Formation, Crystal Structure and Physical Properties of Novel Thermoelectric Skutterudites: Eu y Fe 4-x Ni x Sb 12 Andriy Grytsiv 1 , Peter Rogl 1 , Stefan Berger 2 , Christoph Paul 2 , Ernst Bauer 2 , Claude Godart 3 , Adriana Saccone 4 , Ricardo Ferro 4 , and Darek Kaczorowski 5 1 Institut für Physikalische Chemie, Universität Wien, Währingerstr. 42, A-1090 Wien, Austria 2 Institut für Experimentalphysik, T.U. Wien, Wiedner Hauptstr. 8-10 A-1040 Wien, Austria 3 CNRS-UPR209, 2-8 rue Henri Dunant, F94320 Thiais, and LURE, CNRS, 91405 Orsay, France 4 Dip. Chimica e Chimica Industriale, Univ. Genova, Via Dodecaneso 31, I-16146 Genova, Italy 5 W. Trzebiatowski Institute for Low Temperature and Structure Research Polish Academy of Sciences, P-50-950 Wroclaw, P. O. Box 1410, Poland ABSTRACT Quantitative X-ray powder Rietveld refinements for a series of alloys from the solid solution Eu y Fe 4-x Ni x Sb 12 , synthesized by argon arc-melting followed by long term annealing, established in all cases isotypism with the partially filled skutterudite-type structure, LaFe 4 P 12 . The Eu- content of the samples was determined from the combined data obtained results of Rietveld refinements and electron microprobe measurements. These investigations confirmed a systematic trend for the Eu-occupancy y in the parent lattice, revealing a gradual decrease of the maximum Eu-content from practically full occupancy, y = 0.83, in Eu 0.83 Fe 4 Sb 12 to y ~ 0.5 for Eu ~0.5 Fe 2 Ni 2 Sb 12 . Eu 0.83 Fe 4 Sb 12 orders magnetically below 84 K and the transition temperature decreases as a function of Fe/Ni substitution. As a further consequence of the Fe/Ni substitution electronic transport crosses over from a hole conductivity regime into electron dominated behaviour. Concomitantly, the transition metal exchange increases the Seebeck coefficient significantly, hence the figure of merit enhances. INTRODUCTION Recently we reported on novel thermoelectric skutterudites Yb y (Fe 1-x Co x ) 4 Sb 12 , Yb y (Fe 1- x Ni x ) 4 Sb 12 and Eu y (Fe 1-x Co x ) 4 Sb 12 [1-5], the materials properties of which being dominated by the rare earth content formed as a function of the 3d metal replacement. In the present paper we attempt to investigate the physical and structural properties relevant to the thermoelectric behaviour of the homologous skutterudite series, Eu y (Fe 1-x Ni x ) 4 Sb 12 . EXPERIMENTAL For a detailed description of experimental conditions and procedures regarding alloy preparation, characterisation of crystal structure and the various physical properties the reader is referred to our previous papers on ternary europium containing skutterudites [4,5]. Mat. Res. Soc. Symp. Proc. Vol. 691 © 2002 Materials Research Society G8.36.1