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Te–O, Bi–O and Nb–O bond lengths, co-ordinations in bismuth tellurite, bismuth niobium tellurite glasses and Bi2Te4O11 anti-glass by HEXRD, RMC and Riteveld analysis.

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Abstract. Tellurite and borotellurite glasses containing Bi 2 O 3 and TiO 2 were prepared and structure-property correlations were carried out by density measurements, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman and UV-visible spectroscopy. Titanium tellurite glasses require high melt-cooling rates and were fabricated by splat quenching. On adding B 2 O 3 , the glass forming ability (GFA) enhances, and 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 (N Te-O ) decreases with the increase in B 2 O 3 as well as Bi 2 O 3 content while, TiO 2 produce only a small decrease in N Te-O , which explains the lower GFA of titanium tellurite glasses that do not contain Bi 2 O 3 and B 2 O 3 . DSC studies show that the glass transition temperature (T g ) increases with B 2 O 3 and TiO 2 concentrations and that T g correlates well with bond enthalpy of the metal oxides.