Abstract Si 3 N 4 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 (Y 2 O 3 ‐MgF 2 and Y 2 O 3 ‐MgSiN 2 ) and oxygen‐free sintering additives (YF 3 ‐MgF 2 and YF 3 ‐MgSiN 2 ) on the microstructure, flexural strength, and thermal conductivity of Si 3 N 4 ceramics has been performed. It demonstrates that the Si 3 N 4 ceramic sintered with the YF 3 ‐MgSiN 2 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 Si 3 N 4 ceramics. These exceptional properties are attributed to the use of YF 3 ‐MgSiN 2 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 MgSiN 2 at high temperatures plays a key role in purifying the grain boundaries. This study provides a promising approach for developing high‐performance Si 3 N 4 ceramics with excellent thermal conductivity and mechanical strength.
Zhang et al. (2025) studied this question.