On the basis of an analysis of the electron paramagnetic resonance spectra of Cr3+-doped α-phase material, models were proposed for a low-temperature centre, Cr3+L, and 2 high-temperature centres: Cr3+H1 and Cr3+H2. In the case of Cr3+L, the Cr3+ ion replaced the Li+ ion, and the excess charge was compensated by the 2 nearest Li+ vacancies on the same axis. In the case of Cr3+H1 and Cr3+H2, the Li+ vacancies below and above the Cr3+ ion, respectively, were dissociated from the low-temperature centre, Cr3+L. This proposal was supported by theoretical calculations of the electron paramagnetic resonance parameters for the three Cr3+ centres.

Defect Models of the Low and High Temperature Centres of Cr3+ in a-LiIO3:Cr3+ Crystals. W.C.Zheng, S.Y.Wu: Journal of Physics - Condensed Matter, 1999, 11[15], 3127-32