Structural analysis of La2-xSrxNiO4 + δ by high temperature X-ray diffraction

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Abstract

High temperature X-ray diffraction measurements were made on oxygen nonstoichiometric La2 - xSrxNiO4 + δ in N2-O2 atmosphere at 873-1173 K. Crystal structure of La2-xSrxNiO4 + δ at high temperatures was analyzed using the tetragonal symmetry, I4/mmm. As the amount of excess oxygen increases, the lattice parameter perpendicular to the perovskite and the rock salt layers increases and that parallel to the layers decreases. As a consequence, the cell volume is almost constant regardless of the oxygen content variation. The lattice parameters essentially depend on temperature and δ. The relationship among the lattice parameters, temperature, and δ is expressed by the total differential form of the lattice parameters. The model with linear approximation can well explain the variation of the lattice parameters with δ and temperature. Apparent and true thermal expansion coefficients were calculated from the variation of the lattice parameters with temperature. Crystal structure of La2 - xSrxNiO4 + δ was estimated by the Rietveld analysis. It is elucidated that the space in the rock salt layer decreases as the acceptor concentration (x + 2δ) increases. The variation of the space in the rock salt layer is consistent with the oxygen nonstoichiometric behavior that the interstitial oxygen formation is suppressed as x and δ increase.

Original languageEnglish
Pages (from-to)292-299
Number of pages8
JournalSolid State Ionics
Volume181
Issue number5-7
DOIs
Publication statusPublished - 2010 Mar 11

Keywords

  • High temperature X-ray diffractometry
  • KNiF type oxides
  • LaNiO
  • Oxygen nonstoichiometry
  • Rietveld analysis

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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