Preparation and near-infrared luminescence properties of Bi-doped BaF2 crystal

Bi2O3:BaF2 and BiF3:BaF2 crystals were prepared by TGT (temperature gradient method). Near-infrared broadband luminescence was observed in as-grown Bi2O3:BaF2 crystal. The emission band peaks at 961 nm in the range of 850—1250 nm，with FWHM about 202 nm. The luminescence of Bi2+ and Bi3+ ions in the visible region was observed in BiF3:BaF2 crystal, but there was no near-infrared emission. Then the BiF3: BaF2 crystal was exposed to γ-rays in order to reduce valence states of Bi ions. Near-infrared broadband luminescence was observed in γ-irradiated BiF3:BaF2 crystal. The emission band peaks at 1135 nm in the range of 850—1500 nm，with FWHM about 192 nm. The mechanisms of near-infrared luminescence in Bi2O3:BaF2 crystals and γ-irradiated BiF3:BaF2 crystals were discussed.