Sintering Atmosphere and Polytype Effects on Porous Silicon Carbide Ceramics

This study investigates the effects of sintering atmosphere and polytype on the electrical and thermal conductivities and flexural strength of porous SiC ceramics. The porosity was maintained at approximately 38.2%. The nitrogen sintered porous SiC ceramic fabricated from β-SiC powder exhibited the electrical conductivity of 1.2 × 10¹ (Ωcm)^-1 which was two orders of magnitude higher than that of a porous SiC ceramic fabricated from α-SiC powder (5.0 × 10^-1 (Ωcm)^-1). The highest thermal conductivity of 19.5 W/mK and flexural strength of 22.0 MPa showed porous SiC ceramics fabricated from α-SiC powder when sintered in argon and nitrogen atmosphere, respectively. The lowest thermal conductivity of 12.0 W/mK and flexural strength of 5.8 MPa porous SiC ceramics fabricated from β-SiC powder when sintered in nitrogen and argon atmospheres, respectively. Electrical conductivity was primarily determined by the incorporation of nitrogen into the SiC crystal lattice, whereas the thermal conductivity and flexural strength mainly dependent on the microstructure of the material.