Re-distribution of oxide sintering aids in liquid-phase-sintered silicon carbide due to heat treatment

Silicon carbide compacts were pressurelessly sintered with additives of alumina and yttria at 1900 degrees C for Ih in a powder bed of which composition is the same as the compact. Both Al and Y were homogeneously distributed in the as-sintered specimens. After the specimens were heat-treated at 1900 degrees C for 4h in a SiC powder bed, AZ was homogeneously distributed and its concentration reduced by half, whereas Y concentrated at surface area. Grains near the surface of the sintered body were small and irregular, but those inside grew large and platelike.