SiC-based cermet with electrically conductive grain boundaries

The present paper deals with the characterization of structural and electrical properties of SiC-based cermets prepared by in situ reaction. The surface structure and electrical conductivity of the samples was investigated by the standard four-point probe method, SEM, TEM, AFM, and STM techniques. It was found that the electrical conductivity of the SiC-based ceramic-metal composites increases with increased fraction of metallic phases. Interestingly, samples containing app. 12 vol.% of non-percolated (isolated) metallic phases exhibit up to 2 orders of magnitude better electrical conductivity compared with the base-line liquid phase sintered SiC (LPS SiC). This effect results from doping of the SiC grains by diffusion of metallic components as well as from chemical modification of the grain boundary phases due to the reaction of sintering aids and metallic particles at high sintering temperatures. Absorbed current measurements using SEM, as well as AFM in spreading resistance and STM in tunneling mode were used for visualization of electrical pathways.