Influence of self-substitution on the thermoelectric Fe2VAl Heusler alloy

Improved Power Factor in Self-Substituted Fe2VAl Thermoelectric Thin Films Prepared by Co-sputtering

“…It corresponds to twice the maximum power factor obtained at 350 K by Mikami et al in Ti-substituted Fe 2 VAl thin films and at 300 K by Kudo et al in Fe 2–x V 1+x Al films grown by the MBE technique . It should be mentioned that our results are close to the highest values obtained in Fe 2 VAl-based alloys in the bulk state with P F = 7.6 mW/K 2 m recently obtained at 300 K in a 1653 K-quenched stoichiometric Fe 2 VAl sample or P F = 6.7 mW/K 2 m reported in bulk n-type Fe 1.98 V 1.02 Al 0.9 Si 0.1 at 300 K and Fe 2 V 1.03 Al 0.97 at 250 K.…”

“…The lattice parameter increases linearly when moving away from the ratio V/Al = 1 and varies from 5.745 to 5.775 Å. This variation of the lattice parameter has already been reported in the literature 3,4,24,25 but is not explained by the atomic radii differences between vanadium (135 pm) and aluminum (125 pm) nor by the valence electron concentration. Based on DFT calculations and a Bader analysis, Diack-Rasselio et al recently demonstrated that Fe 2 VAl could be seen as a "charge transfer" compound (Fe 2 1.3 − V 0.8+ Al 1.8+ ) where such unusual lattice parameter variation occurring with the V/Al ratio change in the Fe 2 V 1+x Al 1−x series could be due to these interatomic charge transfer variations.…”

“…Based on DFT calculations and a Bader analysis, Diack-Rasselio et al recently demonstrated that Fe 2 VAl could be seen as a "charge transfer" compound (Fe 2 1.3 − V 0.8+ Al 1.8+ ) where such unusual lattice parameter variation occurring with the V/Al ratio change in the Fe 2 V 1+x Al 1−x series could be due to these interatomic charge transfer variations. 4…”

“…Fe 2 VAl alloy shows high S when the valence electron concentration (VEC) per atom is close to 6. 1,2 Miyazaki et al 3 and Diack-Rasselio et al 4 also observed that the thermoelectric power factor (P F = S 2 /ρ) is enhanced in ntype off-stoichiometric Fe 2−x V 1+x Al bulk alloys (x ∼ 0.03− 0.05). The highest power factors P F = 7.6 5 and 6.7 mW/K 2 m 6 at room temperature are larger for such alloys than that for Bi 2 Te 3 materials.…”

“…The figure of merit is expressed by ZT = ( S 2 /ρλ )­T , where S , ρ, λ, and T are, respectively, the Seebeck coefficient, electrical resistivity, thermal conductivity, and absolute temperature. Fe 2 VAl alloy shows high S when the valence electron concentration (VEC) per atom is close to 6. , Miyazaki et al and Diack-Rasselio et al also observed that the thermoelectric power factor ( P F = S 2 /ρ) is enhanced in n-type off-stoichiometric Fe 2– x V 1+ x Al bulk alloys ( x ∼ 0.03–0.05). The highest power factors P F = 7.6 and 6.7 mW/K 2 m at room temperature are larger for such alloys than that for Bi 2 Te 3 materials.…”