Controlled Moderate Interfacial Reaction Facilitates High‐Strength Low‐Resistivity Barrier Layer for Half‐Heusler Thermoelectrics

ABSTRACT Half‐Heusler compounds serve as a compelling solution for medium‐ and high‐temperature waste heat recovery owing to their exceptional thermal stability and superior thermoelectric properties. However, the practical application of their corresponding thermoelectric devices has long been constrained by thermal stress‐induced cracking, particularly at the interface between electrodes and thermoelectric material. Here, we engineer an atomically bonded interface via a well‐controlled interfacial reaction and propose a novel barrier layer design paradigm based on the thermodynamic parameters. By screening thermodynamic parameters, we have successfully fabricated a ZrNiSn/Co ₂₅ Fe ₅₀ Ni ₂₅ thermoelectric junction exhibiting high bonding strength (77.0 MPa), low contact resistivity (1.16 µΩ·cm ² ), and excellent thermal stability at 923 K. The corresponding single‐leg device achieves a power density exceeding 6.78 W/cm ² and a conversion efficiency of over 6.13%. After annealing at 923 K for 168 h, the junction maintains a bonding strength of 60.0 MPa and a contact resistivity less than 5 µΩ·cm ² . These results underscore the pivotal role of controlled interfacial reactions in advancing medium‐ and high‐temperature half‐Heusler thermoelectric devices, providing a solid foundation for waste heat recovery applications.