1. Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education & International Center for Dielectric Research School of Electronic and Information Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
2. Frontier Institute of Science and Technology and State Key Laboratory for Mechanical Behaviour of Materials Xi'an Jiaotong University Xi'an 710049 P. R. China
3. State Key Laboratory for Mechanical Behaviour of Materials Xi'an Jiaotong University Xi'an 710049 P. R. China