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Showing papers on "Perovskite (structure) published in 1975"


Journal ArticleDOI
TL;DR: In this article, a simple technique is described for ascertaining trial models for the structures of perovskites, which relies on an understanding of the fundamental components of the structure and rules are given for determining trial models rapidly.
Abstract: A simple technique is described for ascertaining trial models for the structures of perovskites. The method relies on an understanding of the fundamental components of the structure. Rules are given for determining trial models rapidly.

1,409 citations


Journal ArticleDOI
TL;DR: In this paper, a cubic perovskite-type 3olymorph of CaSiO 3 has been obtained from synthetic crystalline (wollastonite) and glass forms of the material and has been compressed to loading pressures above 160 kbar and heated to about 1500° C by a laser in a diamond anvil cell.

225 citations


Journal ArticleDOI
TL;DR: Several metal oxides of the perovskite structure have been prepared and used as catalyst for the oxidation of CO and C2H4 as mentioned in this paper, and the reaction rates are positive fractional order with respect to both oxygen and the oxidant, and are slightly inhibited by H2O.

143 citations


Journal ArticleDOI
TL;DR: In this article, the lattice parameters for the perovskite phase of MgSiO3 are ao = 4.790 ± 0.002, bo = 4,943 ± 0.,002, and co = 6.897 ± 0,003 A with Z= 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures.
Abstract: Both forsterite (Mg2SiO4) and enstatite (MgSiO3) enter a post-oxide phase characterized by the orthorhombic perovskite structure when subjected to high pressure and temperature in the diamond-anvil press coupled with laser heating. The lattice parameters for the perovskite phase of MgSiO3 are ao = 4.790 ± 0.002, bo = 4.943 ± 0.002, and co = 6.897 ± 0.003 A with Z = 4. The calculated density of MgSiO3 (perovskite) is thus 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures. The density of a mixture of MgSiO3 (perovskite) plus MgO (periclase) is 1.9% greater than that of the mixed oxides with the forsterite stoichiometry.

135 citations



Journal ArticleDOI
TL;DR: In this paper, single crystals of CaCu 3 Mn 4 O 12, a new ferromagnetic perovskite-like compound (T c − 160°C), have been synthesized at 50 kbar and 1000°C.

115 citations


Journal ArticleDOI
TL;DR: The phase equilibria in the FeFe2O3Y 2O3 system have been established at 1200°C and the standard free energies of formation of yttria, hematite, magnetite, wustite, metallic iron, yttrium-iron perovskite, and a new phase YFe 2O4 belonging to a rhombohedral crystal system were determined in this article.

99 citations


Journal ArticleDOI
TL;DR: In this article, the lattice parameters of the perovskite phase of (Fe,Mg)TiO3 at room temperature and 1 bar are a 0 = 4.471 ± 0.004, b 0 = 5.753 −0.005, and c 0 = 7.429 ±0.006 A with 4 molecules per cell.

77 citations


Journal ArticleDOI
TL;DR: In this paper, a linear diffusion model of oxygen ions in the crystal, which was theoretically derived, was used to calculate the diffusion constants at 25°C and 60°C, respectively.
Abstract: The compounds , which show high electrical conductivity, are electrochemically reduced in an aqueous alkaline solution to give rise to the oxygen deficient state . The electrochemical redox reactions are reversible in the range . The electrode potentials of in a solution have been measured as a function of δ. From these data and the measurements of potential change in the cathodic processes under constant current density, the oxygen ion diffusion constants have been calculated on the basis of a linear diffusion model of oxygen ions in the crystal, which was theoretically derived. The calculated diffusion constants at 25°C are for and, respectively. These values are very large as compared with ordinary oxides.

77 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the oxygen atom coordination is fourfold and fivefold, the average Al-O distance is 1.93 A, and Sc3+ has six near-neighbor oxygen atoms at an average distance of 2.12 A and two more at 2.25 A.
Abstract: ScAlO3 has been synthesized at 1000°C and 120 kbar as an orthorhombic perovskite with unit cell dimensions a = 4.933 ± 0.003 A, b = 5.226 ± 0.003 A, and c = 7.193 ± 0.005 A. Ions as small as 0.73 A in radius can thus occupy the A site of this ABO3 structure type. Refinement of the structure from X ray powder diffraction data shows that the oxygen atom coordination is fourfold and fivefold, the average Al-O distance is 1.93 A, and Sc3+ has six near-neighbor oxygen atoms at an average distance of 2.12 A and two more at 2.64 A to give an average eight-coordinate distance of 2.25 A. It is inferred that both Mg2+ and Fe2+, with radii of 0.72 and 0.77 A, respectively, as well as Mn2+ (0.82 A) and Ca2+, could occupy the A sites of silicate perovskites to give mantle assemblages denser than those available to any other known structural type. These densities are deduced from the systematics of perovskite unit cell volumes, and by comparison with Hugoniot data for shocked high-pressure assemblages they are consistent with enstatite, bronzitite, fayalite, and dunite compositions forming perovskite or perovskite assemblages at very high pressures.

56 citations


Journal ArticleDOI
TL;DR: The perovskite-type compounds LaNiO3 (M: Ca, Sr and Ba) were synthesized and their crystallographic, electric and thermochemical properties were investigated as discussed by the authors.
Abstract: The perovskite-type compounds La1-xMxNiO3 (M: Ca, Sr and Ba) were synthesized and their crystallographic, electric and thermochemical properties were investigated. The regions of perovskite formation were determined. The solubility limits or alkaline earth elements into La sites are around 5% for Sr and Ba, and less than 1% for Ca. The charge compensation of divalent ion substitution into a trivalent La ion site takes place by the formation of oxygen ion vacancies. Lanthanoid elements other than La did not form perovskite-type oxides. The compound LaNiO3 undergoes a rhombohedral-cubic transition at 940?C and decomposes above 1120?C. Resistivity of LaNiO3 is 9?10-3 ?cm at room temperature and increases as the temperature is raised.

Journal ArticleDOI
TL;DR: In this paper, the authors verified the presence of oxygen stability range in ternary oxides for molybdenum(IV) perovskites, and the widths of stability range were determined of BaMoO 3, SrMoO 2, and CaMoO 4.

Journal ArticleDOI
TL;DR: The magnetic and structural properties of the solid solution SrFexRu1−xO3−y (0 ⩽ x⩽ 0.5) have been studied using 57Fe and 99Ru Mossbauer spectroscopy and other techniques as discussed by the authors.

Patent
10 Feb 1975
TL;DR: In this paper, a perovskite-related battery was proposed, in which the cathode active material is an oxide having a pervskite or perovsite related structure and the general formula ABO 3, wherein A is an element selected from Group IIA of the Periodic Table of the Elements and B is a non-noble transition metal selected from group VIIB and VIII of the periodic Table of Elements.
Abstract: A novel battery is disclosed in which the cathode active material is an oxide having a perovskite or perovskite related structure and the general formula ABO 3 , wherein A is an element selected from Group IIA of the Periodic Table of the Elements and B is a non-noble transition metal selected from Group VIIB and VIII of the periodic Table of the Elements. The anode is a metal selected from cadmium, zinc, lead, lithium, sodium and potassium.

Journal ArticleDOI
TL;DR: A number of the Te-containing perovskite compounds (about 50) with compositions A2+2B2+Te6+O6, (A2+A3+)B 1+Te 6+O 6 and (A3+A1+)B 2+TeO 6 were synthesized and a thorough investigation of their crystal structure and dielectric properties has been carried out.

Journal ArticleDOI
TL;DR: In this article, the far-infrared reflectivity of (CH3NH3)3MnCl4(=MAMC) and of single crystals was studied at several temperatures.
Abstract: The far-infrared reflectivity of (CH3NH3)3MnCl4(=MAMC) and of (CH3NH3)2FeCl4(=MAFC) single crystals was studied at several temperatures. By means of a Kramers-Kronig analysis, the frequencies of the long-wavelength infrared-active phonons were determined. Because of the considerable gap (300-900 cm-1) between the external and the internal modes of the organic ions these can be treated as rigid bodies at far-infrared frequencies. In addition, the authors present the results of a structure analysis of MAMC above and below the continuous phase transition at 394K which turns out to be of the order-disorder type. In the high-temperature tetragonal modification, three strong and two weak IR-active modes are observed for E perpendicular to c.

Journal ArticleDOI
TL;DR: In this paper, the catalytic activities of cobalt perovskites and various cobalt oxides for the reduction of nitric oxide with carbon monoxide were studied under plug flow reactor conditions.
Abstract: The catalytic activities of cobalt perovskites and various cobalt oxides for the reduction of nitric oxide with carbon monoxide were studied under plug flow reactor conditions. Cobalt tetroxide showed the greatest catalytic activity after pretreatment with CO, and lanthanum strontium cobalt trioxide showed the least catalytic activity. The perovskite lanthanum cobalt trioxide displayed an intermediate activity between the two extremes. The reaction rates for all cobalt oxide and perovskite catalysts tested were zero order in CO and fractional order in NO. Nitric oxide was converted principally to nitrogen between 380 and 500/sup 0/C; at lower temperatures more nitrous oxide was formed. The adsorption rate for a barium-dope perovskite which was a better catalyst for the NO-CO reaction that was LaCoO/sub 3/ exceeded the rate for the latter, suggesting that the NO-CO reaction rate was influenced by the chemisorption rate of NO on the respective catalysts.

Journal ArticleDOI
P.D. Dernier1, J. P. Remeika1
TL;DR: In this paper, the perovskite compounds PbHfO3 and CdHmO3 have been shown to undergo a series of structural phase transformations at high temperature X-ray diffraction experiments.


Book ChapterDOI
01 Jan 1975
TL;DR: The solid state properties of perovskite-type compounds of transition metals which are of importance in NO catalytic chemistry are: (1) the presence of mixed valence ions (e.g., Mn3+/Mn4+), (2) the binding of oxygen in the lattice, and (3) binding of N-containing fragments to the surface.
Abstract: The solid state properties of perovskite-type compounds of transition metals which are of importance in NO catalytic chemistry are: (1) the presence of mixed valence ions (e.g., Mn3+/Mn4+), (2) the binding of oxygen in the lattice, and (3) the binding of N-containing fragments to the surface. On the surface, both molecular and dissociative chemisorption of NO contribute to the reduction of NO. The importance of the mixed valence and of the binding of lattice oxygen is linked to the simultaneous presence of cation vacancies and oxygen vacancies. Systematic substitution of cations in the dodecahedral and octahedral positions of the perovskite structure is used to demonstrate the importance of the solid-state chemistry for the catalytic activity and selectivity.

Journal ArticleDOI
TL;DR: New divalent europium ternary oxides have been isolated and studied by X-ray diffraction and electronic microscopy as mentioned in this paper, and 15 of them cristallize with tetragonal bronzelike structure: EuM 2 O 6 ; Eu 9 M 34 O 94 (M = Ta, Nb); EuBCM 5 O 15 (B = Ca, Eu, Ba; C = Na, K; M = Ta and Nb).

Patent
29 Jul 1975
TL;DR: A sensor element for detecting smoke and/or reducing gases, which comprises a shaped body formed from a material consisting essentially of: A. a complex metal oxide having a perovskite type crystal structure and represented by the general formula ABO3-δ wherein A is at least one element selected from the group consisting of yttrium, a rare earth element having an atomic number of from 57 to 71 and an alkaline earth metal as discussed by the authors.
Abstract: A sensor element for detecting smoke and/or reducing gases, which comprises a shaped body formed from a material consisting essentially of: A. a complex metal oxide having a perovskite type crystal structure and represented by the general formula ABO3-δ wherein A is at least one element selected from the group consisting of yttrium, a rare earth element having an atomic number of from 57 to 71 and an alkaline earth metal, B is at least one element selected from the group consisting of transition metals having atomic numbers from 21 to 30, O is oxygen and δ is a nonstoichiometric parameter which may vary from 0 to 0.25 and B. at least one metal oxide selected from the group consisting of CdO, In2 O3, SnO, Tl2 O3 and PbO.

Journal ArticleDOI
TL;DR: In this article, evidence is obtained for a series of tungsten-antimony bronzes, through reaction of antimony with tengsten trioxide at 900°C, and five phases are characterized: monoclinic, orthorhombic, tetragonal and cubic.

Journal ArticleDOI
TL;DR: In this article, single crystals of the ordered perovskite Ba2CoWO6 have been grown by the top-seeded solution technique from a flux of BaCl2.

Journal ArticleDOI
TL;DR: In this article, the magnetic hyperfine fields of 119 Sn(Sn 4+ ) were measured by the Mossbauer effect and two kinds of spin transfer processes contributing to the hyperfine field were considered, and spin transfer via a divalent cation was emphasized particularly.
Abstract: Ca 1- x Sr x Mn 0.99 Sn 0.01 O 3 (0≦ x ≦1) with (nearly) cubic perovskite structures were prepared and the magnetic hyperfine fields of 119 Sn(Sn 4+ ) were measured by the Mossbauer effect. The hyperfine fields arise from unpaired s electron spin densities transferred from Mn 4+ ions (super-transferred hyperfine interaction). The hyperfine field for a tin ion was found to depend linearly upon the numbers of Ca 2+ and Sr 2+ ions in the neighboring divalent cation sites, with proportional coefficients having opposite signs. To explain experimental results two kinds of spin transfer processes contributing to the hyperfine field oppositely to each other have been considered, and spin transfer via a divalent cation is emphasized particularly. The hyperfine field at 0 K for Sn 4+ in CaMnO 3 is -75 kOe, while +20 kOe for Sn 4+ in SrMnO 3 .

Journal ArticleDOI
TL;DR: In this article, the perovskite-like compound [NaMn3+3]O12 undergoes a crystallographic phase transition at 190 K. The lowering of the symmetry from cubic to monoclinic is the result of a cooperative Jahn-Teller effect which induces a 1:1 order between the Mn3+ and the Mn4+ cations occupying the octahedral sites.


Journal ArticleDOI
01 Nov 1975-Pramana
TL;DR: In this paper, the lattice imaging technique of high resolution electron microscopy has been employed to examine 4H, 6H and 9R ABO3 perovskite polytypes.
Abstract: Lattice imaging technique of high resolution electron microscopy has been employed to examine 4H, 6H and 9R ABO3 perovskite polytypes. The lattice images can be correlated with the lattice periodicity and the stacking sequence of AO3 layers and BO6 octahedra. The study shows the utility and validity of the lattice imaging technique for the study of relatively close-packed systems.


Journal ArticleDOI
TL;DR: In this paper, the ion exchange properties of TlNbO3 in molten or solid nitrates were checked and the thermal stability of the solid solutions was described and competition between pyrochlore and perovskite type is discussed.