Enhanced luminescent properties and optical absorption of γ-irradiated KI: Ce3+, Tb3+ crystals

This paper reports that KI doped with Ce3+ or double doped with Tb3+ and Ce3+ 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 gamma irradiation process. It was attempted to incorporate abroad band of Ce3+ activator into the narrow band emission of Tb3+ in the KI host without the reduction of emission intensity. Ce3+-co-doped KI and Tb crystals showed a broad band emission due to the d-f transition of Ce3+ and a reduction in the intensity of emission peaks due to the D-5(3)-F-7(j) (j = 3,4,5,6) transition of Tb3+, when they were excited at 240 nm. These results supported that an effective energy transfer occurs from Tb3+ to Ce3+ in the KI host. Co-doping Ce3+ ions greatly intensified the excitation peak at 260 nm for the emission at 393 nm of Tb3+, which means that more lattice defects, involved in the energy absorption and transfer to Tb3+, are formed by the Ce3+ 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. (C) 2008 Elsevier B.V. All rights reserved.