Improvement of permittivity of SiC with Al doping by combustion synthesis using Al2O3

Al-doped SiC powders were synthesized via combustion reaction of the Si/C system in a 0.1 MPa nitrogen atmosphere using alumina as the dopant. The prepared powders have fine spherical particles and narrow particle size distribution. The electric permittivities of SiC samples were determined in the frequency range of 8.2–12.4 GHz. Results show that the permittivity of SiC increases with the increasing alumina contents. The real part ɛ′ and imaginary part ɛ″ of permittivity of the sample increase by about 20% and 60%, respectively, when the alumina content is 5%. The improvement mechanism in permittivity by doping has been discussed.