Dielectric and infrared properties of silicon carbide nanopowders

The dielectric properties at high frequencies and infrared spectra of pure, aluminum, and nitrogen-doped SiC nanopowders have been investigated. The powders were prepared by a sol-gel process. Dielectric constants (ε′) and dielectric loss tangents (tanδ) were measured within the microwave frequency range from 4 to 18 GHz. Both ε′ and tanδ of pure SiC nanopowder are much higher (ε′ = 40-50, tanδ = 0.6-0.7) than for the doped ones over the frequency range. The dielectric parameters decreased with increasing aluminum and nitrogen contents. Infrared (IR) spectra were measured in the range from 500 to 4000 cm^-1, showing that the background of pure SiC nanopowder is also much higher than for the doped ones. The possible mechanisms of these promising features of undoped SiC nanopowder are discussed.