Transport and degradation in transition metal oxides in chemical potential gradients

The transport processes in transition metal oxides exposed to an oxygen potential gradient are analyzed as the prerequisite for an understanding of their degradation. For model systems, chemical diffusion, tracer self-diffusion and impurity tracer diffusion are studied, and both cation vacancies and cation interstitials are considered as defects in the oxide. The theoretical and experimental results for these transport processes in an applied oxygen potential gradient are reviewed. Using these results, two degradation processes in an oxygen potential gradient are investigated: demixing in doped oxides and morphological changes of the crystal during transport.