Thermoelectric Properties of Metals and Alloys
Thermocouples have been used extensively for well over 100 years as devices for the measurement of temperature and for process control. Practically all of the thermocouple elements in common use are alloys of transition elements. These alloys have been selected by trial and error, over many years, because they show nearly linear thermoelectric behavior as functions of temperature and because of the relatively large emfs that they generate. The use of ATP enables the examination and understanding of the thermoelectric properties of single thermoelements and pairs forming thermocouples without reference to other thermoelements, such as platinum. In attempting to describe the behavior of thermocouples in terms of the temperatures and Peltier effects at the two junctions, Thomson derived a relationship for the emf of a thermocouple based only upon the entropy of the junctions. Thermoelectric devices have been used for the generation of electric current in remote situations.