Investigations on the augmented physical, thermal and optical properties of tellurite glasses containing WO3 and TiO2

Novel tellurite glasses with compositional dependence of (90-x)TeO₂-10TiO₂-xWO₃ (0 ≤ x ≤ 30) were synthesized at 900 °C through melt quenching. XRD, EDX, FE-SEM, Color mappings, XPS, FTIR, Raman, DSC, optical absorption techniques were employed for characterizing the prepared samples. XRD, DSC and FE-SEM measurements testified the amorphous nature of the glasses. The Raman and FTIR analyses manifest the presence of TeO₃, TeO₃₊₁, TeO₄, WO₄, WO₆ structural units alongside the non-bridging oxygen's (NBO's) with increasing WO₃ content. The DSC studies showed that the addition of WO₃ content for TeO₂ reduced the crystallization by retaining the amorphous nature of these glasses which is a key for drawing optical fibers. Te-O-W/Ti-O-W/W-O-W linkages are observed to be accountable for increasing in glass transition temperature (T_g) of these glasses. On increasing WO₃ content, the crystal peaks shifted to higher temperature region which increased ΔT. The calculated optical band gap (E_opt) of the glasses suggests that the width of the valence and conduction bands increases by reducing the optical band gap energy. The Urbach energy (ΔE) values are observed to be increased and demonstrated that the glasses with higher mol% of WO₃ are having more structural disorder defects. The electron donating ability of O²⁻ ions in Te-O/W-O/Ti-O increases with increasing WO₃. The variations in α_O²⁻ and A_th clearly manifest that the degree of covalent bonds increases in the glass matrix with WO₃ content. The FTIR, Raman, DSC and Optical absorption analyses confirmed that these glasses possess higher refractive index, larger thermal stability and lowering the phonon energy due to the addition of WO₃ content. Thus, it is believed that these glasses might useful for making the optical lenses and promising material for fiber drawing applications.