Effect of Ta substitution on the electronic structure of Heusler-type Fe_2VAl-based alloy

摘要

The electronic structures of Heusler-type Fe_2V_(1-x)Ta_xAl and Fe_2VAl_(1-x)Ta_x alloys were investigated by electronic band structure calculations and synchrotron radiation photoelectron spectroscopy measurements to elucidate the change in the electronic structure due to the Ta substitution. While V and Ta atoms have the same electron configuration, the hybridization between Fe 3 d and V 3 d states gradually decreases in Ta-substituted Fe_2VAl alloy and the valence band is only shifted to lower binding energy side. This change of the electronic structure is hypothesized to be the underlying reason behind the improved p-type thermoelectric performance in Fe_2V_(1-x)Ta_xAl alloy, but the degraded n-type thermoelectric performance in Fe_2VAl_(1-x)Ta_x alloy. Ta substitution is a promising way to further improve the thermoelectric properties of p-type Heusler-type Fe_2 VAl-based alloy because of not only an increasing power factor but also decreasing thermal conductivity.