In this paper, the dielectric properties of nano-sized SiC powders have bee
n investigated in the GHz frequency range. The polytypes of SiC have been c
hanged from beta type (3C) to alpha type (12H and 21R) by varying the alumi
num contents and the reaction atmospheres. The beta -SiC powder has much hi
gher relative permittivity (epsilon (r)' = 30 similar to 50) and loss tange
nt (tg delta = similar to 0.7) than alpha -SiC powders. Though the doping o
f 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 relax
ation, namely the reorientation of lattice defect pairs (V-Si-V-C, Si-C-C-S
i). The conductivity of SiC has little effect on the dielectric behaviors.
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