Grain boundary re-crystallization and sub-nano regions leading to high plateau figure of merit for Bi2Te3 nanoflakes

• Published in: Energy & environmental science 2023-11, Vol.16 (11), p.5123-5135
• Main Authors: Wei-Di, Liu, Liang-Cao, Yin, Li, Lei, Yang, Qishuo, De-Zhuang, Wang, Li, Meng, Xiao-Lei, Shi, Liu, Qingfeng, Bai, Yang, Gentle, Ian, Wang, Lianzhou, Chen, Zhi-Gang
• Format: Article
• Language: English
• Subjects: Carrier density; Crystallization; Figure of merit; Grain boundaries; Nanoengineering; Nanostructure; Optimization; Phonons; Scattering; Synergistic effect; Thermal conductivity; Thermoelectric materials
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d3ee02370b

Nanoengineering is an effective strategy to strengthen phonon scattering, reduce lattice thermal conductivity and boost thermoelectric material performance. However, nanostructure features are generally in the size of ∼10 nm, and the fine control of nanostructure characteristics down to the sub-nano level (below several nanometers) remains as a key challenge. Here, we demonstrate that solvothermally synthesized Bi2Te3 can re-crystallize preferentially at the grain boundaries to form sub-nano boundary regions with width 1.2 (from ∼323 to ∼423 K) and a high average zT of ∼1.18 (from 303 to 473 K) have been achieved in the Bi2Te3 pellet sintered at 593 K. This study not only reveals the formation mechanism of sub-nano boundary regions but also demonstrates that these sub-nano boundary regions and their formation process can effectively induce synergistic effects contributing to high thermoelectric performance, and guide the design of high-performance thermoelectric materials.