Stoichiometric and off-stoichiometric full Heusler 𝐅𝐞_2𝐕_1-𝐱𝐖_𝐱𝐀𝐥 thermoelectric systems

A series of full-Heusler alloys, Fe_2V_1-xW_xAl, 0 ≤ x ≤ 0.2, was prepared, characterized and relevant physical properties to account for the thermoelectric performance were studied in a wide temperature range. Additionally, off-stoichiometric samples with similar compositions have been included, and a 10 % improvement of the thermoelectric figure of merit was obtained. The V/W substitution causes i) a change of the main carrier type, from holes to electrons as evidenced from Seebeck and Hall measurements and ii) a substantial reduction of the lattice thermal conductivity due to a creation of lattice disorder by means of a distinct different mass and metallic radius upon the V/W substitution. Moreover ZT values above 0.2 have been obtained. A microscopic understanding of the experimental data observed is revealed from ab-initio calculations of the electronic and phononic structure.