Studies of the spectroscopic properties of lead-gallium oxyfluoride (LGOF) glasses and glass-ceramics activated by Pr3+ ions

Lead-gallium glasses, due to the absence of typical glass-forming components, are characterized by an increased tendency to crystallization. Despite this, they are interesting materials due to a shift of IR absorption edge up to 6 and 7 μm. The paper studies thermal stability, the UV-vis and IR transmission and luminescence spectroscopy of the lead-gallium glass. The base lead-gallium glass 0.65PbO·0.20Ga2O3·0.15SiO2 was modified by the addition of 2 mol% BaF2 and 1 mol% Pr6O11. DTA/DSC data showed that the glasses are characterized by the multi-stage crystallization. Unusual luminescence excitation spectra confronted with emission spectra, measured for glass (as made) and glass ceramic (annealed) phase, have been tentatively interpreted by means of single configuration coordinate diagrams. It seems that in both phases the praseodymium ions occur in two sites: lower- and higher-field environment. We propose the fluorine-affected sites as the lower field sites and purely oxide sites as the higher field sites. It seems likely that O-Pr-O sites can be treated as the higher filed sites whereas the fluorine affected sites, i.e. F-Pr-F and/or O-Pr-F sites, as the lower field sites.