The deviation from stoichiometry of (CrxFe1-x)3O4 was measured thermogravimetrically, at 1200C, as a function of the O activity and cationic composition, x. Cation tracer diffusion coefficients were determined experimentally by using 60Co, 51Cr, 59Fe and 54Mn isotopes. It was found that stoichiometric deviation versus log[O-activity] plots, for various x-values, had S-shaped curves. The experimental data suggested that cation vacancies and cation interstitials were the major defects at high and low O activities, respectively. It was found that V-shaped curves were observed in the case of diffusivity versus log[O-activity] plots. The observed O activity-dependence indicated that the diffusion of Co, Cr, Fe and Mn in this material at high O activities was governed by cation vacancies. At low O activities, it was governed by cation interstitials. The mean cation mobilities were deduced by combining the data on non-stoichiometry and cation diffusion.

J.Töpfer, S.Aggarwal, R.Dieckmann: Solid State Ionics, 1995, 81[3-4], 251-66