Studies of LiF-BeF2 and KF-BeF2 glasses by differential scanning calorimetry

Liquid Fragility and the Glass Transition in Water and Aqueous Solutions

“…This is well-known in the case of silicate glasses, and sub-liquidus liquid−liquid demixing in the system BeF 2 −LiF has also been well documented by the electron microscopy studies of Vogel and Gerth . However, the striking behavior of T g , in BeF 2 -rich glasses in the BeF 2 + LiF system (included in Figure ), had not been recorded until recently . According to these authors, T g for the solutions must increase some 200 K as the last 2 mol % of LiF is removed.…”

“…By forming the glass at high pressures and observing its behavior at lower pressures, Kanno was able to observe the upper glass temperature approach the value of the lower one. This suggests that a high-density glassy water might, like the quartz-like polyamorph of BeF 2 discussed earlier, have a lower value of T g than the open network form. Thus, the possibility is raised of obtaining vitreous water in one or other polyamorph by low-temperature phase separation from the binary solution glass.…”

“…118 However, the striking behavior of T g , in BeF 2 -rich glasses in the BeF 2 + LiF system (included in Figure 8), had not been recorded until recently. 119 According to these authors, T g for the solutions must increase some 200 K as the last 2 mol % of LiF is removed. The suggestion is that the behavior of the LiF-containing glass is dominated by quartz polymorph-like BeF 2 behavior, whereas pure BeF 2 is crystobalite polymorph-like, as indicated by its crystallization products.…”