Electrical properties of biomorphic SiC ceramics and SiC/Si composites fabricated from medium density fiberboard

A study has been made of the dependences of the electrical resistivity and the Hall coefficient on the temperature in the range 1.8-1300K and on magnetic fields of up to 28kOe for the biomorphic SiC/Si (MDF-SiC/Si) composite and biomorphic porous SiC (MDF-SiC) based upon artificial cellulosic precursor (MDF - medium density fiberboards). It has been shown that electric transport in MDF-SiC is effected by carriers of n-type with a high concentration of ∿1020cm-3 and a low mobility of ∿0.4cm2V-1s-1. The specific features in the conductivity of MDF-SiC are explained by quantum effects arising in disordered systems and requiring quantum corrections to conductivity. The TEM studies confirmed the presence of disordering structural features (nanocrystalline regions) in MDF-SiC. The conductivity of MDF-SiC/Si composite originates primarily from Si component in the temperature range 1.8-500K and since ∿500 to 600K the contribution of MDF-SiC matrix becomes dominant. © 2010 Elsevier Ltd.
This study was supported by the Russian Basic Research Foundation (project no. 7-03-91353NNF_a), the Presidium of the Russian Academy of Sciences (program no. P-03), and the Spanish Projects MAT 2007-30141-E and PET 2006-0658.