Mixed-valence state and structure changes of EuHx (x = 2 and 2 < x ≤ 3) under high-pressure H2 atmosphere

Keiji Kuno, Takahiro Matsuoka, Ryo Masuda, Takaya Mitsui, Makoto Seto, Akihiko Machida, Hiroshi Fujihisa, Naohisa Hirao, Yasuo Ohishi, Katsuya Shimizu, Shigeo Sasaki

Research output: Contribution to journalArticlepeer-review


Raman scattering, Mössbauer spectroscopy, and X-ray diffraction measurements have revealed that EuHx compressed in high-pressure H2 exhibits the crystal structure changes and the divalent (Eu2+) to trivalent (Eu3+) changes via two Eu2+/Eu3+ mixed-valence phases: EuHx-I (Pnma, x = 2, Eu2+) → EuHx-II (P63/mmc, x = 2, 7.0 GPa, Eu2+) → EuHx-III (I4/m, x ≃ 2.2, 7.0–9.0 GPa, Eu2+/Eu3+) → EuHx-V (x ≃ 2.8, 9.0–12.4 GPa, Eu2+/Eu3+) → EuHx-VI (x ≃ 3, 12.4–14.4 GPa, Eu3+) → EuHx-VII (x ≃ 3, 14.4–16 GPa, Eu3+) → EuHx-IV (I4/mmm, x ≃ 3, 16 GPa –, Eu3+). The EuHx-II transforms to EuHx-III at a constant pressure near 7.0 GPa due to the reaction with H2. Our results also demonstrate that Mössbauer spectroscopy can be a useful marker to detect the hydrogen storing in metal hydrides.

Original languageEnglish
Article number158637
JournalJournal of Alloys and Compounds
Publication statusPublished - 2021 Jun 5
Externally publishedYes


  • High pressure
  • Mixed-valence state
  • Mössbauer spectroscopy
  • Raman scattering
  • Rare-earth metal hydrides
  • X-ray diffraction

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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