FORMATION AND BLEACHING OF INDUCED COLOR-CENTERS IN GAMMA-IRRADIATED VANADIUM-CONTAINING ALKALI-BORATE GLASSES

The nature of radiation-induced defects and defect generation process in glasses of the base composition B2O3 and R(2)O + 0.5 g V2O5, where R is Li2O, Na2O or K2O were studied. The glasses were exposed to succe ssive irradiation doses up to 17 kGy and their optical absorption spec tra were measured in the range 200-1100 nm. Three factors were investi gated: the role of V2O5, the effect of chemical composition, irradiati on doses and the decay of colour centres by heat treatment at 200 degr ees C. The optical spectra have been shown to reveal the presence of V 3+, V4+ and V5+ ions altogether in varying proportions. The response o f the glass to irradiation is related to the competition between forma tion and annihilation of induced defects and hence the observed charac teristic colour centres. The rate of thermal bleaching at interval tim es was discussed. Copyright (C) 1996 Elsevier Science Ltd