APPC12 A2-PTu-23
The 12th Asia Pacific Physics Conference
Proton conduction path in Rb3H(SeO4)2 studied by high temperature
neutron single crystal diffraction
R. Kiyanagi, Y. Ishikawa a, Y. Noda b
J-PARC center, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
a
High Energy Accelerator Research Institute, Tsukuba, Ibaraki, Japan
b
IMRAM, Tohoku University, Sendai, Miyagi, Japan
ryoji.kiyanagi@j-parc.jp
The materials represented as M3H(XO4)2 (M = K, Rb, Cs, X = S, Se) are known to
exhibit high protonic conductivity above 400 – 500 K. The protonic conductivity
emerges accompanied by a structural phase transition. This structural transition
involves disordering of hydrogen bonds and XO4 tetrahedrons that are regarded to be
responsible for the protonic conductivity. However, the detailed mechanism of the
phase transition and the proton-conduction has not been understood, including the
conduction path of the protons. In order to clarify the details of the phase transition
and the protonic conduction, structural studies of Rb3H(SeO4)2 by neutron single
crystal diffraction were carried out at several temperatures using FONDER at JRR-3.
Nuclear density distributions were obtained from the measured Bragg reflections
by the Fourier synthesis method (Fig. 1). The distribution in the proton-conducting
phase clearly displayed the conduction path of the protons. The conduction path
spreads over two-dimensionally, which is consistent with the reported anisotropy in
the conductivity. In addition, small bumps were found in the distribution of the
protons, suggesting the existence of an intermediate state of the conducting protons.
Fig.1 Obtained nuclear density distribution at room temperature (left) and at 480 K (right).
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