SENSITIVITY OF IONIC THERMOCURRENT SPECTRA TO THE PRESENCE OF DIVALENT NICKEL IN ANNEALED NACL-CRYSTALS

Ionic thermocurrent measurements were performed for solution-treated N aCl:Ni crystals additionally annealed in a wide temperature range. It has been shown that the decay of the impurity-vacancy (IV) dipoles at temperatures in the range 333 K less than or equal to T-an less than o r equal to 463 K is accompanied by the formation of some vacancy-rich clusters which are of metastable character. These clusters transform i nto the nuclei of the stable NiCl2 phase. The decay of IV dipoles has been described in terms of an Avrami approach for precipitation of the dopant within stress fields of dislocations.