half-Heusler system (original) (raw)

Half Heusler alloys, MNiSn (M= Zr, Hf, Ti) systems, have recently been studied for their potential as new thermoelectric materials." *, 32 They have shown both high thermopower (a) values (40-250 pVK) and reasonable values of electrical resistivity, p, (0.1-8 mR-cm). However, the thermal conductivity in these systems is high for a potential thermoelectric material, on the order of 4-10 W/m-K. In an effort to reduce the thermal conductivity through alloy scattering, Sb is substituted on the Sn site with compositions TiNiSnl.xSbx where x = 0 to 0.1. With this substitution, the thermopower is only slightly reduced while the resistivity is reduced by approximately one order of magnitude resulting in a marked improvement in the power factor (a2T/p). Thermopower, resistivity, and thermal conductivity have been measured on a series of Sb doped TiNiSn samples from 10K < T < 300K. Heat capacity and Hall measurements on these same samples are measured from 2K to 350K and will be discussed. A room temperature power factor in this system has been calculated to be as high as 1.4 W/m-K, making these materials interesting for potential thermoelectric applications.