Journal of Inorganic Materials ›› 2021, Vol. 36 ›› Issue (9): 959-966.DOI: 10.15541/jim20200705

Special Issue: 【结构材料】超高温结构陶瓷

• RESEARCH ARTICLE • Previous Articles     Next Articles

Preparation of Silicon Nitride with High Thermal Conductivity and High Flexural Strength Using YbH2-MgO as Sintering Additive

WANG Weide1,2(), CHEN Huanbei3, LI Shishuai1,2, YAO Dongxu1(), ZUO Kaihui1, ZENG Yuping1   

  1. 1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. Nanjing Electronic Devices Institute, Nanjing 210016, China
  • Received:2020-12-08 Revised:2021-01-31 Published:2021-09-20 Online:2021-03-01
  • Contact: YAO Dongxu, associate professor. E-mail:
  • About author:WANG Weide, PhD candidate. E-mail:
  • Supported by:
    National Key Research and Development Project(2017YFB0310400)


Silicon nitride with high thermal conductivity was obtained by two-step sintering method using YbH2-MgO as sintering additive. The effect of YbH2-MgO on shrinkage behavior, phase composition, microstructure, thermal conductivity, and flexural strength was investigated. The nitrogen-riched and oxygen-lacked oxynitride liquid phase was generated owing to the elimination of SiO2 by YbH2. Both the removal of lattice oxygen and the growth of β-Si3N4 were stimulated by the liquid phase. Therefore, compared to Yb2O3-MgO doped sample, silicon nitride with enlarged grains, purified lattice and reduced intergranular phase was obtained. Ultimately, its thermal conductivity increased by 13.7% from 115.32 to 131.15 W·m-1·K-1 after sintering at 1900 ℃ for 24 h by substituting Yb2O3 with YbH2. Although the replacement of Yb2O3 by YbH2 leads to enhanced flexural strength at low temperature, it tends to reduce the flexural strength at high temperature. The optimal flexural strength of (1008±35) MPa was achieved after sintering at 1800 ℃ for 4 h. This variation related mainly to the exaggerated bimodal microstructure. This work signifies that YbH2-MgO is effective for obtaining Si3N4 ceramics with both high flexural strength and high thermal conductivity.

Key words: silicon nitride, YbH2, thermal conductivity, flexural strength

CLC Number: