Abstract
Perovskite oxides 
, [
and 
, 
] containing A site defects were studied by thermal analysis, measuring of the temperature dependence of electrical conductivity (373–1273 K) and x‐ray diffraction. The results showed that 
underwent a phase transition accompanied by oxygen desorption at about 1000 K in air. The electrical conduction mechanism also changed from small‐polaron conduction. The amount of oxygen desorption accompanying the phase transition decreased stoichiometrically with increasing Sr content.