Enhanced thermoelectric performance of Sb-doped Mg2Si0.4Sn0.6 via doping, alloying and nanoprecipitation

With the advantages of eco-friendliness, low cost, and low density, Mg2(Si,Sn) solid solutions are promising candidates for thermoelectric applications. In this work, Sb-doped Mg2Si0.4Sn0.6 bulks were prepared with a combined method of solid-state reaction and high pressure synthesis, followed by spark plasma sintering. Our investigations show that Sb doping optimizes the carrier concentration, while Si/Sn alloying effectively suppresses the lattice thermal conductivity and induces a convergence of the two lowest-lying conduction bands. Additionally, numerous coherent Sn-rich nanoprecipitates are formed within micron-sized grains. All these factors contribute synergistically to improving the thermoelectric properties of Mg2Si0.4Sn0.6. The optimal Mg2(Si0.4Sn0.6)0.985Sb0.015 exhibits a power factor higher than 4 000 mW center dot m-1 center dot K-2 and a lattice thermal conductivity less than 0.8 W center dot m-1 center dot K-1 at temperatures higher than 600 K, leading to the highest ZT of 1.61 at 823 K. Current work demonstrates an effective approach to enhancing the thermoelectric performance of n-type Mg2X solid solutions through doping, alloying, and microstructure modification. (c) 2023 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).