[Chen Chuan-sheng;Lin Liang-wu] Cent S Univ, State Key Lab Powder Met, Changsha 410083, Peoples R China.^[Chen Chuan-sheng;Chen Xiao-hua;Liu Qi-cheng;Xia Qing;Ning Zhen-wu] Changsha Univ Sci & Technol, Coll Phys & Elect Sci, Changsha 410114, Hunan, Peoples R China.^[Liu Tian-gui] Hunan Univ, Coll Phys & Microelect Sci, Changsha 410082, Hunan, Peoples R China.