Effect of Cr2O3, Fe2O3 and TiO2 nucleants on the crystallization behaviour of SiO2-Al2O3-CaO-MgO(R2O) glass-ceramics

The effects of Cr2O3, Fe2O3 and TiO2 on the crystallization behaviour of glass compositions in the SiO2-Al2O3-CaO-MgO(R2O) system were investigated by DTA, XRD and SEM. It was shown that the simultaneous addition of Cr2O3, Fe2O3 and TiO2 was more effective in inducing bulk crystallization in these glasses. The Avrami constant, n, and activation energy for crystallization of the most promising glass specimens were determined as 3.23 and 253.60 kJ/mol, respectively, suggesting a two-dimensional bulk crystallization mechanism. In this work the best nucleation temperature was determined to be 740 °C. The main crystalline phase detected in the most promising specimens after a two stage 3 h heat treatment at 740 °C and at 885 °C was an aluminium diopside.