Redox behavior of the SOFC electrode candidate NdBaMn2O5+: δ investigated by high-temperature in situ neutron diffraction: First characterisation in real time of an Ln BaMn2O5.5 intermediate phase

F. Tonus 1 M. Bahout 2 V. Dorcet 2 G.H. Gauthier 3 S. Paofai 2 R.I. Smith 4 S.J. Skinner 1
1 Imperial College London
2 ISCR - Institut des Sciences Chimiques de Rennes
3 UIS - Universidad Industrial de Santander [Bucaramanga]
4 RAL - STFC Rutherford Appleton Laboratory
Abstract : The structural behavior of the tetragonal NdBaMn2O5 phase, a member of the family of A-site ordered layered manganites that have been recently suggested as possible mixed ionic and electronic conductors, has been investigated by means of in situ neutron powder diffraction. Considering applications in energy production and storage devices and use of NdBaMn2O5+δ as an electrode in symmetrical cells, the study was carried out in relevant atmosphere conditions, i.e. dilute hydrogen (wet and dry) and dry air in the temperature range 25-800 °C. Neutron data under flowing hydrogen allowed monitoring of the structural phase transition from the charge-ordered to the charge-disordered state as a function of temperature. Slow reduction of the fully oxidised phase, NdBaMn2O6, previously formed from quick oxidation of the pristine material, enabled real-time observation of the intermediate NdBaMn2O5.5 phase and its crystal characterization up to 700 °C in the course of its conversion to NdBaMn2O5. Oxygen vacancy ordering within the Nd layers of NdBaMn2O5.5 correlated with antiferrodistortive orbital ordering of the Jahn-Teller Mn3+ ion in the square pyramids and octahedra results in large thermal expansion and relatively slow anisotropic oxygen diffusion occurring in the NdO layer. The four heating/cooling cycles evidenced no oxygen miscibility between the three distinct phases detected in the NdBaMn2O5+δ system with δ ∼ 0, 0.5 and 1 and clearly demonstrated that reversible oxygen intercalation/deintercalation underpins the phase stability of the LnBaMn2O5+δ materials to redox cycling and to wet atmosphere in high temperature electrochemical devices.
Keywords : Atmospheric temperature Structural phase transition Situ neutron powder diffractions Real time observation Oxygen vacancy orderings Oxygen intercalation Thermal expansion Solid oxide fuel cells (SOFC) Mixed ionic and electronic conductors Virtual storage High-temperature electrochemical High-temperature in situ Characterization Digital storage Electrodes Hydrogen storage Manganese Neutrons Oxygen Oxygen vacancies Reaction intermediates
Type de document :
Article dans une revue
Journal of Materials Chemistry. A, Royal Society of Chemistry, 2016, 4 (30), pp.11635--11647. 〈10.1039/c6ta03224a〉
Domaine :
Liste complète des métadonnées
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367218
Contributeur : Laurent Jonchère <>
Soumis le : jeudi 14 septembre 2017 - 15:39:15
Dernière modification le : vendredi 25 mai 2018 - 01:26:14

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F. Tonus, M. Bahout, V. Dorcet, G.H. Gauthier, S. Paofai, et al.. Redox behavior of the SOFC electrode candidate NdBaMn2O5+: δ investigated by high-temperature in situ neutron diffraction: First characterisation in real time of an Ln BaMn2O5.5 intermediate phase. Journal of Materials Chemistry. A, Royal Society of Chemistry, 2016, 4 (30), pp.11635--11647. 〈10.1039/c6ta03224a〉. 〈hal-01367218〉

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