1. College of Chemistry and Materials ScienceSichuan Normal University Chengdu 610066 China
2. Inorganic Functional Materials Research InstituteNational Institute of Advanced Industrial Science and Technology (AIST) Ikeda Osaka 563-8577 Japan
3. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS)CNRS-Université de Strasbourg (UMR 7504) 23 rue du Loess, BP43 67034 Strasbourg, Cedex 2 France