Thermoelectric properties of the new skutterudites (Ce-Yb)y(Fe-Co-Ni)4Sb12
D. Bérardan1, E. Alleno1, C. Godart1, M. Puyet2, B. Lenoir2, A. Dauscher2, D. Ravot3, E. Bauer4
1Laboratoire de Chimie Métallurgique des Terres-Rares, ISCSA-CNRS UPR209, 2-8 rue Henri Dunant 94320 Thiais, France
2Laboratoire de Physique des Matériaux, UMR7556, ENSMN, Parc de Saurupt, 54042 Nancy, France
3Laboratoire de Physico-Chimie de la Matière Condensée, UMR 5617, Université de Montpellier 2, 34095 Montpellier cedex 5, France
4Institute of Solid State Physics, Vienna University of Technology, A-1040 Wien, Austria
Skutterudites, with general formula MX3 (M=Co, Rh, Ir and X=P, As, Sb), can be optimised for thermoelectric applications by both substitution on the covalent framework of the structure and filling of the void by an electropositive element (rare-earth, alkaline earth, actinide). Since this filling leads to a strong reduction of the lattice thermal conductivity and thus to an enhancement of ZT, filled skutterudites have been extensively studied in the past few years. The nature and the valence of the electropositive filler also have a strong influence on the carriers concentration and mobility (which directly influence the thermopower and the electrical conductivity) and on the p-n nature of the compound. Recently, we reported the first synthesis of Ce+Yb double filled skutterudites and the effect of this double filling on the thermopower, which is enhanced as compared to that of CeFe4Sb12 and YbFe4Sb12. These double filled skutterudites have been optimised by substitution on the M site with Co and Ni to form the new series (Ce-Yb)yFe4-xCoxSb12 and (Ce-Yb)yFe4-xNixSb12 containing both n and p type skutterudites. This paper will present the synthesis, chemical properties (XRD, EPMA, Yb mixed valence deduced from XAS) and thermoelectric properties between 4K and 800K of these new systems.