Glass transition temperature-structural studies of tungstate tellurite glasses

Raman, IR and DSC studies have been carried on the (100 − x)TeO2–xWO3 (TW) glasses with 10 ≤ x ≤ 40 mol%. The Raman, IR spectra of these samples show that glass network consists of [TeO3]/[TeO3+1], [TeO4], [WO4] and [WO6] groups as basic structural units. The W ion coordination state changes from 4 to 6 when WO3 concentration increases beyond 30 mol%. Addition of WO3 oxide to the TW glasses increases the amount of lower coordination of [TeO3]/[TeO3+1] units and decreases the higher coordination [TeO4] units, Te–O–Te chains. From DSC thermogram, thermal properties such as the glass transition temperature (Tg), onset crystallization (To) of the glass systems were calculated. The compositional variation of glass transition temperature (Tg) is found to linear with an increase in WO3 content.