Non-linear AC dielectric properties of epoxy composites filled with core–shell SiC particles

Abstract Core–shell structured silicon carbide (SiC)/epoxy (EP) composites exhibit superior non–linear DC conductivity. However, the high voltage alternative current dielectric properties of the composites are rarely reported. In this paper, the time–domain measurement was employed to obtain the basic dielectric characteristics, AC conductivity, and relative permittivity of the SiC/EP and SiC@Al 2 O 3 /EP composites under less than the breakdown strength of the SiC/EP (i.e. the amplitude of 1–5 kV mm −1 ). In addition, in the high AC electric field (i.e. the amplitude of 6–20 kV mm −1 ), the non–linear AC dielectric properties of the SiC@Al 2 O 3 /EP composite are also investigated. The experimental results suggest that the SiC@Al 2 O 3 /EP composite shows more obvious non–linear AC dielectric properties than the SiC/EP composite. In the high AC electric field, the AC conductivity of the SiC@Al 2 O 3 /EP composite presents the relaxation phenomenon, which is attributed to the excitation field and its derivative. This work lays a foundation for further research on the AC steady–state and transient dielectric properties of the field grading materials, which are widely used to homogenize the nonuniform electric field distribution in many electrical and electronic equipment.