High-performance ZrNiSn-based half-Heusler thermoelectrics with hierarchical architectures enabled by reactive sintering
- Xin Ai
- Yu Wu
- Haiyan Lyu
- Lars Giebeler
- Wenhua Xue
- Andrei Sotnikov
- Yumei Wang
- Qihao Zhang
- Denys Makarov
- Yuan Yu
- G. Jeffrey Snyder
- Kornelius Nielsch
- Ran He
2025-07-15
Half-Heusler compounds are promising thermoelectric materials for high-temperature applications, yet their performance is limited by high lattice thermal conductivity. Here, we present an alternative approach to synthesize ZrNiSn-based half-Heusler compounds with hierarchical architectures across multiple length scales. By utilizing short-duration mechanical alloying to produce nonequilibrium precursors, followed by reactive sintering, we enable precise control over phase composition and microstructural features. This approach results in multi-scale architectures comprising interstitial defects, grain boundaries, nanoprecipitates, and pores, enabling strong phonon scattering. The optimized Zr 0.75 Hf 0.25 NiSn 0.99 Sb 0.01 alloy exhibits a lattice thermal conductivity as low as 1.9 W m −1 K −1 and a high power factor of 50 µW cm −1 K −2 , yielding an impressive dimensionless figure of merit ( zT ) of 1.33 at 873 K. This performance surpasses that of ZrNiSn-based compounds synthesized via conventional methods such as arc melting and solid-state reaction. Our method, distinguished from conventional melting synthesis approaches through its simplicity, cost-effectiveness, and scalability, provides a versatile framework for achieving efficient hierarchical phonon scattering while preserving high carrier mobility in half-Heusler compounds and highlights the potential of reactive sintering for advancing thermoelectric materials.