Diffusion in single crystals was studied by annealing specimens at 700 to 760C. For short annealing times, the diffusion profiles exhibited only one region. After annealing for long times, a region of slow diffusion was detected close to the surface, in addition to the region of normal diffusion (figure 13). This anomalous behavior was attributed to an effect of the poor solubility of CoCl42- ions. It was concluded that the region of normal diffusion was due to migration of this ion via a vacancy mechanism. The activation energy for CoCl42- diffusion, and the migration enthalpy, were 1.71 and 1.12eV, respectively.

Diffusion of Cobalt in KCl Single Crystals. D.Damien, K.V.Reddy: Indian Journal of Pure and Applied Physics, 1983, 21[3], 133-6