Raman studies of Ag2O·WO3·TeO2 ternary glasses

A Raman study was carried out on xAg2O·(1-x)[yWO3·(1-y)TeO2] (x=0.3, 0.4) ternary glasses with respect to composition and temperature. The crystallization process and structural units making up the ternary glasses were analyzed in detail. Ag2O addition was found to promote the formation of TeO3 tetragonal pyramid and WO4 units in the glasses at the expense of TeO4 tetragonal bipyramid and WO6 units. The addition of Ag2O also lengthens the Te—O bond, whereas WO3 increases the vibrational wavenumber of the TeO3 units. The crystallization of the glasses is a two-step ordering process of the TeO4 units and complete ordering is hindered by the more rigid WO4 units. However, the onset of crystallization does not follow a simple pattern with the content of WO3. The proportion of the TeO4 units is always small at the onset of crystallization and increases close to the completion of crystallization, regardless of whether the crystal is formed from the melt by cooling or from the glass state by heating.