Diffusion-induced grain boundary phenomena in metals and oxide ceramics

Abstract

In the first part of the paper recent experimental results on diffusion-induced grain boundary migration in ceramics are reviewed. It is demonstrated that all types of diffusion-driven phenomena known from the study of metallic systems occur also in oxide ceramics. Amorphous films on grain boundaries in ceramics play an important role in migration processes. It is shown that none of the existing theories of diffusion-induced grain boundary migration can describe satisfactorily the whole set of experimental data. In the second part of the paper, a new approach to the phenomenon is proposed, based on the gradient term in the expression for the free energy of binary alloys. The developed theory describes satisfactorily the stationary grain boundary migration and initial stages of diffusion-induced grain boundary migration. A new vacancy theory of the phenomenon is also reviewed.