1. CAS Key Laboratory of Materials for Energy Conversion Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 P. R. China
2. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Corning Research Center China Shanghai 201206 P.R. China
4. Corning Incorporated Corning NY 14831 USA
5. State Key Lab High Performance Ceram & Superfine Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 China