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

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1624 ◽  
Author(s):  
Loreto Troncoso ◽  
Carlos Mariño ◽  
Mauricio D. Arce ◽  
José Antonio Alonso

The title compounds exhibit a K2NiF4-type layered perovskite structure; they are based on the La1.2Sr0.8InO4+δ 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 °C). The subtleties of their crystal structures were investigated from neutron powder diffraction (NPD) data. They crystallize in the orthorhombic Pbca space group. Interstitial O3 oxygen atoms were identified by difference Fourier maps in the NaCl layer of the K2NiF4 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 InO6 octahedra. The short O2–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.

1997 ◽  
Vol 496 ◽  
Author(s):  
Masami Kanzaki ◽  
Akihiko Yamaji ◽  
Kazuya Kawakami

ABSTRACTBrownmillerite(Ca2Al2O5-Ca2Fe2O5 solid solution) structure can be regarded as an oxygen-ion deficient perovskite structure. Because of high proportion of the oxygen vacancies in the structure, this material could be a candidate of fast oxide-ion conductor. Goodenough et al. indeed observed a first-order transition to a fast oxide-ion conductor at 930° C for Ba2In2O5 which adapts brownmillerite structure at ambient temperature. Molecular dynamics simulation was employed to study oxygen ion diffusion and phase transition of Ba2In2O5. The structure was well simulated at 300 K. When the system was heated, the original orthogonal cell transformed to a tetragonal cell at 2300 K. Inspection of the structure revealed that oxygen ions started to migrate from their original sites to nearest vacant oxygen sites at this temperature. The diffusion was restricted for the oxygen sites around In-tetrahedron, resulting highly anisotropie diffusion on the ac plane. At 4600 K it further transformed to an oxygen vacancies-disordered cubic perovskite structure. Although predicted transition temperature were apparently overestimated, the transition way to the phases with high oxygen ion diffusivity is consistent with the experimental results from electrical conductivity measurements. The high temperature cubic phase shows large ion conductivity. It is of interest to examine whether or not the cubic phase stabilizes in the low temperature region by making solid solution of another elements. We found that the cubic phase is stabilized below 500° C without any decrease of conductivity in BaIn1.9Ce0.1Oy and Ba2In1.8Nb0.2O5.


2009 ◽  
Vol 182 (5) ◽  
pp. 1009-1016 ◽  
Author(s):  
Gwenaël Corbel ◽  
Pierrick Durand ◽  
Philippe Lacorre

2018 ◽  
Vol 6 (13) ◽  
pp. 5290-5295 ◽  
Author(s):  
K. S. McCombie ◽  
E. J. Wildman ◽  
S. Fop ◽  
R. I. Smith ◽  
J. M. S. Skakle ◽  
...  

The crystal structure of the novel oxide ion conductor Ba3WNbO8.5.


1997 ◽  
pp. 313-314 ◽  
Author(s):  
Darren P. Scarfe ◽  
Sai Bhavaraju ◽  
Allan J. Jacobson

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