ICT2014 Abstracts

ZrNiSn-based alloys have recently attracted tremendous interests because they are promising high-efficiency thermoelectric materials containing low-cost elements. ZrNiSn thermoelectric thin films have many potential applications in portable devices, power electronics, and wireless sensor networks, and thus it is urgent to develop thin-film materials with high thermoelectric figure of merit ZT. However, the typical ZT of ZrNiSn-based alloys is around 1.0, which is limited by the relatively high thermal conductivity of these alloys. In this paper, n-type ZrNiSn thin films with a thickness of 60-400 nm were deposited by radiofrequency magnetron sputtering. The microstructure of ZrNiSn thin films was examined by X-ray diffraction and high-resolution transmission electron microscopy, and an amorphous microstructure was observed for all the films. The thermal conductivity of the amorphous films was measured by thermoreflectance technique and the values were 1.4-2.2 W/mK, which was very low compared with the data reported in the literature and was likely due to the amorphous microstructure. The effects of the film composition on the Seebeck coefficient and electrical conductivity were investigated. The Seebeck coefficient decreased and the electrical conductivity increased when the Zr content increased and the Ni content decreased. With an optimal composition, the largest Seebeck coefficient was -114.3 μVK^-1 and the largest power factor was 2.77 mWK^-2m^-1 at 473 K. The low thermal conductivity and high power factor indicate that amorphous Zr-Ni-Sn thin film could be a very promising thermoelectric material.