Thermoelectric properties of Heusler-type off-stoichiometric Fe₂V_1+<i>x</i>Al_1−<i>x</i>alloys

Abstract

We report the thermoelectric properties of Heusler-type off-stoichiometric Fe2V1+xAl1�x alloys. Due to the off-stoichiometric effect, which is the substitution of V/Al atoms with Al/V atoms, semiconductor-like electric resistivity behavior in Fe2VAl is changed to metallic behavior in Fe2V1+xAl1�x alloys and both positive and negative absolute Seebeck coefficients are drastically increased. The maximum thermoelectric power factor of Fe2V1+xAl1�x alloys is 4.3 × 10 �3 (x = �0.03: p-type) and 6.8 × 10 �3 WmK �2 (x = 0.05: n-type) with a peak temperature in the range 300–600 K, exceeding the values of previously reported Fe-based Heusler alloys as well as those of available thermoelectric materials such as Bi-Te semiconductors. Based on x-ray diffraction and photoemission spectroscopy results, it is thought that the maintenance of the Heusler-type (L21) crystal structure and the modification of the electronic structure due to the offstoichiometry could explain the large thermoelectric power factor and high peak temperature in Fe2V1+xAl1�x alloys.