[Si, Jiayong] Cent South Univ Forestry & Technol, Coll Mech & Elect Engn, Changsha 410004, Hunan, Peoples R China.
[Si, Jiayong; Hirosaki, Naoto; Liu, Lihong; Takeda, Takashi] Natl Inst Mat Sci, Sialon Grp, Namiki1-1, Tsukuba, Ibaraki 3050044, Japan.
[Liang, Qifeng] Shaoxing Univ, Dept Phys, Shaoxin 312000, Zhejiang, Peoples R China.
[Yi, Wei] MANA, Nano Elect Device Mat Grp, Namiki 1-1, Tsukuba, Ibaraki 3050044, Japan.
[Cai, Gemei] Cent South Univ, Sch Mat Sci & Engn, Changsha 410083, Hunan, Peoples R China.