Preparation and dielectric properties of Si3N4/SiCw composite ceramic

Abstract

Gelcasting was employed to fabricate Si 3 N 4 /SiC whisker (SiCw) composite ceramics, and the effects of heattreatment temperature on the length-to-diameter ratio of the whiskers and SiCw content on microwave dielectric properties were studied. Compared with pure SiCw of spherical structure obtained at temperature of 1,750°C(Ar), pure SiCw treated at 1,600°C(Ar) showed rod-like structure, higher dielectric properties and more evenly distribution in Si 3 N 4 /SiCw composite ceramics. Both the real (e 0 ) and imaginary (e 00 ) permittivity of Si 3 N 4 /SiC whisker (SiCw) composite ceramics decreased with increasing frequency and increased as the whisker content raised owing to the interface and SiCw playing a role of dipole in the frequency range of 8. 2-12.4 GHz. In addition, comparing the ceramics with lower content of SiCw, the reflectivity of the composite ceramics moved to a lower frequency; the maximum absorption peak reached -22.4 dB at the whisker content of 15 wt%.