Enhancing the Thermoelectric Performance of n-Type Mg3.2Sb1.5Bi0.5 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.