<b>Defect models of the low and high temperature centres of in crystals</b>

Abstract

By analysing the EPR spectra of , the defect models of a low temperature centre and two high temperature centres and are suggested. In centre , the ion replaces the ion and excess charge is compensated by two nearest vacancies on the same axis. In centres and , the vacancies below and above the ion are, respectively, dissociated from the low temperature centre . The suggestions are supported by the theoretical calculations of EPR parameters D, and for the three centres. The reasonableness of these models is discussed.