Thermoelectric properties of a high entropy half-Heusler alloy processed by a fast powder metallurgy route

A half-Heusler (HH) type high entropy alloy (HEA) Ti 2 NiCoSnSb has been synthesized by a fast powder metallurgy route for the first time. Mechanical alloying (MA) by wet milling produced a powder with a minor fraction of the HH phase. The dry milling route resulted in the desired single-phase HH material. Consolidation of the nanocrystalline mechanically alloyed (MA) powder by spark plasma sintering (SPS) resulted in a majority HH phase. Interestingly, the nanocrystalline alloy exhibited simultaneous enhancement in the Seebeck coefficient and electrical conductivity, with a maximum ZT of 0.13 at 973 K observed for the dry milled alloy. The band structure obtained by density functional theory (DFT) was in good agreement with the ultraviolet-visible-near infrared (UV-Vis-NIR) absorption spectroscopy results. The DFT calculations and microstructural analysis suggest that phase separation strongly influenced the thermoelectric properties. The band structure calculations provided a good rationale for the phase evolution and thermoelectric properties. • High entropy half-Heusler alloy was synthesized by mechanical alloying. • Milling was done under Toluene (wet MA) and under Argon (dry MA). • The dry MA alloy exhibited higher figure of merit than reported arc melted alloys. • The electronic band structure was obtained by first principles calculations • It was found to be in good agreement with UV-Vis-NIR spectroscopy results.