BixSb2−xTe3 nanoplates with enhanced thermoelectric performance due to sufficiently decoupled electronic transport properties and strong wide-frequency phonon scatterings. (February 2016)

• Record Type: Journal Article
• Authors: Hong, Min; Chen, Zhi G.; Yang, Lei; Zou, Jin
• Is Part Of: Nano energy. Volume 20(2016:Feb.)
• Page Start: 144
• Page End: 155
• Publication Date: 2016-02
• Subjects: BixSb2−xTe3 nanoplates -- Microwave-assisted solvothermal -- Thermoelectric -- Decoupling factor -- Phonon scattering; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2015.12.009
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Thermoelectric materials enable the direct conversion between heat and electricity, offering a sustainable technology to overcome the upcoming energy crisis. p -Type Bi x Sb2− x Te3 systems potentially satisfy the criteria ( i.e. large power-factor, and low thermal conductivity) for thermoelectric applications. Nanostructuring has been considered as an effective approach to enhance the thermoelectric performance. Here, we employed a rapid microwave-assisted solvothermal method to fabricate Bix Sb2−x Te3 nanoplates, securing a peak figure-of-merit of 1.2, caused by the obtained high power-factor of 28.3×10 −4 Wm −1 K −2 and ultra-low thermal conductivity of 0.7 Wm −1 K −1 . Based on the single Kane band model with a newly introduced variable ( λE def — the dimensionless λ representing the square root of ratio between the initial effective mass and the free electron mass, and E def representing the deformation potential) to serve as the decoupling factor, we found that Bi x Sb2− x Te3 nanoplates with tunable compositions can decrease λE def and simultaneously optimize the reduced Fermi level to ultimately enhance the power-factor. Moreover, detailed structural characterizations reveal dense grain boundaries and dislocations in our nanostructures. These two phonon scattering sources in conjunction with the inherently existed Bi–Sb lattice disorders lead to a strong wide-frequency phonon scattering, and consequently result in a significantly decreased thermal conductivity. This study provides strategic guidance to develop high-performance thermoelectric materials by nanostructuring and compositional engineering to achieve ultra-low thermal conductivity and to maximize the power-factor. Graphical abstract: Highlights: Large-scale Bi x Sb2− x Te3 nanoplates with enlarged ZT are successfully synthesized by the rapid microwave-assisted solvothermal method. Based on simulation studies using band engineering, the decoupling factor for Seebeck coefficient and electrical conductivity is found. Compositional tuning in Bi x Sb2− x Te3 nanoplates enables to reduce the decoupling factor and optimize the reduced Fermi level, resulting in an enhanced powder-factor. High-density dislocations, grain boundaries in conjunction with lattice disorders achieve the strong wide-frequency phonon scattering, leading to an ultra-low thermal conductivity.