Investigation on Preparation of Tb2Fe17 by Direct Electrochemical Reduction of Tb4O7-Fe2O3 Pellet in Molten Calcium Chloride

To simplify the preparation process of Tb2Fe17 magnetic intermetallic compound, direct electrochemical reduction of solid pellet of mixture of Tb4O7 and Fe2O3 powder (Tb: Fe = 2: 17) to Tb2Fe17 in molten CaCl2 at 850 oC was investigated. Well stoichiometric Tb2Fe17 powder was obtained through electrolysis at 3.1V for 6h, the oxygen content in the sample was as low as 3900ppm. The reduction process was studied through the composition characterization of the products obtained at different electrolysis times. It was found that Fe2O3 was preferentially deoxidized to metallic Fe within the first hour, and then Tb4O7 was reduced assistantly by forming FeTbx and finally Tb2Fe17 was obtained with the under-potential reduction of Tb4O7 on iron. This was further confirmed by cyclic-voltammetry measurement of a novel Tb4O7 powder filling stainless steel sieve electrode.