Thermoelectric Properties of Nearly Single-Phase Half-Heusler NbCoSn Alloys and Importance of Microstructures for Improving Performance

摘要

In order to evaluate the thermoelectric properties of n-type half-Heusler compound NbCoSn, single-phase NbCoSn alloy was prepared using directional solidification based on the phase diagram information of the Nb-Co-Sn ternary system which was investigated in this work. The isotherm at 1273 K and the reaction scheme together with the projection of liquidus surface were determined. Thermoelectric properties of NbCoSn based alloys were evaluated by Seebeck coefficient, electrical resistivity and power factor, which were measured in a temperature range from 300 K to 1073 K. NbCoSn has excellent Seebeck coefficient exceeding -250 μV/K at around 900 K and shows the metal-like temperature dependence of electrical resistivity.