Texture, microstructures, and mechanical properties of AlN-based ceramics with Si3N4-Y2O3 additives

Textured AlN-based ceramics with improved mechanical properties were prepared by hot pressing using Si3N4 and Y2O3 as additives. The introduction of Si3N4-Y2O3 into AlN matrix led to the formation of secondary Y3AlSi2O7N2 and fiber-like 2Hd(delta) AlN-polytypoid phases, the partial texture of all crystalline phases, and the fracture mode change from intergranular to transgranular. Consequently, Vickers hardness, fracture toughness and flexural strength of AlN-based ceramics by the replacement of Y2O3 by Si3N4-Y2O3 increased significantly from 10.4 +/- 0.3 GPa, 2.4 +/- 0.3 MPa m(1/2) and 333.3 +/- 10.3 MPa to 14.2 +/- 0.4 GPa, 3.4 +/- 0.1 MPa m(1/2) and 389.5 +/- 45.5 MPa, respectively.