Thermoelectric semiconductor iron disilicides produced by sintering elemental powders

Development of a sintering process to fabricate iron disilicides with a line grain structure is pursued using elemental powders as starting materials with additions of Al. The Al additions are expected to involve liquid Al-rich phase during sintering to accelerate the reaction kinetics. At the same time, additions are made of Co and Cu, the former being an n-type dopant while the latter might promote metal-to-semiconductor transition upon annealing after sintering. The effects of such additions on the sintering kinetics, constituent phases in the products, and their thermoelectric properties are examined. It is shown that fabrication of sintered iron disilicides using elemental powders, heretofore believed to be difficult, becomes possible with Al additions. Then a mechanism of sintering in the Fe-Si-Al ternary system is proposed, and finally a series of demonstrations is given for the changes in thermoelectric properties depending upon the doping element used. It becomes evident that the thermoelectric figure of merit of the present materials is equivalent to that of the conventionally fabricated iron disilicides. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.