Enhancing the Thermoelectric Performance of Mg2Sn Single Crystals via Point Defect Engineering and Sb Doping

Mg 2 Sn is a potential thermoelectric (TE) material that exhibits environmental compatibility. In this study, we fabricated Sb-doped Mg 2 Sn (Mg 2 Sn 1- x Sb x ) single-crystal ingots and demonstrated the enhancement of TE performance via point defect engineering and Sb doping. The Mg 2 Sn 1- x Sb x single-crystal ingots exhibited considerably enhanced electrical conductivity because of the donor-doping effect in addition to high carrier mobility. Moreover, the Mg 2 Sn 1- x Sb x single-crystal ingots contained Mg vacancy (V Mg ) as a point defect. The introduced V Mg and doped Sb atoms formed nanostructures, both acting as phonon-scattering centers. Consequently, lower lattice thermal conductivity was achieved for the Mg 2 Sn 1- x Sb x single-crystal ingots compared with polycrystalline counterparts. Owing to the significant enhancement in the electrical conductivity and the reduction in the lattice thermal conductivity, the maximum power factor of 5.1(4) × 10 -3 W/(K 2 m) and the maximum dimensionless figure of merit of 0.72(5) were achieved for the Mg 2 Sn 0.99 Sb 0.01 single-crystal ingot, which are higher than those of single-phase Mg 2 Sn 1- x Sb polycrystals.