Structure of PbF2-TeO2 glasses and glass-ceramics

XRD, SEM, TEM, Raman and FTIR have been used to study the structure of PbF2-TeO2 glasses and glass-ceramics (10 <= PbF2 <= 90 mol%). Raman and FTIR spectra have been analyzed to track the change in fraction of Te04 units (N4) with increasing PbF2. The results showed almost a linear decrease of N-4 for PbF2 <= 10 mol%, and then steadily decreased with increasing PbF2 contents. It is deduced that PbF2 entirely modifies the structure in the region of PbF2 < 10 mol% and plays the dual role (modifier and former) for PbF2 > 10 mol%. The modifier PbF2 converts TeO4 units to Pb-1/2(2+)[TeO3+1](-) and TeO3/2F units, while former PbF2 builds its own matrix. XRD patterns revealed formation of crystalline Te2O3 F-2 and PbF2 phases and the latter becomes the dominant phase for PbF2 > 50 mol%. (C) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).