Theoretical Investigations of the Thermoelectric Properties of Fe2NbGa1−x Al x (x = 0, 0.25, 0.5) Alloys

Abstract

Ab initio calculations are performed to investigate the electronic structure of Fe2NbGa1−x Al x (x = 0, 0.25, 0.5) alloys. The structures are found to exhibit a semiconducting behavior with an indirect band gap of 0.08 eV along the Γ–X symmetry line for Fe2NbGa full-Heusler alloy and direct band gaps of 0.16 eV and 0.23 eV at the Γ-point for the nonstoichiometric Fe2NbGa0.75Al0.25 and Fe2NbGa0.5Al0.5 alloys, respectively. The stoichiometric Fe2NbGa alloy is found to exhibit the highest Seebeck coefficient (S) values for the n-type doping, whereas less values are obtained for the p-type. The nonstoichiometric Fe2NbGa0.5Al0.5 alloy also exhibits both n- and p-type dopings at both sides of the Fermi level and shows higher S values than the Fe2NbGa alloy. However, Fe2Nb0.75Al0.25 alloy exhibits only n-type doping near the Fermi level with S values close to those of the n-type Fe2NbGa alloy at 300 K.