Enhanced thermoelectric performance of half-Heusler compound HfIrAs via pressure-induced strain

Zero-bandgap half-Heusler compound HfIrAs, belonging to the cubic XYZ-type structure with space group F43m, undergoes topological phase transitions under pressure-induced strain, potentially enhancing its electronic and thermoelectric (TE) properties. In this work, the TE performance of HfIrAs has been systematically investigated under various compressive strain using first-principles calculations. Under a compressive strain of -2%, HfIrAs undergo a topological phase transition from a topological semimetal to a conventional semiconductor, accompanied by an increase in the band gap to 0.14 eV. The application of compressive strain significantly enhances the Seebeck coefficient, resulting in a high power factor. Furthermore, due to the presence of three heavy elements in HfIrAs, strong phonon anharmonicity leads to relatively low lattice thermal conductivity. Consequently, the optimal ZT value for p-type HfIrAs at strain levels of Δa/a = 0%, -2%, -4%, -6% are 0.81, 1.50, 1.87, and 1.34, respectively-surpassing those of many traditional half-Heusler materials. These findings indicate that applying compressive strain to the half-Heusler compound HfIrAs represents a promising approach for enhancing thermoelectric performance.