Enhanced Thermoelectric Performance in Ge0.955−xSbxTe/FeGe2 Composites Enabled by Hierarchical Defects

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2021-06, Vol.17 (25), p.n/a
• Main Authors: Xie, Li, Liu, Ruiheng, Zhu, Chenxi, Bu, Zhonglin, Qiu, Wujie, Liu, Jianjun, Xu, Fangfang, Pei, Yanzhong, Bai, Shengqiang, Chen, Lidong
• Format: Article
• Language: English
• Subjects: Carrier density; Defects; Figure of merit; GeTe; hierarchical structures; Iron; Lattice vacancies; Nanotechnology; Optimization; Phonons; Power factor; Scattering; scattering effect; Seebeck effect; Structural hierarchy; Thermal conductivity; Thermoelectricity; thermoelectrics; Transport properties; vacancies
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202100915

Manipulations of carrier and phonon scatterings through hierarchical structures have been proved to be effective in improving thermoelectric performance. Previous efforts in GeTe‐based materials mainly focus on simultaneously optimizing the carrier concentration and band structure. In this work, a synergistic strategy to tailor thermal and electrical transport properties of GeTe by combination with the scattering effects from both Ge vacancies and other defects is reported. The addition of Fe in GeTe‐based compounds introduces the secondary phase of FeGe2, synchronously increasing the concentration of Ge vacancies and arousing more Ge planar defects. These hierarchical defects contribute to a large scattering factor, leading to a significant enhancement of Seebeck coefficient and further a splendid power factor. Meanwhile, benefiting from the reinforced phonon scatterings by multiscale hierarchical structures, an extremely low lattice thermal conductivity is successfully achieved. With simultaneously optimized electrical and thermal transport properties, a maximum figure of merit, zT, value of 2.1 at 750 K and an average zT value of 1.5 in 400–800 K are realized in Ge0.875Sb0.08Te/1.5%FeGe2. This work demonstrates that manipulation of hierarchical defects is an effective strategy to optimize the thermoelectric properties. Ge vacancies are generally considered as adverse effects for the promotion of electrical performance of GeTe. Here, hierarchical defects including Ge vacancies and other defects are introduced by the formation of FeGe2. The simultaneously optimized electrical and thermal transport properties demonstrate manipulation of hierarchical defects is an effective strategy to realize high thermoelectric performance in GeTe‐based materials.