Thermophysical characterization of TeO2-WO3-Bi2O3 glasses for optical applications

Heat capacity, glass transition and crystallization characteristics of high-purity tungsten-tellurite glasses (78-x) TeO2-22WO(3)-xBi(2)O(3) (x = 2, 5, 8 mol%) were studied by differential scanning calorimetry in the temperature range of 300-950 K. Density and coefficient of thermal expansion (CTE) were measured at the room temperature. Density increases from 5.94 to 6.32 +/- 0.02 g/cm(3) with an increase in the content of Bi2O3. CTE at 298 K is equal to (36.3 +/- 0.6).10(-6) K-1 for the series. As a result of theoretical processing of calorimetric and volumetric data, standard thermodynamic functions, density and CTE were calculated for each glass composition in a wide temperature ranges, and a method for their parametric prediction was proposed for intermediate unstudied compositions. The most crystallization resistant compositions of glasses were revealed. The obtained thermodynamic parameters, including temperature dependences of density and CTE, are useful for the production of bismuth-containing tellurite glasses and for predicting their properties.