Oxygen Nonstoichiometry and Transport Properties of Selected La1-xSrxCo1-y-zFeyNizO3-delta Perovskites

Crystal structure, high temperature oxygen nonstoichiometry and transport properties of two members of La 1-x Sr x Co 1-y-z Fe y Ni z O 3-δ group ofperovskite type oxides are presented. La 0.6 Sr 0.4 Co 0.2 Fe 0.6 Ni 0.2 O 3-δ and La 0.9 Sr 0.1 Co 1/3 Fe 1/3 Ni 1/3 O 3-δ compositions possess high electrical conductivity at high temperatures in air. However, the observed characteristics of the electrical conductivity as a function of the oxygen partial pressure for these materials are significantly different. A discussion of the observed effects is provided, which shows strong correlation between chemical composition, crystal structure, oxygen nonstoichiometry and the observed transport properties. An interesting phenomenon related to an irreversible oxygenation of the quenched La 0.6 Sr 0.4 Co 0.2 Fe 0.6 Ni 0.2 O 3-δ samples was observed. This reaction takes place at 200-300°C range which is well below a typical nonstoichiometry related reactions. A possible explanation of this effect is discussed.