Direct Observation of Defect Dynamics in Nanocrystalline CaF2: Results from F-19 MAS NMR Spectroscopy

作者：Jain Pragati; Kim Sangtae; Youngman Randall E; Sen Sabyasachi^*

来源：Journal of Physical Chemistry Letters, 2010, 1(7): 1126-1129.

DOI：10.1021/jz100152j

The structure and F--ion dynamics in nanocrystalline CaF2 is studied using F-19 fast magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy in the temperature range 22 degrees C <= T <= 240 degrees C. The F-19 MAS NMR spectra of nanocrystalline CaF2 (diameter similar to 25 nm) shows the presence of similar to 0.55% of the F- ions in interstitial sites that are found to be highly mobile at elevated temperatures and undergo rapid site exchange with regular fluorine sites in the lattice via hopping. It is shown that an increased concentration of these defects formed in nanocrystalline CaF2 may result in an enhancement in ionic conductivity by nearly 3 orders of magnitude compared to that of bulk CaF2.

• 出版日期2010-4-1