RELATIONSHIP BETWEEN MICROTEXTURE AND ELECTRICAL-PROPERTIES DURING HEAT-TREATMENT OF SIC FIBER PRECURSOR

During the heat treatment from 800 to 1400°C of a polycarbosilane, a dramatic increase in conductivity occurs. High resolution transmission electron microscopy ( including specific techniques such as the radial and azimuthal exploration of the reciprocal space ) was used to reveal what structural or textural changes could explain the electrical behaviour of the material. Excess carbon was found to become rearranged in small turbostratic stacks lying flat upon the SiC crystal faces. Between 1000 and 1020°C, the turbostratic carbon stacks form a continuous network of incomplete cages surrounding the SiC crystals. The increase in conductivity is assumed to be due to the release of heteroatoms ( mainly hydrogen ), which ensures contact between the turbostratic carbon stacks, and to the completion of the carbon cages. © 1989.