Effect of Al₂O₃/SiO₂ Ratio on the Viscosity and Workability of High-alumina Soda-lime-silicate Glasses

Viscosity, glass transition temperature (T_g) and dilatometric softening temperature (T_f) of high-alumina soda-lime-silicate glasses with different Al₂O₃/SiO₂ ratios were investigated using a rotating crucible viscometer and linear dilatometry. The relation between melting temperature and viscosity as a function of temperature for glass were derived on the basis of Vogel-Fulcher-Tamman (VFT) equation. The viscosity during the forming temperature region of the tin bath was estimated, and the activation energy for viscous flow calculated by Arrhenius equation was used to analyze the effect of Al₂O₃ on the workability of glass melt. Structural information from the variation of the [SiO₄] tetrahedron structural unit Qⁿ (n = 1, 2, 3, 4) was obtained by Raman spectroscopy. The results demonstrated that the addition of Al₂O₃ substitute for SiO₂ in high-alumina soda-lime-silicate glass produces an increase of the viscosity and a decrease of the workability for the glass melt, with a response factor of the Q³/Q₂ ratio decreasing, meanwhile, the forming temperature range of tin bath was obtained.