Effect of Hf Concentration on Thermoelectric Properties of Nanostructured N-Type Half-Heusler Materials HfxZr1-xNiSn0.99Sb0.01

Half-Heusler n-type thermoelectric materials MNiSn (M = Hf, Zr) have been shown to exhibit peak thermoelectric dimensionless figure-of-merit (ZT) of approximate to 1.0 at 600-700 degrees C with a composition of Hf0.75Zr0.25NiSn0.99Sb0.01. This work demonstrates that it is possible to achieve the same ZT by reducing the concentration of the most expensive component Hf to one third of the previously reported best composition, i.e., Hf0.25Zr0.75NiSn0.99Sb0.01, which corresponds to an overall 50% reduction on material cost. The samples are prepared by ball milling the arc melted ingot and hot pressing the finely ground powders. The reduction of Hf concentration is crucial for such materials to be used in large-scale waste heat recovery.