Complex Permittivity and Microwave Absorbing Property of Si3N4{SiC Composite Ceramic

Si 3 N 4 —SiC composite ceramics were fabricated by chemical vapor infiltration using porous Si 3 N 4 ceramic as preform. The average grain size of SiC was 30 nm. Relationship between SiC content and relative complex permittivity of Si 3 N 4 –SiC within the frequency range of 8.2–12.4 GHz ( X -band) was investigated. The average real part of relative complex permittivity ɛ' of Si 3 N 4 –SiC increased from 3.7 to 14.9 and the relative imaginary part ɛ″ increased from 0.017 to 13.4 when the content of SiC increased from 0 to 10 vol.%. The Si 3 N 4 –SiC ceramic with 3 vol.% SiC achieved a reflection loss below −10 dB (90% absorption) at 8.6–11.4 GHz, and the minimum value was −27.1 dB at 9.8 GHz when the sample thickness was 2.5 mm. The excellent microwave absorbing abilities of Si 3 N 4 –SiC ceramic were attributed to the interfacial polarization at interface between Si 3 N 4 and SiC and at grain boundary between SiC nanocrystals.