Thermoelectric properties of directionally solidified half-Heusler compound NbCoSn alloys.

Single- and multiphase samples of the n-type half-Heusler NbCoSn were prepared by directional solidification using the optical floating zone melting method, and the thermoelectric properties of these samples were evaluated. NbCoSn has an excellent thermoelectric power which exceeds -250 μV K-1 at around 900 K and a relatively high carrier concentration, 4.82×1026 m-3. A metalliclike temperature dependence of the electrical resistivity indicates that NbCoSn is a degenerate semiconductor. NbCoSn also shows an excellent power factor, 2.5 mW m-1 K-2 at about 650 K, even without any tuning of the electrical properties which are susceptible to coexisting metallic phases. [ABSTRACT FROM AUTHOR]