Excellent thermoelectric performance of Full-Heusler Fe2NbAl alloy induced by strong anharmonic rattling and high band degeneracy

Abstract Full-Heusler alloys with earth-abundant elements exhibit high mechanical strength and favorable electrical transport behavior, but their high intrinsic lattice thermal conductivity limits potential thermoelectric application. Here, the thermoelectric transport properties of Fe-based Full-Heusler Fe2MAl (M = V, Nb, Ta) alloys are comprehensively investigated utilizing density functional theory. The results suggest that Fe2NbAl exhibits exceptionally low lattice thermal conductivity due to the strong anharmonic scattering induced by weakly bound Fe atoms and the low phonon velocities caused by heavy Nb atoms. Meanwhile, the high band degeneracy and large electrical conductivity lead to a maximum p-type power factor of 255.6 μW·K-2·cm-1 at 900 K. The combination of low lattice thermal conductivity and favorable electrical transport properties results in a maximum p-type dimensionless figure of merit of 1.7. Our work indicates Fe2NbAl, as a low-cost, environmentally friendly compound, is a potential high-performance p-type thermoelectric material.