1. State Key Laboratory of Material Processing and Die & Mould TechnologyLaboratory of Solid State IonicsSchool of Materials Science and EngineeringHuazhong University of Science and Technology Wuhan 430074 P. R. China
2. School of Optical and Electronic InformationHuazhong University of Science and Technology Wuhan 430074 P. R. China
3. Department of Mechanical and Aerospace EngineeringThe Hong Kong University of Science and Technology Clear Water Bay Hong Kong P. R. China
4. Center for Information Photonics and Energy MaterialsShenzhen Institutes of Advanced TechnologyChinese Academy of Sciences Shenzhen 518055 P. R. China
5. Department of Chemical and Biological EngineeringThe Hong Kong University of Science and Technology Clear Water Bay Hong Kong P. R. China
6. Institute for Superconducting & Electronic MaterialsUniversity of Wollongong Wollongong New South Wales 2522 Australia