Effect of Ta substitution on the electronic structure of Heusler-type Fe2VAl-based alloy

Abstract

The electronic structures of Heusler-type Fe2V1−xTaxAl and Fe2VAl1−xTax 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 Fe2VAl 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 Fe2V1-xTaxAl alloy, but the degraded n-type thermoelectric performance in Fe2VAl1−xTax alloy. Ta substitution is a promising way to further improve the thermoelectric properties of p-type Heusler-type Fe2VAl-based alloy because of not only an increasing power factor but also decreasing thermal conductivity.