Higher-order anharmonicity is found in copper and manganese doped tin telluride (SnTe) alloys, and its effect on thermoelectric performance is systematically studied. Analyzation of thermal expansion shows that the ionic potential not only consists of cubic term, but also quartic term. Short phonon lifetime derived from more diffused peak of Brillouin spectrometer results from the higher-order anharmonicity. As a result, an ultra-low lattice thermal conductivity of 0.5 Wm⁻¹K⁻¹ is achieved. Soft optical phonon mode was observed from Raman spectrometer, the transverse optical - longitudinal acoustic phonon interaction may be the reason for the enhanced anharmonicity. Combining with the enlarged power factor caused by band convergence, the highest figure of merit reaches 1.3 at 873 K for doped samples. Additionally, the large temperature difference of 600 K and high output power densities of 291 mWmm⁻³ of simulated SnTe uni-leg module are achieved. This work supplies way for revealing the anharmonicity experimentally, and proves modification of intrinsic anharmonicity is an avenue for enhancing the thermoelectric performance of SnTe alloys.

在铜和锰掺杂的碲化锡 (SnTe) 合金中发现了高阶非谐性，并系统地研究了其对热电性能的影响。热膨胀分析表明，离子势不仅包含三次项，还包含四次项。来自布里渊光谱仪的更扩散峰的短声子寿命是由高阶非谐性引起的。^{结果，0.5 Wm -1} K ^-1的超低晶格热导率已完成。从拉曼光谱仪观察到软光学声子模式，横向光学-纵向声子相互作用可能是增强非谐性的原因。结合带收敛引起的放大功率因数，掺杂样品的最高品质因数在 873 K 时达到 1.3。此外，模拟的SnTe单腿模块实现了600 K的大温差和291 mWmm ^{-3的高输出功率密度。}该工作为实验揭示非谐性提供了途径，并证明了对固有非谐性的修改是提高SnTe合金热电性能的途径。