Microstructure and properties of translucent Mg–sialon ceramics prepared by spark plasma sintering

Translucent Mg–sialon ceramics were prepared using spark plasma sintering (SPS) α-Si3N4 powders with 9 wt% AlN and 3 wt% MgO as sintering additives. Microstructural observations indicate that the optical and mechanical properties of Mg–sialon ceramics are affected by the density and α′:β′-phase ratio in sintered bodies, which are tailored by controlling the content of formed liquid phase and optimizing the parameters of spark plasma sintering in present study. The material is toughened by the existence of a small amount of β′-sialon. The reason that the two-phase composite does not greatly compromise optical property could be attributed to the fine equiaxed microstructures and low content of β′-phase. Translucent Mg–sialon ceramics achieving 66.4% of maximum transmittance, 21.4 ± 0.3 GPa hardness, and 6.1 ± 0.1 MPa m1/2 fracture toughness were prepared by spark plasma sintering at 1850 °C for 5 min.