Effects of Y₃Si₂C₂ on Microstructure and Mechanical/Thermal Properties of Si₃N₄ Ceramics

Si₃N₄ ceramics have great application prospects in the fields of heat dissipation and packaging of electronic components, because of their excellent chemical stability, mechanical and thermal properties. In order to prepare Si₃N₄ ceramics with excellent bending strength and thermal conductivity, Y₃Si₂C₂-MgO binary composite sintering additive was used in this work. The effects of Y₃Si₂C₂ content and high temperature soaking time on relative density, mechanical properties and thermal conductivity of Si₃N₄ ceramics were systematically studied. The optimization mechanisms of mechanical/thermal properties of the Si₃N₄ ceramics were explained based on their microstructure and phase composition analyses. Thermal conductivity and bending strength of the Si₃N₄ ceramics, prepared after high temperature soaking for 4 h and 12 h, increased first and then decreased with increasing content of Y₃Si₂C₂. The bending strength of the Si₃N₄ ceramics prepared by high temperature soaking for time for 4 h is mainly dependent on relative density, while that of the Si₃N₄ ceramics prepared by high temperature soaking for time for 12 h is related to the microstructure uniformity and Si₃N₄ grain size. The prolonging of holding time is conducive to eliminating pores and increasing grain size, resulting in enhanced densification and increased thermal conductivity. Si₃N₄ ceramics, with relative density of 99.0%, thermal conductivity of (106.80±2.64) W·m^-1·K^-1 and bending strength of (590.21±25.69) MPa, were prepared by using gas pressure sintering, at 1900 ℃ for 12 h, with the addition of 1.5 mol % Y₃Si₂C₂. Such Si₃N₄ ceramics has excellent comprehensive mechanical/thermal properties, which is conducive to improving the service safety and reliability of Si₃N₄ ceramic packaged electronic components.