Spectroscopic and luminescence studies of thulium doped strontium borate glass

Un-doped as well as Tm doped strontium borate glasses were prepared and characterized by different spectroscopic techniques. 11B MAS-NMR studies on the glass samples have shown the presence of BO3 structural units in addition to the tetrahedrally coordinated BO4 structural units confirming glass formation. Optical absorption and photoluminescence studies of these samples showed stabilization of thulium as Tm3+ ions in the virgin sample, while, on γ-irradiation, partial reduction to Tm2+ was observed. EPR investigations of virgin and γ-irradiated samples showed the presence of BO32- centered radicals in the latter samples only. TSL studies of γ-irradiated Tm doped strontium borate glass showed two glow peaks around 423 and 528 K. Tm3+ was identified as the luminescent center from spectral studies. Temperature dependence studies of EPR spectra have shown the thermal destruction of BO32- radical ion to be associated with the TSL glow peak at 423 K. Based on these investigations, the mechanism for the processes occurring during γ-irradiation and subsequent thermal treatment is proposed.