Structural study and physical properties of tellurite glasses containing lead bromide

In this work, a suggested approach based on ion exchange process (IXP) between Br  ions from PbBr2 and O ions from Ag2O was applied to obtain crystalline glass ceramic directly from glasses. Silver-borate glasses in the system: xPbBr2-(45-x) Ag2O-55TeO2, with (x = 0, 10, 15, 20, 22.5, and 25 mol.% PbBr2) were synthesized by melt quenching technique. X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) were used to investigate the structure and properties of the as prepared glasses. According to both Raman and FTIR studies, as PbBr2 content increases, some of the TeO4 and TeO3+1 units are converted to TeO3, which contains more NBO. Increasing the latter with increasing PbBr2 content was discussed on the basis of the ion exchange process. According to X-ray results, the addition of lead bromide causes a noticeable change in the nature of the glass. The lead-bromide-free glass implies two crystalline extremes that can be attributed to the formation of the silver tellurite crystalline phase (Ag2TeO3). Upon the addition of lead bromide, even with small concentrations up to 20 mol.%, the most prominent structure is amorphous. On the other hand, increasing the concentration of lead bromide forms lead tellurite crystalline phase (Pb3TeO6). Data based on density, packing density, molar volume, free molar volume, and oxygen molar volume were discussed and correlated with the structural changes caused by addition of PbBr2. In view of a potential application on ion exchange process, formation of crystalline dispersed phases in host tellurite matrices will be object of a further investigation.