Thermal Conductivity of Mullite/Al2O3 Ceramics Sintered with Li2O, CaO and Y2O3

Dense Mullite/Al2O3 ceramics with a thermal conductivity of 45 W/m.K were obtained at the sintering temperature of 1500°C using Li2O, CaO and Y2O3 as additives. At temperature below 1500°C, the shrinkage of Mullite/Al2O3 ceramics is promoted by liquid LiAlSi2O6 and Al2Y4O9. Liquid LiAlSi2O6 mainly improves the densification of the sample when the sintering temperature increases to 1500°C. The formation of liquid phase at a relatively low temperature results in homogeneous Al2Y4O9 and Ca(Al2Si2O8) distributed around the Mullite/Al2O3 particles, which benefits the thermal conductivity improved.