Correlation between the variation of the diffusion coefficient of the vacancies and their concentration in the partially oxidized spinels in defect phase γ
Abstract The oxidation kinetics of preoxidized magnetites (Fe 2+ 1−3 γ □Fe 3+ 2(1+ γ ) ) O 2- 4 and zinc substituted magntites (Zn 2+ x Fe 2+ 1− x Fe 3+ 2 )O 2− 4 into the γ defect phases is found to be governed by the diffusion with a chemical diffusion coefficient depending on vacancy concentration and decreasing with δ and x . For low substitution extents, the rate law written as v = kP n O 2 with n= 1 2 agrees with a total association of defects. For Zn-rich compounds, the law written as v=kP 1 5 O 2 is in better agreement with a partial association of defects.