Anisotropy of Seebeck coefficient in un-doped Mg₂Sn single crystal

Un-doped Mg₂Sn single crystal has been revealed to be anisotropic in Seebeck coefficient at different orientations and possesses orientation-dependent conduction sign reversal (OCSR). At room temperature, the [111] orientation of the crystal shows the n-type conduction with a Seececk coefficient value of −265μVK⁻¹ and the p-type conduction behavior in the [11¯0] and [112¯] orientations with 148μVK⁻¹ and 115μVK⁻¹, respectively. First principle calculation on the anisotropic Seebeck coefficient of the crystal matches well with the experimental results, showing that the conducting effective mass plays an important role in determining the value of Seebeck coefficient. The single crystal Mg₂Sn with the preferred [111] orientation is expected to have the best thermoelectric performance due to its large Seebeck coefficient value and the same electrical and thermal conductivities compared with other orientations of the crystal.