High-temperature thermoelectric properties of half-Heusler phases Er${}_{1-x}$Ho${}_x$NiSb

Abstract

Polycrystalline samples of Er${}_{1-x}$Ho${}_x$NiSb ($x$ = 0, 0.2, 0.3, 0.5, 0.7, 0.8, 1) were characterized by means of x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and optical metallography. The results proved the formation of half-Heusler alloys in the entire composition range. Their electrical transport properties (resistivity, thermoelectric power) were studied in the temperature interval 350-1000 K. The measured electrical resistivity spanned between 5 and 25 $\mu \Omega$m. The maximum thermopower of 50-65 $\mu$V/K was observed at temperatures 500-650 K. Replacing Ho for Er resulted in a non-monotonous variation of the thermoelectric power factor ($PF=S^2/\rho$). The largest $PF$ of 4.6 $\mu$WcmK${}^{-2}$ was found at 660 K for Er${}_{0.5}$Ho${}_{0.5}$NiSb. This value is distinctly larger than PF determined for the terminal phases ErNiSb and HoNiSb.

5 pages, 2 figures, accepted for publication in Materials Today: Proceedings