High entropy engineering p-type half Heusler with high thermoelectric performance

Thermoelectric generators offer eco-friendly energy conversion technology to directly convert heat into electricity through the Seebeck effect. High-entropy design of thermoelectric materials can effectively reduce the lattice thermal conductivity, however, the chemical complexity of multiple elements in high-entropy materials often leads to phase segregation which hamper their electrical transport properties and thus, thermoelectric performance is limited. We demonstrated a p-type high entropy half-Heusler alloy which exhibits low thermal conductivity due to phonon group velocity reduction and strong phonon scattering from lattice strain generated through distorted lattices while maintaining a high power-factor through single-phase stabilization. The material demonstrated an outstanding figure-of-merit (zT) of 1.5 at 1060 K, with an average zT of ~0.92 over 300-1060 K. Further, we observed a superior conversion efficiency of 15 % for single-leg and 14% for a unicouple module at a large temperature difference of ΔT ~ 671 K. Our results provide a new approach for enhancing TE materials performance through high-entropy design.