High thermoelectric properties of Mg₂Sn single crystals with engineered lattice defects

Crystal structure, microstructure, and thermoelectric (TE) properties of Mg2Sn single crystals (SCs) have been reviewed. The Mg2Sn SCs were grown under Ar atmosphere. By increasing the Ar pressure and/or by applying chemical pressure through element doping, Mg vacancies (VMg) were introduced. The VMg aggregated to form nanoparticle-like VMg regions, around which there were dislocations. These lattice defects effectively reduced lattice thermal conductivity κlat, whereas less affected electrical transport. The κlat and Hall carrier mobility of the nondoped and elementally-doped Mg2Sn SCs were, respectively, lower and higher than those of previously reported SCs and polycrystals. The highest dimensionless figure of merit was achieved for the n-type (Sb+B)-doped and p-type (Li+B)-doped Mg2Sn SCs. A simulation of output power demonstrates that these SCs are potential TE materials utilizing low-mid temperature waste heat.