Photoluminescence and crystallization in europium-doped fluorobromozirconate glass-ceramics

We have investigated barium bromide crystallization in glasses which have an overall composition of 53% ZrF4, 20% BaF2, 5% NaF, 15% NaBr, 1% LaF3, 3% AlF3, 2% YF3, and 1% EuF2. The glasses were prepared by melting at 850 degreesC in an inert atmosphere and quenching into a brass mold. Subsequent thermal treatment of the glass yields a transparent or translucent fluorozirconate glass containing BaBr2 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 degreesC are transparent and show no photoluminescence from the europium ions. When the glasses are subsequently heated above about 263 degreesC, crystals of BaBr2 in the hexagonal phase start to precipitate and photoluminescence from Eu2+ 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 Eu2+ ions replacing Ba2+ ions in the BaBr2 crystals. (C) 2001 Elsevier Science B.V. All rights reserved.