Effects of partial substitution of Co by Ni on the electrical transport properties of TiCoSb-based half-Heusler compounds

The effects of partial substitution of Co by Ni on the electrical transport properties of TiCoSb-based half-Heuster compounds at high temperature were studied. Samples were prepared by solid-state reaction method. Then, a spark plasma sintering (SPS) technique was used to consolidate the obtained powers. The densities of the compounds were more than 95% of the theoretical ones. The absolute value of Seebeck coefficient of TiCoSb was high and the maximum value was about 300 muV/K, and the maximum value of power factor was 4.8 muW/cm K-2 at 650K. Doping Ni on Co site, it significantly enhances the electrical conductivity, and the maximum value is 1 X 10(5) Omega(-1) m(-1) for TiCo0.9Ni0.1Sb compound, and it slightly decreases the absolute values of Seebeck coefficient. The power factors of these compounds are greatly increased with doping of Ni on Co sites, and the maximum values reach 16muW/cm K-2 at 800K for TiCo0.95Ni0.05Sb compound, which are about three times increased compared with TiCoSb compound.