Effect of Fe2O3 and MgO on the crystallization behaviour, sinterability and properties of the CaO-Al2O3-SiO2 glass-ceramics

This study explores the roles of Fe2O3 (3-5 wt%) and/or MgO (0.6-2.4 wt%) on the crystallization behaviour, microstructure, sinterability and mechanical properties of 17.02CaO-7.04Al(2)O(3)-58.84SiO(2) (CAS, wt%) glass-ceramics. With increasing Fe2O3 and/or MgO contents, the peak temperature of glass crystallization decreased, and the main crystal phase (wollastonite) was suppressed, while the secondary phases of hardystonite and diopside were crystallized and promoted. Wollastonite crystals grew larger, and their distribution became scattered as Fe2O3 and/or MgO contents increased. The concentrations of elemental Fe and Zn in the glass matrix influence the formation of hardystonite (Ca2ZnSi2O7), and Mg2+ can participate in the formation of diopside and melilite-type solid solution Ca2ZnSi2O7-Ca2MgSi2O7. Vickers hardness was decreased by the increasing amount of glass matrix while density was increased. The optimum heat treatment temperature range of the CAS glass-ceramics was narrowed by the addition of Fe2O3 and/or MgO due to rapid crystallization and a degree of fusion or overburning.