Effect of nucleating agents on the crystallization behaviour and microstructure of SiO2–CaO–MgO (Na2O) glass-ceramics

The crystallization behaviour of the ternary SiO2–MgO–CaO system comprising different nucleating agents was investigated using DTA and XRD techniques. The effect of compositional changes on bulk crystallization and growth morphology were also studied. After a two-stage heat treatment, the phases such as wollastonite, diopside and in some cases, cristobalite, were identified. The microstructures were investigated by SEM. It was found that the pairs of V2O5+MoO3 and CaF2+MoO3 are more effective nucleants compared with that of Fe2O3+WO3. The coarse fibrous morphology with directional surface crystallization was observed for some specimens containing Fe2O3+WO3 as nucleants