Transactions of Nonferrous Metals Society of China
JOURNAL OF RAILWAY SCIENCE AND ENGINEERING
|Vol. 16 No. 4 August 2006|
（Institute of Material Physics and Microstructure, College of Materials and Chemical Engineering, Zhejiang University, Hangzhou 310027, China）
Abstract: The ionic conductivity (at room temperature) of nano-LaF3 bulk material and a new discovered phenomenon of increasing ionic conductivity caused by grain boundary relaxation activated by AC (alternating current) shocking were reported. Nano-crystalline powder of LaF3 with average grain size of 16.7 nm was synthesized with a method of direct precipitation from aqueous solution. Particle size and shape of LaF3 nano-crystalline powder were analyzed by XRD and TEM. Nano-LaF3 bulk material was prepared by compacting the powder to 1 GPa at room temperature and vacuum of 10−4 Pa. The ionic conductivity of nano-LaF3 bulk material was studied with complex impedance spectra at room temperature. The ionic conductivity of nano-LaF3 bulk material (10−5 S/cm) at room temperature is significantly increased compared with that of single crystal LaF3 (10−6 S/cm). A special phenomenon is observed for the first time that the ionic conductivity increases gradually with AC scanning times.
Key words: nano-LaF3; bulk material; nano-crystalline; ionic conductivity; impedance spectra