Luminescence Properties and Optical Absorption of X ray-Irradiated KBr: Ce3+, Tb3+ Crystals

This paper reports that KBr doubly doped with Tb3+ and Ce3+ were prepared by Bridgman-Stockbarger method and characterized by Optical absorption, Photoluminescence (PL), Thermoluminescence (TL), Photo stimulated emission (PSL) and TL emission, after X-ray irradiation have been observed. The optical absorption measurement indicates that F and Z3 centers are formed in the crystal during X-ray irradiation process. It was attempted to incorporate a broad band of Ce3+ sensitizer into the narrow band emission of Tb3+ in the KBr host without reduction of emission intensity. Co-doping of Ce3+ ions in KBr:Tb3+ crystal showed a broad band emission due to the d-f transition of Ce3+ and a reduction in the intensity of emission peaks due to 5 days → 7 F6 transition of Tb3+ when they were excited at 250 nm. These results supported that an effective energy transfer occurs from Ce3+ to Tb3+ in the KBr host. Co-doping Ce3+ ions greatly intensified the excitation peak at 260 nm for the emission at 390 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 two orders of magnitude higher as compared to the undoped samples for similar doses of irradiation and heating rate. Thermoluminescence process has been identified due to thermal mobilization of F-electrons and this causes peaks at 371 K and at 427 K, 457 K in KBr: Ce3+, Tb3+ crystals. The defects generated by irradiation were monitored by optical absorption and trap parameters for the TL process were calculated and presented.