Defects in highly nonstoichiometric oxides

Abstract

A number of important physical and chemical properties of nonstoichiometric transition metal oxides are strongly dependent on the kind and concentration of point defects in the crystalline lattice of these materials. If the concentration of these defects is sufficiently small they do not interact and the defecteed crystal can be treated as ideal solid solution of defects in its crystalline lattice. However, in many cases the concentration of defects in transition metal oxides is high enough for them to interact, what can result in formation of extended defects, i.e. of three-dimensional complexes and defect clusters, or of two-dimensional planar defects. For these cases the point defect model is not applicable and transport processes cannot be described in terms of solid state diffusion theory. An attempt has been made to systematize the current knowledge of extended defects and to formulate some conclusions concerning transport phenomena in crystals containing these defects.