Phase evolution, thermal and microwave dielectric properties of cordierite-Al2O3 composite were investigated. As the content of Al2O3 increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al2O3. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al2O3 increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al2O3 composite sintered at 1,425℃ were 2.9×10-6 K-1, 5.1, and 34,844 GHz, respectively.
