Analysis of viscosity equations relevant to silicate melts and glasses

• Voegel-Fulcher-Tammann, Adam-Gibbs, Avramov, Mauro-Yue-Ellison-Gupta-Allan and Arrhenian models have been analysed in application to silicate melts and glasses;
• The model parameters have been obtained by the least-square fitting into both high- and low-temperature experimental data for selected systems;
• Correlations between different parameters of the above models have been found;
• Two Arrhenian regions have been found in the experimental viscosity-temperature curves;
• A systematic temperature-dependent deviation between experimental data and predictions by the models has been found in all the silicate systems;

A number of equations (Voegel–Fulcher-Tammann, Adam–Gibbs, Avramov, Mauro–Yue–Ellison–Gupta–Allan and Arrhenian) used for modelling viscosities of oxide melts and glasses have been analysed in application to binary, ternary and quaternary silicates. The model parameters have been obtained by the least-square fitting into both high- and low-temperature experimental data for selected systems. It has been found that (i) there are correlations between different parameters of the above models; (ii) two Arrhenian regions are observed in the experimental viscosity–temperature curves, (iii) there is a systematic temperature-dependent deviation between experimental data and predictions by the above models. These findings as well as applicability of the model equations to the whole temperature range and to the viscosities of pure oxides (B2O3, GeO2 and SiO2) has critically been evaluated and discussed.