A good thermoelectric material shows a high Seebeck coefficient, a high electrical conductivity and a low thermal conductivity. The performance of a thermoelectric materials is described by the thermoelectric figure of merit ZT. The most important state of the art thermoelectric materials are semiconductors like Bismuth Telluride-based alloys for near room temperature applications;
Chalcogenides (PbTe, TAGS), Skutterudites and half-Heusler compounds for the mid-temperature applications and SiGe for high temperatures (above 1000 K).
The thermoelectric figure of merit ZT depends on the temperature range and on the materials itself. Research in thermoelectric materials suggests that significant improvements in efficiency are possible by the “Phonon-Glass, Electron-Crystal” concept which must be always accompanied by suitable doping. New developments investigate also oxides and organics as thermoelectric materials for special applications.
Besides the thermo-mechanical stability it is important for applications to use materials with the best mean ZT values over the addressed temperature range.