GeTe with rhombohedral‐to‐cubic phase transition is a promising lead‐free thermoelectric candidate. Herein, theoretical studies reveal that cubic GeTe has superior thermoelectric behavior, which is linked to (1) the two valence bands to enhance the electronic transport coefficients and (2) stronger enharmonic phonon–phonon interactions to ensure a lower intrinsic thermal conductivity. Experimentally, based on Ge_1−xSb_xTe with optimized carrier concentration, a record‐high figure‐of‐merit of 2.3 is achieved via further doping with In, which induces the distortion of the density of states near the Fermi level. Moreover, Sb and In codoping reduces the phase‐transition temperature to extend the better thermoelectric behavior of cubic GeTe to low temperature. Additionally, electronic microscopy characterization demonstrates grain boundaries, a high‐density of stacking faults, and nanoscale precipitates, which together with the inevitable point defects result in a dramatically decreased thermal conductivity. The fundamental investigation and experimental demonstration provide an important direction for the development of high‐performance Pb‐free thermoelectric materials.

中文翻译：

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通过降低相变温度和引入共振能量掺杂在Ge1-x-ySbxInyTe中实现2.3的zT

具有菱形-立方相变的GeTe是有前途的无铅热电候选物。在这里，理论研究表明，立方晶格特具有优异的热电性能，这与（1）两个价带可提高电子输运系数和（2）较强的共谐声子-声子相互作用以确保较低的固有热导率有关。实验上，基于Ge _{1− x} Sb _x在优化载流子浓度的情况下，通过进一步掺杂In可以达到2.3的创纪录高品质因数，这会引起费米能级附近的态密度失真。此外，Sb和In共掺杂降低了相变温度，从而将立方GeTe的更好的热电性能扩展到了低温。此外，电子显微镜表征还显示出晶界，高密度堆垛层错和纳米级析出物，再加上不可避免的点缺陷，导致热导率急剧下降。基础研究和实验演示为高性能无铅热电材料的开发提供了重要方向。