Temperature dependence of crystal nucleation in BaO·2SiO2 and 5BaO·8SiO2 glasses using differential thermal analysis

A differential thermal analysis (DTA) based method is used to estimate the temperature range for crystal nucleation in BaO·2SiO2 and 5BaO·8SiO2 glasses. For the BaO·2SiO2 glass, the temperature range for significant nucleation is approximately 660 °C to 770 °C, with a maximum rate near 712 °C. These results are in good agreement with those determined from traditional two-step annealing, microscopy-based studies. Having verified the DTA approach with this glass, the method is used to study the 5BaO·8SiO2 composition, for which nucleation data do not exist. The temperature range for significant nucleation is found to be slightly higher than in the BaO·2SiO2 system, approximately 675 °C to 790 °C, with a maximum rate near 725 °C. Measurements of the peak height, peak temperature, and peak area are used to determine the temperature where growth starts to overlap significantly with nucleation. The peak height appears to be the more sensitive indicator for determining this.