Investigations of thermal, structural and optical properties of tellurite glass with WO3 adding

The optical band gap energy values corresponding to the direct and indirect allowed transitions and the Urbach energy values of the prepared tellurite glasses have been calculated from optical absorption edges. The results show an important decrease of the optical band gap with the increase of WO3 concentration. It was assigned to W6 + ions that could have a role as network modifier. The Urbach energy was found to decrease with WO3 compositions which suggest the possibility of long range order. The refractive index and extinction coefficient were obtained by spectroscopic ellipsometry. Higher values for the refractive index are recorded due to the high polarizability of non-bridging oxygen. It is observed also that the refractive index, n increases with increasing WO3 content. It is established that there is a trend by which the energy gap decreases with increasing refractive index and increasing the polarizability of the oxide ions. The complex dielectric function ε, relative to each sample, was estimated from regression analysis. The material studied here has potential application as optical fiber.