Partially filled skutterudite compounds have been considered as potential candidates for highly efficient thermoelectric materials. The unfilled skutterudite compound MX3 (M = Co, Rh and Ir, X = P, As and Sb), which is a cage-like material, shows excellent thermoelectric (TE) performance. However, the compounds have a disadvantage of high lattice thermal conductivity κL compared to conventional TE materials. The vacancy inside the cage of MX3 (M4X12) can accept a relatively small guest ion R. The vacancy can be partially occupied by R (RxM4X12), such as alkaline-earth, rare-earth and group 13 elements, resulting in a large decrease in κL and improve the TE performance. Namely, R ions are located inside the cages and a marked rattling effect occurs. The reduction in κL for a partially filled skutterudite is a promising method for improving the TE performance. For several RxM4X12, κL decreases with increasing filling ratio x of guest ions. Therefore, partially filled skutterudite compounds with high filling ratio are expected for high-performance TE materials. High pressure benefits the entrance of R into the voids of unfilled skutterudite structure than ambient pressure. We have succeeded in filling unfilled skutterudite compounds with R at a high filling rate x by high-pressure synthesis. Furthermore, we succeeded in filling heavy rare earth ions (Tb and Dy), which cannot be filled at ambient pressure. In this study, we also focused on a pressure-induced self-insertion reaction. Namely, X atom enters the void of X cage by the reaction under high pressure. The κL of SbxM4Sb12-x (M = Co and Rh) were significantly reduced. This suggests that the pressure-induced structural change could be beneficial for improving TE performance.
Prof. Sekine is a Visiting Researcher at LQMEC hosted by Prof. Larrea inside the PRINT USP CAPES grant.
New development of skutterudite-type thermoelectric materials using high-pressure technique
LQMEC Synergy com Prof. Chihiro Sekine (Muroran Institute of Technology)
21/08, 4ª feira, 15h. No Instituto de Física da USP – Ed. Principal, auditório Marcello Damy. Via Zoom: sala 894 3319 0915 senha 469640 (https://usp-br.zoom.us/j/89433190915)
*Informações disponíveis em https://portal.if.usp.br/ifusp/pt-br/evento/new-development-skutterudite-type-thermoelectric-materials-using-high-pressure-technique