Thermal, structural and optical properties of Bi2O3-Na2O-TiO2-ZnO-TeO2 glass system

Abstract

Tellurite glasses have found wide applications in laser, nonlinear optics and optical communication. This paper describes the role of Bi2O3 on the physical and optical properties of glasses with molar composition of xBi2O3-5Na2O-5TiO2-10ZnO-(80-x)TeO2, where x = 5, 8, 10, 12, and 15 mol.% synthesized using conventional melt quenching technique. The thermal properties of the sample glasses, such as glass transition temperature (Tg), onset crystallization temperature (Tx), and glass stability (S), were estimated from the differential scanning calorimetry measurements. The glass stability was found to decrease as Bi2O3 content increased. The decrement was due to: (i) the decomposition of strong TeO4 units into TeO3+1 polyhedra and TeO3 units; (ii) the replacement of strong Te‒O‒Te bonds by weaker Te‒O‒Bi bonds; and (iii) the formation of weak Bi‒O‒Bi bonds that were shown in Raman and FTIR results contributed to the weakening of the glass stability. The measurements from the UV-Vis spectrophotometer indicated a drop in the optical band gap with increasing Bi2O3 content. A low energy band gap is evidence of glasses with high polarizability which could be due to thehigh polarizability of non-bridging oxygen. This finding, among others in this study, shows that the synthesized bismuth-based tellurite glass is suitable as a potential optical material in the optical and photonic applications.