Photoluminescence and crystallization in europium-doped fluorobromozirconate glass-ceramics

Abstract We have investigated barium bromide crystallization in glasses which have an overall composition of 53% ZrF 4 , 20% BaF 2 , 5% NaF, 15% NaBr, 1% LaF 3 , 3% AlF 3 , 2% YF 3 , and 1% EuF 2 . The glasses were prepared by melting at 850°C in an inert atmosphere and quenching into a brass mold. Subsequent thermal treatment of the glass yields a transparent or translucent fluorozirconate glass containing BaBr 2 crystals; this glass-ceramic material has potential applications as an X-ray storage phosphor. The glasses and glass-ceramics were investigated using photoluminescence, optical density, X-ray diffraction, and differential scanning calorimetry methods. Glasses which have been quenched to temperatures below 260°C are transparent and show no photoluminescence from the europium ions. When the glasses are subsequently heated above about 263°C, crystals of BaBr 2 in the hexagonal phase start to precipitate and photoluminescence from Eu 2+ ions is observed. It is possible to prepare the resulting glass-ceramic in transparent form by heating to temperatures just below the temperature of most rapid crystallization, T x =280 C. The photoluminescence is attributed to Eu 2+ ions replacing Ba 2+ ions in the BaBr 2 crystals.