J. Mater. Sci. Technol. ›› 2022, Vol. 119: 182-189.DOI: 10.1016/j.jmst.2021.12.038

• Research Article • Previous Articles     Next Articles

High-entropy Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides with highly disordered B-site cations for ultralow thermal conductivity

Liang Xu, Lei Su, Hongjie Wang(), Hongfei Gao, Pengfei Guo, Min Niu, Kang Peng, Lei Zhuang, Zhiwei Dai   

  1. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China
  • Received:2021-10-19 Revised:2021-12-11 Accepted:2021-12-20 Published:2022-03-05 Online:2022-03-05
  • Contact: Hongjie Wang
  • About author:* E-mail address: hjwang@xjtu.edu.cn (H. Wang).

Abstract:

Materials with ultralow thermal conductivity and good thermal stability are of great interest in numerous applications such as energy storage and conversion devices, and thermal insulation components. In this work, a family of high-entropy Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) oxides with highly disordered cations on the B-site has been synthesized by introducing large atomic-size mismatch, mass and charge disorder. Through tuning the composition, the high-entropy Sm2B2O7 oxides can be engineered from pyrochlore to fluorite structure, accompanied with an order-disorder transition. The pyrochlore Sm2(Nb0.2Sn0.2Ti0.2Y0.2Zr0.2)2O7 and fluorite Sm2(Nb0.2Ta0.2Y0.2Yb0.2Zr0.2)2O7 exhibit low thermal conductivities of 1.35 W·m-1·K-1 and 1.23 W·m-1·K-1, respectively, indicating their good thermal insulation. In addition, the high-entropy fluorite Sm2(Nb0.2Ta0.2Y0.2Yb0.2Zr0.2)2O7 also shows average thermal expansion coefficient of 10.2 × 10-6 °C-1 and high-temperature stability even after thermal exposure at 1600 °C in air for 30 h. These results indicate that the high-entropy Sm2B2O7 (B=Ti, Zr, Sn, Hf, Y, Yb, Nb, and Ta) can be promising candidates for thermal barrier coatings and thermally insulators.

Key words: High-entropy oxides, Atomic sizes mismatch, Mass and charge disorder, Thermal conductivity, Thermal barrier coatings materials