Abstract
The structure of NaF-TeO2 glasses and glass-ceramics has been studied by XRD, TEM, SEM, Raman and FTIR techniques. The results suggest that, for NaF <= 10 mol%, the entire NaF content enters the structure to convert TeO4 units into TeO3/2F and Na+ [TeO3+1](-) units. It has also been shown that NaF partially forms amorphous and/or crystalline phases for higher NaF content, where the relative concentration of each phase depends on the NaF content. SEM images show agglomerates of different sizes, which are discrete and spread within the structure. XRD revealed formation of crystalline Te2O3F2 for NaF <= 50 mol%, and a dominant phase of crystalline NaF for NaF > 50 mol%. Raman and FTIR spectra have been analyzed to calculate the concentrations of the various structural units in glasses and glass-ceramics.