https://doi.org/10.1140/epjb/e2004-00255-1
Two dimensional fluoride ion conductor RbSn2F5 studied by impedance spectroscopy and 19F, 119Sn, and 87Rb NMR
1
Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan
2
Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt, Germany
Corresponding author: a mmahmad@sci.hiroshima-u.ac.jp
Received:
4
April
2003
Revised:
25
May
2004
Published online:
12
August
2004
RbSn2F5 is a two-dimensional fluoride ion conductor. It undergoes
a first-order phase transition to a superionic state at 368 K. The structure
of the low temperature phase has been determined from the Rietveld analysis
of the X-ray powder diffraction. The dynamic properties of the fluoride ions
in RbSn2F5 have been studied by impedance spectroscopy and solid
state NMR. The dc ionic conductivity of this sample shows an abrupt increase
at the phase transition temperature. We have obtained the hopping frequency
and the concentration of the charge carriers (F- ions) at different
temperatures from the analysis of the conductivity spectra using Almond-West
formalism. The estimated values of the charge carriers' concentration agree
well with that determined from the structure and were found to be
independent of temperature. The relatively small value of the power-law
exponent, , supports the two-dimensional property of the
investigated material. Furthermore, 19F NMR with simulation has
suggested the diffusive motions of the fluoride ions between different
sites. In contrast, 119Sn and 87Rb NMR spectra below 250 K
supported the intrinsic disordered nature due to the random distribution of
the fluoride ion vacancies.
PACS: 66.30.Hs – Self-diffusion and ionic conduction in nonmetals / 77.22.Gm – Dielectric loss and relaxation / 76.60.-k – Nuclear magnetic resonance and relaxation
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2004