Crystallization behaviour of Y2O3 doped germanate oxyfluoride glass-ceramics.

Glass-ceramics in the CaF₂–BaO–Al₂O₃–SiO₂–GeO₂ system with the addition of 9•30 wt% Y₂O₃ were prepared using the conventional melt quenching and subsequent heat treated crystallization method. The influence of Y₂O₃ on the crystallization behaviour and properties of germanate glasses were investigated by DSC, XRD, SEM and crystallization kinetics analysis. It was found that the addition of Y₂O₃ into the studied system led to an increase in the glass transition temperature (Tg), but a decrease in the thermal expansion, the initial crystallization temperature (Tx) and crystallization peak temperature (Tp). The analysis of crystallization kinetics showed that the glass prepared with Y₂O₃ had an increased Avrami index of 2•61 compared to 2•27 and a decreased activation energy of crystallization of 285 kJ/mol compared to 305 kJ/mol. In other words, the addition of Y₂O₃ promotes the crystallization tendency of germanate oxyfluoride glass. [ABSTRACT FROM AUTHOR]