Identification of vacancy formation sites in LaNi 5Cu during hydrogenation using in situ coincidence doppler broadening technique

Kouji Sakaki, Yumiko Nakamura, Etsuo Akiba

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1 Citation (Scopus)

Abstract

To study the formation mechanism of lattice defects introduced during hydrogenation, we developed equipment that can measure in situ positron lifetime and coincidence Doppler broadening (CDB) simultaneously with pressure-composition (P-C) isotherms at room temperature. The equipment, which consisted of a high-pressure sample holder, reduced the intensity of the background signals in the relatively high momentum region of the Doppler broadening spectrum by more than 2 orders of magnitude in comparison to the background shown by conventional Doppler broadening equipment. Further, the quality of data obtained by our instrument was similar to that obtained from ex situ CDB equipment without a high-pressure sample holder. The substitution effect on the positron annihilation behavior was observed from the ratio curves of CDB spectra for LaNi 5Cu and LaNi 5-xAl x. In addition, using the equipment we developed, we attempted to identify the vacancy formation sites introduced in LaNi 5Cu during hydrogenation. Changes in positron lifetime and the S parameter indicated that the vacancies were introduced above 0.35 H/M during hydrogenation and the introduced vacancies were completely recovered below 0.33 H/M during dehydrogenation. The changes in the ratio curves suggested that vacancies were introduced at Ni sites during hydrogenation.

Original languageEnglish
Pages (from-to)22238-22244
Number of pages7
JournalJournal of Physical Chemistry C
Volume116
Issue number42
DOIs
Publication statusPublished - Oct 25 2012

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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