Journal Article

Vacancies tailoring lattice anharmonicity of Zintl-type thermoelectrics

Lisi Li, Xin Tong, Miao He, Chin-Wei Wang, Cuiping Zhang, Chen Wang, Jinfeng Zhu, Zhenxiang Cheng, Chen Chen, Mingfang Shu, Shuki Torri, Zhe Qu, Jie Ma, Mingzai Wu, Qingyong Ren, Manh Duc Le, Yuxuan Jiang, Yue Chen, Qian Zhang, Jianli Wang, Guohua Wang

2024

Overview

While phonon anharmonicity affects lattice thermal conductivity intrinsically and is difficult to be modified, controllable lattice defects routinely function only by scattering phonons extrinsically. Here, through a comprehensive study of crystal structure and lattice dynamics of Zintl-type Sr(Cu,Ag,Zn)Sb thermoelectric compounds using neutron scattering techniques and theoretical simulations, we show that the role of vacancies in suppressing lattice thermal conductivity could extend beyond defect scattering. The vacancies in Sr 2 ZnSb 2 significantly enhance lattice anharmonicity, causing a giant softening and broadening of the entire phonon spectrum and, together with defect scattering, leading to a ~ 86% decrease in the maximum lattice thermal conductivity compared to SrCuSb. We show that this huge lattice change arises from charge density reconstruction, which undermines both interlayer and intralayer atomic bonding strength in the hierarchical structure. These microscopic insights demonstrate a promise of artificially tailoring phonon anharmonicity through lattice defect engineering to manipulate lattice thermal conductivity in the design of energy conversion materials. Vacancies are traditionally considered to play a role of phonon-defect scattering. Here, the authors show that vacancies can induce phonon softening, enhance phonon anharmonicity, and cause a dramatic reduction in the lattice thermal conductivity.

• Publisher: Springer Science and Business Media LLC,Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 639/301/299/2736 / 639/4077/4107 / Anharmonicity / Atomic bonding / Bonding strength / Charge density / Chemical bonds / Controllability / Crystal defects / Crystal lattices / Crystal structure / Design defects / Energy conversion / Heat conductivity / Heat transfer / Humanities and Social Sciences / Interlayers / Lattice vacancies / multidisciplinary / Neutron scattering / Phonons / Q / Science / Science (multidisciplinary) / Softening / Thermal conductivity