Extremely low lattice thermal conductivity is always the pursuit of thermoelectric materials research. In this work, we reported an exceptional effect of Ag₂S addition in MnTe, an emerging promising mid-temperature thermoelectric material, to enable the realization of minimum lattice thermal conductivity, namely ∼0.4 Wm⁻¹K⁻¹. Such a low lattice thermal conductivity is guaranteed by the incorporation of in-situ formed Ag rich phase (Ag₂Te) with ultralow lattice thermal conductivity and further scattering of phonons from the partial doping effects induced point defects and boundaries between various phases. Apart from the dramatically decreased lattice thermal conductivity, the partial doping of Ag and S simultaneously enhance the electrical conductivity, further contributing to enhanced thermoelectric performance. Meanwhile, an inverse sign of Seebeck and Hall coefficient was observed and rationalized by the influence of highly electron-conductive Ag₂Te phase. Thanks to the synergetic modulation of electrical and thermal transport properties by in-situ formed composite, a high ZT value of 1.1 was achieved in MnTe based thermoelectric materials, which also demonstrates the importance of compositing approaches to design state-of-the-art thermoelectric materials.

极低的晶格导热率一直是热电材料研究的追求。在这项工作中，我们报告了在MnTe（一种新兴的中温热电材料）中添加Ag ₂ S的特殊效果，以实现最小的晶格热导率，即〜0.4 Wm ^-1 K ^-1。通过掺入原位形成的富Ag相（Ag ₂Te）具有极低的晶格导热率，并且由于部分掺杂效应而进一步分散了声子，从而引起点缺陷和各相之间的边界。除了晶格热导率显着降低之外，Ag和S的部分掺杂同时提高了电导率，进一步有助于提高热电性能。同时，观察到塞贝克和霍尔系数的倒数，并通过高电子传导性的Ag ₂ Te相的影响使之合理化。得益于原位形成的复合材料对电和热传输性能的协同调节，高ZT 在基于MnTe的热电材料中达到1.1的值，这也证明了复合方法在设计最先进的热电材料中的重要性。