In situ XRD study of La2Ni7Hx during hydrogen absorption-desorption

Kenji Iwase, Kouji Sakaki, Yumiko Nakamura, Etsuo Akiba

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Abstract

Structural changes of La2Ni7Hx during the first and second absorption-desorption processes along the P-C isotherm were investigated by in situ X-ray diffraction (XRD). Orthorhombic (Pbcn) and monoclinic (C2/c) hydrides coexisted in the first absorption plateau, but only a monoclinic (C2/c) hydride was observed in the first desorption plateau. Phase transformation of La2Ni7Hx was irreversible between the first as well as the second absorption-desorption process. The lattice parameters and expansion of the La2Ni4 and LaNi5 cells during the absorption-desorption process were refined using the Rietveld method. The lattice parameters a and b of the orthorhombic hydride (Pbcn) decreased, while the lattice parameter c increased with increasing hydrogen content in the first absorption. During the first absorption, the volume of the orthorhombic La2Ni4 cell expanded by more than 50%, while the expansion of the LaNi5 cell was below 10%. The monoclinic La2Ni4 cell expanded to approximately four times the size of the LaNi5 cell in the first absorption. The lattice parameters a, b, and c of the monoclinic hydride (C2/c) decreased with decreasing hydrogen content in the first desorption. These La2Ni4 and LaNi5 cells contracted isotropically in the first desorption.

Original languageEnglish
Pages (from-to)10105-10111
Number of pages7
JournalInorganic Chemistry
Volume52
Issue number17
DOIs
Publication statusPublished - Sep 2 2013

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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    Iwase, K., Sakaki, K., Nakamura, Y., & Akiba, E. (2013). In situ XRD study of La2Ni7Hx during hydrogen absorption-desorption. Inorganic Chemistry, 52(17), 10105-10111. https://doi.org/10.1021/ic401419n