Viscosity of alumina doped soda lime silicate glasses – observation of anomaly in the linear increase as Al2O3 replaces SiO2

Adding alumina to the conventional soda lime silicate glass composition improves many properties, however, also increases melting temperature. In current paper, doping of glasses and its implications high temperature viscosity are investigated in order verify linearity when replacing SiO2 for Al2O3. An anomaly linearly increasing was found ratio CaO/Al2O3 is <1, which explained by Ca2+ acting as an inhibitor viscous flow. The Angell Rao Waterton-MYEGA models show very similar results, even extrapolated Tg. Thermodynamic data extracted using Ojovan method generally with Al2O3 content. Doremus fragility index shows a deviation while on other hand linear increase