Investigation of melt-spinning speed on the property of Yb_0.2Ba_0.1Al_0.1Ga_0.1In_0.1La_0.05Eu_0.05Co_3.75Fe_0.25Sb₁₂ skutterudites

Skutterudites are the most promising thermoelectric materials for the medium-temperature thermoelectric generation. Yb_0.2Ba_0.1Al_0.1Ga_0.1In_0.1La_0.05Eu_0.05Co_3.75Fe_0.25Sb₁₂ skutterudites have been developed recently to enhance the figure of merit. However, the effects of the melt-spinning speeds on the figure of merit have not been investigated, thus far. In the present study, we find that the melt-spinning speed significantly affects the microstructure morphologies of the skutterudites. As the grain size was decreased, the atomic diffusion rate speeded up and the formation of the secondary phases were inhibited, leading to a reduction in the thermal conductivity and an improvement of the thermoelectric properties. Interestingly, when the melt-spinning speed increased from 25 m/s to 60 m/s, the average grain size decreased. The mass fraction of the skutterudite phase was improved from 88.3% to 93.1%. Overall, the ZT value reached an optimal value of 1.07 at 773 K.