Thermoelectric properties of Cu-Doped Heusler compound Fe2-xCuxVAl

We investigated the effects on thermoelectric properties of Cu doping in Fe2-xCuxVAl at Fe site of full-Heusler type compound. It is found that the Cu doping for Fe sites causes a significant increase in the absolute value of Seebeck coefficient |S| and a decrease in thermal conductivity. The Seebeck coefficient (S)=-148 mu V/K and the Power factor (PF)=4.0 mWK(-2)m(-1) have been observed for Fe1.9Cu0.1VAl (x=0.1) at 300 K. To further improve it, we fixed the Cu doping level at x=0.1 in Fe2-xCuxVAl and co-doped the material with Si at Al site, namely, Fe1.9Cu0.1VAl1-ySiy. The thermoelectric properties have been improved by Si doping to a certain limit. We observed a decrease in electrical resistivity and lattice thermal conductivity by Si doping for Al. The maximum power factor of 4.5 mWK(-2)m(-1) has been achieved for Fe1.9Cu0.1Al0.9Si0.1 at 350 K. More precisely, the thermoelectric performance has been improved with co-doping of Cu for Fe sites and Si for Al sites. The largest ZT value is 0.13 for Fe1.9Cu0.1VAl1-ySiy (y=0.15). Magnetic susceptibility suggests that all the measured compounds are showing paramagnetic behavior. The magnetic character is the most pronounced in Fe1.9Cu0.1VAl among the materials investigated, pointing to a possible correlation between the magnetic character due to electronic correlation and the larger Seebeck coefficient in this sample.