Effects of CdF2 and WO3 additions on the microstructural and thermal properties of TeO2-CdF2-WO3 glass system

This paper presents microstructural characterization investigations and the crystallization behavior of some glasses in the ternary TeO2-CdF2-WO3 system. Differential thermal analysis (DTA) showed that the glass forming ability of the ternary TeO2-CdF2-WO3 system which is in between the values of 21 and 34, is lower than most of the studied tellurite glasses. It is possible to obtain amorphous glass structure for the compositions of 0.80TeO2-0.10CdF2-0.10WO3 and 0.75TeO2-0.10CdF2-0.15WO3. On the other hand, the 0.85TeO2-0.10CdF2-0.05WO3 and 0.75TeO2-0.15CdF2-0.10WO3 compositions do not form glass with conventional quenching techniques. During crystallization of these glasses, the formation of the alpha, delta and gamma TeO2, WO3 and CdTe2O5 phases were observed with the addition of a new unidentified phase. Three compositions of 0.85TeO2-0.10CdF2-0.05WO3, 0.80TeO2-0.10CdF2-0.10WO3 and 0.75TeO2-0.10CdF2-0.15WO3 demonstrated two exothermic peaks in the DTA curves. SEM/EDS investigations confirmed the existence of the alpha, delta and gamma TeO2, WO3 and CdTe2O5 phases for the annealed glasses. The microstructure of the δ-TeO2 phase was clearly observed in the as-cast 0.75TeO2-0.10CdF2-0.15WO3 composition.