Since mid- and low frequency phonons (MLFPs) dominate heat transport in multi-component alloys/compounds, it is vital to block MLFPs to reduce lattice thermal conductivity k_L. Here we show that through creating high-dense stacking faults (SFs) via lowing SFs energy and endo-grown AgInSnSe₄ nanoneedles via solid-state reaction in (Ag, Fe, In)-doped Cu₂SnSe₃ thermoelectric compound its k_L is reduced to theoretical minimum ~0.2 WK⁻¹ m⁻¹ (at 848 K). Theoretical analysis reveals that aspect ratio ξ of nanoneedles works as an extra degree of freedom and similar to SFs strong scattering of MLFPs occurs as $\xi$=10= 10 (radius $\bar{\mathit{a}}$=50 nm). Besides, the intrinsic cause of AgInSnSe₄ nanoneedle growth is found to be its large surface energy in [112] direction. In addition, Fe and Ag (In) doping can simultaneously enhance electronic density of states, with the former bringing extra hole conduction paths, resulting in 3-fold increase in power factor (12 $\mu$Wcm⁻¹ K⁻² at ~800 K). At last, a large figure of merit ZT= 1.61 is achieved at 848 K, demonstrating that synergetic phonon-scattering by both high dense SFs and nanoneedles with large ξ combined with regulation of electronic structures is an effective way to improve its thermoelectric performance.

由于中低频声子 (MLFP) 在多组分合金/化合物中主导热传输，因此阻断 MLFP 以降低晶格热导率 k _L至关重要。在这里，我们展示了通过降低 SFs 能量和内生 AgInSnSe _{4纳米针通过在 (Ag, Fe, In) 掺杂的 Cu 2} SnSe ₃热电化合物中的固态反应产生高密度堆垛层错 (SFs)，其 k _L为减少到理论最小值~0.2 WK ^-1 m ^-1（在848 K）。理论分析表明，纳米针的纵横比 ξ 作为一个额外的自由度，类似于 SF，MLFP 的强散射发生在$\xi$=10= 10（半径$\overline{\mathit{一个}}$= 50纳米）。_{此外，发现AgInSnSe 4}纳米针生长的内在原因是其在[112]方向上的大表面能。此外，Fe 和 Ag (In) 掺杂可以同时提高电子态密度，前者带来额外的空穴传导路径，导致功率因数增加 3 倍（12$\mu$Wcm ^-1 K ^-2在~800 K)。最后，在 848 K 处实现了较大的品质因数 ZT=1.61，这表明高密度 SFs 和具有大 ξ 的纳米针的协同声子散射与电子结构的调节相结合是提高其热电性能的有效方法。