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, 15 Prospect Street, New Haven, Connecticut 06520-8284 (United States); Department of Mechanical Engineering and Materials Science, Yale University, 10 Hillhouse Avenue, New Haven, Connecticut 06520-8267 (United States)

    2014-02-10

    We present electrical transport measurements of heterostructures comprised of BaTiO{sub 3} and Ba{sub 1−x}Sr{sub x}TiO{sub 3} epitaxially grown on Ge. Sr alloying imparts compressive strain to the BaTiO{sub 3}, which enables the thermal expansion mismatch between BaTiO{sub 3} and Ge to be overcome to achieve c-axis oriented growth. The conduction bands of BaTiO{sub 3} and Ba{sub 1−x}Sr{sub x}TiO{sub 3} are nearly aligned with the conduction band of Ge, which facilitates electron transport. Electrical transport measurements through the dielectric stack exhibit rectifying behavior and hysteresis, where the latter is consistent with ferroelectric switching.

  18. Spectroscopic Proprieties of Crystals Mf 2 (M=Cd, Sr, Ba) Doped to ...

    African Journals Online (AJOL)

    In the present work, we are interested by studying the spectroscopic properties for optical applications, mainly laser amplification, of MF2 crystals, where M is an alkaline earth (Ba, Sr) or Cadmium (Cd) doped with rare earth ions (Tb3+, Er3+, Ho3+. So far, we present the absorption and emission properties and also the ...

  19. Influence of bismuth on properties and microstructures of Sr0⋅ 5Ba0 ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 29; Issue 5. Influence of bismuth on properties and microstructures of Sr0.5Ba0.5–Bi TiO3 thin films. Tao Wenhong Wang Yin Fu Xinghua Wei Qihong. Thin Films Volume 29 Issue 5 October 2006 pp 523-527 ...

  20. Physical and magnetic properties of (Ba/Sr) substituted magnesium nano ferrites

    Science.gov (United States)

    Ateia, Ebtesam E.; Takla, E.; Mohamed, Amira T.

    2017-10-01

    In the presented paper, strontium (Sr) and barium (Ba) nano ferrites were synthesized by citrate auto combustion method. The investigated samples are characterized by X-ray diffraction technique (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The structural properties of the obtained samples were examined by XRD analysis showing that the synthesized nanoparticles are in cubic spinel structure. The average crystallite sizes are in the range of 22.66 and 21.95 nm for Mg0.7Ba0.3Fe2O4 and Mg0.7 Sr0.3Fe2O4 respectively. The VSM analysis confirms the existence of ferromagnetic nature of Sr2+/Ba2+ substituted magnesium nano particles. Exchange interaction between hard (Sr/Ba) and soft (Mg) magnetic phases improves the structural and magnetic properties of nano ferrite particles. Rigidity modulus, longitudinal and shear wave velocities are predicted theoretically from Raman spectroscopy and structural data of the investigated spinel ferrite. The magnetic and structural properties of magnesium are enhanced by doping with barium and strontium nano particles. The saturation magnetization, remanent magnetization and coercivity reported on vibrating sample magnetometer curve illustrate the promising industrial and magnetic recording applications of the prepared samples.

  1. Heat capacity measurement of Ba3SrNb2O9

    International Nuclear Information System (INIS)

    Singh, B.M.; Samui, Pradeep; Agarwal, Renu; Mukerjee, S.K.

    2016-01-01

    Barium, Strontium and Niobium are important fission products in nuclear reactor with reasonable fission yields. During irradiation of oxide fuels, they can combine to form compounds of Ba-Sr-Nb-O system. Therefore, thermodynamic properties of Ba 3 SrNb 2 O 9 are required for modelling fuel behaviour however thermodynamic data of this compound is not available in literature. Ba 3 SrNb 2 O 9 was prepared by solid state route, by mixing stoichiometric amounts of finely grounded SrCO 3 , BaCO 3 and Nb 2 O 5 . Finally mixed powder was pressed into a pellet at 5 ton pressure for 2 minutes in a hydraulic press and the pellet was heated at 1123 K for 60 h in air. The pellet was cooled, finely grounded, re-pelletised and heated at 1473 K for 120 h. The formation of compound was confirmed by X-ray diffraction pattern, collected at room temperature using Cu-K α radiation (λ = 1.54 nm), scanned over the angular range 20-80° (2θ) with steps of 0.02°. Heat capacity of the compound was measured by the classical three-step method, in continuous mode, using LABSYS EVO, in temperature range of 370 and 950 K. No transition was observed in the investigated temperature range

  2. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

    Indian Academy of Sciences (India)

    Administrator

    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 ...

  3. Photoluminescence properties of X5SiO4Cl6:Tb (X = Sr, Ba) green ...

    Indian Academy of Sciences (India)

    Energy-level diagram of Tb3+ showing transitions that produce emission in visible region. bands that are correlated with some 4 f → 4 f electronic transitions in the activating terbium ions. In the emission spectra of X5SiO4Cl6:Tb3+ (X = Sr, Ba) phosphor, cha- racteristic blue and green emission peaks corresponding to.

  4. Ca2+ alternans in a cardiac myocyte model that uses moment equations to represent heterogeneous junctional SR Ca2+.

    Science.gov (United States)

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

    2010-07-21

    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 predicts that the distribution of junctional SR [Ca2+] across a large population of Ca2+ release units is distinct on alternating cycles. Load-release and release-uptake functions computed from this model give insight into how Ca2+ fluxes and stimulation frequency combine to determine the presence or absence of Ca2+ alternans. Our results show that the conditions for the onset of Ca2+ alternans cannot be explained solely by the steepness of the load-release function, but that changes in the release-uptake process also play an important role. We analyze the effect of the junctional SR refilling time constant on Ca2+ alternans and conclude that physiologically realistic models of defective Ca2+ cycling must represent the dynamics of heterogeneous junctional SR [Ca2+] without assuming rapid equilibration of junctional and network SR [Ca2+]. Copyright (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  5. Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

    Science.gov (United States)

    Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel

    2017-04-01

    Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca

  6. Influence of the Ba2+/Sr2+ content and oxygen vacancies on the stability of cubic Ba(x)Sr(1-x)Co(0.75)Fe(0.25)O(3-δ).

    Science.gov (United States)

    Lumeij, Marck; Gillessen, Michael; Bouwmeester, Henny; Markus, Torsten; Barthel, Juri; Roitsch, Stefan; Mayer, Joachim; Dronskowski, Richard

    2014-01-28

    We present a theoretical and experimental study on the influence of the Ba/Sr and Co/Fe ratios as well as the oxygen-non-stoichiometry on the stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF). Thin-layer depositions are analysed by looking at TEM images and EDX spectra. Bond-analytical calculations are performed to explain the stability difference between hexagonal and cubic BSCF. Finally, annealing experiments analysed using XRD give an insight into the differences of phase-fraction growth with respect to the Ba/Sr ratio.

  7. Structural studies and c dependence in La 2- Dy Ca Ba 2 ...

    Indian Academy of Sciences (India)

    ... 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).

  8. Sr/Ca ratios of modern and fossil Favia corals from the Korea Strait; implications for application of coral Sr/Ca thermometry in a middle latitude region

    Science.gov (United States)

    Seo, I.; Lee, Y.; Watanabe, T.; Shimamura, M.; Yamano, H.; Yoo, C.; Hyeong, K.

    2011-12-01

    Favia, a hermatypic reef building coral, is widely distributed from equator to northern latitudinal limit of coral distribution. An 150-mm-long living, grown for 21 years, and 50-mm-long fossil (2600 cal yr BP) Favia specimens, grown for 13 years, were collected from the Iki Island, Japan (34°48'N, 129°39'E) and analyzed for Sr/Ca ratios, in order to test for a high-resolution paleo-SST proxy. The modern and fossil Favia samples reveal clear annual seasonality in density bands and the measured Sr/Ca ratios. In the modern coral, however, the large inter-annual variability of winter Sr/Ca indicates smoothing of environmental signals during cold season due to very slow growth or frequent growth cessations. An SST - Sr/Ca equation, Sr/Ca (mmol/mol) = 10.428 - 0.049 × SST (°C), constructed under the assumption of growth stopping below 14°C, predicts the observed annual summer maximums within an error range of ± 1.2°C. Large inter-annual variability of Sr/Ca is also observed in the fossil coral, but even in the warm season, indicating more frequent coral growth disturbances due to colder condition at 2600 cal yr BP. With an assumption that growth disturbance had the least effect on the lowest Sr/Ca, the equation predicts summer maximum temperature of 24.6°C, ~ 2°C lower than the present. The SST - Sr/Ca equation established in this study successfully reconstructs SSTs of a subtropical region from reported literature values, suggesting the applicability of Sr/Ca thermometry of Favia in a wide range of climate settings.

  9. Physiological studies in heterozygous calcium sensing receptor (CaSR gene-ablated mice confirm that the CaSR regulates calcitonin release in vivo

    Directory of Open Access Journals (Sweden)

    Kovacs Christopher S

    2004-04-01

    Full Text Available Abstract Background The calcium sensing receptor (CaSR regulates serum calcium by suppressing secretion of parathyroid hormone; it also regulates renal tubular calcium excretion. Inactivating mutations of CaSR raise serum calcium and reduce urine calcium excretion. Thyroid C-cells (which make calcitonin express CaSR and may, therefore, be regulated by it. Since calcium stimulates release of calcitonin, the higher blood calcium caused by inactivation of CaSR should increase serum calcitonin, unless CaSR mutations alter the responsiveness of calcitonin to calcium. To demonstrate regulatory effects of CaSR on calcitonin release, we studied calcitonin responsiveness to calcium in normal and CaSR heterozygous-ablated (Casr+/- mice. Casr+/- mice have hypercalcemia and hypocalciuria, and live normal life spans. Each mouse received either 500 μl of normal saline or one of two doses of elemental calcium (500 μmol/kg or 5 mmol/kg by intraperitoneal injection. Ionized calcium was measured at baseline and 10 minutes, and serum calcitonin was measured on the 10 minute sample. Results At baseline, Casr+/- mice had a higher blood calcium, and in response to the two doses of elemental calcium, had greater increments and peak levels of ionized calcium than their wild type littermates. Despite significantly higher ionized calcium levels, the calcitonin levels of Casr+/- mice were consistently lower than wild type at any ionized calcium level, indicating that the dose-response curve of calcitonin to increases in ionized calcium had been significantly blunted or shifted to the right in Casr+/- mice. Conclusions These results confirm that the CaSR is a physiological regulator of calcitonin; therefore, in response to increases in ionized calcium, the CaSR inhibits parathyroid hormone secretion and stimulates calcitonin secretion.

  10. Deposition and patterning of Tl-Ca-Ba-Cu-O superconducting thin films

    International Nuclear Information System (INIS)

    Subramanyam, G.; Radpour, F.; Kapoor, V.J.; Lemon, G.H.

    1990-01-01

    This paper reports on high temperature superconducting Tl-Ca-Ba-Cu-O which were sputter deposited from a single composite powder target on SrTiO 3 and LaAlO 3 substrates, in an rf magnetron sputtering system. The as-deposited thin films were sintered and annealed in an excess Tl partial pressure to obtain superconductivity. The superconducting films were characterized by scanning electron microscope (SEM), x-ray diffraction (XRD) and resistance vs temperature (R vs T) measurements. Fine line features as small as 25 μm were obtained in as-deposited thin films using standard photolithography and wet chemical etching in a weak acid. From the XRD and SEM results, the annealed thin films were found to be highly c-axis oriented, with smooth platelets of 2-10 μm in size. The R vs T measurements showed zero resistance at temperatures as high as 107 K on SrTiO 3 and 103 K on LaAlO 3

  11. Floating zone growth of Ba-substituted ruthenate Sr2-xBaxRuO4

    Science.gov (United States)

    Li, Z. W.; Liu, C.-F.; Skoulatos, M.; Tjeng, L. H.; Komarek, A. C.

    2015-10-01

    We report on the exploration to synthesize Sr2-xBaxRuO4, the large volume variant of the unconventional superconductor Sr2RuO4. We have succeeded in growing single crystals for x-values up to 0.4 by making use of the traveling solvent floating zone method. The quality of the obtained crystals is confirmed by X-ray and neutron diffraction measurements and the properties of these Ba-substituted ruthenates were studied with magnetic and electrical transport measurements.

  12. Continuous drawing of Bi-Ca-Sr-Cu-O glass fibers from a preform

    International Nuclear Information System (INIS)

    Zheng, H.; Hu, Y.; Mackenzie, J.D.

    1991-01-01

    Several issues related to drawing Bi-Ca-Sr-Cu-O glass fibers from a preform are discussed. Continuous drawing of Bi-Ca-Sr-Cu-O glass fibers was successfully accomplished. Bi-Ca-Sr-Cu-O glass fibers are drawn above the crystallization temperature. Minimizing crystallization of the glass preforms is a key for successful drawing of the glass fibers. Two effective means, high glass melting temperature and V 2 O 5 doping, have been used to minimize the crystallization of the preforms, thus assuring the continuous drawing of Bi-Ca-Sr-Cu-O glass fibers

  13. The Sr/Ca-temperature relationship in coralline aragonite: Influence of variability in (Sr/Ca)[sub seawater] and skeletal growth parameters

    Energy Technology Data Exchange (ETDEWEB)

    de Villiers, S.; Shen, G.T.; Nelson, B.K. (Univ. of Washington, Seattle, WA (United States))

    1994-01-01

    This paper provides an evaluation of two of the most likely pitfalls of Sr/Ca thermometry, i.e., the effect of biogenic cycling of Sr vs. Ca in the surface ocean and the effect of variable extension rate on Sr incorporation in coralline aragonite. The authors also report calibration of the Sr/Ca-temperature relationship for three coral species, Porites lobata, Pocillopora eydouxi, and Pavona clavus, collected for the Hawaiian and Galapagos islands. Analyses of seawater samples show significant spatial and depth variability in the Sr:Ca ratio. The uncertainty introduced by this effect is estimated to be <0.2[degrees]C for corals located in tropical oligotrophic waters, and potentially larger for corals located in upwelling areas. Sr/Ca along two different growth axes of a Galapagos Pavona clavus, with annual extension rates of [approximately]6 and 12 mm/y, respectively, indicate an offset of 1-2[degrees]C, with higher Sr/Ca values associated with slower extension rates. The offset observed between the two growth axes may be the result of variations in extension and/or calcification rate. These results are important in determining past sea surface temperatures for reconstruction of paleoclimates.

  14. Numerical solutions of anharmonic vibration of BaO and SrO molecules

    Science.gov (United States)

    Pramudito, Sidikrubadi; Sanjaya, Nugraha Wanda; Sumaryada, Tony

    2016-03-01

    The Morse potential is a potential model that is used to describe the anharmonic behavior of molecular vibration between atoms. The BaO and SrO molecules, which are two almost similar diatomic molecules, were investigated in this research. Some of their properties like the value of the dissociation energy, the energy eigenvalues of each energy level, and the profile of the wavefunctions in their correspondence vibrational states were presented in this paper. Calculation of the energy eigenvalues and plotting the wave function's profiles were performed using Numerov method combined with the shooting method. In general we concluded that the Morse potential solved with numerical methods could accurately produce the vibrational properties and the wavefunction behavior of BaO and SrO molecules from the ground state to the higher states close to the dissociation level.

  15. 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.

  16. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

    Indian Academy of Sciences (India)

    Administrator

    Bull. Mater. Sci., Vol. 33, No. 2, April 2010, pp. 129–134. © Indian Academy of Sciences. 129. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic. P S SAHOO. †. , A PANIGRAHI. ††. , S K PATRI and R N P CHOUDHARY*. Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302, ...

  17. Petrogenesis of Post-collisional high Ba-Sr granitoids: the Solarya Pluton, NW Turkey

    Science.gov (United States)

    Unal, Alp; Kamaci, Omer; Altunkaynak, Safak

    2015-04-01

    In NW Turkey, the Late Oligocene-Early Miocene phase of post-collisional magmatism is characterized by widespread granitic pluton emplacements straddling the continental collision zone marked by the Izmir-Ankara suture zone (IASZ). This granitic magmatism produced both low Ba-Sr- and high Ba-Sr granitoids with distinct geochemical properties. One of the major plutons emplaced to the north of İzmir-Ankara suture zone, the Solarya pluton is representative of high Ba-Sr granitoids. We present here whole-rock chemical and Sr-Nd-Pb-O isotopic compositions, as well as 40Ar/39Ar ages of the Solarya pluton to evaluate the timing, nature and genesis of potassic, high Ba-Sr granites. The Solarya pluton consists of three coeval granitic members (K-Feldspar megacrystalline granodiorite, fine grained granodiorite and haplogranite) and associated mafic magmatic enclaves/dykes of gabbroic diorite to dioritic in composition. K-feldspar megacrystalline granodiorite, fine grained granodiorite and haplogranite are high K calc-alkaline in character whereas low silica mafic magmatic enclaves and dykes are mildly alkaline and display shoshonitic affinity. Both granitic members and mafic enclaves/dykes are characterized by high Ba (710-2489 ppm), Sr (305-708ppm), low Y and HREE contents and lack of significant negative Eu anomalies. They are metaluminous and display enrichment in LILE and depletion in P, Ta, Nb and Ti. Sr-Nd-Pb and O isotope compositions of mafic enclaves and dykes are similar to their host granitoids. They have initial 87Sr/86Sr values of 0.70702- 0.70805 and 143Nd/144Nd values of 0.51235-0.51250 and their ɛNd values range between -4,9 and -2,05. 206Pb/204Pb and 207Pb/204 Pb isotopic values vary from 18,75 to 18,88 and 15,68 to 15,73, respectivelly. Whole rock and quartz 18O isotopic ratios range between 8 and 10,6. All these isotopic characteristics and major-trace element compositions of Solarya pluton and associated mafic enclaves/dykes suggest a subcontinental

  18. 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)

  19. Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.F., E-mail: wangshifa2006@yeah.net [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Science and technology on vacuum technology and physics laboratory, Lanzhou Institute of Physics, Lanzhou 730000, Gansu (China); Li, Q. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Zu, X.T., E-mail: xtzu@uestc.edu.cn [Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Xiang, X.; Liu, W. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Li, S., E-mail: sean.li@unsw.edu.au [School of Material Science and Engineering, University of New South Wales, Sydney 2052 (Australia)

    2016-12-01

    (Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M{sup 2+} ion active sites were coordinated by −OH of the water molecules except for EDTA anions. The MFe{sub 2}O{sub 4} magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe{sub 2}O{sub 4} of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly. - Graphical abstract: Schematic representation of the proposed model for MFe{sub 2}O{sub 4} nanoparticle synthesis, starting from EDTA-chelated M{sup 2+} (M=Mg, Ca, or Ba) cations (left). High dispersion (Mg, Ca, Ba)-ferrite magnetic nanoparticles were prepared by a modified polyacrylamide gel route. Optimized utilization of polysaccharide, chelating agent, and sintering temperature allowed the formation of (Mg, Ca, Ba)-ferrite nanoparticles with a narrow diameter distribution. - Highlights: • We report a modified polyacrylamide gel route to synthesize (Mg, Ca, Ba)-ferrite magnetic nanoparticles. • Chelate mechanism of metal ions (Mg, Ca, Ba) and EDTA has been discussed. • Phase transformation process of (Mg, Ca, Ba)-ferrites has been discussed. • The preparation method increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles.

  20. 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.

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

    International Nuclear Information System (INIS)

    Holesinger, T.G.; Miller, D.J.; Viswanathan, H.K.; Chumbley, L.S.

    1993-01-01

    The solidification processes for the compositions Bi 2 Sr 2 CaCu 2 O y (2212) and Bi 2 Sr 1.75 Ca 0.25 CuO y (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 Bi 2 Sr 1.75 Ca 0.25 CuO y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 2-x Ca x O y (22x) and Cu 2 O while solidification of Bi 2 Sr 2 CaCu 2 O y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 3-x Ca x O y (23x) and Cu 2 O. Solidification of Bi 2 Sr 1.75 Ca 0.25 CuO y in O 2 resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22x and CuO/Cu 2 O. Solidification of Bi 2 Sr 2 CaCu 2 O y 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

  2. Variability of Mg/Ca and Sr/Ca between and within the planktonic foraminifers Globigerina bulloides and Globorotalia truncatulinoides

    NARCIS (Netherlands)

    Anand-Jha, P.; Elderfield, H.

    2005-01-01

    The variability in Mg/Ca and Sr/Ca within individual tests and chambers of tests, and samples consisting of differing numbers of individuals, was determined for Globigerina bulloides and Globorotalia truncatulinoides in a North Atlantic core top sample (52.918°N 16.917°W'). The variability in Mg/Ca

  3. Photoluminescence properties of X5SiO4Cl6: Tb 3 (X= Sr, Ba) green ...

    Indian Academy of Sciences (India)

    , 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 ...

  4. 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......, leading to gradually lower seawater 87Sr/86Sr associated with the parallel and strong decrease in seawater Sr/Ca ratios. This downward trend was reversed by enhanced continental input in the Toarcian and Aalenian, but resumed in the Bajocian and continued to the Callovian. Parallel changes of seawater 87...... the role of biomineral evolution in influencing strontium chemistry of seawater in the mid-Mesozoic....

  5. Ca doping effect on the magnetic and electronic transport properties in double perovskite PrBaCo2O5+δ films

    Science.gov (United States)

    Bao, Shanyong; Pang, Shengli; Wang, Wenzhi; Chen, Jiahui; Chen, Mingfeng; Ma, Jing; Nan, Ce-Wen; Chen, Chonglin

    2017-12-01

    Ca doped double perovskite PrBa1-xCaxCo2O5+δ (x = 0, 0.3, and 0.5) thin films were epitaxially grown on the (001) SrTiO3 substrates to systematically investigate the A' site doping effect on the magnetic and electronic transport properties. With the increase in the Ca content, the magnetization measurements on the films show that the magnetic moments are significantly increased and the largest magnetic moment of 88 emu/cm3 can be achieved in the film with x = 0.5 or about 90 times larger than that from the undoped PrBaCo2O5+δ film. The electronic transport property measurements on the films indicate that the electrical conductivity can be altered by various Ca doping contents. It is interesting to note that both undoped PrBaCo2O5+δ and PrBa0.5Ca0.5Co2O5+δ films exhibit simple activation behavior, but the PrBa0.7Ca0.3Co2O5+δ film exhibits the 3D variable-range hopping mode conduction.

  6. Uniaxial-strain mechanical detwinning of CaFe2As2 and BaFe2As2 crystals: Optical and transport study

    International Nuclear Information System (INIS)

    Tanatar, M.A.; Blomberg, E.C.; Kreyssig, A.; Kim, M.G.; Ni, N.; Thaler, A.; Bud'ko, S.L.; Canfield, P.C.; Goldman, A.I.; Mazin, I.I.; Prozorov, R.

    2010-01-01

    The parent compounds of iron-arsenide superconductors, AFe 2 As 2 (A=Ca, Sr, Ba), undergo a tetragonal to orthorhombic structural transition at a temperature T TO in the range 135-205 K depending on the alkaline-earth element. Below T TO the free standing crystals split into equally populated structural domains, which mask intrinsic, in-plane, anisotropic properties of the materials. Here we demonstrate a way of mechanically detwinning CaFe 2 As 2 and BaFe 2 As 2 . The detwinning is nearly complete, as demonstrated by polarized light imaging and synchrotron x-ray measurements, and reversible, with twin pattern restored after strain release. Electrical resistivity measurements in the twinned and detwinned states show that resistivity, ρ, decreases along the orthorhombic a o axis but increases along the orthorhombic b o axis in both compounds. Immediately below T TO the ratio ρ bo /ρ ao = 1.2 and 1.5 for Ca and Ba compounds, respectively. Contrary to CaFe 2 As 2 , BaFe 2 As 2 reveals an anisotropy in the nominally tetragonal phase, suggesting that either fluctuations play a larger role above T TO in BaFe 2 As 2 than in CaFe 2 As 2 or that there is a higher temperature crossover or phase transition.

  7. Influence of Bi-Sr and Ca-Sr interactions on the Si particle characteristics in 319 alloy

    International Nuclear Information System (INIS)

    El-Hadad, S.; Samuel, A.M.; Samuel, F.H.; Doty, H.W.; Valtierra, S.

    2002-01-01

    The effects of bismuth and calcium additions on the Si particle characteristics in Sr-modified 319 alloys (modified with 80 ppm Sr), with and without 0.4 wt% Mg addition, were studied using thermal analysis, optical microscopy, image and SEM/EDX analyses. Bismuth additions were made in the range 50 to 9000 ppm, and calcium additions in the range 50 to 200 ppm. The effects of Bi and Ca were monitored through (i) correlation of the eutectic temperature, and (ii) correlation of the microstructural changes with the trace element additions, (iii) evaluation and quantification of the eutectic Si particles, and (iv) identification of the different phases that precipitated as a result of the additions. It was found that the modification effect of Sr continuously diminished with Bi addition up to ∼3000 ppm Bi, following which, further Bi addition led to the modification of the Si particles due to the presence of Bi. In the Ca-containing alloys, it was found that a coarse eutectic Si structure resulted with Ca additions of 50 ppm, due to the formation of Al x (Ca,Sr)Si y compounds. Increased Ca additions (up to 200 ppm) did not alter the Si particle size. The Al x (Ca,Sr)Si y phase particles appeared in rod-like form in the Sr-modified alloys and in plate-like form in the 0.4 wt% Mg-containing alloys. The presence of MgO, Al 2 0 3 , and AlP particles at the center of the plate-like Al x (Ca,Sr)Si y phase appear to act as nucleants for the precipitation of the latter, aiding its growth through an impurity induced twinning mechanism. (author)

  8. Transcription factor CREB is involved in CaSR-mediated cytoskeleton gene expression.

    Science.gov (United States)

    Huang, Shuaishuai; Ren, Yu; Wang, Ping; Li, Yanyuan; Wang, Xue; Zhuang, Haihui; Fang, Rong; Wang, Yuduo; Liu, Ningsheng; Hehir, Michael; Zhou, Jeff X

    2015-03-01

    Our previous studies illustrated that a steady increase of intracellular calcium concentration ([Ca2+]i) was important for maintaining microtubules (MTs) rearrangement in apoptotic cells. However, little is known about the effect of calcium sensing receptor (CaSR)-mediated increase in [Ca2+]i on cytoskeleton gene expression. We examined the impact of taxol or CaSR agonist/antagonist on the regulation of [Ca2+]i concentration, cytoskeleton arrangement, phosphorylated CREB and cytoskeleton gene expressions in HeLa cells with dominant negative plasmid of CREB (PM). This study demonstrated that Gdcl3 (a specific CaSR agonist) evoked a rapid increase of [Ca2+]i, formed a rigid bundle of MTs which surrounded the nucleus and decreased the cytoskeleton gene expressions in HeLa cells. These effects were rescued by addition of NPS2390 (a specific CaSR antagonist). Moreover, CaSR activity affected cytoskeleton gene expression through transcription factor CREB. Histoscores of pCREB immunoreactivity in tissues of cervical adenocarcinoma, renal clear cell carcinoma, and diffuse large B-cell lymphoma were markedly increased compared with non malignant tissue. These data demonstrate, for the first time, that CaSR-mediated increase in [Ca2+]i probably modulate cytoskeleton organization and gene expression via transcription factor. © 2014 Wiley Periodicals, Inc.

  9. On the ternary compounds of the BaO-CaO-CuO system

    Science.gov (United States)

    Nguyen Xuan, H.; Bertrand, C.; Beauquis, S.; Pisch, A.; Galez, Ph.

    2004-12-01

    The crystal structure and the stability of the two ternary compounds Ba4CaCu3O8+δ and Ba6CaCu3O10+vardelta have been investigated by means of X-ray diffraction, differential thermal analysis and thermogravimetry analysis. We find that the Ba4CaCu3O8+vardelta phase has a cubic structure (Im-3m, a = 8.1515(1) Å for δ = + 0.8) for an oxygen content in the range 8.7-9.3 as reported in the literature but undergoes a transformation into a tetragonal structure (I4/mmm, a = 8.1888(1) Å, c = 8.0634(1) Å for δ = - 0.3) when the oxygen content is lowered (7.7-8.7). Both Ba4CaCu3O8+δ and Ba6CaCu3O10+vardelta phases are metastable at low temperature in p(O2) = 1 bar. The DTA/TGA curves indicate an equilibrium recovery between 300°C and 400°C corresponding to the decomposition into BaO2, CaO and Ba2Cu3O6. La structure cristallographique et la stabilité des deux composés ternaires Ba4CaCu3O8+vardelta et Ba6CaCu3O10+vardelta ont été étudiées par diffraction des rayons X, analyse thermique différentielle et analyse thermogravimétrique. Nous trouvons que la phase Ba4CaCu3O8+vardelta a une structure cubique (Im-3m, a = 8.1515(1) Å, δ = + 0.8) pour des contenus en oxygène élevés (8.7-9.3) comme cela est reporté dans la littérature mais subit une transition vers une structure tétragonale (I4/mmm, a = 8.1888(1) Å, c = 8.0634(1) Å, δ = - 0.3) lorsque ce contenu est diminué (7.7-8.7). Ces deux composés ternaires sont métastables à basse température sous p(O2) = 1 bar. Les courbes d'ATD/TG indiquent en effet un retour à l'équilibre entre 300°C et 400°C qui correspond à une décomposition en BaO2, CaO et Ba2Cu3O6.

  10. Stability of Tl-Ba-Ca-Cu-O superconducting thin films

    International Nuclear Information System (INIS)

    Siegal, M. P.; Overmyer, D. L.; Venturini, E. L.; Padilla, R. R.; Provencio, P. N.

    1999-01-01

    We report the stability of TlBa 2 CaCu 2 O 7 and Tl 2 Ba 2 CaCu 2 O 8 on LaAlO 3 (100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N 2 or O 2 ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 degree sign C in N 2 and 700 degree sign C in O 2 , the onset of degradation occurs at somewhat lower temperatures for TlBa 2 CaCu 2 O 7 than for Tl 2 Ba 2 CaCu 2 O 8 . (c) 1999 Materials Research Society

  11. Photoconductivity of transparent perovskite semiconductor BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin

    2016-02-01

    We measured the photoconductivity of transparent semiconductor BaSnO3 and compared it with that of SrTiO3. Epitaxial BaSnO3 and SrTiO3 films were grown on MgO substrates to exclude any contribution to photoconductivity from the substrate due to its large bandgap. In spite of the same perovskite structure and similar bandgap sizes (3.1-3.2 eV), the photoconductive behaviors of the two materials are quite different in terms of their magnitude and time dependence. The photoconductivity of BaSnO3 persists for many hours after removal from light exposure, whereas the photoconductivity of SrTiO3 shows little persistent conductivity. In addition, the photoconductivity of BaSnO3 increases to a value over 25 times higher than that of SrTiO3, after 3 h of illuminations. The spectral photoconductive responses of both BaSnO3 and SrTiO3 show their highest peaks below 400 nm, suggesting that the electron-hole pair generation is the main mechanism of the photoconductivity for the both materials. The large persistent photoconductivity of BaSnO3 seems related with deep level defects with relatively large barriers for charge trapping and detrapping.

  12. Structural phase transition and magnetic properties of double perovskites Ba2CaMO6 (M=W, Re, Os)

    International Nuclear Information System (INIS)

    Yamamura, Kazuhiro; Wakeshima, Makoto; Hinatsu, Yukio

    2006-01-01

    Structures and magnetic properties for double perovskites Ba 2 CaMO 6 (M=W, Re, Os) were investigated. Both Ba 2 CaReO 6 and Ba 2 CaWO 6 show structural phase transitions at low temperatures. For Ba 2 CaReO 6 , the second order transition from cubic Fm3-bar m to tetragonal I4/m has been observed near 120K. For Ba 2 CaWO 6 , the space group of the crystal structure is I4/m at 295K and the transition to monoclinic I2/m has been observed between 220K. Magnetic susceptibility measurements show that Ba 2 CaReO 6 (S=1/2) and Ba 2 CaOsO 6 (S=1) transform to an antiferromagnetic state below 15.4 and 51K, respectively. Anomalies corresponding to their structural phase transition and magnetic transition have been also observed through specific heat measurements

  13. Oxygen ordering and superconductivity in DyBaSrCu3Oy

    International Nuclear Information System (INIS)

    Wang, X.Z.; Steger, P.L.; Reissner, M.; Steiner, W.

    1992-01-01

    A new superconducting compound, DyBaSrCu 3 O y , has been synthesized. By different thermal treatments, this compound was crystallized in either orthorhombic or quasitetragonal structure, with oxygen content of y ≅ 6.93 to 6.94. Superconducting properties are similar for both phases. The magnetic moment of the Dy atoms is not influenced by the difference in structures and is close to the value for Dy 3+ . At low temperatures a tendency towards magnetic ordering was observed. (orig.)

  14. Ca and Sr isotope records support ocean acidification during end-Permian mass extinction

    Science.gov (United States)

    Wang, J.; Jacobson, A. D.; Zhang, H.; Ramezani, J.; Sageman, B. B.; Hurtgen, M.; Bowring, S. A.; Shen, S.

    2017-12-01

    The end-Permian mass extinction represents the most devastating loss of biodiversity during the Phanerozoic. A negative carbon isotope (δ13C) excursion that accompanies the event suggests a significant perturbation to the global carbon cycle, likely induced by CO2 emissions during eruption of the Siberian Traps large igneous province. The carbon cycle is linked with the Ca and Sr cycles through chemical weathering and carbonate precipitation. Therefore, analyses of Ca (δ44/40Ca), radiogenic Sr (87Sr/86Sr), and stable Sr (δ88/86Sr) isotope abundance variations in marine carbonate rocks spanning the Permian-Triassic Boundary (PTB) can reveal key information about biogeochemical changes that occurred during this time. We report δ44/40Ca, 87Sr/86Sr, and δ88/86Sr records analyzed by TIMS for the Meishan and Dajiang sections in China. δ44/40Ca values exhibit similar patterns in both sections. The values remain unchanged across the extinction event layer (EXT) and then decrease by 0.20‰ before increasing by 0.20‰ to 0.40‰ around the PTB. In the Meishan section, 87Sr/86Sr ratios increase after the EXT and return to pre-excursion levels by the PTB. Simultaneously, δ88/86Sr values decrease by 0.12‰ across the EXT and increase by 0.08‰ by the PTB. The patterns of our data support the hypothesis that elevated atmospheric CO2 levels enhanced chemical weathering inputs and might have caused transient ocean acidification, with an "alkalinity overshoot" and increased carbonate deposition occurring after the extinction. Additional measurements and model calculations are underway to help refine and improve these preliminary interpretations.

  15. 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.

  16. The Ca(PO3)2-Sr(PO3)2 system

    International Nuclear Information System (INIS)

    Bukhalova, G.A.; Tokman, I.A.

    1977-01-01

    Phase diagram of the system Ca(PO 3 ) 2 -Sr(PO 3 ) 2 has been studied and plotted with the aid of differential thermal, visual polythermal, X-ray analysis, and infrared spectroscopy. Continuous solid solutions are formed in the system with a minimum at 968 deg C and 25 mol.% of Sr(PO 3 ) 2 . Solid solutions decompose with the formation of about 30 mol.% of Sr(PO 3 ) 2

  17. 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.

  18. Converse flexoelectric coefficient f1212 in bulk Ba0.67Sr0.33TiO3

    Science.gov (United States)

    Shu, Longlong; Huang, Wenbin; Ryung Kwon, Seol; Wang, Zhao; Li, Fei; Wei, Xiaoyong; Zhang, Shujun; Lanagan, Michael; Yao, Xi; Jiang, Xiaoning

    2014-06-01

    The converse flexoelectric effect, referred as the electric field gradient induced strain, widely exists in dielectric materials, but its experimental studies have been reported by few research groups so far. In this Letter, we report our studies on the converse flexoelectric behavior of (Ba0.67Sr0.33)TiO3 ceramics and present the measured value of its flexoelectric coefficient f1212. In the experiments, the electric field gradient was generated by applying an electric field across the two lateral sides of trapezoid (Ba0.67Sr0.33)TiO3 samples. The shear displacement was measured using a laser vibrometer. The converse flexoelectric coefficient f1212 was found to be 124 ± 14 μC/m at room temperature. This result was in good agreement with the theoretical prediction of the flexoelectricity of the (Ba, Sr)TiO3 ceramics.

  19. Ca-for-Sr substitution in the thermoelectric [(Sr,Ca)2(O,OH)2]q[CoO2] misfit-layered cobalt-oxide system

    International Nuclear Information System (INIS)

    Yamauchi, Hisao; Karvonen, Lassi; Egashira, Takayuki; Tanaka, Yoshiaki; Karppinen, Maarit

    2011-01-01

    Calcium-for-strontium substituted samples of the misfit-layered cobalt-oxide system, [(Sr 1-x Ca x ) 2 (O,OH) 2 ] q [CoO 2 ], were successfully synthesized up to x=0.2 with a sample-encapsulation technique originally developed for the x=0 end phase. While the x=0 sample has a commensurate match between the two layer blocks (i.e. q=0.5), isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time the Seebeck coefficient gets increased, but the increase in resistivity results in suppressing the thermoelectric power factor. The magnetic anomaly in the x=0 sample gets released upon the Ca substitution for the x=0.2 sample to exhibit an almost Curie-Weiss behavior. It is concluded that with increasing x in [(Sr 1-x Ca x ) 2 (O,OH) 2 ] q [CoO 2 ] the properties smoothly evolve towards those previously reported for the x=1.0 end member, [Ca 1.7 O 2.1 H 2.4 ] 0.58 [CoO 2 ]. -- Graphical abstract: In the misfit-layered [(Sr 1-x Ca x ) 2 (O,OH) 2 ] q [CoO 2 ] (0.0≤x≤0.2) system the x=0 phase has a commensurate match between the two layer blocks (i.e. q=0.5), while isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time Seebeck coefficient gets increased. Simultaneous increase in resistivity however outweighs this benefit, and accordingly the thermoelectric power factor is decreased. Display Omitted

  20. Rarotonga Sr/Ca and SST Reconstruction Data for 1726 to 1997

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 271 year record of Sr/Ca variability in a coral from Rarotonga in the South Pacific gyre. Calibration with monthly sea surface temperature (SST) from satellite and...

  1. Epitaxial growth of solution deposited Bi2Sr2CaCu2Ox films

    NARCIS (Netherlands)

    Gobel, OF; Du, [No Value; Hibma, T; von Lampe, [No Value; Steiner, U

    The epitaxial growth of Bi2Sr2CaCu2Ox (Bi2212) high temperature superconducting thin films was studied. The films were solution-deposited from a polymer-containing precursor onto SrTiO3 (001) substrates. Bi2212 formed an epitaxial phase with the c-axis parallel to the substrate normal and an in-lane

  2. Consequences of Ca multisite occupation for the conducting properties of BaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zulueta, Y.A., E-mail: yohandysalexis.zuluetaleyva@student.kuleuven.be [Departamento de Física, Facultad de Ciencias Naturales, Universidad de Oriente, CP-90500 Santiago de Cuba (Cuba); Department of Chemistry, KU Leuven, B-3001 Leuven (Belgium); Dawson, J.A. [Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom); Leyet, Y. [Departamento de Engenharia de Materiais, Universidade Federal do Amazonas, Av. General Rodrigo Otávio, 6200 – Coroado I, 69077-000 Manaus (Brazil); Departamento de Física, Universidade Federal do Amazonas, Av. General Rodrigo Otávio, 6200 – Coroado I, 69077-000 Manaus, Amazonas (Brazil); Anglada-Rivera, J. [Instituto Federal de Educação Ciência e Tecnologia do Amazonas, Av. 7de Setembro, 1975, 69020-120 Manaus (Brazil); Guerrero, F. [Departamento de Física, Universidade Federal do Amazonas, Av. General Rodrigo Otávio, 6200 – Coroado I, 69077-000 Manaus, Amazonas (Brazil); Silva, R.S. [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristóvão, SE (Brazil); Nguyen, Minh Tho [Department of Chemistry, KU Leuven, B-3001 Leuven (Belgium)

    2016-11-15

    In combination with the dielectric modulus formalism and theoretical calculations, a newly developed defect incorporation mode, which is a combination of the standard A- and B-site doping mechanisms, is used to explain the conducting properties in 5 mol% Ca-doped BaTiO{sub 3}. Simulation results for Ca solution energies in the BaTiO{sub 3} lattice show that the new oxygen vacancy inducing mixed mode exhibits low defect energies. A reduction in dc conductivity compared with undoped BaTiO{sub 3} is witnessed for the incorporation of Ca. The conducting properties of 5 mol% Ca-doped BaTiO{sub 3} are analyzed using molecular dynamics and impedance spectroscopy. The ionic conductivity activation energies for each incorporation mode are calculated and good agreement with experimental data for oxygen migration is observed. The likely existence of the proposed defect configuration is also analyzed on the basis of these methods. - Graphical abstract: Oxygen vacancy formation as a result of self-compensation in Ca-doped BaTiO{sub 3}.

  3. Pulsed laser deposition of Tl-Ca-Ba-Cu-O films

    International Nuclear Information System (INIS)

    Ianno, N.J.; Liou, S.H.; Woollam, J.A.; Thompson, D.; Johs, B.

    1990-01-01

    Pulsed laser deposition is a technique commonly used to deposit high quality thin films of high temperature superconductors. This paper discusses the results obtained when this technique is applied to the deposition of Tl-Ca-Ba-Cu-O thin films using a frequency doubled Nd:YAG laser operating at 532 nm and an excimer laser operating at 248 nm. Films with onset temperatures of 125 K and zero resistance temperatures of 110 K deposited on (100) oriented MgO from a composite Tl2Ca2Ba2Cu3Ox target were obtained at both wavelengths upon appropriate post deposition annealing. Films deposited at 532 nm exhibit a rough surface, while those deposited at 248 nm are smooth and homogeneous. Upon annealing, films deposited at both wavelengths are single phase Tl2Ca2Ba2Cu3Ox. 12 refs

  4. Study of the effects of additives on structural properties of the Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} hexaferrite; Estudo do efeito de aditivos nas propriedades estruturais da hexaferrita Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19}

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Y.S.; Pereira, C.A.; Farias, F.C.; Mello, P.S.; Alves, A.G.; Pereira, F.M.; Barroso, M.B., E-mail: yuri.link2@gmail.com [Universidade Federal do Cariri (UFCA), Juazeiro do Norte, CE (Brazil); Saraiva, I.R.; Conde, W.S. [DeVry Fanor, Fortaleza, CE (Brazil); Sombra, A.B. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia de Materiais (LOCEM/UFC), Fortaleza, CE (Brazil)

    2016-07-01

    The Hexaferrites are magnetic ceramic materials chemically and thermally stable, low-cost and easy processing. The objective of this work was to study the effects of SiO2 and CaO additives on structural properties of hexaferrite Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19}. The samples were characterized by scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and quantified by the Rietveld method. The doped samples showed no structural change. With the concentration of dopant employed, there was a decrease in the sintering temperature of all samples Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} 1100 °C/5h to 1000 °C/2h. After addition of dopants, it was observed that the growth of the grains in the samples did not occur uniformly. This uneven growth can is being influenced by the concentrations of Ba and Sr atoms present in the samples, as well as some sort of reaction with the dopant elements. (author)

  5. Reverse micellar synthesis, structural characterization and dielectric properties of Sr-doped BaZrO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Tokeer, E-mail: tahmad3@jmi.ac.in [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi, 110025 (India); Ubaidullah, Mohd [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi, 110025 (India); Department of Chemistry, Banasthali University, Tonk, Rajasthan, 304022 (India); School of Science and Technology, Glocal University, Mirzapur, Saharanpur, 247121, Uttar Pradesh (India); Shahazad, Mohd [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi, 110025 (India); Kumar, Dinesh [Department of Chemistry, Banasthali University, Tonk, Rajasthan, 304022 (India); Al-Hartomy, Omar A. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, 21589 (Saudi Arabia)

    2017-01-01

    Sr-doped BaZrO{sub 3} nanoparticles with strontium content varying from 5 to 20 mol % were successfully synthesized by reverse micellar method at 900 °C for the first time. Systematic studies have been carried out to establish the structural and electrical properties of the as prepared nanoparticles. These nanoparticles were characterized using powder X-ray diffraction, transmission electron microscopy, BET surface area and dielectric measurements. X-ray diffraction analysis showed the formation of monophasic and highly crystalline nanoparticles which could be indexed in cubic BaZrO{sub 3} with contraction of lattice on strontium substitution. A monotonic shift of diffraction pattern towards higher angel confirms the formation of solid solutions of Ba{sub 1−x}Sr{sub x}ZrO{sub 3} (0.05 ≤ x ≤ 0.20) which was corroborating well with lattice parameter studies. Transmission electron microscopic studies showed the formation of cubic, spherical and hexagonal nanoparticles with an average grain size of 40–65 nm. Energy dispersive X-ray spectroscopic studies confirmed the presence of dopant (Sr{sup 2+}) in the BaZrO{sub 3} matrix and estimated chemical species corroborate well with the loaded composition. Specific surface area of the solid solution comes out to be in the range of 104–244 m{sup 2} g{sup -1}. Smallest particle of size 40 nm shows highest surface area 244 m{sup 2} g{sup -1} for 20 mol% Sr-doped BaZrO{sub 3}. Dielectric and impedance studies were also carried out as a function of frequency and temperature to explore the electrical properties of Sr-doped BaZrO{sub 3}. The dielectric constant of Ba{sub 1−x}Sr{sub x}ZrO{sub 3} (0.05 ≤ x ≤ 0.20) was found to be in the range of 13–25 for x = 0.05 to x = 0.20 with nearly similar dielectric loss of the order of 0.02. The conductance increases linearly with increase in frequency at room temperature, however the impedance has an inverse effect. - Highlights: • Monophasic nanocrystalline Ba{sub 1−x}Sr

  6. Reaction products between Bi-Sr-Ca-Cu-oxide thick films and alumina substrates

    International Nuclear Information System (INIS)

    Alarco, J.A.; Ilushechkin, A.; Yamashita, T.; Bhargava, A.; Barry, J.; Mackinnon, I.D.R.

    1997-01-01

    The structure and composition of reaction products between Bi-Sr-Ca-Cu-oxide (BSCCO) thick films and alumina substrates have been characterized using a combination of electron diffraction, scanning electron microscopy and energy dispersive X-ray spectrometry (EDX). Sr and Ca are found to be the most reactive cations with alumina. Sr 4 Al 6 O 12 SO 4 is formed between the alumina substrates and BSCCO thick films prepared from paste with composition close to Bi-2212 (and Bi-2212+10 wt.% Ag). For paste with composition close to Bi(Pb)-2223 +20 wt.% Ag, a new phase with f.c.c. structure, lattice parameter about a=24.5 A and approximate composition Al 3 Sr 2 CaBi 2 CuO x has been identified in the interface region. Understanding and control of these reactions is essential for growth of high quality BSCCO thick films on alumina. (orig.)

  7. 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.

  8. Oxygen excess in the '114' cobaltite hexagonal structure: The ferrimagnet CaBaCo4O7.50

    International Nuclear Information System (INIS)

    Pralong, V.; Caignaert, V.; Sarkar, T.; Lebedev, O.I.; Duffort, V.; Raveau, B.

    2011-01-01

    The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its excess oxygen. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic with the same T C (60 K), but differently exhibits an unusual magnetic hysteresis. This exceptional behavior of CaBaCo 4 O 7 with respect to oxidation as well as the magnetic properties of CaBaCo 4 O 7.50 is interpreted in terms of the presence of defects due to oxidation. - Graphical Abstract: The study of the oxidation of the '114' orthorhombic cobaltite CaBaCo 4 O 7 , using first electrochemistry and then soft chemistry based on oxidation by NaClO, has allowed a new phase, CaBaCo 4 O 7.50 , to be prepared topotactically. The structural study of this phase shows that its hexagonal structure, closely related to that of orthorhombic CaBaCo 4 O 7 , is curiously similar to that of the members of the LnBaCo 4 O 7 series, in spite of its oxygen excess. Its magnetic study shows that this phase, like CaBaCo 4 O 7 , is ferrimagnetic. Highlights: → Topotactic oxidation by means of electrochemistry and soft chemistry of the '114' orthorhombic cobaltite CaBaCo 4 O 7 . → This new phase, CaBaCo 4 O 7.5 shows an hexagonal structure, is closely related to that of orthorhombic mother phase CaBaCo 4 O 7 . → CaBaCo 4 O 7.5 is ferrimagnetic and exhibits an unusual magnetic hysteresis, due to defect pinning centers.

  9. A coprecipitation technique to prepare Sr0⋅5Ba0⋅5Nb2O6

    Indian Academy of Sciences (India)

    Unknown

    vity and hence low sintering temperatures. Here we give a simple coprecipitation procedure to prepare Sr0⋅5Ba0⋅5Nb2O6. (SBN) ceramics at low temperatures. Coprecipitation is one of the more successful techniques for synthesizing ultrafine ceramic powders having narrow particle size distribution (Dhage et al 2003).

  10. Solid electrolytes Sr(Ba)6Nb(Ta)2O11 with structural disordering of oxygen sublattice

    International Nuclear Information System (INIS)

    Nejman, A.Ya.; Podkorytov, A.L.; Yurkovskaya, N.Yu.; Zhukovskij, V.M.

    1986-01-01

    Electric conductivity at alternating and direct current and ratio of ionic component of conductivity in M 2 O-M 2 5 O 5 systems (M 2 -Sr, Ba; M 5 -Nb, Ta) are measured. High ionic conductivity of M 6 2 M 2 5 O 11 compounds is shown to be conducted by structural disordering of oxygen sublattice

  11. 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

  12. Effects of Ba doping on physical properties of La-Ca-Mn-O thin films

    CERN Document Server

    Hong, N H; Sakai, J; Iwasaki, H

    2003-01-01

    Transport and magnetic properties of La-Ba-Ca-Mn-O thin films fabricated by the pulsed laser deposition technique had been investigated systematically to see the effects of substitution of the small atom Ca by Ba which is much bigger. The induced insulator-to-metal (IM) transition was obtained not only in compositions near 0.5 and 0.18 which are boundaries between metallic and insulating phases but also in the heavily doped region. In the region of x > 0.5, the Ba doping causes an anomalous response of the system to the magnetic field and a positive magnetoresistance was observed. Besides, our results concerning the vicinity of 0.5 imply the existence of phase separation. As for x < 0.5, the doping enhances remarkably the paramagnetism-ferromagnetism transition and the IM transition temperatures.

  13. Stability of Tl-Ba-Ca-Cu-O superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Venturini, E. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Padilla, R. R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Provencio, P. N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)

    1999-12-01

    We report the stability of TlBa{sub 2}CaCu{sub 2}O{sub 7} and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} on LaAlO{sub 3}(100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N{sub 2} or O{sub 2} ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 degree sign C in N{sub 2} and 700 degree sign C in O{sub 2}, the onset of degradation occurs at somewhat lower temperatures for TlBa{sub 2}CaCu{sub 2}O{sub 7} than for Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}. (c) 1999 Materials Research Society.

  14. Neutron diffraction studies on La 2- Dy Ca 2 Ba 2 Cu 4+2

    Indian Academy of Sciences (India)

    Structural studies on Dy-substituted La-2125 type superconductors have been carried out by neutron diffraction experiments at room temperature using a monochromatic neutron beam of wavelength () = 1.249 Å. A series of samples with La2-DyCa2Ba2Cu4+2O stoichiometric composition, for = 0.1-0.5, have ...

  15. Sr/Ca-Sea surface temperature calibration in the branching Caribbean coral Acropora palmata

    Science.gov (United States)

    Gallup, Christina D.; Olson, Donna M.; Edwards, R. Lawrence; Gruhn, Leah M.; Winter, Amos; Taylor, Frederick W.

    2006-02-01

    We measured Sr/Ca ratios by thermal ionization mass spectrometry in radial and axial growth of modern Caribbean Acropora palmata corals. Comparison of our results with sea surface temperature (SST) allows radial and axial Sr/Ca-SST calibrations of Sr/Ca (mmol/mol) = 11.30 - 0.07072 × SST (°C) and Sr/Ca (mmol/mol) = 11.32 - 0.06281 x SST (°C), respectively. Application of the calibrations to fossil Acropora palmata from the last glacial maximum in Barbados (Guilderson et al., 1994) imply ~7°C cooler conditions than the present, much larger than the 1-1.5° cooling suggested by modern analog technique foraminifera-based estimates (Trend-Staid and Prell, 2002). If the foraminifera-based estimates are correct, then the excess cooling suggested by the Barbados corals could be explained by a 5% shift in the marine Sr/Ca ratio or an addition of ~20% abiotic secondary aragonite.

  16. Extracellular calcium and CaSR drive osteoinduction in mesenchymal stromal cells.

    Science.gov (United States)

    González-Vázquez, Arlyng; Planell, Josep A; Engel, Elisabeth

    2014-06-01

    Bone is the main store of calcium and progenitor cells in the body. During the resorption process, the local calcium concentration reaches 8-40mM, and the surrounding cells are exposed to these fluctuations in calcium. This stimulus is a signal that is detected through the calcium sensing receptor (CaSR), which modulates chemotactic and proliferative G protein-dependent signaling pathways. The objective of the present work is to evaluate the roles of extracellular calcium ([Ca(2+)]o) and the CaSR in osteoinduction. Rat bone marrow mesenchymal stromal cells (rBMSCs) were stimulated with 10mM of Ca(2+). Several experiments were conducted to demonstrate the effect of [Ca(2+)]o on chemotaxis, proliferation and differentiation on the osteoblastic lineage. It was found that [Ca(2+)]o induces rBMSCs to migrate and proliferate in a concentration-dependent manner. Real-time polymerase chain reaction and immunofluorescence also revealed that 10mM Ca(2+) stimulates overexpression of osteogenic markers in rBMSCs, including alkaline phosphatase (ALP), bone sialoprotein, collagen Ia1 and osteocalcin. Functional assays determining ALP activity and mineralization tests both corroborate the increased expression of these markers in rBMSCs stimulated with Ca(2+). Moreover, CaSR blockage inhibited the cellular response to stimulation with high concentrations of [Ca(2+)]o, revealing that the CaSR is a key modulator of these cellular responses. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

    International Nuclear Information System (INIS)

    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

    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.

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

    International Nuclear Information System (INIS)

    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

  20. 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.

  1. Polarization properties and crystal structures of ferroelectric (Ba,CaTiO3 single crystals

    Directory of Open Access Journals (Sweden)

    Ryota Imura

    2014-01-01

    Full Text Available We have investigated the spontaneous polarization (Ps of Ba1-xCaxTiO3 (BCT by polarization hysteresis measurements using single crystals and by density functional theory (DFT calculations. Single crystals of BCT (x = 0.07 were grown by a top-seeded solution growth (TSSG method. The polarization measurements show that the crystals (x = 0.07 have a Ps of 26.0 μC/cm2, which is slightly small compared with BaTiO3 (27.3 μC/cm2. Our DFT calculations based on a supercell approach show that Ca atoms are markedly displaced cooperatively with the adjacent Ti atoms along the Ps direction. It is suggested that the CaTiO3-like octahedral rotation is constructed in the BCT supercell around the Ca atoms, which is the origin of the smaller Ps observed for the BCT crystals.

  2. Interface Control of Ferroelectricity in an SrRuO3/BaTiO3/SrRuO3Capacitor and its Critical Thickness.

    Science.gov (United States)

    Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung-Jin; Nahm, Ho-Hyun; Murugavel, Pattukkannu; Kim, Jeong Rae; Cho, Myung Rae; Wang, Lingfei; Yang, Sang Mo; Yoon, Jong-Gul; Chung, Jin-Seok; Kim, Miyoung; Zhou, Hua; Chang, Seo Hyoung; Noh, Tae Won

    2017-05-01

    The atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (PO2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3 /BaTiO 3 /SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of RuO 2 -BaO and SrO-TiO 2 terminations. By reducing PO2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Bond length (Ti-O) dependence of nano ATO3-based (A = Pb, Ba, Sr) perovskite structures: Optical investigation in IR range

    Science.gov (United States)

    Ghasemifard, Mahdi; Ghamari, Misagh; Okay, Cengiz

    2018-01-01

    In the current study, ABO3 (A = Pb, Ba, Sr and B = Ti) perovskite structures are produced by the auto-combustion route by using citric acid (CA) and nitric acid (NA) as fuel and oxidizer. The X-ray diffraction (XRD) patterns confirmed the perovskite nanostructure with cubic, tetragonal, and rhombohedral for SrTiO3, PbTiO3, and BaTiO3, respectively. Using Scherrer’s equation and XRD pattern, the average crystallite size of the samples were acquired. The effect of Ti-O bond length on the structure of the samples was evaluated. The type of structures obtained depends on Ti-O bond length which is in turn influenced by A2+ substitutions. Microstructural studies of nanostructures calcined at 850∘C confirmed the formation of polyhedral particles with a narrow size distribution. The values of optical band gaps were measured and the impact of A2+ was discussed. The optical properties such as the complex refractive index and dielectric function were calculated by IR spectroscopy and Kramers-Kronig (K-K) relations. Lead, as the element with the highest density as compared to other elements, changes the optical constants, remarkably due to altering titanium and oxygen distance in TO6 groups.

  4. Synthesis of highly phase pure (Bi, Pb)-Sr-Ca-Cu-O superconductor

    Science.gov (United States)

    Dorris, Stephen E.; Poeppel, Roger B.; Prorok, Barton C.; Lanagan, Michael T.; Maroni, Victor A.

    1994-01-01

    An article and method of manufacture of (Bi,Pb)-Sr-Ca-Cu-O superconductor. The superconductor is manufactured by preparing a first powdered mixture of bismuth oxide, lead oxide, strontium carbonate, calcium carbonate and copper oxide. A second powdered mixture is then prepared of strontium carbonate, calcium carbonate and copper oxide. The mixtures are calcined separately with the two mixtures then combined. The resulting combined mixture is then subjected to a powder in tube deformation and thermal processing to produce a substantially phase pure (Bi,Pb)-Sr-Ca-Cu-O superconductor.

  5. 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.

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

    International Nuclear Information System (INIS)

    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 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

  7. Evidence for surface chemical reactions between gold and BiCaSrCuO

    International Nuclear Information System (INIS)

    Hwu, Y.; Lozzi, L.; La Rosa, S.; Onellion, M.

    1991-01-01

    We explored the reactivity of gold on cleaved 2212 BiCaSrCuO by synchrotron-radiation photoemission spectroscopy. We found no evidence for reactivity when the substrate was at room temperature, similar to what has been reported for very low temperatures (20 K). At intermediate temperatures (100 K), however, clear evidence was found of a chemical reaction with formation of a localized nonmetallic phase. These findings have potentially important implications for the manufacturing of devices based on BiCaSrCuO

  8. Thermodynamics of the solid solution - Aqueous solution system (Ba,Sr,Ra)SO$_{4}$ + H$_{2}$O: I. The effect of strontium content on radium uptake by barite

    OpenAIRE

    Vinograd, Victor; Kulik, D. A.; Brandt, F.; Klinkenberg, M.; Weber, J.; Winkler, B.; Bosbach, D.

    2017-01-01

    Thermodynamic properties of mixing in the ternary (Ba,Sr,Ra)SO4 solid solution are determined using first principles based total energy calculations and Monte Carlo simulations. Two levels of theory, which correspond to the regular mixing and the generalized Ising model, are considered. The results show that the regular mixing parameters increase along the row of Ba-Ra, Ba-Sr and Sr-Ra binary systems proportionally to the squared difference of molar volumes of the end-members. The magnitudes ...

  9. On the nature of change in Ni oxidation state in BaTiO3-SrTiO3 system

    OpenAIRE

    Lebedev, A. I.; Sluchinskaya, I. A.

    2016-01-01

    XAFS studies of Ni-doped Ba$_{1-x}$Sr$_x$TiO$_3$ solid solution reveal that the Ni oxidation state changes from 4 in SrTiO$_3$ to 2.5 in BaTiO$_3$ when varying $x$. This change is accompanied by a noticeable change in the interatomic Ni-O distances in the first shell. The first-principles calculations show that nickel creates an impurity band in the forbidden band gap of BaTiO$_3$ and SrTiO$_3$, which explains the appearance of intense absorption of Ni-doped samples in the visible region. The...

  10. 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.

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

    Science.gov (United States)

    Santos, P. R.; Added, N.; Aburaya, J. H.; Rizzutto, M. A.

    2008-04-01

    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.

  12. Fractal formation of a Y-Ba-Cu-O thin film on SrTiO3

    International Nuclear Information System (INIS)

    Chow, L.; Chen, J.; Desai, V.; Sundaram, K.; Arora, S.

    1989-01-01

    Fractal formation has been observed after thermal annealing of the rf-sputtered Y-Ba-Cu-O thin film on SrTiO 3 substrate. Through energy-dispersive x-ray analysis, it was found that the composition of the fractal was YBa 2 Cu 3 O x and the surrounding film composition wasY 2 Ba 2 Cu 3 O x . The fractal dimensions D ranging from 1.26 to 1.65 were obtained using the standard sandbox method with different thresholds

  13. Topotactic reduction as a synthetic route for the preparation of low-dimensional Mn(II) oxide phases: the structure and magnetism of LaAMnO(4-x) (A = Sr, Ba).

    Science.gov (United States)

    Kitchen, Helen J; Saratovsky, Ian; Hayward, Michael A

    2010-07-14

    Reaction of LaSrMnO(4) with CaH(2) at 420 degrees C yields LaSrMnO(3.67(3)). Raising the temperature to 480 degrees C yields the Mn(II) phase LaSrMnO(3.50(2)). Neutron powder diffraction data show both phases adopt body-centred orthorhombic crystal structures (LaSrMnO(3.67(3)), Immm: a = 3.7256(1) A, b = 3.8227(1) A, c = 13.3617(4) A; LaSrMnO(3.50(2)), Immm: a = 3.7810(1) A, b = 3.7936(1) A, c = 13.3974(3) A) with anion vacancies located within the equatorial MnO(2-x) planes of the materials. Analogous reactivity is observed between LaBaMnO(4) and CaH(2) to yield body-centred tetragonal reduced phases (LaBaMnO(3.53(3)), I4/mmm: a = 3.8872(1)A, c = 13.6438(2) A). Low-temperature neutron diffraction and magnetisation data show that LaSrMnO(3.5) and LaBaMnO(3.5) exhibit three-dimensional antiferromagnetic order below 155 K and 135 K respectively. Above these temperatures, they exhibit two-dimensional antiferromagnetic order with paramagnetic behaviour observed above 480 K in both phases. The origin of the low dimensional magnetic order and ordering of the anion vacancies in the reduced phases is discussed.

  14. 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.

  15. The Pr and Ca substitution in GdBa2Cu3O7-8

    International Nuclear Information System (INIS)

    Shakeri, H.; Akhavan, M.

    2002-01-01

    The granular Gd 1 -x-zPr x Ca z Ba 2 Cu 3 O 7 -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 BaCuO 2 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 T c (x,z=etc) versus x. Moreover, the T c (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, T c 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 H C 1 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

  16. Influence of Mixing Time to Crystal Structure and Dielectric Constant of Ba0,9Sr0,1TiO3

    Directory of Open Access Journals (Sweden)

    Dianisa Khoirum Sandi

    2015-12-01

    Full Text Available Barium Strontium Titanate (Ba1-xSrxTiO3 or BST has been synthesized using solid state reaction method. Raw materials of BST were BaCO3, SrCO3, and TiO2. Those materials were mixed, pressed, and sintered at temperature 1200oC for 2 h. Mixing time of raw materials was varied to identify its effects on crystal structures and dielectrics constant of Ba0.9Sr0.1TiO3 using X-Ray Diffraction (XRD and LCR meter instrument, respectively. The results of XRD showed that crystals structure of Ba0.9Sr0.1TiO3 is tetragonal. Lattice parameter of Ba0.9Sr0.1TiO3 for 6 h of mixing time is a = b = 3.988 Å and c = 3.998 Å. Lattice parameter of Ba0.9Sr0.1TiO3 for 8 h of mixing time is a = b = 3.976 Å and c = 4.000 Å. Crystalline size of Ba0.9Sr0.1TiO3 was calculated using Scherrer equation. Crystalline size, crystallinity, and dielectric constant of Ba0.9Sr0.1TiO3 for 6 h of mixing time is 38 nm, 96%, and 115 at frequency 1 KHz, respectively while their value for 8 h of mixing time is 39 nm, 96%, and 196 at frequency 1 KHz, respectively. Thus it can be concluded that mixing time affects the lattice parameters of Ba0.9Sr0.1TiO3 crystal. The longer mixing time causes crystalline size, crystallinity, and dielectrics constant increase.

  17. Superconductivity in the Tl-Ca-Ba-Cu-O System:. Synthesis, Characterization and Mechanism

    Science.gov (United States)

    Ganguli, A. K.; Swamy, K. S. Nanjunda; Subbanna, G. N.; Rajumon, M. K.; Sarma, D. D.; Rao, C. N. R.

    Synthesis and characterization of some of the members of the Tl-Ca-Ba-Cu-O system are presented. Tc in both the TlCan-1Ba2CunO2n+3 and Tl2Can-1Ba2CunO2n+4 series increase with the number of Cu-O layers, n; Tc in the latter series with two Tl-O layers are generally higher than in the former with a single Tl-O layer. Tl in the cuprates is in the 3+ state while Cu is in the 1+ and 2+ states, showing the importance of oxygen holes. The concentration of these holes seems to increase with the number of Tl-O layers.

  18. Structure-CaSR-Activity Relation of Kokumi γ-Glutamyl Peptides.

    Science.gov (United States)

    Amino, Yusuke; Nakazawa, Masakazu; Kaneko, Megumi; Miyaki, Takashi; Miyamura, Naohiro; Maruyama, Yutaka; Eto, Yuzuru

    2016-01-01

    Modulation of the calcium sensing receptor (CaSR) is one of the physiological activities of γ-glutamyl peptides such as glutathione (γ-glutamylcysteinylglycine). γ-Glutamyl peptides also possess a flavoring effect, i.e., sensory activity of kokumi substances, which modifies the five basic tastes when added to food. These activities have been shown to be positively correlated, suggesting that kokumi γ-glutamyl peptides are perceived through CaSRs in humans. Our research is based on the hypothesis that the discovery of highly active CaSR agonist peptides will lead to the creation of practical kokumi peptides. Through continuous study of the structure-CaSR-activity relation of a large number of γ-glutamyl peptides, we have determined that the structural requirements for intense CaSR activity of γ-glutamyl peptides are as follows: existence of an N-terminal γ-L-glutamyl residue; existence of a moderately sized, aliphatic, neutral substituent at the second residue in an L-configuration; and existence of a C-terminal carboxylic acid, preferably with the existence of glycine as the third constituent. By the sensory analysis of γ-glutamyl peptides selected by screening using the CaSR activity assay, γ-glutamylvalylglycine was found to be a potent kokumi peptide. Furthermore, norvaline-containing γ-glutamyl peptides, i.e., γ-glutamylnorvalylglycine and γ-glutamylnorvaline, possessed excellent sensory activity of kokumi substances. A novel, practical industrial synthesis of regiospecific γ-glutamyl peptides is also required for their commercialization, which was achieved through the ring opening reaction of N-α-carbobenzoxy-L-glutamic anhydride and amino acids or peptides in the presence of N-hydroxysuccinimide.

  19. Structure refinement of (Sr,Ba)Nb2O6 ceramic powder from neutron and X-Ray diffraction data

    International Nuclear Information System (INIS)

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

    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 Sr 0 .61 Ba 0.39 Nb 2 O 6 , corroborating with the quantitative X-ray dispersive spectroscopy (EDS) measurements. The structure is tetragonal with cell parameters a, b 12.4504(3) Angstrom and c = 3.9325(1) Angstrom 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. (author)

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    J.G. Carrio

    2002-03-01

    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.

  2. Synthesis, structure, and electrical conductivity of A'[A(sub 2)B(sub 3)O(sub 10)] (A'=Rb, Cs A=Sr, Ba; B=Nb, Ta)

    International Nuclear Information System (INIS)

    Thangadurai, Venkataraman; Schmid-Beurmann, Peter; Weppner, Werner

    2001-01-01

    New members of Dion-Jacobson (D-J)-type layered perovskites of the general formula A'[A(sub 2)B(sub 3)O(sub 10)] (A'=Rb, Cs; A=Sr, Ba; B=Nb, Ta) were prepared by solid-state reactions between the metal oxides, nitrates, and carbonates under specific conditions. The crystal structures were determined using powder X-ray diffraction data in combination with Rietveld analysis. The c-axis lattice parameter increases as the size of the alkaline earth ion increases. Both Sr and Ba compounds crystallize in a tetragonal cell, while the corresponding Ca compounds crystallize in an orthorhombic cell. The electrical conductivity of the layered perovskites was determined using AC impedance analysis and DC methods. Among the compounds with the same alkali ion and different alkaline earth ions, the Ca compound exhibits a higher electrical conductivity than the corresponding Sr and Ba compounds. DC measurements reveal that the layered perovskites exhibit both ionic and electronic conduction

  3. Using coral Ba/Ca records to investigate seasonal to decadal scale biogeochemical cycling in the surface and intermediate ocean.

    Science.gov (United States)

    LaVigne, M.; Cobb, K. M.; DeLong, K. L.; Freiberger, M. M.; Grottoli, A. G.; Hill, T. M.; Miller, H. R.; Nurhati, I. S.; Richey, J. N.; Serrato Marks, G.; Sherrell, R. M.

    2016-12-01

    Dissolved barium (BaSW), a bio-intermediate element, is linked to several biogeochemical processes such as the cycling and export of nutrients, organic carbon (Corg), and barite in surface and intermediate oceans. Dynamic BaSW cycling has been demonstrated in the water column on short timescales (days-weeks) while sedimentary records have documented geologic-scale changes in barite preservation driven by export production. Our understanding of how seasonal-decadal scale climate variability impacts these biogeochemical processes currently lacks robust records. Ba/Ca calibrations in surface and deep sea corals suggest barium is incorporated via cationic substitution in both aragonite and calcite. Here we demonstrate the utility of Ba/Ca for reconstructing biogeochemical variability using examples of surface and deep sea coral records. Century-long deep sea coral records from the California Current System (bamboo corals: 900-1500m) record interannual variations in Ba/Ca, likely reflecting changes in barite formation via bacterial Corg respiration or barite saturation state. A surface Porites coral Ba/Ca record from Christmas Island (central equatorial Pacific: 1978-1995) shows maxima during low productivity El Niño warm periods, suggesting that variations in BaSW are driven by biological removal via direct cellular uptake or indirectly via barite precipitation with the decomposition of large phytoplankton blooms at this location. Similarly, a sixteen-year long Siderastera siderea surface coral record from Dry Tortugas, FL (Gulf of Mexico: 1991-2007) shows seasonal Ba/Ca cycles that align with annual chlorophyll and δ13C. Taken together, these records demonstrate the linkages among Corg, nutrient cycling and BaSW in the surface and intermediate ocean on seasonal to decadal timescales. Multi-proxy paleoceanographic reconstructions including Ba/Ca have the potential to elucidate the mechanisms linking past climate, productivity, nutrients, and BaSW cycling in the past.

  4. Submillimeter and microwave residual losses in epitaxial films of Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D.; Richards, P.L. [Lawrence Berkeley Lab., CA (United States); Garrison, S.M.; Newman, N. [Conductus, Inc., Sunnyvale, CA (United States); Eom, C.B.; Geballe, T.H. [Stanford Univ., CA (United States). Dept. of Applied Physics; Etemad, S.; Inam, A.; Venkatesan, T. [Bell Communications Research, Inc., Red Bank, NJ (United States); Martens, J.S. [Sandia National Labs., Albuquerque, NM (United States); Lee, W.Y. [International Business Machines Corp., San Jose, CA (United States); Bourne, L.C. [Superconductor Technologies, Inc., Santa Barbara, CA (United States)

    1992-03-01

    We have used a novel bolometric technique and a resonant technique to obtain accurate submillimeter and microwave residual loss data for epitaxial thin films of YBa{sub 2}Cu{sub 3}O{sub 7}, Tl{sub 2}Ca{sub 2}Ba{sub 2}Cu{sub 3}O{sub 10} and Tl{sub 2}CaBa{sub 2}Cu{sub 2}O{sub 8}. For all films we obtain good agreement between the submillimeter and microwave data, with the residual losses in both the Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O films scaling approximately as frequency squared below {approximately} 1 THz. We are able to fit the losses in the Y-Ba-Cu-O films to a weakly coupled grain model for the a-b plane conductivity, in good agreement with results from a Kramers-Kronig analysis of the loss data. We observe strong phonon structure in the Tl-Ca-Ba-Cu-O films for frequencies between 2 and 21 THz, and are unable to fit these losses to the simple weakly coupled grain model. This is in strong contrast to the case for other high {Tc} superconductors such as YBa{sub 2}Cu{sub 3}O{sub 7}, where phonon structure observed in ceramic samples is absent in epitaxial oriented films and crystals because of the electronic screening due to the high conductivity of the a-b planes.

  5. Blastomogenic effect of Cs137, Sr90 and Ca45 in single and chronic administration

    International Nuclear Information System (INIS)

    Zapol'skaya, N.A.; Fedorova, A.V.; Borisova, V.V.

    1978-01-01

    The blastomogenic actions of 137 Cs, 90 Sr, and 45 Ca were considered in experiments on white rats, and it was found that the site and type of tumor were determined by the organotropism of the radionuclide. With chronic administration of radionuclides, the tumor rate was low as compared to single-occasion administration

  6. Electron impact excitation of the D states of Mg, Ca and Sr atoms ...

    Indian Academy of Sciences (India)

    Electron impact excitation of the states of Mg, Ca and Sr atoms: Complete experiment results. Sachin Saxena Kshamata Muktavat Rajesh Srivastava. Research Articles Volume 63 Issue 5 November 2004 pp 977-991 ... Good agreement is found on comparison and the importance of relativistic effects is also explored.

  7. Phonons in high- Tc CaBi 2Sr 2Cu 2O 8

    Science.gov (United States)

    Gupta, H. C.

    1989-02-01

    The phonons have been investigated in CaBi 2Sr 2Cu 2O 8 using radial and tangential force constants. From the point of view of superconductivity, it is found that the phonons associated with the Bi-O layers will play an analogous role to the phonons due to Cu-O perovskite-like layers.

  8. Effect of doping Ca on polaron hopping in LaSr 2 Mn 2 O 7

    Indian Academy of Sciences (India)

    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 ...

  9. Effect of doping Ca on polaron hopping in LaSr 2 Mn 2 O 7

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 5-6. Effect of doping Ca on polaron hopping in LaSr2Mn2O7. S N Bhatia Osama A Yassin. Colossal Magnetoresistance & Other Materials Volume 58 Issue 5-6 May-June 2002 pp 1061- ...

  10. Lattice site location and annealing behaviour of Ca and Sr implanted GaN

    CERN Document Server

    De Vries, Bart; Wahl, Ulrich; Correia, J G; Araújo, João Pedro; Lojkowski, W; Kolesnikov, D

    2006-01-01

    We report on the lattice location of ion-implanted Ca and Sr in thin films of single-crystalline wurtzite GaN. Using the emission channeling technique the angular distributions of $\\beta\\!^{-}$−particles emitted by the radioactive isotopes $^{45}$Ca(t$_{ 1/2}$=163.8 d) and $^{89}$Sr(t$_{ 1/2}$=50.53 d) were monitored with a position-sensitive detector following 60 keV room-temperature implantation. Our experiments give direct evidence that $\\sim$90% of Ca and > 60% of Sr atoms were occupying substitutional Ga sites with root mean square displacements of the order of 0.15–0.30 Å, i.e., larger than the expected thermal vibration amplitude of 0.074 Å. Annealing the Ca implanted samples at 1100–1350 °C in high-pressure N$_{2}$ atmosphere resulted in a better incorporation into the substitutional Ga site. The Sr implanted sample showed a small decrease in rms displacements for vacuum annealing up to 900 °C, while the substitutional fraction remained nearly constant. The annealing behavior of the rms disp...

  11. Tunneling properties of Bi2 Sr2 Ca Cu2 Ox/Ag junction

    International Nuclear Information System (INIS)

    Chiang, Yu.N.; Shevchenko, O.B.; Nalbat, Yu.S.

    1993-01-01

    The tunnel-type junction which is naturally formed during firing of Ag paste on the surface of Bi-Sr-Ca-Cu-O crystal has been investigated. It was found that the contact exhibit less than the bulk one in the HTSC. We connect the low gap parameter value with the surface superconductivity in Ag induced by the proximity effect

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

    International Nuclear Information System (INIS)

    Hinton, T.G.; Whicker, F.W.; Ibrahim, S.A.; Pinder, J.E. III

    1992-01-01

    The kinetics of 47 Ca, 85 Sr and 226 Ra 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 85 Sr absorption. The absorption of 85 Sr and 226 Ra 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 85 Sr and 0.26 ± 0.18 for 226 Ra. 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)

  13. 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).

  14. Study of non-stoichiometric BaSrTiFeO3 oxide dedicated to semiconductor gas sensors

    International Nuclear Information System (INIS)

    Fasquelle, D.; Verbrugghe, N.; Deputier, S.

    2016-01-01

    Developing instrumentation systems compatible with the European RoHS directive (restriction of hazardous substances) to monitor our environment is of great interest for our society. Our research therefore aims at developing innovating integrated systems of detection dedicated to the characterization of various environmental exposures. These systems, which integrate new gas sensors containing lead-free oxides, are dedicated to the detection of flammable and toxic gases. We have firstly chosen to study semiconductor gas sensors implemented with lead-free oxides in view to develop RoHS devices. Therefore thick films deposited by spin-coating and screen-printing have been chosen for their robustness, ease to realize and ease to finally obtain cost-effective sensors. As crystalline defects and ionic vacancies are of great interest for gas detection, we have decided to study a non-stoichiometric composition of the BaSrTiFeO 3 sensible oxide. Nonstoichiometric BaSrTiFeO 3 lead-free oxide thick films were deposited by screen-printing on polycrystalline AFO 3 substrates covered by a layer of Ag-Pd acting as bottom electrode. The physical characterizations have revealed a crystalline structure mainly composed of BaTiO 3 pseudo-cubic phase and Ba 4 Ti 12 O 27 monoclinic phase for the powder, and a porous microstructure for the thick films. When compared to a BSTF thick film with a stoichiometric composition, a notable increase in the BSTF dielectric constant value was observed when taking into account of a similar microstructure and grain size. The loss tangent mean value varies more softly for the non-stoichiometric BaSrTiFeO 3 films than for the perovskite BSTF film as tanδ decreases from 0.45 to 0.04 when the frequency increases from 100 Hz to 1 MHz. (paper)

  15. Study of non-stoichiometric BaSrTiFeO3 oxide dedicated to semiconductor gas sensors

    Science.gov (United States)

    Fasquelle, D.; Verbrugghe, N.; Deputier, S.

    2016-11-01

    Developing instrumentation systems compatible with the European RoHS directive (restriction of hazardous substances) to monitor our environment is of great interest for our society. Our research therefore aims at developing innovating integrated systems of detection dedicated to the characterization of various environmental exposures. These systems, which integrate new gas sensors containing lead-free oxides, are dedicated to the detection of flammable and toxic gases. We have firstly chosen to study semiconductor gas sensors implemented with lead-free oxides in view to develop RoHS devices. Therefore thick films deposited by spin-coating and screen-printing have been chosen for their robustness, ease to realize and ease to finally obtain cost-effective sensors. As crystalline defects and ionic vacancies are of great interest for gas detection, we have decided to study a non-stoichiometric composition of the BaSrTiFeO3 sensible oxide. Nonstoichiometric BaSrTiFeO3 lead-free oxide thick films were deposited by screen-printing on polycrystalline AFO3 substrates covered by a layer of Ag-Pd acting as bottom electrode. The physical characterizations have revealed a crystalline structure mainly composed of BaTiO3 pseudo-cubic phase and Ba4Ti12O27 monoclinic phase for the powder, and a porous microstructure for the thick films. When compared to a BSTF thick film with a stoichiometric composition, a notable increase in the BSTF dielectric constant value was observed when taking into account of a similar microstructure and grain size. The loss tangent mean value varies more softly for the non-stoichiometric BaSrTiFeO3 films than for the perovskite BSTF film as tanδ decreases from 0.45 to 0.04 when the frequency increases from 100 Hz to 1 MHz.

  16. Stability of Tl-Ba-Ca-Cu-O Superconducting Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M.P.; Overmyer, D.L.; Venturini, E.L.; Padilla, R.R.; Provencio, P.N.

    1999-08-23

    We report the stability of TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (T1-2212) thin films and by inference, the stability of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9} (Tl-1223) and Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Tl-2223) thin films, under a variety of conditions. In general, we observe that the stability behavior of the single Tl-O layer materials (Tl-1212 and Tl-1223)are similar and the double Tl-O layer materials (Tl-2212 and Tl-2223) are similar. All films are stable with repeated thermal cycling to cryogenic temperatures. Films are also stable in acetone and methanol. Moisture degrades film quality rapidly, especially in the form of vapor. Tl-1212 is more sensitive to vapor than Tl-2212. These materials are stable to high temperatures in either N{sub 2}, similar to vacuum for the cuprates, and O{sub 2} ambients. While total degradation of properties (superconducting and structural) occur at the same temperatures for all phases, 600 C in N{sub 2} and 700 C in O{sub 2}, the onset of degradation occurs at somewhat lower temperatures for Tl-1212 than for Tl-2212 films. In all cases, sample degradation is associated with Tl depletion from the films.

  17. Naturally occurrence of Sr and Ca in the stem of a Japanese cedar (Cryptomeria japonica D. Don) using PIXE

    International Nuclear Information System (INIS)

    Katayama, Y.; Aoki, T.; Ko, S.; Yoshida, K.

    2000-01-01

    Distribution profiles of Sr and Ca occurring naturally in the stem of a Japanese cedar (Cryptomeria japonica D. Don) were determined using PIXE. The average concentration of Sr was around 7.5 ppm and the average Ca concentration was about 540 ppm. (author)

  18. 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.

  19. Impedance spectroscopy and structural properties of the perovskite-like Sn(Ba,Sr)O3 stagnate

    International Nuclear Information System (INIS)

    Cuervo Farfán, J.; Olaya, J.J.; Vera López, E.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    An exhaustive study of structural, electrical and transport properties on the perovskite stagnate Sn(Ba,Sr)O 3 was performed. Samples of SnBa 1-x Sr x O 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 3 and SnBaO 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.

  20. An efficient and stable green phosphor SrBaSiO4:Eu2+ for light-emitting diodes

    International Nuclear Information System (INIS)

    Zhang Xinguo; Tang Xueping; Zhang Jilin; Gong Menglian

    2010-01-01

    Eu 2+ -activated strontium-barium silicate, SrBaSiO 4 :Eu 2+ , which is an intermediate phase between Sr 2 SiO 4 and Ba 2 SiO 4 , was synthesized by a solid-state reaction. The synthesized phosphor was efficiently excited by a broad spectral range of near UV between 300 and 450 nm, and exhibited a strong and wide green emission. As the doped Eu 2+ concentration increased from 0.005 to 0.18 (molar ratio), the emission wavelength shifted from 509 to 521 nm, and this red-shift phenomenon was discussed through a band-gap model. The concentration quenching mechanism was calculated to be a dipole-quadrupole interaction. It showed good thermal stability with T 1/2 of 170 o C and high internal quantum efficiency (78%). A green LED was fabricated with SrBaSiO 4 :Eu 2+ and a 395 nm-emitting InGaN chip and it showed a superior current tolerant property. All the results indicate that this phosphor is a good candidate as green component in fabrication of phosphor-converted white LEDs.

  1. First-principles study of structural, electronic and magnetic properties of AeX (Ae=Be, Mg, Sr, Ba; X=Si, Ge and Sn) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Jaiganesh, G. [Department of Physics, Anna University, Chennai 600 025, Tamil Nadu (India); Kalpana, G., E-mail: g_kalpa@yahoo.com [Department of Physics, Anna University, Chennai 600 025, Tamil Nadu (India)

    2013-01-15

    The first-principles study of the electronic structure and ferromagnetism of AeX (Ae=Be, Mg, Sr and Ba; X=Si, Ge and Sn) compounds have been performed in the ground-state CrB-type and hypothetical NaCl- and zinc blende-type structures by spin-polarization and non-spin-polarization calculations. The TBLMTO-ASA program was used for the purpose. In the CrB-type structure, all these compounds exhibit non-magnetic and metallic behavior. The calculations show that in the NaCl- and ZB-type structures BeSi, BeGe, BeSn, MgSi, MgGe and MgSn compounds are non-magnets whereas SrSi, SrGe, SrSn, BaSi, BaGe and BaSn compounds are ferromagnetic and metallic. Apart from this the ZB-type SrSi, SrGe, BaSi and BaGe compounds exhibit half-metallicity at their equilibrium volume with a magnetic moment of 2.0 {mu}{sub B} per formula unit. However, ZB-type SrSn and BaSn compounds are found to exhibit half-metallic property under expansion of volume. The magnetism arises mainly from the anion p-like states and partial involvement of cation d-like states. The ground state properties like equilibrium lattice parameters, bulk modulus, cohesive energy, magnetic moment, spin-flip-gap and majority spin band gap are calculated and compared with available results. The band structure and density of states are also presented. These materials will be useful for the study of p-electron magnetism and in spintronic devices. - Highlights: Black-Right-Pointing-Pointer Electronic Structure and ferromagnetism in AeX (Ae=Be, Mg, Sr, Ba; X=Si, Ge and Sn) compounds. Black-Right-Pointing-Pointer AeX (Ae=Sr, Ba; X=Si, Ge and Sn) compounds in the NaCl- and ZB- structure are ferromagnetic metals. Black-Right-Pointing-Pointer ZB-type SrSi, SrGe, BaSi and BaGe show half-metallicity with a magnetic moment of 2.00 {mu}{sub B}. Black-Right-Pointing-Pointer Magnetism arises from anion p-like states and cation d-like states (p-electron magnetism). Black-Right-Pointing-Pointer These compounds may be useful spintronic

  2. Emergence of the sub-THz central peak at phase transitions in artificial BaTiO{sub 3}/(Ba,Sr)TiO{sub 3} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonov, Yu.A.; Razumnaya, A.G.; Torgashev, V.I.; Zakharchenko, I.N.; Yuzyuk, Yu.I. [Faculty of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); El Marssi, M. [Laboratoire de Physique de la Matiere Condensee, Universite de Picardie Jules Verne, Amiens (France); Ortega, N.; Kumar, A.; Katiyar, R.S. [Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, PR (United States)

    2015-01-01

    A prominent central peak in the sub-THz frequency range was observed in the Raman spectra of BaTiO{sub 3}/(Ba,Sr)TiO{sub 3} (BT/BST) superlattice grown on (001)MgO substrate. Both soft and central mode show an anomaly around 200 K and 280 K, which can be correlated with orthorhombic to monoclinic phase transition of BST and BT, respectively. The observed temperature dependence of the central mode enabled us to explain rather broad temperature dependence of the dielectric permittivity previously observed in BT/BST superlattices. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Influence of the Ba2+/Sr2+ content and oxygen vacancies on the stability of cubic BaxSr1-xCo0.75Fe0.25O3-d

    NARCIS (Netherlands)

    Lumeij, Mark; Gillessen, Michael; Bouwmeester, Henricus J.M.; Markus, Torsten; Barthel, Juri; Roitsch, Stefan; Mayer, Joachim; Dronskowski, Richard

    2014-01-01

    We present a theoretical and experimental study on the influence of the Ba/Sr and Co/Fe ratios as well as the oxygen-non-stoichiometry on the stability of Ba0.5Sr0.5Co0.8Fe0.2O3 d (BSCF). Thin-layer depositions are analysed by looking at TEM images and EDX spectra. Bondanalytical calculations are

  4. Magnetic properties of BaRu1-xRhxO3 and Sr2Ru1-xRhxO4

    Science.gov (United States)

    Battle, P. D.; Gore, J. G.; Frost, J. R.

    1995-04-01

    The magnetic susceptibilities of polycrystalline BaRu1-xRhxO3 (x=1/3,1/2) and Sr2Ru1-xRhxO4 (x=1/2,2/3) have been measured as a function of temperature. In all cases hysteresis is apparent below ~100 K, and the zero-field-cooled susceptibility of Sr2Ru1-xRhxO4 shows a maximum below 20 K. The data suggest an increase in the extent of electron localization in comparison with isostructural compounds (BaRuO3, Sr2RuO4, and Sr2RhO4), but there is no evidence for the weak ferromagnetism found in the Ir analogs (BaIrO3 and Sr2IrO4).

  5. 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.

  6. Luminescence in Eu2+ and Ce3+ doped SrCaP2O7 phosphors

    Directory of Open Access Journals (Sweden)

    K.N. Shinde

    Full Text Available Eu2+ and Ce3+ doped SrCaP2O7 has been achieved by modified solid state diffusion in reducing atmosphere. The prepared phosphor powders have been identified by their characteristic X-ray diffraction patterns. The mixed phases of α-Sr2P2O7 type with orthorhombic and α-Ca2P2O7 type with monoclinic form were investigated. Its excitation wavelength ranging from 250 to 430 nm fits well with the characteristic emission of UV light-emitting diode (LED. The excitation and emission spectra indicate that these phosphors can be effectively excited by the near-UV light, and emits blue (visible range due to 4f7 → 4f65d1 transition of Eu2+ particularly, SrCaP2O7: Eu2+ whereas, photoluminescence excitation spectrum measurements of Ce3+ activated SrCaP2O7 shows that the phosphor can be efficiently excited by UV–Vis light from 280 to 310 nm to realize emission in the near visible range due to the 5d–4f transition of Ce3+ ions which is applicable for scintillation purpose. The impacts of doping of divalent europium and trivalent cerium on photoluminescence properties on SrCaP2O7 pyrophosphate phosphors were investigated and I propose a feasible interpretation. Keywords: Phosphor, Luminescence, XRD, LED, FTIR

  7. Experimental study of REE, Ba, Sr, Mo and W partitioning between carbonatitic melt and aqueous fluid with implications for rare metal mineralization

    Science.gov (United States)

    Song, WenLei; Xu, Cheng; Veksler, Ilya V.; Kynicky, Jindrich

    2016-01-01

    Carbonatites host some unique ore deposits, especially rare earth elements (REE). Hydrothermal fluids have been proposed to play a significant role in the concentration and transport of REE and other rare metals in carbonatites, but experimental constraints on fluid-melt equilibria in carbonatitic systems are sparse. Here we present an experimental study of trace element (REE, Ba, Sr, Mo and W) partitioning between hydrous fluids and carbonatitic melts, bearing on potential hydrothermal activity associated with carbonatite ore-forming systems. The experiments were performed on mixtures of synthetic carbonate melts and aqueous fluids at 700-800 °C and 100-200 MPa using rapid-quench cold-seal pressure vessels and double-capsule assemblages with diamond traps for analyzing fluid precipitates in the outer capsule. Starting mixtures were composed of Ca, Mg and Na carbonates spiked with trace elements. Small amounts of F or Cl were added to some of the mixtures to study the effects of halogens on the element distribution. The results show that REE, Ba, Sr, Mo and W all preferentially partition into carbonatite melt and have fluid-melt distribution coefficients ( D f/m) below unity. The REE partitioning is slightly dependent on the major element (Ca, Mg and Na) composition of the starting mixtures, and it is influenced by temperature, pressure, and the presence of halogens. The fluid-melt D values of individual REE vary from 0.02 to 0.15 with D_{Lu}^{f} / {fm}{m} being larger than D_{La}^{f} / {fm}{m} by a factor of 1.1-2. The halogens F and Cl have strong and opposite effects on the REE partitioning. Fluid-melt D REE are about three times higher in F-bearing compositions and ten times lower in Cl-bearing compositions than in halogen-free systems. D_{W}^{f} / {fm}{m} and D_{Mo}^{f} / {fm}{m} are the highest among the studied elements and vary between 0.6 and 0.7; D_{Ba}^{f} / {fm}{m} is between 0.05 and 0.09, whereas D_{Sr}^{f} / {fm}{m} is at about 0.01-0.02. The

  8. 87Sr/86Sr Across the Devonian-Carboniferous Transition Within the Pho Han Formation, Cat Ba Island, Vietnam: New Data Outside of an Old Orogeny

    Science.gov (United States)

    Paschall, O. C.; Carmichael, S. K.; Dombrowski, A. D.; Batchelor, C. J.; Coleman, D. S.; Waters, J. A.; Königshof, P.

    2017-12-01

    The Devonian-Carboniferous (D-C) transition is a period of mass extinction and rapid global faunal changes that affected both marine and terrestrial ecosystems. Although the paleontology and carbon and oxygen isotopes across of the D-C boundary have been studied in detail, there is very little continuous 87Sr/86Sr isotope data for this time iteration due to unconformities and/or diagenetic alteration in many sections. Conodont biostratigraphy indicates that the D-C boundary is present within the Pho Han Formation on Cat Ba Island in northeastern Vietnam. This unit represents a starved basinal facies on the South China carbonate platform, and has continuous sedimentation across the D-C boundary. Whole rock geochemical results indicate increased clastic input at the D-C transition, potentially due to the regression observed in many Hangenberg Event localities around the world, but the isolated nature of the basin could instead indicate complete shutdown of the carbonate factory. New 87Sr/86Sr measurements of carbonate across the D-C boundary in the Pho Han Formation indicate oscillating fluctuations from 0.708052 to 0.708672. Many of these values are within the McArthur et al. (2012) LOWESS fit for seawater, with excursions towards higher values tentatively identified at the boundary between the Palmatolepis expansa and lower Siphonodella praesulcata conodont zones, and within the Siphonodella duplicata zone. There is a lack of correlation between 87Sr/86Sr values with whole rock geochemistry and δ18O isotope values across the section, suggesting that these 87Sr/86Sr values are not due to clastic contamination and that the samples have not experienced major diagenetic alteration. The continuous sedimentation in this section and its location in an area far from the Variscan orogeny make this unit a valuable site in which to compare 87Sr/86Sr ratios to existing studies in Europe and North America which experienced substantial sediment shedding from the Appalachian

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

    Science.gov (United States)

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

    2015-11-04

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

  10. Controls over δ44/40Ca and Sr/Ca variations in coccoliths: New perspectives from laboratory cultures and cellular models

    Science.gov (United States)

    Mejía, Luz María; Paytan, Adina; Eisenhauer, Anton; Böhm, Florian; Kolevica, Ana; Bolton, Clara; Méndez-Vicente, Ana; Abrevaya, Lorena; Isensee, Kirsten; Stoll, Heather

    2018-01-01

    Coccoliths comprise a major fraction of the global carbonate sink. Therefore, changes in coccolithophores' Ca isotopic fractionation could affect seawater Ca isotopic composition, affecting interpretations of the global Ca cycle and related changes in seawater chemistry and climate. Despite this, a quantitative interpretation of coccolith Ca isotopic fractionation and a clear understanding of the mechanisms driving it are not yet available. Here, we address this gap in knowledge by developing a simple model (CaSri-Co) to track coccolith Ca isotopic fractionation during cellular Ca uptake and allocation to calcification. We then apply it to published and new δ 44 / 40 Ca and Sr/Ca data of cultured coccolithophores of the species Emiliania huxleyi and Gephyrocapsa oceanica. We identify changes in calcification rates, Ca retention efficiency and solvation-desolvation rates as major drivers of the Ca isotopic fractionation and Sr/Ca variations observed in cultures. Higher calcification rates, higher Ca retention efficiencies and lower solvation-desolvation rates increase both coccolith Ca isotopic fractionation and Sr/Ca. Coccolith Ca isotopic fractionation is most sensitive to changes in solvation-desolvation rates. Changes in Ca retention efficiency may be a major driver of coccolith Sr/Ca variations in cultures. We suggest that substantial changes in the water structure strength caused by past changes in temperature could have induced significant changes in coccolithophores' Ca isotopic fractionation, potentially having some influence on seawater Ca isotopic composition. We also suggest a potential effect on Ca isotopic fractionation via modification of the solvation environment through cellular exudates, a hypothesis that remains to be tested.

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

    International Nuclear Information System (INIS)

    Yanagida, Takayuki; Kawaguchi, Noriaki; Fujimoto, Yutaka; Fukuda, Kentaro; Watanabe, Kenichi; Yamazaki, Atsushi; Uritani, Akira

    2013-01-01

    Dopant free eutectic scintillators 6 LiF–SrF 2 and 6 LiF–CaF 2 were developed by the vertical Bridgeman method for the purpose of thermal neutron detection. The molar ratio of LiF and Ca/SrF 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 2 layers. When the samples were irradiated with 252 Cf neutrons, 6 LiF–SrF 2 and 6 LiF–CaF 2 exhibited the light yields of 4700 and 9400 ph/n, respectively. Scintillation decay times of 6 LiF–SrF 2 and 6 LiF–CaF 2 were accepted for scintillation detectors, 90 and 250 ns, respectively. -- Highlights: • Nondoped LiF–CaF 2 and LiF–SrF 2 eutectic scinitillators are reported for the first time. • Two sample showed self-trapped exciton emission. • LiF–SrF 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 2 and LiF–SrF 2 were 250 and 90 ns, respectively

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

    International Nuclear Information System (INIS)

    Hinton, T.G.

    1989-01-01

    The accumulation of 45 Ca, 47 Ca, 88 Sr, and 226 Ra 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 45 Ca 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

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  14. Unraveling the Role of Structural Order in the Transformation of Electrical Conductivity in Ca2FeCoO6-δ, CaSrFeCoO6-δ, and Sr2FeCoO6-δ.

    Science.gov (United States)

    Hona, Ram Krishna; Huq, Ashfia; Ramezanipour, Farshid

    2017-12-04

    The ability to control the electrical conductivity of solid-state oxides using structural parameters has been demonstrated. A correlation has been established between the electrical conductivity and structural order in a series of oxygen-deficient perovskites using X-ray and neutron diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and electrical conductivity studies at a wide temperature range, 25-800 °C. The crystal structure of CaSrFeCoO 6-δ has been determined, and its stark contrast to Ca 2 FeCoO 6-δ and Sr 2 FeCoO 6-δ has been demonstrated. The Fe/Co distribution over tetrahedral and octahedral sites has been determined using neutron diffraction. There is a systematic increase in the structural order in progression from Sr 2 FeCoO 6-δ (δ = 0.5) to CaSrFeCoO 6-δ (δ = 0.8) and Ca 2 FeCoO 6-δ (δ = 0.9) . The oxygen contents of these materials were determined using iodometric titration and TGA. At room temperature, there is an inverse correlation between the electrical conductivity and structural order. The ordered Ca 2 and CaSr compounds are semiconductors, while the disordered Sr 2 compund shows metallic behavior. The metallic nature of the Sr 2 material persists up to 1073 K (800 °C), while the Ca 2 and CaSr compounds undergo a semiconductor-to-metal transition above 500 and 300 °C, respectively, highlighting another important impact of the structural order. At high temperature, the CaSr compound has the highest conductivity compared to the Ca 2 and Sr 2 materials. There appears to be an optimum degree of structural order that leads to the highest conductivity at high temperature. Another consequence of the structural order is the observation of mixed ionic-electronic conductivity in CaSr and Ca 2 compounds, as is evident from the hysteresis in the conductivity data obtained during heating and cooling cycles. The average ionic radius required for each structural transition was

  15. Structural, electronic properties and intra-atomic bonding in new ThCr 2Si 2-like arsenides SrRu 2As 2, BaRu 2As 2, SrRh 2As 2 and BaRh 2As 2 from first principles calculations

    Science.gov (United States)

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

    2009-11-01

    Based on first-principle FLAPW-GGA calculations, we have investigated the systematic trends in structural and electronic properties of a newly discovered group of ThCr 2Si 2-like arsenides: SrRu 2As 2, BaRu 2As 2, SrRh 2As 2 and BaRh 2As 2. Our results show that the replacement of an alkaline earth metal (SrBa) and 4d metal (Ru ↔ Rh) leads to various types of anisotropic deformations of the crystal structure caused by strong anisotropy of inter-atomic bonds. The band structure, density of states and Fermi surfaces have been evaluated and discussed. Appreciable changes in the near-Fermi bands and the Fermi surface topology found as going from (Sr,Ba)Ru 2As 2 to (Sr,Ba)Rh 2As 2 reflect the growth of the 3D-like type of dispersion for these systems, which is accompanied by an increase in the near-Fermi density of states. The inter-atomic bonding in (Sr,Ba)(Ru,Rh) 2As 2 phases adopts a complex anisotropic character, where the bonding in [ (Ru,Rh) 2As 2] blocks is of a mixed metallic-ionic-covalent type whereas between adjacent [ (Ru,Rh) 2As 2] blocks and (Sr, Ba) atomic sheets, ionic interactions emerge; thus these systems may be classified as ionic metals.

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

    International Nuclear Information System (INIS)

    Luna-Lopez, J.A.; Portelles, J.; Raymond, O.; Siqueiros, J.M.

    2009-01-01

    Sr 0.3 Ba 0.7 Nb 2 O 6 (SBN) and La 0.030 Sr 0.255 Ba 0.700 Nb 2 O 6 (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 A 1 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.

  17. Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

    Science.gov (United States)

    Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

    2017-10-01

    Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of

  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. First-principles study of structural, electronic and magnetic properties of AeX (Ae=Be, Mg, Sr, Ba; X=Si, Ge and Sn) compounds

    Science.gov (United States)

    Jaiganesh, G.; Kalpana, G.

    2013-01-01

    The first-principles study of the electronic structure and ferromagnetism of AeX (Ae=Be, Mg, Sr and Ba; X=Si, Ge and Sn) compounds have been performed in the ground-state CrB-type and hypothetical NaCl- and zinc blende-type structures by spin-polarization and non-spin-polarization calculations. The TBLMTO-ASA program was used for the purpose. In the CrB-type structure, all these compounds exhibit non-magnetic and metallic behavior. The calculations show that in the NaCl- and ZB-type structures BeSi, BeGe, BeSn, MgSi, MgGe and MgSn compounds are non-magnets whereas SrSi, SrGe, SrSn, BaSi, BaGe and BaSn compounds are ferromagnetic and metallic. Apart from this the ZB-type SrSi, SrGe, BaSi and BaGe compounds exhibit half-metallicity at their equilibrium volume with a magnetic moment of 2.0 μB per formula unit. However, ZB-type SrSn and BaSn compounds are found to exhibit half-metallic property under expansion of volume. The magnetism arises mainly from the anion p-like states and partial involvement of cation d-like states. The ground state properties like equilibrium lattice parameters, bulk modulus, cohesive energy, magnetic moment, spin-flip-gap and majority spin band gap are calculated and compared with available results. The band structure and density of states are also presented. These materials will be useful for the study of p-electron magnetism and in spintronic devices.

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

    International Nuclear Information System (INIS)

    Poeppel, R.B.; Goretta, K.C.; Balachandran, U.; Biondo, A.C.; Dorris, S.E.; Hathcox, S.C.; Kaufman, D.Y.; Lanagan, M.T.; Prorok, B.C.; Wu, C.T.; Hu, J.G.; Holesinger, T.G.; Miller, D.J.

    1992-10-01

    Ag-clad Bi 2 Sr 2 CaCu 2 O x (2212) and (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x (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

  1. Superconducting thin films of BiSrCaCuO made by sequential electron beam evaporation

    Science.gov (United States)

    Steinbeck, J.; Anderson, A. C.; Tsaur, B.-Y.; Strauss, A. J.

    1989-03-01

    Superconducting thin films of Bi2Sr2Ca1Cu2O(x) have been made by sequential electron-beam evaporation of multiple layers of Bi and Cu metals and (Sr, Ca)F2 on MgO substrates. The films were annealed at high temperature, first in wet O2 and then in dry O2, and cooled to room temperature in dry O2. The resulting films, which are about 1-micron thick, have transition temperatures of about 85 K. X-ray diffraction shows that the films are preferentially oriented with their c-axis perpendicular to the MgO substrate. The best film has a zero-resistance temperature of 90 K and critical-current densities of 8 x 104 A/sq cm at 77 K and 2.5 x 105 A/sq cm at 4.2 K.

  2. Influence of oxofluorine doping on superconducting properties of superconductor Bi-Pb-Sr-Ca-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Bunda, V.; Kun, A.; Bunda, S. [Uzhorod State Univ. (Ukraine). Dept. of Physics of Semiconductors; Kovac, J. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Experimental Physics

    1994-03-01

    The samples of nominal composition Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 3}Cu{sub 4}O{sub 12{minus}x}F{sub x} consist of {alpha},{beta},{gamma}, and {delta}-modifications of phase 2234. The authors observed the superconducting transition in the temperature region 110--132 K for samples z {<=} 0.25. The possible model of creating superconducting state in Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 3}Cu{sub 4}O{sub 12{minus}x}F{sub x} samples is proposed.

  3. Structural, electronic and optical characteristics of SrGe{sub 2} and BaGe{sub 2}: A combined experimental and computational study

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh, E-mail: mkgarg79@gmail.com [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); Umezawa, Naoto [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); Imai, Motoharu [Superconducting Properties Unit, National Institute for Materials Science, Ibaraki 305-0047 (Japan)

    2015-05-05

    Highlights: • Charge transfer between cation and anion atoms observed first time in digermandies. • Study yields a band gap of ∼1 eV and ∼0.85 eV for SrGe{sub 2} and BaGe{sub 2}, respectively. • Band gap decrease with the application of hydrostatic pressure. • Localized cation d states lead to a large absorption coefficient (>7.5 × 10{sup 4} cm{sup −1}). - Abstract: SrGe{sub 2} and BaGe{sub 2} were characterized for structural, electronic and optical properties by means of diffuse reflectance and first-principles density functional theory. These two germanides crystallize in the BaSi{sub 2}-type structure, in which Ge atoms are arranged in tetrahedral configuration. The calculation indicates a charge transfer from Sr (or Ba) atoms to Ge atoms along with the formation of covalent bonds among Ge atoms in Ge tetrahedral. The computational results confirm that these two germanies are Zintl phase described as Sr{sub 2}Ge{sub 4} (or Ba{sub 2}Ge{sub 4}), which are characterized by positively charged [Sr{sub 2} (or Ba{sub 2})]{sup 2.59+} and negatively charged [Ge{sub 4}]{sup 2.59−} units acting as cation and anion, respectively. These compounds are indirect gap semiconductors with band gap estimated to be E{sub g} = 1.02 eV for BaGe{sub 2} and E{sub g} = 0.89 eV for SrGe{sub 2} which are in good agreement with our experimental measured values (E{sub g} = 0.97 eV for BaGe{sub 2} and E{sub g} = 0.82 eV for SrGe{sub 2}). Our calculations demonstrate that the band gaps are narrowed by application of hydrostatic pressure; the pressure coefficients are estimated to be −10.54 for SrGe{sub 2} and −10.06 meV/GPa for BaGe{sub 2}. Optical properties reveal that these compounds have large absorption coefficient (∼7.5 × 10{sup 4} cm{sup −1} at 1.5 eV) and the estimated high frequency (static) dielectric constant are, ε{sub ∞}(ε{sub 0}) ≈ 12.8(20.97) for BaGe{sub 2} and ε{sub ∞}(ε{sub 0}) ≈ 14.27(22.87) for SrGe{sub 2}.

  4. Effects of hole doping on the electronic transport properties of PrBa sub 1 sub . sub 8 Sr sub 0 sub . sub 2 Cu sub 3 O sub y and PrSr sub 2 Cu sub 2 sub . sub 7 Mo sub 0 sub . sub 3 O sub y

    CERN Document Server

    Yang, C F; Zhang, H

    2002-01-01

    We investigate the effect of Ca doping on the electronic transport properties and superconductivity of Pr sub 1 sub - sub x Ca sub x Ba sub 1 sub . sub 8 Sr sub 0 sub . sub 2 Cu sub 3 O sub y and Pr sub 1 sub - sub x Ca sub x Sr sub 2 Cu sub 2 sub . sub 7 Mo sub 0 sub . sub 3 O sub y systems. It is found that when PrBa sub 2 Cu sub 3 O sub y (Pr123) is in a highly localized state, the Ca doping mainly decreases the 4f-2p hybridized states and thus releases the holes into the CuO sub 2 planes. Whereas when Pr123 is in a less localized state, the Ca doping not only introduces holes into the CuO sub 2 planes, but also induces dramatic charge transfer. Our results suggest that only when the hole concentration in both the CuO chain and the CuO sub 2 planes reaches a proper value, can the superconductivity be restored in the Pr123 system.

  5. Electronic structure of TlBa2CaCu2O7-δ

    Science.gov (United States)

    Vasquez, R. P.; Novikov, D. L.; Freeman, A. J.; Siegal, M. P.

    1997-06-01

    The core levels of TlBa2CaCu2O7-δ (Tl-1212) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (EF) for the stoichiometric compound (δ=0), while for 50% oxygen vacancies in the Tl-O layer (δ=0.5) EF is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher Tc, consistent with a shift of EF closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O8+δ (Tl-2212) and HgBa2CaCu2O6+δ (Hg-1212). The similarity of the Cu 2p3/2 spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p3/2 signals exhibit differences which suggest that the replacement of Tl3+ with Hg2+ results in a decrease in the O 2p-->Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states.

  6. Electronic structure of TlBa2CaCu2O7-δ

    International Nuclear Information System (INIS)

    Vasquez, R.P.; Novikov, D.L.; Freeman, A.J.; Siegal, M.P.

    1997-01-01

    The core levels of TlBa 2 CaCu 2 O 7-δ (Tl-1212) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E F ) for the stoichiometric compound (δ=0), while for 50% oxygen vacancies in the Tl-O layer (δ=0.5) E F is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T c , consistent with a shift of E F closer to the VHS. Comparisons are made to the core levels and valence bands of Tl 2 Ba 2 CaCu 2 O 8+δ (Tl-2212) and HgBa 2 CaCu 2 O 6+δ (Hg-1212). The similarity of the Cu 2p 3/2 spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p 3/2 signals exhibit differences which suggest that the replacement of Tl 3+ with Hg 2+ results in a decrease in the O 2p→Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states. copyright 1997 The American Physical Society

  7. Electronic Structure of TlBa2CaCu2O(7-Delta)

    Science.gov (United States)

    Vasquez, R. P.; Novikov, D. L.; Freeman, A. J.; Siegal, M. P.

    1997-01-01

    The core levels of TlBa2CaCu2O(7-delta) (Tl-1212) epitaxial films have been measured with X-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin-tin-orbital band-structure method and measured with XPS. The calculations show that a van Hove singularity (VHS) lies above the Fermi level (E(sub F)) for the stoichiometric compound (delta = 0.5), while for 50% oxygen vacancies in the Tl-O layer (delta = 0.5) E(sub F) is in close proximity to the VHS. Samples annealed in nitrogen (to reduce the hole overdoping by the removal of oxygen) exhibit higher core-level binding energies and a higher T(sub c), consistent with a shift of E(sub F) closer to the VHS. Comparisons are made to the core levels and valence bands of Tl2Ba2CaCu2O(8 + delta)(Tl-2212) and HgBa2CaCu2O)6 + delta) (Hg- 1212). The similarity of the Cu 2p(sub 3/2) spectra for Tl-1212 and Tl-2212 indicates that the number of Tl-O layers has little effect on the Cu-O bonding. However, the Tl-1212 and Hg-1212 Cu 2p(sub 3/2) signals exhibit differences which suggest that the replacement of T(sup 3+) with Hg(sup 2+) results in a decrease in the O 2p right arrow Cu 3d charge-transfer energy and differences in the probabilities of planar vs apical oxygen charge transfer and/or Zhang-Rice singlet-state formation. Differences between the Tl-1212 and the Tl-2212 and Hg-1212 measured valence bands are consistent with the calculated Cu 3d and (Tl,Hg) 6s/5d partial densities of states.

  8. Flux creep in Bi2Sr2CaCu2O8 epitaxial films

    International Nuclear Information System (INIS)

    Zeldov, E.; Amer, N.M.; Koren, G.; Gupta, A.

    1990-01-01

    We incorporate the experimentally deduced flux line potential well structure into the flux creep model. Application of this approach to the resistive transition in Bi 2 Sr 2 CaCu 2 O 8 epitaxial films explains the power law voltage-current characteristics and the nonlinear current dependence of the activation energy. The results cannot be accounted for by a transition into a superconducting vortex-glass phase

  9. Fabrication and Film Qualification of Sr Modified Pb(Ca) TiO3 Thin Films

    International Nuclear Information System (INIS)

    Naw Hla Myat San; Khin Aye Thwe; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    Strontium and calcium - modified lead titanate (Pb0.7 Ca0.15 Sr0.15 ) TiO3 (PCST)thin films were prepared by using spin coating technique. Phase transition of PCST was interpreted by means of Er-T characteristics. Process temperature dependence on micro-structure of PCST film was studied. Charge conduction mechanism of PCST thin film was also investigated for film qualification.

  10. Zone centre phonons in high Tc CaBi 2Sr 2Cu 2O 8

    Science.gov (United States)

    Gupta, H. C.

    1988-10-01

    The zone centre phonons have been investigated in CaBi 2Sr 2Cu 2O 8 using radial and tangential force constants. It is found that the phonons due to Bi O layers do not play an important role from the point of view of superconductivity. The calculation provides an information on the phonons which may be important for explaining the high temperature superconductivity.

  11. Resistance noise in Bi_2Sr_2CaCu_2O$_{8+\\delta}$

    OpenAIRE

    Fruchter, L.; Raffy, H.; Li, Z. Z.

    2007-01-01

    The resistance noise in a Bi_2Sr_2CaCu_2O$_{8+\\delta}$ thin film is found to increase strongly in the underdoped regime. While the increase of the raw resistance noise with decreasing temperature appears to roughly track the previously reported pseudogap temperature for this material, standard noise analysis rather suggests that the additional noise contribution is driven by the proximity of the superconductor-insulator transition.

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

    International Nuclear Information System (INIS)

    Fuente, G.F. de la; Ruiz, M.T.; Sotelo, A.; Larrea, A.; Navarro, R.

    1993-01-01

    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.)

  13. 110K Bi-Sr-Ca-Cu-O superconductor oxide and method for making same

    Science.gov (United States)

    Veal, Boyd W.; Downey, John W.; Lam, Daniel J.; Paulikas, Arvydas P.

    1992-01-01

    A superconductor 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 Bi.sub.2 O.sub.3, SrCO.sub.3, CaCO.sub.3 and CuO into aparticulate compact wherein the atom ratios are Bi.sub.2, Sr.sub.1.2-2.2, Ca.sub.1.8-2.4, Cu.sub.3. 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.

  14. 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.

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

    International Nuclear Information System (INIS)

    Zhong, L.; Guo, H.; Shen, H.; Li, X.; Tang, W.; Liu, J.; Jin, J.; Mi, Y.

    2007-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh, E-mail: Kumar.Mukesh@nims.go.jp, E-mail: mkgarg79@gmail.com [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); Umezawa, Naoto [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); TU-NIMS Joint Research Center, School of Materials Science and Engineering, Tianjin University, 92 Weijin Road, Nankai District, Tianjin (China); Imai, Motoharu [Superconducting Properties Unit, National Institute for Materials Science, Ibaraki 305-0047 (Japan)

    2014-05-28

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

  17. Transformation of Structure, Electrical Conductivity, and Magnetism in AA'Fe2O6-δ, A = Sr, Ca and A' = Sr.

    Science.gov (United States)

    Hona, Ram Krishna; Huq, Ashfia; Mulmi, Suresh; Ramezanipour, Farshid

    2017-08-21

    The ability to control electrical properties and magnetism by varying the crystal structure using the effect of the A-site cation in oxygen-deficient perovskites has been studied in AA'Fe 2 O 6-δ , where A = Sr, Ca and A' = Sr. The structure of Sr 2 Fe 2 O 6-δ , synthesized at 1250 °C in air, contains dimeric units of FeO 5 square pyramids separated by FeO 6 octahedra. Here we show that this ordering scheme can be transformed by changing the A-site cations from Sr to Ca. This leads to a structure where layers of corner-sharing FeO 6 octahedra are separated by chains of FeO 4 tetrahedra. Through systematic variation of the A-site cations, we have determined the average ionic radius required for this conversion to be ∼1.41 Å. We have demonstrated that the magnetic structure is also transformed. The Sr 2 compound has an incommensurate magnetic structure, where magnetic moments are in spin-density wave state, aligning perpendicular to the body diagonal of the unit cell. With the aid of neutron diffraction experiments at 10 and 300 K, we have shown that the magnetic structure is converted into a long-range G-type antiferromagnetic system when one Sr is replaced by Ca. In this G-type ordering scheme, the magnetic moments align in the 001 direction, antiparallel to their nearest neighbors. We have also performed variable-temperature electrical conductivity studies on these materials in the temperature range 298-1073 K. These studies have revealed the transformation of charge transport properties, where the metallic behavior of the Sr 2 compound is converted into semiconductivity in the CaSr material. The trend of conductivity as a function of temperature is reversed upon changing the A-site cation. The conductivity of the Sr 2 compound shows a downturn, while the conductivity of the CaSr material increases as a function of temperature. We have also shown that the CaSr compound exhibits temperature-dependent behavior typical of a mixed ionic-electronic conducting

  18. Surface morphology analysis of nanostructured (Ba sub x , Sr sub 1 sub - sub x)TiO sub 3 thin films using fractal method

    CERN Document Server

    Hong, K J; Choi, W K; Cho, J C

    2003-01-01

    Based on the fractal theory, this paper uses scanning electron microscopy images to investigate the roughness characteristics of nanostructured (Ba Sr)TiO sub 3 thin films by sol-gel methods. The percentage grain area, surface fractal dimensions and 3D image are evaluated using image analysis methods. The thickness of the (Ba Sr)TiO sub 3 thin films was 260-280 nm. The surface fractal dimensions were increased with strontium doping, and grain area, were decreased with it. The fractal dimension and the grain areas of the (Ba sub 0 sub . sub 7 Sr sub 0 sub . sub 3)TiO sub 3 thin films were 1.81 and 81%. Based on the image analysis, the roughness height of 3D images as 256 levels was about 3 nm and its distribution was about 35-40% for the (Ba sub 0 sub . sub 8 Sr sub 0 sub . sub 2)TiO sub 3 and (Ba sub 0 sub . sub 7 Sr sub 0 sub . sub 3)TiO sub 3 thin films. The roughness height of the BST thin films was distributed from 35% to 40% ranging from 3 nm to 4 nm. By increasing the strontium doping, the roughness hei...

  19. Magnetic, thermal, and transport properties of layered arsenides BaRu2As2 and SrRu2As2

    Science.gov (United States)

    Nath, R.; Singh, Yogesh; Johnston, D. C.

    2009-05-01

    The magnetic, thermal, and transport properties of polycrystalline BaRu2As2 and SrRu2As2 samples with the ThCr2Si2 structure were investigated by means of magnetic susceptibility χ(T) , electrical resistivity ρ(T) , and heat capacity Cp(T) measurements. The temperature (T) dependence of ρ indicates metallic character for both compounds with residual resistivity ratios ρ(310K)/ρ(2K) of 17 and 5 for the Ba and Sr compounds, respectively. The Cp(T) results reveal a low- T Sommerfeld coefficient γ=4.9(1) and 4.1(1)mJ/molK2 and Debye temperature ΘD=271(7) and 271(4) K for the Ba and Sr compounds, respectively. The χ(T) was found to be diamagnetic with a small absolute value for both compounds. No transitions were found for BaRu2As2 above 1.8 K. The χ(T) data for SrRu2As2 exhibit a cusp at ˜200K , possibly an indication of a structural and/or magnetic transition. We discuss the properties of BaRu2As2 and SrRu2As2 in the context of other ThCr2Si2 -type and ZrCuSiAs-type transition metal pnictides.

  20. An assessment of the Sr/Ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature

    Science.gov (United States)

    Marshall, John F.; McCulloch, Malcolm T.

    2002-09-01

    The high precision measurement of the Sr/Ca ratio in corals has the potential for measuring past sea surface temperatures at very high accuracy. However, the veracity of the technique has been questioned on the basis that there is both a spatial and temporal variation in the Sr/Ca ratio of seawater, and that kinetic effects, such as the calcification rate, can affect the Sr/Ca ratio of corals, and produce inaccuracies of the order of 2-4 °C. In the present study, a number of cores of the massive hermatypic scleractinian coral Porites, from the central Great Barrier Reef, have been analyzed for Sr/Ca at weekly to monthly resolution. Results from a 24 year record from Myrmidon Reef show an overall variation from 22.7 °C to 30.4 °C. The record shows a warming/cooling trend with maximum warming centred on the 1986-1987 summer. While some bleaching was reported to have occurred at Myrmidon Reef in 1982, the Sr/Ca record indicates that subsequent summer temperatures were much higher. The 4.5 year record from Stanley Reef shows a maximum SST of 30 °C during the 1997-1998 El Niño event. The calibrations from Myrmidon and Stanley Reefs are in excellent agreement with previously published calibrations from nearby reefs. While corals do not calcify in equilibrium with seawater due to physiological control on the uptake of Sr and Ca into the lattice of coralline aragonite, it can be argued that, provided only a single genus such as Porites sp. is used, and that the coral is sampled along a major vertical growth axis, then the Sr/Ca ratio should vary uniformly with temperature. Similarly, objections based on the spatial and temporal variability of the Sr/Ca activity ratio of seawater can be countered on the basis that in most areas where coral reefs grow there is a uniformity in the Sr/Ca activity ratio, and there does not appear to be a change in this ratio over the growth period of the coral. Evidence from several corals in this study suggest that stress can be a major

  1. An apparent "vital effect" of calcification rate on the Sr/Ca temperature proxy in the reef coral Montipora capitata

    Science.gov (United States)

    Kuffner, Ilsa; Jokiel, Paul L.; Rodgers, Kuulei; Andersson, Andreas; Mackenzie, Fred T.

    2012-01-01

    Measuring the strontium to calcium ratio in coral skeletons reveals information on seawater temperatures during skeletal deposition, but studies have shown additional variables may affect the ratio. Here we measured Sr/Ca in the reef coral, Montipora capitata, grown in six mesocosms continuously supplied with seawater from the adjacent reef flat. Three mesocosms were ambient controls, and three had seawater chemistry simulating "ocean acidification" (OA). We found that Sr/Ca was not affected by the OA treatment, and neither was coral calcification for these small colonies (larger colonies did show an OA effect). The lack of OA effects allowed us to test the hypothesis that coral growth rate can affect Sr/Ca using the natural range in calcification rates of the corals grown at the same temperature. We found that Sr/Ca was inversely related to calcification rate (Sr/Ca = 9.39 - 0.00404 mmol/mol * mg day-1 cm-2, R2 = 0.32). Using a previously published calibration curve for this species, a 22 mg day-1 colony-1 increase in calcification rate introduced a 1°C warmer temperature estimate, with the 27 corals reporting "temperatures" ranging from 24.9 to 28.9, with mean 26.6 ± 0.9°C SD. Our results lend support to hypotheses invoking kinetic processes and growth rate to explain vital effects on Sr/Ca. However, uncertainty in the slope of the regression of Sr/Ca on calcification and a low R-squared value lead us to conclude that Sr/Ca could still be a useful proxy in this species given sufficient replication or by including growth rate in the calibration.

  2. Enhanced magnetism of perovskite oxides, Sr(Sn,Fe)O3- δ , by substitution of nonmagnetic Ca and Ti ions

    Science.gov (United States)

    Nomura, Kiyoshi; Suzuki, Shigeyo; Mizunuma, Tomoya; Koike, Yuya; Okazawa, Atsushi

    2017-11-01

    Magnetic properties of perovskite oxides, SrSn1- x Fe x O3- δ ( x ≤ 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr1- y Ca y )(Sn1- x Fe x )O3- δ and Sr(Sn1- x- y Fe x Ti y )O3- δ . The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O3- δ showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O3- δ showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe3+ and a doublet of Fe4+ were observed in Mössbauer spectra of Ca-substituted Sr(Sn, Fe)O3- δ with weak ferromagnetism, and two sextets of high spin Fe3+ were additionally observed in Mössbauer spectra of Ca-doped Sr(Sn, Fe)O3- δ with relatively strong ferromagnetism. When Sr(Sn, Fe)O3- δ were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe3+ species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides.

  3. Fabrication and patterning of Tl-Ca-Ba-Cu-O superconducting thin films on LaAlO3 substrates

    International Nuclear Information System (INIS)

    Subramanyam, G.; Radpour, F.; Kapoor, V.J.; Lemon, G.H.

    1990-01-01

    This paper reports on high critical transition temperature (high T c ) superconducting thin films of Tl-Ca-Ba-Cu-O (TlCaBaCuO) that were fabricated on LaAlO 3 substrates in an rf magnetron sputtering system. As-deposited thin films were sintered and annealed in a thallium rich ambient to obtain superconductivity with a zero resistance critical temperature (T c ) at 103 K. X-ray diffraction (XRD) results showed that the thin films were highly c-axis oriented with both Tl 2 Ca 2 Ba 2 Cu 3 O x (2223) and Tl 2 Ca 1 Ba 2 Cu 2 O x (2122) phases present. A wet chemical etching process was used for patterning the as-deposited TlCaBaCuO thin films. Linewidths as small as 25 μm were patterned using standard photolithography and wet chemical etching techniques. A ring resonator designed for a center frequency of 30 GHz has been fabricated

  4. Laser cooling of SrOH and magneto-optical trapping of CaF

    Science.gov (United States)

    John Doyle, Harvard University

    2017-04-01

    Several promising goals of modern quantum science will be aided by the extension of precision control beyond atoms and bi-alkali molecules to a diverse set of molecular species with varying complex internal structures. Direct laser cooling and trapping of molecules is one promising route. For example, diatomic molecules with one or more unpaired electron spins and polyatomic molecules with closely spaced opposite parity levels have features advantageous for quantum simulation and precision measurement. Frontier research goals include the creation of new types of ultracold quantum molecular gases, optically trapped samples of molecules that can be read out and addressed individually, and new molecules for searches for particle physics beyond the standard model. Toward this goal, we have recently demonstrated laser slowing and magneto-optical trapping of CaF. Using a two stage cryogenic buffer-gas beam (CBGB) and white light slowing, more than 10,000 molecules are loaded and trapped in a MOT with a temperature below 10 mK. We create a `dual frequency' DC MOT as also demonstrated in and compare its properties to a RF MOT previously achieved with SrF. We will present our most recent progress with CaF. We have also recently demonstrated laser cooling of SrOH, a molecule whose structure illuminates some of the possibilities of ultracold polyatomic molecules. With three distinct vibrational modes, SrOH can be optically prepared in excited vibrational states resulting in nearly degenerate opposite parity levels that can be easily mixed in small electric fields. Using optical cycling, we have demonstrated Doppler and Sisyphus laser cooling of this polyatomic radical. By re-pumping the molecules that decay to the excited Sr-O stretching and bending modes, we reduce the transverse temperature of molecular beam from 50 mK to below 1 mK in one dimension. We will also present other recent work on SrOH. Our approach could be applied to more complex species like SrOCH3 and SrOCH2

  5. Hardness of CaF2 and BaF2 solid lubricants at 25 to 670 deg C

    Science.gov (United States)

    Deadmore, Daniel L.; Sliney, Harold E.

    1987-01-01

    Plastic deformation is a prominent factor in determining the lubricating value of solid lubricants. Little information is available and its direct measurement is difficult so hardness, which is an indirect measure of this property was determined for fluoride solid lubricant compositions. The Vickers hardness of BaF2 and CaF2 single crystals was measured up to 670 C in a vacuum. The orientation of the BaF2 was near the (013) plane and the CaF2 was about 16 degrees from the degrees from the (1'11) plane. The BaF2 has a hardness of 83 kg/sq mm at the 25 C and 9 at the 600 C. The CaF2 is 170 at 25 C and 13 at 670 C. The decrease in hardness in the temperature range of 25 to 100 C is very rapid and amounts to 40% for both materials. Melts of BaF2 and CaF2 were made in a platinum crucible in ambient air with compositions of 50 to 100 wt% BaF2. The Vickers hardness of these polycrystalline binary compositions at 25 C increased with increasing CaF2 reaching a maximum of 150 kn/sq mm near the eutectic. The polycrystalline CaF2 was 14% softer than that of the single crystal surface and BsF2 was 30% harder than the single crystal surface. It is estimated that the brittle to ductile transition temperature for CaF2 and BaF2 is less than 100 C for the conditions present in the hardness tester.

  6. Preparation and characterisation of LaBaCaCu3Ox and La1.3Ba1.7Cu3Ox

    International Nuclear Information System (INIS)

    Takriti, S.; Ulug, B.; Stastny, P.; Mechdadi, F.; Poddar, A.; Placskowski, T.; Ares, O.

    1990-07-01

    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. LaCaBaCu 3 O 7 .1 sample reached zero resistivity at 83 K, while La 1 .3Ba 1 .7Cu 3 O 7 .1 sample reached zero resistivity at 33 K and it has almost metalic behaviour. 4 refs., 9 figs., 4 tabs. (author)

  7. Microwave loss mechanisms in Ba0.25Sr0.75TiO3 films

    International Nuclear Information System (INIS)

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

    2005-01-01

    Trilayer Au(Pt)/Ba 0.25 Sr 0.75 TiO 3 /(Pt)Au thin film varactors are fabricated on high resistive Si substrate and characterized at dc, rf and microwave frequencies. In the frequency range of 10-45 GHz the varactors reveal relatively low losses, the loss tangent is less than 0.025 at 45 GHz. Due to the thick and highly conductive Pt/Au electrodes the metal losses are less than 10%. However, the loss tangent of the ferroelectric film is still 3-5 times higher than that in Ba 0.27 Sr 0.73 TiO 3 single crystal. The analysis of the dc field dependent loss tangent and permittivity in a wide frequency range show that these additional losses are mainly due to the charged defects. Extrapolation of measured low frequency (1 MHz) loss tangents to the microwave region using the power law ω 1/3 is in good agreement with the experiment. We assume that the oxygen vacancies within the grain boundaries of ferroelectric film act as charged defects and cause extrinsic microwave losses. The knowledge of the extrinsic loss mechanism and corresponding microstructure defects is useful in optimization of the varactor design, deposition, and/or annealing process and further improvement of the varactor performance

  8. Study of prediction of fission product behaviors in severe accident. Scoping experiment and basic findings of Cs, Ba and Sr

    International Nuclear Information System (INIS)

    Yamawaki, Michio; Huang, Jintao; Tonegawa, Masahisa; Ono, Futaba; Yasumoto, Masaru; Yamaguchi, Kenji; Sugimoto, Jun.

    1998-02-01

    Fission product release experiment (VEGA: Verification Experiments for fission product Gas/Aerosol release) has been started at JAERI, aiming at accurate source term evaluation during severe accident. Behaviors of fission products released from fuels largely differ with species due to different vapor pressures, which depend on the chemical forms. In response with VEGA, a complementary and basic experiment has been initiated in order to clarify the fission product behaviors up to FP collection chamber by estimating with high accuracy the chemical forms and vapor pressure of released fission products under high temperature environment, and to develop analytical models to evaluate the fission product behaviors in reactor situations. In the present study, as a first step a scoping experiment has been conducted for the estimation of chemical forms and vapor pressure of fission products under high temperature conditions, by introducing oxide compounds of Cs, Ba, and Sr into Knudsen cell. Basic findings have been obtained for Cs, Ba, and Sr, which are important species for the source term evaluation. (author)

  9. 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.

  10. 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...

  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. Properties of half metallic (Ba0.8Sr0.2)2-x La2x/3x/3FeMoO6 double perovskites

    International Nuclear Information System (INIS)

    Serrate, D.; De Teresa, J.M.; Blasco, J.; Morellon, L.; Ibarra, M.R.

    2005-01-01

    Previous work in (Ba 0.8 Sr 0.2 ) 2- x La x FeMoO 6 and Ba 1+ x Sr 1-3 x La 2 x FeMoO 6 have stated electron doping as the most important parameter in terms of T c enhancement. Here we report complementary structural, magnetic and transport properties, say a series where there is no doping and only structural parameters are changed: (Ba 0.8 Sr 0.2 ) 2- x La 2 x /3 x /3 FeMoO 6 . We propose a complete phase diagram where structural and bandfilling impact on the Curie temperature is clearly evidenced

  13. Giant Tc shift in HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ superconductors due to Hg-Tl exchange

    International Nuclear Information System (INIS)

    Gapud, A.A.; Wu, J.Z.; Kang, B.W.; Yan, S.L.; Xie, Y.Y.; Siegal, M.P.

    1999-01-01

    The irreversibility lines of epitaxial thin films of HgBa 2 CaCu 2 O 6+δ and TlBa 2 CaCu 2 O 7-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/T c c >0.8 (where T c 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 T c is not determined by anisotropy. copyright 1999 The American Physical Society

  14. 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.

  15. Phytoremediation modelling - phytoextraction of 137Cs, 133Ba, and 90Sr from liquid media and artificially contaminated soil

    International Nuclear Information System (INIS)

    Smrcek, S.; Masnerova, G.

    2002-01-01

    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 137 Cs, 133 Ba, and 90 Sr 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 90 Sr, 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 90 Sr, 1.5 to 4 % for 137 Cs, and 1 to 6.2 %, for 133 Ba), but in this process, the equilibrium between the soil particles

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    1992-01-01

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

  18. 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.

  19. Ferromagnetism and half metallicity induced by oxygen vacancies in the double perovskite BaSrNiWO{sub 6}: DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Aharbil, Y. [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Labrim, H. [Unité Science de la Matière/DERS/Centre National de l’Energie, des Sciences et des Techniques Nucléaires (CNESTEN), Rabat (Morocco); Benmokhtar, S.; Haddouch, M. Ait [Laboratoire de Chimie Physique des Matériaux LCPM, Faculté des Sciences Ben M' Sik, Casablanca (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco); Belhaj, A. [LIRST, Département de Physique, Faculté Poly-disciplinaire, Université Sultan Moulay Slimane, Béni Mellal (Morocco); Ez-Zahraouy, H.; Benyoussef, A. [Mohammed V University in Rabat, Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E. URAC-12, B.P. 1014, Rabat (Morocco)

    2016-11-01

    Using the spin polarized density functional theory (DFT) and exploring the Plane-Wave Self-Consistent Field (PWscf) code implemented in Quantum-ESPRESSO package, we investigate the effect of the Oxygen vacancies (V{sub O}) and the Oxygen interstitial (O{sub i}) on the double perovskite BaSrNiWO{sub 6}. This deals with the magnetic ordering and the electronic structure in such a pure sample exhibiting the insulating anti-ferromagnetic (AFM) state. This study shows that the presence of oxygen deficient defects converts the insulating to half metal with ferromagnetic or anti-ferromagnetic states. The magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell. However, it has been shown that the Oxygen interstitial preserves the anti-ferromagnetic propriety. We have computed the formation energies of different positions of the Oxygen vacancy (V{sub O}) and the Oxygen interstitial (O{sub i}) in the BaSrNiWO{sub 6} compound. We showed that the formation of V{sub O} is easier and vice versa for the O{sub i} formation. The obtained results reveal(V{sub O}) and the Oxygen interstitial (O{sub i}) that the anti-ferromagnetic can be converted to ferromagnetic in the double perovskite BaSrNiWO{sub 6} induced by Oxygen vacancies V{sub O}. - Highlights: • We have studied the ferromagnetism and Half Metallicity in Double Perovskite BaSrNiWO{sub 6}. • We have applied the Ab-inito calculations using the DFT approach. • We showed the effects induced by Oxygen Vacancies and Oxygen interstitial. • We found that the magnetic ordering in BaSrNiWO{sub 6−δ} depends on the position of the Oxygen vacancy in the unit cell.

  20. Ca isotope fractionation and Sr/Ca partitioning associated with anhydrite formation at mid-ocean ridge hydrothermal systems: An experimental approach

    Science.gov (United States)

    Syverson, D. D.; Scheuermann, P.; Pester, N. J.; Higgins, J. A.; Seyfried, W. E., Jr.

    2016-12-01

    The elemental and isotopic mass balance of Ca and Sr between seawater and basalt at mid-ocean ridge (MOR) hydrothermal systems is an integrated reflection of the various physiochemical processes, which induce chemical exchange, in the subseafloor. Specifically, the processes of anhydrite precipitation and recrystallization are recognized to be important controls on governing the Ca and Sr elemental and isotope compositions of high temperature vent fluids, however, few experimental data exist to constrain these geochemical effects. Thus, to better understand the associated Sr/Ca partitioning and Ca isotope fractionation and rate of exchange between anhydrite and dissolved constituents, anhydrite precipitation and recrystallization experiments were performed at 175, 250, and 350°C and 500 bar at chemical conditions indicative of active MOR hydrothermal systems. The experimental data suggest that upon entrainment of seawater into MOR hydrothermal systems, anhydrite will precipitate rapidly and discriminate against the heavy isotopes of Ca (Δ44/40Ca(Anh-Fluid) = -0.68 - -0.25 ‰), whereas Sr/Ca partitioning depends on the saturation state of the evolving hydrothermal fluid with respect to anhydrite at each PTX (KD(Anh-Fluid) = 1.24 - 0.55). Coupling experimental constraints with the temperature gradient inferred for high temperature MOR hydrothermal systems in the oceanic crust, data suggest that the Ca isotope and Sr elemental composition of anhydrite formed near the seafloor will be influenced by disequilibrium effects, while, at higher temperatures further into the oceanic crust, anhydrite will be representative of equilibrium Sr/Ca partitioning and Ca isotope fractionation conditions. These experimental observations are consistent with analyzed Sr/Ca and Ca isotope compositions of anhydrites and vent fluids sampled from modern MOR hydrothermal systems1,2 and can be used to further constrain the geochemical effects of hydrothermal circulation in the oceanic crust

  1. Electronic states of doped spin ladders (Sr,Ca)14Cu24O41

    International Nuclear Information System (INIS)

    Mizuno, Yoshiaki; Tohyama, Takami; Maekawa, Sadamichi.

    1997-01-01

    We examine the electronic states of Sr 14-x Ca x Cu 24 O 41 by the ionic and cluster model approach. It is found that self-doped holes are likely to stay on the chain at x = 0 and Ca substitution drives the holes to move to the ladder. This feature is caused by changes of the positions of (Sr,Ca) layers, which results in enhancement of the electrostatic potentials in the chain. The optical conductivity is calculated with application of the exact diagonalization method to small Cu-O clusters. It is shown that the excitations below 2 eV are governed by the ladder, giving rise to the spectral weight transfer from the charge-transfer excitation at around 2 eV to low energy Drude excitation, while the contribution from the chain mainly emerges in a higher energy region showing large spectral weight at around 3 eV. These findings provide a consistent explanation for the results of a recent experiment. (author)

  2. Multicentennial Record of North Atlantic Primary Productivity and Sea-Ice Variability Archived in Coralline Algal Ba/Ca

    Science.gov (United States)

    Chan, P. T. W.; Halfar, J.; Adey, W.; Hetzinger, S.; Zack, T.; Moore, K.

    2016-02-01

    Accelerated warming and melting of Arctic sea-ice has been associated with significant increases in phytoplankton productivity. However, satellite-based chlorophyll estimates and in-situ instrumental observations of marine productivity have only been available in select regions for the last few decades. Barium has previously been shown to be severely depleted in surface waters due to biological scavenging during periods of intense phytoplankton blooms. Here we present an annually-resolved multicentennial record of coralline algal barium-to-calcium ratios (Ba/Ca), as a proxy for North Atlantic phytoplankton productivity associated with sea-ice variability in Labrador, Canada extending well into the Little Ice Age (LIA). Coralline algal Ba/Ca demonstrates statistically significant correlations to observational and proxy records of sea-ice cover, extent, and transport variability, and shows a persistent pattern of covariability that is broadly consistent with the timing and phasing of the Atlantic Multidecadal Oscillation (AMO). Higher (lower) algal Ba/Ca values are interpreted as decreased (increased) primary productivity coinciding with cooling (warming) sea surface temperatures and the expansion (melting) of sea-ice. Comparison to a tree-ring proxy AMO index demonstrates more frequent positive Ba/Ca excursions (indicating reduced productivity) associated with AMO cool phases during the LIA, followed by a decline in Ba/Ca beginning in 1910 to present. Our multicentennial record of coralline algal Ba/Ca ratios indicates that the sharp rise in primary productivity since 1950 in the Subarctic North Atlantic is unprecedented in the last 365 years, and is in agreement with recent observations of increasing productivity in the Arctic Ocean. The ongoing increase in phytoplankton productivity is expected to fundamentally alter marine biodiversity and trophic dynamics as warming and freshening of the surface layer is projected to intensify over the coming century.

  3. Luminescent properties of Sr2.5−3x/2Ba0.5SmxAlO4F oxyfluorides

    International Nuclear Information System (INIS)

    Park, Sangmoon

    2012-01-01

    Effective orange Sm 3+ -doped Sr 2.5 Ba 0.5 AlO 4 F phosphors excited at 254 and 408 nm excitation were prepared by the solid-state method. The excitation and emission spectra of Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4 F and Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4−α F 1−δ (x=0.001∼0.1) based on photoluminescence spectroscopy are investigated. The defects in anion-deficient Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4−α F 1−δ (x=0.001, 0.01) are monitored by broad-band photoluminescence emission centered near 480 nm along with the orange emission transitions of Sm 3+ . CIE values and relative luminescent intensities of Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4 F and Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4−α F 1−δ by changing the Sm 3+ content (x=0.001∼0.1) are discussed. - Highlights: ► Under the excitation of 408 nm competent orange emitting Sr 2.5−3x/2 Ba 0.5 Sm x AlO 4 F phosphor is initiated. ► Sm 3+ -activated oxyfluoride phosphor is quite effective to prepare white-emitting light for near-UV LED applications. ► Defects could be visibly created in the Sr 2.5−3x/2 Ba 0.5 Sm x Al O 4 F host lattices when Sm 3+ ions are doped less than 5 mol %. ► The gradual substitution of Sm 3+ contents in oxyfluoride hosts is amenable to change CIE values and desired emitting intensity.

  4. Structure and oxygen stoichiometry of SrCo0.8Fe0.2O3-d and Ba0.5Sr0.5Co0.8Fe0.2O3-d

    NARCIS (Netherlands)

    McIntosh, Steven; McIntosh, S.; Vente, Jaap F.; Haije, Wim G.; Blank, David H.A.; Bouwmeester, Henricus J.M.

    2006-01-01

    High temperature X-ray diffraction (HT-XRD), temperature programmed desorption (TPD), thermogravimetric analysis–differential thermal analysis (TGA/DTA) and neutron diffraction were combined to determine the structure and oxygen stoichiometry of SrCo0.8Fe0.2O3−δ (SCF) and Ba0.5Sr0.5Co0.8Fe0.2O3−δ

  5. 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 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. (C) 2004 Elsevier Ltd. All rights reserved....

  6. Flux pinning in hot isostatically pressed Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Miller, D.J.; Sengupta, S.; Hettinger, J.D.; Shi, D.; Gray, K.E.; Nash, A.S.; Goretta, K.C.

    1992-01-01

    Magnetic hysteresis data were taken from 4.2 to 35 K on Bi 2 Sr 2 CaCu 2 O x samples that were hot isostatically pressed at 105 MPa in an inert atmosphere at 825 degree C. One set of samples was pressed for only 15 min while the other was pressed for 120 min. The samples pressed for 15 min contained a high density of dislocations and planar faults, while the samples pressed for 120 min contained fewer dislocations and faults, with most dislocations present within subgrain boundaries. The samples with the complex dislocation/planar fault structures exhibited substantially larger hysteresis loops, suggesting enhanced flux pinning

  7. Combined effect of 131I and osteotropic radionuclide of 90Sr and 45Ca

    International Nuclear Information System (INIS)

    Borisova, V.V.; Vetukh, V.A.; Rusanova, O.V.

    1988-01-01

    Combined effect of 131 I and osteotropic 45 Ca and 90 Sr on blood formation, reproduction and life span of laboratory animals was considered. It was shown that combined irradiation of thyroid and bone marrow with doses not exceeding or equal 1 Gy doesn't result in changes of blood formation or life span, but leads to definite violations in stem spermatogonia which bring about intra-uterine death of progeny. This fact is explained as a result of indirect radiation effect for the dose for gonads was 0.1 Gy. 3 tabs

  8. CO2-laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

    Science.gov (United States)

    Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J. B.; Danforth, S.; Wilkens, B. J.

    1990-03-01

    We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO2-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-Å thin films have a Tc (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm2.

  9. Complex cubic metallides AM{sub ∝6} (A=Ca, Sr; M=Zn, Cd, Hg). Synthesis, crystal chemistry and chemical bonding

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Michael; Wendorff, Marco; Roehr, Caroline [Freiburg Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-09-01

    In a systematic synthetic, crystallographic and bond theoretical study, the stability ranges as well as the distribution of the isoelectronic late d-block elements Zn, Cd and Hg (M) in the polyanions of the YCd{sub 6}-type phases (Ca/Sr)Cd{sub 6} have been investigated. Starting from Ca(Cd/Hg){sub 6}, 12-30% of the M atoms can be substituted by Zn, which gradually occupies the center of the empty cubes. In all ternary compounds, smaller/less electronegative Zn/Cd atoms occupy the disordered tetrahedra explaining the lack of the YCd{sub 6}-type for pure mercurides. Along the section SrCd{sub 6}-SrHg{sub 6}, the ordered Eu{sub 4}Cd{sub 25}-type is formed (Sr{sub 4}Cd{sub 16.1}Hg{sub 8.9}: cF1392, Fd anti 3, a=3191.93(5) pm, R1=0.0404). Besides, two new complex cubic Ca phases appear at increased Zn proportion: Ca{sub 2}Zn{sub 5.1}Cd{sub 5.8}, which exhibits a nearly complete site preference of Zn and Cd, crystallizes in the rare cubic Mg{sub 2}Zn{sub 11}-type structure (cP39-δ, Pm anti 3, a=918.1(1) pm, R1=0.0349). In the Ca-Hg system, an increased Zn proportion yielded the new compound CaZn{sub 1.31}Hg{sub 3.69} (cF480, F anti 43m, a=2145.43(9) pm, R1=0.0572), with a complex cubic structure closely related to Ba{sub 20}Hg{sub 103}. All structures, which are commonly described using nested polyhedra around high-symmetric sites, are alternatively described in accordance with the calculated electron densities and charge distribution: building blocks are face-sharing [M{sub 4}] tetrahedra (star polyhedra such as TS, IS, OS), each with a cage-critical point in its center, and [M{sub 8}] cubes (deformed TS), which are either empty, distorted or filled. The M element distribution in the anion is determined by size criteria and the difference in electronegativity, which induces a preferred formation of heteroatomic polar bonds.

  10. Microscopic origins of the large piezoelectricity of leadfree (Ba,Ca)(Zr,Ti)O3.

    Science.gov (United States)

    Nahas, Yousra; Akbarzadeh, Alireza; Prokhorenko, Sergei; Prosandeev, Sergey; Walter, Raymond; Kornev, Igor; Íñiguez, Jorge; Bellaiche, L

    2017-06-20

    In light of directives around the world to eliminate toxic materials in various technologies, finding lead-free materials with high piezoelectric responses constitutes an important current scientific goal. As such, the recent discovery of a large electromechanical conversion near room temperature in (1-x)Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 compounds has directed attention to understanding its origin. Here, we report the development of a large-scale atomistic scheme providing a microscopic insight into this technologically promising material. We find that its high piezoelectricity originates from the existence of large fluctuations of polarization in the orthorhombic state arising from the combination of a flat free-energy landscape, a fragmented local structure, and the narrow temperature window around room temperature at which this orthorhombic phase is the equilibrium state. In addition to deepening the current knowledge on piezoelectricity, these findings have the potential to guide the design of other lead-free materials with large electromechanical responses.

  11. Synthesis and properties of Tl endash Ba endash Ca endash Cu endash O superconductors

    International Nuclear Information System (INIS)

    Siegal, M.P.; Venturini, E.L.; Morosin, B.; Aselage, T.L.

    1997-01-01

    We review the synthesis methods and properties of single crystal, powder and thin film TlBaCaCuO high-temperature superconducting (Tl-HTS) materials. With transition temperatures ≥100K for several compounds, Tl-HTS materials present real opportunities for applications above 77 K. Experiments using (1) single crystals: determined precise structural parameters and identified the complex Tl 1+ -Tl 3+ equilibrium model; (2) powders: studied the complex thermodynamic phase diagram; and (3) epitaxial films: have studied fundamental properties such as electron pair symmetry and the effect of controlled extrinsic defects on flux pinning strength, as well as providing the large-area surfaces required for device applications. copyright 1997 Materials Research Society

  12. Cross-bridge blocker BTS permits direct measurement of SR Ca2+ pump ATP utilization in toadfish swimbladder muscle fibers.

    Science.gov (United States)

    Young, Iain S; Harwood, Claire L; Rome, Lawrence C

    2003-10-01

    Because the major processes involved in muscle contraction require rapid utilization of ATP, measurement of ATP utilization can provide important insights into the mechanisms of contraction. It is necessary, however, to differentiate between the contribution made by cross-bridges and that of the sarcoplasmic reticulum (SR) Ca2+ pumps. Specific and potent SR Ca2+ pump blockers have been used in skinned fibers to permit direct measurement of cross-bridge ATP utilization. Up to now, there was no analogous cross-bridge blocker. Recently, N-benzyl-p-toluene sulfonamide (BTS) was found to suppress force generation at micromolar concentrations. We tested whether BTS could be used to block cross-bridge ATP utilization, thereby permitting direct measurement of SR Ca2+ pump ATP utilization in saponin-skinned fibers. At 25 microM, BTS virtually eliminates force and cross-bridge ATP utilization (both BTS. At 25 microM, BTS had no effect on SR pump ATP utilization. Hence, we used BTS to make some of the first direct measurements of ATP utilization of intact SR over a physiological range of [Ca2+]at 15 degrees C. Curve fits to SR Ca2+ pump ATP utilization vs. pCa indicate that they have much lower Hill coefficients (1.49) than that describing cross-bridge force generation vs. pCa (approximately 5). Furthermore, we found that BTS also effectively eliminates force generation in bundles of intact swimbladder muscle, suggesting that it will be an important tool for studying integrated SR function during normal motor behavior.

  13. Melt processing of the Bi2Sr2CaCu2Oy superconductor in oxygen and argon atmospheres

    International Nuclear Information System (INIS)

    Holesinger, T.G.; Miller, D.J.; Chumbley, L.S.

    1992-08-01

    Solidification and subsequent annealing of Bi 2 Sr 2 CaCu 2 O y (2212) in oxygen and argon atmospheres were investigated in order to identify alternative processing routes for controlling microstructures and superconducting properties. In addition to 2212, several other phases formed on cooling in O 2 and did not disappear upon subsequent annealing. Crystallization in Ar resulted in a divorced eutetic structure of Bi 2 Sr 3-x Ca x O y and Cu 2 O/CuO. The superconductor was formed on subsequent anneals. Samples melted in Ar and then annealed generally possessed a more uniform microstructure compared with samples that were melted in oxygen and annealed. Compositional measurements of the 2212 phase suggest that CaO segregation in the melt may be minimized with an overall composition such as Bi 2.15 Sr 2 Ca 0.85 Cu 2 O y

  14. Effect of Sintering Time on Superconducting Wire Bi-Pb-Sr-Ca-Cu-O With Dopant MgO Sheated Ag Using Powder in Tube Method

    Directory of Open Access Journals (Sweden)

    Hariyati Lubis

    2018-01-01

      DAFTAR PUSTAKA Abbas M.M., Abass L.K and Salman U., (2012, Influences of Sintering Time on the Tc of Bi2-xCuxPb0.3Sr2Ca2Cu3010+ High Temperature Superconductors, Energy Procedia 18, 215-224  Abbas, M.M., Abbas, L.K., Bahedh, H.S. 2015. Superconducting Properties of Bi2-SbxPb0,3Sr1,9Ba0,1Ca2Cu3O10+δ Compounds. Journal of Applied Science Research. 11. 22: 164-172 Darsono, N., Imaduddin, A., Raju, K., Yoon, D.H., (2015, Synthesis and Characterization of Bi1.6Pb0.4Sr2Ca2Cu3O7 Superconducting Oxide by High-Energy Milling, J Supercond Nov Magn. E. Chew,. (2010, Superconducting Transformer Design And Construction, University of Canterbury, Christchurch, New Zealand. March Hamadneh, I., Halim, S. A., dan Lee, C. K., (2006,  Characterization of Bi1.6Pb0.4Sr2Ca2Cu3Oy Ceramic Superconductor Prepared Via Coprecipitation Method at Different Sintering Time, J. Mater. Sci, 41: 5526-5530. Hermiz G.Y., Aljurani B.A., Beayaty M.A., (2014, Effect of Mn Substitution on the Superconducting Properties of Bi1.7Pb0,3Sr2Ca2-xMnxCu3O10+, International Journal Of Engineering and Advanced Technology (IJEAT. 3. 4: 213-217 John R Hull, (2003, Applications of high-temperature superconductors in power technology, Reports on Progress in Physics, Volume 66, Number 11 Lu, X.Y., Yi, D., Chen, H., Nagata, A. 2016. Effect of Sn, MgO and Ag2O mix-doping on the formation and superconducting properties of Bi-2223 Ag/tapes. Physics Procedia. 81: 129-132 Meretliev Sh., Sadykov K.B., Berkeliev A., (2000, Doping of High Temperature Superconductors, Turk J Phy.24: 39-48 Mohammed, N. H., Ramadhan A., Ali I. A., Ibrahim, I. H., dan Hassan, M. S, (2012, Optimizing the Preparation Conditions of Bi-2223 Superconducting Phase Using PbO and PbO2, Materials Sciences and Applications, 3: 224-233. Roumie, M., Marhaba, S., Awad R., Kork M., Hassan I., Mawassi R., (2014, Effect of Fe2O3 Nano-Oxide Addition on the Superconducting Properties of the (Bi,Pb-2223 Phase, Journal of Supercond Nov Magn, 27: 143-153 Serkan

  15. Sr/Ca ratios in cold-water corals - a 'low-resolution' temperature archive?

    Science.gov (United States)

    Rüggeberg, Andres; Riethdorf, Jan-Rainer; Raddatz, Jacek; López Correa, Matthias; Montagna, Paolo; Dullo, Wolf-Christian; Freiwald, André

    2010-05-01

    One of the basic data to understand global change and past global changes is the measurement and the reconstruction of temperature of marine water masses. E.g. seawater temperature controls the density of seawater and in combination with salinity is the major driving force for the oceans circulation system. Geochemical investigations on cold-water corals Lophelia pertusa and Desmophyllum cristagalli indicated the potential of these organisms as high-resolution archives of environmental parameters from intermediate and deeper water masses (Adkins and Boyle 1997). Some studies tried to use cold-water corals as a high-resolution archive of temperature and salinity (Smith et al. 2000, 2002; Blamart et al. 2005; Lutringer et al. 2005). However, the fractionation of stable isotopes (delta18O and delta13C) and element ratios (Sr/Ca, Mg/Ca, U/Ca) are strongly influenced by vital effects (Shirai et al. 2005; Cohen et al. 2006), and difficult to interpret. Nevertheless, ongoing studies indicate the potential of a predominant temperature dependent fractionation of distinct isotopes and elements (e.g. Li/Ca, Montagna et al. 2008; U/Ca, Mg/Ca, delta18O, Lòpez Correa et al. 2008; delta88/86Sr, Rüggeberg et al. 2008). Within the frame of DFG-Project TRISTAN and Paläo-TRISTAN (Du 129/37-2 and 37-3) we investigated live-collected specimens of cold-water coral L. pertusa from all along the European continental margin (Northern and mid Norwegian shelves, Skagerrak, Rockall and Porcupine Bank, Galicia Bank, Gulf of Cadiz, Mediterranean Sea). These coral samples grew in waters characterized by temperatures between 6°C and 14°C. Electron Microprobe investigations along the growth direction of individual coral polyps were applied to determine the relationship between the incorporation of distinct elements (Sr, Ca, Mg, S). Cohen et al. (2006) showed for L. pertusa from the Kosterfjord, Skagerrak, that ~25% of the coral's Sr/Ca ratio is related to temperature, while 75% are influenced

  16. Formation mechanism of the (Bi,Pb)-Sr-Ca-Cu-O system 2223 phase

    International Nuclear Information System (INIS)

    Malachevsky, M.T.; Esparza, D.A.

    1995-01-01

    Isothermal treatments were used to investigate the transformation mechanism from 2212 to 2223 phase on the (Bi,Pb)-Sr-Ca-Cu-O system. Silver was added in 10 wt% to observe modifications in the reaction. With the aid of Rietveld refinement, the fractional conversion of 2223 phase with time was calculated. Silver addition was observed to slow down the formation of the 2212 phase, and hence of the 2223 phase, and stabilized the Pb Ca 2 O 4 phase. SEM analysis showed that the 110 K phase grew by deposition of a viscous liquid in layers over the platelets. We assigned this mechanism to the content superficial nucleation of 2223 phase on 2212 plates, the rate of formation being controlled by nuclei growth, that is by the velocity of migration of the liquid

  17. Open-Framework Structures of Anhydrous Sr(CF3COO)2 and Ba(CF3COO)2.

    Science.gov (United States)

    Dissanayake, K Tauni; Mendoza, Laura M; Martin, Philip D; Suescun, Leopoldo; Rabuffetti, Federico A

    2016-01-04

    Anhydrous Sr(CF3COO)2 and Ba(CF3COO)2 open-framework structures featuring three-dimensional connectivity of metal-oxygen polyhedra were crystallized from a mixture of water and CF3COOH. Crystallization was induced via evaporation of the solvent mixture under a dry nitrogen flow. This approach differs from that routinely employed for crystallization of metal trifluoroacetates, which achieves solvent evaporation by heating under air and yields hydrated salts. Thermogravimetric and differential thermal analysis as well as single-crystal and synchrotron powder X-ray diffraction were employed to characterize the alkaline-earth trifluoroacetate products. Neither thermal analysis nor single-crystal X-ray diffraction detected the presence of crystallization water molecules, demonstrating these trifluoroacetates can be obtained in anhydrous form. Single-crystal X-ray diffraction studies showed that Sr(CF3COO)2 and Ba(CF3COO)2 are isostructural and crystallize in the rhombohedral R3̅ space group. Both compounds belong to the class of organic-inorganic extended hybrids and exhibit an open-framework structural motif with three-dimensional connectivity of the metal-oxygen polyhedra and one-dimensional channels along the c axis. The channels are decorated with the trifluoromethyl groups of the trifluoroacetate ligands, and their average (minimum) diameters are ∼3.75 (2.60) and 3.45 (2.25) Å for Sr(CF3COO)2 and Ba(CF3COO)2, respectively. This size range is comparable to the kinetic diameter of small molecules such as hydrogen (2.3 Å). Chemical substitution of barium for strontium affects not only the diameter of the channels but also the spatial arrangement of the trifluoromethyl groups within the channels and the coordination environment of the metal atoms. The different coordination requirements of the strontium and barium atoms are accommodated through the displacement of one of the two chemically distinct trifluoroacetate ligands relative to the metal center.

  18. 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.

  19. Superconducting thin films of BiSrCaCuO made by sequential electron beam evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, J.; Anderson, A.C.; Tsauer, B.Y.; Strauss, A.J.

    1989-03-01

    Superconducting thin films of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ have been made by sequential electron-beam evaporation of multiple layers of Bi and Cu metals and (Sr,Ca)F/sub 2/ on MgO substrates. The films were annealed at high temperature, first in wet O/sub 2/ and then in dry O/sub 2/, and cooled to room temperature in dry O/sub 2/. The resulting films which are -- 1 ..mu..m thick, have transition temperatures of -- 85 K. X-ray diffraction shows that the films are preferentially oriented with their c-axis perpendicular to the MgO substrate. The authors' best film has a zero-resistance temperature of 90 K and critical current densities of 8 x 10/sup 4/ A/cm/sup 2/ at 77 K and 2.5 x 10/sup 5/ A/cm/sup 2/ at 4.2 K.

  20. Electrical conductivity of cobalt–titanium substituted SrCaM hexaferrites

    International Nuclear Information System (INIS)

    Eraky, M.R.

    2012-01-01

    A series of polycrystalline M-type hexagonal ferrites with the composition Sr 0.5 Ca 0.5 Co x Ti x Fe 12−2x O 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, σ dc , exhibited a semiconductor behavior. The negative sign of thermoelectric power coefficient S reveals that all samples are n-type semiconductors. Both σ dc and mobility, μ d , increases with the substitution of Co 2+ and Ti 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: ► SrCaCoTiM hexaferrites have been prepared by conventional ceramic technique. ► The electrical conductivity exhibited a semiconductor behavior. There is an increase in conductivity up to x=0.4 for Co and Ti substitution. ► The hopping conduction is the predominant conduction mechanism.

  1. Ultrasonic study of structural instability of monocrystalline and polycrystalline Bi-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Wang, Yening; Wu, Jin; Shen, Huimin; Zhu, Jinsong; Chen, Xiaohua; Yan, Yifeng; Zhao, Zhongxian

    1990-01-01

    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 Bi 2 Sr 2 CaCu 2 O 8 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 T c . The origin of the overall trend of elastic stiffening that appears in the measurements so far for high-T c oxides is discussed

  2. Defects and Disorder in Magnetoresistive Double Perovskite A_2FeMoO6 (A=Sr,Ba)

    Science.gov (United States)

    Kruk, R.; Brown, D. E.; Chmaissem, O.; Feng, R.; Dabrowski, B.; Kimball, C. W.; Johnson, C. E.; Alp, E. E.; Jorgensen, J. D.

    2001-03-01

    A_2FeMoO6 (A = Sr, Ba) is a double perovskite having an ordered ferrimagnetic structure of Fe and Mo magnetic superlattices. The Fe and Mo atoms are ordered on alternating, corner-shared octahedral sites, however, the ordered array can have imperfections that are dependent upon synthesis conditions. Mossbauer spectroscopy was used to examine the local magnetic and structural environment around the Fe atoms. Measurements were made on polycrystalline samples with varying degrees of stoichiometry using magnetic fields of 0 and 7 Telsa. We were able to clearly resolve the iron nuclei with flipped magnetic moments (iron having a magnetic dipole moment parallel to the Mo magnetic dipoles). The amount of disorder induced by various synthesis conditions was consistent with magnetization measurements that consistently show a lower than expected average magnetic dipole moment.

  3. Strain profile and polarization enhancement in Ba0.5Sr0.5TiO3 thin films

    International Nuclear Information System (INIS)

    Amir, F.Z.; Donner, W.; Aspelmeyer, M.; Noheda, B.; Xi, X.X.; Moss, S.C.

    2012-01-01

    The sensitivity of spontaneous polarization to epitaxial strain for both 10 and 50 nm thick Ba 0.5 Sr 0.5 TiO 3 (BSTO) ferroelectric thin films has been studied. Crystal truncation rod (CTR) profiles in the 00L directions at different wavelengths, and grazing incidence diffraction (GID) in the 0K0 direction on a single crystal have been recorded. Modeling of the CTR data gives a detailed picture of the strain and provides clear evidence of the film out-of-plane expansion at the surface, an increase of the polarization, as well as a contraction at the interface. GID data confirm the fitting of the CTR, showing an in-plane expansion of the BSTO film at the interface and a contraction at the surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Kinetics and thermodynamics of B-site cation order in (Sr,Ba)2FeSbO6 perovskite

    Science.gov (United States)

    Tiittanen, T.; Karppinen, M.

    2018-02-01

    Several sample series of the (Sr0.5Ba0.5)2FeSbO6 double-perovskite compound are synthesized under various heat-treatment conditions starting from a sol-gel prepared precursor to investigate the kinetics and thermodynamics of the B-site cation ordering. The synthesis yields samples with different levels of Fe/Sb ordering ranging from essentially disordered up to fully ordered depending on the synthesis temperature and duration. In the temperature range 1050-1200 °C the degree of order is kinetically controlled following Johnson-Mehl-Avrami-Kolmogorov type kinetics, while at 1300 °C the thermodynamic equilibrium is quickly reached such that higher than 95% ordering degrees are obtained in heat-treatment periods as short as couple of hours. Also importantly, for the differently synthesized single-phase samples a linear relationship between the degree of order and the cubic sub-cell dimension is seen.

  5. 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.

  6. K2MoO4-CaMoO4-BaMoO4 system

    International Nuclear Information System (INIS)

    Gasanaliev, A.M.; Trunin, A.S.; Dibirov, M.A.

    1979-01-01

    The liquidus of the K 2 MoO 4 -CaMoO 4 -BaMoO 4 ternary system has been studied by differential thermal (DTA) and by visual polythermal (VPT) analyses. The compositions and temperatures of non-variant points have been determined, the borders between the crystallizing phase regions being found

  7. Influence of bismuth on properties and microstructures of Sr0⋅5Ba0 ...

    Indian Academy of Sciences (India)

    tric detectors, tunable microwave devices, phase shifters, electroluminescence display etc (Liou and Chiou 1997;. Liu et al 2000). So, Sr1–xBaxTiO3 films have gained in- creasing interest in the investigation and fabrication of thin films. The exploitation of BST thin films for applications in nonvolatile memory of high memory ...

  8. Dielectric and Energy Storage Properties of Ba0.65Sr0.35TiO3 Ceramics Modified by BiNbO4

    Science.gov (United States)

    Zheng, Yi; Zhang, Jihua; Wei, Meng; Dong, Xiangxiang; Huang, Jiapeng; Wu, Kaituo; Chen, Hongwei

    2018-02-01

    (1 - x) (Ba0.65Sr0.35TiO3)-xBiNbO4 (x = 0.0-0.15) ceramic were prepared by solid-state reaction method. The phase composition, microstructure, dielectric properties, polarization-electric field, breakdown strength and energy storage behaviors for the BiNbO4-modified Ba0.65Sr0.35TiO3 ceramics were investigated. With the addition of BiNbO4, the remnant polarization and saturation polarization decreased and the nonlinearity was suppressed. When x = 0.07, the maximum recoverable energy storage achieved was 0.5 J/cm3, 1.5 times that of un-doped Ba0.65Sr0.35TiO3 ceramics, with an efficiency of 96.89% and a breakdown electric field reaching 15.3 kV/mm. Therefore, BiNbO4 doping could improve the energy storage properties of Ba0.65Sr0.35TiO3 for high-energy pulse capacitor application.

  9. Effects of Sr2+ substitution on photoluminescence characteristics of Ba1−x−ySryZrSi3O9:xEu2+ phosphors

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  10. In situ templating synthesis of conic Ba0⋅ 5 Sr0⋅ 5 Co0⋅ 8 Fe0⋅ 2 ...

    Indian Academy of Sciences (India)

    Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of Ba0.5Sr0.5CoO3 (BSC) in hexagonal lattice structure and with conic particle shape was preferentially formed during calcination at low temperature. BSCF perovskite was then produced by the in situ templating of BSC with iron diffusing into ...

  11. The effect of diameter ratio between transducers and reactor in sonication-assisted synthesis of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Manaf, A., E-mail: azwar@ui.ac.id; Fahmi, Agam Aidil [Department of Physics, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Yustanti, Erlina [Department of Physics, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Department of Metallurgy, Faculty of Engineering, University of Sultan AgengTirtayasa Jl. Jenderal Sudirman KM 03 Cilegon-Banten 65134 (Indonesia)

    2016-04-19

    This paper describes the particle size characterization of mechanically alloyed Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} prepared with the aid of a high-power ultrasonic destruction. Analytical-grade BaCO{sub 3}, TiO{sub 2} and SrCO{sub 3} with a purity greater than 99 wt.% were used as precursors for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3}. The mechanically powders were respectively sintered at 1200 °C for 3 hours to form crystalline powders. This work is aimed at studying the effect of diameter ratio between reactor and transducer of a high power sonicator on the Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} nanoparticles formation. The presence of a single phase of the two materials was confirmed by X-Ray Diffraction (XRD). The concentration of the particles in demineralized water was 3.0 g / 100 mL which become the object of 3 hours ultrasonic destruction subjected to the application of transducer in which the ratio between the diameter of the reactor and the transducer (D/d) was fixed at 1.4, 1.6 and 1.8 respectively. It was found that the mean particle size before the ultrasonic destruction was 538 nm for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and 480 nm for Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3}. With D/d of 1.8, the mean particle size of the two materials was found to decrease drastically to 38 nm and 24 nm, respectively. These mean particle sizes were respectively comparable with that of the crystallite size of the particles derived using the Whole Powder Pattern Modelling (WPPM) from which the mean crystallite size of 22 nm for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and 14 nm for Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} were obtained. It is then confirmed single nanocrystallite Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} particles were already achieved. We can conclude that the ultrasonic destruction to mechanically milled crystalline particles would be one

  12. Accumulation of 90Sr, Ca, Mg, K and Na in crane's-bill plants cultavated on soil and hydroponics

    International Nuclear Information System (INIS)

    Analyan, V.L.; Sarkisyan, G.A.

    1981-01-01

    Accumulation of 90 Sr in plants under the conditions of soil and hydroponic cultures from the viewpoint of the possibility of obtaining ''pure'' vegetable production has been studied. Predominant absorption of 90 Sr by soil plants as compared with calcium is shown. In the course of using the hydroponic cultivation method redominant radiostrontium absorption has been manifested to all investigated nuclides including potassium. The accumulation coefficients analysis has shown that among soil plants the fisarst place is occupied by potassium, while the 90 Sr coefficients are greater than Ca on hydroponics, where the true, not distorted by soil sorption processes absorptive plant capacity has been manifested, the first places in the series are occupied by 90 Sr and K, then come Ca and Mg

  13. Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

    Science.gov (United States)

    Navarro, H.; Sirena, M.; González Sutter, J.; Troiani, H. E.; del Corro, P. G.; Granell, P.; Golmar, F.; Haberkorn, N.

    2018-01-01

    We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current-voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

  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. Structural effects of hydrostatic pressure in Sr1-xMxCuO2 (M=La,Ca) and Sr4Cu6O10

    International Nuclear Information System (INIS)

    Shaked, H.; Shimakawa, Y.; Hunter, B.A.; Radaelli, P.G.; Dabrowski, B.; Hitterman, R.L.; Jorgensen, J.D.; Han, P.D.; Payne, D.A.; Kikkawa, S.; Er, G.; Kanamaru, F.

    1994-01-01

    Pressure effects on the tetragonal infinite-layer structure were studied in superconducting Sr 0.9 La 0.1 CuO 2 (electron-doped) and Sr 0.7 Ca 0.3 CuO 2 (hole-doped) samples, and in an insulating nonsuperconducting Sr 0.14 Ca 0.86 CuO 2 sample, using time-of-flight neutron powder diffraction. Neutron-diffraction measurements, with the sample at room temperature, were performed at several hydrostatic pressures up to ∼0.6 GPa on each of the three samples, using a helium-gas pressure cell. The measured compressibilities, which are similar for the three samples, show a large anisotropy, and are in a good agreement with first-principles calculations performed for undoped Sr 0.7 Ca 0.3 CuO 2 . Atomic size effects of the A atom in ACuO 2 on the crystal lattice are discussed and are compared with the pressure effects. A relation is found between the in-plane compressibilities among n-layer (n=1,2,3 . . .,∞) structures of high-T c superconductors

  16. Structure and magnetic properties of double perovskites SrCaLnRuO6 (Ln = La, Pr, Nd)

    International Nuclear Information System (INIS)

    Sasaki, Akira; Doi, Yoshihiro; Hinatsu, Yukio

    2009-01-01

    Double perovskite compounds SrCaLnRuO 6 (Ln = La, Pr, Nd) were prepared as a single phase. X-ray diffraction measurements show that Ca 2+ and Ln 3+ ions are partially disordered at the A site and half of the B site of the perovskite ABO 3 , and that Ca 2+ /Ln 3+ and Ru 5+ ions are regularly ordered at the B site. These compounds should be represented by SrCa 1-x Ln x [Ln 1-x Ca x ]RuO 6 and x = 0.83-0.93 for Ln = La, Pr, and Nd. Magnetic and specific heat measurements show that any of these compounds orders antiferromagnetically at 10-12 K, which is due to the magnetic interactions between Ru 5+ ions. The analysis of the magnetic entropy change indicates that the ground states of Ru 5+ and Ln 3+ ions are both doublet.

  17. 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.

  18. Excessive signal transduction of gain-of-function variants of the calcium-sensing receptor (CaSR are associated with increased ER to cytosol calcium gradient.

    Directory of Open Access Journals (Sweden)

    Marianna Ranieri

    Full Text Available In humans, gain-of-function mutations of the calcium-sensing receptor (CASR gene are the cause of autosomal dominant hypocalcemia or type 5 Bartter syndrome characterized by an abnormality of calcium metabolism with low parathyroid hormone levels and excessive renal calcium excretion. Functional characterization of CaSR activating variants has been so far limited at demonstrating an increased sensitivity to external calcium leading to lower Ca-EC50. Here we combine high resolution fluorescence based techniques and provide evidence that for the efficiency of calcium signaling system, cells expressing gain-of-function variants of CaSR monitor cytosolic and ER calcium levels increasing the expression of the Sarco-Endoplasmic Reticulum Calcium-ATPase (SERCA and reducing expression of Plasma Membrane Calcium-ATPase (PMCA. Wild-type CaSR (hCaSR-wt and its gain-of-function (hCaSR-R990G; hCaSR-N124K variants were transiently transfected in HEK-293 cells. Basal intracellular calcium concentration was significantly lower in cells expressing hCaSR-wt and its gain of function variants compared to mock. In line, FRET studies using the D1ER probe, which detects [Ca2+]ER directly, demonstrated significantly higher calcium accumulation in cells expressing the gain of function CaSR variants compared to hCaSR-wt. Consistently, cells expressing activating CaSR variants showed a significant increase in SERCA activity and expression and a reduced PMCA expression. This combined parallel regulation in protein expression increases the ER to cytosol calcium gradient explaining the higher sensitivity of CaSR gain-of-function variants to external calcium. This control principle provides a general explanation of how cells reliably connect (and exacerbate receptor inputs to cell function.

  19. MODIFIKASI KATALIS CaO DENGAN SrO PADA REAKSI TRANSESTERIFIKASI MINYAK JELANTAH MENJADI BIODIESEL MENGGUNAKAN

    Directory of Open Access Journals (Sweden)

    N Widiarti

    2016-03-01

    Full Text Available Minyak jelantah merupakan salah satu jenis minyak nabati yang dapat digunakan sebagai sumber produksi biodiesel yang murah. Biodiesel dapat diperoleh melalui proses esterifikasi dengan katalis asam maupun transesterifikasi dengan menggunakan katalis homogen basa kuat. Pengolahan minyak jelantah menjadi biodiesel merupakan langkah yang tepat dan efektif untuk menurunkan harga biodiesel karena bahan baku yang murah dan memanfaatkan limbah minyak goreng yang dapat mengatasi masalah pembuangan minyak dan kesehatan masyarakat. Pada penelitian ini dilakukan reaksi transesterifikasi dari minyak jelantah menjadi biodiesel menggunakan katalis CaO dan SrO. Tujuan penelitian ini adalah untuk mengetahui karakteristik katalis dan aktivitas katalitiknya pada reaksi transesterifikasi minyak jelantah. Modifikasi katalis dilakukan dengan metode impregnasi SrNO3 pada katalis CaO. Katalis digunakan pada reaksi transesterifikasi minyak jelantah dengan variasi energi  (input daya 80 dan 100 watt, variasi waktu (30, 60, 90, 120 dan 150 detik dan variasi jumlah SrO/CaO (1%, 2%, 4%, 8% dan 16% b/b sebagai katalis. Karakterisasi katalis dilakukan dengan XRD dan FTIR. Hasil analisis XRD menunjukkan bahwa katalis SrO/CaO bersifat kristalin dan mempunyai karakteristik pola difraksi gabungan CaO dan SrO. Reaksi transesterifikasi optimal terjadi dengan aktivitas katalis terbaik pada energi  100 watt, waktu reaksi 120 detik dan jumlah katalis SrO/CaO sebesar 4% b/b dengan produk reaksi metil ester sebesar 92,86%. Wasted cooking oil is one type of vegetable oil that can be used as an inexpensive source of biodiesel production. Biodiesel can be obtained through esterification process with acid catalyst or transesterification using homogeneous catalyst of strong bases. Processing of wasted cooking oil into biodiesel is an appropriate and effective measures to reduce the high price of biodiesel because of cheap raw materials and it can overcome the problem of oil disposal and

  20. Effect of Ag on the peritectic decomposition of Bi2Sr2CaCu2Ox

    International Nuclear Information System (INIS)

    Margulies, L.; Dennis, K.W.; Kramer, M.J.; McCallum, R.W.

    1995-01-01

    During the melt processing of superconducting wires and tapes a number of partial liquid phase regions are entered, and the type and amount of second phases that exist in the melt before cooling are critical in determining the microstructure of the final material. Decomposition pathway of Bi 2 Sr 2 CaCu 2 O x (Bi2212) with 0, 2, and 10 wt% Ag added was examined at 1 bar PO 2 by performing SAME/EDS analysis on oil quenched samples. A variety of quaternary phase diagrams were constructed to describe the evolution of the phase assemblage with temperature. At all Ag contents, Bi2212 first undergoes a peritectic reaction producing (Sr 1-x Ca x ) 14 Cu 24 O 41 (14,24), Bi 2 (Sr 1-x Ca x ) 4 O x (24x), and liquid

  1. 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)

    Sudirman; Ridwan; Mujamilah; Karo Karo, Aloma; Handayani, Ari; Rukihati

    2004-01-01

    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 (SrFe 12 O 19 ) or Ba M (BaFe 12 O 19 ) 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

  2. 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.

  3. Preparation of thermal infrared and microwave absorber using SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/polyaniline nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Seyed Hossein, E-mail: shhosseini@iiau.ac.ir [Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Zamani, Parisa [Department of Applied Chemistry, Faculty of Pharmaceutical Chemistry, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2016-01-01

    In this research, first, SrTiO{sub 3} was synthesized as thermal infrared (TIR) absorbent and core and then BaFe{sub 12}O{sub 19} as microwave absorbent was prepared on SrTiO{sub 3} via co-precipitation method as first shell. Second, polyaniline (PANI) was coated on SrTiO{sub 3}/BaFe{sub 12}O{sub 19} NPs (NPs) via in situ polymerization by multi core–shell structures (SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/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 SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/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 SrTiO{sub 3}/BaFe{sub 12}O{sub 19} as core and independent to increasing PANI as final shell. - Graphical abstract: The light reflectivity times of samples on human body are higher than metallic disks. So, they are suitable for TIR as absorbers. The light reflectivity times of samples were increased by increasing weight ratio and thickness. Human temperature could not transmit to samples by increasing weight ratio of core. Therefore weight ratio (SrTiO{sub 3}/BaFe{sub 12}O{sub 19} as core) above 40% and 1 mm diameter are the best result as TIR absorber. The SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/PANI enhanced broad band IR light absorption was observed in the wavelength range of 10–40 µm. A minimum RL of −19 dB was observed at 9.2 GHz for a 1.5-mm thickness nanocomposite. The application of these samples may improve the IR thermographic detection, catalysis, sensors

  4. Normal modes of Bi-Sr-Ca-Cu-O high-temperature superconductors: layer-by-layer approach

    International Nuclear Information System (INIS)

    Bush, A.A.; Kitaev, Yu.E.; Limonov, M.F.; Markov, Yu.F.; Novikov, A.A.; Evarestov, R.A.

    1992-01-01

    The non-superconducting Bi 1-x (Sr 1-y Ca y ) x O 1.5-x/2 compounds and the Bi 2 Sr 2 Ca n-1 Cu n O 2n+4 (n=1.2) superconductors have been synthesized and investigated. Using the method of band representations of space groups the complete group symmetry analysis of the normal vibrational modes has been made. Comparing the Raman spectra of the row of bismuth compounds and using the results of the group theory analysis all the strong RSS-lines have been attributed. (orig.)

  5. Novel biocompatible magnesium alloys design with nutrient alloying elements Si, Ca and Sr: Structure and properties characterization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Weidan; Han, Junjie [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Yang, Xuan; Li, Mei [Department of Orthopedics, Guangdong Key Lab of Orthopaedic Technology and Implant Materials, Guangzhou General Hospital of Guangzhou Military Command, 111 Liuhua Road, Guangzhou 510010 (China); Wan, Peng, E-mail: pwan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Tan, Lili [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Zhang, Yu [Department of Orthopedics, Guangdong Key Lab of Orthopaedic Technology and Implant Materials, Guangzhou General Hospital of Guangzhou Military Command, 111 Liuhua Road, Guangzhou 510010 (China); Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2016-12-15

    Highlights: • A non-toxic Mg-based alloy system with nutrient elements Si, Sr, Ca is proposed. • Properties improved due to morphology of coarse Mg{sub 2}Si change into small polygon. • Fewer, finer and homogenized Mg{sub 2}Si particles are obtained after anneal-treated. • Cytocompatibility results indicate a potential application in orthopedic. - Abstract: Magnesium has been widely studied as a biodegradable material, where its mechanical property and biocompatibility make it preferred candidate for orthopedic implant. Proper alloying can further improve the properties of Mg. First and foremost, to guarantee the biosafety for biomedical application, the alloying element should be toxic free. To address this point, nutrient elements including Si, Sr and Ca were selected due to their biological functions in human body, especially in bone regeneration and repair. In this study, 0.5–1.0 wt% Sr and Ca were used to refine and modify the morphology of coarse Mg{sub 2}Si in Mg-1.38wt% Si to obtain an uniform microstructure. Microstructure, mechanical and degradation properties of as-cast and homogenizing-annealed quaternary Mg-1.38Si-xSr-yCa (x, y = 0.5–1 wt%) alloys were investigated by optical microscopy, scanning electronic microscopy, X-ray diffraction, tensile and electrochemical measurement. Addition of Sr and Ca element cause a morphological change in Mg{sub 2}Si particles from coarse Chinese script shape to small polygonal type. The presences of intermetallic phases, such as Mg{sub 2}Si, CaMgSi and Mg{sub 17}Sr{sub 2}, were confirmed in quaternary alloys, of which content was applied to interpret the results for the quaternary system. Compared with the as-cast state, fewer, finer and homogenized microstructure were observed after an anneal heat treatment under 500 °C. The mechanical properties were improved with increase of Ca and Sr additions, which was related to the evolution of the microstructure and second phases, however, also causing an

  6. Crystalline phases and electronic structures in superconducting Bi endash Sr endash Ca endash Cu oxides

    International Nuclear Information System (INIS)

    Giardina, M.D.; Feduzi, R.; Inzaghi, D.; Manara, A.; Giori, C.; Sora, I.N.; Dallacasa, V.

    1997-01-01

    Two classes of samples, designated A and B, of layered Bi endash Sr endash Ca endash Cu oxides having the same nominal composition 4:3:3:4, but different thermal histories, were investigated by using field modulated microwave absorption (ESR), powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near the edge structure (XANES). Previous electrical resistivity measurements showed that the B samples only presented two superconducting phases with midpoints of the transition temperatures at ∼80K and ∼105K. The microwave absorption technique indicated instead the presence of islands which became superconducting at the above-mentioned temperatures also in the A samples. The crystalline and electronic structures of the two types of samples are illustrated and discussed. A plausible theoretical interpretation of the experimental results, based on a quantum percolation model with Coulomb interaction, is also given. copyright 1997 Materials Research Society

  7. Conductivity and superconductivity of (Bi,Pb)-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Gazda, M.; Kusz, B.; Klimczuk, T.; Natali, R.; Stizza, S.

    2007-01-01

    The (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics may be considered as disordered metal and superconductor. Depending on the heat treatment conditions the materials are either composed of the oval grains of the 2212 or 2201 phases embedded in the insulating matrix or they mainly contain the 2212 plate-like crystallites weakly connected one with another. The materials have large resistivity and usually large negative temperature coefficient of resistivity (TCR). The granular and disordered character of the materials is also reflected in their superconducting properties. Both the normal-state and superconducting properties correlate one with another. The glass-ceramic samples were obtained by annealing the amorphous solid at temperatures between 840 and 860 deg. C. The measurements of the temperature dependence of resistivity in annealed samples were carried out with the conventional four-terminal method in a temperature range from 3 to 300 K

  8. Retrograde densification in Bi2Sr2CaCu2O8 superconductors

    International Nuclear Information System (INIS)

    Johnson, D.W. Jr.; Rhodes, W.W.

    1989-01-01

    Bi 2 Sr 2 CaCu 2 O 8 was prepared using the mixed oxide-carbonate method and sintered at temperatures ranging from 850 degrees to 911 degrees C. The samples were characterized for density, mechanical strength, phase composition, microstructure, and superconducting transition temperatures. A unique retrograde densification characteristic is demonstrated in the temperature range 850 degrees to 890 degrees C whereby the material first becomes less dense as the sintering temperature is raised, and only in a narrow temperature range from 900 degrees to 905 degrees C does the material densify then with the formation of a liquid phase. This retrograde densification, coupled with a narrow sintering range overlapping the melting temperature, makes this compound a difficult one to process

  9. The mechanical deformation of superconducting BiSrCaCuO/Ag composites

    International Nuclear Information System (INIS)

    Han, Z.; Skov-Hansen, P.; Freltoft, T.

    1997-01-01

    The mechanical deformation of BiSrCaCuO/Ag composites made by the powder-in-tube method is a multi-step process. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. A key parameter is the core density, which changes during mechanical deformation. In this review, basic concepts of the classical mechanical deformation theory are briefly discussed. Simple descriptions of deformation processes like pressing, rolling, drawing and extrusion are also presented. The term 'freedom parameter', Δ f , is introduced to illustrate the influence of various constraint factors on the mass-flow behaviour. Simple pictures including mass redistribution and the powder-flow model are presented for interpreting the plastic deformation process of the composites. Experimental results are reviewed and our proposed pictures and models are applied for discussion. (author)

  10. Strain induced enhancement of magnetization in Ba{sub 2}FeMoO{sub 6} based heterostructure with (Ba{sub x}Sr{sub 1-x})TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyeong-Won; Norton, David P. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ghosh, Siddhartha, E-mail: ghoshsid@gmail.com; Buvaev, Sanal; Hebard, Arthur F. [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

    2016-05-14

    High quality epitaxial Ba{sub 2}FeMoO{sub 6} thin films and Ba{sub 2}FeMoO{sub 6}–(Ba{sub x}Sr{sub 1−x})TiO{sub 3} bi-layer (BL) and superlattice (SL) structures were grown via pulsed laser deposition under low oxygen pressure, and their structural, magnetic, and magneto-transport properties were examined. Superlattice and bi-layer structures were confirmed by X-ray diffraction patterns. Low temperature magnetic measurement shows that the saturation magnetization (M{sub S}) is significantly higher for SLs and almost similar or lower for BLs, when compared to phase pure Ba{sub 2}FeMoO{sub 6} thin films. The variation of the coercive field (H{sub C}) follows exact opposite trend, where BL samples have higher H{sub C} and SL samples have lower H{sub C} than pure Ba{sub 2}FeMoO{sub 6} thin films. Also, a significant decrease of the Curie temperature is found in both BL and SL structures compared to pure Ba{sub 2}FeMoO{sub 6} thin films. Negative magneto-resistance is seen in all the BL and SL structures as well as in pure Ba{sub 2}FeMoO{sub 6} thin films. In contrast to the magnetic properties, the magneto-transport properties do not show much variation with induced strain.

  11. Superconducting TlCa2Ba2Cu3O9 thick films

    International Nuclear Information System (INIS)

    1994-01-01

    GE Corporate Research and Development's (GE-CRD) program to develop the two-zone silver addition (TZSA) process for fabricating superconducting films of TlCa 2 Ba 2 Cu 3 O 9 has activities in the areas of (1) precursor preparation, (2) the thallium oxide vapor process, (3) the effects of post-synthesis annealing ambient and temperature on superconducting properties, (4) the influence of film stoichiometry and composition on superconducting properties, (5) microstructure and film growth mechanism, (6) the preparation of thicker films, (7) the fabrication of films on flexible substrates, and (8) process scale-up. As part of its effort under the ANL Pilot Center Agreement, GE-CRD has supplied to ANL a complete two-zone furnace, has provided consultation on its use and on the planning of experiments, has processed ANL samples in GE's furnaces to help define optimum process conditions, and has provided precursor and finished films as requested. These contributions are described more fully in the descriptions of the work performed at ANL presented elsewhere in this report. Under the Pilot Center Agreement work at GE-CRD has been directed toward the optimization of the TZSA process with emphasis on (A) process improvement, (B) effects of silver content on film properties, (C) the relationship between microstructure and J c , and (D) toward the assessment of the compatibility of silver substrates with the process chemistry

  12. Electronic structure and bonding interactions in Ba1- x Sr x Zr0.1Ti0.9O3 ceramics

    Science.gov (United States)

    Mangaiyarkkarasi, Jegannathan; Sasikumar, Subramanian; Saravanan, Olai Vasu; Saravanan, Ramachandran

    2017-06-01

    An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1- x Sr x Zr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

  13. Supercurrents in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gapud, A.A.; Wu, J.Z.; Fang, L.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    1999-06-01

    The availability of high-quality epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) and TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) with high critical current densities (J{sub c}) has made it possible to examine and compare the J{sub c} of these species. Results reveal that the J{sub c} of 1212 species have very similar temperature behavior at low fields, strongly suggesting that the 30 K shift in critical temperature (T{sub c}) induced by the exchange of Hg and Tl in the 1212 structure is due largely to a change in charge carrier density and/or electronic band structure. {copyright} {ital 1999 American Institute of Physics.}

  14. Investigation on gamma and neutron radiation shielding parameters for BaO/SrO‒Bi2O3‒B2O3 glasses

    Science.gov (United States)

    Sayyed, M. I.; Lakshminarayana, G.; Dong, M. G.; Ersundu, M. Çelikbilek; Ersundu, A. E.; Kityk, I. V.

    2018-04-01

    In this work, mass attenuation coefficients (μ/ρ), effective atomic number (Zeff), electron density (Ne), mean free path (MFP), and half-value layer (HVL) of 20 BaO/SrO‒(x) Bi2O3‒(80‒x) B2O3 glasses (where x=10, 20, 30, 40, 50 and 60 mol%) were calculated using WinXCom program and MCNP5 code. The obtained (μ/ρ) results using both MCNP5 code and WinXCom program were in good agreement. It is found that the addition of Bi2O3 leads to increase the Zeff values in both BaO/SrO‒Bi2O3‒B2O3 glass systems. However, the Zeff values of the BaO‒Bi2O3‒B2O3 glass system are higher than those of the SrO‒Bi2O3‒B2O3 glasses. The fast neutrons effective removal cross sections (ΣR) for 20 SrO‒40 Bi2O3‒40 B2O3 glass is the highest among all studied glasses. The calculated half-value layer values were compared with different glass systems and it was found that the shielding properties of the selected glasses are comparable or even better than other glass systems such as phosphate glasses.

  15. Increased Curie Temperature Induced by Orbital Ordering in La0.67Sr0.33MnO3/BaTiO3 Superlattices

    Science.gov (United States)

    Zhang, Fei; Wu, Biao; Zhou, Guowei; Quan, Zhi-Yong; Xu, Xiao-Hong

    2018-01-01

    Recent theoretical studies indicated that the Curie temperature of perovskite manganite thin films can be increased by more than an order of magnitude by applying appropriate interfacial strain to control orbital ordering. In this work, we demonstrate that the regular intercalation of BaTiO3 layers between La0.67Sr0.33MnO3 layers effectively enhances ferromagnetic order and increases the Curie temperature of La0.67Sr0.33MnO3/BaTiO3 superlattices. The preferential orbital occupancy of eg( x 2 -y 2 ) in La0.67Sr0.33MnO3 layers induced by the tensile strain of BaTiO3 layers is identified by X-ray linear dichroism measurements. Our results reveal that controlling orbital ordering can effectively improve the Curie temperature of La0.67Sr0.33MnO3 films and that in-plane orbital occupancy is beneficial to the double exchange ferromagnetic coupling of thin-film samples. These findings create new opportunities for the design and control of magnetism in artificial structures and pave the way to a variety of novel magnetoelectronic applications that operate far above room temperature.

  16. Determination of Sr-90, Cs-137, Na, K, Cs, Ca, Sr and Ba in Milk Powder (A-7)

    International Nuclear Information System (INIS)

    1973-01-01

    The samples were made from fresh skim milk by spray drying. The homogeneity was achieved by stirring the original liquid milk and the powder itself. No spiking with active or inactive materials was made. Each participating laboratory received 800 g sub-samples of the material. 26 participants submitted a total of 99 laboratory means and 365 results of individual determinations. Some of the laboratories submitted two different sets of results for the same radionuclides or stable elements which were obtained either by different analysts. The results are presented separately for all the radionuclides and stable elements (except cesium)

  17. Preparation of MAl O : Eu2+, Sm3+ (M = Ca, Sr, Ba) Phosphors by ...

    African Journals Online (AJOL)

    NJD

    2007-10-15

    Oct 15, 2007 ... clearly show that most peaks are assigned to those of the MAl2O4 structure. Moreover, their structures change with change of M. Samples A and B exhibit monoclinic crystal systems and sample. C a hexagonal structure. The doping Eu2+ and co-doping Sm3+ have very little influence on the structure of the ...

  18. Heterostructures (CaSrBa)F2 on InP for Optoelectronics

    Science.gov (United States)

    1995-01-01

    material particles which are thermolized in the counter flow . The ratio between the target and the substrate particles depends on the laser power density...target flow caused sputtering of the substrate and of the growing film [43,48]. This sputtering effect in LVE method was directly observed during...1995) 213 39. R.P.Khosla, Phys. Rev. 183 (1969) 695 40. J.M.Langer, T.Langer and B.Krukowska- Fuide , J. Phys. D12 (1979) L95 41.H.-S. Kim, Y.Kim, M

  19. Relativistic semiempirical-core-potential calculations in Ca$^+$, Sr$^+$, and Ba$^+$ ions on Lagrange meshes

    OpenAIRE

    Filippin, Livio; Schiffmann, Sacha; Dohet-Eraly, Jérémy; Baye, Daniel; Godefroid, Michel

    2017-01-01

    Relativistic atomic structure calculations are carried out in alkaline-earth-metal ions using a semiempirical-core-potential approach. The systems are partitioned into frozen-core electrons and an active valence electron. The core orbitals are defined by a Dirac-Hartree-Fock calculation using the grasp2k package. The valence electron is described by a Dirac-like Hamiltonian involving a core-polarization potential to simulate the core-valence electron correlation. The associated equation is so...

  20. Influence of SrO substitution for CaO on the properties of bioactive glass S53P4.

    Science.gov (United States)

    Massera, Jonathan; Hupa, Leena

    2014-03-01

    Commercial melt-quenched bioactive glasses consist of the oxides of silicon, phosphorus, calcium and sodium. Doping of the glasses with oxides of some other elements is known to affect their capability to support hydroxyapatite formation and thus bone tissue healing but also to modify their high temperature processing parameters. In the present study, the influence of gradual substitution of SrO for CaO on the properties of the bioactive glass S53P4 was studied. Thermal analysis and hot stage microscopy were utilized to measure the thermal properties of the glasses. The in vitro bioactivity and solubility was measured by immersing the glasses in simulated body fluid for 6 h to 1 week. The formation of silica rich and hydroxyapatite layers was assessed from FTIR spectra analysis and SEM images of the glass surface. Increasing substitution of SrO for CaO decreased all characteristic temperatures and led to a slightly stronger glass network. The initial glass dissolution rate increased with SrO content. Hydroxyapatite layer was formed on all glasses but on the SrO containing glasses the layer was thinner and contained also strontium. The results suggest that substituting SrO for CaO in S53P4 glass retards the bioactivity. However, substitution greater than 10 mol% allow for precipitation of a strontium substituted hydroxyapatite layer.

  1. Magnetic, Thermodynamic, and Transport Properties of Layered Arsenides BaRu2As2 and SrRu2As2

    Science.gov (United States)

    Nath, R.; Singh, Y.; Johnston, D. C.

    2009-03-01

    As part of our effort to search for novel superconductors related to the FeAs high-T superconductors, we have synthesized polycrystalline samples of BaRu2As2 and SrRu2As2. The magnetic, transport and thermodynamic properties of the samples were investigated by means of magnetic susceptibility χ(T), electrical resistivity ρ(T), and heat capacity Cp(T) measurements. The temperature dependence of ρ indicates metallic character for both compounds with a residual resistivity ratio ρ(310 K)/ρ(2 K) of 17 and 7 for the Ba and Sr compounds, respectively. The Cp(T) results indicate a low density of states at the Fermi level with the low-T Sommerfeld coefficient γ˜4.9 and 4.13 mJ/mole K^2 for the Ba and Sr compounds, respectively. The Debye temperature θD was estimated to be 270 K and 260 K for the Ba and Sr compounds, respectively. The χ(T) was found to be diamagnetic with a small absolute value for both the compounds. No evidence for superconductivity, a spin density wave, or a structural transition was observed from the Cp(T) and ρ(T) measurements down to 2 K. However, the χ(T) data for SrRu2As2 exhibit a cusp at ˜190 K, possibly an indication of a structural and/or magnetic transition.* Supported by the USDOE under contact No. DE-AC02-07CH11358.

  2. Sea Surface Temperature Records Using Sr/Ca Ratios in a Siderastrea siderea Coral from SE Cuba

    Science.gov (United States)

    Fargher, H. A.; Hughen, K. A.; Ossolinski, J. E.; Bretos, F.; Siciliano, D.; Gonzalez, P.

    2015-12-01

    Sea surface temperature (SST) variability from Cuba remains relatively unknown compared to the rest of the Caribbean. Cuba sits near an inflection point in the spatial pattern of SST from the North Atlantic Oscillation (NAO), and long SST records from the region could reveal changes in the influence of this climate system through time. A Siderastrea siderea coral from the Jardínes de la Reina in southern Cuba was drilled to obtain a 220 year long archive of environmental change. The genus Siderastrea has not been extensively studied as an SST archive, yet Sr/Ca ratios in the Cuban core show a clear seasonal signal and strong correlation to instrumental SST data (r2 = 0.86 and 0.36 for monthly and interannual (winter season) timescales, respectively). Annual growth rates (linear extension) of the coral are observed to have a minor influence on Sr/Ca variability, but do not show a direct correlation to SST on timescales from annual to multidecadal. Sr/Ca measurements from the Cuban coral are used to reconstruct monthly and seasonal (winter, summer) SST extending back more than two centuries. Wintertime SST in southern Cuba is compared to other coral Sr/Ca records of winter-season SST from locations sensitive to the NAO in order to investigate the stationarity of the NAO SST 'fingerprint' through time.

  3. Metal-organic deposition of YBa 2 Cu 3 O and Bi 2 Sr 2 Ca Cu 2 O ...

    Indian Academy of Sciences (India)

    YBa2Cu3O (Y-123 ) and Bi2Sr2Ca1Cu2O (Bi-2212) films on various substrates have been prepared by Metal-Organic Deposition starting from different metallorganic fluorine-free compounds and using a very simple instrumentation. The processing conditions include a rapid pyrolysis step in air and an annealing step in ...

  4. Dipole polarizability of alkali-metal (Na, K, Rb)-alkaline-earth-metal (Ca, Sr) polar molecules: Prospects for alignment

    Science.gov (United States)

    Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

    2014-06-01

    Electronic open-shell ground-state properties of selected alkali-metal-alkaline-earth-metal polar molecules are investigated. We determine potential energy curves of the 2Σ+ ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes (23Na, 39K, 85Rb)-(40Ca, 88Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields.

  5. Microwave plasma CVD of oxide films relating to high Tc Bi-Sr-Ca-Cu-O superconductor

    International Nuclear Information System (INIS)

    Hashimoto, T.; Kosaka, T.; Yoshida, Y.; Yoshimoto, M.; Koinuma, H.

    1989-01-01

    Microwave plasma CVD was applied to the synthesis of Bi, Sr, Ca, and Cu oxide films at relatively low temperatures. Gas source materials used were Bi(C 6 H 5 ) 3 , Sr(PPM) 2 , Ca(PPM) 2 , and Cu(HFA) 2 , where PPM and HFA represent C 2 F 5 COCHCOC(CH 3 ) 3 and CF 3 COCHCOCF 3 , respectively. Films were deposited on MgO (100) substrate at temperatures between 200 C and 400 C under an atmosphere of 1000mTorr Ar-O 2 (50/100) mixture which was partially excited by plasma. From Bi(C 6 H 5 ) 3 , Bi 2 O 3 was formed at 200 C without containing carbon above the detection level by XPS analysis. From Cu(HFA) 2 , CuO was prepared at 400 C by increasing oxygen partial pressure to 0.1Torr. (At lower oxygen partial pressure, CuF 2 or amorphous films were deposited.) From Sr(PPM) 2 and Ca(PPM) 2 , SrF 2 and CaF 2 were obtained at 400 C. The attempt to fabricate superconducting films is also reported

  6. The role of selenium in the metabolism of 45Ca and 99Sr in the bones of hens

    International Nuclear Information System (INIS)

    Nowosad, R.

    1977-01-01

    Under experimental conditions it was stated that the application of selenium at the dose of 5 mcg per animal led to some disturbances in mineral metabolism in the skeletal system of hens. That was expressed by a decrease of ash content in died mass, a decrease of 45 Ca and 90 Sr in bones, and the diminished activity of calcium. (author)

  7. 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.

  8. EuAuGe type indides RAgIn (R = Ca, Sr, La, Eu)

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Sebastian; Schmolke, Kai Heinz; Block, Theresa; Heletta, Lukas; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany)

    2017-08-03

    The equiatomic intermetallic phases CaAgIn [a = 482.75(7), b = 750.0(1), c = 835.5(1) pm], SrAgIn [a = 495.86(5), b = 794.71(9), c = 851.89(9) pm], LaAgIn [a = 489.99(5), b = 767.93(9), c = 837.53(9) pm], and EuAgIn [a = 493.02(7), b = 781.6(1), c = 844.2(1) pm] were synthesized from the elements in sealed niobium containers. They crystallize with the EuAuGe type structure, space group Imm2. The four structures were refined from single-crystal X-ray data. The silver and indium atoms build up orthorhombically distorted, puckered Ag{sub 3}In{sub 3} hexagons, which are stacked in AA' sequence, leading to direct Ag-Ag and In-In interlayer bonding (e.g. 303 and 304 pm in CaAgIn). Temperature dependent magnetic susceptibility measurements show a magnetic moment of 7.40(1) μ{sub B} per europium atom. EuAgIn orders antiferromagnetically at 5.7(5) K. The divalent nature of europium is also evident from {sup 151}Eu Moessbauer spectra: δ = -10.50(1) mm.s{sup -1} at 78 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Highly oriented Tl2Ba2Ca2Cu3O10 thin films by pulsed laser evaporation

    Science.gov (United States)

    Liou, S. H.; Aylesworth, K. D.; Ianno, N. J.; Johs, B.; Thompson, D.

    1989-01-01

    Superconducting thin films on MgO (100) substrates with nearly pure Tl2Ba2Ca2Cu3O10 (2:2:2:3) phase using pulsed laser evaporation and postannealing have been fabricated. The films had c axes perpendicular to the substrates. Superconducting films with onset temperatures of 125 K and zero resistance at 110 K were obtained. X-ray microprobe fluorescence measurements indicate that a typical composition of films is Tl(0.66)Ba(1.77)Ca(1.46)Cu3O(x) which is low in Tl compared to that expected for the 2:2:2:3 phase. A typical grain size is greater than 10 microns revealed by scanning electron microscopy.

  10. Structural and Transition Temperature of HgPbxBa2Ca2Cu3O8+δ Superconductor

    International Nuclear Information System (INIS)

    Hermiz, G.Y.; Abbass, M.M.

    2005-01-01

    Solid state reaction technique (SSR) was used to prepare high-T c phase in HgPb x Ba 2 Ca 2 Cu 3 O 8+δ superconductors. The effect of additional Pb to HgBa 2 Ca 2 Cu 3 O 8+δ was investigated. It has been found that the maximum transition temperature T c =133K is at x=0.1.X-ray diffraction showed a tetragonal structure with an average value of e=15.816 A . The average value of the valence of copper (v) is equal to 2.025. There is an increasing of density with the enhancement of the concentration of Pb 2

  11. 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)

  12. A new SrBi4Ti4O15/CaBi4Ti4O15 thin-film capacitor for excellent electric stability.

    Science.gov (United States)

    Noda, Minoru; Nomura, Shuhei; Uchida, Hiroshi; Yamashita, Kaoru; Funakubo, Horoshi

    2012-09-01

    SrBi(4)Ti(4)O(15) (SBTi) and CaBi(4)Ti(4)O(15) (CBTi) dielectric films of bismuth layered-structure dielectrics (BLSD) are prepared on Pt(100) film for constructing stacked-type dielectric capacitors; it is observed that they are c-axis singleoriented crystalline films. Compared with the perovskite barium titanate family of (Ba,Sr)TiO(3) (BST), it is observed that the SBTi film keeps a low leakage of 10(-7) A/cm(2) at 250 kV/ cm, which is smaller by an order of magnitude than the BST film, even with thinner SBTi film. The temperature coefficient of capacitance (TCC) of the SBTi or CBTi film is about 100 to 250 ppm/K and is much smaller than that of the perovskite BST film. Because the SBTi and CBTi films have opposite polarities of TCC in this experiment, they are expected to cancel out the temperature dependence in the SBTi/CBTi composite capacitor. These results indicate that the BLSD films of SBTi and CBTi are effective for application in high-temperature and high-permittivity capacitors with the practical barium perovskite oxide family.

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

    OpenAIRE

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

    2014-01-01

    We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metalinsulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlatio...

  14. 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.

  15. 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.

  16. Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant

    Energy Technology Data Exchange (ETDEWEB)

    Bornapour, M., E-mail: mandana.bornapour@mail.mcgill.ca [Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5 (Canada); Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Mahjoubi, H. [Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Vali, H. [Department of Anatomy and Cell Biology, McGill University, Montreal, Qc, H3A 0C7 (Canada); Shum-Tim, D. [Department of Cardiac Surgery and Surgical Research, McGill University, Montreal, Qc H3G 1A1 (Canada); Cerruti, M. [Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Pekguleryuz, M. [Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5 (Canada)

    2016-10-01

    Magnesium-based alloys are attractive candidate materials for medical applications. Our earlier work showed that the ternary Mg-0.3Sr-0.3Ca alloy exhibits slower degradation rates than both binary Mg-Sr and Mg-Ca alloys. The ternary alloy immersed in simulated body fluid (SBF) forms a compact surface layer of corrosion products that we hypothesized to be a Sr-substituted hydroxyapatite (HA). The main objectives of the current work are to understand the bio-degradation mechanism of Mg-0.3Sr-0.3Ca, to identify the exact nature of its protective layer and to evaluate the in vitro and in vivo biocompatibility of the alloy for cardiovascular applications. To better simulate the physiological environment, the alloy was immersed in SBF which was daily refreshed. Raman spectroscopy and X-Ray photoelectron spectroscopy (XPS) confirmed the formation of a thin, Sr-substituted HA layer at the interface between the alloy and the corrosion products. In vitro biocompatibility evaluated via indirect cytotoxicity assays using HUVECs showed no toxicity effect and ions extracted from Mg-0.3Sr-0.3Ca in fact increased the viability of HUVECs after one week. In vivo tests were performed by implanting a tubular Mg-0.3Sr-0.3Ca stent along with a WE43 control stent into the right and left femoral artery of a dog. Post implantation and histological analyses showed no thrombosis in the artery with Mg-0.3Sr-0.3Ca stent after 5 weeks of implantation while the artery implanted with WE43 stent was extensively occluded and thrombosed. Microscopic observation of the Mg-0.3Sr-0.3Ca implant-tissue interface confirmed the in situ formation of Sr-substituted HA on the surface during in vivo test. These results show that the interfacial layer protects the surface of the Mg-0.3Sr-0.3Ca alloy both in vitro and in vivo, and is the key factor in the bio-corrosion resistance of the alloy. - Highlights: • The surface active elements of Sr and Ca alter the corrosion of Mg alloy in SBF • Sr

  17. Eu2+-activated Ba3Ca3(PO4)4 phosphor with doping-concentration dependent luminescence

    Science.gov (United States)

    Tang, Huidong; Yang, Rong; Li, Rongzhu

    2017-10-01

    A color tunable phosphor of Eu2+-activated monophosphate Ba3Ca3(PO4)4 was developed via facile solid-state reaction synthesis. The samples were tested by X-ray powder diffraction (XRD) patterns, morphological properties, luminescence and decay lifetime measurements. The structural characteristics were discussed. The excitation bands of the phosphors cover the UV-, near-UV and blue-wavelength bands extending from 300 to 440 nm. The luminescence spectra of the phosphors show a great dependence on the Eu2+-concentration in Ba3Ca3(PO4)4, which can give blue to yellow emission colors. There are two kinds of Eu2+ centers in Ba3Ca3(PO4)4 lattices, which give yellow (EuI) and blue (EuII) luminescence with the maximum wavelength at 565 nm and 450 nm, respectively. The structural occupations and luminescence properties of EuI and EuII centers were discussed. EuI (yellow center) has a dominant contribution to the total luminescence with the increase of the Eu2+-doping level. The luminescence internal quantum efficiency and thermal stability (activation energy) were reported. The reported results could be helpful for the further potential application of the phosphor.

  18. Plasmodium falciparum GPCR-like receptor SR25 mediates extracellular K+ sensing coupled to Ca2+ signaling and stress survival

    OpenAIRE

    Moraes, Miriam S.; Budu, Alexandre; Singh, Maneesh K.; Borges-Pereira, Lucas; Levano-Garcia, Julio; Curr?, Chiara; Picci, Leonardo; Pace, Tomasino; Ponzi, Marta; Pozzan, Tullio; Garcia, C?lia R. S.

    2017-01-01

    The malaria parasite Plasmodium falciparum is exposed, during its development, to major changes of ionic composition in its surrounding medium. We demonstrate that the P. falciparum serpentine-like receptor PfSR25 is a monovalent cation sensor capable of modulating Ca2+ signaling in the parasites. Changing from high (140?mM) to low (5.4?mM) KCl concentration triggers [Ca2+]cyt increase in isolated parasites and this Ca2+ rise is blocked either by phospholipase C (PLC) inhibition or by depleti...

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    Understanding the nature of flexoelectricity, which is the linear response of electric polarization to a strain gradient, has recently become crucial for nanostructured dielectrics and ferroelectrics because of their complicated strain distribution. This paper presents a direct and full approach at the atomic level to predict flexoelectricity for dielectrics based on first-principles calculations. The flexoelectric coefficients of BaTiO 3 and SrTiO 3 are directly calculated as the representatives of ferroelectric and paraelectric materials, respectively. For SrTiO 3 , the flexoelectric coefficients predicted from our approach are in good agreement with the experimental measurements. For BaTiO 3 , our predictions have a large discrepancy from the experimental measurements. In a practical situation, defect and surface effects are inevitable, and have a significant influence on the flexoelectricity. Direct methods have the advantage of including the extrinsic contributions from surface and defect effects. (paper)

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

    Science.gov (United States)

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

    2013-10-16

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

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

    Science.gov (United States)

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

    2013-10-01

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

  2. Luminescence and energy transfer in Ce3+, Mn2+- doped K2AEP2O7 (AE = Ca, Sr) phosphor.

    Science.gov (United States)

    Hatwar, L R; Wankhede, S P; Moharil, S V; Muthal, P L; Dhopte, S M

    2015-09-01

    Pyrophosphates K2AEP2O7 (AE = Ca, Sr) prepared by the classical solid-state technique and activated with Ce(3+) are described. Intense emission was observed in K2AEP2O7 (AE = Ca, Sr). The effect of Mn(2+) co-doping was studied. The broad emission peak of Mn(2+) was observed at 534 nm in K2 rP2O7:Ce(3+) and at 539 nm in K2CaP2O7:Ce(3+), Mn(2+). Mn(2+) emission was greatly enhanced by addition of the sensitizer Ce(3+) due to efficient energy transfer from Ce(3+) to Mn(2+). Copyright © 2015 John Wiley & Sons, Ltd.

  3. The crystal structure of bøgvadite (Na2SrBa2Al4F20)

    DEFF Research Database (Denmark)

    Balic Zunic, Tonci

    2014-01-01

    The crystal structure of bøgvadite, Na2SrBa2Al4F20, has been solved and refined to a R1 factor of 4.4% from single-crystal data (MoKα X-ray diffraction, CCD area detector) on a sample from the cryolite deposit at Ivittuut, SW Greenland. Bøgvadite is monoclinic, P21/n space group, with unit cell...... parameters a= 7.134(1), b= 19.996(3) and c= 5.3440(8) Å, β = 90.02(1)o. A close proximity of the crystal structure to an orthorhombic symmetry and the presence of the two twin components in a nearly 1:1 ratio suggest that the investigated bøgvadite crystal has originally formed as a high......-temperature orthorhombic polymorph which on cooling transformed to the stable low temperature monoclinic structure. The bøgvadite crystal structure has groupings of cation-fluoride coordination polyhedra similar to those found in the crystal structures of the genetically closely associated minerals jarlite...

  4. Preparation and properties of the (Sr,BaNb2O6 thin films by using the sputtering method

    Directory of Open Access Journals (Sweden)

    Diao Chien-Chen

    2017-01-01

    Full Text Available Strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN thin films were deposited on silicon substrate by using the radio frequency magnetron sputtering and under different deposition power and time at room temperature. Surface morphology and thicknesses of the SBN thin films were characterized by field emission scanning electron microscopy. The crystallization films at different deposition power and time were analyzed by X-ray diffraction (XRD using CuKα radiation from a Rigaku rotating anode with an incident angle of 2°. The remnant polarization (Pr, saturation polarization (Ps, and minimum coercive field (Ec properties of the metal-ferroelectric-metal (MFM structure were measured using ferroelectric material test instrument. The SBN thin films deposited at 90 min and 125 W had the maximum Pr, Ps, and minimum Ec of 1.26 μC/cm2, 2.41 μC/cm2, and 201.6 kV/cm, respectively. From above results, it knows that the SBN thin films suit for application on ferroelectric random access memory (FeRAM.

  5. Aerosol deposition of Ba0.8Sr0.2TiO3 thin films

    Directory of Open Access Journals (Sweden)

    Branković Zorica

    2009-01-01

    Full Text Available 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 temperature of 85ºC. After deposition films were slowly heated up to 650ºC, annealed for 30 min, and slowly cooled. Grain size of BST films deposited on Si substrate were in the range 40-70 nm, depending on deposition conditions, while the same films deposited on Pt substrates showed mean grain size in the range 35-50 nm. Films deposited under optimal conditions were very homogeneous, crackfree, and smooth with rms roughness lower than 4 nm for both substrates.

  6. Photoconductivity of transparent perovskite oxide semiconductors BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin; Institute of Applied Physics, Department of Physics; Astronomy, Seoul National University, Seoul Team

    We have measured the photoconductivity (PC) of epitaxial thin films of transparent semiconductor BaSnO3 (BSO) and SrTiO3 (STO) at room temperature. The epitaxial thin films of BSO and STO were grown by pulsed laser ablation technique on the MgO substrates to exclude any conductance from the substrate owing to its large bandgap (~7.8 eV). Despite the same crystalline structure and similar band gap sizes (~3.2 eV), the PC of BSO behaved very differently. The slowly varying component in the PC of BSO is much larger than that of STO; the PC of BSO increased slowly, reached higher magnitude after the same duration of illumination, and persisted longer than many hours after the light was turned off, whereas the PC of STO showed little persistent conductivity. The spectral responses of the PC of BSO and STO showed their highest peaks below 400 nm when measured by a UV monochromator system, suggesting that the electron-hole pair generation is the main mechanism of the PC for both materials. The higher mobility of BSO should be partially responsible for the higher PC. The large persistent PC of BSO seems related to the dislocations that trap electrons easily.

  7. Dielectric Relaxation Behavior of Bismuth Doped (Ba0.2Sr0.8 TiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Baptista, J. L.

    1999-12-01

    Full Text Available The dielectric properties of bismuth doped (Ba0.2Sr0.8TiO3 ceramics are investigated. The temperature dependence of the dielectric permittivity and loss factor were measured from 102 to 106Hz in the temperature range 12-320K. As the amount of Bi increases, the ferroelectric-paraelectric phase transition gets diffused and relaxed. In addition to this ferroelectric-paraelectric phase transition, other two sets of dielectric anomalies, located at 50-100K and 200-300K respectively, are also found. The possible relaxation mechanisms are briefly discussed.Las propiedades dieléctricas de cerámicos dopados con bismuto son investigadas. La dependencia con la temperatura de la permitividad dieléctrica y el factor de pérdidas se midieron entre 02 y 106Hz en el rango de temperatura 12-320K. Con el aumento del contenido en Bi, la transición de fase ferroeléctrica-paraléctrica se hace difusa y reloja. Junto a esta transición de fase los conjuntos de anomalías dieléctricas, localizados a 50-100k y 200-300k respectivamente, también se encontraron. Se discute brevemente los posibles mecanismos de relajación.

  8. Solvent extraction of Ca2+, Ba2+, Cu2+, Zn2+, Cd2+, Pb2+, UO22+, Mn2+, Co2+ and Ni2+ into nitrobenzene using strontium dicarbol-lylcobaltate and tetra-tert-butyl p-tert-butylcalix[4]arene tetraacetate

    Directory of Open Access Journals (Sweden)

    E. MAKRLÍK

    2008-12-01

    Full Text Available The exchange extraction constants corresponding to the general equilibrium M2+(aq + SrL2+(nb D ML2+ (nb + Sr2+ (aq occurring in the two-phase water–nitrobenzene system (M2+ = Ca2+, Ba2+, Cu2+, Zn2+, Cd2+, Pb2+, UO22+, Mn2+, Co2+ or Ni2+; L = tetra-tert-butyl p-tert-butylcalix[4]arene tetraacetate; aq = aqueous phase; nb = nitrobenzene phase were evaluated from extraction experiments and -activity measurements. Furthermore, the stability constants of the ML2+ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Ba2+ < Mn2+ < Pb2+, Co2+ < Cu2+, Zn2+ < Cd2+, Ni2+ < UO22+ < Ca2+.

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

    International Nuclear Information System (INIS)

    Xia Zhengqiang; Chen Sanping; Wei Qing; Qiao Chengfang

    2011-01-01

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

  10. Closed-circuit domain quadruplets in BaTiO.sub.3./sub. nanorods embedded in a SrTiO.sub.3./sub. film

    Czech Academy of Sciences Publication Activity Database

    Stepkova, Vilgelmina; Márton, Pavel; Setter, N.; Hlinka, Jiří

    2014-01-01

    Roč. 89, č. 6 (2014), "060101-1"-"060101-6" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/1011 Institutional support: RVO:68378271 Keywords : Ginzburg-Landau-Devonshire model * phase-field approach * nanorods * BaTiO 3 /SrTiO 3 heterostructures Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  11. Oxygen tracer diffusion and surface exchange kinetics in Ba0.5Sr0.5Co0.8Fe0.2O3-δ

    NARCIS (Netherlands)

    Berenov, A.; Atkinson, A.; Kilner, J.; Ananyev, M.; Eremin, V.; Porotnikova, N.; Farlenkov, A.; Kurumchin, E.; Bouwmeester, Henricus J.M.; Bucher, E.; Sitte, W.

    2014-01-01

    The oxygen tracer diffusion coefficient, Db⁎, and the oxygen tracer surface exchange coefficient, k, were measured in Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF5582) over the temperature range of 310–800 °C and the oxygen partial pressure range of 1.3 × 10−3–0.21 bar. Several measurement techniques were used:

  12. Structural and electronic properties of Sr{sub x}Ba{sub 1-x}SnO{sub 3} from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, E. [Departamento de Fisica Teorica e Experimental, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil); Henriques, J.M. [Centro de Educacao e Saude, Universidade Federal de Campina Grande, Campus Cuite, 58175-000 Cuite-PB (Brazil); Azevedo, D.L. [Departamento de Fisica, Universidade Federal do Maranhao, Centro de Ciencias Exatas e Tecnologia, 65085-580 Sao Luis-MA (Brazil); Caetano, E.W.S., E-mail: ewcaetano@gmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Ceara, 60040-531 Fortaleza-CE (Brazil); Freire, V.N. [Departamento de Fisica, Universidade Federal do Ceara, Centro de Ciencias, Caixa Postal 6030, Campus do Pici, 60455-760 Fortaleza-CE (Brazil); Albuquerque, E.L. [Departamento de Biofisica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil)

    2012-03-15

    Neutron diffraction data for Sr{sub x}Ba{sub 1-x}SnO{sub 3} (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) solid solutions were used as inputs to obtain optimized geometries and electronic properties using the density functional theory (DFT) formalism considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The crystal structures and SnO{sub 6} octahedra tilting angles found after total energy minimization agree well with experiment, specially for the GGA data. Elastic constants were also obtained and compared with theoretical and experimental results for cubic BaSnO{sub 3}. While the alloys with cubic unit cell have an indirect band gap, tetragonal and orthorhombic alloys exhibit direct band gaps (exception made to x=1.0). The Kohn-Sham minimum electronic band gap oscillates from 1.52 eV (cubic x=0.0, LDA) to 2.61 eV (orthorhombic x=1.0, LDA), and from 0.74 eV (cubic BaSnO{sub 3}, GGA) to 1.97 eV (orthorhombic SrSnO{sub 3}, GGA). Parabolic interpolation of bands has allowed us to estimate the effective masses for charge carriers, which are shown to be anisotropic and larger for holes. - Graphical Abstract: Highlights: Black-Right-Pointing-Pointer DFT calculations were performed on Sr{sub x}Ba{sub 1-x}SnO{sub 3} solid solutions. Black-Right-Pointing-Pointer Calculated crystal structures agree well with experiment. Black-Right-Pointing-Pointer Alloys have direct or indirect gaps depending on the Sr molar fraction. Black-Right-Pointing-Pointer The Kohn-Sham gap variation from x=0.0 to x=1.0 is close to the experimental value. Black-Right-Pointing-Pointer Carrier effective masses are very anisotropic, specially for holes.

  13. In situ templating synthesis of conic Ba0⋅ 5 Sr0⋅ 5 Co0⋅ 8 Fe0⋅ 2 ...

    Indian Academy of Sciences (India)

    The treatment of the solid precursor with concentrated nitric acid resulted in the mismatch of ionic radius at -site and -site of the ABO3 perovskite, due to the oxidation of cobalt/iron ions, and the formation of Ba0.5Sr0.5(NO3)2 solid solution. Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of ...

  14. Hydrothermal crystal growth and structure determination of double hydroxides LiSb(OH)₆, BaSn(OH)₆, and SrSn(OH)₆.

    Science.gov (United States)

    Mizoguchi, Hiroshi; Bhuvanesh, Nattamai S P; Kim, Young-Il; Ohara, Satoshi; Woodward, Patrick M

    2014-10-06

    Colorless single crystals of LiSb(OH)6, SrSn(OH)6, and BaSn(OH)6, which are useful as precursors for the synthesis of LiSbO3, SrSnO3, and BaSnO3, were synthesized by a low-temperature hydrothermal method using a Teflon-lined autoclave at 380 K. The crystal structures were determined by single-crystal X-ray diffraction measurements. LiSb(OH)6 crystallizes in the trigonal space group P3̅1m with a = 5.3812(3)A, c = 9.8195(7)A, V = 246.25(3)A(3), Z = 2. In this layered structure, [Li2Sb(OH)6](+) and [Sb(OH)6](-) layers are alternately stacked along the c-direction. The [Li2Sb(OH)6](+) layer can be regarded as a cation-ordered CdCl2 layer. The [Sb(OH)6)](-) layer is built up from isolated [Sb(OH)6](-) octahedra, which are linked to each other via hydrogen bonding within the layer. BaSn(OH)6 and SrSn(OH)6 crystallize with monoclinic P21/n space group symmetry. The monoclinic structure possesses a CsCl-type packing of Ba(2+)/Sr(2+) cations and [Sn(OH)6](2-) anions. The [Sn(OH)6](2-) polyhedra are connected to each other through hydrogen bonding to form a three-dimensional framework. The factors that favor these hitherto unknown crystal structures are discussed using a structure map that compares various M(OH)3 and M'M″(OH)6 compounds.

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

    Energy Technology Data Exchange (ETDEWEB)

    Keane, P.M. [Chicago Univ., IL (United States). Dept. of Chemistry][Argonne National Lab., IL (United States); Burdett, J.K. [Chicago Univ., IL (United States). Dept. of Chemistry

    1994-06-01

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

  16. Structural properties and chemical homogeneity of underdoped La{sub 2{minus}x}M{sub x}CuO{sub 4} cuprates (M = Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Ferretti, M.; Magnone, E.; Napoletano, M. [Univ. degli Studi di Genova (Italy)

    1999-04-20

    The present work reports a systematic and accurate study on crystal structure and chemical homogeneity of underdoped La{sub 2{minus}x}M{sub x}CuO{sub 4} (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.

  17. Performance and stability of niobium-substituted Ba0.5Sr0.5Co0.8Fe0.2O3-¿ membranes

    NARCIS (Netherlands)

    Fang, S.; Yoo, C.-Y.; Bouwmeester, Henricus J.M.

    2011-01-01

    The phase stability, thermal expansion, electrical conductivity, and oxygen permeation of perovskite-type oxides Ba0.5Sr0.5(Co0.8Fe0.2)1 − xNbxO3 − δ (x = 0 − 0.2) have been investigated. Room-temperature X-ray diffraction of as-prepared powders indicates that in the investigated compositional range

  18. Preparation and photocatalytic properties of BaZrO3 and SrZrO3 modified with Cu2O/Bi2O3 quantum dots

    Science.gov (United States)

    Miodyńska, Magdalena; Bajorowicz, Beata; Mazierski, Paweł; Lisowski, Wojciech; Klimczuk, Tomasz; Winiarski, Michał Jerzy; Zaleska-Medynska, Adriana; Nadolna, Joanna

    2017-12-01

    In this study, we report a novel method of BaZrO3 and SrZrO3 surface modification by two different types of quantum dots (QDs, Cu2O and Bi2O3), which improved the photocatalytic performance of the obtained materials under UV-Vis light irradiation. Pristine BaZrO3 and SrZrO3 were prepared by the hydrothermal method. The deposition of Cu2O- and Bi2O3-QDs was carried out by chemical reduction. The morphology of the nanoparticles was estimated based on microscopic analysis (SEM, TEM). The perovskite structure and phase composition of polycrystals were confirmed by X-ray powder diffraction analysis (XRD). The elemental surface composition and the chemical character of detected elements were identified by X-ray photoelectron spectroscopy (XPS). The absorption ability and luminescence properties of nanocomposites were investigated by UV-Vis diffuse-reflectance spectroscopy (DRS UV-Vis) and luminescence spectroscopy. The influence of Cu2O/Bi2O3-QDs modification on the photocatalytic activity of BaZrO3 and SrZrO3 was evaluated by the phenol photodegradation process in the liquid phase under UV-Vis and toluene degradation in the gas phase under Vis irradiation. The highest photoactivity under UV-Vis light was observed for BaZrO3/1% Cu2O/33% Bi2O3 and SrZrO3/1% Cu2O/33% Bi2O3 samples. Research also demonstrated that single-type QD deposition (Cu2O or Bi2O3) on the zirconate surface decreases the photoactivity in comparison with pristine zirconates. The mechanism of photocatalytic activity of the obtained nanocomposites was investigated by the formation of hydroxyl radicals under UV-Vis irradiation in the presence of terephthalic acid.

  19. Preparation and dielectric properties of BaCu(B2O5)-doped SrTiO3-based ceramics for energy storage

    International Nuclear Information System (INIS)

    Li, Lingxia; Yu, Xiaoxu; Cai, Haocheng; Liao, Qingwei; Han, Yemei; Gao, Zhengdong

    2013-01-01

    Highlights: • BaCu(B 2 O 5 ) is added to the multi-ions doped SrTiO 3 ceramics as sintering aid. • The sintering temperature is decreased from 1300 °C to 1075 °C. • The incorporation of Ba 2+ into the matrix increases the dielectric constant. • The breakdown strength increases due to the decrease of grain size and porosity. • The dissolution of BCB contributes to the improvement of dielectric properties. -- Abstract: BaCu(B 2 O 5 ) (BCB) was used as sintering aids to lower the sintering temperature of multi-ions doped SrTiO 3 ceramics effectively from 1300 °C to 1075 °C by conventional solid state method. The effect of BCB content on crystalline structures, microstructures and properties of the ceramics was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurements, respectively. The addition of BCB enhanced the breakdown strength (BDS) while did not sacrifice the dielectric constant. The enhancement of BDS should be due to the modification of microstructures, i.e., smaller and more homogeneous grain sizes after BCB addition. The dielectric constant of BCB-doped ceramics maintained a stable value with 1.0 mol% BCB, which was dominated by the combination of two opposite effects caused by the presence of second phases and the incorporation of Cu 2+ and Ba 2+ , while further increase was owing to the increase of dissolved Ba 2+ ions when the content of BCB is more than 2.0 mol%. The multi-ions doped SrTiO 3 ceramics with 1.0 mol% BCB addition showed optimal dielectric properties as follows: dielectric constant of 311.37, average breakdown strength of 28.78 kV/mm, discharged energy density of 1.05 J/cm 3 and energy efficiency of 98.83%

  20. The cause of ‘weak-link’ grain boundary behaviour in polycrystalline Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 superconductors

    Science.gov (United States)

    Wang, Guanmei; Raine, Mark J.; Hampshire, Damian P.

    2018-02-01

    The detrimental effects of grain boundaries have long been considered responsible for the low critical current densities ({J}{{c}}) in high temperature superconductors. In this paper, we apply the quantitative approach used to identify the cause of the ‘weak-link’ grain boundary behaviour in YBa2Cu3O7 (Wang et al 2017 Supercond. Sci Technol. 30 104001), to the Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 materials that we have fabricated. Magnetic and transport measurements are used to characterise the grain and grain boundary properties of micro- and nanocrystalline materials. Magnetisation measurements on all nanocrystalline materials show non-Bean-like behaviour and are consistent with surface pinning. Bi2Sr2CaCu2O8: our microcrystalline material has very low grain boundary resistivity ({ρ }{{GB}}), which is similar to that of the grains ({ρ }{{G}}) such that {ρ }{{GB}}≈ {ρ }{{G}}=2× {10}-5 {{Ω }}{{m}} (assuming a grain boundary thickness (d) of 1 nm) equivalent to an areal resistivity of {ρ }{{G}}=2× {10}-14 {{{Ω }}{{m}}}2. The transport {J}{{c}} values are consistent with well-connected grains and very weak grain boundary pinning. However, unlike low temperature superconductors (LTS) in which decreasing grain size increases the pinning along the grain boundary channels, any increase in pinning produced by making the grains in our Bi2Sr2CaCu2O8 materials nanocrystalline was completely offset by a decrease in the depairing current density of the grain boundaries caused by their high resistivity. We suggest a different approach to increasing {J}{{c}} from that used in LTS materials, namely incorporating additional strong grain and grain boundary pinning sites in microcrystalline materials to produce high {J}{{c}} values. Bi2Sr2Ca2Cu3O10: both our micro- and nanocrystalline samples have {ρ }{{GB}}/{ρ }{{G}} of at least 103. This causes strong suppression of {J}{{c}} across the grain boundaries, which explains the low transport {J}{{c}} values we find

  1. Raman scattering, magnetization and magnetotransport study of SrFeO3-δ, Sr3Fe2O7-δ and CaFeO3

    International Nuclear Information System (INIS)

    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 SrFeO 3-δ , Sr 3 Fe 2 O 7-δ and CaFeO 3 as a function of temperature. We describe the preparation of nearly stoichiometric SrFeO 3-δ crystals with δ 3.00 in order to assign the phonon modes observed in infra-red experiments. We have measured the Raman spectra of the tetragonal phase in the temperature range 13 K to 300 K and of the orthorhombic phase in the temperature range 6 K to 475 K. We have measured the temperature dependence of the magnetization for the magnetic field along high-symmetry axes of the crystal structure. We have also performed neutron diffraction measurements. The resistivity and the magnetoresistance were measured in the range 10 K to 300 K. Finally we have measured the Raman spectra of the same sample in the temperature range 15 K to 440 K. In order to assign the observed modes, we have performed lattice dynamics calculations based on the published crystal structure of Sr 3 Fe 2 O 7 . (orig.)

  2. Structure and Dynamics Investigations of Sr/Ca-Doped LaPO4 Proton Conductors

    Energy Technology Data Exchange (ETDEWEB)

    al-Wahish, Amal [Univ. of Missouri, Columbia, MO (United States). Research Reactor; al-Binni, U. [Univ. of Washington, Seattle, WA (United States). Dept. of Physics and Astronomy; Tetard, L. [Univ. of Central Florida, Orlando, FL (United States). NanoScience Technology Center; Bridges, Craig A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Kharel, Krishna [Lamar Univ., Beaumont, TX (United States). Dept. of Chemistry and Biochemistry; Günaydın-Şen, Özge [Lamar Univ., Beaumont, TX (United States). Dept. of Chemistry and Biochemistry; Huq, A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division; Musfeldt, J. L. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Paranthaman, M. P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Mandrus, D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering

    2017-05-15

    Proton conductors loom out of the pool of candidate materials with great potential to boost hydrogen alternatives to fossil-based resources for energy. Acceptor doped lanthanum orthophosphates are considered for solid oxide fuel cells (SOFCs) for their potential stability and conductivity at high temperature. By exploring the crystal and defect structure of x% Sr/Ca-doped LaPO4 with different nominal Sr/Ca concentrations (x = 0 – 10) with Neutron powder diffraction (NPD) and X-ray powder diffraction (XRD), we confirm that Sr/Ca-doped LaPO4 can exist as self-supported structures at high temperatures during solid oxide fuel cell operation. Thermal stability, surface topography, size distribution are also studied to better understand the proton conductivity for dry and wet compounds obtained at sintering temperatures ranging from 1200 to 1400 °C using a combination of scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). In conclusion, the results suggest that Sr doped samples exhibit the highest proton conductivity of our samples and illustrate the impact of material design and versatile characterization schemes on the development of proton conductors with superior functionality.

  3. The effect of changing seawater Ca and Mg concentrations upon the distribution coefficients of Mg and Sr in the skeletons of the scleractinian coral Pocillopora damicornis

    Science.gov (United States)

    Giri, Sharmila J.; Swart, Peter K.; Devlin, Quinn B.

    2018-02-01

    The skeletal composition of calcifying organisms, in particular Mg/Ca and Sr/Ca ratios, have been widely used to understand fluctuations in seawater chemistry throughout the Phanerozoic. While the success of applying these data to the geologic record depends on a knowledge of the distribution coefficients for these elements (DMg and DSr), there are scarcely any studies which have described how these values vary as a result of changing seawater Mg/Ca ratios. To address this, we have cultured the scleractinian coral, Pocillopora damicornis, in seawater with ranges of Mg and Ca concentrations. Here, we demonstrate that Mg/Ca and Sr/Ca ratios of coral skeletons correlate with total seawater Mg/Ca and Sr/Ca molar ratios, but that apparent DMg and DSr values do not remain constant across the range of experimental seawater treatments, with DMg values significantly increasing with seawater Mg/Ca ratios and DSr values significantly increasing with seawater Ca concentrations. These trends are not rate dependent and may be best explained by a Rayleigh distillation model, in which the calcifying space is semi-isolated from seawater during skeletogenesis (i.e. leaky). As there is a slight increase in DMg and decrease in DSr values between our "Jurassic" and "Modern" seawater treatments, the application of a constant distribution coefficient to estimate changes in ancient seawater chemistry may underestimate seawater Mg/Ca ratios and overestimate Sr/Ca throughout the Mesozoic and Cenozoic. We suggest that interpretations of seawater chemistry from fossil corals may be improved by using the relationships derived for skeletal and seawater Mg/Ca and Sr/Ca ratios established by our experiments, as they incorporate the effect of seawater Mg/Ca ratios on skeletal Mg/Ca and Sr/Ca ratios.

  4. Stoichiometry and phase purity control of radio frequency magnetron sputter deposited Ba0.45Sr0.55TiO3 thin films for tunable devices

    Science.gov (United States)

    Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin

    2013-11-01

    The systematic study of the oxygen partial pressure (OPP) and total chamber gas pressure (TGP) effects on the stoichiometry and crystal structure of rf sputtered Ba0.45Sr0.55TiO3 (BST) films and their phase purity allowed identifying close to optimal sputtering parameters for BST single phase polycrystalline film. The film with a Ba/Sr ratio equal to that of the source target and (Ba + Sr)/Ti ratio close to unity demonstrated the enhanced permittivity value of 553 and tunability of 69%. It was confirmed that the increase of TGP enables better match of the film and target stoichiometry. However, using O2/Ar ratio as a parameter should be utilized cautiously since exceeding a threshold OPP (2 mTorr in our case) may facilitate secondary phase formation. Relatively large dielectric losses were observed in both films sputtered at high (30 mTorr) and low (5 mTor) TGPs. The presence of oxygen vacancies was identified as a probable cause of losses, which is indirectly confirmed by the deviation of the film lattice constant from that of the bulk target.

  5. Half-integer flux quantum effect in tricrystal Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Kirtley, J.R.; Tsuei, C.C.; Raffy, H.; Sun, J.Z.; Megtert, S.

    1996-01-01

    We have used a scanning SQUID microscope to directly observe the half-integer flux quantum effect, in epitaxial films of Bi 2 Sr 2 CaCu 2 O 8+δ , at the meeting point of a tricrystal substrate of SrTiO 3 in a geometry chosen to show this effect for a d-wave superconductor. This observation, when considered along with recent photoemission results, proves that the in-plane order parameter for this high-T c cuprate superconductor closely follows d x 2 -y 2 symmetry. (orig.)

  6. Sr-doped nanowire modification of Ca-Si-based coatings for improved osteogenic activities and reduced inflammatory reactions

    Science.gov (United States)

    Li, Kai; Hu, Dandan; Xie, Youtao; Huang, Liping; Zheng, Xuebin

    2018-02-01

    Biomedical coatings for orthopedic implants should facilitate osseointegration and mitigate implant-induced inflammatory reactions. In our study, Ca-Si coatings with Sr-containing nanowire-like structures (NW-Sr-CS) were achieved via hydrothermal treatment. In order to identify the effect of nanowire-like topography and Sr dopant on the biological properties of Ca-Si-based coatings, the original Ca-Si coating, Ca-Si coatings modified with nanoplate (NP-CS) and similar nanowire-like structure (NW-CS) were fabricated as the control. Surface morphology, phase composition, surface area, zeta potential and ion release of these coatings were characterized. The in vitro osteogenic activities and immunomodulatory properties were evaluated with bone marrow stromal cells (BMSCs) and RAW 264.7 cells, a mouse macrophage cell line. Compared with the CS and NP-CS coatings, the NW-CS coating possessed a larger surface area and pore volume, beneficial protein adsorption, up-regulated the expression levels of integrin β1, Vinculin and focal adhesion kinase and promoted cell spreading. Furthermore, the NW-CS coating significantly enhanced the osteogenic differentiation and mineralization as indicated by the up-regulation of ALP activity, mineralized nodule formation and osteoblastogenesis-related gene expression. With the introduction of Sr, the NW-Sr-CS coatings exerted a greater effect on the BMSC proliferation rate, calcium sensitive receptor gene expression as well as PKC and ERK1/2 phosphorylation. In addition, the Sr-doped coatings significantly up-regulated the ratio of OPG/RANKL in the BMSCs. The NW-Sr-CS coatings could modulate the polarization of macrophages towards the wound-healing M2 phenotype, reduce the mRNA expression levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and enhance anti-inflammatory cytokines (IL-1ra, IL-10). The Sr-doped nanowire modification may be a valuable approach to enhance osteogenic activities and reduce inflammatory reactions.

  7. Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

    International Nuclear Information System (INIS)

    Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

    2002-01-01

    Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

  8. Effects studies of H2SO4/Na2SO4 on separation of Sr-90 from liquid Sr-90 waste by coprecipitation method using BaSO4 as a carrier

    International Nuclear Information System (INIS)

    Soetjipto.

    1978-01-01

    Treatment of radioactive liquid waste of Sr-90 less than 10 -3 Uci/ml by coprecipitation method using BaSO 4 as carrier has been studied. The experiment shows that the removal efficiency of Sr-90 is high, if the molarity of H 2 SO 4 /Na 2 SO 4 is high. If Na 2 SO 4 is used as source SOsub(4)sup(2-), the removal efficiency is higher than H 2 SO 4 as source SOsub(4)sup(2-). The high value of pH which is equivalent to the low concentration of HCl will result in the high removal efficiency of Sr-90 in the waste treatment using H 2 SO 4 as source SOsub(4)sup(2-). (author)

  9. Constraining the 40K decay constant with 87Rb-87Sr - 40K-40Ca chronometer intercomparison

    Science.gov (United States)

    Naumenko-Dèzes, Maria O.; Nägler, Thomas F.; Mezger, Klaus; Villa, Igor M.

    2018-01-01

    A literature survey reveals that the K-Ar chronometer gives ages that are ca. 1% younger than U-Pb ages. This offset is generally attributed to an inaccurate 40K decay constant. Three geological samples selected from a shortlist of eight with known U-Pb ages were investigated using detailed petrological methods and subsequently the Rb-Sr and K-Ca chronometers in order (a) to evaluate if they meet the requirement of a geological history reflecting a ;point-like; event (i.e. isochronous formation and subsequent ideal closure of chronometers) and (b) to narrow down the systematic uncertainty on the 40K decay constant by investigating the metrologically traceable K-Ca decay branch. Lepidolite of the Rubikon pegmatite, Namibia, was dated with Rb-Sr at 504.7 ± 4.2 Ma and the phlogopite and apatite from the Phalaborwa carbonatite complex, South Africa, yielded a Rb-Sr age of 2058.9 ± 5.2 Ma. Both Rb-Sr ages agree with published U-Pb ages. The Rb-Sr age of the late Archean Siilinjärvi carbonatite, Finland, records a later regional metamorphic event at 1869 ± 10 Ma. Only the samples from the Phalaborwa complex represent a ;point-like; magmatic event and meet all the criteria to make them suitable for the 40K decay constant intercalibration. The Phalaborwa K-Ca isochron has a slope of 1.878 ± 0.012. Forcing the K-Ca isochron to coincide with the U-Pb and Rb-Sr ages gives one equation with two unknowns. Assuming that the branching ratio of the K-Ca branch, BCa, lies in the interval (k = 2) of all published references, 0.8925 < BCa < 0.8963, then the most reliable uncertainty interval (k = 2) for the total 40K decay constant, λtot, is calculated as 5.484 × 10-10 a-1 < λtot < 5.498 × 10-10 a-1. This confirms that the currently used IUGS recommendation is inaccurate.

  10. Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

    Science.gov (United States)

    Bedekar, M. M.; Safari, A.; Wilber, W.

    1992-11-01

    Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.

  11. Eu(2+) luminescence in SrCaP2 O7 pyrophosphate phosphor.

    Science.gov (United States)

    Kohale, R L; Dhoble, S J

    2013-01-01

    A series of Eu(2+) activated SrCaP2 O7 pyrophosphate phosphors were synthesized by the modified solid-state reaction method. The X-ray diffraction (XRD) and photoluminescence (PL) properties of these phosphors were investigated at room temperature. The excitation spectra indicate that these phosphors can be effectively excited by Hg-free excitation. The emission spectra exhibit strong blue performance, which is due to the 4f(6) 5d(1) →4f(7) transition of Eu(2+) . The Fourier transform infrared spectrum at room temperature was investigated and surface morphology has been studied by scanning electron microscope. The prepared phosphor exhibited intense blue emission at the 427 nm owing to Eu(2+) ion by Hg-free excitation at 330 nm, that is, solid-state lighting excitation. Hence, the availability of such a phosphor will significantly help in the growth of blue-emitting solid-state lighting applications. Copyright © 2012 John Wiley & Sons, Ltd.

  12. Preparation and characterizations of Ba0.8Ca0.2TiO3 by complex polymerization method (CPM)

    International Nuclear Information System (INIS)

    Motta, F.V.; Marques, A.P.A.; Escote, M.T.; Melo, D.M.A.; Ferreira, A.G.; Longo, E.; Leite, E.R.; Varela, J.A.

    2008-01-01

    Ba 0.8 Ca 0.2 TiO 3 (BCT) was prepared by the complex polymerization method (CPM) using Ba 0.8 Ca 0.2 CO 3 and [Ti[OCH(CH 3 ) 2 ] 4 as starting materials. The powders were crystallized at several temperatures from 400 to 1200 deg. C using different times (from 1 to 8 h). The phase evolution and the physical properties were characterized by X-ray diffraction, Raman and IR spectroscopy. Such results indicate that the precursor Ba 0.8 Ca 0.2 CO 3 used in the synthesis of Ba 0.8 Ca 0.2 TiO 3 promotes an effective complexation of the ions Ca 2+ in the matrix of BaTiO 3 . After heat treatment for 2 h at 600 deg. C the phase BCT was obtained with absence of the CaTiO 3 or BaCO 3 phases. The CPM is an efficient method in the synthesis of the BCT, using small reaction time and low temperature and cost for the preparation of these powders

  13. Ca, Sr, O and D isotope approach to defining the chemical evolution of hydrothermal fluids: example from Long Valley, CA, USA

    Science.gov (United States)

    Brown, Shaun T.; Kennedy, B. Mack; DePaolo, Donald J.; Hurwitz, Shaul; Evans, William C.

    2013-01-01

    We present chemical and isotopic data for fluids, minerals and rocks from the Long Valley meteoric-hydrothermal system. The samples encompass the presumed hydrothermal upwelling zone in the west moat of the caldera, the Casa Diablo geothermal field, and a series of wells defining a nearly linear, ∼16 km long, west-to-east trend along the likely fluid flow path. Fluid samples were analyzed for the isotopes of water, Sr, and Ca, the concentrations of major cations and anions, alkalinity, and total CO2. Water isotope data conform to trends documented in earlier studies, interpreted as indicating a single hydrothermal fluid mixing with local groundwater. Sr isotopes show subtle changes along the flow path, which requires rapid fluid flow and minimal reaction between the channelized fluids and the wallrocks. Sr and O isotopes are used to calculate fracture spacing using a dual porosity model. Calculated fracture spacing and temperature data for hydrothermal fluids indicate the system is (approximately) at steady-state. Correlated variations among total CO2, and the concentration and isotopic composition of Ca suggest progressive fluid degassing (loss of CO2), which drives calcite precipitation as the fluid flows west-to-east and cools. The shifts in Ca isotopes require that calcite precipitated at temperatures of 150–180 °C is fractionated by ca. −0.3‰ to −0.5‰ relative to aqueous species. Our data are the first evidence that Ca isotopes undergo kinetic fractionation at high temperatures (>100 °C) and can be used to trace calcite precipitation along hydrothermal fluid flow paths.

  14. Physical Properties of ( {BaSnO}_{3})_mathrm{x}/ {Cu}_{0.5} {Tl}_{0.5} {Ba}_{2} {Ca}_{2} {Cu}_{3} {O}_{10{-}delta } ( BaSnO 3 ) x / Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10 - δ Superconductor Composite

    Science.gov (United States)

    Srour, A.; Awad, R.; Malaeb, W.; Barakat, M. ME.

    2017-11-01

    The influence of barium tin oxide nanoparticles addition on the structural and superconducting properties of the Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10{-}δ } phase, (CuTl)-1223, was studied. A different wt% of BaSnO3, ranging from 0.00 to 1.50, were added into (CuTl)-1223 phase, and this composite was synthesized using the solid-state reaction technique. The phase formation and lattice parameters were calculated from X-ray powder diffraction measurements. The grain connectivity and surface morphology were identified using scanning electron microscope. Energy dispersive X-ray spectroscopy gave the real elemental composition of the prepared samples. Superconducting transition temperature ({T_c}) and critical current density ({J_c}) were determined from the electrical resistivity and I-V measurements, respectively. A complete study about the vibration modes of different atoms was carried out using Fourier transform infrared (FTIR) absorption spectroscopy of (BaSnO3)_x/CuTl-1223 composite. The increase in {T_c} and {J_c} up to x=0.25 wt% is an evidence for improving the superconducting properties of (BaSnO3)_x/CuTl-1223 composites by enhancing both the inter-grains coupling and volume fraction of the (CuTl)-1223 phase.

  15. Examining the Utility of Coral Ba/Ca as a Paleo-Proxy for Interannual River Discharge Variability Along the Pacific Coast of Panamá

    Science.gov (United States)

    Brenner, L. D.; Linsley, B. K.; Dunbar, R. B.

    2016-02-01

    Climate along the Pacific coast of Panamá is largely dictated by seasonal N/S shifts in the Intertropical Convergence zone (ITCZ) and the consequent oscillations in precipitation. During the Panamanian wet season (May-Nov.) river discharge (Q) reaches its maximum and serves as a potential source of trace elements, such as Ba, to reefs. Near shore corals can record the waterborne trace metal history in their aragonite skeletons, which can then be exploited as a paleo-proxy for river discharge. We present two high-resolution Ba/Ca records from nearby Porites corals in the Gulf of Chiriquí, Panamá in an effort to better understand the long-term discharge and precipitation history of the region. Both corals record similar annual average Ba/Ca values throughout the time series' (R=0.55) suggesting that they are faithfully recording water column Ba levels at a large scale. A monthly composite average of both coral Ba/Ca records is positively correlated to an average of all available river discharge data (n= 5) (R=0.42). While instrumental data are relatively sparse and discontinuous, there is a significant relationship between the two variables producing a Ba/Ca-discharge relationship where Q (m3/s)= Ba/Ca(μmol/mol)×49.97(μmol/mol)(m3/s)-1-190.85. The Ba/Ca peaks correspond to the annual minima in our paired near-monthly resolved coral δ18O measurements, further supporting that maximum Q in the Gulf is concurrent with the annual salinity minima and precipitation maximum. Coral Ba/Ca in the Gulf of Chiriquí indicates that annual average river Q into the Gulf has varied from 50 to 133 m3/s over from 1966 to 1983. As inferred from our Ba/Ca data, interannual variability of river Q accounts for 25% of total variance (after removing the seasonal cycle) and a long-term secular trend of increasing river Q accounts for 30%. Our Porites coral Ba/Ca records from the Pacific side of Panamá provide an opportunity to supplement the limited instrumental river discharge data

  16. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia shell calcite precipitated at constant temperature

    Directory of Open Access Journals (Sweden)

    P. S. Freitas

    2009-07-01

    Full Text Available Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

  17. A novel approach to Ca-Sr separation in the determination of 90Sr using inorganic exchangers

    International Nuclear Information System (INIS)

    Stella, R.; Pavia Univ.; Valentini, M.T.G.; Maggi, L.

    1992-01-01

    A procedure for 90 Sr determination in calcium rich samples is presented. It is based on the precipitation of calcium oxalate in homogeneous solution and under controlled conditions to minimize the comprecipitation of strontium. The latter is subsequently separated as carbonate and radiochemical purification is completed by ion exchange chromatography on two inorganic exchangers: PRTD (partially reduced tin dioxide) and CUCR (copper chromate). The procedure was applied to environmental samples such as ashed sediment, fish and vegetable and results are reported. (author) 15 refs.; 2 tabs

  18. Nitridogermanate Nitrides Sr7[GeN4]N2 and Ca7[GeN4]N2

    OpenAIRE

    Junggeburth, Sebastian C.; Oeckler, Oliver; Johrendt, Dirk; Schnick, Wolfgang

    2008-01-01

    The alkaline earth nitridogermanate nitrides AE7[GeN4]N2 (AE = Ca, Sr) have been synthesized using a Na flux technique in sealed Ta tubes. According to single-crystal X-ray diffraction the isotypic compounds crystallize in space group Pbcn (No. 60) with Z = 4, (Sr7[GeN4]N2: a = 1152.6(2), b = 658.66(13), c = 1383.6(3) pm, V = 1050.5(4) × 106 pm3, R1 = 0.049; Ca7[GeN4]N2: a = 1082.6(2), b = 619.40(12), c = 1312.1(3) pm, V = 879.8(3) × 106 pm3, R1 = 0.016). Owing to the high N/Ge ratio, the com...

  19. Tren kenaikan suhu permukaan laut pada abad ke-14 berdasarkan data geokimia Sr/Ca dari fosil koral Mentawai

    Directory of Open Access Journals (Sweden)

    Sri Y. Cahyarini

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v5i2.96Sr/Ca content ratio in coral is a promising tool for a sea surface temperature reconstruction. In this study, Sr/Ca was analyzed from the top core of fossil coral from Central Mentawai, Indonesia (BLS. The dating of U/Th is used for the age determination of the fossil coral. Based on the U/Th dating, the fossil coral used in this study was deposited in 14th century which approximately has a time range 11 years. The result of this study shows that in the 14th century, the sea surface temperature increased by 3.20 C during 11 years period.

  20. Anisotropic strain relaxation in (Ba0.6Sr0.4)TiO3 epitaxial thin films

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.

    2005-05-01

    We have studied the evolution of anisotropic epitaxial strains in ⟨110⟩-oriented (Ba0.60Sr0.40)TiO3 paraelectric (m3m) thin films grown on orthorhombic (mm2) ⟨100⟩-oriented NdGaO3 by high-resolution x-ray diffractometry. All the six independent components of the three-dimensional strain tensor were measured in films with 25-1200-nm thickness, from which the principal stresses and strains were obtained. Pole figure analysis indicated that the epitaxial relations are [001]m3m‖[001]mm2 and [1¯10]m3m‖[010]mm2 in the plane of the film, and [110]m3m‖[100]mm2 along the growth direction. The dislocation system responsible for strain relief along [001] has been determined to be ∣b ∣(001)=3/4∣b∣. Strain relief along the [1¯10] direction, on the other hand, has been determined to be due to a coupled mechanism given by ∣b∣(1¯10)=∣b∣ and ∣b∣(1¯10)=√3 /4∣b∣. Critical thicknesses, as determined from nonlinear regression using the Matthews-Blakeslee equation, for misfit dislocation formation along [001] and [1¯10] direction were found to be 5 and 7 nm, respectively. The residual strain energy density was calculated as ˜2.9×106J/m3 at 25 nm, which was found to relax an order of magnitude by 200 nm. At 200 nm, the linear dislocation density along [001] and [1¯10] are ˜6.5×105 and ˜6×105cm-1, respectively. For films thicker than 600 nm, additional strain relief occurred through surface undulations, indicating that this secondary strain-relief mechanism is a volume effect that sets in upon cooling from the growth temperature.

  1. Grain Boundary Analysis of the Garnet-like Oxides Li7+X-YLa3-XAXZr2-YNbYO12 (A = Sr or Ca

    Directory of Open Access Journals (Sweden)

    Shingo Ohta

    2016-07-01

    Full Text Available Garnet-like oxides having the formula Li7+X-YLa3-XAXZr2-YNbYO12 (A = Sr or Ca were synthesized using a solid-state reaction and their bulk and grain boundary resistivities were assessed by AC impedance measurements. A difference in grain boundary resistivity was identified between the Sr and Ca materials and so the grain boundaries were examined using electron probe microanalysis (EPMA. The difference in the grain boundary resistivities was attributed to the core-shell structure of the Sr-substituted samples. In contrast, the Ca-substituted materials exhibited accumulations of impurities at the grain boundaries.

  2. Triadin/Junctin double null mouse reveals a differential role for Triadin and Junctin in anchoring CASQ to the jSR and regulating Ca(2+ homeostasis.

    Directory of Open Access Journals (Sweden)

    Simona Boncompagni

    Full Text Available Triadin (Tdn and Junctin (Jct are structurally related transmembrane proteins thought to be key mediators of structural and functional interactions between calsequestrin (CASQ and ryanodine receptor (RyRs at the junctional sarcoplasmic reticulum (jSR. However, the specific contribution of each protein to the jSR architecture and to excitation-contraction (e-c coupling has not been fully established. Here, using mouse models lacking either Tdn (Tdn-null, Jct (Jct-null or both (Tdn/Jct-null, we identify Tdn as the main component of periodically located anchors connecting CASQ to the RyR-bearing jSR membrane. Both proteins proved to be important for the structural organization of jSR cisternae and retention of CASQ within them, but with different degrees of impact. Our results also suggest that the presence of CASQ is responsible for the wide lumen of the jSR cisternae. Using Ca(2+ imaging and Ca(2+ selective microelectrodes we found that changes in e-c coupling, SR Ca(2+content and resting [Ca(2+] in Jct, Tdn and Tdn/Jct-null muscles are directly correlated to the effect of each deletion on CASQ content and its organization within the jSR. These data suggest that in skeletal muscle the disruption of Tdn/CASQ link has a more profound effect on jSR architecture and myoplasmic Ca(2+ regulation than Jct/CASQ association.

  3. Microstructure and bio-corrosion behaviour of Mg-5Zn-0.5Ca -xSr alloys as potential biodegradable implant materials

    Science.gov (United States)

    Yan, Li; Zhou, Jiaxing; Sun, Zhenzhou; Yang, Meng; Ma, Liqun

    2018-04-01

    Magnesium alloys are widely studied as biomedical implants owing to their biodegradability. In this work, novel Mg-5Zn-0.5Ca-xSr (x = 0, 0.14, 0.36, 0.50, 0.70 wt%) alloys were prepared as biomedical materials. The influence of strontium (Sr) addition on the microstructure, corrosion properties and corrosion morphology of the as-cast Mg-5Zn-0.5Ca-xSr alloys is investigated by a variety of techniques such as scanning electron microscopy, x-ray diffraction, and electrochemical measurements. The Sr-free alloy is composed of three phases, namely, α-Mg, CaMg2 and Ca2Mg6Zn3, while the alloys with the Sr addition consist of α-Mg, CaMg2 and Ca2Mg6Zn3 and Mg17Sr2. Corrosion experiments in Hank’s solution show that the addition of a small amount of Sr can improve the corrosion resistance of the Mg-5Zn-0.5Ca alloy. The corrosion products include Mg(OH)2, Zn(OH)2, Ca(OH)2, and HA (Ca5(PO4)3(OH)). Mg-5Zn-0.5Ca-0.36Sr alloy has the minimum weight loss rate (0.68 mm/a), minimal hydrogen evolution (0.08 ml/cm2/d) and minimum corrosion current density (7.4 μA/cm2), indicating that this alloy shows the best corrosion resistance.

  4. Fabrication and characterization of high-quality (Hg,Re)Ba sub 2 CaCu sub 2 O sub y thin films on LSAT substrates

    CERN Document Server

    Ogawa, A; Sugano, T; Adachi, S; Suzuki, K; Nakagaki, N; Enomoto, Y; Tanabe, K

    2002-01-01

    We have succeeded in fabricating high-quality (Hg,Re)Ba sub 2 CaCu sub 2 O sub y ((Hg,Re)-1212) thin films with a thickness of 300 nm on (LaAlO sub 3) sub 0 sub . sub 3 -(SrAl sub 0 sub . sub 5 Ta sub 0 sub . sub 5 O sub 3) sub 0 sub . sub 7 (LSAT) substrates. The films were fabricated by repeating the two-step process, which consists of the preparation of a precursor film and the heat treatment in Hg-vapour atmosphere. For the purpose of improving their crystal quality, the heat treatment in the final process was carried out in a lower Hg-vapour pressure for a longer time. The obtained films had a flat surface and no appreciable outgrowth. The films exhibited a T sub c value of 120 K and a J sub c value of 4.4 x 10 sup 6 A cm sup - sup 2 at 77 K in a self-field, which are substantially higher than those for the films fabricated in higher Hg-vapour atmosphere. Their electrical transport properties in magnetic fields up to 7 T were investigated. Their lower irreversibility fields at 77 K as well as the higher ...

  5. Novel dielectric properties of glasses prepared by quenching melts of Bi-Ca-Sr-Cu-O cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Varma, K.B.R.; Subbanna, G.N.; Ramakrishnan, T.V. (Materials Research Centre, Indian Inst. of Science, Bangalore (India) Dept. of Physics, Indian Inst. of Science, Bangalore (India)); Rao, C.N.R. (Solid State and Structural Chemistry Unit, Indian Inst. of Science, Bangalore (India))

    1989-12-01

    Glasses, prepared from the melts of Bi{sub 2}(Ca,Sr){sub n+1}Cu{sub n}O{sub 2n+4} (n=1, 2 and 3) have been characterized by various techniques. These glasses exhibit relatively high dielectric constants, high electrical conductivity, a ferroelectric-like dielectric hysteresis loop and pyroelectric effect at 300K. They also show weak microwave absorption at 77K. (orig.).

  6. Laser ablation deposition of superconducting Bi-Sr-Ca-Cu-O thin films on zirconia-buffered crystalline quartz

    International Nuclear Information System (INIS)

    Thin films of Bi-Sr-Ca-Cu-O have been deposited on crystalline quartz substrates by laser ablation. Without a buffer layer, superconducting regions exist in the films as detected by magnetically modulated microwave absorption. However, with a 1000-A zirconia buffer layer, also deposited by laser ablation, continuous, superconducting thin films were obtained. It is shown that both annealing temperature and annealing time greatly affect the film quality

  7. The influence of the mechanical treatment on the properties of the superconductors Bi-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Smrckova, O.; Sykorova, D.; Novakova, K.

    1995-01-01

    The aim of the present paper was to verify the influence of consolidation of the micro-structure of the samples on electrical properties (T c , J c ) of the superconductors with the composition Bi 3.2 Pb 0. 8Sr 4 Ca 5 Cu 7 O x . The samples which were pressed up to 1.1 GPa and annealed the critical flow current density was increased triple in comparison with original samples

  8. High-density Bi-Pb-Sr-Ca-Cu-O superconductor prepared by rapid thermal melt processing

    Science.gov (United States)

    Moon, B. M.; Lalevic, B.; Kear, B. H.; McCandlish, L. E.; Safari, A.; Meskoob, M.

    1989-10-01

    A high quality, dense Bi-Pb-Sr-Ca-Cu-O superconductor has been successfully synthesized by rapid thermal melt processing. Conventionally sintered pellets were melted at 1200 °C, cooled rapidly, and then annealed. As-melted samples exhibited semiconductor behavior, which upon annealing became superconducting at 115 K [Tc(zero)=105 K]. A detailed study of various processing techniques has been carried out.

  9. Atrial SERCA2a Overexpression Has No Affect on Cardiac Alternans but Promotes Arrhythmogenic SR Ca2+ Triggers.

    Science.gov (United States)

    Nassal, Michelle M J; Wan, Xiaoping; Laurita, Kenneth R; Cutler, Michael J

    2015-01-01

    Atrial fibrillation (AF) is the most common arrhythmia in humans, yet; treatment has remained sub-optimal due to poor understanding of the underlying mechanisms. Cardiac alternans precede AF episodes, suggesting an important arrhythmia substrate. Recently, we demonstrated ventricular SERCA2a overexpression suppresses cardiac alternans and arrhythmias. Therefore, we hypothesized that atrial SERCA2a overexpression will decrease cardiac alternans and arrhythmias. Adult rat isolated atrial myocytes where divided into three treatment groups 1) Control, 2) SERCA2a overexpression (Ad.SERCA2a) and 3) SERCA2a inhibition (Thapsigargin, 1μm). Intracellular Ca2+ was measured using Indo-1AM and Ca2+ alternans (Ca-ALT) was induced with a standard ramp pacing protocol. As predicted, SR Ca2+ reuptake was enhanced with SERCA2a overexpression (poverexpression or inhibition when compared to controls (p = 0.73). In contrast, SERCA2a overexpression resulted in increased premature SR Ca2+ (SCR) release compared to control myocytes (28% and 0%, p overexpression in atrial myocytes can increase SCR, which may be arrhythmogenic.

  10. Preparation of superconducting Bi-Sr-Ca-Cu-O thin films by sequential electron beam evaporation and oxygen annealing

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, J.; Tsaur, B.; Anderson, A.C.; Strauss, A.J.

    1989-01-30

    Superconducting films with nominal composition Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ have been prepared on <100> MgO substrates by sequential electron beam evaporation of Cu, Bi, and Sr/sub 2/3/ Ca/sub 1/3/ F/sub 2/, followed by annealing in flowing wet, then dry, O/sub 2/. X-ray diffraction data show that the films contain the two Bi-Sr-Ca-Cu-O phases that have been identified in the literature as a superconducting phase with capprox.31 A and a semiconducting phase with capprox.24 A. Both phases are strongly textured with the c axis perpendicular to the substrate. For the best film, which was annealed at 870 /sup 0/C for 30 min, zero resistance was observed at 90 K, and the critical current density increased from 0.8 x 10/sup 5/ A/cm/sup 2/ at 77 K to 2.3 x 10/sup 5/ A/cm/sup 2/ at 4.2 K.

  11. Preparation of superconducting Bi-Sr-Ca-Cu-O thin films by sequential electron beam evaporation and oxygen annealing

    Science.gov (United States)

    Steinbeck, J.; Tsaur, B.-Y.; Anderson, A. C.; Strauss, A. J.

    1989-01-01

    Superconducting films with nominal composition Bi2Sr2Ca1Cu2Ox have been prepared on MgO substrates by sequential electron beam evaporation of Cu, Bi, and Sr2/3 Ca1/3 F2, followed by annealing in flowing wet, then dry, O2. X-ray diffraction data show that the films contain the two Bi-Sr-Ca-Cu-O phases that have been identified in the literature as a superconducting phase with c˜31 Å and a semiconducting phase with c˜24 Å. Both phases are strongly textured with the c axis perpendicular to the substrate. For the best film, which was annealed at 870 °C for 30 min, zero resistance was observed at 90 K, and the critical current density increased from 0.8×105 A/cm2 at 77 K to 2.3×105 A/cm2 at 4.2 K.

  12. Luminescence properties of undoped CsCaCl3 and CsSrCl3 crystalline scintillators

    International Nuclear Information System (INIS)

    Fujimoto, Yutaka; Saeki, Keiichiro; Koshimizu, Masanori; Asai, Keisuke; Yanagida, Takayuki

    2015-01-01

    Intrinsic luminescence properties of undoped CsCaCl 3 and CsSrCl 3 crystalline scintillators were studied. The crystal samples were grown by a vertical Bridgman method. Photoluminescence spectra of the crystals showed Auger-free luminescence (AFL) at 310 nm and self-trapped emission (STE) at 400 nm for CsCaCl 3 and 465 nm for CsSrCl 3 , when vacuum ultraviolet (VUV) light at 84 nm and 160 nm excited the crystals. X-ray excited radioluminescence spectra of the crystals showed some emission bands in the 280-600 nm wavelength range, which are owing to AFL, STE, and other origins such as lattice defects and impurities. Scintillation light yield was 400-300 ph/MeV, and the principal scintillation decay time about 2.5 ns and 12 ns for CsCaCl 3 and 1.8 ns and 13 ns for CsSrCl 3 . (author)

  13. Oxygen mobility in Bi:Sr:Ca:Cu:O ceramic measured using anelastic relaxation methods

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque Gimenez, J.M. de; Almeida, L.H. de; Grandini, C.R.; Souza, F.L. de; Santos, D. lara [UNESP, Dept. de Fisica, Bauru, SP (Brazil)

    2003-07-01

    Since the discovery of YBaCuO, experiments have shown that its superconducting properties are strongly affected by the oxygen content. More recently, anelastic relaxation measurements in La{sub 2}CuO{sub 4+{delta}}, showed that the decrease in the oxygen content can be related to two events. One is the decrease in mobility between two adjacent CuO planes, and the other is the increase in the number of tilting patterns of the CuO{sub 6} octahedra. In the case of the bismuth-based ceramic, it is known that the oxygen content, within some limits, does not affect its superconducting properties. In order to evaluate the mobility and the effect of the oxygen content on this material we have prepared BSCCO ceramic and tested regarding its internal friction and electrical resistivity as a function of the temperature while the oxygen content was being reduced by a sequence of vacuum annealing at 620 K. The samples were prepared in the Bi:Sr:Ca:Cu=2212 and 2223 proportion, using powder obtained by the sol-gel route and conventional solid state reaction. The anelastic relaxation measurements were performed using a torsion pendulum operating with frequency about 15-35 Hz between 77 to 700 K. The diffraction pattern of the as sintered and the vacuum annealed material were also presented. The results have shown complex anelastic relaxation structures that were associated to the jump of interstitial oxygen atoms between two adjacent CuO planes. The vacuum annealing showed to be deleterious to the critical temperature of the superconducting ceramic. (orig.)

  14. Oxygen mobility in Bi:Sr:Ca:Cu:O ceramic measured using anelastic relaxation methods

    International Nuclear Information System (INIS)

    Albuquerque Gimenez, J.M. de; Almeida, L.H. de; Grandini, C.R.; Souza, F.L. de; Santos, D. lara

    2003-01-01

    Since the discovery of YBaCuO, experiments have shown that its superconducting properties are strongly affected by the oxygen content. More recently, anelastic relaxation measurements in La 2 CuO 4+δ , showed that the decrease in the oxygen content can be related to two events. One is the decrease in mobility between two adjacent CuO planes, and the other is the increase in the number of tilting patterns of the CuO 6 octahedra. In the case of the bismuth-based ceramic, it is known that the oxygen content, within some limits, does not affect its superconducting properties. In order to evaluate the mobility and the effect of the oxygen content on this material we have prepared BSCCO ceramic and tested regarding its internal friction and electrical resistivity as a function of the temperature while the oxygen content was being reduced by a sequence of vacuum annealing at 620 K. The samples were prepared in the Bi:Sr:Ca:Cu=2212 and 2223 proportion, using powder obtained by the sol-gel route and conventional solid state reaction. The anelastic relaxation measurements were performed using a torsion pendulum operating with frequency about 15-35 Hz between 77 to 700 K. The diffraction pattern of the as sintered and the vacuum annealed material were also presented. The results have shown complex anelastic relaxation structures that were associated to the jump of interstitial oxygen atoms between two adjacent CuO planes. The vacuum annealing showed to be deleterious to the critical temperature of the superconducting ceramic. (orig.)

  15. Interaction between endoplasmic/sarcoplasmic reticulum stress (ER/SR stress), mitochondrial signaling and Ca(2+) regulation in airway smooth muscle (ASM).

    Science.gov (United States)

    Delmotte, Philippe; Sieck, Gary C

    2015-02-01

    Airway inflammation is a key aspect of diseases such as asthma. Several inflammatory cytokines (e.g., TNFα and IL-13) increase cytosolic Ca(2+) ([Ca(2+)]cyt) responses to agonist stimulation and Ca(2+) sensitivity of force generation, thereby enhancing airway smooth muscle (ASM) contractility (hyper-reactive state). Inflammation also induces ASM proliferation and remodeling (synthetic state). In normal ASM, the transient elevation of [Ca(2+)]cyt induced by agonists leads to a transient increase in mitochondrial Ca(2+) ([Ca(2+)]mito) that may be important in matching ATP production with ATP consumption. In human ASM (hASM) exposed to TNFα and IL-13, the transient increase in [Ca(2+)]mito is blunted despite enhanced [Ca(2+)]cyt responses. We also found that TNFα and IL-13 induce reactive oxidant species (ROS) formation and endoplasmic/sarcoplasmic reticulum (ER/SR) stress (unfolded protein response) in hASM. ER/SR stress in hASM is associated with disruption of mitochondrial coupling with the ER/SR membrane, which relates to reduced mitofusin 2 (Mfn2) expression. Thus, in hASM it appears that TNFα and IL-13 result in ROS formation leading to ER/SR stress, reduced Mfn2 expression, disruption of mitochondrion-ER/SR coupling, decreased mitochondrial Ca(2+) buffering, mitochondrial fragmentation, and increased cell proliferation.

  16. In-field {sup 57}Fe Mössbauer study of multiferroic Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} Y-type hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Raju, N.; Shravan Kumar Reddy, S.; Gopal Reddy, Ch. [Department of Physics, Osmania University, Hyderabad 500007 (India); Yadagiri Reddy, P., E-mail: yadagirireddy@yahoo.com [Department of Physics, Osmania University, Hyderabad 500007 (India); Rama Reddy, K. [Department of Physics, Osmania University, Hyderabad 500007 (India); Raghavendra Reddy, V. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

    2015-06-15

    The structural, magnetic, and in-field {sup 57}Fe Mössbauer studies of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} polycrystalline multiferroic, which belongs to Y-type hexaferrite class, are presented in this paper. Sr{sup 2+} substitution at Ba{sup 2+} site effects the redistribution of Zn{sup 2+} and Fe{sup 3+} ions at tetrahedral sites in the crystal. The magnetization data reveals the magnetic field induced transitions in the M–H curve. The in-field Mössbauer study reveals that the occupancy of Fe{sup 3+} ions in the tetrahedral sites is more than that in the octahedral sites because of doping of Sr{sup 2+} at Ba{sup 2+} site, which plays an important role in field induced multiferroic property at low temperature. - Highlights: • The structural, magnetic, and in-field {sup 57}Fe Mössbauer studies of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} are reported. • Doping of Sr at Ba site yielded the field induced transitions in the material. • The Fe{sup +3} ions at tetrahedral sites are more than the octahedral sites by Sr doping.

  17. Photoluminescence performance of thulium doped Li4SrCa(SiO4)2 under irradiation of ultraviolet and vacuum ultraviolet lights

    International Nuclear Information System (INIS)

    Wang, Zhaofeng; Li, Yezhou; Liu, Xiong; Wei, Xingmin; Chen, Yueling; Zhou, Fei; Wang, Yuhua

    2014-01-01

    Highlights: • A novel blue-emitting phosphor Li 4 SrCa(SiO 4 ) 2 :Tm 3+ was reported. • Li 4 SrCa(SiO 4 ) 2 :Tm 3+ exhibited excellent thermal and irradiation stability. • Li 4 SrCa(SiO 4 ) 2 :Tm 3+ was found to possess high color purity. - Abstract: In this work, we synthesized Tm 3+ doped Li 4 SrCa(SiO 4 ) 2 phosphors and investigated their photoluminescence properties under the excitation of ultraviolet and vacuum ultraviolet lights. The crystal structure analysis and variation of cell parameters confirm that Tm 3+ ions have been successfully doped in the structure of Li 4 SrCa(SiO 4 ) 2 host by occupying the sites of Ca 2+ with the coordination number of 6. The luminescence results suggest that Li 4 SrCa(SiO 4 ) 2 :Tm 3+ is a good blue-emitting phosphor when excited by ultraviolet and vacuum ultraviolet irradiations. In addition, it is observed that there is nearly no degradation for Li 4 SrCa(SiO 4 ) 2 :Tm 3+ after undergoing thermal and irradiation treatments. Possible mechanisms for the luminescence processes are proposed on the basis of the discussion of excitation and emission spectra. In particular, the emission color of Li 4 SrCa(SiO 4 ) 2 :Tm 3+ by excitation of 147 and 172 nm irradiations is very close to the standard blue color, suggesting that it could be potentially applied in plasma display panels and mercury-free fluorescence lamps

  18. Crystal structure and surface characteristics of Sr-doped GdBaCo2O6−δ double perovskites: oxygen evolution reaction and conductivity

    KAUST Repository

    Pramana, Stevin S.

    2017-12-04

    A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

  19. The impact of anion ordering on octahedra distortion and phase transitions in SrTaO2N and BaTaO2N.

    Science.gov (United States)

    Wang, Chun Hai; Kennedy, Brendan J; Menezes de Oliveira, André L; Polt, Julia; Knight, Kevin Steven

    2017-06-01

    In this work we synthesized BaTaO 2 N and SrTaO 2 N using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaO 2 N [P4/mmm (No. 123)] and SrTaO 2 N [I4/mcm (No. 140)]. In contrast to an anion-disordered cubic perovskite (Pm \\overline{3}m No. 221) with Ta at the cell center, both systems show a site preference for oxygen anions in the two opposite corners (along the c axis) of the Ta-O/N octahedra rather than the four square corners in the ab plane (Γ 3 + occupancy distortion), which induces a tetragonal elongation of the unit cell with the c axis being longer than the a axis. A further Ta-O/N octahedra displacement [R 5 - (a,0,0), rotation about the c axis] distortion was observed in SrTaO 2 N. This distortion mode is accompanied by an increased unit-cell distortion that decreases as the temperature increases. Ultimately a second-order phase transition caused by the loss of the R 5 - (a,0,0) mode was observed at 400-450 K.

  20. Electronic Phase Separation in Pr1x(Ca, Sr)xMnO3δ and Tunneling Magnetoresistance in Sr2FeMoO6

    International Nuclear Information System (INIS)

    Niebieskikwiat, Dario

    2003-01-01

    In this work, we approach two aspects of the physics of magnetic perovskites presenting colossal magnetoresistance (CMR). Firstly, we go deeply into the phase separation (PS) between the ferromagnetic (FM) metallic state and the antiferro-magnetic (AFM) charge ordered (CO) insulating state, in manganites of the type Pr 1x (Ca,Sr) x MnO 3δ . Secondly, and more briefly, we analyze the problem of the influence of the grain boundary insulating barriers on the tunneling magnetoresistance in the Sr 2 FeMoO 6 double perovskite.The use of different measurement techniques allowed us to make a complete characterization of the PS state in the compounds Pr 0 .65Ca 0.35-y Sr y MnO 3 for 0≤ y ≤ 0.20, Pr 0 .5Sr 0.5-z Ca z MnO 3 for z = 0, 0.1 and 0.2 and Pr 1 -x Ca x-0.3 Sr 0 .3MnO 3 (0.46≤ x ≤ 0.54), that were prepared in our laboratory.The structural studies of these materials were performed at room temperature by means of X-ray diffraction. At low temperatures, the phase coexistence was observed by global magnetic techniques, as SQUID magnetometry and neutron diffraction, as well as measurements sensitive to the local magnetic environment, as electron spin resonance (ESR).The electrical characterization, performed through resistivity and thermoelectric power (Seebeck effect) measurements, allowed us to elucidate the characteristics of the metal-insulator transitions, which are directly related to the magnetic properties of the PS state. In Pr 0 .65Ca 0.35-y Sr y MnO 3 compound we studied the effects of the average ionic radius of the A site of the perovskite ( A > ) keeping constant the carrier concentration (x = 0.35). This material presents an evolution from a CO insulating phase for small A > (y =0), towards the FM metallic phase for large A > (y = 0.20). In the intermediate region, where a first order metal-insulator transition occurs, the strong competition between both phases induces the PS state in a wide temperature range. In order to quantify this coexistence

  1. Preparation of (001)-Oriented CaBi4Ti4O15 and SrBi4Ti4O15 Films Using LaNiO3 Nucleation Layer on Pt-passivated Si Wafer

    Science.gov (United States)

    Mizutani, Yuki; Uchida, Hiroshi; Funakubo, Hiroshi; Koda, Seiichiro

    2009-09-01

    Thin films of CaBi4Ti4O15 and SrBi4Ti4O15 with preferential crystal orientation were prepared by the chemical solution deposition (CSD) technique on a (100)LaNiO3/(111)Pt/(100)Si substrate. The films consisted of a crystalline phase of bismuth-layer-structured dielectric (BLSDs). The (00l) planes of a BLSD crystal were preferentially oriented to the surface of the (100)LaNiO3/(111)Pt/(100)Si substrate, which is ascribed to the lattice matching between pseudo perovskite blocks in the BLSD crystal and the (100)LaNiO3 plane with a perovskite structure. Frequent heat treatment for crystallization, i.e., once after each coating, also enhanced the degree of crystallinity and crystal orientation of the BLSD films. The dielectric constants (ɛr) of SrBi4Ti4O15 and CaBi4Ti4O15 thin films were approximately 250 at room temperature. The ɛr values of both films increased with ambient temperature. The variations in capacitance in the temperature range from 25 to 200 °C were approximately 3 and 5% respectively, which were significantly smaller than that in the (Ba,Sr)TiO3 thin film.

  2. Sem-EDAX'S Application For Characterization Of Superconductor Material Of (Bi,Pb)-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Handayani, Ari; Wuryanto; Prambudi, Bambang

    1996-01-01

    The microstructure and composition analysis of superconductor material of (Bi,Pb)-Sr-Ca-Cu-O which were synthesized by two different processes (CA and CD Process) by varying the sintering time, i.e. 20,60 and 100 hours were done by using SEM-EDAX method. The standard sample of superconductor material of Bi-Sr-Ca-Cu-O with 1112, 2212 and 2223 phase from Stream has been used for comparison, At 25 kV, the composition analysis showed that, at 20 and 60 hours of sintering, a mixture of phases existed while 100 hours of sintering resulted in a phase close to phase 2223. The result of microstructure observation showed significant differences. At synthesized CA process, 100 hours of sintering gives bigger and clearer platelet microstructure shape than that given by 20 and 60 hours of sintering. Also from the synthesized CD process, the 60 and 100 hours of sintering gives bigger and clearer platelet microstructure shape than that given by the 20 hours of sintering

  3. Voltage clamp methods for the study of membrane currents and SR Ca2+ release in adult skeletal muscle fibres

    Science.gov (United States)

    Hernández-Ochoa, Erick O.; Schneider, Martin F.

    2012-01-01

    Skeletal muscle excitation-contraction (E-C)1 coupling is a process composed of multiple sequential stages, by which an action potential triggers sarcoplasmic reticulum (SR)2 Ca2+ release and subsequent contractile activation. The various steps in the E-C coupling process in skeletal muscle can be studied using different techniques. The simultaneous recordings of sarcolemmal electrical signals and the accompanying elevation in myoplasmic Ca2+, due to depolarization-initiated SR Ca2+ release in skeletal muscle fibres, have been useful to obtain a better understanding of muscle function. In studying the origin and mechanism of voltage dependency of E-C coupling a variety of different techniques have been used to control the voltage in adult skeletal fibres. Pioneering work in muscles isolated from amphibians or crustaceans used microelectrodes or ‘high resistance gap’ techniques to manipulate the voltage in the muscle fibres. The development of the patch clamp technique and its variant, the whole-cell clamp configuration that facilitates the manipulation of the intracellular environment, allowed the use of the voltage clamp techniques in different cell types, including skeletal muscle fibres. The aim of this article is to present an historical perspective of the voltage clamp methods used to study skeletal muscle E-C coupling as well as to describe the current status of using the whole-cell patch clamp technique in studies in which the electrical and Ca2+ signalling properties of mouse skeletal muscle membranes are being investigated. PMID:22306655

  4. Hypermethylation of the CaSR and VDR genes in the parathyroid glands in chronic kidney disease rats with high-phosphate diet.

    Science.gov (United States)

    Uchiyama, Taketo; Tatsumi, Norifumi; Kamejima, Sahoko; Waku, Tsuyoshi; Ohkido, Ichiro; Yokoyama, Keitaro; Yokoo, Takashi; Okabe, Masataka

    2016-10-01

    Chronic kidney disease (CKD) disrupts mineral homeostasis and its representative pathosis is defined as secondary hyperparathyroidism (SHPT). SHPT occurs during the early course of progressive renal insufficiency, and is associated with mortality and cardiovascular events. SHPT results in reduction of calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) in the parathyroid glands during CKD. However, the precise mechanism of CaSR and VDR reduction is largely unknown. CKD was induced through two-step 5/6 nephrectomy, and then CKD rats and sham-operated rats were maintained for 8 weeks on diets containing 0.7 % phosphorus (normal phosphate) or 1.2 % phosphorus (high phosphate). In gene expression analysis, TaqMan probes were used for quantitative real-time polymerase chain reaction. Finally, CaSR and VDR protein expressions were analyzed using immunohistochemistry. DNA methylation analysis was performed using a restriction digestion and quantitative PCR. CaSR and VDR mRNA were reduced only in CKD rats fed the high-phosphorus diets (CKD HP), then CaSR and VDR immunohistochemical expressions were compatible with gene expression assay. SHPT was then confirmed only in CKD HP rats. Furthermore, sole CKD HP rats showed the hypermethylation in CaSR and VDR genes; however, the percentage methylation of both genes was low. Although CaSR and VDR hypermethylation was demonstrated in PTGs of CKD HP rats, the extent of hypermethylation was insufficient to support the relevance between hypermethylation and down-regulation of gene expression because of the low percentage of methylation. Consequently, our data suggest that mechanisms, other than DNA hypermethylation, were responsible for the reduction in mRNA and protein levels of CaSR and VDR in PTGs of CKD HP rats.

  5. High homogeneity powder of Ti-Ba-Ca-Cu-O (2223) prepared by Freeze-Drying method

    International Nuclear Information System (INIS)

    Al-Shakarchi, Emad Kh.; Toma, Ziad A.

    1999-01-01

    Full text.Homogeneous high temerature superconductor ceramic powder of TI-Ba-Ca-Cu-O with transition temperature [Tc=123K] have been successfully prepared from the mixture of nitrate salts [TlNO 3 , Ba(NO 3 ) 2 , Ca(NO 3 ) 2 .4H 2 O and Cu(NO 3 ) 2 .3H 2 O] by using freeze-drying method. Freeze-dryer that was used in this work designed locally in our laboratory. This technique consider a better to get a fine powder of ceramic materials by depending on the procedure of frozen droplets with present of liquid nitrogen. SEM pictures showed the size of grains of about [0.8 μm]. We conclude that the high sintering temperature, for the prepared powders in this technique, for long time [120 hrs] will increase the inter diffusion between the grains ahich caused the decreasing in the density of the sample which may be given a better results than the obtained in a previous works

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

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Farooq, Saima [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2009-11-15

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

  7. X-ray diffraction, dielectric, and Raman spectroscopy studies of BaSrTiO{sub 3}-NaNbO{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Abdessalem, L. Ben; Aydi, S.; Aydi, A.; Maalej, A.; Khemakhem, H. [Universite de Sfax, Laboratoire des Materiaux Multifonctionnels et Applications (LaMMA), Faculte des Sciences de Sfax (FSS), Sfax (Tunisia); Sassi, Z. [Laboratoire de Genie Electrique et Ferroelectricite (LGEF) de L' INSA de Lyon, Villeurbanne (France)

    2017-05-15

    Ba{sub 0.837}Sr{sub 0.093}Na{sub 0.07}Ti{sub 0.93}Nb{sub 0.07}O{sub 3} (BSNTN) ceramic was synthesized by the solid-state reaction at 1350 C for 3 h. The crystal structure, investigated by X-ray diffraction at room temperature, revealed a single-phase perovskite crystallizing with tetragonal P4mm group space. Dielectric properties were investigated as a function of applied frequency. The ferroelectric behavior has been confirmed by hysteresis investigation. The evolution of the Raman spectra was used to study the variations of the basic phase transition of BaTiO{sub 3}, at room temperature. It shows the introduction of a disorder in this composition, thus favoring a ferroelectric relaxor behavior. (orig.)

  8. Understanding cold bias: Variable response of skeletal Sr/Ca to seawater pCO2 in acclimated massive Porites corals

    Science.gov (United States)

    Cole, Catherine; Finch, Adrian; Hintz, Christopher; Hintz, Kenneth; Allison, Nicola

    2016-01-01

    Coral skeletal Sr/Ca is a palaeothermometer commonly used to produce high resolution seasonal sea surface temperature (SST) records and to investigate the amplitude and frequency of ENSO and interdecadal climate events. The proxy relationship is typically calibrated by matching seasonal SST and skeletal Sr/Ca maxima and minima in modern corals. Applying these calibrations to fossil corals assumes that the temperature sensitivity of skeletal Sr/Ca is conserved, despite substantial changes in seawater carbonate chemistry between the modern and glacial ocean. We present Sr/Ca analyses of 3 genotypes of massive Porites spp. corals (the genus most commonly used for palaeoclimate reconstruction), cultured under seawater pCO2 reflecting modern, future (year 2100) and last glacial maximum (LGM) conditions. Skeletal Sr/Ca is indistinguishable between duplicate colonies of the same genotype cultured under the same conditions, but varies significantly in response to seawater pCO2 in two genotypes of Porites lutea, whilst Porites murrayensis is unaffected. Within P. lutea, the response is not systematic: skeletal Sr/Ca increases significantly (by 2–4%) at high seawater pCO2 relative to modern in both genotypes, and also increases significantly (by 4%) at low seawater pCO2 in one genotype. This magnitude of variation equates to errors in reconstructed SST of up to −5 °C. PMID:27241795

  9. Internal residual stress studies and enhanced dielectric properties in La0.7Sr0.3CoO3 buffered (Ba,Sr)TiO3 thin films

    Science.gov (United States)

    Lu, Shengbo; Xu, Zhengkui

    2009-09-01

    Ba0.6Sr0.4TiO3 (BST) thin films were deposited on La0.7Sr0.3CoO3 (LSCO) buffered and unbuffered Pt (111)/Ti/SiO2/Si substrates by pulsed laser deposition. The former exhibits a (100) preferred orientation and the latter a random orientation, respectively. Grazing incident x-ray diffraction study revealed that the tensile residual stress observed in the latter is markedly reduced in the former. As a result, the dielectric property of the LSCO buffered BST thin film is greatly improved, which shows a larger dielectric constant and tunability, smaller loss tangent, and lower leakage current than those of the unbuffered BST thin film. The relaxation of the larger tensile residual stress is attributed to the larger grain size in the buffered BST thin film and to a closer match of thermal expansion coefficient between the BST and the LSCO buffer layer.

  10. Mechanisms of Vanadium Recovery from Stone Coal by Novel BaCO3/CaO Composite Additive Roasting and Acid Leaching Technology

    Directory of Open Access Journals (Sweden)

    Zhenlei Cai

    2016-03-01

    Full Text Available In this report, the vanadium recovery mechanisms by novel BaCO3/CaO composite additive roasting and acid leaching technology, including the phase transformations and the vanadium leaching kinetics, were studied. The purpose of this manuscript is to realize and improve the vanadium recovery from stone coal using BaCO3/CaO as the composite additive. The results indicated that during the composite additive BaCO3/CaO roasting process, the monoclinic crystalline structure of muscovite (K(Al,V2[Si3AlO10](OH2 was converted into the hexagonal crystalline structure of BaSi4O9 and the tetragonal crystalline structure of Gehlenite (Ca2Al2SiO7, which could, therefore, facilitate the release and extraction of vanadium. Vanadium in leaching residue was probably in the form of vanadate or pyrovanadate of barium and calcium, which were hardly extracted during the sulfuric acid leaching process. The vanadium leaching kinetic analysis indicated that the leaching process was controlled by the diffusion through a product layer. The apparent activation energy could be achieved as 46.51 kJ/mol. The reaction order with respect to the sulfuric acid concentration was 1.1059. The kinetic model of vanadium recovery from stone coal using novel composite additive BaCO3/CaO could be finally established.

  11. Oxygen tracer diffusion in dense Ba0.5Sr0.5Co0.8Fe0.2O3-δ films

    Science.gov (United States)

    Wang, L.; Merkle, R.; Maier, J.; Acartürk, T.; Starke, U.

    2009-02-01

    Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is an interesting material for high temperature oxygen permeation membranes and solid oxide fuel cell cathodes, applications for which oxygen transport properties are crucial. Here oxygen isotope exchange is performed on dense BSCF films prepared by pulsed laser deposition on MgO single crystal substrates. The oxygen isotope profile is analyzed by secondary ion mass spectrometry to extract tracer diffusion coefficients D∗ and effective surface exchange constants k∗. Tracer diffusion has a low activation energy of 0.5 eV. At moderate temperatures, the related oxygen vacancy diffusion coefficient DVaccent="true">Ö is significantly larger than that for (La,Sr)(Fe,Co)O3-δ perovskites.

  12. Magnetic and electrical transport properties of LaBaCo2O(5.5+δ) thin films on vicinal (001) SrTiO3 surfaces.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Collins, Gregory; Wang, Haibin; Bao, Shanyong; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Lin, Yuan; Whangbo, Myung-Hwan

    2013-01-23

    Highly epitaxial LaBaCo(2)O(5.5+δ) thin films were grown on the vicinal (001) SrTiO(3) substrates with miscut angles of 0.5°, 3.0°, and 5.0° to systemically study strain effect on its physical properties. The electronic transport properties and magnetic behaviors of these films are strongly dependent on the miscut angles. With increasing the miscut angle, the transport property of the film changes from semiconducting to semimetallic, which results most probably from the locally strained domains induced by the surface step terraces. In addition, a very large magnetoresistance (34% at 60 K) was achieved for the 0.5°-miscut film, which is ~30% larger than that for the film grown on the regular (001) SrTiO(3) substrates.

  13. Dual ferroic properties of hexagonal ferrite ceramics BaFe{sub 12}O{sub 19} and SrFe{sub 12}O{sub 19}

    Energy Technology Data Exchange (ETDEWEB)

    Kostishyn, V.G. [National University of Science and Technology MISIS, Leninskiy Aven. 4, Moscow 119049 (Russian Federation); Panina, L.V., E-mail: lpanina@plymouth.ac.uk [National University of Science and Technology MISIS, Leninskiy Aven. 4, Moscow 119049 (Russian Federation); Timofeev, A.V.; Kozhitov, L.V.; Kovalev, A.N. [National University of Science and Technology MISIS, Leninskiy Aven. 4, Moscow 119049 (Russian Federation); Zyuzin, A.K. [Science and Technology Institute of Interbranch Information, Sorge, St. 22, Moscow 125252 (Russian Federation)

    2016-02-15

    Dual ferroic properties of a strong magnetism and large ferroelectricity have been observed in barium BaFe{sub 12}O{sub 19} and strontium SrFe{sub 12}O{sub 19} hexaferrite ceramics. The samples were fabricated by a modified ceramic technique from highly purified raw materials with addition of boron oxide allowing the control of grain size and enhancement of bulk resistivity. Whereas the samples of PbFe{sub 12}O{sub 19} fabricated by the same technological method did not have sufficient electric resistivity to support an electric field and did not exhibit the ferroelectric properties. The structure of the samples examined by X-ray diffraction is consistent with a single hexagonal phase. The grains are randomly oriented with the average grain size of 300–400 nm coated with boron oxide. The magnetic properties are characterised by standard ferrimagnetic behavior with the Neel temperature of about 450 °C. Large spontaneous polarization was observed with the maximal values of 45–50 μC/cm{sup 2} under an applied electric field of 100–300 kV/m. A strong coupling between magnetic and electric ordering was confirmed by measuring the magnetoelectric (ME) parameter and magnetodielectric ratio. These ME characteristics are more advanced than those for well-known room temperature multiferroic BiFeO{sub 3}. Furthermore, by applying an electric field, the manipulation of magnetization in the range of up to 9% was observed, which is even greater than in some substituted hexaferrites with a non-collinear magnetic structure. The obtained results on electrical polarization are similar to the values reported for the corresponding hexaferrites sintered by polymer precursor technique. This suggests a promising potential of M-type hexaferrite ceramics in devices utilizing magnetoelectric coupling. - Highlights: • Ba(Sr)Fe{sub 12}O{sub 19}-hexaferrites show large room-temperature multiferroic properties. • Small addition of B{sub 2}O{sub 3} increases the hexaferrite

  14. Josephson junction in cobalt-doped BaFe2As2 epitaxial thin films on (La,Sr)(Al,Ta)O3 bicrystal substrates

    Science.gov (United States)

    Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

    2010-04-01

    Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10-μm-wide microbridges spanning a 30°-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppressed remarkably by a magnetic field. Microbridges without a BGB did not show the RSJ-like behavior, and their critical current densities were 20 times larger than those of BGB bridges, confirming BGB bridges display a Josephson effect originating from weakly-linked BGB.

  15. Microwave Assisted Synthesis and Sintering of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite

    OpenAIRE

    Nuernberg,Rafael Bianchini; Morelli,Márcio Raymundo

    2015-01-01

    Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskite-type oxide is currently one of the most promising materials for applications in solid-oxide fuel cells (SOFCs), protonic ceramic fuel cells (PCFCs), oxygen separation membranes, and catalytic membranes for methane conversion. BSCF powder synthesis has received considerable attention and new synthesis methods have been proposed to obtain nanoscale powders with high chemical homogeneity. In this study, BSCF perovskite powder has been successfully ...

  16. Chemical Stability of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Under Different Oxygen Partial Pressure

    Science.gov (United States)

    Wang, Fang; Yashiro, Keiji; Amezawa, Koji; Mizusaki, Junichiro

    2013-07-01

    Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is an outstanding material for cathode materials of solid oxide fuel cells (SOFCs). However the chemical stability of BSCF is still not well-understood. In this paper, in situ HT-XRD measurement was performed as a function of temperature and oxygen partial pressure, p(O2), to evaluate the chemical stability window of BSCF. The results inferred the phase transition of BSCF produced two kinds of impurity phases coexisted with BSCF at 800 °C in the relatively higher p(O2).

  17. Preparation and dielectric properties of BaCu(B{sub 2}O{sub 5})-doped SrTiO{sub 3}-based ceramics for energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lingxia, E-mail: lilx106@163.com; Yu, Xiaoxu; Cai, Haocheng; Liao, Qingwei; Han, Yemei; Gao, Zhengdong

    2013-12-01

    Highlights: • BaCu(B{sub 2}O{sub 5}) is added to the multi-ions doped SrTiO{sub 3} ceramics as sintering aid. • The sintering temperature is decreased from 1300 °C to 1075 °C. • The incorporation of Ba{sup 2+} into the matrix increases the dielectric constant. • The breakdown strength increases due to the decrease of grain size and porosity. • The dissolution of BCB contributes to the improvement of dielectric properties. -- Abstract: BaCu(B{sub 2}O{sub 5}) (BCB) was used as sintering aids to lower the sintering temperature of multi-ions doped SrTiO{sub 3} ceramics effectively from 1300 °C to 1075 °C by conventional solid state method. The effect of BCB content on crystalline structures, microstructures and properties of the ceramics was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurements, respectively. The addition of BCB enhanced the breakdown strength (BDS) while did not sacrifice the dielectric constant. The enhancement of BDS should be due to the modification of microstructures, i.e., smaller and more homogeneous grain sizes after BCB addition. The dielectric constant of BCB-doped ceramics maintained a stable value with 1.0 mol% BCB, which was dominated by the combination of two opposite effects caused by the presence of second phases and the incorporation of Cu{sup 2+} and Ba{sup 2+}, while further increase was owing to the increase of dissolved Ba{sup 2+} ions when the content of BCB is more than 2.0 mol%. The multi-ions doped SrTiO{sub 3} ceramics with 1.0 mol% BCB addition showed optimal dielectric properties as follows: dielectric constant of 311.37, average breakdown strength of 28.78 kV/mm, discharged energy density of 1.05 J/cm{sup 3} and energy efficiency of 98.83%.

  18. Preparation and properties of Ba xSr 1- xCo yFe 1- yO 3- δ cathode material for intermediate temperature solid oxide fuel cells

    Science.gov (United States)

    Zhao, Hailei; Shen, Wei; Zhu, Zhiming; Li, Xue; Wang, Zhifeng

    Ba xSr 1- xCo yFe 1- yO 3- δ (BSCF) materials with perovskite structure were synthesized via solid-state reaction. Their structural characteristics, electrical-conduction behavior and cathode performance were investigated. Compared to A-site elements, B-site elements show a wide solid-solution range in BSCF. The electrical-conduction behavior of BSCF obeys the small polaron-hopping mechanism. An increase of Ba or Co content in the BSCF samples results in a decrease of electrical conductivity, which is mainly attributable to the preferential existence of B 3+ rather than B 4+ in Ba- or Co-rich samples. At the same time, this leads to increases in the lattice parameter a and the number of oxygen vacancies. BSCF samples with high Ba content show a high structural stability (high oxygen-loss temperature). Ba 0.6Sr 0.4Co 0.8Fe 0.2O 3- δ and Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ materials present good thermal-cycling stability of the electrical conductivity. Compared with Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ, Ba 0.6Sr 0.4Co 0.8Fe 0.2O 3- δ exhibits a better cathode performance in a Ce 0.8Gd 0.2O 2- δ (GDC)-supported half cell. The cell performance can be improved by introducing a certain amount of GDC electrolyte into the BSCF cathode material.

  19. Red, Green, and Blue Photoluminescence of Ba2SiO4:M (M = Eu3+, Eu2+, Sr2+ Nanophosphors

    Directory of Open Access Journals (Sweden)

    Claudia Wickleder

    2013-07-01

    Full Text Available Divalent europium doped barium orthosilicate is a very important phosphor for the production of light emitting diodes (LEDs, generally associated to the green emission color of micron-sized crystals synthesized by means of solid-state reactions. This work presents the combustion synthesis as an energy and time-saving preparation method for very small nano-sized Ba2SiO4 particles, flexibly doped to acquire different emission energies. The size of the resulting spherical nanoparticles (NPs of the green emitting Ba2SiO4:Eu2+ was estimated to about 35 nm applying the Scherrer equation and further characterized with aid of atomic force microscopy (AFM as well as scanning electron microscopy (SEM. This phosphor is able to build homogeneous luminescent suspensions and was successfully down-sized without changing the optical properties in comparison to the bulk phosphors. Besides the X-ray diffraction (XRD analysis and the different types of microscopy, the samples were characterized by luminescence spectroscopy. Undoped Ba2SiO4 NPs are not luminescent, but show characteristic red emission of the 5D0 → 7FJ (J = 0–4 electronic transitions when doped with Eu3+ ions. Moreover, these orthosilicate nanoparticles generate blue light at low temperatures due to impurity-trapped excitons, introduced by the partial substitution of the Ba2+ with Sr2+ ions in the Ba2SiO4 lattice causing a substantial distortion. A model for the temperature behavior of the defect luminescence as well as for their nature is provided, based on temperature-dependent luminescence spectra and lifetime measurements.

  20. Crystallisation of Ba1-xSrxZn2Si2O7 from BaO/SrO/ZnO/SiO2 glass with different ZrO2 and TiO2 concentrations

    Science.gov (United States)

    Vladislavova, Liliya; Kracker, Michael; Zscheckel, Tilman; Thieme, Christian; Rüssel, Christian

    2018-04-01

    The effect of different nucleation agents such as ZrO2 and TiO2 was investigated for a first time with respect to their crystallisation behaviour in the glass system BaO-SrO-ZnO-SiO2. In all studied glasses, a Ba1-xSrxZn2Si2O7 (0.1 ≤ x ≤ 0.9) solid solution crystallized. This phase was first described in 2015 to possess a similar structure as the high temperature phase of BaZn2Si2O7 and a thermal expansion close to zero or even negative. It may find applications e.g. as cook panels, telescope mirrors, and furnace windows. Kinetic parameters of the crystallisation process were determined by supplying different heating rates in a differential scanning calorimeter (DSC). The results were evaluated using the equations of Ozawa and Kissinger with respect to the activation energies. Furthermore, the Ozawa method was used for the determination of Avrami parameters, which provides further information on the nucleation and crystallisation processes. Scanning electron microscopy including electron backscatter diffraction (EBSD) was used to characterise the microstructure, to determine the crystallite size and the crystal orientation. For the characterisation of the occurring crystalline phases, X-ray diffraction was used.

  1. Synthesis and Microstructure Properties of (Bi,Pb2Sr2Ca1Cu2Oy Ceramic Superconductor

    Directory of Open Access Journals (Sweden)

    nurmalita .

    2015-11-01

    Full Text Available Properties of (Bi, Pb2Sr2Ca1Cu2Oy ceramic superconductors were prepared by the melt textured growth methods in order to investigate the effects of the slow cooling time on the microstructur.  Phase analyses of the samples by X-ray diffraction (XRD has been carried out to assess the effects of the slow cooling time. From XRD analyses, the addition to the sample of  the slow cooling time degrades formation of the high-Tc Bi-2212 phase. The possible reasons for the observed degradation in the microstructure properties due to the slow cooling time addition were discussed.

  2. Dielectric properties of glasses prepared by quenching melts of superconducting Bi-Ca-Sr-Cu-O cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Varma, K. B. R.; Subbanna, G. N.; Ramakrishnan, T. V.; Rao, C. N. R.

    1989-07-03

    Glasses obtained from quenching melts of superconducting bismuth cuprates of the formula Bi/sub 2/(Ca,Sr)/sub /ital n/+1/Cu/sub /ital n//O/sub 2/ital n/+4/ with /ital n/=1 and 3 exhibit novel dielectric properties. They possess relatively high dielectric constants as well as high electrical conductivity. The novel dielectric properties of these cuprate glasses are likely to be of electronic origin. They exhibit a weak microwave absorption due to the presence of microcrystallites.

  3. Characterization of hot isostatically pressed Bi-Sr-Ca-Cu-O as a function of consolidation variables

    International Nuclear Information System (INIS)

    Goretta, K.C.; Miller, D.J.; Poeppel, R.B.; Nash, A.S.

    1992-01-01

    This paper reports that fully dense, bulk Bi 2 Sr 1.7 CaCu 2 O x superconductor pellets were made by hot isostatic pressing in an inert atmosphere. Electron microscopy revealed that rotation and bending of the platelike 2212 grains were responsible for much of the densification. Under processing conditions of 825 degrees C and 105 MPa, dense pellets were obtained in 15 min. Many dislocations, planar faults, and, perhaps, intergrowths of the Bi 2 Cr 2 CuO x phase were produced during pressing. The dislocations were largely present in subgrain boundaries when the pressing times were increased to 45-120 min

  4. Neutron scattering from the flux-line lattice in Bi2Sr2CaCu2O8+#gamma#

    DEFF Research Database (Denmark)

    Paul, D.M.; Forgan, E.M.; Cubitt, R.

    1995-01-01

    Neutron small-angle diffraction has been used to investigate the flux-line lattice structure within single crystals of the high-temperature superconductor Bi2.15Sr1.95CaCu2O8+x. The diffracted intensity goes rapidly to zero as the magnetic field or the temperature is increased. Melting at low...... fields as a function of temperature coincides with the appearence of finite resistance within the superconducting state. At low temperatures the diffracted intensity disappears in fields greater than similar to 70 mT, probably due to the decomposition of the flux-line lattice into randomly pinned 2d...

  5. Crystallography, chemistry and structural disorder in the new high-Tc Bi-Ca-Sr-Cu-O superconductor

    Science.gov (United States)

    Veblen, D. R.; Heaney, P. J.; Angel, R. J.; Finger, L. W.; Hazen, R. M.

    1988-01-01

    Diffraction experiments are reported which indicate that the new Bi-Ca-Sr-Cu-O layer-structure superconductor possesses a primitive orthorhombic unit cell with probable space group Pnnn. The material exhibits severe structural disorder which is primarily related to stacking within the layers. The apparent orthorhombic structure is an average resulting from orthorhombic material mixed with monoclinic domains in two twinned orientations. Two distinct types of structural disorder that are common in materials synthesized to date are also described. This disorder complicates the crystallographic analysis and suggests that X-ray and neutron diffraction methods may yield only an average structure.

  6. Flux Creep Investigation in Bi2Sr2CaCu2O8+d High-Temperature Superconductor

    Directory of Open Access Journals (Sweden)

    G. R. Blanca

    2004-12-01

    Full Text Available The flux creep process in a c-axis Bi2Sr2CaCu2O8+d thin film was investigated at different temperatures and applied fields using the Kim-Anderson (KA approach. The peaked behavior shown in the magnetoresistance profile was attributed to the competing mechanisms of flux motion and sample-intrinsic transition near Tc.Within the temperature range where the competition occurs, U increases with temperature and consequently a decrease in the superconducting volume corresponds to a decrease in the flux creep. Moreover, the flux creep potential barrier varies with applied current I at all temperatures consistent with the KA model.

  7. Plastic Flow of the Vortex Solid in Bi_2Sr_2CaCu_2O_8+δ Crystals

    Science.gov (United States)

    Keener, C. D.; Ammirata, S. M.; Trawick, M. L.; Hebboul, S. E.; Garland, J. C.

    1997-03-01

    We have recently presented evidence in electrical transport data for a first order vortex lattice melting transition in Bi_2Sr_2CaCu_2O_8+δ single crystals. Below the melting temperature T_m, current-induced motion of the vortex solid causes dissipation for sufficiently high currents. We have measured resistance vs. temperature curves in magnetic fields 50 Oe = 1 mA). Below Tm (≈ 80 K at 100 Oe), we find large temporal resistance fluctuations which are characteristic of vortex plastic flow. This vortex motion seems to be well described as ``intermittently flowing rivers" of vortices.(F. Nori, Science 271, 1373 (1996).)

  8. Effect of lead content on nonstoichiometric Bi2-xPbySr2Ca2Cu3Oδ ceramic superconductors

    International Nuclear Information System (INIS)

    Diaz-Valdes, E.; Pacheco-Malagon, G.; Contreras-Puente, G.; Mejia-Garcia, C.; Andrade-Garay, G.; Ortiz-Lopez, J.; Conde-Gallardo, A.; Falcony, C.

    1993-01-01

    Ceramic superconducting samples of the type Bi 2-x Pb y Sr 2 Ca 2 Cu 3 O δ were processed with a nonstoichiometric content of Bi and Pb (x≠y) with respect to the 2223 phase in this system. The resistance vs. temperature characteristics and the presence of the 2223 and 2212 phases as a function of the sample preparation conditions and the lead content (Bi/Pb ratio) are reported. The growth of unwanted phases such as PbO was observed for those samples with a high content of Pb (y=0.9) and Bi (x=0.1). (orig.)

  9. Magneto-optical observation of macrovortices in Bi_2Sr_2CaCu_2Ox single crystals.

    Science.gov (United States)

    Polyanskii, A. A.; Gurevich, A.; Pashitski, A. E.; Cai, X. Y.; Larbalestier, D. C.

    1996-03-01

    Magneto-optical imaging of flux penetration in Bi_2Sr_2CaCu_2Ox single crystals revealed localized domains of enhanced magnetic field H(x,y) having the opposite circulation of magnetization currents as compared to bulk currents. The positions of such macrovortices strongly depend on temperature and magnetic pre-history, rather than on the material defect structure. The macrovortex structure was observed in the temperature range 10KHp and H

  10. Theoretical Investigation of Half-Metallic Oxides XFeO3 (X = Sr, Ba) via Modified Becke-Johnson Potential Scheme

    Science.gov (United States)

    Maqsood, Saba; Rashid, Muhammad; Din, Fasih Ud; Saddique, M. Bilal; Laref, A.

    2018-03-01

    The cubic XFeO3 (X = Sr, Ba) perovskite oxides are studied for their thermodynamic stability in the ferromagnetic phase by using density functional theory calculations. We also explore the elastic properties of these compounds in terms of elastic constants C ij, bulk modulus B, shear modulus G, anisotropy factor A, Poisson's ratio ν and the B/ G ratio. The electronic properties are examined to elucidate the magnetic order, and the thermoelectric properties of XFeO3 (X = Sr, Ba) materials are also presented. The modified Becke-Johnson local density approximation scheme has been used to compute the electronic band structure and density of states, which show that these materials are half-metallic ferromagnetic. We study the magnetic properties by computing the crystal field energy (ΔCF), John-Teller energy (ΔJT) and the exchange splitting energies Δx( d) and Δx( pd). Our results indicate that strong hybridization causes a decrease in the magnetic moment of Fe, which then produces permanent magnetic moments in the nonmagnetic sites.

  11. Effect of Na Content on the Physical Properties of Ba0.5Sr0.5TiO3 Powders

    Directory of Open Access Journals (Sweden)

    Tassanee Tubchareon

    2014-01-01

    Full Text Available The different Na contents (0 ≤ Na ≤ 0.35, based on mole of NaOH of doped Ba0.5Sr0.5TiO3 (BST powders synthesized via sol-gel process were studied. The substitution of Na+ ions into a partial A-site of BST powders provided the reduction in vacancy defects as confirmed by electron paramagnetic resonance (EPR and UV-visible spectroscopy. Photoluminescence (PL spectra appeared in violet, blue, and green emissions. The phase structure, oxygen deficiency, and titanium deficiency of BST powders were further investigated as a function of Na content. X-ray diffraction (XRD result was found that low Na content (0 ≤ Na ≤ 0.15 exhibited the tetragonal structure, while it was transformed to the cubic phase when high Na content. Moreover, X-ray photoelectron spectroscopy (XPS result revealed that the partial oxidation of Ti3+ ions to Ti4+ ions was observed at Na content lower than 0.05 mole, while more addition of Na content resulted in the increasing of the oxygen and the titanium deficiency. Furthermore, the result indicated the oxygen deficiency significantly formed at the A-site of Sr atoms more than that of Ba atoms.

  12. Electrical characteristics and preparation of (Ba0.5Sr0.5)TiO3 films by spray pyrolysis and rapid thermal annealing

    International Nuclear Information System (INIS)

    Koo, Horngshow; Ku, Hongkou; Kawai, Tomoji; Chen Mi

    2007-01-01

    Functional films of (Ba 0.5 Sr 0.5 )TiO 3 on Pt (1000 A)/Ti (100 A)/SiO 2 (2000 A)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba 0.5 Sr 0.5 )TiO 3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400degC and 57.7% weight loss up to 1000degC. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750degC for 5 min while leakage current density is 1.5x10 -6 A/cm 2 in the film annealed at 550degC for 5 min. (author)

  13. Thermal, electrical, and electrochemical properties of Lanthanum-doped Ba0.5Sr0.5 Co0.8Fe0.2O3 δ

    Science.gov (United States)

    Li, Shuyan; Lü, Zhe; Huang, Xiqiang; Wei, Bo; Su, Wenhui

    2007-09-01

    Crystal structure, thermogravimetry (TG), thermal expansion coefficient (TEC), electrical conductivity and AC impedance of (Ba0.5Sr0.5)1 xLaxCo0.8Fe0.2O3 δ (BSLCF; 0.05⩽x⩽0.20) were studied in relation to their potential use as intermediate temperature solid oxide fuel cell (IT-SOFC) cathode. A single cubic pervoskite was observed by X-ray diffraction (XRD). The TEC of BSLCF was increasing slightly with the increasing content of La, and all the compounds showed abnormal expansion at high temperature. Proved by the TG result, it was associated with the loss of lattice oxygen. The electrical conductivity, which is the main defect of Ba0.5Sr0.5 Co0.8Fe0.2O3 δ (BSCF), was improved by La doping, e.g., the compound of x=0.20 demonstrated a conductivity of σ=376 S cm-1 at 392 °C. The increase of electrical conductivity resulted from the increased concentration of charge carrier induced by La doping. In addition, the AC impedance revealed the better electrochemical performance of BSLCF. For example, at 500 °C, the sample with composition x=0.15 yielded the resistance values of 2.12 Ω cm2, which was only 46% of BSCF.

  14. Physical characteristics and magnetic properties of BaFe12O19/SrTiO3 based composites derived from mechanical alloying

    International Nuclear Information System (INIS)

    Widodo, Rahmat Doni; Manaf, Azwar

    2016-01-01

    A composite system BaFe 12 O 19 /SrTiO 3 with ferrimagnetic BaFe 12 O 19 phase (BHF) and ferroelectric SrTiO 3 phase (STO) have been prepared by mechanical alloying and subsequent heat treatment. The composite powders were studied by Particle Size Analyze, X-ray diffraction and magnetic measurement. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ∼8 µm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean grain size of the particles was found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100°C the milled powder transformed into particles of nanograin. In this report, microstructure as well as magnetic properties for the composite is also briefly discussed.

  15. Ethylene production by ODHE in catalytically modified Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) membrane reactors.

    Science.gov (United States)

    Lobera, M Pilar; Escolástico, Sonia; Garcia-Fayos, Julio; Serra, José M

    2012-08-01

    Process intensification by the integration of membranes and high-temperature reactors offers several advantages with regard to conventional process schemes, that is, energy saving, safe operation, reduced plant/unit size, and higher process performance, for example, higher productivity, catalytic activity, selectivity, or stability. We present the study of oxidative dehydrogenation of ethane at 850 °C on a catalytic membrane reactor based on a mixed ionic-electronic conducting membrane. The surface of the membrane made of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) has been activated by using different porous catalytic layers based on perovskites. The layer was deposited by screen printing, and the porosity and thickness was studied for the catalyst composition. The different catalyst formulations are based on partial substitution of A- and B-site atoms of doped strontium ferrite/cobaltites (A(0.6)Sr(0.4)Co(0.5)Fe(0.5)O(3-δ) and Ba(0.6)Sr(0.4)BO(3-δ)) and were synthesized by an ethylenediaminetetraacetic acid-citrate complexation route. The use of a disk-shaped membrane in the reactor enabled the direct contact of gaseous oxygen and hydrocarbons to be avoided, and thus, the ethylene content increased. High ethylene yields (up to ≈81 %) were obtained by using a catalytic coating based on Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ), which included macropores produced by the addition of graphite platelets into the screen-printing ink. The promising catalytic results obtained with this catalytically modified membrane reactor are attributed to the combination of 1) the high activity, as a result of the high temperature and oxygen species diffusing through the membrane; 2) the control of oxygen dosing and the low concentration of molecules in the gas phase; and 3) suitable fluid dynamics, which enables appropriate feed contact with the membrane and the rapid removal of products. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Void species determination of Ba 1- xCa xTiO 3 ceramics with FSDP-related XRD

    Science.gov (United States)

    Panigrahi, M. R.; Panigrahi, S.

    2010-07-01

    Void species nanostructure is studied in Ba 1- xCa xTiO 3 ceramics using X-ray diffraction with respect to first sharp diffraction peak (FSDP-related XRD). The FSDP parameters such as the interlayer separation, quasi-periodic in nature with an effective periodicity R, correlation length L, over which such periodicity is maintained, of atomic-density fluctuations, regardless of the precise atomic origin of such fluctuations, were calculated using general expressions. Void-based model may be a very useful experimental tool to study the above nanostructural peculiarities in crystalline solids. The present work is aimed to clarify methodological possibilities of this approach with calcium-modified barium titanate ceramics for the first time. In this paper we have reported for the first time, the effect of doping concentration of calcium on BaTiO 3 on different parameters like structural correlation length, periodicity, nano-void diameter, the first coordination sphere radius, the magnitude of scattering vector, etc.

  17. Ba/Ca in Planktonic Foraminifera as a Recorder of Freshwater Input to the Ocean: Proxy Refinement in the Gulf of Papua, Papua New Guinea

    Science.gov (United States)

    Gibson, K.

    2015-12-01

    In the study of paleoclimate, the past several decades have seen large strides in the advancement of proxies designed to reconstruct changes in sea surface temperature (SST); however, techniques for reconstructing ocean salinity are less well developed. The ratio of Ba/Ca in planktic foraminiferal tests has shown initial promise as a tool for reconstructing salinity in continental margin sites near river mouths. In these environments, Ba/Ca shows an inverse correlation with salinity, and often a less clear correlation to nutrients or indicators of productivity, as is more typical in open-ocean settings. An ideal area in which to apply and test foraminiferal Ba/Ca as a proxy for freshwater input is the Western Pacific Warm Pool (WPWP), where temperatures are relatively stable, but large variations in precipitation are today driven by the El Nino Southern Oscillation (ENSO) and strength of the Australian-Indonesian monsoon. Foraminiferal Ba/Ca in sediments proximal to a river mouth should therefore reflect changes in riverine input, which in turn reflect variations in precipitation on different timescales. We present here planktic foraminiferal δ18O, Ba/Ca, and Mg/Ca records spanning the last glacial-interglacial transition from marine sediment cores in the Gulf of Papua, located in the WPWP. The δ18O records show an increase in the magnitude of glacial-interglacial (G-IG) δ18O change (Δ18O) moving away from the coastline and the mouth of the primary local freshwater source, the Fly River. The reduced amplitude in G-IG Δ18O in the cores closer to shore, manifested by more negative δ18O values before ~20 kyr ago, is likely due to freshwater input from the Fly River, with the effects diminishing with distance from the Fly River source. Temperature and sea level are also changing over the deglaciation, however, contributing to the signal recorded in the calcite δ18O. We use planktic Mg/Ca analyses and independent records of sea level change to isolate the

  18. Loparite, a rare-earth ore (Ce, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3

    Science.gov (United States)

    Hedrick, James B.; Sinha, Shyama P.; Kosynkin, Valery D.

    1997-01-01

    The mineral loparite (Ce, NA, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3 is the principal ore of the light-group rare-earth elements (LREE) in Russia. The complex oxide has a perovskite (ABO3) structure with coupled substitutions, polymorphism, defect chemistry and a tendency to become metamict. The A site generally contains weakly bonded, easily exchanged cations of the LREE, Na and Ca. The B site generally contains smaller, highly charged cations of Ti, Nb or Fe+3. Mine production is from Russia's Kola Peninsula. Ore is beneficiated to produce a 95% loparite concentrate containing 30% rare-earth oxides. Loparite concentrate is refined by either a chlorination process or acid decomposition process to recover rare-earths, titanium, niobium and tantalum. Rare-earths are separated by solvent extraction and selective precipitation/dissolution. The concentrate is processed at plants in Russia, Estonia and Kazakstan.

  19. Films minces ferroélectriques Ba{2/3}Sr{1/3}TiO3 par ablation laser pour applications hyperfréquences

    Science.gov (United States)

    Delage, T.; Champeaux, C.; Catherinot, A.; Seaux, J. F.; Madrangeas, V.; Cros, D.

    2003-06-01

    Les matériaux oxydes ferroélectriques semblent des candidats potentiels intéressants pour les composants d'application dans le domaine des télécommunications. Parmi les matériaux ferroélectriques, le Titanate de Baryum Strontium BaxSr(1-x)TiO3 a l'avantage d'avoir une température de transition qui varie suivant son taux x de substitution en baryum. Les films de Ba{2/3}Sr{1/3}TiO3 sont élaborés sur substrats monocristallins MgO par ablation laser pulsée avec un laser KrF (248 nm, durée d'impulsion 14 ns), à un taux de répétition de 10 Hz avec une fluence de 3 J/cm^2 sur la surface de la cible et sous une atmosphère d'oxygène de 3.10^{-1} mbar. Les échantillons réalisés ont été étudiés en diffraction des rayons X en configuration 0-20 afin de déterminer l'orientation des films déposés. Les échantillons sont ensuite caractérisés dans une cavité résonante en hyperfréquence (12,5 GHz) afin de déterminer leur permittivité diélectrique. L'introduction d'une sous-couche de Ba{2/3}Sr{1/3}TiO3 déficitaire en oxygène permet d'obtenir des filnis d'épaisseur micronique possédant de bonnes caractéristiques cristallines et diélectriques.

  20. Hanford 100N Area Apatite Emplacement: Laboratory Results of Ca-Citrate-PO4 Solution Injection and Sr-90 Immobilization in 100N Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Burns, Carolyn A.; Moore, Robert C.; Fruchter, Jonathan S.; Vermeul, Vincent R.; Williams, Mark D.; Girvin, Donald C.; McKinley, James P.; Truex, Michael J.; Phillips, Jerry L.

    2007-10-01

    This report summarizes laboratory scale studies investigating the remediation of Sr-90 by Ca-citrate-PO4 solution injection/infiltration to support field injection activities in the Hanford 100N area. This study is focused on experimentally testing whether this remediation technology can be effective under field scale conditions to mitigate Sr-90 migration 100N area sediments into the Columbia River. Sr-90 is found primarily adsorbed to sediments by ion exchange (99% adsorbed, < 1% in groundwater) in the upper portion of the unconfined aquifer and lower vadose zone. Although primarily adsorbed, Sr-90 is still considered a high mobility risk as it is mobilized by seasonal river stage increases and by plumes of higher ionic strength relative to groundwater. This remediation technology relies upon the Ca-citrate-PO4 solution forming apatite precipitate [Ca6(PO4)10(OH)2], which incorporates some Sr-90 during initial precipitation and additionally slowly incorporates Sr-90 by solid phase substitution for Ca. Sr substitution occurs because Sr-apatite is thermodynamically more stable than Ca-apatite. Once the Sr-90 is in the apatite structure, Sr-90 will decay to Y-90 (29.1 y half-life) then Zr-90 (64.1 h half-life) without the potential for migration into the Columbia River. For this technology to be effective, sufficient apatite needs to be emplaced in sediments to incorporate Sr and Sr-90 for 300 years (~10 half-lives of Sr-90), and the rate of incorporation needs to exceed the natural groundwater flux rate of Sr in the 100N area. A primary objective of this study is to supply an injection sequence to deliver sufficient apatite into subsurface sediments that minimizes initial mobility of Sr-90, which occurs because the injection solution has a higher ionic strength compared to groundwater. This can be accomplished by sequential injections of low, then high concentration injection of Ca-citrate-PO4 solutions. Assessment of low concentration Ca-citrate-PO4, citrate-PO4

  1. Structures and magnetic properties of double perovskites A2LnMO6 and 6H-perovskites Ba3LnRu2O9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru)

    International Nuclear Information System (INIS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2003-01-01

    This account describes the synthesis, crystal structures and magnetic properties of double perovskites A 2 LnMO 6 and 6H-perovskites Ba 3 LnRu 2 O 9 (A=Sr, Ba; Ln=Y, lanthanides; M=Nb, Ta, Ru). The double perovskites A 2 LnMO 6 have two kinds of cations, Ln and M, in the B site of the perovskite ABO 3 . These cations adopt the alternative ordered arrangement. Measurements of the magnetic susceptibility, specific heat, and powder neutron diffraction showed that all of the A 2 LnRuO 6 compounds exhibited an antiferromagnetic transition at low temperatures and a complex temperature dependence of the magnetic susceptibility below their transition temperatures. In these compounds, the magnetic interaction between the Ln (4f electrons) and Ru (4d electrons) ions via the Ln-O-Ru pathway contributes greatly to their magnetic cooperative phenomena. The structural and magnetic studies for the 6H-perovskites Ba 3 LnRu 2 O 9 show that the Ln cations occupy the corner-sharing octahedra (LnO 6 octahedron) and the Ru cations occupy the face-sharing octahedra (Ru 2 O 9 dimer). The Ba 3 LnRu 2 O 9 compounds show a characteristic temperature-dependence of the magnetic susceptibilities, that is, a broad maximum at temperatures above 135 K and a magnetic transition at 5-15 K. These magnetic properties mainly reflect two kinds of the magnetic interactions: the interaction between Ln and Ru ions and that between Ru ions in the Ru 2 O 9 dimer. (author)

  2. The influence of source powder composition on the electroluminescence of Ca 1- xSr xS:Eu thin films

    Science.gov (United States)

    Van Haecke, J. E.; Smet, P. F.; Poelman, D.

    2004-10-01

    CaS:Eu has been studied as a red emitter for AC thin film electroluminescent (ACTFEL) devices in the beginning of the 1990s. This phosphor has not yet been used for practical display purposes because of the limited luminance and the slow response of the devices. Part of the CaS:Eu emission spectrum is situated at wavelengths longer than 650 nm where the eye sensitivity is very low. The partial replacement of the Ca-ions by Sr-ions causes a shift of the Eu emission to shorter wavelengths and thus an increase in the apparent luminous efficiency. To obtain a high luminance and a good temporal response, very homogeneous, crystalline and pure Ca 1- xSr xS:Eu thin films were found to be necessary. Several powder preparation techniques were applied to mix CaS and SrS powders on a microscopic scale, in order to achieve a single Ca 1- xSr xS:Eu phase. The overall phase distribution was determined by θ-2 θ X-ray diffraction (XRD) measurements and by assessing the photoluminescent properties of the Eu-activated powders. Scanning electron microscopy (SEM) images were useful in the determination of the grain size and the porosity of the material. The combination with energy-dispersive X-ray analysis (EDX) allowed mapping of the microscopic distribution of Ca and Sr. A single-phase of Ca 1- xSr xS:Eu could be obtained using wet chemical synthesis, which considerably improved the luminance of the corresponding ACTFEL devices.

  3. The system Ba(H2PO4)2-Sr(H2PO4)2-H3PO4(30%)-H2O at 25, 40 and 60 deg C

    International Nuclear Information System (INIS)

    Taranenko, N.P.; Serebrennikova, G.M.; Stepin, B.D.; Oboznenko, Yu.V.

    1982-01-01

    The system Ba(H 2 PO 4 ) 2 -Sr(H 2 PO 4 ) 2 -H 3 PO 4 (30%)-H 2 O (25 deg C) belongs to eutonic type systems. Solubility isotherms of salt components at 40 and 60 deg C are calculated. Polytherms (25-60 deg C) of solubility of monosubstituted barium and strontium phosphates in 30-60% H 3 PO 4 are obtained. The value of cocrystallization coefficient of Sr 2 + and Ba(H 2 PO 4 ) 2 Dsub(Sr)=0.042+-0.005 remains stable in the temperature range of 25-60 deg C and concentrations 30-60% phosphoric acid at initial content [Sr 2 + ]=1x10 - 2 mass%

  4. Low-Temperature Sintering of Ba0.5Sr0.5TiO3-SrMoO4 Dielectric Tunable Composite Ceramics for LTCC Applications

    Science.gov (United States)

    Tang, Linjiang; Wang, Jinwen; Zhai, Jiwei

    2013-08-01

    A sintering-aid system using melting of B-Li glass for barium strontium titanate (BST)-based compositions to be used in low-temperature cofired ceramic (LTCC) layers is introduced. The effects of the sintering aid on the microstructure, dielectric properties, and application in LTCC were investigated. The composition Ba0.5Sr0.5TiO3-SrMoO4 with 3 wt.% B-Li glass sintered at 950°C exhibits optimized dielectric properties, including low dielectric constant (368), low dielectric loss (0.007), and moderate tunability (13%, 60 kV/cm) at 10 kHz. At 1.44 GHz, it possesses a dielectric constant of 218 and Q value of 230. LTCC multilayer ceramic capacitors fabricated by the tape-casting process have steady relative tunability of 12% at 300 V, suggesting that BST50-SrMoO4-B-Li glass composite ceramic is a promising candidate for electrically tunable LTCC microwave device applications.

  5. Long time relaxation of resistance in La0.8Sr0.2MnO3 ceramics and La0.65Ca0.35 MnO3 films on ferroelectric substrates

    International Nuclear Information System (INIS)

    Medvedev, Yu.V.; Mezin, N.I.; Nikolaenko, Yu.M.; Pigur, A.E.; Shishkova, N.V.; Ishchuk, V.M.; Chukanova, I.N.

    2004-01-01

    Galvanomagnetic properties of La 0.65 Ca 0.35 MnO 3 films with a thickness of 0.2 μm on Pb 2.9 Ba 0.05 Sr 0.05 (Zr 0.4 Ti 0.6 )O 3 ferroelectric ceramics substrates have been investigated. We have discovered the monotonic irreversible increase of the film resistance by 3-5 time of value during several hours after multiple inversion of substrate polarization. The long-time relaxation (LTR) of film resistance is explained by dielecrtrization of film intercrystallite boundaries as a result of oxygen redistribution under action of inhomogeneous mechanical stress. In addition, the LTR of resistance of La 0.8 Sr 0.2 MnO 3 and La 0.6 Sr 0.2 Mn 1.2 O 3 ceramic samples has been investigated under action of different kind of mechanical stress: stretch, compression and hydrostatic press. Time dependence of resistance is described by R 0 +ΔRexp(-t/τ). The magnitude of LTR is 5-10 time greater then fast variation of resistance under action of stress. The sign of ΔR is dependent on the kind of stress. The time constant (τ) has the value of 3-9 hours. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Structural, dielectric and magnetic properties of Ba{sub 3}SrLn{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) filled tungsten bronze ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wang [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Yang, Wen Zhi [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Ningbo Branch of China Academy of Ordnance Science, Ningbo, 315103 (China); Liu, Xiao Qiang [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Chen, Xiang Ming, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China)

    2016-08-05

    Structural, dielectric and magnetic properties have been investigated for Ba{sub 3}SrLn{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) ceramics. The single phase tetragonal filled tungsten bronze structure in space group P4/mbm is obtained for Ba{sub 3}SrLa{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30}, while such tungsten bronze major phase is determined together with minor amount of secondary phases in Ba{sub 3}SrNd{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} and Ba{sub 3}SrSm{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30}. The saturated magnetic hysteresis loops with enhanced M{sub r} are obtained in the present ceramics at room temperature comparing to the Ba{sub 4}Ln{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) ceramics. Meanwhile, the typical relaxor behaviors are determined: a broad dielectric peak with strong frequency dispersion and the peak temperature following well with the Vogel–Fulcher relationship. - Highlights: • The tetragonal filled tungsten bronze structure in space group P4/mbm is obtained. • The typical relaxor behaviors are determined. • The magnetic hysteresis loops with enhanced Mr are obtained at room temperature.

  7. Structure, luminescence and thermal quenching properties of Eu doped Sr{sub 2−x}Ba{sub x}Si{sub 5}N{sub 8} red phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.H.; Chen, L.; Zhou, X.F.; Liu, R.H., E-mail: griremlrh@126.com; Zhuang, W.D.

    2017-02-15

    Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were synthesized at 1610 ℃ for 4 h via the solid-state reaction method. The XRD results confirm that the complete solid solutions are formed. With the increase of x, the emission spectra show an obvious blue-shift from 610 nm to 585 nm under the excitation of 460 nm. The color tone can be tuned from yellow to red. The corresponding mechanism for the blue-shift of peak-wavelength is studied in detail. The results of decomposed Gaussian spectra and fluorescence lifetime show that the local coordination structure surrounding activator ions changes with increasing x value. It is found that the probability of Eu occupying Sr1 and Sr2 site is dependent on Ba/Sr ratio. The variation of thermal quenching properties and the corresponding mechanism is discussed in detail. The results indicate that Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} is a promising orange red-emitting phosphor for near UV or blue light-pumped white light-emitting-diodes (wLEDs). - Graphical abstract: Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} solid solutions were prepared by the solid-state reaction method. The structure, luminescence and thermal quenching properties with varying Ba/Sr ratio were investigated in detail. - Highlights: • The stucture and luminescence properties of Eu doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were investigated. • The samples with the intermediate compositions(x=1.0,1.5) show better stability than the end members of both Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} and Ba{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+}. • The possible mechanism for the improvement of thermal quenching properties was proposed.

  8. Effect of cooling rate on the transition temperature in Bi-Pb-Sr-Ca-Cu-O system

    International Nuclear Information System (INIS)

    Wang Yugui; Wang Jinsong; Wang Nanlin; Jiao Xinping; Han Guchang; Chen Zhaojia; Wang Keqin; Wu Xiaoguang

    1989-12-01

    The resistance and a.c. susceptibility measurement show that cooling rate of the cast-annealing samples in heat treatment process has some effect on the 110K superconducting phase in Bi-Pb-Sr-Ca-Cu-O system. Rapid quenching of the sample in air from 845 deg C causes oxygen deficiency in lattice and brings about a trifling change of unit cell size along c-axis direction. The d.c. magnetization and specific heat anomaly Δc measurements demostrate that fast cooling rate can reduce the transition temperature of high-T c phase and the lower critical field, and weaken the pinning forces for vertex lines. The peak value of specific heat anomaly of the sample with nominal composition of Bi 1.7 Pb 0.3 Sr 2 Ca 2 Cu 4.5 O v is still small in comparison with YBa 2 Cu 3 O 7 . From the magnetization curve the authors estimate that the superconducting volume fraction is about 20%

  9. Chemical reactivities of the superconducting oxides, YBa2Cu3Oy and BiSrCaCu2Oy

    International Nuclear Information System (INIS)

    Toyama, Hisashi; Mizuno, Noritaka; Misono, Makoto

    1989-01-01

    The chemical reactivities of YBa 2 Cu 3 O y and BiSrCaCu 2 O y with various gases have been studied. It was found that large quantities of NO, CO, and NO 2 were rapidly absorbed (or intercalated) in the bulk of YBa 2 Cu 3 O y (T c : 90 K) at 573 K. The amount absorbed was in the order NO ∼ CO ∼ NO 2 > O 2 ∼ CO 2 > N 2 O ∼ 0. The amount for NO was more than two times the amount of YBa 2 Cu 3 O y in molar ratio and elongation by about 0.2 angstrom along c-axis was observed. NO absorbed was almost completely recovered as NO by the evacuation at 773 K. This absorption-desorption cycle proceeded reversively. The electronic resistivity at 573 K of YBa 2 Cu 3 O y increased upon the NO absorption and was restored by the evacuation at 773 K. CO was also absorbed rapidly accompanied by evolution of CO 2 . BiSrCaCu 2 O y did not absorb either NO or CO

  10. Trapping control of phase development in zone melting of Bi-Sr-Ca-Cu-O superconducting fibres

    International Nuclear Information System (INIS)

    Costa, F M; Carrasco, M F; Silva, R F; Vieira, J M

    2003-01-01

    Highly-texturized polycrystalline fibres of the Bi-Sr-Ca-Cu-O system have been grown by the laser floating zone technique at seven different pulling rates: (1.1, 2.2, 4.17, 8.3, 16.7, 33.3, 60.5) x 10 -6 m s -1 . The assessment of the cation segregation at the solid/liquid interface allowed us to calculate their equilibrium and effective distribution coefficients. The equilibrium distribution coefficients (k 0,Bi = 0.55, k 0,Sr = 0.97, k 0,Ca = 1.67, k 0,Cu = 1.10) were estimated using the Burton, Primm and Slichter (BPS) theory by taking into account the determined effective values. The effective distribution coefficients tend to unity as long as the pulling rate increases. The composition profiles along the initial transient region of the solidified fibres show a fast approach to the nominal composition as the pulling rate increases. The outstanding effect of the growth speed on superconducting phase type development is explained based on the solute trapping phenomena. The sequence of crystallization for superconducting phases ('2212' → '4413' → '2201') with pulling rate is a spontaneous effect of the system thermodynamics in order to balance the Bi trapping. This phase sequence corresponds to the smallest change of Bi chemical potential from the liquid phase to the solid phase. A diagram of free energy curves of the interdendritic superconducting phases illustrates the partitionless solidification phenomena at the highest growth speed

  11. Transfer of alkaline earth elements in mothers' milk and doses from 45Ca, 90Sr and 226Ra

    International Nuclear Information System (INIS)

    Smith, T.J.; Phipps, A.W.; Fell, T.P.; Harrison, J.D.

    2003-01-01

    An international programme of work is currently under way to develop methods for calculating doses to infants from ingestion of radionuclides present in mothers' milk. This paper considers the special case of the alkaline earth elements. Models have been developed for 45 Ca, 90 Sr and 226 Ra and the sensitivity of results to various changes in parameter values is discussed. A complication when calculating doses from intakes of radium is that the International Commission on Radiological Protection has previously recommended that doses from decay products of radium should be calculated using element-specific biokinetic models (so-called independent biokinetics). An extension of this method to the models for breastfeeding is proposed. Preliminary estimates of the doses received by the infant for a number of maternal intake scenarios show that doses to the infant can exceed the corresponding adult dose, such as for 45 Ca (ratio = 3.1) while, in other cases such as 90 Sr, the infant dose can be a significant fraction of the adult dose. (author)

  12. The Crystal Structure and Magnetic Behavior of Quinary Osmate and Ruthenate Double Perovskites LaABB'O6(A = Ca, Sr; B = Co, Ni; B' = Ru, Os).

    Science.gov (United States)

    Morrow, Ryan; McGuire, Michael A; Yan, Jiaqiang; Woodward, Patrick M

    2018-02-23

    Six LaABB'O 6 (A = Ca, Sr; B = Co, Ni; B' = Ru, Os) double perovskites were synthesized, several for the first time, and their crystal structures and magnetic behavior were characterized with neutron powder diffraction and direct-current and alternating-current magnetometry. All six compounds crystallize with P2 1 /n space group symmetry, resulting from a - a - c + octahedral tilting and complete rock salt ordering of transition-metal ions. Despite the electronic configurations of the transition-metal ions, either d 8 -d 3 or d 7 -d 3 , not one of the six compounds shows ferromagnetism as predicted by the Goodenough-Kanamori rules. LaSrNiOsO 6 , LaSrNiRuO 6 , and LaCaNiRuO 6 display long-range antiferromagnetic order, while LaCaNiOsO 6 , LaCaCoOsO 6 , and LaSrCoOsO 6 exhibit spin-glass behavior. These compounds are compared to the previously studied LaCaCoRuO 6 and LaSrCoRuO 6 , both of which order antiferromagnetically. The observed variations in magnetic properties can be attributed largely to the response of competing superexchange pathways due to changes in B-O-B' bond angles, differences in the radial extent of the 4d (B' = Ru) and 5d (B' = Os) orbitals, and filling of the t 2g orbitals of the 3d ion.

  13. Distribution Pattern of Fe, Sr, Zr and Ca Elements as Particle Size Function in the Code River Sediments from Upstream to Downstream

    International Nuclear Information System (INIS)

    Sri Murniasih; Muzakky

    2007-01-01

    The analysis of Fe, Sr, Zr and Ca elements concentration of granular sediment from upstream to downstream of Code river has been done. The aim of this research is to know the influence of particle size on the concentration of Fe, Sr, Zr and Ca elements in the Code river sediments from upstream to downstream and its distribution pattern. The instrument used was x-ray fluorescence with Si(Li) detector. Analysis results show that more Fe and Sr elements are very much found in 150 - 90 μm particle size, while Zr and Ca elements are very much found in < 90 μm particle size. Distribution pattern of Fe, Sr, Zr and Ca elements distribution in Code river sediments tends to increase relatively from upstream to downstream following its conductivity. The concentration of Fe, Sr, Zr and Ca elements are 1.49 ± 0.03 % - 5.93 ± 0.02 % ; 118.20 ± 10.73 ppm - 468.21 ± 20.36 ppm; 19.81 ppm ± 0.86 ppm - 76.36 ± 3.02 ppm and 3.22 ± 0.25 % - 11.40 ± 0.31 % successively. (author)

  14. Thin CaSO{sub 4}:Dy thermoluminescent dosimeters for calibration of {sup 90}Sr+{sup 90}Y applicators

    Energy Technology Data Exchange (ETDEWEB)

    Antonio, Patricia L. [Instituto de Pesquisas Energeticas e Nucleares, Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes, 2242, 05508-000, Sao Paulo, SP (Brazil); Oliveira, Mercia L. [Centro Regional de Ciencias Nucleares, Comissao Nacional de Energia Nuclear, Av. Prof. Luis Freire, 200, 50740-540, Recife, PE (Brazil); Caldas, Linda V.E., E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares, Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes, 2242, 05508-000, Sao Paulo, SP (Brazil)

    2012-04-15

    Clinical applicators are used in brachytherapy to treat superficial lesions of skin and eye. They should be periodically calibrated according to quality control programs and international recommendations. Thin CaSO{sub 4}:Dy thermoluminescent dosimeters were used to calibrate various applicators with a dermatological applicator as a reference. The obtained absorbed dose rates were compared with those quoted in their calibration certificates. Depth-dose curves were constructed for all the applicators. A mail dosimetry system was developed for calibration of clinical applicators. - Highlights: Black-Right-Pointing-Pointer Absorbed dose rates were obtained for {sup 90}Sr+{sup 90}Y applicators using CaSO{sub 4}:Dy pellets. Black-Right-Pointing-Pointer Depth-dose curves were obtained for all studied applicators. Black-Right-Pointing-Pointer CaSO{sub 4}:Dy dosimeters presented satisfactory results in all realized tests. Black-Right-Pointing-Pointer A mail dosimetry system was developed with CaSO{sub 4}:Dy pellets.

  15. Effect of Wood Aging on Wine Mineral Composition and87Sr/86Sr Isotopic Ratio.

    Science.gov (United States)

    Kaya, Ayse D; Bruno de Sousa, Raúl; Curvelo-Garcia, António S; Ricardo-da-Silva, Jorge M; Catarino, Sofia

    2017-06-14

    The evolution of mineral composition and wine strontium isotopic ratio 87 Sr/ 86 Sr (Sr IR) during wood aging were investigated. A red wine was aged in stainless steel tanks with French oak staves (Quercus sessiliflora Salisb.), with three industrial scale replicates. Sampling was carried out after 30, 60, and 90 days of aging, and the wines were evaluated in terms of general analysis, phenolic composition, total polysaccharides, multielement composition, and Sr IR. Li, Be, Mg, Al, Sc, Ti, V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Mo, Sb, Cs, Ba, Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb, Lu, Tl, and Pb elements and 87 Sr/ 86 Sr were determined by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and Na, K, Ca, and Fe by flame atomic absorption spectrometry (FAAS). Two-way ANOVA was applied to assess wood aging and time effect on Sr IR and mineral composition. Wood aging resulted in significantly higher concentrations of Mg, V, Co, Ni, and Sr. At the end of the aging period, wine exhibited statistically identical Sr IR compared to control. Study suggests that wood aging does not affect 87 Sr/ 86 Sr, not precluding the use of this parameter for wine traceability purposes.

  16. Spin glass properties of Y0.7Ca0.3MnO3 and Th0.35Ba0.37Ca0.28MnO3

    Science.gov (United States)

    Sedmidubský, D.; Hejtmánek, J.; Maryško, M.; Jirák, Z.; Hardy, V.; Martin, C.

    2002-05-01

    Two perovskite manganites with the same nominal concentration of Mn4+ have been studied by the magnetic susceptibility and specific heat measurements: the Y0.7Ca0.3MnO3 single crystal (YCa) with low tolerance factor and negligible ionic radii variance and the Th0.35Ba0.37Ca0.28MnO3 (ThBaCa) ceramics with favorable tolerance factor but huge substitution induced disorder. Both systems were found to possess an insulating ground state with activated conductivity. The ac susceptibility data exhibit a frequency dependent peak at Tsg=32 K for YCa and Tsg=43 K for ThBaCa. The Cole-Cole analysis revealed a sharper than exponential increase of the relaxation time for the former sample while almost linear slowly growing characteristics below Tsg were observed for the latter one. Using the heat capacity curves, the magnetic contribution was separated and magnetic peaks with typical linear on-set tails were obtained. This observation and the abovementioned characteristics are all indicative of spin or cluster glass character. The necessary magnetic frustration is here induced by a considerable tilting of MnO6 octahedra and deformation of Mn-O bonds which occur in a cooperative manner for YCa and locally for ThBaCa.

  17. Investigation of the phase equilibria and phase transformations associated with the Bi2Sr2CaCu2Oy superconductor

    International Nuclear Information System (INIS)

    Holesinger, T.

    1993-01-01

    The solid solution region and reaction kinetics of the Bi 2 Sr 2 CaCu 2 O y (2212) superconductor were examined as a function of temperature and oxygen partial pressure. Crystallization studies from the glassy and molten states were undertaken to determine the phase transformation and kinetics associated with the formation of 2212 and other competing phases. Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi 2 Sr 2-x Ca x CuO y (2201) and Cu 2 O followed by Bi 2 Sr 3-x Ca x O y , CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures. However, its formation below 800 C was kinetically limited. At 800 C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. In low oxygen partial pressures, the solidus is reduced to approximately 750 C. Solidification studies revealed an eutectic structure separating the incongruently melting 2212/2201 phases at high oxygen partial pressures from the congruently melting Bi 2 Sr 3-x Ca x O y (23x) and Bi 2 Sr 2-x Ca x O y (22x) phases present at low oxygen partial pressures. During solidification in various oxygen partial pressures, the separation of CaO in the melt and the initial crystallization of alkaline-earth cuprates leaves behind a Bi-rich liquid from which it is impossible to form single-phase 2212. Hence, significant amounts of 2201 were also present in these samples. These problems could be reduced by melt processing in inert atmospheres. Bulk 2212 material produced in this manner was found to possess high transition temperatures, high intergranular critical current densities below 20K, and modest critical current densities at 77K

  18. Synthesis and characterization of the double perovskite BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} like cathode for solid oxide fuel cells; Sintesis y caracterizacion de la doble perovskita BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} como catodo para celdas SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Alvarado F, J.; Avalos R, L.; Viramontes G, G. [Universidad Michoacana de San Nicolas de Hidalgo, Facultad de Ingenieria Electrica, Santiago Tapia 403, Morelia 58030, Michoacan (Mexico); Reyes R, A. [Centro de Investigacion en Materiales Avanzados, Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31109, Chihuahua (Mexico)

    2013-08-01

    Have been synthesized via sol-gel method and characterized by X-ray diffraction, electrical conductivity and thermal expansion coefficient, new material composites BaSrCoFe{sub 1{sub x}}Ni{sub x}O{sub 5.5} (double perovskite type) with the addition of Ni in solid solution Ni{sub x} (x = 0.025, 0.05, 0.075, 0.1 and 0.2), as alternative cathodes for solid oxide fuel cells of intermediate temperature (Sofc-It). X-ray diffraction confirmed the formation of the tetragonal structure perovskite phase BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5}, with the presence of small peaks identified in 2{theta} values below 30 degrees as BaCO{sub 3} and CoFe{sub 2}O{sub 4}. The electrical conductivity increases with the temperature between 350-470 degrees C and then decreases due to the loss of oxygen in the net, which causes differences in conductivity. Semiconductor behavior was obtained in all compositions. Thermal expansion coefficient determination, showed a linear dependence inversely proportional to the concentration of Ni. Our results of electrical conductivity and thermal expansion coefficient, reach to the conclusion that the cathodes between 0.1 and 0.2 Ni, have the greatest possibility for application in Sofc-It. (Author)

  19. Single Phase Melt Processed Powellite (Ba,Ca) MoO{sub 4} For The Immobilization Of Mo-Rich Nuclear Waste

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, Kyle [Savannah River Site (SRS), Aiken, SC (United States); Marra, James [Savannah River Site (SRS), Aiken, SC (United States); Fox, Kevin [Savannah River Site (SRS), Aiken, SC (United States); Reppert, Jason [Savannah River Site (SRS), Aiken, SC (United States); Crum, Jarrod [Paci fic Northwest National Laboratory , Richland, WA (United States); Tang, Ming [Los Alamos National Laboratory , Los Alamos, NM (United States)

    2012-09-17

    Crystalline and glass composite materials are currently being investigated for the immobilization of combined High Level Waste (HLW) streams resulting from potential commercial fuel reprocessing scenarios. Several of these potential waste streams contain elevated levels of transition metal elements such as molybdenum (Mo). Molybdenum has limited solubility in typical silicate glasses used for nuclear waste immobilization. Under certain chemical and controlled cooling conditions, a powellite (Ba,Ca)MoO{sub 4} crystalline structure can be formed by reaction with alkaline earth elements. In this study, single phase BaMoO{sub 4} and CaMoO{sub 4} were formed from carbonate and oxide precursors demonstrating the viability of Mo incorporation into glass, crystalline or glass composite materials by a melt and crystallization process. X-ray diffraction, photoluminescence, and Raman spectroscopy indicated a long range ordered crystalline structure. In-situ electron irradiation studies indicated that both CaMoO{sub 4} and BaMoO{sub 4} powellite phases exhibit radiation stability up to 1000 years at anticipated doses with a crystalline to amorphous transition observed after 1 X 10{sup 13} Gy. Aqueous durability determined from product consistency tests (PCT) showed low normalized release rates for Ba, Ca, and Mo (<0.05 g/m{sup 2}).

  20. Fabrication of lead-free piezoelectric Li2CO3-added (Ba,Ca)(Ti,Sn)O3 ceramics under controlled low oxygen partial pressure and their properties

    Science.gov (United States)

    Noritake, Kouta; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

    2018-02-01

    Reduction-resistant lead-free (Ba,Ca)(Ti,Sn)O3 piezoceramics with high piezoelectric constants were fabricated by optimizing the amount of Li2CO3 added. Oxygen partial pressure was controlled during the sintering of (Ba,Ca)(Ti,Sn)O3 ceramics in a reducing atmosphere using H2-CO2 gas. Enhanced grain growth and a high-polarization state after poling treatment were achieved by adding Li2CO3. Optimizing the amount of Li2CO3 added to (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics sintered under a low oxygen partial pressure resulted in improved piezoelectric properties while maintaining the high sintered density. The prepared Li2CO3-added ceramic samples had homogeneous microstructures with a uniform dispersion of each major constituent element. However, the residual Li content in the 3 mol % Li2CO3-added (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics after sintering was less than 0.3 mol %. Sintered bodies of this ceramic prepared in a CO2 (1.5%)-H2 (0.3%)/Ar reducing atmosphere (PO2 = 10-8 atm at 1350 °C), exhibited sufficient electrical resistivity and a piezoelectric constant (d 33) exceeding 500 pC/N. The piezoelectric properties of this nonreducible ceramic were comparable or superior to those of the same ceramic sintered in air.