Partial cationic order at the B site of the n = 3 Ruddlesden-Popper phases LaSr3(Fe,Co,Ga)3O10-δ studied by Neutron Powder Diffraction and X-ray Absorption Spectroscopy

VEGA-CASTILLO, J.; CUELLO, G.J.; PRADO, F.

JOURNAL OF SOLID STATE CHEMISTRY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2020 vol. 290 p. 121584 - 121584

0022-4596

The crystal chemistry of the Ruddlesden-Popper phases LaSr3Fe1.5Co1.5O10-δ, LaSr3Fe1.35Co1.35Ga0.3O10δ, LaSr3Fe1.8Co0.6Ga0.6O10δ and LaSr3Fe2.4Ga0.6O10δ with tetragonal symmetry has been studied by NeutronPowder Diffraction (NPD) and X-ray Absorption Spectroscopy (XAS) varying Fe, Co and Ga content. NPD datashows that oxygen vacancies are located at the O(2) and O(4) crystal sites at the central octahedra of theperovskite block. Furthermore, Fe, Co and Ga cations are not homogeneously distributed, showing certain preferencefor particular crystal sites in the perovskite block. For instance, Fe cations tend to accommodate in siteswith a lower concentration of oxygen defects, i.e. the B(2) crystal sites of the perovskite layers next to the rock salt layer, while Ga cations noticeably prefer the B(1) sites at the central perovskite layer. This cationic distribution was confirmed by Extended X-ray Absorption Fine Structure (EXAFS) analysis, which shows the average coordination number of Fe is always higher than the coordination number obtained for Co and Ga, in agreement with the preferential location of the oxygen vacancies at the central perovskite layer where Ga cations are located according to NPD data. The combination of NPD and XAS data was found effective to describe the crystalchemistry and defect structure of the LaSr3FexCoyGa3xyO10δ system.