Jeff Sharp

Thermoelectrics is an old field. In 1823, Thomas Seebeck discovered that a voltage drop appears across a sample that has a temperature gradient. This phenomenon provided the basis for thermocouples used for measuring temperature and for thermoelectric power generators. In 1838, Heinrich Lenz placed a drop of water on the junction of metal wires made of bismuth and antimony. Passing an electric current through the junction in one direction caused the water to freeze, and reversing the current caused the ice to quickly melt; thus thermoelectric refrigeration was demonstrated (figure 1).

Seebeck, electrical, and thermal conductivity data are reported on CoSb3, and doped and undoped alloys of Co1−xIrxSb3−yAsy from 20 to 700 K. n-type semiconductors were obtained by doping with Ni, Te, or Pd, and the hole concentration in p-type samples was increased by substitution of Fe, Ru, Os, and Ge. An estimated maximum value for ZT of 0.6 (Z is the figure of merit) was found for a Te-doped (n-type) alloy at 700 K. For p-type alloys, the maximum value of ZT was found to be 0.3 at 550 K. Electrical and thermal transport data also are reported for CoAs3, RhSb3, and IrSb3. Most of the samples investigated were polycrystalline, but a few measurements on CoSb3 single crystals also are discussed.