DRIFT OF IMPURITIES TOWARD DISLOCATIONS IN NACL-NI2+ CRYSTALS

The effect of thermal and mechanical treatment upon dielectric charact eristics was investigated for NaCl crystals doped with divalent nickel . The behaviour of two ionic thermocurrent (ITC) bands was followed du ring room temperature (RT) storage of the pretreated samples. The isot hermal annealing curves are of the t(an)-m type, with m characteristic of segregation of the impurities near dislocations accompanied by Ost wald ripening. The activation energy of this process is equal to the m igration activation energy for cation vacancies in NaCl crystals, i.e. , the migration of impurities is controlled by the diffusion of vacanc ies. Prolonged annealing of supersaturated solid solution (ST) samples at RT results in the appearance of a third ITC band, probably related to the formation of secondary-phase particles rich in cation vacancie s.