1. State Key Laboratory of Power Equipment and Electrical Insulation, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
2. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
3. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China
4. Institute for Superconducting and Electronic Materials, Australia Institute of Innovative Materials, University of Wollongong, Wollongong, NSW 2500, Australia