TaFeSb-Based Half-Heusler Thermoelectrics with High zT > 1 through the Alloying Effect

Ternary half-Heusler (HH) alloys have been extensively studied because of their various intriguing functionalities, such as thermoelectric (TE), magnetic, superconductive, and topological properties. Recently, TaFeSb-based HH alloys have been determined to be potential high-temperature TE materials with a dimensionless TE figure of merit zT > 1 for the application of power generation. Herein, we simultaneously optimize the electrical and thermal properties of TaFeSb-based materials through the alloying effect of elemental substitution, leading to a maximum zT of 1.20 at 1025 K. Furthermore, the co-alloying effect not only optimizes the electrical transport performances but also significantly diminishes the lattice thermal conductivity. In comparison with that of pristine TaFeSb, a remarkable reduction of 65% is achieved at room temperature for the (Ta 0.8 V 0.2 ) 0.84 Ti 0.16 FeSb sample, which can be correlated to the mass and strain field fluctuations. Our work highlights the significance of the alloying effect as a design factor and demonstrates the advantages of p-type TaFeSb-based HHs due to their excellent TE performance.