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 ε′ and dielectric loss tan δ of undoped powder have maximum values (ε′ = 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.