Effect of Al2O3 Content on Crystallization Behavior, Microstructure, and Mechanical Properties of SiO2-Al2O3-CaO-MgO Glass-Ceramics

The crystallization of glasses with general composition (61.87-x) %SiO2, x%Al2O3, 22.01% CaO, 6.24% MgO, 2.54% Na2O, 2.72% K2O, 0.58% TiO2, 3.34% Fe2O3, and 0.7% Cr2O3 (wt%) where x varies between 0% and 22% was investigated using differential thermal analysis, X-ray diffraction analysis, and scanning electron microscopy. The increase of Al2O3 content at the expense of SiO2 had a marked effect on the mechanism of crystallization and microstructure of glass-ceramics. The glass specimen containing 18 wt% Al2O3 demonstrating the most efficient bulk nucleation and an activation energy and Avrami exponent of 243 +/- 11 kJ/mol and 3.8 +/- 0.3, respectively, exhibited a fine microstructure, comprising < 0.5 mu m particles of diopside, showed a bending strength of 122 +/- 9 MPa.