It was recalled that this perovskite-type oxide was known to contain large numbers of O vacancies. High-resolution electron microscopy revealed that these were ordered. When the O stoichiometry was varied, the perovskite framework (metal cation positions) did not change, but a markedly high O anion mobility was maintained. A study was made here of the O mobility in various phases which exhibited O-vacancy ordered structures. In the sequence of compounds, the Mn oxidation state changed from Mn4+ to Mn3+. In order to simulate these defect structures, the interatomic potential method was applied to a simple rigid-ion model.

A.V.Petrov, S.C.Parker, A.Reller: Phase Transitions, 1995, B55[1-4], 229-44