Abstract: A novel technique of electrodeoxidation was studied for preparation of metal niobium. Nb₂O₅ was electrodeoxided in a eutectic melt of CaC1₂-NaCl with a sintered compact as a cathode and graphite as an anode. Nb₂O₅ cathodes with different density were prepared by sintered and influence of density of the cathodes on electrodeoxidation was investigated. The results show that density of sintered Nb₂O₅ cathodes has important effect on electrodeoxidaion of Nb₂O₅ in a eutectic melt of CaC1₂NaCl. The lower the density of sintered Nb₂O₅ cathode, the larger the electricity is started at the beginning of and during electrodeoxidation. Valence of the residual oxide niobium in the same time of electrolysis was lowered with decrease of the density of sintered Nb₂O₅ cathode. It had better electrochemistry activity and was reduced by electrolysis at 850 ℃ for 150 minutes for the sintered Nb₂O₅ cathode prepared under the condition of compaction of Nb₂O₅ powder at 8 MPa pressure and sintering at 1 150 ℃ for 8 hours. The reactive rate of electrodeoxidation gradually became low with increasing electrolyzing time. The experiment indicates that electrodeoxidation is a process of interconnection between electrolyte and oxide powder particle, and between reaction and ionization. The electrodeoxidation reaction of oxide niobium is a step-by-step progress from high valence to low valence and to pure metal, i.e. Nb⁵⁺→Nb⁴⁺→Nb²⁺→Nb.

Key words: electrodeoxidation, molten salt electrochemistry, Nb₂O₅ reduction, niobium preparation