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

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 x 10(-1) Omega cm to 4.5 x 10(-2) Omega cm with increasing carbon content from 0 to 16 wt% at room temperature. Raman spectroscopy investigation revealed the existence of a graphite phase characterized by a carbon-carbon sp(2)-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 sp(2)-bonds promoted by carbon precipitation in an amorphous SiOC matrix. The resistivities of the SiOC specimens exhibited slow increases with decreasing temperature in the 2-300 K range, the slowest one (16 wt% C) being 4.5 x 10(-2) Omega cm (300 K) and 5.2 x 0(-2) Omega cm (2 K). (C) 2016 Elsevier Ltd. All rights reserved.