Enhancing the Thermoelectric Performance of n-Type Mg 3.2 Sb 1.5 Bi 0.5 by Reducing Lattice Thermal Conductivity through the Incorporation of Chlorine-Containing Compounds.

Mg ₃ Sb ₂ -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, LaCl ₃ and CeCl ₃ , into Mg _3.2 Sb _1.5 Bi _0.5 under the guidance of first-principles calculations. The Mg _3.2 Sb _1.5 Bi _0.5 + 0.03CeCl ₃ sample reached a maximum ZT value of approximately 1.6 at 723 K. The calculations indicate that two n-type dopants, LaCl ₃ and CeCl ₃ , can adequately improve the band structure of Mg ₃ Sb ₂ , 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 _3.2 Sb _1.5 Bi _0.5 + 0.03CeCl ₃ sample achieved an exceptionally low κ _L of 0.3 W m ^-1 K ^-1 at 723 K, thereby validating the effectiveness of LaCl ₃ and CeCl ₃ doping. This work provides valuable insights into achieving thermoelectric decoupling in Mg ₃ Sb ₂ -based thermoelectric materials.