As a top candidate for competing with the conventional n-Bi₂Te₃ thermoelectrics, Mg₃Sb₂-based materials have attracted increasing attentions for low-grade (<300 °C) waste heat recovery applications, due to the high thermoelectric performance, low cost, abundance and nontoxicity. Because of its anisotropic crystal structure as that of Bi₂Te₃, possible property anisotropy and the resultant similar requirement of texturing for preferential performance remain not entirely clear Mg₃Sb₂-thermoelectrics at working temperatures. This motivates the current work to focus on the transport-property anisotropy of n-type Mg₃Sb₂, centimeter-sized single crystals of which are successfully grown by a flux-assisted vertical Bridgman technique with a post-annealing under a Mg vapor pressure. This enables a revelation of nearly isotropic transport properties in this anisotropically structured material, guaranteeing reasonably high performances in polycrystalline materials achievable by cheap and scalable processing approaches such as powder-metallurgy. In addition, this work uncovers the strong lattice anharmonicity and large band degeneracy are respectively the origins for the low lattice thermal conductivity and superior electronic performance.

作为与传统 n-Bi ₂ Te ₃热电材料竞争的首选材料，Mg ₃ Sb ₂基材料在低品位（<300°C）废热回收应用中引起了越来越多的关注，因为它具有较高的热电性能，成本低、资源丰富且无毒。由于其各向异性晶体结构与 Bi ₂ Te _{3 的}晶体结构相同，因此可能的性能各向异性和由此产生的对优先性能的织构的类似要求在工作温度下仍然不完全清楚 Mg ₃ Sb _{2 -}热电材料。这促使当前的工作将重点放在 n 型 Mg ₃的输运性质各向异性上Sb ₂，其厘米大小的单晶通过助焊剂辅助垂直布里奇曼技术成功生长，并在镁蒸气压下进行后退火。这使得能够揭示这种各向异性结构材料的近乎各向同性的输运特性，保证多晶材料具有合理的高性能，可通过粉末冶金等廉价且可扩展的加工方法实现。此外，这项工作揭示了强晶格非谐性和大能带简并性分别是低晶格热导率和优异电子性能的根源。