Preparation And Mechanism Study Of Samarium Based Functional Compounds By Molten Salt Electrolysis

It is an effective way to promote the development of rare earth industries through combining the functionality of rare earth materials with the application requirements and developing new rare earth materials.Molten salt electrolysis has the advantages of simple process,low energy consumption and no crystal defects.Hence,molten salt electrolysis was employed in this paper.Sm-based compounds were prepared to achieve excellent physical and chemical properties in the fields of magnetism,catalysis and light.First of all,the electrochemical behaviors of Sm???correlation with Ni???,Co???,Cu???,O???and S???ions have been studied in LiCl-KCl molten salt system by different electrochemical methods.Sm-based alloys and compounds were prepared by co-electrodeposition and cathodic alloying.Finally,the microstructure and morphology of Sm-based compounds were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,high-resolution electron microscope?HRTEM?and transmission electron microscopy?TEM?.In addition,the magnetic,catalytic and optical properties of Sm-based compounds were emphatically studied.In order to prepare the Sm-based compounds,the kinetics and thermodynamics properties of the Sm???ions were investigated.The diffusion coefficients of Sm???ions in the melts,the thermodynamics parameter and the relationship between the equilibrium potential and temperature were also discussed.The redox mechanism of LiCl-KCl-SmCl3-NiCl2,LiCl-KCl-SmCl₃-CuCl₂,LiCl-KCl-SmCl₃-CoCl₂ and LiCl-KCl-SmCl₃-KSCN melts were investigated by cyclic voltammetry,square wave voltammetry and open circuit chronopotentiometry.The test results show that Sm???ions could codeposition with Ni???,Cu???,Co???,O???and S???ions to form Sm-based compounds.In order to synthesize single-phase Sm-based compounds,the temperature,composition of molten salt electrolytes and current efficiency were analyzed.In LiCl-KCl-SmCl3-NiCl2melts,the effects of electrolysis parameters on the morphology and the formation rule of phases of Sm-Ni compounds were also investigated.The crystal nucleation,growth,crystal structure and magnetic properties of Sm-Ni compounds were discussed.In LiCl-KCl-SmCl₃-CuCl₂ melts,a series of Sm-Cu dendrites with higher specific surface area were prepared.It reveals their growth mechanism,and the relationship between the structure and catalytic properties.In LiCl-KCl-SmCl3-CoCl2 melts,Sm-Co compounds were successfully obtained.The relationship between magnetization,magnetic anisotropy and temperature were investigated.In LiCl-KCl-SmCl3-KSCN melts,a one-step method was developed for the preparation of rare earth oxysulfides luminescent matrix.At the same time,rare earth oxysulfide Sm2O2S with activator Eu³⁺and Tb³⁺doped were synthesized.Fluorescence spectra of Sm₂O₂S:Eu³⁺/Tb³⁺and energy transfer mechanism were studied.