1. Electronic Materials Research Laboratory; Key Laboratory of the Ministry of Education and International Center for Dielectric Research; School of Electronic and Information Engineering; Xi'an Jiaotong University; Xi'an 710049 China
2. School of Materials Science and Engineering; Shaanxi University of Science and Technology; Xi'an 710021 China
3. Institute for Superconducting and Electronic Materials; Australian Institute of Innovative Materials; University of Wollongong; NSW 2500 Australia