Enhanced thermoelectric performance in p-type Mg₃Sb₂ via lithium doping

The Zintl compound Mg₃Sb₂ has been recently identified as promising thermoelectric material owing to its high thermoelectric performance and cost-effective, nontoxicity and environment friendly characteristics. However, the intrinsically p-type Mg₃Sb₂ shows low figure of merit (zT = 0.23 at 723 K) for its poor electrical conductivity. In this study, a series of Mg_3-xLixSb₂ bulk materials have been prepared by high-energy ball milling and spark plasma sintering (SPS) process. Electrical transport measurements on these materials revealed significant improvement on the power factor with respect to the undoped sample, which can be essentially attributed to the increased carrier concentration, leading to a maximum zT of 0.59 at 723 K with the optimum doping level x = 0.01. Additionally, the engineering zT and energy conversion efficiency are calculated to be 0.235 and 4.89%, respectively. To our best knowledge, those are the highest values of all reported p-type Mg₃Sb₂-based compounds with single element doping.