Research status on the electroreductive synthesis of Eu/Gd-Fe-based rare earth metal compounds

Rare earth-iron metal compounds (RE-IG IMs) serve as the basic phases that underpin extraordinary performance of many electromagnetic functional materials, and the in-depth analysis of their synthesis mechanism and structural evolution is crucial for developing preparation technologies for high-performance rare-earth alloys. This paper compared and summarized the high-temperature physical/chemical and electrochemical reduction synthesis methods of preparing rare earth-iron metal compounds (RE-IG IMs), and analyzed the advantages and future prospects of the electrolysis/deposition synthesis method in high-temperature molten salt systems. Current studies on the electrochemical synthesis mechanisms of rare earth-iron group metal intermediate compounds in aqueous/non-aqueous carriers rely on transient analysis techniques to capture the electrochemical information of the electrode process. However, the data obtained had limitations in deeply interpreting complex electrode coupling reactions and alloying process. Furthermore, issues such as instability of reference electrodes in high-temperature halide-molten-salt system, poor experimental reproducibility, and insufficient reliability of derived thermodynamic/kinetic parameters persisted. To address these challenges, this paper proposed to take the synthesis mechanism of Eu/Gd_mIG_n-system rare-earth interphase compounds as a breakthrough. By transcending conventional research paradigms, this work aimed to empirically explain the electroreduction mechanisms of dissolved rare earth ions at iron group active metal electrodes, the relaxation behavior of electric double-layer structures, and the mechanisms of coupled electrode reactions. The findings are expected to provide insights into the electrochemical synthesis mechanisms and structural evolution laws of rare earth-iron interphases in halide molten salt environment.