The iron is intrinsically 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:
Fe(p) - Fe12%Al(n): Delta alpha = 38 microV/K
Fe12%Al12%Si(p) - Fe12%Al(n): Delta alpha = 70 microV/K
(mass contents in %)
Thermoelectric generation offers 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 consisted 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
experi-mentally 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.