[摘要]：Single-phase skutterudite compounds of composition CoSb(2.75)Ge(0.25-x)Te(x) (x = 0.125-0.20) were synthesized by the traditional melt-quench-anneal technique followed by spark plasma sintering. Rather than filling the skutterudite structure to reduce the thermal conductivity, the aim here is to use disorder on the pnicogen rings created by doping with both Te and Ge. Since heat-carrying phonons in CoSb(3) are those associated with the vibrational modes of the Sb-rings, such disorder should be effective in suppressing heat transport. The electrical transport properties can be tuned by adjusting the relative content of Te and Ge. The electrical conductivity and the thermoelectric power factor of the samples increase with the increasing Te content while the absolute value of the Seebeck coefficient decreases. Compared with the undoped CoSb(3), the lattice thermal conductivity is significantly suppressed because of an enhanced solubility of Te leading to an increase in the number of pnicogen rings being distorted. High resolution transmission electron microscopy images reveal an in situ nanostructure consisting of circular, 30 nm diameter dots of a skutterudite phase enriched with the dopants that are embedded in the skutterudite matrix poor in Ge and Te. Apart from phonon point-defect scattering, this nanostructure may also contribute to the overall low lattice thermal conductivity. The thermoelectric figure of merit for the CoSb(2.75)Ge(0.05)Te(0.20) compound reaches values in excess of 1.1 at 800 K. This value is competitive with single-filled n-type skutterudite compounds.
