Preparation, microstructure, and properties of GPS silicon nitride ceramics with β‐Si 3 N 4 seeds and nanophase additives

Si3N4 ceramics with high thermal conductivity and outstanding mechanical properties were prepared by adding β-Si3N4 seeds and nanophase α-Si3N4 powders as modifiers. The introduction of β-Si3N4 seeds enhanced the growth of β-Si3N4 grains. Owing to the interlocked structure induced by the β-Si3N4 grains, the fracture toughness of Si3N4 ceramics reached a high value of 7.6 MPa·m1/2; also, the large-sized grains increased the contact possibility of Si3N4 grains, improving the thermal conductivity of Si3N4 ceramics (64 W/(m·K)). Because of the introduction of nanophase α-Si3N4, the flexural strength, fracture toughness, and thermal conductivity of the Si3N4 ceramics increased to 754 MPa, 7.2 MPa·m1/2, and 54 W/(m·K), respectively. According to the analysis of the growth kinetics of Si3N4 grains, the rapid growth of Si3N4 grains was ascribed to the reduction in the activation energy resulting from the introduction of β-Si3N4 seeds and nanophase α-Si3N4.