1. Institute of Mining Engineering, Inner Mongolia University of Science and Technology, Baotou 014010, P. R. China
2. Fujian Research Center for Rare Earth Engineering Technology, Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, P. R. China
3. CAS Key Laboratory of Design and Assembly of Functional Nanostructures, and Fujian Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China
4. University of Chinese Academy of Sciences, Beijing 100039, P. R. China
5. Jiangxi Province Key Laboratory of Cleaner Production of Rare Earths, Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou, Jiangxi 341000, P. R. China