High-entropy-driven half-Heusler alloys boost thermoelectric performance

High-entropy engineering effectively reduces lattice thermal conductivity (κ_L) in thermoelectric (TE) materials; however, the chemical complexity of multiple elements in high-entropy materials often leads to phase segregation, limiting their electrical transport properties and overall TE performance. Herein, we report a p-type high-entropy stabilized single-phase half-Heusler alloy, MFeSb, specifically designed to enhance configurational entropy by introducing multiple element species on a single atomic site. This material exhibited low κ_L due to phonon group velocity reduction and strong phonon scattering from lattice strain generated through distorted lattices while maintaining a high power factor. The material demonstrated a record high figure of merit (zT) of 1.5 at 1,060 K, with an average zT of ∼0.92 over 300–1,060 K. Furthermore, superior conversion efficiencies of 15% and 14% for a single-leg and a unicouple module at a temperature difference of ΔT ∼671 K were achieved. Our findings provide a new avenue for enhancing TE material performance through high-entropy engineering.