Tantalum and niobium powder preparation from their oxides by calciothermic reduction in the molten CaCl2

Calciothermic reductions of Ta2O5 and Nb2O5 are proposed aiming at the fine powder preparation for the larger capacitance of condensers. Because the molten CaCl2 can coexist stably with metallic Ca, and because it can dissolve a few mol%Ca and about 20 mol%CaO, the reductant Ca can be supplied to the oxide via molten CaCl2, and the reaction by-product CaO can be in situ eliminated from the reaction interface. The metallic powder was obtained after an hour at 1173 K. In the prolonged time the particles sintered together, but oxygen was gradually removed to the level of a few thousands ppm. (c) 2004 Elsevier Ltd. All rights reserved.