Formation and bleaching of induced colour centres in gamma-irradiated vanadium-containing alkali-borate glasses

Abstract

The nature of radiation-induced defects and defect generation process in glasses of the base composition B 2O 3 and R 2O+0.5g V 2O 5, where R is Li 2O, Na 2O or K 2O were studied. The glasses were exposed to successive irradiation doses up to 17 k Gy and their optical absorption spectra were measured in the range 200–1100 nm. Three factors were investigated: the role of V 2O 5, the effect of chemical composition, irradiation doses and the decay of colour centres by heat treatment at 200°C. The optical spectra have been shown to reveal the presence of V 3+, V 4+ and V 5+ ions altogether in varying proportions. The response of the glass to irradiation is related to the competition between formation and annihilation of induced defects and hence the observed characteristic colour centres. The rate of thermal bleaching at interval times was discussed.