Nanostructuring SnTe to improve thermoelectric properties through Zn and Sb co-doping

Abstract

The suitability of tin telluride (SnTe) as a potential alternative thermoelectric material avidly continues and the outcome so far has been superbly promising. In our research, both Zn doped and Zn and Sb co-doped SnTe were studied. We show that introducing the ZnTe second phase plays a significantly crucial role in improving the thermoelectric properties of pristine SnTe. In addition, the Sb-rich layered structure has a paramount effect on specially reducing the phonon mean free path (PMFP) during dispersion. An anomalous behavior is observed in Zn doped SnTe, where slight doping results in increased electrical conductivity. On the other hand, Sb co-doping significantly reduces the carrier concentration and electrical conductivity is seen to decrease with increasing Sb concentration. A maximum Seebeck coefficient of ∼170 μV K⁻¹ in a 15 mol% Sb co-doped sample emanates from the band convergence effect of Zn in SnTe and reduction of the carrier concentration; and an overall maximum power factor (PF) of ∼17.2 μW cm⁻¹ K⁻² at 773 K is also reported. The astounding effect of Sb addition on modulation of the carrier concentration is evident in the ultra-low electronic thermal contribution (κ_e). An improved Vickers hardness value of up to 130 Hv and a two-fold improved ZT of Zn doped SnTe to a value of ∼0.6 is promising but there still remains room for further improvement.