Effects of in-situ loaded rare earth Yb on sintering properties of silicon nitride ceramics

WANG Yu; LYU Jie; LIU Pengfei; HAN Zhao

doi:10.13732/j.issn.1008-5548.2026.01.010

Abstract：Objective To fabricate high-performance silicon nitride(Si3N4)ceramics and enhance their application potential under high-temperature and high-thermal-load conditions,this study investigated the effects of in-situ loaded rare earth ytterbium(Yb)on the sintering behavior and final properties of Si3N4 ceramics.By introducing rare earth modification,the aim is to optimize the ceramic's microstructure and significantly enhance its thermal conductivity to meet the urgent demand for high-thermal-conductivity ceramic materials in fields such as electronic packaging and heat dissipation substrates. Methods Rare earth metal Yb was dissolved in liquid ammonia,utilizing its coordination with ammonia molecules to form an active precursor,and then coated onto the surface of Si3N4 powder via a dissolution-precipitation mechanism.After subsequent heat treatment in an inert atmosphere,YbN@Si3N4 core-shell structured powder was obtained,and this powder was subjected to hot-press sintering.The morphology and elemental distribution of the Yb-loaded Si3N4 powder were analyzed.The effects of the Yb loading content on the relative density,phase composition,microstructure,and thermal conductivity of the Si3N4 ceramics was investigated. Results and Discussion High-performance Si3N4 ceramics were successfully produced through hot-press sintering.As the mass fraction of metallic Yb increased,the density of Si3N4 ceramics showed an upward trend,while the relative density gradually decreased.The grain size of β-Si3N4 initially increased with higher Yb content but subsequently stabilized.After heat treatment at 1 850 ℃ for 5 hours,the thermal conductivity of Si3N4 ceramics was significantly improved,increasing from 36.8 W/(m·K)to 66.8 W/(m·K),representing an 82％enhancement.During this process,the loaded metallic Yb was transformed into ytter-bium nitride(YbN),which preferentially reacted with the inherent SiO2 on the surface of Si3N4 powder.This reaction increased the nitrogen-to-oxygen ratio in the sintering liquid phase and reduced the oxygen content in the Si3N4 lattice.Consequently,the thermal conductivity of the Si3N4 ceramics was improved. Conclusion In a liquid ammonia medium,rare-earth Yb,characterized by its high oxygen affinity,was in-situ loaded onto the surface of Si3N4 powder as a sintering aid.This approach not only optimized the properties of the sintering liquid phase and promoted densification and grain growth,but more critically,reduced the oxygen content in the lattice of the Si3N4 ceramics,fundamentally improving their thermal conductivity.The study provides a new strategy for fabricating high-thermal-conductivity Si3N4 ceramics.