Chemical pressure effect on the transport and electronic band structure of Fe₂V_1-xNb_xAl

We report the effects of partial substitution of Nb onto the V sites of Fe2 VAl by measuring the electrical resistivity, Seebeck coefficient, and thermal conductivity as a function of temperature. It is found that the Nb substitution effectively produces a negative chemical pressure in the system. As a result, the Nb-substituted materials show enhanced semiconductinglike behavior in their electrical resistivity. In addition, the Seebeck coefficient changes sign from positive to negative while replacing V with Nb. These phenomena have been associated with the change of the band features, mainly due to the decrease in the number of the hole carriers. To identify this scenario, we performed ab initio calculations to investigate the electronic band structures of Fe2 V1-x Nbx Al, focusing on the band variation around the Fermi level. Theoretical results indicate a significant reduction in the hole pockets through Nb substitution, which is consistent with experimental observations.