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.
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