High-performance Si3N4 ceramics prepared by gas pressure sintering with Y2O3-MgO-MgSiN2 ternary additives

Si 3 N 4 ceramics are highly valued for their exceptional thermal conductivity and mechanical properties. This study investigated the effects of different addition ratios of Y 2 O 3 -MgO-MgSiN 2 ternary sintering additives on liquid phase viscosity, densification, microstructure, thermal conductivity and mechanical properties. The incorporation of MgSiN 2 as sintering additives introduced additional Si and N into the liquid phase, forming a nitrogen-rich liquid phase that promoted the grain growth showing a bimodal distribution. When the MgO/MgSiN 2 ratio reached 2/3, the moderate liquid phase viscosity facilitated enhanced densification and grain growth. This resulted in an increased number of large grains, a moderate grain size distribution, and a good bimodal microstructure. Consequently, the 2M3N exhibited superior properties, including a thermal conductivity of 105.22 W m −1  K −1 , a fracture toughness of 5.91 MPa m 1 / 2 , and a bending strength of 726.12 MPa. The study demonstrates that precise control of the Y 2 O 3 -MgO-MgSiN 2 ratio can effectively regulate the microstructure, leading to improved thermal and mechanical performance.