Elasticity and viscosity of BaOTiO2SiO2 glasses in the 0.9 to 1.2Tg temperature interval

• Large size transparent glasses along the 0.3BaOxTiO2(0.7 − x)SiO2 composition line were synthesized by melt-quenching.
• Ti is mostly 5-fold coordinated, although some Ti(VI) may be present.
• The specific mass, the atomic packing density, Tg, and the elastic moduli increase with the titanium content.
• The sensitivity of the elastic moduli and of the shear viscosity coefficient increase with temperature when TiO2 is added.
• Ba-rich channels are responsible for a large Poisson's ratio and a rapid softening with temperature.

In spite of the potential applications of glasses in the BaOTiO2SiO2 (BTS) system, the mechanical properties of these glasses were little studied so far. Several centimeters large batches of glasses along the 0.3BaOxTiO2(0.7 − x)SiO2 composition line were prepared. Their creep behavior and elastic moduli were investigated as a function of x (from x = 0 to x = 0.3). Titanium increases the atomic packing density as well as the volume density of energy and so do the elastic moduli. An excellent agreement is found between the elastic softening index (α) and the liquid fragility (m) (according to Angell's concept [1]). Nevertheless, as TiO2 is added the glass-forming liquid becomes more “fragile”. The explanation might lie in the structural similarity between the fresnoite crystal and the glass structure consisting of island-like SiTi rich units surrounded by barium-rich channels. These islands would contribute to the increase in rigidity whereas the Ba-rich channels, acting as a lubricant, would make the viscous flow more temperature sensitive.