Defect models of the low and high temperature centres of Cr3+ in alpha-LiIO3 : Cr3+ crystals

By analysing the EPR spectra of alpha-LiIO3:Cr3+ the defect models of a low temperature centre Cr3+L and two high temperature centres Cr3+H1 and Cr3+H 2 are suggested. In centre Cr3+L, the Cr3+ ion replaces the Li+ ion and exc ess charge is compensated by two nearest Li+ vacancies on the same axis. In centres Cr3+H1 and Cr3+H2, the Li+ vacancies below and above the Cr3+ ion are, respectively, dissociated from the low temperature centre Cr3+L. The s uggestions are supported by the theoretical calculations of EPR parameters D, g(parallel to) and g(perpendicular to) for the three Cr3+ centres. The r easonableness of these models is discussed.