Research output: Contribution to journal › Article › peer-review
The distribution of motional correlation times in superionic conductors : 19F nuclear magnetic resonance of tysonite-like LaF3. / Privalov, A. F.; Ceniani, A.; Fujara, F.; Gabriel, H.; Murin, I. V.; Vieth, H. M.
In: Journal of Physics Condensed Matter, Vol. 9, No. 43, 27.10.1997, p. 9275-9287.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - The distribution of motional correlation times in superionic conductors
T2 - 19F nuclear magnetic resonance of tysonite-like LaF3
AU - Privalov, A. F.
AU - Ceniani, A.
AU - Fujara, F.
AU - Gabriel, H.
AU - Murin, I. V.
AU - Vieth, H. M.
PY - 1997/10/27
Y1 - 1997/10/27
N2 - Fluorine mobility at different structural positions in monocrystalline LaF3 with the tysonite structure is analysed using 19F NMR line-shape analysis. The method is sensitive to ionic exchange with correlation times in the range 10-6-10-3 s. For the temperature range between 240 K and 400 K the motion is restricted mainly to the F- ions in the fluorine layers perpendicular to the main symmetry axis (the F1 sublattice), while F- ions in the La plane (F2,3) remain immobile. No significant anisotropy of the F1-ionic diffusion within the layers and along the c-axis is found (D∥c ≈ D⊥c ≈ 6 × 10-14 m2 s-1 at 400 K). From NMR spectra it is clear that F1 mobility is strongly heterogeneous. The motional disorder can be described well by a broad distribution of correlation times, G(τ), which has a shape close to a log-Gaussian function and reflects the potential energy landscape in the superionic state. The variation of the centre position and width of G(τ) with temperature differs from an Arrhenius law behaviour. Ionic mobility on the microscopical scale, therefore, cannot be considered a process which is activated only thermally. Applying MD techniques shows that the presence of vacancies may lead to pronounced changes of the potential energies, and supports the idea that there is a distribution of activation energies.
AB - Fluorine mobility at different structural positions in monocrystalline LaF3 with the tysonite structure is analysed using 19F NMR line-shape analysis. The method is sensitive to ionic exchange with correlation times in the range 10-6-10-3 s. For the temperature range between 240 K and 400 K the motion is restricted mainly to the F- ions in the fluorine layers perpendicular to the main symmetry axis (the F1 sublattice), while F- ions in the La plane (F2,3) remain immobile. No significant anisotropy of the F1-ionic diffusion within the layers and along the c-axis is found (D∥c ≈ D⊥c ≈ 6 × 10-14 m2 s-1 at 400 K). From NMR spectra it is clear that F1 mobility is strongly heterogeneous. The motional disorder can be described well by a broad distribution of correlation times, G(τ), which has a shape close to a log-Gaussian function and reflects the potential energy landscape in the superionic state. The variation of the centre position and width of G(τ) with temperature differs from an Arrhenius law behaviour. Ionic mobility on the microscopical scale, therefore, cannot be considered a process which is activated only thermally. Applying MD techniques shows that the presence of vacancies may lead to pronounced changes of the potential energies, and supports the idea that there is a distribution of activation energies.
UR - http://www.scopus.com/inward/record.url?scp=0031246007&partnerID=8YFLogxK
U2 - 10.1088/0953-8984/9/43/012
DO - 10.1088/0953-8984/9/43/012
M3 - Article
AN - SCOPUS:0031246007
VL - 9
SP - 9275
EP - 9287
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
SN - 0953-8984
IS - 43
ER -
ID: 88061520