Preparation and microwave permittivity of nano-sized Si/C/N powder

Nano-sized Si/C/N powders are prepared from hexamethyldisilazane ((CH ₃)₃Si)₂NH) by chemical vapor deposition (CVD) at different pyrolysis temperatures from 900 °C to 1200°C. The as-formed Si/C/N nano powder is amorphous, and after controlled heat-treatment, SiC crystals formed. The composition of the Si/C/N powders prepared at different conditions is analyzed and the result shows that the nitrogen content of the Si/C/N powder is related to the synthesizing temperature. Si/C/N powders heat-treated at different temperatures are mixed with paraffin wax and the microwave permittivity of the mixture is measured. The result shows that the ε′, ε″, and the dissipation factor tgδ (ε″/ε′) of the mixture are high at the frequency of 8.2-12.4GHz, and the nitrogen content and the degree of crystallization have influence on the microwave permittivity. We believe that the high value of ε′, ε″, and tgδ are due to the dielectric relaxation as the result of nitrogen atoms doped in silicon carbide lattice.