Correlation between thermodynamic and thermomechanical quantities of selected perovskite-type oxides

Abstract

Oxygen deficiencies, lattice parameters and thermal expansion of Ca 0.5Sr 0.5Mn 1− b Fe b O 3− x ( b = 0.1, 0.2, 0.5) have been measured by thermogravimetry, dilatometry, high-temperature diffraction of synchrotron radiation and compared with other familiar perovskite-type oxides A 1 − a A ′ a B 1 − b B ′ b O 3 − x (A, A′ = La, Sr, Ba; B, B′ = Mn, Fe, Co). The oxygen-to-metal (O/M)-stoichiometry (3 − x) as well as negative partial molar free energy ( Δ G ′ o x ) for oxidation reaction of perovskites decrease with increasing temperature, decreasing oxygen partial pressure and B-site substitution in the series Mn–Fe–Co. Thermal expansion and unit cell volume increase with increasing oxygen deficiency. Correlations between thermodynamic stability and thermal expansion with chemical composition and lattice parameters are investigated.