JIANG QiangGuo, GU Shangxian, ZHOU Maopeng, CHU Quanquan, CHENG Lixia, WU Shanghua

(Guangdong University of Technology, Guangzhou 510006, Guangdong, China)

Abstract: Si₃N₄ ceramics with high mechanical properties were prepared by an introduction of MgO-Lu₂O₃-Re₂O₃ (Re= La, Sm, Gd, Er) multiple additives. The effect of ternary additives on relative density, second phase, micro-structure and mechanical properties were studied.Results showed that the addition of MgO-Lu₂O₃-Re₂O₃ (Re= Sm, Er) into Si₃N₄ ceramics led to the formation of Lu₄Si₂N₂O₇. And the addition of MgO-Lu₂O₃-Re₂O₃ (Re= La, Gd, Er) into Si₃N₄ ceramics led to distinctly bimodal structure distributions, weak grain boundary, and then resulted in high flexure strength (above 900 Mpa) and high fracture toughness (above 9 MPa • m^1/2). However, the introduction of MgO-Lu₂O₃- Sm₂O₃ led to some exaggerated grains growth, which resulted in low flexure strength and low fracture toughness.

Key words: silicon nitride, ternary additives, flexure strength, fracture toughness