Crystal structure and physicochemical properties of doped lanthanum manganites

Abstract

Substituted lanthanum-strontium manganites La 0.7Sr 0.3Mn 0.9Me 0.1O3 ± δ (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La 0.7Sr 0.3Mn 0.9Me 0.1O3 ± δ oxides. It is shown that in the range 298-1023 K in air, La 0.7Sr 0.3Mn 0.9Me 0.1O3 ± δ manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La 0.7Sr 0.3Mn 0.9Me 0.1O3 ± δ oxides. The conductivity of La 0.7Sr 0.3Mn 0.9Me 0.1O3 ± δ is studied as a function of temperature in the range 500 K ≥ T ≥ 1200 K in air. It is shown that substituting 3d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O 3 ± δ. The chemical stability of iron-substituted manganite La 0.7Sr 0.3Mn 0.9Fe 0.1O3 ± δ is studied with respect to the electrolyte material. © Pleiades Publishing, Ltd., 2012.