Tantalum oxide is a suitable precursor for electro-deoxidation, where a cathodic potential is applied to the oxide, immersed in a molten salt, to remove oxygen from the oxide leaving tantalum metal. The electro-deoxidation reactions take place in a melt of CaCl2-CaO and, unlike the reduction of other metal oxides where little or no reaction occurs between the melt and oxide until the application of a cathodic potential, tantalum oxide readily reacts with the calcium oxide to form CaTa4O11, CaTa2O6 and Ca2Ta2O7. These phases have completely different morphologies which convert a robust pellet into a collection of poorly connected particles.