Structural and physical properties of a novel TeO2-BaO-SrO-Ta2O5 glass system for photonic device applications

A detailed study on a novel TeO2-BaO-SrO-Ta2O5 glass system developed for photonic device applications is reported in this paper. The glass transition and crystallization temperatures could be selected by varying the Ta2O5 content in this glass system. This glass system is found to have good thermal stability among tellurite glasses. Raman spectroscopy has been used as a tool to analyze the structural details of this technologically important glass system. In addition to the TeO4 trigonal bipyramid and TeO3 trigonal pyramid structural units, glasses in this system revealed the presence of an additional Raman band attributed to TaO6 octahedra. The Raman bandwidth of the present glasses are broader compared to the conventional tellurite glasses by 35%. The influence of a gradual addition of the modifier oxides on the coordination geometry of tellurium atoms has been elucidated. Unlike the other tellurite glasses, even at higher modifier concentrations the TeO4 structural units dominate in the glass network compared to TeO3 trigonal pyramids. The ratio of TeO4/TeO3 structural units was discussed for different series of glass compositions.