Effects of dopants on electrical, thermal, and mechanical properties of porous SiC ceramics

Nitrogen-, vanadium-, aluminum-, boron-, and scandium-doped porous SiC ceramics were fabricated to investigate the effects of dopants on electrical, thermal, and mechanical properties of porous SiC ceramics. The electrical resistivity of a nitrogen-doped porous SiC ceramic was 2.1 × 10−1 Ω cm four orders of magnitude lower than that of an undoped porous SiC ceramic (1.2 × 103 Ω cm). A B-doped porous SiC ceramic exhibited the highest thermal conductivity (16.6 W/(m K)) and flexural strength (25.9 MPa), whereas a Sc-doped porous SiC ceramic exhibited the lowest thermal conductivity (7.7 W/(m K)) and flexural strength (10.5 MPa) among the doped porous SiC ceramics. The electrical resistivity was strongly influenced by the doping, whereas the thermal and mechanical properties were dependent primarily on the necking area between SiC grains. The results suggest that the electrical conductivities of porous SiC ceramics can be successfully tuned independently of the thermal conductivity by a suitable doping.