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Sample records for ca sr ba

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

    Science.gov (United States)

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

    1984-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-15

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

  3. 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 (materials and trend toward those of plants growing on fresh volcanic deposits. In contrast the isotope composition of exchangeable Ba in deeper soil horizons (> 10 cm depth) at those sites is consistently heavier than the volcanic parent materials. The isotope compositions of exchangeable Ca and Sr trend toward heavier compositions with depth more gradually, reflecting increasing leakiness from these soils in the order Ba recycling flux returned to the surface as litterfall. This observation implicates an uptake flux from an additional source which we attribute to biolifting. We view the heavy exchangeable Ba relative to soil parent values in deeper soils at sites where P is enriched in surface soils, and indeed at all but the wettest site across the climosequence, to represent the complement of an isotopically light Ba fraction removed from these soils by plant roots consistent with the biolifting hypothesis. We further suggest that

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-02-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-15

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

  8. 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}.

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

    International Nuclear Information System (INIS)

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2004-01-01

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

  11. 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.

  12. Electrical conductivity and thermal expansion behavior of MMoO{sub 4} (M = Ca, Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Maji, Binoy Kumar; Jena, Hrudananda, E-mail: hruda66@yahoo.co.in; Asuvathraman, R.; Kutty, K.V. Govindan

    2015-08-15

    Highlights: • CaMoO{sub 4}, SrMoO{sub 4} and BaMoO{sub 4} are scheelite type oxides exhibit electrical conduction. • These are the interaction products of radio-nuclides in the nuclear fuel cycle. • Decrease in thermal expansion shows decrease in bond strength from CaMoO{sub 4} to BaMoO{sub 4}. • Decrease in σ from CaMoO{sub 4} to BaMoO{sub 4} is due to decrease in electropositive character. • Diffusion coefficient (D) of oxide ion conduction decreases from CaMoO{sub 4} to BaMoO{sub 4}. - Abstract: Alkaline earth (Ca, Sr, Ba) molybdates were synthesized by solid state reaction route. The compounds were characterized by powder-XRD, TG–DTA techniques. The electrical conductivities of these compounds were measured by AC-impedance technique at 673–1073 K. The activation energies of electrical conduction of CaMoO{sub 4}, SrMoO{sub 4} and BaMoO{sub 4} were found to be 1.29 ± 0.01 eV, 1.33 ± 0.01 eV and 1.31 ± 0.01 eV respectively. The linear thermal expansion of these molybdates was measured by dilatometry. The mean coefficients (α{sub m}) of thermal expansion for these compounds were found to be in the range of 9.38 ± 0.18 × 10{sup −6}–12.96 ± 0.25 × 10{sup −6} K{sup −1} at 305–1005 K temperature range. The diffusion coefficient (D) values of oxide ion conduction for these molybdates were determined and found to be in the range of 9.48 ± 0.02 × 10{sup −14}–3.32 ± 0.01 × 10{sup −10} for CaMoO{sub 4}, 5.86 ± 0.02 × 10{sup −14}–2.50 ± 0.01 × 10{sup −10} for SrMoO{sub 4} and 3.46 ± 0.02 × 10{sup −14}–1.22 ± 0.01 × 10{sup −10} cm{sup 2} s{sup −1} for BaMoO{sub 4} at 673–1073 K range of temperature.

  13. 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.

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

    CERN Document Server

    Tomza, Michał

    2015-01-01

    The Ca$^+$, Sr$^+$, Ba$^+$, and Yb$^+$ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. \\textit{Ab initio} techniques are applied to investigate electronic-ground-state properties of the (CaCr)$^+$, (SrCr)$^+$, (BaCr)$^+$, and (YbCr)$^+$ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), and the multireference configuration interaction method restricted to single and double excitations, MRCISD, are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction co...

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

    Science.gov (United States)

    Tomza, Michał

    2015-12-01

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

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

    Science.gov (United States)

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

    2012-05-30

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

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

    Indian Academy of Sciences (India)

    S J Dhoble; N S Dhoble; R B Pode

    2003-06-01

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

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

    OpenAIRE

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

    2016-01-01

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

  19. 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.

  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

    . A new procedure for the separation of Sr from Ba and Ra is also investigated, which is based on the difference in solubility of the chlorides of Sr, Ba and Ra in HCl media. In 9.5 mol 1(-1) HCl or 7.5 mol 1(-1) HCl-10% acetone media, >97% of Ba and Ra can be removed by Ba(Ra)Cl-2 precipitation, and >94......% of Sr was recovered. In the determination of Sr-90 by measuring Y-90, the separation of Ra and Ba can easily be carried out by precipitation of Ba and Ra as Ba(Ra)SO4, while Y can be quantitatively recovered in the solution. By this method, a further separation of Y-90 from radiostrontium can...

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Science.gov (United States)

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

    2014-02-01

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

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

    International Nuclear Information System (INIS)

    The parent compounds of recently discovered iron-arsenide superconductors, AFe2As2 with alkaline earth A=Ca,Sr,Ba, undergo simultaneous structural and magnetic phase transitions at a temperature TSM. Using a combination of polarized light microscopy and spatially resolved high-energy synchrotron x-ray diffraction we show that the orthorhombic distortion leads to the formation of 45o-type structural domains in all parent compounds. Domains penetrate through the sample thickness in the c direction and are not affected by crystal imperfections such as growth terraces. The domains form regular stripe patterns in the plane with a characteristic dimension of 10--50 μm. The direction of the stripes is fixed with respect to the tetragonal (100) and (010) directions but can change by 90o on thermal cycling through the transition. This domain pattern may have profound implications for intrinsic disorder and anisotropy of iron arsenides.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

  7. Structural and Dielectric Properties of Dy-doped( Ba, Sr, Ca) TiO3 Thick Films

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Preparation and electrocatalytic activities of Pt-TiO2 nanotubes (Ba0.57Sr0.33Ca0.10)TiO3 powders, prepared by the sol-gel method, were doped MnCO3 as acceptor and Dy2O3 as donor. This powder was mixed with an organic vehicle and BSCT thick films were fabricated by the screen-printing techniques on alumina substrate. The structural and dielectric properties of BSCT thick films were investigated with variation of Dy2O3 amount. As a result of the differential thermal analysis (DTA), exothermic peak was observed at around 670℃ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films showed the XRD patterns of a typical polycrystalline perovskite structure. The average grain size of BSCT thick films decreased with increasing amount of Dy2O3. The relative dielectric constant and dielectric loss of the BSCT thick film doped Dy2O3 0. 1mol% were 4637.4 and 1.6% at 1kHz, respectively.

  8. 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.

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

    Indian Academy of Sciences (India)

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

    2014-12-01

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

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

    Indian Academy of Sciences (India)

    Purnendu Parhi; V Manivannan; Sandeep Kohli; Patrick Mccurdy

    2008-11-01

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

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

    Science.gov (United States)

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

    2007-05-01

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

  12. 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.

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

    Indian Academy of Sciences (India)

    Abdul Manan; Yaseen Iqbal

    2014-10-01

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

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-10-15

    Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patterns were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-01-27

    Multilayered compounds typically present exotic functionalities, and some of them have been suggested as potential materials for thermoelectric conversion owing to their unique capability to decouple electronic and heat transport. Here we report new [CoO2] and [Cu2Se2] layered A2CoO2Cu2Se2 compounds in which Sr at the intervening alkaline-earth A site is partially replaced with Ca or Ba. The parent Sr2CoO2Cu2Se2 phase is a direct gap p-type semiconductor, and density functional theory (DFT) calculations indicate its topmost valence band consists of Cu 3d-Se 4p states. Upon the isovalent cation substitution the lattice modification in the ab plane is constrained by the stiff [CoO2] layer such that the lattice shrinkage/expansion mainly happens along the c axis. Substitution of Sr with the heavier and larger Ba significantly enhances the thermopower but more hole states would be required to optimize the thermoelectric performance. Thermal stability is related to the inter-oxide-selenide-layer interaction, and our thermogravimetric measurement data reveal that the A2CoO2Cu2Se2 materials could operate in the intermediate temperature region. PMID:26702873

  19. Structural and transport properties of A{sub 2}HoTaO{sub 6} [A=Ba, Sr, and Ca

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Alo, E-mail: alo_dutta@yahoo.com [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700009 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700009 (India); Das, Dipankar [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Salt Lake, Kolkata 700098 (India)

    2014-06-01

    Double perovskite oxides A{sub 2}HoTaO{sub 6} [A=Ba, Sr, and Ca] are synthesized by a solid state reaction technique. The Rietveld refinement of the X-ray diffraction pattern shows that Ba{sub 2}HoTaO{sub 6} crystalizes in cubic Fm3m symmetry whereas Sr{sub 2}HoTaO{sub 6} and Ca{sub 2}HoTaO{sub 6} adopt the monoclinic P2{sub 1}/n symmetry. The field cooled and zero field cooled magnetic susceptibilities of the materials are measured in the temperature range from 5 K to 300 K. The temperature dependence of inverse magnetic susceptibility shows the antiferromagnetic behavior of these systems. The dielectric relaxation of the samples is investigated by the Cole–Cole model in the frequency range from 50 Hz to 1 MHz and in the temperature range from 303 K to 673 K. The frequency dependent conductivity spectra follow the power law. The scaling behavior of the imaginary part of the impedance spectra suggests that the relaxation shows the same mechanism at various temperatures. - Highlights: • The Rietveld refinement indicates that B{sub 2}HoTaO{sub 6} has cubic Fm3m symmetry. • Sr{sub 2}HoTaO{sub 6} and Ca{sub 2}HoTaO{sub 6} adopt the monoclinic P2{sub 1}/n crystal symmetry. • The temperature dependence of inverse magnetic susceptibilities follows the Curie–Wiess law. • The superexchange interaction between the Ho ions leads to antiferromagnetism in these systems. • Dielectric relaxation mechanism is explained using the Cole–Cole model.

  20. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2012-01-01

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

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

    Science.gov (United States)

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology. PMID:26891039

  3. Synthesis of photocatalytic La(1-x)AxTiO3.5-δ(A=Ba, Sr, Ca) nano perovskites and their application for photocatalytic oxidation of congo red dye in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    M Bradha; T Vijayaraghavan; SP Suriyaraj; R Selvakumar; Anuradha M Ashok

    2015-01-01

    A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites were prepared by sol-gel method and characterized using thermogravimetry/differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectros-copy and transmission electron microscopy (TEM). XRD analysis showed that the La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites derived after calcination at 800 ºC were in single phase with orthorhombic structure. The particle size of all nano perovskites was found to be~20 nm. The synthesized nano perovskites were tested for the photocatalytic decomposition of an azo dye, Congo red. The sequential behavior of La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nanoperovskites for photocatalytic decomposition of congo red in aque-ous solution by visible light at room temperature was studied at various time intervals and the efficiency of degradation of the nanop-erovskites was compared. Among all the A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites, Ba substituted com-pound showed the highest dye degradation.

  4. Sign Change of Thermopower at Low Temperatures in Nd0.7(Ca,Sr,Ba)0.3MnO3

    Institute of Scientific and Technical Information of China (English)

    ZHOU Sheng-Ming; DONG Qiu-Zhao; ZHOU Gui-En; ZHANG Yu-Heng

    2000-01-01

    The temperature dependence of thermopower and resistivity for the series of Nd0.7(Ca,Sr, Ba)0.3MnO3 with a fixed average A-site cation radius have been measured. Infrared spectra revealed that the size differences between various A-site ions cause large local distortions of MnO6 octahedra. The thermopower is enhanced above metal-insulator transition temperature Tm and is reduced below Tm by increasing amount of A-site cation disorder.The sign change of thermopower induced by A-site cation disorder has been observed at low temperatures. The observed thermopower behaviors have been explained by Mott's formula and the effect of the spin disorder scattering.

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

    Science.gov (United States)

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

    2015-03-01

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

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

    International Nuclear Information System (INIS)

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

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

    Indian Academy of Sciences (India)

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

    2014-11-01

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

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

    International Nuclear Information System (INIS)

    Nanocrystalline Scheelite type Dy doped AMoO4 [where A = Ba, Sr and Ca] samples were prepared by acrylamide assisted sol–gel process and characterized by XRD, FT-Raman, FTIR, SEM and photoluminescence (PL). PL of undoped sample shows blue/green emission in CaMoO4 and SrMoO4 but multicolour visible emission leading to near white light in BaMoO4 nanoparticles; the origin of which is explained. It was observed that on doping 0.5 mol% of Dy3+ in molybdate samples complete energy transfer takes place in case of SrMoO4 and BaMoO4, but host contributed substantially in Dy doped BaMoO4 sample, resulting in biexponential decay. It was also observed that symmetry around Dy3+ decreases as the size of alkaline earth ion increases. Due to combined blue, yellow and red colour emission in dysprosium doped sample; all samples showed near white light emission under UV and near UV excitation

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-15

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

  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)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

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

    2009-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    OpenAIRE

    Karo Karo, Justaman Arifin

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-09-15

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

  19. 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.

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

    Directory of Open Access Journals (Sweden)

    Mrinmoy Garai

    2015-01-01

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

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

    Science.gov (United States)

    Jami-Alahmadi, Yasaman; Fridgen, Travis D

    2016-01-21

    M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures. PMID:26685890

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  4. 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.

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

    Science.gov (United States)

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

    2016-09-01

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

  6. 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.

  7. Enhanced magnetic response in single-phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) ceramics

    Science.gov (United States)

    Sharma, Poorva; Kumar, Ashwini; Varshney, Dinesh

    2015-10-01

    Single phase Bi0.80La0.15A0.05FeO3-δ (A=Ca, Sr, Ba) dense ceramics were synthesized via solid state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics crystallized in a rhombohedrally (R 3 barC)distorted BiFeO3 structure with compressive lattice distortion induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning electron micrograph of the compounds showed the uniform distribution of grains on the sample surface with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g and remnant magnetization of 2.72 emu/ g at 300 K. Clear ferromagnetic ground state was observed in Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and dielectric loss were found to decrease with increase in frequency for all the compounds. These improved properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability and makes very promising for industrial applications such as new devices in information storage.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-12-31

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

  9. 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

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

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

    Directory of Open Access Journals (Sweden)

    R. Kumar

    2011-01-01

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

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

    Science.gov (United States)

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

    2016-09-01

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

  12. Structural and relaxor characteristics of Ca{sub 0.18}Sr{sub 0.226}Ba{sub 0.594}Nb{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Preethi Meher, K.R.S.; Varma, K.B.R. [Indian Institute of Science, Bangalore (India). Materials Research Centre; Vaish, Rahul [Indian Institute of Science, Bangalore (India). Materials Research Centre; Cambridge Univ. (United Kingdom). Dept. of Materials Science and Metallurgy; Indian Institute of Technology Mandi, Himachal Pradesh (India). School of Engineering; Hou, J. [Cambridge Univ. (United Kingdom). Dept. of Materials Science and Metallurgy; Tianjin Univ. (China). Key Laboratory for Advanced Ceramic and Machining Technology; Krsmanovic, Dalibor; Kumar, R.V. [Cambridge Univ. (United Kingdom). Dept. of Materials Science and Metallurgy

    2013-02-15

    Polycrystalline Ca{sub 0.18}Sr{sub 0.226}Ba{sub 0.594}Nb{sub 2}O{sub 6} (CSBN18) was synthesized via the solid-state reaction route. X-ray structural studies confirmed it belonged to the tetragonal tungsten bronze family. Rietveld refinement of the X-ray data has been carried out for CSBN18 where the atomic positions and site occupancy factors for A-sites have been determined. The dielectric properties of CSBN18 ceramic were studied as a function of temperature in the 100 Hz - 1 MHz frequency range. The dielectric relaxation followed the Vogel-Fulcher relation wherein E{sub a} = 37.4 meV; T{sub f} = 131.5 C and {omega}{sub 0} =4.31 x 10{sup 9} rad s{sup -1}. A high pyroelectric coefficient of {proportional_to} 250 {mu}C m{sup -2}. K was obtained around the transition temperature ({proportional_to} 150 C). This is significantly higher than that reported for polycrystalline Sr{sub x}Ba{sub 1-x}Nb{sub 2}O{sub 6} (SBN). However, the piezoelectric coefficient (d{sub 33}) of the title composition was as low as 6 pC N{sup -1}. (orig.)

  13. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  15. 10-π-Electron arenes à la carte: structure and bonding of the [E-(CnHn)-E](n-6) (E = Ca, Sr, Ba; n = 6-8) complexes.

    Science.gov (United States)

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

    2016-04-28

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-12-31

    Epitaxial (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} (Tl,Bi)-1223 thin films on (100) single crystal LaAlO{sub 3} substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field-cooled magnetization, and transport critical current density (J{sub c}) were measured. The zero-resistance temperature was 105-111 K. J{sub c} at 77 K and zero field was > 2 x 10{sup 6} A/cm{sup 2}. The films exhibited good flux pinning properties.

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

    Science.gov (United States)

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

    2016-05-01

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

  18. 4f and 5d energy levels of the divalent and trivalent lanthanide ions in M{sub 2}Si{sub 5}N{sub 8} (M=Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-01-15

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

  19. Separation Sr and Ba From Fission Products Using Sr-spec Resin Column

    Institute of Scientific and Technical Information of China (English)

    WANG; Xiu-feng

    2013-01-01

    Sr and Ba are the IIA group elements,with the same outer electronic structure,and the very similar properties,so separation of the two elements becomes very difficult.The traditional separation method of Sr and Ba in fission products is repeated precipitation of BaCl2·H2O in hydrochloric acid-ether medium.Four times repeated precipitation steps are needed to ensure the decontamination factor of Sr to be better

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

    Directory of Open Access Journals (Sweden)

    Manisha Rangi

    2014-08-01

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

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

    Science.gov (United States)

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

    2016-08-31

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

  2. 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.

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

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

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

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

    Institute of Scientific and Technical Information of China (English)

    郭凯; 操齐高; 赵景泰

    2013-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  7. 120-K Tl-Ca-Ba-Cu-O superconducting system

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    H Salamati

    2010-09-01

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

  9. The impedance spectroscopic study and dielectric relaxation in A(Ni{sub 1/3}Ta{sub 2/3})O{sub 3} [A=Ba, Ca and Sr

    Energy Technology Data Exchange (ETDEWEB)

    Hoque, Md M. [Department of Physics, Jadavpur University, Kolkata 700032 (India); Dutta, A. [Department of Physics, Bose Institute, 93/1, A. P. C. Road, Kolkata 700009 (India); Kumar, S., E-mail: kumars@jdvu.ac.in [Department of Physics, Jadavpur University, Kolkata 700032 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1, A. P. C. Road, Kolkata 700009 (India)

    2012-09-15

    We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni{sub 1/3}Ta{sub 2/3})O{sub 3} (BNT), Calcium Nickel Tantalate Ca(Ni{sub 1/3}Ta{sub 2/3})O{sub 3} (CNT) and Strontium Nickel Tantalate Sr(Ni{sub 1/3}Ta{sub 2/3})O{sub 3} (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 A and 3.98 A respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 A, b=13.45 A and c=5.47 A with {beta}=118.3 Degree-Sign . The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole-Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M Double-Prime suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan {delta}/tan {delta}{sub m} and M Double-Prime /M Double-Prime {sub m} versus log {omega} for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

  10. Anomalous Ba/Ca signals associated with low temperature stresses in Porites corals from Daya Bay, northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    Tianran Chen; Kefu Yu; Shu Li; Tegu Chen; Qi Shi

    2011-01-01

    Barium to calcium (Ba/Ca) ratio in corals has been considered as a useful geochemical proxy for upwelling,river flood and other oceanic processes.However,recent studies indicated that additional environmental or biological factors can influence the incorporation of Ba into coral skeletons.In this study,Ba/Ca ratios of two Porites corals collected from Daya Bay,northern South China Sea were analyzed.Ba/Ca signals in the two corals were 'anomalous' in comparison with Ba behaviors seen in other near-shore corals influenced by upwelling or riverine runoff.Our Ba/Ca profiles displayed similar and remarkable patterns characterized by low and randomly fluctuating background signals periodically interrupted by sharp and large synchronous peaks,clearly indicating an environmental forcing.Further analysis indicated that the Ba/Ca profiles were not correlated with previously claimed environmental factors such as precipitation,coastal upwelling,anthropogenic activities or phytoplankton blooms in other areas.The maxima of Ba/Ca appeared to occur in the period of Sr/Ca maxima,coinciding with the winter minimum temperatures,which suggests that the anomalous high Ba/Ca signals were related to winter-time low sea surface temperature.We speculated that the Ba/Ca peaks in corals of the Daya Bay were most likely the results of enrichment of Ba-rich particles in their skeletons when coral polyps retracted under the stresses of anomalous winter low temperatures.In this case,Ba/Ca ratio in relatively high-latitude corals can be a potential proxy for tracing the low temperature stress.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-02-01

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

  12. MAl2O4:Eu3+红色荧光粉的制备及其发光性质研究%Synthesis and luminescent properties of MAl2 O4:Eu3+(M=Ca, Sr, Ba) red phosphor

    Institute of Scientific and Technical Information of China (English)

    刘娟; 王玮; 周立亚

    2014-01-01

    MAl2O4:Eu3+(M=Ca, Sr, Ba) red phosphors were synthesized by sol-gel method re-spectively.The optimum calcinations temperature for CaAl2 O4:Eu3+ phosphor is 900 ℃, the size of the particles are about 1 ~2 μm, and the luminous intensity reaches the maximum when the mol concentration of activator Eu3+ions increased to 4%;the optimum calcinations temperature for SrAl2 O4:Eu3+ red phosphor is 1 100 ℃, the size of the particles are about 3~4 μm, and the luminous intensity reaches the maximum when the mol concentration of activator Eu3+ ions increased to 4%;the optimum calcinations temperature for BaAl2 O4:Eu3+ Red Phosphor is 1 100 ℃, the size of the particles are about 4 ~5 μm, and the luminous intensity reaches the maximum when the mol concentration of activator Eu3+ ions increased to 2%.Upon excitation with 392 nm light, all the MAl2O4:Eu3+(M=Ca, Sr, Ba) powders show bright red emission due to the 4f-4f transitions of Eu3+ ions.The excitation and emission spectra showed that the phosphor can be effectively excited by ultraviolet light(392 nm) , nicely fitting in with the widely applied emission wavelengths of ultravio-let light-emitter diodes (LED) chips.The MAl2O4:Eu3+(M=Ca, Sr, Ba) phosphors may be good candidate phosphor for LED application.%采用溶胶-凝胶法分别制备MAl2 O4:Eu3+( M=Ca, Sr, Ba)系列红色荧光粉,并对所制备的样品进行了XRD、SEM以及荧光光谱等表征,结果表明:CaAl2 O4:Eu3+红色荧光粉的适宜焙烧温度为900℃,其粒径大小约1~2μm,当激活剂Eu3+的摩尔浓度增加到4%时,其发光强度达到最大;SrAl2 O4:Eu3+红色荧光粉的适宜焙烧温度为1100℃,其粒径大小约3~4μm,当激活剂Eu3+的摩尔浓度增加到4%时,其发光强度达到最大;BaAl2 O4:Eu3+红色荧光粉的适宜焙烧温度为1100℃,其粒径大小约4~5μm,当激活剂Eu3+的摩尔浓度增加到2%时,其发光强度达到最大。以392 nm 的近紫外光激发样品,MAl2 O4:Eu3+( M=Ca, Sr, Ba)

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  15. 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.)

  16. Structures of [M(Ura-H)(H2 O)n ](+) (M = Mg, Ca, Sr, Ba; n = 1-3) complexes in the gas phase by IRMPD spectroscopy and theoretical studies.

    Science.gov (United States)

    Power, Barry; Haldys, Violette; Salpin, Jean-Yves; Fridgen, Travis D

    2016-03-01

    The structures of singly and doubly (and for Mg, triply) hydrated group 2 metal dications bound to deprotonated uracil were explored in the gas phase using infrared multiple photon dissociation spectroscopy in the mid-infrared region (1000-1900 cm(-1) ) and the O-H/N-H stretching region (2700-3800 cm(-1) ) in a Fourier transform ion cyclotron resonance mass spectrometer. The infrared multiple photon dissociation spectra were then compared with the computed IR spectra for various isomers. Calculations were performed using B3LYP with the 6-31 + G(d,p) basis set for all atoms except Ba(2+) and Sr(2+) , for which the LANL2DZ or the def2-TZVPP basis sets with relativistic core potentials were used. Atoms-in-molecules analysis was conducted for all lowest energy structures. The lowest energy isomers in all cases are those in which the one uracil is deprotonated at the N3 position, and the metal is coordinated to the N3 and O4 of uracil. Regardless of the degree of solvation, all water molecules are bound to the metal ion and participate in a hydrogen bond with a carbonyl of the uracil moiety.

  17. 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.

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

    OpenAIRE

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

    2012-01-01

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

  20. Dynamical plasma study during CaCu{sub 3}Ti{sub 4}O{sub 12} and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} pulsed laser deposition by local thermodynamic equilibrium modelling

    Energy Technology Data Exchange (ETDEWEB)

    Lagrange, J F; Wolfman, J; Motret, O [Laboratoire d' Electrodynamique des Materiaux Avances (LEMA), UMR 6157 CNRS-CEA, Universite Francois Rabelais de Tours, Faculte des Sciences and Techniques, Parc Grandmont - bat. E-37200 Tours (France); Hermann, J [Laboratoire Lasers, Plasmas et Procedes Photoniques (LP3), UMR 6182 CNRS, Universite Aix-Marseille II, 163 Avenue de luminy, C. 917-13288 Marseille (France)

    2010-07-21

    We performed space- and time-resolved plasma diagnostics during pulsed laser deposition of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} (BSTO) thin films. A KrF excimer laser irradiation at 248 nm with 25 ns pulse duration irradiates targets with a fluence varying from 1 to 2 J cm{sup -2} under an oxygen pressure varying from 5 to 30 Pa. The plasma is shown to be optically thick and strongly non-uniform during the early expansion stage and the resonance lines Ca II 393 and 396 nm are strongly self-reversed during this time. Plasma temperature, electron density and relative elemental concentrations were obtained by comparing the experimental emission spectra with the spectral radiance computed for a non-uniform plasma in local thermal equilibrium. In this way, it was possible to evaluate very low concentrations of pollutants present in irradiated samples.

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

    Science.gov (United States)

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

    2015-12-01

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

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

    International Nuclear Information System (INIS)

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

  3. TlBaCaCuO High Temperature Superconducting Bolometer

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

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

  4. 120 K superconductor TlBaCaCu2Oy

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  6. Separation of Red(Y_2O_3:Eu~(3+)),Blue(Sr,Ca,Ba)_(10)(PO_4)_6Cl_2:Eu~(2+)and Green(LaPO_4:Tb~(3+),Ce~(3+))Rare Earth Phosphors by Liquid/Liquid Extraction

    Institute of Scientific and Technical Information of China (English)

    MEI Guangjun; RAO Peng; MITSUAKI Matsuda; TOYOHISA Fujita

    2009-01-01

    A novel process for separation of red(Y_2O_3:Eu~(3+)),blue(Sr,Ca,Ba)_(10)(PO_4)_6Cl_2:Eu~(2+) and green(LaPO_4:Tb~(3+),Ce~(3+) )fine tricolor phosphor powders was established.First,the green phosphor was extracted and separated from three phosphor mixtures in heptane/DMF(N,N-Dimethylformamide)system using stearylamine or laurylamine(DDA)as the cationic surfactant.Then,after being treated with 99.5%ethanol,the blue and red phosphors could be separated in Heptane/DMF system in presence of 1-octanesulfonic acid sodium salt as the anionic surfactant.Satisfactory separation results have been achieved through two steps extractions with their artificial mixtures.The grades and recovery of separated products reached respectively as follows:red product was 95.3%and 90.9%,blue product was 90.0%and 95.2%,and green product was 92.2%and 91.8%.

  7. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-28

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

  9. Growth rate effects on Mg/Ca and Sr/Ca ratios constrained by belemnite calcite

    Science.gov (United States)

    Vinzenz Ullmann, Clemens

    2016-04-01

    Multiple temperature proxies from single species are important to achieve robust palaeotemperature estimates. Besides the commonly employed oxygen isotope thermometer, also Mg/Ca and Sr/Ca ratios perform well as proxies for calcification temperature in the shells of some species. While salinity changes affect the ratios of earth alkaline elements much less than the δ18O thermometer, metabolic effects may exert a strong control on the expression of element ratios. Such effects are hard to study because biomineralization experiments have to overcome large intraspecific variability and can hardly ever isolate the controls of a single parameter on shell geochemistry. The unique geometry of the belemnite rostrum constitutes an exception to this rule. Its shape, large size, and the visibility of growth increments as bands enable the analysis of multiple, correlatable, high resolution geochemical profiles in a single fossil. The effects of the growth rate variability amongst these profiles on Mg/Ca and Sr/Ca ratios has been tested here. Within a specimen of Passaloteuthis bisulcata (Early Toarcian, Cleveland Basin, UK), Mg/Ca and Sr/Ca data were obtained from four profiles. With respect to growth rate in the first profile, which was taken as a reference, the relative growth rates in the remaining three profiles varied by a factor of 0.9 to 2.7. Results suggest that relative growth rate is linearly correlated with Mg/Ca and Sr/Ca, with a decrease of Mg/Ca by 8 % and increase of Sr/Ca by 6 % per 100 % increase in relative growth rate. The observed trends are consistent with abiogenic precipitation experiments and suggest that crystal precipitation rate exerts a significant, predictable control on the element distribution in biogenic calcite.

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

    CERN Document Server

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

    2014-01-01

    It has been noted that, in classical extremely metal-poor (EMP) stars, the abundance ratio of Sr and Ba, is always higher than [Sr/Ba] = -0.5, the value of the solar r-only process; however, a handful of EMP stars have recently been found with a very low Sr/Ba ratio. We try to understand the origin of this anomaly by comparing the abundance pattern of the elements in these stars and in the classical EMP stars. Four stars with very low Sr/Ba ratios were observed and analyzed within LTE approximation through 1D (hydrostatic) model atmosphere, providing homogeneous abundances of nine neutron-capture elements. In CS 22950-173, the only turnoff star of the sample, the Sr/Ba ratio is, in fact, found to be higher than the r-only solar ratio, so the star is discarded. The remaining stars (CS 29493-090, CS 30322-023, HE 305-4520) are cool evolved giants. They do not present a clear carbon enrichment. The abundance patterns of the neutron-capture elements in the three stars are strikingly similar to a theoretical s-pro...

  11. Molecular Dynamics Simulations for Melting Temperatures of SrF2and BaF2

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  12. 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...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-28

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

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

    Indian Academy of Sciences (India)

    Vishnu Shanker; Tokeer Ahmad; Ashok K Ganguli

    2004-10-01

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

  15. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2006-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Kumar Shivesh

    2012-08-01

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

  18. 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.

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

    Science.gov (United States)

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

    2010-10-01

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

  20. Thermodynamic Study on BaO-CaO-CaF2 Slags for Dephosphorization of Molten Steel

    Institute of Scientific and Technical Information of China (English)

    TIAN Zhi-hong; CAI Kai-ke; WANG Xin-hua; ZHU Li-xin; WANG Tao; SHI Hong-zhi; YIN Xiao-dong

    2005-01-01

    The molten steel was dephosphorized by high basic BaO-based slags (BaO-CaO-CaF2) to achieve ultra low phosphorus level. The dephosphorization ability of the BaO-CaO-CaF2 slags was tested. The phosphate capacity of this slag system at 1 620 C varied from 1018.03 to 1019.11 with an activity coefficient of P2O5 ranging from 10-19.47 to 10-18.09. The effect of BaO content, initial phosphorus content and oxygen potential of molten steel on dephosphorization was discussed. The phosphorus pick-up by the BaO-based slags was studied.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-08-01

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

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

    Science.gov (United States)

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

    2015-08-01

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

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

    International Nuclear Information System (INIS)

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

  5. Analysis of coupled Sr/Ca and 87Sr/ 86Sr variations in enamel using laser-ablation tandem quadrupole-multicollector ICPMS

    Science.gov (United States)

    Balter, Vincent; Telouk, Philippe; Reynard, Bruno; Braga, José; Thackeray, Francis; Albarède, Francis

    2008-08-01

    We present in this study results obtained with a laser-ablation coupled with both a quadrupole and a multi-collector ICPMS. The simultaneous in situ Sr/Ca and 87Sr/ 86Sr measurements along growth profiles in enamel allows the concomitant diet and migration patterns in mammals to be reconstructed. Aliquots of the powdered international standard NIST "SRM1400 Bone Ash" with certified Sr and Ca contents, was sintered at high pressure and temperature and was adopted as the reference material for external reproducibility and calibration of the results. A total of 145 coupled elemental and isotopic measurements of herbivores enamel from the Kruger National Park, South Africa, gives intra-tooth Sr/Ca and 87Sr/ 86Sr variations that are well larger than external reproducibility. Sr/Ca profiles systematically decrease from the dentine-enamel junction to the outer enamel whereas 87Sr/ 86Sr profiles exhibit variable patterns. Using a simple geometric model of hypsodont teeth growth, we demonstrate that a continuous recording of the 87Sr/ 86Sr variations can be reconstructed in the tooth length axis. This suggests that the mobility of a mammal can be reconstructed over a period of more than a year with a resolution of a ten of days, by sampling enamel along growth profiles. Our geometric model of hypsodont teeth growth predicts that an optimal distance between two successive profiles is equal to the enamel thickness. However, this model does not apply to the Sr/Ca signal which is likely to be altered during the enamel maturation stage due to differential maturation processes along enamel thickness. Here, the observed constant decreases of the Sr/Ca ratios in the ungulates of Kruger National Park suggests that they did not changed of diet, while some of them were migrating.

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

    Science.gov (United States)

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

    2005-05-01

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

  7. 习水地区不同类型水主要离子及Sr2+、ρ(Sr)/ρ(Ca)、ρ(Sr)/ρ(Mg)组成特征%Composition Characteristics of Major Ions and ρ (Sr2 +) ,ρ (Sr)/ρ (Ca),ρ (Sr)/ρ (Mg) Value in Different Types of Water in Xishui

    Institute of Scientific and Technical Information of China (English)

    黄奇波; 覃小群; 唐建生; 苏春田

    2012-01-01

    After sampling and analyzing major ions concentration and ρ(Sr2 + ) ,ρ(Sr)/ρ(Ca) ,ρ(Sr)/ρ(Mg) value in different types of water from Xishui basin, low major ions concentration is found in bedrock fracture water. But TDS content and pH value are higher than in the karst water. The concentration of Ca2 +, HCO3-, TDS and the value of ρ( Sr)/ρ( Ca) and ρ( Sr)/ρ( Mg) in outlet water of under ground river are as the value in limestone water ture dolomite water, bedrock fracture water, and rainwater, reflecting that the underground river water is the mixtave of these four types of water. The underground water flowing over different rock formation has different value of ρ(Sr2 + ) , ρ(Sr)/ρ(Ca) , ρ( Sr)/ρ( Mg). Generally speaking, the bedrock fracture water flowing over sandstone formation contains low ρ( Sr2 + ) but high ρ( Sr ) /ρ(Ca ) ,ρ( Sr) /ρ( Mg ). Recharged by the water from limestone or coal measure formation, the fracture water of sandstone has high ρ(Sr2+ ) ,ρ(Sr)/ ρ(Ca) and ρ(Sr)/ρ(Mg). The value of ρ(Sr)/ρ(Ca) ,ρ(Sr)/ρ(Mg) is low in recharge area of karst water, but high in runoff and discharge area, yet highest in slow runoff area, not affected by environmental pollution, ref-leciting the formation environment of karst water.%通过对习水地区不同类型水的主要阴阳离子及Sr2+、ρ(Sr)/ρ(Ca)、ρ(Sr)/ρ(Mg)组成分析,发现水中各种主要离子及TDS含量基岩裂隙水小于岩溶水,ρH则相反.地下河出口水的Ca2+、HCO3-、TDS浓度及ρ(Sr)/ρ (Ca)、ρ(Sr)/ρ (Mg)值均位于灰岩水、白云岩水、基岩裂隙水、雨水之间,反映出地下河水是由这4种水混合而成.流经不同岩层的地下水具有不同的Sr2+、ρ(Sr)/ρ (Ca)、ρ(Sr)/ρ(Mg)值.一般来说,流经砂岩层的基岩裂隙水Sr2+含量低,而ρ(Sr)/ρ (Ca)、ρ(Sr)/ρ (Mg)值较高,当砂岩中的基岩裂隙水受到灰岩水或煤系地层水补给时,其Sr2+、ρ(sr)/ρ (Ca)、ρ(Sr)/ρ(Mg)值均较高;岩溶

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

    OpenAIRE

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

    2010-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-01-01

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

  10. Testing coral paleothermometers (B/Ca, Mg/Ca, Sr/Ca, U/Ca andδ18O) under impacts of large riverine runoff

    Institute of Scientific and Technical Information of China (English)

    CHEN Tianran; YU Kefu; ZHAO Jianxin; YAN Hongqiang; SONG Yinxian; FENG Yuexing; CHEN Tegu

    2015-01-01

    Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, Sr/Ca, U/Ca andδ18O were analyzed in the skeleton of aPorites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemical proxies are influenced by river runoff and this area of the northern South China Sea is strongly affected by seasonal freshwater floods. We assessed the robustness of each SST proxy through comparison with the local instrumental SST. Coral Sr/Ca shows the highest correlation with SST variations (r2=0.59), suggesting Sr/Ca is the most robust SST proxy. In contrast, coralδ18O (r2=0.46), B/Ca (r2=0.43) and U/Ca (r2=0.41) ratios were only moderately correlated with SST variations, suggesting that they are disturbed by some other factors in addition to SST. The poor correlation (r2=0.27) between SST and Mg/Ca indicates that Mg/Ca in coral skeletons is not a simple function of SST variations. This may ultimately limit the use of Mg/Ca as a coral paleothermometer.

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

    International Nuclear Information System (INIS)

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

  12. Dielectric Properties of Dy2O3 -Doped ( Ba, Sr) TiO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Huang Xinyou; Gao Chunhua; Chen Xiangchong; Zheng Xialian; Huang Guojun; Liu Huiping

    2004-01-01

    The effects of Dy2O3 doping on the dielectric properties of (Ba, Sr)TiO3 series capacitor ceramics prepared using solid-state reaction method were studied. With the increasing of Dy2O3 additive , the dielectric constant (ε) of materials increases to a maximum when w(Dy2O3 ) is about 0.5% ,while the dielectric loss(tanδ) decreases. The BST ceramics with highε ( = 5245 ), low tanδ ( = 0. 0026 ) and high DC breakdown voltage ( = 5.5 mV ·m-1 ) were obtained. The influencing mechanism of Dy2O3 on the dielectric properties of (Ba, Sr)TiO3 ceramics was studied, thus providing the basis for preparation of capacitor ceramics.

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

    International Nuclear Information System (INIS)

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  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. Growth kinetics of Cu1-xTlxBa2Ca3Cu4O12-y thin films

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-20

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Lee, C. Y.

    2014-12-01

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

  1. 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)

  2. Improvement of dielectric tunability and loss tangent of (Ba,Sr)TiO3 thin films with K doping

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Jie; Dai Jian-Ming; Zhu Xue-Bin; Chang Qing; Liu Qiang-Chun; Sun Yu-Ping

    2012-01-01

    Ba0.6Sr0.4TiO3 thin films doped with K were deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method.The structure,surface morphology and the dielectric and tunable properties of Ba0.6Sr0.4TiO3 thin films have been studied in detail. The K content in Ba0.6Sr0.4TiO3 thin films has a strong influence on the material's properties including surface morphology and the dielectric and tunable properties.It was found that the Curie temperature of K-doped Ba0.6Sr0.4TiO3 films shifts to a higher value compared with that of undoped Ba0.6Sr0.4TiO3 thin films,which leads to a dielectric enhancement of K-doped Ba0.6Sr0.4TiO3 films at room temperature.At the optimized content of 0.02 mol,the dielectric loss tangent is reduced significantly from 0.057 to 0.020.Meanwhile,the tunability is enhanced obviously from 26% to 48% at the measured frequency of 1 MHz and the maximum value of the figure of merit is 23.8.This suggests that such films have potential applications for tunable devices.

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

    International Nuclear Information System (INIS)

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

  4. The effect of Yttrium on the Ca and Sr planes of Y-doped Bi 2Sr 2Ca 1Cu 2O 8

    Science.gov (United States)

    Alméras, P.; Berger, H.; Margaritondo, G.

    1993-08-01

    Photoemission spectromicroscopy experiments on a series of Y-doped Bi 2Sr 2Ca 1Cu 2O 8 single crystals show that the doping changes the valence of copper as required for the observed modification of the critical temperature. The doping, however, affects with substitutional reactions not only the CaO planes, but also the SrO planes. Des expériences de photoémission sur une série de monocristaux de Bi 2Sr 2Ca 1Cu 2O 8 dopés avec de l'yttrium montrent que le dopage change la valence du cuivre, comme on dopage, pourtant, ne modifie pas seulement les plans CaO par des réactions de substitution, mais également les plans SrO. Esperimenti di fotoemissione condotti su una serie di monocristalli di Bi 2Sr 2Ca 2O 8 con impurezze di Y mostrano che tali impurezze modificano la valenza del rame, com'é indipendentemente reso necessario dal fatto che si osservano dei cambiamenti della temperature di transizione. Si nota peraltro che le impurezze non modificano solamente i piani CaO mediante reazioni di sostituzione, ma anche i piani SrO.

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

    Science.gov (United States)

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

    2002-03-01

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

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

    Science.gov (United States)

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

    2015-08-25

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

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

    International Nuclear Information System (INIS)

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

  8. Effect of composition and interface intermixing on polarization behaviors of BaTiO{sub 3}/(Ba,Sr)TiO{sub 3} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Chew, Khian-Hooi; Lim, Kok-Geng [Department of Physics, University of Malaya, 50603, Kuala Lumpur (Malaysia); Ong, Lye-Hock [School of Physics, Universiti Sains Malaysia, 11800, Minden, Penang (Malaysia); Iwata, Makoto [Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Aichi, 4668555 (Japan)

    2014-08-15

    We have developed a thermodynamic model based on the Landau-Ginzburg theory to study the effect of composition and interface intermixing on ferroelectric properties of BaTiO{sub 3}/Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BT/BST) superlattices. Dependence of the lattice parameter and the substrate-induced misfit strain of BST layer in BT/BST superlattices on Ba/Sr content are obtained. Effect of composition and interface intermixing on ferroelectricity of superlattices are examined by investigating the modulated profiles of polarization and the mismatch in polarization at interface. Our study reveals that the polarization behaviors of BT/BST superlattices can be manipulated by varying the Ba/Sr content in BST layer without changing the period thickness of superlattices. The effect of Ba/Sr content on polarization behavior of BT/BST superlattices is stronger than the effect of interface intermixing on polarization of the superlattices. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    Indian Academy of Sciences (India)

    B Ramdas; R Vijayaraghavan

    2010-02-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2012-08-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2010-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-12-31

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

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

    Indian Academy of Sciences (India)

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

    2004-10-01

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

  16. SPECTROSCOPIC PROPRIETIES OF CRYSTALS MF2 (M=Cd, Sr, Ba DOPED TO RARE EARTH IONS

    Directory of Open Access Journals (Sweden)

    M. Diaf

    2015-07-01

    Full Text Available 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 fluorescence dynamics at room temperature of visible and near infrared transitions of the Er3+ ion doping these matrices. We also use the formalism of Judd-Ofelt by use of absorption spectra recorded at room temperature in order to identify the spectroscopic properties inherent in all radiative transitions which can occur.

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

    Science.gov (United States)

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

    2011-11-01

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

  18. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hongwei, E-mail: hhw@cugb.edu.cn; Wang, Shuobo; Zhang, Yihe, E-mail: zyh@cugb.edu.cn; Han, Xu

    2015-02-15

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

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

    International Nuclear Information System (INIS)

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

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

    OpenAIRE

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  6. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

    Indian Academy of Sciences (India)

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

    2010-04-01

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

  7. Thin films of the Bi2Sr2Ca2Cu3O(x) superconductor

    Science.gov (United States)

    Mei, YU; Luo, H. L.; Hu, Roger

    1990-01-01

    Using RF sputtering technique, thin films of near single phase Bi2Sr2Ca2Cu3O(x) were successfully prepared on SrTiO3(100), MgO(100), and LaAlO3(012) substrates. Zero resistance of these films occurred in the range of 90-105 K.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-10-15

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

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

    International Nuclear Information System (INIS)

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

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

    OpenAIRE

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

    2009-01-01

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

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

    OpenAIRE

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

    2001-01-01

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

  12. Thermoluminescence studies of bismuth doped Ba xCa 1- xS nanostructures

    Science.gov (United States)

    Singh, Surender; Lochab, S. P.; Kumar, Ravi; Singh, Nafa

    2011-01-01

    Bismuth doped Ba 1- xCa xS:Bi ( x=0-1) nanocrystallities have been prepared by the solid state reaction method and characterized by XRD and TEM. X-ray diffraction analysis shows the formation of the compounds in cubic structure at room temperature. Only partial replacement of Ba is possible and we found that Ba 0.5Ca 0.5S:Bi could not be prepared due to the difference between ionic radii of barium and calcium. Thermoluminescence studies of these samples after exposure to UV radiation have been carried out. The TL glow curve of Ba xCa 1 -xS:Bi has been found to be a simple structure with a single peak at 405, 428 and 503 K for x=1, 0.8 and 0, respectively. The kinetic parameters at various heating rates namely activation energy ( E), order of kinetics ( b) and frequency factor ( s) of the Ba 1- xCa xS:Bi ( x=0.2) (0.4 mol%) sample have been determined using Chen’s method. The deconvolution of curve was done using the GCD function suggested by Kitis. The effect of different heating rates and different amount of dose has also been discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-08-01

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

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

    CERN Document Server

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

    2016-01-01

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

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

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2009-11-01

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

  16. Room temperature epitaxial stabilization of a tetragonal phase in ARuO3 (A = Ca and Sr) thin films

    NARCIS (Netherlands)

    Vailionis, Arturas; Siemons, Wolter; Koster, Gertjan

    2008-01-01

    We demonstrate that SrRuO3 and CaRuO3 thin films undergo a room temperature structural phase transition driven by the substrate imposed epitaxial biaxial strain. As tensile strain increases, ARuO3 (A = Ca and Sr) films transform from the orthorhombic phase which is usually observed in bulk SrRuO3 an

  17. 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.

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

    Institute of Scientific and Technical Information of China (English)

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

    2012-01-01

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

  19. 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

    The Jurassic Period (ca. 201–145 Ma) is marked by fundamental reorganizations of paleogeography, paleoceanography, ecosystems, and the progressive shift from aragonite to calcite as the favored marine biogenic carbonate polymorph. Sr/Ca ratios of well-preserved Jurassic oysters and belemnites fro...

  20. Effects of Ca and Sr chemical doping on the average superconducting kinetic energy of YBa2Cu3O7-δ

    Science.gov (United States)

    Vieira, V. N.; Mendonça, A. P. A.; Dias, F. T.; Hneda, M. L.; Pureur, P.; Schaf, J.; Mesquita, F.

    2015-03-01

    In this brief communication we applied the MZFC(T) and MFCC(T) reversible dc magnetizations to get the average superconducting kinetic energy density, kS(T,B) of YBa2Cu3O7-δ, Y0.95Ca0.05Ba2Cu3O7-δ and YBa1.75Sr0.25Cu3O7-δ ceramic samples with the aim of study the effects of Ca and Sr doping on the kS(T,B). The MZFC(T) and MFCC(T) measurements were performed with a SQUID magnetometer from quantum design to dc magnetic fields up to 50kOe. The determination of the kS(T,B) from reversible dc magnetization is supported by virial theorem of superconductivity [kS(T,B) = - MB]. The kS(T,B) results show an common temperature profile for all the samples which is smoothly affected by the magnetic field. On the other hand the kS(T,B) results to T > Tc could not be associated to the pseudogap phenomenon. The Ca doping affects more effectively the kS(T,B) behaviour then Sr doping. A possible explanation to this feature could be associated to the fact that the hole doping promoted by Ca doping depress more considerably the superconducting state and enhances the granular character of the YBa2Cu3O7-δ superconductor than the chemical pressure effect promoted by Sr doping.

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

    International Nuclear Information System (INIS)

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

  2. Solubility of BaS in BaO-BaF2 slag and the Influence of FeOx, SiO2, Cr2O3, BaCI2, CaO, and MgO on the sulfide capacity of this system

    Science.gov (United States)

    Rachev, Ivan P.; Tsukihashi, Fumitaka; Sano, Nobuo

    1992-03-01

    The influence of SiO2, FeOx, Cr2O3, BaCl2, CaO, and MgO on the sulfide capacity of the BaO-BaF2 system was measured at 1473 K, using a gas-slag-metal equilibration technique. It was found that the substitution of BaF2 by SiO2, FeOx, Cr2O3, and BaCl2 decreases the sulfide capacity of the BaO-BaF2 system. Similar results were obtained for the carbonate capacity. The CaO-saturated BaO-BaF2 flux, however, was found to have slightly higher sulfide and carbonate capacities than the pure BaO-BaF2 flux. The solubility of CaO increased with increasing BaF2 content and was 18 mol pet in BaF2 at 1473 K. The solubility of MgO in the BaO-BaF2 system at the same temperature is very low, and it has no effect on the sulfide and carbonate capacities. The solubility of BaS in the BaO-BaF2 system was also measured at 1473 K and had its maximum for the slag containing 40 mass pet BaO. The activity of BaO in the system was calculated from those data.

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

    International Nuclear Information System (INIS)

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

  4. 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

  5. Tracing thermal aquifers of El Chichón volcano-hydrothermal system (México) with 87Sr/ 86Sr, Ca/Sr and REE

    Science.gov (United States)

    Peiffer, L.; Taran, Y. A.; Lounejeva, E.; Solís-Pichardo, G.; Rouwet, D.; Bernard-Romero, R. A.

    2011-08-01

    The volcano-hydrothermal system of El Chichón volcano, Chiapas, Mexico, is characterized by numerous thermal manifestations including an acid lake, steam vents and boiling springs in the crater and acid and neutral hot springs and steaming ground on the flanks. Previous research on major element chemistry reveals that thermal waters of El Chichón can be divided in two groups: (1) neutral waters discharging in the crater and southern slopes of the volcano with chloride content ranging from 1500 to 2200 mg/l and (2) acid-to-neutral waters with Cl up to 12,000 mg/l discharging at the western slopes. Our work supports the concept that each group of waters is derived from a separate aquifer (Aq. 1 and Aq. 2). In this study we apply Sr isotopes, Ca/Sr ratios and REE abundances along with the major and trace element water chemistry in order to discriminate and characterize these two aquifers. Waters derived from Aq. 1 are characterized by 87Sr/ 86Sr ratios ranging from 0.70407 to 0.70419, while Sr concentrations range from 0.1 to 4 mg/l and Ca/Sr weight ratios from 90 to 180, close to average values for the erupted rocks. Waters derived from Aq. 2 have 87Sr/ 86Sr between 0.70531 and 0.70542, high Sr concentrations up to 80 mg/l, and Ca/Sr ratio of 17-28. Aquifer 1 is most probably shallow, composed of volcanic rocks and situated beneath the crater, within the volcano edifice. Aquifer 2 may be situated at greater depth in sedimentary rocks and by some way connected to the regional oil-gas field brines. The relative water output (l/s) from both aquifers can be estimated as Aq. 1/Aq. 2-30. Both aquifers are not distinguishable by their REE patterns. The total concentration of REE, however, strongly depends on the acidity. All neutral waters including high-salinity waters from Aq. 2 have very low total REE concentrations (hydrothermal vapors, REE distribution in thermal waters reflects the dissolution of volcanic rocks close to the surface or lake sediments as is the case

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

    Science.gov (United States)

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

    2016-05-01

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

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

    International Nuclear Information System (INIS)

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

  8. 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.

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

    Indian Academy of Sciences (India)

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

    2011-02-01

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

  10. Neutron diffraction studies on Ca1-BaZr4P6O24 solid solutions

    Indian Academy of Sciences (India)

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

    2008-11-01

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

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

    Indian Academy of Sciences (India)

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

    2002-05-01

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

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

    Science.gov (United States)

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

    2011-05-01

    As paleoceanographic archives, deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating, but have not been fully investigated for geochemical reconstructions of past ocean conditions. Here we assess the utility of skeletal P/Ca, Ba/Ca and U/Ca in the deep sea coral D. dianthus as proxies of dissolved phosphate (remineralized at shallow depths), dissolved barium (trace element with silicate-type distribution) and carbonate ion concentrations, respectively. Measurements of these proxies in globally distributed D. dianthus specimens show clear dependence on corresponding seawater properties. Linear regression fits of mean coral Element/Ca ratios against seawater properties yield the equations: P/Ca coral (μmol/mol) = (0.6 ± 0.1) P/Ca sw(μmol/mol) - (23 ± 18), R2 = 0.6, n = 16 and Ba/Ca coral(μmol/mol) = (1.4 ± 0.3) Ba/Ca sw(μmol/mol) + (0 ± 2), R2 = 0.6, n = 17; no significant relationship is observed between the residuals of each regression and seawater temperature, salinity, pressure, pH or carbonate ion concentrations, suggesting that these variables were not significant secondary dependencies of these proxies. Four D. dianthus specimens growing at locations with Ωarag ⩽ 0.6 displayed markedly depleted P/Ca compared to the regression based on the remaining samples, a behavior attributed to an undersaturation effect. These corals were excluded from the calibration. Coral U/Ca correlates with seawater carbonate ion: U/Ca coral(μmol/mol) = (-0.016 ± 0.003) [CO32-] (μmol/kg) + (3.2 ± 0.3), R2 = 0.6, n = 17. The residuals of the U/Ca calibration are not significantly related to temperature, salinity, or pressure. Scatter about the linear calibration lines is attributed to imperfect spatial-temporal matches between the selected globally distributed specimens and available water column chemical data, and potentially to unresolved additional effects. The uncertainties of these initial proxy calibration regressions

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

    Science.gov (United States)

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

    1990-01-01

    Researchers produced superconducting ceramics of the Bi-Pb-Sr-Ca-Cu-O system started from a glass. To form the glass, the mixed oxide powder was melted at 1200 C in air. The liquid was quenched rapidly by pouring it onto an aluminum plate and rapidly pressing with another plate. The quenched compound was in the form of black amorphous solid, whose x-ray powder pattern has no crystalline peaks. After heat treatment at high temperatures, the glass crystallized into a superconductor. The crystalline phases in the superconductor identified using x-ray diffraction patterns. These phases were that associated with the superconducting phases of T(sub c) = 80 K (Bi2Ca1Sr2Cu2Ox) and of T(sub c) = 110 K (Bi2Ca2Sr2Cu3Ox). The dc resistivity and the ac susceptibility of these superconductors were studied.

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

    Science.gov (United States)

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

    2016-07-18

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

  15. Luminescence, Concentration Quenching and Thermal Stability of White Emitting Phosphor Ba2Ca(BO3)2:Dy3+

    Institute of Scientific and Technical Information of China (English)

    SONG Huiling; ZHOU Fen; CAO Heying; GUO Mingchao; ZHAO Jiawei; WANG Zhijun; LIU Haiyan; GAO Shaojie; LI Panlai

    2015-01-01

    A white emitting phosphor Ba2Ca(BO3)2:Dy3+ was synthesizedvia a high temperature solid state reaction at 1000℃ for 5 h. The luminescence, mole fraction quenching and thermal stability of Ba2Ca(BO3)2:Dy3+ were investi-gated. According to the phase composition analyzed by X-ray powder diffraction, there is no crystalline phase except Ba2Ca(BO3)2 in the sample. Ba2Ca(BO3)2:Dy3+ can produce white emission under 348 nm excitation. The emission in-tensities of Ba2Ca(BO3)2:Dy3+ are affected by Dy3+ concentration. The concentration quenching effect was analyzed, and the concentration quenching mechanism was verified as dipole-dipole interaction. The critical distance (Rc) obtained based on the crystal structure data is 2.911 nm. At 150℃, the emission intensity of Ba2Ca(BO3)2:Dy3+ is 68.0% of the initial value at room temperature. The activation energy for the thermal quenching calculated is 0.202 eV. Moreover, the CIE chromaticity coordinates of Ba2Ca(BO3)2:Dy3+ locate in the white region of (0.319, 0.356).

  16. 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.

  17. 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.

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

    International Nuclear Information System (INIS)

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

  19. 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.

  20. Investigation of thermoluminescence characteristics of CaSrS: Ce nanophosphors

    Science.gov (United States)

    Sharma, Geeta; Lochab, S. P.; Singh, Nafa

    2010-11-01

    Thermoluminescence characteristics of Ca 0.75Sr 0.25S: Ce nanophosphors exposed to UV radiations have been investigated. Solid state diffusion method was employed to synthesize the nanophosphors. The confirmation for the formation of the mixed lattice was done by XRD. The particles formed were found to have 45 nm size as calculated by the Debye Scherrer formula. TEM results were in close agreement with the XRD as the nanoparticles formed possess capsule like structure with an average diameter of 50 nm. TL glow curves for the low doses (110-1680 mJ/cm 2) of UV show a main peak around 381 K and another peak of very low intensity around 570 K. The TL intensity increases up to 450 mJ/cm 2 of UV exposure. At higher doses (3.5-80 J/cm 2) the peak position varies slightly but the high temperature peak becomes more intense. Thermoluminescence characteristics of UV irradiated Ca 1- xSr xS: Ce as a function of x (0.25, 0.50, and 0.75) have also been investigated. TL glow curves of Ca 1- xSr xS: Ce (0.25, 0.50, and 0.75) recorded after 450 mJ/cm 2 of exposure of UV radiations show almost similar structure except slight variation in the peak position. Ca 0.25Sr 0.75S: Ce and Ca 0.50Sr 0.50S: Ce have single peak at 373 and 367 K, respectively, while Ca 0.75Sr 0.25S: Ce has a main peak at 381 K and a less intense peak at 570 K. Ca 0.75Sr 0.25S: Ce shows the most intense TL peak. The trap parameters namely, activation energy ( E), order of kinetics ( b), and frequency factor ( s) of Ca 0.75Sr 0.25S: Ce have been determined using Chen’s peak shape method and GCD function suggested by Kitis for second order kinetics.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-15

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

  2. 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.

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

    International Nuclear Information System (INIS)

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

  4. A new oxochromate: SrNi2Cr8O15 of the BaV10O15 type

    International Nuclear Information System (INIS)

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

  5. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G. (Los Alamos National Lab., NM (United States))

    1991-03-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, an approach to the electrical characterization of these films on a conductive substrate is discussed and compared in this paper, with SEM, XRD and RBS measurements as a function of differing annealing protocols.

  6. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G.

    1990-01-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate is discussed and compared with SEM, XRD and RBS measurements as a function of differing annealing protocols. 3 refs., 9 figs.

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

    Science.gov (United States)

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

    2009-07-01

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

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

    Indian Academy of Sciences (India)

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

    2016-06-01

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

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

    Science.gov (United States)

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

    2016-08-01

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

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

    International Nuclear Information System (INIS)

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

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

    Indian Academy of Sciences (India)

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

    2006-06-01

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

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

    International Nuclear Information System (INIS)

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

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    M. Gabryś

    2008-11-01

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

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

    Science.gov (United States)

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

    1990-01-01

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

  16. 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...

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    NARCIS (Netherlands)

    Kunkel, Nathalie; Meijerink, Andries; Kohlmann, Holger

    2014-01-01

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

  1. Microwave Absorbing Properties of Ba0.6Sr0.4Fe12-zMnzO19 (z = 0 – 3 Materials in XBand Frequencies

    Directory of Open Access Journals (Sweden)

    Yohanes Edi Gunanto

    2016-03-01

    Full Text Available Ba0.6Sr0.4Fe12-zMnzO19 (z = 0,1,2, and 3 were successfully synthesized by solid state reaction through a mechanical milling method. Stoichiometric quantities of analytical-grade MnCO3, BaCO3, Fe2O3, and SrCO3 precursors with purity greater than 99% were mixed. It was found that the best phase composition, having an absorber with high performance, was Ba0.6Sr0.4Fe11MnO19. Refinement of the X-ray diffraction patterns revealed that the Ba0.6Sr0.4Fe11MnO19 was single-phase and had a hexagonal structure (P63/mmc. Mechanical milling of Ba0.6Sr0.4Fe11MnO19 powders produced particles with a mean size of ~850 nm. SEM images revealed the morphology of the particles as being aggregates of fine grains. The magnetic properties of the Ba0.6Sr0.4Fe11MnO19 particles showed a low coercivity and a high remanent magnetization. The Ba0.6Sr0.4Fe11MnO19 has certain microwave absorber properties in the frequency range of 8-14 GHz, with an absorbing peak value of ‑8 dB and -10 dB at frequencies of 8.5 and 12.5 GHz, respectively. The study concludes that the Ba0.6Sr0.4Fe12-zMnzO19 that was successfully synthesized is a good candidate for use as an electromagnetic absorber material.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  4. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-03-15

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

  6. 57Fe hyperfine interaction parameters and selected magnetic properties of high purity MFe12O19 (M = Sr, Ba)

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2008-10-01

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

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

    Science.gov (United States)

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

    2002-02-01

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

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

    International Nuclear Information System (INIS)

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

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

    Institute of Scientific and Technical Information of China (English)

    葛水兵; 沈明荣; 宁兆元

    2002-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    Graphical abstract: Polarization hysteresis (P–E) loops of the (Pb0.85Ba0.08Sr0.03La0.03) (Zr0.74Sn0.22Ti0.04) samples: (a) measured at different applied electric-field and (b) measured at different temperatures is shown. It is typical antiferroelectrics whose remnant polarization is zero. As the remnant polarization of AFE is small and the ceramics are accompanied by the formation of the anti-parallel domain structure, energy stored in PLZST can be effectively released. Thus we calculated the energy density from the P–E loop and obtained the power density was up to 1.2 J/cm3 at 55 °C, and at 45 °C the energy density was ∼1.24 J/cm3. As usual, for bulk ceramics, the switching between the AFE and FE states occurs at lower field. This value is much higher than that reported previously for the PLZT bulk ceramic (0.4 J/cm3). - Highlights: • Ba2+, Sr2+ co-doping caused the Tc of PLZST moved to the lower temperature (Tc ≈ 40 °C). • The ΔE was so smaller, EAF ≈ 90 kV/cm and EFA ≈ 85 kV/cm. • Ba, Sr co-doped PLZST ceramic exhibited slanted P–E loops with a large breakdown field (100 kV/cm). • A high energy density was up to 1.2 J/cm3. - Abstract: (Pb0.85Ba0.08Sr0.03La0.03)(Zr0.74Sn0.22Ti0.04) (Ba, Sr co-doped PLZST) co-doping antiferroelectric (AFE) ceramics with orthorhombic perovskite structure were prepared by the traditional solid state reaction process. It was observed that the doping of barium and strontium caused the Curie temperature of PLZST move to the lower temperature (Tc ≈ 40 °C). Ba, Sr co-doped PLZST AFE ceramics exhibited excellent electrical properties, the AFE to ferroelectric (FE) transition occurred at field EAF ≈ 90 kV/cm, and the transition from FE to AFE occurred at EFA ≈ 85 kV/cm. The maximum relative permittivity was about 4800, occurring at a field near the AFE to FE transition point, with a dielectric loss of 0.006. The samples exhibited small ΔE and slanted hysteresis loops with a large breakdown field of 100 k

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

    International Nuclear Information System (INIS)

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

  15. Distinct Ca2+ and Sr2+ binding properties of synaptotagmins. Definition of candidate Ca2+ sensors for the fast and slow components of neurotransmitter release.

    Science.gov (United States)

    Li, C; Davletov, B A; Südhof, T C

    1995-10-20

    Ca(2+)-dependent neurotransmitter release consists of at least two components: a major fast component that is insensitive to Sr2+ and a minor slow component that is potentiated by Sr2+ (Goda, Y., and Stevens, C. F. (1994) Proc. Natl. Acad. U. S. A. 91, 12942-12946). These results suggest that at least two Ca2+ sensors act in synaptic vesicle fusion with distinct Ca2+ and Sr2+ binding properties. We have now investigated the relative Ca2+ and Sr2+ binding activities of synaptotagmins to evaluate their potential roles as Ca2+ sensors for the fast and slow components. Our results demonstrate that the first C2 domains of synaptotagmins I, II, III, V, and VII have very similar Ca2+ requirements for phospholipid binding (range of EC50 = 2.6 microM to 5.0 microM), but distinct Sr2+ requirements (EC50 range = 23 microM to 133 microM); synaptotagmins I and II had the lowest Sr2+ affinity, and synaptotagmin III the highest Sr2+ affinity. Purified synaptotagmin I from bovine brain exhibited similar properties as its recombinant first C2 domain, suggesting that the first C2 domain fully accounts for its Ca(2+)-dependent phospholipid binding properties. Sr2+ was unable to trigger syntaxin binding by synaptotagmin I at all concentrations tested, whereas it was effective for synaptotagmin III. These results suggest that different C2 domains have distinct Sr2+ binding properties. They support the hypothesis that synaptotagmins localized on the same vesicle perform distinct functions, with synaptotagmins I and II serving as candidate Ca2+ sensors for the fast component in release and synaptotagmin III for the slow component.

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

    Science.gov (United States)

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

    2014-04-01

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

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

    International Nuclear Information System (INIS)

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

  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. Synchrotron X-ray diffraction study of the Ba1−xSrSnO3 solid solution

    International Nuclear Information System (INIS)

    At room temperature the sequence of phases with increasing amounts of strontium in the stannate perovskite system Ba1−xSrSnO3 has been established from high resolution synchrotron X-ray powder diffraction. The observed sequence orthorhombic (Pbnm), orthorhombic (Ibmm), tetragonal (I4/mcm), and cubic (Pm3-bar m) is a consequence of the sequential introduction of cooperative tilting of the corner sharing SnO6 octahedra. The cell volume changes smoothly across the series with no obvious discontinuities associated with the phase transitions. - Graphical abstract: Portions of the synchrotron X-ray diffraction profiles (λ=0.82453 Å) from selected Ba1−xSrxSnO3 samples together with the results of fitting by the Rietveld method. Highlights: ► Structures of the stannate perovskites Ba1−xSrSnO3 refined from synchrotron XRD. ► The sequence Pm3-bar m→I4/mcm→Ibmm→Pbnm results from tilting of the octahedra. ► The tilting maintains optimal bonding of the cations seen from the BVS analysis

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

    Science.gov (United States)

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

    2015-03-01

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

  1. Sr/Ca and Mg/Ca vital effects correlated with skeletal architecture in a scleractinian deep-sea coral and the role of Rayleigh fractionation

    Science.gov (United States)

    Gagnon, Alexander C.; Adkins, Jess F.; Fernandez, Diego P.; Robinson, Laura F.

    2007-09-01

    Deep-sea corals are a new tool in paleoceanography with the potential to provide century long records of deep ocean change at sub-decadal resolution. Complicating the reconstruction of past deep-sea temperatures, Mg/Ca and Sr/Ca paleothermometers in corals are also influenced by non-environmental factors, termed vital effects. To determine the magnitude, pattern and mechanism of vital effects we measure detailed collocated Sr/Ca and Mg/Ca ratios, using a combination of micromilling and isotope-dilution ICP-MS across skeletal features in recent samples of Desmophyllum dianthus, a scleractinian coral that grows in the near constant environment of the deep-sea. Sr/Ca variability across skeletal features is less than 5% (2σ relative standard deviation) and variability of Sr/Ca within the optically dense central band, composed of small and irregular aragonite crystals, is significantly less than the surrounding skeleton. The mean Sr/Ca of the central band, 10.6 ± 0.1 mmol/mol (2σ standard error), and that of the surrounding skeleton, 10.58±0.09 mmol/mol, are statistically similar, and agree well with the inorganic aragonite Sr/Ca-temperature relationship at the temperature of coral growth. In the central band, Mg/Ca is greater than 3 mmol/mol, more than twice that of the surrounding skeleton, a general result observed in the relative Mg/Ca ratios of D. dianthus collected from separate oceanographic locations. This large vital effect corresponds to a ˜ 10 °C signal, when calibrated via surface coral Mg/Ca-temperature relationships, and has the potential to complicate paleoreconstructions. Outside the central band, Mg/Ca ratios increase with decreasing Sr/Ca. We explain the correlated behavior of Mg/Ca and Sr/Ca outside the central band by Rayleigh fractionation from a closed pool, an explanation that has been proposed elsewhere, but which is tested in this study by a simple and general relationship. We constrain the initial solution and effective partition

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

    International Nuclear Information System (INIS)

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

  3. Multifunctional dual-tunable multiferroic Ba0.25Sr0.75TiO3-BiFeO3-Ba0.25Sr0.75TiO3 trilayered structure for tunable microwave applications

    International Nuclear Information System (INIS)

    A multiferroic trilayered structure composed of a BiFeO3 (BFO) layer and two Ba0.25Sr0.75TiO3 (BST) layers is grown on a Pt/TiO2/SiO2/Si substrate by pulsed laser deposition. The trilayered BST/BFO/BST thin film structure exhibits a significant tuning response for the dielectric constant with an electric field and a magnetic field, respectively. Microwave devices based on such multifunctional materials can offer dual, i.e. electric and magnetic, tuning possibility and extra flexibility in designing and shaping the device performances.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    1991-01-01

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

  6. Effect of doping Ca on polaron hopping in LaSr2Mn2O7

    Indian Academy of Sciences (India)

    S N Bhatia; Osama A Yassin

    2002-05-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-01

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

  11. 110K Bi-Sr-Ca-Cu-O superconductor oxide and method for making same

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-07-15

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

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

    International Nuclear Information System (INIS)

    In order to meet the increasing demand for electric power generation from solar energy conversion, the development of efficient light absorber materials has been awaited. To this end, the electronic and optical properties of advanced alkaline-earth-metals disilicides and digermanides (SrSi2, BaSi2, SrGe2, and BaGe2) are studied by means of the density functional theory using HSE06 exchange-correlation energy functional. Our calculations show that all these orthorhombic structured compounds have fundamental indirect band gaps in the range Eg ≈ 0.89–1.25 eV, which is suitable for solar cell applications. The estimated lattice parameters and band gaps are in good agreement with experiments. Our calculations show that the electronic band structures of all four compounds are very similar except in the vicinity of the Γ-point. The valence band of these compounds is made up by Si(Ge)-p states, whereas the conduction band is composed of Sr(Ba)-d states. Their band alignments are carefully determined by estimating the work function of each compound using slab model. The optical properties are discussed in terms of the complex dielectric function ε(ω) = ε1(ω) + iε2(ω). The static and high-frequency dielectric constants are calculated, taking into account the ionic contribution. The absorption coefficient α(ω) demonstrates that a low energy dispersion of the conduction band, which results in a flat conduction band minimum, leads to large optical activity in these compounds. Therefore, alkaline-earth-metals disilicides and digermanides possess great potential as light absorbers for applications in thin-film solar cell technologies.

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

    International Nuclear Information System (INIS)

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

  15. Enhanced ferroelectric properties of Mg doped (Ba,Sr)TiO3 thick films grown on (001) SrTiO3 substrates

    International Nuclear Information System (INIS)

    Highly (001)-oriented 1 mol% Mg doped (Ba0.67,Sr0.33)TiO3 (BST) films with a thickness of 1.25 μm were grown on (110) SrRuO3/(001) SrTiO3 substrates by pulsed laser deposition. X-ray diffraction measurements reveal that the BST thick films have very high crystalline quality, and have a distorted lattice with a large tetragonality a/c = 1.012. The BST thick films have a remanent polarization (Pr) value as large as 10.1 μC/cm2 and a coercive electric field (Ec) value of 65.0 kV/cm. The films possess dielectric constant and loss values of εr = 385.36 and tgδ = 0.038 at 1 kHz and room temperature. The leakage currents of the films are on the order of 10−5 A/cm2 at ± 150 kV/cm. The mechanism for enhancing electric properties of the Mg doped BST films was also discussed.

  16. Enhanced ferroelectric properties of Mg doped (Ba,Sr)TiO{sub 3} thick films grown on (001) SrTiO{sub 3} substrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hong, E-mail: liuh@scu.edu.cn; Zhu Jianguo; Chen Qiang; Yu Ping; Xiao Dingquan

    2012-02-29

    Highly (001)-oriented 1 mol% Mg doped (Ba{sub 0.67},Sr{sub 0.33})TiO{sub 3} (BST) films with a thickness of 1.25 {mu}m were grown on (110) SrRuO{sub 3}/(001) SrTiO{sub 3} substrates by pulsed laser deposition. X-ray diffraction measurements reveal that the BST thick films have very high crystalline quality, and have a distorted lattice with a large tetragonality a/c = 1.012. The BST thick films have a remanent polarization (P{sub r}) value as large as 10.1 {mu}C/cm{sup 2} and a coercive electric field (E{sub c}) value of 65.0 kV/cm. The films possess dielectric constant and loss values of {epsilon}{sub r} = 385.36 and tg{delta} = 0.038 at 1 kHz and room temperature. The leakage currents of the films are on the order of 10{sup -5} A/cm{sup 2} at {+-} 150 kV/cm. The mechanism for enhancing electric properties of the Mg doped BST films was also discussed.

  17. Electrostrictive resonances in (Ba0.7Sr0.3)TiO3 thin films at microwave frequencies

    OpenAIRE

    Tappe, S.; Bottger, U.; Waser, R.

    2004-01-01

    The bias-voltage-dependent permittivity of (Ba0.7Sr0.3)TiO3 (BST) thin films with thicknesses ranging from 100 to 250 nm is investigated in the frequency range from 500 MHz to 40 GHz by impedance spectroscopy of integrated BST capacitors. The dielectric spectra of the films exhibit resonance phenomena in the 4-7 GHz range when a bias field is applied. It is shown that the main controlling parameter of the resonance frequency is the film thickness. Calculations based on the strong electrostric...

  18. Aerosol deposition of Ba0.8Sr0.2TiO3 thin films

    OpenAIRE

    Branković Zorica; Branković G.; Tucić A.; Radojković A.; Longo E.; Varela J.A.

    2009-01-01

    In this work we optimized conditions for aerosol deposition of homogeneous, nanograined, smooth Ba0.8Sr0.2TiO3 thin films. Investigation involved optimization of deposition parameters, namely deposition time and temperature for different substrates. Solutions were prepared from titanium isopropoxide, strontium acetate and barium acetate. Films were deposited on Si (1 0 0) or Si covered by platinum (Pt (1 1 1) /Ti/SiO2/Si). Investigation showed that the best films were obtained at substrate te...

  19. Synthesis and dielectric properties of MXTi7O16 (M = Ba and Sr;X = Mg and Zn) hollandite ceramics

    Indian Academy of Sciences (India)

    V M Manisha; K P Murali; S N Potty; V Priyadarsini; R Ratheesh

    2004-04-01

    MXTi7O16 (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (r), loss tangent (tan ) and temperature variation of dielectric constant ($\\tau_{\\varepsilon r}$) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.

  20. Seasonal dripwater Mg/Ca and Sr/Ca variations driven by cave ventilation: Implications for and modeling of speleothem paleoclimate records

    Science.gov (United States)

    Wong, C.I.; Banner, J.L.; Musgrove, M.

    2011-01-01

    A 4-year study in a central Texas cave quantifies multiple mechanisms that control dripwater composition and how these mechanisms vary at different drip sites. We monitored cave-air compositions, in situ calcite growth, dripwater composition and drip rate every 4-6weeks. Three groups of drip sites are delineated (Groups 1-3) based on geochemical variations in dripwater composition. Quantitative modeling of mineral-solution reactions within the host carbonate rock and cave environments is used to identify mechanisms that can account for variations in dripwater compositions. The covariation of Mg/Ca (and Sr/Ca) and Sr isotopes is key in delineating whether Mg/Ca and Sr/Ca variations are dictated by water-rock interaction (i.e., calcite or dolomite recrystallization) or prior calcite precipitation (PCP). Group 1 dripwater compositions reflects a narrow range of the extent of water-rock interaction followed by varying amounts of prior calcite precipitation (PCP). Group 2 dripwater compositions are controlled by varying amounts of water-rock interaction with little to no PCP influence. Group 3 dripwater compositions are dictated by variable extents of both water-rock interaction and PCP. Group 1 drip sites show seasonal variations in dripwater Mg/Ca and Sr/Ca, whereas the other drip sites do not. In contrast to the findings of most previous dripwater Mg/Ca-Sr/Ca studies, these seasonal variations (at Group 1 drip sites) are independent of changes in water flux (i.e., rainfall and/or drip rate), and instead significantly correlate with changes in cave-air CO2 concentrations. These results are consistent with lower cave-air CO2, related to cool season ventilation of the cave atmosphere, enhancing calcite precipitation and leading to dripwater geochemical evolution via PCP. Group 1 dripwater Mg/Ca and Sr/Ca seasonality and evidence for PCP as a mechanism that can account for that seasonality, have two implications for many other regions where seasonal ventilation of caves

  1. Growth of Nucleation Sites on Pd-doped Bi_2Sr_2Ca1 Cu_2O_8+δ

    Science.gov (United States)

    Kouzoudis, D.; Finnemore, D. K.; Xu, Ming; Balachandran

    1996-03-01

    Enviromental Scanning Electron Microscope has shown evidence that during the growth of Bi_2Sr_2Ca_2Cu_3O_10+δ from mixed powders of Pb-doped Bi_2Sr_2Ca_1Cu_2O_8+δ and other oxides, a dense array of hillocks or mesas grow at the interface between an Ag overlay and Pb doped Bi_2Sr_2Ca_1Cu_2O_8+δ grains. These hillocks develop a texture that looks like ''chicken pox'' during the ramp up to the reaction temperature starting at about 700^circ C and they are about 500 to 1000 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurments indicate that the hillocks are re-crystallization of (Bi,Pb)_2Sr_2Ca_1Cu_2O_8+δ and are definetely not a Pb rich phase

  2. 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

  3. Growth and superconducting properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} thin films incorporated with iridate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    De Vero, Jeffrey C.; Hwang, Inwoong; Shin, Hyeonseop; Song, Jong Hyun [Department of Physics, Chungnam National University, Daejeon, 305-764 (Korea, Republic of); Santiago, Alvin Carl; Sarmago, Roland V. [National Institute of Physics, University of the Philippines, Diliman, 1101 (Philippines); Lee, Doopyo [Department of Physics, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of); Chang, Jungwon [Department of Display and Semiconductor Physics, Korea University, Sejong Campus, Sejong, 339-700 (Korea, Republic of); Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of); Kim, Jinhee [Korea Research Institute of Science and Standards, Daejeon, 305-340 (Korea, Republic of)

    2014-08-15

    Iridate nanoparticle AIrO{sub 3} (A = Sr, Ba) incorporated Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} {sub +} {sub δ} (Bi-2212) thin films were successfully grown using pulsed laser deposition with post-growth ex situ heat treatment. Nanosized particles of SrIrO{sub 3} (Sr-iridate) and BaIrO{sub 3} (Ba-iridate) were deposited on top of MgO (100) substrate, followed by Bi-2212 layers to investigate their effects on the physical and superconducting properties of Bi-2212 thin films. The number of laser pulses was changed from 450 to 1800 to control the density of iridates in the Bi-2212 matrix. The composite film is then partial-melted at 890 C for 15 min and annealed at 850 C for 5 h in ambient air. Scanning electron microscopy shows that the surfaces of thin films with iridates are more compact with minimal voids and porosity than those of pure Bi-2212 thin films. Both types of iridate incorporation suppress T{sub c-zero} of Bi-2212 thin films. Incorporating Sr-iridate in the Bi-2212 strongly affects T{sub c-zero} than those with Ba-iridate at low density. However, both iridate incorporations result in the expansion of the c-axis lattice constant and variation of Bi/Sr ratio of Bi-2212 films. On the other hand, we observed improvement of the activation energy, U{sub 0}, as well as the self-field critical current density, J{sub c}(0), of Bi-2212 films with incorporated iridates even with suppressed T{sub c-zero}. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Effects of Mg or Sr Doping on the Intrinsic Characteristics and Absorption Properties of Micro-nano BaFe12O19 Hollow Multiphase Ceramic Microspheres

    International Nuclear Information System (INIS)

    Micro-nano BaM hollow multiphase ceramic microspheres (HMCMs) and Mg-doped and Sr-doped BaM HMCMs were prepared by combining the low-temperature self-reactive quenching method with heat treatment. The effects of Mg or Sr doping on the intrinsic characteristics and absorption properties of micro-nano BaM HMCMs were investigated. The results showed that Mg or Sr doping modified the phase compositions and particle size distributions of the HMCMs. The Mg- and Sr-doped BaM HMCMs had large real and imaginary permittivities and large real permeabilities at low frequencies relative to the, undoped HMCM. To maximize the absorption properties of the undoped and Sr- and Mg-doped HMCMs, optimal thicknesses of 8, 10 and 10 mm were used with corresponding reflectivities of −8.2, −31.5 and −26.6 dB, respectively. - Highlights: • Three HMCMs were prepared using the low-temperature self-reactive quenching method. • Changes and mechanisms of intrinsic characteristics of Mg or Sr doping were investigated. • Relationships between the intrinsic characteristics and absorption properties were studied

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

    International Nuclear Information System (INIS)

    The irreversibility lines of epitaxial thin films of HgBa2CaCu2O6+δ and TlBa2CaCu2O7-δ, whether deduced from field-induced magnetoresistive broadening or onset of nonhysteretic magnetization, were found to coincide when plotted against reduced temperature, showing the same exponential-decay temperature behavior for T/Tcc>0.8 (where Tc is zero-field, zero-resistivity critical temperature). These results indicate that replacing Tl with Hg has no noticeable effect on the anisotropy and suggests that Tc is not determined by anisotropy. copyright 1999 The American Physical Society

  6. 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.

  7. Effect of Sr/Zr doping and polishing on structure and dielectric properties of BaTiO3 ceramics%Sr/Zr掺杂以及抛光对BaTiO3陶瓷结构和介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    李雪翠; 路大勇

    2010-01-01

    采用冷压陶瓷技术制备了(Ba0.75Sr0.25)TiO3、Ba(Ti0.8Zr0.2)O3、(Ba0.75Sr0.25)(Ti0.8Zr0.2)O3陶瓷.XRD结果表明,Sr和Zr在BaTiO3的Ba位、Ti位、及Ba/Ti双位并入均具有高固溶性,且为没有超结构特征的单相钙钛矿结构.Sr/Zr的双位并入加快介电峰向低温的移动.Sr掺杂对Ba(Ti0.8Zr0.2)O3介电峰移动率的贡献为-1.5℃/mol% Sr.抛光技术对介电温谱的影响研究表明,尽管水抛光导致(Ba0.75Sr0.25)(Ti0.8Zr0.2)O3陶瓷颜色变暗,但晶体结构不变、介电峰值降低.

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

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, A.; Stanescu, D.; Jegou, P.; Magnan, H. [CEA, IRAMIS, SPCSI, F-91191 Gif-sur-Yvette (France); Mocuta, C. [Synchrotron SOLEIL, L' Orme des Merisiers Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Jedrecy, N. [Institut des Nano Sciences de Paris, UPMC-Sorbonne Universites, CNRS-UMR7588, 75005 Paris (France)

    2012-12-01

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

  9. Photoluminescence properties of Ca-doped BaMgAl10O17:Eu2+,Mn2+blue phosphor using BaF2 and CaF2 as co-flux

    Institute of Scientific and Technical Information of China (English)

    冶林琴; 朋兴平; 张水合; 王育华; 常文瑞

    2014-01-01

    Ca-doped BaMgAl10O17:Eu2+,Mn2+(BAM) blue phosphors were synthesized by flux assisted solid-state reaction method using CaF2 and BaF2 as co-flux. Good dispersity and particle size homogenization of hexagonal pure phase BAM were obtained by sintering at 1400 °C. The effects of the Ca2+ions content on the structure, morphology and photoluminescence properties of the phosphors were studied. The results indicated that the incorporation of Ca could decrease the lattice constant, improve the homogene-ity and dispersity and enhance the photoluminescence (PL) intensity of the phosphor effectively. The optimum Ba0.86Ca0.04Mg0.97Al10O17:0.1Eu2+,0.03Mn2+PL intensity was enhanced for about 30%and relative brightness was improved about 4%. Furthermore, the synthesized BAM and commercial BAM phosphors were annealed for 30 min at 600 ºC in air. The Ca-doped phos-phors had stronger emission intensity, higher brightness and better chromaticity stability than that of the commercial phosphor. These results indicated that Ca-doped blue phosphors had good potential applications in the commercial tricolor fluorescent lamps as well as in other display and lamps.

  10. The influences of mole composition of strontium (x) on properties of barium strontium titanate (Ba{sub 1−x}Sr{sub x}TiO{sub 3}) prepared by solid state reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Sandi, Dianisa Khoirum; Supriyanto, Agus; Iriani, Yofentina, E-mail: yopen-2005@yahoo.com [Physics Department, Faculty of Mathematics and Natural Science, Sebelas Maret University (Indonesia); Jamaluddin, Anif [Physics Department, Faculty of Teacher Training and Education, Sebelas Maret University (Indonesia)

    2016-02-08

    Barium Strontium Titanate (Ba{sub 1-x}Sr{sub x}TiO{sub 3}) or BST was prepared by solid state reaction method. Raw materials are BaCO{sub 3}, SrCO{sub 3}, and TiO{sub 2}. Those materials are mixed for 8 h, pressed, and sintered at temperature 1200°C for 2 h. Mole composition of Sr (x) was varied to study its influences on structural, morphological, and electrical properties of BST. Variation of (x) are x = 0; x = 0.1; and x = 0.5. XRD patterns showed a single phase of BST, which mean that mixture of raw materials was homogenous. Crystal structure was influenced by x. BaTiO{sub 3} and Ba{sub 0.9}Ti{sub 0.1}TiO{sub 3} have tetragonal crystal structure, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is cubic. The diffraction angle shifted to right side (angle larger) as the increases of x. Crystalline size of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3}, and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} are 38.13 nm; 38.62 nm; and 37.13 nm, respectively. SEM images showed that there are still of pores which were influenced by x. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface (pores are few and small in size). Sawyer Tower circuit showed that BaTiO{sub 3} and Ba{sub 0.9}Sr{sub 0.1} TiO{sub 3} is ferroelectric, while Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} is paraelectric. The dielectric constants of BaTiO{sub 3}, Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} and Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} at frequency of 1 KHz are 156; 196; and 83, respectively. Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has relatively highest dielectric constant. It is considered that Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} has densest surface.

  11. Effects of La{sub 2}O{sub 3}-doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Hong Wei; Chang, Chun Rui [College of Science, North China University of Science and Technology, Hebei Province (China); Li, Yuan Liang [Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, North China University of Science and Technology, Hebei Province (China); Yan, Chun Liang [Analysis and Testing Center, North China University of Science and Technology, Hebei Province (China)

    2016-03-15

    Using BaCO{sub 3}, SrCO{sub 3} and TiO{sub 2}, et al as crude materials, La{sub 2}O{sub 3} as dopant, Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) Ceramics of perovskite structure were prepared by solid state reaction method. We investigated the effects of La{sub 2}O{sub 3} -doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics. The experiment results show that: The amount of La{sub 2}O{sub 3} can increase the dielectric constant of the sample, with the doping amount increasing, the dielectric constant increases. The sintering temperature has also significant impact on the dielectric properties. The dielectric constant of the sample reaches its highest point at 1280 °C. (author)

  12. Millimeter wave inducing subharmonic steps in the Tl2Ba2CaCu2O8 thin film bicrystal Josephson junction

    Science.gov (United States)

    Liu, X.; Hu, L.; Xie, W.; Wang, P.; Ma, L. J.; Zhao, X. J.; He, M.; Zhang, X.; Ji, L.

    2015-04-01

    The bicrystal Josephson junction (BJJ) was fabricated by patterning microbridge into Tl2Ba2CaCu2O8 (Tl-2212) thin film grown epitaxially on the bicrystal SrTiO3 (STO) substrate. The millimeter wave responses of BJJ were researched by experiment and numerical simulation. Shapiro steps and subharmonic steps were both observed in the current-voltage (I-V) curve at the liquid nitrogen temperature. In the resistive-capacitive-inductive shunted junction (RCLSJ) model, both of the Shapiro steps and subharmonic steps were reproduced with varying capacitances and inductances. The result of simulation has a good agreement with the experiment. The relative large capacitance and inductance correspond to distinct subharmonic steps.

  13. 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.

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

    Science.gov (United States)

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

    2015-12-01

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

  15. Dielectric dynamics of the polycrystalline Ba0.5Sr0.5TiO3 thin films

    Science.gov (United States)

    Pečnik, Tanja; Eršte, Andreja; Matavž, Aleksander; Bobnar, Vid; Ivanov, Maksim; Banys, Juras; Xiang, Feng; Wang, Hong; Malič, Barbara; Glinšek, Sebastjan

    2016-05-01

    Polycrystalline Ba0.5Sr0.5TiO3 films, with thicknesses between 90 and 600 nm, were prepared on alumina substrates at 900 °C by chemical solution deposition (CSD) and a dielectric spectroscopy investigation of the in-plane properties was performed. The 5-kHz permittivity ε‧ shows a non-monotonic thickness dependence, reaching 1230 at room temperature for the 310-nm-thick film, whose grain size is ∼75 nm. Its 15-GHz-value and losses are 1105 and 0.05, respectively. The temperature of the permittivity maximum T max at 5 kHz decreases with increasing thickness from 277 to 250 K for the 170- and 600-nm-thick films, respectively, which has been linked to the residual biaxial stress. A hysteresis is observed in the permittivity ε‧-electric field E DC characteristics in all the films up to ∼50 K above T max . Frequency dispersion in which permittivity decreases with increasing frequency is present below T max in films thicker than 90 nm. The high permittivity values of the thinnest films, which are among the highest reported in the (Ba,Sr)TiO3 films with grain sizes below 75 nm, are a direct proof of the optimized CSD processing conditions.

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

    International Nuclear Information System (INIS)

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

  17. 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.

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

    Directory of Open Access Journals (Sweden)

    C. Kajtoch

    2009-10-01

    Full Text Available Purpose: The purpose of this work was to determinate the influence of the 20% Sr substitutions (in sublattice A on changes of the character of phase transition (PT in comparison with pure barium titanate BaTiO3 (BT.Design/methodology/approach: Polycrystalline samples of (Ba0.80Sr0.20TiO3 (BS20T were prepared by calcinations method at temperature 1620 K. X-ray measurements were executed from 10 deg to 120 deg with the 0.008 deg step. Images of the morphology of the samples were taken by means of electron microscope Philips SEM 525M at room temperature. Dielectric measurements were performed with application of Quatro Cryosystem 4.0 Agilent Precision LRC meter HP4824A equipped with WinDETA 5.62 software Novocontrol. Measurements were taken under cooling with 2 K/min speed. Measuring electric field frequency was from the range 20 Hz - 1 MHz.Findings: The difference between the value of temperature of structural transition (cubic-tetragonal equal 310K and the temperature Tm (the temperature of maximum of real part electric permittivity equal 340 K was affirmed. It was affirmed, that 20% substitution of Sr ions changed the type of phase transition. The transition was strongly diffused (DPT. The polar character of this solid solution was also observed in a broad temperature range (in the paraelectric phase too. It is connected with the occurrence of polar regions (clusters.Research limitations/implications: The results can be used to describe changes of PT in the DPT solid solutions with ferroactive substitutions in sublattice A.Originality/value: Value of this work relies on the experimental examination of the dielectric properties of (Ba0.80Sr0.20TiO3 (BS20T solid solution. The temperature of the DPT was calculated. The low value of phase angle is connected with the existence of the polar regions.

  19. Relationship between coccolith Sr/Ca ratios and coccolithophore production and export in the Arabian Sea and Sargasso Sea

    Science.gov (United States)

    Stoll, Heather M.; Ziveri, Patrizia; Shimizu, Nobumichi; Conte, Maureen; Theroux, Susanna

    2007-03-01

    Coccolithophore CaCO 3 production can account for 20-80% of biogenic carbonate exported from the photic zone, and coccoliths are a dominant biogenic carbonate in many deep-sea sediments. A new method for picking individual coccoliths from sediment traps and sediments for analysis using Secondary Ion Mass Spectrometry (ion probe) allows us to make precise Sr/Ca and Mg/Ca determinations on coccoliths from single species even in samples where material is limited. There are large biological effects in Sr/Ca partitioning in coccoliths that have been related to variations in coccolithophore productivity. In sediment traps from the Sargasso Sea at Bermuda and Arabian Sea in the Somali Basin, we can identify Sr/Ca variations in several species that are consistent with inferred seasonal variations in coccolithophore productivity in surface waters. In the Arabian Sea, coccolith Sr/Ca ratios in Calcidiscus leptoporus and Helicosphaera carteri are lowest during the nonproductive intermonsoon. They are highest during the upwelling of southwest monsoon and during the nutrient entrainment from strong winds of the northeast monsoon. These Sr/Ca variations match seasonal trends in coccolith export flux. Furthermore, Sr/Ca variations in C. leptoporus are larger, and this species also has the greater variation in export flux between southwest monsoon and intermonsoon seasons. At Bermuda, a 1996 fall bloom, driven by passage of a warm mode water eddy, induced a large increase in Sr/Ca of C. leptoporus coincident with an increase of C. leptoporus export. Over an annual series for 2004, highest Sr/Ca ratios of C. leptoporus in the summer months match the typical summer peak in surface standing stock of this species and the stimulation of its productivity by mesoscale cyclonic eddies and eddy-eddy interactions. High Sr/Ca did not coincide with the highest export of C. leptoporus coccoliths, likely because cyclonic eddies, unlike mode-water eddies, are dominated by small phytoplankton

  20. Doubling of the Bands in Overdoped Bi2Sr2CaCu2O

    International Nuclear Information System (INIS)

    We present high resolution angle resolved photoemission data of the bilayer superconductor Bi2Sr 2CaCu2O8+δ (Bi2212) showing a clear doubling of the near EF bands. This splitting approaches zero along the (0,0)→(π,π) nodal line and is not observed in single layer Bi2Sr 2CuO 6+δ (Bi2201), indicating that the splitting is due to the long sought after bilayer splitting effect. The splitting has a magnitude of approximately 75 meV near the middle of the zone, extrapolating to about 110 meV near the (π,0) point. The existence of these two bands also helps to clear up the recent controversy concerning the topology of the Fermi surface

  1. Linking large piezoelectric coefficients to highly flexible polarization of lead free BaTiO3-CaTiO3-BaZrO3 ceramics

    Science.gov (United States)

    Benabdallah, F.; Simon, A.; Khemakhem, H.; Elissalde, C.; Maglione, M.

    2011-06-01

    We report a large d31 piezoelectric coefficient and corresponding electromechanical coupling factor, Kp, of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCTZ50) and 0.68Ba(Zr0.2Ti0.8)O3-0.32(Ba0.7Ca0.3)TiO3 (BCTZ32) lead-free piezoceramics. The piezoelectric coefficient, d31, reaches a high value of 200 pC/N for BCTZ50 at room temperature which is comparable to the one of the soft PZT. This confirms the previously reported d33 for the same material. A useful way to achieve such performances at the expense of a smaller thermal budget is suggested, enabling better control of the ceramics composition and microstructure. Based on pyroelectric and ferroelectric hysteresis loops measurements, we show that such outstanding properties are likely due to the high flexibility of polarization under thermal and electric stresses.

  2. Preparation and characterization of composites from Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} and polystyrene

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Q. [College of Chemistry, Chemical Engineering and Materials Science and Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); Hong, R.Y., E-mail: rhong@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science and Key Laboratory of Organic Synthesis of Jiangsu Province, Soochow University, SIP, Suzhou 215123 (China); School of Chemical Engineering, Fuzhou University, Fuzhou 350108 (China); Feng, W.G. [Suzhou Nanocomp Inc., Suzhou New District, Suzhou 215011 (China)

    2014-10-01

    Highlights: • Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} was synthesized through the method of co-precipitation. • Inexpensive TiOSO{sub 4} was used as raw material. • The molten salt contributes to better crystal morphology. • Composites with modified particles showed good thermal and dielectric properties. - Abstract: Pure perovskite phase Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} powders were synthesized by facile co-precipitation using inexpensive TiOSO{sub 4} as the raw material. The post-calcining treatment was at the low temperature of 950 °C, which was about 200 °C lower than that of the conventional solid-state method. The effects of two types of precipitation agents on the properties of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} powders were investigated, and cubic Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} particles were obtained at the optimal conditions. Afterwards, the obtained Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} ceramics were ground into fine ceramic powders, and modified with oleic acid to improve the compatibility with the polystyrene (PS) matrix. The modified ceramic powders were dispersed in PS via solution co-blending to obtain Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites. The structure and morphology of the Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites were characterized through X-ray diffraction (XRD), and scanning electron microscopy (SEM). The SEM images showed that the modified ceramic powders had good dispersion in the PS resin. Moreover, the dielectric and thermal properties of the Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}/PS composites were investigated, and the results showed that the modified ceramic powders could enhance the dielectric constants and thermal stability of ceramic–polymer composites.

  3. Photoluminescence properties of X5SiO4Cl6:Tb3+ (X = Sr, Ba) green phosphor prepared via modified solid state method

    Indian Academy of Sciences (India)

    A N Yerpude; S J Dhoble

    2013-08-01

    Luminescence property of a new halo silicate phosphor, X5SiO4Cl6:Tb3+ (X = Sr, Ba) prepared by modified solid state method is reported here. It is characterized by powder X-ray diffraction and studied by photoluminescence excitation and emission spectra. In the emission spectra of X5SiO4Cl6:Tb3+ (X = Sr, Ba) phosphor, characteristic blue and green emission peaks are present corresponding to Tb3+ intra 4 transition. Emission spectrum shows a dominant peak at 544 nm due to the ${}^{5}D_{4} \\rightarrow {}^{7}F_{5}$ transition of Tb3+.

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

    Science.gov (United States)

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

    2016-05-01

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

  5. Structure determination at room temperature and phase transition studies above $T_c$ in ABi4Ti4O15 (A = Ba, Sr or Pb)

    Indian Academy of Sciences (India)

    G Nalini; T N Guru Row

    2002-08-01

    The room temperature structure of three compounds belonging to the Aurivillius family ( = 4), ABi4Ti4O15 (A = Ba, Sr or Pb) has been analysed. BaBi4Ti4O15 crystallizes in a tetragonal 4/ space group whereas SrBi4Ti4O15 and PbBi4Ti4O15 crystallize in the orthorhombic space group $A2_1am$. The starting model for the Sr and Pb analogues was derived from ab initio methods and refined using the Rietveld method. The cations Ba and Sr are disordered over the Bi sites while the Pb cation is found exclusively in the [Bi2O2]2+ layers. The TiO6 octahedra are tilted with the Ti–O bonds forming zigzag chains along the `’ axis. The displacement of Bi atoms along the `’ axis might be responsible for ferroelectricity in these compounds. The high temperature X-ray data above $T_c$ indicate no structural transition for A = Ba and Pb while A = Sr transforms to the tetragonal structure.

  6. 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...

  7. Liquid Be, Ca and Ba. An orbital-free ab-initio molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Rio, B. G. del; González, L. E. [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2015-08-17

    Several static and dynamic properties of liquid beryllium (l-Be), liquid calcium (l-Ca) and liquid barium (l-Ba) near their triple point have been evaluated by the orbital-free ab initio molecular dynamics method (OF-AIMD), where the interaction between valence electrons and ions is described by means of local pseudopotentials. These local pseudopotentials used were constructed through a force-matching process with those obtained from a Kohn-Sham ab initio molecular dynamics study (KS-AIMD) of a reduced system with non-local pseudopotentials. The calculated static structures show good agreement with the available experimental data, including an asymmetric second peak in the structure factor which has been linked to the existence of a marked icosahedral short-range order in the liquid. As for the dynamic properties, we obtain collective density excitations whose associated dispersion relations exhibit a positive dispersion.

  8. Multiple caloric effects in geometrically frustrated "114" CaBaCo4O7 Cobaltite

    Science.gov (United States)

    Dhanasekhar, C.; Das, A. K.; Venimadhav, A.

    2016-11-01

    We have investigated the magnetocaloric and electrocaloric effects in "114" CaBaCo4O7 (CBCO) sample prepared by solid state method. Magnetization study has revealed the ferrimagnetic transition (TC) at 60 K and another transition at 66 K. Observation of irreversibility and first order nature of magnetic transition above TC has suggested a complicated magnetic nature of the system. A maximum magnetic entropy change of ~6.8 J/Kg-K has been found at TC and further a broadening of the entropy peak with the increase of magnetic field indicates the field induced transition above TC. From temperature dependent pyrocurrent measurements, we have measured the electric polarization under different electric fields and the change in isothermal electrocaloric entropy is found to be ~0.50 J-m-3 K-1 (for 150 kV/m) just above magnetic transition temperature.

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

    Science.gov (United States)

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

    2014-11-28

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

  10. Luminescence Properties of SrCaS:Cu Thin Film Phosphors

    Science.gov (United States)

    Mohammed, Edris; Park, Won; Tong, Wusheng; Stock, Stuart; Summers, Chris

    2000-03-01

    Luminescence Properties of SrxCa1-xS:Cu Thin Film Phosphors E. Mohammed, W. Park, W. Tong, S. Stock and C. J. Summers Phosphor Technology Center of Excellence Georgia Institute of Technology, Atlanta, GA 30332-0560 The luminescence properties of MBE grown thin film SrCaS:Cu phosphors are investigated. 10K photoluminescence (PL) results showed a broad emission band of Cu that shifted between 2.98eV and 2.58eV, with a large increase in linewidth ranging from 0.36eV for CaS:Cu to 0.49eV as the Sr composition was increased. The significant increase in linewidth suggested that the broad emission band of Cu was composed of two closely spaced bands suggesting a possible spin-orbit or Jahn-Teller splitting of the emitting level. Curve fitting of the 10K PL showed that the splitting varied from 100meV for x=0 to 240 meV for x=0.98. In the excitation spectra, the optical absorption edge shifted from 5.1eV to 4.7eV while the energies of the two direct excitation bands of Cu shifted from 4.4 to 4.8eV and 4.0 to 4.2eV respectively. The crystal field parameter 10Dq obtained from experiments showed a linear as the composition of Sr was varied between x=0 to x=0.98 and the result was in excellent agreement with crystal field calculations.

  11. Rectification in (La,Sr)MnO3/(Ba,Sr)TiO3/(La,Ce)2CuO4 trilayer p-i-n junctions

    International Nuclear Information System (INIS)

    Oxide trilayer p-i-n junctions, with p-type La0.67Sr0.33MnO3 (LSMO) manganite layer and n-type La1.89Ce0.11CuO4 (LCCO) cuperate layer separated by Ba0.7Sr0.3TiO3 (BST) titanite insulator layer, have been deposited in situ and characterized. With the increment of the insulator layer thickness, the I-V characteristic of such p-i-n junctions changes from symmetric to asymmetric, and then to symmetric again, given the highest rectifying performance at the BST layer of about 25 nm thick. The largest asymmetry, defined as the ratio of dI/dV at +2 V and -2 V, respectively, is found >1000. The insulator layer thickness dependency indicates that the transport properties of the p-i-n junctions are dominated by the interplay between the interior fields at the LSMO/BST and BST/LCCO interfaces

  12. Gamma-ray shielding properties of CaO-SrO-B 2O 3 glasses

    Science.gov (United States)

    Singh, Kulwant; Singh, Harvinder; Sharma, Gopi; Gerward, Leif; Khanna, Atul; Kumar, Rajesh; Nathuram, Rohila; Sahota, Hari Singh

    2005-02-01

    Mass attenuation coefficients, effective atomic numbers and effective electron densities have been determined experimentally for the glass system xCaO·(0.3- x)SrO·0.7B 2O 3 at photon energies 511, 662, 1173, and 1332 keV. The results are compared with theoretical calculations. In addition, the molar volume of the glasses has been derived from density measurements, and the excess volume has been determined as a function of composition. The reported data should be useful for potential applications of these glasses in radiation shielding.

  13. Preparation and luminescence properties of the red-emitting phosphor (Sr1-xCax) 2Si5N8:Eu2+ with different Sr/Ca ratios

    Institute of Scientific and Technical Information of China (English)

    TENG Xiaoming; LIU Yuanhong; LIU Yuzhu; Hu Yunsheng; HE Huaqiang; ZHUANG Weidong

    2009-01-01

    A series of Eu2+-doped ternary nitride phosphors, with a formula of (Sr1-xCax)2Si5N8: Eu2+, were synthesized by high-temperature solid-state method. The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes. The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of (Sr1-xCax)2Si5N8: Eu2+ and coexisted in the range of 0.5≤x≤0.75. The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2+ ions. The emission peak changed with the variations in Ca2+ concentration.

  14. Coupled magnetic and elastic properties in LaPr(CaSr)MnO manganites

    Science.gov (United States)

    Eslava, G. G.; Parisi, F.; Bernardo, P. L.; Quintero, M.; Leyva, G.; Cohen, L. F.; Ghivelder, L.

    2016-09-01

    We investigate a series of manganese oxides, the La0.225Pr0.4(Ca1-xSrx)0.375MnO3 system. The x = 0 sample is a prototype compound for the study of phase separation in manganites, where ferromagnetic and charge ordered antiferromagnetic phases coexist. Replacing Ca2+ by Sr2+ gradually turns the system into a homogeneous ferromagnet. Our results show that the material structure plays a major role in the observed magnetic properties. On cooling, at temperatures below ∼ 100 K, a strong contraction of the lattice is followed by an increase in the magnetization. This is observed both through thermal expansion and magnetostriction measurements, providing distinct evidence of magneto-elastic coupling in these phase separated compounds.

  15. Superconducting Bi-Ca-Sr-Cu oxide thin films by spray pyrolysis of metal acetates

    International Nuclear Information System (INIS)

    Superconducting Bi-Ca-Sr-Cu oxide thin films have been prepared on ZrO2-coated silicon (111) wafers by spray pyrolysis of metal acetate precursors followed by rapid annealing to 850 0C in air. Resistivity measurements indicate a broad superconducting transition with T/sub c/ onset near 90 K and zero resistivity below 60 K. The films are highly oriented with the c axis normal to the substrate surface and can be indexed to a tetragonal structure with lattice parameters of a = 3.832(1) A and c = 30.78(5) A. Both x-ray photoelectron spectroscopy and x-ray diffraction measurements indicate the loss of Ca to the ZrO2 buffer layer

  16. 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.

  17. Electrical conductivity of cobalt-titanium substituted SrCaM hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Eraky, M.R., E-mail: moharamderak@yahoo.com [Physics Department, Faculty of Science, Kafrelsheikh University, 33516 Kafrelsheikh (Egypt)

    2012-03-15

    A series of polycrystalline M-type hexagonal ferrites with the composition Sr{sub 0.5}Ca{sub 0.5}Co{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (where x=0.0-0.8) were prepared by the conventional ceramic technique. The electrical conductivity has been measured from 300 to 590 K. The dc conductivity, {sigma}{sub dc}, exhibited a semiconductor behavior. The negative sign of thermoelectric power coefficient S reveals that all samples are n-type semiconductors. Both {sigma}{sub dc} and mobility, {mu}{sub d}, increases with the substitution of Co{sup 2+} and Ti{sup 4+} ions, reach maximum at x=0.4 and start decreasing at x>0.4. Many conduction mechanisms were discussed to explain the electric conduction in the system. It was found that the hopping conduction is the predominant conduction mechanism. For samples with compositional parameter x=0.0 and 0.8, the band conduction mechanism shares in electric conduction beside the hopping process. - Highlights: Black-Right-Pointing-Pointer SrCaCoTiM hexaferrites have been prepared by conventional ceramic technique. Black-Right-Pointing-Pointer The electrical conductivity exhibited a semiconductor behavior. There is an increase in conductivity up to x=0.4 for Co and Ti substitution. Black-Right-Pointing-Pointer The hopping conduction is the predominant conduction mechanism.

  18. Acropora interbranch skeleton Sr/Ca ratios: Evaluation of a potential new high-resolution paleothermometer

    Science.gov (United States)

    Sadler, James; Nguyen, Ai D.; Leonard, Nicole D.; Webb, Gregory E.; Nothdurft, Luke D.

    2016-04-01

    The majority of coral geochemistry-based paleoclimate reconstructions in the Indo-Pacific are conducted on selectively cored colonies of massive Porites. This restriction to a single genus may make it difficult to amass the required paleoclimate data for studies that require deep reef coring techniques. Acropora, however, is a highly abundant coral genus in both modern and fossil reef systems and displays potential as a novel climate archive. Here we present a calibration study for Sr/Ca ratios recovered from interbranch skeleton in corymbose Acropora colonies from Heron Reef, southern Great Barrier Reef. Significant intercolony differences in absolute Sr/Ca ratios were normalized by producing anomaly plots of both coral geochemistry and instrumental water temperature records. Weighted linear regression of these anomalies from the lagoon and fore-reef slope provide a sensitivity of -0.05 mmol/mol °C-1, with a correlation coefficient (r2 = 0.65) comparable to those of genera currently used in paleoclimate reconstructions. Reconstructions of lagoon and reef slope mean seasonality in water temperature accurately identify the greater seasonal amplitude observed in the lagoon of Heron Reef. A longer calibration period is, however, required for reliable reconstructions of annual mean water temperatures.

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

    International Nuclear Information System (INIS)

    Two internal-friction (attenuation) peaks around 95 and 130 K in the polycrystal and single crystal of Bi-Sr-Ca-Cu-O are found to be related to the superconducting transition at 84 and 107 K, respectively. The jump of lattice parameter and shape-memory effect occurring at the peak temperatures reveal the characteristics of a martensitic transition. The velocity and attenuation versus temperature of ultrasonic longitudinal waves propagating along two directions in the a-b plane at 10 degree to the a and b axes and of [010] shear waves with [100] polarization were measured for the Bi2Sr2CaCu2O8 single crystals. The anisotropic elasticity in the c plane is manifested. Only the longitudinal waves in a direction and the shear waves show an obvious softening minimum of velocity around 250 K, which is associated with an attenuation peak due to a phaselike transition, but other longitudinal waves reveal a monotonic stiffening from room temperature down to Tc. The origin of the overall trend of elastic stiffening that appears in the measurements so far for high-Tc oxides is discussed

  20. BaTiO3和SrTiO3薄膜生长初期化学分子反应机理%Reaction mechanism of chemical molecules in early growth of BaTiO3 and SrTiO3 thin films

    Institute of Scientific and Technical Information of China (English)

    梁晓琴; 张姝; 黄平; 杨春

    2012-01-01

    Density functional theory(DFT) is applied to study microscopic reaction mechanism of the formation of BaTiO3 and Sr-TiOjby BaO,SrO and TiO2 molecules and Ti2O3by two TiO2 molecules. The reaction intermediates,transition states and activation energies have been obtained. NBO is used to analyze bonding process,orbital interactions and atomic charges in intermediates and transition states of the reaction process. The calculated results show activation energies of the formation of BaTiO3 ,SrTiO,and Ti2O4 are respectively 16.3,17. 3 and 9.6 kJ/moL Activation energies of Ti2O4 is relatively lower ,TiO2 dimer observed in the experiment can theoretically be explained. However,the reaction enthalpies of the formation of the first intermediates of BaTiO3 and SrTiO3 are respectively-484.7 and-534.7 kj/mol. Activation energies are low. And strong orbital interactions and static gravitations are found in molecules. These results indicate that BaO and SrO acts as a combining center TiO2in the early growth of BaTiO3and SrTiO3thin films,which should be propitious to form of primary unit cell.%本文采用B3LYP密度泛函方法,研究了BaO、SrO与TiO2形成BaTiO3、SrTiO3及TiO2二聚形成Ti2O4的微观反应机理,获得了相应的中间体、过渡态及反应活化能.采用自然键轨道NBO方法分析了反应过程中各中间体和过渡态的成键情况、轨道间的相互作用以及原子的电荷.计算结果表明,形成BaTiO3、SrTiO3和Ti2O4反应活化能分别为16.3、17.3和9.6 kJ/mol,TiO2形成二聚体活化能相对较小,从理论上解释了实验过程中观测到TiO2二聚体;但SrO、BaO和TiO2形成BaTiO3、SrTiO3的反应过程中,形成最初的稳定中间体时分别放热484.7和534.7 kJ/mol,且活化能较低,轨道间相互作用较强,静电引力作用显著,有利于SrTiO3和BaTiO3薄膜生长初期以TiO2为中心,结合BaO和SrO成核生长,从而有利予单元胞的进一步形成.

  1. Laser molecular-beam epitaxy and second-order optical nonlinearity of BaTiO3/SrTiO3 superlattices

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of c-axis oriented BaTiO3/SrTiO3 superlattices with the atomic-scale precision were epitaxially grown on single-crystal SrTiO3 (100) substrates using laser molecular-beam epitaxy (LMBE). A periodic modulation of the intensity of reflection high-energy electron diffraction (RHEED) in BaTiO3 and SrTiO3 layers was observed and attributed to the lattice-misfit-induced periodic variation of the terrace density in film surface. The relationship between the second-order nonlinear optical susceptibilities and the superlattice structure was systematically studied. The experimental and theoretical fitting results indicate that the second-order nonlinear optical susceptibilities of BaTiO3/SrTiO3 superlattices were greatly enhanced with the maximum value being more than one order of magnitude larger than that of bulk BaTiO3 crystal. The mechanism of the enhancement of the second-order optical nonlinearity was discussed by taking into account the stress-induced lattice distortion and polarization enhancement.

  2. Structure and conductivity of layered oxides (Ba,Sr){sub n+1}(Sn,Sb){sub n}O{sub 3n+1}

    Energy Technology Data Exchange (ETDEWEB)

    Green, M.A. [Royal Institution of Great Britain, London (United Kingdom); Prassides, K. [Royal Institution of Great Britain, London (United Kingdom)]|[School of Chemistry and Molecular Science, Sussex Univ., Brighton (United Kingdom); Day, P. [Royal Institution of Great Britain, London (United Kingdom); Stalick, J.K. [Research Radiation Div., National Inst. of Standards and Technology, Gaithersburg, MD (United States)

    1995-04-01

    Structures of various members of the Ruddlesdon-Popper homologous series, (Ba,Sr){sub n+1}(Sn,Sb){sub n}O{sub 3n+1}, solved by Rietveld refinement of powder neutron diffraction data are summarised. Predictions of band gaps are made on the basis of extended Hueckel calculations. (orig.)

  3. Water oxidation catalysis: an amorphous quaternary Ba-Sr-Co-Fe oxide as a promising electrocatalyst for the oxygen-evolution reaction.

    Science.gov (United States)

    Zhang, Cuijuan; Berlinguette, Curtis P; Trudel, Simon

    2016-01-25

    We present an amorphous quaternary Ba-Sr-Co-Fe oxide (a-BSCF) with a specific stoichiometry, readily fabricated via a photochemical decomposition method. a-BSCF demonstrates high catalytic activity towards the oxygen-evolution reaction (OER). PMID:26659269

  4. Influence of Ba{sup 2+}-doping on structural and luminescence properties of Sr{sub 2}SiO{sub 4}:Eu{sup 2+} phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Pan Zhengwei [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); He Hong [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China); Fu Renli, E-mail: renlifu@nuaa.edu.c [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Agathopoulos, Simeon [Materials Science and Engineering Department, University of Ioannina, GR-451 10 Ioannina (Greece); Song Xiufeng [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2009-09-15

    Ba{sup 2+}-doped Sr{sub 2}SiO{sub 4}:Eu{sup 2+} phosphors were synthesized with the high-temperature solid-state reaction technique. The experimental results, summarized in the successful production of a single-phase powder with fine microstructure of spherical particles with smooth surface, suggest that Ba{sup 2+}-doping favors the stabilization of alpha'-Sr{sub 2}SiO{sub 4}. Rietveld refinement of X-ray diffractograms suggests that Ba{sup 2+} and Eu{sup 2+} ions occupy the sites of Sr{sup 2+} in the lattice of alpha'-Sr{sub 2}SiO{sub 4}. The produced phosphors show two intense emission bands at green and yellow regions of spectrum, originated from Eu{sup 2+} ions accommodated at two different sites in the host crystal, whose peaks depend on the concentrations of Ba{sup 2+} and Eu{sup 2+}. Intense and broad excitation spectra extend from ultraviolet to the blue region.

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

    Science.gov (United States)

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

    2016-10-01

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

  6. Selective removal of Cs-137, Sr-90, Ba-133, Co-60 and Pb-210 radioisotopes with proton-ionizable lariat ethers in the ion flotation process

    International Nuclear Information System (INIS)

    Authors present procedure for the selective removal of Cs-137, Sr-90, Ba-133, Co-60 and Pb-210 radioisotopes with proton-ionizable lariat ethers in the ion flotation process from dilute aqueous solutions in the presence of nonionic foaming agent, which might have a practical meaning for the decontamination of industrial (toxic, radioactive) aqueous solutions

  7. The Luminescence Properties of New FED Phosphor MSi2N2O2: Eu2+ (M = Sr, Ba)%新型FED荧光粉MSi2N2O2∶Eu2+(M=Sr,Ba)的发光性能

    Institute of Scientific and Technical Information of China (English)

    王灵利; 倪海勇; 张秋红

    2011-01-01

    采用高温固相法合成了一系列新型绿色FED(Field Emission Display)荧光粉MSi2N2O2∶Eu2+(M=Sr,Ba),研究了该荧光粉在不同电压和电流密度下的发光特性.在电子束激发下,SrSi2N2O2:Eu2+的发射主峰位于541 nm,属于黄绿光发射;BaSi2N2O2∶Eu2+的发射主峰位于492 nm,属于蓝绿光发射.BaSi2N2O2∶Eu2+的电流饱和性能要比SrSi2N2O2∶Eu2+好.但在相同电流密度的激发下,SrSi2N2O2∶Eu2+的发光强度明显高于BaSi2N2O2∶Eu2+,因此,SrSi2N2O2∶Eu2+更适合应用于FED中.%A series of new FED (Field Emission Display) green phosphors of MSi2N2O2: Eu2+ (M = Sr, Ba) are synthesized by solid state reaction, and their luminescence properties under the excitation of different voltage and current density are studied. Under the excitation of electron beams, SrSi2N2O2: Eu2+ emits yellow green light with the peak at 541 nm, and BaSi2N2O2: Eu + shows a blue-green emission dominates at 492 nm. The current saturation character of BaSi2N2O2: Eu2+ is better than that of SrSi2N2O2: Eu2+ . While, under the excitation of the same current density, the luminescence intensity of SrSi2 N2 02: Eu + is much higher than that of BaSi2N2O2: Eu2+. So, SrSi2N2O2: Eu2+ is more suitable for FED application.

  8. Effect of Ca doping on thermally activated flux flow in the Y3Ba5Cu8O18 superconductor

    Indian Academy of Sciences (India)

    Mustafa Akyol; Ali Osman Ayaş; Gönül Akça; Selda Kiliç Çeti̇n; Ahmet Eki̇ci̇bi̇l

    2015-09-01

    Y3Ba5Cu8O18 (Y-358) and Y3Ba5Ca2Cu8O18 (YCa-358) compounds were prepared by the so-called sol–gel method. The effect of doping Ca atoms into the Y3Ba5Cu8O18 superconductor is studied by employing the electrical resistivity measurements at various magnetic fields. The possible degradation in microstructural and superconducting properties due to the addition of Ca was discussed. The resistivity as a function of temperature measurements shows that the depression in superconducting temperature is more pronounced for both samples. A systematic analysis of the magnetoresistivity of the Y-358 and YCa-358 compounds has been carried out by using the thermally activated flux flow (TAFF) model. The TAFF activation energy, , is field dependent and obeys the power law = –, where increases while decreases with the addition of Ca. Furthermore, and the calculated upper critical field, 2, decrease with the addition of Ca.

  9. 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.

  10. Frequency Dependent Electrical Properties of Ferroelectric Ba0.8Sr0.2TiO3 Thin Film

    Directory of Open Access Journals (Sweden)

    Ala’eddin A. SAIF

    2011-07-01

    Full Text Available The frequency dependent electrical parameters, such as impedance, electric modulus, dielectric constant and AC conductivity for ferroelectric Ba0.8Sr0.2TiO3 thin film have been investigated within the range of 1 Hz and 106 Hz at room temperature. Z* plane shows two regions corresponding to the bulk mechanism and the distribution of the grain boundaries-electrodes process. M" versus frequency plot reveals a relaxation peak, which is not observed in the ε″ plot and it has been found that this peak is a non-Debye-type. The frequency dependent conductivity plot shows three regions of conduction processes, i. e., a low-frequency region due to DC conduction, a mid-frequency region due to translational hopping motions and a high-frequency region due to localized hopping and/or reorientational motion.http://dx.doi.org/10.5755/j01.ms.17.2.490

  11. Interfacial characteristics and dielectric properties of Ba0.65Sr0.35TiO3 thin films

    International Nuclear Information System (INIS)

    Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) depth profiling data show that each element component of the BST film possesses a uniform distribution from the outermost surface to subsurface, but obvious Ti-rich is present to BST/Pt interface because Ti4+ cations are partially reduced to form amorphous oxides such as TiOx (x -7 A/cm2 at 1.23 V and lower than 5.66 x 10-6 A/cm2 at 2.05 V as well as breakdown strength is above 3.01 x 105 V/cm

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

    Science.gov (United States)

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

    2015-04-01

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

  13. Synthesis, vacuum ultraviolet and ultraviolet spectroscopy of Ce3+ ion doped olgite Na(Sr, Ba)PO4

    International Nuclear Information System (INIS)

    Ce3+ ion doped olgite mineral samples, Na(Sr, Ba)PO4, were prepared by a high temperature solid-state reaction. The sample was investigated through x-ray powder diffraction, FT-IR and FT-Raman spectra measurements. The optical properties under vacuum ultraviolet (VUV) synchrotron radiation and ultraviolet (UV) irradiation are reported for the first time. The investigated samples show a strong absorption in the VUV and UV ranges. The bands corresponding to the 4f1 → 4f05d1 transitions of Ce3+ ions in the host lattices are identified. The barycentre of Ce3+ ions in the host lattices, the host absorption, the crystal field splitting, the emission and the Stokes shifts are presented and discussed. This Ce3+ ion doped material is a potential candidate for plasma display panel (PDP) application

  14. Nano structure formation on the surfaces of SrTiO{sub 2} and BaF{sub 2} induced by impact of slow highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Heller, Rene; El-Said, Ayman S.; Wilhelm, Richard A.; Facsko, Stefan [Helmholtz-Zentrum Dresden Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany)

    2011-07-01

    The interaction of slow highly charged ions with solid surfaces with particular interest on the nano structure formation ability was investigated intensively within the last years. The rapid release of the HCI's potential energy as a unique feature of this kind of projectiles can cause local energy densities at the surface which are comparable to those induced by ultra short laser pulses or swift heavy ions. Thus HCI give strong rise to be a promising tool for nano structure formation on solid surfaces. Since the potential energy release is strongly restricted to the surface proximity the amount of damage created in the bulk can be strongly suppressed. In recent time the authors spent much effort in the exploration of the microscopic mechanisms of HCI nanostructure creation on the surfaces of the alkali halide KBr and the earth alkali halide CaF{sub 2}, respectively. Motivated by the promising results and the predictions of the developed models we extended our investigation to the surfaces of SrTiO{sub 2} as well as of BaF{sub 2}. The results of these measurements are presented and discussed in the present contribution.

  15. Photoluminescence properties of Pb{sup 2+} doped M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Mergen, Ayhan [Marmara University, Faculty of Engineering, Department of Metallurgical and Materials Science Engineering, Istanbul 34722 (Turkey); Pekgoezlue, Ilhan, E-mail: ayhan.mergen@marmara.edu.tr [Bartin University, Faculty of Engineering, Department of Environmental Engineering, Bartin 74100 (Turkey)

    2013-02-15

    Pure and Pb{sup 2+} doped M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) materials were synthesized at 900 Degree-Sign C for 12 h in air. The phases of the synthesized materials were determined using the powder XRD. The photoluminescence properties of the synthesized phosphors were investigated using a spectrofluorometer at room temperature. The emission and excitation bands of Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} were observed at 330 and 260 nm, respectively. And, the emission and excitation bands of Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} were observed at 381 and 293 nm, respectively. The dependence of the emission intensity on the Pb{sup 2+} concentration for the M{sub 2-x}Pb{sub x}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) was studied in detail. It was observed that the optimum concentrations of Pb{sup 2+} in Sr{sub 2}Mg(BO{sub 3}){sub 2} and Ba{sub 2}Mg(BO{sub 3}){sub 2} are 0.06 and 0.01 mol, respectively. The Stokes shifts of Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} phosphors were calculated to be 8159 and 7883 cm{sup -1}, respectively. The luminescence behavior of the Pb{sup 2+} ion in M{sub 2}Mg(BO{sub 3}){sub 2} (M=Sr, Ba) is discussed. - Highlights: Black-Right-Pointing-Pointer We have synthesized two novel inorganic borate phosphors for the first time. Black-Right-Pointing-Pointer Sr{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}: Pb{sup 2+} phosphors emit at 330 and 381 nm, respectively. Black-Right-Pointing-Pointer Consequently, they are promising phosphors for UV lamp phosphors.

  16. 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.

  17. Thermoluminescence study of BaMgAl10O17 and SrMgAl10O17 doping with Mn2+ by γ-irradiation

    International Nuclear Information System (INIS)

    The synthesis of Mn2+ doped BaMgAl10O17 and SrMgAl10O17 phosphor by combustion method at 500°C. For the TL study, Mn2+ doped BaMgAl10O17 shows two intensive TL glow peak around at 403.5K and ∼488K respective to BaMgAl10O17: Mn2+ and 650 K for SrMgAl10O17:Mn2+. The trapping parameter were calculated by Chen's peak shape method. The maximum intensity and the glow curve obtained by γ-irradiation at 2Gy/min. These results are supported by corresponding X-ray diffraction measurements which exhibit crystalline nature. Overall results suggest the possibility of utilizing this material in futuristic dosimeter application. (author)

  18. 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.

  19. CaSR function in the intestine: Hormone secretion, electrolyte absorption and secretion, paracrine non-canonical Wnt signaling and colonic crypt cell proliferation.

    Science.gov (United States)

    Macleod, R John

    2013-06-01

    Expression and function of the CaSR have been shown in some mammalian taste buds and basal cells of the esophagus. Signaling cascades responsible for CaSR-mediated stimulation of H(+)-K(+)-ATPase on human parietal cells have been defined. Transgenic mice and reductionistic cell culture models have shown that the CaSR promotes gastrin secretion from G cells, cholecystokinin (CCK) secretion from duodenal I cells and BMP-2 secretion from sub-epithelial myofibroblasts. In addition, the CaSR mediates a novel paracrine relationship between myofibroblasts and overlying epithelial cells in the colon. Thus, CaSR activators stimulate secretion of Wnt5a from myofibroblasts and expression of the Wnt5a receptor Ror2 in epithelial cells. CaSR-mediated Wnt5a/Ror2 engagement stimulates epithelial differentiation and reduces expression of the receptor for tumor necrosis factor (TNFR1). CaSR activators also modulate intestinal motility, inhibit Cl(-) secretion and stimulate Na(+) absorption in both the small intestine and colon. Colonic epithelia from conditional and global CaSR knockout mice exhibit increased proliferation with increased Wnt/β-catenin signaling, demonstrating that the CaSR negatively modulates colonic epithelial growth.

  20. The Effect Of Coupling Agent On Composite Magnet Characteristic Based On Hexa ferrite (Sr M/Ba M) With Polyester And Epoxy Binder

    International Nuclear Information System (INIS)

    Magnetic composites are mixtures of hexa ferrite powder and non magnetic materials such as polymers as binders. These composites have been investigated because they are light, elastic, and cheap. In this study thermoset polymer (epoxy and polyester) were used as binders. Inside study of coupling agent added effect on mechanical properties, hardness and microstructure. The composites were prepared by mixture thermoset polymer epoxy or polyester with hexa ferrite powder Sr M (SrFe12O19) or Ba M (BaFe12O19) with volume fraction of 40,50 and 60 % v/v, coupling agent of the Tetra Isopropyl Titanate in the amount of 5 ml or 10 ml are added before mix turing of the thermoset polymer epoxy or polyester with hexa ferrite powder. The resulting composite were characterized mechanically (tensile strength), hardness and microstructure test. The results showed that the tensile strength and hardness of the composite magnet were increased by increasing the composition of magnetic powder, either Sr M or Ba M, it caused by microstructure of particle Sr M magnetic powder 1.6 μm in the form splinter, where as the Ba M magnetic powder 1,2 μm in nodular form. Thermoset polymer epoxy as binder have tensile strength and hardness is bigger than composite magnet based on polyester, either Sr M or Ba M. The addition of coupling agent is very influenced on the tensile strength and hardness composite magnet, the more coupling magnet addition causes the more tensile strength and hardness of the composite magnet

  1. 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.

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

    International Nuclear Information System (INIS)

    An important subject for understanding the mechanism of high temperature superconductivity is the investigation of the substituted compounds of the 123 system. A new superconductor compounds have been prepared by solid state reaction from the stochiometric amounts of oxide and carbonite materials. crystal structures were found to be tetragonal for both samples, and the electrical resistivity data obtained by the four probe technique. LaCaBaCu3O7.1 sample reached zero resistivity at 83 K, while La1.3Ba1.7Cu3O7.1 sample reached zero resistivity at 33 K and it has almost metalic behaviour. 4 refs., 9 figs., 4 tabs. (author)

  3. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Science.gov (United States)

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

    2016-09-01

    The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials.

  4. Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

    Science.gov (United States)

    Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

    2016-01-01

    The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials. PMID:27580744

  5. Mass spectrometric analysis of laser evaporation products of ceramics of Bi2Sr2CaCu2Ox composition

    International Nuclear Information System (INIS)

    Mass spectrometric analysis is used to study mechanism of laser evaporation of superconducting ceramics of Bi2Sr2CaCu2Ox composition. During evaporation as a result of pulsed laser irradiation of a sample placed in vaccum ions of all metals containing in ceramics and also neutral O2, Ca, Sr, Cu, Bi and metal oxides were detected on yttrium aluminate. Time-of-flight spectra had two peaks corresponding to ion and neutral components. Comparison of neutral components. Comparison of neutral particle rates points to the fact that gas dynamic processes connected with formation of dense gas cloud near the target surface play an important

  6. Thermopower of ceramic HgBa2Ca2Cu3O8+x and HgBa2Ca3Cu4O10+x superconductors under pressure

    International Nuclear Information System (INIS)

    The temperature dependence of thermopower α of a sample, contained 75% HgBa2Ca2Cu3O8+x (Hg-1223 phase) and 10% HgBa2Ca3Cu4O10+x (Hg-1234 phase), was studied in a 95-300 K temperature range under hydrostatic pressure up to 10 kbar. Two superconductive transitions were observed at 132 and 118 K, which were thought to be associated with Hg-1223 and Hg-1234 phases, respectively. Pressure increases Tc of both phases with a rate of 0.2 K/kbar. At T=200 K, d ln α/dP ≅ 3,8 centre dot 10-3 kbar-1

  7. Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2

    International Nuclear Information System (INIS)

    We have performed low-temperature specific heat C and thermal conductivity κ measurements on the Ni-pnictide superconductors BaNi2As2 (Tc = 0.7K) and SrNi2P2 (Tc = 1.4K). The temperature dependences C(T) and κ(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual κ for BaNi2As2 rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba0.6La0.4Ni2As2 shows a mild suppression of Tc and Hc2 relative to BaNi2As2.

  8. Pharmacological evidence that potentiation of plasmalemmal Ca(2+)-extrusion is functionally coupled to inhibition of SR Ca(2+)-ATPases in vascular smooth muscle cells.

    Science.gov (United States)

    Zhang, Wen-Bo; Kwan, Chiu-Yin

    2016-04-01

    Cyclopiazonic acid (CPA), a specific inhibitor of sarcoplasmic reticulum (SR) Ca(2+)-ATPases, causes slowly developing and subsequently diminishing characteristic contractions in vascular smooth muscle, and the second application of CPA has incompletely repeatable effects, depending on the vessel type. The objective of the present study was to examine the mechanisms underlying the significant decrease of CPA-induced contractions upon the second application. A pharmacological intervention of Ca(2+) extrusion process as a strategy was performed to modulate vasoconstrictor effects of CPA in rat aortic ring preparations. CPA-induced contractions, expressed as percentages of the contractions induced by KCl (80 mM), were significantly decreased from 44.1 ± 5.7 to 7.6 ± 1.8 % (P CPA-induced contractions were sustained and completely repeatable in Na(+)-free and low Na(+) medium. Furthermore, we found that the contractions were completely repeatable in the presence of 2',4'-dichlorobenzamil, an inhibitor of the forward mode of Na(+)/Ca(2+) exchangers, but not of KBR7943, an inhibitor of the reverse mode of Na(+)/Ca(2+) exchangers. Our findings indicate that CPA by inducing a transient rise in cytosolic Ca(2+) level causes a long-lasting upregulation of plasma membrane (PM) Ca(2+) extruders and thus leads to a diminished contraction upon its second application in blood vessels. This suggests that there is a functional coupling between PM Ca(2+) extruders and SR Ca(2+)-ATPases in rat aortic smooth muscle cells. PMID:26842648

  9. The records and implications of Mg,Sr and Ba in cave water and active speleothems in Jiguan Cave,western Henan Province%豫西鸡冠洞洞穴水及现代沉积物Mg,Sr和Ba记录及其意义

    Institute of Scientific and Technical Information of China (English)

    任小凤; 张志钦; 杨琰; 彭涛; 赵景耀; 张银环; 聂旭东; 刘肖; 李建仓; 凌新有

    2014-01-01

    Speleothems contain a number of suitable proxies reconstructing climate environmental changes, which is a top topic in current research.Due to the variety of sources and complex factors,trace elements are less frequently used than the oxygen isotopes in climate studies.However,they are used to reveal the groundwater runoff in the epikarst overlying the cave with the process and the surface environment.Induc-tively coupled plasma mass spectrometry (ICP-MS)and inductively coupled plasma optical emission spec-trometry(ICP-OES)have been used to analyse the trace elements of Ca、Mg、Sr and Ba in cave water and ac-tive formations in Jiguan Cave during December,2009 and August,2013.Jiguan Cave (33°46′N,111°34′E) is located in Luanchuan county,western Henan Province,which is north of the Qinling ranges-Huaihe River and southeast of Loess Plateau,while at the foot of the northern watershed of the Yangtze River and the Yellow River.It main exposed rocks are Sinian chlorite marbles.Located in the typical east Asian monsoonal zone,the Jiguan Cave area is typically has cold/dry winters and warm/wet summers.More than 50 % of the total annual precipitation occurs in summer.The mean annual temperature and precipitation recorded at a nearby meteorological station are 12.1±0.9 ℃ and 846±181 mm (1957-2009)respectively.In the paper, trace elements such as Ca,Mg,Sr and Ba in cave water and active formations collected in Jiguan Cave were analyzed with ICP-MS and ICP-OES.The Mg/Ca,Sr/Ca and Ba/Ca of cave water varied between 0.2-0.8, (1.2-6.0)×10-3 and (0.3-2.0)×10-3 respectively.Mg/Ca can respond to the environment outside the cave faithfully.The wet-dry condition of the karst system is suggested as the dominant controller of Mg/Ca ratios in cave pool water and underground rivers,whereas the Sr/Ca and Ba/Ca may have nothing to do with precipitation and temperature.The Mg/Ca,Sr/Ca and Ba/Ca ratios in active speleothems varied between (9-50)×10-3 ,(0.1-1.2)×10-3 and (0

  10. Decoupling of the CuO2 plane and superconductivity in Cu0.5Tl0.5Ba2(Ca2‑ySry)Cu3O10‑δ(y = 0-0.4) samples

    Science.gov (United States)

    Khan, Nawazish A.; Usman Muzaffar, M.

    2016-05-01

    Cu0.5Tl0.5Ba2(Ca2‑ySry)Cu3O10‑δ(y = 0-0.4) samples have been synthesized at normal pressure at 860∘C. The main objectives of these experiments to study the role of inter-plane decoupling in suppressing the superconductivity of high temperature superconductors (HTSC). These samples have shown orthorhombic crystal structure and the c-axis length increases with increased Sr-doping. All the samples have shown metallic variations of resistivity (ρ) from room temperature down to the onset of superconductivity. The magnitude of the superconductivity is suppressed and the apical oxygen modes are hardened with Sr-doping. These studies have shown that Sr-doping promotes decoupling of conducting CuO2 planes which suppress the superconducting properties of final compound. The excess conductivity analyses have shown increases in the width of two-dimensional (2D) Lawrence-Doniach (LD) regime with Sr-doping. The coherence length along the c-axis ξc(0), the inter-layer coupling J, the phase relaxation time of the carriers τφ and the Fermi velocity vF of superconductor carriers is suppressed. The underlying reason for the suppression of superconductor properties is the decrease in the density of carriers in the superconductor planes. However, the values of Bc0(T), Bc1(T) and Jc(0) have been found to increase with the increased Sr-doping, which is suggested to be originating from the enhancement in the flux pinning character which is induced by Sr-doping. The values of magnetic field penetration depth λp.d and the Ginzburg-Landau (GL) parameter κ decrease with Sr-doping and it is also suggested to be originating from the increase of flux pinning character of the samples with Sr-doping.

  11. Optimization of the 120 K superconducting phase in the BiSrCaCuO system

    International Nuclear Information System (INIS)

    The formation of the 120 K superconducting phase in the BiSrCaCu2Oy system has been investigated by microwave absorption. This material is characterized by an intense, low-field microwave absorption (LFMA) below the superconducting transition temperature Tc and a g = 2 electron spin resonance (ESR) signal above Tc. The LFMA is used to follow the formation of the high Tc phases in this compound. The purity of these superconducting phases is also reflected by the intensity of the g = 2 signal. Various stages of sample preparation are studied to optimize the reaction conditions for the formation of the 120 K phase. LFMA and ESR results are also compared and contrasted with resistance measurements

  12. Quantitative procedure for evaluation of microstructure of cast Mg-Al-Ca-Sr magnesium alloy

    Directory of Open Access Journals (Sweden)

    T. Rzychoń

    2010-01-01

    Full Text Available In this paper the microstructural characterization of ingot MRI-230D magnesium alloy and quantitative procedure for evaluation of microstructure are presented. The optical and scanning electron microscopy were used to study the morphology of microstructural compounds in this alloy. The X-ray diffraction was used to determination of phase composition. The as-cast microstructure of MRI-230D magnesium alloy containing aluminum, calcium and strontium consists of the dendritic α-Mg and such intermetallic compounds as: Al2Ca, Al4Sr and AlxMny. In the purpose quantitative description of microstructure semi-automatic procedures using Met-Ilo image analysis were developed. Prepared semi-automatic procedures allow a fast determination of phase content in MRI-230D alloy using light microscopy and will be useful in the quality control of MRI-230D ingots.

  13. Spin-mixed doubly excited resonances in Ca and Sr spectra

    International Nuclear Information System (INIS)

    We present a joint theoretical and experimental investigation to demonstrate explicitly how the combined spin-dependent interaction and the configuration interaction may affect the mixing of different spin states along various doubly excited autoionization series for Ca and Sr as energy increases across several ionization thresholds. In particular, our study has identified the inversion of energy levels between members of a number of multiplets, i.e., in contrast to the Hund's rules, due to the presence of perturber from other overlapping resonance series. We are also able to demonstrate the beginning of the breakdown of the LS coupling for resonance series corresponding to electron configurations with higher orbital angular momenta and those above the third ionization threshold.

  14. Energy gaps in Bi2Sr2CaCu2O8+δ cuprate superconductors

    Science.gov (United States)

    Ren, J. K.; Zhu, X. B.; Yu, H. F.; Tian, Ye; Yang, H. F.; Gu, C. Z.; Wang, N. L.; Ren, Y. F.; Zhao, S. P.

    2012-01-01

    The relationship between the cuprate pseudogap (Δp) and superconducting gap (Δs) remains an unsolved mystery. Here, we present a temperature- and doping-dependent tunneling study of submicron Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions, which provides a clear evidence that Δs closes at a temperature Tc0 well above the superconducting transition temperature Tc but far below the pseudogap opening temperature T*. We show that the superconducting pairing first occurs predominantly on a limited Fermi surface near the node below Tc0, accompanied by a Fermi arc due to the lifetime effects of quasiparticles and Cooper pairs. The arc length has a linear temperature dependence, and as temperature decreases below Tc it reduces to zero while pairing spreads to the antinodal region of the pseudogap leading to a d-wave superconducting gap on the entire Fermi surface at lower temperatures. PMID:22355760

  15. Studies on structural and thermo-chemical behavior of MFe12O19(s) (M = Sr, Ba and Pb) prepared by citrate-nitrate gel combustion method

    International Nuclear Information System (INIS)

    The citrate-nitrate gel combustion route was used to prepare SrFe12O19(s), BaFe12O19(s) and PbFe12O19(s). The compounds were characterized by Rietveld profile analysis of the X-ray powder diffraction data. The thermal expansion coefficients of MFe12O19 (M = Sr, Ba and Pb) were determined using high temperature powder X-ray diffraction data. The lattice parameters of these compounds were fitted into polynomial expressions as a function of temperature. Melting points of MFe12O19 (M = Sr, Ba and Pb) were determined using high temperature calorimeter and the values are; 1632 K, 1611 K and 1538 K, respectively. Standard molar heat capacities of BaFe12O19(s) and PbFe12O19(s) were determined from 130 K to 850 K using a heat flux type differential scanning calorimeter (DSC) and heat capacity anomalies were observed at 725 K and 718 K, respectively. This heat capacity anomaly is due to the magnetic order-disorder transition from ferrimagnetic state to paramagnetic state

  16. Preparation and characterizations of Ba(Zr,Ti)O{sub 3}/(Ba,Sr)TiO{sub 3} heterostructures grown on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} single crystal substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chan, N.Y.; Gao, G.Y.; Wang, Y. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University (Hong Kong); Chan, H.L.W., E-mail: apahlcha@inet.polyu.edu.h [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University (Hong Kong)

    2010-10-01

    Epitaxial perovskite (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} (BST), Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} (BZT), Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}/(Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3}(BZT/BST) and Ba{sub 0.85}Sr{sub 0.15}Zr{sub 0.1}Ti{sub 0.9}O{sub 3} (BSZT) thin films were grown on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} (LSAT)[001]single crystal substrate coated with conducting oxide LaNiO{sub 3}(LNO) by pulsed laser deposition. X-ray diffraction, atomic force microscopy and electrical measurements were used to characterize the thin films. The {theta}-2{theta} linear scan indicated that the thin films with LNO layer show (001) orientations perpendicular to the substrate. Smooth and dense surface with grain size of 30 nm-80 nm were observed. The relative permittivity of the BST, BZT/BST, BZT and BSZT thin films are 1101, 799, 584 and 1784 respectively at 10 kHz. The tunability of the thin films are 39%, 32%, 44% and 60%. The results show that BSZT film has the highest tunability.

  17. Preparation and characterizations of Ba(Zr,Ti)O3/(Ba,Sr)TiO3 heterostructures grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 single crystal substrates by pulsed laser deposition

    International Nuclear Information System (INIS)

    Epitaxial perovskite (Ba0.7Sr0.3)TiO3 (BST), Ba(Zr0.2Ti0.8)O3 (BZT), Ba(Zr0.2Ti0.8)O3/(Ba0.7Sr0.3)TiO3(BZT/BST) and Ba0.85Sr0.15Zr0.1Ti0.9O3 (BSZT) thin films were grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT)[001]single crystal substrate coated with conducting oxide LaNiO3(LNO) by pulsed laser deposition. X-ray diffraction, atomic force microscopy and electrical measurements were used to characterize the thin films. The θ-2θ linear scan indicated that the thin films with LNO layer show (001) orientations perpendicular to the substrate. Smooth and dense surface with grain size of 30 nm-80 nm were observed. The relative permittivity of the BST, BZT/BST, BZT and BSZT thin films are 1101, 799, 584 and 1784 respectively at 10 kHz. The tunability of the thin films are 39%, 32%, 44% and 60%. The results show that BSZT film has the highest tunability.

  18. Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

    International Nuclear Information System (INIS)

    The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high Tc, chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO2 laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with Tc(0)'s of 76 K could be deposited using the KrF laser at substrate temperatures of 5 degrees C to 20 degrees C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in Tc(0) was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component

  19. Dosimetry characterization of the commercial CaF{sub 2} for beta radiation of {sup 90}Sr + {sup 90}Y; Caracterizacao dosimetrica de CaF{sub 2} comercial para radiacao beta de {sup 90}Sr + {sup 90}Y

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Mercia L.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)], e-mail: mlolivei@ipen.br, e-mail: lcaldas@ipen.br

    2003-07-01

    This work studies the dosimetric characteristics of the CaF{sub 2} commercial dosimetry for detection of {sup 90}Sr + {sup 90}Y beta radiation for using in the calibration of flat and concave appliers. Were determined the repetitiousness and linearity of answers of the samples, and their calibration curves.

  20. 用PLD在不同衬底上制备Ba0.5Sr0.5Ti03薄膜

    Institute of Scientific and Technical Information of China (English)

    马维云

    2011-01-01

    用固相反应法制备了Ba0.5Sr0.5Ti03靶材,采用在LaA103 (100)衬底上PLD法制备Ba0.5Sr0.5Ti03薄膜的最佳条件(村底温度760℃,生长氧压5Pa,脉冲激光能量350mj,频率5Hz,不退火直接降温),利用PLD技术在LaA103 (100),SrTi03 (100),LSAT(1 00)单晶平衬底上制备了Ba0.5Sr0.5Ti03薄膜.通过分析x射线衍射图谱,晶格失配度,单θ摇摆曲线半高宽,表明在三种衬底上薄膜是沿[00I]取向的近外延生长,影响薄膜生长的主要因素并不是村底与品格的失配度,如希望消除失配度对薄膜生长造成的不利影响,我们可以通过优化PLD工艺参数,这在一定程度上是有效的.

  1. In situ stress measurements during pulsed laser deposition of BaTiO3 and SrTiO3 atomic layers on Pt(0 0 1)

    Science.gov (United States)

    Premper, J.; Sander, D.; Kirschner, J.

    2015-04-01

    We apply the cantilever deflection technique to measure stress in nm thin BaTiO3 and SrTiO3 films during pulsed laser deposition on a Pt(0 0 1) single crystal cantilever substrate. We find a compressive film stress of -4.2 GPa for BaTiO3 on Pt(0 0 1) (misfit = -2.3%), whereas the deposition of SrTiO3 (misfit = +0.4%) induces a tensile stress of +1.5 GPa. The stress measurements are augmented by in situ low energy electron diffraction experiments which indicate an epitaxial order of the films. We apply continuum elasticity to calculate film stress. We conclude that sign and magnitude of the measured stress are due to the epitaxial misfit between film and substrate, which is -2.3% and +0.4% for BaTiO3 and SrTiO3, respectively. We identify that in addition to misfit also the oxygen partial pressure during PLD film growth influences film stress. PLD growth in an oxygen-free environment leads to factor of two increased tensile stress in SrTiO3 on Pt(0 0 1) as compared to growth at pO2 =10-4 mbar. The role of film stoichiometry for film stress is discussed.

  2. Electrical properties of SrBa1−Fe0.6Sn0.4O3− NTC thermistors

    Indian Academy of Sciences (India)

    C L Yuan; X Y Liu; J W Xu; X W Zhang; C R Zhou

    2012-06-01

    Polycrystalline thermistor ceramics with the stoichiometric formula, SrBa1−Fe0.6Sn0.4O3− (0.2 ≤ ≤ 0.8), had been prepared by a standard solid state reaction route. X-ray diffraction analysis indicates that the ceramic system remains cubic perovskite structure with a very small lattice change. The electrical properties of SrBa1−Fe0.6Sn0.4O3− thermistors were studied using a digital thermometer over a wide range of 298–400 K. The thermistors showed an excellent negative temperature coefficient (NTC) thermistor behaviour. The values of resistivity at 298 K (ρ982), thermistor constant (298/358) and activation energy (a) of the SrBa1−Fe0.6Sn0.4O3− thermistors, decreasing with the increase of Sr content, were in the range of 0.37–11.0 k.cm, 2466–3703 K and 0.212–0.319 eV, respectively. For the thermistors with the compositions = 0.2 and 0.4, the fitting equivalent circuit was composed of three RCPE elements corresponding to grain, grain boundary and ceramic–electrode interface, respectively. From the impedance plots, it was found that the fitting data showed good agreement with the experimental data. The extracted grain boundary resistance exhibited a NTC thermistor behaviour.

  3. Chemistry of the M (M=Fe, Ca, Ba-Se-H2O Systems at 25 °C

    Directory of Open Access Journals (Sweden)

    Fumihiko Hasegawa

    2009-09-01

    Full Text Available The chemistry of the M (M=Fe, Ca, Ba-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III-Se(IV-H2O, Ca-Se(IV,VI-H2O and Ba-Se(IV,VI-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L.

  4. Chemistry of the M (M=Fe, Ca, Ba)-Se-H2O Systems at 25 °C

    OpenAIRE

    Fumihiko Hasegawa; Tadahisa Nishimura; Ryosuke Hata

    2009-01-01

    The chemistry of the M (M=Fe, Ca, Ba)-Se-H2O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H2O, Ca-Se(IV,VI)-H2O and Ba-Se(IV,VI)-H2O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high con...

  5. 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)

  6. 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.

  7. Study of gel grown mixed crystals of BaCa(1–)(IO3)4

    Indian Academy of Sciences (India)

    S L Garud; N K Mahajan; K B Saraf

    2009-04-01

    The growth of mixed crystals of BaCa1–(IO3)4 were carried out with simple gel method. The effect of various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants on the growth was studied. Crystals having different morphologies and habits were obtained. The grown crystals were characterized by XRD, FT–IR, EDAX, TGA, DTA and DSC.

  8. 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.

  9. Monte Carlo simulation of gamma-ray response of BaF{sub 2} and CaF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gao, F.; Xie, Y. L.; Wang, Z. G.; Kerisit, S.; Wu, D. X.; Campbell, L. W.; Van Ginhoven, R. M.; Prange, M. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)

    2013-11-07

    We have employed a Monte Carlo (MC) method to study intrinsic properties of two alkaline-earth halides, namely, BaF{sub 2} and CaF{sub 2}, relevant to their use as radiation detector materials. The MC method follows the fate of individual electron-hole (e-h) pairs and thus allows for a detailed description of the microscopic structure of ionization tracks created by incident γ-ray radiation. The properties of interest include the mean energy required to create an e-h pair, W, Fano factor, F, the maximum theoretical light yield, and the spatial distribution of e-h pairs resulting from γ-ray excitation. Although W and F vary with incident photon energy at low energies, they tend to constant values at energies higher than 1 keV. W is determined to be 18.9 and 19.8 eV for BaF{sub 2} and CaF{sub 2}, respectively, in agreement with published data. The e-h pair spatial distributions exhibit a linear distribution along the fast electron tracks with high e-h pair densities at the end of the tracks. Most e-h pairs are created by interband transition and plasmon excitation in both scintillators, but the e-h pairs along fast electron tracks in BaF{sub 2} are slightly clustered, forming nanoscale domains and resulting in the higher e-h pair densities than in CaF{sub 2}. Combining the maximum theoretical light yields calculated for BaF{sub 2} and CaF{sub 2} with those obtained for CsI and NaI shows that the theoretical light yield decreases linearly with increasing band gap energy.

  10. High temperature phase equilibria studies in the Bi-Sr-Ca-Cu-O-Ag system

    Energy Technology Data Exchange (ETDEWEB)

    Margulies, Lawrence

    1999-11-08

    A variety of experimental techniques were utilized to examine the high temperature phase equilibria in the Bi-Sr-Ca-Cu-O-Ag system. Quenching studies were used to determine the liquid solubility of Ag in the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi2212) melt and the details of the peritectic decomposition pathway of Bi2212 as a function on Ag content and oxygen partial pressure (PO{sub 2}). A liquid immiscibility region between oxide and Ag liquids in the 8--98 at% range was found above 900 C. Two eutectics were found in the Bi2212-Ag pseudobinary. On the oxide rich side, a eutectic exists at approximately 4 at% Ag. On the Ag rich side, a eutectic exists at approximately 98 at% Ag at a temperature of 15 C below the melting point of pure Ag. Six distinct solid phases were found to be in equilibrium with the partial melt within the Ag content and PO{sub 2} range studied. The stability of these solid phases were found to be highly sensitive to PO{sub 2}, and to a much lesser extent Ag content. High temperature x-ray diffraction (HTXRD) studies of this system are in conflict with these results. It is suggested that these discrepancies are due to experimental artifacts caused by the significant thermal gradients and lack of full bulk sampling which is inherent in conventional HTXRD designs. In part 2, a new furnace design compatible with synchrotron radiation sources is introduced to address these problems. This design allows for full bulk sampling in a low thermal gradient environment using Debye-Scherrer transmission geometry. Sample spinning is also introduced in the design to eliminate preferred orientation and incomplete powder averaging and allow for quantitative phase analysis and structural refinement. Studies on model systems are presented to demonstrate the capabilities for high resolution structural studies (Al{sub 2}O{sub 3}) and time resolved phase transformation studies (SrCO{sub 3}). Finally, the Bi2212 system is examined to confirm the quenching results

  11. Lattice instabilities and superconductivity in La2-x(Ba,Sr)xCuO4

    International Nuclear Information System (INIS)

    In this paper, the authors present the result of two experiments on the anomalous physical properties of La2-xBaxCuO4 with x = 0.125. The suppression of a low-temperature tetragonal phase by introduction of Sr in the La2-xBaxCuO4 correlates well with the recovery of 30-K superconductivity. Hydrogenation of La2-xBaxCuO4 revealed that the carrier density, rather than the amount of divalent ions, is an essential parameter which governs the anomaly

  12. A Comparative Study of Si-BaSO4 and Si-CaSO4 Pyrotechnic Time-Delay Compositions

    Science.gov (United States)

    Tichapondwa, Shepherd M.; Focke, Walter W.; del Fabbro, Olinto; Gisby, John; Kelly, Cheryl

    2016-07-01

    Slow-burning Si-BaSO4 pyrotechnic delay compositions are employed commercially for intermediate to long-time delays. However, there is very little information on this composition available in open literature. The reactivity of this composition was therefore characterized and compared to that of Si-CaSO4. The Si-BaSO4 composition supported combustion in the range of 20-60 wt% Si in the bomb calorimeter. However, burning was only sustained between 20 and 40 wt% Si in rigid aluminum tubes, with burning rates of between 8.4 and 16 mm s-1. These values are comparable to those for the Si-CaSO4 system (6.9-12.5 mm s-1). However, the CaSO4-based formulations tended to have higher energy output and produced more transient pressure compared to the barium sulfate compositions. Both formulations were insensitive to impact, friction, and electrostatic discharge stimuli. The reaction products were a complex mixture that contained crystalline phases in addition to an amorphous phase. Although barium sulfate is insoluble in water and decidedly nontoxic, the reaction products produced by the Si-BaSO4 compositions were found to release soluble barium ions when contacted with water. This ranged from 50 to 140 mg per gram of barium sulfate reacted.

  13. Study on Ca8Mg(SiO4)4Cl2:Eu2+ Doped with Sr2+

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Ca8Mg(SiO4)4Cl2:Eu2+ phosphor doped with Sr2+ cation for Ca2+ partially, was synthesized by solid-state reaction at high temperature under reducing atmosphere, and its luminescent properties were investigated. The experimental results indicate that the emission intensity of the phosphor increases after being doped with a few amount of Sr2+ ion. The emission peak of the phosphor blue shift to about 464 nm when the phosphor is doped with large quantity of Sr2+ ions. The excitation spectrum indicates that the phosphor can be well excited by UV and blue light from 300 to 460 nm, and the phosphor was fitted well for the excitation by UV or blue-LED.

  14. Layer-by-layer deposition of superconducting Sr-Ca-Cu-O films by the spray pyrolysis technique

    International Nuclear Information System (INIS)

    Layer-by-layer deposition of Sr-Ca-Cu-O films has been carried out using the spray pyrolysis technique. Reagent-grade nitrates of strontium, calcium and copper were used to prepare starting solutions for spray pyrolysis. A two-step procedure was used for every layer of the constituents in the sequence Sr-Cu-Ca-Cu-Sr: first, deposition onto silver substrate at 350 C, then firing at T≥450 C, both at atmospheric pressure. The films were 2-3 μm thick and showed adequate adhesion to the substrate. The films were then characterised by studying their electron micrographs, X-ray diffraction patterns and electrical resistivity. The films showed superconductivity below 104 K. ((orig.))

  15. 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.

  16. Soft X-ray magnetic dichroism of (Ca,Sr)RuO{sub 3}: Evidence for strain-dependent magnetism

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

    The 4d transition metal oxide Ca{sub 1-x}Sr{sub x}RuO{sub 3} exhibits ferromagnetic order in the doping range 0.4Ca{sub 1-x}Sr{sub x}RuO{sub 3} remains essentially isostructural and has a similar electronic configuration throughout the doping series, the differences in the magnetic properties might be caused by chemical pressure or magnetic dilution. To verify a possible dependence of the magnetic moments on pressure, (Ca,Sr)RuO{sub 3} films were deposited on different substrates (LSAT, STO, DyScO{sub 3}=DSO), with the lattice mismatch imposing a specific strain on the epitaxial films that increases when going from LSAT to STO and DSO. The magnetic and electronic structure of the strained samples was studied by soft x-ray absorption and magnetic circular dichroism at the Ru M{sub 2,3} and O K edges. It turns out that at 20 K, the magnetic moments strongly depend on the strain: while the spin moment of samples on LSAT almost vanishes, a distinct moment is found for (Ca,Sr)RuO{sub 3} films deposited on STO and DSO. Furthermore, a significant magnetic anisotropy is observed, with the spin moments mainly oriented perpendicular to the substrate plane. Implications are discussed.

  17. 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.

  18. EPR and optical spectroscopy of Yb3+ ions in CaF2 and SrF2

    International Nuclear Information System (INIS)

    The Yb3+ paramagnetic center of the trigonal symmetry ('oxygen' paramagnetic center T2) in CaF2 and SrF2 single crystals is studied by EPR and optical spectroscopy. The Stark level energies of the Yb3+ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated

  19. Growth of nucleation sites on Pb-doped Bi2Sr2Ca1Cu2O8 + delta

    Science.gov (United States)

    Finnemore, D. K.; Xu, Ming; Kouzoudis, D.; Bloomer, T.; Kramer, M. J.; McKernan, Stuart; Balachandran, U.; Haldar, Pradeep

    1996-01-01

    In the growth of Bi2Sr2Ca2Cu3O10+δ from mixed powders of Pb-doped Bi2Sr2Ca1Cu2O8+δ and other oxides, it has been discovered that a dense array of hillocks or mesas grow at the interface between a Ag overlay and Pb-doped Bi2Sr2Ca1Cu2O8+δ grains during the ramp up to the reaction temperature. As viewed in an environmental scanning electron microscope, the Ag coated grains develop a texture that looks like ``chicken pox'' growing on the grains at about 700 °C. These hillocks are about 100 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurements indicate that the hillocks are a recrystallization of (Bi,Pb)2Sr2Ca1Cu2O8+δ, and are definitely not a Pb rich phase.

  20. Penta-substituted benzimidazoles as potent antagonists of the calcium-sensing receptor (CaSR-antagonists).

    Science.gov (United States)

    Gerspacher, Marc; Altmann, Eva; Beerli, René; Buhl, Thomas; Endres, Ralf; Gamse, Rainer; Kameni-Tcheudji, Jacques; Kneissel, Michaela; Krawinkler, Karl Heinz; Missbach, Martin; Schmidt, Alfred; Seuwen, Klaus; Weiler, Sven; Widler, Leo

    2010-09-01

    A series of novel benzimidazole derivatives has been designed via a scaffold morphing approach based on known calcilytics chemotypes. Subsequent lead optimisation led to the discovery of penta-substituted benzimidazoles that exhibit attractive in vitro and in vivo calcium-sensing receptor (CaSR) inhibitory profiles. In addition, synthesis and structure-activity relationship data are provided.

  1. Millimeter wave inducing subharmonic steps in the Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} thin film bicrystal Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X.; Hu, L.; Xie, W. [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Wang, P. [Beijing Institute of Radio Measurement, Beijing 100854 (China); Ma, L.J.; Zhao, X.J.; He, M. [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Zhang, X., E-mail: nkzhangxu@nankai.edu.cn [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Ji, L. [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China)

    2015-04-15

    Highlights: • We observed the subharmonic steps based on Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (Tl-2212) film which epitaxial grown on bicrystal SrTiO{sub 3} (STO) substrate. • The simulation of the RCLSJ model matched up well with the experimental results. • The dI/dV–V curves highlight the subharmonic steps. - Abstract: The bicrystal Josephson junction (BJJ) was fabricated by patterning microbridge into Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} (Tl-2212) thin film grown epitaxially on the bicrystal SrTiO{sub 3} (STO) substrate. The millimeter wave responses of BJJ were researched by experiment and numerical simulation. Shapiro steps and subharmonic steps were both observed in the current–voltage (I–V) curve at the liquid nitrogen temperature. In the resistive–capacitive–inductive shunted junction (RCLSJ) model, both of the Shapiro steps and subharmonic steps were reproduced with varying capacitances and inductances. The result of simulation has a good agreement with the experiment. The relative large capacitance and inductance correspond to distinct subharmonic steps.

  2. Synthesis and luminescence properties of europium activated Ca3Al2O6-Sr3Al2O6 system

    Institute of Scientific and Technical Information of China (English)

    ZHOU Tianliang; SONG Zhen; BIAN Liu; REN Qingyong; LIU Quanlin

    2012-01-01

    Divalent europium activated tristrontium dialuminum hexaoxide phosphor,(Sr1-xEux)3Al2O6,was obtained by solid state reaction.Crystal structure and luminescence properties of synthesized (Sr1-xEux)3Al2O6 were investigated.The major excitation band of (Sr1-xEux)3Al2O6 located in blue light region,the photoluminescence spectrum showed red light emission peaked at 618 nm which could be attributed to the d-f transition of the Eu2+.The influence of Ca2+ substitution for Sr2+ on structural and luminescence properties of Eu2+ doped Sr3Al2O6 was also studied.The photoluminescence peak position of (Sr1-yCay)2.94Eu0.06Al2O6 varied from 618 to 655 nm with increasing y value.The reason for redshift in the emission band of (Sr1-yCay)2.94Eu0.06Al2O6 phosphor was also discussed.

  3. Structural characterisation of BaTiO3 thin films deposited on SrRuO3/YSZ buffered silicon substrates and silicon microcantilevers

    OpenAIRE

    Colder, Héloïse; Domengès, B.; Jorel, Corentin; Marie, P.; Boisserie, M.; Guillon, Samuel; Nicu, Liviu; Galdi, Alice; Mechin, Laurence

    2014-01-01

    We report on the progress towards an all epitaxial oxide layer technology on silicon substrates for epitaxial piezoelectric microelectromechanical systems. (101)-oriented epitaxial tetragonal BaTiO3 (BTO) thin films were deposited at two different oxygen pressures, 5.10 2 mbar and 5.10 3 mbar, on SrRuO3/Yttria-stabilized zirconia (YSZ) buffered silicon substrates by pulsed laser deposition. The YSZ layer full (001) orientation allowed the further growth of a fully (110)-oriented conductive Sr...

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

    Science.gov (United States)

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

    1994-03-01

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

  5. New perovskite-related oxides having high dielectric constant: Ln2Ba2CaZn2Ti3O14 (Ln = La and Pr)

    Indian Academy of Sciences (India)

    Pika Jha; Ashok K Ganguli

    2003-10-01

    Two new oxides, La2Ba2CaZn2Ti3O14 and Pr2Ba2CaZn2Ti3O14, have been synthesized by the ceramic route at 1100°C. These oxides crystallize in the disordered cubic structure with an `a’ lattice parameter of 3.9728 (2) and 3.9448 (5) respectively. These oxides show high dielectric constant (70 and 57) and low loss (0.003 and 0.013 at 100 kHz) for La2Ba2CaZn2Ti)3O14 and Pr2Ba2CaZn2Ti3O14 respectively. The dielectric constant is highly stable with frequency and temperature.

  6. Influence of cetyltrimethylammonium bromide on the morphology of AWO{sub 4} (A = Ca, Sr) prepared by cyclic microwave irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Thongtem, Titipun [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)], E-mail: ttpthongtem@yahoo.com; Kaowphong, Sulawan; Thongtem, Somchai [Department of Physics, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2008-09-30

    AWO{sub 4} (A = Ca, Sr) was prepared from metal salts [Ca(NO{sub 3}){sub 2}.4H{sub 2}O or Sr(NO{sub 3}){sub 2}], Na{sub 2}WO{sub 4}.2H{sub 2}O and different moles of cetyltrimethylammonium bromide (CTAB) in water by cyclic microwave irradiation. The structure of AWO{sub 4} was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the presence of nanoparticles in clusters with different morphologies; spheres, peaches with notches, dumb-bells and bundles, influenced by CTAB. Six Raman vibrational peaks of scheelite structure were detected at 908, 835, 793, 399, 332 and 210 cm{sup -1} for CaWO{sub 4} and 917, 833, 795, 372, 336 and 192 cm{sup -1} for SrWO{sub 4}, which are assigned as {nu}{sub 1}(A{sub g}), {nu}{sub 3}(B{sub g}), {nu}{sub 3}(E{sub g}), {nu}{sub 4}(B{sub g}), {nu}{sub 2}(A{sub g}) and {nu}{sub f.r.}(A{sub g}), respectively. Fourier transform infrared (FTIR) spectra provided the evidence of W-O stretching vibration in [WO{sub 4}]{sup 2-} tetrahedrons at 793 cm{sup -1} for CaWO{sub 4} and 807 cm{sup -1} for SrWO{sub 4}. The peaks of photoluminescence (PL) spectra were at 428-434 nm for CaWO{sub 4}, and 447-451 nm for SrWO{sub 4}.

  7. Magnetoresistance and noise of electric transportation in ceramics samples of (Bi-Pb)2 Sr2 Ca2 Cu3 O10+delta

    International Nuclear Information System (INIS)

    In the work is a study of the influence of the structure on the magnetoresistance and the noise of electric transport (measured via transportation) granular polycrystalline superconducting (Bi-Pb)2 Sr2 Ca2 Cu3 O10+delta. The samples were obtained for different pressures of uniaxial compaction in the range of 100 to 250 MPa. A comparative analysis of the diffraction patterns of X-rays carried out a sample in the form of powder and ceramic samples obtained at different compaction pressures shows that all have a similar chemical composition. The values of the parameters a, b and c of the unit cell are similar in all cases. In addition, found that the increase in uniaxial compaction pressure improves alignment of grains, preferably with axis parallel to the direction of compaction c. To show the influence of variations in structure granular on the transport properties of the material were carried out measurements of magnetoresistance, R (Ba). These curves adjustment was carried out within the framework of the flow trapped immunoregulating model, this polycrystalline material was considered as an arrangement series - parallel of Josephson devices. The results reveal differences in dependency (R) (Ba) measured in samples obtained at different compaction pressures. These differences are reproduced in the model by varying the parameters of the distribution of beads border angles. At the same time, changes in dependence on R (Ba) are reflected in the noise of transport, which is defined as the sudden redeployment of local electrical currents in arrangement with the increase of the applied magnetic field. Analysis of the noise of transport proves to be a technique suitable for the study of the microstructural for being sensitive to minor changes changes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Hakikat, E-mail: sharmahakikat@yahoo.in; Arya, G. S.; Pramar, Kusum; Negi, N. S. [Department of physics Himachal Pradesh University, Shimla (H. P.) India (India)

    2015-05-15

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

  9. Formation and electrical characterization of Ti-modified Sr0.3Ba0.7Nb2O6 ceramic system

    International Nuclear Information System (INIS)

    Titanium modified Sr0.3Ba0.7Nb2O6 ceramic system has been studied in a wide range of compositions. As the sintering temperature exceeds the 1250 deg. C, the substitution of niobium by titanium induces liquid phase formation, which enhances the densities of the samples with compositions in the monophasic range. X-ray diffraction analysis shows a linear titanium incorporation into the Sr0.3Ba0.7Nb2-yTi yO6-y/2 system up to a solubility limit 0.07 m r 420) of the sample with a titanium content of 0.07 are two times higher than the reported for the SBN (30/70) system

  10. (Cu,Tl)Ba2Ca3Cu4Ox compositions: II. Heating rate applied to synthesis of superconducting ceramics

    International Nuclear Information System (INIS)

    Superconducting samples with a starting composition Cu0.5TlxBa2Ca3Cu4O12 (x=1-0.35) were prepared in Au tubes from oxides by using different heating rates. The optimum heating rate was 0.11 deg. C min-1 applied between 860 and 880 deg. C. These samples show the highest content of 1234 phase and the lowest of Ba-Cu-O phases as well as the highest critical temperatures. The highest values were Tc=119.2 K and Tc0=115.1 K. All samples show Jc values around 6x105 A cm-2, at 60 K and 0.5 T. In the rest of the samples, heated by using lower or higher heating rates, a high concentration of 1223 and/or 1245 phases is detected. The content of the 1234 phase and of Ba(Ca,Tl)-Cu-O residual liquid phase, in the samples synthesized for the optimum heating rate, depends on the Tl content in the starting mixture. The influence of the oxygen content in the starting mixture on phase composition is not as strong as of Tl, but it has a major role in establishing the superconducting behaviour of the 1234 grains. Some arguments that suggest the dependence of the transport properties of the non-superconducting matrix on oxygen content will be discussed. In our technological arrangement the determined optimum heating rate can be applied to the synthesis of other single-layered superconducting phases, e.g. 1212 phase from a Cu0.25Tl0.75Ba2CaCu2O8.115 starting composition. (author)

  11. Surface modifications of BaF2 and CaF2 single crystals by slow highly charged ions

    International Nuclear Information System (INIS)

    Highlights: • The 1st observation of surface nanostructures induced by irradiation of BaF2 surface with highly charged ions (HCI) at higher potential energy is shown. • Evidence for the significance of the deposited potential energy in the creation of surface hillocks in BaF2 is confirmed. • The existence of potential energy threshold for the creation of surface etch pits in CaF2 is shown. • Similarities and differences for the creation of HCI-induced nanohillocks and etch pits in CaF2 and BaF2 of the same crystalline structure are discussed. • We compare the results with modifications induced by swift heavy ions. - Abstract: Ion-irradiation of solid surfaces is considered as one of the promising and powerful techniques for material nanostructuring. Recently, slow highly charged ions (HCI) have shown their potential in creating surface nanostructures in various solids. Here, we focus on the surface modifications of BaF2 and CaF2 single crystals by HCI. Despite the fact that both materials belong to alkaline-earth fluorides with the same crystalline structure, they exhibit different sensitivity for HCI-induced nanostructure. We discuss similarities and differences for the creation of HCI-induced nanohillocks and etch pits in both materials and their dependence on potential and kinetic energy deposition. Furthermore, we compare the results with modifications induced by swift heavy ions (SHI), in order to reach a better understanding of the mechanisms responsible for the creation of nanostructures in ionic fluoride single crystals

  12. Anisotropic s-wave superconductivity in graphite intercalation compounds: CaC{sub 6} and SrC{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun Sung; Boeri, Lilia; Kremer, Reinhard [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Razavi, Feridoon [Department of Physics, Brock University, St. Catharines, Ontario, L2S 3A1 (Canada)

    2008-07-01

    We have investigated the anisotropy of the superconducting properties for newly-discovered superconducting graphite intercalation compounds, CaC{sub 6} and SrC{sub 6} using specific heat (C{sub p}). The electronic C{sub p} for CaC{sub 6} shows an exponential temperature dependence at low temperatures, consistent with a fully gapped s-wave superconducting order parameter. However, the detailed comparison with an isotropic superconducting gap model shows significant deviation between experiment and theory. From the magnetic field dependence of C{sub p}, the anisotropy of upper critical fields (H{sub c2}) for CaC{sub 6} is {proportional_to}5, consistent with that obtained from the magnetic field dependence of Sommerfeld coefficient, but much larger than that of SrC{sub 6}. In comparison with electronic structure calculations, we found that the isotropic gap model cannot explain observed superconducting properties, suggesting significant anisotropy in the superconducting gap for both CaC{sub 6} and SrC{sub 6}. Recent investigations on a directional point-contact spectroscopy on CaC{sub 6} along the c-axis and ab-plane are also discussed.

  13. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF2/Alq3

    Science.gov (United States)

    Kim, Tae Gun; Lee, Hyunbok; Yi, Yeonjin; Lee, Seung Mi; Kim, Jeong Won

    2015-07-01

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq3 [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF2/Alq3 are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF2 interlayer initially prevents direct contact between Alq3 and the reactive Ca metal, but it is dissociated into Ba and CaF2 by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq3. This series of chemical reactions takes place irrespective of the BaF2 buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq3 generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq3, forming new occupied states below the Fermi level.

  14. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF{sub 2}/Alq{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Gun; Kim, Jeong Won, E-mail: jeongwonk@kriss.re.kr [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of); Korea University of Science and Technology (UST), 206 Gajeong-ro, Daejeon 305-350 (Korea, Republic of); Lee, Hyunbok [Department of Physics, Kangwon National University, 1 Gangwondaehak-gil, Chuncheon-si, Gangwon-do 200-701 (Korea, Republic of); Yi, Yeonjin [Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemoon-Gu, Seoul 120-749 (Korea, Republic of); Lee, Seung Mi [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of)

    2015-07-14

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq{sub 3} [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF{sub 2}/Alq{sub 3} are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF{sub 2} interlayer initially prevents direct contact between Alq{sub 3} and the reactive Ca metal, but it is dissociated into Ba and CaF{sub 2} by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq{sub 3}. This series of chemical reactions takes place irrespective of the BaF{sub 2} buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq{sub 3} generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq{sub 3}, forming new occupied states below the Fermi level.

  15. Dielectric properties and microstructure of nano-MgO dispersed Ba0.3Sr0.7TiO3 thin films prepared by sputter deposition

    International Nuclear Information System (INIS)

    In this study, thin films prepared from the targets of Ba0.3Sr0.7TiO3 (BST), BST/5 mol % MgO, BST/10 mol % MgO, and BST/20 mol % MgO composites, using radio frequency magnetron sputtering, have been reported. As-deposited films were found to be amorphous and began to crystallize after annealing at temperatures of 650 deg. C and above. The addition of MgO in the BST films resulted in the hindrance of crystallization and inhibition of grain growth. MgO was substituted into the BST lattices to a certain degree. High-resolution transmission electron microscopy results revealed some MgO dispersed in the BST matrix. The MgO dispersed in the dense BST matrix was found to be around 25 nm in size. The dielectric constant was estimated to be 90 for the pure BST film annealed at 700 deg. C, and observed to be slightly reduced with the MgO addition. The dielectric losses of the Ba0.3Sr0.7TiO3 (0.006) and BST/MgO films (0.002-0.004) were much less than those of the Ba0.6Sr0.4TiO3(0.013) and Ba0.7Sr0.3TiO3 films (0.11-0.13). The leakage current was smaller for the BST/10 mol % MgO film compared to the pure BST film and this low leakage current may be attributed to the substitution of Mg in the B sites of BST lattices which might have behaved as an electron acceptors

  16. 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)

    Two new energetic compounds, [M(BTE)(H2O)5]n (M=Sr(1), Ba(2)) [H2BTE=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 Sr2(H2O)10/Ba2(H2O)10 SBUs linked up by two independent binding modes of H2BTE, 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 Sr2(H2O)10/Ba2(H2O)10 SBUs and two independent binding modes of H2BTE 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 Sr2(H2O)10/Ba2(H2O)10 SBUs and two distinct H2BTE coordination modes.→ The dehydrated products of the compounds possess good thermostability and significant catalytic effects on thermal decomposition of AP.

  17. Cristalização de vidros InF3-SrF2 e InF3-BaF2

    OpenAIRE

    Diniz, R. E. O.; Ribeiro, Sidney J.L.; Messaddeq, Younes; Aegerter, Michel A.

    1994-01-01

    - Crystallization process of binary fluoride glasses InF3-SrF2 and InF3-BaF2 has been studied. From DSC scans we obtained the characteristics temperatures and the kinetics parameters E (activation energy) and n (Avrami exponent). Stability against devitrification is discussed in terms of structural modification with different compositions. Crystalline phases obtained from heat treatments have been studied by x-ray diffraction.

  18. Sol–gel synthesis, characterization and luminescent properties of Tb{sup 3+} doped MLa{sub 2}O{sub 4} (M = Sr or Ba) nanophosphors

    Energy Technology Data Exchange (ETDEWEB)

    Sonika [Maharshi Dayanand University, Rohtak 124001 (India); Han, Sang-Do [Korea Institute of Energy Research (KIER), P.O. Box 103, Yuseong, Daejeon (Korea, Republic of); Khatkar, S.P.; Kumar, Mukesh [Maharshi Dayanand University, Rohtak 124001 (India); Taxak, V.B., E-mail: v_taxak@yahoo.com [Maharshi Dayanand University, Rohtak 124001 (India)

    2013-12-01

    Highlights: • Tb{sup 3+} doped MLa{sub 2}O{sub 4} (M = Sr or Ba) nanophosphors have been synthesized first time by tartaric acid assisted sol–gel synthesis. • Synthesis process being in solution phase provide homogenous product. • The process is simple, versatile and saves time as well as energy, so it is affordable. • The nanophosphors have been characterized by XRD, SEM, TEM and PL, i.e. emission and excitation spectra. • The nanophosphors emit characteristic green color due to Tb{sup 3+} ions on excitation under UV. -- Abstract: Tb{sup 3+} doped SrLa{sub 2}O{sub 4} and BaLa{sub 2}O{sub 4} nanophosphors were successfully synthesized via tartaric acid assisted sol–gel method and their luminescent properties were investigated. The crystal structure and morphology of SrLa{sub 2}O{sub 4}:Tb{sup 3+} and BaLa{sub 2}O{sub 4}:Tb{sup 3+} was studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Thermal decomposition behavior of the dried gels was investigated by thermogravimetry (TG) and differential thermal analysis (TGA). Photoluminescence (PL) behaviors of these nanophosphors were checked by the excitation and emission spectra. These SrLa{sub 2}O{sub 4} and BaLa{sub 2}O{sub 4} nanophosphors displayed green color under a UV source due to characteristic transition of Tb{sup 3+} from {sup 5}D{sub 4} → {sup 7}F{sub 5} at 544 nm. The dependence of photoluminescence intensity on Tb{sup 3+} ion concentration, tartaric acid concentration and annealing temperature were also studied in detail. In addition, the optimum doping concentration and time-resolved luminescence spectroscopy were also investigated.

  19. Photoluminescence properties of M{sub 2}Mg(BO{sub 3}){sub 2}:Sm{sup 3+} (M:Sr and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    PEKGOeZLUe, Ilhan, E-mail: pekgozluilhan@yahoo.com [Bartin University, Faculty of Engineering, Department of Environmental Engineering, Bartin 74100 (Turkey)

    2013-02-15

    M{sub 2}Mg(BO{sub 3}){sub 2}:Sm{sup 3+} (M:Sr and Ba) phosphors were synthesized by a solution combustion synthesis method followed by heating of the precursor combustion ash at 900 Degree-Sign C in air. The synthesized materials were characterized by using the powder XRD. The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorometer. Both Sr{sub 2}Mg(BO{sub 3}){sub 2}:Sm{sup 3+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}:Sm{sup 3+} phosphors emit a strong in orange-red region. It was observed that the optimum concentration of Sm{sup 3+} in Sr{sub 2}Mg(BO{sub 3}){sub 2} and Ba{sub 2}Mg(BO{sub 3}){sub 2} are 0.01 and 0.04 mol, respectively. Finally, the relation between the photoluminescence properties of Sm{sup 3+} and host compositions was discussed in detail. - Highlights: Black-Right-Pointing-Pointer It has synthesized two novel inorganic borate phosphors for the first time. Black-Right-Pointing-Pointer The synthesized materials were characterized by using the powder X Ray Diffraction. Black-Right-Pointing-Pointer The photoluminescence properties of both phosphors were investigated using a spectrofluorometer. Black-Right-Pointing-Pointer Both Sr{sub 2}Mg(BO{sub 3}){sub 2}: Sm{sup 3+} and Ba{sub 2}Mg(BO{sub 3}){sub 2}: Sm{sup 3+} phosphors emit a strong in orange-red region.

  20. 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.

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

    Science.gov (United States)

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

    2016-10-01

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

  2. Preparation and characterizations of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} by complex polymerization method (CPM)

    Energy Technology Data Exchange (ETDEWEB)

    Motta, F.V. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil)], E-mail: fabiana@liec.ufscar.br; Marques, A.P.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Escote, M.T. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Melo, D.M.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Ferreira, A.G. [Laboratorio de Ressonancia Magnetica Nuclear, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Longo, E. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Leite, E.R. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Varela, J.A. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil)

    2008-10-06

    Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} (BCT) was prepared by the complex polymerization method (CPM) using Ba{sub 0.8}Ca{sub 0.2}CO{sub 3} and [Ti[OCH(CH{sub 3}){sub 2}]{sub 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{sub 0.8}Ca{sub 0.2}CO{sub 3} used in the synthesis of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} promotes an effective complexation of the ions Ca{sup 2+} in the matrix of BaTiO{sub 3}. After heat treatment for 2 h at 600 deg. C the phase BCT was obtained with absence of the CaTiO{sub 3} or BaCO{sub 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.

  3. 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.

  4. Electrical properties of (Ba, Sr)TiO3 thin films with Pt and ITO electrodes: dielectric and rectifying behaviour

    International Nuclear Information System (INIS)

    The electrical properties of (Ba, Sr)TiO3 (BST) thin films are studied using different combinations of Pt and tin-doped indium oxide (In2O3:Sn, ITO) as electrode material. With Pt as bottom and top electrode the films show insulating behaviour with a low leakage current. A rectifying current-voltage characteristic is obtained by replacing the top electrode with ITO. As shown by photoemission as well as by electrical measurements, the property of the BST/ITO interface depends strongly on the deposition sequence, and can be related to the level of oxidation of the ITO film. Highly doped ITO as top electrode forms an Ohmic contact with BST. This enables the preparation of highly rectifying diodes that exhibit a space-charge-limited current behaviour. Larger barriers are obtained when ITO is used as bottom electrode. This is related to the oxidation of the ITO layer during BST deposition and results in a low interface-limited current. Due to the large energy gaps of both BST and ITO, the combination of these materials provides an additional route to transparent electronics.

  5. Effects of high working pressure on dielectric properties of sputtered (Ba,Sr)TiO3 films on Ir electrodes

    International Nuclear Information System (INIS)

    High working pressure (47 mTorr) was used for rf-sputtered (Ba,Sr)TiO3 (BST) films on Ir bottom electrodes to enhance the in situ formation of IrO2 without postannealing. We verified that oxygen plasma bombardment on the Ir surface during the deposition of BST films was the dominant mechanism for in situ IrO2 formation under the condition of high working pressure. The as-deposited BST film of 100 nm grown at 500 deg. C shows a high dielectric constant of 630 (at 10 kHz); however, the leakage current is relatively large (6x10-5 A/cm2 at 100 kV/cm). The large leakage current results from the rough interface due to the formation of thick IrO2. To reduce leakage current, the double-layer technology was used, in which a thin BST film (5 nm) was first deposited with pure Ar, and followed by the deposition of a thick film (95 nm) with mixture gas (Ar/O2=1). The thin BST layer can significantly reduce the roughness of IrO2, resulting in lower leakage current (4x10-7 A/cm2); however, since the thin BST layer is oxygen deficient, the dielectric constant is reduced to 443

  6. Influence of Composition on Properties of Medium Temperature Sintering (Ba, Sr)TiO3 Series Capacitor Ceramics

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The influence of the composition (Yb2O3, MgO, CeO2, Li2CO3) on the dielectric properties of medium temperature sintering (Ba,Sr)TiO3(BST) series capacitor ceramics was investigated by means of conventional technology process and orthogonal design experiments. The major secondary influencing factors and the influencing tendency of various factor′s levels for the dielectric properties of BST ceramics were obtained. The optimum formula for maximum dielectric constant (ε) and for minimum dielectric loss (tanδ) was obtained under the experimental conditions. The BST ceramics with optimum comprehensive properties was obtained by means of orthogonal design experiments, with the sintering temperature at 1200 ℃, the dielectric constant 5239, the dielectric loss 0.0097, withstand electric voltage over 6 MV·m-1, capacitance temperature changing rate (ΔC/C) -75.67%, and suited for Y5V character. The mechanism of the influence of various components on the dielectric properties of medium temperature sintering BST ceramics was studied, thus providing the basis for preparation of multilayer capacitor ceramics and single-chip capacitor ceramics.

  7. Dielectric Characteristics and Layer Periodic Effects of Ferroelectric Superlattice BaTiO3/SrTiO3

    Institute of Scientific and Technical Information of China (English)

    张建; 尹真; 张明生; 陈万春

    2001-01-01

    A pseudospin-phonon coupled model in double-time Green's function theory has been developed to investi- gate the dielectric susceptibility of the ferroelectric-dielectric superlattice BaTiO3/SrTiO3 (BTO/STO). As the pseudospin-pseudospin and pseudospin-phonon interactions increase, the dielectric susceptibility changes from a narrow shape into the strong and broad shape with the peak shifting to a higher temperature region. With increasing pseudospin-phonon interaction in the BTO layer and at smallpseudospin-pseudospin interaction in BTO layer, the dielectric susceptibility was sensitively adjusted around the transition temperature of strontium titanate, and at large pseudospin-pseudospin interaction in the BTO layer, the dielectric susceptibility was increased in the high-temperature region covering the tetragonal-cubic transition temperature of barium titanate. A critical period of 10/I0 in the BTO/STO superlattice has been obtained, which is in good agreement with the experimental data of 40A, for ten unit cells.

  8. Synchrotron X-ray diffraction study of the Ba{sub 1−x}SrSnO{sub 3} solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Prodjosantoso, Anti K., E-mail: Prodjosantoso@yahoo.com [Jurusan Pendidikan Kimia, UNY Yogyakarta, DIY 55281 (Indonesia); Zhou, Qingdi; Kennedy, Brendan J. [School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia)

    2013-04-15

    At room temperature the sequence of phases with increasing amounts of strontium in the stannate perovskite system Ba{sub 1−x}SrSnO{sub 3} has been established from high resolution synchrotron X-ray powder diffraction. The observed sequence orthorhombic (Pbnm), orthorhombic (Ibmm), tetragonal (I4/mcm), and cubic (Pm3-bar m) is a consequence of the sequential introduction of cooperative tilting of the corner sharing SnO{sub 6} octahedra. The cell volume changes smoothly across the series with no obvious discontinuities associated with the phase transitions. - Graphical abstract: Portions of the synchrotron X-ray diffraction profiles (λ=0.82453 Å) from selected Ba{sub 1−x}Sr{sub x}SnO{sub 3} samples together with the results of fitting by the Rietveld method. Highlights: ► Structures of the stannate perovskites Ba{sub 1−x}SrSnO{sub 3} refined from synchrotron XRD. ► The sequence Pm3-bar m→I4/mcm→Ibmm→Pbnm results from tilting of the octahedra. ► The tilting maintains optimal bonding of the cations seen from the BVS analysis.

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

    Science.gov (United States)

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

    2016-06-01

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

  10. A comparative study on the magnetic and electrical properties of MFe12O19 (M=Ba and Sr)/BiFeO3 nanocomposites

    International Nuclear Information System (INIS)

    M-type hexaferrite (MFe12O19), M=Ba or Sr nanoparticles with hexagonal crystal structure have been successfully synthesized by a citrate auto-combustion method. BiFeO3 (BFO) was prepared by the flash auto-combustion technique. Different nanocomposites were prepared according to the formula [(1−X) MFe12O19+XBiFeO3; M=Ba or Sr, X=0.3, 0.4, 0.5 and 0.6]. The structure and morphology of the obtained nanocomposites have been determined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). From the results, it is observed that the value of saturation magnetization decreases with increasing BFO content, which was mainly due to the contribution of the volume of the weak-magnetic BFO to the total sample volume. - Highlights: • M-type nanohexaferrite (MFe12O19) as M=Ba and Sr powders were synthesized by the citrate autocombustion method. • The lattice parameters of composite were negligibly smaller than those of M-type. • FESEM showed that the samples were hexagonal plate-like shape. • Ms, Mr, μeff. and HC were improved to be suitable for perpendicular high density recording media. • ε′ increased with BFO ratio which is useful in microwave devices

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

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Jahangeer; Blakely, Colin K.; Bruno, Shaun R. [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Poltavets, Viktor V., E-mail: poltavets@chemistry.msu.edu [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)

    2012-09-15

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

  12. Magnetoelectric coupling at the n-doped interface BaTiO3/SrTcO3 studied from first principles

    International Nuclear Information System (INIS)

    Antiferromagnetically induced magnetoelectric coupling at the interface BaTiO3/SrTcO3, which combines a robust ferroelectric and a stable antiferromagnetic perovskite, is studied from first principles. For the BaO/TcO2-terminated interface, the magnetic order may change from G- to C-type antiferromagnetism upon the electric polarization reversal in the ferroelectric side. By inspecting the two-dimensional band structure and orbital occupation of the Tc 4d-states we conclude that the polarization-dependent charge transfer is responsible for a two-dimensional electron gas at the interface between two insulating perovskites. The case of paraelectric BaTiO3 is also discussed in the context of the effect.

  13. Magnetoelectric coupling at the n-doped interface BaTiO{sub 3}/SrTcO{sub 3} studied from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Borisov, Vladislav; Ostanin, Sergey [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Mertig, Ingrid [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Institut fuer Physik, Martin-Luther-Universitaet Halle-Wittenberg, D-06099 Halle (Germany)

    2013-07-01

    Antiferromagnetically induced magnetoelectric coupling at the interface BaTiO{sub 3}/SrTcO{sub 3}, which combines a robust ferroelectric and a stable antiferromagnetic perovskite, is studied from first principles. For the BaO/TcO{sub 2}-terminated interface, the magnetic order may change from G- to C-type antiferromagnetism upon the electric polarization reversal in the ferroelectric side. By inspecting the two-dimensional band structure and orbital occupation of the Tc 4d-states we conclude that the polarization-dependent charge transfer is responsible for a two-dimensional electron gas at the interface between two insulating perovskites. The case of paraelectric BaTiO{sub 3} is also discussed in the context of the effect.

  14. Influence of Cu-site substitution on La2Ca1Ba2Cu5Oz superconducting system

    Science.gov (United States)

    Bhalodia, J. A.; Mankadia, S. R.; Dalsaniya, S. M.; Gonal, M. R.

    2012-07-01

    We have prepared a series of La2CaBa2Cu5-xCoxOz; x = 0.0, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 (La-2125) compounds by the standard solid state reaction method and characterized for their structural, superconducting, magnetic properties and oxygen content through X-ray diffraction, scanning electron microscopy, d. c. resistivity, magnetic susceptibility and iodometric titration respectively. All the compounds crystallize with the tetragonal LaBa2Cu3Oz type structure, space group P4/mmm. Here the effect of higher Co substitution for Cu in the La2CaBa2Cu5-xCoxOz system has been studied. It is observed that only 2 at. % Co substitution for Cu destroys the superconductivity of the sample. For heavily doped samples (with x >= 0.1) are found non-superconducting presumably because of magnetic pair- breaking effect. These samples do not show superconductivity but are of interest for understanding the interplay between superconductivity and magnetism. Possible reasons for destruction of superconductivity are discussed in this communication.

  15. Raman scattering, magnetization and magnetotransport study of SrFeO3-δ, Sr3Fe2O7-δ and CaFeO3

    International Nuclear Information System (INIS)

    In this thesis we have determined the Raman spectra as well as the magnetization, resistance and magnetoresistance of the compounds SrFeO3-δ, Sr3Fe2O7-δ and CaFeO3 as a function of temperature. We describe the preparation of nearly stoichiometric SrFeO3-δ crystals with δ3.00 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 Sr3Fe2O7. (orig.)

  16. Structural dependence of the photocatalytic properties of double perovskite compounds A2InTaO6 (A = Sr or Ba) doped with nickel.

    Science.gov (United States)

    Lv, Meilin; Wang, Yawei; Lu, Lingwei; Wang, Ruinan; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

    2016-08-01

    The crystal structure of photocatalysts generally plays a pivotal role in controlling their electronic structure as well as catalytic performance. In this work, a series of double perovskite compounds A2InTaO6 (A = Sr or Ba) and their Ni doped counterparts were investigated with the aim of understanding how doping and structural modification will affect their photocatalytic activity. Our results show that Ni doping is effective in improving the optical absorption of these wide band gap semiconductors and accommodating the Sr cation in the A sites leads to severe structural distortion, i.e. the In(Ni)-O-Ta bond angle deviates largely from 180°. A better photocatalytic performance was observed for samples with Ni doping and Ba in the A sites. The best photocatalytic hydrogen production rate recorded was ∼293.6 μmol h(-1) for Ba2In0.9Ni0.1TaO6 under full range irradiation, corresponding to an apparent quantum efficiency of 2.75%. DFT calculations reveal the role of Ni doping by forming additional spin-polarized bands inside the intrinsic band gap of the native perovskite. The better photocatalytic activity of Ba2In0.9Ni0.1TaO6 can then be understood as a result of a reduced band gap as well as a linear In(Ni)-O-Ta bond arrangement that is favorable for the strong metal-oxygen-metal interactions. PMID:27427497

  17. Growth of Co-doped (Ba,Sr)TiO 3 single crystals and their characterization

    Science.gov (United States)

    Madeswaran, S.; Giridharan, N. V.; Jayavel, R.; Subramanian, C.

    2002-04-01

    Single crystals of Co-doped B 1- xSr xTiO 3 (Co:BST) have been grown by high-temperature solution growth technique. The dopant has significant effect on the growth parameters and considerably reduced the twin formation in the grown crystal. Bulk single crystals of dimensions 5×5×4 mm 3 have been grown with optimized growth parameters. Layer growth and vein-like structure patterns, indicative of 2D nucleation mechanism, have been observed on the grown crystals. The presence of dopant in the grown crystals was confirmed by EDX analysis. For lower doping concentration (0.1 mol%), the crystal possesses tetragonal structure and changes to cubic for higher dopant level (1 and 5 mol%) Co doping in BST increases the dielectric constant values and decreases the Curie temperature ( Tc). The spontaneous polarization ( Ps) value for 0.1 mol% of Co-doped BST crystal is measured to be 22 μc/cm 2 and the value decreases with increasing Co concentration.

  18. Phonons and stability of infinite-layer iron oxides SrFeO2 and CaFeO2

    Science.gov (United States)

    Gupta, M. K.; Mittal, R.; Chaplot, S. L.; Tassel, Cédric; Kageyama, Hiroshi; Tomiyasu, K.; Taylor, Jon

    2016-09-01

    We present detailed ab-initio lattice dynamical analysis of the Fe-O infinite-layer compounds CaFeO2 and SrFeO2 in various magnetic configurations. These indicate strong spin-phonon coupling in SrFeO2 in contrast to that in case of CaFeO2. From our ab-initio calculations in SrFeO2 as a function of volume, we suggest that the distortion in SrFeO2 above 300 K is similar to that in CaFeO2 at ambient conditions. The distortion of the planer structure of CaFeO2 involves doubling of the planer unit cell that may be usually expected to be due to a soft phonon mode at the M-point (1/2 1/2 0). However, our ab-initio calculations show quite unusually that all the M-point (1/2 1/2 0) phonons are stable, but two stable M3+ and M2- modes anharmonically couple with an unstable Bu mode at the zone center and lead to the cell doubling and the distorted structure. Magnetic exchange interactions in both the compounds have been computed on the basis of the ideal planar structure (P4/mmm space group) and with increasing amplitude of the Bu phonon mode. These reveal that the magnetic exchange interactions reduce significantly with increasing distortion. We have extended the ab-initio phonon calculation to high pressures, which reveal that, above 20 GPa of pressure, the undistorted planer CaFeO2 becomes dynamically stable. We also report computed phonon spectra in SrFeO3 that has a cubic structure, which is useful to understand the role of the difference in geometry of oxygen atoms around the Fe atom with respect to planer SrFeO2. Finally, powder neutron inelastic scattering experiments on SrFeO2 have also been performed at temperatures from 5 K to 353 K in the antiferromagnetic phase. The 5-K data are compared to the ab-initio calculations.

  19. Growth of Bi2Sr2CaCu2O8+δ thin films with enhanced superconducting properties by incorporating CaIrO3 nanoparticles

    Science.gov (United States)

    De Vero, J. C.; Hwang, I.; Santiago, A. C. L.; Chang, J.; Kim, J.; Sarmago, R. V.; Song, J. H.

    2014-04-01

    We synthesized Bi2Sr2CaCu2O8+δ (Bi-2212) thin films with incorporated CaIrO3 (Ca-iridate) nanoparticles, by using pulsed laser deposition and post-growth ex situ annealing. We found that the density of incorporated Ca-iridate strongly affected the superconducting properties and microstructure of the Bi-2212 thin films. Incorporating a low density of Ca-iridate (450 laser pulses) in the Bi-2212 improved its superconducting properties (Tc-onset = 97 K, Tc-zero = 84 K) over those of pure Bi-2212 (Tc-onset = 94 K, Tc-zero = 80 K). However, incorporating a higher density (1800 pulses) significantly reduced Tc-zero to ≈ 57 K. Incorporating a low density of Ca-iridate also decreased the c-axis lattice constant. Films with incorporated Ca-iridate exhibited greater critical current density, Jc(B), than the pure Bi-2212 film. These results indicate that incorporating low densities of Ca-iridate nanoparticles into Bi-2212 can improve its superconducting properties.

  20. PHOTOELECTRIC PROPERTIES OF PbSe/BaF2/CaF2 FILMS ON Si(111)%硅基PbSe/BaF2/CaF2薄膜及其光电特性

    Institute of Scientific and Technical Information of China (English)

    金进生; 常勇; 等

    2001-01-01

    PbSe films were grown on Si(111) by incorporation of BaF2/CaF2 buffers using molecular beam epitaxy. The measurements of both scanning electronic microscopy and high-resolution X-ray diffraction showed high crystalline quality of the PbSe films. The surface of PbSe was mirror-like and no cracks were observed. The full width at half-maximum of PbSe diffraction peak was only 153 arcsec. The epitaxial PbSe films were used to fabricate photodiodes. For the first time, metallic aluminum was used to form Al-PbSe Schottky diodes, which demonstrated better and more stable current-voltage characteristics than that obtained from Pb-PbSe Schottky diodes.%采用分子束外延方法在Si(111)衬底上生长了PbSe/BaF2/CaF2薄膜,扫描电镜和X-光衍射分析显示,通过生长BaF2/CaF2缓冲层的方法,在Si(111)衬底上外延的PbSe薄膜晶体质量高,PbSe表面光亮,无开裂现象发生,X-光衍射峰峰宽窄(153arcs).外延生长的PbSe薄膜被应用于制作光电二极管,首次采用热蒸发金属铝膜在PbSe表面形成Al-PbSe肖特基结光电二极管,获得了比Pb-PbSe肖特基结更为稳定和理想的电流-电压特性曲线.

  1. Ruthenate-ferrites AMRu{sub 5}O{sub 11} (A = Sr, Ba; M = Ni, Zn). Distortion of kagome nets via metal-metal bonding

    Energy Technology Data Exchange (ETDEWEB)

    Shlyk, Larysa; Strobel, Sabine; Niewa, Rainer [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie; Schleid, Thomas

    2012-11-01

    Crystals of the three novel oxorhutenates SrNiRu{sub 5}O{sub 11} (a = 11.7374(2) Aa, c = 13.2088(4) Aa), SrZnRu{sub 5}O{sub 11} (a = 11.7271(2) Aa, c = 13.4246(4) Aa), and Sr{sub 0.63(1)}Ba{sub 0.37}ZnRu{sub 5}O{sub 11} (a = 11.7245(4) Aa, 13.5268(4)) were obtained applying a flux-growth technique. A superstructure of the R-type ferrite crystal structure with doubled hexagonal a-axis (space group P6{sub 3}/m, Z = 8) originates from Ru-Ru pair formation within the kagome nets extending in (001). No indication for an intermixing of 3d metals at the Ru sites was observed. (orig.)

  2. Structural and superconducting properties of LaCaBaCu{sub 3}O{sub 7-5} system: A neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Awana, V.P.S.; Green, T.J.; Moss, S.; Dou, S.X. [Wollongong Univ., NSW (Australia); Malik, S.K. [Tata Institute of Fundamental Research, Bombay, (India); Yelon, W.B. [Missouri Univ., Columbia, MO (United States). Research Reactor Facility

    1998-06-01

    The results on structural aspects and superconductivity of LaBaCaCu{sub 3}O{sub 7}, (La: 1113) are reported. Both X-ray and neutron diffraction studies reveal that the La:1113 compound crystallises in P4/mmm tetragonal structure. Detailed Rietveld analysis of the neutron diffraction patterns reveals that in this compound the La, Ca and Ba sites are intermixed with each other. Nearly 46% of Ca occupies the usual La-site, while the remaining 54% stays at the Ba-site. In stoichiometric La:1113 compound, a corresponding amount of La substitutes at the Ba-site. These occupancy refinements explain the tetragonal structure of the compound, despite having an oxygen content close to 7.04. The compound studied presently shows a T{sub c} of 68K. (authors). 9 refs., 2 tabs., 2 figs.

  3. NUMERICAL SIMULATION OF MECHANICAL BEHAVIORS OF SUPERCONDUCTING POWDER BSCCO (BiSrCaCuO)

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yinghong; LEI Liping; ZENG Pan

    2007-01-01

    An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO (BiSrCaCuO) aggregate are studied systematically. The equivalent continuum model idealizes the aggregation of the powder as an equivalent continuum material. The powder aggregate yielding is caused by not only the deviatoric stress but also the hydrostatic stress and the modified Drucker-Prager/Cap model is adopted to describe the mechanical behaviors of BSCCO powder aggregate in continuum method. The deformable discrete model is known as a direct model, which considers the discrete nature of the powder particles. Its framework encompasses the local behaviors between the particles, such as particles contact, sliding and rolling. Based on commercial finite element software ABAQUS, the equivalent continuum model and the deformable discrete model are used to simulate the confined compression of superconducting powder BSCCO, and the numerical results show agreement with experimental results, which verify the correctness of these built models. Compared with the equivalent continuum model based on macroscopic statistics method, the deformable discrete model can present the microscopic information during processing and can describe the nature of mechanical behaviors of superconducting powder BSCCO. But from an industrial viewpoint, the equivalent continuum model has a definitive edge over the microscopic models in that the gross behavior of the powder mass can be modeled and simulated on an industrial scale.

  4. Electrical and magnetic properties of variously annealed Bi(Pb)-Sr-Ca-Cu-O thick films

    International Nuclear Information System (INIS)

    Superconducting thick films with the nominal composition of Bi1.9Pb0.4Sr1.9Ca2.1Cu3.2O10 were prepared by the screen-printing method, using an oxalate synthesis for making the paste, and different heat treatments for final samples. A large difference in the structural and superconducting properties between the unmelted and melted samples, and small deviations between the melted and variously annealed specimens were observed. In the first case, the structure is determined by randomly distributed small microcrystals, while in the second, by highly orientated big ones, which results in dissimilar electrical and magnetic features. Therefore the magnetic moment and superconducting material ratio are bigger in the unmelted samples, but in the melted ones, the superconductivity can be characterized by much higher electrical and magnetic parameters. In particular, the transport critical current has conspicuously greater values in the melted as compared to the unmelted samples. In some melted specimens a hyperdiamagnetic signal has been found up to 242 K, induced by the fine details of the preparation technique. The simplest possible reason for this is the diamagnetic Cu-O content in the samples. (orig.)

  5. Experimental determination of the partition coefficient for Ba in Neogloboquadrina dutertrei suggests calcification occurs in a Ba-enriched microenvironment

    Science.gov (United States)

    Fehrenbacher, J. S.; Russell, A. D.; Davis, C. V.; Spero, H. J.; Chu, E.

    2015-12-01

    The Ba/Ca ratio in several spinose planktic foraminifer species varies as a function of the Ba/Ca concentration of seawater and is not affected by other parameters such as the seawater salinity, temperature and pH (Honisch et al., 2011). Since seawater Ba concentration is linearly related to Ba in nearshore environments, Ba/Ca ratios in spinose species shows promise as an indicator of past changes in monsoon strength and river runoff (e. g. Weldeab et al. 2007). In contrast, the non-spinose foraminifers often have intrashell variability in Ba/Ca, with Ba/Ca ratios much higher than expected for the range of Ba concentrations observed in the ocean. Furthermore, the Ba/Ca ratio can vary by over a factor of 10 within a single specimen. This suggests either 1) the partition coefficient for Ba in non-spinose species differs from that determined for spinose species, or 2) non-spinose species calcify in a micro-environment that is enriched in Ba. We conducted experiments on live specimens to determine the partition coefficient for Ba in the non-spinose foraminifer N. dutertrei. Specimens were collected via plankton net from the Southern California Bight and cultured at the Wrigley Marine Science Center, Santa Catalina Island during the summer of 2013-2015. We use isotopically labeled seawater (87Sr) to identify discrete portions of calcite that grew in culture. We use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for trace element analyses and to identify ocean grown vs. culture grown calcite. We show that the partition coefficient is similar to the spinose species: N. dutertrei incorporates Ba as a function of seawater chemistry. We conclude from these observations that N. dutertrei forms its calcite from fluids enriched in Ba, and hypothesize that this process occurs via attachment to organic-rich particles such as marine snow.

  6. 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 ...

  7. The effect of skeletal mass accumulation in Porites on coral Sr/Ca and δ18O paleothermometry

    Science.gov (United States)

    Gagan, Michael K.; Dunbar, Gavin B.; Suzuki, Atsushi

    2012-03-01

    Paleotemperature estimates based on coral Sr/Ca have not been widely accepted because the reconstructed glacial-Holocene shift in tropical sea-surface temperature (˜4-6°C) is larger than that indicated by foraminiferal Mg/Ca (˜2-4°C). We show that corals over-estimate changes in sea-surface temperature (SST) because their records are attenuated during skeletogenesis within the living tissue layer. To quantify this process, we microprofiled skeletal mass accumulation within the tissue layer of Porites from Australasian coral reefs and laboratory culturing experiments. The results show that the sensitivity of the Sr/Ca and δ18O thermometers in Porites will be suppressed, variable, and dependent on the relationship between skeletal growth rate and mass accumulation within the tissue layer. Our findings help explain why δ18O-SST sensitivities for Porites range from -0.08‰/°C to -0.22‰/°C and are always less than the value of -0.23‰/°C established for biogenic aragonite. Based on this observation, we recalibrated the coral Sr/Ca thermometer to determine a revised sensitivity of -0.084 mmol/mol/°C. After rescaling, most of the published Sr/Ca-SST estimates for the Indo-Pacific region for the last ˜14,000 years (-7°C to +2°C relative to modern) fall within the 95% confidence envelope of the foraminiferal Mg/Ca-SST records. We conclude that two types of calibration scales are required for coral paleothermometry; an attenuated Porites-specific thermometer sensitivity for studies of seasonal to interannual change in SST and, importantly, the rescaled -0.084 mmol/mol/°C Sr/Ca sensitivity for studies of 20th-century trends and millennial-scale changes in mean SST. The calibration-scaling concept will apply to the development of transfer functions for all geochemical tracers in corals.

  8. 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.

  9. Structural and dielectric behavior of pulsed laser ablated Sr 0.6Ca 0.4TiO 3 thin film and asymmetric multilayer of SrTiO 3 and CaTiO 3

    Science.gov (United States)

    Chakraborty, Pradip; Choudhury, Palash Roy; Krupanidhi, S. B.

    2011-12-01

    Homogeneous thin films of Sr 0.6Ca 0.4TiO 3 (SCT40) and asymmetric multilayer of SrTiO 3 (STO) and CaTiO 3 (CTO) were fabricated on Pt/Ti/SiO 2/Si substrates by using pulsed laser deposition technique. The electrical behavior of films was observed within a temperature range of 153 K-373 K. A feeble dielectric peak of SCT40 thin film at 273 K is justified as paraelectric to antiferroelectric phase transition. Moreover, the Curie-Weiss temperature, determined from the ɛ'( T) data above the transition temperature is found to be negative. Using Landau theory, the negative Curie-Weiss temperature is interpreted in terms of an antiferroelectric transition. The asymmetric multilayer exhibits a broad dielectric peak at 273 K, and is attributed to interdiffusion at several interfaces of multilayer. The average dielectric constants for homogeneous Sr 0.6Ca 0.4TiO 3 films (˜650) and asymmetric multilayered films (˜350) at room temperature are recognized as a consequence of grain size effect. Small frequency dispersion in the real part of the dielectric constants and relatively low dielectric losses for both cases ensure high quality of the films applicable for next generation integrated devices.

  10. Inelastic neutron scattering and lattice dynamics of NaNbO3 and Sr0.70Ca0.30TiO3

    Indian Academy of Sciences (India)

    S K Mishra; R Mittal; N Choudhury; S L Chaplot; D Pandey

    2008-11-01

    NaNbO3 and (Sr,Ca)TiO3 exhibit an unusual complex sequence of temperature- and pressure-driven structural phase transitions. We have carried out lattice dynamical studies to understand the phonon modes responsible for these phase transitions. Inelastic neutron scattering measurements using powder samples were carried out at the Dhruva reactor, which provide the phonon density of states. Lattice dynamical models have been developed for SrTiO3 and CaTiO3 which have been fruitfully employed to study the phonon spectra and vibrational properties of the solid solution (Sr,Ca)TiO3.

  11. Ferroelectric phase transitions studies in 0.5Ba(Zr0.2Ti0.8) O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

    OpenAIRE

    J.P.B. Silva; Queirós, E. C.; Tavares, P. B.; Sekhar, K C; Kamakshi, Koppole; Moreira, J. A.; Almeida, A; Pereira, M.; Gomes, M. J. M.

    2015-01-01

    The ferroelectric phase transitions in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT 50/50) ceramics,fabricatedbyasolidstatereaction,werestudiedbyusing X-Ray diffraction, Raman spectroscopy, and measuring electric polarization, dielectric permittivity and pyroelectric current. Xraydiffraction(XRD)confirmsthecoexistenceoftetragonal(T) andrhombohedral(R)phasesatroomtemperature.Thetemperature dependence of the Raman modes frequency reveals the existenceoftwophasetransitionscorrespondingtotherhom...

  12. Study of the electronic structure and half-metallicity of CaMnO3/BaTiO3 superlattice

    Science.gov (United States)

    Wang, Kai; Jiang, Wei; Chen, Jun-Nan; Huang, Jian-Qi

    2016-09-01

    In this paper, the electronic structure, magnetic properties and half-metallicity of the CaMnO3/BaTiO3 superlattice are investigated by employing the first-principle calculation based on density functional theory within the GGA or GGA + U exchange-correlation functional. The CaMnO3/BaTiO3 superlattice is constructed by the cubic CaMnO3 and the tetragonal ferroelectric BaTiO3 growing alternately along (0 0 1) direction. The cubic CaMnO3 presents a robust half-metallicity and a metastable ferromagnetic phase. Its magnetic moment is an integral number of 3.000 μB per unit cell. However, the CaMnO3/BaTiO3 superlattice has a stable ferromagnetic phase, for which the magnetic moment is 12.000 μB per unit cell. It also retains the robust half-metallicity which mainly results from the strong hybridization between Mn and O atoms. The results show that the constructed CaMnO3/BaTiO3 superlattice exhibits superior magnetoelectric properties. It may provide a theoretical reference for the design and preparation of new multiferroic materials.

  13. Radio frequency surface resistance of Tl-Ba-Ca-Cu-O films on metal and single-crystal substrates

    Science.gov (United States)

    Arendt, P. N.; Reeves, G. A.; Elliott, N. E.; Cooke, D. W.; Gray, E. R.; Houlton, R. J.; Brown, D. R.

    1990-01-01

    Films of Tl-Ba-Ca-Cu were dc magnetron sputtered from a single multielement target. The films were deposited onto substrates of: (1) magnesium oxide, (2) a silver based alloy (Consil 995), (3) a nickel based alloy (Haynes 230), and (4) buffer layers of barium fluoride or copper oxide on Consil. To form superconducting phases, post-deposition anneals were made on these films using an alumina crucible with an over pressure of thallium and flowing oxygen. After annealing, the film phases were determined using x-ray diffraction. The film surface resistances (Rs) were measured at 22 GHz in a TE011 cavity.

  14. Neutron diffraction studies on La2-DyCa2Ba2Cu4+2O superconductors

    Indian Academy of Sciences (India)

    S Rayaprol; Rohini Parmar; D G Kuberkar; Keka R Chakraborty; P S R Krishna; M Ramanadham

    2004-08-01

    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 been studied for their structural properties. A tetragonal Y-123 unit cell was taken as the starting model for the Rietveld analysis. All the samples fit into the starting model, with no structural transition taking place with increasing dopant concentration. The results of Rietveld analysis and structural properties will be discussed in detail.

  15. Electron-phonon superconductivity in APt3P (A=Sr, Ca, La) compounds: From weak to strong coupling

    Science.gov (United States)

    Subedi, Alaska; Ortenzi, Luciano; Boeri, Lilia

    2013-04-01

    We study the newly discovered Pt phosphides APt3P (A=Sr, Ca, La) [T. Takayama , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.108.237001 108, 237001 (2012)] using first-principles calculations and Migdal-Eliashberg theory. Given the remarkable agreement with the experiment, we exclude the charge-density wave scenario proposed by previous first-principles calculations, and give conclusive answers concerning the superconducting state in these materials. The pairing increases from La to Ca and Sr due to changes in the electron-phonon matrix elements and low-frequency phonons. Although we find that all three compounds are well described by conventional s-wave superconductivity and spin-orbit coupling of Pt plays a marginal role, we show that it could be possible to tune the structure from centrosymmetric to noncentrosymmetric opening new perspectives towards the understanding of unconventional superconductivity.

  16. 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.

  17. Triadin/Junctin double null mouse reveals a differential role for Triadin and Junctin in anchoring CASQ to the jSR and regulating Ca(2+) homeostasis.

    Science.gov (United States)

    Boncompagni, Simona; Thomas, Monique; Lopez, Jose R; Allen, Paul D; Yuan, Qunying; Kranias, Evangelia G; Franzini-Armstrong, Clara; Perez, Claudio F

    2012-01-01

    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. PMID:22768324

  18. Effect of neutron irradiation on Tc of Pb-doped BiSrCaCuO superconductor

    Science.gov (United States)

    Herr, Young-Hoi; Lee, Kwang-Hee; Kim, Chan-Joong; Lee, Hee-Gyoun; Kim, Chun-Taik

    1989-09-01

    A Pb-doped BiSrCaCuO superconductor was irradiated in a TRIGA MARK III reactor up to a neutron fluence of 7.6 x 10 to the 17th n/sq cm. The measured superconducting transition temperature (Tc) after irradiation was decreased to 92.5 K from nonirradiated data of 102 K. The fractional decrease of the Tc was compared with results for other superconducting materials. Some recovery of irradiation-induced Tc decrease was observed.

  19. Temperature and wavevector dependence of overdoped Bi_2Sr_2CaCu_2O_8+x single crystal samples

    Science.gov (United States)

    Rast, S.; Klohs, A.; Frazer, B. H.; Hirai, Y.; Schmauder, T.; Gatt, R.; Abrecht, M.; Pavuna, D.; Margaritondo, G.; Onellion, M.

    2000-03-01

    We report on measuring the temperature and wavevector change of angle-resolved photoemission spectra for overdoped Bi_2Sr_2CaCu_2O_8+x single crystal samples. Spectra taken from close to to close to were analyzed. The changes of spectral lineshape with temperature and wave vector indicate qualitatively different behavior in different parts of the Brillouin zone and will be analyzed and presented.

  20. Temperature-dependent photoemission features for overdoped Bi2Sr2CaCu2O8 + x cuprates

    Science.gov (United States)

    Rast, S.; Frazer, B. H.; Onellion, M.; Schmauder, T.; Abrecht, M.; Touzelet, O.; Berger, H.; Margaritondo, G.; Pavuna, D.

    2000-07-01

    We report temperature-dependent angle-resolved photoemission spectra for overdoped Bi2Sr2CaCu2O8 + x single-crystal samples. The data indicate that there is a special temperature (T+) where the spectral function changes intensity, and where the energy difference between the peak and dip features changes. The data also demonstrate that immediately above the superconducting transition temperature, the system exhibits a non-Lorentzian lineshape. We discuss implications of the data.

  1. Reliable electrical contacts on Bi2Sr2CaCu2O8+x single crystals

    International Nuclear Information System (INIS)

    We investigate the making of reliable electrical contacts on Bi2Sr2CaCu2O8+x single crystals. Numerous silver pastes and the corresponding application procedures do not yield satisfactory results. Although the electrical contacts are initially of low resistance, they deteriorate in time. We present a procedure which overcomes this degradation of the contacts and ensures low-resistance contacts for at least a year, with no sign of possible future departure from the initial quality. (author)

  2. Positron-annihilation 2D-ACAR measurements in Bi2Sr2CaCu2O8+x

    International Nuclear Information System (INIS)

    The authors present a brief account of measurements of the two-dimensional angular correlation of annihilation radiation (2D-ACAR) in a single crystal of approximate composition Bi2Sr2CaCu2O8+x (Tc 85 K) at 6 and 92 K. The most noteworthy result is that the anisotropic part of the spectra displays a fine-structure which is sharpest at the higher of these two temperatures. (author). 17 refs.; 1 fig

  3. Vortex dynamics in a ring-like irradiated Bi2Sr2CaCu2O8 crystal

    International Nuclear Information System (INIS)

    A Bi2Sr2CaCu2O8 crystal selectively irradiated near the edges is studied using a Hall-sensor array. Vortices penetrating into the central Jc = 0 region are open-quotes focusedclose quotes in the center of the sample on increasing the applied field. In decreasing field, vortices leave the center and a large vortex accumulation is observed on the inner rim of the irradiated region. Spatially resolved magnetization measurements confirm the developed theoretical model

  4. The interfacial structures of (Ba, Sr)TiO3 films deposited by radio frequency magnetron sputtering

    International Nuclear Information System (INIS)

    Ba0.6Sr0.4TiO3 (BST) films were deposited on Pt/SiO2/Si substrates by radio frequency magnetron sputtering. The deposited films were crystallized by conventional thermal annealing (CTA) and rapid thermal annealing (RTA). The interfacial structures of BST/Pt were studied. High-resolution transmission electron microscopy (HRTEM) observation shows that there is a transition layer at BST/Pt interface, and the layer is 4-5 nm thick for CTA and 2-3 nm for RTA. X-ray photoelectron spectroscopy (XPS) investigations show that the layer is composed of perovskited BST phase and non-perovskited BST phase. The content of the non-perovskited BST phase is most for CTA, whereas that of the perovskited BST phase is most for RTA. It is found that the transition layer thickens with the increase of annealing temperature, and CTA corresponds to faster thickening rate. XPS shows that the non-perovskited BST phase does not come from the absorbed CO2 or CO contaminations, but from other interfacial elements. Also, it is indicated that the RTA-annealed BST film capacitor shows much better dielectric properties, with an average value of 150 higher dielectric constant and almost two orders of magnitude lower leakage current density than the CTA-annealed film capacitor. Grazing X-ray diffraction (GXRD) patterns exhibit that the RTA-annealed BST films present more compact structure. It is such a compact structure that can effectively prevent the absorbed elements further diffusing toward two sides, and cause thinner transition layer, thus result in higher dielectric constant and lower leakage current density

  5. Investigation on the dielectric properties of (Ba, Sr)TiO3 thin films on hybrid electrodes

    International Nuclear Information System (INIS)

    Ba0.65Sr0.35TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si, RuO2/SiO2/Si and RuO2/Pt/Ti/SiO2/Si substrates by radio frequency magnetron sputtering technique. The effects of these bottom electrodes on the microstructure and dielectric properties of the BST thin films were investigated by using X-ray diffraction (XRD), atomic force microscope (AFM), transmission electron microscopy (TEM) and electrical measurements. The BST thin films on RuO2/Pt hybrid bottom electrodes exhibit good crystalline and interfacial structure with a thinner transition layer. Dielectric measurement reveals that the films on RuO2/Pt hybrid electrodes have comparable dielectric constant and loss tangent with the films on Pt electrode, and the dielectric tunability of BST films on RuO2/Pt reaches 38.2%, which is higher than that of BST films on a single Pt or RuO2 electrode. The BST thin films on RuO2/Pt exhibit lower leakage current density by nearly two orders' of magnitude than that on RuO2 electrode. The higher tunability and lower leakage current of the films on RuO2/Pt hybrid bottom electrodes are mainly attributed to the RuO2 layer, which facilitates the nucleation and growth of BST films, and inhibits the interfacial diffusion between the BST films and bottom electrodes. The results show a potential for RuO2/Pt hybrid electrodes replacing Pt electrode in microelectronic device applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nadaud, Kevin, E-mail: kevin.nadaud@etu.univ-nantes.fr; Borderon, Caroline, E-mail: caroline.borderon@univ-nantes.fr; Renoud, Raphaël; Gundel, Hartmut W. [IETR, UMR CNRS 6164, University of Nantes, Nantes (France)

    2015-02-28

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

  7. Effect of manganese doping of BaSrTiO3 on diffusion and domain wall pinning

    International Nuclear Information System (INIS)

    In the present paper, the influence of manganese doping on the dielectric properties of BaSrTiO3 thin films is presented. The real and imaginary parts of the material's permittivity have been measured in a large frequency range (100 Hz–1 MHz) and as a function of the electric field. The tunability and the figure of merit of the material have been obtained from the measurement of the permittivity under an applied DC bias electric field. For the undoped material, the dielectric losses become important for a large DC bias which leads to breakdown. At a suitable dopant rate, this effect disappears. In order to better understand the origin of the related phenomena, we measure the permittivity as a function of the AC excitation amplitude and we decompose the obtained permittivity with the hyperbolic law. This enables to extract the different contributions of the bulk (low frequency diffusion and high frequency lattice relaxation) and of the domain wall motions (vibration and pinning/unpinning) to the material's dielectric permittivity and to understand the effect of manganese doping on each contribution. Knowledge of the related mechanisms allows us to establish the optimum dopant rate (mainly conditioned by the lattice contribution) and to reduce the domain wall motion, which finally is beneficial for the desired properties of the ferroelectric thin film. A particular attention is paid to low frequency diffusion, an especially harmful effect when a DC biasing is mandatory (tunable electronic component in mobile telecommunication devices for example)

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

    Science.gov (United States)

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

    2016-05-01

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

  9. Pressure dependence of the superconducting critical temperature of HgBa2Ca2Cu3O8+y and HgBa2Ca3Cu4O10+y up to 30 GPa

    International Nuclear Information System (INIS)

    By performing experiments on samples as pure as presently available, the origin of the reported pressure-induced Tc values well above 150 K in the mercury-based high-Tc superconductors has been investigated. For HgBa2Ca2Cu3O8+y (Hg-1223) maximum Tc values between 142 K and 146 K are obtained under pressure up to 30 GPa, while for HgBa2Ca3Cu4O10+y (Hg-1234) Tc never exceeds 121 K. To verify the reproducibility between different laboratories the pressure dependence of a sample from the same batch as the sample on which Nunez-Regueiro reported a Tc value of 157 K at 23.5 GPa has also been measured. Below 10 GPa the agreement with his results is rather good and a possible explanation for the disagreement above 10 GPa is given. It appears that the reported high Tc values in non-single-phase Hg-1223 samples are due to the presence of Hg-1234 phase impurities. Also some of the adopted definitions of Tc have led to somewhat optimistic values of Tc: The high-pressure results on Hg-1223 found in the literature are therefore reviewed and reanalyzed. copyright 1996 The American Physical Society

  10. Thermoelectric Characterization of (Na1-yMy)1.6Co2O4(M=K,Ca,Sr)

    Institute of Scientific and Technical Information of China (English)

    Ying LI; Guiying XU; Maofa JIANG

    2006-01-01

    Oxide materials NaCo2O4 and (Na1-yMy)1.6Co2O4 (M=K, 0.05≤y≤0.35; M=Ca, Sr, 0.10≤y≤0.40) were prepared by a sol-gel method. Experimental results indicated that the Seebeck coefficient and the Powerfactor of NaCo2O4 were improved by doping Ca and Sr but not by K. The Power-factor of NaCo2O4 is in its maximum, 1.68×10-4 W·m-1·K-2 and 11% bigger than that of the original one when the dopant fraction of Ca was 0.1. Doping Sr makes NaCo2O4 have the biggest Power-factor, 1.68×10-4 W·m-1·K-2 that is 50% bigger than the non-doping oxide. The experimental results indicate that suitable dopants and addition amounts could improve the thermoelectric properties of NaCo2O4 greatly.

  11. Luminescence characteristics of Sr{sub 1-x}Ba{sub x}Si{sub 2}O{sub 2}N{sub 2}:Eu{sup 2+} phosphors for white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Anoop, G.; Cho, I.H.; Suh, D.W.; Yoo, J.S. [Display Materials Laboratory, School of Chemical Engineering and Materials Science, Chung-Ang University, Heukseok-Dong 221, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

    2012-12-15

    Sr{sub 1-x}Ba{sub x}Si{sub 2}O{sub 2}N{sub 2}:Eu{sup 2+} phosphors were synthesized using high temperature solid state reaction. The effect of Ba incorporation on the structural and luminescence characteristics of SrSi{sub 2}O{sub 2}N{sub 2}:Eu{sup 2+} phosphors were studied. The phosphors were crystallized in triclinic crystal structure and the cell volume increases monotonically with Ba addition. The PL emission peak wavelength red shifts with Ba up to x = 0.50 beyond which no red shift is observed. The XPS analysis shows that nitrogen is being incorporated into the host lattice along with Ba addition up to x = 0.50. The as synthesized phosphors show high thermal stability. Phosphor converted light emitting diodes were realized using Sr{sub 1-x}Ba{sub x}Si{sub 2}O{sub 2}N{sub 2}:Eu{sup 2+} phosphors (x = 0 and x = 0.40) showing luminance efficacies of 108 and 101 lm W{sup -1}. The CIE chromaticity coordinates of Sr{sub 1-x}Ba{sub x}Si{sub 2}O{sub 2}N{sub 2}:Eu (x = 0 and x = 0.40) phosphors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

    Science.gov (United States)

    Takesue, R.K.; VanGeen, A.

    2004-01-01

    This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ???1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell ??13C values (upwelling events. The Mg contents of P. staminea midden shells dated to ???3 ka and ???9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated ??13C values in the ???3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon. Copyright ?? 2004 Elsevier Ltd.

  13. Calcilytic Ameliorates Abnormalities of Mutant Calcium-Sensing Receptor (CaSR) Knock-In Mice Mimicking Autosomal Dominant Hypocalcemia (ADH).

    Science.gov (United States)

    Dong, Bingzi; Endo, Itsuro; Ohnishi, Yukiyo; Kondo, Takeshi; Hasegawa, Tomoka; Amizuka, Norio; Kiyonari, Hiroshi; Shioi, Go; Abe, Masahiro; Fukumoto, Seiji; Matsumoto, Toshio

    2015-11-01

    Activating mutations of calcium-sensing receptor (CaSR) cause autosomal dominant hypocalcemia (ADH). ADH patients develop hypocalcemia, hyperphosphatemia, and hypercalciuria, similar to the clinical features of hypoparathyroidism. The current treatment of ADH is similar to the other forms of hypoparathyroidism, using active vitamin D3 or parathyroid hormone (PTH). However, these treatments aggravate hypercalciuria and renal calcification. Thus, new therapeutic strategies for ADH are needed. Calcilytics are allosteric antagonists of CaSR, and may be effective for the treatment of ADH caused by activating mutations of CaSR. In order to examine the effect of calcilytic JTT-305/MK-5442 on CaSR harboring activating mutations in the extracellular and transmembrane domains in vitro, we first transfected a mutated CaSR gene into HEK cells. JTT-305/MK-5442 suppressed the hypersensitivity to extracellular Ca(2+) of HEK cells transfected with the CaSR gene with activating mutations in the extracellular and transmembrane domains. We then selected two activating mutations locating in the extracellular (C129S) and transmembrane (A843E) domains, and generated two strains of CaSR knock-in mice to build an ADH mouse model. Both mutant mice mimicked almost all the clinical features of human ADH. JTT-305/MK-5442 treatment in vivo increased urinary cAMP excretion, improved serum and urinary calcium and phosphate levels by stimulating endogenous PTH secretion, and prevented renal calcification. In contrast, PTH(1-34) treatment normalized serum calcium and phosphate but could not reduce hypercalciuria or renal calcification. CaSR knock-in mice exhibited low bone turnover due to the deficiency of PTH, and JTT-305/MK-5442 as well as PTH(1-34) increased bone turnover and bone mineral density (BMD) in these mice. These results demonstrate that calcilytics can reverse almost all the phenotypes of ADH including hypercalciuria and renal calcification, and suggest that calcilytics can become a

  14. Photophysical electronic structure of double-perovskites A{sub 2}GdTaO{sub 6} (A = Ba and Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Binita, E-mail: ghosh.binita@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)

    2015-11-05

    X-ray photoemission spectroscopy (XPS) measurements of double perovskite oxides, Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} are performed in the energy window of 0–1300 eV. Density functional theory calculations are initiated with the Vienna ab initio Simulation Package to understand the electronic structure of the systems. The calculated DOS has been compared with the experimental valence band XPS spectra. It has been observed that the Ta-5d and O-2p states are hybridized in the valence band. The chemical shifts of these compounds suggest a mixed ionic and covalent character of the bonds, which has been used to explain the electrical conduction mechanism of the systems. The calculated ratio of the spin-orbit interaction energy for Ba 3d and 4d states matches well with the observed experimental results. - Highlights: • DFT calculations of Ba{sub 2}GdTaO{sub 6} and Sr{sub 2}GdTaO{sub 6} have been performed with VASP. • XPS measurements are performed in the energy window of 0–1300 eV. • The calculated DOS has been compared with the valence band XPS spectra. • Chemical shifts from XPS spectra have been used to explain the conduction mechanism.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xuan [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China); Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamada, Tomoaki [Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Lin, Ruoqian; Xin, Huolin L.; Su, Dong, E-mail: dsu@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Kamo, Takafumi; Funakubo, Hiroshi [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Wu, Di [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China)

    2015-10-05

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

  16. Effect of Strong Basic Oxide (Li2O, Na2O, K2O and BaO) on Property of CaO-Based Flux

    Institute of Scientific and Technical Information of China (English)

    LI Gui-rong

    2003-01-01

    It is found that strong basic oxides including Li2O, Na2O, K2O and BaO, which are used to replace a part of CaO in CaO-based fluxes, can lower the melting point and the viscosity and enhance the dephosphorizing ability. The mechanism was analysed and the addition of Li2O to CaO-based fluxes was recommended.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chan, N. Y., E-mail: ngaiyuichan@gmail.com; Wang, Y.; Chan, H. L. W. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Wang, D. Y. [School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Dai, J. Y. [Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Shenzhen Research Institute, The Hong Kong Polytechnic University (China)

    2014-06-21

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

  18. Effects of growth temperature on structure and electrical properties of dielectric (Ba,Sr)TiO3 capacitors with transparent conducting oxide electrodes

    International Nuclear Information System (INIS)

    Highlights: → High growth temperature results in more oxygen vacancies or defects in the Ba0.6Sr0.4TiO3 thin film. → Serious interdiffusion between the Ba0.6Sr0.4TiO3 and Zr-doped In2O3 thin films might occur at a growth temperature of 750 deg. C. → The BST film grown at 650 deg. C on the Zr-doped In2O3 electrode showed good dielectric properties and a mean optical transmittance above 70% in the visible wavelength regions. - Abstract: 200 nm-thick BST thin films were grown on Zr-doped In2O3/SrTiO3 (1 0 0) substrates at 550-750 deg. C. X-ray diffraction results show that the as-deposited BST films were polycrystalline with random crystallographic orientations. X-ray diffraction patterns reveal that the BST film grown at 650 deg. C had the best crystalline quality of all the deposition temperatures. Atomic force microscopy and secondary ion mass spectrometry showed that the surface and interface structures of the BST films became rough as the growth temperature increased. The BST film grown at 650 deg. C showed the best electrical properties, with a dielectric constant of 420 at 1 MHz, dielectric tunability of 32.1%, dielectric loss of 0.015 at 300 kV/cm, and a mean optical transmittance in visible wavelength of 71.3%.

  19. Sr{sup 2+} doping effects on the transport and magnetic properties of GdBaCo{sub 2}O{sub 5+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Janaki, J. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. (India)], E-mail: jjanaki@igcar.gov.in; Bharathi, A.; Gayathri, N.; Yasodha, P.; Premila, M.; Sastry, V.S.; Hariharan, Y. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. (India)

    2008-03-01

    Studies on some new members of the cobalt perovskite Gd{sub 1-x}Sr{sub x}BaCo{sub 2}O{sub 5+{delta}} with low strontium concentrations (0BaCo{sub 2}O{sub 5+{delta}} system by hole doping. Low temperature electrical resistivity, magnetic susceptibility and thermopower of the above system have been studied. The pristine compound with x=0 and {delta}{approx}0.5 exhibits a semiconductor-like behavior and two magnetic transitions below room temperature. Upon Sr{sup 2+} substitution, there is a fall in resistivity by 2-3 orders of magnitude at low temperature and also a dramatic reduction in the ferromagnetic to antiferromagnetic transition temperature. These changes can be explained on the basis of hole doping (and increase in the Co{sup 4+}content). Evidence for an increase in Co{sup 4+} with Sr{sup 2+} substitution is provided by iodometric analysis.

  20. Sr7U(PO4)6 and Ba7U(PO4)6 : structure and thermophysical properties

    International Nuclear Information System (INIS)

    Many crystalline ceramic matrices like Monazite, Hollandite, Kosnarite, NZP, Eulytine etc. have been proposed as a host material for nuclear Waste Immobilization (WI) due to their favourable stability against temperature, pressure and chemical reactivity. In Eulytine structure type, Sr7Th(PO4)6 was proposed with respect to WI, but no detailed report on the analogues U(IV) compounds and their thermo-physical properties are available in literature. Hence, we report here the preparation, structure and thermophysical properties of Sr7U(PO4)6 (1) and Ba7U(PO4)6 (2) compounds. The Compounds 1 and 2 were prepared by solid state reaction route (reaction is shown below) by mixing appropriate molar proportions of alkaline earth metal carbonates (Sr and Ba), UO2 and NH4H2PO4 (ADHP) and heated in high purity Ar atmosphere at 1373 K for 10 h with intermittent grinding. Powder XRD, TG-DTA, HT-XRD and DSC techniques were used for the characterization of phases, thermal stability, coefficients of thermal expansion and heat capacity (Cp) measurements, respectively

  1. 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.

  2. Composition dependence of ferroelectric and piezoelectric properties of epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} thin films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Q.R.; Wang, D.Y., E-mail: dy.wang@unsw.edu.au; Luo, B.C.; Ding, R.; Lorenzen, D.L.; Li, S.

    2015-03-15

    Highlights: • Epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) thin films were successfully grown on (0 0 1)-oriented SrTiO{sub 3} (STO) substrates by pulsed laser deposition (PLD). • Both structural and physical properties of BZT–xBCT thin films exhibited strong composition dependence. • An MPB-like behaviour was found at around x = 0.5 with highest dielectric, ferroelectric and piezoelectric properties. • The piezoelectric coefficients of our BZT–0.5BCT thin films were in upper range of the existing piezoelectric thin film materials. - Abstract: Lead-free (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) (x = 0.3, 0.4, 0.5, 0.6, 0.7) thin films were deposited on SrRuO{sub 3} (SRO)-electroded (0 0 1)-oriented SrTiO{sub 3} (STO) single crystal substrates by pulsed laser deposition (PLD). X-ray diffraction and selected area electron diffraction (SAED) patterns verified epitaxial growth for all the thin films. High ferroelectric activities were evidenced by the well-defined polarization-electric field hysteresis loops. Both structural and physical properties of the thin films demonstrated a strong composition dependence and an MPB-like behaviour was found at around x = 0.5, which is in agreement with that of its bulk counterparts. The superior ferroelectric and piezoelectric responses were attained at x = 0.5 with remanent polarization P{sub r} of 17.8 μC/cm{sup 2} and piezoelectric coefficient d{sub 33} of 100 ± 5 pm/V.

  3. Growth of single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers using optimized starting compositions for glassy precursors

    CERN Document Server

    Sugimata, E; Kume, E; Sakai, S

    2003-01-01

    Single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers were grown by optimized starting compositions for glassy precursors. The most optimal starting composition ratio and the composition after the whisker growth were found to be Bi : Sr : Ca : Al = 0.96 : 1.10 : 0.37 : 1.21 : 0.61 and Bi sub 2 sub . sub 2 sub 5 Sr sub 2 sub . sub 0 sub 9 Ca sub 0 sub . sub 8 sub 7 Cu sub 2 sub . sub 0 sub 0 O sub x , respectively. From the results of R-T characteristics, it was determined that there was no intergrowth of the Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub x phase. (author)

  4. Muscle Glycogen Content Modifies SR Ca2 + Release Rate in Elite Endurance Athletes

    DEFF Research Database (Denmark)

    Gejl, Kasper Degn; Hvid, Lars G; Frandsen, Ulrik;

    2014-01-01

    The aim of the present study was to investigate the influence of muscle glycogen content on sarcoplasmic reticulum (SR) function and peak power output (Wpeak) in elite endurance athletes.......The aim of the present study was to investigate the influence of muscle glycogen content on sarcoplasmic reticulum (SR) function and peak power output (Wpeak) in elite endurance athletes....

  5. High Permittivity (1 - x)Ba(Zr(0.2)Ti(0.8))O3 - x(Ba(0.7)Ca(0.3))TiO3 (x = 0.45) Epitaxial Thin Films with Nanoscale Phase Fluctuations.

    Science.gov (United States)

    Scarisoreanu, Nicu D; Craciun, Floriana; Moldovan, Antoniu; Ion, Valentin; Birjega, Ruxandra; Ghica, Corneliu; Negrea, Raluca F; Dinescu, Maria

    2015-11-01

    Epitaxial (1 - x)Ba(Ti0.8Zr0.2)TiO3 - x(Ba0.7Ca0.3)TiO3, x = 0.45 (BCZT 45), thin films have been deposited on (001) SrTiO3 (STO) and (001/100) SrLaAlO4 (SLAO) substrates by pulsed laser deposition. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) confirmed the epitaxial growth of the films. A high structural quality has been evidenced for the BCZT/STO films. Geometric phase analysis (GPA) associated with the HRTEM enabled us to obtain microstrain analysis and the in-plane and out-of-plane lattice parameter variation on different areas. Tetragonality ratio fluctuations at nanoscale level which are relevant for the existence of nanodomains have been evidenced on the BCZT/STO films. The in-plane dielectric constant has been measured on interdigital electrodes deposited by lift-off technique on the top of the films. High values of dielectric permittivity (>3000) combined with low dielectric loss (reading domains during topography scanning. PMID:26488203

  6. The effect of Sr concentration on bioactivity and biocompatibility of sol-gel derived glasses based on CaO-SrO-SiO2-P2O5 quaternary system

    International Nuclear Information System (INIS)

    In the present study, sol-gel derived glasses based on CaO-SrO-SiO2-P2O5 system were prepared and the effect of Sr concentration on in vitro bioactivity and cellular properties of the glasses were investigated. SrO was substituted for CaO in the glass formula up to 10 mol% and in vitro bioactivity of the samples was evaluated by soaking them in simulated body fluid followed by structural characterization using XRD, FTIR and SEM techniques. The effects of various glass compositions on proliferation and differentiation of osteoblastic cells were also evaluated. The results showed that the substitution of Sr for Ca in the glass composition retarded formation of apatite layer onto the glass surfaces. Morphologies of the apatite layers were also different in which abundance of the crystals decreased with increasing Sr concentration. The bioactive glasses did not exert cytotoxic effect on the cells, however the proliferation and alkaline phosphatase activity of the cells on the samples containing low doses of Sr were higher than those of control and the samples with high dose of Sr. Glass specimen with 5 mol% of Sr exhibited appropriate bioactivity with optimal cell proliferation and ALP activity.

  7. Thermodynamics of the amalgam cells {M-Amalgam|MCl or MCl2 (m)|AgCl|Ag} (M=Rb, Cs, Sr, Ba) and primary medium effects in (acetonitrile + water)

    International Nuclear Information System (INIS)

    The potential difference E of the amalgam cell {MxHg1-x|MCl or MCl2 (m)| AgCl |Ag} (M=Rb, Cs, Sr, Ba) has been measured as a function of the mole fraction xM of M metal in amalgams and of the molality m of MCl (or MCl2) in (acetonitrile [A] + water [W]) solvent mixtures containing up to acetonitrile mass fraction wA=0.50, at T=298.15 K. The respective molal-scale standard potential differences E0m have been determined together with the relevant activity coefficients γ± functions of the MCl (or MCl2) molality. The E0m dependence on the mole fraction xA of acetonitrile in the solvent mixture within the range explored turns out to be linear for all the four metals M in the amalgams considered. Of course, also the difference ([E0m]W-[E0m]A), which is a measure of the primary medium effect upon transferring MCl (or MCl2) from pure water [W] to the acetonitrile [A] mixture, is linear in xA. In this context, following Feakins and French's scheme, which implies volume fraction statistics, analysis of the relevant mol · dm-3 scale primary medium effects, i.e., ([E0c]W-[E0c]A), upon MCl (or MCl2), as a linear function of the logarithm of water volume fraction, would lead to primary hydration numbers of 4.2 for RbCl, 4.0 for CsCl, 10.7 for SrCl2, and 10.3 for BaCl2, respectively, in acceptable agreement with literature data by Bockris based on different methods

  8. Ba_(0.7)Sr_(0.3)TiO_3及其含Pb弥散相铁电体介电性能的研究%Dielectric properties of Ba_(0.7)Sr_(0.3)TiO_3 and Ba_(0.7-x)Pb_xSr_(0.3)TiO_3 ferroelectric ceramics with diffuse phase transition

    Institute of Scientific and Technical Information of China (English)

    王梦; 贺建龙; 杨卫明; 李建军; 王耘波; 于军

    2009-01-01

    B_(0.7)Sr_(0.3)TiO_3(BST) and Ba_(0.7-x)Pb_xSr_(0.3)TiO_3CBPST) ceramics derived from different amount of initial PbO excess were prepared by conventional solid-state method. Both permittivity and dielectric loss of all samples were measured in a temperature range. The substitution of Pb for Ba in BST system has revealed to raise the Curie temperature from 44-175'C ,and exhibited a diffused phase transition(DPT), expecially for the ceramic Ba_(0.5) Pb_(0.1) TiO_3 which can improve the temperature stability of tunability for phase shifter than others. Moreover,some ferroelectric model parameters were calculated to interpret the DPT by adopting Smolenski' s theory and Curie-Wise law. For example,values of diffuseness exponent a,Curie constant and transition region have varied from 1.29-1. 88,from 1. 25×10~5-1. 47×10~5K,and from 13.4-22. 8℃,respectively.%用固相反应法制备了Ba_(0.7)Sr_(0.3)TiO_3及其含Pb钛酸锶钡(BPST)陶瓷,运用修正的Smolenski的成分起伏理论和居里外斯定律,结合介电常数温度谱,研究了钙钛矿结构的BST及铅取代的钛酸锶铅钡(BPST)的弥散相,对其相变行为进行了分析,得出了的一些铁电模型参数.结果表明,该系列样品在弥散相变区的弥散指数α为1.29~1.88,相变区间为13.4~22.8℃;在顺电相其居里常量为1.25×10~5~1.47×10~5K数量级.当Pb含量为0.1(即Ba_(0.6)Pb_(0.1)TiO_3)时,居里峰较宽,弥散相明显,故具有较高的调谐温度稳定性.另外铅的加入提高了铁电体的相变温度,从44℃上升到175℃.

  9. Transport Barkhausen-like noise in uniaxially pressed Bi1.65Pb0.35Sr2Ca2Cu3O10+δ ceramic samples

    International Nuclear Information System (INIS)

    We report on the detection of the transport Barkhausen-like noise (TBN) in polycrystalline samples of Bi1.65Pb0.35Sr2Ca2 Cu3O10+δ (Bi-2223) which were subjected to different uniaxial compacting pressures. The transport Barkhausen-like noise was measured when the sample was subjected to an ac triangular-shape magnetic field (f ∼ 1 Hz) with maximum amplitude Bmax ∼ 5.5 mT, in order to avoid the flux penetration within the superconducting grains. Analysis of the TBN signal, measured for several values of excitation current density, indicated that the applied magnetic field in which the noise signal first appears, Ba(ti), is closely related to the magnetic-flux pinning capability of the material. The combined results are consistent with the existence of three different superconducting levels within the samples: (i) the superconducting grains; (ii) the superconducting clusters; and (iii) the weak-links. We finally argue that TBN measurements constitute a powerful tool for probing features of the intergranular transport properties in polycrystalline samples of high-Tc superconductors.

  10. MB82- (M=Be,Mg,Ca,Sr,and Ba):Planar octacoordinate alkaline earth metal atoms enclosed by boron rings

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Complexes involving planar octacoordinate alkaline earth metal atoms in the centers of eight-membered boron rings have been investigated by two density functional theory (DFT) methods.BeB82-with D8h symmetry is predicted to be stable,both geometrically and electronically,since a good match is achieved between the size of the central beryllium atom and the eight-membered boron ring.By contrast,the other alkaline earth metal atoms cannot be stabilized in the center of a planar eight-membered boron ring because of their large radii.By following the out-of-plane imaginary vibrational frequency,pyramidal C8v MgB82-,CaB82-,SrB82-,and BaB82-structures are obtained.The presence of delocalized π and σ valence molecular orbitals in D8h BeB82-gives rise to aromaticity,which is reflected by the value of the nucleus-independent chemical shift.The D8h BeB82-structure is confirmed to be the global minimum on the potential energy surface.

  11. Microstructure and magnetic properties of Ca-substituted M-type SrLaCo hexagonal ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xin; Liu, Xiansong, E-mail: xiansongliu@ahu.edu.cn; Yang, Yujie; Huang, Kai; Niu, Xiaofei; Jin, Dali; Gao, Shang; Ma, Yuqi; Huang, Feng; Lv, Farui; Feng, Shuangjiu

    2015-03-15

    M-type strontium hexaferrites with chemical composition of Sr{sub 0.80−x}Ca{sub x}La{sub 0.20}Fe{sub 11.85}Co{sub 0.15}O{sub 19} (x=0−0.15) were prepared by the ceramic process. The samples were sintered at temperatures of 1175, 1185 and 1195 °C for 2 h in air. Effects of the substituted amount x of Ca{sup 2+} on the ferrites microstructure and magnetic properties have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and B–H hysteresis curve measurements. As a result, at x≤0.12, all samples are single phase after the Ca substitution. At x=0.15, another phase of hematite (α-Fe{sub 2}O{sub 3}) is present. In addition, the maximum values of the remanence (B{sub r}) and maximum energy product ((BH){sub max}) for the magnets have been obtained at x=0.08 for sintering temperature=1185 °C. The maximum value of the intrinsic coercive force (H{sub cj}) for the magnets has been obtained at x=0.12 when the magnets were sintered at 1185 °C. - Highlights: • For the chemical composition of Sr{sub 0.80−x}Ca{sub x}La{sub 0.20}Fe{sub 11.85}Co{sub 0.15}O{sub 19} (x=0–0.15), the secondary phase (α-Fe{sub 2}O{sub 3}) appears when x>0.12. • The Sr{sub 0.80−x}Ca{sub x}La{sub 0.20}Fe{sub 11.85}Co{sub 0.15}O{sub 19} (x=0–0.15) ferrites obtained the favorable microstructure and magnetic properties when x=0.08. • A proper temperature (1185 °C) in the synthesis of Sr{sub 0.80−x}Ca{sub x}La{sub 0.20}Fe{sub 11.85}Co{sub 0.15}O{sub 19} ferrites can obtain preferable magnetic properties.

  12. Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2

    Energy Technology Data Exchange (ETDEWEB)

    Kurita, N [Los Alamos National Laboratory (LANL); Ronning, F. [Los Alamos National Laboratory (LANL); Miclea, C. F. [Los Alamos National Laboratory (LANL); Tokiwa, Y. [Los Alamos National Laboratory (LANL); Bauer, E. D. [Los Alamos National Laboratory (LANL); Subedi, Alaska P [ORNL; Singh, David J [ORNL; Sakai, H [Japan Atomic Energy Agency (JAEA); Thompson, J. D. [Los Alamos National Laboratory (LANL); Movshovich, R [Los Alamos National Laboratory (LANL)

    2011-01-01

    We have performed low-temperature specific heat C and thermal conductivity {kappa} measurements on the Ni-pnictide superconductors BaNi{sub 2}As{sub 2} (T{sub c} = 0.7K) and SrNi{sub 2}P{sub 2} (T{sub c} = 1.4K). The temperature dependences C(T) and {kappa}(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual {kappa} for BaNi{sub 2}As{sub 2} rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba{sub 0.6}La{sub 0.4}Ni{sub 2}As{sub 2} shows a mild suppression of Tc and H{sub c2} relative to BaNi{sub 2}As{sub 2}.

  13. 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

    2016-05-01

    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.

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

    Science.gov (United States)

    Malea, Paraskevi; Kevrekidis, Theodoros

    2013-10-01

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

  15. Determination of traces of uranium and thorium in (Ba, Sr) TiO3 ferroelectrics by inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Traces of uranium and thorium in barium(II), strontium(II) titanate ((Ba, Sr)TiO3) ferroelectric materials were determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were completely dissolved by a mixture of 1.4% H2O2 and 1.0 mol.l-1 HNO3. For a complete separation of the analytes from the matrix elements, a two step separation technique involving leaching and anion-exchange was applied. By the leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-exchange step was carried out on a BIO.RAD AG1-X8 column with a mixture of 1.0 mol.l-1 HF and 0.5 mol.l-1 HNO3 as eluent. The content of uranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were 0.043 ng g-1 and 0.035 ng g-1 for U and Th, respectively. The reproducibility was satisfactory with a relative standard deviation of less than 3% (at the 1 ng g-1 level, n=5). The matrix concentrations in the final solution were reduced to the sub-μg ml-1 level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy). The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the analytes at levels of 1, 5 and 10 ng g-1 and three (Ba, Sr)TiO3 ferroelectric samples containing sub-ng g-1 levels of the analytes. (orig.)

  16. Preparation and Luminescence of Single-Host White-Light-Emitting BaSrMg(PO4)2 ∶ Eu2+ Phosphor for Ultraviolet LEDs%白光LED用单基质荧光粉BaSrMg( PO4)2∶Eu2+的制备及发光性能研究

    Institute of Scientific and Technical Information of China (English)

    潘再法; 刘爽; 朱澄静; 徐娟; 刘文涵; 王丽丽

    2011-01-01

    A single-host white-light-emitting phosphor BaSrMg(PO4)2:Eu2+ was prepared by high temperature solid-state reaction method, and the luminescence characteristics and XRD pattern were investigated. The results show that BaSrMg(PO1)2 phase was obtained by sintering at 1 200℃ for 3 hours. BaSrMg(PO4 )2: Eu2+ phosphor exhibits two main emission bands peaking at 424 and 585 nm, respectively. The emission band peaking at 424 nm is attributed to the 4f6 5d1→4f7 transition of Eu2+ substituting Sr2+ , while the emission band peaking at 585 nm originates from the 4f6 5d1→4f7 transition of Eu2+ replacing Ba2+ in host lattice. The excitation spectra of the two emission peaks are range from 250 to 400 nm and both peaking at 360 nm. The effect of the proportion of Ba and Sr, and the Eu2+ doping concentration on the emission intensity were discussed in detail. Different chromaticity coordinates were obtained for each phosphor, that is, the chromaticity coordinates of the designed phosphor is tunable for the white-emitting LED or for special purpose. Quantum efficiency was also examined for the phosphors with different Eu2+ doping concentration, and concentration quenching took place obviously when Eu2+ doping concentration was lager than 6% in mole ratio. The obtained phosphor BaSrMg(PO4)2 : Eu2+ can be excited by near ultraviolet radiation effectively and emit full color lighting, which is a promising single-host white-light-emitting phosphor for white LED.%采用高温固相反应法在1 200℃下制备了 Eu2+激活的BaSrMg( PO4)2高亮度白光荧光粉,并对其晶体结构和发光性能进行了研究.荧光光谱研究表明该荧光粉的发射光谱由两个谱带组成,其中心分别位于424和585 nm处,归结为Eu2+分别占据了基质中Sr2+,Ba2+格位而导致的4f 65d1→4f7电子跃迁.两个发射峰的激发光谱均分布在250~400nm的波长范围内,峰值位于360nm左右.表明该荧光粉可被INGaN管芯产生的近紫外辐射有效激发,是

  17. Magnetic and magnetocaloric properties of La 0.7Ca 0.3- xBa xMnO 3 compounds

    Science.gov (United States)

    Phan, Manh-Huong; Tian, Sheng-Bo; Yu, Seong-Cho; Ulyanov, A. N.

    2003-01-01

    Magnetic properties and magnetocaloric effect in La 0.7Ca 0.3- xBa xMnO 3 ( x=0.12, 0.24, 0.3) compounds were investigated. It is shown that there is a large magnetic entropy change associated with the ferromagnetic-paramagnetic transition. The Curie temperature ( TC) increases with the barium addition, while the maximum entropy change ( ΔS Mmax) slightly decreases. La 0.7Ca 0.18Ba 0.12MnO 3 exhibits the largest ΔS Mmax value of 1.85 J/kg/K at 298 K among the compounds investigated up to 10 kOe applied field. Through these results, La 0.7Ca 0.3- xBa xMnO 3 materials are strongly suggested for the use of active refrigerants for magnetic refrigeration technology near and above room temperature.

  18. Leakage current transport mechanisms of La0.67Sr0.33MnO3/BaTiO3 bilayer films grown on Nb:SrTiO3

    Indian Academy of Sciences (India)

    Pan Ruikun; Liu Panke; Li Mingkai; Tao Haizheng; Li Pai; He Yunbin

    2015-06-01

    La0.67Sr0.33MnO3/BaTiO3(LSMO/BTO) bilayer films were epitaxially grown on Nb:SrTiO3 (NSTO) substrates by the pulsed laser deposition technique. Current–voltage (–) characteristics of the LSMO/BTO bilayer films were studied. – curves were measured at room temperature, which show rectifying behaviour and can be well fitted by the space-charge-limited current mechanism under forward bias while thermionic emission model under reverse bias. Analysis indicates that a modulating Schottky barrier exists at the LSMO/BTO interface, which dominates the leakage current transport properties of LSMO/BTO bilayer films.

  19. Photoluminescence properties of Er3+-doped Ba0.5Sr0.5TiO3 prepared by sol-gel synthesis

    International Nuclear Information System (INIS)

    Er3+-doped Ba0.5Sr0.5TiO3 (BST) powders were prepared by using barium nitrate, strontium nitrate, tetrabutyl titanate, and ammonia via citrate-nitrate combustion process, along with the XRD, DSC/TGA, and SEM analytic reports. The Er3+ luminescence intensity reached a maximum value in the sample with 3 mol% Er3+ ions concentration sintered at temperature 1300 deg. C. We also showed that 1 mol% Er dopant improved the dielectric property of BST and the BST:Er materials may have potential use for electroluminescence devices

  20. Magnetic control of dielectric properties of Ba0.6Sr0.4TiO3 in a trilayer system

    International Nuclear Information System (INIS)

    Dielectric properties of Ba0.6Sr0.4TiO3 (BST) in a layered terfenol-D/BST/terfenol-D system were investigated. Dielectric properties of the BST layer can be adjusted by magnetostrictive strain of terfenol-D layers under applied magnetic fields. Our results show that the small-signal dielectric constant of BST can be tuned ranging from about 2300 to 4000 by a small magnetic field. By adjusting the relative layer thickness ratio, a more broad adjustable dielectric constant and tunability of BST layer can be designed, which may have potential applications in sensitive multifunctional devices and microwave devices

  1. Calculation Model of Mass Action Concentration for Mg-Al, Sr-Al and Ba-Al Melts and Determination of Their Thermodynamic Parameters

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Based on the phase diagrams and the mass action law in combination with the coexistence theory of metallic melts structure, the calculation model of mass action concentration for Mg-Al, Sr-Al and Ba-Al was built, and their thermodynamic parameters were determined. The agreement between calculated and measured results shows that the model and the determined thermodynamic parameters can reflect the structural characteristics of relevant melts. However, the fact that the thermodynamic parameters from literature don′t give the value agree with the measured result may be due to unconformity of these parameters to real chemical reactions in metallic melts.

  2. Structural, electrochemical and magnetic characterization of the layered-type PrBa0.5Sr0.5Co2O5+δ perovskite

    International Nuclear Information System (INIS)

    Structural, electrical and magnetic properties of the layered cobaltite PrBa0.5Sr0.5Co2O5+δ have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrOδ] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2ap and c≈2ap (ap is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573 K in air, structural rearrangement takes place and the structure can be defined as a≈ap and c≈2ap in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373 K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973 K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573 K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153 Ωcm2 and 0.286 Ωcm2 at 973 K and 923 K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order. - Graphical abstract: Structural phase changes in PrBa0.5Sr0.5Co2O5+δ at elevated temperatures determined by neutron powder diffraction. Depending on oxygen occupancy it form different phases at different temperatures. This pictures show the schematic 3D diagram of PrBa0.5Sr0.5Co2O5+δ at 295 K (a), 373 K (b) and 573 K (c). Co atoms are inside the octahedra/pyramid. Ba and Sr occupy the same site. Oxygens are in the corner of polyhedra. - Highlights: • Structural phase

  3. The electron emission characteristics of Sol-Gel (Ba0.67Sr0.33)TiO3 (BST) thin film coated silicon tips

    OpenAIRE

    Kang, Weng Poo; Gürbüz, Yaşar; Gurbuz, Yasar; Davidson, Jimmy L.; Tan, O. K.; Zhu, W. G.; Q. Li; Xu, J. F.

    2006-01-01

    Field emission characteristics of Sol-Gel (Ba0.67Sr0.33)TiO3 (BST) ferroelectric thin film coated silicon emitters have been systemically investigated. The effects of BST coating, BST annealing temperature, and biasing at BST-silicon junction on field emission characteristics of BST coated silicon tips have been studied. We have found that field emission characteristics of silicon tips can be significantly improved by BST coating. The turn-on electric field required between the silicon tips a...

  4. Synthesis of Ba3ZnNb2O9–Sr3ZnNb2O9 solid solution and their dielectric properties

    Indian Academy of Sciences (India)

    M Thirumal; A K Ganguli

    2002-08-01

    Oxides of the type, Ba3–SrZnNb2O9 (0 ≤ ≤ 3), were synthesized by the solid state route. Oxides calcined at 1000°C show single cubic phase for all the compositions. The cubic lattice parameter (a) decreases with increase in Sr concentration from 4.0938(2) for = 0 to 4.0067(2) for = 3. Scanning electron micrographs show maximum grain size for the = 1 composition (∼ 2 m) at 1200°C. Disks sintered at 1200°C show dielectric constant variation between 28 and 40 (at 500 kHz) for different values of with the maximum dielectric constant at = 1.

  5. Toward complete isotopic analysis of individual presolar silicon carbide grains : C, N, Si, Sr, Zr, Mo, and Ba in single grains of type X.

    Energy Technology Data Exchange (ETDEWEB)

    Pellin, M. J.; Calaway, W. F.; Davis, A. M.; Lewis, R. S.; Amari, S.; Clayton, R. N.

    2000-03-01

    Presolar silicon carbide grains form in a variety of types of stars, including asymptotic giant branch red giant stars and supernovae. The dominant mechanisms of heavy element nucleosynthesis, the s-process and r-process, are thought to occur mainly in AGB stars and supernovae, respectively [1]. We have previously reported that mainstream SiC grains have strong enrichments in the s-process isotopes of Sr, Zr and Mo [2-4] and initial results for X-type SiC grains showing enrichments in the r-process isotopes of Mo[5]. We report here the first measurements of Zr, Sr, and Ba isotopes along with expanded studies of Mo in individual X-type SiC grains, which have previously been identified as having formed from supernova ejects.

  6. Effect of bottom electrodes on dielectric properties of high frequency Ba0.5Sr0.5TiO3 parallel plate varactor

    International Nuclear Information System (INIS)

    Three types of Ba0.5Sr0.5TiO3 (BST) thin film parallel plate varactor with different bottom electrodes were fabricated. The bottom electrodes of three types of varactor were perovskite conducting oxide La0.7Sr0.3MnO3 (LSMO), Pt and Au, respectively. Dielectric properties of the BST thin films were characterized in the frequency range from 10 MHz to 15 GHz. The microstructure of the BST thin films was investigated by X-ray diffraction and scanning electron microscope. The microstructural analysis shows that the BST thin films grown on LSMO and Pt bottom electrodes are polycrystalline textured with columnar grains. Dielectric measurement indicates that the BST thin film grown on LSMO bottom electrode has a maximum dielectric constant and a little higher loss tangent.

  7. NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy

    CERN Document Server

    Andrievsky, S M; Korotin, S A; Francois, P; Spite, M; Bonifacio, P; Cayrel, R; Hill, V

    2011-01-01

    Heavy element abundances in extremely metal-poor stars provide strong constraints on the processes of forming these elements in the first stars. We attempt to determine precise abundances of strontium in a homogeneous sample of extremely metal-poor stars. The abundances of strontium in 54 very or extremely metal-poor stars, was redetermined by abandoning the local thermodynamic equilibrium (LTE) hypothesis, and fitting non-LTE (NLTE) profiles to the observed spectral lines. The corrected Sr abundances and previously obtained NLTE Ba abundances are compared to the predictions of several hypothetical formation processes for the lighter neutron-capture elements. Our NLTE abundances confirm the previously determined huge scatter of the strontium abundance in low metallicity stars. This scatter is also found (and is even larger) at very low metallicities (i. e. early in the chemical evolution). The Sr abundance in the extremely metal-poor (EMP) stars is compatible with the main r-process involved in other processe...

  8. MBE growth of compounds on the copper rich side of the (Sr,Ca)CuO system

    International Nuclear Information System (INIS)

    Thin films belonging to the copper rich family in the (Sr,Ca)-Cu-O system have been synthesized using molecular beam epitaxy (MBE) deposition. The growth conditions have been optimized on two different substrates, MgO (100) and SrTiO3 (100). We discuss in this paper the variations of the electron diffraction pattern (RHEED) during the growth. The films obtained present a single orientation with good crystallization. The average composition measured by Rutherford backscattering spectroscopy (RBS) is (Sr,Ca)0.6CuOz. This stoichiometry is close to the composition expected for the first members of the spin ladders homologous series Srn-1Cun+1O2n. High resolution electron microscopy (HREM) and X-ray diffraction measurements on a four circles diffractometer are in progress. Preliminary results confirm that the structure is consistent with spin-ladders structures. Typical room temperature resistivity is of the order of 0.5 mΩ cm. The search for superconducting properties in these compounds is discussed. (orig.)

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

    Science.gov (United States)

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

    2016-07-01

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

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

    Science.gov (United States)

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

    2013-04-01

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

  11. Texture analysis of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x tapes by electron backscatter diffraction (EBSD)

    Science.gov (United States)

    Koblischka-Veneva, A.; Koblischka, M. R.; Qu, T.; Han, Z.; Mücklich, F.

    2008-02-01

    Using automated orientation imaging, the grain orientations and texture of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x (Bi-2223) tape is analysed in detail by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase scans including Bi-2223, Bi 2Sr 2CaCu 2O x, Bi 2Sr 2CuO x, (Sr,Ca) 14Cu 24O 41 and Ag to be performed. Two areas are selected for the EBSD analysis, one close to the silver sheath, the other located in the center of the sample. The grain orientation maps are presented for each phase separately allowing a new insight into the microtexture of Ag-sheathed Bi-2223 tapes. Furthermore, the EBSD analysis provides the possibility for a misorientation angle analysis within each individual phase.

  12. Experimental electronic structure of Bi2CaSr2Cu2O/sub 8+//sub δ/

    International Nuclear Information System (INIS)

    Highly oriented polycrystalline Bi2CaSr2Cu2O/sub 8+//sub δ/ has been studied by x-ray photoemission spectroscopy (XPS) to determine the oxidation states of its constituents and the valence electronic structure. Core-level shifts indicate 3+ and 2+ as main oxidation states for Bi and Cu, respectively. The Ca and Sr core levels exhibit pronounced shifts to lower binding energy compared to the metals. The Ca lines show two main components, indicating either inequivalent sites or the presence of a different phase. The XPS and ultraviolet photoemission spectroscopy valence-band spectra show weak but reproducible metallic emission at the Fermi level (E/sub F/) which we ascribe to states originating in the Bi-O planes. The main Cu d--O p band is between 2 and 8 eV below E/sub F/; this is about 1 eV lower than predicted by band-structure calculations. We argue that this is due to electronic correlations tending to increase the anisotropy in the ground-state charge distribution compared to that obtained in local-density-approximation calculations

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

    Science.gov (United States)

    Chen, Hongwei; Yang, Chuanren; Zheng, Shanxue; Zhang, Jihua; Zhang, Qiaozhen; Lei, Guanhuan; Lou, Feizhi; Yang, Lijun

    2011-12-01

    Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO-Al2O3-SiO2 (CaAlSi) high temperature glaze with proper additives on the rough-95% Al2O3 ceramics substrates. (Ba0.6Sr0.4)TiO3 (BST) thin films were deposited on modified Al2O3 substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al2O3 substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al2O3 substrates were almost consistent with that of BST thin films grown on LaAlO3 (1 0 0) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al2O3 substrates.

  14. Magnetic-field irreversibility in superconducting Cu(Ba0.8Sr0.2)2(Yb1-xCax)Cu2O6+z with controlled distribution of holes

    International Nuclear Information System (INIS)

    The dependence of the irreversibility field (Hirr) on the concentration and distribution of holes over crystals of superconducting cuprates of the Cu-1212:P (or '123') structure was investigated. A series of samples, Cu(Ba0.8Sr0.2)2(Yb1-xCax)Cu2O6+z, exhibiting a variety of doping levels and distributions of holes caused by Ca substitution for Yb (x = 0.25 and 0.35) and O doping (0.55≤z≤0.96) was employed. The x-ray absorption near-edge-structure results previously obtained for the same samples were used to derive the hole distributions among the different oxygen sites. Moreover, the neutron-diffraction data previously measured for the crystal structure of the samples were utilized to observe gradual changes in the local crystallographic structure in accordance with Ca substitution and/or O doping, and to estimate the local hole concentrations via bond-valence-sum calculations. It was generally concluded that the more homogeneous the hole distribution was, the more improved were the Hirr characteristics. Detailed discussions are given for the individual contributions to the Hirr characteristics from (i) the hole concentration in the infinite-layer block, (ii) the thickness of the charge-reservoir block and (iii) the hole concentration in the charge-reservoir block. (author)

  15. Effect of cationic size in Hg(Tl/Bi)Ba2Ca2Cu3O8+ on superconducting and microstructural characteristics

    Indian Academy of Sciences (India)

    Rajiv Giri; H K Singh; R S Tiwari; O N Srivastava

    2001-10-01

    In this paper we have reported investigations on the effect of simultaneous substitution of Bi and Tl at the H site in the oxygen deficient HO layer of HBa2Ca2Cu3O8+ cuprate superconductor. Bulk polycrystalline samples have been prepared by the two-step solid state reaction process (precursor route). It has been observed that the as grown HBi0.2–TlBa2Ca2Cu3O8+ (with = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 phase. It has been found that the c varies with the average cationic size $\\langle R_d \\rangle$ of the dopantcations. The optimum c of ∼ 131 K has been found for the composition HBi0.15Tl0.05Ba2Ca2Cu3O8+. This composition leads to the average dopant cation size of ∼ 1.108 Å which is very close to the size of H2+ (∼ 1.11 Å). The microstructure for HBi0.15Tl0.05Ba2Ca2Cu3O8+ has been found to be most dense and this phase exhibits the highest stability. The c of the optimum material HBi0.15Tl0.05Ba2Ca2Cu3O8+ is found to be ∼ 1.29 × 103 A/cm2 at 77 K.

  16. 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 (∆18O) moving away from the coastline and the mouth of the primary local freshwater source, the Fly River. The reduced amplitude in G-IG ∆18O 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

  17. 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.

  18. Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant.

    Science.gov (United States)

    Bornapour, M; Mahjoubi, H; Vali, H; Shum-Tim, D; Cerruti, M; Pekguleryuz, M

    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 5weeks 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. PMID:27287101

  19. Enhancement of Sinter Densification of SrO-BaO-Nb2O5-SiO2 Tungsten-Bronze Glass-Ceramics by Doping with P2O5

    Institute of Scientific and Technical Information of China (English)

    J.C.Chen; Y.Zhang

    2013-01-01

    Densification behaviors of SrO-BaO-Nb2O5-SiO2 based glass-ceramics prepared by conventional sintering were investigated with an emphasis on the influence of P2O5 content.Although P2O5 dopant did not modify the surface crystallization mechanism,it resulted in a decrease of the glass transition temperature,which facilitates the viscous glass flow necessary for sintering.However,premature crystallization of (Sr,Ba)Nb2O6 induced by addition of excess amount of P2O5 essentially retarded sintering due to the formation of closed pores in the matrix.The SrO-BaO-Nb2O5-SiO2 glass with 1.0 mol% P2O5 (SBN-1P) showed the best sinter densification,which was accomplished at about 850 ℃.

  20. Detection of a Cooper-pair density wave in Bi2Sr2CaCu2O8+x.

    Science.gov (United States)

    Hamidian, M H; Edkins, S D; Joo, Sang Hyun; Kostin, A; Eisaki, H; Uchida, S; Lawler, M J; Kim, E-A; Mackenzie, A P; Fujita, K; Lee, Jinho; Davis, J C Séamus

    2016-04-21

    The quantum condensate of Cooper pairs forming a superconductor was originally conceived as being translationally invariant. In theory, however, pairs can exist with finite momentum Q, thus generating a state with a spatially modulated Cooper-pair density. Such a state has been created in ultracold (6)Li gas but never observed directly in any superconductor. It is now widely hypothesized that the pseudogap phase of the copper oxide superconductors contains such a 'pair density wave' state. Here we report the use of nanometre-resolution scanned Josephson tunnelling microscopy to image Cooper pair tunnelling from a d-wave superconducting microscope tip to the condensate of the superconductor Bi2Sr2CaCu2O8+x. We demonstrate condensate visualization capabilities directly by using the Cooper-pair density variations surrounding zinc impurity atoms and at the Bi2Sr2CaCu2O8+x crystal supermodulation. Then, by using Fourier analysis of scanned Josephson tunnelling images, we discover the direct signature of a Cooper-pair density modulation at wavevectors QP ≈ (0.25, 0)2π/a0 and (0, 0.25)2π/a0 in Bi2Sr2CaCu2O8+x. The amplitude of these modulations is about five per cent of the background condensate density and their form factor exhibits primarily s or s' symmetry. This phenomenology is consistent with Ginzburg-Landau theory when a charge density wave with d-symmetry form factor and wavevector QC = QP coexists with a d-symmetry superconductor; it is also predicted by several contemporary microscopic theories for the pseudogap phase. PMID:27074504

  1. Preparation and Luminescence Properties of MZrO3:Eu3+, A (M=Ca2+, Ba2+; A=Li+, Na+, K+) Phosphors with Perovskite Structure

    Institute of Scientific and Technical Information of China (English)

    MAR B; CEMBRERO-COCA P; SINGH K C; KAUSHIK R D; OM Hari

    2013-01-01

    Calcium and barium zirconate powders based upon CaZrO3:Eu3+, A and BaZrO3:Eu3+, A (A=Li+, Na+, K+) were prepared by combustion synthesis method and heating to ~1000 °C to improve crystal inity. The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results showed that CaZrO3:Eu3 +, A and BaZrO3:Eu3 +, A (A=Li +, Na +, K +) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of al powders were very similar consisting of smal , coagulated, cubical particles with narrow size distributions and smooth and regular surfaces. The characteristic luminescences of Eu3+ ions in CaZrO3:Eu3+, A (A=Li+, Na+, K+) lattices were present with strong emissions at 614 and 625 nm for 5D0→7F2 transitions with other weaker emissions observed at 575, 592, 655, and 701 nm corresponding to 5D0→7Fn transitions (where n=0, 1, 3, 4, respectively). In BaZrO3:Eu3 + both the 5D0→7F1 and 5D0→7F2 transitions at 595 and 613 nm were strong. Photoluminescence intensities of CaZrO3:Eu3+ samples were higher than those of BaZrO3:Eu3+ lattices. This remarkable increase of photoluminescence intensity (corresponding to 5D0→7Fn transitions) was observed in CaZrO3:Eu3 + and BaZrO3:Eu3 + if co-doped with Li + ions. An additional broad band composed of many peaks between 440 to 575 nm was observed in BaZrO3:Eu3 +, A samples. The intensity of this band was greatest in Li+ co-doped samples and lowest for K+ doped samples.

  2. Structural, dielectric and electrical properties of CaBa4SmTi3Nb7O30 ferroelectric ceramic

    Indian Academy of Sciences (India)

    Prasun Ganguly; A K Jha

    2011-07-01

    The polycrystalline sample of CaBa4SmTi3Nb7O30, a member of tungsten bronze family, was prepared by solid-state reaction method. X-ray diffraction analysis shows the formation of single-phase compound with an orthorhombic structure at room temperature. Scanning electron micrograph of the material shows uniform distribution of grains. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 198°C, and exhibits non-relaxor kind of diffuse phase transition. The ferroelectric nature of the compound has been confirmed by recording polarization–electric field hysteresis loop. Piezoelectric and pyroelectric studies of the compound have been discussed in this paper. Electrical properties of the material have been analyzed using complex impedance technique. The Nyquist plots manifest the contribution of grain boundaries (at higher temperature), in addition to granular contribution (at all temperatures) to the overall impedance. The temperature dependence of dc conductivity suggests that the compound has negative temperature coefficient of resistance (NTCR) behaviour. The frequency dependence of ac conductivity is found to obey Jonscher’s universal power law. The observed properties have been compared with calcium free Ba5SmTi3Nb7O30 compound.

  3. (Hg, Sb)Ba2Ca2Cu3O8+δ thick films on YSZ substrates

    International Nuclear Information System (INIS)

    Superconducting thick films of (Hg, Sb)Ba2Ca2Cu3O8+δ have been fabricated on polycrystalline yttria-stabilized-zirconia substrates utilizing an Hg-free precursor film reacted with Hg vapour, released from a solid Hg source, in a sealed quartz tube. The resulting films have been studied by x-ray diffraction, scanning electron microscopy, ac susceptibility and resistance measurement techniques. A high quality Hg(Sb)-1223 superconducting thick film on YSZ can be fabricated by using a pre-melted Hg-free precursor film. The zero resistance superconducting transition temperature in the post-growth oxygenated thick film is in excess of 130 K and the transport critical current density for the film is 510 A cm-2 at 77 K. (author)

  4. Flux pinning in Tl1-xCxBa2Ca3Cu4O12-δ superconductor

    International Nuclear Information System (INIS)

    The dissipation mechanism in Tl1-xCxBa2Ca3Cu4O12-δ (x = 0, 0.25, 0.5 and 0.75) superconductor under the influence of external magnetic fields have been studied. The sample with x = 0.25 have shown strong flux pinning characteristic as compared to the Tl1-xCx-1234 (x = 0, 0.5 and 0.75) samples. The scanning electron micrographs of Tl1-xCx-1234 shows well connected grains in x = 0 and 0.25 samples. Whereas, x = 0.5 and 0.75 samples have relatively poor grain morphology, which shows that the source of pinning in Tl0.75C0.25-1234 sample is intrinsic one. The transition width data was also fitted to the thermally activated flux flow model. The apical phonon modes of vibrations were studied through FTIR absorption measurements.

  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. Spectroscopic Signatures of Defect-Induced Pair Breaking in Bi2Sr2CaCu2O8+x

    Science.gov (United States)

    Vobornik, I.; Berger, H.; Pavuna, D.; Onellion, M.; Margaritondo, G.; Rullier-Albenque, F.; Forró, L.; Grioni, M.

    1999-04-01

    We investigated the effect of disorder on the spectral properties of the high temperature superconductor Bi2Sr2CaCu2O8+x. We find that small defect densities, in the low 10-3 range, already suppress the characteristic spectral signature of the superconducting state, while new excitations appear within the gap. We conclude that, due to defect-induced pair breaking, superconducting pairs and normal carriers coexist below Tc. At higher levels of disorder the normal state is also strongly affected, and the quasiparticle features progressively smeared out.

  7. Thermal annealing study of high-Tc YBaCuO and BiSrCaCuO superconducting wires

    International Nuclear Information System (INIS)

    High-Tc YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire-type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times

  8. 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.

  9. Resonant phase escape in Bi2Sr2CaCu2O8+δ surface intrinsic Josephson junctions

    Science.gov (United States)

    Yu, H. F.; Zhu, X. B.; Ren, J. K.; Peng, Z. H.; Cui, D. J.; Deng, H.; Cao, W. H.; Tian, Ye; Chen, G. H.; Zheng, D. N.; Jing, X. N.; Lu, Li; Zhao, S. P.

    2013-09-01

    We present a study of phase escape in surface Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions in the presence of microwave radiation. The measured switching current distributions display clear double-peak structures in the microwave field, which result from the single- and two-photon resonant escape processes accompanied by microwave-induced potential barrier suppression. We show that these results can be well explained by a quantum-mechanical model proposed by Fistul et al (2003 Phys. Rev. B 68 060504), from which the power and frequency dependences of the switching current distributions can be reproduced.

  10. Magnetic Excitations in Thin Film Ba2 IrO4 and Sr2 IrO4 Probed by Resonant Inelastic X-ray Scattering

    Science.gov (United States)

    Clancy, J. P.; Lupascu, A.; Gretarsson, H.; Upton, M. H.; Kim, J.; Islam, Z.; Uchida, M.; Schlom, D. G.; Shen, K. M.; Nichols, J.; Terzic, J.; Cao, G.; Seo, S. S. A.; Katukuri, V. M.; Hozoi, L.; van den Brink, J.; Stoll, H.; Kim, Y.-J.

    2014-03-01

    We have performed resonant inelastic x-ray scattering (RIXS) measurements on epitaxial thin film samples of the layered perovskite iridates Ba2IrO4 and Sr2IrO4. These materials display a novel Jeff = 1/2 Mott insulating ground state driven by strong 5d spin-orbit coupling effects. By studying 10 to 50 nm thin film samples grown on a variety of different substrates (GSO, STO, LSAT), we have investigated the impact of applied tensile/compressive strain on the characteristic magnetic and electronic excitations of these materials. Unlike other perturbations, such as doping or applied magnetic field, we find that applied strain does not alter the magnetic structure of Ba2IrO4 or Sr2IrO4. However, strain does affect the magnetic energy scales of these systems, providing a means of tuning both the ordering temperature (Tn) and the magnetic exchange interactions (J). In addition, we show that the dispersion of the low-lying magnon and spin-orbit exciton modes is renormalized by strain-induced structural changes.

  11. The structural and in-plane dielectric/ferroelectric properties of the epitaxial (Ba, Sr)(Zr, Ti)O3 thin films

    Science.gov (United States)

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

    2014-06-01

    Epitaxial (Ba1-xSrx)(Zr0.1Ti0.9)O3 (BSZT, x = 0 - 0.45) thin films were deposited on (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT) substrates by pulsed laser deposition. The experimental results demonstrate that the structural, dielectric, and ferroelectric properties of the BSZT thin films were greatly dependent on the strontium content. The BSZT thin films transformed from tetragonal to cubic phase when x ≥ 0.35 at room temperature. The Curie temperature and room-temperature remnant polarization decrease with increasing strontium concentration. The optimal dielectric properties were found in (Ba0.55Sr0.45)(Zr0.1Ti0.9)O3 thin films which is in paraelectric state, having tunability of 47% and loss tangent of 0.0338 under an electric field of 20 MV/m at 1 MHz. This suggests that BSZT thin film is a promising candidate for tunable microwave device applications.

  12. Temperature dependence of the optical properties of Ba{sub 0.75}Sr{sub 0.25}TiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Železný, V., E-mail: zelezny@fzu.cz [Institute of Physics, ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Chvostová, D.; Pajasová, L.; Jelínek, M.; Kocourek, T. [Institute of Physics, ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Daniš, S.; Valvoda, V. [Charles University, Faculty of Mathematics Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic)

    2014-11-28

    Optical properties of Ba{sub 0.75}Sr{sub 0.25}TiO{sub 3} (BST(75/25)) ferroelectric thin film have been investigated by spectroscopic ellipsometry in a broad temperature interval from 10 to 300 K. The polycrystalline perovskite-phase BST films were prepared by pulsed laser deposition technique. The complex dielectric functions and optical parameters of the films were determined in the 1.5–5.5 eV spectral range. The spectra can be divided into two distinctive regions according to the magnitude of absorption coefficient separated by a band gap. An apparent reduction of the band gap was observed on increasing temperature. This can be ascribed to the renormalization of electronic band structure due to the electron–phonon interaction, which follows the Bose–Einstein model. - Highlights: • Spectroscopic ellipsometry of Ba{sub 0.75}Sr{sub 0.25}TiO{sub 3} from 10 to 300 K • Response functions were determined in the 1.5–5.5 eV interval. • Band gap reduction with increasing temperature was observed. • The band gap reduction follows the Bose–Einstein model.

  13. Three-dimensional supercapacitors composed of Ba0.65Sr0.35TiO3 (BST)/NiSi2/silicon microchannel plates

    International Nuclear Information System (INIS)

    Three-dimensional (3D) supercapacitors consisting of Ba0.65Sr0.35TiO3 (BST)/NiSi2/silicon microchannel plate (MCP) stacked structure have been fabricated. The silicon MCP produced by electrochemical etching is utilized as a backbone of the 3D structure on which a nickel silicide current collector layer and Ba0.65Sr0.35TiO3 dielectric layer are deposited successively by electroless plating and the sol-gel method, respectively. The morphology and structure of the 3D BST/NiSi2/Si-MCP structure are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and the electrochemical properties are determined by cyclic voltammetry (CV) and chronopotentiometry. The structure exhibits excellent capacitive behavior with a maximum capacitance of 784 F g-1. After 700 charging/discharging cycles, the Cf decreases slightly with only a 5.7% loss and is stable after more than 700 cycles. The BST/NiSi2/Si-MCP 3D structure is a potential supercapacitor in industrial applications.

  14. Structural and multiferroic properties of Fe-doped Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} solids

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhengang, E-mail: guozg1986@126.com [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Pan, Liqing [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); College of Science, China Three Gorges University, Yichang, Hubei 443002 (China); Bi, Chong; Qiu, Hongmei; Zhao, Xuedan; Yang, Lihong; Rafique, M. Yasir [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China)

    2013-01-15

    The structural, dielectric, ferroelectric, and magnetic properties of bulk Fe-doped Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (Ba{sub 0.5}Sr{sub 0.5}Ti{sub 1-x}Fe{sub x}O{sub 3}; BSTF) solids prepared by standard solid-state reaction were investigated. X-ray diffraction (XRD) patterns confirmed the tetragonal structure of BSTF samples. Rietveld refinements of XRD data revealed that the doping ions lead to unit cell expansion in three directions. Ferroelectric and ferromagnetic orders of the samples were observed simultaneously at room temperature. According to experimental and simulated results, two possible exchange coupling mechanisms exist in the BSTF systems, namely, nearest-site antiferromagnetic coupling and next-nearest-site ferromagnetic coupling. The two coupling mechanisms coexist in BSTF systems, leading to extraordinary ferromagnetic behavior. - Highlights: Black-Right-Pointing-Pointer Rietveld refinements of XRD data reveal that the doping Fe ions lead to an expansion of BSTF unit cell in three directions. Black-Right-Pointing-Pointer Ferroelectric and ferromagnetic orders of BSTF samples are observed simultaneously at room temperature. Black-Right-Pointing-Pointer There are two possible exchange coupling mechanisms in the Fe-doped BST systems, the nearest-site antiferromagnetic coupling and the next-nearest-site ferromagnetic one.

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

    CERN Document Server

    Cescutti, Gabriele

    2014-01-01

    Context. Thanks to the heroic observational campaigns carried out in recent years we now have large samples of metal-poor stars for which measurements of detailed abundances exist. [...] These data hold important clues on the nature of the contribution of the first stellar generations to the enrichment of our Galaxy. Aims. We aim to explain the scatter in Sr, Ba, Y, and Eu abundance ratio diagrams unveiled by the metal-poor halo stars. Methods. We computed inhomogeneous chemical evolution models for the Galactic halo assuming different scenarios for the r-process site: the electron-capture supernovae (EC) and the magnetorotationally driven (MRD) supernovae scenario. We also considered models with and without the contribution of fast-rotating massive stars (spinstars) to an early enrichment by the s-process. A detailed comparison with the now large sample of stars with measured abundances of Sr, Ba, Y, Eu, and Fe is provided (both in terms of scatter plots and number distributions for several abundance ratios)...

  16. Thickness-dependent Electrical and Piezoelectric Properties of Lead-Free Ferroelectric Ba0.8Sr0.2TiO3 Thin Films

    Directory of Open Access Journals (Sweden)

    D.A. Kiselev

    2016-10-01

    Full Text Available The thickness dependent of electrical and piezoelectric properties of lead-free ferroelectric Ba0.8Sr0.2TiO3 thin films is reported. Ba0.8Sr0.2TiO3 (BST 80/20 thin films for various thickness, ranging from 150 nm to 550 nm, were prepared by high-frequency reactive sputtering of a ceramic target in an oxygen atmosphere on p-type Si substrate. Memory windows and effective dielectric constant of the BST film in Au/BST/Si thin film capacitors is found to increase with the increasing thickness of the film. Domain structure, domain switching and hysteresis loops of the BST 80/20 thin film were investigate via the piezoresponse force microscopy. Complete domain switching and strong piezoresponse are found in the ferroelectric BST film. The piezoelectric coefficient ( and the remnant piezoelectric response (ΔPR of BST 80/20 films is found to increase with the thickness of the film.

  17. Step Coverage and Electrical Properties of (Ba, Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition Using TiO(DPM)2

    Science.gov (United States)

    Kawahara, Takaaki; Yamamuka, Mikio; Makita, Tetsuro; Naka, Jiro; Yuuki, Akimasa; Mikami, Noboru; Ono, Kouichi

    1994-09-01

    Thin films of (Ba, Sr)TiO3 (BST) with high dielectric constant were prepared on Pt/ SiO2/Si substrates of 6-inch-diameter by liquid source chemical vapor deposition using Ba(DPM)2, Sr(DPM)2 and TiO(DPM)2 (DPM=dipivaloylmethanato; C11H19O2) dissolved in tetrahydrofuran (THF). The reproducibility of ±3 % for the film composition was achieved by optimizing the deposition procedures. It was found that the coverage of 72%, obtained at the substrate temperature T s=753 K, was better than those obtained using other Ti sources such as Ti(O-i-Pr)4 (TTIP) and Ti(O-i-Pr)2(DPM)2. The electrical properties of the 480-Å-thick BST film, deposited at T s=753 K using TiO(DPM)2, were as follows: dielectric constant ɛ=230, equivalent SiO2 thickness t eq=7.8 Å, leakage current density J L=6.7×10-6 A/cm2 at 1.65 V and dielectric loss tan δ=0.013.

  18. Effect of Ba and Zr doping in Sr0.8Bi2.2Ta2O9 thin films

    International Nuclear Information System (INIS)

    The influence of large ion doping in Sr0.8Bi2.2Ta2O9 (SBT) thin films grown on Pt/Ti/Si(1 0 0) substrates was studied from the view point of changing the ferroelectric and dielectric parameters such as remanent polarization (Pr), coercive field (EC) and dielectric constant (εr) by adding 5, 10 and 15 mol% of Ba and Zr relative to constituent Sr and Ta, respectively. Ferroelectric hysteresis loops measured at a frequency of 10 kHz indicated that (2Pr) significantly decreased to approximately 12, 7.6, 1.6 μC/cm2 (compared to 14.4 μC/cm2 of SBT) and (2EC) enhanced to approximately 180, 200 kV/cm and 150 (compared to 145 kV/cm of SBT) and by 5, 10, 15 mol% doping, respectively. Dielectric constants decreased to 135, 115 and 75 (compared to 190 of SBT) by 5, 10, 15 mol% doping, respectively. It is observed that the doping causes a slight increase in the leakage current density but it is still on the order of 10-7 A/cm2 at electric field of 300 kV/cm. Such parameters would make Ba and Zr doped SBT as a candidate ferroelectric-gate in FET memory applications.

  19. The lone-pairs enhanced birefringence and SHG response: A DFT investigation on M2B5O9Cl (M = Sr, Ba, and Pb)

    International Nuclear Information System (INIS)

    Highlights: • Enhanced birefringence and SHG response of Pb2B5O9Cl comparison with its isostructural M2B5O9Cl. • The enhancement originates from the covalent interaction of Pb and O atoms. • The interaction of Pb–O reduces the bandgap comparison with its isostructural M2B5O9Cl. - Abstract: It is important to investigate the electronic structures and optical properties of the UV NLO compound containing lone-pairs electrons, aiming to make a subtle balance among relative large SHG response, big birefringence and deep bandgap. In this paper, the electronic structures and optical properties of M2B5O9Cl (M = Sr, Ba, and Pb) have been investigated using the DFT method. The results show that the enhanced birefringence and SHG response are found in Pb2B5O9Cl comparison with that of Sr2B5O9Cl and Ba2B5O9Cl. And the enhanced birefringence and SHG response in Pb2B5O9Cl originate from the covalent interaction between the oxygen and lead atoms

  20. Influence of bismuth on properties and microstructures of Sr0.5Ba0.5–Bi TiO3 thin films

    Indian Academy of Sciences (India)

    Tao Wenhong; Wang Yin; Fu Xinghua; Wei Qihong

    2006-10-01

    The influence of bismuth (Bi) on the dielectric and ferroelectric properties of Sr0.5Ba0.5–Bi TiO3 (BST, 0 < < 0.030 mol) thin films was studied. The results showed that the dielectric constant (r) and dielectric loss (tan ) decreased, and temperature, m, for maximum and r (Curie temperature), moved to lower temperature with increasing Bi content. The r, s and c were 0.22 C/cm2, 0.32 C/cm2 and 60 kV/cm, respectively for Sr0.5Ba0.485Bi0.015TiO3 thin films measured at 100 Hz, 20 V. The microstructure of BST thin films was studied by XRD and TEM. Tetragonal perovskite grains existed in BST thin films, but the grain size decreased with increasing doping ratio in BST. The characteristic absorption band for octahedron [TiO2] (471.65 cm-1) was shifted to lower wave number.