Uncovering High Thermoelectric Figure of Merit in (Hf,Zr)NiSn Half-Heusler Alloys

摘要

Half-Heusler alloys (MgAgSb structure) are promising thermoelectricmaterials. RNiSn half-Heusler phases (R=Hf, Zr, Ti) are the most studied inview of their thermal stability. The highest dimensionless figure of merit (ZT)obtained is ~1 in the temperature range ~450-900oC, primarily achieved innanostructured alloys. Through proper annealing, ZT~1.2 has been obtained in aprevious ZT~1 n-type (Hf,Zr)NiSn phase without the nanostructure. There is anappreciable increase in the power factor, decrease in charge carrier density,and increase in carrier mobility. The findings are attributed to theimprovement of structural order. Present approach may be applied to optimizethe functional properties of Heusler-type alloys.