An analysis of creep transients in polycrystalline material, which followed sudden changes in O partial pressure, permitted the determination of the chemical diffusion coefficient of the minority point defects which controlled cation diffusion. That is, the sudden change in O partial pressure created a chemical potential gradient in the material; thus producing a defect migration which brought the compound back to uniformity. Under the experimental conditions, the cations were the slowest-moving species. The diffusion coefficients which were deduced here (such as a value of 2.0 x 10-6cm2/s at 840C) were close to those, for O diffusion, which had been found by thermogravimetry. This indicated that the change in cation point defect concentration was directly linked to the diffusion of O defects to or from the surface.

J.Jiménez, F.García, M.Jiménez-Melendo, A.Domínguez-Rodríguez: Materials Science Forum, 1997, 239-241, 439-42