Showing papers on "Perovskite (structure) published in 1984"
TL;DR: In this paper, the defect structure of these materials and the resulting transport properties (electrical conductivity, diffusion and transference number) are discussed as a function of temperature, oxygen partial pressure and composition.
278 citations
TL;DR: Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C as discussed by the authors.
Abstract: Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C. The films deposited on platinum substrates were smooth and uniform, but microcrackings were observed in the films deposited on fused silica substrates. The ratio of metal composition in the PZT film agreed with that in the mixture of starting materials. Films obtained at 700° C on platinum substrate showed a hysteresis loop. A spontaneous polarization was 35.65μC cm−2, a saturation remanent polarization was 30.56μC cm−2 and a coercive field was 45 kV cm−1. Dielectric constant and dielectric loss angle were about 300 and 0.05, respectively.
162 citations
TL;DR: In this paper, the nature of two types of oxygen desorption, α and β, from perovskite-type oxides was studied by TPD and TG experiments.
Abstract: The nature of two types of oxygen desorption, α and β, from perovskite-type oxides was studied by TPD and TG experiments. The results show that α oxygen is accomodated in the oxygen vacancies formed by the partial substitution of A site cations, while the desorption of β oxygen corresponds to the reduction of B site cations to lower valencies.
144 citations
TL;DR: In this article, the crystal structure of the ordered, distorted perovskite Sr2YRuO6 was refined using time-of-flight powder neutron diffraction data.
141 citations
TL;DR: In this paper, the Ionic conductivity of phases with general formulaLi x Ln 1/3 Nb 1− x Ti x O 3 (Ln =La, Nd) has been determined for materials with a small value of x, i.e., in composition range with a Ln1/3 nbO 3 perovskite related structure.
104 citations
TL;DR: In this article, the authors investigated the metal-insulator transition in perovskite systems LaNi1-xMxO3 (M = Cr, Mn, Fe, and Co) by transport measurements over the temperature range 12-300 K.
89 citations
TL;DR: In this paper, the authors measured the adiabatic single-crystal elastic moduli of three perovskite-structure compounds, i.e., SmAlO3, GdAlO2 and ScAlO 3, under ambient conditions and found that they are nearly equal and insensitive to distortions from cubic symmetry.
89 citations
TL;DR: In this article, a pressure-induced transition from frozen to relaxing impurity behavior and evidence for an off-center to on-center transition of the Nb ion at the B site of the perovskite lattice was found.
Abstract: High-pressure studies have shown that KTa/sub 1-x/Nb/sub x/O/sub 3/ crystals with small x (roughly-equal002) exhibit relaxational glasslike behavior rather than a static ferroelectric structural phase transition as previously thought The results show a pressure-induced transition from frozen to relaxing impurity behavior and evidence for an off-center to on-center transition of the Nb ion at the B site of the perovskite lattice
66 citations
TL;DR: In this article, profile analysis of constant-wavelength powder neutron diffraction data has been used to refine the crystal structure of the ordered perovskite Ca2YRuO6.
54 citations
TL;DR: In this article, the EPR spectra of Yb3+ and U5+ have been observed for the first time in potassium tantalate by employing crystals co-doped with both impurities.
Abstract: Single crystals of the cubic perovskite host, potassium tantalate (KTaO3), doped with iron group, lanthanide, and actinide impurities have been investigated using the technique of electron paramagnetic resonance (EPR). The EPR spectra of Yb3+ and U5+ have been observed for the first time in potassium tantalate by employing crystals co‐doped with both impurities. Multiple doping of the material during the crystal growth process avoided the production of semiconducting KTaO3 and resulted in the incorporation of adequate concentrations of the trivalent lanthanide ion Yb3+. The EPR results indicate that Yb3+ occupies a site in which the local symmetry is axial as a result of nearby charge compensation. Pentavalent uranium is found to occupy a substitutional cubic symmetry site. EPR investigations of Cu2+, Co2+, Mn2+, Ni3+, and Fe3+ were also carried out.
47 citations
TL;DR: In this article, the true space group and structure of koechlinite γ-Bi2O3-MoO3 due to uncertainties in the light atoms positions, has been resolved by neutron powder profile refinement.
Abstract: The continuing controversy about the true space group and structure of koechlinite γ-Bi2O3-MoO3 due to uncertainties in the light atoms positions, has been resolved by neutron powder profile refinement The original structure of Van den Elzen is correct, but contrary to his coordinates there are no unusually short oxygen-oxygen distancesThe structure may be related to a series consisting of Bi2O2 layers interleaved with perovskite like layers having the formula Bin-1MnX3n + 1 (Aurivillius, 1952; Wells, 1975) For n = 1, M = Mo and ' = O the perovskite layer is reduced to MoO4, which corresponds to the actual composition of the koechlinite Bi2MoO6 Complex oxides and oxyhalides of bismuth formed according to that principle have a pseudo-tetragonal symmetry Deviations from tetragonal symmetry are due to MoO6 octahedra tilts Further distortions are revealed by octahedra rotations and displacement of molybdenum atoms from the centers of the octahedra
TL;DR: FeIIFeIII2F8(H2O)2 and MnFe2F 8(H 2O2)2 have been shown to have an "idle spin" behavior as mentioned in this paper, where only Fe3+ spins order at TN, while the Fe2+ spins remain paramagnetic between 157 and 35 K.
TL;DR: In this article, the authors studied the kinetics of reduction in H 2 of perovskite LaMnO 3 and also of O 2 adsorption on this oxide and found that the reduction process starts at 755 K; up to 950 K the reduction rate is low because of the slowness of nuclei formation and growth.
Journal Article•
TL;DR: In this article, the authors describe the preparation of BaTiO 3 a partir d'alcoolates en utilisant les techniques de pressage a froid and de frittage.
Abstract: Preparation de BaTiO 3 a partir d'alcoolates en utilisant les techniques de pressage a froid et de frittage. Le dopage peut se faire avec une terre-rare ou du Niobium. Etude des proprietes electriques des produits ainsi obtenus
TL;DR: In this article, the structural determination of the Li 0.02 Na 0.98 NbO 3 phase has been carried out by single crystal diffraction analysis, and the space group of the orthorhombic cell is Pc2 1 b ; the cell parameters are a = 5.494, b = 15.461, c =5.551A˚.
TL;DR: In this article, single-crystal perovskite borides of LnRh3B (Ln ≡ Sm, Gd, Er or Yb) were prepared by the flux method.
Abstract: Single-crystal perovskite borides of LnRh3B (Ln ≡ Sm, Gd, Er or Yb) were prepared by the flux method. X-ray analysis revealed that the crystal structures were of the cubic perovskite type with cell dimensions of 4.193 A for SmRh3B, 4.183 A for GdRh3B, 4.147 A for ErRh3B and 4.136 A for YbRh3B. These data are in good agreement with those obtained for arc-melted polycrystalline ingots. The stability of these compounds is considered in terms of a charge transfer mechanism from the lanthanide to the Rh—B bonds to form three non-metal p orbitals or two non-metal p Orbitals and two hybrid sp orbitals. The nonstoichiometry of boron and the valence state of the rare earth elements are also discussed.
TL;DR: In this paper, a new polymorph of NaNbO3 with ilmenite-type structure was prepared under the hydrothermal conditions by using sodium polyniobate as a starting material.
TL;DR: In this article, lead oxide additions from 0 to 10 wt % were investigated in dielectric compositions of the solid-solution system: (1−x) Pb (Mg1/3Nb2/3)03 − x Pb(Zn 1/3 Nb2)/3) 03.
Abstract: Lead oxide additions (y) from 0 to 10 wt % were investigated in dielectric compositions of the solid-solution system : (1−x) Pb (Mg1/3Nb2/3)03 − x Pb (Zn1/3Nb2/3) 03. For x : 0 and x : 0.1, lead oxide lowers the firing temperature (900°C) and can prevent the formation of a parasite phase (pyrochlore type). Correlatively, an important improvement of the dielectric characteristics is observed in these ceramics which could be used as dielectrics in large capacitance multilayer ceramic capacitors.
TL;DR: In this article, a perovskite pseudocell and hexagonal superstructure were constructed for the dielectric resonator of the Ba(Ni,Ta)O3-BaZrO3 system.
Abstract: Microwave characteristics of the system Ba(Zn1/3Ta2/3)O3-BaZrO3 were investigated. Ba(Zn,Ta)O3 has a perovskite pseudocell and hexagonal superstructure; the superstructure was not formed after addition of BaZrO3. Both sintering and crystallization of Ba(Zn,Ta)O3-BaZrO3 were accelerated compared to those of Ba(Zn,Ta)O3 alone, and the microwave Q value was also improved. The material optimized for the dielectric resonator, Ba(Ni,Ta)O3-Ba(Zr,Zn,Ta)O3, has a dielectric constant of 30, Q value of 10000 at 10 GHz, and temperature coeficient of resonant frequency of 0 ppm/°C.
TL;DR: In this paper, the fine structure parameter D in the spin Hamiltonian increases with lattice constant for the Cr 3+ -Li + center in KZnF 3, RbCdF 3 and CsCdFs 3 co-doped with Cr 3 + and Li + ions.
Abstract: Centres with tetragonal symmetry in KZnF 3 , KCdF 3 , RbCdF 3 and CsCdF 3 co-doped with Cr 3+ and Li + ions have been studied by EPR in the cubic phase of host crystals. Due to charge compensation some of Cr 3+ ions are associated with a cation vacancy (V M ) or a Li + ion at the nearest divalent-cation site. The magnitude of the fine structure parameter D in the spin Hamiltonian increases with lattice constant for the Cr 3+ -Li + centre. In KZnF 3 the magnitude of D for the Cr 3+ -Li + centre is smaller than that for the Cr 3+ -V M centre as expected from point charge model, whereas in KCdF 3 , RbCdF 3 and CsCdF 3 the former is larger than the latter against the expectation from the point charge model. The dependence of D on lattice constant is discussed.
TL;DR: In this article, the authors report REE and minor element distributions for perovskites from seven kimberlites (South Africa and U.S.A.) and show an expected close correlation with whole-rock analyses.
TL;DR: In this article, a deux transitions de phases a 35 and 39°C liees a des reorientations des chaines decylammonium dans leur ensemble and a la fusion des parties hydrocarbures.
Abstract: Le compose du titre presente deux transitions de phases a 35 et 39°C liees a des reorientations des chaines decylammonium dans leur ensemble et a la fusion des parties hydrocarbures
TL;DR: In this article, three allotropic versions of Mg2NiD0.30 with monoclinic orthorhombic and cubic symmetry were identified and three hypotheses were considered for the determination of the coordinates of the deuterium atoms.
Abstract: Mg2NiD0.30 was prepared by the in situ decomposition of cubic Mg2NiD4. Three hypotheses were considered for the determination of the coordinates of the deuterium atoms. It was shown that hydrogen diffusion in Mg2NiD0.30 occurs by preferential paths. Three allotropic varieties of Mg2NiH4 with monoclinic orthorhombic and cubic symmetry were identified. An irreversible transformation from the monoclinic to the cubic variety was observed. The distribution of the hydrogen atoms in the monoclinic and cubic modifications of Mg2NiH4 was determined by neutron diffraction examination. The framework of the monoclinic phase consists of a threedimensional network of distorted [MgD6] octahedra with shared vertices. It can be considered to be constructed from alternating perovskite and ReO3 type units. In the cubic modification the metal atoms form a fluorite-type structure. At 240 °C most of the deuterium atoms are distributed among the 48h sites (x, x, 0) of space group Fm3m (x ≈ 0.2). The ideal positions form octahedra around the magnesium atoms with Mg−D = 1.66 A . Such a distance suggests a preferential Mg-D bond and may explain why the thermal stability of Mg2NiD4 is close to that of MgD2.
Journal Article•
TL;DR: A new oxygen defect perovskite Ca3Mn1.35Fe1.65O8.02 has been isolated in the orthorhombic system as discussed by the authors.
TL;DR: In this article, single crystals of the perovskite-type solid solutions La1-xSrxFeO3 with x=0.1, 0.2 and 0.3 were grown by the floating-zone method using an Xe arc-lamp imaging furnace.
Abstract: Single crystals of the perovskite-type solid solutions La1-xSrxFeO3 with x=0.0, 0.1, 0.25 and 0.4 and La1-xSrxCoO3 with x=0.0, 0.02 and 0.1 were grown by the floating-zone method using an Xe arc-lamp imaging furnace. Under the optimum conditions, single crystals about 5 mm in diameter and 40 mm in length were obtained. High-power X-ray diffraction analysis, optical microscopy and SEM-XMA showed the crystals to consist of a single phase and the distribution of the metal elements to be uniform. Preparation of raw material with precise composition was crucial for the synthesis of the single crystals. In the case of La1-xSrxCoO3 with x=0.2 and 0.3, CoO and a K2NiF4-type (La1-ySry)2CoO4 phase were observed in the perovskite-type solid solutions.
TL;DR: In this article, a crystal structure determination showed that the 10-layer packing sequence corresponds to a new structural arrangement of CsF3 layers and divalent cations, which is characterized by units of four octahedra linked by faces and connected to each other by an octahedral sharing only corners.
Abstract: Above 850°C Cs4Ni3CdF12 (which corresponds to the x = 0.25 composition of the CsNi1−xCdxF3 solid solution) shows an allotropic transformation from a 12 R to a 10 H-type structure. The high temperature form crystallizes in the hexagonal P63/mmc space group with a = 6.238 A and c = 25.362 A. A crystal structure determination shows that the 10-layer packing sequence corresponds to a new structural arrangement of CsF3 layers and divalent cations. The structure is characterized by units of four octahedra linked by faces and connected to each other by an octahedron sharing only corners. Ni and Cd atoms are partially disordered in the tetrameric units, while the unique octahedron is occupied by cadmium. A phase corresponding to the Cs5Ni4CdF15 formula has been isolated, which shows an isostructural powder pattern.
Kristallstruktur der neuen Hochtemperaturform von Cs4Ni3CdF12; ein neuer 10 H-hexagonaler Perowskit-Typ
Oberhalb 850°C zeigt Cs4Ni3CdF12 (welches bis zur Zusammensetzung mit x = 0,25 den Mischkristallen CsNi1−xCdxF3 entspricht) eine allotrope Umwandlung von einem 12 R-zu einem 10 H-Strukturtyp. Die Hochtemperaturform kristallisiert hexagonal (Raumgruppe P63/mnc, a = 6,238 A, c = 25,362 A). Die Bestimmung der Kristallstruktur ergibt, das die 10-Schichten-Packungsfolge einer neuen Anordnung-von CsF3-Schichten und 2-wertigen Kationen entspricht. Die Struktur ist charakterisiert durch Einheiten von 4 Oktaedern mit gemeinsamen Flachen, die mit einem Oktaeder nur uber Ecken verknupft sind. Ni- und Cd-Atome in den tetrameren Einheiten sind teilweise ungeordnet, wahrend das einzelne Oktaeder nur vom Cd besetzt ist. Eine Phase mit der Formel Cs5Ni4CdF15 ist isoliert worden und zeigt ein isostrukturelles Pulverdiagramm.
TL;DR: In this article, the preparation of solid solution perovskite 70% Pb(Fe 1 2 Nb 1 2 ) O 3 -30% P b(Fe 2 3 W 1 3 ) O3 is described for use as a thick film capacitor on ceramic chip carriers.
TL;DR: In this article, the 151Eu Mossbauer effect has been used to study the quadrupole interactions in the orthorhombic perovskite series EuMO3 (M = Co, Cr, Mn, Fe and Sc).