Nanometer silicon carbide powder synthesis and its dielectric behavior in the GHz range

In this paper, the dielectric properties of nano-sized SiC powders have been investigated in the GHz frequency range. The polytypes of SiC have been changed from β type (3C) to α type (12H and 21R) by varying the aluminum contents and the reaction atmospheres. The β-SiC powder has much higher relative permittivity (ε′r=30∼50) and loss tangent (tgδ=∼0.7) than α-SiC powders. Though the doping of Al and N decrease the resistivity of SiC to the order of 102 Ω cm, the pivotal factor on the dielectric behaviors is ion jump and dipole relaxation, namely the reorientation of lattice defect pairs (VSi–VC, SiC–Csi). The conductivity of SiC has little effect on the dielectric behaviors.