Fabrication of ternary iron disilicides as thermoelectric semiconductors by sintering using elemental powders

Sintering process to fabricate iron disilicides with a fine grain structure is pursued using elemental powders as starting materials. Additions of Al to the binary Fe-Si system are attempted. This is because Al has a considerably lower melting point than Fe and Si and hence liquid Al phase would be involved upon sintering to help accelerate the reaction kinetics to form iron disilicides. Sintering of ternary iron disilicides is attempted also with additions of Co and Cu, the former being an n-type dopant while the latter might promote metal-to-semiconductor transition upon annealing after sintering. Effects of such additions are examined on the sintering kinetics, constituent phases in the products, and their thermoelectric properties. It is shown that fabrication of sintered iron disilicides using elemental powders becomes possible with Al additions, for which a mechanism of sintering in the Fe-Si-Al ternary system is proposed. Also a series of demonstrations is given for the changes in thermoelectric properties with difference in doping element.