Diffusion in single crystals was studied by annealing specimens at temperatures of between 700 and 760C. After 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 in the halide. It was concluded that the region of normal diffusion was due to the migration of this complex ion via a vacancy mechanism. The activation energy for CoCl42- ion diffusion, and the enthalpy of migration, were 1.71 and 1.12eV, respectively.

D.Damien, K.V.Reddy: Indian Journal of Pure and Applied Physics, 1983, 21[3], 133-6

Figure 13

Diffusion of Co in KCl