A NEW DEFECT MODEL TO DESCRIBE THE OXYGEN DEFICIENCY IN PEROVSKITE-TYPE OXIDES

The defect chemistry of LaMO3-δ (M =Mn, Fe, Co) perovskite-type oxides has been studied in order to describe the composition versus oxygen partial pressure phase diagrams in these systems. It is proposed that these systems can be described with extended defects. Literature data on LaMnO3-δ and LaCoO3-δ indicate that the phase diagrams can be described by a simple cluster model. The simple cluster model is suggested to be the building block for a number of highly defective perovskite-type phases that are known from the literature, like La4Mn4O11 and La4Ni4O11, that have different coordination sites for the transition metal ions (tetragonal and square planar, respectively). Other oxygen-deficient perovskite-type oxides probably can be described by similar, but more complicated cluster models, as will be discussed. © 1991 Academic Press, Inc.