Thermal characteristics, Raman spectra and structural properties of newlurite glasses within the Bi{sub 2}O{sub 3}-TiO{sub 2}-TeO{sub 2} systemp. 3

Within the Bi{sub 2}O{sub 3}-XO{sub 2}-TeO{sub 2} (X=Ti, Zr) systems, a large glass-forming domain was found for X=Ti, but no glass formation was evidenced for X=Zr. Densities, glass transition (T {sub g}), crystallization (T {sub c}) temperatures and Raman spectra of the relevant glasses were studied as functions of the composition. The Raman spectra of the glasses were interpreted in terms of the structural transformations produced by the modifiers. It was established that the addition of Bi{sub 2}O{sub 3} and TiO{sub 2} content to TeO{sub 2} glass influences the T {sub g} temperature in a similar manner: this value progressively increases with the increase of the modifier concentration. However, the structural evolutions are different: (a) the addition of TiO{sub 2} to TeO{sub 2} glass keeps the polymerized framework structure in transforming a number of Te-O-Te bridges into the Te-O-Ti ones without producing any tellurite anions (i.e., the [TeO{sub 3}]{sup 2-} groups); (b) on the rary, the addition of Bi{sub 2}O{sub 3} destroys the glass framework by giving rise to the island-type [Te {sub n} O {sub m} ]{sup 2(m-2n)-} complex tellurites anions, thus causing a depolymerization of the glass. - Graphical abstract: Raman spectra of the titanium tellurite glasses and of the relevant crystalline compounds.