Microstructure and thermoelectric properties of doped p-type CoSb3 under TGZM effect

Abstract

The Co-96.9wt% Sb hypoeutectic alloy doped by 0.12wt% YbFe was solidified in a Bridgman-type furnace based on temperature gradient zone melting (TGZM) effect. A mushy zone was observed between the complete liquid zone and the solid zone at different thermal stabilization time ranging from 15min to 40h. The mushy-zone solidified microstructures of the alloy only consist of CoSb3 and Sb phase. After 40h thermal stabilization time, the volume fraction of CoSb3 in the mushy zone increases significantly up to 99.6% close to the solid-liquid interface. The hardness and fracture toughness of doped CoSb3 can reach 7.01±0.69GPa and 0.78±0.08MPa·m1/2, respectively. Meanwhile, the thermoelectric properties of the alloy were measured ranging from room temperature (RT) to 850K. The Seebeck coefficient of the specimen prepared by TGZM effect after 40h could reach 155μV/K and the ZT value is 0.47 at 660K, showing that it is feasible to prepare CoSb3 bulk material via TGZM effect. As a simple and one-step solidification method, the TGZM technique could be applied in the preparation of skutterudite compounds.