Dislocation structure in non-stoichiometric oxides

Abstract

A departure from stoichiometry is known to affect transport properties in oxides. Thus at temperatures where the formation is diffusion controlled, it is also affected by stoichiometry. To illustrate this point, a series of experiments on a variety of oxides is described. However, accurate interpretation of the results requires a detailed understanding of the dislocation core structures in oxides and how these structures can be influenced by a deviation from stoichiometry.

A review is given of our present knowledge of dislocation cores in oxides. Special emphasis is given to the dissociation properties of dislocation cores and their interaction with point defects.

The unambiguous observation of climb dissociated dislocations is restricted to only a few oxides. The conditions for the observation of such configurations are discussed together with the possible changes in crystal composition that may occur near stacking faults.

The experimental examples of climb dissociation in sapphire and spinel are compared and contrasted in terms of the respective properties of these crystals towards compositional changes. The effect of the so-called non-stoichiometry in magnesium aluminate spinel are described. Further effects of stoichiometry-related properties on dissociation and on mechanical properties are conjectured.