Influence of Morphology of LaF3 Nano-crystals on Fluorine Dynamics Studied by NMR Diffusometry
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Ionic dynamics in nano-structured 2D superionic conductors LaF3 obtained by a synthesis at the gas–solution interface has been analyzed using 19F NMR Static Field Gradient (SFG) diffusometry in a temperature range up to 800 K. The fluorine diffusion in 2D materials is significantly higher as compared to that in bulk LaF3 and is strongly dependent on the nano-crystalline sheet thickness. Its decrease from 18 nm to 6 nm leads to an increase of mobility by almost two orders of magnitude, resulting in an overall mobility enhancement of more than three orders of magnitude compared to mono-crystalline LaF3. Moreover, the activation energy is reduced from 1.2 eV for mono-crystals to 0.23 eV for 6 nm thin nano-crystalline powder samples.
The reported study was supported by a grant of the Russian Science Foundation, research project No 16-13-10223. The XRD research was carried out in the X-ray Diffraction Centre of SPbSU. The SEM study was carried out by the Nanotechnology Centre of SPbSU.
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