1. Electronic Materials Research Laboratory; Key Laboratory of the Ministry of Education and International Center for Dielectric Research; School of Electronic and Information Engineering; State Key Laboratory for Mechanical Behaviour of Materials; Xi'an Jiaotong University; Xi'an 710049 China
2. Materials Research Institute; Pennsylvania State University; University Park PA 16802 USA
3. Institute for Superconducting and Electronic Materials; Australia Institute of Innovative Materials; University of Wollongong; NSW 2500 Australia
4. Group for Ferroelectrics and Functional Oxides; Swiss Federal Institute of Technology in Lausanne-EPFL; 1015 Lausanne Switzerland