Mechanism study on preparation of Sm2Fe17 alloy by molten salt electrolysis

Abstract:

Sm₂Fe₁₇ alloy as the precursor of a potential permanent magnet (Sm₂Fe₁₇N_x) has been paid attention to, but the pure one obtained has been still very difficult until now due to having a distinct difference of melting point between the Fe and Sm metals as raw materials, it impairs seriously the magnetic performance of Sm₂Fe₁₇N_x. In this work, this problem was resolved successfully using a method of molten salt electrolysis. A chronopotentiometry was used at 1160℃ to obtain different thicknesses (17.22 ~ 40.34 μm) of single-phase Sm₂Fe₁₇ alloy as the product on the iron cathode in LiF-CaF₂-SmF₃, simultaneous a cyclic voltammetry and a square wave voltammetry were carried out to reveal the electrochemical behavior of Sm^₃₊. The result shows that the reduction of Sm^₃₊ to Sm^₀ on the iron electrode included two steps. Firstly, a soluble-soluble reaction appears at -0.33 V vs. Cr/Cr₂O₃ corresponds to the electroreduction of Sm^₃₊ to Sm^₂₊. Secondly, results of CV that Sm^₂₊ can be reduced at -0.78 V vs. Cr/Cr₂O₃ on the iron electrode in LiF-CaF₂-SmF₃ melts due to lower activity of metallic samarium in the Sm₂Fe₁₇ alloy than that of samarium metal and makes samarium in Sm-Fe alloy more stable.

Key words:Molten;salt electrolysis, Sm₂Fe₁₇, LiF-CaF₂, chronopotentiometry, pre-electrolysis