Powdered and bulk sintered samples of the Mn-Zn ferrite were studied by means of mass spectrometry and electron-probe micro-analysis. Equilibrium vapor pressures were measured by using powdered samples, and the predominant vapor species was found to be gaseous Zn, with small fractions of gaseous FeO and MnO. The vapor pressures of these species over bulk sintered samples decreased exponentially with time, and approached limiting values. The surface was severely depleted in Zn and slightly in O, but was enriched in Mn and Fe. The diffusion equation was solved for the Zn profile, by using a time-dependent boundary condition for the surface. This yielded an activation energy for diffusion of 410kJ/mol. This value was some 3 times greater than published data which had been obtained by using tracer methods.

H.Inaba, T.Matsui: Journal of Solid State Chemistry, 1996, 121[1], 143-8