Lattice creation and annihilation of LaMnO3+δ caused by nonstoichiometry change

In order to identify the majority ionic defect of La1−xSrxMnO3+δ in the oxygen-excess region, a dilatometry was made on La0.96MnO2.94+δ at a fixed temperature (1273 K) by varying the ambient oxygen partial pressure. The specimen of La0.96MnO2.94+δ expanded with increasing PO2 in the region of δ>0, while the unit cell volume was known to decrease with increasing PO2. The morphological evolution was also observed on the surface of the La0.96MnO2.94+δ specimen after annealing in an oxidizing atmosphere, indicating that the new lattices were created. From these results, it is concluded that the majority ionic defect of the perovskite oxide, La1−xSrxMnO3+δ, is cation vacancies in the oxygen-excess region.