Silicon nitride ceramics consolidated by oscillatory pressure sintering

We report the fabrication of silicon nitride (Si3N4) ceramics with high flexural strength by oscillatory pressure sintering (OPS). The effects of the sintering procedure on the grain growth, microstructure evolution, and mechanical properties of Si3N4 were investigated. It was found that, in comparison to the traditional gas pressure sintering technique, the OPS process produced Si3N4 ceramics with higher density with a shorter sintering time and lower sintering temperature, leading to products with higher bending strength and Vickers hardness. Furthermore, the OPS promoted the alpha-beta phase transformation of Si3N4, which facilitated the ion diffusion rate in the liquid phase and increased the aspect ratio of the formed beta-Si3N4 grains. The Si3N4 ceramics sintered at 1720 degrees C by OPS exhibited high bending strength and Vickers hardness of 1432 +/- 51 MPa and 16.14 +/- 0.38 GPa, respectively, representing their potential for exploring ceramics with high performances.