Influence of Ni on the thermoelectric properties of the partially filled calcium skutterudites CayCo4 − xNi xSb12
Résumé
We have synthesized and studied the structural and thermoelectric properties of Ni-substituted partially filled CayCo4−xNixSb12 (y ~0.10 and 0.18; 0 < x < 0.10) skutterudites. Electrical and thermal properties have been measured in a wide range of temperature (2-800 K). It was found that the presence of Ni increases drastically the dimensionless figure of merit at moderated temperature with respect to the Ni-free analogous samples. These greater thermoelectric properties are discussed in view of electronic structure features near EF as resulted from KKR-CPA calculations. Both experimental findings and computed DOS characteristics point to the conclusion that another channel of electrical conductivity, related to the presence of d-Ni states and opening additional electron Fermi surface pocket, is presumably responsible for the drop of electrical resistivity with respect to the Ni-free samples. In the same time, important DOS variations near EF were found in CayCo4−xNixSb12, as previously in CayCo4Sb12. This gives rise to a large thermopower detected in the two series of compounds.
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