Molten salt synthesis of neodynium oxyfluoride in various fluoride media with different fluoride ion activities  

作　　者：Yusheng Yang Tuoyao Wang Ran Zhao Shuyan Zhang Zengwu Zhao 

机构地区：[1]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 [2]School of Energy&Environment,Inner Mongolia University of Science and Technology,Baotou 014010,China [3]Collaborative Innovation Center of Integrated Exploitation of Bayan Obo Multi-Metal Resources,Inner Mongolia University of Science and Technology,Baotou 014010,China

出　　处：《Journal of Rare Earths》2022年第12期1935-1944,I0005,共11页稀土学报（英文版）

基　　金：Project supported by National Key Research and Development Program of China(2020YFC1909102);Natural Science Foundation of Inner Mongolia(2020BS05033);Inner Mongolia Major Basic Research Open Project(0406091701);Major Projects of Natural Science Foundation of Inner Mongolia of China(2018ZD07)。

摘　　要：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 rareearth cations with F^(-)and O_(2)^(-)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-CaF_(2)-NdF_(3),LiF-NdF_(3),NaF-CaF_(2)-NdF_(3)and NaF-KF-NdF_(3)are observed in situ by a confocal scanning laser microscope.The expansion of neodymium oxide particle is observed in the LiF-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts,and the growth of needle crystals on neodymium oxide particle is clearly observed in molten NaF-CaF_(2)-NdF_(3).Based on scanning 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-CaF_(2)-NdF_(3),LiF-NdF_(3),and NaF-KF-NdF_(3)melts is a tetragonal structure.However,in molten NaF-CaF_(2)-NdF_(3),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-CaF_(2)-NdF_(3)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 1 s.The ratio of adsorbed oxygen to lattice oxygen for neodymium oxyfluoride prepared in molten LiF-NdF_(3)is larger than those in the other three fluoride media,so it can have better catalytic p

关 键 词：Molten salt synthesis Neodynium oxyfluoride Molten fluorides Fluoride ion activity Rare earths 

分 类 号：TQ133.3[化学工程—无机化工]