Correlation of boron content and high temperature stability in Si-B-C-N ceramics

The preparation and characterization of precursor derived Si-B-C-N ceramics with similar Si/C/N ratios but variable boron content are reported. The polymeric precursors were prepared via hydroboration of poly(methylvinylsilazane) using different BH3. SMe2/polymer stoichiometries. High temperature thermogravimetric analysis of as-pyrolysed ceramics as well as XRD studies of post-annealed samples display a retarding effect of boron on both crystallization of SiC and Si3N4 and stabilization of crystalline beta -Si3N4. (C) 2000 Elsevier Science Ltd. All rights reserved.