1. School of Materials Science and Engineering Hunan Provincial Key Laboratory of Electronic Packaging and Advanced Functional Materials Central South University Changsha Hunan 410083 P. R. China
2. School of Minerals Processing and Bioengineering Central South University Changsha Hunan 410083 P. R. China
3. School of Physics and Electronics Hunan University Changsha Hunan 410082 P. R. China
4. College of Chemistry and Chemical Engineering Jishou University Jishou Hunan 416000 P. R. China