Dielectric properties of diamond/SiC composite fabricated by Si vapor infiltration process

The dielectric properties and polarization mechanism are important for the application of high thermal conductivity electronic packaging materials. In this work, diamond/SiC composites were prepared by the silicon vapor infiltration process, and the effect of diamond content on permittivity of composites was investigated in detail in the range of 100 MHz to 1 GHz, and the mechanism of dielectric polarization was also discussed. The results show that the real part of permittivity of composite is greater than that of either component, due to the presence of interfaces and defects. As the diamond content increases, both the real and imaginary parts of permittivity show a trend of rapid decrease and then slow increase. Particularly, the minimum values of the real and imaginary parts of permittivity of diamond/SiC composite are 27 and 0.3, respectively. In the low frequency stage (<400 MHz), the dielectric loss of the composite is mainly caused by the conductivity loss, while in the high frequency stage (400 MHz∼1 GHz), the polarization loss plays a dominant role. The polarization loss of diamond/SiC composite mainly originates from several Debye relaxation processes, which are the interfacial polarization formed at the diamond/graphite and graphite/SiC interfaces.