Microstructure and properties of (Sm,Er)-α-Sialon ceramic materials

The Ln-alpha-Sialon (Ln=Sm and Er) ceramics with the composition of Ln(1.0/3)Si(9.3)Al(2.7)O(1.7)N(14.3) were fabricated by hot pressing (HP). The effect of different rare-earth elements and their proportion on the microstructure and mechanical properties of Ln-a-Sialon ceramics were studied. Phase assembly and microstructure of as-prepared samples were characterized by XRD, SEM and EDS. The results showed that with the decreasing of the Sm:Er mol ratio, equiaxed grain morphology of alpha-Sialon became elongated gradually. Micro-hardness value was increased with the highest of 19.5 GPa, while flexual strength and fracture toughness values decreased slowly. The extra addition of 2.5wt% rare-earth oxide based on the starting composition could facilitate the growth of elongated alpha-Sialon grains, and the mechanical properties enhanced to some extent.