Introducing alkali impurities into BaFBr:Eu2+ crystals and their effect on photo-stimulated luminescence

In alkali doped BaFBr:Eu2+ a considerable increase of photostimulated luminescence (PSL) intensity is observed. Upon Na doping the intensity of the PSL is increased by a factor of 15 in contrast to undoped samples. Moreover, the PSL peak shifted on 0.08 eV in the red region of spectrum upon Na doping. The potassium and rubidium doping results in the same effects, but with less efficiency. We prepared undoped BaFBr:Eu2+ crystals and those doped with varied concentrations of NaF, KF, RbF. The concentrations of alkali, which we doped before growth, were in the region of 0.1–5%. Atomic-Emission Analysis shows that the real alkali concentrations in the crystals are 0.0002–0.0025%. However, even such a small alkali doping concentration in BaFBr:Eu2+ influences effectively the PSL process.