Electrical properties of liquid-phase sintered silicon carbide ceramics: a review

Silicon carbide (SiC) is an electrical semiconductor with a wide bandgap. Recently, highly conductive liquid-phase sintered SiC (LPS-SiC) ceramics have been developed by the successful doping of N atoms into a SiC lattice. Fully dense N-doped SiC ceramics with electrical conductivity as high as 300 S·cm−1 at 25 °C have been obtained. These ceramics can be formed into complex shapes by electrical discharge machining. This article reviews the influence of critical factors on the electrical conductivity of LPS-SiC ceramics, including SiC polytype, grain boundary structure, soluble atoms, porosity, second-phase addition (nitride, carbide, boride, graphene), grain size, and neutron irradiation. We also discuss the relationship between the solubility of nitrogen in the liquid phase and the electrical conductivity of the resulting ceramics, along with the mechanism for N doping in the SiC lattice and the possibility of controlling the electrical conductivity of the LPS-SiC ceramics. The N doping method used for LPS-SiC ceramics may also be applied for doping other soluble atoms in liquid-phase sintered ceramics.