Time-resolved luminescence study of CaF2:Eu2+ nanocrystals in glass-ceramics

CaF2:EU2+ nanocrystals are prepared by heating 45SiO(2)-20Al(2)O(3)-10CaO-25CaF(2)-0.1Eu(2)O(3) glasses above T-g = 630 degrees C. The size of grown crystals in glass-ceramics appears to be 5-35nm from XRD and TEM measurements, depending on the heating temperature and holding time. Time-resolved luminescence spectra due to Eu2+ ions are measured at 77 and 300 K under the excitation with the third harmonics of a Nd:YAG laser. It is found that the main band peaking at 2.97eV in glass-ceramics at delay time tau(D) = 0 mu s is high-energy shifted by 0.04eV relative to that of CaF2:Eu2+ single crystals. When tau(D) increases to 9 mu s, a new band is observed at around 2.7 eV in both glass and glass-ceramics. On the basis of the present results, the formation process and luminescence properties of nanosized CaF2:Eu2+ crystals in glass-ceramics are discussed. (c) 2004 Elsevier B.V. All rights reserved.