Silicon carbide powders: Temperature-dependent dielectric properties and enhanced microwave absorption at gigahertz range

The dielectric properties of SiC powders are investigated in the temperature range of 373-773 K at gigahertz range (8.2-12.4 GHz). The complex permittivity ε and the loss tgδ exhibit frequency-dependent characteristics with the frequency, and they also show temperature-dependent characteristic with the temperature. From the Cole-Cole plots, the relaxation and electrical conductance both affect the dielectric properties at high temperature. First principle calculations are employed to analyze the electronic structure of SiC, which infer the influence of relaxation and conductance on dielectric behaviors. The reflection loss R_L peak is below -10 dB in temperatures of 373-773 K with the sample in thickness 2.1 mm. More importantly, the microwave absorption coupled with widening effective absorption bandwidth demonstrates positive temperature effects on the absorption with the increasing temperature, indicating promising potential applications in high-temperature microwave absorption fields.