Preparation of Precursor Powders of Cordierite-Mullite Composites from Metal Alkoxides and Its Sintering

Homogeneous precursor powders for obtaining cordierite composites with uniformly dispersed mullite particles were prepared by partial hydrolysis of alkoxides. The precursor powders crystallized into mullite and MgAl2O4 at 900°C. Cordierite crystal was formed above 1200°C, which was formed through the solid-solid reactions among MgAl2O4, β-quartz solid solution, sapphirine and unknown phases. The crystalline phases in the composites sintered above 1300°C were cordierite and mullite. The dense composite containing 40mol% mullite which was obtained by firing at 1300°C for 2h had the mean 4-point bending strength of 125MPa and the thermal expansion coefficient of about 3.1×10-6/°C, respectively.