Thermoelectric properties of Sb-doping in the TiNiSn/sub 1-x/Sb/sub x/ half-Heusler system

Abstract

Half Heusler alloys, MNiSn (M=Zr, Hf, Ti) systems, have recently been studied for their potential as new thermoelectric materials. They have shown both high thermopower (/spl alpha/) values (40-250 /spl mu/V/K) and reasonable values of electrical resistivity, /spl rho/ (0.1-8 m/spl Omega/-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 TiNiSn/sub 1-x/Sb/sub x/ 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 marked improvement in the power factor (/spl alpha//sup 2/T//spl rho/). Thermopower, resistivity, and thermal conductivity have been measured on a series of Sb doped TiNiSn samples from 10 K<T<300 K. Heat capacity and Hall measurements on these same samples are measured from 2 K to 350 K 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.