RF dielectric properties of SiC ceramics at low temperatures

Two products of SiC Ceramics, which were adopted as HOM absorbing materials for the KEKB ARES cavity, have typical dielectric relaxation properties. These properties can be explained by polycrystalline structure model with electrically conductive (extrinsic semiconductor) grains and non-conductive grain boundaries. We have measured the dielectric responses of the SiC ceramics to the RF frequency from room temperature to 40 K to verify this model. The results of the experiment have shown that the dielectric relaxation time in the SiC ceramics increases with decreasing temperature. These behaviors of the dielectric properties can be explained by the polycrystalline structure model. In this paper, the RF dielectric properties of the SiC ceramics at low temperatures are discussed based on the model. (author)