Enhancing the Thermoelectric Performance of n-Type Mg_3.2Sb_1.5Bi_0.5 by Reducing Lattice Thermal Conductivity through...

Mg₃Sb₂-based thermoelectric materials are characterized by their economic efficiency, nontoxicity, and environmental friendliness and represent a highly promising and eco-friendly functional material for midtemperature applications. To achieve a higher thermoelectric performance, we introduced two compounds, LaCl₃ and CeCl₃, into Mg_3.2Sb_1.5Bi_0.5 under the guidance of first-principles calculations. The Mg_3.2Sb_1.5Bi_0.5 + 0.03CeCl₃ sample reached a maximum ZT value of approximately 1.6 at 723 K. The calculations indicate that two n-type dopants, LaCl₃ and CeCl₃, can adequately improve the band structure of Mg₃Sb₂, and the introduction of Cl atoms will also lead to lattice distortion and reduce the lattice thermal conductivity (κ_L). Experimental results demonstrate that the introduction of Cl atoms efficiently reduces the thermal conductivity while improving the electrical transport properties. Specifically, the Mg_3.2Sb_1.5Bi_0.5 + 0.03CeCl₃ sample achieved an exceptionally low κ_L of 0.3 W m^-1 K^-1 at 723 K, thereby validating the effectiveness of LaCl₃ and CeCl₃ doping. This work provides valuable insights into achieving thermoelectric decoupling in Mg₃Sb₂-based thermoelectric materials.