1. State Key Laboratory of Rare Earth Resource UtilizationChangchun Institute of Applied ChemistryChinese Academy of Sciences Changchun 130022 P. R. China
2. Key Laboratory of Automobile MaterialsMinistry of EducationDepartment of Materials Science and Engineering, Jilin University Changchun 130012 Jilin P. R. China
3. Hunan Key Laboratory for Micro-Nano Energy Materials and DeviceDepartment of PhysicsXiangtan University Xiangtan 411105 Hunan P. R. China