Six different sintering aids (Lu2O3, Yb2O3, Y2O3, Sm2O3, Nd2O3 and La2O3) were used for the processing of dense Si3N4/SiC micro/nano composites.

Thermal shock resistance: A critical temperature difference increased with an increasing ionic radius of RE3+ for both the composites and the monoliths.

Wear behavior: The friction coefficient as well as the specific wear rate decreased with a decreasing ionic radius of rare-earth elements in both the monoliths and the composites. High bonding strength and the high fracture toughness are the reasons why the ceramics doped by Lu exhibited the best wear resistance. Oxidation resistance: Composites exhibited predominately parabolic oxidation behavior indicated diffusion as the rate limiting mechanism. Exception was only the Si3N4-SiC composite sintered with Lu2O3. In this case diffusion of cation has been strongly suppressed because of the beneficial effect of stable grain boundary phase and the presence of the SiC particles predominately located at the grain boundaries of Si3N4.