Control of the Thermoelectric Properties of Mg2Sn Single Crystals via Point-Defect Engineering

Mg 2 Sn is a potential thermoelectric (TE) material that can directly convert waste heat into electricity. In this study, Mg 2 Sn single-crystal ingots are prepared by melting under an Ar atmosphere. The prepared ingots contain Mg vacancies (V Mg ) as point defects, which results in the formation of two regions: an Mg 2 Sn single-crystal region without V Mg (denoted as the single-crystal region) and a region containing V Mg (denoted as the V Mg region). The V Mg region is embedded in the matrix of the single-crystal region. The interface between the V Mg region and the single-crystal region is semi-coherent, which does not prevent electron carrier conduction but does increase phonon scattering. Furthermore, electron carrier concentration depends on the fraction of V Mg , reflecting the acceptor characteristics of V Mg . The maximum figure of merit zT max of 1.4(1) × 10 −2 is realised for the Mg 2 Sn single-crystal ingot by introducing V Mg . These results demonstrate that the TE properties of Mg 2 Sn can be optimised via point-defect engineering.