The Linseis DSC PT-1600 was used to analyse the thermal properties of four glasses with the compositions (23.1-x)Na2O/23.1BaO/23TiO2/9.8B2O3/21SiO2/xAl2O3 x = 3, 7, 11 and 15 mol%. The results showed that the glass transition temperature Tg and the temperature of the crystallisation maximum Tc increase with increasing aluminium oxide concentration from 450°C to 570°C and 660°C to 695°C respectively. The difference Tg-Tc, which is used as a criterion for glass stability, was highest for the glass with 3 mol% Al2O3 and lowest for the composition with 15 mol% Al2O3.
