BixSb2-xTe3 nanoplates with enhanced thermoelectric performance due to sufficiently decoupled electronic transport properties and strong wide-frequency phonon scatterings

Thermoelectric materials enable the direct conversion between heat and electricity, offering a sustainable technology to overcome the upcoming energy crisis. p-Type BixSb2-xTe3 systems potentially satisfy the criteria (i.e. large power-factor, and tow 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 BixSb2-xTe3 nanoplates, securing a peak figure-of-merit of 1.2, caused by the obtained high power-factor of 28.3 x 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 (lambda E-def - the dimensionless lambda 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 BixSb2-xTe3 nanoplates with tunable compositions can decrease lambda E-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. (C) 2015 Elsevier Ltd. All rights reserved.