1. Department of Physics, University of South Florida, Tampa, Florida 33620
2. Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700032, India
3. State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
4. Ceramics Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899