Filled skutterudites EpyT4X12 (T is a group VIII transition element; X is a pnictide and the electropositive element Ep fills the icosahedral voids in Wyckoff position 2a of space group Im-3) are among the most promising thermoelectric materials fulfilling the PGEC concept as worked out by G. Slack. While the rigid host structure of skutterudites maintains electronic transport, the guest atoms in the icosahedral voids of the skutterudite structure exhibit localised vibrational (“rattling”) modes. This perturbs the propagation of phonons and thereby significantly reduces the phonon contribution to the thermal conductivity. Besides a large variety of interesting ground state properties like superconductivity, or heavy fermion behaviour - some of them will be reviewed here - the possibility of substituting and doping at the various lattice sites of the crystalline unit cell allows fine-tuning the charge carrier density of this material class in order to reach those optimal levels required for superior thermoelectricity. Further improvements of the thermoelectric performance, which is measured by the dimensionless figure of merit, are possible considering nanostructuring of bulk materials as previously proposed by M. Dresselhaus.
In the present work we will show how promising thermoelectric materials can be derived within the family of filled skutterudites and how auspicious routes for further improvements of this material class can be read-off from ab-initioelectronic structure calculations carried out for some members of the family of filled skutterudites. Furthermore, we will show how this knowledge, initially derived on a laboratory scale, can be used to set-up an industrial production process of filled skutterudites.
Research supported by the “Christian Doppler Laboratory for Thermoelectricity”and by the Austrian FWF, P24380.