Cation Diffusion Coefficients and Vacancy Densities in Mn-Zn Ferrites

Abstract

Cation diffusion in Mn-Zn ferrites having excess iron was investigated by means of the isotope tracer method using single and polycrystalline samples. In polycrystalline samples “volume diffusion” and “grain boundary diffusion” were observed and separated from each other. The results are: (1) The volume diffusion coefficient of ⁵⁹ Fe varied with the oxygen content, i.e. , the density of cation vacancies in the sample. Activation energy of the diffusion was 1.50±0.05 eV, being independent of the vacancy density. This value means the migration energy of vacancies. (2) The volume diffusion coefficients obtained were same for ⁵⁴ Mn, ⁵⁹ Fe, ⁶⁰ Co and ⁶⁵ Zn, but slightly different for ⁴⁵ Ca. (3) The grain boundary diffusion coefficient was as sensitive as the volume diffusion coefficient to sintering atmospheres.