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

The microstructure and thermoelectric properties of Ba and In double-filled Ba(0.3)In(0.2)Co(3.95)Ni(0.05)Sb(12) 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 vertical bar alpha vertical bar in the starting period is due to the reduction in sigma induced by the secondary precipitates. The reductions in sigma, kappa and kappa(E) are attributed to the secondary precipitates. The increase in kappa(L) is assumed to be due to the separation of Ba filler from the Sb-icosahedron voids. A promising ZT value of similar to 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. Crown Copyright (C) 2011 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.