Optimization of thermoelectric properties of n-type Ti, Pb co-doped SnSe

Abstract

n-Type polycrystalline SnSe with Ti, Pb co-doping was synthesized by combining mechanical alloying (MA) with spark plasma sintering (SPS). It is revealed that Ti is an effective cationic dopant to convert SnSe from a p-type to an n-type semiconductor, and the thermoelectric performance of the Ti-doped SnSe is also improved in comparison with the pristine sample due to an enhanced power factor. Furthermore, after further Pb doping, an obviously improved electrical conductivity together with a moderate Seebeck coefficient can be achieved, which results in an improvement of the power factor with a maximum value of 300 μW m⁻¹ K⁻² at 773 K. Meanwhile, the lattice thermal conductivity is significantly reduced because of the enhanced phonon scattering owing to the mass and strain fluctuations. Therefore, a final ZT value of 0.4 was obtained for composition of Sn_0.74Pb_0.20Ti_0.06Se at 773 K, which is a conservative value for n-type SnSe with cationic dopant prepared by the simple preparation process of MA and SPS.