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 percent Ca and about 20 mol percent 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.