Effects of carbon addition on the electrical properties of bulk silicon-oxycarbide ceramics

Abstract

The effects of carbon addition on the electrical properties of silicon-oxycarbide (SiOC) ceramics were investigated. The electrical resistivity of the dense bulk SiOC specimen decreased gradually from 4.9×10−1Ωcm to 4.5×10−2Ωcm with increasing carbon content from 0 to 16wt% at room temperature. Raman spectroscopy investigation revealed the existence of a graphite phase characterized by a carbon-carbon sp2-bond with increasing density with increasing C content in the SiOC specimen. The decrease in electrical resistivity with increasing C content can be explained in terms of an increase in the density of conductive sp2-bonds promoted by carbon precipitation in an amorphous SiOC matrix. The resistivities of the SiOC specimens exhibited slow increases with decreasing temperature in the 2–300K range, the slowest one (16wt%C) being 4.5×10−2Ωcm (300K) and 5.2×10−2Ωcm (2K).