Abstract
► Thermal, structural, and optical properties of TeO2–La2O3–TiO2 glasses, with different TiO2 composition, were investigated. ► The thermal stability factor ΔT=Tx−Tg was found to increase with TiO2 composition. ► Both Raman and FTIR results show that Ti is incorporated in the Te–O–Te interchains to form Te–O–Ti–O–Te– ones. ► The band gap of the glass is reduced and the Urbach energy increases with TiO2 composition due to creation of non-bridging oxygens.
Tellurite glasses with different TiO2 composition are elaborated and characterized. Differential Scanning Calorimetry (DSC) measurements show an improvement of the stability factor ΔT of the glass with the increase of TiO2 composition which can indicate a reinforcement of the network. Both Raman and FTIR results prove that the Te–O–Te inter-chain linkages are progressively substituted by stronger Te–O–Ti bridges that are at the origin of the increase of the thermal stability of the glass. However, for glasses with high TiO2 composition, some TiO4 polyhedron and crystalline phases of TiTe3O8 can be formed in the amorphous phase.
It was found that TiO2 contributes in the highest extent to decrease the glass energy gap and to increase the refraction index due to Ti4+ that could have a role as network modifier. The Urbach energy Eu was found to decrease with TiO2 compositions which suggest the possibility of long range order locally arising from the formation of TiTe3O8 groups.