Hydrogen diffusion in bulk and nanocrystalline palladium: A quasielastic neutron scattering study

Maiko Kofu, Naoki Hashimoto, Hiroshi Akiba, Hirokazu Kobayashi, Hiroshi Kitagawa, Madhusudan Tyagi, Antonio Faraone, John R.D. Copley, Wiebke Lohstroh, Osamu Yamamuro

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15 Citations (Scopus)

Abstract

The diffusion dynamics of hydrogen in bulk and nanocrystalline palladium has been examined using quasielastic neutron scattering (QENS). With respect to bulk PdH0.73, two relaxation processes were found. For both processes, the variation of the relaxation times with momentum transfer was well reproduced by a model of jump diffusion between adjacent octahedral sites. Upon cooling the fast relaxation fraction decreases. The result suggests that the slow relaxation corresponds to jumps between the ground states and the fast one between excited states. In nanocrystalline PdH0.47 with a size of 8 nm, we found a fast diffusion process with a smaller activation energy in addition to the one observed in the bulk sample. This process could be due to the motion of hydrogen atoms in the subsurface region where the potential energy surface is substantially modified by surface strain/distortion effects.

Original languageEnglish
Article number064303
JournalPhysical Review B
Volume94
Issue number6
DOIs
Publication statusPublished - Aug 29 2016
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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