Viscosity and liquidus-based predictor of glass-forming ability of oxide glasses

Glass-forming ability (GFA) is a measure of the easiness to vitrify a given substance. Theoretically, it is possible to make a glass from any liquid provided it is quenched from its liquidus temperature with a cooling rate above a critical value R-c to avoid crystallization. However, measuring GFA is a laborious and time-consuming task. Moreover, predicting the GFA of substances that have never been vitrified is of greater interest. Here, we propose and evaluate a new parameter that can predict the glass forming ability of oxide mixtures. We derived a mother parameter, GFA = 1/R-c proportional to [U(T-max) x T-L](-1), where U(T-max) is the maximum crystal growth rate, and T-L is the liquidus temperature, which strongly correlates with the experimental critical cooling rates of oxide glass-formers. A simplified version derived from the mother parameter-which does not need (scarce) crystal growth rate data and only relies on viscosity eta and T-L, GFA proportional to [eta(T-L)/TL2]-also correlates well with the R-c of several oxide compositions. This new GFA parameter, dubbed Jezica, works when heterogeneous nucleation prevails. It corroborates the widespread concept that substances having high viscosity at T-L, and a low T-L can be easily vitrified, and provides a powerful tool for the quest and design of novel glasses.