Enhanced luminescent properties and optical absorption of γ-irradiated KI: Ce 3+, Tb 3+ crystals

Abstract

This paper reports that KI doped with Ce 3+ or double doped with Tb 3+ and Ce 3+ were prepared by the Bridgman–Stockbarger method and characterized by optical absorption photoluminescence (PL), thermoluminescence (TL), photostimulated emission (PSL) and TL emission. The optical absorption measurement indicates that F and V 1, V 2 centers are formed in the crystals during the γ irradiation process. It was attempted to incorporate a broad band of Ce 3+ activator into the narrow band emission of Tb 3+ in the KI host without the reduction of emission intensity. Ce 3+-co-doped KI and Tb crystals showed a broad band emission due to the d–f transition of Ce 3+ and a reduction in the intensity of emission peaks due to the 5D 3– 7F j ( j=3,4,5,6) transition of Tb 3+, when they were excited at 240 nm. These results supported that an effective energy transfer occurs from Tb 3+ to Ce 3+ in the KI host. Co-doping Ce 3+ ions greatly intensified the excitation peak at 260 nm for the emission at 393 nm of Tb 3+, which means that more lattice defects, involved in the energy absorption and transfer to Tb 3+, are formed by the Ce 3+ co-doping. The integrated light intensity is an order of magnitude higher as compared to the undoped samples for similar doses of irradiation and heating rates. The defects generated by irradiation were monitored by optical absorption and TSL Trap parameters for the TL process are calculated and presented.