Determination of the chemical width of grain boundaries of boron- and carbon-doped hot-pressed beta-SiC by HAADF imaging and ELNES line-profile

A residue of sintering additives is often found at the grain boundaries in sintered ceramics. This can be used to determine the macroscopic properties of the sintered polycrystalline materials. A combination of both high-angl e annular dark-field (HAADF) imaging and energy-loss near edge-structure (E LNES) line-profile methods was carried out to measure the chemical width of grain boundaries using the sintering additives. Application of both HRTEM and HAADF imaging methods for boron- and carbon-doped hot-pressed SiC leads to the identification of the structural differences either within the matr ix or at the grain boundaries very clearly. Additionally, EELS analysis was also carried out to identify the chemistries and bondings at the grain bou ndaries. The segregation of both boron and nitrogen is clearly shown, as we ll as the chemical width measured at the grain boundaries by the ELNES line -profile method. Incorporation of nitrogen within the grain interior was al so detected by ELNES analysis. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.