Enthalpy‐Driven Microstructure Reconfiguration for High‐Performance Half‐Heusler Alloys

ABSTRACT Half‐Heusler (HH) alloys have attracted extensive attention due to their exceptional mechanical properties and high‐temperature thermal stability. However, simultaneously optimizing their power factor ( PF ) and figure of merit ( zT ) remains challenging due to the conflict of tuning electron and phonon behavior. Here, a microstructure reconfiguration strategy based on tuning the enthalpy‐dominated atomic chemical affinity is proposed to decouple electrical and thermal transport properties. The introduction of Yb into Hf‐doped ZrNiSn alloys weakens the d ‐ d orbital hybridization, which reduces the negative mixing enthalpy and diminishes the atomic affinity, thereby suppressing the formation of Hf precipitates. The Hf precipitates are transformed into superstructures, which promote the electron mobility with a 55% increase by eliminating the electron scattering around discontinuous lattices and introducing strong phonon scattering to suppres the thermal conductivity. Therefore, a “double‐high” Zr 0.66 Hf 0.3 Yb 0.04 NiSn 0.98 Sb 0.02 material with a high PF of 58 µW·cm − 1 ·K − 2 and a peak zT of 1.32 at 950 K was obtained, contributing to a high experimental conversion efficiency of 10.2% in the fabricated module, which is among the highest values in HH alloys. This work highlights enthalpy‐dominated microstructure reconfiguration as an effective pathway for developing high performance thermoelectric power generations.