Densification, Mass Loss, and Mechanical Properties of Low‐Temperature Pressureless‐Sintered Si ₃ N ₄ with LiYO ₂ Additive: The Effects of Additive Content and Annealing

The effects of annealing on the residual Li content, microstructure, and mechanical properties of pressureless‐sintered LiYO ₂ –Si ₃ N ₄ were investigated. The bending strength and fracture toughness of the as‐fabricated specimens were fair (∼640 MPa, ), in spite of the sintering at a low temperature (1600°C). The strength, Young's modulus, and hardness were improved up to 697 MPa, 284 GPa, and 13.9 GPa, respectively, by annealing treatments. Residual Li could be reduced to 0.008 wt% by annealing at 1650°C in Ar. Si ₃ N ₄ could be sintered at a low temperature to give materials with a relatively low elastic modulus but reasonable strength values.