非化学量論組成Fe₂V_1−xAl_1+x焼結体の熱電特性と熱電発電モジュール設計

抄録

  Heusler-type Fe₂V_1−xAl_1+x alloys having off-stoichiometric composition were fabricated by the powder metallurgical process using mechanical alloying and pulsed current sintering. Depending on the valence electron concentration, a positive (x>0) or negative (x<0) Seebeck coefficient was obtained resulting from a Fermi level shift. The electrical resistivity was reduced via the carrier doping effect, resulting in an increase of the thermoelectric power factor of 2.8 mW/mK² for p-type and 5.0 mW/mK² for n-type. In addition, the thermal conductivity was reduced by phonon scattering at crystal lattice defects induced by the off-stoichiometry. Consequently the thermoelectric figure-of-merit, ZT, was enhanced and reached 0.07 for p-type and 0.18 for n-type at around 500 K. Using the measured thermoelectric properties, the power generation ability was estimated. Owing to the enhancement of thermoelectric performance especially at high temperatures, power generation efficiency reaches 2% at temperature difference between 300 K and 773 K.