Ionic thermo-current measurements were carried out on solution-treated Ni-doped crystals that had been annealed within a wide temperature range. It was shown that a decay of the impurity-vacancy dipoles, at temperatures ranging from 333 to 463K, was associated with the formation of vacancy-rich clusters which were metastable in nature. These clusters transformed into nuclei of the stable NiCl2 phase. The decay of IV dipoles was described in terms of an Avrami approach to the precipitation of the dopant within the stress fields of dislocations.

B.Macalik, M.Suszynska: Materials Chemistry and Physics, 1996, 43[1], 62-5