1. College of Physics and Lab of New Fiber Materials and Modern Textile, Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071, China
2. Electronic Ceramics Center, Dong-Eui University, Busan 614-714, South Korea
3. Department of Materials Science/CENIMAT-I3N, Faculty of Science and Technology, New University of Lisbon and CEMOP-UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal