All-Scale Hierarchical Structure Contributing to Ultralow Thermal Conductivity of Zintl Phase CaAg0.2Zn0.4Sb

Jie Chen; Wenhua Xue; Chen Chen; Hongxing Li; Canying Cai; Qian Zhang; Yumei Wang

doi:10.1002/advs.202100109

All-Scale Hierarchical Structure Contributing to Ultralow Thermal Conductivity of Zintl Phase CaAg_0.2Zn_0.4Sb

Adv Sci (Weinh). 2021 Apr 10;8(11):2100109. doi: 10.1002/advs.202100109. eCollection 2021 Jun.

Authors

Jie Chen^{1

2}, Wenhua Xue^{1

3}, Chen Chen³, Hongxing Li², Canying Cai⁴, Qian Zhang³, Yumei Wang¹

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Science Beijing 100190 P. R. China.
² School of Physics and Optoelectronics Xiangtan University Xiangtan 411105 P. R. China.
³ Department of Materials Science and Engineering and Institute of Materials Genome & Big Data Harbin Institute of Technology Shenzhen 518055 P. R. China.
⁴ School of Materials Science and Engineering Xiangtan University Xiangtan 411105 P. R. China.

Abstract

TiNiSi-type Zintl phase CaAgSb can transform into LiGaGe-type Zintl phase CaAg _x Zn_(1- _x _)/2Sb when some of the Ag atoms are substituted by Zn atoms, leading to an ultralow thermal conductivity of ≈0.4 W m^-1 K^-1 in the whole measured temperature range of CaAg_0.2Zn_0.4Sb. The microstructure is then investigated by spherical aberration-corrected electron microscopy on an atomic scale, which reveals an all-scale hierarchical structure that can scatter the phonons in a wide frequency range. There exist a large quantity of CaAgSb nanometer precipitates as well as quite a lot of edge dislocations close to these nanometer precipitates, thus releasing the stress caused by the mismatch between the precipitates and the parent phase. Many twin boundaries also exist around the CaAgSb precipitates. High-density point defects contain the randomly dispersed Ag vacancies and Zn atoms substituted for the Ag atoms. All these widely distributed multidimensional defects contribute to the decrease of lattice thermal conductivity in a wide temperature range.

Keywords: multidimensional defects; spherical aberration‐corrected electron microscopy; ultralow thermal conductivity; zintl phase.