1. State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an 710049 P. R. China
2. Department of Chemical and Process Engineering University of Strathclyde Glasgow G11XQ UK
3. Energy Materials Center Korea Institute of Ceramic Engineering and Technology 101, Soho‐ro Jinju‐si Gyeongsangnam‐do 52851 South Korea