Origin of activation energy in a superionic conductor

O. Kamishima, K. Kawamura, T. Hattori, J. Kawamura

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The characteristics of cation diffusion with many-body effects are discussed using Ag β-alumina as an example of a superionic conductor. Polarized Raman spectra of Ag β-alumina have been measured at room temperature. The interatomic potentials were determined by a non-linear least square fitting between the phonon eigenvalues from the Raman observations and a dynamical matrix calculation based on a rigid-ion model. The obtained potential parameters for the model crystal of Ag β-alumina successfully reproduce the macroscopic properties with respect to the heat capacity, isothermal compressibility and self-diffusion constant. A molecular dynamics (MD) calculation has been carried out using the model crystal of Ag β-alumina to understand the many-body effects for the fast ionic diffusion. It was found that the Ag-Ag repulsion by excess Ag defects significantly reduced the cost of the energy difference of the occupancy between the stable and metastable sites. It is possible for the system to take various configurations of the mobile ions through defects easily, and then the fast ionic diffusion will appear. On the other hand, the Ag-Ag repulsion changes the dynamics of the Ag ions from a random hopping to a cooperative motion. In the cooperative motion, the ionic transport becomes difficult due to the additional energy required for the structural relaxation of the surrounding Ag ions. We propose a new insight into the superionic conduction, that is, the activation energy for the ionic transport is composed of two kinds of elements: a 'static' activation energy and a 'dynamic' one. The static activation energy is the cost of the averaged energy difference in the various structural configurations in the equilibrium state. The dynamic activation energy is the additional energy required for the structural relaxation induced by the jump process.

Original languageEnglish
Article number225404
JournalJournal of Physics Condensed Matter
Volume23
Issue number22
DOIs
Publication statusPublished - 2011
Externally publishedYes

Fingerprint

Aluminum Oxide
Alumina
conductors
aluminum oxides
Activation energy
Ions
activation energy
ionic diffusion
Structural relaxation
ions
costs
Defects
Crystals
energy
defects
configurations
Compressibility
compressibility
Specific heat
crystals

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)

Cite this

Origin of activation energy in a superionic conductor. / Kamishima, O.; Kawamura, K.; Hattori, T.; Kawamura, J.

In: Journal of Physics Condensed Matter, Vol. 23, No. 22, 225404, 2011.

Research output: Contribution to journalArticle

Kamishima, O. ; Kawamura, K. ; Hattori, T. ; Kawamura, J. / Origin of activation energy in a superionic conductor. In: Journal of Physics Condensed Matter. 2011 ; Vol. 23, No. 22.
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