CHANGE OF THERMAL-EXPANSION COEFFICIENT AND ELECTRICAL-CONDUCTIVITY OF LACO1-XMXO3 (M = FE, NI)

The thermal expansion coefficient of LaCo1-xFexO3 averaging between 25 and 1000-degrees-C decreased linearly with the Fe content, x. The thermal expansion of LaCo1-xNixO3 decreased with increasing the Ni content, but those for x = 0.67 and 1.0 were almost identical at 1000-degrees-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. LaCo0.67Ni0.33O3, which has the electrical conductivity of 4 X 10(2) S/cm, could be a good candidate for the air electrode material.