Electrical conductivity of cellular Si/SiC ceramic composites prepared from plant precursors

Electrical conductivity (sigma(dc)) of the cellular Si/SiC ceramic composites has been measured over a temperature range of 25-1073 K, while the thermoelectric power (S) has been measured over 25-300 K. Remarkably, these cellular compounds developed through the biomimetic route-where the ceramic system grows within a plant biotemplate retaining the imprint of structural intricacies of the native templates-are found to exhibit excellent mechanical, thermal, and electrical properties quite comparable to or even better than those of the systems prepared through the conventional ceramic route. The electrical conductivity, measured parallel (sigma(parallel to)) and perpendicular (sigma(perpendicular to)) to the growth axes of the native plants, depicts nearly temperature-independent anisotropy (sigma(perpendicular to)/sigma(parallel to)) of the order similar to 2, while the thermoelectric power is nearly isotropic. The charge conduction across the entire temperature regime is found to follow closely the variable range hopping mechanism. The conductivity anisotropy appears to be driven primarily by the unique microcellular morphology of the biotemplates, which can be exploited in many electrical applications. (c) 2007 American Institute of Physics.