Change of thermal expansion coefficient and electrical conductivity of LaCo₁–_xM_xO₃ (M = Fe, Ni)

The thermal expansion coefficient of LaCo_1−xFe_xO₃ averaging between 25 and 1000 °C decreased linearly with the Fe content, x. The thermal expansion of LaCo_1−xNi_xO₃ decreased with increasing the Ni content, but those for x = 0.67 and 1.0 were almost identical at 1000 °C due to the transition of the crystal system of LaNiO₃. The behavior of thermal expansion was interpreted in terms of the formation enthalpy of the perovskites and the bond length between a B-site cation and an oxide anion. LaCo_0.67Ni_0.33O₃, which has the electrical conductivity of 4 × 10² S/cm, could be a good candidate for the air electrode material.