Microstructure and high-temperature strength of silicon carbide with 2000 ppm yttria

摘要

A dense silicon carbide (SiC) ceramic with a very high flexural strength at 2000°C (981 ±128 MPa) was obtained by conventional hot-pressing with extremely low additive content (2000 ppm Y_2O_3). Observations using high-resolution transmission electron microscopy (HRTEM) showed that (1) homophase (SiC/SiC) boundaries were clean without an intergranular glassy phase and (2) junction pockets consisted of nanocrystalline Y-containing phase embedded in an amorphous Y-Si-O-C-N phase. The excellent strength at 2000 C was attributed to the clean SiC/SiC boundary and the strengthening effect of plastic deformation.