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 (ε¹_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 behaviours 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 behaviours.