Effect of Bi addition on microstructure and thermoelectric properties of Heusler Fe2VAl-sintered alloy

Using pulse-current sintering, Fe2VAl0.9Si0.1/Bi composites incorporating different amounts of Bi were synthesized, yielding composites consisting of micrometer-sized Bi grains and nanometer-sized Fe2VAl particles. Liquid-phase Bi facilitated densification of the composite at low sintering temperatures, at which the grain growth of Fe2VAl phase progressed slowly. Enhanced density attributable to the presence of liquid-phase Bi at the sintering process contributed to the reduction of electrical resistivity. Grain growth was suppressed by low-temperature sintering. Then nanometer-sized microstructural Fe2VAl0.9Si0.1 was obtained, resulting in the reduction of thermal conductivity. The Seebeck coefficient was less affected by the modification of microstructure. Therefore, the thermoelectric figure of merit was improved.