Neodymium oxyfluoride has received much attention in the fields of anionic solid electrolytes,luminescent,catalytic and magnetic materials because of its structure combined advantages of rare-earth cations with F-and O2-anions.In this work,neodynium oxyfluoride was synthesized by the reaction between neodymium oxide and four fluoride media with different fluoride ion activities.The synthesis processes in molten LiF-CaF2-NdF3,LiF-NdF3,NaF-CaF2-NdF3 and NaF-KF-NdF3 are observed in situ by a confocal scanning laser microscope.The expansion of neodymium oxide particle is observed in the LiF-CaF2-NdF3,LiF-NdF3,and NaF-KF-NdF3 melts,and the growth of needle crystals on neodymium oxide particle is clearly observed in molten NaF-CaF2-NdF3.Based on scan-ning electron microscopy(SEM)-energy dispersive X-ray spectroscopy(EDS)and X-ray diffraction(XRD)analyses of products,neodynium oxyfluoride was successfully synthesized in the four fluoride media.The neodynium oxyfluoride generated in the LiF-CaF2-NdF3,LiF-NdF3,and NaF-KF-NdF3 melts is a tetragonal structure.However,in molten NaF-CaF2-NdF3,neodynium oxyfluoride with a rhombohedral structure is formed.It is suggested that the substitution of Na(Ⅰ)and Ca(Ⅱ)for Nd(Ⅲ)can transform NdOF from tetragonal structure to rhombohedral structure.The growth rate of needle crystals generated in molten NaF-CaF2-NdF3 was calculated based on the result of a confocal scanning laser microscope,and it is found that the reaction kinetics of crystal formation is zero-order reaction.The effect of fluoride media on the structure and morphology of formed NdOF were evaluated by XRD,X-ray photoelectron spectroscopy(XPS)and SEM.The neodymium oxyfluoride prepared in the fluoride media with high fluoride ion activity has low binding energy of F 1s.The ratio of adsorbed oxygen to lattice oxygen for neodymium oxyfluoride prepared in molten LiF-NdF3 is larger than those in the other three fluoride media,so it can have better catalytic performance.

Yusheng Yang;Tuoyao Wang;Ran Zhao;Shuyan Zhang;Zengwu Zhao

Key Laboratory of Integrated Exploitation of Bayan Obo Multi-Metal Resources,School of Material and Metallurgy,Inner Mongolia University of Science and Technology,Baotou 014010,China;School of Energy&Environment,Inner Mongolia University of Science and Technology,Baotou 014010,China;Collaborative Innovation Center of Integrated Exploitation of Bayan Obo Multi-Metal Resources,Inner Mongolia University of Science and Technology,Baotou 014010,China

稀土学报（英文版）

[1]Yusheng Yang;Tuoyao Wang;Ran Zhao;Shuyan Zhang;Zengwu Zhao-.Molten salt synthesis of neodynium oxyfluoride in various fluoride media with different fluoride ion activities)[J].稀土学报（英文版）,2022(12):1935-1944

neodynium,Neodymium,NdF3,NdOF

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