Aspects determining dielectric properties of SiC-based ceramic grain boundary capacitors

Silicon carbide (SiC) particles with high thermal conductivity and semi-conductive features ranging from 3 to 28 mum were chosen to fabricate ceramic grain boundary capacitors (GBC) with the highly insulative glassy boundary phases composed of Al2O3-MgO-SiO2 eutectic compositions. Specimens were prepared by single-firing process in the air and N-2 atmosphere, respectively. The dielectric constants drop with increasing frequencies. Y2O3 or SrCO3 can improve the dielectric constant as well as the wetting behavior of boundary phase with SiC grains due to the generation of dislocations at the interface. The oxidation of SiC into SiO2 lowers the dielectric constant but increases the insulation resistivities drastically.