Preparation and dielectric properties of B-doped SiC powders by combustion synthesis

The SiC(B) solid solution powders were synthesized via combustion reaction of Si/C system in Ar atmosphere, using boron powder as the dopant and polytetrafluoroethylene as the chemical activator, which were investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM) and Raman spectra. Results show that the prepared powders are C-enriched SiC with C antisites and sp2 carbon defects in which the sp2 carbon is transformed to the sp3 carbon due to boron doping. The electric permittivities of the prepared powders were determined in the frequency range of 8.2–12.4 GHz. The dielectric real part ɛ′ and dielectric loss tan δ of undoped powder have maximum values (ɛ′ = 5.5–5.3, tan δ = 0.23–0.20), and decrease with increasing boron content. The mechanism of dielectric loss by doping has been discussed.