Direct current conduction in SiC powders

Silicon carbide (SiC) powder is used in nonlinear field grading materials. The composite material, consisting of an insulating polymer matrix filled w ith the SiC-grains, is usually a percolated system with established conduct ing paths. In order to explain the properties, the electrical characteristi c and conduction mechanisms of the SiC powder itself are of interest. SiC p owders have been studied by current-voltage measurements and the influences of grain size and doping have been investigated. The macroscopic current c haracteristics of green and black SiC powders can be described by the trans port mechanisms at the grain contacts, which can be modeled by Schottky-lik e barriers. The SiC is heavily doped and tunneling by field emission is the dominating conduction mechanism over the major part of the nonlinear volta ge range. It is suggested that preavalanche multiplication influences the c urrent at the highest voltages, especially for p-type black SiC. (C) 2001 A merican Institute of Physics.