Directional Solidification and Thermoelectric Properties of Undoped Mg₂Sn Crystal

Single-phase Mg₂Sn crystal has been successfully directionally solidified from the melt with a high temperature gradient of 185 K cm⁻¹. The solidified distance for the growth of single-phase Mg₂Sn crystal was predicted theoretically and agreed well with the experimental result. The grown Mg₂Sn crystals exhibit better thermoelectric performance and high thermoelectric figure of merit along the growth direction. In the temperature range from 300 K to 700 K, the maximum Seebeck coefficient S and electrical conductivity σ reached −261 μV K⁻¹ and 525 Ω⁻¹ m⁻¹, respectively. The minimum thermal conductivity κ was measured to be 4.3 W m⁻¹ K⁻¹, and the lattice thermal conductivity approximated 90% of the bulk thermal conductivity of the crystal. The method developed in this work provides a methodological reference for preparation of Mg₂B^IV and its doped and solid-solution compounds.