ABSTRACT
Diagrams of the concentrations of defects in the spinel (Fe1−x Cr x )3±δO4 with the chromium content of x Cr = 0.1–0.5 mol were determined with the use of the data on the deviation from the stoichiometry at 1473 K. It was found that chromium doping in magnetite only slightly affects the character of the oxygen pressure dependence of the deviation from the stoichiometry compared to that for the pure magnetite. For the chromium content up to x Cr > 0.2 mol, the structure of point defects practically does not change. In the range of higher oxygen pressures, cation vacancies [V‴ Fe ] dominate; their concentration changes only slightly with the chromium content in the spinel. In the range of low oxygen pressures, interstitial cations [Fe 3• i] dominate; their concentration decreases with the chromium content. The ratio of the coefficient of diffusion (mobility) of tracer ions, (59Fe, 60Co, 53Mn and 51Cr), via interstitial cations to the coefficient of diffusion via cation vacancies was determined with the use of the concentration of ionic defects and the values of coefficients of self-diffusion of tracers M*. It was found that when the chromium content increases up to x Cr = 0.2 mol in the spinel (Fe1−x Cr x )3±δO4, the mobility via interstitial cations is significantly higher than the mobility via cation vacancies.
