Search results for "strontium"
showing 10 items of 195 documents
Theoretical and Experimental Study of the Crystal Structures, Lattice Vibrations, and Band Structures of Monazite-Type PbCrO4, PbSeO4, SrCrO4, and Sr…
2015
The crystal structures, lattice vibrations, and electronic band structures of PbCrO4, PbSeO4, SrCrO4, and SrSeO4 were studied by ab initio calculations, Raman spectroscopy, X-ray diffraction, and optical-absorption measurements. Calculations properly describe the crystal structures of the four compounds, which are isomorphic to the monazite structure and were confirmed by X-ray diffraction. Information is also obtained on the Raman- and IR-active phonons, with all of the vibrational modes assigned. In addition, the band structures and electronic densities of states of the four compounds were determined. All are indirect-gap semiconductors. In particular, chromates are found to have band gap…
Apparent molar volumes of strontium chloride in ethanol + water at 298.15 K
1997
Densities of ethanol + water + strontium chloride mixtures have been measured with an oscillating-tube densimeter over a large range of concentrations of the salt and ethanol, at 298.15 K. From these densities, apparent molar volumes of the electrolyte in these mixtures have been calculated, and partial molar volumes at infinite dilution have been evaluated.
Probing Nanoscale Ferroelectricity by Ultraviolet Raman Spectroscopy
2006
We demonstrated that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature ( T c ) in ferroelectric ultrathin films and superlattices. We showed that one-unit-cell-thick BaTiO 3 layers in BaTiO 3 /SrTiO 3 superlattices are not only ferroelectric (with T c as high as 250 kelvin) but also polarize the quantum paraelectric SrTiO 3 layers adjacent to them. T c was tuned by ∼500 kelvin by varying the thicknesses of the BaTiO 3 and SrTiO 3 layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.
Relaxation of electronic excitations in strontium titanate
2002
The transient absorption spectra and kinetics were studied for undoped, lead doped and high purity SrTiO 3 single crystals. The pulsed electron beam induced transient absorption is studied in all crystals. The strong absorption at 0.8 v eV was observed only in high purity SrTiO 3 . This absorption is suggested to arise from intrinsic electron polaron. The bound electron polarons are likely responsible for absorption band at 1.4 v eV. The main luminescence band under excitation pulse is observed at 2.75 v eV. The luminescence decay is faster than that of transient absorption.
Study of Low Work Function Materials for Hot Cavity Resonance Ionization Laser Ion Sources
2008
The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization on the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high-temperature, low-work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place …
First observation of nonyrast levels inZr103and level systematics ofN= 63 Sr, Zr, and Mo isotones
1996
The {beta} decay of the very-neutron-rich nucleus {sup 103}Y has been studied at the isotope separator IGISOL, allowing for the first time the observation of nonyrast levels in its daughter {sub 40}{sup 103}Zr{sub 63}. The level structure is similar to that of its isotones {sup 101}Sr and {sup 105}Mo, suggesting a large ground-state deformation of {beta}{approx_equal} 0.4. Level systematics allows for new level assignments in both {sup 103}Zr and {sup 105}Mo. {copyright} {ital 1996 The American Physical Society.}
Ocean acidification impairs vermetid reef recruitment
2014
Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum. We found that although D. petraeum were able to reproduce and brood at elevated levels of CO2, recruitment success was adversely affected. Long-term exposure to acidified conditions…
Dielectric properties of barium strontium titanate / non ferroelectric oxide ceramic composites
2001
International audience; Barium strontium titanate ceramics present high dielectric permittivity and tunability. In order to reduce their permettivity and loss tangent while keeping tunability, various composites of barium strontium titanate oxide...
Incomplete retention of radiation damage in zircon from Sri Lanka
2004
A suite of 18 zircon gemstones from placers in the Highland/Southwestern Complex, Sri Lanka, were subjected to a comprehensive study of their radiation damages and ages. The investigation included X-ray diffraction, Raman and PL spectroscopy, electron microprobe, PIXE and HRTEM analysis, as well as (U-Th)/He and SHRIMP U-Th-Pb age determinations. Zircon samples described in this study are virtually homogeneous. They cover the range from slightly metamict to nearly amorphous. Generally concordant U-Th-Pb ages averaging 555 ± 11 Ma were obtained. Late Ordovician zircon (U-Th)/He ages scattering around 443 ± 9 Ma correspond reasonably well with previously determined biotite Rb-Sr ages for rock…
Electrode–Electrolyte Compatibility in Solid-Oxide Fuel Cells: Investigation of the LSM–LNC Interface with X-ray Microspectroscopy
2015
Ca:LaNbO4 (LNC) constitutes the last real breakthrough in high-temperature proton conductors, with better chemical and mechanical stability with respect to cerate and zirconate perovskites. However, the low amount of bivalent dopant that can be hosted in the LaNbO4 matrix poses a limit to the proton concentration in the electrolyte. Using synchrotron X-ray microspectroscopy, we investigated the compatibility of annealed LNC/LSM electrolyte/cathode bilayers for proton-conducting SOFCs. The element maps are complemented by microEXAFS and microXANES, giving information on the fate of different cations after diffusion. The X-ray microspectroscopy approach described here is applied for the first…