Enhancing Si3N4 Ceramic Performance by Microstructure Control through Sintering Additive Optimization and Grain Orientation Control

With the advancement of power electronics, packaging materials are facing more stringent requirements, especially in mechanical reliability and thermal conductivity. Silicon nitride (Si 3 N 4 ) ceramics are promising due to their excellent mechanical properties, but their relatively low thermal conductivity limits wider applications. In this study, we propose a dual strategy of optimizing sintering aids during hot-press sintering to facilitate convenient regulation of β -Si 3 N 4 crystal-axis orientation, and applying heat treatment to enhance thermal conductivity while retaining excellent mechanical properties. The results show that the composition ratio of MgSiN 2 -Y 2 O 3 composite sintering aids significantly influences the crystallographic orientation (Lotgering orientation factors ranging from 0.19 to 0.29) and the anisotropy in thermal conductivity, with the aligned direction exhibiting a ∼24% higher thermal conductivity than the non-aligned direction. Post-sintering heat treatment at different temperatures further improved the grain boundary structure, leading to an additional ∼17% increase in thermal conductivity while maintaining high flexural strength (>800 MPa). This approach enables the effective tuning of grain alignment and boundary characteristics, balancing thermal and mechanical performance. The findings offer a new pathway for developing high thermal conductivity Si 3 N 4 ceramics, expanding their potential for high-power electronic packaging applications.