Photoluminescence of Eu2+ in BaF2-rich fluorohalides and photostimulation after X-ray irradiation

The luminescence of Eu 2+ has been investigated in two families of BaF 2 -rich fluorohalides, Ba 12 Cl 5(1− x ) Br 5 x F 19 ( x ≤0.8) and Ba 7 Cl 2(1− x ) Br 2 x F 12 ( x ≤0.5). In the two kinds of host lattices, under UV excitation Eu 2+ shows an intense blue 5d→4f band emission at 300 K. At low temperature, in addition to the latter, 4f→4f lines are present in the near UV. The efficiency of the photostimulated luminescence (PSL) after X-ray irradiation has been measured and compared with that of BaXF:Eu (X=Cl, Br). High conversion efficiencies have been obtained with compositions Ba 12 Cl 5(1− x ) Br 5 x F 19 for stimulation at 532 nm. The presence of bromine is beneficial. For all compositions a high stimulation energy (SE) is needed to excite Eu 2+ ions through colour centres.