1. Materials R&D Laboratory, Japan Fine Ceramics Centre, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan
2. Department of Environmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
3. Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, PR China
4. Department of Material Science and Engineering andHVEM Laboratory, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan