Fracture Resistance Behavior of High‐Thermal‐Conductivity Silicon Nitride Ceramics

Abstract

Silicon nitride ceramics were prepared from a high‐purity silicon powder doped with 2 mol% Y2O3 and 5 mol% MgO as sintering additives via a route of sintering of reaction‐bonded silicon nitride (SRBSN). The materials sintered at 1900°C for 3, 6, 12, and 24 h had thermal conductivities of 109, 125, 146, and 154 W/m/K, and four‐point bending strengths of 786, 676, 608, and 505 MPa, respectively. The fracture toughness values, determined by the single‐edge‐precracked‐beam (SEPB) method, were 8.4, 8.6, 9.7, and 10.7 MPa m1/2 for the materials sintered for 3, 6, 12, and 24 h, respectively, which were similar to the results measured by the chevron‐notched‐beam (CNB) test method. The materials sintered for longer times (12 and 24 h) showed stronger R‐curve behaviors over longer range of crack extension, in comparison with the materials sintered for shorter times (3 and 6 h).

Effects of yttria and magnesia on densification and thermal conductivity of sintered reaction‐bonded silicon nitrides

“…Effects of these factors are closely related to sintering additives, which are indispensible for facilitating liquid‐phase‐sintering of silicon nitride. Our previous research revealed that a mixture of 2 mol% of Y 2 O 3 and 5 mol% of MgO was an effective sintering additive for preparing dense Si 3 N 4 ceramics with high thermal conductivity using an SRBSN method, while it was not clear whether the combination of 2 mol% of Y 2 O 3 and 5 mol% of MgO was an optimal additive composition or not . In the present study, a variety of amount and combinations of Y 2 O 3 and MgO mixtures were used as sintering additives to prepare Si 3 N 4 ceramics by the SRBSN method, and the effects of these sintering additives on nitridation, sintering and thermal conductivity property of the Si 3 N 4 ceramics were studied, with the purpose of searching appropriate sintering additives for preparing Si 3 N 4 ceramics with improved thermal conductivity.…”

“…However, little attention had been paid to its thermal conduction property and it was not classified as a high thermal conductivity ceramic such as AlN and SiC. Recent studies have shown that thermal conductivity of silicon nitride ceramic could be drastically improved through minimizing impurity content and tailoring microstructure when prepared by a sintering of reaction‐bonded silicon nitride (SRBSN) method . By the SRBSN method, a silicon nitride ceramic attained a record‐high thermal conductivity of 177 Wm −1 K −1 , while it possessed a fracture toughness as high as 11.2 MPa·m 1/2 .…”

A novel method for joining aluminum and silicon nitride by polysiloxane

“…7), 8) This reveals that silicon nitride with high thermal conductivity should be a superior substrate material compared to aluminum nitride for future high power electronic devices and other new applications.…”

Development of high-thermal-conductivity silicon nitride ceramics

“…Motivated by such an idea, our research group proposed a strategy of preparing high thermal conductivity Si 3 N 4 via a route of sintering of reactionbonded silicon nitride (SRBSN), which is a well-known process of fabricating Si 3 N 4 ceramics from an Si starting powder instead of a Si 3 N 4 powder [14][15][16][17], in consideration of the fact that Si powders containing much less oxygen and metallic impurities than Si 3 N 4 powders are commercially available thanks to the advancement of modern semiconductor industry. Our experimental results have verified the effectiveness of the SRBSN strategy, by which both higher thermal conductivity and higher mechanical strength were achieved, compared to the conventional sintering of silicon nitride powder (SSN) route [18][19][20][21][22][23][24][25][26][27][28].…”

“…It is worth noting that the material sintered for 3 h already attained a fracture toughness as high as 8.4 MPa m 1/2 . The fracture toughness values became higher for the materials sintered for longer times, especially when the sintering times were longer than 12 h. The material sintered for 24 h possessed a fracture toughness of 10.7 MPa m 1/2 [28]. Fig.…”