2008 Volume 49 Issue 8 Pages 1858-1862
We report on the effect of Co and Ti co-doping on the thermoelectric behavior of Fe2VAl based alloys. The doped alloys, (Fe2−xCox)(V1−yTiy)Al, with compositions x=0.01–0.07 and y=0.04–0.20 exhibit a p-type thermoelectric property when the total valence electron number is below 24. The co-doping of cobalt and titanium is believed to cause a substantial shift of the Fermi level from the center of the pseuodgap to a lower energy position. In particular, the alloy with x=0.03 and y=0.10 exhibits a p-type thermoelectric behavior with a large Seebeck coefficient of S=85 μV/K as well as a low electrical resistivity of ρ=2.3 μΩ m at 400 K, so that the power factor, P=S2⁄ρ, reaches 3.2×10−3 W/m K2. The power factor is larger than that of the Ti doped Fe2VAl alloy so far reported. The high power factor caused by the co-doping of Co and Ti might be due to a modification in the band structure on the valence band side around the Fermi level. The co-doping of Co and Ti is also effective in reducing the thermal conductivity, mainly due to phonon scattering.