Improved materials for thermoelectric conversion (generation)

Thermoelectric conversion (TEC) presents several advantages compared to the other energy conversion technology: it is reliable, can operate untainted in hostile environments, and is also environmentally friendly. However the application has been limited up to now because of the relatively low conversion efficiency of traditional thermoelectric materials used in the devices. New more efficient materials are needed. The value of a material for thermoelectric power generation is defined by the thermoelectric figure of merit Z which is a function of the Seebeck coefficient S, electrical resistivity p, and thermal conductivity k and is defined as Z=S²/pk. A choice of the optimal techniques for the leg formation from synthesized thermoelectric materials, which are capable to provide the leg required forms and leg geometrical sizes, are determined by mechanical properties. Several methods for thermoelectric efficiency increase have been put forward over the past years. Among them we wish to focus our attention to produce segment thermoelectric legs with variation of the composition along the legs. Calculated efficiency in this case is more than 10% (Th=500°C, Tc=50°C). The first experimental results on a 2-stage composite leg indicate high efficiency in the thermoelectric energy conversion. Crystal-growth techniques with high crystalline perfection stimulates us to use this method for preparation the thermoelectric generator material