Thermal-Expansion Behaviors and Mechanisms for Ca- or Sr-Doped Lanthanum Manganite Perovskites under Oxidizing Atmospheres

The thermal expansion behavior and mechanism of A‐site‐deficient lanthanum manganite perovskites, La 1 − x MnO 3 ( 0 < x ≤ 0.1 ) , and alkaline earth metal (AE)‐doped lanthanum manganite perovskites, La 1 − x AE x MnO 3 ( AE = Ca and Sr , 0 ≤ x ≤ 0.4 ) , under oxidizing atmospheres have been investigated. The average linear thermal expansion coefficients of the AE‐doped lanthanum manganites decreased with increasing Ca content up to 20 mol % and with increasing Sr content up to 10 mol %, and then increased. During the thermal cycle measurement, the La 1 − x MnO 3 ( 0 ≤ x ≤ 0.1 ) perovskite samples and the La 1 − x AE x MnO 3 perovskites (0 ≤ x ≤ 0.3) shrank, while no anomalous shrinkage behavior was observed for the La 0.6 AE 0.4 MnO 3 samples. From the results of high‐temperature X‐ray diffraction analysis, no dependency of cell volume of the perovskites on aging time at selected temperatures and on thermal cycles was observed.