A study of the properties of ZrNiSb defective half-Heusler alloy for thermoelectric and spintronic applications

초록

The development of green, cost-effective thermoelectric (TE) materials is gaining traction in the drive for sustainable energy solutions. This study explores Fe and Co doping effects on the structure, composition, and multifunctional properties of the Zr1.05NiSb (ZNS) system, providing a rudimentary roadmap for its optimization in future TE and spintronic applications. ZNS, Zr1.05Ni0.97Co0.03Sb (CoZNS), and Zr1.05Ni0.97Fe0.03Sb (FeZNS) samples were synthesized via arc melting, cold pressing, annealing, and hot pressing, followed by comprehensive microstructural and property characterization. ZNS was confirmed to crystallize in an orthorhombic phase with a weak but notable sintering-direction-induced texture, producing anisotropic TE behavior favoring the in-plane direction. Although Co showed poorer solubility at the Ni site than Fe, it proved more effective in enhancing the PF and suppressing thermal conductivity, leading to a 65 % increase in zT for CoZNS relative to ZNS at 973 K. While the zT values remain modest, the observed potential for further improvement via forced texturing and stabilization of the zinc blende-like structure phase offers optimism for future enhancement. Additionally, magnetic measurements revealed soft ferromagnetism in ZNS, positioning it as a potential ferromagnetic semiconductor for spintronic applications. Finally, Vickers hardness measurements confirmed the superior mechanical robustness of ZNS compared to other TE material classes. Overall, this study highlights the promising multifunctional potential of the ZNS system and establishes a framework for future optimization efforts targeting both TE and spintronic functionalities.

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