Microstructure and properties of self-reinforced α-sialon ceramics doped with Lu2O3

Lu-α-sialon ceramics containing elongated grains embedded into fine α-sialon matrix were obtained by applying a two-step hot-press procedure. Incorporation of excess Lu2O3 could promote anisotropic growth of α-sialon grains, and the quantity and aspect ratio of elongated α-sialon grains increase with the amount of Lu2O3 addition. The elongated α-sialon grains nucleate and grow epitaxially on the α-Si3N4 core, and the initial precipitation on the core is richer in Lu and Al content than the subsequent precipitation. The obtained Lu-α-sialons possess improved mechanical properties, the Vickers hardness, flexural strength and fracture toughness of the materials with 4 wt%Lu2O3 could reach with value of 22 GPa, 620.4 MPa and 4.8 MPa m1/2, respectively. The Lu-α-sialons also demonstrate excellent high-temperature strength due to the presence of the refractory intergranular phase. The strength of the material with 4 wt%Lu2O3 at 1400 °C could retain 87% of its room-temperature strength.