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Dual Oxygen Defects in Layered La1.2Sr0.8−xBaxInO4+δ (x = 0.2, 0.3) Oxide-Ion Conductors: A Neutron Diffraction Study

AuthorsTroncoso, Loreto; Mariño, Carlos; Arce, Mauricio D.; Alonso, José Antonio
Issue Date17-May-2019
PublisherMultidisciplinary Digital Publishing Institute
CitationMaterials 12 (10): 1624 (2019)
AbstractThe title compounds exhibit a K<sub>2</sub>NiF<sub>4</sub>-type layered perovskite structure; they are based on the La<sub>1.2</sub>Sr<sub>0.8</sub>InO<sub>4+&delta;</sub> oxide, which was found to exhibit excellent features as fast oxide-ion conductor via an interstitial oxygen mechanism. These new Ba-containing materials were designed to present a more open framework to enhance oxygen conduction. The citrate-nitrate soft-chemistry technique was used to synthesize such structural perovskite-type materials, followed by annealing in air at moderate temperatures (1150 &deg;C). The subtleties of their crystal structures were investigated from neutron powder diffraction (NPD) data. They crystallize in the orthorhombic <i>Pbca</i> space group. Interstitial O3 oxygen atoms were identified by difference Fourier maps in the NaCl layer of the K<sub>2</sub>NiF<sub>4</sub> structure. At variance with the parent compound, conspicuous oxygen vacancies were found at the O2-type oxygen atoms for x = 0.2, corresponding to the axial positions of the InO<sub>6</sub> octahedra. The short O2&ndash;O3 distances and the absence of steric impediments suggest a dual oxygen-interstitial mechanism for oxide-ion conduction in these materials. Conductivity measurements show that the activation energy values are comparable to those typical of ionic conductors working by simple vacancy mechanisms (~1 eV). The increment of the total conductivity for x = 0.2 can be due to the mixed mechanism driving both oxygen vacancies and interstitials, which is original for these potential electrolytes for solid-oxide fuel cells.
Identifiersdoi: 10.3390/ma12101624
Appears in Collections:Colección MDPI
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