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 Sr₂ZnSb₂ 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.

虽然声子非谐性本质上影响晶格热导率并且难以改变，但可控晶格缺陷通常仅通过外在散射声子来发挥作用。在这里，通过使用中子散射技术和理论模拟对 Zintl 型 Sr(Cu,Ag,Zn)Sb 热电化合物的晶体结构和晶格动力学进行全面研究，我们表明空位在抑制晶格热导率方面的作用可以超越缺陷散射。 Sr ₂ ZnSb ₂中的空位显着增强了晶格非和谐性，导致整个声子谱的巨大软化和展宽，并与缺陷散射一起导致最大晶格热导率与 SrCuSb 相比下降约 86%。我们表明，这种巨大的晶格变化是由电荷密度重建引起的，这破坏了分级结构中的层间和层内原子键合强度。这些微观见解证明了通过晶格缺陷工程人为调整声子非谐性的前景，以在能量转换材料的设计中操纵晶格热导率。