Optimization of the average figure-of-merit zT in medium-entropy GeTe-based materials via entropy engineering
Xu‐Sheng Liu, Keli Wang, Peng Li, Qiqi Tang, Zhenlong Huang, Lin Yuan, Wu Wang, Binbin Jiang, Jiaqing He
Abstract
Entropy engineering has emerged as an effective strategy for improving the figure-of-merit zT by decelerating the phonon transport while maintaining good electrical transport properties of thermoelectric materials. Herein, a high average zT of 1.54 and a maximum zT of 2.1 are achieved in the mid-entropy GeTe constructed by Ag, Sb, and Pb alloying. At room temperature, the mid-entropy GeTe tends to a cubic structure. And the power factor is improved from 7.7 μW·cm−1·K−2 to 16.2 μW·cm−1·K−2 due to the large increase in effective mass and the optimized carrier concentration. The increasing disorder created by heavy and off-centering Ag, Sb, and Pb atoms induces strong mass/strain fluctuations and phonon scattering to decelerate the phonon transport in GeTe. A low lattice thermal conductivity is obtained in the medium-entropy GeTe-based material. Moreover, a GeTe-based thermoelectric cooler is fabricated with the cooling temperature difference of 66.6 K with the hot end fixed at 363 K. This work reveals the effectiveness of entropy engineering in improving the average zT in GeTe and shows potential application of GeTe as a thermoelectric cooler.