Fluorescence properties of Eu3+ doped lead bearing fluoro-chloro phosphate glasses

Lead bearing glasses belonging to the family PbF2-PbCl2-P2O5 have been prepared and their absorption edges and Urbach energies reported. The influence of composition on the ratios of red-to-orange emission intensities (R/O) of EU3+ and yellow-to-blue emission intensities (Y/B) of Dy3+ doped in these glass systems are studied, these ratios being sensitive to covalency and site asymmetry effects. The local structure and multiphonon relaxation mechanisms of Eu3+ ions are investigated by measuring the phonon side band spectra associated with the F-7(0) --> D-5(2) transition. The phonon energies are correlated with vibrational modes observed in the infra-rid spectra considering 4-fold coordination of phosphorus ions in the present glass system. The electron-phonon coupling strengths are found to be much higher compared to other phosphate and fluoride glass matrices resulting in larger non-radiative rates from higher energy states, D-5(f(j = 1,2,3)). The line positions of D-5(0) --> F-7(0) emission transition suggest 7-9 coordination of EU3+ ions with the surrounding oxygen ligand atoms. The relatively large line widths of D-5(0) --> F-7(0), emission transition show compositional influence of the non-bridged oxygens (NBOs) and phosphate linkages having double bonded oxygens (DBOs) coordinated to Eu3+ ions. (C) 1999 Elsevier Science B.V. All rights reserved.