Structure-property correlations in TiO2-Bi2O3-B2O3-TeO2 glasses

Tellurite and borotellurite glasses containing Bi2O3 and TiO2 were prepared and structure-property correlations were carried out by density measurements, X-ray diffraction, Differential Scanning Calorimetry (DSC), Raman, FTIR, UV-visible and 11B MAS-NMR studies. Titanium-tellurite and titanium bismuth tellurite glasses require high melt-cooling rates and were prepared by splat quenching. On adding B2O3, the glass forming ability (GFA) enhances considerably and bulk glasses could be synthesized at lower quenching rates. The density of glasses shows a direct correlation with molecular mass of the constituents. UV-visible studies were used to determine the optical band gap and refractive index. Raman studies found that the co-ordination number of tellurium ions with oxygen (NTeO) remains constant with variation in TiO2 molar content, while the incorporation of B2O3 and Bi2O3 decreases NTeO. DSC studies show that the glass transition temperature (Tg) increases with B2O3 and TiO2 concentrations and that Tg correlates well with bond enthalpy of the metal oxides. 11B MAS-NMR studies found that the co-ordination number of boron with oxygen (NBO) decreases with increase in B2O3 content while increasing TiO2 and Bi2O3 concentration does not significantly modify NBO.