Crystallization behavior and properties of non-stoichimetric cordierite glass–ceramics: Effects of talc, MgO/SiO2 ratio, and Al2O3 content

Abstract

Non-stoichimetric cordierite glass-ceramics were obtained by powder sintering method, using talc mineral as sintering aid. Effects of talc, MgO/SiO2(M/S) ratio and Al2O3 content on the crystallization behavior, densification behavior, physical properties and thermal expansion coefficients of the glass-ceramics were investigated. Results showed that, 15 wt% talc addition reduced the crystallization temperature of cordierite in the glass-ceramics from 1085 °C to 1052.2 °C by increasing the M/S ratio. Adding talc decreased the Al2O3 content and provided alkali oxides to promote the liquid formation. The decreasing Al2O3 content from 30.47 wt% to 21.67 wt% resulted in the dissolution–reprecipitation–recrystallization–redissolution process of cordierite due to the enhancing liquid formation. Adding talc could decrease the thermal expansion coefficient by increasing the cordierite content, and the low thermal expansion coefficient of 1.90 × 10−6 ℃−1 was obtained. The decreasing Al2O3 content promoted the densification behavior, but increased the thermal expansion coefficient of the glass-ceramics by increasing the amount of glass. The sample having the 15 wt% talc addition and the lowest Al2O3 content of 21.67 wt% obtained the low porosity of 0.3%, which was much lower than 25.1% of the original sample without talc addition.