Effect of B2O3 addition on thermal and optical properties of TeO2–ZnO–Bi2O3–TiO2 glasses

New tellurite glasses with composition (in mol%): 60TeO _2 –(30-x)ZnO–5Bi _2 O _3 –5TiO _2 -xB _2 O _3 (where x = 0, 2.5, 5.0, 7.5 and 10.0) were fabricated using conventional melt quenching method. Compositional dependence of the glasses on their density, thermal, refractive index and optical properties were investigated. X-Ray Diffraction analysis was carried out to confirm the nature of the thus formed glasses. Density, refractive index, and absorption spectra were measured at room temperature from which other glass characteristics such as polaron radius, oxygen packing density, field strength, B ^3+ interatomic distance, band gap energy, and Urbach tail were determined. Thermal characterisation to determine the change in glass transition temperature, glass crystallisation, melting point, and glass stability was carried out using Differential Scanning Calorimetry. A discussion was made in order to understand the results in terms of the ratio of bridging oxygen to non-bridging oxygen ions (BO/NBO). It was found that the addition of B _2 O _3 results in increasing oxygen packing density, glass transition temperature, BO/NBO ratio and band gap energy, while decreasing density, refractive index, field strength, glass stability and Urbach tail energy. With increasing B _2 O _3 concentration density changed from 5.879 to 5.646 g cm ^−3 , refractive index 1.875 to 1.741, working temperature range (Δ T = 66 °C) and phonon energy within the range of 736–740 cm ^−1 .