Microstructural characterization of high-thermal-conductivity SiC ceramics

High-thermal-conductivity SiC ceramic with very small amount of BeO additive, having a value of 270 W m(-1) K-1 corresponding to roughly 50% of the intrinsic SiC value of 490 W m(-1) K-1, is characterized by high-resolution transmission electron microscopy. Crack in BeO crystalline phase, strain contrast between BeO and SiC, and stacking disorders in SiC grains are observed, and they are considered as reducing factors on the thermal conductivity. Presence of secondary phase including Fe, Ti, Al and Ni elements and Be2SiO4 phase reveals that liquid in the BeO-SiO2-SiC system forms partially, traps metal impurities to purify SiC grains and precipitates at triple-grain junctions. A distinctive feature of intergranular film between the SiC grains is also reported. (C) 2004 Elsevier Ltd. All rights reserved.