By using tracer and sectioning techniques, the migration of divalent and trivalent cations was investigated at temperatures of between about 500 and 750C; under conditions of heterodiffusion at infinite dilution. This was achieved by allowing radiotracers with a high specific activity to diffuse in the intrinsic range of high-purity single crystals. Although reported to exhibit anomalous diffusion in this halide, Co2+ here gave very good diffusion profiles for the carrier-free isotope 58Co. Analysis of the results indicated that, for Co2+, the migration enthalpy was 0.66eV. The migration entropy was -1.45k. The overall Co diffusivities could be described by the relationship:

D (cm2/s) = 0.12 exp[-1.27(eV)/kT]

Diffusion of Heterovalent Ions in Ionic Crystals. F.Bénière, K.V.Reddy: Journal of Physics and Chemistry of Solids, 1986, 47[1], 69-77

Table 62

Diffusivity of Co2+ Ions in KCl Melts at 700C