Glass liquidus temperature

Liquidus Temperature. The Hquidus temperature determines the susceptibiUty of a glass to devitrification and therefore influences its forming limitations and often its heat-treating requirements. 

On the other hand, the presence of the salt, LiPEe, assists the occurrence of supercooling by increasing the solution viscosity and by depressing the liquidus temperature. At practical concentrations of LiPFe ( 1.0 M), even the solidus temperature can be circumvented, since there is no crystallization process observed for LiPFe/EC/EMC solution down to —120 °C, while the glass transition occurs at —103 °C. In such concentrated solutions, even the presence of MCMB cannot initiate crystallization, and the supercooling is completely suppressed at the cooling rate of 10 °C/min. 

The three most important factors in the equation are the viscosity and the thermodynamic parameters G and Gm- The viscosity can be approximated between the liquidus temperature, Tuq, and the liquid-+glass transition temperature, Tg, by a Doolittle expression involving the relative free volume (Ramachandrarao et al. 1977) while G can be calculated using the relationship... 

Riley, B. J., Vienna, J. D. Schweiger, M. J. 2000. Liquidus temperature of rare earth-alumino-borosilicate glasses for treatment of americium and curium. Materials Research Society Symposium Proceedings, 608, 677 - 682. 

A reduced glass temperature can be defined as T, = TJTi. which represents a measure of glass-forming ability. The higher the Tt and the lower the liquidus temperature. T. the easier it is to supercool the inelal melt to a glassy stale. Conventional theory predicts 7.= 0 65 — 0.7 for good glass formers. 

Figure 1 Thermal analysis of a fluoride glass showing characteristic temperatures Tg is the glass transition temperamre Tx corresponds to the beginning of the crystalMzation is where the crystalline phase starts to melt 7i is the liquidus temperature corresponding to the end of the melting process...

FIG. 38. The effect of AI2O3 on the liquidus temperature of soda—lime— silica glass (Morey, 1930). 

The liquidus curves in Fig. 38 indicate the reason why industrial soda-lime-silica glasses contain small amounts of AI2O3 the liquidus temperature is thus decreased into the higher viscosity region which is favourable for machine forming. 

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