Microstructure and thermoelectric properties of pulse-current sintered Fe2 VAl alloy

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