Sample records for rb sr ba

  1. Alkaline-alkaline earth fluoride carbonate crystals ABCO3F (A = K, Rb, Cs; B = Ca, Sr, Ba) as nonlinear optical materials.

    Zou, Guohong; Ye, Ning; Huang, Ling; Lin, Xinsong


    A new series of alkaline-alkaline earth fluoride carbonates (KSrCO(3)F, RbSrCO(3)F, KCaCO(3)F, RbCaCO(3)F, CsCaCO(3)F, and Cs(3)Ba(4)(CO(3))(3)F(5)) were synthesized by spontaneous crystallization with molten fluxes. Their crystal structures, except for Cs(3)Ba(4)(CO(3))(3)F(5), exhibit the stacking of [AF](∞) (A = K, Rb, Cs) and [B(CO(3))](∞) (B = Ca, Sr) layers, and the coplanar alignment of [CO(3)] triangles. The results from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges were all below 200 nm, except for Cs(3)Ba(4)(CO(3))(3)F(5), which is about 210 nm. Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that these carbonates are all phase-matchable materials in both visible and the UV region, and their measured SHG coefficients were about 3.33, 3.33, 3.61, 1.11, 1.11, and 1.20 times as large as that of d(36) (KDP), respectively. © 2011 American Chemical Society

  2. Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: early results for Gale crater from Bradbury Landing Site to Rocknest

    Ollila, Ann M.; Newsom, Horton E.; Clark, Benton; Wiens, Roger C.; Cousin, Agnes; Blank, Jen G.; Mangold, Nicolas; Sautter, Violaine; Maurice, Sylvestre; Clegg, Samuel M.; Gasnault, Olivier; Forni, Olivier; Tokar, Robert; Lewin, Eric; Dyar, M. Darby; Lasue, Jeremie; Anderson, Ryan; McLennan, Scott M.; Bridges, John; Vaniman, Dave; Lanza, Nina; Fabre, Cecile; Melikechi, Noureddine; Perett, Glynis M.; Campbell, John L.; King, Penelope L.; Barraclough, Bruce; Delapp, Dorothea; Johnstone, Stephen; Meslin, Pierre-Yves; Rosen-Gooding, Anya; Williams, Josh


    The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.

  3. Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: Early results for Gale crater from Bradbury Landing Site to Rocknest

    Ollila, Ann M.; Newsom, Horton E.; Clark, Benton; Wiens, Roger C.; Cousin, Agnes; Blank, Jen G.; Mangold, Nicolas; Sautter, Violaine; Maurice, Sylvestre; Clegg, Samuel M.; Gasnault, Olivier; Forni, Olivier; Tokar, Robert; Lewin, Eric; Dyar, M. Darby; Lasue, Jeremie; Anderson, Ryan; McLennan, Scott M.; Bridges, John; Vaniman, Dave; Lanza, Nina; Fabre, Cecile; Melikechi, Noureddine; Perrett, Glynis M.; Campbell, John L.; King, Penelope L.; Barraclough, Bruce; Delapp, Dorothea; Johnstone, Stephen; Meslin, Pierre-Yves; Rosen-Gooding, Anya; Williams, Josh


    ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.

  4. Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: early results for Gale crater from Bradbury Landing Site to Rocknest

    Ollila, Ann M.; Newsom, Horton E.; Clark, Benton; Wiens, Roger C.; Cousin, Agnes; Blank, Jen G.; Mangold, Nicolas; Sautter, Violaine; Maurice, Sylvestre; Clegg, Samuel M.; Gasnault, Olivier; Forni, Olivier; Tokar, Robert; Lewin, Eric; Dyar, M. Darby; Lasue, Jeremie; Anderson, Ryan; McLennan, Scott M.; Bridges, John; Vaniman, Dave; Lanza, Nina; Fabre, Cecile; Melikechi, Noureddine; Perett, Glynis M.; Campbell, John L.; King, Penelope L.; Barraclough, Bruce; Delapp, Dorothea; Johnstone, Stephen; Meslin, Pierre-Yves; Rosen-Gooding, Anya; Williams, Josh


    The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.

  5. 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

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


    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.

  6. Single Variable and Multivariate Analysis of Remote Laser-Induced Breakdown Spectra for Prediction of Rb, Sr, Cr, Ba, and V in Igneous Rocks

    Clegg, Samuel M [Los Alamos National Laboratory; Wiens, Roger C. [Los Alamos National Laboratory; Speicher, Elly A [MT HOLYOKE COLLEGE; Dyar, Melinda D [MT HOLYOKE COLLEGE; Carmosino, Marco L [MT HOLYOKE COLLEGE


    Laser-induced breakdown spectroscopy (LIBS) will be employed by the ChemCam instrument on the Mars Science Laboratory rover Curiosity to obtain UV, VIS, and VNIR atomic emission spectra of surface rocks and soils. LIBS quantitative analysis is complicated by chemical matrix effects related to abundances of neutral and ionized species in the resultant plasma, collisional interactions within plasma, laser-to-sample coupling efficiency, and self-absorption. Atmospheric composition and pressure also influence the intensity of LIBS plasma. These chemical matrix effects influence the ratio of intensity or area of a given emission line to the abundance of the element producing that line. To compensate for these complications, multivariate techniques, specifically partial least-squares regression (PLS), have been utilized to predict major element compositions (>1 wt.% oxide) of rocks, PLS methods regress one or multiple response variables (elemental concentrations) against multiple explanatory variables (intensity at each pixel of the spectrometers). Because PLS utilizes all available explanatory variable and eliminates multicollinearity, it generally performs better than univariate methods for prediction of major elements. However, peaks arising from emissions from trace elements may be masked by peaks of higher intensities from major elements. Thus in PLS regression, wherein a correlation coefficient is determined for each elemental concentration at each spectrometer pixel, trace elements may show high correlation with more intense lines resulting from optical emissions of other elements. This could result in error in predictions of trace element concentrations. Here, results of simple linear regression (SLR) and multivariate PLS-2 regression for determination of trace Rb, Sr, Cr, Ba, and V in igneous rock samples are compared. This study focuses on comparisons using only line intensities rather than peak areas to highlight differences between SLR and PLS.

  7. Mass measurements of neutron-rich Rb and Sr isotopes

    Klawitter, R; Brodeur, M; Chowdhury, U; Chausdhuri, A; Fallis, J; Gallant, A T; Grossheim, A; Kwiatkowski, A A; Lascar, D; Leach, K G; Lennarz, A; Macdonald, T D; Pearkes, J; Seeraji, S; Simon, M C; Simon, V V; Schultz, B E; Dilling, J


    We report on the mass measurements of several neutron-rich $\\mathrm{Rb}$ and $\\mathrm{Sr}$ isotopes in the $A \\approx 100$ region with the TITAN Penning-trap mass spectrometer. Using highly charged ions in the charge state $q=10+$, the masses of $^{98,99}\\mathrm{Rb}$ and $^{98-100}\\mathrm{Sr}$ have been determined with a precision of $6 - 12\\ \\mathrm{keV}$, making their uncertainty negligible for r-process nucleosynthesis network calculations. The mass of $^{101}\\mathrm{Sr}$ has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of $3\\sigma$ when compared to the Atomic Mass Evaluation. We also confirm the mass of $^{100}\\mathrm{Rb}$ from a previous measurement. Furthermore, our data indicates the existance of a low-lying isomer with $80\\ \\mathrm{keV}$ excitation energy in $^{98}\\mathrm{Rb}$. We show that our updated mass values lead to minor changes in the r-process by calculating fractional abundances in the $A\\approx 100$ re...

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

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


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

  9. The van der Waals potentials of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa

    Wei, L. M.; Li, P.; Tang, K. T.


    Based on the facts that the potential energy curves of the homo-nuclear group 2 dimers (group IIA metal), except Be2, are conformal, and they can be described by the Tang-Toennies potential model, a set of simple combining rules are proposed for the parameters of the reduced potentials of the hetero-nuclear dimers. Together with the well-established combining rules of the range parameters of the exponential repulsion and the known dispersion coefficients, these rules enable us to determine the ground state potential energy curves of MgCa, MgSr, MgBa, CaSr, CaBa, and SrBa from those of Mg2, Ca2, Sr2, and Ba2. The determined potentials are comparable to some ab initio calculations and in excellent agreement with the experiment.

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

    WANG; Xiu-feng


    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

  11. Rb, Sr and strontium isotopic composition, K/Ar age and large ion lithophile trace element abundances in rocks and glasses from the Wanapitei Lake impact structure

    Winzer, S. R.; Lum, R. K. L.; Schuhmann, S.


    Shock metamorphosed rocks and shock-produced melt glasses from the Wanapitei Lake impact structure have been examined petrographically and by electron microprobe. Eleven clasts exhibiting varying degrees of shock metamorphism and eight impact-produced glasses have been analyzed for Rb, Sr and Sr isotopic composition. Five clasts and one glass have also been analyzed for large ion lithophile (LIL) trace element abundances including Li, Rb, Sr, and Ba and the REE's. The impact event forming the Wanapitei Lake structure occurred 37 m.y. ago based on K/Ar dating of glass and glassy whole-rock samples. Rb/Sr isotopic dating failed to provide a meaningful whole-rock or internal isochron. The isotopic composition of the glasses can be explained by impact-produced mixing and melting of metasediments.

  12. Stabilization of 3d Transition Metal Hydrido Complexes in SrH2Mg2[Co(I)H5], BaH2Mg5[Co(-I)H4]2, and RbH2Mg5[Co(-I)H4 Ni(0)H4] via Easily Polarizable Hydride Ligands.

    Fahlquist, Henrik; Moser, David; Noréus, Dag; Refson, Keith; Parker, Stewart F


    A combined study using neutron diffraction, inelastic neutron scattering, and first-principles calculations describe cobalt with a very low formal oxidation state of (-I) in a slightly distorted tetrahedral Co(-I)H4-complex in BaH2Mg5[Co(-I)H4]2 and in the structurally related RbH2Mg5[Co(-I)H4 Ni(0)H4]. This indicates that the electron "back donating" effect via the polarizable hydride ions to the counterions in the solid state hydrides, can be compared to more conventional "back bonding" able to reduce the oxidation state down to -I. The hydrides were synthesized by hot sintering of transition metal powders with corresponding binary alkali- and alkaline earth hydrides. In the similarly synthesized SrH2Mg2[Co(I)H5], cobalt is formally + I-valent, showing a high sensitivity to differences in the counterion framework, which can also influence electrical properties.

  13. Decoupled Rb-Sr and Sm-Nd isotopic evolution of the continental crust

    Goldstein, S. L.


    Evidence was presented that the Rb-Sr and Sm-Nd isotopic systems are decoupled in crust-mantle evolution. Rare earth element (including Sm and Nd) residue principally in silicates, and are resistant to mobilization by weathering and metamorphism. In contrast, Rb and Sr are easily fractionated by crustal processes and residue in carbonates as well as in silicates. As a result, continental Sr, but not Nd, can be recycled into the mantle by exchange of seawater with basalt at spreading ridges and by subduction of carbonates associated with ridge processes. These effects result in mean Rb-Sr ages of the continental crust and of the upper mantle that are too young. Crustal growth curves based largely on Rb-Sr data, such that of Hurley and Rand, are therefore incorrect.

  14. Derivation of Apollo 14 High-Al Basalts at Discrete Times: Rb-Sr Isotopic Constraints

    Hui. Hejiu; Neal, Clive, R.; Shih, Chi-Yu; Nyquist, Laurence E.


    Pristine Apollo 14 (A-14) high-Al basalts represent the oldest volcanic deposits returned from the Moon [1,2] and are relatively enriched in Al2O3 (>11 wt%) compared to other mare basalts (7-11 wt%). Literature Rb-Sr isotopic data suggest there are at least three different eruption episodes for the A-14 high-Al basalts spanning the age range approx.4.3 Ga to approx.3.95 Ga [1,3]. Therefore, the high-Al basalts may record lunar mantle evolution between the formation of lunar crust (approx.4.4 Ga) and the main basin-filling mare volcanism (basalts were originally classified into five compositional groups [5,6], and then regrouped into three with a possible fourth comprising 14072 based on the whole-rock incompatible trace element (ITE) ratios and Rb-Sr radiometric ages [7]. However, Rb-Sr ages of these basalts from different laboratories may not be consistent with each other because of the use of different 87Rb decay constants [8] and different isochron derivation methods over the last four decades. This study involved a literature search for Rb-Sr isotopic data previously reported for the high-Al basalts. With the re-calculated Rb-Sr radiometric ages, eruption episodes of A-14 high-Al basalts were determined, and their petrogenesis was investigated in light of the "new" Rb-Sr isotopic data and published trace element abundances of these basalts.

  15. K-Ca and Rb-Sr Dating of Lunar Granite 14321 Revisited

    Simon, Justin I.; Shih, C.-Y.; Nyquist, L. E.


    K-Ca and Rb-Sr age determinations were made for a bulk feldspar-rich portion of an Apollo rock fragment of the pristine lunar granite clast (14321,1062), an acid-leached split of the sample, and the leachate. K-Ca and Rb-Sr data were also obtained for a whole rock sample of Apollo ferroan anorthosite (FAN, 15415). The recent detection [1] of widespread intermediate composition plagioclase indicates that the generation of a diversity of evolved lunar magmas maybe more common and therefore more important to our understanding of crust formation than previously believed. Our new data strengthen the K-Ca and Rb-Sr internal isochrons of the well-studied Apollo sample 14321 [2], which along with a renewed effort to study evolved lunar magmas will provide an improved understanding of the petrogenetic history of evolved rocks on the Moon.

  16. Magnetic comparison of BaCa and BaSr substituted hexaferrite powders

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


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

  17. Derivation of Apollo 14 High-Al Basalts at Discrete Times: Rb-Sr Isotopic Constraints

    Hui, H.; Neal, C. R.; Shih, C.-Y.; Nyquist, L. E.


    Four eruption episodes were identified for A-14 high-Al basalts. Rb-Sr isotopic data and ITE ratios show that their parental melt compositions of are correlated through mixing of evolved components with a relatively primitive magma ocean cumulate.

  18. Reactive two-body and three-body collisions of Ba$^+$ in an ultracold Rb gas

    Krükow, Artjom; Härter, Arne; Denschlag, Johannes Hecker


    We analyze reactive collisions of a single Ba$^+$ ion in contact with an ultracold gas of Rb atoms at mK$\\times k_{\\mathrm{B}}$ collision energies. Mapping out the Ba$^+$ loss rate dependence on the Rb atom density we can discern two-body reactive collisions from three-body ones and for the first time determine both rate coefficients which are $k_2=3.1(6)(6)\\times 10^{-13}\\textrm{cm}^{3}\\textrm{s}^{-1}$ and $k_3=1.04(4)(45)\\times 10^{-24}\\textrm{cm}^{6}\\textrm{s}^{-1}$, respectively (statistical and systematic errors in parenthesis). Thus, the measured ternary recombination dominates over binary reactions even at moderate atom densities of $n\\approx 10^{12}\\: \\textrm{cm}^{-3}$. The results for Ba$^+$ and Rb are representative for a wide range of cold ion-atom systems and can serve as a guidance for the future development of the field of hybrid atom-ion research.

  19. Ba2+-inhibitable /sup 86/Rb+ fluxes across membranes of vesicles from toad urinary bladder

    Garty, H.; Civan, M.M.


    /sup 86/Rb+ fluxes have been measured in suspensions of vesicles prepared from the epithelium of toad urinary bladder. A readily measurable barium-sensitive, ouabain-insensitive component has been identified; the concentration of external Ba2+ required for half-maximal inhibition was 0.6 mM. The effects of externally added cations on /sup 86/Rb+ influx and efflux have established that this pathway is conductive, with a selectivity for K+, Rb+ and Cs+ over Na+ and Li+. The Rb+ uptake is inversely dependent on external pH, but not significantly affected by internal Ca2+ or external amiloride, quinine, quinidine or lidocaine. It is likely, albeit not yet certain, that the conductive Rb+ pathway is incorporated in basolateral vesicles oriented right-side-out. It is also not yet clear whether this pathway comprises the principle basolateral K+ channel in vivo, and that its properties have been unchanged during the preparative procedures. Subject to these caveats, the data suggest that the inhibition by quinidine of Na+ transport across toad bladder does not arise primarily from membrane depolarization produced by a direct blockage of the basolateral channels. It now seems more likely that the quinidine-induced elevation of intracellular Ca2+ activity directly blocks apical Na+ entry.

  20. Rb-Sr and Sm-Nd Study of Asuka 881394: Evidence of "Late" Metamorphism

    Nyquist, L. E.; Shih, C.-Y.; Reese, Y.; Takeda, H.


    The Asuka 881394 achondrite contains fossil Al-26 and Mn-53 [1,2,3] and has a Pb-207/Pb-206 age of 4566.5 plus or minus 0.2 Ma [3], the oldest for an achondrite. Preliminary results showed initial Sm-146/Sm-144 = (7.4 plus or minus 1.2) x 10(exp -3), indicative of an ancient age, but Rb-87 - Sr-87 and Sm-147 - Nd-143 ages of 4370 plus or minus 60 and 4490 plus or minus 20 Ma, resp. [1], were younger than expected from the presence of short-lived nuclides. We revisit the Rb-Sr and Sm-Nd chronology of A881394 in an attempt to establish whether late metamorphism led to inconsistency in its apparent ages.

  1. Ar-Ar and Rb-Sr Ages of the Tissint Olivine-phyric Martian Shergottite

    Park, J.; Herzog, G. F.; Nyquist, L. E.; Shih, C.-Y.; Turin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Agee, C.


    The fifth martian meteorite fall, Tissint, is an olivine-phyric shergottite that contains olivine macrocrysts (approximately 1.5 mm) [1]. [2] reported the Sm-Nd age of Tissint as 596 plus or minus 23 Ma along with Rb-Sr data that defined no isochron. [3] reported Lu-Hf and Sm-Nd ages of 583 plus or minus 86 Ma and 616 plus or minus 67 Ma, respectively. The cosmic-ray exposure ages of Tissint are 1.10 plus or minus 0.15 Ma based on 10Be [4], and 1.0-1.1 Ma, based on 3He, 21Ne, and 38Ar [5,6].We report Ar-Ar ages and Rb-Sr data.

  2. Absolute branching intensities in the decay of 92Rb to 92Sr

    Lhersonneau, G; Rizzi, V; Alyakrinskiy, O; Lanchais, A; Volkov, Yu.M; Barzakh, A.E; Fedorov, D.V; Ionan, A.M; Ivanov, V.S; Mezilev, K.A; Moroz, F.V; Orlov, S.Yu; Panteleev, V.N; Lau, C; Bajeat, O; Essabaa, S; Leroy, R; Jardin, P; Stroe, L; 10.1103/PhysRevC.74.017308


    The branching of the 2+ to 0+ transition in 92Sr has been measured to 0.032(4) per 92Rb decay. It confirms an earlier measurement however discarded in nuclear data evaluations since in contradiction with accepted lower logft limits. The conflict could be solved assuming that close to half of the decay intensity, mostly as high-energy ground-state transitions, is missing in th edecay scheme.

  3. Rb-Sr And Sm-Nd Ages, and Petrogenesis of Depleted Shergottite Northwest Africa 5990

    Shih, C. Y.; Nyquist, L. E.; Reese, Y.; Irving, A. J.


    Northwest Africa (NWA) 5990 is a very fresh Martian meteorite recently found on Hamada du Draa, Morocco and was classified as an olivine-bearing diabasic igneous rock related to depleted shergottites [1]. The study of [1] also showed that NWA 5990 resembles QUE 94201 in chemical, textural and isotopic aspects, except QUE 94201 contains no olivine. The depleted shergottites are characterized by REE patterns that are highly depleted in LREE, older Sm-Nd ages of 327-575 Ma and highly LREE-depleted sources with Nd= +35+48 [2-7]. Age-dating these samples by Sm-Nd and Rb-Sr methods is very challenging because they have been strongly shocked and contain very low abundances of light rare earth elements (Sm and Nd), Rb and Sr. In addition, terrestrial contaminants which are commonly present in desert meteorites will compromise the equilibrium of isotopic systems. Since NWA 5990 is a very fresh meteorite, it probably has not been subject to significant desert weathering and thus is a good sample for isotopic studies. In this report, we present Rb-Sr and Sm-Nd isotopic results for NWA 5990, discuss the correlation of the determined ages with those of other depleted shergottites, especially QUE 94201, and discuss the petrogenesis of depleted shergottites.

  4. Clathrate formation in the systems Sr-Cu-Ge and {Ba,Sr}-Cu-Ge

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


    In the ternary system Sr-Cu-Ge, a novel clathrate type-I phase was detected, Sr8CuxGe46-x (5.2≤xtemperature interval. Sr8Cu5.3Ge40.7 decomposes eutectoidally on cooling at 730±3 °C into (Ge), SrGe2 and τ1-SrCu2-xGe2+x. Phase equilibria at 700 °C have been established for the Ge rich part and are characterized by the appearance of only one ternary compound, τ1-SrCu2-xGe2+x, which crystallizes with the ThCr2Si2 structure type and forms a homogeneity range up to x=0.4 (a=0.42850(4), c=1.0370(1) nm). Additionally, the extent of the clathrate type-I solid solution Ba8-ySryCuxGe46-x (0≤y≤~5.6; 5.2≤x≤5.4, from as cast alloys) has been studied at various temperatures. The clathrate type-I crystal structure (space group Pm3barn) has been proven by X-ray single crystal diffraction on two single crystals with the composition (from refinement): Sr8Cu5.36Ge40.64 (a=1.06368(2) nm at 300 K) and Ba4.86Sr3.14Cu5.36Ge40.64 (a=1.06748(2) nm at 300 K) measured at 300, 200 and 100 K. From the temperature dependence of the lattice parameters and the atomic displacement parameters, thermal expansion coefficients, Debye- and Einstein-temperatures and the speed of sound have been determined. From heat capacity measurements of Sr8Cu5.3Ge40.7 at low temperatures the Sommerfeld coefficient (γ=24 mJ/mol K2) and the Debye temperature (ΘDLT=273 K) have been extracted. From a detailed analysis of these data at higher temperatures, Einstein branches of the phonon dispersion relation have been derived and compared to those obtained from the atomic displacement parameters. Electrical resistivity measurements of Sr8Cu5.3Ge40.7 reveal a rather metallic behavior in the low temperature range (<300 K). Density function theory calculations provide densities of states, electronic resistivity and Seebeck coefficient as well as the vibrational spectrum and specific heat.

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



    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.

  6. Rb-Sr geochronological study on Tatehira granodiorite, Oshima Peninsula, Southwest Hokkaido, Japan

    Iizumi, Shigeru; Kobayashi, Hideo; Toyoda, Minoru


    It has been known that Tatehira granodiorite, a pluton which occurs sporadically in the southwest region of Hokkaido, is related with Kanoite formation. The radiometric age of this granodiorite still remains unknown. The Tatehira granodiorite intrudes into late Paleozoic or early Mesozoic Matsumae group, and is overlain by Miocene Usubetsu formation unconformably. It occurs as several separated small plutons. The samples for Rb-Sr analysis were collected from one of the plutons in southern part. The determination of the isochron age of rock-minerals and the initial Sr isotopic ratio of Tatehira granodiorite were carried out. This granodiorite is able to be classified into two phases, namely melanocratic (WRM) and leucocratic (WRL) phases. The samples of WRM and WRL were powdered and subjected to X-ray analysis. It was found that the chemical compositions were similar except slight differences in FeO + Fe2O3, CaO and K2O. The Sr isotopic ratio was determined with a MAT 261 mass spectrometer, and the results were analyzed statistically. The Rb and Sr concentrations and the Sr isotopic ratio of WRM, WRL, and PRF (plagio-clase rich fraction) and BRF (biotite rich fraction) separated from the WRL were determined, and the age of 102.5 +- 0.3 Ma and the initial ratio of 0.70538 +- 0.00001 were obtained. The ratio of Tatehira granodiorite is comparable to that of Okushiri Island. Comparing with the data obtained from other region, the granodiorites of Tatehira and Okushiri Island should be related with the granitoids of Abukuma granite province.

  7. Electroluminescence of SrS, BaS and SrSe Phosphors Activated by Cu and Er

    Kulkarni, V. W.; Patwardhan, S. S.; Ghanbahadur, R. Y.


    Results of the investigations of the spectral characteristics of electroluminescence of SrS:Cu, Er, BaS:Cu, Er and SrSe:Cu, Er phosphors are presented. Some new features of the voltage and frequency dependence of EL-emission are reported.

  8. Rb-Sr age of Gaik granite, Ladakh Batholith, northwest Himalaya

    Trivedi, J.R.; Gopalan, K. (Physical Research Lab., Ahmedabad (India)); Sharma, K.K.; Gupta, K.R.; Choubey, V.M. (Wadia Inst. of Himalayan Geology, Dehra Dun (India))


    The Gaik Granite is a part of Ladakh batholith outcropping between Gaik and Kiari in NW Himalaya. This is a pink porphyritic granite rich in biotite and poor in hornblende. Rb-Sr analyses have been made on six whole-rock samples of the Gaik Granite. Though the samples are poorly enriched in radiogenic Sr, they define a reliable isochron corresponding to an age of 235+-13(2sigma) m.y. and initial /sup 87/Sr//sup 86/Sr ratio of 0.7081+-0.0004 (2sigma), Biotite, plagioclase and potash feldspar fractions separated from two of the samples have yielded a much younger mineral isochron at 30+-1.5 m.y. indicating a nearly complete redistribution of Sr isotopes between mineral phases at a time much later than the primary emplacement of the granite. The present results show that at least some components of the Ladakh batholith are of Permo-Triassic aqe. These rocks were isotopically re-equilibrated on a mineral scale during Upper Oligocene in response to the Himalayan orogeny.

  9. Superconductivity in novel Ge-based skutterudites: {Sr,Ba}pt4Ge12.

    Bauer, E; Grytsiv, A; Chen, Xing-Qiu; Melnychenko-Koblyuk, N; Hilscher, G; Kaldarar, H; Michor, H; Royanian, E; Giester, G; Rotter, M; Podloucky, R; Rogl, P


    Combining experiments and ab initio models we report on SrPt4Ge12 and BaPt4Ge12 as members of a novel class of superconducting skutterudites, where Sr or Ba atoms stabilize a framework entirely formed by Ge atoms. Below T(c)=5.35 and 5.10 K for BaPt4Ge12 and SrPt4Ge12, respectively, electron-phonon coupled superconductivity emerges, ascribed to intrinsic features of the Pt-Ge framework, where Ge-p states dominate the electronic structure at the Fermi energy.

  10. Rb-Sr middle Devonian age of cordierite bearing migmatites from Lyonnais area (French Massif Central). Age Rb-Sr, Devonien moyen des migmatites a cordierite du Lyonnais (Massif central Francais)

    Duthou, J.L. (Clermont-Ferrand-2 Univ., 63 - Aubiere (France)); Chenevoy, M.; Gay, M. (Lyon-1 Univ., 69 - Villeurbanne (France))


    On the basis of Rb-Sr whole rock data, a middle Devonian age (384[+-]16 Ma) is ascribed to the cordierite bearing migmatites (gneiss d'Aubusson) in the Lyonnais area. In the barrovian domain, this anatexis is therefore synchronous throughout the northern part of the french ''Massif Central''. Rb and Sr concentrations were determined by X-ray fluorescence analysis, and isotopic compositions by mass spectrometry. (A.B.). 28 refs., 2 figs. 1 tab.

  11. Adsorption removal of Sr by Barium impregnated 4A Zeolite(BaA) from high radioactive seawater waste

    Lee, Eil Hee; Lee, Keun Young; Kim, Kwang Wook; Kim, Ik Soo; Chung, Dong Yong; Moon, Jei Kwon; Choi, Jong Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)


    This study investigated the removal of Sr, which was one of the high radioactive nuclides, by adsorption with Barium (Ba) impregnated 4A zeolite (BaA) from high-radioactive seawater waste (HSW). Adsorption of Sr by BaA (BaA-Sr), in the impregnated Ba concentration of above 20.2wt%, was decreased by increasing the impregnated Ba concentration, and the impregnated Ba concentration was suitable at 20.2wt%. The BaA-Sr adsorption was added to the co-precipitation of Sr with BaSO4 precipitation in the adsorption of Sr by 4A (4A-Sr) within BaA. Thus, it was possible to remove Sr more than 99% at m/V (adsorbent weight/solution volume)=5 g/L for BaA and m/V >20 g/L for 4A, respectively, in the Sr concentration of less than 0.2 mg/L (actual concentration level of Sr in HSW). It shows that BaA-Sr adsorption is better than 4A-Sr adsorption in for the removal capacity of Sr per unit gram of adsorbent, and the reduction of the secondary solid waste generation (spent adsorbent etc.). Also, BaA-Sr adsorption was more excellent removal capacity of Sr in the seawater waste than distilled water. Therefore, it seems to be effective for the direct removal of Sr from HSW. On the other hand, the adsorption of Cs by BaA (BaA-Cs) was mainly performed by 4A within BaA. Accordingly, it seems to be little effect of impregnated Ba into BaA. Meanwhile, BaA-Sr adsorption kinetics could be expressed the pseudosecond order rate equation. By increasing the initial Sr concentrations and the ratios of V/m, the adsorption rate constants (k2) were decreased, but the equilibrium adsorption capacities (qe) were increasing. However, with increasing the temperature of solution, k2 was conversely increased, and qe was decreased. The activation energy of BaA-Sr adsorption was 38 kJ/mol. Thus, the chemical adsorption seems to be dominant rather than physical adsorption, although it is not a chemisorption with strong bonding form.

  12. Sympathetic cooling of the Ba$^+$ ion by collisions with ultracold Rb atoms: theoretical prospects

    Krych, Michał; Moszynski, Filip Pawłowski Robert; Idziaszek, Zbigniew


    State-of-the-art {\\em ab initio} techniques have been applied to compute the potential energy curves of the (BaRb)$^+$ molecular ion in the Born-Oppenheimer approximation. The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the X$^1\\Sigma\\; \\rightarrow\\; ^1\\Sigma, \\; ^1\\Pi$ have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements, as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit coupled (relativistic) potential energy curves for the 0$^+$ and 1 states relevant for the running experiments have been obtained. Finall...

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

    Terekhin, M.A. [P.N. Lebedev Physical Institute, Leninskij Prospekt 53, 119991 Moscow (Russian Federation); Makhov, V.N., E-mail: [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)


    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.

  14. Precision-controlled elution of a 82Sr/82Rb generator for cardiac perfusion imaging with positron emission tomography

    Klein, R.; Adler, A.; Beanlands, R. S.; de Kemp, R. A.


    A rubidium-82 (82Rb) elution system is described for use with positron emission tomography. Due to the short half-life of 82Rb (76 s), the system physics must be modelled precisely to account for transport delay and the associated activity decay and dispersion. Saline flow is switched between a 82Sr/82Rb generator and a bypass line to achieve a constant-activity elution of 82Rb. Pulse width modulation (PWM) of a solenoid valve is compared to simple threshold control as a means to simulate a proportional valve. A predictive-corrective control (PCC) algorithm is developed which produces a constant-activity elution within the constraints of long feedback delay and short elution time. The system model parameters are adjusted through a self-tuning algorithm to minimize error versus the requested time-activity profile. The system is self-calibrating with 2.5% repeatability, independent of generator activity and elution flow rate. Accurate 30 s constant-activity elutions of 10-70% of the total generator activity are achieved using both control methods. The combined PWM-PCC method provides significant improvement in precision and accuracy of the requested elution profiles. The 82Rb elution system produces accurate and reproducible constant-activity elution profiles of 82Rb activity, independent of parent 82Sr activity in the generator. More reproducible elution profiles may improve the quality of clinical and research PET perfusion studies using 82Rb.

  15. An In-Situ Rb-Sr Dating & Organics Characterization Instrument For A MER+ Sized Rover

    Anderson, F.; Whitaker, T.; Nowicki, K.; Zacny, K.; Pierce, J.


    We posit that a Mars in-situ geochronology mission that will triage and validate samples for Mars Sample Return (MSR) is technically feasible in the 2018-2022 time frame and addresses the competing scientific, political, and fiscal requirements for flight in this decade.The mission must be responsive to the astrobiological and chronological science goals of the MEPAG, Decadal Survey (DS), and E2E-iSAG, and avoid the MSR appearance of long term political commitment and cost. These requirements can best be accomplished by a rover with a coring drill. JPL has reassessed the MER landing system performance, and determined that the system is capable of significantly higher landed mass (~40-60 kg plus reserve), allowing more sophisticated instruments to be carried. The instrument package is comprised of a time of flight (TOF) mass spectrometer combined with a laser desorption resonance ionization source to sensitively measure isobar free Rb-Sr isotopes for geochronology and organics characterization. The desorption laser is also used with a μRaman/LIBS for mineral characterization, which in combination with the TOF, will additionally provide measurements of K-Ar isotopes for a second form of radiometric dating. The laser desorption resonance ionization mass spectrometry (LDRIMS) technique avoids the interference and mass resolution issues associated with geochronology measurements, and has miniaturization potential. A sample is placed in the TOF mass spectrometer and surface atoms, molecules, and ions are desorbed with a 213 nm laser. Ions are suppressed by an electric field and the plume of expanding particles is present for many μs, during which it is first illuminated with laser light tuned to ionize only Sr, and then 1-3 μs later, for Rb. We have partially miniaturized the instrument, including Sr lasers, ablation laser, and mass spectrometer, and will soon to start using the instrument for field measurements. Our current prototype can measure the isotope ratio of

  16. Rb-Sr and Sm-Nd isotope geochemistry and chronology of cherts from the Onverwacht Group (3.5 AE), South Africa

    Weis, D.; Wasserburg, G. J.


    An Rb-Sr and Sm-Nd isotopic analysis of Archean chert samples from the Onverwacht Group, South Africa is presented, showing the same characteristic Rb and Sr concentrations as Phanerozoic cherts, with a very large range of Rb-87/Sr-86 ratios. A good correlation line in the Rb-87 to Sr-87 evolution diagram, corresponding to an age of about 2119 My and an initial Sr-87/Sr-86 ratio of about 0.72246, is derived which may be interpreted as reflecting the age of rehomogenization of the Sr in the protolith and the recrystallization of these cherts due to circulating hydrothermal fluids during regional metamorphism about 1.4 AE after deposition of the Onverwacht Group. The Sm-Nd systematics reflect an ancient source age of about 3.5 AE.

  17. Sm-Nd and Rb-Sr Ages for Northwest Africa 2977, A Young Lunar Gabbro from the PKT

    Nyquist, L. E.; Shih, C.-Y.; Reese, Y. D.; Irving, A. J.


    Northwest Africa (NWA) 2977 is an olivine gabbro cumulate equivalent to one of the lithologies in lunar mare breccia NWA 773 [1,2,3]. The Ar-39-Ar-40 age is 2.77+/-0.04 Ga based on the last approx.57% of the gas release [4], similar to results for NWA 773 [5]. A Sm-Nd age (T) of 2.865+/-0.031 Ga and Epsilon(sub Nd) = -7.84+/-0.22 for the NWA 773 gabbro reported by [6] has been revised to T = 2.993+/-=0.032 Ga, Epsilon(sub Nd) -4.5+/-0.3 [7]. Sm-147-Nd-143 isochron for NWA 2977: Whole rock, pyroxene, olivine, plagioclase, whole rock leachate (approx.phosphate) and the combined leachates from the mineral separates yield a well defined Sm-Nd isochron for an age T = 3.10+/-0.05 Ga and Epsilon(sub Nd-CHUR) = -3.74+/-0.26 [8], or Epsilon(sub Nd-HEDR) = -4.61+/-0.26 [9]. Rb-87-Sr-87 isochron: NWA 2977 contains only a modest amount of Rb and/or Sr contamination. The Sr-isotopic composition of the contaminant closely resembles that of seawater. The whole rock residue after leaching combined with leach residues for plagioclase and pyroxene define an isochron age of 3.29+/-0.11 Ga for initial Sr-87/Sr-86 = 0.70287+/-18. The olivine residue, with lower Sr abundance of approx 1.5 ppm, is only slightly displaced from the isochron. The relatively small uncertainties of the Rb-Sr isochron parameters and near-concordancy with the Sm-Nd age indicate that both the Rb-Sr and the Sm-Nd ages are reliable.

  18. Rb-Sr and Sm-Nd Isotopic Studies of Lunar Green and Orange Glasses

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.


    Lunar volcanic glassy beads have been considered as quenched basaltic magmas derived directly from deep lunar mantle during fire-fountaining eruptions [1]. Since these sub-mm size glassy melt droplets were cooled in a hot gaseous medium during free flight [2], they have not been subject to mineral fractionations. Thus, they represent primary magmas and are the best samples for the investigation of the lunar mantle. Previously, we presented preliminary Rb- Sr and Sm-Nd isotopic results for green and orange glassy samples from green glass clod 15426,63 and orange soil 74220,44, respectively [3]. Using these isotopic data, initial Sr-87/Sr-86 and Nd ratios for these pristine mare glass sources can be calculated from their respective crystallization ages previously determined by other age-dating techniques. These isotopic data were used to evaluate the mineralogy of the mantle sources. In this report, we analyzed additional glassy samples in order to further characterize isotopic signatures of their source regions. Also, we'll postulate a relationship between these two major mare basalt source mineralogies in the context of lunar magma ocean dynamics.

  19. Rb-Sr, Pb-Pb, U-Pb dating in the Bandja plutonic series of Western Cameroon. Donnees geochronologiques (Rb-Sr, Pb-Pb, U-Pb) sur le complexe plutonique de Bandja (Centre-Ouest Cameroun)

    Tchankam, C.N. (Nancy-1 Univ., 54 (France)); Vialette, Y. (Clermont-Ferrand-2 Univ., 63 - Aubiere (France))


    The results of U-Pb zircon and Pb-Pb on minerals and whole rocks are reported on a charnockite syn-D1 from the Bandja series in the western Cameroon. Data are interpreted as representing a plutonic emplacement at 640 Ma. A syn- to post-tectonic pluton is dated at 557 [+-] 8 Ma (Rb-Sr whole rocks isochron). These results confirm the Pan-African age of the charnockitic intrusive body. Initial isotopic [sup 87]Sr/[sup 86]Sr ratios of charnockite (0.709) and granite (0.7089) show the importance of crustal imprint in the magma genesis. (authors).

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

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


    After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

  1. Sm-Nd, Rb-Sr, and Mn-Cr Ages of Yamato 74013

    Nyquist, L. E.; Shih, C.- Y.; Reese, Y.D.


    Yamato 74013 is one of 29 paired diogenites having granoblastic textures. The Ar-39 - Ar-40 age of Y-74097 is approximately 1100 Ma. Rb-Sr and Sm-Nd analyses of Y-74013, -74037, -74097, and -74136 suggested that multiple young metamorphic events disturbed their isotopic systems. Masuda et al. reported that REE abundances were heterogeneous even within the same sample (Y-74010) for sample sizes less than approximately 2 g. Both they and Nyquist et al. reported data for some samples showing significant LREE enrichment. In addition to its granoblastic texture, Y-74013 is characterized by large, isolated clots of chromite up to 5 mm in diameter. Takeda et al. suggested that these diogenites originally represented a single or very small number of coarse orthopyroxene crystals that were recrystallized by shock processes. They further suggested that initial crystallization may have occurred very early within the deep crust of the HED parent body. Here we report the chronology of Y-74013 as recorded in chronometers based on long-lived Rb-87 and Sm-147, intermediate- lived Sm-146, and short-lived Mn-53.

  2. The solubility of (Ba,Sr)SO 4 precipitates: Thermodynamic equilibrium and reaction path analysis

    Felmy, Andrew R.; Rai, Dhanpat; Moore, Dean A.


    The solubility of (Ba,Sr)SO 4 precipitates, varying in SrSO 4 mole fraction from 0.05-0.90, was investigated at room temperature with an equilibration period extending to almost three years. The data show that on or before 315 days of equilibration the precipitates reach a reversible equilibrium with the aqueous solution. The reversibility of this equilibrium was verified both by the attainment of steady-state concentrations with time and by heating the samples to perturb the equilibrium and then observing the slow return to the initial equilibrium state. The dissolution of the (Ba,Sr)SO 4 precipitates does not, in general, follow limiting reaction paths as defined by the Lippmann solutus or stoichiometric dissolution curves. In addition, activity coefficient calculations for the BaSO 4 and SrSO 4 components of the solid phase, using either total bulk analysis or near-surface analysis of the component mole fractions, do not satisfy the Gibbs-Duhem equation, demonstrating that a single solid-solution phase does not control both the aqueous Ba and Sr concentrations. Instead, our long-term equilibration data can be explained by the unavoidable formation of small amounts of barite and substitution of Sr into a solid-solution phase with the BaSO 4 component of the solid-solution phase never reaching thermodynamic equilibrium with the aqueous phase.

  3. Rb-Sr and Nd-Sr isotope geochemistry and petrogenesis of the Misho Mountains mafic dikes (NW Iran

    Maryam Ahankoub


    Full Text Available Introduction There are some theories about the Paleotethys event during the Paleozoic that have been proposed by geologists (Metcalfe, 2006. Some scientist offered some pieces of evidence about the northern margin of Gondwana (Zhu et al., 2010. The Paleotethys Ocean and Hercynian orogenic report first in Iran, have been Offered from the Morrow and Misho Mountain (Eftekharnejad, 1981. Misho Mountains is located between the north and south Misho faults and cause the formation of a positive flower structure (Moayyed and Hossainzade, 2011. There is theory about Misho southern fault as the best candidate of the Paleotethys suture zone (Moayyed and Hossainzade, 2011. Geochemistry and Sr –Nd isotopic data of the A2 granitic and Synite rocks of the East Misho, indicate that the magmatism post collision has occurred in the active continental margin by extensional zones of the following the closure of the Paleotethys (Ahankoub, 2012. Granite and syenite rocks have been cut by mafic dikes. Mafic dikes are often formed in extensional tectonic settings related to mantle plume or continental break –up (Zhu et al., 2009. In this paper, we use the geochemistry and Nd-Sr isotope data to determined petrogenesis, tectono-magmatic setting and age of Misho mafic dikes. Materials and methods After petrography study of 30 thin sections of mafic dike rocks, 8 samples were selected for whole-rock chemical analyses using ICP-MS and ICP-AES instruments by ACME Company in Vancouver, Canada. We prepared 6 sample For Sm-Nd and Rb-Sr analysis. Sr and Nd isotope ratios were measured with a thermal ionization mass spectrometer, VG Sector 54–30 at the Nagoya University. The isotope abundances of Rb, Sr, Nd, and Sm were measured by the ID method with a Finnigan MAT Thermoquad THQ thermal ionization quadrupole mass spectrometer at the Nagoya University. NBS987 and JNdi-1 were measured as natural Sr and Nd isotope ratio standards (Tanaka et al., 2000. Averages and 2σ errors

  4. Role of Ba2+ Ion in the Crystal Growth of Sr(NO3)2

    WU Li-Jun; LI Chao-Rong; CHEN Wan-Chun; LIANG Jing-Kui


    A series of crystals of BaxSr1-x(NO3)2 (x=0-0.98) were grown from aqueous solutions by the evaporation method and characterized by x-ray powder diffraction and high resolution x-ray diffraction. All diffraction data are well indexed according to simple cubic structure. The variation of lattice constants with the concentrations of Ba2+ in the crystals accorded quite well to the Vegard's Law. The results of high-resolution x-ray diffraction show that the crystalline quality of BaxSr1-x(NO3)2 decreases with x increasing. The distribution of Ba2+ between the solution and solid phase indicated that Ba2+ is enriched in the solid phase. It could be attributed to the solubility of Ba(NO3)2 in water being less than that of Sr(NOs)2.

  5. Rb-Sr and Sm-Nd chronology and genealogy of mare basalts from the Sea of Tranquility

    Papanastassiou, D. A.; Depaolo, D. J.; Wasserburg, G. J.


    Rb-Sr and Sm-Nd ages of two Apollo 11 mare basalts, high-K basalt 10072 and low-K basalt 10062, are reported. Rb-Sr, Sm-Nd, and Ar-40-Ar-39 ages are in good agreement and indicate an extensive time interval for filling of the Sea of Tranquility, presumably by thin lava flows, in agreement with similar observations for the Ocean of Storms. Initial Sr and Nd isotopic compositions on Apollo 11 basalts reveal at least two parent sources producing basalts. The Sm-Nd isotopic data demonstrate that low-K and high-Ti basalts from Apollo 11 and 17 derived from distinct reservoirs, while low-Ti Apollo 15 mare basalt sources have Sm/Nd similar to the sources of Apollo 11 basalts. Groupings of mare basalt based on Ti content and on isotopic data do not coincide.

  6. Single grain Rb-Sr dating of euhedral and cataclastic pyrite from the Qiyugou gold deposit in western Henan,central China

    HAN YiGui; LI XiangHui; ZHANG ShiHong; ZHANG YuanHou; CHEN FuKun


    The Rb-Sr isotopic dating of pyrite mineral from ore deposits can directly provide mineralization age. However,many geological factors may affect the Rb-Sr isotopic system,which baffles application of this method. Employing ultra-low procedural blank Rb-Sr method,we have dated pyrites separated from the No. 4 breccia pipe of the Qiyugou gold deposit,western Henan Province. Single grains of euhedral pyrite crystal with few micro-cracks yield an isochron age of 126 ± 11 Ma,which represents time of the main mineralization stage of the deposit. Pyrite grains of cataclastic type show nevertheless scattered Rb-Sr isotopic composition and no reasonable isochron can be defined. Crystal morphology and mineral inclusion studies reveal that Rb and Sr of pyrite mineral probably are preserved mainly in biotite,K-feldspar,and sericite mineral inclusions. The dating results likely suggest that cataclastic pyrite is not suitable for the Rb-Sr dating due to modification of the Rb-Sr isotopic system by later hydrothermal activity of fluid.

  7. Sm-Nd and Rb-Sr Isotopic Studies of Meteorite Kalahari 009: An Old VLT Mare Basalt

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Bischoff, A.


    Lunar meteorite Kalahari 009 is a fragmental basaltic breccia contain ing various very-low-Ti (VLT) mare basalt clasts embedded in a fine-g rained matrix of similar composition. This meteorite and lunar meteorite Kalahari 008, an anorthositic breccia, were suggested to be paired mainly due to the presence of similar fayalitic olivines in fragment s found in both meteorites. Thus, Kalahari 009 probably represents a VLT basalt that came from a locality near a mare-highland boundary r egion of the Moon, as compared to the typical VLT mare basalt samples collected at Mare Crisium during the Luna-24 mission. The concordant Sm-Nd and Ar-Ar ages of such a VLT basalt (24170) suggest that the extrusion of VLT basalts at Mare Crisium occurred 3.30 +/- 0.05 Ga ag o. Previous age results for Kalahari 009 range from approximately 4.2 Ga by its Lu-Hf isochron age to 1.70?0.04 Ga of its Ar-Ar plateau ag e. However, recent in-situ U-Pb dating of phosphates in Kalahari 009 defined an old crystallization age of 4.35+/- 0.15 Ga. The authors su ggested that Kalahari 009 represents a cryptomaria basalt. In this r eport, we present Sm-Nd and Rb-Sr isotopic results for Kalahari 009, discuss the relationship of its age and isotopic characteristics to t hose of other L-24 VLT mare basalts and other probable cryptomaria ba salts represented by Apollo 14 aluminous mare basalts, and discuss it s petrogenesis.

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

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


    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...

  9. Molecular Dynamics Simulations for Melting Temperatures of SrF2and BaF2

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


    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.

  10. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.


    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

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

    Vishnu Shanker; Tokeer Ahmad; Ashok K Ganguli


    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.

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

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


    @@ 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.

  13. New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana

    Flowerdew, M.J.; Daly, J.S.; Riley, T.R.


    Five of six Rb-Sr muscovite mineral isochron ages from the Scotia Metamorphic Complex of the South Orkney Islands, West Antarctica, average 190 ± 4 Ma. The muscovite ages are interpreted to date foliation-formation and thus also accretion and subduction at the Gondwana margin. Coincident picrite and ferropicrite magmatism, indicative of melts from deep-seated depleted mantle, permits a causative link between accretion and the arrival of the Karoo – Ferrar – Chon Aike mantle plume in the Early Jurassic. Three biotite Rb-Sr mineral isochron ages are consistently younger and average 176 ± 5 Ma. The biotite ages may record post-metamorphic cooling or more likely retrogressive metamorphic effects during uplift.

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

    Junichi Shiogai


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

  15. Sm-Nd and Rb-Sr isotopic data on the sanukitoid intrusions of the Karelia, Baltic Shield

    Kovalenko, A. V.; Savatenkov, V. M.


    Sanukitoid intrusions from the Baltic Shield form post-tectonic differentiated intrusions 2.74-2.72 Ga old (Chekulaev, 1999, Lobach-Zhuchenko et al., 2000). They are represented by alkaline and calc-alkaline types which have high mg# (up to 0.6), strong LREE enrichment (Ce(N)=80-150, Yb(N)=4-7, Ce(N)/Yb(N)>20), high Sr, Ba (>1000 ppm), P2O5 (up to 1.5%) and Cr, Ni concentrations. Some intrusions contain rocks varying from ultramafite to quartz syenite. All sanukitoids are intruded by lamprophyre dykes having similar geochemical signatures. In this study we focus on the Karelian greenstone terrain within the Baltic Shield, in which sanukitoids are restricted to the younger western and central domains (2.7-2.9 Ga). Sanukitoids appear to be absent from the older Vodlozero domain (>3.0 Ga) in eastern Karelia (Lobach-Zhuchenko et al., 2000, Lobach-Zhuchenko et al., in press). About 70 Sm-Nd isotopic data on the sanukitoids of the Karelia were obtained. There is the regional distinction of the isotope composition of the rocks between the Central and West Karelian domains. The initial Epsilon Nd values and TDM range from +1.1 to +2.0 and 2.70-2.85 Ga accordingly in the youngest Central Karelian domain. The West Karelian intrusions yield an initial Epsilon Nd of -0.3- +0.7 and give the older TDM of about 2.82-2.92 Ga. It is to be noted that some intrusions of the Central Karelia domain, occurred closely to the ancient Vodlozero domain, also exhibit a similar range of initial Epsilon Nd and TDM to the intrusions of the West Karelia. There are narrow Nd isotopic compositional ranges within the individual intrusions. Rb-Sr isotopic system was studied in sanukitoids and lamprophyres of differentiated Panozero intrusion, Central Karelia. The initial 87Sr/86Sr isotope ratios range from 0.7000 to 0.7021 in these rocks indicating the derivation of these magmas from depleted mantle. Very low initial 87Sr/86Sr isotope ratios of the sanukitoids confirm the Nd isotopic characteristics

  16. Ground and excited state properties of the polar and paramagnetic RbSr molecule: a comparative study

    Żuchowski, Piotr S; Dulieu, Olivier


    This paper deals with the electronic structure of RbSr, a molecule possessing both a permanent magnetic and electric dipole moment in its own frame allowing its manipulation with external fields. Two complementary ab-initio approaches are used for the ground and lowest excited states: first, an approach relying on optimized effective core potentials with core polarization potentials based on a full configuration interaction involving three valence electrons, and second, an approach using a small-size effective core potential with 19 correlated electrons in the framework of coupled-cluster theory. We have found excellent agreement between these two approaches for the ground state properties including the permanent dipole moment. We have focused on studies of excited states correlated to the two lowest asymptotes Rb(5p)+Sr(5s) and Rb(5s)+Sr(5s5p) relevant for ongoing experiments on quantum degenerate gases. We present also the Hund c) case potential curves obtained using atomic spin-orbit constants. These poten...

  17. Sr/Ca and Ba/Ca variations in environmental and biological sources: A survey of marine and terrestrial systems

    Peek, Stephanie; Clementz, Mark T.


    The relative concentrations of strontium to calcium (Sr/Ca) and barium to calcium (Ba/Ca) in mammalian bioapatite are common biogeochemical indicators for trophic level and/or dietary preferences in terrestrial foodwebs; however, similar research in marine foodwebs is lacking. This study combined environmental and biological Sr/Ca and Ba/Ca data from both terrestrial and marine settings from 62 published books, reports, and studies along with original data collected from 149 marine mammals (30 species) and 83 prey items (18 species) and found that variations in Sr/Ca and Ba/Ca ratios of biological and environmental samples are appreciably different in terrestrial and marine systems. In terrestrial systems, environmental sources account for most of the variations in Sr/Ca and Ba/Ca ratios. In contrast, environmental sources in marine systems (i.e., seawater) are comparatively invariant, meaning most of the variations in Sr/Ca and Ba/Ca ratios originate from biological processes. Marine consumers, particularly non-mammalian and mammalian vertebrates, show evidence of biopurification of Ca relative to Sr and Ba, similar to what is observed in terrestrial systems; however, unlike terrestrial systems, variations in Sr/Ca and Ba/Ca ratios of environmental sources are overprinted by bioaccumulation of Sr and Ba at the base of marine foodwebs. This demonstrates that in marine systems, spatial or temporal differences may have little to no effect on Sr/Ca and Ba/Ca ratios of marine vertebrates, making Sr/Ca, and to a lesser extent Ba/Ca, potentially useful global proxies for trophic level and dietary preferences of marine vertebrates.

  18. Utilisation of Rb/Sr as proxy for mass wasting events in peat records from the Romanian Carpathians

    Longman, Jack; Ersek, Vasile; Veres, Daniel; Salzmann, Ulrich


    Mass wasting events, including landslides, avalanches and flooding related to heavy rains can have a major impact on the local environment. Due to their association to extreme precipitation and glacial retreat, their occurrence is likely to increase as the climate changes in the future. As such, understanding their causation, and predicting their future impact is of paramount importance. To make such predictions, understanding of the relationship between the climate and the mass-wasting event is key. For this to happen, we must use historical records of mass wasting and climate to tie the two together. As a result, a reliable, quick and easy method for determining these events in the sedimentological record must be developed. The Rb/Sr ratio has been suggested as one indicator of mass wasting events, particularly based on lake sediment research in glaciated terrain. Our work was initially developed upon the behaviour of the two elements during weathering, considering that Rb commonly substitutes for K in mineral lattices and Sr commonly for Ca, due to similar ionic radii. Minerals containing K are much more resistant than Ca-bearing ones, and so there is enrichment in weathering products of Ca, and therefore Sr. As a result, Sr should be enriched in weathered material, resulting in a lowering of the Rb/Sr ratio. This assumption has been proven as reliable in similar research involving aeolian deposits and lake sediments. Here we present the first Holocene record based on this proxy from a peat archive from a raised mountain bog in the Romanian Carpathians, nested at the foot of an avalanche-prone glacial cirque. Our geochemical assessments are based on complete digestion of samples, and analysis via ICP-OES, rather than based only on core scanning. Initial results look promising, with the peat core below the active layer (acrotelm) and above the minerogenically-influenced zone producing strong correlation to the estimates of the minerogenic input over the bog based

  19. Dipole Polarizability of Alkali-Metal (Na, K, Rb) - Alkaline-Earth-Metal (Ca,Sr) Polar molecules - Prospects of Alignment

    Gopakumar, Geetha; Hada, Masahiko; Kajita, Masatoshi


    Electronic open-shell ground-state properties of selected alkali-metal (AM) - alkaline-earth-metal (AEM) polar molecules are investigated. We determine potential energy curves of the 2{\\Sigma}+ ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes (23Na, 39K, 85Rb) - (40Ca, 88Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields.

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

    Bullen, Thomas D.; Chadwick, Oliver A.


    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

  1. Growth and interface engineering in thin-film Ba0.6Sr0.4TiO3 /SrMoO3 heterostructures

    Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert; Komissinskiy, Philipp


    Epitaxial heterostructures of ferroelectric Ba0.6Sr0.4TiO3 and highly conducting SrMoO3 were grown by pulsed laser deposition on SrTiO3 (0 0 1) substrates. Surface oxidation of the SrMoO3 film is suppressed using a thin cap interlayer of Ba0.6Sr0.4TiO3-δ grown in reduced atmosphere. As shown by X-ray photoelectron spectroscopy, the Mo4+ valence state of the SrMoO3 films is stable upon annealing of the sample in oxygen up to 600 °C. The described oxygen interface engineering enables utilization of the highly conducting material SrMoO3 in multilayer oxide ferroelectric varactors.

  2. Rb-Sr and Sm-Nd Ages of Zagami DML and SR Isotopic Heterogeneity in Zagami

    Nyquist, L.aurenceE.; Shih, C.-Y.; Reese, Y. D.


    Zagami contains lithologic heterogeneity suggesting that it did not form in a homogeneous, thick lava flow [1]. We have previously investigated the Sr and Nd isotopic systematics of Coarse-Grained (CG) and Fine-Grained (FG) lithologies described by [2]. Both appear to belong to Normal Zagami (NZ) [1,3], but their initial Sr-isotopic compositions differ [4,5]. Here we report new analyses of the Dark Mottled Lithology (DML, [3]) that show its age and initial Sr and Nd isotopic compositions to be identical within error limits with those of CG, but Sr initial isotopic compositions differ from those of FG.

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

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


    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.

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

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


    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.

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

    Pramudito, Sidikrubadi; Sanjaya, Nugraha Wanda [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Sumaryada, Tony, E-mail: [Theoretical Physics Division, Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia); Computational Biophysics and Molecular Modeling Research Group (CBMoRG), Department of Physics, Bogor Agricultural University, Jalan Meranti Kampus IPB Dramaga Bogor 16680 (Indonesia)


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

  6. Effect of (Ba+Sr)/Ti ratio on dielectric and tunable properties of Ba0.6Sr0.4TiO3 thin film prepared by sol-gel method

    ZHU Wei-cheng; PENG Dong-wen; CHENG Jin-rong; MENG Zhong-yan


    Ba0.6Sr0.4TiO3 (BST) thin films were fabricated on Pt coated Si (100) substrates by sol-gel techniques with molar ratio of (Ba+Sr) to Ti changing from 0.76 to 1.33. The effect of (Ba+Sr)/Ti ratio deviating from the stoichiometry on microstructure,grain growth,dielectric and tunable properties of BST thin films were investigated. TiO2 and (Ba,Sr)2TiO4 were found as a second phase at the ratios of 0.76 and 1.33,respectively. The variation of the ratio reveals more significant effect on the grain size in B-site rich samples than that in A-site rich samples. The dissipation factor decreases rapidly from 0.1 to 0.01 at 1 MHz with decreasing (Ba+Sr)/Ti ratio. The tunability increases with decreasing ratio from 1.33 to 1.05,and then decreases with decreasing ratio from 1.05 to 0.76. The film with (Ba+Sr)/Ti ratio of 1.05 has a maximum tunability of 32% and a dissipation factor of 0.03 at 1 MHz.

  7. Structural and electronic properties of Fe-doped BaTiO3 and SrTiO3

    Zhang Chao; Wang Chun-Lei; Li Ji-Chao; Yang Kun


    We have performed first principles calculations of Fe-doped BaTiO3 and SrTiO3. Dopant formation energy, structure distortion, band structure and density of states have been computed. The dopant formation energy is found to be 6.8 eV and 6.5 eV for Fe-doped BaTiO3 and SrTiO3 respectively. The distances between Fe impurity and its nearest O atoms and between Fe atom and Ba or Sr atoms are smaller than those of the corresponding undoped bulk systems. The Fe defect energy band is obtained, which mainly originates from Fe 3d electrons. The band gap is still an indirect one after Fe doping for both BaTiO3 and SrTiO3, but the gap changes from Г-R point to Г-X point.

  8. Molecular Dynamics Simulations of Chemically Disordered Ferroelectric (Ba,Sr)TiO3 with a Semi-Empirical Effective Hamiltonian

    Nishimatsu, Takeshi; Grünebohm, Anna; Waghmare, Umesh V.; Kubo, Momoji


    We present a semi-empirical effective Hamiltonian to capture effects of disorder associated with Ba and Sr cations occupying A sites in (BaxSr1-x)TiO3 on its ferroelectric phase transition. Averaging between the parameters of first-principles effective Hamiltonians of end members BaTiO3 and SrTiO3, we include a term with an empirical parameter to capture the local polarization and strains arising from the difference between ionic radii of Ba and Sr. Using mixed-space molecular dynamics of the effective Hamiltonian, we determine T-dependent ferroelectric phase transitions in (BaxSr1-x)TiO3 which are in good agreement with experiment. Our scheme of determination of semi-empirical parameters in effective Hamiltonian should be applicable to other perovskite-type ferroelectric solid solutions.

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

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


    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)

  10. Nuclear geochronology. Chapter 6: Sedimentary rocks dating by the Rubidium-Strontium (Rb/Sr) and Potassium-Argon (K/Ar) radiometric methods; Geocronologia nuclear. Capitulo 6: Datacao de rochas sedimentares pelos metodos radiometricos rubidio-estroncio (Rb/Sr) e potassio-argonio (K/Ar)

    Thomaz Filho, Antonio [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Inst. de Geociencias; Mizusaki, Ana Maria Pimentel [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Geociencias; Kawashita, Koji [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias; Torquato, Joaquim Raul [Ceara Univ., Fortaleza, CE (Brazil). Dept. de Geologia


    The paper deals with the Rubidium/Strontium (Rb/Sr) and Potassium/Argon (K/Ar) radiometric methods application in the sedimentary rocks dating, including the methodology, the method restrictions and the ages meaning. The work concludes that the sedimentary rocks radiometric dating, by the Rb/Sr method is possible, furnishing results geologically significant. The {sup 87} Sr/{sup 86} Sr of marine carbonates has propitiated, mainly in the last years, the dating possibility of sedimentary rocks. The K/Ar radiometric method has been applied to determine the diagenetic events age of the sedimentary rocks, including its application in mesozoic and recent rocks, where the RB/Sr radiometric method presents some limitations 71 refs., 18 figs.

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

    Shukla, Aarti, E-mail: [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)


    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.

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

    Lee, C. Y. [Hannam University, Daejon (Korea, Republic of)


    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{sub 1}, τ{sub 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.

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

    Ali, Zahid, E-mail: [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)


    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.

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

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


    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.

  15. Accurate calculations of the ground state and low-lying excited states of the (RbBa)+ molecular ion: a proposed system for ultracold reactive collisions

    Knecht, Stefan; Sørensen, Lasse Kragh; Jensen, Hans Jørgen Aagaard


    Collisions of ultracold Ba+ ions on a Rb Bose–Einstein condensate have been suggested as a possible benchmark system for ultracold ion-neutral collision experiments. However, a priori knowledge of the possible processes is desirable. For this purpose, we here present high-level four-component cou...

  16. Synthesis and structure of (Rb0.50Ba0.25)[UO2(CH3COO)3

    Serezhkina, L. B.; Peresypkina, E. V.; Virovets, A. V.; Klepov, V. V.


    A new compound (Rb0.50Ba0.25)[UO2(CH3COO)3] is synthesized and its crystal structure is studied by X-ray diffraction. The compound crystallizes in the form of yellow plates belonging to the cubic crystal system. The unit cell parameter a = 17.0367(1) Å, V = 4944.89(5) Å3, space group I bar 4 3 d, Z = 16, and R = 0.0182. The coordination polyhedron of the uranium atom is a hexagonal bipyramid with oxygen atoms of three acetate groups and the uranyl group in the vertices. The crystal chemical formula of the uranium-containing group is AB {3/01}( A = UO{2/2+}, B 01 = CH3COO-). The oxygen atoms of the acetate groups that enter the coordination polyhedron of uranium are bound to barium and rubidium atoms.

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

    Balter, Vincent; Lécuyer, Christophe


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

  18. Very high or close to zero thermal expansion by the variation of the Sr/Ba ratio in Ba(1-x)Sr(x)Zn2Si2O7- solid solutions.

    Thieme, Christian; Rüssel, Christian


    The compound BaZn2Si2O7 shows a highly positive coefficient of thermal expansion. At a temperature of 280 °C, it transforms to a high temperature phase, which exhibits a coefficient of thermal expansion near zero. The partial replacement of Ba(2+) against Sr(2+) leads to a decrease of the phase transition temperature. If more than 10% of Ba(2+) are replaced by Sr(2+), the high-temperature phase is completely stable at room temperature and consequently, the thermal expansion is near zero or negative. The effect of the Sr(2+)/Ba(2+)-ratio on the phase transition temperature and the thermal expansion behavior is measured using high-temperature X-ray diffraction up to 1000 °C. The Sr(2+)/Ba(2+)-ratio strongly affects the overall thermal expansion as well as the anisotropy. The latter increases with decreasing Sr-concentration. The strong differences in the thermal expansion behavior between phases with the structure of the low-temperature phase and the high-temperature phase of BaZn2Si2O7 can be explained by a comparison of the ZnO4-chains inside these two crystal structures.

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

    B Ramdas; R Vijayaraghavan


    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.

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

    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)


    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)

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

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


    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.

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

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


    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.

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

    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)


    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}.

  4. Spatial and temporal changes of summer monsoon on the Loess Plateau of Central China during the last 130 ka inferred from Rb/Sr ratios

    陈旸; 陈骏; 刘连文; 季峻峰; 张建新


    The Rb/Sr ratios for samples from six loess-paleosol sections on the Chinese Loess Plateau during the last glacial-interglacial cycle, and for samplesfrom 18 modern surface soils, have been analyzed. The six sections are along north-south and west-east transects respectively. The results show that the spatial distribution of Rb/Sr is characterized by a remarkable increase from north to south while Rb/Sr ratio changes little from west to east, whose latitude indicates shift of summer monsoon intensity. A regression equation between Rb/Sr ratiosand mean annual precipitation(MAP) has been constructed through statistical analysis for the modern surface soils. Paleorainfall during the last 130 ka is estimated for the six sections based on the regression equation. It is evident thatprecipitation increased remarkably during marine isotope stages 3 and 5, exhibiting the high and similar gradients of variation with latitude. This demonstrates that the environmental effect is more prominent in the south of the Loess Plateau than in the north during the dominance of summer monsoon.

  5. TiO2 controlling photoluminescence of AWO4 (A =Ca,Sr,Ba) nanofilms

    Jia, Runping; Zhang, Guoxin; Wu, Qingsheng; Ding, Yaping


    AWO4 (A =Ca,Sr,Ba) nanofilms are prepared by a self-inventive technique using collodion to disperse nanoparticles and form film, and their photoluminescence (PL) properties are controlled by a nano-TiO2 doping method. This cannot only reach the results of uniform film and PL enhancement, but also realize a PL increase/decrease shift effect. The PL behaviors of AWO4 nanofilms doped by TiO2 are in good agreement with Gaussion function relation. In addition, there is a positive correlation between the critical concentrations of TiO2 in AWO4-TiO2 nanofilm series and A's ionic potential.

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

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


    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.

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

    Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal; De, S. K., E-mail: [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)


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

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

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


    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.

  9. Rb-Sr and Sm-Nd study of granite-charnockite association in the Pudukkottai region and the link between metamorphism and magmatism in the Madurai Block

    Sekaran, M. Chandra; Bhutani, Rajneesh; Balakrishnan, S.


    Pudukkottai region in the northeastern part of the Madurai Block exposes the garnetiferous pink granite that intruded the biotite gneiss. Charnockite patches are associated with both the rock types. Rb-Sr biotite and Sm-Nd whole-rock isochron ages indicate a regional uplift and cooling at ˜550 Ma. The initial Nd isotope ratios (\\varepsilon _{ {Nd}}t=-20 to -22) and Nd depleted-mantle model ages (TDM = 2.25 to 2.79 Ga) indicate a common crustal source for the pink-granite and associated charnockite, while the biotite gneiss and the charnockite within it represent an older crustal source (\\varepsilon _{ {Nd}}t= -29 and TDM = > 3.2 Ga). The Rb-Sr whole-rock data and initial Sr-Nd isotope ratios also help demonstrate the partial but systematic equilibration of Sr isotope and Rb/Sr ratios during metamorphic mineral-reactions resulting in an `apparent whole-rock isochron'. The available geochronological results from the Madurai Block indicate four major periods of magmatism and metamorphism: Neoarchaean-Paleoproterozoic, Mesoproterozoic, mid-Neoproterozoic and late-Neoproterozoic. We suggest that the high-grade and ultrahigh-temperature metamorphism was preceded by magmatism which `prepared' the residual crust to sustain the high P- T conditions. There also appears to be cyclicity in the tectono-magmatic events and an evolutionary model for the Madurai Block should account for the cyclicity in the preserved records.

  10. Nd isotopic disequilibrium be- tween minerals and Rb-Sr age of the secondary phengite in eclogite from the Yangkou area, Qingdao, eastern China


    There are two generations of white micas in retrograded coesite-bearing eclogite from the Yangkou area near Qingdao, eastern China. The secondary phengite developed along the folliations in eclogite is the majority of the white micas. Nd and Sr isotopic disequilibriums between garnet and retrograded omphacite as well as secondary phengite have been observed. Consequently, the Rb-Sr ages ((193 ± 4) Ma―(195 ± 4) Ma) given by the tie lines of the secondary phengite + garnet or whole rock may predate the formation time of the phengite. The Rb-Sr age of (183 ± 4) Ma given by the secondary phengite + retrograde omphacite is much closer to the formation time of the phengite indicating the retrograde age of eclogite instead of a cooling age of eclogite at 500℃.

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

    Huang, Hongwei, E-mail:; Wang, Shuobo; Zhang, Yihe, E-mail:; Han, Xu


    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.

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

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


    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.

  13. Characterization of MeWO 4 (Me = Ba, Sr and Ca) nanocrystallines prepared by sonochemical method

    Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai


    Metal tungstates (MeWO 4, Me = Ba, Sr and Ca) were successfully prepared using the corresponding Me(NO 3) 2·2H 2O and Na 2WO 4·2H 2O in ethylene glycol by the 5 h sonochemical process. The tungstate phases with scheelite structure were detected with X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their calculated lattice parameters are in accord with those of the JCPDS cards. Transmission electron microscopy (TEM) revealed the presence of nanoparticles composing the products. Their average sizes are 42.0 ± 10.4, 18.5 ± 5.1 and 13.1 ± 3.3 nm for Me = Ba, Sr and Ca, respectively. Interplanar spaces of the crystals were also characterized with high-resolution TEM (HRTEM). Their crystallographic planes are aligned in systematic array. Six different vibration wavenumbers were detected using Raman spectrometer and are specified as ν1(A g), ν3(B g), ν3(E g), ν4(B g), ν2(A g) and free rotation. Fourier transform infrared (FTIR) spectra provided the evidence of scheelite structure with W-O anti-symmetric stretching vibration of [WO 4] 2- tetrahedrons at 786-883 cm -1. Photoluminescence emission of the products was detected over the range of 384-416 nm.

  14. Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

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


    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.

  15. Genesis of the Khaluta alkaline-basic Ba-Sr carbonatite complex (West Transbaikala, Russia)

    Doroshkevich, Anna G.; Ripp, German S.; Moore, Kathryn R.


    The Khaluta carbonatite complex comprizes fenites, alkaline syenites and shonkinites, and calcite and dolomite carbonatites. Textural and compositional criteria, melt inclusions, geochemical and isotopic data, and comparisons with relevant experimental systems show that the complex formed by liquid immiscibility of a carbonate-saturated parental silicate melt. Mineral and stable isotope geothermometers and melt inclusion measurements for the silicate rocks and carbonatite all give temperatures of crystallization of 915-1,000°C and 890-470°C, respectively. Melt inclusions containing sulphate minerals, and sulphate-rich minerals, most notably apatite and monazite, occur in all of the lithologies in the Khaluta complex. All lithologies, from fenites through shonkinites and syenites to calcite and dolomite carbonatites, and to hydrothermal mineralisation are further characterized by high Ba and Sr activity, as well as that of SO3 with formation of the sulphate minerals baryte, celestine and baryte-celestine. Thus, the characteristic features of the Khaluta parental melt were elevated concentrations of SO3, Ba and Sr. In addition to the presence of SO3, calculated fO2 for magnetites indicate a high oxygen fugacity and that Fe+3>Fe+2 in the Khaluta parental melt. Our findings suggest that the mantle source for Khaluta carbonatite and associated rocks, as well as for other carbonatites of the West Transbaikalia carbonatite province, were SO3-rich and characterized by high oxygen fugacity.

  16. Geología y geocronología Rb-Sr de granitoides de Sierra Grande, provincia de Río Negro

    Ricardo Varela


    Full Text Available Al este de Sierra Grande la unidad más antigua es la Ectinita El Jagüelito, metagrauvacas y pizarras, cortadas por granitoides ordovícicos (Rb-Sr en roca total 467 ± 16 Ma; U-Pb en circón 476 ± 4 Ma. Ectinitas y granitoides son cubiertos discordantemente por sedimentitas clásticas fosilíferas silúricas de la Formación Sierra Grande y el total de unidades deformado por pliegues y fallas. Al sur de Sierra Grande, Mina Hiparsa, afloran la Ectinita El Jagüelito, la Formación Sierra Grande y granitoides, en un contexto de fuerte deformación tectónica. Desde mitad de siglo pasado se discute si los granitoides constituyen el basamento de la Formación Sierra Grande o si son intrusivos en la misma. La Formación Sierra Grande está afectada por metamorfismo térmico. Datos radimétricos previos de granitoides son discordantes (Rb-Sr en roca total 252 ± 5 Ma; 363 ± 57 Ma; 318 ± 28 Ma; U-Pb SHRIMP en circón 476 ± 6 Ma. Se efectuaron nuevos análisis Rb-Sr en roca total y minerales y se propone la existencia de dos unidades graníticas. En granitoides del noroeste de la mina, Granito Mina Hiparsa, se obtuvieron dos isocronas (262 ± 6 Ma, 87Sr/86Sr inicial = 0,7162 ± 0,0003 y 263 ± 9 Ma, 87Sr/86Sr inicial = 0,7149 ± 0,0009. En los granitoides al oeste de la Mina Hiparsa, Granodiorita Laguna Medina, se efectuó una isocrona (260 ± 3 Ma, 87Sr/86Sr Inicial = 0,7078 ± 0,0012. Las rocas estudiadas son el producto de plutonismo ordovícico temprano y pérmico tardío-temprano. Las tres isocronas roca total-minerales son pérmicas, pero dos por metamorfismo y reseteo de rocas ordovícicas (87Sr/86Sr inicial ~ 0,7150 y una por cristalización (87Sr/86Sr inicial ~ 0,7080.

  17. Negative Thermal Expansion in Ba0.5Sr0.5Zn₂SiGeO₇.

    Thieme, Christian; Rüssel, Christian


    Solid solutions with the composition Ba0.5Sr0.5Zn₂Si2-xGexO₇ and BaZn₂Si2-xGexO₇ were prepared with different values of x using a conventional mixed oxide route. Both compounds exhibit very different thermal expansion, which is due to the different crystal structures. Ba0.5Sr0.5Zn₂Si2-xGexO₇ solid solutions exhibit the structure of high-temperature BaZn₂Si₂O₇ and show negative thermal expansion, which was proven via high-temperature X-ray diffraction. Up to around x = 1, the crystal structure remains the same. Above this value, the low-temperature phase becomes stable. The Sr-free solid solutions have the crystal structure of low-temperature BaZn₂Si₂O₇ and show also a limited solubility of Ge. These Sr-free compositions show transitions of low- to high-temperature phases, which are shifted to higher temperatures with increasing Ge-concentration.

  18. Negative Thermal Expansion in Ba0.5Sr0.5Zn2SiGeO7

    Thieme, Christian; Rüssel, Christian


    Solid solutions with the composition Ba0.5Sr0.5Zn2Si2-xGexO7 and BaZn2Si2-xGexO7 were prepared with different values of x using a conventional mixed oxide route. Both compounds exhibit very different thermal expansion, which is due to the different crystal structures. Ba0.5Sr0.5Zn2Si2-xGexO7 solid solutions exhibit the structure of high-temperature BaZn2Si2O7 and show negative thermal expansion, which was proven via high-temperature X-ray diffraction. Up to around x = 1, the crystal structure remains the same. Above this value, the low-temperature phase becomes stable. The Sr-free solid solutions have the crystal structure of low-temperature BaZn2Si2O7 and show also a limited solubility of Ge. These Sr-free compositions show transitions of low- to high-temperature phases, which are shifted to higher temperatures with increasing Ge-concentration. PMID:28773746

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

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


    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.

  20. BaMnO3 and Ba1/2Sr1/2MnO3 Nanoparticles Synthesized by CHM Method%CHM法合成BaMnO3、Ba1/2Sr1/2MnO3纳米晶体

    夏川茴; 胡陈果; 韩向宇; 王娜; 张祖伟


    采用复合碱媒介法(CHM),以BaCl和MnO2为原料在200 ℃、24 h的生长条件下合成了纳米BaMnO3单晶颗粒.采用同样方法,以Sr(NO3)2、BaCO3以及MnO2为原料,在200 ℃、24 h的生长条件下,用50%的Sr替代50%的Ba,成功合成了Ba1/2Sr1/2MnO3.用X射线衍射仪(XRD)、扫描电镜(SEM)及能量散射X射线谱(EDS)对产物的晶相、形貌和成分进行了分析,并且解释了BaMnO3及Ba1/2Sr1/2MnO3的生长机理.

  1. 87Sr/86Sr Ratios in Carbonate From the Red Lake and Steep Rock Groups in Canada Suggest Rb-enriched Continental Crust was Influencing Seawater Chemistry Prior to 3.0 Ga

    Satkoski, A.; Fralick, P. W.; Beard, B. L.; Johnson, C.


    Previous work has suggested that prior to 2.5 Ga, Sr isotope compositions of seawater were essentially mantle buffered and the effects of continental weathering on seawater chemistry were negligible. To test this, we collected Sr isotope data from 2.93 and 2.80 Ga carbonates that are part of the Red Lake and Steep Rock groups (Canada), respectively. To better understand carbonate formation and any post-depositional alteration, Sr isotopes are considered with O isotopes and REEs, as well as Rb and Sr contents, including correction for decay of 87Rb. All samples have Y/Ho ratios higher than chondrite and have positive La anomalies, which, combined with low Rb contents suggests that clastic contamination is negligible. Samples we consider near pristine have δ18O (VSMOW) values >20‰. Samples with the highest Y/Ho ratios and largest La anomalies from Red Lake and Steep Rock have initial 87Sr/86Sr ratios of 0.7018-0.7020. This Sr isotope composition is significantly more radiogenic than contemporaneous mantle (0.7011-0.7012), especially at a time when the isotopic difference between the crust and mantle was much less than today. This implies that radiogenic continental crust was emergent and shed detritus into the world's oceans prior to 3.0 Ga, in contrast with proposals for submerged continental crust, but in line with new estimates that continental crust at 3.0 Ga was 60-70% of current volume. We contend that this large amount of crust combined with enhanced Archean weathering could account for the radiogenic Sr isotope compositions we report here, and suggests a significant impact from continental weathering on ocean chemistry during the Archean.

  2. Geochemistry of the Serra das Melancias Pluton in the Serra da Aldeia Suite: a classic post-collisional high Ba-Sr granite in The Riacho do Pontal Fold Belt, NE Brazil

    Marcela Paschoal Perpétuo

    Full Text Available ABSTRACT: The Serra da Aldeia Suite is composed by circular or oval-shaped plutons, intrusive in meta-sedimentary and meta-volcanosedimentary rocks in the Riacho do Pontal Fold Belt, NE Brazil. The Serra das Melancias Pluton, belonging to Serra da Aldeia Suite, is located southeastern of Piaui state, near Paulistana city. These plutons represent a major magmatic expression in this area and contain important information about the late magmatic/collisional geologic evolution of the Brasiliano Orogeny. Based on petrographic and geochemical data, three facies were defined in the Serra das Melancias Pluton: granites, syenites and quartz monzonites. The rocks display high-K and alkaline to shoshonitic affinities, are metaluminous and show ferrous character. They are enriched in Light Rare Earth Elements and Large Ion Lithophile Elements, with negative anomalies in Nb, Ta and Ti. Their high Ba, Sr, K/Rb, low Rb, relatively low U, Th, Nb to very low Heavy Rare Earth Elements and Y resemble those of typical high Ba-Sr granitoids. The geochemical data suggest the emplacement of Serra das Melancias Pluton in a transitional, late to post-orogenic setting in the Riacho do Pontal Fold Belt during the late Brasiliano-Pan African Orogeny.

  3. Dielectric tunable properties of BaTi4Og-doped Ba0.6Sr0.4TiO3 microwave composite ceramics

    ZHANG JingJi; ZHAI JiWei; JIANG HaiTao; YAO Xi


    BaTi4O9-doped Ba0.6Sr0.4TiO3 (BST) composite ceramics were prepared by the conventional solid-state reaction and their structure, dielectric nonlinear characteristics and microwave dielectric properties were investigated. The secondary phase of the orthorhombic structure Ba4Ti13O30 is formed among BST composite ceramics with the increase of BaTi4O9. At the same time, a duplex or bimodal grains size distribution shows fine grains in a coarse grain matrix. The degree of frequency dispersion of dielectric permittivity below Tm is increased initially and then decreased with respect to BaTi4O9. As the BaTi4O9 content increases, the tunability of composite ceramics decreases, while the Q value increases. Inter-estingly, 70 wt% BaTi4O9-doped BST has a tunability -4.0% (under 30 kV/cm biasing) versus a permit-tivity ~68 and quality factor ~134.1 (at ~3.2 GHz).

  4. Dielectric tunable properties of BaTi4O9-doped Ba0.6Sr0.4TiO3 microwave composite ceramics


    BaTi4O9-doped Ba0.6Sr0.4TiO3 (BST) composite ceramics were prepared by the conventional solid-state reaction and their structure, dielectric nonlinear characteristics and microwave dielectric properties were investigated. The secondary phase of the orthorhombic structure Ba4Ti13O30 is formed among BST composite ceramics with the increase of BaTi4O9. At the same time, a duplex or bimodal grains size distribution shows fine grains in a coarse grain matrix. The degree of frequency dispersion of dielectric permittivity below Tm is increased initially and then decreased with respect to BaTi4O9. As the BaTi4O9 content increases, the tunability of composite ceramics decreases, while the Q value increases. Inter-estingly, 70 wt% BaTi4O9-doped BST has a tunability ~4.0% (under 30 kV/cm biasing) versus a permit- tivity ~68 and quality factor ~134.1 (at ~3.2 GHz).

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

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


    <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.

  6. Excitation functions of 85Rb(p,xn)(85m,g,83,82,81)Sr reactions up to 100 MeV: integral tests of cross section data, comparison of production routes of 83Sr and thick target yield of 82Sr.

    Kastleiner, S; Qaim, S M; Nortier, F M; Blessing, G; van der Walt, T N; Coenen, H H


    The beta+ emitter 83Sr (T(1/2) = 32.4 h, Ebeta+ = 1.23 MeV, Ibeta+ = 24%) is a potentially useful radionuclide for therapy planning prior to the use of the beta+ emitter 89Sr (T(1/2) = 50.5 d). In order to investigate its production possibility, cross section measurements on the 85Rb(p,xn)-reactions, leading to the formation of the isotopes (85m,g)Sr, 83Sr, 82Sr and 81Sr, were carried out using the stacked-foil technique. In a few cases, the products were separated via high-performance liquid chromatography. For 82Sr, both gamma-ray and X-ray spectrometry were applied; in other cases only gamma-ray spectrometry was used. From the measured excitation functions, the expected yields were calculated. For the energy range Ep = 37 --> 30 MeV the 83Sr yield amounts to 160 MBq/microA h and the level of the 85gSr (T(1,2) = 64.9 d) and 82Sr (T(1/2) = 25.5 d) impurities to functions. The results of the 85Rb(p,3n)83Sr reaction were compared with the data on the production of 83Sr via the 82Kr(3He,2n)-process. In the energy range E3Hc = 18 --> 10 MeV the theoretical yield of 83Sr amounts to 5 MBq/microA h and the 82Sr impurity to about 0.2%. The method of choice for the production of 83Sr is thus the 85Rb(p,3n)-process, provided a 40 MeV cyclotron is available. During this study some supplementary information on the yield and purity of 82Sr was also obtained.

  7. Hydrostatic pressure effect on the superconducting properties of BaBi3 and SrBi3 single crystals

    Jha, Rajveer; Avila, Marcos A.; Ribeiro, Raquel A.


    We demonstrate the superconducting properties of, and hydrostatic pressure effect on, BaBi3 and SrBi3 superconductors. We measure the dc magnetic susceptibility under hydrostatic pressure for both compounds, which shows a positive pressure coefficient of dT c/dP = 1.22 K GPa-1 for BaBi3 and a negative pressure coefficient of dT c/dP = -0.43 K GPa-1 for SrBi3. The normal state electrical resistivity shows that both compounds are highly metallic in nature. The upper critical fields H c2 evaluated by resistivity under magnetic fields ρ(T,H) are 22 kOe for BaBi3 and 2.9 kOe for SrBi3. A specific heat jump of ΔC e/γT c = 1.05 suggests weak coupling superconductivity in BaBi3, whereas ΔC e/γT c = 2.08 for SrBi3 is higher than the Bardeen-Cooper-Schrieffer theory value of 1.43, indicating a strong coupling superconductor.

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

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


    @@ 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.

  9. Dy$^{3+}$-activated M$_2$SiO$_4$ (M $=$ Ba, Mg, Sr)-type phosphors



    The alkaline orthosilicates of M$_2$SiO$_4$ (M $=$ Ba, Mg, Sr) activated with Dy$^{3+}$ and co-doped with Ho$^{3+}$ are prepared through conventional solid-state method, i.e., mixing and grinding of solid form precursors followedby high-temperature heat treatments of several hours in furnaces, generally under open atmosphere and investigated by X-ray diffraction (XRD) to get phase properties and photoluminescence (PL) analysis to get luminescenceproperties. The thermal behaviours of well-mixed samples were determined by differential thermal analysis (DTA)/thermogravimetry (TG). The PL spectra show that the 478 and 572nm maximum emission bands are attributed, respectively, to ${}^{4}$F$_{9/2}$ $\\to$ ${}^{6}$H$_{15/2}$ and ${}^{4}$F$_{9/2}$ $\\to$ ${}^{6}$H$_{13/2}$ transitions of Dy$^{3+}$ ions.

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

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


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

  11. Emission color variation of (Ba,Sr)3BP3O12:Eu2+ phosphors for white light LEDs.

    Kuo, Te-Wen; Liu, Wei-Ren; Chen, Teng-Ming


    A series of alkaline earth borophosphate phosphors, (Ba,Sr)(3)BP(3)O(12) doped with Eu(2+) ions, were synthesized by a solid state reaction. Two emission bands at 465 nm and 520 nm were attributed to the f-d transitions of doped Eu(2+) ions occupying in two different cation sites in host lattices and emission color variation was observed by substituting the M(2+) sites, which was rationalized in terms of two competing factors of the crystal field strength and bond covalence. Green and bluish-white pc-LEDs were fabricated by combination of a 370 nm near-UV chip and composition-optimized Ba(3)BP(3)O(12):Eu(2+) and (Ba,Sr)(3)BP(3)O(12):Eu(2+) phosphors, respectively. The series of phosphors may serve as a promising green and bluish-white luminescent materials used in fabrication of near UV-based white pc-LEDs.

  12. Solid state (47,49)Ti, (87)Sr and (137)Ba NMR characterisation of mixed barium/strontium titanate perovskites.

    Gervais, Christel; Veautier, Delphine; Smith, Mark E; Babonneau, Florence; Belleville, Philippe; Sanchez, Clément


    Solid state (47,49)Ti, (137)Ba, (87)Sr NMR spectra have been recorded on BaxSrl-xTiO3 (0 strontium) in the coordination second sphere of the probed titanium site: substitution of strontium by barium induces the broadening of the peaks, due to quadrupolar effects, while the isotropic chemical shift increases. (137)Ba NMR spectra exhibit a distribution of the quadrupolar interaction, that could be tentatively quantified, CQ increasing with the amount of strontium. Preliminary results were also obtained on (87)Sr NMR showing behaviour comparable to (137)Ba NMR, i.e. a broadening of the peaks due to an increasing quadrupolar interaction with the amount of barium distorting the environment of the strontium sites.

  13. Unreported Emission Lines of Rb, Ce, La, Sr, Y, Zr, Pb and Se Detected Using Laser-Induced Breakdown Spectroscopy

    Lepore, K. H.; Mackie, J.; Dyar, M. D.; Fassett, C. I.


    Information on emission lines for major and minor elements is readily available from the National Institute of Standards and Technology (NIST) as part of the Atomic Spectra Database. However, tabulated emission lines are scarce for some minor elements and the wavelength ranges presented on the NIST database are limited to those included in existing studies. Previous work concerning minor element calibration curves measured using laser-induced break-down spectroscopy found evidence of Zn emission lines that were not documented on the NIST database. In this study, rock powders were doped with Rb, Ce, La, Sr, Y, Zr, Pb and Se in concentrations ranging from 10 percent to 10 parts per million. The difference between normalized spectra collected on samples containing 10 percent dopant and those containing only 10 parts per million were used to identify all emission lines that can be detected using LIBS (Laser-Induced Breakdown Spectroscopy) in a ChemCam-like configuration at the Mount Holyoke College LIBS facility. These emission spectra provide evidence of many previously undocumented emission lines for the elements measured here.

  14. Dating Melt Rock 63545 By Rb-Sr and Sm-Nd: Age of Imbrium; Spa Dress Rehearsal

    Nyquist, L. E.; Shih, C. Y.; Reese, Y. D.


    Apollo 16 sample 63545 was initially described as one of a group of 19 generally rounded, fine-grained, crystalline rocks that were collected as rake samples [1]. This 16 g "rocklet" was collected at Station 13 on the ejecta blanket of North Ray Crater at the foot of Smoky Mountain [2]. Originally classified as a Very High Alumina (VHA) basalt on geochemical grounds [3], it was later argued to be an impact melt rock [4]. Here we report a Rb-Sr and Sm-Nd isotopic study that shows that some portions of the rock failed to reach isotopic equilibrium on last melting in agreement with the impact melt rock interpretation. Nevertheless, by omitting mineral fractions that are discordant with the majority of the data, we arrive at the time of last melting as 3.88 plus or minus 0.05 Ga ago. This age is in agreement with the Ar-39/Ar-40 plateau age of 3839 plus or minus 23 Ma [5], if the latter is adjusted for the 1.4-1.8% revision in the age of the hornblende monitor [6]. This investigation was undertaken in part as proof-of-concept for SPA-basin sample return.

  15. Single crystal growth and physical properties of SrCu2As2, SrCu2Sb2 and BaCu2Sb2

    Anand, V. K.; Perera, P. K.; Pandey, A.; Goetsch, R. J.; Kreyssig, A.; Johnston, D. C.


    We present the physical properties of self-flux-grown single crystals of SrCu2As2, SrCu2Sb2, SrCu2(As0.84Sb0.16)2 and BaCu2Sb2 investigated by magnetic susceptibility χ, specific heat Cp and electrical resistivity ρ vs. temperature T measurements. Contrasting structures occur for SrCu2As2 (ThCr2Si2-type), SrCu2Sb2 (CaBe2Ge2-type) and BaCu2Sb2 (a distorted intergrowth of ThCr2Si2-type and CaBe2Ge2-type unit cells). The χ(T) data for all these compounds exhibit weakly anisotropic diamagnetic behaviors. For 1.8 Debye lattice contributions. From the low-T Cp(T) data, we infer Sommerfeld coefficients γ = 2.2--3.9 mJ/mol,^2 and Debye temperatures θD = 204--246 K@. The electronic properties indicate that these compounds are sp metals containing Cu in a nonmagnetic 3d^10 electronic configuration.ootnotetextD. J. Singh, Phys. Rev. B 79, 153102 (2009).

  16. Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar, silicate melts, and hydrothermal solutions

    Blundy, J.D.; Wood, B.J. (Bristol Univ. (England))


    The aim of this paper is to evaluate the factors which control the partitioning of alkaline earth elements (Ba and Sr) between plagioclase feldspar and silicate melts, specifically the respective role of crystal chemistry, melt chemistry, and temperature. We have selected plagioclase because of the wealth of volcanic and experimental data, the compositional simplicity of plagioclase, and its relevance to many petrological problems. We begin our study by examining experimental data on Sr partitioning between plagioclase and hydrothermal solutions in an attempt to constrain the role of crystal chemistry. We establish a simple thermodynamic model for trace element partitioning between plagioclase and hydrothermal solutions. This treatment is then extended to the plagioclase-melt system using available data from both experimental and volcanic systems in order to derive a general equation for Sr and Ba partitioning. Finally we consider the geochemical applications and implications of our findings.

  17. Structural and crystallization behavior of (Ba,Sr)TiO3 borosilicate glasses

    Yadav, Avadhesh Kumar; Gautam, C. R.; Gautam, Arvind; Mishra, Vijay Kumar


    Various glass samples were prepared by melt quench technique in the glass system [(Ba1- x Sr x ) TiO3]-[2SiO2-B2O3]-[K2O] doped with 1 mole% of La2O3. Infrared spectra show the number of absorption peaks with different spliting in the wave number range from 450 to 4000 cm-1. Absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B-O of trigonal BO3. Raman spectra show the Raman bands due to ring-type metaborate anions, symmetric breathing vibrations BO3 triangles replaced by BO4 tetrahedra, and symmetric breathing vibrations of six-member rings. The differential thermal analysis of a glass sample corresponding to composition x = 0.0 shows crystallization temperature at 847°C and glass transition temperature at 688°C. X-ray diffraction (XRD) pattern of glass ceramic samples shows the major crystalline phase of BaTiO3 whereas pyrochlore phases of barium titanium silicate. Scanning electron micrographs confirm the results of XRD as barium titanate is major crystalline phase along with pyrochlore phase of barium titanium silicate.

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

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


    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.

  19. Complex permittivity and complex permeability of Sr ions substituted Ba ferrite at X-band

    Singh, Charanjeet [Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab (India); Bindra Narang, S. [Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab (India)], E-mail:; Hudiara, I.S. [Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab (India); Sudheendran, K.; James Raju, K.C. [School of Physics, Central University Hyderabad, Andhra Pradesh (India)


    M-type hexagonal ferrite composition, Ba{sub (1-x)}Sr{sub x}Fe{sub 12}O{sub 19} (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), was prepared by a two route ceramic method. Complex permittivity ({epsilon}'-j{epsilon}'') and complex permeability ({mu}'-j{mu}'') have been measured using a network analyzer from 8.2 to 12.4 GHz X-ray diffraction confirmed the M-type hexagonal structure and a scanned electron micrograph was used to analyze the grain size distribution of ferrite. Substitution of Sr{sup 2+} ions causes an increase in porosity that deteriorates the electromagnetic and microstructural properties in the doped samples. Both dielectric constant and dielectric loss are enhanced in comparison to the permeability and magnetic loss over the entire frequency region. This is due to a resistivity variation and the formation of Fe{sup 2+} ions, which increases the hopping mechanism between Fe{sup 2+} and Fe{sup 3+} ions.

  20. Abundances of C, N, Sr and Ba on the red giant branch of omega Centauri

    Stanford, Laura M; Norris, John E


    Abundances relative to iron for carbon, nitrogen, strontium and barium are presented for 33 stars on the red giant branch of the globular cluster omega Centauri. They are based on intermediate-resolution spectroscopic data covering the blue spectral region analyzed using spectrum synthesis techniques. The data reveal the existence of a broad range in the abundances of these elements, and a comparison with similar data for main sequence stars enables insight into the evolutionary history of the cluster. The majority of the red giant branch stars were found to be depleted in carbon, i.e. [C/Fe]<0, while [N/Fe] for the same stars shows a range of ~1 dex, from [N/Fe]~0.7 to 1.7 dex. The strontium-to-iron abundance ratios varied from solar to mildly enhanced (0.0<=[Sr/Fe]<=0.8), with [Ba/Fe] generally equal to or greater than [Sr/Fe]. The carbon and nitrogen abundance ratios for the one known CH star in the sample, ROA 279, are [C/Fe]=0.6 and [N/Fe]=0.5 dex. Evidence for evolutionary mixing on the red gia...

  1. 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

    Chen, Q.J.; Hou, Xiaolin; Yu, Y.X.


    be completed. The new separation procedure has been successfully used for the determination of Sr-90 in samples with high Ca content, such as 451 of seawater and 2001 of drinking water. The analytical quality of the results is comparable to that of the traditional method using fuming nitric acid and BaCrO4...

  2. Luminescent nitridophosphates CaP2 N4 :Eu(2+) , SrP2 N4 :Eu(2+) , BaP2 N4 :Eu(2+) , and BaSr2 P6 N12 :Eu(2.).

    Pucher, Florian J; Marchuk, Alexey; Schmidt, Peter J; Wiechert, Detlef; Schnick, Wolfgang


    Nitridophosphates MP2 N4 :Eu(2+) (M=Ca, Sr, Ba) and BaSr2 P6 N12 :Eu(2+) have been synthesized at elevated pressures and 1100-1300 °C starting from the corresponding azides and P3 N5 with EuCl2 as dopant. Addition of NH4 Cl as mineralizer allowed for the growth of single crystals. This led to the successful structure elucidation of a highly condensed nitridophosphate from single-crystal X-ray diffraction data (CaP2 N4 :Eu(2+) (P63 , no. 173), a=16.847(2), c=7.8592(16) Å, V=1931.7(6) Å(3) , Z=24, 2033 observed reflections, 176 refined parameters, wR2 =0.096). Upon excitation by UV light, luminescence due to parity-allowed 4f(6) ((7) F)5d(1) →4f(7) ((8) S7/2 ) transition was observed in the orange (CaP2 N4 :Eu(2+) , λmax =575 nm), green (SrP2 N4 :Eu(2+) , λmax =529 nm), and blue regions of the visible spectrum (BaSr2 P6 N12 :Eu(2+) and BaP2 N4 :Eu(2+) , λmax =450 and 460 nm, respectively). Thus, the emission wavelength decreases with increasing ionic radius of the alkaline-earth ions. The corresponding full width at half maximum values (2240-2460 cm(-1) ) are comparable to those of other known Eu(2+) -doped (oxo)nitrides emitting in the same region of the visible spectrum. Following recently described quaternary Ba3 P5 N10 Br:Eu(2+) , this investigation represents the first report on the luminescence of Eu(2+) -doped ternary nitridophosphates. Similarly to nitridosilicates and related oxonitrides, Eu(2+) -doped nitridophosphates may have the potential to be further developed into efficient light-emitting diode phosphors.

  3. Structural evidence for enhanced polarization in a commensurate short-period BaTiO3/SrTiO3 superlattice

    Tian, W.; Jiang, J. C.; Pan, X. Q.; Haeni, J. H.; Li, Y. L.; Chen, L. Q.; Schlom, D. G.; Neaton, J. B.; Rabe, K. M.; Jia, Q. X.


    A short-period (BaTiO3)6/(SrTiO3)5 superlattice was characterized by x-ray diffraction and transmission electron microscopy. The superlattice is epitaxially oriented with the c axes of BaTiO3 and SrTiO3 normal to the (001) surface of the SrTiO3 substrate. Despite the large in-plane lattice mismatch between BaTiO3 and SrTiO3 (˜2.2%), the superlattice interfaces were found to be nearly commensurate. The crystallographic c /a ratio of the superlattice was measured and the results agree quantitatively with first-principles calculations and phase-field modeling. The agreement supports the validity of the enhanced spontaneous polarization predicted for short-period BaTiO3/SrTiO3 superlattices.

  4. Rb-Sr isotopic composition of granites in the Western Krušné hory/Erzgebirge pluton, Central Europe: record of variations in source lithologies, mafic magma input and postmagmatic hydrothermal events

    Dolejš, David; Bendl, Jiří; Štemprok, Miroslav


    The late Variscan (327-318 Ma) Western Krušné hory/Erzgebirge pluton (Czech Republic and Germany) represents a multiply emplaced intrusive sequence ranging from low-F biotite monzogranites (with rare minor bodies of gabbrodiorites and granodiorites) to high-F topaz-zinnwaldite alkali-feldspar granites. This granite suite is characterized by progressively increasing concentrations of incompatible elements (Li, Rb, F), monotonous decrease in mafic components and compatible elements (FeOtot, MgO, TiO2, CaO, Sr) with increasing silica. Consequently, this leads to extreme variations in the Rb/Sr ratios (0.52 to 59), which impose highly variable 87Rb/86Sr and 87Sr/86Sr signatures. The low-F biotite monzogranites represent isotopically heterogeneous mixture with (87Sr/86Sr)323 = 0.707-0.709 between partial melts from the Saxothuringian metasediments and mantle-derived mafic precursors. The medium-F two-mica microgranites show variable (87Sr/86Sr)323 = 0.708-0.714, indicating involvement of multiple precursors and more mature crustal protoliths. The evolved high-F topaz-zinnwaldite alkali-feldspar granites were derived from a precursor with (87Sr/86Sr)320 = 0.707-0.708 at 324-317 Ma by differentiation, which produced the extreme Rb/Sr enrichment and variations. The Li/Rb ratios remain nearly constant (~0.5), thus insensitive to the degree of geochemical differentiation. In comparison to terrestrial variations, the high Li/Rb values indicate derivation of granitic magmas from predominantly sedimentary precursors, in accord with 7Li-6Li and 143Nd-144Nd isotope composition reported previously. The Rb-Sr element variations in each granite unit are sligthly different and indicate ascent and emplacement of separate magma batches, which do not form a single liquid line of descent. We consider the enrichment of granites in incompatible elements (Li, Rb, F) and compatible depletion of ferromagnesian components, CaO and Sr as a combined effect of multiple precursors, changes in

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

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


    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.

  6. XANES at Eu-L3 edge and valence of europium in SrB4O7: Eu and BaB8O13: Eu

    LIANG, Hong- Bin(梁宏斌); HU, Tian-Dou(胡天斗); WANG, Shu-Bin(王淑彬); ZENG, Qing-Hua(曾庆华); PEI, Zhi-Wu(裴治武); SU, Qiang(苏锵)


    The luminescent materials SrB4O7: Eu and BaB8O13: Eu were synthesized, and the valence states of europium in the materials were measured by means of XANES at Eu-L3 edge. It is found that the Eu3+ and Eu2+ ions are all present in the materials, and more Eu3+ ions can be reduced in SrB4O7:Eu than in BaB8O13:Eu. The excitation and emission spectra of Eu3+in SrB4O7:Eu and BaB8O13:Eu were determined.

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

    B. Kasenov


    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.

  8. Interface Control of Ferroelectricity in an SrRuO3 /BaTiO3 /SrRuO3 Capacitor and its Critical Thickness.

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


    The atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (PO2) during growth plays an important role in controlling the interfacial terminations of SrRuO3 /BaTiO3 /SrRuO3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of RuO2 -BaO and SrO-TiO2 terminations. By reducing PO2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    H. B. Zhang


    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.

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

    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: [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:; 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)


    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}.

  11. The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices

    Zhu Zhen-Ye; Wang Biao; Wang Hai; Zheng Yue; Li Qing-Kun


    We have performed the first-principles calculation to investigate the origins of ferroelectricities and different polarization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3- The density of state (DOS) and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/rTiO3 and PbTiO3/SrTiO3. Owing to the decline of internal electric field in SrTiO3 (ST) layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are enhanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.

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

    David Parker and David J Singh


    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.

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

    Wen, Zheng [College of Physics, Qingdao University, Qingdao 266071 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China and Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China); Wu, Di, E-mail:; Li, Aidong [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China and Department of Materials Science and Engineering, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093 (China)


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

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

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


    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).

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

    Tomza, Michał


    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...

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

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


    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.

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

    J.G. Carrio


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

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

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


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

  19. NMR study of filled skutterudite superconductors MPt{sub 4}Ge{sub 12}(M=Sr,Ba)

    Magishi, K., E-mail: [Inst. of Socio-Arts and Sciences, Univ. of Tokushima, Tokushima 770-8502 (Japan); Sugawara, H.; Ohta, N.; Saito, T.; Koyama, K. [Inst. of Socio-Arts and Sciences, The Univ. of Tokushima, Tokushima 770-8502 (Japan)


    We report on the results of the {sup 195}Pt NMR measurements for MPt{sub 4}Ge{sub 12}(M=Sr,Ba) to clarify the microscopic electronic states at low temperatures. In SrPt{sub 4}Ge{sub 12} and BaPt{sub 4}Ge{sub 12}, the isotropic component of the Knight shift, that is, the contribution from the Pt 5s states is smaller than that in LaPt{sub 4}Ge{sub 12}. In the superconducting state, 1/T{sub 1} shows a small coherence peak just below T{sub C}, followed by an exponential decrease at low temperatures revealing on energy gap {Delta}/k{sub B}T{sub C}=1.6, which suggests a conventional BCS superconductor.

  20. Variation of Ca, Sr, Ba and Mg in the otolith of mudskipper in west coast of Peninsular Malaysia.

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


    A study on elemental composition in the otolith of giant mudskipper, Periophthalmodon schlosseri, was done from June to October 2003. Specimens were obtained from the mangrove areas of Kuala Selangor, Sepang and Melaka in the west coast of Peninsular Malaysia. A total of 70 sagitta otoliths were analyzed to detect variation of Sr, Ba and Mg, replacing the natural chemical composition of the otolith, which is the calcium carbonate (CaCO3). The average ratio of Sr:Ca was 0.11 x 10(-4), Ba:Ca was 5.7 x 10(-3) and Mg:Ca was 0.2 x 10(-3). Strong correlation (R > 0.8) between fish body size and otolith weight ofmudskipper (p < 0.01) also found during this study.

  1. Overview of the geochemistry and Rb/Sr, Sm/Nd isotopes of Middle Jurassic and Tertiary granitoid intrusions: a new insight on tectono-magmatism and mineralization of this period in Iran

    Mohammad Ali Jazi


    Full Text Available One of the most intensive occurrences of magmatism in Iran was in the middle Jurassic period. Among the granitoid intrusions in this period as discrete bodies or complexes can be pointed to Aligoodarz, Alvand, Astaneh, Boroujerd, Malayer, and Chah-Dozdan in the Sanandaj-Sirjan zone; Shir-kuh and Ayrakan in the Central Iran zone; Shah-kuh, Sorkh-kuh and Kalateh-Ahani in the Lut Block. These granitoids are mostly peraluminous and belong to high-K calc-alkaline series. CaO/Na2O ratios (0.12 to 8.37 mostly suggest a clay-free source for formation of the intrusive rocks magma. Chondrite-normalized Rare Earth Elements (REEs diagram do not display high enrichment of Light Rare Earth Elements (LREEs than Heavy Rare Earth Elements (HREEs and general pattern is relatively flat. In addition, diagram shows Eu negative anomaly, which can be attributed to indicate reducing conditions in formation of magma and/or magma derived from plagioclase depth as source. The lower continental crust-normalized spider diagram indicates enrichment in LILE (Rb, Cs, and K and LREE (La and Ce and depletion in Ba, Nb, Ta, Sr, and Ti. Initial 87Sr/86Sr ratios are 0.70609 to 0.71938 and initial εNd values are negative (from -6.51 to -1.1 indicating that magma derived from continental crust. Geochemical and isotopic evidence of the intrusive rocks shows continental crust origin (S-type granitoid and due to continental collision. Geological findings such as stop in sedimentation, regional metamorphism, ophiolite displacement, and continental collision-related mineralization confirm continental collision between Iranian and Arabian plates in the Middle Jurassic period.

  2. Large-scale parallel configuration interaction. I. Nonrelativistic and scalar-relativistic general active space implementation with application to (Rb-Ba)+.

    Knecht, Stefan; Jensen, Hans Jorgen Aa; Fleig, Timo


    We present a parallel implementation of a string-driven general active space configuration interaction program for nonrelativistic and scalar-relativistic electronic-structure calculations. The code has been modularly incorporated in the DIRAC quantum chemistry program package. The implementation is based on the message passing interface and a distributed data model in order to efficiently exploit key features of various modern computer architectures. We exemplify the nearly linear scalability of our parallel code in large-scale multireference configuration interaction (MRCI) calculations, and we discuss the parallel speedup with respect to machine-dependent aspects. The largest sample MRCI calculation includes 1.5x10(9) Slater determinants. Using the new code we determine for the first time the full short-range electronic potentials and spectroscopic constants for the ground state and for eight low-lying excited states of the weakly bound molecular system (Rb-Ba)+ with the spin-orbit-free Dirac formalism and using extensive uncontracted basis sets. The time required to compute to full convergence these electronic states for (Rb-Ba)+ in a single-point MRCI calculation correlating 18 electrons and using 16 cores was reduced from more than 10 days to less than 1 day.

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

    Maji, Binoy Kumar; Jena, Hrudananda, E-mail:; Asuvathraman, R.; Kutty, K.V. Govindan


    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.

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

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


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

  5. Rb-Sr, Sm-Nd, K-Ca, O, and H isotopic study of Cretaceous-Tertiary boundary sediments, Caravaca, Spain: Evidence for an oceanic impact site

    DePaolo, D.J.; Kyte, F.T.; Marshall, B.D.; O' Neil, J.R.; Smit, J.


    Isotopic ratios and trace element abundances were measured on samples of IR-enriched clay at the Cretaceous-Tertiary boundary, and in carbonate and marl from 5 cm below and 3 cm above the boundary. Samples were leached with acetic acid to remove carbonate, and with hydrochloric acid. Leachates and residues were measured. The Sr, Nd, O and H isotopic compositions of the boundary clay residues are distinct from those of the stratigraphically neighboring materials. The data indicate that most of the clay material was derived from a terrestrial source with relatively low /sup 87/Sr//sup 86/Sr and high /sup 143/Nd//sup 144/Nd ratios. The delta/sup 18/O data suggest that the detritus has been modified by submarine weathering. K-Ca and Rb-Sr systematics, as well as O isotope ratios of K-feldspar spherules within the boundary clay, suggest that they are predominantly authigenic and may have formed after the time of deposition. However, Sm-Nd and Rb-Sr isotopic data indicate that the spherules contain relict material that provides information on the nature of the original detritus. The isotopic evidence for foreign terrestrial detritus in the boundary clay, the low rare earth element concentrations and high Ni concentration, support the hypothesis of a terminal Cretaceous asteroidal impact that produced a global layer of fallout. The data are most easily explained if the impact sites was on oceanic crust rather than continental crust, and if a substantial fraction of the fallout was derived from relatively deep within the lithosphere (> 3 km). This would probably require a single large impactor. 60 references.

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

    Yohanes Edi Gunanto


    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.

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

    Janek, Joanna, E-mail:; Sołtys, Marta; Żur, Lidia; Pietrasik, Ewa; Pisarska, Joanna; Pisarski, Wojciech A.


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

  8. Stabilisation of the tetragonal structure in (Ba,Sr)CuSi{sub 2}O{sub 6}

    Puphal, Pascal; Well, Natalija van; Ritter, Franz; Assmus, Wolf; Krellner, Cornelius [Physikalisches Institut, Goethe-Uni. Frankfurt (Germany); Sheptyakov, Denis V. [Lab. for Neutron Scattering and Imaging, PSI (Switzerland); Rueegg, Christian [Lab. for Neutron Scattering and Imaging, PSI (Switzerland); Dept. of Quantum Matter Physics, Uni. of Geneva (Switzerland)


    BaCuSi{sub 2}O{sub 6} is a spin dimer system presenting a 2D Bose-Einstein condensation of triplons at low temperatures and high magnetic fields. BaCuSi{sub 2}O{sub 6} undergoes a structural phase transition below 100 K into an orthorhombic structure with two different dimer layers, leading to a complex Hamiltonian. Presently, the role of frustration in the orthorhombic structure is under debate. We present results for strontium substitution on the barium side and investigate the structural transition with low temperature x-ray and neutron powder diffraction. In addition the results of magnetic and specific-heat measurements are discussed. Surprisingly, we found that already small amounts of Sr (x = 0.05) lead to a suppression of the structural phase transition and the higher symmetric tetragonal crystal structure with only one sort of Cu-dimers is stable down to lowest temperatures. With increasing Sr-content the unit cell volume decreases and the intra-dimer spacing increases. Therefore, (Ba{sub 1-x}Sr{sub x})CuSi{sub 2}O{sub 6} is a spin dimer system in a well-defined tetragonal crystal structure with the possibility to control the exchange interactions. Further manipulation is possible in substituting silicon by germanium (especially considering co-substitution) resulting in an increased cell volume and intra-dimer spacing.

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

    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: [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 5997, Bogota DC (Colombia)


    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.

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

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


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

  11. Microwave Dielectric Properties of A2P2O7 (A = Ca, Sr, Ba; Mg, Zn, Mn)

    Bian, Jian-jiang; Kim, Dong-Wan; Hong, Kug Sun


    Microwave dielectric properties of A2P2O7 (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10 GHz. It was found that A2P2O7 ceramics could be sintered at relatively lower temperature below 1150°C, although the thortveitite type series, Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A2P2O7 is lower than 10. The Q× f value increased according to the sequence of δ-Ba2P2O7, α-Sr2P2O7 and β-Ca2P2O7 in dichromatic type series, and the sequence of Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 in thortveitite type series, respectively. The temperature coefficient of resonant frequency τf for all samples exhibits negative value. Larger τf for α-Zn2P2O7, α-Mg2P2O7 and δ-Ba2P2O7 is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.

  12. Dating fault-generated pseudotachylytes: comparison of 40Ar/39Ar stepwise-heating, laser-ablation and Rb-Sr microsampling analyses

    Müller, Wolfgang; Kelley, Simon; Villa, Igor


    Three different geochronological techniques (stepwise-heating, laser-ablation 40Ar/39Ar, Rb-Sr microsampling) have been evaluated for dating fault-generated pseudotachylytes sampled along the Periadriatic Fault System (PAF) of the Alps. Because pseudotachylytes are whole-rock systems composed of melt, clast and alteration phases, chemical control from both Ar isotopes (Cl/K, Ca/K ratios) and EMPA analyses is crucial for their discrimination. When applied to stepwise-heating 40Ar/39Ar analyses, this approach yields accurate melt-related ages, even for complex age spectra. The spatial resolution of laser-ablation 40Ar/39Ar analyses is capable of contrasting melt, clast and alteration phases in situ, provided the clasts are not too fine grained, the latter of which results in integrated "mixed" ages without geological information. Elevated Cl/K and Ca/K ratios were found to be an invaluable indicator for the presence of clast admixture or inherited 40Ar. Due to incomplete isotopic resetting during frictional melting, Rb-Sr microsampling dating did not furnish geologically meaningful ages. On the basis of isotopic disequilibria among pseudotachylyte matrix phases, and independent Rb-Sr microsampling dating of cogenetic (ultra)mylonites, the concordant 40Ar/39Ar pseudotachylyte ages are interpreted as formation ages. The investigated pseudotachylytes altogether reveal a Cretaceous to Miocene history for the entire PAF, consistent with independent geological evidence. Individual faults, however, consistently reveal narrower intervals of enhanced activity lasting a few million years. Electronic supplementary material to this paper can be obtained by using the Springer LINK server at

  13. Comparative ab initio calculations of SrTiO{sub 3}/BaTiO{sub 3} and SrZrO{sub 3}/PbZrO{sub 3} (0 0 1) heterostructures

    Piskunov, Sergei, E-mail:; Eglitis, Roberts I., E-mail:


    Using a B3PW hybrid exchange–correlation functional within the density functional theory (DFT) we calculated from the first principles the electronic structure of BaTiO{sub 3}/SrTiO{sub 3} and PbZrO{sub 3}/SrZrO{sub 3} (0 0 1) interfaces. The optical band gap of both BaTiO{sub 3}/SrTiO{sub 3} and PbZrO{sub 3}/SrZrO{sub 3} (0 0 1) interfaces depends mostly from BaO or TiO{sub 2} and SrO or ZrO{sub 2} termination of the upper layer, respectively. Based on the results of our calculations we predict increase of the Ti–O and Zr–O chemical bond covalency near the SrTiO{sub 3}/BaTiO{sub 3} and SrZrO{sub 3}/PbZrO{sub 3} (0 0 1) interfaces as compared to the BaTiO{sub 3} and PbZrO{sub 3} bulk.

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

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


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

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

    E. Avigliano

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

  16. Phase stability in the systems AeAl(2-x)Mgx (Ae = Ca, Sr, Ba): electron concentration and size controlled variations on the laves phase structural theme.

    Amerioun, Shahrad; Yokosawa, Tadahiro; Lidin, Sven; Häussermann, Ulrich


    The systems AeAl(2-x)Mgx (Ae = Ca, Sr, Ba) display electron concentration induced Laves phase structural changes. However, the complete sequence MgCu2 --> MgNi2 --> MgZn2 with increasing x (decreasing electron count) is only observed for Ae = Ca. Compounds SrAl(2-x)Mgx (0 MgNi2 --> MgZn2 occurs with increasing Mg content x. Thus, larger Sr does not allow the realization of the MgCu2 structure at low x. For Ae = Ba a binary compound BaAl2 does not exist, but more Ba-rich Ba7Al13 forms. The reinvestigation of the crystal structure of Ba7Al13 by selected area and convergent beam electron diffraction in a transmission electron microscope revealed a superstructure, which subsequently could be refined from single X-ray diffraction data. The formula unit of the superstructure is Ba21Al40 (space group P31m, Z = 1, a = 10.568(1) angstroms, c = 17.205(6) angstroms). In Ba21Al40 a size match problem between Ba and Al present in Ba7Al13 is resolved. The structure of Ba7Al13 (Ba21Al40) can be considered as a Ba excess variant of the hexagonal MgNi2 Laves phase type structure. An incommensurately modulated variant of the MgNi2 structure is obtained for phases BaAl(2-x)Mgx with x = 0.8-1. At even higher Mg concentrations a structural change to the proper MgZn2 type structure takes place. Copyright 2004 American Chemical Society

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

    葛水兵; 沈明荣; 宁兆元


    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.

  18. Optical properties of A Fe2As2 (A =Ca , Sr, and Ba) single crystals

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


    The detailed optical properties have been determined for the iron-based materials A Fe2As2 , 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 TN=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 TN, the free-carrier response consists of a weak, narrow Drude term, and a strong, broad Drude term, both of which show only a weak temperature dependence. Below TN there is a slight decrease of the plasma frequency but a dramatic drop in the scattering rate for the narrow Drude term, and for the broad Drude term there is a significant decrease in the plasma frequency, while the decrease in the scattering rate, albeit significant, is not as severe. The small values observed for the scattering rates for the narrow Drude term for T ≪TN may be related to the Dirac conelike dispersion of the electronic bands. Below TN new features emerge in the optical conductivity that are associated with the reconstruction Fermi surface and the gapping of bands at Δ1≃45 -80 meV, and Δ2≃110 -210 meV. The reduction in the spectral weight associated with the free carriers is captured by the gap structure; specifically, the spectral weight from the narrow Drude term appears to be transferred into the low-energy gap feature, while the missing weight from the broad term shifts to the high-energy gap.

  19. Synthesis of Long Afterglow Phosphors MAl2O4:Eu2+, Dy3+(M=Ca, Sr, Ba) by Microemulsion Method and Their Luminescent Properties

    Qiu Guanming; Chen Yongjie; Geng Xiujuan; Xiao Linjiu; Tian Yiguang; Sun Yanbin


    Long afterglow phosphors MAl2O4:Eu2+, Dy3+ (M=Ca, Sr, Ba) were synthesized by microemulsion method, and their crystal structure and luminescent properties were compared and investigated. XRD patterns of samples indicate that phosphors CaAl2O4:Eu2+, Dy3+ and SrAl2O4:Eu2+, Dy3+ are with monoclinic crystal structure and phosphor BaAl2O4:Eu2+, Dy3+ is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4:Eu2+, Dy3+ (M=Ca,Sr,Ba) indicates that the luminescent materials can be excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4:Eu2+, Dy3+ (M=Ca, Sr, Ba) is found mainly at λem of 440 nm (M=Ca), 520 nm (M=Sr) and 496 nm (M=Ba) respectively, the corresponding colors of emission light are blue, green and cyna-green respectively. The afterglow decay tendency of phosphors can be summarized as three processes: initial rapid decay, intermediate transitional decay and very long slow decay. Afterglow decay curves coincide with formula I=At-n, and the sequence of afterglow intensity and time is Sr>Ca>Ba.

  20. Thermally stable white-emitting single composition Na(Sr,Ba)PO4:Eu2+, Mn2+ phosphor for near-ultraviolet-pumped light-emitting diodes.

    Choi, Sungho; Yun, Young Jun; Kim, Sue Jin; Jung, Ha-Kyun


    Eu(2+) and Mn(2+) codoped, white-emitting Na(Sr,Ba)PO(4) phosphors are prepared, and their emission properties, especially for thermal stability, are thoroughly investigated. The thermal quenching and Eu(2+)/Mn(2+) energy transfer efficiency are totally different in the ratio of alkaline earth metals in host composition, NaBaPO(4), Na(Sr(0.5)Ba(0.5))PO(4), and NaSrPO(4), respectively. Furthermore, by using near-ultraviolet light-emitting diodes (LEDs) and the corresponding Na(Sr(0.5)Ba(0.5))PO(4):Eu(2+), Mn(2+) phosphor as light converters, we demonstrate a bright and thermally stable white-emitting LED. The resultant LED exhibits a warm white light [~4900 K, CIE coordinates of (0.33, 0.31)] with excellent thermal and hydrolytic stabilities comparable to those of commercially available ones, Y(3)Al(5)O(12):Ce(3+) and BaMg(2)Al(16)O(27):Eu(2+). The proposed composition, with its efficient energy transfer, could enable Eu(2+) and Mn(2+) codoped Na(Sr,Ba)PO(4) to be a promising single component phosphor for cost-effective white-emitting LEDs.

  1. Rb-Sr, Sm-Nd, K-Ca, O, and H isotopic study of Cretaceous-Tertiary boundary sediments, Caravaca, Spain Evidence for an oceanic impact site

    Depaolo, D.J.; Kyte, F.T.; Marshall, B.D.


    The results of isotopic and trace-element-abundance analyses of Ir-enriched Cretaceous-Tertiary-boundary clay sediments from Caravaca, Spain, and of adjacent carbonate and marl layers, are presented. Acetic-acid and HCl leachates and residues were analyzed by isotope dilution to determine K, Rb, Sr, Sm, and Nd concentrations and Sr-87/Sr-86 and Nd-143/Nd-144 ratios. The stable isotope ratios delta-D, delta-(C-13), and delta-(0-18) were also determined. The results are presented in tables and graphs and compared with published data on the Caravaca sediments and on samples from other locations. The boundary clay is found to be distinguished from the adjacent layers by its isotopic ratios and to be of mainly terrestrial, lithospheric (deeper than 3-km) origin. Although submarine-weathering effects are evident and difficult to quantify, the degree of variation in Ni, Ir, Sr, and REE concentrations is considered too large to be attributed to postdepositional processes alone. These findings are seen as evidence for the ocean impact of a large single asteroid producing a worldwide blanket of ejecta, a large injection of water vapor into the atmosphere, and perhaps a gigantic tsunami, at the end of the Cretaceous period.

  2. Lanthanide doped BaTiO{sub 3}−SrTiO{sub 3} solid-solution phosphors: Structure, optical spectroscopy and upconverted temperature sensing behavior

    Chen, Daqin, E-mail:; Xu, Wei; Zhou, Yang; Chen, Yan, E-mail:


    Lanthanide doped Ba{sub 1-x}Sr{sub x}TiO{sub 3} (x = 0–1) solid-solution phosphors were successfully prepared by a conventional solid-state reaction. Using Eu{sup 3+} dopants as the structural probe, the variation of {sup 5}D{sub 0} → {sup 7}F{sub 2}/{sup 5}D{sub 0} → {sup 7}F{sub 1} emission intensity ratio with increase of Eu{sup 3+} content and the excitation-wavelength-dependent luminescence in the Ba{sub 1-x}Sr{sub x}TiO{sub 3} sample were demonstrated to be originated from the different emission behaviors of Eu{sup 3+} in Ba{sup 2+}/Sr{sup 2+} site and Ti{sup 4+} site. Furthermore, upconversion luminescence for the Yb{sup 3+}/Er{sup 3+} co-doped Ba{sub 1-x}Sr{sub x}TiO{sub 3} samples were investigated, and it was found that the emission intensity of Yb{sup 3+}/Er{sup 3+}: Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} phosphor was about 5 and 2 times as high as those of Yb{sup 3+}/Er{sup 3+}: BaTiO{sub 3} and Yb{sup 3+}/Er{sup 3+}: SrTiO{sub 3} ones. Using the investigated Yb{sup 3+}/Er{sup 3+}: Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} solid-solution as the optical thermometric medium, the temperature sensitivity was determined to be 0.76% K{sup −1} at the temperature of 610 K based on the temperature-dependent fluorescence intensity ratio of the thermally coupled {sup 2}H{sub 11/2} and {sup 4}S{sub 3/2} emitting-states of Er{sup 3+}. - Highlights: • Lanthanide doped Ba{sub 1-x}Sr{sub x}TiO{sub 3} (x = 0–1) solid-solutions were fabricated. • Excitation-wavelength-dependent Eu{sup 3+} emissions were recorded. • Enhanced Er{sup 3+} luminescence was realized by partial substitution of Ba{sup 2+} by Sr{sup 2+}. • T-sensitive emissions of two Er{sup 3+} thermally coupled states were observed. • The upconversion phosphor exhibited a high sensitivity of 0.76% K{sup −1}.

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

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


    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.

  4. Solid-Phase Equilibria for Metal-Silicon-Oxygen Ternary Systems I: Mg, Ca, Sr and Ba


    Sr AND Ba Accesstloi For NTIS ,r .&-I by I LTIC TAB UT I’r ~o’u-- d El SJUZt ificntion H. Yuan and R.S. Williams i y. (in preparation ) ByDJ . s t r...1latin Ref. 11 S󈧆 -910.94 (ac quartz) -909.48 (ac cristobalite ) -909.06 (ac tridymile) -903.5 (amo.) NA9J -601.70 -597.98 (micro) Mg 2Si -77.8 Mg2SiO4

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

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


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

  6. Tilting structures in inverse perovskites, M3TtO (M = Ca, Sr, Ba, Eu; Tt = Si, Ge, Sn, Pb).

    Nuss, Jürgen; Mühle, Claus; Hayama, Kyouhei; Abdolazimi, Vahideh; Takagi, Hidenori


    Single-crystal X-ray diffraction experiments were performed for a series of inverse perovskites, M3TtO (M = Ca, Sr, Ba, Eu; Tt = tetrel element: Si, Ge, Sn, Pb) in the temperature range 500-50 K. For Tt = Sn, Pb, they crystallize as an 'ideal' perovskite-type structure (Pm3m, cP5); however, all of them show distinct anisotropies of the displacement ellipsoids of the M atoms at room temperature. This behavior vanishes on cooling for M = Ca, Sr, Eu, and the structures can be regarded as `ideal' cubic perovskites at 50 K. The anisotropies of the displacement ellipsoids are much more enhanced in the case of the Ba compounds. Finally, their structures undergo a phase transition at ∼ 150 K. They change from cubic to orthorhombic (Ibmm, oI20) upon cooling, with slightly tilted OBa6 octahedra, and bonding angles O-Ba-O ≃ 174° (100 K). For the larger Ba(2+) cations, the structural changes are in agreement with smaller tolerance factors (t) as defined by Goldschmidt. Similar structural behavior is observed for Ca3TtO. Smaller Tt(4-) anions (Si, Ge) introduce reduced tolerance factors. Both compounds Ca3SiO and Ca3GeO with cubic structures at 500 K, change into orthorhombic (Ibmm) at room temperature. Whereby, Ca3SiO is the only representative within the M3TtO family where three polymorphs can be found within the temperature range 500-50 K: Pm3m-Ibmm-Pbnm. They show tiny differences in the tilting of the OCa6 octahedra, expressed by O-Ca-O bond angles of 180° (500 K), ∼ 174° (295 K) and 170° (100 K). For larger M (Sr, Eu, Ba), together with smaller Tt (Si, Ge) atoms, pronounced tilting of the OM6 octahedra, and bonding angles of O-M-O ≃ 160° (295 K) are observed. They crystallize in the anti-GdFeO3 type of structure (Pbnm, oP20), and no phase transitions occur between 500 and 50 K. The observed phase transitions are all accompanied by multiple twinning, in terms of pseudo-merohedry or reticular pseudo-merohedry.

  7. Dating and source determination of volcanic rocks from Khunik area (South of Birjand, South Khorasan using Rb-Sr and Sm-Nd isotopes

    Somayeh Samiee


    Full Text Available The Khunik area is located in the south of Birjand, Khorasan province, in the eastern margin of Lut block. Tertiary volcanic rocks have andesite to trachy-andesite composition. Dating analyzing by Rb-Sr method on plagioclase and hornblende as well as whole-rock isochron method was performed on pyroxene-hornblende andesite rock unit. On this basis the emplacement age is Upper Paleocene (58±11 Ma. These rocks have initial 87Sr/86Sr and εNd 0.7046-0.7049 and 2.16-3.12, respectively. According to isotopic data, volcanic rocks originated from depleted mantle and have the least crust contamination while it was fractionated. Geochemically, Khunik volcanic rocks have features typical of calk-alkaline to shoshonite and are metaluminous. Enrichment in LILEs and typical negative anomalies of Nb and Ti are evidences that the volcanic rocks formed in a subduction zone and active continental margin. Modeling suggests that these rocks were derived dominantly from 1–5% partial melting of a mainly spinel garnet lherzolite mantle source that is metasomatized by slab-derived fluid.

  8. Solid Electrolyte Based on Perovskite-type BaCeO3 and SrCeO3%BaCeO3和SrCeO3基钙钛矿型固体电解质

    张俊英; 张中太


    综述了BaCeO3基和SrCeO3基钙钛矿型固体电解质.从结构、不同气氛中导电性方面进行了介绍,对其应用方面进行了较为详细的分析.在燃料电池、电解池、薄膜反应器、气体传感器等方面的应用分析表明这2类固体电解质有广泛的应用前景.%Solid electrolyte based on perovskite-type BaCeO3 and SrCeO3 was reviewed .Microstructure and conductivity in different atmosphere were introduced while application was analyzed in detail. Applications in fuel cell, steam electrolysis cell, membrane reactor, gas sensor indicate that these kinds of solid electrolytes may be prospective materials that can be used in many fields.

  9. A combined Sm-Nd, Rb-Sr, and U-Pb isotopic study of Mg-suite norite 78238: Further evidence for early differentiation of the Moon

    Edmunson, J; E.Borg, L; Nyquist, L E; Asmerom, Y


    Lunar Mg-suite norite 78238 was dated using the Sm-Nd, Rb-Sr, and U-Pb isotopic systems in order to constrain the age of lunar magma ocean solidification and the beginning of Mg-suite magmatism, as well as to provide a direct comparison between the three isotopic systems. The Sm-Nd isotopic system yields a crystallization age for 78238 of 4334 {+-} 37 Ma and an initial {var_epsilon}{sub Nd}{sup 143} value of -0.27 {+-} 0.74. The age-initial {var_epsilon}{sub Nd}{sup 143} (T-I) systematics of a variety of KREEP-rich samples, including 78238 and other Mg-suite rocks, KREEP basalts, and olivine cumulate NWA 773, suggest that lunar differentiation was completed by 4492 {+-} 61 Ma assuming a Chondritic Uniform Reservoir bulk composition for the Moon. The Rb-Sr isotopic systematics of 78238 were disturbed by post-crystallization processes. Nevertheless, selected data points yield two Rb-Sr isochrons. One is concordant with the Sm-Nd crystallization age, 4366 {+-} 53 Ma. The other is 4003 {+-} 95 Ma and is concordant with an Ar-Ar age for 78236. The {sup 207}Pb-{sup 206}Pb age of 4333 {+-} 59 Ma is concordant with the Sm-Nd age. The U-Pb isotopic systematics of 78238 yield linear arrays equivalent to younger ages than the Pb-Pb system, and may reflect fractionation of U and Pb during sample handling. Despite the disturbed nature of the U-Pb systems, a time-averaged {mu} ({sup 238}U/{sup 204}Pb) value of the source can be estimated at 27 {+-} 30 from the Pb-Pb isotopic systematics. Because KREEP-rich samples are likely to be derived from source regions with the highest U/Pb ratios, the relatively low {mu} value calculated for the 78238 source suggests the bulk Moon does not have an exceedingly high {mu} value.

  10. La-(Ca-Ba-Sr)-Mn-O锰氧化物高低温输运特性%Transport Property at Low and High Temperatures in La-(Ca-Ba-Sr)-Mn-O Manganite Perovskite

    陈志高; 陈水源; 黄志高; 赖恒; 都有为


    Polycrystalline samples La2/3Ca1/3MnO3 (LCMO), La2/3(Ca0.5Ba0.5)1/3MnO3 (LCBMO), La2/3Ba1/3MnO3 (LBMO),La2/3(Sr0.5Ba0.5)1/3MnO3 (LSBMO) and La2/3Sr1/3MnO3 (LSMO) have been prepared by a solid state reaction method. We have observed the temperature dependences of the electric resistivity and magnetoresistance from 77 K up to 800 K. Experimental results indicate that the presence of grain boundaries in the colossal magnetoresistance (CMR) materials prepared by the mechanical alloyed method leads to a large magnetoresistance effect at low temperature, and there exists a pronounced metal-semiconductor transition around Tc. According to the models of spin-polarized electron tunneling and percolation, the magnetoresistance as a function of temperature has been explained well. The temperature dependence of resistivity at high temperature is well fit by nonadiabatic small polaron hopping model for LCBMO and LSBMO samples, and their activation energies are obtained. Also it has been found that annealing processing affects the resistivity significantly.%用固相反应烧结法制备了多晶体材料La2/3Ca1/3MnO3(LCMO),La2/3(Ca0.5Ba0.5)1/3MnO3(LCBMO)、La2/3Ba1/3MnO3(LBMO),La2/3(Sr0.5Ba0.5)1/3MnO3(LSBMO)和La2/3Sr1/3MnO3(LSMO),测量了它们在77 K~800 K的电阻和磁电阻特性.实验发现,通过一定的工艺技术制备出的CMR材料有强烈的相界效应,在低温下有大的磁电阻,且在Tc附近存在明显的从金属态向半导体态的转变;用自旋极化电子隧道效应和靠近居里点逾渗模型较好地解释了电阻和磁电阻行为;用非绝热小极化子跃迁模型对高温的电阻特性进行拟合处理,得到了激活能;同时发现退火处理对样品的电阻率有重要的影响.

  11. Role of film stoichiometry and interface quality in the performance of (Ba,Sr)TiO3 tunable capacitors with high figures of merit

    Freeze, Christopher R.; Stemmer, Susanne


    Parallel plate capacitors with quality factors exceeding 1000 were fabricated using Ba0.3Sr0.7TiO3 (BST) thin films grown by hybrid molecular beam epitaxy on epitaxial Pt bottom electrodes. The influence of film stoichiometry was investigated by varying the (Ba + Sr)/Ti ratio around the stoichiometric composition. The quality factor is highest for stoichiometric films, but (Ba + Sr)-rich films can be biased to higher fields. Furthermore, two different processes were used to deposit the top electrodes of the parallel plate capacitors. While the quality of the top contact/BST interface did not strongly affect the device quality factor, an enhancement in the dielectric tunability was seen for capacitors with top electrodes deposited at high temperatures, which effectively removes interfacial contamination layers.

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

    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)


    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)

  13. 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

    Sandi, Dianisa Khoirum; Supriyanto, Agus; Iriani, Yofentina, E-mail: [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)


    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.

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

    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)


    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.

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

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


    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.

  16. The amounts Fe, Ba, Sr, K, Ca and Ti in some lichens growing in Erzurum province (Turkey)

    Aslan, Ali; Budak, Goekhan E-mail:; Karabulut, Abdulhalik E-mail:


    The amounts of Fe, Ba, Sr, K, Ca and Ti were determined qualitatively and quantitatively by using energy-dispersive X-ray fluorescence in eight lichen species, Pinus sylvestris, rock and soil in district of Erzurum province (Turkey). Lichen species were Cetraria pinastri (Scop.) Gray, Dermatocarpon miniatum (L.) W. Mann, Lecanora muralis (Schreb.) Rabenh., Pseudevernia furfuracea (L.) Zopf., Ramalina capitata (Ach.) Nyl., Rhizoplaca chrysoleuca (sm.) Zopf., Rhizoplaca melanophthalma (DC.) Leuckert and Poelt, and Xanthoparmelia somloensis (Gyeln.) Hale. The standard addition method was used for the determination of the concentration of Fe, Ba, Sr, K, Ca and Ti. The experimental setup consists of a Si(Li) detector with a resolution of 147 eV at 5.9 keV and annular {sup 55}Fe and {sup 241}Am radioactive sources. By the use of intersite, interelement and interspecies comparisons, it is concluded that some metals within the thalli of lichens in Erzurum province may reach high levels even when these plants are growing in rural and isolated sites.

  17. Ultrathin oxide films and heterojunctions: CaO layers on BaO and SrO.

    Mohn, Chris E; Allan, Neil L; Harding, John H


    We examine the form of the islands formed by CaO on BaO and SrO substrates using both periodic density functional theory and atomistic simulation techniques. (100) edges dominate the island morphology and we examine how the CaO adjusts to the substrate in small and medium sized islands and at much larger coverages. There is no direct overlay of CaO ion pairs over OBa or OSr pairs in the top substrate layer. Rather, island bond lengths are all much shorter than those even in bulk CaO, even in the interior of the islands, and more similar to those in CaO clusters and isolated thin films. Corner atoms are associated with particularly short Ca-O bond lengths and the low coordination numbers at such positions. The islands show a marked deviation from planarity which can be broadly rationalized in terms of different preferential bond lengths for Ca and O with substrate O and Ba (Sr), respectively. The marked preferences for particular bond lengths lead to the formation of loops or gaps in non-square islands, areas where islands interact and along the mid-edges of large islands. Exchange with the much larger cations in the substrate is surprisingly facile. Our results indicate the difficulties of preparing sharp, ordered thin oxide films even at low temperatures.

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

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


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

  19. Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体的合成及气敏性质研究%Study on Synthesis and Gas Sensitivity Property of Ba0.8Sr0.2Ti0.5Mn0.5O3 nanorods

    夏川茴; 韩向宇; 殷鹏飞


    Ba0.8Sr0.2 Ti0.5 Mn0.5 O3 nanorods started from Sr(NO3)2 ,BaCO3 , MnO2 and TiQ2 were successfully synthesized by a composite-hydroxide-mediated(CHM) method at 200℃ for 24h. Morphology, composition and crys-talline phase were investigated by XRD,SEM and EDS. Gas sensitivity was investigated on the Ba0.8Sr0.2Ti0.5Mn0.5O3 nanorods for O2. The results show that the nanorods may be adopted for development of gas sensors with performa-nces suitable for practical applications.%采用复合碱媒介法(CHM),在合成BaMnO3和Ba0.5Sr0.5 MnO3的基础上,以Sr(NO3)2、BaCO以及MnO2和TiO2为原料,在200℃、24h的生长条件下,用20%的Sr离子替代20%的Ba离子,用50%的Ti离子替代50%的Mn离子成功合成了Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体.采用XRD、SEM及EDS对产物的晶相、形貌和成分进行了分析,对Ba0.8 Sr0.2 Ti0.5 Mn0.5 O3制作的电极进行了气敏性质的测定.

  20. Penning-trap mass spectrometry of highly charged, neutron-rich Rb and Sr isotopes in the vicinity of $A\\approx100$

    Simon, V V; Chowdhury, U; Eberhardt, B; Ettenauer, S; Gallant, A T; Mané, E; Simon, M C; Delheij, P; Pearson, M R; Audi, G; Gwinner, G; Lunney, D; Schatz, H; Dilling, J


    The neutron-rich mass region around $A\\approx100$ presents challenges for modeling the astrophysical $r$-process because of rapid shape transitions. We report on mass measurements using the TITAN Penning trap at TRIUMF-ISAC to attain more reliable theoretical predictions of $r$-process nucleosynthesis paths in this region. A new approach using highly charged ($q=15+$) ions has been applied which considerably saves measurement time and preserves accuracy. New mass measurements of neutron-rich $^{94,97,98}$Rb and $^{94,97-99}$Sr have uncertainties of less than 4 keV and show deviations of up to 11$\\sigma$ to previous measurements. An analysis using a parameterized $r$-process model is performed and shows that mass uncertainties for the A=90 abundance region are eliminated.

  1. Erosion of the Alps: use of Rb-Sr isotopic data from molassic sediments to identify the ages of the metamorphism recorded by the eroded rocks; Erosion des Alpes: histoire metamorphique des roches erodees par l`analyse du couple Rb-Sr des sediments molassiques

    Henry, P.; Deloule, E. [Centre National de la Recherche Scientifique (CNRS), 54 - Nancy (France). Centre de Recherches Petrographiques et Geochimiques; Michard, A. [Aix-Marseille-3 Univ., 13 - Marseille (France)


    Rb-Sr isotopic data from Oligocene and Miocene peri-alpine molassic sediments allow us to identify the different periods for which the eroded rocks have or have not recorded an alpine metamorphism. The Chattian and the Burdigalian sediments result from the erosion of rocks for which the latest metamorphic event was variscan, while the Stampian, Aquitanian and ``Helvetian`` sediments show evidence for the erosion of rocks which have recorded alpine metamorphic events. The application of this method to old detrital sediments could permit determination of the ages of the tectonic events which occurred in the sediment source regions. (authors). 18 refs., 6 figs.

  2. Vibronic Transitions in the X-Sr Series (X=Li, Na, K, Rb): on the Accuracy of Nuclear Wavefunctions Derived from Quantum Chemistry

    Meyer, Ralf; Pototschnig, Johann V.; Hauser, Andreas W.; Ernst, Wolfgang E.


    Research on ultracold molecules has seen a growing interest recently in the context of high-resolution spectroscopy and quantum computation. The preparation of molecules in low vibrational levels of the ground state is experimentally challenging, and typically achieved by population transfer using excited electronic states. On the theoretical side, highly accurate potential energy surfaces are needed for a correct description of processes such as the coherent de-excitation from the highest and therefore weakly bound vibrational levels in the electronic ground state via couplings to electronically excited states. Particularly problematic is the correct description of potential features at large intermolecular distances. Franck-Condon overlap integrals for nuclear wavefunctions in barely bound vibrational states are extremely sensitive to inaccuracies of the potential at long range. In this study, we compare the predictions of common, wavefunction-based ab initio techniques for a known de-excitation mechanism in alkali-alkaline earth dimers. It is the aim to analyze the predictive power of these methods for a preliminary evaluation of potential cooling mechanisms in heteronuclear open shell systems which offer the experimentalist an electric as well as a magnetic handle for manipulation. The series of X-Sr molecules, with X = Li, Na, K and Rb, has been chosen for a direct comparison. Quantum degenerate mixtures of Rb and Sr have already been produced, making this combination very promising for the production of ultracold molecules. B. Pasquiou, A. Bayerle, S. M. Tzanova, S. Stellmer, J. Szczepkowski, M. Parigger, R. Grimm, and F. Schreck, Phys. Rev. A, 2013, 88, 023601

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

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


    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.

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

    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: [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)


    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.

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

    A N Yerpude; S J Dhoble


    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+.

  6. Structure-property relations in Sr, Nb, Ba doped lead zirconate titanate

    Zheng, H


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

    Koen Van den Eeckhout


    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.

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

    G Nalini; T N Guru Row


    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.

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

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


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

  10. Strain Dependent Electronic Structure and Band Offset Tuning at Heterointerfaces of ASnO3 (A=Ca, Sr, and Ba) and SrTiO3

    Baniecki, John D.; Yamazaki, Takashi; Ricinschi, Dan; Van Overmeere, Quentin; Aso, Hiroyuki; Miyata, Yusuke; Yamada, Hiroaki; Fujimura, Norifumi; Maran, Ronald; Anazawa, Toshihisa; Valanoor, Nagarajan; Imanaka, Yoshihiko


    The valence band (VB) electronic structure and VB alignments at heterointerfaces of strained epitaxial stannate ASnO3 (A=Ca, Sr, and Ba) thin films are characterized using in situ X-ray and ultraviolet photoelectron spectroscopies, with band gaps evaluated using spectroscopic ellipsometry. Scanning transmission electron microscopy with geometric phase analysis is used to resolve strain at atomic resolution. The VB electronic structure is strain state dependent in a manner that correlated with a directional change in Sn-O bond lengths with strain. However, VB offsets are found not to vary significantly with strain, which resulted in ascribing most of the difference in band alignment, due to a change in the band gaps with strain, to the conduction band edge. Our results reveal significant strain tuning of conduction band offsets using epitaxial buffer layers, with strain-induced offset differences as large as 0.6 eV possible for SrSnO3. Such large conduction band offset tunability through elastic strain control may provide a pathway to minimize the loss of charge confinement in 2-dimensional electron gases and enhance the performance of photoelectrochemical stannate-based devices. PMID:28195149

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

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


    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.

  12. Effect of Sr{sup 2+} addition on electrical properties of BaTiO{sub 3} PTCR ceramics; Efeito da adicao de Sr{sup 2+} nas propriedades eletricas de ceramicas do tipo PTC a base de BaTiO{sub 3}

    Manfredini, J.P.; Paulin Filho, P.I.; Gheno, S.M. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Dept. de Engenharia de Materiais


    Semiconducting PTCR (Positive Temperature Coefficient of Resistivity) ceramics based in BaTiO{sub 3}, Ba{sub 0,8}Sr{sub 0,2}TiO{sub 3} e Ba{sub 0,6}Sr{sub 0,4}TiO{sub 3} compositions with 0.3at% La-doped have been investigated. The substitution of Ba{sup 2+} by Sr{sup 2+} in the lattice resulted in a decrease of tetragonal to cubic transition temperature (T{sub c}) observed by X-ray diffraction. The results have shown a strong dependence of structure with the resistivity measured in d.c. mode. Using impedance spectroscopy technique was possible to attribute the PTC effect entirely to grain boundary region resistance. AFM and EFM images have shown potential barriers on the grain boundaries of evaluated samples below and above T{sub c}.(author)

  13. Algumas idades Rb-Sr e K-Ar de rochas granitóides da região de Vilarinho da Castanheira-Foz do Sabor (Carrazeda de Anciães-Nordeste de Portugal)

    Silva, Antero Ferreira da; KAWASHITA,KOJI


    Neste trabalho apresentam-se algumas determinações isotópicas Rb/Sr e K/Ar de idades absolutas em rochas granitóides do antiforma de Alijó-Carviçais, correspondente à região es-sudeste de Carrazeda de Anciães (Vilarinho da Castanheira-Foz do Sabor). A rocha total de duas amostras dos granitos de Castedo-Cabanas de Cima e Zêdes-Cabeça Boa-Especiarias, indiferenciados localmente, proporcionaram as idades convencionais Rb/Sr de 361.1±23.8 e 404.7±22.3M.a., com razão inicial (87Sr/86S...

  14. Rb-Sr and Sm-Nd Studies of Olivine-Phyric Shergottites RBT 04262 and LAR 06319: Isotopic Evidence for Relationship to Enriched Basaltic Shergottites

    Nyquist, L.E.; Shih, C.-Y.; Reese, Y.


    RBT 04262 and LAR 06319 are two Martian meteorites recently discovered in Antarctica. Both contain abundant olivines, and were classified as olivine-phyric shergottites. A detailed petrographic study of RBT 04262 suggested it should be reclassified as a lherzolitic shergottite. However, the moderately LREE-depleted REE distribution pattern indicated that it is closely related to enriched basaltic shergottites like Shergotty, Zagami, Los Angeles, etc. In earlier studies of a similarly olivinephyric shergottite NWA 1068 which contains 21% modal olivine, it was shown that it probably was produced from an enriched basaltic shergottite magma by olivine accumulation . As for LAR 06319, recent petrographic studies suggested that it is different from either lherzolitic shergottites or the highly LREE-depleted olivine-phyric shergottites. We performed Rb-Sr and Sm-Nd isotopic analyses on RBT 04262 and LAR 06319 to determine their crystallization ages and Sr and Nd isotopic signatures, and to better understand the petrogenetic relationships between them and other basaltic, lherzolitic and depleted olivine-phyric shergottites.

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

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


    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.

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

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


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

  17. Interrelation of the structure, vibrational spectra and critical temperature of (123)-superconductors. [YScBaSrCuO; YBaSrCuAlO; GdBaCuO; YBaCuO

    Limonov, M.F.; Markov, Yu.F.; Panfilov, A.G.; Razbirin, B.S.; Syrnikov, P.P. (A.F. Ioffe Physico-Technical Inst., St. Petersburg (Russia)); Bush, A.A. (Inst. of Informatics MIREA, Moscow (Russia))


    Raman spectrum changes resulting from different variations of the crystal lattice YBa{sub 2}Cu{sub 3}O{sub {delta}} (such as the substitutions Y {yields} rare-earth element R, Ba {yields} Sr, {delta}=6{yields}{delta}=7) have been studied. The concentration associated shift of vibrational frequencies of the oxygen atoms located in different layers of the lattice is shown to obey a general law: certain vibrations soften whereas the others harden. This vibrational behaviour is explained by the wave-like reconstruction of the crystal lattice (123). For the whole superconductor family RBa{sub 2}Cu{sub 3}O{sub 7} and for YBa{sub 2}Cu{sub 3}O{sub 7} at hydrostatic pressure the increase in Tc with increasing frequency of the highest frequency A{sub g}-vibration is established. The results show the essential role of phonons in the high-Tc superconductivity mechanism. (orig.).

  18. Synthesis and structure of (Rb{sub 0.50}Ba{sub 0.25})[UO{sub 2}(CH{sub 3}COO){sub 3}

    Serezhkina, L. B., E-mail: [Samara State University (Russian Federation); Peresypkina, E. V.; Virovets, A. V. [Russian Academy of Sciences, Institute of Inorganic Chemistry, Siberian Branch (Russian Federation); Klepov, V. V. [Samara State University (Russian Federation)


    A new compound (Rb{sub 0.50}Ba{sub 0.25})[UO{sub 2}(CH{sub 3}COO){sub 3}] is synthesized and its crystal structure is studied by X-ray diffraction. The compound crystallizes in the form of yellow plates belonging to the cubic crystal system. The unit cell parameter a = 17.0367(1) A, V = 4944.89(5) A{sup 3}, space group I 4 bar 3d, Z = 16, and R = 0.0182. The coordination polyhedron of the uranium atom is a hexagonal bipyramid with oxygen atoms of three acetate groups and the uranyl group in the vertices. The crystal chemical formula of the uranium-containing group is AB{sub 3}{sup 01}(A = UO{sub 2}{sup 2+}, B{sup 01} = CH{sub 3}COO{sup -}). The oxygen atoms of the acetate groups that enter the coordination polyhedron of uranium are bound to barium and rubidium atoms.

  19. Direct evidence for a pressure-induced nodal superconducting gap in the Ba0.65Rb0.35Fe2As2 superconductor

    Guguchia, Z.; Amato, A.; Kang, J.; Luetkens, H.; Biswas, P. K.; Prando, G.; von Rohr, F.; Bukowski, Z.; Shengelaya, A.; Keller, H.; Morenzoni, E.; Fernandes, Rafael M.; Khasanov, R.


    The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. In contrast to other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba0.65Rb0.35Fe2As2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant. More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap. PMID:26548650

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

    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)


    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.)

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

    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: [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)


    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.

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


    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.

  3. White-light-emitting diodes based on Ba2+ co-doped Sr3SiO5: Ce3+, Li+ phosphor

    Shen, Changyu; Li, Ke; Yang, Yi


    A yellow-orange-emitting Ba2+ codoped Sr3SiO5: Ce3+, Li+ phosphor was prepared by high-temperature solid-state reaction. Through transitions of 5d-->4f in Ce3+, the phosphor showed a very broad and strong yellow emission under near ultraviolet (UV) or blue light excitation. The shifts of the emission band to longer wavelength (yellow-orange) of the Sr3SiO5: Ce3+, Li+ yellow phosphor under the 450-470 nm excitation range have been achieved by adding the element Ba2+ in the Sr3SiO5 host. White light could be obtained by combining this phosphor with 460nm light-emitting diodes. As the concentrations of the Ba2+, Ce3+ and Li+ ions in the phosphor were 0.35mol, 0.024mol and 0.024mol respectively, the InGaN-based Ba2+ codoped Sr3SiO5: Ce3+, Li+ LED presented intense white emitting and good color rendering of 88.

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

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


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

  5. Transmission electron microscopy investigation of Pt/Ba0.7Sr0.3TiO3/Pt capacitors with different annealing processes

    Qin, Y.L.; Jia, C.L.; Liedtke, R.; Waser, R.; Urban, K.


    The effects of postannealing in oxygen ambient and forming gas atmosphere (FGA) on the microstructure and chemistry of Pt/Ba0.7Sr0.3TiO3 (BST)/Pt capacitors prepared by chemical solution deposition have been investigated by means of transmission electron microscopy. The as-deposited film layers of t

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

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


    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.

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

    Thieme, Christian; Görls, Helmar; Rüssel, Christian


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

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

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


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

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

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


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

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

    Ala’eddin A. SAIF


    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.

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

    Yi, M.


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

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

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


    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. Theoretical study of the new zintl phases compounds K{sub 2}ACdSb{sub 2} (A=(Sr, Ba))

    Azam, Sikander [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Reshak, A.H., E-mail: [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)


    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.

  14. Late Caledonian microdiorites and felsic porphyrites from Northern Scotland: implications for the petrogenesis of high Ba-Sr granites

    Fowler, Mike; Jacklin, Holly


    A suite of sharply cross-cutting microdiorite - felsic porphyrite dykes, emplaced into the southern part of the Northern Highlands Terrane, is thought to be coeval with the local Caledonian high Ba-Sr granites. On occasion they can be seen to pillow into, and mix with the granites (e.g. Strontian) in the manner of synplutonic dykes. In the least-deformed examples small-scale mixing and mingling textures are preserved between basic and acid variants, and the felsic porphyrites (rarely) have mafic marginal facies. Microdiorites also grade into rocks of the appinite suite. Thus, the compositional range of the suite is considerable, linking mafic magmas to more evolved compositions via many intermediate stages. These therefore offer a window into the processes of Caledonian magma evolution. A selection of some 50 dykes has ben collected and analysed for major and trace elements, mostly from the environs of Strontian, but also as far north as Loch Quoich and west to Arisaig. They show a continuous chemical range from 47% to 74% SiO2, 18% to high-Mg andesite of sanukite affinity. Petrogenetically-informative trace elements bear the hallmarks of a subduction-related source, with general enrichment in LILEs and relative depletion in HFSEs (in particular Nb-Ta). The chemistry of the felsic porphyrites is closely comparable with the local Strontian and Cluanie granites, and cumulus-enriched mafic microdiorites are chemically similar to local discrete appinites. Such data can therefore be used to test alternative petrogenetic hypotheses: that the high Ba-Sr granites evolved by crystal fractionation (± crustal contamination) from mantle-derived appinitic parents, or that they are crustal melts associated with genetically unrelated but contemporaneous mafic magmas.

  15. An Ldrims Instrument for Portable Rb-Sr Dating with Accuracy of Better than ±150 MA for the MARS-2020 Rover

    Anderson, F. Scott; Whitaker, Tom; Hamilton, Victoria; Nowicki, Keith


    Using a laser desorption resonance ionization mass spectrometer (LDRIMS), we can now demonstrate repeatable dates with portable hardware that could be carried on MER- or MSL-sized rovers. This is important because NASA is developing science requirements for a Mars 2020 rover mission based on MSL hardware, and for Mars, the National Research Council Decadal Survey (NRC DS) specifically supports: "...long-term development of instruments ... focusing on the most important future in situ measurements... [including] ... in situ geochronology experiments". The LDRIMS instrument can produce these science measurements today, and in so doing, triage samples for Mars Sample Return. The LDRIMS technique can be miniaturized and avoids the mass interference issues requiring unwieldy chemical separation for traditional geochronology techniques. With LDRIMS sample is placed in a time-of-flight (TOF) mass spectrometer and surface atoms, molecules, and ions are desorbed with a 213 nm laser. Ions are suppressed by an electric field and the plume of expanding particles is present for many μs, during which it is first illuminated with laser light tuned to ionize only Sr, and then 1-3 μs later, for Rb. This eliminates isobars for Rb and Sr, insures that the measured atoms come from the same ablation event, and hence target materials, and reduces the total number of measurements required. The LDRIMS system has demonstrated a sensitivity of 300 parts-per-trillion, and isotope ratio precisions of ±0.3 to ±0.1% in 3000-5000 ablations of one spot on a sample in 3-5 minutes. The bench top prototype has been tested on the Boulder Creek Granite (BCG) from Elephant Butte, Colorado, comprised primarily of a gneissic quartz monzonite and granodiorite. Whole rock Rb-Sr TIMS measurements of the BCG, and our own preliminary micro-drill TIMS measurements of individual minerals, are consistent with an age of 1700±40 Ma. To obtain a LDRIMS date using the BCG sample, we measured hundreds of spots

  16. Structure and electrical properties of (1-x)BaTiO3+(x)La2/3-Sr1/3MnO3 composites

    Zhengyou ZHOU; Yu LEI


    Liquid-phase sintering method was used to prepare BaTiO3 powders and the structure and electrical properties of (1-x)BaTiO3+(x)La2/3Sr1/3MnO3 (LSMO) composites were investigated. The results of X-ray diffraction showed that the prepared BaTiO3 powders were pure and fine,indicating that sintering temperature was effectively lowered when the NaCl sintering aid was added.X-ray diffraction patterns of (1-x)BaTiO3+(x)La2/3Sr1/3MnO3 (LSMO) composites showed that LSMO and BaTiO3 phases were coexistent and no other phases were detected.The impedance spectra showed that the resistance of grain boundaries for LSMO-doped samples was suppressed. The resistivity-temperature measurements showed that roomtemperature resistivity of the composites was lowered from insulator for pure BaTiO3 ceramic to 103 Ω·m for the x=0.3 sample.The sample of x≤0.2 showed the positive temperature coefficient (PTC) effect whereas the x=0.3 sample exhibited PTC effect at temperatures below 68 ℃ and then negative temperature coefficient (NTC) effect at temperatures above 68 ℃.The related mechanism has been elucidated.

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

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


    In this research, first, SrTiO{sub 3} was synthesized as thermal infrared (TIR) absorbent and core and then BaFe{sub 12}O{sub 19} as microwave absorbent was prepared on SrTiO{sub 3} via co-precipitation method as first shell. Second, polyaniline (PANI) was coated on SrTiO{sub 3}/BaFe{sub 12}O{sub 19} NPs (NPs) via in situ polymerization by multi core–shell structures (SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/PANI). Nanometer size and structures of samples were measured by TEM, XRD and FTIR. Morphology of nanocomposite was showed by SEM images. The magnetic and electric properties were also performed by VSM and four probe methods. The TIR absorption and microwave reflection loss of nanocomposites were investigated at 10–40 µm and 8–12 GHz, TIR and microwave frequencies, respectively. The results showed that the SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/PANI nanocomposites have good compatible electric and magnetic properties and hence the microwave absorbency show wide bandwidth properties. The infrared thermal image testing showed that the ability of infrared thermal imaging was increased by increasing SrTiO{sub 3}/BaFe{sub 12}O{sub 19} as core and independent to increasing PANI as final shell. - Graphical abstract: The light reflectivity times of samples on human body are higher than metallic disks. So, they are suitable for TIR as absorbers. The light reflectivity times of samples were increased by increasing weight ratio and thickness. Human temperature could not transmit to samples by increasing weight ratio of core. Therefore weight ratio (SrTiO{sub 3}/BaFe{sub 12}O{sub 19} as core) above 40% and 1 mm diameter are the best result as TIR absorber. The SrTiO{sub 3}/BaFe{sub 12}O{sub 19}/PANI enhanced broad band IR light absorption was observed in the wavelength range of 10–40 µm. A minimum RL of −19 dB was observed at 9.2 GHz for a 1.5-mm thickness nanocomposite. The application of these samples may improve the IR thermographic detection, catalysis, sensors

  18. Effect of Wood Aging on Wine Mineral Composition and (87)Sr/(86)Sr Isotopic Ratio.

    Kaya, Ayse D; Bruno de Sousa, Raúl; Curvelo-Garcia, António S; Ricardo-da-Silva, Jorge M; Catarino, Sofia


    The evolution of mineral composition and wine strontium isotopic ratio (87)Sr/(86)Sr (Sr IR) during wood aging were investigated. A red wine was aged in stainless steel tanks with French oak staves (Quercus sessiliflora Salisb.), with three industrial scale replicates. Sampling was carried out after 30, 60, and 90 days of aging, and the wines were evaluated in terms of general analysis, phenolic composition, total polysaccharides, multielement composition, and Sr IR. Li, Be, Mg, Al, Sc, Ti, V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Mo, Sb, Cs, Ba, Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb, Lu, Tl, and Pb elements and (87)Sr/(86)Sr were determined by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and Na, K, Ca, and Fe by flame atomic absorption spectrometry (FAAS). Two-way ANOVA was applied to assess wood aging and time effect on Sr IR and mineral composition. Wood aging resulted in significantly higher concentrations of Mg, V, Co, Ni, and Sr. At the end of the aging period, wine exhibited statistically identical Sr IR compared to control. Study suggests that wood aging does not affect (87)Sr/(86)Sr, not precluding the use of this parameter for wine traceability purposes.

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

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


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

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

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


    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.

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

    S. He


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

  2. Fabrication and characterization of Ba sub x Sr sub 1 sub - sub x TiO sub 3 /YBa sub 2 Cu sub 3 O sub x /SrTiO sub 3 structure

    Choi, J; Park, S Y; Lee Jae Sik; No, K; Sung, T H; Park, Y


    Ba sub x Sr sub 1 sub - sub x TiO sub 3 (BST)/YBa sub 2 Cu sub 3 O sub x (YBCO)/SrTiO sub 3 (STO) structures were deposited, and the microstructure, orientation and electrical characteristics were investigated. (00l) oriented YBCO thin films were deposited on STO substrates using pulsed laser deposition, and (h00) oriented BST thin films were deposited on YBCO/STO substrates using electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapor deposition (MOCVD). A new phase was formed at the interface between YBCO and BST films and was speculated to be (Ba sub x Y sub 1 sub - sub x)(Ti sub y Y sub 1 sub - sub y)O sub 3. Ba-rich BST films showed a higher dielectric loss than Sr-rich BST films did, which indicates that Sr-rich BST films are more suited for application to microwave devices. The dielectric loss of the films was reduced as temperature decreased, which may be due to the conductivity change of YBCO film and the formation of a conduction path rather than a dielectric property change ...

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

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


    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, 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.

  4. Effect of Sr doping on the electrochemical properties of bi-functional oxygen electrode PrBa1-xSrxCo2O5+δ

    Wu, Zhouling; Sun, Li-Ping; Xia, Tian; Huo, Li-Hua; Zhao, Hui; Rougier, Aline; Grenier, Jean-Claude


    Sr-doped double perovskite oxides PrBa1-xSrxCo2O5+δ (x = 0.0-1.0) are prepared and characterized by X-ray diffraction, X-ray photoelectron spectra, cyclic voltammetry and linear sweep voltammetry, respectively. Sr2+ doping is found to promote the electrocatalytic activity towards both oxygen evolution reduction and oxygen reduction reaction, due to the concentration enhancement of Co4+ (eg = 1) on the oxide surface. The PrBa0.25Sr0.75Co2O5.95 catalyst, with the highest concentration of Co4+, exhibits the superior electrocatalytic activity. The onset potential, Tafel slope and the overpotential at given current density of 10.0 mA·cmgeom-2 for the OER are 1.52 V, 75.8 mV·dec-1 and 0.42 V, respectively, comparable to the currently reported high performance OER catalysts. At the same time, the onset potential, Tafel slope, limiting current density and electron transfer number of PrBa0.25Sr0.75Co2O5.95 for ORR are 0.753 V, 58.3 mV·dec-1, 4.081 mA·cmgeom-2 and n = 3.92, respectively, implying much improved ORR activity.

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

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


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

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

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


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

  7. Spectroscopy of laser properties of Nd(3+)-doped CaF2, SrF2, and BaF2

    Payne, Stephen A.; Caird, John A.; Chase, L. L.; Smith, L. K.; Nielsen, N. D.; Krupke, William F.


    The optical properties of Nd(3+) in CaF2, SrF2, and BaF2 were investigated in order to determine if these materials are useful as laser-pumped amplifier media. The CaF2:Nd crystal was found to not be useful because the impurities tend to cluster at very low concentration, leading to the formation of nonluminescent centers. On the other hand, the Nd(3+) centers in BaF2 exhibit unacceptably low transition strengths. SrF2:Nd appears to have adequate absorption strength, and, in addition, to have a remarkably long emission lifetime of 1280 microns. A maximum doping of 0.20 atomic percent Nd(3+) can be tolerated in SrF2 without the occurrence of detrimental clustering. The peak emission cross section of SrF2:Nd is 1.7 x 10(exp -20) sq cm at 1036.5 nm. Direct measurement of the gain spectrum of SrF2:Nd(3+) reveals the presence of the F-4(sub 3/2) yields G-2(sub 9/2) excited state absorption lines, although the impact on the emission cross section is minor.

  8. The crystal structure of bøgvadite (Nasub>2sub>SrBa>2sub>Al>4sub>F>20sub>)

    Balic Zunic, Tonci


    in the same direction. Na is coordinated by nine F atoms if its full surrounding is taken in consideration, but makes significant chemical bonds only to closest five. The chains of AlF6 and NaF9 coordination polyhedra form double layers. In the centre of layers, relatively large voids in the form...... of pentagonal antiprisms are occupied by Sr atoms which make chemical bonds with the closest six F atoms. Between the SrF10 coordinations in the centre of layers run empty channels. The double layers are interconnected by Ba atoms which are coordinated by eight F atoms and fill the spaces between the layers...

  9. (Ba,Sr)TiO3纳米棒的反相微乳法制备与表征%Preparation and Characterization of (Ba, Sr)TiO3 Nanorods by Reverse Microemulsion Method

    朱启安; 陈万平; 宋方平; 王树峰


    在氢氧化钡和氢氧化锶水溶液/Triton X-100/环己烷/正己醇四元W/O型反相微乳液中制备了钛酸锶钡纳米棒,研究了ω0值(水与表面活性剂TritonX-100的物质的量之比)、反应物浓度、陈化时间对产品形貌和尺寸的影响,用TEM,SAED,SEM,EDS和XRD等技术对产品进行了表征.结果表明,所得Ba0 7Sr0 3TiO3纳米棒长约500~1200nm、直径约为50~120 nm;具有立方相单晶结构.产品中钡、锶、钛的物质的量之比约为0.7∶0.3∶1.

  10. Structural, elastic and electronic properties of C14-type Al2M (M=Mg, Ca, Sr and Ba) Laves phases

    Lishi, Ma; Yonghua, Duan; Runyue, Li


    The structural and mechanical properties, Debye temperatures and anisotropic sound velocities of the Laves phases Al2M (M=Mg, Ca, Sr and Ba) with C14-type structure were investigated using the first-principles corresponding calculations. The corresponding calculated structural parameters and formation enthalpies are in good agreement with the available theoretical values, and Al2Ca has the best phase stability. The mechanical properties, including elastic constants, bulk modulus B, shear modulus G, Young's modulus E, and Poisson ratio ν, were deduced within the Voigt-Reuss-Hill approximation. The brittleness and ductility were estimated by the values of Poisson ratio, B/G and Cauchy pressure. Moreover, the elastic anisotropy was investigated by calculating and discussing several anisotropy indexes. Finally, the electronic structures were used to illustrate the bonding characteristics of C14-Al2M (M=Mg, Ca, Sr and Ba) phases.

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

    Kolodiazhnyi, T., E-mail:; Sakurai, H.; Vasylkiv, O.; Borodianska, H. [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S4M1 (Canada)


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

  12. Structural, elastic and electronic properties of C14-type Al{sub 2}M (M=Mg, Ca, Sr and Ba) Laves phases

    Lishi, Ma; Yonghua, Duan, E-mail:; Runyue, Li


    The structural and mechanical properties, Debye temperatures and anisotropic sound velocities of the Laves phases Al{sub 2}M (M=Mg, Ca, Sr and Ba) with C14-type structure were investigated using the first-principles corresponding calculations. The corresponding calculated structural parameters and formation enthalpies are in good agreement with the available theoretical values, and Al{sub 2}Ca has the best phase stability. The mechanical properties, including elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν, were deduced within the Voigt-Reuss-Hill approximation. The brittleness and ductility were estimated by the values of Poisson ratio, B/G and Cauchy pressure. Moreover, the elastic anisotropy was investigated by calculating and discussing several anisotropy indexes. Finally, the electronic structures were used to illustrate the bonding characteristics of C14-Al{sub 2}M (M=Mg, Ca, Sr and Ba) phases.

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

    Purnendu Parhi; V Manivannan; Sandeep Kohli; Patrick Mccurdy


    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.

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

    Kumar Shivesh


    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

  15. Diffuse second harmonic generation under the ferroelectric switching in Sr0.75Ba0.25Nb2O6 crystals

    Isakov, D. V.; Belsley, M. S.; Volk, T. R.; Ivleva, L. I.


    In this work, we present observations of the polarization process in strontium barium niobate Sr0.75Ba0.25Nb2O6 (SBN-0.75) crystals by measuring the diffuse generation of the second harmonic converted by the random ferroelectric domains. The ability of a field-controlling intensity of the diffuse second harmonic generation is analyzed and discussed in terms of the specific switching scenario in SBN crystals.

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

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


    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.

  17. Structural and electronic properties of Sr{sub x}Ba{sub 1-x}SnO{sub 3} from first principles calculations

    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: [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)


    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.

  18. Synthesis, crystal structure, and properties of the nitridosilicates SrYbSi{sub 4}N{sub 7} and BaYbSi{sub 4}N{sub 7}; Synthese, Kristallstruktur und Eigenschaften der Nitridosilicate SrYbSi{sub 4}N{sub 7} und BaYbSi{sub 4}N{sub 7}

    Huppertz, H. [Bayreuth Univ. (Germany). Lehrstuhl fuer Anorganische Chemie I; Schnick, W. [Bayreuth Univ. (Germany). Lehrstuhl fuer Anorganische Chemie I


    Pure SrYbSi{sub 4}N{sub 7} and BaYbSi{sub 4}N{sub 7} were obtained by reaction of silicon diimide with metallic strontium/barium and ytterbium. The reactions have been carried out under nitrogen atmosphere in a high-frequency furnace at 1650 C, SrYbSi{sub 4}N{sub 7} (P6{sub 3}mc, a = 598.80(3), c = 974.99(9) pm, Z = 2, R1 = 0.023, wR2 = 0.038) and BaYbSi{sub 4}N{sub 7} (P6{sub 3}mc, a = 603.07(2), c = 981.98(4) pm, Z = 2, R1 = 0.021, wR2 = 0.048) are isotypic and contain M{sup 2+} ions (M = Sr, Ba), Yb{sup 3+} ions, as well as a three-dimensional covalent network structure of corner-sharing SiN{sub 4} tetrahedra. SrYbSi{sub 4}N{sub 7} and BaYbSi{sub 4}N{sub 7} are the first compounds with one central nitrogen connecting four silicon. These N{sup [4]} bridges significantly extend the spectrum of possible linkages in Si-N network structures. (orig.)

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


    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.

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

    Branković Zorica


    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.

  1. Preparation and properties of the (Sr,BaNb2O6 thin films by using the sputtering method

    Diao Chien-Chen


    Full Text Available Strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN thin films were deposited on silicon substrate by using the radio frequency magnetron sputtering and under different deposition power and time at room temperature. Surface morphology and thicknesses of the SBN thin films were characterized by field emission scanning electron microscopy. The crystallization films at different deposition power and time were analyzed by X-ray diffraction (XRD using CuKα radiation from a Rigaku rotating anode with an incident angle of 2°. The remnant polarization (Pr, saturation polarization (Ps, and minimum coercive field (Ec properties of the metal-ferroelectric-metal (MFM structure were measured using ferroelectric material test instrument. The SBN thin films deposited at 90 min and 125 W had the maximum Pr, Ps, and minimum Ec of 1.26 μC/cm2, 2.41 μC/cm2, and 201.6 kV/cm, respectively. From above results, it knows that the SBN thin films suit for application on ferroelectric random access memory (FeRAM.

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

    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


    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.

  3. Dielectric Relaxation Behavior of Bismuth Doped (Ba0.2Sr0.8 TiO3 Ceramics

    Baptista, J. L.


    Full Text Available The dielectric properties of bismuth doped (Ba0.2Sr0.8TiO3 ceramics are investigated. The temperature dependence of the dielectric permittivity and loss factor were measured from 102 to 106Hz in the temperature range 12-320K. As the amount of Bi increases, the ferroelectric-paraelectric phase transition gets diffused and relaxed. In addition to this ferroelectric-paraelectric phase transition, other two sets of dielectric anomalies, located at 50-100K and 200-300K respectively, are also found. The possible relaxation mechanisms are briefly discussed.Las propiedades dieléctricas de cerámicos dopados con bismuto son investigadas. La dependencia con la temperatura de la permitividad dieléctrica y el factor de pérdidas se midieron entre 02 y 106Hz en el rango de temperatura 12-320K. Con el aumento del contenido en Bi, la transición de fase ferroeléctrica-paraléctrica se hace difusa y reloja. Junto a esta transición de fase los conjuntos de anomalías dieléctricas, localizados a 50-100k y 200-300k respectivamente, también se encontraron. Se discute brevemente los posibles mecanismos de relajación.

  4. Effect of ion irradiation on optoelectronic properties of Ba0.12Sr0.88SO4: Eu phosphor

    Choubey, A.; Sharma, S. K.; Lochab, S. P.; Shripathi, T.


    Nanocrystalline Ba0.12Sr0.88SO4 phosphor doped with Eu at 0.1 mol% optimum concentration was prepared by the chemical co-precipitation method. X-ray diffraction study of the prepared sample suggests the orthorhombic structure with an average grain size of 62 nm. The band gap was found to be 4.3 eV. The samples were irradiated with 1.2 MeV argon ions at fluences varying between 1011 and 1015 ions/cm2, i.e. in the dose range of 59 kGy to 590 MGy. A prominent photoluminescence (PL) emission peak is seen around 376 nm due to transition from an excited state 4f65d to 8S7/2 state of Eu2+ ions. The broadening of bands in FTIR spectrum at 1110, 990, 643 and 617 cm-1 is an evidence of the generation of SO4-, SO3-, SO2-, O-, etc. radicals after ion irradiation. The effect of ion irradiation on luminescence properties was studied.

  5. Fabrication and microwave properties of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O thin films

    Sobolewski, R.; Konopka, J.; Kula, W.; Gierlowski, P.; Konopka, A.; Lewandowski, S.J.


    The authors report their studies on the interaction of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O thin films with microwaves. The films were prepared on cubic zirconia and magnesium oxide substrates using a modified spray deposition technique. The tested films were about 1-3 /mu/m thick and exhibited good superconducting properties (e.g. for YBCO-on zirconia films the 10-90% transition width was 2 K, and the zero resistance was reached at 89 K). Several test structures have been designed by spraying a mixture of nitrate precursors on heated substrates through very thin stencil masks. The supercurrent dependence on millimeter wavelength microwave illumination was measured, and microwave detection and mixing experiments were performed. The films of both materials exhibited proper ties characteristic for granular superconductors, with Josephson-type coupling at the intergrain connections. The studies also demonstrated that these materials can be successfully used as very sensitive millimeter radiation detectors operational at liquid nitrogen temperatures.

  6. Influence of Composition on Properties of Medium Temperature Sintering (Ba, Sr)TiO3 Series Capacitor Ceramics


    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. Self-consistent (DFT + U) study of electronic, structural and magnetic properties in A2NiMoO6 (A = Ba, Sr) compounds

    Aharbil, Y.; Labrim, H.; Benmokhtar, S.; Ait Haddouch, M.; Bahmad, L.; Laanab, L.


    This work aims to study the double perovskites A2NiMoO6 (A = Ba, Sr) by using the first principle calculation, within the framework of the self-consistent Hubbard correction. The value of this correction, for Ni and Mo depends strongly on the type of the studied compounds. Such values are determinate as 7.35 eV for Ni and 5.42 eV for Mo in the compound Ba2NiMoO6, whereas in the case of Sr2NiMoO6 the calculated values are 8.71 eV and 5.48 eV for Ni and Mo compound respectively. Based on the densities of state calculation we show that both the compounds are semiconductors with gap energies of 2.20 eV and 2.10 eV for Ba2NiMoO6 for Sr2NiMoO6, respectively. The total energies comparison shows clearly that the ground state is G-type anti-ferromagnetic order in agreement with experimental results, the magnetic interactions are due to the super-exchange mechanism acting in long range via hybridization throw Ni-O-Mo-O-Ni path.

  8. Effects of B2 O3-SiO2 doping on electrical properties of Ba0.65 Sr0.35 TiO3 ceramics

    ZHANG Tian-jin; JIANG Juan; ZHANG Bai-shun; GU Hao-shuang; LIU Jiang-hua


    Ba0.65 Sr0.35 TiO3 ceramics doped with B2 O3-SiO2 glass composition were prepared by using conventional solid-state reaction method. The effects of glass dopant on the dielectric and ferroelectric properties were investigated. The results show that the dielectric constant decreases while the dielectric loss increases after doping. And as the glass content increases the dielectric constant decreases while the dielectric loss changes slightly. From the complex impedance analysis the resistance and the relaxation time of the grain and the grain boundary can be calculated.Comparing the P-E hysteresis loop of undoped Ba0.65 Sr0.35 TiO3 ceramics with that of B2 O3-SiO2 doped Ba0.65Sr0.35 TiO3 ceramics, it can be seen that the remanent polarization decreases when the B2 O3-SiO2 content is lower than 8 % (molar fraction), and the coercive field increases with the increase of B2O3-SiO2 content.

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

    Abdul Manan; Yaseen Iqbal


    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.

  10. Band-gap tuning and magnetic properties of heterovalent ions (Ba, Sr and Ca) substituted BiFeO3 nanoparticles

    Chauhan, Sunil; Kumar, Manoj; Katyal, S. C.


    A Comparative study of heterovalent Ba, Sr and Ca ions substitution on the structural, vibrational, optical and magnetic properties of BiFeO3 nanoparticles was carried out. The distorted rhombohedral structure was confirmed from both X-ray diffraction and Raman spectroscopy techniques in pure BiFeO3 and Bi0.85A0.15FeO3 (A= Ba, Sr and Ca) samples. UV-Visible spectroscopy results show that the band-gap of BiFeO3 nanoparticles can be tuned by heterovalent ions substitution from 2.12 eV for BiFeO3 to 2.10, 2.06 and 2.03 eV for Ca, Sr and Ba substituted BiFeO3 nanoparticles respectively. The magnetic measurements indicate enhancement in magnetization for heterovalent A2+ substituted BiFeO3 samples and the magnetization increases with increase of ionic radius of the substituted ions.

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

    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: [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: [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)


    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.

  12. Rb-Sr and single - zircon grain 207Pb / 206Pb chronology of the Monesterio granodiorite and related migmatites. Evidence of a Late Cambrian melting event in the Ossa-Morena Zone, Iberian Massif

    Bea, F.


    Full Text Available The Monesterio granodiorite, a small granodioritic body placed in a migmatitic complex in the SW of the Olivenza-Monesterio antiform, is a key plutonic body to understanding the relationships among the magmatism, metamorphism, and deformation in the Ossa-Morena Zone, SW Iberian Massif. We dated the granodiorite with the single zircon stepwise-evaporation 207Pb/206Pb method, and the related migmatization event with the Rb-Sr method on leucosomes. Our results indicate that the Monesterio granodiorite crystallised at 510 ± 7 Ma and its protolith had a component with Upper Proterozoic zircons with a minimum age of 1696 Ma. Leucosomes give a Rb-Sr age of 511 ± 40 Ma (MSWD =1,7 with initial 87Sr/86Sr =0.70914 ± 0.00048. The lower initial 87Sr/86Sr of the granodiorite and its calc-alkaline chemistry precludes it from having derived from the same protolith as the migmatites. The existence of different magmatic bodies in the Ossa-Morena Zone with ages clustering around 500-510 Ma reveals the existence of a significant melting event during the Late Cambrian that involved protoliths with very different geochemical and isotopic signatures.La granodiorita de Monesterio es un pequeño cuerpo emplazado en un complejo migmatítico en el SO del antiforme Olivenza-Monesterio, importante para entender las relaciones entre magmatismo, metamorfismo y deformación en la Zona de Ossa-Morena. Se ha datado la granodiorita por el método de evaporación secuencial de 207Pb/206Pb en cristal único de circón y los leucosomes de las migmatitas circundantes por el método Rb-Sr. Los datos indican una edad de cristalización de la granodiorita de 510 ± 4 Ma y un posible protolito Proterozoico Superior con una edad mínima de ∼1.700 Ma, obtenida a partir de núcleos heredados de los circones analizados. Los leucosomes dan una edad Rb-Sr de 511 ± 40 Ma, con una relación 87Sr/86Sr=0,70914 ± 0,00048. La relación inicial de 87Sr/86Sr en la granodiorita (

  13. Evaluating crustal contributions to enriched shergottites from the petrology, trace elements, and Rb-Sr and Sm-Nd isotope systematics of Northwest Africa 856

    Ferdous, J.; Brandon, A. D.; Peslier, A. H.; Pirotte, Z.


    The origin of the incompatible trace element (ITE) characteristics of enriched shergottites has been critical for examining two contradicting scenarios to explain how these Martian meteorites form. The first scenario is that it reflects ITE enrichment in an early-formed mantle reservoir whereas the second scenario attributes it to assimilation of ancient Martian crust (∼4-4.5 Ga) by ITE-depleted magmas. Strongly differentiated shergottite magmas may yield added constraints for determining which scenario can best explain this signature in enriched shergottites. The meteorite Northwest Africa (NWA) 856 is a basaltic shergottite that, unlike many enriched shergottites, lacks olivine and has undergone extensive differentiation from more primitive parent magma. In similarity to other basaltic shergottites, NWA 856 is comprised primarily of compositionally zoned clinopyroxenes (45% pigeonite and 23% augite), maskelynite (23%) and accessory minerals such as ulvöspinel, merrillite, Cl-apatite, ilmenite, pyrrhotite, baddeleyite and silica polymorph. The CI-chondrite normalized rare earth element (REE) abundance patterns for its maskelynite, phosphates, and its whole rock are flat with corresponding light-REE depletions in clinopyroxenes. The 87Rb-87Sr and 147Sm-143Nd internal isochron ages are 162 ± 14 (all errors are ±2σ) Ma and 162.7 ± 5.5 Ma, respectively, with an initial εNdI = -6.6 ± 0.2. The Rb-Sr isotope systematics are affected by terrestrial alteration resulting in larger scatter and a less precise internal isochron age. The whole rock composition is used in MELTS simulations to model equilibrium and fractional crystallization sequences to compare with the crystallization sequence from textural observations and to the mineral compositions. These models constrain the depth of initial crystallization to a pressure range of 0.4-0.5 GPa (equivalent to 34-42 km) in anhydrous conditions at the Fayalite-Magnetite-Quartz buffer, and consistently reproduce the

  14. Structural dependence of the photocatalytic properties of double perovskite compounds A2InTaO6 (A = Sr or Ba) doped with nickel.

    Lv, Meilin; Wang, Yawei; Lu, Lingwei; Wang, Ruinan; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang


    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.

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

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


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

  16. Sm-Nd and Rb-Sr Isotopic Systematics of a Heavily Shocked Martian Meteorite Tissint and Petrogenesis of Depleted Shergottites

    Shih, C.-Y.; Nyquist, L. E.; Park, J.; Agee, Carl B.


    Tissint is a very fresh Martian meteorite that fell near the town of Tissint in Morocco on July 18, 2011. It contains abundant olivine megacrysts (23%) in a fine-grained matrix of pyroxene (55%), maskelynitized plagioclase (15%), opaques (4%) and melt pockets (3%) and is petrographically similar to lithologies A and C of picritic shergottite EETA 79001 [1,2]. The presence of 2 types of shock-induced glasses and all 7 high-pressure mineral phases that were ever found in melt pockets of Martian meteorites suggests it underwent an intensive shock metamorphism of 25 GPa and 2000 C localized in melt pockets [2]. Mineral textures suggest that olivines, pyroxenes and plagioclases probably did not experience such hightemperature. Earlier determinations of its age yielded 596+/-23 Ma [3] and 616+/-67 Ma [4], respectively, for the Sm-Nd system and 583+/-86 Ma for the Lu-Hf system [4], in agreement with the 575+/-18 Ma age of the oldest olivine-phyric depleted shergottite Dho 019 [5]. However, the exposure ages of Tissint (1 Ma [1, 6, 7]) and Dho 019 (20 Ma [8]) are very different requiring two separate ejection events. These previously determined Sm-Nd and Lu-Hf ages are older than the Ar-Ar maskelynite plateau age of 524+/-15 Ma [9], reversing the pattern usually observed for Martian meteorites. In order to clarify these age issues and place models for Tissint's petrogenesis on a firm basis, we present new Rb-Sr and Sm- Nd isotopic results for Tissint, and discuss (a) the shock effects on them and the Ar-Ar chronometer, (b) correlation of the determined ages with those of other depleted shergottites, and (c) the petrogenesis of depleted shergottites. Since the meteorite is a recent fall, terrestrial contamination is expected to be minimal, but, the strong shock metamorphism might be expected to compromise the equilibrium of the isotopic systems.

  17. Oxygen Partial Pressure during Pulsed Laser Deposition: Deterministic Role on Thermodynamic Stability of Atomic Termination Sequence at SrRuO3/BaTiO3 Interface.

    Shin, Yeong Jae; Wang, Lingfei; Kim, Yoonkoo; Nahm, Ho-Hyun; Lee, Daesu; Kim, Jeong Rae; Yang, Sang Mo; Yoon, Jong-Gul; Chung, Jin-Seok; Kim, Miyoung; Chang, Seo Hyoung; Noh, Tae Won


    With recent trends on miniaturizing oxide-based devices, the need for atomic-scale control of surface/interface structures by pulsed laser deposition (PLD) has increased. In particular, realizing uniform atomic termination at the surface/interface is highly desirable. However, a lack of understanding on the surface formation mechanism in PLD has limited a deliberate control of surface/interface atomic stacking sequences. Here, taking the prototypical SrRuO3/BaTiO3/SrRuO3 (SRO/BTO/SRO) heterostructure as a model system, we investigated the formation of different interfacial termination sequences (BaO-RuO2 or TiO2-SrO) with oxygen partial pressure (PO2) during PLD. We found that a uniform SrO-TiO2 termination sequence at the SRO/BTO interface can be achieved by lowering the PO2 to 5 mTorr, regardless of the total background gas pressure (Ptotal), growth mode, or growth rate. Our results indicate that the thermodynamic stability of the BTO surface at the low-energy kinetics stage of PLD can play an important role in surface/interface termination formation. This work paves the way for realizing termination engineering in functional oxide heterostructures.

  18. 山东微山稀土矿矿床成因:来自云母Rb-Sr年龄、激光Nd同位素及流体包裹体的证据%Genesis of the Weishan REE deposit, Shandong Province: Evidences from Rb-Sr isochron age, LA-MC-ICPMS Nd isotopic compositions and fluid inclusions

    蓝廷广; 范宏瑞; 胡芳芳; 杨奎锋; 王永


    Weishan REE deposit, a pegmatite-type REE deposit related to alkaline rocks, is located in Luxi Block, southeastern North China Craton. Muscovite Rb-Sr isochron yields an age of 119.5 Ma, which belonged to the Early Cretaceous large-scale mineralization in the North China Craton. LA-ICPMS Nd isotopic compositions of bastnaesite and monazite indicate that the source of the REE deposit is the enriched lithospheric mantle. Four types of fluid inclusions have been identified in quartz, fluorite and barite, including (1) H2O inclusions (H), (2) pure CO2 inclusions (C), (3) H2O+CO2 inclusions (HC) and (4) H2O+CO2+daughter mineral inclusions (HCD). The H inclusions are secondary while others are primary. The daughter minerals in HCD inclusions include thenardite, barite, celestine, calcite, aphthitalite and glauberite. The homogenization and capture pressures of HC and HCD inclusions range from 205-433 ℃ and 120-200 Mpa, respectively. Coupled with the existence of abundant daughter minerals and S stable isotopic compositions, it can be deduced that the initial ore-forming fluidswere high-temperature, moderate-pressure and high-concentration orthomagmatic fluids, which were characterized by enrichment of HCO-3/CO2-3, SO2-4 and F~ and multi-component (e.g., Na+, K+, Ca+, Ba2+, Sr2+ and REE3+). The coexistence of C, HC and HCD inclusions and the wide range of liquid/vapor ratios between these inclusions suggest that fluid unmixing may have occurred during ore-forming process. REE were most probably transported as [REEF]2+ and precipitated through fluid unmixing. Fluids mixing, which contributed little to the REE precipitation, also happened in the late stage of the ore-forming process.%微山稀土矿位于华北克拉通东南缘的鲁西地块,为与碱性岩相关的伟晶岩型稀土矿床.根据单颗粒云母Rb-Sr定年,其形成于119.5 Ma,属于华北克拉通早白垩世大规模成矿事件的一部分.稀土矿物氟碳铈矿和独居石的激光Nd同位素研

  19. Hysteresis Behavior of Capacitance-Voltage Curve in (Ba0.6Sr0.4)TiO3 Thick Films Caused by Strained Heterostructure

    Kawae, Takeshi; Fukuda, Yuji; Morito, Kentaro; Munetomo, Kenshiro; Morimoto, Akiharu


    (Ba0.6Sr0.4)TiO3 (BST) films with 300-1700 nm thicknesses were deposited on SrTiO3 (STO), 0.5 wt % Nb-doped STO and (La0.5Sr0.5)CoO3-coated STO substrates by pulsed laser deposition. X-ray diffraction analysis results indicate that the deposited BST thick films were epitaxially grown on the substrates and c-lattice parameter of BST was increased compared with that of the bulk material owing to stress in the film. The fabricated film capacitors showed a hysteresis curve in the capacitance-voltage curve at room temperature. Hysteresis width linearly increased with increasing BST c-lattice parameter.

  20. Ruthenate-ferrites AMRu{sub 5}O{sub 11} (A = Sr, Ba; M = Ni, Zn). Distortion of kagome nets via metal-metal bonding

    Shlyk, Larysa; Strobel, Sabine; Niewa, Rainer [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie; Schleid, Thomas


    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.)

  1. Effects of BaTiO3 and SrTiO3 as the buffer layers of epitaxial BiFeO3 thin films

    Feng, Yu; Wang, Can; Tian, ShiLu; Zhou, Yong; Ge, Chen; Guo, HaiZhong; He, Meng; Jin, KuiJuan; Yang, GuoZhen


    BiFeO3 (BFO) thin films with BaTiO3 (BTO) or SrTiO3 (STO) as buffer layer were epitaxially grown on SrRuO3-covered SrTiO3 substrates. X-ray diffraction measurements show that the BTO buffer causes tensile strain in the BFO films, whereas the STO buffer causes compressive strain. Different ferroelectric domain structures caused by these two strain statuses are revealed by piezoelectric force microscopy. Electrical and magnetical measurements show that the tensile-strained BFO/BTO samples have reduced leakage current and large ferroelectric polarization and magnetization, compared with compressively strained BFO/STO. These results demonstrate that the electrical and magnetical properties of BFO thin films can be artificially modified by using a buffer layer.

  2. Experimental determination of carbon partitioning between upper mantle minerals and silicate melts: initial results and comparison to trace element partitioning (Nb, Rb, Ba, U, Th, K)

    Rosenthal, A.; Hauri, E. H.; Hirschmann, M. M.; Davis, F. A.; Withers, A. C.; Fogel, M. L.


    Inventories of C in the mantle and magmatic fluxes of C between the mantle and the Earth's outer envelopes are poorly constrained in part owing to challenges in determining undegassed C concentrations of pristine basalts. Saal et al. [1] proposed that the behavior of Nb could be used as a proxy for C, owing to apparently similar behavior of the two elements in Siqueiros Transform MORB, but higher C/Nb ratios in popping rocks [2] call into question the applicability of the C/Nb proxy. Here, we present experimentally determined carbon partition coefficients (D's) between nominally volatile-free mantle minerals (olivine, OL; orthopyroxene, OPX; clinopyroxene, CPX; garnet, GA) and melts at 0.8-3 GPa, and 1250-1500°C. We conducted piston-cylinder experiments using an olivine-tholeiite + 4 wt% CO2, doped with Nb, Rb, U, Th, and 13C to enhance detection limits. To promote growth of crystals big enough for SIMS analyses, experiments were either long (D12C, but a few have the opposite. Continuous exchange of the liquid (initially rich in 13C) with the graphite capsules (rich in 12C) may yield D's with 13C>12C. D's with 12C>13C are likely owing to either low count rates or comparatively high analytical contamination. Concentrations in minerals vary from 0.20-3.46 ppm for C, 25-176 ppm for H2O, and 0.05-1.21 ppm for F, whereas liquids tend to much higher values (C≤0.9 wt%; H2O≤1.5 wt%; F≤34 ppm; P≤0.25 wt%; S≤43 ppm; Cl≤77 ppm). Resulting D's indicate that C is highly incompatible in all major mantle mineral phases, with D's for OL, OPX and CPX of close to 5x10-4, and for GA ~2.2x10-4. D's for H2O (2x10-4 to ~3x10-2) and F (~2.3x10-3 to ~5.8x10-2) are comparable to those found in previous studies. Trace element partition determinations are in progress, but comparison to previous studies indicates that carbon is significantly more incompatible during mantle melting than Nb, U, or Th, and has behavior approximately similar to Ba. We therefore suggest that

  3. Shrinking of anionic polyacrylate coils induced by Ca2+, Sr2+ and Ba2+: a combined light scattering and ASAXS study.

    Schweins, R; Goerigk, G; Huber, K


    Anionic polyacrylate chains (NaPA) form precipitates if alkaline earth cations are added in stoichiometric amounts. Accordingly, precipitation thresholds were established for three different alkaline earth cations Ca(2+), Sr(2+) and Ba(2+). Close to the precipitation threshold, the NaPA chains significantly decrease in size. This shrinking process was followed by means of combined static and dynamic light scattering. Intermediates were generated by varying the ratio [MCl(2)]/[NaPA] with M denoting the respective alkaline earth cation. All experiments were performed at an inert salt level of 0.01M NaCl. Similar coil-to-sphere transitions could be observed with all three alkaline earth cations Ca(2+), Sr(2+) and Ba(2+). Based on these findings, supplementary conventional and anomalous small-angle X-ray scattering experiments using selected intermediates close to the precipitation threshold of SrPA were performed. The distribution of Sr counterions around the polyacrylate chains in aqueous solution provided the desired scattering contrast. Energy-dependent scattering experiments enabled successful separation of the pure-resonant terms, which solely stem from the counterions. The Sr(2+) scattering roughly reflects the monomer distribution of the polyacrylate chains. Different ratios of the concentrations of [ SrCl(2)]/[NaPA] revealed dramatic changes in the scattering curves. The scattering curve at the lowest ratio indicated an almost coil-like behaviour, while at the higher ratios the scattering curves supported the model of highly contracted polymer chains. Most of X-ray scattering experiments on intermediate states revealed compact structural elements which were significantly smaller than the respective overall size of the NaPA particles.

  4. Structure and Luminescence Properties of Sr4Al14O25:Eu2+, Dy3+ by Ba2+ Substitution%Ba2+替代对Sr4Al14O25:Eu2+,Dy3+结构和发光性能的影响

    谢伟; 王银海; 胡义华; 吴浩怡; 邓柳咏


    采用高温固相反应按化学式Sr4-xBaxAl14O25:Eu2+,Dy3+(x=0,0.8,1.6,2.4,3.2,4)配比原料,合成长余辉发光材料.X射线衍射分析表明,当x=0.8时,产物物相为单斜结构SrAl2O+和磁铅矿结构SrAl12O19共存;当x>1.6时,产物主相转变为BaAl2O+六角结构.对所得样品采用360nm光照,发射光谱表明,样品发光是以Eu2+为发光中心,由Eu2+电子4f65d-4f7跃迁所致,并且随着Ba掺入量的增加,样品发射光谱峰位产生移动,这是由于Sr2+取代产物中Ba2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂,从而影响电子4f65d-4f7跃迁.余辉光谱显示x>1.6时,产物的余辉发光是以BaAl2O+基质中Eu2+为发光中心.余辉衰减检测和热释光谱分析发现不同掺Ba量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长.%The rare-earth doped strontium aluminate phosphors Sr4-xBaxAll4O25:Eu2+,Dy3+ (x=0, 0.8, 1 .6. 2.4, 3.2, 4) were synthesized by a high temperature solid-state reaction method.The phase structures of the phosphors were characterized by X-ray diffraction.The results show that the monoclinic SrAl2O4 and hexagonal SrAl12o19 co-exist in the sample with x=0.8.The major phase of phosphors is hexagonal BaAl2O4 when x>1.6.It is indicated that the phase structure of the samples changes from Sr4Al14O21 to BaA1204 when the value of x changes from O to 4.The emission spectra of 360 nm irradiation reveal that Eu2+ is the luminescence center of the samples due to 4f65d-4f7 transition of Eu2+ electron.With the Ba doping content increasing, the shift of emission spectra peak occurs, because the lattice shrinkage caused by Sr2+ substitution for Ba2- affects the Sd level cleavage of Eu2+ and thus influences the 4f55d-4f7 transition.The afterglow spectra show that Eu2+ of BaAl2O4 is the luminescence center for the products when x>1.6.The decay characteristics show that the phosphor samples with different Ba2+ content

  5. Sr and Nd isotopic and trace element compositions of Quaternary volcanic centers of the southern Andes

    Futa, Kiyoto; Stern, C.R.


    Isotopic compositions of samples from six Quaternary volcanoes located in the northern and southern extremities of the Southern Volcanic Zone (SVZ, 33-46/sup 0/S) of the Andes and from four centers in the Austral Volcanic Zone (AVZ, 49-54/sup 0/S) range for /sup 87/Sr//sup 86/Sr from 0.70280 to 0.70591 and for /sup 143/Nd//sup 144/Nd from 0.51314 to 0.51255. Basalts and basaltic andesites from three centers just north of the Chile Rise-Trench triple junction have /sup 87/Sr//sup 86/Sr, /sup 143/Nd//sup 144/Nd, La/Yb, Ba/La and Hf/Lu that lie within the relatively restricted ranges of the basic magmas erupted from the volcanic centers as far north as 35/sup 0/S in the SVZ of the Andes. The trace element and Sr and Nd isotopic characteristics of these magmas may be explained by source region contamination of subarc asthenosphere, with contaminants derived from subducted pelagic sediments and seawater-altered basalts by dehydration of subducted oceanic lithosphere. In the northern extremity of the SVZ between 33/sup 0/ and 34/sup 0/S, basaltic andesites and andesites have higher /sup 87/Sr//sup 86/Sr, Rb/Cs, and Hf/Lu, and lower /sup 143/Nd//sup 144/Nd than basalts and basaltic andesites erupted farther south in the SVZ, which suggests involvement of components derived from the continental crust. In the AVZ, the most primitive sample, high-Mg andesite from the southernmost volcanic center in the Andes (54/sup 0/S) has Sr and Nd isotopic compositions and K/Rb and Ba/La similar to MORB. The high La/Yb of this sample suggests formation by small degrees of partial melting of subducted MORB with garnet as a residue. Samples from centers farther north in the AVZ show a regionally regular northward increase in SiO/sub 2/, K/sub 2/O, Rb, Ba, Ba/La, and /sup 87/Sr//sup 86/Sr and decrease in MgO, Sr, K/Rb, Rb/Cs, and /sup 143/Nd//sup 144/Nd, suggesting increasingly greater degrees of fractional crystallization and associated intra-crustal contamination. (orig./SHOE).

  6. Sr and Nd isotopic and trace element compositions of Quaternary volcanic centers of the Southern Andes

    Futa, K.; Stern, C.R.


    Isotopic compositions of samples from six Quaternary volcanoes located in the northern and southern extremities of the Southern Volcanic Zone (SVZ, 33-46??S) of the Andes and from four centers in the Austral Volcanic Zone (AVZ, 49-54??S) range for 87Sr 86Sr from 0.70280 to 0.70591 and for 143Nd 144Nd from 0.51314 to 0.51255. The ranges are significantly greater than previously reported from the southern Andes but are different from the isotopic compositions of volcanoes in the central and northern Andes. Basalts and basaltic andesites from three centers just north of the Chile Rise-Trench triple junction have 87Sr 86Sr, 143Nd 144Nd, La Yb, Ba La, and Hf Lu that lie within the relatively restricted ranges of the basic magmas erupted from the volcanic centers as far north as 35??S in the SVZ of the Andes. The trace element and Sr and Nd isotopic characteristics of these magmas may be explained by source region contamination of subarc asthenosphere, with contaminants derived from subducted pelagic sediments and seawater-altered basalts by dehydration of subducted oceanic lithosphere. In the northern extremity of the SVZ between 33?? and 34??S, basaltic andesites and andesites have higher 87Sr 86Sr, Rb Cs, and Hf Lu, and lower 143Nd 144Nd than basalts and basaltic andesites erupted farther south in the SVZ, which suggests involvement of components derived from the continental crust. In the AVZ, the most primitive sample, high-Mg andesite from the southernmost volcanic center in the Andes (54??S) has Sr and Nd isotopic compositions and K Rb and Ba La similar to MORB. The high La Yb of this sample suggests formation by small degrees of partial melting of subducted MORB with garnet as a residue. Samples from centers farther north in the AVZ show a regionally regular northward increase in SiO2, K2O, Rb, Ba, Ba La, and 87Sr 86Sr and decrease in MgO, Sr, K Rb, Rb Cs, and 143Nd 144Nd, suggesting increasingly greater degrees of fractional crystallization and associated intra

  7. Frequency-dependent impedance spectroscopy on the 0.925(Bi0.5Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 ceramic

    Ullah, Amir; Rahman, Muneeb-ur; Iqbal, Muhammad Javid; Ahn, Chang Won; Kim, Ill Won; Ullah, Aman


    The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10 -2 ~ 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance ( R b ) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.

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

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


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

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

    Nadaud, Kevin, E-mail:; Borderon, Caroline, E-mail:; Renoud, Raphaël; Gundel, Hartmut W. [IETR, UMR CNRS 6164, University of Nantes, Nantes (France)


    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)

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

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


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

  11. In-field {sup 57}Fe Mössbauer study of multiferroic Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} Y-type hexaferrite

    Raju, N.; Shravan Kumar Reddy, S.; Gopal Reddy, Ch. [Department of Physics, Osmania University, Hyderabad 500007 (India); Yadagiri Reddy, P., E-mail: [Department of Physics, Osmania University, Hyderabad 500007 (India); Rama Reddy, K. [Department of Physics, Osmania University, Hyderabad 500007 (India); Raghavendra Reddy, V. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)


    The structural, magnetic, and in-field {sup 57}Fe Mössbauer studies of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} polycrystalline multiferroic, which belongs to Y-type hexaferrite class, are presented in this paper. Sr{sup 2+} substitution at Ba{sup 2+} site effects the redistribution of Zn{sup 2+} and Fe{sup 3+} ions at tetrahedral sites in the crystal. The magnetization data reveals the magnetic field induced transitions in the M–H curve. The in-field Mössbauer study reveals that the occupancy of Fe{sup 3+} ions in the tetrahedral sites is more than that in the octahedral sites because of doping of Sr{sup 2+} at Ba{sup 2+} site, which plays an important role in field induced multiferroic property at low temperature. - Highlights: • The structural, magnetic, and in-field {sup 57}Fe Mössbauer studies of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} are reported. • Doping of Sr at Ba site yielded the field induced transitions in the material. • The Fe{sup +3} ions at tetrahedral sites are more than the octahedral sites by Sr doping.

  12. The Ternary Alkaline-Earth Metal Manganese Bismuthides Sr2MnBi2 and Ba2Mn1-xBi2 (x ≈ 0.15).

    Ovchinnikov, Alexander; Saparov, Bayrammurad; Xia, Sheng-Qing; Bobev, Svilen


    Two new ternary manganese bismuthides have been synthesized and their structures established based on single-crystal X-ray diffraction methods. Sr2MnBi2 crystallizes in the orthorhombic space group Pnma (a = 16.200(9) Å, b = 14.767(8) Å, c = 8.438(5) Å, V = 2018(2) Å(3); Z = 12; Pearson index oP60) and is isostructural to the antimonide Sr2MnSb2. The crystal structure contains corrugated layers of corner- and edge-shared [MnBi4] tetrahedra and Sr atoms enclosed between these layers. Electronic structure calculations suggest that Sr2MnBi2 is a magnetic semiconductor possessing Mn(2+) (high-spin d(5)) ions, and its structure can be rationalized within the Zintl concept as [Sr(2+)]2[Mn(2+)][Bi(3-)]2. The temperature dependence of the resistivity shows behavior consistent with a degenerate semiconductor/poor metal, and magnetic susceptibility measurements reveal a high degree of frustration resulting from the two-dimensional nature of the structure. The compositionally similar Ba2Mn1-xBi2 (x ≈ 0.15) crystallizes in a very different structure (space group Imma, a = 25.597(8) Å, b = 25.667(4) Å, c = 17.128(3) Å, V = 11253(4) Å(3); Z = 64; Pearson index oI316) with its own structure type. The complex structure boasts Mn atoms in a variety of coordination environments and can be viewed as consisting of two interpenetrating 3D frameworks, linked by Bi-Bi bonds. Ba2Mn1-xBi2 can be regarded as a highly reduced compound with anticipated metallic behavior.

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

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


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

    S J Dhoble; N S Dhoble; R B Pode


    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.

  15. Photophysical electronic structure of double-perovskites A{sub 2}GdTaO{sub 6} (A = Ba and Sr)

    Ghosh, Binita, E-mail: [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)


    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.

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

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


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

  17. The superconducting phase and electronic excitations of (Rb,Cs) Fe 2 As 2

    Kanter, J.; Shermadini, Z.; Khasanov, R.; Amato, A.; Bukowski, Z.; Batlogg, B.


    We present specific heat, transport and Muon-Spin Rotation (μ SR) results on (Rb,Cs) Fe 2 As 2 . RbFe 2 As 2 was only recently found to be superconducting below 2.6 K by Bukowski et al. Compared to the related BaFe 2 As 2 the electron density is lower and no magnetic order is observed. For the superconducting phase the superfluid density was calculated from μ SR data. The temperature dependence of the superfluid density and the magnetic penetration depth is well described by a multi-gap scenario. In addition the electronic contribution the specific heat was studied for different compositions and magnetic fields and reveals a high value for the Sommerfeld coefficient γ .

  18. Sr{sup 2+} doping effects on the transport and magnetic properties of GdBaCo{sub 2}O{sub 5+{delta}}

    Janaki, J. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India. (India)], E-mail:; 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)


    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.

  19. Investigation of Carbon ion-implanted waveguides in tungsten bronze (Ca0.28Ba0.72)0.25(Sr0.6Ba0.4)0.75Nb2O6 single crystal

    Jiao, Yang; Wang, Chuan-Kui; Li, Zong-Liang; Ren, Ying-Ying


    Planar optical waveguides were fabricated in (Ca0.28Ba0.72)0.25(Sr0.6Ba0.4)0.75Nb2O6 (CSBN25) crystal by 6.0-MeV C+ ion implantation with fluences of 2, 4 and 6 × 1014 ions/cm2 at room temperature. The mode parameters, refractive indices profiles are measured and the refractive indices behavior in the waveguide region is discussed. The shape of nuclear energy loss distribution of the C+ implantation was similar to those of the waveguide refractive index profiles, which means an inherent relationship between the waveguide formation and the energetic energy deposition. The extraordinary refractive index has a small positive change in the surface region after the implantation.

  20. Cooling age of the Birimian juvenile crust in West Africa. U-Pb, Rb-Sr and K-Ar data on the 2. 1 Ga granite-greenstone terrains from SW-Niger. Age de refroidissement de la croute juvenile birimienne d'Afrique de l'Ouest. Donnees U-Pb, Rb-Sr et K-Ar sur les formations a 2. 1 Ga du SW-Niger

    Lama, C.; Dautel, D.; Zimmermann, J.L. (Centre National de la Recherche Scientifique (CNRS), 54 - Nancy (France). Centre de Recherches Petrographiques et Geochimiques); Barbey, P. (Nancy-1 Univ., 54 (France)); Cheilletz, A. (Centre National de la Recherche Scientifique (CNRS), 54 - Nancy (France). Centre de Recherches Petrographiques et Geochimiques Ecole Nationale Superieure de Geologie Appliquee et de Prospection Miniere, 54 - Nancy (France)); Pons, J. (Orleans Univ., 45 (France))


    A comparison between zircon U-Pb, whole-rock Rb-Sr and biotite-amphibole K-Ar data on Birimian granite-greenstone terrains from SW-Niger indicates that the youngest granitic plutons were emplaced at 2.115 [+-] 5 Ma and that both the plutons and the surrounding greenstones yield cooling ages around 2.118 Ma. The age similarity between the end of the plutonism and the cooling of plutons and surrounding greenstone further suggests rapid cooling at the end of the plutonic event and, thus, corroborates a model of greenstone metamorphism linked to the thermal effect of the plutons. (authors).

  1. Distribution and Environmental Information of Rb and Sr in the Mawo Karst Basin Sediments of Weining in Guizhou%贵州威宁麻窝山岩溶盆地剖面中Rb、Sr分布及环境信息

    曹振兴; 吴攀; 顾尚义; 彭德海; 杨绍章


    The evolution of karst basin plays a crucial role in earth surface processes, which well records the history of watershed erosion and chemical weathering. Rb/Sr has been widely used for revealing environmental information among different palaeoclimatic archives. In this study, based upon the 14C dates and characteristics of K and Ca in the Mawo karst basin sediments from Weining county of Guizhou province, the geochemical behaviour of Rb and Sr were analysed and Rb/Sr were compiled for the palaeoclimate in Northwest Guizhou. The results showed that concentrations of Rb in the four studied profiles were mostly greater than Sr, and strong positive correlations between Rb and K and between Sr and Ca were observed, which further confirmed the notion that Sr was more mobile than Rb in the evolution of Mawo karst basin. The vertical variation of Rb/Sr in all profiles suggested periodic sedimentary environment in the studied area, which corresponded to the field characteristics, especially the color variation of the sediments. High Rb/Sr primarily controlled by Rb indicated the arid climate or a low water level of the basin, otherwise the opposite.There existed 3 -1/2 dry-moist climate cycles in the past 40ka of the karst basin that could be used as ideal archive for reconstructing palaeoclimate in karst areas.%岩溶盆地的演化清晰地记录了流域侵蚀和化学风化等重要过程,Rb/Sr是有效获取地表过程中环境信息的重要手段之一.本文基于14C定年方法,结合研究剖面中K、Ca等元素的组成特征,对贵州威宁麻窝山岩溶盆地中4个沉积剖面的Rb、Sr分布和地球化学行为进行了分析,并讨论了Rb/Sr指示的环境意义和盆地的演化历程.结果表明,剖面中Rb元素含量普遍高于Sr元素且波动幅度较Sr元素大.此外,Rb与K,Sr与Ca之间均有较好的正相关关系,即在流域物质的侵蚀、搬运和盆地沉积物的形成演化过程中,Sr的活动性明显高于Rb.各剖面Rb、Sr

  2. Displacement-type ferroelectricity with off-center magnetic ions in perovskite Sr(1-x)Ba(x)MnO3.

    Sakai, H; Fujioka, J; Fukuda, T; Okuyama, D; Hashizume, D; Kagawa, F; Nakao, H; Murakami, Y; Arima, T; Baron, A Q R; Taguchi, Y; Tokura, Y


    We report a ferroelectric transition driven by the off-centering of magnetic Mn(4+) ions in antiferromagnetic Mott insulators Sr(1-x)Ba(x)MnO(3) with a perovskite structure. As x increases, the perovskite lattice shows the typical soft-mode dynamics, as revealed by the momentum-resolved inelastic x-ray scattering and far-infrared spectroscopy, and the ferroelectricity shows up for x ≥ 0.45. The observed polarization is comparable to that for a prototypical ferroelectric BaTiO(3). We further demonstrate that the magnetic order suppresses the ferroelectric lattice dilation by ∼70% and increases the soft-phonon energy by ∼50%, indicating the largest magnetoelectric effects yet attained.

  3. X-ray diffraction, dielectric, and Raman spectroscopy studies of BaSrTiO{sub 3}-NaNbO{sub 3} ceramic

    Abdessalem, L. Ben; Aydi, S.; Aydi, A.; Maalej, A.; Khemakhem, H. [Universite de Sfax, Laboratoire des Materiaux Multifonctionnels et Applications (LaMMA), Faculte des Sciences de Sfax (FSS), Sfax (Tunisia); Sassi, Z. [Laboratoire de Genie Electrique et Ferroelectricite (LGEF) de L' INSA de Lyon, Villeurbanne (France)


    Ba{sub 0.837}Sr{sub 0.093}Na{sub 0.07}Ti{sub 0.93}Nb{sub 0.07}O{sub 3} (BSNTN) ceramic was synthesized by the solid-state reaction at 1350 C for 3 h. The crystal structure, investigated by X-ray diffraction at room temperature, revealed a single-phase perovskite crystallizing with tetragonal P4mm group space. Dielectric properties were investigated as a function of applied frequency. The ferroelectric behavior has been confirmed by hysteresis investigation. The evolution of the Raman spectra was used to study the variations of the basic phase transition of BaTiO{sub 3}, at room temperature. It shows the introduction of a disorder in this composition, thus favoring a ferroelectric relaxor behavior. (orig.)

  4. Surfactant-assisted synthesis of Ba0.7Sr0.3TiO3 nanoparticles by mechanical alloying and ultrasonic irradiation

    Yustanti, Erlina; Hafizah, Mas Ayu Elita; Manaf, Azwar


    Ba0.7Sr0.3TiO3 nanoparticles were successfully synthesized by mechanical alloying and successive ultrasonic irradiation method with an addition of surfactant. Fine crystalline particles were first obtained after re-milled the sintered mechanically alloyed powders of BaCO3, TiO2 and SrCO3 precursors for 20 hours in which the size of particles was found below 300 nm. These fine particles were further refined their size under a high power ultrasonic treatment for 6 hours. Various types of surfactant namely amphoteric, cationic, anionic and non-ionic were brought into studies to find out their effectiveness in preventing the agglomeration due to strong attractive forces between fine particles. It was found that all surfactant prove effective to prevent the agglomeration. This was indicated in the distribution of particle size measurement in which mean size of particles added surfactants (139 nm-158 nm) was less than that of surfactant free (173 nm). However, among all surfactant which added in the media containing particles, only the non-ionic surfactant showed a particle size distribution with the smallest (139 nm) mean particle size. The effectiveness of surfactant in preventing the agglomeration depends on the concentration of surfactant and density of media containing particles. The study concluded that the addition of 0.1% non-ionic surfactant into media containing particles has resulted in Ba0.7Sr0.3TiO3 nanoparticles with the mean size of 139 nm.

  5. 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.

    Malea, Paraskevi; Kevrekidis, Theodoros


    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.

  6. 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

    潘再法; 刘爽; 朱澄静; 徐娟; 刘文涵; 王丽丽


    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

  7. Preparation structure and dielectric properties of tungsten bronze ceramics Sr0.5 Ba0.5 Nb2O6%钨青铜陶瓷Sr0.5Ba0.5Nb2O6的制备结构与介电性能研究

    丁剑; 俞建长; 郑兴华; 梁国栋


    采用固相反应法合成Sr0.5Ba0.5Nb2O6陶瓷,并对其结构、介电性能进行表征.研究结果表明,Sr0.5Ba0.5Nb2O6陶瓷为四方钨青铜结构单相,其在100℃附近存在一个明显的弥散介电峰,峰值随测试频率增加而减小,为典型的弛豫铁电相变.室温时,10 kHz频率下,其介电常数约为450,介电损耗为0.121.

  8. 钨青铜陶瓷Sr0.6Ba0.4Nb2O6的合成、结构与介电性能%Synthesis, Structure and Dielectric Properties of Tungsten Bronze Ceramic Sr0.6Ba0.4Nb2O6

    郑兴华; 丁剑; 俞建长; 梁国栋



  9. An investigation of the optical properties and water splitting potential of the coloured metallic perovskites Sr{sub 1−x}Ba{sub x}MoO{sub 3}

    Hopper, H.A.; Le, J.; Cheng, J. [Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom); Weller, T.; Marschall, R. [Institute of Physical Chemistry, Justus-Liebig-University Giessen, 35392 Giessen (Germany); Bloh, J.Z. [DECHEMA Research Institute, Theodor-Heuss-Allee 25, 60486 Frankfurt am Main (Germany); Macphee, D.E.; Folli, A. [Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom); Mclaughlin, A.C., E-mail: [Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom)


    The solid solution Sr{sub 1−x}Ba{sub x}MoO{sub 3} (x=0.00, 0.025, 0.050, 0.075, 0.100 and 1.00) has been synthesised. Rietveld refinement of X-ray diffraction data shows that all materials crystallise with cubic (Pm-3m) symmetry and that a miscibility gap exists from x=0.1–1.0. The optical properties of the metallic perovskites Sr{sub 1−x}Ba{sub x}MoO{sub 3} have been investigated by a combination of UV–vis spectroscopy and density functional theory (DFT). Upon increasing x from 0 to 1 in Sr{sub 1−x}Ba{sub x}MoO{sub 3} there is a reduction in the measured band gap from 2.20 eV to 2.07 eV. The measured band gap is attributed to the electronic transition from the Mo 4d t{sub 2g} band to the e{sub g} band. The potential of SrMoO{sub 3} and BaMoO{sub 3} as water-splitting photocatalysts was explored but there was no evidence of hydrogen or oxygen evolution, even with the presence of a Pt co-catalyst. - Graphical abstract: Ultraviolet–visible absorbance spectra (converted from diffuse reflectance spectra) for SrMoO{sub 3} and BaMoO{sub 3}. - Highlights: • The solid solution Sr{sub 1-x}Ba{sub x}MoO{sub 3} has been synthesised. • A miscibility gap exists from x=0.1–1.0 in Sr{sub 1−x}Ba{sub x}MoO{sub 3.} • Upon increasing x from 0 to 1 in Sr{sub 1−x}Ba{sub x}MoO{sub 3} there is a reduction in the measured band gap from 2.20 eV to 2.07 eV. • The potential of SrMoO{sub 3} and BaMoO{sub 3} as water-splitting photocatalysts was explored but there was no evidence of hydrogen or oxygen evolution, even with the presence of a Pt co-catalyst.

  10. Leakage current transport mechanisms of La0.67Sr0.33MnO3/BaTiO3 bilayer films grown on Nb:SrTiO3

    Pan Ruikun; Liu Panke; Li Mingkai; Tao Haizheng; Li Pai; He Yunbin


    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.

  11. Toward complete isotopic analysis of individual presolar silicon carbide grains : C, N, Si, Sr, Zr, Mo, and Ba in single grains of type X.

    Pellin, M. J.; Calaway, W. F.; Davis, A. M.; Lewis, R. S.; Amari, S.; Clayton, R. N.


    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.

  12. Synthesis of Ba3ZnNb2O9–Sr3ZnNb2O9 solid solution and their dielectric properties

    M Thirumal; A K Ganguli


    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.

  13. NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy

    Andrievsky, S M; Korotin, S A; Francois, P; Spite, M; Bonifacio, P; Cayrel, R; Hill, V


    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...

  14. Visible and infrared transparency in lead-free bulk BaTiO{sub 3} and SrTiO{sub 3} nanoceramics

    Liu Jing; Shen Zhijian [Department of Physical, Inorganic and Structural Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden); Yao Wenlong; Zhao Yonghao; Mukherjee, Amiya K, E-mail: [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)


    Multifunctional transparent ferroelectric ceramics have widespread applications in electro-optical devices. Unfortunately, almost all currently used electro-optical ceramics contain a high lead concentration. In this work, via coupling of spark plasma sintering with high pressure, we have successfully synthesized bulk lead-free transparent nanostructured BaTiO{sub 3} (abbreviated as BTO) and SrTiO{sub 3} (STO) ceramics with excellent optical transparency in both visible and infrared wavelength ranges. This success highlights potential ingenious avenues to search for lead-free electro-optical ceramics.

  15. Surface second-harmonic generation in Sr0.6Ba0.4NbO3 with a nonlinear diffusion mechanism

    Zhang, T. H.; Yang, J.; Kang, H. Z.; Feng, L.; Xu, J. J.; Zhang, C. P.; Ren, X. K.; Wang, B. H.; Lu, Y. Z.; Jia, F.; Shao, W. W.


    Surface second-harmonic generation excited by photorefractive surface electromagnetic wave with a diffusion mechanism of nonlinearity has been observed at the surface of the negative c axis of a Sr0.6Ba0.4NbO3 (SBN:60) experimentally. The second-harmonic 532nm wavelength light is generated by 1064nm laser in a passive guiding manner in the experiment, for the wavelength of the fundamental beam is insensitive to the SBN crystal. The transfer efficiency of surface second-harmonic generation is 1%/W.

  16. Effect of local A-site strain on dipole stability in A6GaNb9O30 (A = Ba, Sr, Ca) tetragonal tungsten bronze relaxor dielectrics.

    Miller, Andrew J; Rotaru, Andrei; Arnold, Donna C; Morrison, Finlay D


    A series of isovalently A-site substituted relaxor dielectric tetragonal tungsten bronzes of general formula Ba(6-x-y)Sr(x)Ca(y)GaNb(9)O(30) were investigated. The long-range (average) crystal structure as determined by conventional diffraction techniques varies monotonically according to Vegard's law. The dielectric properties, however, do not display a similar, simple "average size" dependence and instead show a dependence on the statistical size variance, i.e. size mismatch, of the A-cation. The difficulties in Vogel-Fulcher analysis of relative permittivity and the complementary approach of using dielectric loss data fitted to Jonscher's empirical universal dielectric relaxation model is discussed.




    Single layered Ba0.6Sr0.4TiO3 (BST) thin films were prepared on stainless steel (304) and quartz substrates by solution method. The microstructure, grain size, surface morphology and thickness of the films were reported on the basis of X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and UV-visible spectrometer. Variation in thickness influences the microstructure of the films. The single layered thin film had uniform crack-free surfa...

  18. Significant enhancement in energy density of polymer composites induced by dopamine-modified Ba0.6Sr0.4TiO3 nanofibers

    Song, Yu; Shen, Yang; Hu, Penghao; Lin, Yuanhua; Li, Ming; Nan, C. W.


    Ba0.6Sr0.4TiO3 (BST) nanofibers prepared via electrospinning and modified by dopamine are used as dielectric fillers in polyvinylidene fluoride (PVDF)-based composites. With 4.4 vol. % of BST nanofibers, the extractable energy density of the BST/PVDF composites is more than doubled as compared with pure PVDF matrix. Such significant enhancement is attributed to the combined effect of both surface modification by dopamine and large aspect ratio of the BST nanofibers. Paraelectric or anti-ferroelectric fillers of large aspect ratio may serve as a general strategy for enhanced electric energy density in polymer composites.




    Single layered Ba0.6Sr0.4TiO3 (BST) thin films were prepared on stainless steel (304) and quartz substrates by solution method. The microstructure, grain size, surface morphology and thickness of the films were reported on the basis of X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and UV-visible spectrometer. Variation in thickness influences the microstructure of the films. The single layered thin film had uniform crack-free surfa...

  20. Effect of Electron Beam on the Structure and Crystallization Features of BaO-SrO-TiO2-SiO2 Glass


    Glasses of BaO-SrO-TiO2-SiO2 after electronic radiation treatment of 50-1000 kgy were studied by means of IR spectra, DTA and visible light absorption method.The result shows that the glass structure is changed due to the formation of structure defect from oxygen vacancy and E′ color center,which resultsd in the crystallization process and new precursors,and decreasement of Tg temperature and crystallization peaks by 20-50℃.

  1. Electric modulation of magnetization at the BaTiO3/La0.67Sr0.33MnO3 interfaces

    Lu, H.; George, T. A.; Wang, Y.; Ketsman, I.; Burton, J. D.; Bark, C.-W.; Ryu, S.; Kim, D. J.; Wang, J.; Binek, C.; Dowben, P. A.; Sokolov, A.; Eom, C.-B.; Tsymbal, E. Y.; Gruverman, A.


    We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO3/La0.67Sr0.33MnO3 (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.

  2. Molecular dynamics and reverse Monte Carlo modeling of scheelite-type AWO4 (A = Ca, Sr, Ba) W L 3-edge EXAFS spectra

    Kalinko, Aleksandr; Bauer, Matthias; Timoshenko, Janis; Kuzmin, Alexei


    Classical molecular dynamics (MD) and reverse Monte Carlo methods coupled with ab initio multiple-scattering extended x-ray absorption fine structure (EXAFS) calculations were used for modeling of scheelite-type AWO4 (A = Ca, Sr, Ba) W L 3-edge EXAFS spectra. The two theoretical approaches are complementary and allowed us to perform analysis of full EXAFS spectra. Both methods reproduce well the structure and dynamics of tungstates in the outer coordination shells, however the classical MD simulations underestimate the W-O bond MSRD due to a neglect of quantum zero-point-motion. The thermal vibration amplitudes, correlation effects and anisotropy of the tungstate structure were also estimated.

  3. Calculation Model of Mass Action Concentration for Mg-Al, Sr-Al and Ba-Al Melts and Determination of Their Thermodynamic Parameters


    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.

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

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


    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.

  5. Ab initio calculations of the atomic and electronic structure of layered Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} structures

    Piskunov, S. [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Kotomin, E.A. [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia) and Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)]. E-mail:; Fuks, D. [Materials Engineering Department, Ben-Gurion University of the Negev, POB 653, Beer-Sheva (Israel); Dorfman, S. [Department of Physics, Technion- Israel Institute of Technology, Haifa 32000 (Israel)


    Understanding of the atomic and electronic structure of Ba{sub c}Sr{sub 1-c}TiO{sub 3} (BST) solid solutions is important for several applications including the non-volatile ferroelectric memories (dynamic random access memory, DRAM). We present results of ab initio calculations of several spatial arrangements of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} solid solutions based on DFT-HF B3PW hybrid method. We calculate the atomic and electronic structure, the effective charges, interatomic bond populations, the electronic density distribution, and densities of states for three layered structures with the same composition. The suggested method reproduces experimental lattice parameters of both pure BaTiO{sub 3} and SrTiO{sub 3}. The calculated optical band gaps for the pure SrTiO{sub 3} and BaTiO{sub 3} are in a good agreement with experimental data, much better than those from the standard LDA or HF calculations. In the studied BST structures with the equiatomic composition (c = 0.5) the gap is reduced by ca. 0.2 eV. The electron density maps demonstrate the covalency effects in the Ti-O bonding. The electron density near the Sr atoms is stronger localized, as compared with the Ba ions.

  6. Preparation and dielectric properties of BaCu(B{sub 2}O{sub 5})-doped SrTiO{sub 3}-based ceramics for energy storage

    Li, Lingxia, E-mail:; Yu, Xiaoxu; Cai, Haocheng; Liao, Qingwei; Han, Yemei; Gao, Zhengdong


    Highlights: • BaCu(B{sub 2}O{sub 5}) is added to the multi-ions doped SrTiO{sub 3} ceramics as sintering aid. • The sintering temperature is decreased from 1300 °C to 1075 °C. • The incorporation of Ba{sup 2+} into the matrix increases the dielectric constant. • The breakdown strength increases due to the decrease of grain size and porosity. • The dissolution of BCB contributes to the improvement of dielectric properties. -- Abstract: BaCu(B{sub 2}O{sub 5}) (BCB) was used as sintering aids to lower the sintering temperature of multi-ions doped SrTiO{sub 3} ceramics effectively from 1300 °C to 1075 °C by conventional solid state method. The effect of BCB content on crystalline structures, microstructures and properties of the ceramics was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurements, respectively. The addition of BCB enhanced the breakdown strength (BDS) while did not sacrifice the dielectric constant. The enhancement of BDS should be due to the modification of microstructures, i.e., smaller and more homogeneous grain sizes after BCB addition. The dielectric constant of BCB-doped ceramics maintained a stable value with 1.0 mol% BCB, which was dominated by the combination of two opposite effects caused by the presence of second phases and the incorporation of Cu{sup 2+} and Ba{sup 2+}, while further increase was owing to the increase of dissolved Ba{sup 2+} ions when the content of BCB is more than 2.0 mol%. The multi-ions doped SrTiO{sub 3} ceramics with 1.0 mol% BCB addition showed optimal dielectric properties as follows: dielectric constant of 311.37, average breakdown strength of 28.78 kV/mm, discharged energy density of 1.05 J/cm{sup 3} and energy efficiency of 98.83%.

  7. Enhanced photoluminescence and thermal properties of size mismatch in Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 for high-power white light-emitting diodes.

    Ci, Zhipeng; Que, Meidan; Shi, Yurong; Zhu, Ge; Wang, Yuhua


    In this Study, Mg(2+) and Ba(2+) act to enhance the maximum emission of Sr2.97SiO5:0.03Eu(2+) significantly and redshift the emission band to the orange-red region in Sr(2.97-x-y)Mg(x)Ba(y)SiO5:0.03Eu(2+). Size mismatch between the host and the doped cations tunes the photoluminescence spectra shift systematically. A slight blue shift when increasing the amount of Mg(2+) occurs in the Sr(2.97-x)Eu0.03Mg(x)SiO5 lattices, and a rapid red shift occurs when Ba(2+) is codoped in the Sr(2.57-y)Eu0.03Mg0.4Ba(y)SiO5 lattices. The emission spectra were tuned from 585 to 601 nm by changing the concentration of Ba(2+). Accordingly, we propose the underlying mechanisms of the changes in the photoluminescence properties by adjusting the cation composition of phosphors. The influence of the size mismatch on the thermal quenching is also observed. This mechanism could be widely applied to oxide materials and could be useful in tuning the photoluminescence properties, which are sensitive to local coordination environment. The emission bands of Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 show the blue shift with increasing temperature, which could be described in terms of back tunneling of the excited electrons from the low-energy excited state to the high-energy excited state. Thus, the Sr(2.97-x-y)Eu0.03Mg(x)Ba(y)SiO5 phosphors could have potential applications in the daylight LEDs or warm white LEDs.

  8. Correlation between upconversion photoluminescence and dielectric response in Ba-substituted (Sr{sub 1−x}Ba{sub x}){sub 4}(La{sub 0.85}Ho{sub 0.025}Yb{sub 0.125}){sub 2}Ti{sub 4}Nb{sub 6}O{sub 30}

    Wei, T., E-mail: [College of Science, Civil Aviation University of China, Tianjin 300300 (China); Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wang, X. D. [College of Science, Civil Aviation University of China, Tianjin 300300 (China); Zhao, C. Z. [School of Electronics and Information Engineering, Tianjin Polytechnic University, Tianjin 300160 (China); Liu, M. F.; Liu, J. M., E-mail: [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)


    The filled tetragonal tungsten bronze (Sr{sub 1−x}Ba{sub x}){sub 4}(La{sub 0.85}Ho{sub 0.025}Yb{sub 0.125}){sub 2}Ti{sub 4}Nb{sub 6}O{sub 30} (SBLTNx: Ho-Yb) ceramics with different Ba substitution levels (x) are prepared. The upconversion photoluminescence (UC-PL) and dielectric permittivity are investigated. The substitution of Sr{sup 2+} ions at the A{sub 2}-sites by larger Ba{sup 2+} ions results in substantial variation of the UC-PL intensity as a function of substitution level x. Furthermore, the dielectric response to the substitution of Sr{sup 2+} by Ba{sup 2+} suggests a close correlation between the UC-PL intensity and dielectric permittivity. The origin for this correlation is discussed based on the random stress field (RSF) model.

  9. Effect of Ferroelectric Properties of Zr doping on Ba0.5Sr0.5Nb2O6 Ceramics%锆掺杂对Ba0.5Sr0.5Nb2O6陶瓷铁电性能的影响

    刘玉杰; 隋万美; 苏龙; 张古品


    Lead-free ferroelectric ceramics Ba0.5Sr0.5Nb2O6 with and without Zr4+ dopant were prepared by a partial co-precipitation method,and their phase transformation,density and ferroelectric properties were investigated.Results indicate that with the cooperative effects of Zr4+ doping and silica sintering additive,all the ceramics can be well sintered and exhibit a dense and pure tungsten-bronze structureon the sintering behaviors,the coercive field Ec of ceramics,as well as the remanent polarization Pr and the spontaneous polarizationPs,decrease with increasing Zr4+ content.%采用部分共沉淀法制备了纯相及锆掺杂的Ba0.5Sr05Nb2O6无铅铁电陶瓷,研究了其相组成、致密度及铁电性能.结果表明,适量的掺杂锆,并引入SiO2为烧结助剂,可制备出致密、单一的钨青铜Ba0.5Sr0.5(ZrxNb1-x)2O6陶瓷.随着Zr4+掺杂量的增加,陶瓷的矫顽场Ec有所降低,剩余极化强度Pr和饱和极化强度Ps均减小.

  10. Determination of Sr and Ba partition coefficients between apatite and water from 5°C to 60°C: a potential new thermometer for aquatic paleoenvironments 1

    Balter, V.; Lécuyer, C.


    Apparent partition coefficients of Sr and Ba between calcium phosphate and water were measured experimentally for temperature ranging from 5°C to 60°C. Calcium phosphates were precipitated from an aqueous mixture of Na 2HPO 4 · 2H 2O (10 -2 M) and CaCl 2 · 2H 2O (10 -2 M). Spiked solutions of Sr or Ba were introduced into the CaCl 2 · 2H 2O solution at Sr/Ca and Ba/Ca ratios of 0.1. The experiment consisted in sampling the liquid and solid phases after 1, 6, 48, and 96 h of interaction. The amorphous calcium phosphate (ACP) precipitated early in the experiment was progressively replaced by hydroxylapatite (HAP), except at 5°C where brushite (di-calcium phosphate di-hydrate or DCPD) was formed. We observed that the crystallinity of the solid phase increased with time for a given temperature and increased with temperature for a given time of reaction. With the exception of the experiment at 5°C, yield (R%) and apparent partition coefficients (K a-wSr/Ca and K a-wBa/Ca) both decreased with increasing reaction time. After 96 h, R%, K a-wSr/Ca and K a-wBa/Ca were observed to be constant, suggesting that the solid phases were at steady-state with respect to the aqueous solutions. The thermodependence of Sr and Ba partitioning between apatite and water at low temperature could therefore be calculated: Log( Ka-wSr/Ca)=0.42±0.04(10 3T-1)-1.87±0.12( r2=0.94) Log( Ka-wBa/Ca)=1.96±0.06(10 3T-1)-7.19±0.20( r2=0.99) We also performed competition experiments between Sr and Ba. The thermodependence of the Sr/Ba partitioning between apatite and water was calculated after 96 h of reaction: Log( Ka-wSr/Ba)=-0.75±0.04(10 3T-1)+2.39±0.14( r2=0.97) This relationship reveals a discrimination of Ba in favor of Sr during their incorporation into HAP. Temperature trends deduced from the Ba/Ca of fish teeth recovered from the K/T boundary mimic those estimated from δ 18O(PO 4) measurements carried out on the same sample. Unless Sr, Ba and Ca contents of biogenic apatites are

  11. Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

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


    Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted “experimental” gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atoms from the blocks (MCh); thus, these phases belong to the layered materials with “natural multiple quantum wells”. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M-Ch bonds together with covalent M-Ch and Ch-Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge.

  12. Red, Green, and Blue Photoluminescence of Ba2SiO4:M (M = Eu3+, Eu2+, Sr2+ Nanophosphors

    Claudia Wickleder


    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.

  13. Enhancement of Sinter Densification of SrO-BaO-Nb2O5-SiO2 Tungsten-Bronze Glass-Ceramics by Doping with P2O5

    J.C.Chen; Y.Zhang


    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 ℃.

  14. Preparation and characterization of Ba{sub 1-x}Sr{sub x}TiO{sub 3} (x=0.1, 0.2) fibers by sol-gel process using catechol-complexed titanium isopropoxide

    Lu Qifang; Chen Dairong; Jiao Xiuling


    Sol-gel synthesis of Ba{sub 1-x}Sr{sub x}TiO{sub 3} (x=0.1, 0.2) ceramic fibers with a diameter of 6-10 {mu}m using catechol-complexed titanium isopropoxide, barium acetate hydrate and strontium acetate hydrate as precursors has been investigated. The green fibers and those sintered at different temperatures were characterized by thermogravimetry analysis (TGA), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. Microstructural development of barium strontium titanate (Ba{sub 1-x}Sr{sub x}TiO{sub 3}) ceramic fibers as a function of strontium concentrations was studied. X-ray diffraction indicated that the well-developed cubic phase of (Ba, Sr)TiO{sub 3} was crystallized at 1100 deg. C.

  15. High-temperature behavior of Sr-doped layered cobaltites Y (Ba{sub 1-x}Sr{sub x})Co{sub 2}O{sub 5.5}: phase stability and structural properties

    Aurelio, G; Sanchez, R D; Curiale, J [Consejo Nacional de Investigaciones CientIficas y Tecnicas, Centro Atomico Bariloche-Comision Nacional de EnergIa Atomica, Avenida Bustillo 9500, 8400 S C de Bariloche, RN (Argentina); Cuello, G J, E-mail: [Department of Applied Physics II, Ikerbasque, UPV/EHU, E-48080 Bilbao (Spain)


    In this paper we present a neutron diffraction in situ study of the thermal evolution and high-temperature structure of layered cobaltites Y (Ba, Sr)Co{sub 2}O{sub 5+{delta}.} Neutron thermodiffractograms and magnetic susceptibility measurements are reported in the temperature range 20 K {<=} T {<=} 570 K, as well as high-resolution neutron diffraction experiments at selected temperatures. Starting from the as-synthesized samples with {delta}{approx}0.5, we show that the room temperature phases remain stable up to 550 K, where they start losing oxygen and transform to a vacancy-disordered structure with tetragonal symmetry. Our results also show how the so-called '122' structure can be stabilized at high temperature (around 450 K) in a sample in which the addition of Sr at the Ba site had suppressed its formation. In addition, we present the structural and magnetic properties of the resulting samples with a new oxygen content {delta}{approx}0.25 in the temperature range 20 K {<=} T {<=} 300 K.

  16. The first-principle study of the electronic, optical and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) compounds

    Mubarak, A. A.


    The FP-LAPW method is utilized to investigate the elastic, optoelectronic and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) within the GGA. The calculated lattice constants and bulk modulus are found in agreement with previous studies. The present oxide-perovskite compounds are characterized as elastically stable and anisotropic. CaTiO3 and SrTiO3 are categorized as ductile compounds, whereas the BaTiO3 compound is in the critical region between ductile and brittle. The DOS and the band structure calculations reveal indirect (M-Γ) energy bandgap for the present compounds. The hydrostatic pressure increases the energy bandgap and the width of the valence band. The character of the band structure does not change due to this pressure. The optical parameters are calculated in different radiation regions. Beneficial optics applications are predicted as revealed from the optical spectra. The transport properties are applied as a function of the variable temperatures or carrier concentration. It is found that the compounds under study are classified as a p-type semiconductor. The majority charge carriers responsible for conduction in these calculated compounds are holes rather than electrons.

  17. Influence of bismuth on properties and microstructures of Sr0.5Ba0.5–Bi TiO3 thin films

    Tao Wenhong; Wang Yin; Fu Xinghua; Wei Qihong


    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.

  18. Dielectric relaxation and electrical conduction mechanism in A2HoSbO6 (A=Ba, Sr, Ca) Double Perovskite Ceramics: An impedance spectroscopic analysis

    Halder, Saswata; Dutta, Alo; Sinha, T. P.


    The AC electrical properties of polycrystalline double perovskite oxides A2HoSbO6 (A=Ba, Sr, Ca; AHS) synthesized by solid state reaction technique has been explored by using impedance spectroscopic studies. The Rietveld refinement of the room temperature X-ray diffraction data show that Ba2HoSbO6 (BHS) has cubic phase and Sr2HoSbO6 (SHS) and Ca2HoSbO6 (CHS) crystallize in monoclinic phase. The samples show significant frequency dispersion in their dielectric properties. The polydispersive nature of the relaxation mechanism is explained by the modified Cole-Cole model. The scaling behavior of dielectric loss indicate the temperature independence of the relaxation mechanism. The magnitude of the activation energy indicates that the hopping mechanism is responsible for carrier transport in AHS. The frequency dependent conductivity spectra follow the double power law. Impedance spectroscopic data presented in the Nyquist plot (Z" versus Z‧) are used to identify an equivalent circuit along with to know the grain, grain boundary and interface contributions. The constant phase element (CPE) is used to analyze the experimental response of BHS, SHS and CHS comprehending the contribution of different microstructural features to the conduction process. The temperature dependent electrical conductivity shows a semiconducting behavior.

  19. Thickness-dependent Electrical and Piezoelectric Properties of Lead-Free Ferroelectric Ba0.8Sr0.2TiO3 Thin Films

    D.A. Kiselev


    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.

  20. Effect of Na Content on the Physical Properties of Ba0.5Sr0.5TiO3 Powders

    Tassanee Tubchareon


    Full Text Available The different Na contents (0 ≤ Na ≤ 0.35, based on mole of NaOH of doped Ba0.5Sr0.5TiO3 (BST powders synthesized via sol-gel process were studied. The substitution of Na+ ions into a partial A-site of BST powders provided the reduction in vacancy defects as confirmed by electron paramagnetic resonance (EPR and UV-visible spectroscopy. Photoluminescence (PL spectra appeared in violet, blue, and green emissions. The phase structure, oxygen deficiency, and titanium deficiency of BST powders were further investigated as a function of Na content. X-ray diffraction (XRD result was found that low Na content (0 ≤ Na ≤ 0.15 exhibited the tetragonal structure, while it was transformed to the cubic phase when high Na content. Moreover, X-ray photoelectron spectroscopy (XPS result revealed that the partial oxidation of Ti3+ ions to Ti4+ ions was observed at Na content lower than 0.05 mole, while more addition of Na content resulted in the increasing of the oxygen and the titanium deficiency. Furthermore, the result indicated the oxygen deficiency significantly formed at the A-site of Sr atoms more than that of Ba atoms.

  1. Synthesis, structure, spectroscopic and transport properties of (Ba{sub 1{minus}x}Sr{sub x})NbO{sub 3}

    Garcia-Jaca, J.; Santos, J.; Insausti, M.; Arriortua, M.I.; Rojo, T. [Univ. del Pais Vasco, Bilbao (Spain)


    Oxides of the (Ba{sub 1{minus}x}Sr{sub x})NbO{sub 3} system (x = 0, 0.1, 0.4, 0.5, 0.7, and 1.0) have been synthesized by a solid-state reaction technique with zirconium metal. The oxides with x = 0, 0.1, 0.5, 0.7, and 1.0 present a simple cubic perovskite structure while a distorted perovskite is observed in the oxide with x = 0.4. Infrared spectra showed the presence of two absorption maxima in the case of the cubic perovskites and only one for the distorted perovskite. The observed vibration modes have been associated with stretching vibration modes of a [NbO{sub 6}] octahedral entity. The substitution of barium by strontium influences the transport properties specially in the case of the (Ba{sub 0.6}Sr{sub 0.4})NbO{sub 3} oxide.

  2. On synthesis of BaFe12O19, SrFe12O19, and PbFe12O19 hexagonal ferrite ceramics with multiferroid properties

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


    We analyze the possibility of obtaining M-type hexagonal ferrites of barium, strontium, and lead with multiferroid properties with the help of ceramic technology. Using the modified ceramic technology (especially pure initial raw materials, admixture of B2O3, and sintering in the oxygen atmosphere), we obtained for the first time the BaFe12O19 and SrFe12O19 samples with intense multiferroid properties at room temperature. At the same time, the employed technology does not make it possible to obtain PbFe12O19 samples exhibiting ferroelectricity. The multiferroid characteristics of experimental samples are compared with the characteristics of classical high-temperature multiferroic BiFeO3 and with the characteristics of BaFe12O19, SrFe12O19, and PbFe12O19 ferrite ceramics obtained in accordance with polymer precursor technology. We propose a mechanism explaining multiferroid properties of the hexagonal ferrite ceramic samples and note the importance of our results for applications.

  3. Preparation of Ba0.09Sr0.91TiO3/YBa2Cu3O7-x bilayers and investigation of their dielectric properties

    Jia, Jiqiang; Zhao, Gaoyang; Shi, Xiaoxue; Lei, Li


    YBa2Cu3O7-x (YBCO) films of 110 nm thickness were prepared on LaAlO3 (LAO) substrates via the sol-gel method. Subsequently, about 400 nm thick Ba0.09Sr0.91TiO3 (BST) films were epitaxially grown on the YBCO and LNO films surface; the BST films exhibited a strong c-axis orientation. The dielectric adjustability and relative dielectric constant was investigated in the range of 300-83 K. Results indicate that the tunability of the Ba0.09Sr0.91TiO3/YBa2Cu3O7-x (BST/YBCO) displayed an increase relative to c-axis-oriented BST on LaNiO3 (LNO). The tunability was further enhanced as the operating temperature decreased, yet the loss tangent (tanδ) decreased. The tunability and the tanδ at 100 kHz and 83 K were 58% and 0.029, respectively.

  4. Remarkable influence of heat treatment on the structural and superconducting properties of (Y1-x Prx )(BaSr)Cu3O6+z

    Bouallal, B.; Nafidi, A.; El Abidi, A.; El Kaaouachi, A.


    We report here on the preparation, X-ray diffraction (XRD), Seebeck effect, AC magnetic susceptibility, resistivity measurements and effect of heat treatments in the high Tc superconductor (Y1-x Prx)(BaSr)Cu3O6+z . Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. When x increase, the oxygen content (6+z) of the samples decrease slightly from 6.9 to 6.8 as determined by our iodometry measurements. The orthorhombicity = (b -a)/(b +a) decreases to zero at xt [O] = 0.6 and xt [AO] = 0.75. These indicate a structural phase transition from orthorhombic to tetragonal at xt. Whereas, Tc decrease to zero at xc [O] = 0.7 and xc [A,O] = 0.75. Therefore the [A,O] heat treatment increase xc. Note that decrease with Tc as foreseen. However, for a given x the [AO] heat treatment makes increase (Tc). Independently of heat treatment, a increase with x, whereas b decreased to its minimum at xt. For a given x Prx on the (Sr,Ba) site along c axis, chain oxygen ordering on (O4,O5) sites; increase in p and in-phase purity for the [AO] samples may qualitatively account for the observed data.

  5. Electrical Characteristics and Preparation of (Ba0.5Sr0.5)TiO3 Films by Spray Pyrolysis and Rapid Thermal Annealing

    Koo, Horng-Show; Chen, Mi; Ku, Hong-Kou; Kawai, Tomoji


    Functional films of (Ba0.5Sr0.5)TiO3 on Pt (1000 Å)/Ti (100 Å)/SiO2 (2000 Å)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba0.5Sr0.5)TiO3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400 °C and 57.7% weight loss up to 1000 °C. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750 °C for 5 min while leakage current density is 1.5× 10-6 A/cm2 in the film annealed at 550 °C for 5 min.

  6. 用激光诱导击穿光谱技术定量分析土壤中Ba和Sr%Quantitative Analysis of Ba and Sr in Soil Using Laser-Induced Breakdown Spectroscopy

    陈添兵; 姚明印; 刘木华; 雷泽剑; 彭秋梅; 徐媛; 张旭


    利用激光诱导击穿光谱(laser induced breakdown spectroscopy,LIBS)技术检测土壤标准样品中Ba和Sr的含量,用光纤光谱仪探测等离子体冷却过程中的发射谱线,选取BaⅡ455.41 nm和SrⅠ460.73 nm特征谱线为分析线.为了减小误差,采用Lorenizian函数进行光谱轮廓曲线拟合对数据预处理,提取光谱净强度值.选择多元素谱线强度和作为内标,根据分析线与内标线强度值之比建立定标曲线,Ba和Sr含量与其强度比的线性系数分别达到0.9900和0.9906,采用这种强度比定标法对Ba和Sr的含量进行反演,测定Ba和Sr含量值与标准值的相对偏差分别为5.7%和5.1%.%Laser induced breakdown spectroscopy (LIBS) was applied to measure barium and strontium elements in soil The emission spectrum was emitted as the plasma was cooling off, which was collected and analyzed by fiber spectrometer. Spectral lines of barium(BaII line at 455.41 nm) and strontium(Srl line at 460. 73 ran) were separately used for the determining. In order to reduce the error, fitting of the spectra by using Lorcnizian function was used, the datum was preprocessed and the net intensity value of the spectra was collected. A signal intensity in the proper range of the characteristic spectrum was chosen as the interior label. A calibration curve was drawn according to the ratio between the value of the analytical line and the interior scaling line. The correlation coefficient between the content and the intensity ratio of Ba and Sr were up to 0.990 0 and 0.990 6. The content of Ba and Sr was inversed by means of the intensity scaling method . As a result, the relative deviations between the content values and the standard values of Ba and Sr were 5. 7% and 5.1% respectively.

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

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


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

  8. Ethylene production by ODHE in catalytically modified Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) membrane reactors.

    Lobera, M Pilar; Escolástico, Sonia; Garcia-Fayos, Julio; Serra, José M


    Process intensification by the integration of membranes and high-temperature reactors offers several advantages with regard to conventional process schemes, that is, energy saving, safe operation, reduced plant/unit size, and higher process performance, for example, higher productivity, catalytic activity, selectivity, or stability. We present the study of oxidative dehydrogenation of ethane at 850 °C on a catalytic membrane reactor based on a mixed ionic-electronic conducting membrane. The surface of the membrane made of Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) has been activated by using different porous catalytic layers based on perovskites. The layer was deposited by screen printing, and the porosity and thickness was studied for the catalyst composition. The different catalyst formulations are based on partial substitution of A- and B-site atoms of doped strontium ferrite/cobaltites (A(0.6)Sr(0.4)Co(0.5)Fe(0.5)O(3-δ) and Ba(0.6)Sr(0.4)BO(3-δ)) and were synthesized by an ethylenediaminetetraacetic acid-citrate complexation route. The use of a disk-shaped membrane in the reactor enabled the direct contact of gaseous oxygen and hydrocarbons to be avoided, and thus, the ethylene content increased. High ethylene yields (up to ≈81 %) were obtained by using a catalytic coating based on Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ), which included macropores produced by the addition of graphite platelets into the screen-printing ink. The promising catalytic results obtained with this catalytically modified membrane reactor are attributed to the combination of 1) the high activity, as a result of the high temperature and oxygen species diffusing through the membrane; 2) the control of oxygen dosing and the low concentration of molecules in the gas phase; and 3) suitable fluid dynamics, which enables appropriate feed contact with the membrane and the rapid removal of products.

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

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


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

  10. Structural, dielectric and magnetic properties of Ba{sub 3}SrLn{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) filled tungsten bronze ceramics

    Chen, Wang [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Yang, Wen Zhi [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Ningbo Branch of China Academy of Ordnance Science, Ningbo, 315103 (China); Liu, Xiao Qiang [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China); Chen, Xiang Ming, E-mail: [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027 (China)


    Structural, dielectric and magnetic properties have been investigated for Ba{sub 3}SrLn{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) ceramics. The single phase tetragonal filled tungsten bronze structure in space group P4/mbm is obtained for Ba{sub 3}SrLa{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30}, while such tungsten bronze major phase is determined together with minor amount of secondary phases in Ba{sub 3}SrNd{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} and Ba{sub 3}SrSm{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30}. The saturated magnetic hysteresis loops with enhanced M{sub r} are obtained in the present ceramics at room temperature comparing to the Ba{sub 4}Ln{sub 2}Fe{sub 2}Nb{sub 8}O{sub 30} (Ln = La, Nd, Sm) ceramics. Meanwhile, the typical relaxor behaviors are determined: a broad dielectric peak with strong frequency dispersion and the peak temperature following well with the Vogel–Fulcher relationship. - Highlights: • The tetragonal filled tungsten bronze structure in space group P4/mbm is obtained. • The typical relaxor behaviors are determined. • The magnetic hysteresis loops with enhanced Mr are obtained at room temperature.

  11. 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

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


    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.

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

    Dutta, Alo, E-mail: [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)


    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.

  13. Structural and optical analysis on europium doped AZrO{sub 3} (A=Ba, Ca, Sr) phosphor for display devices application

    Dubey, Vikas, E-mail: [Department of Physics, Bhilai Institute of Technology Raipur, 493661 (India); Tiwari, Neha [Department of Physics, Govt. Model Science College, Jabalpur (India)


    Behavior displayed by europium doped AZrO{sub 3} phosphor which was synthesized by solid state reaction method. For synthesis of BaZrO{sub 3}, SrZrO{sub 3} and CaZrO{sub 3} phosphor with fixed concentration of europium ion was calcination at 1000°C and sintered at 1300°C following intermediate grinding. Synthesized sample was characterized by X-ray diffraction analysis and crystallite sized was calculated by Scherer’s formula. From PL spectra of prepared phosphors shows intense emission centred at 612nm (red emission) with high intensity for SrZrO{sub 3}:Eu{sup 3+}. For europium doped BaZrO{sub 3} and CaZrO{sub 3} (613nm) phosphor shows less intense PL spectra as compared to SrZrO{sub 3}:Eu{sup 3+}. The strong emission peak of AZrO{sub 3}:Eu{sup 3+} phosphor is due to forced electric dipole transition of {sup 5}D{sub 0} to {sup 7}F{sub 2} centered at 612 and 613nm. It is characteristic red emission for europium ion. The excitation spectra of AZrO{sub 3}:Eu{sup 3+} phosphor mainly consists of the charge transfer and (CTB) of Eu{sup 3+} located in 200–350 nm centred at 254nm. The present phosphors can act as single host for red light emission in display devices. The CIE coordinates were calculated by Spectrophotometric method using the spectral energy distribution of the AZrO{sub 3}:Eu{sup 3+} sample.

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

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


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

  15. Temperature-controlled down-conversion luminescence behavior of Eu(3)(+) -doped transparent MF2 (M = Ba, Ca, Sr) glass ceramics.

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


    Eu(3)(+) -doped transparent glass ceramics containing MF2 (M = Ba, Ca, Sr) nanocrystals were fabricated using a melt-quenching method, and the resulting structures were studied using X-ray diffraction. Levels (5) D1 and (5) D0 of Eu(3)(+) ions were verified as thermally coupled levels using the fluorescence intensity ratio method. The fluorescence intensity ratios, optical temperature sensitivity and thermal quenching ratios of the transparent glass ceramics were studied as a function of temperature. With an increase in temperature, the relative sensitivity (SR ) decreased sharply at first, then slowly increased, before finally decreasing. The minimum SR values of GCBaF2 (GCB), GCCaF2 (GCC) and GCSrF2 (GCS) were 2.8 × 10(-4) , 0.8 × 10(-4) and 1.9 × 10(-)(4)  K(-1) at 360, 269 and 319 K, respectively. Glass ceramics with an intense emission intensity can be used to convert the measured spectrum into temperature and may have an important role in temperature detectors. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Commensurate and Incommensurate Phases in the System A4A'Ir 2O 9( A=Sr, Ba; A'=Cu, Zn)

    Battle, Peter D.; Blake, Graeme R.; Sloan, Jeremy; Vente, Jaap F.


    The crystal structure of Sr 4CuIr 2O 9is very sensitive to the conditions of synthesis. Prolonged heating of a commensurate trigonal sample prepared at 1120°C leads to the adoption of an incommensurate structure which can be regarded as a composite of two substructures having common unit cell parameters aand bbut different parameters c1and c2. No detectable change in chemical composition accompanies the structural transition, nor do the magnetic properties of the sample change significantly. The structure of the commensurate form has been determined from neutron powder diffraction data collected at 4.5 K (space group P321, a=9.68540(3) Å, c=8.04726(6) Å). Ir 2O 9octahedral dimers and CuO 6trigonal prisms alternate in chains parallel to z, with the Sr cations located between the chains; the Cu 2+cations are disordered within the prisms. The incommensurate form has been studied by X-ray diffraction and electron microscopy ( a=9.7020(6) Å, c1=4.0069(5) Å, c2=2.6993(4) Å). The relationship between the commensurate and incommensurate unit cells is discussed ( c˜2 c1˜3 c2). No commensurate Ba 4A'Ir 2O 9phases could be prepared, but incommensurate samples having A'=Cu, Zn showed behavior similar to that of Sr 4CuIr 2O 9.

  17. Thermally assisted interlayer magnetic coupling through Ba{sub 0.05}Sr{sub 0.95}TiO{sub 3} barriers

    Carreira, Santiago J.; Steren, Laura B. [Centro Atómico Constituyentes, San Martín, Buenos Aires 1650 (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Avilés Félix, Luis; Alejandro, Gabriela [Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Centro Atómico Bariloche, Bariloche, Rio Negro 8400 (Argentina); Sirena, Martín [Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Autonoma de Buenos Aires C1425FQB (Argentina); Centro Atómico Bariloche, Bariloche, Rio Negro 8400 (Argentina); Instituto Balseiro-CNEA & Univ. Nac. de Cuyo, Bariloche, Rio Negro 8400 (Argentina)


    We report on the interlayer exchange coupling across insulating barriers observed on Ni{sub 80}Fe{sub 20}/Ba{sub 0.05}Sr{sub 0.95}TiO{sub 3}/La{sub 0.66}Sr{sub 0.33}MnO{sub 3} (Py/BST{sub 0.05}/LSMO) trilayers. The coupling mechanism has been analyzed in terms of the barrier thickness, samples' substrate, and temperature. We examined the effect of MgO (MGO) and SrTiO{sub 3} (STO) (001) single-crystalline substrates on the magnetic coupling and also on the magnetic anisotropies of the samples in order to get a deeper understanding of the magnetism of the structures. We measured a weak coupling mediated by spin-dependent tunneling phenomena whose sign and strength depend on barrier thickness and substrate. An antiferromagnetic (AF) exchange prevails for most of the samples and smoothly increases with the barrier thicknesses as a consequence of the screening effects of the BST{sub 0.05}. The coupling monotonically increases with temperature in all the samples and this behavior is attributed to thermally assisted mechanisms. The magnetic anisotropy of both magnetic components has a cubic symmetry that in the case of permalloy is added to a small uniaxial component.

  18. Cretaceous high-pressure metamorphism and low pressure overprint in the Sistan Suture Zone, eastern Iran: Additional temperature estimates for eclogites, geological significance of U-Pb zircon ages and Rb-Sr constraints on the timing of exhumation

    Kurzawa, Timon; Bröcker, Michael; Fotoohi Rad, Gholamreza; Berndt, Jasper; Lisker, Frank


    The Sistan Suture Zone, eastern Iran, includes blocks and lenses of eclogite-, blueschist- and/or epidote amphibolite-facies rocks that provide an excellent opportunity to examine the exhumation history of oceanic HP/LT rocks and their retrograde derivatives. Zr-in-rutile thermometry of eclogites corroborates previous interpretations suggesting metamorphic temperatures of ca. 550-600 °C during the HP stage in the Sistan area. Flat HREE distribution patterns and Ti-in-zircon temperatures of ca. 500-600 °C document that zircon in eclogite is of metamorphic origin. REE patterns of zircon from felsic meta-igneous rocks do not allow to distinguish between a magmatic or metamorphic origin, but relatively low temperatures indicated by Ti-in-zircon thermometry (ca. 500-600 °C) and the close similarity of zircon (U-Pb) and white mica (Rb-Sr, Ar-Ar) ages favor a metamorphic zircon origin. Previously published isotopic ages of the felsic rocks cannot unambiguously be linked to the eclogite- and/or blueschist-facies P-T conditions due to the absence of unequivocal mineralogical and petrological evidence. Instead, these rocks may record contemporaneous metamorphic processes that took place at a different depth within the subduction complex, or may indicate active ridge subduction and/or melt formation in the subduction zone at relatively low pressures. Biotite-based internal Rb-Sr isochrons of newly dated epidote amphibolite and biotite-albite gneisses indicate ages of ca. 74-80 Ma, either dating fluid-infiltration-induced formation of biotite during relatively fast uplift, or the time of final passage through the effective biotite closure temperature. Rb-Sr ages of phengite from both an epidote amphibolite and a biotite-albite gneiss yield ages that correspond to the HP/LT stage. This outcome, combined with textural evidence for derivation from eclogitic precursors documents that white mica ages of some strongly overprinted Sistan rocks are compromised by inheritance and do

  19. Synthesis and characterization of the double perovskite BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} like cathode for solid oxide fuel cells; Sintesis y caracterizacion de la doble perovskita BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5} como catodo para celdas SOFC

    Alvarado F, J.; Avalos R, L.; Viramontes G, G. [Universidad Michoacana de San Nicolas de Hidalgo, Facultad de Ingenieria Electrica, Santiago Tapia 403, Morelia 58030, Michoacan (Mexico); Reyes R, A. [Centro de Investigacion en Materiales Avanzados, Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31109, Chihuahua (Mexico)


    Have been synthesized via sol-gel method and characterized by X-ray diffraction, electrical conductivity and thermal expansion coefficient, new material composites BaSrCoFe{sub 1{sub x}}Ni{sub x}O{sub 5.5} (double perovskite type) with the addition of Ni in solid solution Ni{sub x} (x = 0.025, 0.05, 0.075, 0.1 and 0.2), as alternative cathodes for solid oxide fuel cells of intermediate temperature (Sofc-It). X-ray diffraction confirmed the formation of the tetragonal structure perovskite phase BaSrCoFe{sub 1}-{sub x}Ni{sub x}O{sub 5.5}, with the presence of small peaks identified in 2{theta} values below 30 degrees as BaCO{sub 3} and CoFe{sub 2}O{sub 4}. The electrical conductivity increases with the temperature between 350-470 degrees C and then decreases due to the loss of oxygen in the net, which causes differences in conductivity. Semiconductor behavior was obtained in all compositions. Thermal expansion coefficient determination, showed a linear dependence inversely proportional to the concentration of Ni. Our results of electrical conductivity and thermal expansion coefficient, reach to the conclusion that the cathodes between 0.1 and 0.2 Ni, have the greatest possibility for application in Sofc-It. (Author)

  20. 溶胶凝胶法制备( Ba0.3Sr0.7)(Zn1/3Nb2/3)O3微波介质陶瓷薄膜%FABRICATION OF ( Ba0.3Sr0.7 ) ( Zn1/3Nb2/3 ) O3 MICROWAVE DIELECTRIC CERAMIC THIN FILMS BY SOL-GEL

    杨龙; 王锐; 石锋


    Inexpensive metal nitrates and barium acetate instead of metal alkoxides were used as raw materials, and high quality sol was obtained by utilization of acetylacetone and citric acid. Microwave dielectric ceramic (Ba0 3Sr0 7) (Zn1/3Nb2/3) O3 thin film was fabricated on Pt/Ti/SiO2/Si substrates by spin -coating, then annealed in the environment of oxygen. X - ray diffraction ( XRD) , Fourier transform infrared spectrometer (FTIR) , and scanning electron microscope ( SEM) were used to study the microstructures and morphological properties of the thin film. The results revealed that the main phases of the thin film were (Ba0 3Sr0 7) (Zn1/3Nb2/3) O3 with less second phase. The thin film was compact in surface and well crystallized without crack.%以柠檬酸和乙酰丙酮为络合剂和稳定剂,金属硝酸盐为起始原料制备溶胶.采用甩胶旋涂法在Pt/Ti/SiO2/Si基片上制膜并在O2环境下退火,重复3次制得所需薄膜.采用XRD,FTIR和SEM分析薄膜的结晶性,微观结构和表面形貌.结果表明:制备的薄膜主晶相为(Ba0.3Sr0.7)(Zn1/3Nb2/3)O3,伴有少量的第二相,同时,薄膜表面致密,无气孔,结晶良好,结晶颗粒均匀分布于薄膜的表面.

  1. Synthesis and characterization of nano-sized BaSr1–SO4 (0 ≤ ≤ 1) solid solution by a simple surfactant-free aqueous solution route

    Yu-Feng Li; Jia-Hu Ouyang; Yu Zhou; Xue-Song Liang; Ji-Yong Zhong


    A facile aqueous solution route has been employed to synthesize BaSr1–SO4 (0 4 ≤ 1) solid solution nanocrystals at room temperature without using any surfactants or templates. The as-synthesized products were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), scanning electron microscopy (SEM), and differential scanning calorimetry–thermogravimetry (DSC–TG). The BaSr1–SO4 solid solution nanocrystals exhibit an orthorhombic structure and an ellipsoidal-shaped morphology with an average size of 80–100 nm. The lattice parameters of BaSr1–SO4 solid solution crystals increase with increasing x value. However, they are not strictly coincident with the Vegard’s law, which indicates that the as-obtained products are non-ideal solid solutions. The BaSr1–SO4 solid solution nanocrystals have an excellent thermal stability from ambient temperature to 1300°C with a structural transition from orthorhombic to cubic phase at about 1111°C.

  2. Mathematical model of Boltzmann’s sigmoidal equation applicable to the set-up of the RF-magnetron co-sputtering in thin films deposition of Ba$_x$Sr$_{1−x}$TiO$_3$



    In this work, we present the stoichiometric behaviour of Ba$^{2+}$ and Sr$^{2+}$ when they are deposited to make asolid solution of barium strontium titanate. Bax Sr$_{1−x}$ TiO$_3$ (BST) thin films of nanometric order on a quartz substrate were obtained by means of in-situ RF-magnetron co-sputtering at 495$^{\\circ}$C temperature, applying a total power of 120 W divided into intervals of 15 W that was distributed between two magnetron sputtering cathodes containing targets of BaTiO$_3$ and SrTiO$_3$, as follows: 0–120, 15–105, 30–90, 45–75, 60–60, 75–45, 90–30, 105–15 and 120–0 W. Boltzmann’s sigmoidalmodified equation (Boltzmann’s profile) is proposed to explain the behaviour and the deposition ratio Ba/Sr of the BSTas a function of the RF-magnetron power. The Boltzmann’s profile proposal shows concordance with experimental data ofdeposits of BST on substrates of nichrome under the same experimental conditions, showing differences in the ratio Ba/Srof the BST due to the influence of the substrate.

  3. High K capacitors and OFET gate dielectrics from self-assembled BaTiO{sub 3} and (Ba,Sr)TiO{sub 3} nanocrystals in the superparaelectric limit

    Huang, Limin; O' Brien, Stephen [Department of Chemistry, City University of New York, City College of New York 1131 Marshak Building, New York, NY 10031 (United States); Jia, Zhang; Kymissis, Ioannis [Department of Electrical Engineering, Columbia University New York, NY (United States)


    Nanodielectrics is an emerging field with applications in capacitors, gate dielectrics, energy storage, alternatives to Li-ion batteries, and frequency modulation in communications devices. Self-assembly of high k dielectric nanoparticles is a highly attractive means to produce nanostructured films with improved performance - namely dielectric tunability, low leakage, and low loss - as a function of size, composition, and structure. One of the major challenges is conversion of the nanoparticle building block into a reliable thin film device at conditions consistent with integrated device manufacturing or plastic electronics. Here, the development of BaTiO{sub 3} and (Ba,Sr)TiO{sub 3} superparaelectric uniform nanocrystal (8-12 nm) films prepared at room temperature by evaporative driven assembly with no annealing step is reported. Thin film inorganic and polymer composite capacitors show dielectric constants in the tunable range of 10-30, dependent on composition, and are confirmed to be superparaelectric. Organic thin film transistor (TFT) devices on flexible substrates demonstrate the readiness of nanoparticle-assembled films as gate dielectrics in device fabrication. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  4. Preparation and Comparison of the Photoelectronic Properties of Sr2Nb207 and Ba0.5Sr0.5Nb2O6.


    eV, but a flat-band potential of 0.1 V vs SCE at a pH of 13.3. Hence, the gain of utilizing a larger portion of the solar spectrum obtained from a tetragonally distorted perovskite , ( 3) whereas Sr2Nb2O7 was reported to be orthorhombic (4). - cell with a quartz window, and a current amplifier as nreviously described (8). The electrolyte, 0.2 M sodium acetate (pH 8.3), was purged of

  5. Structural and Optical properties of poly-crystalline BaTiO3 and SrTiO3 prepared via solid state route

    Jarabana, Kanaka M.; Mishra, Ashutosh; Bisen, Supriya


    Polycrystalline BaTiO3 (BTO) and SrTiO3 (STO) were synthesized by solid state route method and properties of made polycrystalline were characterized by X-Ray diffraction (XRD), Raman Spectroscopy & FTIR Spectroscopy. XRD analysis shows that samples are crystalline in nature. In Raman Spectroscopy measurement, the experiment has been done with the help of JOBIN-YOVN HORIBA LABRAM HR800 single monochromator, which is coupled with a “peltier cooled” charge coupled device (CCD). Raman Spectroscopy at low temperature measurement shows the phase transition above & below the curie temperature in samples. Fourier transform Infrared spectroscopy was used to determine the Ti-O bond length position.

  6. Magnetocaloric effect in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe0.92Al0.0812O22

    Wenfei Xu


    Full Text Available Magnetocaloric effect is investigated in multiferroic Ba0.5Sr1.5Zn2(Fe0.92Al0.0812O22 ceramic with Y-type hexagonal system. Three magnetic transitions, from alternating longitudinal conical to mixed conical at ∼240 K, to ferrimagnetic at ∼297 K, further to paramagnetic at ∼702 K, are unambiguously determined. Furthermore, obvious MCE is shown, and the maximum values of the magnetic entropy change and relative cooling power are evaluated to be 1.53 JKg−1K−1 and 280 JKg−1 for a field change of 7 T, respectively. In addition, inverse MCE is also observed, which might be associated with the first-order magnetic phase transition between two incommensurate longitudinal conical phases.

  7. Electric field modulated conduction mechanism in Al/BaTiO3/La0.67Sr0.33MnO3 heterostructures

    Zheng, Dongxing


    Mediating a metastable state is a promising way to achieve a giant modulation of physical properties in artificial heterostructures. A metastable state La0.67Sr0.33MnO3 (LSMO) layer suffering tensile strain was grown on MgO substrates. Incorporating with the ferroelectric BaTiO3 (BTO) layer, an accumulation or depletion state controlled by electric fields can be formed at the BTO/LSMO interface, which drives a switching of the conduction mechanism between space charge limited conduction and Poole-Frenkel emission, corresponding to the low and high resistance states. Our results lighten an effective way for electric-field modulated resistance states in multiferroic magnetoelectric devices.

  8. Thin Film Ba(x)Sr(1-x)TiO3 Ku- and K-Band Phase Shifters Grown on MgO Substrates

    VanKeuls, F. W.; Mueller, C. H.; Miranda, F. A.; Romanofsky, R. R.; Horwitz, J. S.; Chang, W.; Kim, W. J.


    We report measurements of gold circuits fabricated on four Ba(x)Sr(1-x)TiO3 films doped with 1% Mn grown on MgO substrates by laser ablation. Low frequency measurements of epsilon(sub r) and tan(delta) on interdigital capacitors are compared with high frequency measurements of phase shift and insertion loss on coupled microstrip phase shifters done on the same films. The variation in temperature of both high and low frequency device parameters is compared. Annealed and unannealed films are compared. Room temperature figures of merit of phase shift per insertion loss of up to 58.4 C/dB at 18 GHz and 400 V dc bias were measured.

  9. Chemical bond properties and Mossbauer spectroscopy in (La1-xMx)2CuO4 (M=Ba, Sr)


    By using the average band-gap model, the chemical bond properties of (La1-x Mx)2CuO4(M=Ba, Sr) were calculated . The calculated covalencies for Cu(O and La(O bond in the compounds are 0.3 and 0.03 respectively. M?ssbauer isomer shifts of 57Fe doped in La2CuO4 and 119Sn doped in La2CuO4 were calculated by using the chemical surrounding factor defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe and 119Sn doped La2CuO4.

  10. Ac conductivity and relaxation mechanism in Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3}

    Singh, A.K.; Barik, Subrat K. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302 (India); Choudhary, R.N.P. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302 (India)], E-mail:; Mahapatra, P.K. [Department of Physics, Vidyasagar University, Midnapore 721 102 (India)


    The ac conductivity and relaxation mechanism in Ba{sub 0.9}Sr{sub 0.1}TiO{sub 3} ceramics have been investigated systematically. A high-temperature solid-state reaction technique was used to synthesize the compound. The formation of the compound was checked by an X-ray diffraction (XRD) technique. The dielectric permittivity and the loss tangent of the sample were measured in a frequency range from 1 kHz to 1 MHz at different temperatures (30-500 deg. C). A study on dielectric properties reveals the electrical relaxation phenomenon occurs in the material. The activation energy was calculated from the temperature variation of dc conductivity. Studies of frequency and temperature dependence of ac conductivity of the compound suggest that conduction process in the material is thermally activated.

  11. Novel Ba0.5Sr0.5Fe0.8Zn0.2O3-δmembranes for POM

    Hui Xia Luo; Ling Hui Yu; Xin Zhi Chen; Hai Hui Wang; Jürgen Caro


    A novel cobalt-free perovskite based on Ba0.5Sr0.5Fe0.8Zn0.2O3δ(BSFZ)were prepared by EDTA-citric acid method.The lattice constants of the BSFZ perovskite were characterized by in situ high-temperature X-ray diffraction(HTXRD).The thermal expansion coefficient of BSFZ is 10.5×10-6 K-1,which is lower than that of cobalt-based perovskite materials.The BSFZ membrane was also used to construct reactors for the partial oxidation of methane(POM)to syngas.Results show that the BSFZ membrane can be operated for the POM reaction for more than 100 h without any fractures.The CO selectivity of 97% is obtained.The steady oxygen permeation flux reaches around 2.5 mL/min cm2 during POM reaction.

  12. Improvement of critical current density in thallium-based (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) superconductors

    Ren, Z. F.; Wang, C. A.; Wang, J. H.; Miller, D. J.; Goretta, K. C.


    Epitaxial (Tl,Bi)Sr(1.6)Ba(0.4)Ca2Cu3O(x) ((Tl,Bi)-1223) thin films on (100) single crystal LaAlO3 substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field cooled magnetization, and transport critical current density (J(sub c)) were measured. The zero-resistance temperature was 105-111 K. J(sub c) at 77 K and zero field was greater than 2 x 10(exp 6) A/sq cm. The films exhibited good flux pinning properties.

  13. Study of the domain structure evolution in single crystals of relaxor ferroelectric Sr0.61Ba0.39Nb2O6:Ce1

    Shur, V. Ya.; Pelegov, D. V.; Shikhova, V. A.; Kuznetsov, D. K.; Nikolaeva, E. V.; Rumyantsev, E. L.; Yakutova, O. V.; Granzow, T.


    Optical visualization with simultaneous recording of the switching current was used for studying of domain structure evolution in single crystals relaxor ferroelectric strontium barium niobate (Sr0.61Ba0.39Nb2O6) doped by cerium (0.22 mol %) (SBN61:Ce). It was shown that the maze domain structures can be observed during polarization reversal due to local change of refractive index induced by formation of microscale domains with charged domain walls. It was proposed, that optical inhomogeneities occur in the switching regions, while the optical uniform areas correspond to regions where the switching either has not started yet or has already completed. The original mathematical treatment of the obtained images and switching currents has been used for quantitative characterization of the polarization reversal process.

  14. Luminescence in Ba2 Sr2 Al2 O7 :RE (RE = Tb(3) (+) ,Eu(3) (+) and Dy(3) (+) ) novel aluminate phosphors.

    Pardhi, S A; Panse, V R; Dhoble, S J


    The luminescence of novel rare earth (Tb(3) (+) , Eu(3) (+) and Dy(3) (+) )-activated Ba2 Sr2 Al2 O7 phosphors for solid-state lighting is presented. The aluminate phosphors were synthesized using a one-step combustion method. X-Ray diffraction, scanning electron microscopy and photoluminescence characterizations were performed to understand the mechanism of excitation and the corresponding emission in the as-prepared phosphor, as characterized the phase purity and microstructure. Improvements in the luminescence properties of the phosphors with rare earth concentration were observed. The phosphor hue could be tuned from blue, green and red by proper selection of rare earth ions in typical concentrations. Effective absorption in the near-ultraviolet region was observed, which makes the phosphor a potential candidate for ultraviolet light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Annealing of RuO 2 and Ru Bottom Electrodes and Its Effects on the Electrical Properties of (Ba,Sr)TiO 3 Thin Films

    Ahn, Joon-Hyung; Choi, Won-Youl; Lee, Won-Jae; Kim, Ho-Gi


    Crystalline structures and surface morphologies of annealed RuO2 and Ru thin films were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The annealing was performed in oxygen and argon ambient and high vacuum in the temperature range of 400 800° C. In oxygen ambient annealing, the surface morphology was drastically changed due to the evaporation of ruthenium dioxides in the form of RuO3 and RuO4. Annealed RuO2 thin film in vacuum was reduced to the Ru metal phase. The actual variation of RuO2 bottom electrodes during the deposition of (Ba,Sr)TiO3 (BST) thin films and the effects of the thermal stability of bottom electrodes on electrical properties of BST thin films deposited on RuO2/SiO2/Si were also investigated.

  16. Induced Ti magnetization at La0.7Sr0.3MnO3 and BaTiO3 interfaces

    Yaohua Liu


    Full Text Available In artificial multiferroics hybrids consisting of ferromagnetic La0.7Sr0.3MnO3 (LSMO and ferroelectric BaTiO3 epitaxial layers, net Ti moments are found from polarized resonant soft x-ray reflectivity and absorption. The Ti dichroic reflectivity follows the Mn signal during the magnetization reversal, indicating exchange coupling between the Ti and Mn ions. However, the Ti dichroic reflectivity shows stronger temperature dependence than the Mn dichroic signal. Besides a reduced ferromagnetic exchange coupling in the interfacial LSMO layer, this may also be attributed to a weak Ti-Mn exchange coupling that is insufficient to overcome the thermal energy at elevated temperatures.

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

    Smith, Graham; Wermuth, Urs D


    (4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H2O)6](C6H7AsNO3)·4H2O, (I), catena-poly[[[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O']-[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O

  18. Improved photoluminescence of vertically aligned ZnO nanorods grown on BaSrTiO{sub 3} by pulsed laser deposition

    Varanasi, C V [University of Dayton Research Institute, Dayton, OH 45469 (United States); Leedy, K D; Tomich, D H [Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433 (United States); Subramanyam, G [University of Dayton, Dayton, OH 45469 (United States); Look, D C, E-mail: [Semiconductor Research Center, Wright State University, Dayton, OH 45435 (United States)


    ZnO nanorods were grown on a variety of substrates such as Si, SiO{sub 2}/Si and sapphire in a large-area pulsed laser deposition chamber designed for sensor device fabrication. Processing conditions were optimized to grow ZnO nanorods with or without seed layers. Au, Cr and BaSrTiO{sub 3} (BST) seed layers were investigated to compare their effects on the diameter and orientation of ZnO nanorods. ZnO nanorods were observed to align better when grown on sapphire, Cr or BST seed layers as compared to Au or Si layers. The highest quality nanorods were those grown on BST seed layers, as shown by 4 K photoluminescence donor-bound-exciton linewidths of only 0.5 meV.

  19. Flexoelectric Induced Caloric Effect in Truncated Pyramid Shaped Ba0.67Sr0.33TiO3 Ferroelectric Material

    Patel, Satyanarayan; Chauhan, Aditya; Madhar, Niyaz Ahamad; Ilahi, Bouraoui; Vaish, Rahul


    Solid state refrigeration based on ferroelectric materials can potentially be competing in not-in-kind refrigeration technology. However, their functionality is currently limited to Curie temperatures. Through this article, authors have attempted to describe an unexplored component of the stress-driven caloric effect, obtainable beyond the Curie point. The phenomenon, termed as the flexocaloric effect (FCE), relies on inhomogeneous straining of the crystal lattice to induce polarization in centrosymmetric crystals (flexoelectricity). For this study, a truncated pyramid geometry was selected, and the dependence of sample height on caloric capacity was studied. A peak temperature change of 1.75 K (313 K) was estimated for Ba0.67Sr0.33TiO3 (BST) ceramics employing a truncated pyramid configuration.

  20. A comparative study based on the first principles calculations of ATiO3 ( A = Ba, Ca, Pb and Sr) perovskite structure

    Kamruzzaman, M.; Helal, M. A.; Ara, I. E.; Farid Ul Islam, A. K. M.; Rahaman, M. M.


    Structural, electronic, elastic, thermodynamic, vibrational and optical properties of the cubic phase of ATiO3 ( A = Ba, Ca, Pb and Sr) crystals have been carried out based on the density functional theory (DFT). The calculated equilibrium lattice parameters, band structures, elastic constants and the elastic moduli of ATiO3 are in good agreement with the theoretical and experimental results. The ferroelectric phenomenon of the crystals has been analyzed based on the nature of their phonon spectra. The phonon frequencies and the Born effective charges have been calculated to elucidate the ferroelectric instability of the cubic phase of ATiO3 by calculating the interatomic forces for several small displacements consistent with the symmetry of modes.

  1. Microstructure, hysteresis and microwave absorption analysis of Ba{sub (1-x)}Sr{sub x}Fe{sub 12}O{sub 19} ferrite

    Narang, S. Bindra [Department of Electronics Technology, Guru Nanak Dev University, Amritsar, Punjab (India)], E-mail:; Singh, Charanjeet [Department of Electronics and Communication Engineering, Amritsar College of Engineering and Technology, Mananwala, Amritsar, Punjab (India); Bai Yang [School of Materials Science and Engineering, University of Science and Technology Beijing (China); Hudiara, I.S. [KC College of Engg. and IT, Nawanshahar, Punjab (India)


    M-type hexagonal ferrite series, Ba{sub (1-x)}Sr{sub x}Fe{sub 12}O{sub 19} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0), has been synthesized by conventional ceramic method. Hysteresis parameters have been investigated at an applied field of 10 kOe and absorption has been studied at X-band as a function of thickness, substitution and frequency. Microstructure and X-ray diffraction confirmed hexagonal structure of ferrite. The substitution causes profound increase in absorption, coercivity and magnetization. The magnetic parameters have been characterized by taking into account microstructure and preferential site occupancy. Curie temperature decreases with substitution due to the formation of spin canting structure.

  2. Influence of strain on an epitaxial ferroelectric (Ba0.50Sr0.50)TiO3 nanodot under different electrical boundary conditions

    Bin-Omran, S.


    A first-principles-derived effective Hamiltonian approach is used to reveal the temperature-versus-misfit strain phase diagram of an epitaxial (Ba0.50Sr0.50)TiO3 dot under different electrical boundary conditions. The results indicate that the electrical polarization and toroidal moment are highly sensitive to the applied strain and/or electrical boundary conditions, resulting in a wide variety of phases that are not found in a free-standing BST dot and in bulk. The calculations indicate that within a narrow range of surface charge screening an intermediate phase in which the polarization and toroidal moment coexist. The dependences of the electrical polarization, toroidal moment and dielectric permittivity on the misfit strain and electrical boundary conditions at room temperature are also investigated and compared with the available theoretical predictions and experimental measurements.

  3. Processing and characterization of screen printing Ba$_{0.5}$Sr$_{0.5}$Co$_{0.8}$Fe$_{0.2}$O$_{3−\\delta}$ inks



    Oxygen-selective membranes based on thin layers of barium–strontium–cobalt ferrite Ba$_{0.5}Sr$_{0.5}$Co$_{0.8}$Fe$_{0.2}O$_{3−\\delta}$ (BSCF) perovskite oxide were manufactured. Five BSCF inks prepared with differentcarriers and milling treatments were rheologically characterized, screen printed on three different porous alumina substrates and sintered at 1050 and 1150$^{\\circ}$C. The resulting membranes were characterized. The data collected on the rheological properties of inks (flow curves, thixotropic behaviour, linear viscoelasticity), their processability by screen printing, and the quality of the layers obtained after sintering represents an important starting point to set up the next research activities.

  4. Thermoelectric properties of Sr0.61Ba0.39Nb2O6- ceramics in different oxygen-reduction conditions

    李宜; 刘剑; 王春雷; 苏文斌; 祝元虎; 李吉超; 梅良模


    The thermoelectric properties of Sr0.61Ba0.39Nb2O6−δ ceramics, reduced in different conditions, are investigated in the temperature range from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping in the low temperature range, the Fermi glass behavior in the middle temperature range, and the Anderson localized behavior in the high temperature range. The thermal conductivity presents a plateau at high-temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increase of the degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value is obtained to be∼0.19 at 1073 K in the heaviest oxygen reduced sample.

  5. Microwave dielectric and optical properties of amorphous and crystalline Ba0.5Sr0.5TiO3 thin films

    Goud, J. Pundareekam; Joseph, Andrews; Ramakanth, S.; Naidu, Kuna Lakshun; Raju, K. C. James


    The thin films of composition Ba0.5Sr0.5TiO3 (BST5) were deposited by Pulsed Laser Deposition technique on amorphous fused silica substrates at room temperature (RT) and at 700°C. The film deposited at RT is amorphous while the other crystallized in cubic structure. The refractive index (n) and optical band gap (Eg) extracted from transmission spectra in the 190 -2500 nm range. Microwave dielectric properties were investigated using the Split Post Dielectric Resonators (SPDR) technique at spot frequencies of 10GHz and 20GHz. The experimental results show that thin films deposited at high temperature (700°C) shows very high dielectric constant for both 10GHz and 20 GHz. These high dielectric constant films can be used in a wide range of applications such as capacitors, non-volatile high speed random access memories, and electro-optic devices.

  6. Strain profile and polarization enhancement in Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films

    Amir, F.Z. [Physics Department, St John' s University, 8000 Utopia Pkwy, Jamaica, NY 11439 (United States); Donner, W. [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Aspelmeyer, M. [Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Noheda, B. [Department of Chemical Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Xi, X.X. [Physics Department, College of Science and Technology, Temple University, 1900 N.13th Street, Philadelphia, PA 19122 (United States); Moss, S.C. [Department of Physics, University of Houston, 617 Science and Research Building 1, Houston, Texas 77204-5005 (United States)


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

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

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


    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.

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

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


    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 .

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

    Du, Peng; Yu, Jae Su, E-mail:


    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.

  10. Effect of Divalent Ions (A = Ca, Ba and Sr Substitution in La-A-Mn-O Manganite on Structural, Magnetic and Electrical Transport Properties

    K. P. Lim


    Full Text Available Problem statement: Microstructure of the grain will influence the properties of a polycrystalline manganites when different dopant is introduced. In this work, an effort had been made to investigate the influence of Ca, Ba and Sr substitution in La site. Approach: Polycrystalline manganites compound of La0.67A0.33MnO3 where A = Ba, Sr and Ca had been prepared via conventional solid-state reaction method. The structure, microstructure, magnetic and electrical properties had been investigated using XRD, SEM, VSM and four-point probe techniques. Results: XRD spectrums showed that LBMO and LCMO were in single-phase orthorhombic structure whereas LSMO was rhombohedral structure. Scanning electron micrographs showed that LSMO had smaller average grain size as compared to LBMO. However, for LCMO, there was no clear grain boundary that can be observed and all the grains were well connected. The difference in the microstructure image might be due to the variance A-site cation that differs in grain growth. The Curie temperature, Tc of LBMO and LSMO was 343.0 and 363.5 K, respectively. But the Tc for LCMO was lower then 300 K. The Tp for LCMO was 215 K while it was near or above 300K for LBMO and LSMO. All samples showed extrinsic Magnetoresistance (MR effect. Higher MR was observed well below Tc or Tp where MR value increased monotonically with the decrease of temperature. This was associated with the different grain and grain boundary formation when different cation was substituted. LCMO displayed the highest low-field MR value (-15.82% at 0.2 T, 90 K and high-field MR (-25.60% at 1 T, 300 K. Conclusion: Hence, electrical and magnetic transition temperature (Tp and Tc were affected by the average A-site cation radius.

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

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


    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.

  12. Enhancing spin state phase separation by strontium addition in the Y (Ba{sub 1-x}Sr{sub x})Co{sub 2}O{sub 5.5} layered cobaltite

    Aurelio, G; Curiale, J; Sanchez, R D [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche-Comision Nacional de Energia Atomica, Avenida Bustillo 9500, 8400 San Carlos de Bariloche, RN (Argentina); Cuello, G J, E-mail: [Department of Applied Physics II, Ikerbasque, UPV/EHU, E-48080 Bilbao (Spain)


    In this paper we present a neutron diffraction study of the effects of replacing Ba with smaller Sr cations in the layered cobaltite YBaCo{sub 2}O{sub 5+{delta}} for {delta}{approx}0.5. Neutron thermodiffractograms are reported in the temperature range 20 K<=T<=300 K, as well as high-resolution neutron diffraction experiments at selected temperatures. The systematic refinement of the series of samples with Sr substituting at the Ba site permits the understanding of the complex magnetic behaviour of this system, and reinforces a two-phase scenario for the parent compound. We have found that Sr addition destabilizes the ferrimagnetic spin state ordered phase, as well as the '122' order characteristic of cobaltites with delta = 0.5, favouring instead a tetragonal and less ordered structure.

  13. Crystal structures of the four new quaternary copper(I)-selenides A0.5CuZrSe3 and ACuYSe3(A=Sr, Ba)

    Maier, Stefan; Prakash, Jai; Berthebaud, David; Perez, Olivier; Bobev, Svilen; Gascoin, Franck


    The four new quaternary copper(I)-selenides, Sr0.5CuZrSe3 (a=3.8386(7), b=14.197(2), c=10.1577(17) Å), Ba0.5CuZrSe3 (a=3.8386(7), b=14.196(2), c=10.1577(17) Å), SrCuYSe3 (a=10.620(2), b=4.1000(8), c=13.540(3) Å) and BaCuYSe3 (a=4.1800(7), b=13.940(2), c=10.6200(17) Å) were synthesized by high-temperature solid state reactions and their crystal structures were determined using single-crystal X-ray diffraction. A0.5CuZrSe3 (A= Sr, Ba) and BaCuYSe3 crystallize in the KCuZrS3 structure type (Cmcm), while SrCuYSe3 is isostructural to Eu2CuS3 (Pnma). All compounds form layered structures in which the charge of the - ∞ 2[CuZrSe3 and 2 - ∞ 2[CuYSe3 ] layers as well as the site occupancy of the A cations depend on the transition metal. Combining the alkaline earth metals Sr and Ba with tetravalent Zr leads to the formation of cation vacancies between the - ∞ 2[CuZrSe3 ] layers and structure type as well as symmetry are determined by the ratio between the cation and transition metal ionic radii r(A2+)/r(M3+/4+).

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

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


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

  15. Polarization-based perturbations to thermopower and electronic conductivity in highly conductive tungsten bronze structured (Sr,Ba)Nb2O6: Relaxors vs normal ferroelectrics

    Bock, Jonathan A.; Trolier-McKinstry, Susan; Mahan, Gerald D.; Randall, Clive A.


    Electrical conductivity, thermopower, and lattice strain were investigated in the tetragonal tungsten bronze structured (Srx,Ba1-x)Nb2O6-δ system for 0.7>x>0.4 with large values of δ. These materials show attractive thermoelectric characteristics, especially in single-crystal form. Here, the Sr/Ba ratio was changed in order to vary the material between a normal ferroelectric with long-range polarization to relaxor behavior with short-range order and dynamic polarization. The influence of this on the electrical conduction mechanisms was then investigated. The temperature dependence of both the thermopower and differential activation energy for conduction suggests that the electronic conduction is controlled by an impurity band with a mobility edge separating localized and delocalized states. Conduction is controlled via hopping at low temperatures, and as temperature rises electrons are activated above the mobility edge, resulting in a large increase in electrical conductivity. For relaxor ferroelectric-based compositions, when dynamic short-range order polarization is present in the system, trends in the differential activation energy and thermopower show deviations from this conduction mechanism. The results are consistent with the polarization acting as a source of disorder that affects the location of the mobility edge and, therefore, the activation energy for conduction.

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

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


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

  17. Holocene millennium-scale climatic variations as recorded by Rb and Sr concentrations for the MGS1 stratigraphical segment of Milanggouwan section in the Salawusu River Valley of Southeast Mu Us Desert%萨拉乌苏河流域MGS1 Rb和Sr记录的全新世千年尺度气候变化

    牛东风; 李保生; 魏建国; 温小浩; 舒培仙; 司月君


    萨拉乌苏河流域米浪沟湾剖面全新世地层MGS1层段记录了11个由风成砂与河流相或湖沼相构成的沉积旋回。对该层段63个样品的Rb、Sr数据进行了分析,结果显示由沙丘砂至上覆河湖相Rb和Sr含量由低增高,而Rb/Sr比值的分布则显示出与Rb和Sr含量变化相反的趋势,三者与平均粒径Mz(f)的相关系数都在0.43以上。研究表明MGS1至少经历了11次冷干和11次暖湿的气候波动。米浪沟湾剖面MGS1记录的千年尺度气候波动既是对东亚季风环流演变历史的体现,同时也是对全球气候与环境变化的响应。%The MGS1 stratigraphical segment of Milanggouwan section is located in the Salawusu River Valley of southeast Mu Us Desert. The segment documents 11 sedimentary cycles consisting of aeolian facies and fluvial facies or lacustrine-swamp facies. Totally 63 samples were analyzed for rubidium (Rb) and strontium (Sr) concentrations. The results show that Rb and Sr concentrations increase as the sediments vary from aeolian facies to lacustrine-swamp facies, however, variation of the Rb/Sr ratios shows reversed trends in contrast to that of Rb and Sr concentrations. The line correlation coefficients of Rb and Sr concentrations and Rb/Sr ratios with mean grain size are all above 0.43. All these indicate that the MGS1 stratigraphic segment at least records 11 cold-dry and 11 warm-humid millennium-scale climatic oscillations, which represent the evolution history of East Asian monsoon circulation and show good correspondence to global climatic and environment variations.

  18. Transport properties and photo electrochemical characterization of oxygen-deficient ASnO 3- δ (A=Ca, Sr and Ba)

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


    The deficient stannate BaSnO 3- δ, prepared at 980 °C in sealed tube, crystallizes in an ideal perovskite structure. The oxide exhibits a blue color, the bandgap is found to be 2.65 eV and the transition is directly allowed. The non-stoichiometry could not be measured, indicating no appreciable oxygen deficiency. Nevertheless, the transport properties were found to change markedly with the heat treatment. BaSnO 3- δ behaves as degenerate SC with a conductivity σ300 K (=1.63 Ω -1 cm -1) and where the level Ef drops above mobility edge to delocalized states. The electric balance leads to a simultaneous reduction of Sn 4+ inducing n-type behavior. The thermal variation of the thermopower indicates an electron mobility μ300 K (=0.013 cm 2 V -1 s -1) thermally activated. The metal-insulating transition is considered of Anderson type due to the random potential to oxygen vacancies. A predominant variable range hopping is predicted from the non-linearity of Ln σ versus T-1 plot. The capacitance measurement ( C-2- V), measured in KOH media, shows a linear behavior from which a flat band potential Vfb (=-0.67 VSCE) and a density ND (=7.59×10 20 cm -3) are determined. The deficient stannates CaSnO 3 and SrSnO 3 are reported for a comparative purpose. The decrease of Eg is ascribed to the increase of the conduction band width when going from Ba to Ca.

  19. Transport properties and photo electrochemical characterization of oxygen-deficient ASnO{sub 3-{delta} }(A=Ca, Sr and Ba)

    Zidi, N. [Laboratory of Storage and Valorization of Renewable Energies (USTHB, Faculty of Chemistry) BP 32, Algiers 16111 (Algeria); Omeiri, S. [Laboratory of Storage and Valorization of Renewable Energies (USTHB, Faculty of Chemistry) BP 32, Algiers 16111 (Algeria); Centre of Research in Physical and Chemical Analysis (C.R.A.P.C.), BP 248, RP 16004 Algiers (Algeria); Hadjarab, B. [Laboratory of Solid Solutions (USTHB, Faculty of Physics), BP 32, Algiers 16111 (Algeria); Bouguelia, A.; Akroun, A. [Laboratory of Storage and Valorization of Renewable Energies (USTHB, Faculty of Chemistry) BP 32, Algiers 16111 (Algeria); Trari, M., E-mail: [Laboratory of Storage and Valorization of Renewable Energies (USTHB, Faculty of Chemistry) BP 32, Algiers 16111 (Algeria)


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

  20. Interlayer states arising from anionic electrons in the honeycomb-lattice-based compounds A e AlSi (A e =Ca , Sr, Ba)

    Lu, Yangfan; Tada, Tomofumi; Toda, Yoshitake; Ueda, Shigenori; Wu, Jiazhen; Li, Jiang; Horiba, Koji; Kumigashira, Hiroshi; Zhang, Yaoqing; Hosono, Hideo


    We report that the interlayer states common to the compounds A e AlSi (A e =Ca , Sr, Ba) arise from F-center-like electrons arrayed in periodic cavities. The SrPtSb-type intermetallic phases exhibit electrons localized to columns of the trigonal bipyramidal A e3A l2 cages running perpendicular to the honeycomb layers. Ab initio calculations in combination with hard/soft x-ray photoemission spectroscopic measurements reveal that these features correspond to the anionic electrons that hybridize with apical Al 3 pz orbitals from the honeycomb layers above and below. Extra bands with a significant dispersion along the kz direction therefore contribute to the Fermi level in contrast to the apparent two-dimensional connectivity of the bonding in the compounds, and completely account for the presence of interlayer states. Our study demonstrates how the cage centers may serve as electronically important crystallographic sites, and extend the anionic electron concept into honeycomb lattice compounds.

  1. Synergetic pinning centres in BaZrO3-doped YBa2Cu3O7-x films induced by SrTiO3 nano-layers

    Crisan, A.; Dang, V. S.; Mikheenko, P.; Ionescu, A. M.; Ivan, I.; Miu, L.


    We report on the enhancement of critical current density (J c) and the unusual behaviour of its dependence on field orientation in YBa2Cu3O7‑x (YBCO) nanostructured films by a combination of substrate decoration with Ag nano-dots, of the incorporation of BaZrO3 (BZO) nano-particles and nano-rods, and of multilayer architecture (a thin SrTiO3 layer separating two 1.5 μm-thick YBCO layers). SrTiO3 insulating layers were 15, 30 or 45 nm thick. The highest improvement of J c in applied magnetic fields along the c-axis and smaller than 1 T occurs in the bi-layer with 30 nm-thick STO, but the influence of STO thickness is small. Our thick nanostructured films show significant improvement of J c in the magnetic field along the ab-plane direction. The presence of BZO nano-rods, ab-plane defects and nano particles of BZO and Y2O3 was observed in transmission electron microscopy (TEM) images of the film. The peculiarities of artificial pinning centres revealed in the TEM images of the nanostructured films are used to explain an unusual split of the peak in the J c dependence on the magnetic field along the ab-plane of YBCO. Effective pinning potentials in high magnetic fields have rather high values for such thick films.

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

    Oehler, Florian; Ebbinghaus, Stefan G.


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

  3. Structural characterisation of BaTiO{sub 3} thin films deposited on SrRuO{sub 3}/YSZ buffered silicon substrates and silicon microcantilevers

    Colder, H.; Jorel, C., E-mail:; Méchin, L. [GREYC, UMR 6072, CNRS, ENSICAEN, UCBN, 6 bd du Maréchal Juin, 14050 Caen Cedex (France); Domengès, B. [LAMIPS, CRISMAT-NXP Semiconductors-Presto Engineering laboratory, CNRS-UMR 6508, ENSICAEN, UCBN, 2 rue de la Girafe, 14 000 Caen (France); Marie, P.; Boisserie, M. [CIMAP, UMR 6252, CNRS, ENSICAEN, UCBN, CEA, 6 bd du Maréchal Juin, 14050 Caen Cedex (France); Guillon, S.; Nicu, L. [LAAS, CNRS, Univ de Toulouse, 7 avenue du Colonel Roche, 31400 Toulouse (France); Galdi, A. [GREYC, UMR 6072, CNRS, ENSICAEN, UCBN, 6 bd du Maréchal Juin, 14050 Caen Cedex (France); Department of Industrial Engineering, CNR-SPIN Salerno, Università di Salerno, 84084 Fisciano, Salerno (Italy)


    We report on the progress towards an all epitaxial oxide layer technology on silicon substrates for epitaxial piezoelectric microelectromechanical systems. (101)-oriented epitaxial tetragonal BaTiO{sub 3} (BTO) thin films were deposited at two different oxygen pressures, 5.10{sup −2} mbar and 5.10{sup −3} mbar, on SrRuO{sub 3}/Yttria-stabilized zirconia (YSZ) buffered silicon substrates by pulsed laser deposition. The YSZ layer full (001) orientation allowed the further growth of a fully (110)-oriented conductive SrRuO{sub 3} electrode as shown by X-ray diffraction. The tetragonal structure of the BTO films, which is a prerequisite for the piezoelectric effect, was identified by Raman spectroscopy. In the BTO film deposited at 5.10{sup −2} mbar strain was mostly localized inside the BTO grains whereas at 5.10{sup −3} mbar, it was localized at the grain boundaries. The BTO/SRO/YSZ layers were finally deposited on Si microcantilevers at an O{sub 2} pressure of 5.10{sup −3} mbar. The strain level was low enough to evaluate the BTO Young modulus. Transmission electron microscopy (TEM) was used to investigate the epitaxial quality of the layers and their epitaxial relationship on plain silicon wafers as well as on released microcantilevers, thanks to Focused-Ion-Beam TEM lamella preparation.

  4. Ba0.5Sr0.5Co0.8Fe0.2O3–δ–La0.6Sr0.4Co0.8Fe0.2O3–δ Composite Cathode for Solid Oxide Fuel Cell

    Mosiałek M.


    Full Text Available Composite cathodes contain Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ were tested in different configuration for achieving cathode of area specific resistance lower than Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ cathodes. Electrodes were screen printed on samaria-doped ceria electrolyte half-discs and tested in the three electrode setup by the electrochemical impedance spectroscopy. Microstructure was observed by scanning electron microscopy. The lowest area specific resistance 0.46 and 2.77 Ω cm−2 at 700 °C and 600 °C respectively revealed composite cathode contain Ba0.5Sr0.5Co0.8Fe0.2O3–δ and La0.6Sr0.4Co0.8Fe0.2O3–δ in 1:1 weight ratio. The area specific resistance of this cathode is characterized by the lowest activation energy among tested cathodes.

  5. 添加BaO-B2O3-SiO2玻璃对Sr0.3BaO0.7Nb2O6陶瓷烧结和介电性能的影响%Influences of adding BaO-B2O3-SiO2 glass on sintering and dielectric properties of Sr0.3Ba0.7Nb2O6 ceramics

    职利; 陈国华; 刘俊涛; 刘心宇; 周昌荣; 江民红


    以分析纯的BaCO3,SrCO3,Nb2O5,H38O3和SiO2粉末为原料,采用传统的固相合成法制备添加50BaO-4082O3-10SiO2玻璃(物质的量比)的Sro.3Ba0.7Nb2O6(即SBN70)陶瓷.采用X线衍射仪(XRD)、扫描电子显微镜(SEM)和阻抗分析仪研究添加玻璃对SBN70陶瓷的烧结和介电性能的影响.研究结果表明;随着玻璃含量的增加,陶瓷样品的相对密度先增大后减小;当玻璃含量为5%(质量分数,下同)时,样品的密度达到最大值;添加玻璃降低了陶瓷的烧结温度,于1 250℃时添加5%玻璃的SBN70陶瓷已烧结致密,陶瓷的平均晶粒尺寸约2 μm,晶粒呈短柱状结构;当玻璃含量增大时,晶粒尺寸呈增大趋势;当玻璃添加量≤5%时,样品仍为单相四方钨青铜结构;当含量为10%时,出现了第二相SrB4O7;随着玻璃含量的增加,SBN70衍射峰的位置先移向低角度后移向高角度,而居里温度T0逐渐降低,从195℃下降到25℃左右;随玻璃含量的增加,最大介电常数εmax呈先减小后增大的变化趋势,而介电损耗tan δ则随玻璃含量的增大而减小;添加玻璃的SBN70陶瓷具有弥散相变特性,其弥散系数γ随添加玻璃含量的增加而增大.%Sr0.3Ba0.7Nb2O6 (abbreviated as SBN70) ceramics doped with 50BaO40B2O3-10SiO2 glass were fabricated by solid-state synthesis method using the analytic grade powders including BaCO3, SrCO3, Nb2O5, H3BO3 and SiO2 as raw materials. Effects of glass addition on sintering and microstructure as well as dielectric properties of SBN70 ceramics were investigated by means of X-ray diffraction (XRD), scanning electric microscope (SEM) and dielectric property measurements. The results show that the relative density of the samples firstly increases and then slightly decreases with the increase of glass content and the highest density achieved for the ceramic sample with 5% glass. Adding glass decreases the sintering temperature of SBN70 ceramics. The ceramic samples with 5% glass

  6. Microstructural and thermal properties of pure BaFe{sub 12}O{sub 19} and Sr doped barium ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) synthesized by auto combustion method

    Taufeeq, Saba, E-mail:; Parveen, Azra; Agrawal, Shraddha; Azam, Ameer [Department of Applied Physics, Z.H. College of Engineering & Technology, Aligarh Muslim University, Aligarh 202002 (India)


    Nanoparticles (NPs) of Pure BaFe{sub 12}O{sub 19} and Strontium doped Barium Ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) have been successfully synthesized by Auto combustion method using citric acid as a chelating agent and calcined at 450°C for 3 hrs and 850°C for 4 hrs. Microstructural studies were carried by XRD and SEM techniques. Structural studies suggest that the crystal system remains hexagonal even with the doping of Strontium. The XRD analysis confirms the formation of the structures in the nanometer regime and the peaks are the evidence of the crystalline phase. The SEM images shows the morphology of surface of the samples. The thermal property studied by TGA shows the weight loss which is with varying the temperature and weight loss also varies with Sr doping. The TGA analysis exhibits the loss of weight at different temperatures.

  7. Behaviour of the Sm-Nd and Rb-Sr systems of the mafic-ultramafic layered sequence from Ribeirao dos Motas (Archaean), meridional craton Sao Francisco: evidences of mantle source enrichment and isotopic fractionation; Comportamento dos sistemas Sm-Nd e Rb-Sr da sequencia acamadada mafico-ultramafico Ribeirao dos Motas (Arqueano), craton Sao Francisco Meridional: evidencias de enriquecimento mantelico e fracionamento isotopico

    Carneiro, Mauricio Antonio; Carvalho Junior, Irneu Mendes de; Oliveira, Arildo Henrique de [Ouro Preto Univ., (UFOP), MG (Brazil). Dept. de Geologia]. E-mail:; Teixeira, Wilson [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Pimentel, Marcio Martins [Brasilia Univ., DF (Brazil). Inst. de Geociencias. Lab. de Geocronologia


    The Ribeirao dos Motas layered sequence (SARM) crops out in the southern part of the Sao Francisco Craton, Brazil. This sequence comprises phaneritic meta ultramafic and metamafic rocks, which, although slightly deformed and metamorphosed, retain primary igneous layers. Porphyritic rocks with idiomorphic pyroxene crystals and heteradcumulate and adcumulate textures are also present. Eighteen isotopic analyses were performed in the SARM, comprising rocks with primary (relict) textures, as well as rocks in amphibolite facies and retro-metamorphosed to green-schist facies. Seven samples yield a Sm/Nd isochron age of 2.79 +- 0.30 Ga (MSWD=1.2 e epsilon {sub Ndt}=+0.48), constraining the accretion time of the SARM rocks. The positive epsilon {sub Ndt} value coupled with the Rb/Sr evidence is consistent with mantle source relatively enriched in Nd and Sr isotopes. Nevertheless, some SARM samples display isotopic fractionation and disturbance, which can be ascribed to the following processes or their combinations: a) mobilization of the incompatible elements due to regional high grade metamorphism; b) isotopic changes during upper amphibolite facies overprint; c) isotopic resetting by low-grade fluids associated to the Claudio Shear zone, which is located nearby the SARM. (author)

  8. The crystal structure and magnetic properties of Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22}

    Cho, Kwang Lae; Rhee, Chan Hyuk; Kim, Chul Sung, E-mail: [Department of Physics, Kookmin University, Seoul 136-702 (Korea, Republic of)


    We have synthesized the Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22} samples (x = 0.1, 0.2, 0.3, 0.4, 0.5) by the solid-state reaction method and investigated their crystalline and magnetic properties by X-ray diffractometer (XRD), Mössbauer spectrometer, vibrating sample magnetometer, and network analyzer. XRD patterns show that all samples are rhombohedral with space group R-3m. The lattice constants a{sub 0} and c{sub 0} decrease with Sr substitution due to smaller ion radius of Sr{sup 2+} (1.27 Å) than that of Ba{sup 2+} (1.43 Å). The Mössbauer spectroscopy measurements show that the relative area ratios of Fe ion were maintained constant regardless of the Sr concentration. However, average magnetic hyperfine field slightly increased with the Sr concentration. This observation agrees with the fact that the saturation magnetization (M{sub s}) linearly increases due to the increasing super-exchange interaction, originated from the difference in the ionic radius between Ba{sup 2+} and Sr{sup 2+}. To investigate its properties at high frequency range, all samples were sintered at 1100 °C, and complex permeability and permittivity were measured by network analyzer between 100 MHz and 4 GHz. For x below 0.3, the initial permeability at 100 MHz increases, at higher values of x, its value decreases. Our study shows that magnetic properties of Sr{sup 2+} substitution for Ba{sup 2+} in Y-type hexaferrite as well as low magnetic loss less than 0.1 in 1 GHz band, indicating the potential application of Ba{sub 2−x}Sr{sub x}Co{sub 2}Fe{sub 12}O{sub 22} samples for RF and antenna devices in ultra high frequency band.

  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)

    Jena, Paramananda [Department of Physics, Pondicherry University, Pondicherry 605014 (India); Gupta, Santosh K., E-mail: [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: [Department of Physics, Pondicherry University, Pondicherry 605014 (India); Venkateswarlu, M. [R & D Amara Raja Batteries Ltd., Karakambadi 517501, AP (India)


    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. Microstructure and microwave dielectric properties of Ba6-3xSm8+2xTi18Os4ceramics with various BaxSr1-xTiO3 additions

    ZHOU Lingling; ZHOU Hongqing; SHAO Hui; ZHU Haikui


    The Ba6-3xSm8+2xTi18O54 (x=2/3) microwave dielectric ceramics were prepared by traditional solid sate reaction technique.The experiment was based on the Ba6-3xSm8+2xTi18O54 (BST) microwave dielectric ceramics doped with a certain amount of Bi2O3,then the effects of BaxSr1-xTiO3 additives on the structure and microwave dielectric properties of Ba6-3xSm8+2xTi18O54 ceramics were investigated using X-ray diffraction and scanning electron microscopy.In this study,the small amount substitution of Sr for Ba was effective for the microwave dielectric properties of BST,especially the τf could be tuned to near zero.The result showed that the BST possessed excellent dielectric properties when the addition of Bi2O3 and BaxSr1-xTiO3 was 1 wt.% respectively:εr=79.6,Qf=10789 GHz,τf=-1.5 ppm/℃.

  11. Studies on structural and thermo-chemical behavior of MFe{sub 12}O{sub 19}(s) (M = Sr, Ba and Pb) prepared by citrate-nitrate gel combustion method

    Chaudhury, Satyajeet [Fuel Chemistry Division, RC and I Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)], E-mail:; Rakshit, S.K.; Parida, S.C.; Singh, Ziley [Product Development Section, RC and I Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Mudher, K.D. Singh; Venugopal, V. [Fuel Chemistry Division, RC and I Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)


    The citrate-nitrate gel combustion route was used to prepare SrFe{sub 12}O{sub 19}(s), BaFe{sub 12}O{sub 19}(s) and PbFe{sub 12}O{sub 19}(s). The compounds were characterized by Rietveld profile analysis of the X-ray powder diffraction data. The thermal expansion coefficients of MFe{sub 12}O{sub 19} (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 MFe{sub 12}O{sub 19} (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 BaFe{sub 12}O{sub 19}(s) and PbFe{sub 12}O{sub 19}(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.

  12. X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba{sub 2−x}Sr{sub x}MgTeO{sub 6} (0 ⩽ x ⩽ 2)

    Tamraoui, Y. [Equipe Ingénierie et environnement, Laboratoire de Chimie Appliquée et Environnement, Univ. Hassan 1" e" r, 26000 (Morocco); Manoun, Bouchaib, E-mail: [Equipe Ingénierie et environnement, Laboratoire de Chimie Appliquée et Environnement, Univ. Hassan 1" e" r, 26000 (Morocco); Mirinioui, F.; Haloui, R. [Equipe Ingénierie et environnement, Laboratoire de Chimie Appliquée et Environnement, Univ. Hassan 1" e" r, 26000 (Morocco); Lazor, P. [Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala (Sweden)


    Highlights: • Synthesis and characterization of new double perovskites Ba{sub 2−x}Sr{sub x}MgTeO{sub 6} (0 ⩽ x ⩽ 2). • High temperature studies of Ba{sub 2−x}Sr{sub x}MgTeO{sub 6} double perovskite using Raman spectroscopy. • Temperature and compositions induced phase transitions in these materials. • Structural determination/refinement of these compounds as a function of composition. - Abstract: X-ray diffraction and Raman spectroscopy studies of Sr-substituted double perovskite compounds Ba{sub 2−x}Sr{sub x}MgTeO{sub 6} with (0 ⩽ x ⩽ 2) were carried out. At room temperature, both Rietveld refinements and Raman studies showed that two phase transitions occurred as a function of increased strontium content; from cubic to tetragonal structure, at x ∼ 1.5(1), and from the tetragonal to monoclinic structure at x ∼ 1.9(1). Furthermore, upon temperature increase up to 430 °C, the monoclinic and tetragonal perovskites manifest transformations to the tetragonal and cubic symmetries, and to the cubic symmetry, respectively. For this series, the transitions show considerable changes in the compositional and temperature dependencies of the modes, the spectral positions of which exhibit a linear behavior. The symmetry transformations between the encountered three crystal systems is revealed by significant changes of the slopes.

  13. Calculations of S$_{2n}$ and $\\delta<$r$^{2}>$ on long series of Kr, Rb, Sr and Xe, Cs, Ba isotopes

    Epherre-Rey-Campagnolle, Marcelle; Campi, X


    The density dependent Hartree-Fock method has been used to study the variation of the two neutron separation energies (S/sub 2n/) and of the mean square charge radii ( delta (r/sup 2/)). Correlations between anomalous S/sub 2n/, delta (r/sup 2/) and deformations have been analyzed. (5 refs).

  14. Structural study of Sr{sub 0.3}Ba{sub 0.7}Nb{sub 2}O{sub 6} and La{sub 0.030}Sr{sub 0.255}Ba{sub 0.700}Nb{sub 2}O{sub 6} ceramic systems

    Luna-Lopez, J.A., E-mail: [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, Ensenada, Baja California 22800 (Mexico); Portelles, J. [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, Ensenada, Baja California 22800 (Mexico); Facultad de Fisica-IMRE, Universidad de La Habana, Vedado, La Habana 10400 (Cuba); Raymond, O. [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, Ensenada, Baja California 22800 (Mexico); Siqueiros, J.M., E-mail: [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, Ensenada, Baja California 22800 (Mexico)


    Sr{sub 0.3}Ba{sub 0.7}Nb{sub 2}O{sub 6} (SBN) and La{sub 0.030}Sr{sub 0.255}Ba{sub 0.700}Nb{sub 2}O{sub 6} (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 deg. C) and later sintered both at 1400 deg. C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A{sub 1} site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.

  15. Comparison of stripe modulations in La1.875Ba0.125CuO4 and La1.48Nd0.4Sr0.12CuO4

    Wilkins, S. B.; Dean, M. P. M.; Fink, Jörg; Hücker, Markus; Geck, J.; Soltwisch, V.; Schierle, E.; Weschke, E.; Gu, G.; Uchida, S.; Ichikawa, N.; Tranquada, J. M.; Hill, J. P.


    We report combined soft and hard x-ray scattering studies of the electronic and lattice modulations associated with stripe order in La1.875Ba0.125CuO4 and La1.48Nd0.4Sr0.12CuO4. We find that the amplitude of both the electronic modulation of the hole density and the strain modulation of the lattice is significantly larger in La1.875Ba0.125CuO4 than in La1.48Nd0.4Sr0.12CuO4 and is also better correlated. The in-plane correlation lengths are isotropic in each case; for La1.875Ba0.125CuO4, ξhole=255±5 Å, whereas for La1.48Nd0.4Sr0.12CuO4, ξhole=111±7 Å. We find that the modulations are temperature independent in La1.875Ba0.125CuO4 in the low temperature tetragonal phase. In contrast, in La1.48Nd0.4Sr0.12CuO4, the amplitude grows smoothly from zero, beginning 13 K below the LTT phase transition. We speculate that the reduced average tilt angle in La1.875Ba0.125CuO4 results in reduced charge localization and incoherent pinning, leading to the longer correlation length and enhanced periodic modulation amplitude.

  16. Stripe order, depinning, and fluctuations in La1.875 Ba0.125 CuO4 and La1.875 Ba0.075 Sr0.050 CuO4

    Fujita, M.; Goka, H.; Yamada, K.; Tranquada, J. M.; Regnault, L. P.


    We present a neutron scattering study of stripe correlations measured on a single crystal of La1.875Ba0.125CuO4 . Within the low-temperature-tetragonal (LTT) phase, superlattice peaks indicative of spin and charge stripe order are observed below 50K . For excitation energies ℏω⩽12meV , we have characterized the magnetic excitations that emerge from the incommensurate magnetic superlattice peaks. In the ordered state, these excitations are similar to spin waves. Following these excitations as a function of temperature, we find that there is relatively little change in the Q -integrated dynamical spin susceptibility for ℏω˜10meV as stripe order disappears and then as the structure transforms from LTT to the low-temperature-orthorhombic phase. The Q -integrated signal at lower energies changes more dramatically through these transitions, as it must in a transformation from an ordered to a disordered state. We argue that the continuous evolution through the transitions provides direct evidence that the incommensurate spin excitations in the disordered state are an indicator of dynamical charge stripes. An interesting feature of the thermal evolution is a variation in the incommensurability of the magnetic scattering. Similar behavior is observed in measurements on a single crystal of La1.875Ba0.075Sr0.050CuO4 ; maps of the scattered intensity in a region centered on the antiferromagnetic wave vector and measured at ℏω=4meV are well reproduced by a model of disordered stripes with a temperature-dependent mixture of stripe spacings. We discuss the relevance of our results to understanding the magnetic excitations in cuprate superconductors.

  17. Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers for strain tuning of infinite-layer Sr{sub 1−x}La{sub x}CuO{sub 2} thin films

    Sakuma, Keita, E-mail:; Ito, Masataka; He, Yilun; Hajiri, Tetsuya; Ueda, Kenji; Asano, Hidefumi


    We report on the precise tuning of lattice strain in an infinite-layer electron-doped high temperature superconductor Sr{sub 1−x}La{sub x}CuO{sub 2} (SLCO; a{sub SLCO} = 0.3949 nm for x = 0.1), which is a perovskite-related oxide, using perovskite BaTiO{sub 3}–SrTiO{sub 3} (BSTO; Ba{sub y}Sr{sub 1−y}TiO{sub 3}) buffer layers. The BSTO buffer layers formed on (001) (La{sub 0.18}Sr{sub 0.82})(Al{sub 0.59}Ta{sub 0.41})O{sub 3} substrates by magnetron sputtering were fully relaxed with high crystalline quality due to high oxygen partial pressure deposition and post annealing at 950 °C. The lattice constants of the BSTO buffer layers could be controlled in the range of 0.3926–0.3973 nm by changing the Ba content (y = 0.2–0.7). These BSTO buffer layers allow coherent growth of SLCO thin films, and a clear dependence of the superconducting transition temperature on the lattice strain was observed. The fabrication of these BSTO/superconductor heterostructures may provide novel devices composed of functional perovskite thin films, in addition to a general approach for the precise control of lattice strain in functional perovskite thin films. - Highlights: • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers were developed for the strain tuning of perovskite-related oxides. • Strain effect in Sr{sub 1−x}La{sub x}CuO{sub 2} was investigated by using Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers. • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers can be used to tune the strain in other perovskite oxides.

  18. Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

    Bannikov, V.V.; Shein, I.R. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Ivanovskii, A.L., E-mail: [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation)


    Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted 'experimental' gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atoms from the blocks (MCh); thus, these phases belong to the layered materials with 'natural multiple quantum wells'. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M-Ch bonds together with covalent M-Ch and Ch-Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge. - Graphical Abstract: Isoelectronic surface for SrAgSeF and atomic-resolved densities of states for SrAgTeF, and SrCuTeF. Highlights: Black-Right-Pointing-Pointer Very recently six new layered 1111-like chalcogenide fluorides AMChF were synthesized. Black-Right-Pointing-Pointer Electronic, optical properties for AMChF phases were examined from first principles. Black-Right-Pointing-Pointer All these materials are characterized as non-magnetic semiconductors. Black-Right-Pointing-Pointer Bonding is highly anisotropic and includes ionic and covalent contributions. Black-Right-Pointing-Pointer Introduction of magnetic ions in AMChF is proposed for search of novel magnetic materials.

  19. 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

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


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

  20. Blueschist-facies high-Si phengites record the timing of greenschist-facies overprinting: a Rb-Sr and Ar-ar study of marbles from the Cyclades, Greece

    Bieling, D.; Bröcker, M.; Hacker, B.; Gans, P.


    In the Attic-Cycladic crystalline belt (Greece), white mica geochronology (Rb-Sr, K-Ar, Ar-Ar) has established time constraints for at least two metamorphic events: well-preserved high-pressure/low-temperature rocks yielded Eocene ages (c. 50-40 Ma); their greenschist-facies counterparts provided Oligocene-Miocene dates (c. 25-20 Ma). Previous studies indicated that the ages recorded by high-Si phengites may not correspond to the high-pressure stage but to the subsequent greenschist-facies overprint. This hypothesis is based on the observation that the range in Si-contents and the modal proportion of phengites with a specific Si-value are not significantly different between Eocene HP rocks and Oligocene-Miocene greenschists. The possibility that the barometric information and the geochronological record might be decoupled is of general importance for interpretation of phengite ages from polymetamorphic rocks. In order to look in more detail into this problem, we have studied marbles from Tinos and Sifnos. On both islands, HP rocks are best preserved in the upper parts of the metamorphic succession. Towards the base, the degree of greenschist overprinting increases. Phengite populations of blueschist- and greenschist facies rocks mostly show a considerable range in Si-values. However, in marbles which are either associated with HP or strongly retrogressed rocks, homogeneous high-Si phengite populations (>3.5 pfu) were recognized. On Tinos, Rb-Sr and Ar-Ar white mica dating of such samples yielded ages between 40 to 24 Ma. Of special interest are samples which yielded ages of c. 24 Ma. If the earlier metamorphic history is not taken into account, such datasets may suggest the erroneous conclusion of Miocene HP metamorphism. Recent studies [1] have reported large displacements (> 100km) for detachment faults in the Aegean. The critical parameter for such models is the age of HP metamorphism as deduced from white mica dating [1,2]. In the light of the complexities

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

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


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

  2. Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictides A Co2As2 (A =Ba , Sr, Ca)

    Mansart, Joseph; Le Fèvre, Patrick; Bertran, François; Forget, Anne; Colson, Dorothée; Brouet, Véronique


    We use angle-resolved photoemission (ARPES) to study the three-dimensional (3D) electronic structure of Co pnictides A Co2As2 with A =Ba , Sr, Ca or a mixture of Sr and Ca. These compounds are isostructural to Fe based superconductors but have one more electron in the Co 3 d orbitals. Going from Ba to Ca, they become more and more 3D, eventually forming a "collapsed" tetragonal phase, where the distance between CoAs layers is markedly reduced. We observe with ARPES the periodicity of the electronic structure as a function of kz (i.e., perpendicularly to CoAs layers) and find that it matches in each case that expected from the distance between the planes in the bulk. However, the electronic structure is better fitted by a calculation corresponding to a slab with two CoAs layers than to the bulk structure. We attribute this to subtle modifications of the 2D electronic structure induced by the truncation of the 3D dispersion at the surface in the ARPES measurement. We further study how this affects the electronic properties. We show that, despite this distortion, the electronic structure of CaCo2As2 is essentially that expected for a collapsed phase. Electronic correlations produce a renormalization of the electronic structure by a factor 1.4, which is not affected by the transition to the collapsed state. On the other hand, a small shift of the Fermi level reduces the density of states in the eg bands and suppresses the magnetic transition expected in CaCo2As2 . Our study evidences that observing the 3D bulk periodicity is not sufficient to ensure bulk sensitivity. It further gives direct information on the role of 3D interactions, mostly governed by Co-As hybridization, among eg and t2 g orbitals. It is also useful to better understand the electronic structure of Fe superconductors and the range of validity of ARPES measurements.

  3. Magnetocaloric effect of Sr-substituted BaFeO3 in the liquid nitrogen and natural gas temperature regions

    Yoshii, Kenji; Hayashi, Naoaki; Mizumaki, Masaichiro; Takano, Mikio


    We have investigated the magnetocaloric effect (MCE) of Ba1-xSrxFe4+O3 (x≤0.2), a series of cubic perovskites showing a field-induced transition from helical antiferromagnetism to ferromagnetism. The maximum magnetic entropy change (-ΔSmax) at 50 kOe varies from ˜5.8 J kg-1K-1 (x=0) to ˜4.9 J kg-1K-1 (x=0.2), while the refrigerant capacity remains almost the same at ˜165 J kg-1. Interestingly, the temperature of -ΔSmax decreases from ˜116 K to ˜77 K with increasing x, providing this series of rare-earth-free oxides with potential as a magnetic refrigerant for the liquefaction of nitrogen and natural gas.

  4. Permian High Ba-Sr Granitoids:Geochemistry,Age and Tectonic Implications of Erlangshan Pluton,Urad Zhongqi,Inner Mongolia

    LUO Hongling; WU Tairan; ZHAO Lei; HE Yuankai; JIN Xu


    Erlangshan Pluton from Urad Zhongqi.central Inner Mongolia,is located in the middle segment of the northern margin of the North China Plate.The rocks consist mainly of diorites with gneissic structure.Petrochemicai characteristics reveal that the diorites belong to metaluminous,high-potassium calc-alkaline series,with chemical signatures of 1-type granites.They are characterized by low SiO2 contents(56.63%-58.53%)and A/CNK(0.90-0.96),high Al2O3 contents(17.30%-17.96%)and Na2O/K2O ratios(1.20-1.70),enrichment in large ion lithophile elements(LILE,e.g.,Ba=556-915ppm,Sr=463-595 ppm),and relative depletion in high field strength elements(HFSE,e.g.,Nb,Ta,Ti)in primitive mantle-normalized spidergram.and right-declined rare earth element patterns with slightly negative Eu anomalies(δEu=0.72-0.90).They have Sr/Y ratios(20-25)evidently less than Kebu Pluton (49-75)to its east.Sensitive high resolution ion micro-probe U-Pb zircon dating of thediOrites has yieldIed an intrnsive a2e of 270±8 Ma.This leads US to conclude that Erlangshan diorites were formed by mixing between the middle or lower crustal.derived magma and minor mantle-derived mafic magnm,followed by fractional crystallization,which was trigged by crustal extension and fault activity in post-coilisional setting.

  5. Effects of Mo, Zn, Sr and Ba loads on these elements' uptake and oil content and fatty acid composition of rapeseed

    Kastori Rudolf R.


    Full Text Available Studied in the present paper were the long-term effects of the application of high Mo, Zn, Sr and Ba rates (0, 90, 270, and 810 kg ha-1 on rapeseed oil content and oil fatty acid composition. The trace elements were applied in the spring of 1991, while the rapeseed was sown on a calcareous сhernozem soil in 2001. The trace elements differed significantly in their rates of accumulation in rapeseed plants. Relative to the control, the Mo content of the stem increased up to 1,000 times, that of the chaff over 100 times, and that of the seed around 60 times. The levels of the other trace elements increased considerably less relative to the control. The increases were typically twofold to threefold, depending on the plant part involved. The trace elements accumulated the most in the vegetative plant parts, except for Zn, a major quantity of which was found in the seed as well. The application of the high rates of Sr, Zn and, to an extent. Mo reduced the seed oil content of rapeseed. However, the differences were not statistically significant. The application of the trace elements had no significant effect on the fatty acid composition of the rapeseed oil, either. The increased levels of the trace elements found in the rapeseed plants indicate that 11 years after application significant amounts of the applied elements are still present in the soil in a form available to plants. However, the rates were not high enough to affect the synthesis of oil and its fatty acid composition.

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

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


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

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

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


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

  8. Synthesis and structural characterisation of the new K2NiF4-type phases, A2In0.5Sb0.5O4 (A=Sr, Ba)


    In this paper we report the synthesis and structural characterisation of two new K2NiF4-type phases, Ba2In0.5Sb0.5O4 and Sr2In0.5Sb0.5O4. To our knowledge these are the first examples of K2NiF4 compounds of general formula A2MIII0.5M'V0.5O4 with both 3+ and 5+ cations in the octahedral sites. Ba2In0.5Sb0.5O4 is shown to have a tetragonal cell (space group I4/mmm, a=4.1651(1), c=13.299(1) Å) with an essentially disordered arrangement of In and Sb. In the case of Sr2In0.5Sb0.5O4, however, order...

  9. Effect of LaNiO3 Interlayer on the Dielectric Properties of Ba0.5Sr0.5TiO3 Thin Film on Si Substrate

    ZHANG Cong-chun; YANG Chun-sheng; SHI Jin-chuan; RAO Rui


    In this study, (100)-oriented growth of Ba0.5Sr0.5TiO3 (BST) /LaNiO3 (LNO) stacks was obtained on Pt(lll)/SiO2/Si substrates by r.f. magnetron sputtering. The orientation of the subsequently deposited Ba0.5Sr0.5TiO3 thin film was strongly affected by the LNO under layer, and the BST thin film deposited on the (100)LNO-coated Si substrate was also found to have a significant (100)-oriented texture. Effects of LNO interlayer on the dielectric properties of BST thin films were investigated. As a result, the tunability of BST thin film was greatly improved with the insertion of (100)-oriented LNO under layer with proper thickness.

  10. Effect of Mn and Ti substitution on the reflection loss characteristic of Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0, 1, 2 and 3)

    Gunanto, Y. E.; Cahyadi, L.; Adi, W. Ari


    The synthesis and characterization of composition Ba0.6Sr0.4Fe11-zMnTizO19 (z = 0; 1; 2 and 3) compound by solid state reaction using mechanical milling have been performed. The raw materials were BaCO3, SrCO3, Fe2O3, MnCO3, and TiO2. The mixed powder was compacted and sintered at 1000°C for 5 hours. X-ray diffraction studies indicate expansion of hexagonal unit cell and compression of atomic density with substitution of Mn2+ and Ti4+ ions. Effect of substitution upon magnetic properties revealed that total magnetization, remanence, and coercivity changed with substitution due to preferential site occupancy of substituted Mn2+ and Ti4+ ions. Since the coercivity and total magnetization may be controlled by substitution while maintaining resistive properties, this material is useful for microwave absorber.

  11. Oxygen stoichiometry and chemical expansion of Ba0.5Sr0.5Co0.8Fe0.2O3-d measured by in-situ neutron diffraction

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


    The structure, oxygen stoichiometry, and chemical and thermal expansion of Ba0.5Sr0.5Co0.8Fe0.2O3-ä (BSCF) between 873 and 1173 K and oxygen partial pressures of 1 10-3 to 1 atm were determined by in situ neutron diffraction. BSCF has a cubic perovskite structure, space group Pm3hm, across the whole

  12. High-temperature compressive creep behaviour of the perovskite-type oxide Ba0.5Sr0.5Co0.8Fe0.2O3 – d

    Yi, J.; Lein, H.L.; Grande, T.; Bouwmeester, Henricus J.M.; Yakovlev, S.


    Compressive creep tests have been performed on perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3 − δ ceramics. The activation energy, stress exponent and inverse grain size exponent of the steady-state creep rates are evaluated at p(O2) = 0.21 ∙ 105 Pa and 0.01 ∙ 105 Pa in the stress, temperature and grain

  13. Experimental and computational investigation of the group 11-group 2 diatomic molecules: First determination of the AuSr and AuBa bond energies and thermodynamic stability of the copper- and silver-alkaline earth species

    Ciccioli, A.; Gigli, G.; Lauricella, M.


    The dissociation energies of the intermetallic molecules AuSr and AuBa were for the first time determined by the Knudsen effusion mass spectrometry method. The two species were produced in the vapor phase equilibrated with apt mixtures of the constituent elements, and the dissociation equilibria were monitored mass-spectrometrically in the temperature range 1406-1971 K (AuSr) and 1505-1971 K (AuBa). The third-law analysis of the equilibrium data gives the following dissociation energies (D_0°, in kJ/mol): 244.4 ± 4.8 (AuSr) and 273.3 ± 6.3 (AuBa), so completing the series of D_0°s for the AuAE (AE = group 2 element) diatomics. The AuAE species were also studied computationally at the coupled cluster including single, double and perturbative triple excitation [CCSD(T)] level with basis sets of increasing zeta quality, and various complete basis set limit extrapolations were performed to calculate the dissociation energies. Furthermore, the entire series of the heteronuclear diatomic species formed from one group 11 (Cu, Ag) and one group 2 (Be, Mg, Ca, Sr, Ba) metal was studied by DFT with the hybrid meta-GGA TPSSh functional and the def2-QZVPP basis set, selected after screening a number of functional-basis set combinations using the AuAE species as benchmark. Dissociation energies, internuclear distances, vibrational frequencies, and anharmonic constants were determined for the CuAE and AgAE species and their thermal functions evaluated therefrom. On this basis, a thermodynamic evaluation of the formation of these species was carried out under various conditions.

  14. Experimental and computational investigation of the group 11-group 2 diatomic molecules: first determination of the AuSr and AuBa bond energies and thermodynamic stability of the copper- and silver-alkaline earth species.

    Ciccioli, A; Gigli, G; Lauricella, M


    The dissociation energies of the intermetallic molecules AuSr and AuBa were for the first time determined by the Knudsen effusion mass spectrometry method. The two species were produced in the vapor phase equilibrated with apt mixtures of the constituent elements, and the dissociation equilibria were monitored mass-spectrometrically in the temperature range 1406-1971 K (AuSr) and 1505-1971 K (AuBa). The third-law analysis of the equilibrium data gives the following dissociation energies (D(0)°, in kJ/mol): 244.4 ± 4.8 (AuSr) and 273.3 ± 6.3 (AuBa), so completing the series of D(0)°s for the AuAE (AE = group 2 element) diatomics. The AuAE species were also studied computationally at the coupled cluster including single, double and perturbative triple excitation [CCSD(T)] level with basis sets of increasing zeta quality, and various complete basis set limit extrapolations were performed to calculate the dissociation energies. Furthermore, the entire series of the heteronuclear diatomic species formed from one group 11 (Cu, Ag) and one group 2 (Be, Mg, Ca, Sr, Ba) metal was studied by DFT with the hybrid meta-GGA TPSSh functional and the def2-QZVPP basis set, selected after screening a number of functional-basis set combinations using the AuAE species as benchmark. Dissociation energies, internuclear distances, vibrational frequencies, and anharmonic constants were determined for the CuAE and AgAE species and their thermal functions evaluated therefrom. On this basis, a thermodynamic evaluation of the formation of these species was carried out under various conditions.

  15. Propriedades dielétricas de cerâmicas (Sr,BaNb2O6 dopadas com terras raras Dielectric properties of (Sr,BaNb2O6 ceramics doped with rare earths

    I. A. Santos


    Full Text Available Cerâmicas de Sr1-xBaxNb2O6, "puras" e dopadas com óxidos de terras raras, foram preparadas com o objetivo de estudar o seu comportamento dielétrico em função da adição desses dopantes. As amostras foram caracterizadas através de medidas dielétricas efetuadas em função da temperatura (30 K a 500 K e da freqüência (1 kHz a 1 MHz. Em todas as amostras estudadas verifica-se a presença de dois processos distintos de relaxação dielétrica. O primeiro processo é observado a temperaturas inferiores a 100 K. O segundo processo é observado próximo a temperatura ambiente, onde a constante dielétrica apresenta seu maior valor. Observou-se que a adição de dopantes causa efeitos distintos nas temperaturas de máximo das constantes dielétricas nas duas regiões de relaxação dielétrica.Ceramics of SBN, undoped and doped with rare earth oxides, were prepared to the study of the influence of the doping on the dielectric properties. The samples were characterised through dielectric measurements as a function of temperature (30 K to 500 K and frequency (1 kHz to 1 MHz. In all samples two distinct dielectric relaxation processes were observed. The first one at temperatures below 100 K; the second one is near room temperature, where the dielectric constant is maximum. The doping causes distinct effects in the maximum temperatures of the dielectric constants in the two dielectric relaxation regions.

  16. High performing BaCe0.8Zr0.1Y0.1O3-δ-Sm0.5Sr0.5CoO3-δ based protonic ceramic fuel cell

    Dailly, J.; Taillades, G.; Ancelin, M.; Pers, P.; Marrony, M.


    The electrochemical performances of a composite cathode consisted of Sm0.5Sr0.5CoO3-δ and BaCe0.8Zr0.1Y0.1O3-δ coated onto a BaCe0.8Zr0.1Y0.1O3-δ-based half-cell are evaluated in the intermediate temperature range 600-700 °C. Powders for the manufacture of anode substrate and electrolyte are commercial products, whereas a glycine-nitrate process is used to synthesize the cathode material. The complete cell is manufactured by wet chemical routes, using the combination of tape-casting for the anode substrate NiO-BaCe0.8Zr0.1Y0.1O3-δ and wet powder spraying for the elaboration of the electrolyte BaCe0.8Zr0.1Y0.1O3-δ and air electrode Sm0.5Sr0.5CoO3-δ-BaCe0.8Zr0.1Y0.1O3-δ. Thin electrolytes and porous electrodes are successfully elaborated for a cell size of 3 × 3 cm2. A high open circuit voltage of 1.11 V at 600 °C indicates an excellent gas-tightness of the protonic ceramic electrolyte. A maximum power density of 370-530 mW cm-2 in the range 600-700 °C is measured validating Sm0.5Sr0.5CoO3-δ material as promising cathode for protonic-based cells.

  17. Rb-Sr age and content of potassium, rubidium strontium, barium, and rare earths in surface material from the Sea of Fertility

    Allegre, C. J.; Birck, J. L.; Loubet, M.; Provost, A.


    The Luna 16 automatic station returned from the Sea of Fertility a 35 cm long column of lunar surface material. 1 g of the Luna 16 lunar surface material, taken at a depth of 22 cm, consists of fine material: surface material and fine fragments of rocks from 1 to 4 mm in diameter. Analyses made on 17 mg of the fine lunar surface material are presented. The results obtained for the Luna 16 surface material are plotted on the diagram of the isotopic evolution of strontium and show that this surface material is most depleted of radiogenic Sr-87 of all the known lunar surface materials and that the point characterizing Lunar 16 lies somewhat to the right of the line corresponding to an age of 4.6 billion years.

  18. Electrical transport properties and modelling of electrostrictive resonance phenomena in Ba2/3Sr1/3TiO3 thin films

    Ghalem, A.; Huitema, L.; Crunteanu, A.; Rammal, M.; Trupina, L.; Nedelcu, L.; Banciu, M. G.; Dutheil, P.; Constantinescu, C.; Marchet, P.; Dumas-Bouchiat, F.; Champeaux, C.


    We present the conduction mechanisms of Ba2/3Sr1/3TiO3 thin films integrated in metal-insulator-metal (MIM) capacitors and the modelling of the frequency-dependent electrostrictive resonances (in the 100 MHz-10 GHz domain) induced in the devices upon applying different voltage biases. Au/BST/Ir MIM structures on MgO substrates have been fabricated and, depending on their specific polarization, we highlighted different conduction mechanisms in the devices. Depending on the dc bias polarity, the conduction current across the material shows a space-charge-limited-current behavior under negative polarization, whereas under positive bias, the conduction obeys an electrode-limited Schottky-type law at the Au/BST interface. The application of an electric field on the device induces the onset of acoustic resonances related to electrostrictive phenomena in the ferroelectric material. We modeled these acoustic resonances over a wide frequency range, by using a modified Lakin model, which takes into account the dispersions of acoustic properties near the lower electrode/thin film interface.

  19. Ultra high energy density nanocomposite capacitors with fast discharge using Ba0.2Sr0.8TiO3 nanowires.

    Tang, Haixiong; Sodano, Henry A


    Nanocomposites combining a high breakdown strength polymer and high dielectric permittivity ceramic filler have shown great potential for pulsed power applications. However, while current nanocomposites improve the dielectric permittivity of the capacitor, the gains come at the expense of the breakdown strength, which limits the ultimate performance of the capacitor. Here, we develop a new synthesis method for the growth of barium strontium titanate nanowires and demonstrate their use in ultra high energy density nanocomposites. This new synthesis process provides a facile approach to the growth of high aspect ratio nanowires with high yield and control over the stoichiometry of the solid solution. The nanowires are grown in the cubic phase with a Ba0.2Sr0.8TiO3 composition and have not been demonstrated prior to this report. The poly(vinylidene fluoride) nanocomposites resulting from this approach have high breakdown strength and high dielectric permittivity which results from the use of high aspect ratio fillers rather than equiaxial particles. The nanocomposites are shown to have an ultra high energy density of 14.86 J/cc at 450 MV/m and provide microsecond discharge time quicker than commercial biaxial oriented polypropylene capacitors. The energy density of our nanocomposites exceeds those reported in the literature for ceramic/polymer composites and is 1138% greater than the reported commercial capacitor with energy density of 1.2 J/cc at 640 MV/m for the current state of the art biaxial oriented polypropylene.

  20. Synthesis and characterization of Ba0.5Sr0.5Co0.8Fe0.2O3-σ

    WANG Qibao; YUAN Yan; HAN Minfang; ZHU Peiyu


    Perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCFO) powders were synthesized using two methods, solid-state reaction (SSR) method and cit-rate-EDTA complexing method (CC-EDTA). Then the powders were pressed to green disks of 19 mm in diameter and sintered at 1140℃ for 5 h. The shrinkage rate and relative density of the membranes prepared from the perovskite-type powders were determined and calculated, and the powders and derived membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The re-sults show that the shrinkage rates of the two kinds of disks are nearly the same (about 10%). The disks prepared by the SSR method had a bigger grain size and lower relative density than those prepared by the CC-EDTA method. The conductivity of the membranes prepared by the SSR method was about 38 S/cm, higher than that of the membranes prepared by the CC-EDTA method, which was about 30 S/cm, at the same temperature of 600℃.

  1. A combined DFT and post-DFT investigation on cubic XMoO3 (X  =  Sr, Ba) perovskite oxides

    Dar, Sajad Ahmad; Srivastava, Vipul; Sakalle, Umesh Kumar


    Highly precise and accurate density functional theory has been used to check the structural, elasto-mechanical thermo-electronic and thermodynamic properties of XMoO3 (X  =  Sr, Ba). The study was accomplished within different exchange correlation potentials like (GGA, GGA  +  U, mBJ, and GGA  +  U  +  SOC). The optimization for both the compounds was achieved for paramagnetic, ferromagnetic and anti-ferromagnetic phases and the compounds were found to have paramagnetic stable phase. The spin polarized band structure and density of states present metallic nature for both the compounds. The symmetric spin polarized band for both (up, down) states and negligible spin magnetic moment also confirm the paramagnetic nature of these compounds. The post DFT treatment through Boltztrap code was used to check the temperature dependence of electrical conductivity. The elastic constants and mechanical properties like Young modulus, shear modulus, Poisson ratio and anisotropic factor have also been calculated. The calculated value of B/G ratio and Cauchy pressure show that both compounds establish ductile nature. Debye temperature along with melting temperature for both the compounds was predicted. Further the nature of thermodynamic parameters like heat capacity and Debye temperature were also checked under pressure and temperature variation using quasi-harmonic Debye approximation.

  2. Oxygen separating membrane manufactured from Ba0.5Sr0.5Co0.8Fe0.2O3− perovskite-like material

    M Gromada; J Świder; J Trawczyński; M Stępień; M Wierzbicki


    The dense thin membrane for oxygen separation was manufactured from Ba0.5Sr0.5Co0.8Fe0.2O3− (BSCF) mixed oxide with perovskite-like structure prepared by the solid-state method. Properties of both powder and granulate (chemical and phase compositions, the specific surface area and the porosity) as well as sintered material (the apparent density, the apparent porosity, the water absorbability, the chemical composition, the crystallo-graphic structure and microstructure), that affect the process of ion oxygen permeation through membrane, were determined. Parameters influencing on usable properties of membranes viz., the bending strength and the coefficient of thermal expansion were assessed as well. Effect of the sintering temperature on membrane structure was evaluated. The elaborated fabrication procedure enables one to manufacture membrane, in which microstructure is characterized by the presence of big grains as well as decreased concentration of grain boundaries. Measurements of the oxygen permeation through BSCF membrane revealed that the highest oxygen flux reaching 2.6 cm3 O2/ (cm2 min) was obtained at 950°C under air and helium flows equal to 1 dm3 min−1.

  3. Cation size and strain effects in La 2/3(Ca 1- x' Sr x'- x″ Ba x″ ) 1/3MnO 3

    Yuan, S. L.; Peng, G.; Xia, Z. C.; Liu, J.; Liu, S.; Li, Z. Y.; Yang, Y. P.; Liu, L.; Tang, J.; Zhang, G. H.; Zhang, L. J.; Feng, W.; Xiong, C. S.; Xiong, Y. H.


    Based on investigations of metal-insulator transition temperature Tm on La 2/3(Ca 1- x' Sr x'- x″ Ba x″ ) 1/3MnO 3, we point out that considerations based only on the mismatch effect or the strain-field effect cannot provide a reasonable description for the experimental observations. Including two contributions arising from the average A-cation size () and the strain-field effect defined by a quantity S= gives Tm varying as Tm= Tm(,0)- pS, where Tm(,0) is the transition temperature in the absence of the strain-field effect and the parameter p is estimated to be ˜1.05×10 6 K nm -2. It is shown that the strain-corrected Tm shows a behavior expected by the double-exchange mechanism which monotonously increases towards ˜500 K with increasing towards rA0 (the A-cation size of an ideal cubic perovskite).

  4. Life Cycle Testing of Ba(x)Sr(1-x)TiO3 Ferroelectric Thin Films in a Tunable Microwave Device

    Miranda, Felix A.; VanKeuls, Fred W.; Romanofsky, Robert R.; Mueller, Carl H.; Warner, Joseph D.


    Thin film ferroelectrics are being studied as candidates for novel tunable microwave components such as tunable filters, tunable oscillators, and phase shifters for applications in phased array antennas. Much work has been done optimizing the ferroelectric material and in producing proof-of-concepts of these components. However, little attention has been given to their reliability. In this study we present our results on the reliability of high quality K-band phase shifters made of Ba(sub x)Sr(sub 1-x)TiO3 (BSTO) ferroelectric thin films (0.5 to 0.75 micrometers thick) on MgO and LAO. The phase shift and insertion loss were measured at 300 K over 104 operation cycles within a 0 to 400 V dc bias range (0 to 40 V/micrometer) at 15, 18, and 22 GHz. Results for these phase shifters indicate that in general there were no appreciable changes in phase shift after 4x10(exp 4) cycles, suggesting that these phase shifters are robust enough to sustain optimal performance under the operating mode typical of fast tracking phased arrays.

  5. Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo2Fe11AlO22

    Nakajima, Taro; Tokunaga, Yusuke; Matsuda, Masaaki; Dissanayake, Sachith; Fernandez-Baca, Jaime; Kakurai, Kazuhisa; Taguchi, Yasujiro; Tokura, Yoshinori; Arima, Taka-hisa


    We have investigated magnetic orders and excitations in a Y-type hexaferrite BaSrCo2Fe11AlO22 (BSCoFAO), which was reported to exhibit spin-driven ferroelectricity at room temperature [S. Hirose, K. Haruki, A. Ando, and T. Kimura, Appl. Phys. Lett. 104, 022907 (2014), 10.1063/1.4862432]. By means of magnetization, electric polarization, and neutron-diffraction measurements using single-crystal samples, we establish a H -T magnetic phase diagram for magnetic field perpendicular to the c axis (H⊥c). This system exhibits an alternating longitudinal conical (ALC) magnetic structure in the ground state, and it turns into a non-co-planar commensurate magnetic order with spin-driven ferroelectricity under H⊥c. The field-induced ferroelectric phase remains as a metastable state after removing magnetic field below ˜250 K. This metastability is the key to understanding of magnetic field reversal of the spin-driven electric polarization in this system. Inelastic polarized neutron-scattering measurements in the ALC phase reveal a magnetic excitation at around 7.5 meV, which is attributed to spin components oscillating in a plane perpendicular to the cone axis. This phasonlike excitation is expected to be an electric-field active magnon, i.e., electromagnon excitation, in terms of the magnetostriction mechanism.

  6. The MBE growth and optical quality of BaTiO{sub 3} and SrTiO{sub 3} thin films on MgO

    McKee, R.A.; Specht, E.D.; Alexander, K.B. [Oak Ridge National Lab., TN (United States); Walker, F.J. [Tennessee Univ., Knoxville, TN (United States)


    High quality epitaxial BaTiO{sub 3} and SrTiO{sub 3} have been grown on MgO; stabilized at a one unit cell height; and grown to film thicknesses of 0.5--0.7 {mu}m. These relatively thick films remain adherent when thermally cycled between growth temperatures and room temperature, are crack free with high optical quality, and have both in-plane and out-of-plane X-ray rocking curves of 0.3--0.5{degree}. These films have been grown using molecular beam epitaxy (MBE) methods starting with the TiO{sub 2} layer of the perovskite structure. The TiO{sub 2}-layer/MgO interface uniquely satisfies electrostatic requirements for perovskite heteroepitaxy and provides the template structure that leads to the high quality films that are obtained. Wavelength dependence of optical loss has been characterized between 475 nm and 705 nm with loss coefficients < l dB/cm being obtained at the He-Ne wavelength.

  7. Magnetic couplings in the quasi-2D triangular Heisenberg antiferromagnets {alpha}-ACr{sub 2}O{sub 4} (A=Ca, Sr, Ba)

    Hardy, V., E-mail: [Laboratoire CRISMAT, ENSICAEN, UMR 6508 CNRS, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Martin, C. [Laboratoire CRISMAT, ENSICAEN, UMR 6508 CNRS, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France); Damay, F.; Andre, G. [Laboratoire Leon Brillouin, UMR 12, CEA-Saclay, CEA-CNRS, 91191 Gif-sur-Yvette Cedex (France)


    We carried out a comparative study of the A=Ca, Sr, Ba compounds of the {alpha}-ACr{sub 2}O{sub 4} series, a family of layered chromites, which can be classified as S=3/2 quasi-2D triangular Heisenberg antiferromagnets (2DTHAF). The sizeable distortion, with respect to the perfect triangle lattice, of the spin layer topology can be progressively decreased by increasing the size of A{sup 2+}, which leads to an increase of both the average distance between nearest-neighbouring Cr{sup 3+} and of the interplane spacing. The evolution with A{sup 2+} of the antiferromagnetic transition T{sub N}, the intraplane coupling J, and the interplane coupling J Prime has been determined on the basis of magnetization and heat capacity measurements and is discussed in the framework of the standard theoretical models describing quasi 2DTHAF. - Highlights: Black-Right-Pointing-Pointer Increasing the ionic radius of A{sup 2+} has a non-monotonous impact on T{sub N}. Black-Right-Pointing-Pointer The small single-ion anisotropy can split the antiferromagnetic transition. Black-Right-Pointing-Pointer The intraplane coupling is consistent with direct exchange. Black-Right-Pointing-Pointer The interplane coupling derived from standard 2DTHAF models is questionable.

  8. Compositional dependence of the thermoelectric properties of (Sr(x)Ba(x)Yb₁₋₂x)(y)Co₄Sb₁₂ skutterudites.

    Rogl, G; Grytsiv, A; Melnychenko-Koblyuk, N; Bauer, E; Laumann, S; Rogl, P


    High temperature thermoelectric (TE) properties for triple-filled skutterudites (Sr(x)Ba(x)Yb₁₋₂x)(y)Co₄Sb₁₂ were investigated for alloy compositions in two sections of the system: (a) for x = 0.25 with a filling fraction y ranging from 0.1 to 0.25 and (b) for 0 < x < 0.5 and y = 0.11 + 0.259x. The representation of the figure of merit, ZT, as a function of skutterudite composition, defined the compositional range (0.25 < x < 0.4; 0.18 < y < 0.24) with ZT over 1.4 at 800 K. It was shown that an enhanced TE performance for these triple-filled skutterudites is caused by low electrical resistivities and low lattice thermal conductivities, as well as by a fine tuning of the chemical composition. Low temperature measurements for the samples with the highest ZT values showed that even a small change of the filler ratios changes the contribution of scattering effects, the carrier concentration and the mobility.

  9. Thermodynamic properties and mixing thermodynamic parameters of Ba-Al, Mg-Al, Sr-Al and Cu-Al metallic melts



    Application of equations of mixing thermodynamic parameters formulated on the basis of the coexistence theory of metallic melts in Ba-Al, Mg-Al, Sr-A1 and Cu-Al melts leads to fruitful results that not only the evaluated mass action concentrations agree well with the measured activities, but also the calculated mixing thermodynamic parameters are quite coincident with the experimental values. Moreover, the calculated mass action concentrations strictly obey the mass action law. The evaluated mixing thermodynamic parameters have very fine regularity: the mixing free energy is composed of standard free formation energies of all compounds and chemical potentials of all structural units at equilibrium; the mixing enthalpy consists of standard formation enthalpies of all compounds; the mixing entropy is composed of standard entropies of all compounds and configuration entropies of all structural units at equilibrium. As the equations of mixing thermodynamic parameters formulated are widely applicable to metallic melts involving compound formation, they can be used as the second practical criterion to determine whether thermodynamic models of metallic melts are correctly formulated.

  10. Relaxor behaviour of (Ba0.5Sr0.5)(Ti0.6Zr0.4)O3 ceramics

    T Badapanda; S K Rout; S Panigrahi; T P Sinha


    Ba0.5Sr0.5Ti0.6Zr0.4O3 ceramic has been prepared through solid state reaction route. X-ray diffraction shows that the sample has cubic perovskite structure with space group –3 at room temperature. Temperature dependent dielectric study of the ceramic has been investigated in the frequency range 50 Hz–1 MHz. The density of the sample is determined using Archimedes’ principle and is found to be ∼99% of X-ray density. The dielectric study revealed diffuse phase transition of second order. A broad dielectric anomaly coupled with the shift of dielectric maxima toward a higher temperature with increasing frequency indicates the relaxor-type behaviour in the ceramics. The index of relaxation () and the broadening parameter () were estimated from a linear fit of the modified Curie–Weiss law. The value of ∼ 1.72 indicates the strong relaxor nature of the ceramic. A remarkably good fit to the Vogel–Fulcher relation further supports such a relaxor nature.

  11. Phase stability, elastic anisotropy and electronic structure of cubic MAl2 (M = Mg, Ca, Sr and Ba) Laves phases from first-principles calculations

    Kong, Yuanyuan; Duan, Yonghua; Ma, Lishi; Li, Runyue


    By performing first-principles calculations within the generalized gradient approximation, the phase stability, elastic constant and anisotropy, and density of states of cubic C15-type MAl2 (M = Mg, Ca, Sr and Ba) Laves phases have been investigated. Optimized equilibrium lattice parameters and formation enthalpies agree well with the available experimental data. Elastic constants C ij have been evaluated, and these C15-type MAl2 Laves phases are mechanically stable due to the meeting of C ij to the mechanical stability criteria. Polycrystalline elastic moduli have been deduced from elastic constants by Voigt-Reuss-Hill approximation. Plastic properties were characterized via values of B/G, Poisson’s ratio ν and Cauchy pressure (C 12-C 44). The elastic anisotropy has been considered by several anisotropy indexes (A U , A Z , A shear and A comp), anisotropy of shear modulus, and 3D surface constructions of bulk and Young’s moduli. Additionally, the sound velocity anisotropy and Debye temperature were predicted. Finally, electronic structures were carried out to reveal the underlying phase stability mechanism of these Laves phases.

  12. Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M = Ba, Sr, Ca, Mg)

    Liu Zhaoyang; Wang Chunru; Huang Rongbin; Zheng Lansun [Xiamen Univ. (China). Dept. of Chem.


    Laser ablation of YMCuO metal-composite-oxides (M = Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed. (orig.) 19 refs.

  13. Electric field effect on elastic properties of uniaxial relaxor Sr x Ba1‑ x Nb2O6 single crystals with strong random fields

    Aftabuzzaman, Md; Helal, Md Al; Dec, Jan; Kleemann, Wolfgang; Kojima, Seiji


    The elastic properties of uniaxial relaxor Sr x Ba1‑ x Nb2O6 (x = 0.70, SBN70) single crystals with strong random fields (RFs) were studied by Brillouin scattering spectroscopy as functions of temperature and external electric field along the [001] direction. A remarkable diffuseness of a ferroelectric phase transition was observed both on zero field heating and zero field cooling. The analysis of elastic anomaly shows the stretched critical slowing down of polar nanoregions (PNRs). Under 3.0 kV/cm, a complete alignment of nanodomains and an enhancement of the long-range ferroelectric order were observed below the Curie temperature T C = 23 °C. The alignment of quasistatic PNRs above T C was also observed under a sufficiently strong electric field. In a field-dependent measurement, a mixed state consisting of field-induced macrodomains and nanodomains caused by RFs was observed at 3.4 kV/cm. This mixed state persisted up to 9.0 kV/cm due to the incomplete switching of nanodomains to the macro/single domain state.

  14. Dielectric Characteristics of Ba0.65Sr0.35TiO3 Thin Films by Sol-Gel Method

    LIU Gui-jun; HU Wen-cheng; SHEN Yi-dong


    Ferroelectric Ba0.6sSr0.3sTiO3 (BST) thin films on the Pt/Ti/SiO2/Si substrate have been successfully prepared by sol-gel. Such films have approximately 300 nm thicknesses with a remnant polarization of about 2.95 μC/cm2 and a coercive field of about 21.5 kV/cm. The investigations of X-ray diffraction and atomic force microscopy show that the BST films annealed at 650 ℃ exhibit a tetragonal structure and that the films dominantly consist of large column or grains of about 89 nm in diameter. The curves of the temperature dependence of dielectric coefficient in different frequencies display the curie transition at the temperature around 23 ℃.The dielectric loss tangent of BST thin films at 100 kHz is less than 0.04. As a result, the BST thin films are more applicable for fabrication of infrared detector compared with the BST thin films reported previously.

  15. 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

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


    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.

  16. Integration of ferroelectric BaTiO3 with Ge: The role of a SrTiO3 buffer layer investigated using aberration-corrected STEM

    Wu, HsinWei; Lu, Sirong; Aoki, Toshihiro; Ponath, Patrick; Ekerdt, John G.; Demkov, Alexander A.; McCartney, Martha R.; Smith, David J.


    The integration of semiconductors with ferroelectrics having a controlled polarization direction is an ongoing and challenging topic of research. In this work, BaTiO3 (BTO)/SrTiO3 (STO) heterostructures were grown by molecular beam epitaxy either directly with STO substrates or by using 2-nm-thick STO buffer layers on Ge(001) substrates. Sharp, chemically abrupt interfaces and c-axis-oriented BTO films for both types of heterostructures were observed using aberration-corrected scanning transmission electron microscopy and elemental mapping. Anti-phase boundaries as well as ⟨100⟩ misfit dislocations were present in the BTO/STO samples, with the offsets of the dislocation cores varying by distances between 1 and 5 nm away from the BTO/STO interface. Conversely, misfit dislocations were not observed in the BTO/STO/Ge structure although vertical anti-phase boundaries were still common. Overall, the results emphasize the benefits of identifying a suitable buffer layer to ensure the growth of a high quality material having the desired out-of-plane ferroelectric polarization.

  17. Giant tunneling electroresistance induced by ferroelectrically switchable two-dimensional electron gas at nonpolar BaTiO3/SrTiO3 interface

    Wu, Qingyun; Shen, Lei; Yang, Ming; Zhou, Jun; Chen, Jingsheng; Feng, Yuan Ping


    Using first-principles calculations, we investigate the tunneling electroresistance (TER) of ferroelectric tunnel junctions [Pt /BaTiO3(BTO)/SrTiO3(STO )/Pt ]. It is found that the TER of Pt/BTO/STO/Pt junctions can be greatly increased with increasing thickness of STO layers. The underlying physics of this giant TER is the switchable two-dimensional electron gas (2DEG) at a nonpolar BTO/STO interface induced by the ferroelectric polarization. Our calculations show that when the ferroelectric polarization is pointing from BTO to STO, a 2DEG forms at the interface and acts as bridge for electrons to tunnel through the junctions. Nevertheless, there is no 2DEG at the interface under the opposite direction of the ferroelectric polarization, which results in a large tunnel resistance. More importantly, this ferroelectrically switchable 2DEG leads to a low resistance area product for Pt/BTO/STO/Pt junctions, which offers good compatibility with other components in an integrated circuit and is highly desired for industrial applications.

  18. Polar phase transitions and physical properties in fresnoite A2TiSi2O8 (A= Ba, Sr) by first principles calculations

    Song, Nayoung; Momida, Hiroyoshi; Oguchi, Tamio; Kim, Bog G.


    Polar phase transitions of fresnoites, Ba2TiSi2O8 (BTS) and Sr2TiSi2O8 (STS) have been comparatively analyzed by the first principles calculations. We show that both BTS and STS have a polar structure with the space group P4bm as a ground state, and there is a fictitious phase transition in the tetragonal space group from the nonpolar P4/mbm meta-stable phase to the polar P4bm phase. From the analyses of the two atomic structures, we find that a noticeable issue in the phase transition is bond length changes of Si-O and Ti-O which break the inversion symmetry, resulting that one of vertices in the edge-shared Si-O and Ti-O polyhedron is detached in the polar phase. The structural phase transition between the polar and the nonpolar states are discussed in terms of electronic structures and structural symmetry mode analyses. We evaluate the size of spontaneous polarizations of BTS and STS in the polar P4bm phases, and the correlation analysis shows significant contributions of the detached polyhedrons to the strong polar property. We also show second harmonic generation susceptibilities of BTS and STS as a candidate for second-order nonlinear optics materials. Our quantitative studies can provide full understandings of atomic and electronic mechanisms of their polar phase and nonlinear optical properties.

  19. Downscaling at submicrometer scale of the gap width of interdigitated Ba0.5Sr0.5TiO3 capacitors.

    Khalfallaoui, Abderrazek; Burgnies, Ludovic; Blary, Karine; Velu, Gabriel; Lippens, Didier; Carru, Jean-Claude


    The goal of this work was to study the influence of shrinking the gap width between the fingers of interdigitated tunable capacitors (IDCs). Voltage control of the capacitance was achieved with a 500-nm-thick Ba0.5Sr0.5TiO3 film which is in paraelectric state at room temperature. Eight devices with finger spacing ranging from 3 μm down to 0.25 μm were fabricated by the sol-gel deposition technique, electron beam patterning, and gold evaporation. The equivalent capacitance, quality factor, and tunability of the devices were measured subsequently by vector network analysis from 40 MHz to 40 GHz and for a dc bias voltage varying from -30 V to +30 V. This experimental study mainly shows that a decrease of the gap below 1 μm 1) introduces a frequency dependence of the capacitance caused by resonance effects with the finger inductance; 2) degrades the quality factor above 20 GHz, and 3) optimizes the tunability of the devices by enhancing the local electric field values. As a consequence, some trade-offs are pointed out related to the goal of ultra-thin ferroelectric film which can be voltage controlled by means of finger-shaped electrodes with deep submicrometer spacing.

  20. Direct correlation and strong reduction of native point defects and microwave dielectric loss in air-annealed (Ba,Sr)TiO{sub 3}

    Zeng, Z. Q. [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Podpirka, A.; Kirchoefer, S. W. [Naval Research Laboratory, Washington, DC 20375 (United States); Asel, T. J. [Department of Physics and Center for Materials Research, The Ohio State University, Columbus, Ohio 43210 (United States); Brillson, L. J., E-mail: [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics and Center for Materials Research, The Ohio State University, Columbus, Ohio 43210 (United States)


    We report on the native defect and microwave properties of 1 μm thick Ba{sub 0.50}Sr{sub 0.50}TiO{sub 3} (BST) films grown on MgO (100) substrates by molecular beam epitaxy (MBE). Depth-resolved cathodoluminescence spectroscopy (DRCLS) showed high densities of native point defects in as-deposited BST films, causing strong subgap emission between 2.0 eV and 3.0 eV due to mixed cation V{sub C} and oxygen Vo vacancies. Post growth air anneals reduce these defects with 2.2, 2.65, and 3.0 eV V{sub O} and 2.4 eV V{sub C} intensities decreasing with increasing anneal temperature and by nearly two orders of magnitude after 950 °C annealing. These low-defect annealed BST films exhibited high quality microwave properties, including room temperature interdigitated capacitor tunability of 13% under an electric bias of 40 V and tan δ of 0.002 at 10 GHz and 40 V bias. The results provide a feasible route to grow high quality BST films by MBE through post-air annealing guided by DRCLS.

  1. Raman and X-ray diffraction study of (Ba,Sr)TiO{sub 3}/(Bi,Nd)FeO{sub 3} multilayer heterostructures

    Anokhin, A.S., E-mail: [Southern Scientific Centre, Russian Academy of Sciences, 41, Chekhov str., Rostov-on-Don 344006 (Russian Federation); Bunina, O.A. [Faculty of Physics and Research Institute of Physics, Southern Federal University, 5, Zorge str., Rostov-on-Don 344090 (Russian Federation); Golovko, Yu I.; Mukhortov, V.M. [Southern Scientific Centre, Russian Academy of Sciences, 41, Chekhov str., Rostov-on-Don 344006 (Russian Federation); Yuzyuk, Yu I., E-mail: [Faculty of Physics and Research Institute of Physics, Southern Federal University, 5, Zorge str., Rostov-on-Don 344090 (Russian Federation); Simon, P. [CNRS UPR 3079 CEMHTI, 1D, av. de la Recherche Scientifique, F-45071 Orléans (France)


    We report synthesis, X-ray diffraction (XRD) and Raman scattering characterisation of epitaxial heterostructures containing alternating (Bi{sub 0.98}Nd{sub 0.02})FeO{sub 3} (BNFO) and (Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}) (BST) layers deposited on (100) MgO substrates. A significant shift of the BST soft mode and partial depolarisation in the Raman spectra of multilayer heterostructures caused by epitaxial strains were observed. Satellite peaks typical for superlattices were observed in the XRD patterns of multilayer heterostructures with layer thicknesses below 30 nm. Raman spectra of the BNFO/BST superlattice with a modulation period of 10 nm revealed hardening of the soft mode and a dominating symmetric-stretching mode at 705 cm{sup −1} due to distortion in FeO{sub 6} octahedra enforced by the epitaxial strain in the superlattice. - Highlights: • BNFO and BST multilayers and superlattices on (100) MgO. • Raman spectra of superlattices exhibit features not observed in bulk BFO. • Satellites in XRD patterns when layer thickness below 30 nm.

  2. Influence of annealing temperature on the dielectric properties of BaSrTiO3 thin films deposited on various substrates

    Lee, Chil-Hyoung; Oh, Young-Jei; Lee, Deuk Yong; Choi, Doo-Jin


    (Ba0.5Sr0.5)TiO3 (BST) thin films were deposited on various substrates, such as LaAlO3(100), MgO(100), R-plane sapphire[1012], and polycrystalline sapphire, by using RF magnetron sputtering to investigate the influence of annealing temperature on the dielectric properties and the tunability of the films. The BST thin films deposited on LaAlO3(100) exhibited a high tunability of 42 % and a low dielectric loss of 0.004 due to the small differences in the lattice parameters and the thermal expansion coefficients between the BST films and the substrates. In contrast, the BST films deposited on a polycrystalline sapphire, exhibiting a relatively high mismatch factor, showed the tunability of 24 % and a dielectric loss of 0.007. The BST thin films on LaAlO3(100), MgO(100), R-plane sapphire[1012], and polycrystalline sapphire were annealed. The optimized annealing temperatures were found to be 950 °C, 1050 °C, 1100 °C, and 1150 °C, respectively. The difference in annealing temperature is likely due to the differences in the lattice parameters and the thermal expansion coefficients between the films and the substrates.

  3. Thermoelectric and electrical properties of Ba0.5Sr0.5Co x Ru x Fe(12-2 x)O19 ferrite*

    Singh, Charanjeet; Jaroszewski, Maciej; Bindra Narang, Sukhleen; Ravinder, D.


    Thermoelectric and electrical characteristics investigation of M-type hexagonal ferrite, Ba0.5Sr0.5CoxRuxFe(12-2x)O19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2), have been carried out from 303 K to 473 K. The static current density-electric field characteristics have been measured at room temperature. The Seebeck coefficient indicates n-type behavior at lower substitution and p-type conduction at higher substitution. The different electrical parameters are affected by change in grain size with substitution of Co2+ and Ru4+ ions. The existence of polarons is confirmed from increase in conductivity with frequency. The static conduction due to applied electric field is discussed qualitatively in terms of space charge limited current, ionic hopping, Poole-Frenkel and Schottky-Richardson mechanisms. The large current density has been observed at higher substitution. Contribution to the Topical Issue "Materials for Dielectric Applications", edited by Maciej Jaroszewski and Sabu Thomas.

  4. in situ templating synthesis of conic Ba0.5Sr0.5Co0.8Fe0.2O3– perovskite at elevated temperature

    Wei Zhou; Ran Ran; Zongping Shao; Wanqin Jin


    Conic Ba0.5Sr0.5Co0.8Fe0.2O3– (BSCF) functional composite oxide was synthesized via a simple in situ templating process. The treatment of the solid precursor with concentrated nitric acid resulted in the mismatch of ionic radius at -site and -site of the ABO3 perovskite, due to the oxidation of cobalt/iron ions, and the formation of Ba0.5Sr0.5(NO3)2 solid solution. Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of Ba0.5Sr0.5CoO3 (BSC) in hexagonal lattice structure and with conic particle shape was preferentially formed during calcination at low temperature. BSCF perovskite was then produced by the in situ templating of BSC with iron diffusing into the BSC lattice during calcination at high temperature. Wellcrystallized BSCF particles in conic shape were obtained by the calcination of the nitric acid treated precursor at 900°C.

  5. High redox and performance stability of layered SmBa(0.5)Sr(0.5)Co(1.5)Cu(0.5)O(5+δ) perovskite cathodes for intermediate-temperature solid oxide fuel cells.

    Jun, Areum; Shin, Jeeyoung; Kim, Guntae


    Cobalt-containing cathodes often encounter problems such as high thermal expansion coefficients (TEC) and poor stability, making them unsuitable for practical use as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study focuses on the effects of Cu doping in the Co site of SmBa0.5Sr0.5Co2O5+δ in terms of structural characteristics, electrical properties, electrochemical performance, redox properties, and performance stability as an IT-SOFC cathode material. The TEC value of a SmBa0.5Sr0.5Co1.5Cu0.5O5+δ (SBSCCu50) sample is 12.8 × 10(-6) K(-1), which is lower than that (13.7 × 10(-6) K(-1)) of a SmBa0.5Sr0.5Co2O5+δ (SBSCO) sample at 700 °C. SBSCCu50 showed higher redox stability at lower p(O2) and a more stable cell power output while retaining desirable electrochemical performance, as compared with SBSCO. SBSCCu50 displayed reduced TEC values and enhanced redox and performance stability, as well as satisfactory electrical properties and electrochemical performance under typical fuel cell operating conditions. The results indicate that SBSCCu50 is a promising material as a cathode for IT-SOFCs.

  6. A comparative study on the magnetic and electrical properties of MFe{sub 12}O{sub 19} (M=Ba and Sr)/BiFeO{sub 3} nanocomposites

    Ahmed, M.A., E-mail: [Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza (Egypt); Mansour, S.F. [Physics Department, Faculty of Science, Zagazig University (Egypt); Ismael, H. [Materials Science Lab (1), Physics Department, Faculty of Science, Cairo University, Giza (Egypt)


    M-type hexaferrite (MFe{sub 12}O{sub 19}), M=Ba or Sr nanoparticles with hexagonal crystal structure have been successfully synthesized by a citrate auto-combustion method. BiFeO{sub 3} (BFO) was prepared by the flash auto-combustion technique. Different nanocomposites were prepared according to the formula [(1−X) MFe{sub 12}O{sub 19}+XBiFeO{sub 3}; 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 (MFe{sub 12}O{sub 19}) 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. • M{sub s}, M{sub r}, μ{sub eff.} and H{sub C} were improved to be suitable for perpendicular high density recording media. • ε′ increased with BFO ratio which is useful in microwave devices.

  7. Heat capacities and thermodynamic functions of new nanosized ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba)

    Kasenov, B. K.; Kasenova, Sh. B.; Sagintaeva, Zh. I.; Turtubaeva, M. O.; Kakenov, K. S.; Esenbaeva, G. A.


    The heat capacities of nanosized ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) are measured via dynamic calorimetry in the temperature range of 298.15-673 K using an IT-S-400 instrument. It is established that the C°p f( T) function of LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) has λ-type effects, due probably to phase transitions of the second order. Considering the temperatures of the phase transitions, equations of the heat capacity of ferro-chromo-manganites LaM0.5 IIFeCrMnO6.5 (MII-Mg, Ca, Sr, Ba) as a function of temperature are derived on the basis of experimental data. Thermodynamic functions H°( T)- H°(298.15), S°( T), and V xx( T) are calculated in the temperature range of 298.15-675 K.

  8. Dielectric response of MgO-added Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} ceramics under bias electric field: Examination of contributing mechanisms

    Zhang Xiaofei [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); School of Mathematics and Physics, Hubei Ploytechnic University, Huangshi, 435003 (China); Xu Qing, E-mail: [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Zhan Di; Liu Hanxing; Chen Wen; Huang Duanping [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China)


    The structure and dielectric properties of (1-x)wt% Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}-xwt% MgO (x=0.5-60) ceramics were studied. The specimens with x{<=}1 had a single-phase perovskite structure and those with higher MgO contents presented a biphasic structure comprising Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} and MgO phases. The temperature dependence of the dielectric properties showed a frequency-dispersion behavior. The dielectric constants of the ceramics under bias electric field displayed an obvious deviation from the behavior as predicted by the phenomenological Johnson model. These dielectric phenomena were explained in relation to Mg{sup 2+} doping and polar nano-regions (PNRs) in Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} phase. Fitting the dielectric constants to a multipolarization mechanism model resolved intrinsic and extrinsic contributions to the dielectric non-linearity of the ceramics. Characteristic parameters of the contributions were determined from the fitting. Increasing MgO content led to a monotonous enhancement of the anharmonic coefficient ({alpha}). The polarization of PNRs tended to decrease with the increase of MgO content while the size of PNRs was insensitive to MgO content.

  9. Dielectric properties of xNa0.5Bi0.5TiO3-(1 ‑ x)Ba0.66Mg0.04Sr0.3TiO3 composite ceramics

    Wang, Jing; Cheng, Haiyan; Gao, Lan; Wang, Xianling; Duan, Ruijie; Li, Jiali


    The ceramics with the composition of xNa0.5Bi0.5TiO3-(1 ‑ x)Ba0.66Mg0.04Sr0.3TiO3 (NBT-BMST) in which x = 0.2, 0.3, 0.4 and 0.5 were prepared successfully by the solid-state reaction method. The effects of NBT-doping on phase structure, morphology, temperature stability and dielectric properties had been investigated in detail. The XRD results show that the composites are composed of tetragonal perovskite. The phase structure of NBT-BMST is observed by scanning electron microscopy. The dielectric constant of 0.3Na0.5Bi0.5TiO3-0.7Ba0.66Mg0.04Sr0.3TiO3 ceramic is ˜4100, the temperature coefficients of capacitance are ‑15%, 15% and 22% at ‑55∘C, 60∘C and 200∘C, respectively. And the dielectric loss is less than 0.13, which is obviously superior to other compositions. The results of this work showed that the component of 0.3Na0.5Bi0.5TiO3-0.7Ba0.66Mg0.04Sr0.3TiO3 is a promising candidate to high-temperature stable materials.

  10. Particle morphology and magnetic properties of Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12}O{sub 19} powder calcined conventionally and by microwave heating

    Kanagesan, S., E-mail: [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Selangor (Malaysia); Hashim, M. [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Selangor (Malaysia); Physics Department, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Selangor (Malaysia); Jesurani, S. [Department of Physics, Jeyaraj Annapackium College for Women, Periyakulam 625601, Tamil Nadu (India); Kalaivani, T. [Center for material science and Nano Devices, Department of Physics, SRM University, Kattankulathur 603203, Tamil Nadu (India); Ismail, I.; Shafie, M.S.E. [Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Selangor (Malaysia)


    Highlights: Black-Right-Pointing-Pointer Synthesis of Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12}O{sub 19} by sol-gel technique. Black-Right-Pointing-Pointer Crystallization temperature is reduced to 900 Degree-Sign C due to the addition of D-Fructose. Black-Right-Pointing-Pointer Results of conventional and microwave calcined samples are reported. - Abstract: Barium strontium hexaferrite (Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12}O{sub 19}-BSF) has been prepared by sol-gel process involving use of D-Fructose as a fuel. The prepared precursor was calcined in two different calcinations techniques conventional and microwave furnace. X-ray powder diffraction studies confirmed the formation of single phase Ba{sub 0.5}Sr{sub 0.5}Fe{sub 12}O{sub 19}. HR-SEM results show the morphology of the particles is hexagonal structures in platelet form. The average particle size of conventionally calcined BSF powder is 100-250 nm and that of microwave calcined powder is 30-100 nm. The broad hysteresis loop reveals that powder is well crystallized and exhibits hard magnetic properties.

  11. Orange-red emitting Eu2+-activated (Sr0.883Ba0.1Lu0.0.17)3(Si0.95Al0.05)O5 phosphor:structure, photoluminescence, and application in white LEDs

    赵凤阳; 吕雁鹏; 周广洲; 朴贤卿; 孙卓


    Orange-red emitting (Sr0.883–xBa0.1Lu0.0.17Eux)3(Si0.95Al0.05)O5 phosphors were synthesized by conventional solid-state reac-tion. The effect of NH4F flux on structural and luminescent properties of phosphors was investigated. Results suggested that the opti-mal content of NH4F flux was 3 wt.%and the optimal doping concentration of Eu2+was x=0.023 mol. The phosphors showed intense absorption in near-ultraviolet to blue region and exhibited orange-red emissions. The thermal stability of synthesized (Sr0.86Ba0.1Lu0.017Eu0.023)3(Si0.95Al0.05)O5 phosphor were examined and compared with commercial YAG:Ce3+ yellow phosphors. Combining an InGaN blue 460 nm chip and a white-emitting (Sr0.86Ba0.1Lu0.017Eu0.023)3(Si0.95Al0.05)O5 phosphor produced a white-light LED, demonstrating CIE chromaticity coordinates of (0.314, 0.329) and a color temperature of 5595 K. All results showed that this phosphor is a promising candidate as orange-red emitting phosphor for white light emitting diode (w-LED) application.

  12. Electron paramagnetic resonance and optical spectroscopy of Yb sup 3 sup + ions in SrF sub 2 and BaF sub 2; an analysis of distortions of the crystal lattice near Yb sup 3 sup +

    Falin, M L; Latypov, V A; Leushin, A M


    SrF sub 2 and BaF sub 2 crystals, doped with the Yb sup 3 sup + ions, have been investigated by electron paramagnetic resonance and optical spectroscopy. As-grown crystals of SrF sub 2 and BaF sub 2 show the two paramagnetic centres for the cubic (T sub c) and trigonal (T sub 4) symmetries of the Yb sup 3 sup + ions. Empirical diagrams of the energy levels were established and the potentials of the crystal field were determined. Information was obtained on the SrF sub 2 and BaF sub 2 phonon spectra from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyse the crystal lattice distortions in the vicinity of the impurity ion and the F sup - ion compensating for the excess positive charge in T sub 4. Within the frames of a superposition model, it is shown that three F sup - ions from the nearest surrounding cube, located symmetrically with respect to the C sub 3 axis from the side of the ion-compensator, approach the impurity ion and cling to the axis of the...

  13. Microwave firing-incubation of cage-like (Ba, Sr)3MgSi2O8:0.06Eu2+,0.1Mn2+sphere from sprayed template-free xerogel particles

    WANG Lingchang; Lu Qifei; LI Jian; LIN Chengguo; CAO Lisheng; WANG Dajian


    Morphology control of cage-like (Ba,Sr)3MgSi2O8:Eu,Mn luminous sphere in micrometer size with a simultaneous 660 nm/430 nm-featured band emission was investigated via microwave (MW) firing procedure.A firing temperature range associated with distinct reaction of xerogel particles was determined by thermal analysis,at which the pure host phase of (Ba,Sr)3MgSi2O8 was formed and the release of decomposed gas from the precipitated nitrates played a key role in controlling the multi-scale structured morphology.As-prepared Ba1.14Sr1.7MgSi2Os:0.06Eu2+,0.1Mn2+ samples featured in a band emission simultaneously emitting at both 660 and 430 nm under 350 nm light excitation by MW procedure with an enhancement emission compared to the sample by solid state procedure.The results suggested that MW firing procedure affected assembling cage-like particle in meso-,nano-and submicrometers to achieve photoluminescence (PL) enhancement of the simultaneous red/blue emission.

  14. Ba0.5Sr0.5TiO3薄膜电容的尺寸效应研究%Dimension effects on the properties of Ba0.5Sr0.5TiO3 thin film capacitors

    许程源; 肖勇; 张光强; 蒋书文


    采用射频磁控溅射和微细加工技术制备了不同尺寸的钛酸锶钡(Ba0.5Sr0.5TiO3,BST)平行板电容,研究了低频和高频条件下不同尺寸BST平行板电容的电容密度和Q值的变化情况.结果表明,由于存在边缘效应,BST薄膜电容的电容密度及Q值都具有尺寸效应.低频时,随着电容面积增大,电容密度减小,Q值增大.高频时,随着电容面积增大,电容密度及Q值减小.%Barium strontium titanate (Ba0.5Sr0.5TiO3, BST) thin film parallel plate capacitors with different sizes were fabricated by using the radio frequency magnetron sputtering and microfabrication techniques. And, the effects of size on the capacitance density and quality factor of the BST capacitors at low and high frequencies were studied. The results show that both the capacitance density and quality factor of the BST capacitors are size dependent. At low frequencies, the capacitance density decreases while the quality factor increases with the increase in the size of the top electrode. At high frequencies, both the capacitance density and quality factor decrease with the increase in the top electrode size.

  15. In-plane strain modulated magnetization and magnetoelectric effect in La0.7Sr0.3MnO3-BaTiO3 and La0.7Sr0.3MnO3-BaTiO3-BiFeO3 multilayer's

    Kumar, Virendra; Gaur, Anurag; Chaudhury, Ram Janay; Kumar, Dileep


    La0.7Sr0.3MnO3-BaTiO3(LSMO/BTO) and La0.7Sr0.3MnO3-BaTiO3-BiFeO3 (LSMO/BTO/BFO) multilayer thin films are deposited on STO (100) substrate by pulsed laser deposition. In-plane lattice mismatch induced strain is thoroughly investigated with the conclusion, that upper BTO layer of bilayer resides in high strained state, while upper BFO layer of trilayer remains under partially relaxed state. Significantly higher value (∼20) of dielectric constant is observed for LSMO/BTO bilayer in compliance with its higher (12.28 μC/cm2) in-plane strain induced interfacial polarization, which exceeds (2.06 μC/cm2), the observed value of polarization for LSMO/BTO/BFO trilayer. In LSMO/BTO bilayer, antiferromagnetic LSMO phase coexists due to the existence of strong tensile strain between the interfaces, which causes the reduction in value of saturation magnetization up to 50.76 emu/cm3 in comparison to 145.01 emu/cm3 for LSMO/BTO/BFO trilayer. The maximum value of linear magnetoelectric coefficient (α31) observed for LSMO/BTO bilayer is 24.77 mV/cm-Oe, which is higher in comparison to 19.54 mV/cm-Oe for LSMO/BTO/BFO trilayer, where the upper layer undergoes less strain in comparison to the bilayer.

  16. Preparation and dielectric properties of compositionally graded (Ba,Sr)TiO3 thin film by sol-gel technique

    ZHANG Tian-jin; WANG Jun; ZHANG Bai-shun; WANG Jin-zhao; WAN Neng; HU Lan


    Compositional graded BaxSr1-xTiO3 (x=0.6,0.7,0.8,0.9,1.0) (BST) thin films (less than 400 nm) were fabricated on Si and Pt/Ti/SiO2/Si substrates by sol-gel technique. A special heating treatment was employed to form the uniform composition gradients at 700 ℃. The microstructures of the films were studied by means of X-ray diffraction,atomic force microscope and field emission scanning electron microscopy. The results show that the films have uniform and crack-free surface morphology with perovskite structure phase. The small signal dielectric constant (εr) and dielectric loss (tanδ) are found to be 335 and 0.045 at room temperature and 200 kHz. The dielectric properties change significantly with applied dc bias,and the graded thin film show high tunability of 42.3% at an applied field of 250 kV/cm. All the results indicate that the graded BST thin films prepared by sol-gel technique have a promising candidate for microelectronic device.

  17. S=5/2 spin-chain Heisenberg systems SrMn{sub 2}V{sub 2}O{sub 8} and BaMn{sub 2}V{sub 2}O{sub 8}

    Niesen, Sandra; Kolland, Gerhard; Heyer, Oliver; Valldor, Martin; Lorenz, Thomas [II. Physikalisches Institut, Universitaet Koeln (Germany)


    Low-dimensional magnetic systems are commonly studied due to their interesting magnetic properties. For small spin values (S=1/2 or 1), the groundstate and the low-lying excitations are often dominated by strong quantum fluctuations, while a more classical behavior is expected for systems with larger spins. In this context, the series AM{sub 2}X{sub 2}O{sub 8} (A=Ba,Sr,Pb; M=Cu,Co,Ni,Mn; X=V,As) are of particular interest. Depending on the transition metal, different spins are realized and the structure contains screw chains of octahedrally coordinated M{sup 2+} ions along the c axis of the tetragonal structure. These chains are spatially separated by a nonmagnetic matrix, resulting in a quasi-1D magnetic system. The Heisenberg S=5/2 system BaMn{sub 2}V{sub 2}O{sub 8} shows low-dimensional behavior with a broad maximum of {chi}(T) around 170 K but finally orders antiferromagnetically at 37 K. Up to now only few studies of polycristalline BaMn{sub 2}V{sub 2}O{sub 8} were available. Large single crystals of BaMn{sub 2}V{sub 2}O{sub 8} and of the new compound SrMn{sub 2}V{sub 2}O{sub 8} were prepared. The crystal structure and the basic physical properties of this new compound are presented.

  18. A high performance BaZr0.1Ce0.7Y0.2O3-δ-based solid oxide fuel cell with a cobalt-free Ba0.5Sr0.5FeO3-δ–Ce0.8Sm0.2O2-δ composite cathode

    Sun, Wenping; Shi, Zhen; Fang, Shumin; Yan, Litao; Zhu, Zhiwen; Liu, Wei


    A cobalt-free Ba0.5Sr0.5FeO3-δ–Ce0.8Sm0.2O2-δ (BSF–SDC) composite is employed as a cathode for an anode-supported proton-conducting solid oxide fuel cells (H-SOFCs) using BaZr0.1Ce0.7Y0.2O3-δ (BZCY) as the electrolyte. The chemical compatibility between BSF and SDC is evaluated. The XRD results show

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

    Purdey, Mark


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

  20. Synthesis and crystal structure of Sr(AsO{sub 3}OH) and Ba(AsO{sub 3}OH): crystal chemistry of related MHXO{sub 4} (X = As, P, S) compounds

    Mihajlovic, T.; Effenberger, H. [Inst. fuer Mineralogie und Kristallographie, Univ. Wien (Austria)


    Crystals of M(AsO{sub 3}OH) (M = Sr and Ba) were synthesized under hydrothermal conditions; single-crystal X-ray structure investigations were performed. The average structure of Sr(AsO{sub 3}OH) exhibits three crystallographically different hydrogen bonds; two of them are related by anti 1 symmetry [space group P anti 1, a = 7.349(2) A, b = 7.057(2) A, c = 7.460(2) A, {alpha} = 95.20(3) , {beta} = 104.78(3) , {gamma} = 88.11(3) , Z = 4]. Weak superstructure reflections were detected which are responsible for a larger cell volume [space group P anti 1, a = 9.038(2) A, b = 11.732(2) A, c = 15.356(3) A, {alpha} = 71.66(3) , {beta} = 75.16(3) , {gamma} = 89.11(3) , Z = 16]. All inversion centres restricting the hydrogen bonds are avoided in the super cell. As a result, a completely ordered atomic arrangement is obtained. The arsenate tetrahedra are linked by hydrogen bonds to polar chains with branches in [110] and [ anti 1 anti 10], respectively; they are linked by the Sr atoms. The compounds CaHPO{sub 4} (monetite), CaHAsO{sub 4} (weilite), {alpha}-SrHPO{sub 4} {alpha}-NaHSO{sub 4}, and HgHPO{sub 4} have roughly the same arrangements of the M(= Ca, Sr, Na, Hg) and X(= P, As, S) atoms; however their hydrogen-bonding schemas are principally different. For the detailed comparison, the non-standard unit cell was chosen for Sr(AsO{sub 3}OH) [space group F anti 1, a = 14.697(3), b = 28.230(5), c = 14.920(3) A, {alpha} = 95.20(3) , {beta} = 104.78(3) , {gamma} = 88.11(3) , Z = 64]. The structural refinement of Ba(AsO{sub 3}OH) confirmed isotypy with {gamma}-Sr(PO{sub 3}OH), K(SO{sub 3}OH), and K(SeO{sub 3}OH) [space group Pbca a = 8.581(2), b = 9.896(2), c = 19.417(4) A, Z = 16]. Sr(AsO{sub 3}OH) and Ba(AsO{sub 3}OH) are characterized by short (strong) hydrogen bonds. (orig.)

  1. Dielectric properties of BaMg1/3Nb2/3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

    Alema, Fikadu; Pokhodnya, Konstantin


    Ba(Mg1/3Nb2/3)O3 (BMN) doped and undoped Ba0.45Sr0.55TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss (˜38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg2+ whose detrimental effect on tunability is partially compensated by small Nb5+ as the two substitute Ti4+ in the BST. The coupling between MgTi″ and VO•• charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was investigated in the temperature range of 300-450K. A reduced LC measured for the BMN doped BST film was correlated to the formation of defect dipoles from MgTi″, VO•• and NbTi• charged defects. The carrier transport properties of the films were analyzed in light of Schottky thermionic emission (SE) and Poole-Frenkel (PF) emission mechanisms. The result indicated that while the carrier transport mechanism in the undoped film is interface limited (SE), the conduction in the BMN doped film was dominated by bulk processes (PF). The change of the conduction mechanism from SE to PF as a result of BMN doping is attributed to the presence of uncoupled NbTi• sitting as a positive trap center at the shallow donor level of the BST.

  2. Surface morphology and in-plane-epitaxy of SmBa2Cu3O7-δ films on SrTiO3 (001) substrates studied by STM and grazing incidence x-ray diffraction

    Jiang, Q.D.; Smilgies, D.M.; Feidenhans'l, R.


    The surface morphology and in-plane epitaxy of thin films of SmBa(2)Cu3O(7-delta) (Sm-BCO) grown on SrTiO3 (001) substrates with various thicknesses have been investigated by scanning tunneling microscopy (STM) and grazing incidence x-ray diffraction (GIXRD). As revealed by GIXRD, SmBCO films...... as thick as 500 Angstrom grow pseudomorphically on SrTiO3 (001) surfaces, in comparison with a maximum of 130 Angstrom for YBCO. This is probably due to a better lattice match of SmBCO (epsilon(alpha) = 1.2%, epsilon(b)=-0.5%) compared to YBCO (epsilon(alpha)=2.0%, epsilon(b)=0.5%) with the SrTiO3...

  3. Geology, mineralization, Rb-Sr & Sm-Nd geochemistry, and U–Pb zircon geochronology of Kalateh Ahani Cretaceous intrusive rocks, southeast Gonabad

    Mohammad Hassan Karimpour


    Full Text Available Kalateh Ahani is located 27 km southeast of Gonabad within the Khorasan Razavi province. The area is part of Lut Block. Sub-volcanic monzonitic rocks intruded regional metamorphosed Shemshak Formation (Jurassic age. Magnetic susceptibility of less altered monzonitic rocks is 0.6%., As, Pb and Zn > 1%, Au up to 150 ppb and Sn = 133 ppm. The Sn content of vein in the northern part of Kalateh Ahani (Rud Gaz is > 1%. Based on mineralization, alteration and geochemistry, it seems that Sn mineralization is associated with the Cretaceous monzonitic rocks. Zircon U–Pb dating indicates that the age of the monzonitic rocks associated with mineralization is 109 Ma (Lower Cretaceous. Based on (87Sr/86Sri = 0.71089-0.710647 and (143Nd/144Ndi = 0.512113-0.51227 of the monzonitic rocks, the magma for these rocks were originated from the continental crust. This research has opened new window with respect to Sn-Cu mineralization and exploration within the Lut Block which is associated with Cretaceous granitoid rocks (reduced type, ilmenite series originated from the continental crust.

  4. The Rb problem in massive AGB stars.

    Pérez-Mesa, V.; García-Hernández, D. A.; Zamora, O.; Plez, B.; Manchado, A.; Karakas, A. I.; Lugaro, M.


    The asymptotic giant branch (AGB) is formed by low- and intermediate-mass stars (0.8 M_{⊙} develop thermal pulses (TP) and suffer extreme mass loss. AGB stars are the main contributor to the enrichment of the interstellar medium (ISM) and thus to the chemical evolution of galaxies. In particular, the more massive AGB stars (M > 4 M_{⊙}) are expected to produce light (e.g., Li, N) and heavy neutron-rich s-process elements (such as Rb, Zr, Ba, Y, etc.), which are not formed in lower mass AGB stars and Supernova explosions. Classical chemical analyses using hydrostatic atmospheres revealed strong Rb overabundances and high [Rb/Zr] ratios in massive AGB stars of our Galaxy and the Magellanic Clouds (MC), confirming for the first time that the ^{22}Ne neutron source dominates the production of s-process elements in these stars. The extremely high Rb abundances and [Rb/Zr] ratios observed in the most massive stars (specially in the low-metallicity MC stars) uncovered a Rb problem; such extreme Rb and [Rb/Zr] values are not predicted by the s-process AGB models, suggesting fundamental problems in our present understanding of their atmospheres. We present more realistic dynamical model atmospheres that consider a gaseous circumstellar envelope with a radial wind and we re-derive the Rb (and Zr) abundances in massive Galactic AGB stars. The new Rb abundances and [Rb/Zr] ratios derived with these dynamical models significantly resolve the problem of the mismatch between the observations and the theoretical predictions of the more massive AGB stars.

  5. B-site ordered double perovskite LaBa1-xSrxZnSbO6 (0 ≤ x ≤ 1): Sr(2+)-doping-induced symmetry evolution and structure-luminescence correlations.

    Jiang, Pengfei; Zhou, Zhengyang; Gao, Wenliang; Cong, Rihong; Yang, Tao


    The study of perovskites has been active for a long time. Here, we rationally designed and prepared a double perovskite, LaBaZnSbO6, by selecting Zn(2+) and Sb(5+) with large size and charge differences, and, indeed, complete B-site ordering can be achieved. Careful study using powder X-ray diffraction data pinpointed its space group to be I2/m, which has rarely been seen in double perovskites. Thereafter, an interesting observation of Sr(2+)-doping-induced symmetry evolution from I2/m to P21/n was confirmed in the complete solid solutions LaBa1-xSrxZnSbO6, where the tilting system also transferred from a(-)a(-)c(0) to a(-)a(-)c(+). The transition boundary is around x = 0.4. It can also be visualized by the variation of θ (defined as c/[(a + b)/2]), which is associated with the anisotropic shrinkage of the unit cell lattice and indeed shows a minimum at x = 0.4. Such a successive modulation of both the structural symmetry and the average La/Ba/Sr-O bond distances (revealed by Rietveld refinements) motivated us to study the Eu(3+) luminescence in La0.95Eu0.05Ba1-xSrxZnSbO6. Interestingly, the maximum of charge transfer absorption of Eu(3+) shows a precise changing tendency with the A-O bond distances along with the Sr(2+) doping, clearly revealing the structure-luminescence correlations.

  6. Synthesis and characterisation of the n = 2 Ruddlesden–Popper phases Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu)

    Gurusinghe, Nicola N.M. [School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Figuera, Juand de la; Marco, José F. [Instituto de Quimica-Fisica “Rocasolano”, CSIC, Serrano 119, 28006 Madrid (Spain); Thomas, Michael F. [Department of Physics, University of Liverpool, Liverpool. L69 3BX (United Kingdom); Berry, Frank J., E-mail: [School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Greaves, Colin [School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)


    Graphical abstract: - Highlights: • Some Ruddlesden–Popper phases have been characterised. • Substitution on the A site influences cationic order. • The magnetic moment redirects with temperature - Abstract: A series of n = 2 Ruddlesden–Popper phases A{sub 2}B{sub 2}O{sub 7} of composition Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu) have been prepared. La{sub 2}SrFe{sub 2}O{sub 7} and La{sub 2}BaFe{sub 2}O{sub 7} crystallise in the tetragonal space group I4/mmm. The structures of Eu{sub 2}SrFe{sub 2}O{sub 7} and Nd{sub 2}SrFe{sub 2}O{sub 7} are best described in space group P4{sub 2}/mnm. Substitution on the A site with smaller lanthanide- and larger alkaline metal- ions leads to enhanced cationic order in these phases and reflects increasing differences in cationic radii. All the compounds are antiferromagnetically ordered between 298 and 2 K. In La{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment lies along [1 1 0] at all temperatures between 298 and 2 K whereas in La{sub 2}BaFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along the crystallographic x-axis but redirects from the [1 0 0] to the [1 1 0] direction between 210 and 190 K and is retained in this direction until 2 K. In Nd{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along [1 1 0] but rotates from [1 1 0] to [0 0 1] between 17 and 9 K. A series of {sup 57}Fe Mössbauer spectra recorded from La{sub 2}SrFe{sub 2}O{sub 7} between 290 and 600 K indicate a magnetic ordering temperature of T{sub N} ≥ 535 K.

  7. Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

    Miliordos, Evangelos; Xantheas, Sotiris S.


    We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H2O)n]2+, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M2+(H2O)n-1 + H2O) and the two hydrolysis channels resulting to the loss of hydronium ([MOH(H2O)n-2]+ + H3O+) and Zundel ([MOH(H2O)n-3]+ + H3O+(H2O)) cations. The Potential Energy Curves (PECs) corresponding to those three channels were constructed at the Møller-Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H2O)n]+, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.

  8. Contamination of terrestrial gastropods Helix aspersa maxima with {sup 137}Cs, {sup 85}Sr, {sup 133}Ba and {sup 123m}Te by direct and trophic pathways

    Madoz-Escande, C.; Querrec, N.; Bonhomme, T.; Poncet-Bonnard, D. [CEA Cadarache (DEI/SECRE/LRE), Laboratory of Radioecology and Ecotoxicology, Institute for Radioprotection and Nuclear Safety, 13 - Saint-Paul-lez-Durance (France)


    Contaminations of terrestrial gastropod Helix aspersa Maxima by direct deposition or labelled food ingestion of {sup 137}Cs, {sup 85}Sr, {sup 133}Ba and {sup 123m}Te were carried out in laboratory conditions. This study was performed to compare the two pathways of contamination: direct and trophic in terms of individual mortality and, radionuclide uptake, depuration and tissular distribution. A first group of 30 snails (2-year old) was exposed to radioactive aerosols during a twenty-hour period. These aerosols were supposed to be representative of those produced during a nuclear accident occurring on a PWR. A second group of 40 snails (same ages) was submitted to twice-a-week ingestion of food during 10 days (flour at a feeding rate of about 0,2 g) contaminated by these same aerosols. During the 21 days observation period, comparison among the two groups and a reference group (not contaminated by radionuclides) was performed. No significant difference between the three groups was observed neither on the growth nor on the mortality. One day after the deposit, the cesium was the most bioavailable element, distributed homogeneously within the whole body (from 15 to 25% of total Cs respectively in shell and muscle). The strontium accumulated in the shell (about 70%). The barium was found in the muscle (20%) and the shell (65%). Tellurium was mainly present in the shell (70%) and in digestive gland (20%), Later, this element was mostly present in faeces. As regards the contamination by ingestion, it was mainly accumulated in digestive gland. (author)

  9. Preparation Process and Dielectric Properties of Ba(0.5)Sr(0.5)TiO3-P(VDF-CTFE) Nanocomposites

    Zhang, Lin; Wu, Peixuang; Li, Yongtang; Cheng, Z. -Y.; Brewer, Jeffrey C.


    Ceramic-polymer 0-3 nanocomposites, in which nanosized Ba(0.5)Sr(0.5)TiO3 (BST) powders were used as ceramic filler and P(VDF-CTFE) 88/12 mol% [poly(vinylidene fluoridechlorotrifluoroethylene)] copolymer was used as matrix, were studied over a concentration range from 0 to 50 vol.% of BST powders. It is found that the solution cast composites are porous and a hot-press process can eliminate the porosity, which results in a dense composite film. Two different configurations used in the hot-press process are studied. Although there is no clear difference in the uniformity and microstructure of the composites prepared using these two configurations, the composite prepared using one configuration exhibit a higher dielectric constant with a lower loss. For the composite with 40 vol. BST, a dielectric constant of 70 with a loss of 0.07 at 1 kHz is obtained at room temperature. The composites exhibit a lower dielectric loss than the polymer matrix at high frequency. However, at low frequency, the composites exhibit a higher loss than the polymer matrix due to a low frequency relaxation process that appears in the composites. It is believed that this relaxation process is related to the interfacial layer formed between BST particle and the polymer matrix. The temperature dependence of the dielectric property of the composites was studied. It is found that the dielectric constant of these composites is almost independent of the temperature over a temperature range from 20 to 120 C. Key words: A. Polymer-matrix composites (PMCs); B. Electrical Properties; E. Casting; E. Heat treatment; Dielectric properties.

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

    Smet, Philippe F., E-mail: [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)


    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. Diffuse ferroelectric transition and relaxational dipolar freezing in (Ba, Sr)TiO{sub 3:} III. Role of order parameter fluctuations

    Singh, Neelam; Pandey, Dhanajai [School of Materials Science and Technology, Banaras Hindu University, Vanarasi (India); Singh, Anirudh P. [Shaheed Bhagat Singh College of Engineering and Technology, Ferozpor (India); Durga Prasad, Ch. [Naval Materials Research Laboratory, Naval Dockyard, Bombay (India)


    Results of a high-temperature x-ray powder diffraction study of the phase transition between cubic and tetragonal phases of (Ba{sub 1-x}Sr{sub x})TiO{sub 3} are presented for x=0.08 and 0.12 which exhibit sharp and diffuse dielectric anomalies, respectively. Experimental evidence and arguments are advanced to show that the cubic and tetragonal phases coexist over a wide range of temperatures and that this coexistence is due to the fluctuation of the order parameter which is coupled electrostrictively to strains. For x=0.08, the phase coexistence disappears below the dielectric anomaly temperature T{sub m}', indicating the critical nature of the fluctuations. For x=0.12, these fluctuations are non-critical since the phase coexistence persists even below T{sub m}'. The complete conversion to the tetragonal phase occurs at T{sub s} approx. 7.5 deg. C which is nearly 25 deg. C lower than T{sub m}'(= 102 {+-} 1 deg. C). It is shown that the spontaneous polarization also increases gradually below T{sub m}' and levels off at T{sub p} {approx} 75 deg C. The existence of structural and polarization anomalies well below the frequency-independent dielectric anomaly temperature T{sub m}' cannot be rationalized either in terms of the Landau-like theories for ferroelectric transitions which predict T{sub s}=T{sub p}T{sub m}' or in terms of dipole glass transitions and/or relaxor ferroelectric transitions for which T{sub m}' should be frequency dependent. (author)

  12. Librational modes of the water molecules in barium and strontium halide monohydrates, MX 2 · 1H 2O (M = Ba, Sr; X = Cl, Br, I)

    Lutz, H. D.; Christian, H.


    The IR and Raman spectra of the isotypic alkaline earth halide monohydrates, MX 2 · 1H 2O, with M = Sr, Ba and X = Cl, Br, I, and of deuterated samples are presented for the range 200-700 cm -1 and discussed in terms of normal modes, assignment, coupling, correlation with structure data, and temperature dependence of both the H 2O (D 2O) and the HDO librational modes. The normal modes of the out-of-plane librations of HDO molecules are of the wagging and twisting type rather than H and D out-of-plane vibrations [4], at least for water molecules with C2v or nearly C2v symmetry. Thus the observed H 2O/HDO isotopic shifts can be used as a criterion for assigning the H 2O librations. The librational modes of the halide monohydrates (with tetrahedrally coordinated water oxygen atoms) are found in the order ν Rγ ≫ ν Rt ≫ ν Rr. The intensities of the IR and Raman spectra are in the order Rγ ≫ Rr ≫ Rt (or ˜ Rt in the case of strongly distorted H 2O molecules) and Rt ≫ Rr ≫ Rγ, respectively. Correlations of the H 2O librational modes with structural or bonding data are restricted by frequency shifts due to vibrational coupling and by the fact that the oxygen and the hydrogen atoms of the water molecules are generally affected in a different manner by bond interactions. However, in the case of the twisting vibrations, there are clear correlations with both the size of the metal ions, i.e. increase of ν Rt with decreasing size, and the intermolecular bonding of the hydrogen atoms, as shown by the OH stretching frequencies, i.e. increase of ν Rt with decreasing ν OH.

  13. Optical and scintillation properties of Ce:(Gd8AE2)(SiO4)6O2 (AE = Mg, Ca, Sr and Ba) crystals

    Igashira, Takuya; Mori, Masaki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki


    1% Ce-doped and non-doped (Gd8AE2)(SiO4)6O2 (AE = Mg, Ca, Sr and Ba) (denoted as GMS, GCS, GSrS and GBS, respectively) single crystals were grown by the Floating Zone (FZ) method to evaluate their optical and scintillation properties. The Ce:GCS and Ce:GSrS samples exhibited scintillation and photoluminescence (PL) around 400 nm due to the 5d-4f transitions of Ce3+. On the other hand, Ce:GMS and Ce:GBS showed much weaker emissions in the wavelength range of 500-650 nm, in which the origin was associated with the host matrices. The PL decay curves were approximated by a double exponential decay function for all the Ce-doped samples. The decay times ranged around 10-30 and 40-90 ns, and faster components coincided with those of the non-doped samples. The scintillation decay curves of Ce-doped samples, on the other hand, were approximated by single exponential functions with slower decay constants than those of PL decay. These constants were very similar to those of non-doped samples. In the X-ray induced afterglow measurements, Ce:GCS exhibited the lowest afterglow level. The pulse height spectrum of these samples showed a full-energy peak under 241Am 5.5 MeV α-ray irradiation. Among these samples, Ce:GSrS exhibited the highest light yield which was around 600 ph/5.5 MeV-α.

  14. Structure and luminescence properties of SrAl{sub 2}O{sub 4}:Eu{sup 2+}, Dy{sup 3+} by Ba{sup 2+} and Ca{sup 2+} co-doping

    Xie Wei [Research Center of Chemistry and Materials Science, Development Center for New Materials Engineering and Technology in Universities of Guangdong, Zhanjiang Normal University, Zhanjiang 524048 (China); School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); School of Physics Science and Technology, Zhanjiang Normal University, Zhanjiang 524048 (China); Quan Jun [Research Center of Chemistry and Materials Science, Development Center for New Materials Engineering and Technology in Universities of Guangdong, Zhanjiang Normal University, Zhanjiang 524048 (China); School of Physics Science and Technology, Zhanjiang Normal University, Zhanjiang 524048 (China); Wu Haoyi [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Shao Lexi, E-mail: [Research Center of Chemistry and Materials Science, Development Center for New Materials Engineering and Technology in Universities of Guangdong, Zhanjiang Normal University, Zhanjiang 524048 (China) and School of Physics Science and Technology, Zhanjiang Normal University, Zhanjiang 524048 (China); Zou Changwei; Zhang Jun [Research Center of Chemistry and Materials Science, Development Center for New Materials Engineering and Technology in Universities of Guangdong, Zhanjiang Normal University, Zhanjiang 524048 (China); School of Physics Science and Technology, Zhanjiang Normal University, Zhanjiang 524048 (China); Shi Xiaoyu [Research Center of Chemistry and Materials Science, Development Center for New Materials Engineering and Technology in Universities of Guangdong, Zhanjiang Normal University, Zhanjiang 524048 (China); Wang Yinhai [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China)


    Highlights: Black-Right-Pointing-Pointer Sr{sub x}Ca{sub (1-x)/2}Ba{sub (1-x)/2}Al{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+} phosphors were prepared. Black-Right-Pointing-Pointer The high temperature phase of SrAl{sub 2}O{sub 4} was obtained at room temperature. Black-Right-Pointing-Pointer The emit colour of phosphors can be adjusting by the radio of x. Black-Right-Pointing-Pointer The monoclinic structure provide better lattice sites to generate trap level. - Abstract: The long afterglow phosphors with Ca and Ba co-doped equally in Sr{sub x}Ca{sub (1-x)/2}Ba{sub (1-x)/2}Al{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+} (x = 1.0, 0.8, 0.6, 0.4, 0.2, 0) were synthesized using high temperature solid-state reaction method. X-ray powder diffraction (XRD) patterns show that the crystal phase structure of SrAl{sub 2}O{sub 4} changes from monoclinic to hexagonal with the decrease of x from 1 to 0.6, and hexagonal BaAl{sub 2}O{sub 4} and monoclinic CaAl{sub 2}O{sub 4} coexist when x is 0.2. Nevertheless, when x is reduced to 0, the main phase of sample changes to BaAl{sub 2}O{sub 4}. A blue shift is observed in the emission spectra due to the change in nature of the Eu{sup 2+} surroundings when x changes from 0.6 to 0. The results given by scanning electronic microscope (SEM) show that phosphors with different structures have similar irregular morphology. The decay characteristics reflect that the phosphors with different structures have different afterglow time. Samples with monoclinic structure have longer afterglow time than samples with hexagonal structure. The measurement of thermoluminescence reveals that the monoclinic structure of the phosphors provides better sites than that of the hexagonal structure for Dy{sup 3+}ions to generate suitable trap level.

  15. Validity and limitations of the superexchange model for the magnetic properties of Sr2IrO4 and Ba2IrO4 mediated by the strong spin-orbit coupling

    Solovyev, I. V.; Mazurenko, V. V.; Katanin, A. A.


    Layered perovskites Sr2IrO4 and Ba2IrO4 are regarded as the key materials for understanding the properties of magnetic relativistic insulators, mediated by the strong spin-orbit (SO) coupling. One of the most fundamental issues is to which extent these properties can be described by the superexchange (SE) model, formulated in the limit of the large Coulomb repulsion for some appropriately selected pseudospin states, and whether these materials themselves can be classified as Mott insulators. In this work, we address these issues by deriving the relevant models and extracting parameters of these models from the electronic-structure calculations with the SO coupling, based on the density functional theory. First, we construct the effective Hubbard-type model for the magnetically active t2 g bands, by recasting the problem in the language of localized Wannier orbitals. Then, we map the obtained electron model onto the pseudospin model by applying the theory of SE interactions, which is based on the second-order perturbation theory with respect to the transfer integrals. We discuss the microscopic origin of anisotropic SE interactions, inherent to the compass Heisenberg model, and the appearance of the antisymmetric Dzyaloshinskii-Moriya term, associated with the additional rotation of the IrO6 octahedra in Sr2IrO4 . In order to solve the pseudospin Hamiltonian problem and evaluate the Néel temperature (TN), we employ the nonlinear sigma model. We have found that, while for Sr2IrO4 our value of TN agrees with the experimental data, for Ba2IrO4 it is overestimated by a factor of 2. We argue that this discrepancy is related to limitations of the SE model: while for more localized t2 g states in Sr2IrO4 it works reasonably well, the higher-order terms in the perturbation theory expansion play a more important role in the more "itinerant" Ba2IrO4 , giving rise to the new type of isotropic and anisotropic exchange interactions, which are not captured by the SE model. This

  16. Material properties and structural characterization of M3Si6O12N2:Eu2+ (M = Ba, Sr)--a comprehensive study on a promising green phosphor for pc-LEDs.

    Braun, Cordula; Seibald, Markus; Börger, Saskia L; Oeckler, Oliver; Boyko, Teak D; Moewes, Alexander; Miehe, Gerhard; Tücks, Andreas; Schnick, Wolfgang


    The efficient green phosphor Ba(3)Si(6)O(12)N(2):Eu(2+) and its solid-solution series Ba(3-x)Sr(x)Si(6)O(12)N(2) (with x approximately = 0.4 and 1) were synthesized in a radio-frequency furnace under nitrogen atmosphere at temperatures up to 1425 degrees C. The crystal structure (Ba(3)Si(6)O(12)N(2), space group P3 (no. 147), a = 7.5218(1), c = 6.4684(1) A, wR2 = 0.048, Z = 1) has been solved and refined on the basis of both single-crystal and powder X-ray diffraction data. Ba(3)Si(6)O(12)N(2):Eu(2+) is a layer-like oxonitridosilicate and consists of vertex-sharing SiO(3)N-tetrahedra forming 6er- and 4er-rings as fundamental building units (FBU). The nitrogen atoms are connected to three silicon atoms (N3), while the oxygen atoms are either terminally bound (O1) or bridge two silicon atoms (O2) (numbers in superscripted square brackets after atoms indicate the coordination number of the atom in question). Two crystallographically independent Ba(2+) sites are situated between the silicate layers. Luminescence investigations have shown that Ba(3)Si(6)O(12)N(2):Eu(2+) exhibits excellent luminescence properties (emission maximum at approximately 527 nm, full width at half maximum (FWHM) of approximately 65 nm, low thermal quenching), which provides potential for industrial application in phosphor-converted light-emitting diodes (pc-LEDs). In-situ high-pressure and high-temperature investigations with synchrotron X-ray diffraction indicate decomposition of Ba(3)Si(6)O(12)N(2) under these conditions. The band gap of Ba(3)Si(6)O(12)N(2):Eu(2+) was measured to be 7.05+/-0.25 eV by means of X-ray emission spectroscopy (XES) and X-ray absorption near edge spectroscopy (XANES). This agrees well with calculated band gap of 6.93 eV using the mBJ-GGA potential. Bonding to the Ba atoms is highly ionic with only the 4p(3/2) orbitals participating in covalent bonds. The valence band consists primarily of N and O p states and the conduction band contains primarily Ba d and f states

  17. The Magma feeding system of Somma-Vesuvius (Italy)strato-volcano:new inferences from a review of geochemical and Sr,Nd,Pb and O isotope data. Volcanism in the Campania Plain: Vesuvius, Campi Flegrei and Ignimbrites

    Piochi, M.; De Vivo, B.; Ayuso, R. A.


    A large database of major, trace and isotope (Sr, Nd, Pb, O) data exists for rocks produced by the volcanic activity of Somma-Vesuvius volcano. Variation diagrams strongly suggest a major role for evolutionary processes such as fractional crystallization, contamination, crystal trapping and magma mixing, occurring after magma genesis in the mantle. Most mafic magmas are enriched in LILE (K, Rb, Ba), REE (Ce, Sm) and Y, show small Nb–Ta negative anomalies, and have values of Nb/Zr ...

  18. Single crystals of LnFeAsO{sub 1-x}F{sub x} (Ln = La, Pr, Nd, Sm, Gd) and Ba{sub 1-x}Rb{sub x}Fe{sub 2}As{sub 2}: Growth, structure and superconducting properties

    Karpinski, J., E-mail: karpinski@phys.ethz.c [Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich (Switzerland); Zhigadlo, N.D.; Katrych, S.; Bukowski, Z.; Moll, P. [Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich (Switzerland); Weyeneth, S.; Keller, H. [Physik-Institut der Universitaet Zuerich, 8057 Zuerich (Switzerland); Puzniak, R. [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland); Tortello, M.; Daghero, D.; Gonnelli, R. [Dipartimento di Fisica, Politecnico di Torino, 10129 Torino (Italy); Maggio-Aprile, I. [DPMC-MaNEP, University of Geneva, Geneva (Switzerland); Fasano, Y. [DPMC-MaNEP, University of Geneva, Geneva (Switzerland); Low Temperatures Laboratory and Instituto Balseiro, Bariloche (Argentina); Fischer, O. [DPMC-MaNEP, University of Geneva, Geneva (Switzerland); Rogacki, K. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw, P.O. Box 1410 (Poland); Batlogg, B. [Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich (Switzerland)


    A review of our investigations on single crystals of LnFeAsO{sub 1-x}F{sub x} (Ln = La, Pr, Nd, Sm, Gd) and Ba{sub 1-x}Rb{sub x}Fe{sub 2}As{sub 2} is presented. A high-pressure technique has been applied for the growth of LnFeAsO{sub 1-x}F{sub x} crystals, while Ba{sub 1-x}Rb{sub x}Fe{sub 2}As{sub 2} crystals were grown using a quartz ampoule method. Single crystals were used for electrical transport, structure, magnetic torque and spectroscopic studies. Investigations of the crystal structure confirmed high structural perfection and show incomplete occupation of the (O, F) position in superconducting LnFeAsO{sub 1-x}F{sub x} crystals. Resistivity measurements on LnFeAsO{sub 1-x}F{sub x} crystals show a significant broadening of the transition in high magnetic fields, whereas the resistive transition in Ba{sub 1-x}Rb{sub x}Fe{sub 2}As{sub 2} simply shifts to lower temperature. The critical current density for both compounds is relatively high and exceeds 2 x 10{sup 9} A/m{sup 2} at 15 K in 7 T. The anisotropy of magnetic penetration depth, measured on LnFeAsO{sub 1-x}F{sub x} crystals by torque magnetometry is temperature dependent and apparently larger than the anisotropy of the upper critical field. Ba{sub 1-x}Rb{sub x}Fe{sub 2}As{sub 2} crystals are electronically significantly less anisotropic. Point-Contact Andreev-Reflection spectroscopy indicates the existence of two energy gaps in LnFeAsO{sub 1-x}F{sub x}. Scanning Tunneling Spectroscopy reveals in addition to a superconducting gap, also some feature at high energy (approx20 meV).

  19. How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

    Huang, Xiaokun; Zhang, Weiyi


    The misfit layered Bi2A2Co2O8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A’s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi2Ca2Co2O8 and Bi2Sr2Co2O8 and intermediate-spin low-spin mixed-state of Bi2Ba2Co2O8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal.

  20. Effect of Ca{sup 2+} and Sr{sup 2+} alkaline earth ions on luminescence properties of BaAl{sub 12}O{sub 19}:Eu nanophosphor

    Deshmukh, Abhay D., E-mail: [National Environmental Engineering Research Institute, Nagpur 440020 (India); Department of Metallurgical and Materials Engineering, VNIT, Nagpur 440011 (India); Valechha, Arti; Valechha, Dolly; Kumar, Animesh [National Environmental Engineering Research Institute, Nagpur 440020 (India); Peshwe, D.R. [Department of Metallurgical and Materials Engineering, VNIT, Nagpur 440011 (India); Dhoble, S.J. [Kamla Nehru College, Sakkardara Square, Nagpur 440009 (India)


    Nanosized barium aluminate materials was doped by divalent cations (Ca{sup 2+}, Sr{sup 2+}) and Eu{sup 2+} having nominal compositions Ba{sub 1-x}MxAl{sub 12}O{sub 19}:Eu (M=Ca and Sr) (x=0.1-0.5), were synthesized by the combustion method. These phosphors were characterized by XRD, scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS) and photoluminescence measurement. The photoluminescence characterization showed the presence of Eu ion in divalent form which gave emission bands peaking at 444 nm for the 320 nm excitation (solid-state lighting excitation), while for 254 nm it gave the same emission wavelength of low intensity (1.5 times) compared to 320 nm excitation. It was also observed that alkaline earth metal (Ca{sup 2+} and Sr{sup 2+}) dopants increase the intensity of Eu{sup 2+} ion in BaAl{sub 12}O{sub 19} lattice, thus this phosphor may be useful for solid-state lighting.

  1. Syntheses, Vibrational Spectroscopy, and Crystal Structure Determination from X-Ray Powder Diffraction Data of Alkaline Earth Dicyanamides M[N(CN) 2] 2 with M=Mg, Ca, Sr, and Ba

    Jürgens, Barbara; Irran, Elisabeth; Schnick, Wolfgang


    The alkaline earth dicyanamides Mg[N(CN)2]2, Ca[N(CN)2]2, Sr[N(CN)2]2, and Ba[N(CN)2]2 were synthesized by ion exchange using Na[N(CN)2] and the respective nitrates or bromides as starting materials. The crystal structures were determined from X-ray powder diffractometry: Mg[N(CN)2]2, Pnnm, Z=2, a=617.14(3), b=716.97(3), and c=740.35(5) pm; Ca[N(CN)2]2 and Sr[N(CN)2]2, C2/c, Z=4; Ca[N(CN)2]2, a=1244.55(3), b=607.97(1), and c=789.81(1) pm, β=98.864(2)°; Sr[N(CN)2]2, a=1279.63(2), b=624.756(8), and c=817.56(1) pm, β=99.787(1)°; Ba[N(CN)2]2, Pnma, Z=4, a=1368.68(7), b=429.07(7), and c=1226.26(2) pm. The dicyanamides consist of the respective alkaline earth cations and bent planar [N(CN)2]- ions. The structural features were correlated with vibrational spectroscopic data. The thermal behavior was studied by thermoanalytical experiments.

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

    Sharma, Poorva; Kumar, Ashwini; Varshney, Dinesh


    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.

  3. Thermal expansion of layered cobaltites Y(Ba{sub 1-x}Sr{sub x})Co{sub 2}O{sub 5+{delta}} with x = 0, 0.05 and 0.10

    Aurelio, G; Bustingorry, S; Sanchez, R D [Consejo Nacional de Investigaciones CientIficas y Tecnicas, Centro Atomico Bariloche-Comision Nacional de EnergIa Atomica, Av. Bustillo 9500, 8400 S. C. de Bariloche, RN (Argentina); Cuello, G J, E-mail: [Institut Laue-Langevin, F-38042 Grenoble (France)


    The crystal structure and thermal expansion of Sr-doped layered cobaltites Y(Ba{sub 1-x}Sr{sub x})Co{sub 2}O{sub 5+{delta}} (x = 0, 0.05 and 0.10) were studied by means of in situ neutron thermodiffraction in the temperature range 20 K {<=} T {<=} 570 K. The evolution with temperature of lattice parameters for the phases which crystallize in this system is presented, as well as their dependence on the oxygen non-stoichiometry {delta}. Each phase's volume has been fitted using available models based on the Grueneisen approximation to the zero-pressure equation of state and using the Ruffa model based on the Morse potential, both using a Debye model for the internal energy. The coefficient of volumetric thermal expansion, Debye temperature and other thermodynamic parameters are presented and compared with other perovskite compounds.

  4. Optical, ferroelectric and magnetic properties of multiferroelectric BiFeO3-(K0.5Na0.5)0.4(Sr 0.6Ba0.4)0.8Nb2O6 thin films

    Yao, Yingbang


    Multiferroic BiFeO3-(K0.5Na0.5) 0.4(Sr0.6Ba0.4)0.8Nb 2O6 (BFO-KNSBN) trilayer thin films, were epitaxially grown on MgO(0 0 1) and SrTiO3(0 0 1) by using pulsed laser deposition (PLD). Their ferroelectric, magnetic, dielectric and optical properties were investigated. It was found that both ferroelectric polarization and dielectric constant of the films were enhanced by introducing KNSBN as a barrier layer. Meanwhile, ferromagnetism of BFO was maintained. More interestingly, a double hysteresis magnetic loop was observed in the KNSBN-BFO-KNSBN trilayer films, where exchange bias and secondary phase in the BFO layer played crucial roles. Interactions between adjacent layers were revealed by temperature-dependent Raman spectroscopic measurements. © 2013 Elsevier B.V. All rights reserved.

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

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


    EXAFS, X-ray Rietveld refinement and infra-red absorption measurements have been made on Yb sub 1 sub - sub x Ca sub x (Ba sub 0 sub . sub 8 Sr sub 0 sub . sub 2) sub 2 Cu sub 3 O sub 6 sub + subdelta in order to understand the effect of Ca doping on the local structure of planar Cu ion. The study indicates that restoration of superconductivity is due to oxidation of copper ions in the CuO sub 2 planes. (author)

  6. Creep behavior of perovskite-type oxides Ba0.5Sr0.5(Co0.8Fe0.2)1−xZrxO3−δ

    Stournari, V.; Donkelaar, ten S.F.P.; Malzbender, J.; Beck, T.; Singheiser, L.; Bouwmeester, H.J.M.


    Compressive creep tests have been performed on perovskite-type oxides Ba0.5Sr0.5(Co0.8Fe0.2)1–xZrxO3−δ (BSCF-Z100·x), where x = 0.01, 0.03, 0.05 and 0.1, for the use as oxygen transport membrane, in air at 800–950 °C and at nominal stresses of 30 MPa and 63 MPa. X-ray diffraction and microstructural

  7. Creep behavior of perovskite-type oxides Ba0.5Sr0.5(Co0.8Fe0.2)1−xZrxO3−δ

    Stournari, V.; ten Donkelaar, S.F.P.; Malzbender, J.; Beck, T.; Singheiser, L.; Bouwmeester, Henricus J.M.


    Compressive creep tests have been performed on perovskite-type oxides Ba0.5Sr0.5(Co0.8Fe0.2)1–xZrxO3−δ (BSCF-Z100·x), where x = 0.01, 0.03, 0.05 and 0.1, for the use as oxygen transport membrane, in air at 800–950 °C and at nominal stresses of 30 MPa and 63 MPa. X-ray diffraction and microstructural

  8. A study of the impurity-induced phase transition in Ba sub x Sr sub 1 sub - sub x TiO sub 3 within the framework of the transverse-field Ising model

    Wu Hua


    The transverse-field Ising model is successfully applied to the Ba sub x Sr sub 1 sub - sub x TiO sub 3 system. An impurity-induced paraelectric-ferroelectric phase transition is found for proper parameters. An explanation is offered for the results of the susceptibility chi(x, T), the transition temperature T sub m (x), the spontaneous polarization (P ) versus x and versus T, the field dependence of chi(x, T) and that of the polarization (P ) versus E for x, 0.2 <= x <= 0.95.

  9. Suppression of slow capacitance relaxation phenomenon in Pt/Ba0.3Sr0.7TiO3/Pt thin film ferroelectric structures by annealing in oxygen atmosphere

    Altynnikov, A. G.


    The impact of oxygen annealing on the switching time of ferroelectric thin film capacitor structures Pt/Ba0.3Sr0.7TiO3/Pt was investigated. The response of their capacitance on pulsed control voltages before and after annealing was experimentally measured. It was demonstrated that the annealing results in suppression of the capacitance slow relaxation processes and increase of the threshold control voltages. These structures can therefore be attractive for fabrication of fast acting microwave devices. © 2014 Author(s).

  10. Structural, electrochemical and magnetic characterization of the layered-type PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} perovskite

    Azad, Abul K., E-mail: [School of Chemistry, University of St Andrews, Fife KY16 9ST (United Kingdom); Faculty of Integrated Technologies, Universiti Brunei Darussalam, Gadong BE 1410 (Brunei Darussalam); Kim, Jung H. [Department of Applied Materials Science and Engineering, Hanbat National University, San 16-1, Dukmyung-Dong, Yusung-Gu, Daejeon 305-719 (Korea, Republic of); Irvine, John T.S. [School of Chemistry, University of St Andrews, Fife KY16 9ST (United Kingdom)


    Structural, electrical and magnetic properties of the layered cobaltite PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrO{sub δ}] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2a{sub p} and c≈2a{sub p} (a{sub p} is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573 K in air, structural rearrangement takes place and the structure can be defined as a≈a{sub p} and c≈2a{sub p} in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373 K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973 K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573 K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153 Ωcm{sup 2} and 0.286 Ωcm{sup 2} at 973 K and 923 K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order. - Graphical abstract: Structural phase changes in PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at elevated temperatures determined by neutron powder diffraction. Depending on oxygen occupancy it form different phases at different temperatures. This pictures show the schematic 3D diagram of PrBa{sub 0.5}Sr{sub 0.5}Co{sub 2}O{sub 5+δ} at 295 K (a), 373 K (b) and 573 K (c). Co atoms are inside the

  11. Structural and luminescence studies of Eu3+: TeO2sbnd B2O3sbnd AOsbnd AF2 (A = Pb, Ba, Zn, Cd, Sr) glasses

    Selvi, S.; Marimuthu, K.; Muralidharan, G.


    Eu3+ doped oxyfluoro boro-tellurite (TBXFE) with molar composition 29 TeO2sbnd 30B2O3sbnd 20AOsbnd 20AF2sbnd 1Eu2O3 (where A = Pb, Ba, Zn, Cd, Sr) glasses were prepared and investigated by XRD, FTIR, UV-Vis-NIR, luminescence and decay measurements. XRD patterns confirm the glassy nature of the prepared glasses. The influence of metal ions on the structure of boro-tellurite glasses were investigated through FTIR spectra. The intra band (4f-4f) transitions of Eu3+ ions are discussed through UV-Vis-NIR absorption spectra. The covalent nature around the Eu3+ ions with ligands are discussed using the bonding parameter (δ) and nephelauxetic ratio (β). The fundamental absorption edge, direct, indirect band gap, Urbach energy and band tailing parameters are reported. A bright red emission at 616 nm corresponding to the 5D0 → 7F2 transition of Eu3+ ions could be observed in the title glasses. Judd-Ofelt parameters were estimated from the emission spectra of Eu3+ ions. The dependence of these parameters on the composition of the glass is discussed. Judd-Ofelt parameters were used to derive the radiative parameters such as transition probabilities (A, s-1), branching ratios (βR), radiative lifetime (τrad) and stimulated emission cross-section (σPE) for the 5D0 → 7FJ (J = 0, 1, 2, 3 and 4) transitions. The luminescence intensity ratio (LIR) of 5D0 → 7F2/5D0 → 7F1 transitions was estimated to analyze the local site symmetry around the Eu3+ ions in the present glasses. The chromaticity coordinates and colour purity were calculated from the emission spectra and analyzed with Commission International de I'Eclairage (CIE) 1931 diagram. The experimental lifetime of 5D0 level could be fitted to a single exponential indicating the absence of energy transfer between the Eu3+ ions in the present glasses.

  12. Metaheuristics-Assisted Combinatorial Screening of Eu(2+)-Doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N Compositional Space in Search of a Narrow-Band Green Emitting Phosphor and Density Functional Theory Calculations.

    Lee, Jin-Woong; Singh, Satendra Pal; Kim, Minseuk; Hong, Sung Un; Park, Woon Bae; Sohn, Kee-Sun


    A metaheuristics-based design would be of great help in relieving the enormous experimental burdens faced during the combinatorial screening of a huge, multidimensional search space, while providing the same effect as total enumeration. In order to tackle the high-throughput powder processing complications and to secure practical phosphors, metaheuristics, an elitism-reinforced nondominated sorting genetic algorithm (NSGA-II), was employed in this study. The NSGA-II iteration targeted two objective functions. The first was to search for a higher emission efficacy. The second was to search for narrow-band green color emissions. The NSGA-II iteration finally converged on BaLi2Al2Si2N6:Eu(2+) phosphors in the Eu(2+)-doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N compositional search space. The BaLi2Al2Si2N6:Eu(2+) phosphor, which was synthesized with no human intervention via the assistance of NSGA-II, was a clear single phase and gave an acceptable luminescence. The BaLi2Al2Si2N6:Eu(2+) phosphor as well as all other phosphors that appeared during the NSGA-II iterations were examined in detail by employing powder X-ray diffraction-based Rietveld refinement, X-ray absorption near edge structure, density functional theory calculation, and time-resolved photoluminescence. The thermodynamic stability and the band structure plausibility were confirmed, and more importantly a novel approach to the energy transfer analysis was also introduced for BaLi2Al2Si2N6:Eu(2+) phosphors.

  13. Robust NdBa0.5Sr0.5Co1.5Fe0.5O5+δ cathode material and its degradation prevention operating logic for intermediate temperature-solid oxide fuel cells

    Lee, Tae-Hee; Park, Ka-Young; Kim, Nam-In; Song, Sun-Ju; Hong, Ki-Ha; Ahn, Docheon; Azad, Abul K.; Hwang, Junyeon; Bhattacharjee, Satadeep; Lee, Seung-Cheol; Lim, Hyung-Tae; Park, Jun-Young


    We report solutions (durable material and degradation prevention method) to minimize the performance degradation of cell components occurring in the solid oxide fuel cell (SOFC) operation. Reliability testing is carried out with the Nisbnd Nd0.1Ce0.9O2-δ (NDC) anode-supported intermediate temperature-SOFCs. For the cathode materials, single perovskite structured Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and double perovskite structured NdBa0.5Sr0.5Co1.5Fe0.5O5+δ (NBSCF) are prepared and evaluated under harsh SOFC operating conditions. The double perovskite NBSCF cathode shows excellent stability in harsh SOFC environments of high humidity and low flow rate of air. Furthermore, we propose the concurrent fuel and air starvation mode, in which the cell potential is temporarily reduced due to the formation of both fuel-starvation (in the anode) and air-depletion (in the cathode) concurrently under a constant load. This is carried out in order to minimize the performance decay of the stable NBSCF-cell through the periodic and extra reduction of aH2 O (and aO2) in the anode. The operating-induced degradation of SOFCs, which are ordinarily assumed to be unrecoverable, can be completely circumvented by the proposed periodical operation logic to prevent performance degradation (concurrent fuel-starvation and air-depletion mode).

  14. Preparation and performance of Pr-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathode for IT-SOFCs

    ZHU Chengjun; YI Cuishan; CHAO Luomeng


    (Ba0.5Sr0.5)1-xPrxCo0.8Fe0.2O3-δ (BSPCFx;x=0.00-0.30) oxides were synthesized by a sol-gel thermolysis process using combination of PVA and urea,and were also investigated as cathode material for intermediate temperature solid oxide fuel cells(IT-SOFCs).X-ray diffraction (XRD) results showed that all the samples formed a single phase cubic pervoskite-type structure after being calcined at 950 ℃ for 5 h and the lattice constant decreased with the Pr content increasing.The electrical conductivity of Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) was greatly enhanced by Pr- doping.The thermal expansion coefficient (TEC) of BSPCFx was increased with the content of Pr increasing,and all the thermal expansion curves had an inflection at about 250-400 ℃ due to the thermal-induced lattice oxygen loss and the reaction of Co and Fe ion.Ac impedance analysis indicated that BSPCFx possessed better electrochemical performance.The polarization resistance of the sample with x=0.2 was only ~0.948 Ω cm2 at 500 ℃,significantly lower than that of BSCF (~2.488 Ω cm2).

  15. Theoretical investigation of the magnetocaloric effect on La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 compound at room temperature

    Tlili, R.; Hammouda, R.; Bejar, M.; Dhahri, E.


    Based on a phenomenological model, the magnetic and magnetocaloric properties of La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 oxide have been studied. Indeed, the magnetic measurements have demonstrated that the sample exhibits a ferromagnetic-paramagnetic transition at room temperature. The value of the magnetocaloric effect such as magnetic entropy change, full width at half-maximum, relative cooling power and magnetic specific heat change has been determined from the calculation of magnetization as a function of temperature under different external magnetic fields. The maximum magnetic entropy change (- ΔSMmax) and the relative cooling power (RCP) are, respectively, 0.57 J kg-1 K-1 and 28.68 J kg-1 for a 10 kOe field change at 300 K, which are the characteristics of a good magnetocaloric material. Hence, the La0.7(Ba, Sr)0.3Mn0.9Ga0.1O3 compound can be considered as a promising material in magnetic refrigeration technology. According to the master curve behavior for the temperature dependence of ΔSM predicted for different maximum fields, this work has confirmed that the paramagnetic-ferromagnetic phase transition observed for our sample is of a second order.

  16. Study of dielectric and ferroelectric properties of five-layer Aurivillius oxides: A2Bi4Ti5O18 (A = Ba, Pb and Sr) synthesized by solution combustion route

    Shivangi Dubey; Rajnish Kurchania


    This paper presents the ferroelectric and dielectric properties of five-layer Aurivillius oxides (Ba2Bi4Ti5O18, Pb2Bi4Ti5O18 and Sr2Bi4Ti5O18) prepared by a solution combustion route with glycine as a fuel at low calcination temperature. The phase formation of these materials with pseudo-tetragonal structure was achieved after calcination at 750°C for 3 h; as confirmed by X-ray diffraction studies. Scanning electron microscopy of the sintered ceramics shows that the grains exhibit a plate-like morphology. The ferroelectric to paraelectric transition temperature () for Ba-, Pb- and Sr-based bismuth titanate ceramics was found to be 350, 280 and 260°C, respectively. All three materials show multiple relaxation phenomena and their electrical conductivity was found to be temperature dependent. The Pb2Bi4Ti5O18 ceramic possessed the highest value of activation energy (0.68 eV) and hence shows better ferroelectric properties, as compared to barium and strontium bismuth titanates.

  17. The effect of field cooling on a spin-chiral domain structure in a magnetoelectric helimagnet Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22}

    Hiraoka, Y. [Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Tanaka, Y.; Oura, M. [RIKEN SPring-8 Center, Sayo, Hyogo 679-5148 (Japan); Wakabayashi, Y. [Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kimura, T., E-mail: [Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)


    Spin-chiral domain structures near a cleaved crystal face of a magnetoelectric helimagnet, Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22}, were examined after various magnetic and electric field-cooling procedures by means of the scanning resonant X-ray microdiffraction technique using circularly polarized X-rays. We have found that the application of a magnetic field (1–2 k Oe) during the field-cooling procedure stabilizes one of the handedness among the two spin-chiral states (left- or right-handed screw structure) and makes nearly a single spin-chiral domain in the vicinity of the cleaved crystal face. However, it makes the degree of the spin chirality spatially inhomogeneous even within a domain. We discuss the observed field-cooling effect in terms of possible formation of spin-chiral domains with “stripe-type” domain walls accompanied by randomly-distributed ferromagnetic islands. - Highlights: • Spin-chiral domain structures in a magnetoelectric helimagnet, Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22}, were considerably affected by the field-cooling procedure. • The field-cooling with a small magnetic field stabilizes either a left- or right-handed spin-chiral state near a cleaved crystal face perpendicular to the helical axis.

  18. Influence of cerium doping on the dielectric relaxation of Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by the double crucible Stepanov technique

    Bhaumik, Indranil, E-mail: [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Ganesamoorthy, S. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Bhatt, R. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Subramanian, N. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Karnal, A.K.; Gupta, P.K. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Takekawa, S.; Kitamura, K. [Polar Domain Engineering Group, NIMS, Namiki, Tsukuba (Japan)


    Highlights: • Incorporation of Ce in the lattice reduces dielectric maxima in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6}. • It increases degree of diffusiveness and lowers the temperature of dielectric maxima. • These are due to introduction of addition random field via created point defects. • Both of the crystals undergo non-debye type relaxation. • VF fitting revealed that attempt frequency reduced by one order on Ce doping. - Abstract: The effect of Ce doping on the dielectric relaxation in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by double crucible Stepanov technique has been investigated. It has been observed that the incorporation of Ce ion in the lattice reduces the dielectric maxima. It further increases the degree of diffusiveness and lowers the temperature of dielectric maxima as a result of the introduction of additional random field via created point defects. Both the undoped and Ce doped crystals undergo a non-debye type relaxation. Vogel–Fulcher fitting reveals that the attempt frequency reduced by one order of magnitude on Ce doping.

  19. Structure and composition of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} films deposited on (001) MgO substrates and the influence of sputtering pressure

    Twigg, M.E.; Alldredge, L.M.B.; Chang, W.; Podpirka, A.; Kirchoefer, S.W.; Pond, J.M.


    The structure and composition of Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films, sputter deposited on (001) MgO substrates, have been characterized by transmission electron microscopy. Deviations in film stoichiometry are seen to strongly correlate with the structural and dielectric properties of these films, with the films deposited at the lower sputtering pressures either Ti-deficient or capped with a titanium oxide layer similar to the rutile TiO{sub 2} phase. Preferential sputtering of cations is found to be an important factor governing film stoichiometry. The Ti-deficient films deposited at a lower sputtering pressure contain Ruddlesden–Popper faults that increase the average lattice constant of the film and result in compressive strain and low dielectric tunability. - Highlights: • Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) film deposited at very low pressure is capped with TiO{sub 2} layer. • TiO{sub 2} capped film is under only slight compressive strain, but has poor tunability. • BST films deposited at low pressure contain Ruddlesden–Popper Faults (RPFs). • RPF-containing films have high compressive strains and poor dielectric tunability. • High-pressure films have no RPFs, little compression strain, and high tunability.

  20. Dielectric properties of low dielectric constant Ba0.60 Sr0.40Mg0.15Ti0.85O3-Mg2TiO4 composite thin films for tunable applications

    GAO LiNa; ZHAI JiWei; YAO Xi


    Ba0.60Sr0.40Mg0.15Ti0.85O3-xmol%Mg2TiO4 (x = 0-40 mol%) (BSTM-MT) composite thin films were fabricated by sol-gel method.The precursor solution of these composite thin films was prepared through mixing the Ba0.60Sr0.40Mg0.15Ti0.85O3 and Mg2Ti04 solution.The microstructures and dielectric tunability of composite thin films were investigated.The dielectric constant of composite thin films can be tailored from 155 to 55 by changing the concentration of Mg2TiO4.The dielectric loss of these composite thin films were still kept below 0.01 and the tunability was above 20% at a dc-applied electric field of 500 kV/cm.Suitable dielectric constant,low dielectric loss,and high tunability of this kind of composite thin films can be useful for potential microwave tunable applications.