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A structural study of Ruddlesden-Popper phases Sr3-xYx(Fe125Ni075)O7-δ with x ≤ 0.75 by neutron powder diffraction and EXAFS/XANES spectroscopy

Grins, Jekabs; Wardecki, Dariusz; Jansson, Kjell; Carlson, Stefan LU ; Biendicho, Jordi J. and Svensson, Gunnar (2018) In Journal of Materials Chemistry A 6(13).
Abstract

The structures of Ruddlesden-Popper n = 2 member phases Sr3-xYxFe125Ni0.75O7-δ with 0 ≤ x ≤ 0.75 have been investigated using neutron powder diffraction and K-edge Fe and Ni EXAFS/XANES spectroscopy in order to gain information about the evolution of the oxygen vacancy distribution and Fe/Ni oxidation state with x. Both samples prepared at 1300°C under a flow of N2(g), with δ = 1.41-1.00, and samples subsequently annealed in air at 900°C, with δ = 0.44-0.59, were characterized. The as-prepared x = 0.75 phase has δ = 1, the O1 atom site is vacant, and the Fe3+/Ni2+ ions have a square pyramidal coordination. With decreasing x the O3 occupancy decreases nearly... (More)

The structures of Ruddlesden-Popper n = 2 member phases Sr3-xYxFe125Ni0.75O7-δ with 0 ≤ x ≤ 0.75 have been investigated using neutron powder diffraction and K-edge Fe and Ni EXAFS/XANES spectroscopy in order to gain information about the evolution of the oxygen vacancy distribution and Fe/Ni oxidation state with x. Both samples prepared at 1300°C under a flow of N2(g), with δ = 1.41-1.00, and samples subsequently annealed in air at 900°C, with δ = 0.44-0.59, were characterized. The as-prepared x = 0.75 phase has δ = 1, the O1 atom site is vacant, and the Fe3+/Ni2+ ions have a square pyramidal coordination. With decreasing x the O3 occupancy decreases nearly linearly to 81% for x = 0, while the O1 occupancy increases from 0 for x = 0.4 to 33% for x = 0. The air-annealed x = 0.75 sample has a δ value of 0.59 and the Fe3+/Fe4+/Ni2+/Ni3+ ions have both square pyramidal and octahedral coordination. With decreasing x, the δ value decreases to 0.45 for x = 0, implying an increase in the oxidation states of Fe/Ni ions. EXAFS/XANES data show that for the as-prepared samples the coordination changes are predominantly for Ni2+ ions and that the air-annealed samples contain both Fe3+/Fe4+ and Ni2+/Ni3+ ions.

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Contribution to journal
publication status
published
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in
Journal of Materials Chemistry A
volume
6
issue
13
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85044669667
ISSN
2050-7488
DOI
10.1039/c7ta07113b
language
English
LU publication?
yes
id
889d3744-08a7-465c-987b-d5d977490fd7
date added to LUP
2018-04-12 14:39:15
date last changed
2018-10-07 05:05:58
@article{889d3744-08a7-465c-987b-d5d977490fd7,
  abstract     = {<p>The structures of Ruddlesden-Popper n = 2 member phases Sr<sub>3-x</sub>Y<sub>x</sub>Fe<sub>1</sub>25Ni0.75O<sub>7-δ</sub> with 0 ≤ x ≤ 0.75 have been investigated using neutron powder diffraction and K-edge Fe and Ni EXAFS/XANES spectroscopy in order to gain information about the evolution of the oxygen vacancy distribution and Fe/Ni oxidation state with x. Both samples prepared at 1300°C under a flow of N<sub>2</sub>(g), with δ = 1.41-1.00, and samples subsequently annealed in air at 900°C, with δ = 0.44-0.59, were characterized. The as-prepared x = 0.75 phase has δ = 1, the O1 atom site is vacant, and the Fe<sup>3+</sup>/Ni<sup>2+</sup> ions have a square pyramidal coordination. With decreasing x the O3 occupancy decreases nearly linearly to 81% for x = 0, while the O1 occupancy increases from 0 for x = 0.4 to 33% for x = 0. The air-annealed x = 0.75 sample has a δ value of 0.59 and the Fe<sup>3+</sup>/Fe<sup>4+</sup>/Ni<sup>2+</sup>/Ni<sup>3+</sup> ions have both square pyramidal and octahedral coordination. With decreasing x, the δ value decreases to 0.45 for x = 0, implying an increase in the oxidation states of Fe/Ni ions. EXAFS/XANES data show that for the as-prepared samples the coordination changes are predominantly for Ni<sup>2+</sup> ions and that the air-annealed samples contain both Fe<sup>3+</sup>/Fe<sup>4+</sup> and Ni<sup>2+</sup>/Ni<sup>3+</sup> ions.</p>},
  author       = {Grins, Jekabs and Wardecki, Dariusz and Jansson, Kjell and Carlson, Stefan and Biendicho, Jordi J. and Svensson, Gunnar},
  issn         = {2050-7488},
  language     = {eng},
  month        = {01},
  number       = {13},
  publisher    = {Royal Society of Chemistry},
  series       = {Journal of Materials Chemistry A},
  title        = {A structural study of Ruddlesden-Popper phases Sr<sub>3-x</sub>Y<sub>x</sub>(Fe<sub>125</sub>Ni075)O<sub>7-δ</sub> with x ≤ 0.75 by neutron powder diffraction and EXAFS/XANES spectroscopy},
  url          = {http://dx.doi.org/10.1039/c7ta07113b},
  volume       = {6},
  year         = {2018},
}