Reactions which were related to O centers were studied in various fluorite crystals with a wide band-gap. The aggregation of O-vacancy dipoles was observed in all of the crystals, at temperatures above 50 to 100C. Photo-dissociation by excitation into second or higher energy absorption bands was observed in all of the materials, except LaF3. In some of the crystals, O centers were traps for electrons and holes. No new absorption bands were observed in well-quenched O-doped CeF3 crystals. Two different types of O defect were observed in LaF3. The first type had an absorption band near to 7.2eV, and 3 sharp emission lines (2.36, 2.26, 2.23eV) with rather long decay times (0.55ms at 80 and 13K). The intensity of these O centers was greatest in rapidly quenched samples, and was decreased by annealing at 50 to 200C. These defects were attributed to O-vacancy centers. Another type of defect, with broad emission bands near to 2.7eV and a much more rapid decay, was attributed to O-vacancy aggregates.

E.Radzhabov: Materials Science Forum, 1997, 239-241, 261-6