@article{Xing2026, 
author = {Congcong Xing and Na Liu and Yangtao Zhou and Yilai Jiao and Xiang Wang and Kaiyang Xia and Huiping Hu and Aziz Genç and Yu Liu and Xiaolei Fan and Qingyue Wang and Yu Zhang and Khak Ho Lim and Bed Poudel},
title = {Grain-boundary modulation doping for high-power-density thermoelectric generation in ZrNiSn composites},
year = {2026},
journal = {Nano Research},
keywords = {half-Heusler, modulation doping, interface engineering, thermoelectric devices, cost-effective},
url = {https://www.sciopen.com/article/10.26599/NR.2026.94909004},
doi = {10.26599/NR.2026.94909004},
abstract = {ZrNiSn-based half-Heusler compounds are promising thermoelectric materials for mid-to-high temperature power generation, but their widespread application is hindered by the costly reliance on hafnium for performance optimization. Herein, we present a cost-effective, Hf-free strategy that simultaneously enhances the power factor and figure of merit zT in n-type ZrNiSn via grain-boundary-engineered modulation doping. Metallic tungsten (W) nanoparticles are introduced as a secondary phase, where they spontaneously segregate to grain boundaries during consolidation. This microstructure creates a network of internal heterojunctions that perform two synergistic functions: charge injection from the low-work-function W elevates electrical conductivity, while interfacial energy-filtering barriers enhance the Seebeck coefficient. Consequently, the optimized composite achieves a peak power factor of 44 μW cm-1 K-2 and a zT of 0.76 at 910 K. Beyond intrinsic transport improvements, the practical viability of this material system is validated at the device level. When integrated into a thermoelectric unicouple, the material delivers an exceptional power density of 2.1 W cm-2 and a conversion efficiency of 5.2% at a temperature difference of 307 K. Crucially, this approach eliminates expensive Hf, reducing material costs by over 95%. This work establishes grain‑boundary modulation doping as a cost‑effective route to enhance the power factor and zT of Hf‑free ZrNiSn, offering a pragmatic balance between performance and economic viability for mid‑temperature waste‑heat recovery.}
}