Effect of Different Rare-Earth on Microstructure and Properties of α-Sialon Ceramics

Densified Yb-,Y-,Dy-,Sm- and Nd-α-Sialon ceramics were prepared by two-step hot sintering.The variation of microstructure and properties with different rare-earth was investigated.The ceramics doped with smaller cations (Yb;,y;and Dy;) are fully composed ofα-Sialon,while in the larger cations (Sm;and Nd;) doped ceramics also exist a few intergranular phase M′(Re;Si;Al;O;N;) in triple-point pockets.With increasing the radius of the rare-earth cations,the elongatedα-Sialon grains form instead of the equiaxed grains in Yb-α-Sialon,and the aspect ratio of grains increases.All the ceramics possess high hardness and the value of 21 GPa is achieved for Yb- and Y-α-Sialon.With increasing the ionic size of rare-earth the hardness decreases slightly but the toughness tends to increase.Nd-α-Sialon possesses the highest toughness with the value of 5.4 MPa.m;.