Abstract
A good thermoelectric material requires high Seebeck coefficient (S) and electrical conductivity (σ) but low thermal conductivity (κ), which are not common found in traditional metallic alloys. As compound with traditional metallic alloy, high entropy alloy of multi constituent element is a newly developed metallurgical concept. A variety of different forms of the multi-element alloys have been demonstrated to possess superior mechanical and chemical properties. However, the electrical and thermoelectric properties of the multi-element alloys have not been thoroughly explored yet. In this study, multi-element alloys were prepared by arc-melting and thermal annealing. Their thermoelectric properties were characterized after appropriate sample preparation. We find two multi-element alloy systems based on half-Heusler structure：ZrTiSnSiNi2 and ZrTiSnGeNi2. The thermoelectric figure of merits (ZT, Z= S2/(ρ×κ)) of these multi-element alloys were equal to be 0.02 and 0.045, respectively, at room temperature. These multi-element alloys showed 3 times increase in power factor (S2/ρ) in the middle temperature range (250℃ to 300℃). By adding Nb element into the alloy forming Zr0.9Ti0.9Nb0.2SnSiNi2, the thermoelectric figure of merit was found to be 0.078 at room temperature. The multi- element alloys were identified to be a composite material containing semiconductor-like phase and metallic-like phase by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).