Thermoelectric properties of EuyCo4Sb12 filled skutterudites

Polycrystalline filled skutterudite compounds EuyCO4Sb12 with 0 <= y <= 0.6 are synthesized by melting method and sintered by spark plasma sintering technique. The crystallographic properties are characterized by X-ray diffraction and electron probe microanalysis. The maximal filling fraction of Eu in C4Sb12 is experimentally determined to be as high as 60%, highest in all the rare-earth-impurity being able to fill into Co4Sb12 reported so far. The electrical conductivities, thermal conductivities and Seebeck coefficients of those samples are measured in the temperature range of 300-850 K, and the samples show n-type conduction. The lattice thermal conductivity is depressed significantly by Eu-filling, and a room temperature value of similar to 1.8 W/m K for EU0.34CO4Sb12 is obtained, which is the lowest one for ternary filled CO4Sb12 compounds reported so far. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature and reaches a maximal value of 0.9 for EU0.27Co4Sb12 at 850 K. (C) 2008 Elsevier Masson SAS. All rights reserved.