Effect of MgO/SiO2 ratio and Al2O3 content on crystallization behavior and properties of cordierite-based glass–ceramics

Abstract

Cordierite-based glass-ceramics with non-stoichiometric compositions were prepared by powder sintering method. The effects of MgO/SiO2 ratio and Al2O3 content on the crystallization behavior, microstructure and thermal expansion coefficient of the glass-ceramics were studied. Results indicated that the decreasing Al2O3 content showed a greater effect on decreasing the melting temperature and liquid viscosity than the increasing MgO/SiO2. DTA results showed that, at low temperatures, the MgO/SiO2 ratio dominated crystallization of cordierite due to the lack of liquid. At a high sintering temperature of 1340 °C, the Al2O3 content dominated the crystal growth of cordierite due to its great effect on decreasing the liquid viscosity. The chemical composition close to the stoichiometric cordierite and the absence of quartz were two essential factors for obtaining low thermal expansion coefficients. The decreasing MgO/SiO2 ratio and Al2O3 content caused phase separation with an interconnected structure, which followed the crystallization of cordierite in the Al2O3-rich phase.