Boosted carrier mobility and enhanced thermoelectric properties of polycrystalline Na0.03Sn0.97Se by liquid-phase hot deformation

Abstract

SnSe emerges as a promising thermoelectric material due to an ultrahigh ZT value in its single crystal while polycrystalline SnSe offers much lower ZTs resulting from the weak texturing degree. Here, we report a liquid-phase hot deformation technique to enhance the texturing degree of polycrystalline Na_0.03Sn_0.97Se, leading to a significantly boosted carrier mobility of 30.1 cm² V⁻¹ s⁻¹ at room temperature and a remarkable average power factor of 5.73 μW cm⁻¹ K⁻² between 300 and 830 K. Moreover, the liquid-phase hot deformation procedure introduces dense dislocation defects and realizes an obviously reduced lattice thermal conductivity of 0.40 W m⁻¹ K⁻¹ at 747 K. Consequently, a peak ZT of 0.9 at 780 K and a high average ZT_ave of 0.49 from 300 to 830 K were obtained for the polycrystalline Na_0.03Sn_0.97Se sample. This work indicates that liquid-phase hot deformation is a convenient and energy-saving strategy to enhance the texturing degree and improve the thermoelectric performance in polycrystalline SnSe materials.