In 1823,Thomas Seebeck first discovered the thermoelectric effect.A temperature difference across any electric conductor junction will generate a corresponding voltage difference.Probably the most familiar use of this so called Seebeck effect is thermocouple.When an electric current passing through junction which is composed of two dissimilar conductors results in the absorption or release of the heat,this is the Peltier effect.This effect makes thermoelectric refrigerator or heating devices possible.Moreover a power generator can be also invented from the application of thermoelectric materials.Thermoelectric materials are those which possess high thermoelectric figure of merit.The major problem for thermoelectric materials is poor efficiency.They are now used only in the fields in which cost is not a big problem such as space and some other instruments.Thermoelectric materials are not widely used nowadays.
