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PROBLEM TO BE SOLVED : To provide a highly purified earth metal oxide powder used for a capacitor.
SOLUTION : The process produces niobium and/or tantalum powder by reduction of corresponding oxides of niobium and/or tantalum. The reduction is carried out by two stages at controlled temperatures and also by using a reducing agent selected from a group of alkaline earth metals and rare earth metals. The first reaction stage is carried out until the average composition corresponding to (Nb, Ta)Ox, where x is 0.5-1.5, is reached. Before the second stage, the oxide of a reducing agent is washed away by washing with at least one kind of mineral acids from the reduction generated product. Then, the second reduction stage is carried out to produce the above metal powder.
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