Probing anisotropy of Seebeck coefficient and enhanced thermoelectric performance of Mg₂Si_0.35Sn_0.65 single crystal

A single crystal of Sb-doped Mg₂Si_0.35Sn_0.65 has been successfully prepared using high temperature-gradient directional solidification. The composition distribution of the crystal is uniform, and the preferred growth direction of the crystal is [111] orientation. The Seebeck coefficient (S) of the crystal is anisotropic in different orientations, and the electrical and thermal conductivity are isotropic properties. The S value in the [111] orientation can reach −265 μVK⁻¹, which is much larger than the reported results. Also, the power factor in the [111] orientation has a value of 5.56 mWm⁻¹K⁻², which leads to a maximum ZT of 1.3 at 730 K. Results of Hall testing and first principles calculations agree well with the experiment results.