Enhanced Bulk Thermoelectric Performance of Pb0.6Sn0.4Te: Effect of Magnesium Doping

Abstract

Thermoelectric (TE) materials are promising in the context of renewable power generation as they can directly convert waste heat into electricity. Although PbTe is the best known TE material, its use is not encouraged due to concerns of environmental toxicity of lead. A combination of modified self-propagating high-temperature synthesis (SHS) and field-assisted sintering technique (FAST) is employed for the very first time to synthesize a solid solution of PbTe and SnTe. We show that doping of Pb<inf>0.6</inf>Sn<inf>0.4</inf>Te with Mg breaks crystal mirror symmetry and opens up band gap. This results in suppression of bipolar diffusion. Also the increase in degeneracy of valence sub-bands improves Seebeck coefficient. Both these synergistically leads to remarkable enhancement in figure of merit ZT (?2 at 840 K) and ZT<inf>avg</inf> (?1.2 between 500 and 840 K) rendering it into high-performance thermoelectric material by successfully engineering electronic structure. Most importantly, the ZT here is comparable to that of Mg-doped PbTe but has lesser lead content and hence is more environment friendly. The most probable configuration of Pb<inf>0.6</inf>Sn<inf>0.4</inf>Te was also determined for the very first time using site occupancy disorder (SOD) technique. © 2017 American Chemical Society.