Thermoelectric properties of the Fe-Al and Fe-Al-Si alloys for thermoelectric generation utilising low-temperature heat sources

The iron is intrinsically a p-type conductor. When aluminum with three valence electrons is added to the iron, the d-subbands are occupied by electrons, so alloying with the aluminum transforms the iron to the n-type conductor, hence the p-n junction is made possible. Furthermore, when silicon is added to the n-type Fe-Al alloy, this alloy returns to the p-type conductor. Therefore, the thermoelectric p-n junctions with high thermoelectric power have been recognised (figures in % refer to mass contents): Fe(p) - Fe12%Al(n): alpha = 38 mu V/K and Fe12%Al12%Si(p) - Fe12%Al(n): Delta alpha = 70 mu V/K. Thermoelectric generation offers the possibility of a gigantic electric power generation utilising low-temperature sources of energy below 700 K such as exhaust heat from the central-station steam-electric plant, solar heat and terrestrial heat. The immense production of electricity by this principle is made possible exclusively by means of the conversion materials consisting of the iron and iron-based alloy because the generator can be manufactured on an efficient mass production basis, and the alloys mentioned above will meet this requirement. In this paper, the thermoelectric properties of these alloys such as Seebeck coefficient, thermal conductivity and electrical resistivity were experimentally determined in the temperature range between 300 and 700 K to provide basic data on the conversion materials with respect to the thermoelectric generation utilising low-temperature heat sources.