Sintered Reaction‐Bonded Silicon Nitride with High Thermal Conductivity and High Strength

Abstract

Sintered reaction‐bonded silicon nitride (SRBSN) materials were prepared from a high‐purity Si powder doped with Y 2 O 3 and MgO as sintering additives by nitriding at 1400°C for 8 h and subsequently postsintering at 1900°C for various times ranging from 3 to 24 h. Microstructures and phase compositions of the nitrided and the sintered compacts were characterized. The SRBSN materials sintered for 3, 6, 12, and 24 h had thermal conductivities of 100, 105, 117, and 133 W/m/K, and four‐point bending strengths of 843, 736, 612, and 516 MPa, respectively. Simultaneously attaining thermal conductivity and bending strength at such a high level made the SRBSN materials superior over the high‐thermal conductivity silicon nitride ceramics that were prepared by sintering of Si 3 N 4 powder in our previous works. This study indicates that the SRBSN route is a promising way of fabricating silicon nitride materials with both high thermal conductivity and high strength.