Thermoelectric semiconductor iron disilicides produced by sintering elemental powders

Development of a sintering process to fabricate iron disilicides with a lin e grain structure is pursued using elemental powders as starting materials with additions of Al. The Al additions are expected to involve liquid Al-ri ch 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 wh ile the latter might promote metal-to-semiconductor transition upon anneali ng after sintering. The effects of such additions on the sintering kinetics , constituent phases in the products, and their thermoelectric properties a re examined. It is shown that fabrication of sintered iron disilicides usin g elemental powders, heretofore believed to be difficult, becomes possible with Al additions. Then a mechanism of sintering in the Fe-Si-Al ternary sy stem is proposed, and finally a series of demonstrations is given for the c hanges 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 disil icides. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.