1. College of Materials, Xiamen University, Simingnan-Road 422, Xiamen, 361005, P. R. China
2. Graduate School of Human and Environmental
Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto, 606-8501, Japan
3. Sialon Group, Sialon Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan