Enhanced thermal conductivity and flexural strength of sintered reaction‐bonded silicon nitride with addition of (Y _0.96 Eu _0.04 ) ₂ O ₃

Abstract Sintered reaction‐bonded silicon nitride (SRBSN) with high thermal conductivity was obtained using (Y _0.96 Eu _0.04 ) ₂ O ₃ and MgO as sintering additives. Green compacts were nitrided at 1400°C for 4 h. Post‐sintering was carried out at 1850 and 1900°C for 4 h, respectively. In reaction‐bonded silicon nitride (RBSN) doped with Y ₂ O ₃ and MgO, the β‐Si ₃ N ₄ content and nitridation degree were 51.1% and 93.8%, respectively. However, the β‐Si ₃ N ₄ content and nitridation degree were 72.6% and 96.7% in a nitrided compact doped with (Y _0.96 Eu _0.04 ) ₂ O ₃ and MgO. After post‐sintering, the phase composition, microstructure, mechanical properties, and thermal conductivity were investigated. After sintering at 1900°C for 4 h, the thermal conductivity of SRBSN doped with (Y _0.96 Eu _0.04 ) ₂ O ₃ and MgO was increased by 16.5% compared to that of the samples doped with Y ₂ O ₃ and MgO. The highest hardness of 1639 HV and the good flexural strength of 776.4 MPa were also achieved in the sample doped with 2‐mol.% (Y _0.96 Eu _0.04 ) ₂ O ₃ and 5‐mol.% MgO.