Xing Tong, Zhu Chenxi, Song Qingfeng, Huang Hui, Xiao Jie, Ren Dudi, Shi Moji, Qiu Pengfei, Shi Xun, Xu Fangfang, Chen Lidong
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China.
Adv Mater. 2021 Apr;33(17):e2008773. doi: 10.1002/adma.202008773. Epub 2021 Mar 24.
High-efficiency thermoelectric (TE) technology is determined by the performance of TE materials. Doping is a routine approach in TEs to achieve optimized electrical properties and lowered thermal conductivity. However, how to choose appropriate dopants with desirable solution content to realize high TE figure-of-merit (zT) is very tough work. In this study, via the use of large mass and strain field fluctuations as indicators for low lattice thermal conductivity, the combination of (Mg, Bi) in GeTe is screened as very effective dopants for potentially high zTs. In experiments, a series of (Mg, Bi) co-doped GeTe compounds are prepared and the electrical and thermal transport properties are systematically investigated. Ultralow lattice thermal conductivity, about 0.3 W m K at 600 K, is obtained in Ge Mg Bi Te due to the introduced large mass and strain field fluctuations by (Mg, Bi) co-doping. In addition, (Mg, Bi) co-doping can introduce extra electrons for optimal carrier concentration and diminish the energy offset at the top of the valence band for high density-of-states effective mass. Via these synthetic effects, a superhigh zT of ≈2.5 at 700 K is achieved for Ge Mg Bi Te. This study sheds light on the rational design of effective dopants in other TE materials.
高效热电（TE）技术取决于TE材料的性能。掺杂是TE材料中实现优化电学性能和降低热导率的常规方法。然而，如何选择具有理想固溶体含量的合适掺杂剂以实现高热电优值（zT）是一项非常艰巨的工作。在本研究中，通过使用大质量和应变场波动作为低晶格热导率的指标，筛选出GeTe中（Mg，Bi）的组合作为潜在高zT的非常有效的掺杂剂。在实验中，制备了一系列（Mg，Bi）共掺杂的GeTe化合物，并系统地研究了其电输运和热输运性质。由于（Mg，Bi）共掺杂引入了大质量和应变场波动，在GeMgBiTe中获得了超低的晶格热导率，在600K时约为0.3W mK。此外，（Mg，Bi）共掺杂可以引入额外的电子以实现最佳载流子浓度，并减小价带顶部的能量偏移以获得高态密度有效质量。通过这些综合效应，GeMgBiTe在700K时实现了≈2.5的超高zT。本研究为其他TE材料中有效掺杂剂的合理设计提供了思路。
