Thermoelectric properties of p-type Heusler compounds (Fe2-xCox)(V1-yTiy)Al

We report on the effect of Co and Ti co-doping on the thermoelectric behavior of Fe,VAl 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 mu V/K as well as a low electrical resistivity of rho = 2.3 mu Omega m at 400 K, so that the power factor. P = S-2/p, reaches 3.2 x 10(-3) W/m K-2. 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.