Showing papers on "Perovskite (structure) published in 1982"
TL;DR: The perovskite relaxor ferroelectric lead magnesium niobate (PbMg 1 3 Nb 2 3 O 3 ) is an important material because of its high dielectric constant and correspondingly large electrostrictive strains as mentioned in this paper.
1,465 citations
TL;DR: The X-ray and neutron structures of polycrystalline Ca 2 MnO 3.5 by Rietveld analysis have been determined as mentioned in this paper, and the relationship between the CaMnO 3 /CaMnNO 2.5 structures is discussed.
317 citations
TL;DR: In this paper, the precursors CaMnO 3 and Ca 2 MnO 4 were reduced with any one of a variety of inorganic (H 2, NH 3 ) or organic (C 2 H 4, C 3 H 6 ) reducing agents between 300 and 500°C.
196 citations
TL;DR: The electrostrictive properties of relaxor-type ferroelectrics such as PMN have been studied in this paper, where the authors show that the induced elastic strain and electric polarization hold even below the average Curie temperature.
Abstract: Lead magnesium niobate Pb(Mg1/3Nb2/3)O3 (PMN) is a relaxor ferroelectric with a disordered perovskite structure. A statistical inhomogeneity in the distribution of Mg2+ and Nb5+ ions in the B-sites of an ABO3 perovskite lattice leads to a wide Curie temperature range in which the crystal exhibits an intimate mixture of paraelectric and ferroelectric microregions. Relaxor-type ferroelectrics such as PMN show somewhat unusual electrostrictive phenomena. Although the polarization-related electrostrictive coefficients Q (defined as x = QP2 ) are one order of magnitude smaller than those of simple perovskite compounds, large electrostrictive strains can be obtained because of their huge dielectric constants. A quadratic relation between the induced elastic strain and the electric polarization holds even below the average Curie temperature. The electrostrictive properties of PMN and related materials are reviewed in this article. Relaxor ferroelectrics are promising transducer materials for use as acti...
184 citations
TL;DR: In this article, the structural properties of Prx 1− x Ca x MnO 3 perovskite systems were studied by X-ray and magnetic susceptibility measurements, and the results are interpreted as being due to simultaneous action of steric effect, orbit-lattice interactions of Mn 3+ ions and Coulomb interactions among 3 d electrons.
177 citations
TL;DR: In this article, the formation of the Pb (Mg 1 3 Nb 2 3 ) O 3 and Pb(Fe 1 2 Nb 1 2 O 3 )O 3 phases with a perovskite type structure is directly dependent on the reactivity of magnesium and ferric oxides to other phases belonging to the binary system PbO Nb2O5.
130 citations
TL;DR: In this paper, the reactivity and related properties of oxygen both in the bulk and on the surface has been investigated for perovskite-type mixed oxides (La1−xSrxCoO3), in regard to the effects of Sr2+-substitution and calcination temperature.
Abstract: The reactivity and related properties of oxygen both in the bulk and on the surface has been investigated for perovskite-type mixed oxides (La1−xSrxCoO3), in regard to the effects of Sr2+-substitution and calcination temperature. The reducibility and the readiness of oxygen desorption increased with the Sr2+ content, x, but the re-oxidation became slower with x. These results have been explained on the basis of the change in the chemical potential of lattice oxygen. The diffusivity of oxygen in the bulk and the ability to activate the oxygen molecule also increased with x. Oxygen vacancies in the bulk and on the surface, which tended to increase with x, are likely responsible for these reactions. The release of oxygen from the bulk became more difficult as the calcination temperature increased, in conformity with the trend of the catalytic activity.
105 citations
TL;DR: In this article, a special technique was developed to obtain perovskite ceramics exhibiting no co-existence in the boundary compositions, in which no compositional fluctuation occurred in the B site of the structure.
Abstract: Tetragonal and rhombohedral phases always coexist in Pb(ZrxTil1−x)03 near the morphotropic phase boundary compositions (0.52≤x≤0.55) when prepared by solid-solid reaction among the constituent oxides. A special technique was developed to obtain perovskite ceramics exhibiting no co-existence in the boundary compositions, in which no compositional fluctuation occurred in the B site of the perovskite structure. Even these monophasic perovskite ceramics of the morphotropic phase boundary compositions were two-phase with the lapse of time after poling. This phenomenon is interpreted in terms of thermodynamics. It is suggested that this phenomenon may closely relate to the origin of aging in piezoelectrics.
105 citations
86 citations
TL;DR: The perovskite-related cyano compounds CsMIICr(CN)6 (MII = Mn, Zn), CsZnFe(CN), and CsMnCo(CN)-6 are characterized by their IR active C - N and MIII-CN stretching frequencies, their lattice constants and their magnetic susceptibilities (4,2-295 K).
Abstract: Abstract The perovskite-related cyano compounds CsMIICr(CN)6 (MII = Mn, Zn), CsZnFe(CN)6 and CsMnCo(CN)6 (Mn = Mn-Cu) are characterized by their IR active C - N and MIII-CN stretching frequencies, their lattice constants and their magnetic susceptibilities (4,2-295 K). Except for CsCuCo(CN)6, which is tetragonally distorted, all compounds crystallize cubically face-centered (with lattice constants in the range from 1020 to 1084 pm). The magnetic behaviour indicates low spin MIII and high spin MII states, supporting the IR evidence for a strictly ordered MIII-CN-MII arrangement. The compound CsMnCr(CN)6 is ferrimagnetic, with a Néel temperature of TN = 90 K and an extrapolated spontaneous magnetization of a = 2,30 μB at 0 K. Superexchange interactions via the cyano bridges are considered responsible for the ferrimagnetism observed.
80 citations
TL;DR: The phase relationship of the ternary combinations {Ti, Zr, Hf, V, Nb, Ta, Cr, Mn, and Ni}-aluminum-carbon was investigated in this article.
01 Jan 1982
TL;DR: In this paper, the elastic properties of silicate perovskites have been investigated and no experimental data have been reported so far on their elastic properties, and the discovery of the existence of silicates has naturally preceded knowledge of their physical properties.
Abstract: Recent laboratory data on high-pressure and high-temperature experiments of various silicates strongly suggest that silicate minerals having the perovskite-type structure are dominant phases in the earth’s lower mantle (e.g., Liu, 1976; Mao et al, 1977). Discovery of the existence of silicate perovskites has naturally preceded knowledge of their physical properties, and thus no experimental data have been reported so far on their elastic properties.
TL;DR: In this paper, the phonon dispersion curves of the fluoride perovskite materials KMnF3 and KZNF3 were measured by means of coherent neutron inelastic scattering.
Abstract: The authors have measured the phonon dispersion curves of the fluoride perovskite materials KMnF3 and KZnF3 by means of coherent neutron inelastic scattering. The aim of this investigation was to provide the phonon spectrum of KMnF3 which undergoes structural phase transitions and which has been studied by various methods in the last decade and, for comparison, of KZnF3 in which no phase transitions occur. In addition they have found an anomalous temperature dependence of the R15' and M2 modes in KZnF3 which are the modes that soften near the phase transitions of KMnF3. This indicates that there is in general a tendency towards an instability against octahedra rotations in all fluoride perovskites. For the analysis of the phonon spectra, they have employed a lattice dynamical shell model under various conditions. In some of the models, they have successfully used interionic potentials which were derived from experimental data in other materials for some of the short-range interactions. Thus it could be shown that these potentials are also valid in the fluoride perovskites with different interionic distances. Furthermore, the experimental data are compared with the results of infrared spectroscopy and Raman studies at low temperatures as a test of the assignment of optically determined phonon frequencies to normal modes which are at the zone centre Gamma at low temperatures and at zone-boundary points in the cubic perovskite structure.
TL;DR: In this article, the properties and photoconductivity of several binary and ternary lead-containing perovskite-type oxides were investigated and the band gap energies for all studied compounds were measured.
Abstract: Electrophysical properties and photoconductivity of several binary (PbTiO3, PbZrO3, PbHfO3) and ternary (Pb2ScNbO6, Pb2InNbO6) lead-containing perovskite-type oxides were investigated. Band gap energies for all studied compounds were measured to be somewhat smaller than for its perovskite analogs not containing lead. This fact is ascribed to a specific configuration of the outer electronic shell of lead.Owing to high photosensitivity of the lead-containing perovskites, a considerable effect of electronic subsystem (in particular of the non-equilibrium carriers) on crystal properties both in ferroelectric and antiferroelectric crystal phases was observed.
Patent•
29 Apr 1982TL;DR: In this article, a thin film dielectric composition suitable for screenprinting was proposed, consisting of a substituted perovskite, an inorganic dopant, and a low temperature-devitrifiable frit or glass.
Abstract: Thick film dielectric compositions suitable for screen-printing comprising a substituted perovskite, an inorganic dopant, and a low temperature-devitrifiable frit or glass. Upon firing the dielectric composition is highly hermetic.
TL;DR: In this article, it is shown that the doubling of one of the perovskite cell axes appears at random in the a, b or c directions within the same crystal.
TL;DR: Muralt et al. as mentioned in this paper, P Swiss Fed Inst Technol,Solid State Phys Lab,Ch-8093 Zurich,Switzerland E Kardelj Univ Ljubljana,J Stefan Inst,Ljublo, Slovenia,Yugoslavia
Abstract: Note: Muralt, P Swiss Fed Inst Technol,Solid State Phys Lab,Ch-8093 Zurich,Switzerland E Kardelj Univ Ljubljana,J Stefan Inst,Ljubljana,YugoslaviaPj147Times Cited:41Cited References Count:10 Reference LC-ARTICLE-1982-005doi:10.1103/PhysRevLett.49.1019 Record created on 2006-08-21, modified on 2017-05-10
TL;DR: In this paper, the vibrational and diffuse reflectance spectra of a cubic disordered perovskite of the type A2+3B2+M5+2O9 are discussed.
TL;DR: In this article, the conductivity, Seebeck effect and magnetic susceptibility of the oxides La2−xA1+xCu2O6−x/2+σ (A = Ca, Sr) have been investigated.
TL;DR: The perovskite (La1−xCax)CoO3 (0 ≦ x ≦ 0.6) was prepared under high oxygen pressures and the rhombohedral distortion decreases with increasing x and the phase becomes cubic at x = 0.5.
TL;DR: In this paper, the fourth-order parameters in the spin Hamiltonian of both cubic and tetragonal centres are discussed in the series of perovskite fluorides and the superposition model for the fourthorder parameter is examined.
Abstract: EPR measurements for substituted Gd 3+ centres in CsCaF 3 , CsCdF 3 , RbCdF 3 and KCdF 3 have been made at several temperatures in a range 77-487 K. In all the crystals the spectrum with tetragonal symmetry for Gd 3+ centre associated with the nearest-neighbour cation vacancy has been observed together with that for cubic centre. The observed fourth-order parameters in the spin Hamiltonian of both cubic and tetragonal centres are discussed in the series of perovskite fluorides. The result suggests that the parameter b 4 for Gd 3+ in 6-fold cubic coordination changes its sign as the lattice constant decreases. The superposition model for the fourth-order parameter is examined.
TL;DR: In this article, the perovskite structure of KmnCl 3 is shown to be orthorhombic and the space group is Pnma and Z = 4.
TL;DR: Convergent beam diffraction analysis was conducted on two of the four yttrium-aluminum oxide particles in a commercial dispersion strengthened alloy Diffraction analysis on Yttriumaluminum garnet, YAG (5A12O3 • 3Y2O3), and yttium-aluminium perovskite, YAP (A12 O3 • Y2O 3), indicated that diffraction effects in the High Order Laue Zones and symmetry information from the CBD patterns are extremely useful in obtaining additional information about the crystal structure from a single pattern RE
Abstract: Convergent Beam Diffraction (CBD) analysis was conducted on two of the four yttrium-aluminum oxide particles in a commercial dispersion strengthened alloy Diffraction analysis on yttrium-aluminum garnet, YAG (5A12O3 • 3Y2O3), and yttrium-aluminum perovskite, YAP (A12O3 • Y2O3), indicated that diffraction effects in the High Order Laue Zones and symmetry information from the CBD patterns are extremely useful in obtaining additional information about the crystal structure from a single pattern It was also shown that double diffraction effects in the zero layer can explain the presence of the kinematically forbidden reflections The results of the analysis are discussed
TL;DR: In this paper, the photoelectrochemical properties of Ln 2 Ti 2 O 7 and ln 2/3 TiO 3 pyrochlore and perovskite anodes have been investigated.
TL;DR: The thermal diffusivity, specific heat and thermal conductivity of cold-pressed and sintered (CPS) perovskite, zirconolite (CaZrTi2O7), barium hollandite (BaAL2Ti6O16), SYNROC-B and SYNRoc-C were measured in the temperature ranges 20 −700°C (thermal diffusivities) and 20 −500°C as mentioned in this paper.
TL;DR: The ordered perovskite Ba2MgNpO6 has been synthesized and is isomorphous with the corresponding uranium compound Ba2mgUO6 as discussed by the authors.
TL;DR: In this paper, the perovskite phase appears to break down by incongruent dissolution with concurrent precipitation of the titanium oxide, indicating that the oxides are stable in the pressure-temperaturefluid composition regime.
Abstract: Solubility effects were measured on ceramic and single crystal alumina, titania, SrTiO/sub 3/ (perovskite structure), and ceramic zirconia at 300 and 400/sup 0/C for times of 7 and 18 days. Selected fluids were deionized water, a high-bicarbonate, high-sulfate simulated connate water (about 1% total dissolved solids), saturated NaCl brine, and a high-magnesium, high-calcium bittern brine. There is measurable dissolution of Al/sup 3 +/ in the connate water and in the bittern brine only. In both cases this can be related to the low pH conditions expected in these fluids at high temperature and to the increase in aluminum solubility with decreasing pH. The SrTiO/sub 3/ breaks down to some extent in all fluids in the order bittern brine > NaCl > bicarbonate water > deionized water. Dissolution attack on both titanium and zirconium oxides is very small, indicating that the oxides are stable in the pressure-temperature-fluid composition regime. Breakdown of the perovskite phase appears to be by incongruent dissolution with concurrent precipitation of the titanium oxide.
TL;DR: In this paper, the frequencies of optically active phonons of several perovskite-type layer structures, namely of K2ZnF4, K2NiF4 and K2CuF4 were determined by means of far-infrared reflection spectroscopy and by using Raman scattering.
Abstract: The authors have determined the frequencies of the optically active phonons of several perovskite-type layer structures, namely of K2ZnF4, K2NiF4 and K2CuF4 by means of far-infrared reflection spectroscopy and for K2ZnF4 also by means of Raman scattering. The experimental results are compared with rigid-ion model calculations, where the short-range force constants are not only treated as adjustable parameters but also successfully calculated with interionic potentials derived mainly for alkali halides.
TL;DR: In this paper, a variety of metal niobates containing diverse M2O: Nb2O5 ratios are reported in the literature but three definite species could only be recognized: ortho, meta and normal hexaniobates.
TL;DR: In this article, it was shown that ϵ-PAMC is incommensurately modulated with the modulation vector being temperature-dependent and approaching 1 3 b ∗ at the ϵ → ζ phase transition.