The migration of 55Fe, 65Zn and 54Mn radiotracers, in ferrite systems of the form, Mn0.89+xTixFe2.11-2xO4, Mn0.64+xZn0.25TixFe2.11-2xO4 Zn0.89+xTixFe2.11-2xO4, was studied, where x was equal to values of between 0 and 0.15. The diffusivity was determined by using the Gruzin method. The results (table 68) revealed that the Ti concentration profile could be divided into 2 regions; with the boundary at 3mol%Ti. The diffusion coefficient behaved differently in the 2 regions. In one region, there was a smooth increase in the Mn and Zn diffusivities. This was attributed to an increase in the defect content of the tetra sub-lattice. With increasing Ti concentration, the octa sub-lattice became imperfect. This effect was stronger for a Mn ferrite than for a Zn ferrite. A decrease in the Fe diffusion coefficient, relative to that of Mn, was attributed to the fact that Fe diffusion occurred in the octa sub-lattice, where Fe2+-Ti4+ bonds were established. As a result, the Fe jumps became non co-linear and the diffusion coefficient decreased. In this case, the Zn diffusivity increased more rapidly than that of Mn because of the lower strength of the bonds with O.

V.N.Shambalev, L.A.Bashkirov, V.V.Pankov, A.G.Dutov, A.N.Igumentsev: Physica Status Solidi A, 1989, 112[2], K71-3

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Table 68

Activation Energies for the Diffusion of Fe, Mn and Zn in Various Ferrites