Effects of Additives on Thermal Conductivity and Electrical Resistivity of SiC Ceramics by Pressureless Sintering

Effects of additives on the thermal conductivity and electrical resistivity of SiC ceramics prepared by pressureless sintering were studied. α-SiC powder with an average particle size of 0.5μm was treated with HF+HNO3. Additions of 2wt% BeO, 0.2-0.4wt% B4C and 0.2-0.3wt% C to SiC powder gave 92-95% of the theoretical density of SiC after sintering at 2200°C for 0.5h in an argon atmosphere. The highest values of the electrical resistivity and the thermal conductivity at 25°C of dense SiC ceramics were 5×1012Ω·cm and 140W/m·K, respectively. Electrical resistivities and thermal conductivities of SiC ceramics depend on to the amount of additives.