Enhanced thermal conductivity and flexural strength of Si₃N₄ ceramics by using YF₃-MgSiN₂ as sintering additives

Si₃N₄ ceramics stand out as ideal materials for advanced electronic packaging substrates due to their high mechanical strength, high-temperature resilience, and minimal dielectric constant. Optimizing both the mechanical and thermal conductivity is essential for ensuring their reliable performance. In this study, a systematic investigation into the impact of both oxygen-containing sintering additives (Y₂O₃-MgF₂ and Y₂O₃-MgSiN₂) and oxygen-free sintering additives (YF₃-MgF₂ and YF₃-MgSiN₂) on the microstructure, flexural strength, and thermal conductivity of Si₃N₄ ceramics has been performed. It demonstrates that the Si₃N₄ ceramic sintered with the YF₃-MgSiN₂ additive achieves a remarkable thermal conductivity of 111.63 W·m⁻¹·K⁻¹ and a flexural strength of 774.7 MPa, which is relatively rare among the reported Si₃N₄ ceramics. These exceptional properties are attributed to the use of YF₃-MgSiN₂ additive, which leads to a significant reduction in lattice oxygen content, along with a decrease in the liquid phase formation temperature, thereby promoting grain development. Furthermore, the decomposition of MgSiN₂ at high temperatures plays a key role in purifying the grain boundaries. This study provides a promising approach for developing high-performance Si₃N₄ ceramics with excellent thermal conductivity and mechanical strength.