Preparation and characterization of aluminum-doped silicon carbide by combustion synthesis

Al-doped β-SiC powders were synthesized via combustion reaction of the Si/C system in a 0.1 MPa nitrogen atmosphere, using polytetrafluoroethylene as the chemical activator and Al as the dopant. The β-SiC powders produced have fine spherical particles and narrow particle size distribution. The impurity phase of Al₂O₃ is generated and the doped β-SiC contains N component when Al content is up to 10%. The electric permittivities of β-SiC samples were determined in the frequency range of 8.2-12.4 GHz. Results show that the β-SiC doped with 10% Al has the highest real part ε′ and imaginary part ε″ of permittivity. The mechanism of dielectric loss by doping has been discussed.