The influence of porosity on the electrical properties of liquid-phase sintered silicon carbide

The structure and the electrical properties of porous and dense liquid-phase sintered silicon carbide ceramics (LPS-SiC), containing yttria and alumina additives, have been studied. The electrical resistance of LPS-SiC-materials varies in a wide range. This paper is focused on the influence of porosity on the electrical resistance of the sintered SiC. The porosity was controlled by the SiC grain size. Porous LPS-SiC materials were found to have substantially lower electrical resistance in comparison to dense materials of the same type. The structure of the materials was investigated by XRD and FESEM. The porous materials consist of large grains due to the coarser starting powders in comparison to the dense materials. This results in a reduction of the dissolved and re-precipitated fraction of the SiC during sintering. Using the in-lens SEM mode, the high conductivity of the formed rims of the SiC grains could be shown. These observations reveal that the rim volume of dense LPS-SiC is much more extended than the rims of porous materials showing the higher conductivity.