Excellent performance stability of Ba and In double-filled skutterudite thermoelectric materials

The microstructure and thermoelectric properties of Ba and In double-filled Ba0.3In0.2Co3.95Ni0.05Sb12 materials with a figure-of-merit (ZT) of 1.2 at 800 K were carefully investigated by periodic quenching from 723 K to room temperature. The quenching treatment caused enrichment of Ba and loss of Sb and Co on the grain boundaries but had no effect on In and Ni. The enhancement in |α| in the starting period is due to the reduction in σ induced by the secondary precipitates. The reductions in σ, κ and κE are attributed to the secondary precipitates. The increase in κL is assumed to be due to the separation of Ba filler from the Sb-icosahedron voids. A promising ZT value of ∼1.0 remained after quenching 2000 times. It is concluded that the double-filled skutterudite materials have excellent performance stability under periodically fluctuating environmental temperature.

► Periodically quenching was employed to investigate the performance stability of Ba and In double-filled skutterudite materials.
► We examine changes in microstructure and composition on the grain boundaries.
► Secondary precipitates decrease σ, κ, and κE and increase |α|.
► Separation of Ba from the Sb-icosahedron voids enables increase of κL.
► The double-filled skutterudite materials remain excellent thermoelectric performance under periodically fluctuating environmental temperature.