Electrical, thermal, and mechanical properties of porous silicon carbide ceramics with a boron carbide additive

Abstract The effects of the boron carbide (B 4 C) content and sintering atmosphere on the electrical, thermal, and mechanical properties of porous silicon carbide (SiC) ceramics were investigated in the porosity range of 58.3%–70.3%. The electrical resistivities of the nitrogen‐sintered porous SiC ceramics (∼10 –1 Ω·cm) were two orders of magnitude lower than those of argon‐sintered porous SiC ceramics (∼10 1 Ω·cm). Both the thermal conductivities (3.3–19.8 W·m –1 ·K –1 ) and flexural strengths (8.1–32.9 MPa) of the argon‐ and nitrogen‐sintered porous SiC ceramics increased as the B 4 C content increased, owing to the decreased porosity and increased necking area between SiC grains. The electrical resistivity of the porous SiC ceramics was primarily controlled by the sintering atmosphere owing to the N‐doping from the nitrogen atmosphere, and secondarily by the B 4 C content, owing to the B‐doping from the B 4 C. In contrast, the thermal conductivity and flexural strength were dependent on both the porosity and necking area, as influenced by both the sintering atmosphere and B 4 C content. These results suggest that it is possible to decouple the electrical resistivity from the thermal conductivity by judicious selection of the B 4 C content and sintering atmosphere.