Effect of a new nonoxide additive, Y₃Si₂C₂, on the thermal conductivity and mechanical properties of Si₃N₄ ceramics

Abstract

Enhancement of the thermal conductivity of silicon nitride is usually achieved by sacrificing its mechanical properties (bending strength). In this study, β-Si 3 N 4 ceramics were prepared using self-synthesized Y 3 Si 2 C 2 and MgO as sintering additives. It was found that the thermal conductivity of the Si 3 N 4 ceramics was remarkably improved without sacrificing their mechanical properties. The microstructure and properties of the Si 3 N 4 ceramics were analyzed and compared with those of the Y 2 O 3 -MgO additives. The addition of Y 3 Si 2 C 2 eliminated the inherent SiO 2 and introduced nitrogen to increase the N/O ratio of the grain-boundary phase, inducing Si 3 N 4 grain growth, increasing Si 3 N 4 grain contiguity, and reducing lattice oxygen content in Si 3 N 4 . Therefore, by replacing Y 2 O 3 with Y 3 Si 2 C 2 , the thermal conductivity of the Si 3 N 4 ceramics was significantly increased by 31.5% from 85 to 111.8Wm −1 K −1 , but the bending strength only slightly decreased from 704 ± 63MPa to 669 ± 33MPa.

Fabrication of silicon nitride with high thermal conductivity and flexural strength by hot‐pressing flowing sintering

“…This increase was due to the reduction of internal F I G U R E 7 Relation between thermal conductivity and bending strength for Si 3 N 4 sintered by different routes. GPS, 14,28,[40][41][42][43][44][45] gas pressure sintered; SRBSN, sintered reaction-bonded silicon nitride 2,16,18,46,47 ; HP, hot pressing [48][49][50] ; SPS, spark plasma sintering 51,52 ; PLS, pressureless sintering 33 ; HPFS, hot-pressing flowing sintering.…”

Effect of Ultra-High Pressure Sintering and Spark Plasma Sintering and Subsequent Heat Treatment on the Properties of Si3N4 Ceramics

“…Numerous kinds of research have shown that increasing densification was crucial to improving both the thermal and mechanical properties of Si 3 N 4 ceramics [ 9 , 10 ]. Moreover, large grains can improve the heat transmission efficiency, and the low content of inter-granular secondary phase and lattice defects can reduce phonon scattering to improve thermal conductivity [ 11 , 12 , 13 ].…”