GeTe is highly sought-after due to its versatility as a high-performance thermoelectric material and phase change material, as well as a ferroelectric Rashba semiconductor. Compared to most thermoelectric materials, it has an additional degree of freedom of rhombohedral–cubic phase transition at 673 K. At this temperature, the lattice thermal conductivity approaches a theoretical minimum due to ferroelectric instability while the high-energy Σ and low-energy L bands converge to give outstanding electronic properties. Therefore, modulation of the phase transition temperature allows simultaneous and synergistic tuning of the electronic and thermal transport properties to achieve high zT. In this work, Sn alloying together with Bi,Sb doping is used to suppress the phase transition to achieve a pure cubic structure with a lattice thermal conductivity of around 0.4 W m⁻¹ K⁻¹ and peak zT of 1.7 at 723 K with an average zT of 1.23 between 400 and 800 K. Furthermore, the Vickers hardness of 270 and Young's modulus of 63.5 GPa in Ge_0.4Sn_0.4Bi_0.02Sb_0.12Te are by far the highest amongst binary chalcogenides. More importantly, the high quality factor achieved in this work gives ample room for further zT improvements. The fundamental insights drawn from this work provide a pathway towards engineering GeTe-based alloys to achieve high zT at any temperature of interest.

中文翻译：

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调整相变温度以实现高性能的基于立方GeTe的热电器件

由于GeTe作为高性能热电材料和相变材料以及铁电Rashba半导体的多功能性，因此备受追捧。与大多数热电材料相比，它在673 K时具有菱形-立方相变的附加自由度。在此温度下，由于铁电不稳定性，晶格热导率接近理论最小值，而高能Σ和低能L乐队会聚以提供出色的电子性能。因此，相变温度的调制允许同时协同地调节电子和热传输特性，以实现高zT。在这项工作中，锡合金与Bi，Sb掺杂一起用于抑制相变，从而获得纯立方结构，其晶格热导率约为0.4 W m ^-1 K ^-1，在723 K处的峰值zT为1.7。在400和800 K之间的平均zT为1.23。此外，在二元硫属化物中，Ge _0.4 Sn _0.4 Bi _0.02 Sb _0.12 Te的维氏硬度为270，杨氏模量为63.5 GPa 。更重要的是，这项工作中获得的高质量因素为进一步的zT提供了足够的空间改进。从这项工作中获得的基本见解为工程GeTe基合金提供了一条途径，以在任何感兴趣的温度下实现高zT。