A structural study of Ruddlesden-Popper phases Sr3-xYx(Fe125Ni075)O7-δ with x ≤ 0.75 by neutron powder diffraction and EXAFS/XANES spectroscopy
Journal article, 2018

The structures of Ruddlesden-Popper n = 2 member phases Sr 3-x Y x Fe 1 25Ni0.75O 7-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 N 2 (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 3+ /Ni 2+ 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 3+ /Fe 4+ /Ni 2+ /Ni 3+ 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 2+ ions and that the air-annealed samples contain both Fe 3+ /Fe 4+ and Ni 2+ /Ni 3+ ions.


J. Grins

Stockholm University

Dariusz Wojciech Wardecki

Stockholm University

University of Warsaw

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Kjell Jansson

Stockholm University

Stefan Carlson

Lund University

J. J. Biendicho

Stockholm University

Catalonia Institute for Energy Research (IREC)

Gunnar Svensson

Stockholm University

Journal of Materials Chemistry A

20507488 (ISSN) 20507496 (eISSN)

Vol. 6 13 5313-5323

Subject Categories

Inorganic Chemistry

Analytical Chemistry

Materials Chemistry



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