Thermoelectric properties of n-type half-Heusler compounds (Hf0.25Zr0.75)1–Nb NiSn

Abstract A series of Nb doped (Hf 0.25 Zr 0.75 ) 1– x Nb x NiSn ( x = 0–0.03) samples were synthesized and studied by arc-melting the elements to first form ingots, then ball-milling the ingots to obtain fine powders, and finally hot-pressing the fine powder to form bulk samples. Instead of the conventional Sb doping on the Sn site of the n-type half-Heusler, it was found that Nb is also an effective dopant. When the carrier concentration is optimized at 2.2% Nb, a power factor of ∼47 μW cm −1 K −2 is achieved at and above 600 °C, and a peak ZT ∼0.9 is achieved at 700 °C with Nb doping from 1.8 at% to 2.2 at%. An output power density of ∼22 W cm −2 and a leg efficiency of ∼12% are calculated for the Nb doped samples.