Additive‐Free Combustion Synthesis of Ultrafine Equiaxed α‐Si ₃ N ₄ Powder for High‐Performance Ceramics

ABSTRACT Ultrafine equiaxed α‐Si 3 N 4 powder is a promising raw material for next‐generation high‐performance substrates. However, conventional industrial methods are often hampered by high energy consumption, prolonged production cycle, and the use of polluting additives. Thus, the low‐cost production of high‐purity α‐Si 3 N 4 powder remains a persistent technical challenge. In this study, equiaxed α‐ Si 3 N 4 particles were synthesized via an additive‐free combustion synthesis approach. The influences of N 2 pressure and Si/Si 3 N 4 molar ratio on the combustion process, phase composition, and microstructure of the synthesized powders were systematically investigated. Under optimized conditions—specifically, a N 2 pressure of 3 MPa and a Si to Si 3 N 4 molar ratio of 2.5:1—equiaxed α‐Si 3 N 4 particles with an average size of 0.35 µm were obtained. Furthermore, the growth mechanism of α‐Si 3 N 4 particles was elucidated through heat absorption–assisted quenching and thermo‐kinetic analysis. The resulting sintered Si 3 N 4 ceramic exhibited a bending strength of 767 MPa and a thermal conductivity of 94.5 W·m −1 ·K −1 , respectively. This work provides a cost‐effective and efficient strategy for synthesizing high‐quality α‐Si 3 N 4 powder, demonstrating its potential application as a substrate raw powder for microelectronic applications.