CALCULATED THERMOELECTRIC PROPERTIES OF LA-FILLED SKUTTERUDITES

The thermoelectric properties of La-filled skutterudites are discussed from the point of view of their electronic structures. These are calc ulated from first principles within the local-density approximation. T he electronic structure is in turn used to determine transport related quantities. Virtual-crystal calculations for La(Fe,Co)(4)Sb-12 show t hat the system obeys near rigid band behavior with varying Co concentr ation, and has a substantial band gap at a position corresponding to t he composition LaFe3CoSb12. The valence-band maximum occurs at the Gam ma point and is due to a singly degenerate dispersive band, which by i tself would not be favorable for high thermopower. However, very flat transition-metal-derived bands occur in close proximity and become act ive as the doping level is increased, giving a nontrivial dependence o f the properties on carrier concentration and explaining the favorable thermoelectric properties.