1. Division of Advanced Ceramics, Nagoya Institute of Technology, Nagoya 466-8555, Japan
2. Frontier Research Institute for Materials Science, Nagoya Institute of Technology, Nagoya 466-8555, Japan
3. J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1106, Japan
4. Neutron R&D Division, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan