Influences of nanometre Y2O3 and Yb2O3 additives on structure and properties of α/β-Sialon ceramics prepared by spark plasma sintering

Using micrometre α-Si3N4, micrometre AlN, and nanometre Al2O3 powders as starting materials, with nanometre Y2O3, Yb2O3 or Y2O3 + Yb2O3 as sintering additives, multiphase Sialon ceramics were prepared by spark plasma sintering. Influences of different sintering additives on the structure and properties of α/β-Sialon ceramics were discussed in this paper. Sintered specimens were characterised by X-ray diffraction and scanning electron microscopy. Hardness and fracture toughness were determined by Vickers indentation method. The flexural strength was tested by three-point bending method and density was measured by use of Archimedes’s principle. The results showed that Yb2O3 additive had more effect on the precipitation of α-Sialon phase than Y2O3, and the flexural strength and fracture toughness of the specimen with Yb2O3 additive were 583.04 MPa and 4.84 MPa.m1/2, respectively.