Structure of PbF2–TeO2 glasses and glass-ceramics
E.F. El Agammy, H. Doweidar, K. El-Egili, R. Ramadan
Abstract
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 TeO4 units (N4) with increasing PbF2. The results showed almost a linear decrease of N4 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 Pb1/22+TeO3+1− and TeO3/2F units, while former PbF2 builds its own matrix. XRD patterns revealed formation of crystalline Te2O3F2 and PbF2 phases and the latter becomes the dominant phase for PbF2 > 50 mol%.