Luminescence studies in BaFBr and BaFBr : Eu

Photoluminescence (PL), thermostimulated luminescence (TSL) and X-ray induc ed luminescence (XIL) studies of BaFBr:Eu, BaFBrI:Eu (Fuji) and BaFBr (undo ped) reveal that in these phosphors: (i) oxygen impurity and self-trapped e xciton (STE) emissions occur at about 480 and 300 nm, respectively; (ii) TS L peaks below RT display O(F)(2-)emission whereas the TSL peak above RT dis plays 380-400 nm Eu2+ emission; (iii) in the XIL spectra of oxygen rich BaF Br:Eu, the Eu2+ emission builds-up with increasing temperature above 100 K at the expense of 300 nm STE emission which indicates an energy transfer fr om STE to Eu2+; (iv) in BaFBr:Eu2+ with excess oxygen content, PSL is quenc hed; (v) in Fuji BaFBrI:Eu2+ which has a very low oxygen content and high P SL efficiency as revealed in its FL, PSL and TSL spectra, only Eu2+ emissio n is seen in the XIL spectra between 100 and 300 K which indicates an effic ient energy transfer from STE to Eu2+; and (vi) the presence of STE emissio n in BaFBr (undoped) and 400 nm Eu2+ emission in Fuji IP along with O-F(2-) emission in their low temperature TSL spectra is a proof of the trapping o f excitons near the O-F(2-) sites during X-irradiation and their release du ring thermostimulaton. Possible implications of these results on the PSL pr ocess in BaFBr:Eu are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.