A. N. Demina

Effect of doping with Co2O3, TiO2, Fe2O3, and Mn2O3 on the properties of Ce0.8Gd0.2O2−δ

The effects of Co, Fe, Mn, and Ti oxide additions on the sinterability and crystal-chemical, thermal, and electrical properties of Ce0.8Gd0.2O2−δ have been studied. The results indicate that these oxides enhance the sinterability of the mixed oxide, regardless of whether they were introduced before or after synthesis. The most effective sintering aid is Co2O3. The lattice parameters of Ce0.8Gd0.2O2−δ samples containing different metal oxide additions (1 mol %) are refined in space group Fm3m. The temperature-dependent thermal expansion data are used to determine the linear thermal expansion coefficients of the samples. Manganese oxide additions reduce the electrical conductivity of Ce0.8Gd0.2O2−δ, whereas the other dopants increase it in the order Ti < Fe < Co. The activation energy for conduction increases in the order Co < Ti < Fe < Mn.

Phase equilibria in the system LaMnO3-SrMnO3-SrCrO4-LaCrO3

A continuous solid solution LaMn1−yCryO3 with an orthorhombic structure is found to exist in the range of 0.0 ≤ y ≤ 1.0. An orthorhombic solid solution La1−xSrxCrO3 exists in the range of 0.0 ≤ x ≤ 0.1. The stability boundaries are determined for the perovskite phase La1−xSrxMn1−yCryO3. An isobaric-isothermal section LaMnO3-SrMnO3-SrCrO4-LaCrO3 of the system La2O3-SrO-Mn3O4-Cr2O3 in air at 1100°C is designed.

Thermal expansion and electrical conductivity of La0.7Sr0.3Mn1 − yCryO3

The thermal expansion and electrical conductivity of La0.7Sr0.3Mn1 − yCryO3 (y = 0, 0.1, 0.3, 0.4) solid solutions have been studied at temperatures from 300 to 1270 K and oxygen partial pressures from 10−9 to 2.1 × 104 Pa. The solid solutions crystallize in rhombohedral symmetry (sp. gr. R3c). The lattice parameters of La0.7Sr0.3Mn1 − yCryO3 decrease with increasing chromium content. Doping with chromium reduces the conductivity of lanthanum manganite, without changing the conductivity type. The charge transport in the solid solutions is due to small-polaron hopping. Disproportionation of the 3d transition metals is shown to play a key role in determining the electrical properties of the solid solutions. Partial chromium substitution for manganese reduces the thermal expansion coefficient of the manganite, improving its compatibility with yttria-stabilized zirconia, which is of practical importance.

Structural, thermal, and electrical properties of La0.7Sr0.3Mn1−yFeyO3±δ

AbstractThe crystal structure, thermal expansion, and electrical conductivity of the doped manganites La0.7Sr0.3Mn1−yFeyO3±δ (y = 0, 0.1, 0.2, 0.3) are studied. The manganites are shown to crystallize in rhombohedral symmetry (sp. gr.

Regions of stability of variable-composition perovskite phases La1−x Sr x Mn1−y M y O3 (M = Ti, Ni)

R\bar 3c

Phase equilibria in the system LaMnO 3 -SrMnO 3 -SrCrO 4 -LaCrO 3</su

). Their lattice parameters are determined, and their thermal expansion coefficients are measured in the range 600–1223 K in air. The conductivity of the manganites is measured in broad ranges of oxygen partial pressures (pO2 = 0.1 to 10−15 MPa) and temperatures (T = 1073–1273 K). The effects of Fe content, temperature, and pO2 on the dominant defect species and the nature of electrical transport in La0.7Sr0.3Mn1−yFeyO3±δ are analyzed.

Thermal expansion and electrical conductivity of La 0.7 Sr 0.3 Mn 1 - y

The thermal expansion of CaTi0.9M0.1O3−δ (M = Fe, Cu, Al) samples has been measured, and their lattice parameters have been refined in space group Pnma. The three materials are shown to be mixed conductors, p-type at high oxygen partial pressures and n-type at low oxygen pressures. At intermediate oxygen partial pressures, the conductivity varies little. The acceptor dopants studied are shown to raise the conductivity of calcium titanate in the order Al < Cu < Fe.

Structural, thermal, and electrical properties of La 0.7 Sr 0.3 Mn 1- y <

The formation of the orthorhombic solid solution series LaMn1−yTiyO3 with 0.0 ≤ y ≤ 0.15 and LaMn1−yNiyO3 with 0.0 ≤ y ≤ 0.4 was observed. The stability boundaries of the La1−xSrxMn1−yMyO3 (M = Ti, Ni) perovskite phases were determined. Fragments of isobaric-isothermal sections of the phase diagrams of the La2O3-SrO-Mn3O4-TiO2 and La2O3-SrO-Mn3O4-NiO systems in air at 1100°C were suggested.