Enhanced thermoelectric performance in p-type Mg3Sb2 via lithium doping**Project supported by the National Natural Science Foundation of China (Grant Nos. U1601213 and 51572287) and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant No. QYZDB-SSW-SLH013).

Abstract

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 Mg3−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.