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 beta type (3C) to alpha type (12H and 21R) by varying the aluminum contents and the reaction atmospheres. The beta -SiC powder has much higher relative permittivity (epsilon (r)' = 30 similar to 50) and loss tangent (tg delta = similar to 0.7) than alpha -SiC powders. Though the doping of At and N decrease the resistivity of SiC to the order of 10(2) Omega cm, the pivotal factor on the dielectric behaviors is ion jump and dipole relaxation, namely the reorientation of lattice defect pairs (V-Si-V-C, Si-C-C-Si). The conductivity of SiC has little effect on the dielectric behaviors. (C) 2001 Elsevier Science Ltd. All rights reserved.