Synthesis and thermoelectric properties of microstructural Heusler Fe2VAl alloy

A Fe2VAl sintered alloy with fine microstructure was synthesized to evaluate the effect of grain size on thermoelectric properties. Fine powder was first prepared by mechanical alloying. Secondly, to suppress grain growth during heat treatment, the powder was sintered rapidly using pulse-current sintering. Bulk material consisting of 200–300 nm grains was obtained. Compared to the arc-melted sample consisting of 100–400 μm grains, the thermal conductivity was reduced by phonon scattering at grain boundaries. The microstructural modification had little effect on the magnitude of the Seebeck coefficient. The reduction of electrical conductivity by the increase of the number of grain boundaries was less than that of thermal conductivity. Therefore, the thermoelectric figure of merit was improved.