Improving near-room-temperature thermoelectrics in SnTe-MnTe alloys

Abstract

The rich capabilities for both electronic and phonon engineering in SnTe are highly desirable for achieving high thermoelectric performance. Alloying high-solubility MnTe (∼15%) leads to substitutional defects for reducing lattice thermal conductivity and band convergence for enhancing electronic performance, and thus, an improvement of thermoelectric performance of SnTe is realized. However, there is no evidence that the electronic and phonon transport properties are fully optimized in SnTe-15%MnTe thermoelectrics, especially for the near-room-temperature (< 573 K) thermoelectric performance, which still needs a sufficient promotion. Here, the substituted 2% Bi in SnTe-15%MnTe alloys dramatically increases the near-room-temperature zT and peak zT to ∼0.72 (at 550 K) and ∼1.3 (at 850 K), respectively. Combining the experimental evidence and the first-principles calculations, we demonstrate that the prominent enhancement of electronic performance arises from the Bi-doping-driven transport valence band alignment and the carrier concentration optimization. Furthermore, the Debye–Callaway model verifies that the reduction in lattice thermal conductivity is dominated by the Bi substitutional defects. The present findings reveal the importance of transport engineering in achieving high thermoelectric performance particularly near room temperature.

This work was financially supported by the National Key Research and Development Program of China (Grant No. 2018YFA0702100), the Joint Funds of the National Natural Science Foundation (NNSF) of China and the Chinese Academy of Sciences' Large-Scale Scientific Facility (Grant No. U1932106), the NNSF of China (Grant No. 51771126), the Youth Foundation of Science & Technology [Department of Sichuan Province in China (Grant No. 2016JQ0051)], the Thousand Talents Program of Sichuan Province in China, and the World First-Class University Construction Funding of China. F. Xiong and Y. Chen are grateful for the financial support from RGC under Project Nos. 17200017 and 17300018 and the research computing facilities offered by ITS, HKU. The authors thank Professor Yanzhong Pei from Tongji University for his support and discussion on the Hall measurement. Z. Y. Chen and J. Tang contributed equally to this work.

The data that support the findings of this study are available within this article.