A-site order–disorder in the NdBaMn2O5+δ SOFC electrode material monitored in situ by neutron diffraction under hydrogen flow
Sharma, Rakesh K.
Smith, Ronald I.
Skinner, Stephen J.
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AbstractThe A-site disordered perovskite manganite, Nd0.5Ba0.5MnO3, has been obtained by heating the A-site-ordered and vacancy ordered layered double perovskite, NdBaMn2O5, in air at 1300 °C for 5 h. Combined transmission electron microscopy (TEM) images and neutron powder diffraction (NPD) analysis at 25 °C revealed that Nd0.5Ba0.5MnO3 has a pseudotetragonal unit cell with orthorhombic symmetry (space group Imma, √2ap × 2ap × √2ap) at 20 °C with the cell dimensions a = 5.503(1) Å, b = 7.7962(4) Å, c = 5.502(1) Å, in contrast to Pm[3 with combining macron]m or Cmcm that have been previously stated from X-ray diffraction studies. The in situ neutron diffraction study carried out on Nd0.5Ba0.5MnO3 in hydrogen flow up to T ∼ 900 °C, allows monitoring the A-site cation disorder–order structural phase transition of this representative member of potential SOFC anode materials between air sintering conditions and hydrogen working conditions. Oxygen loss from Nd0.5Ba0.5MnO3 proceeds with retention of A-site disorder until the oxygen content reaches the Nd0.5Ba0.5MnO2.5 composition at 600 °C. The phase transition to layered NdBaMn2O5 and localization of the oxygen vacancies in the Nd layer proceeds at 800 °C with retention of the oxygen content. Impedance spectroscopy measurements for the oxidized A-site ordered electrode material, NdBaMn2O6, screen printed on a Ce0.9Gd0.1O2−δ (CGO) electrolyte showed promising electrochemical performance in air at 700 °C with a polarization resistance of 1.09 Ω cm2 without any optimization.
CitationTonus F, Bahout M, Dorcet V, Sharma RK, Djurado E, et al. (2017) A-site order–disorder in the NdBaMn2O5+δ SOFC electrode material monitored in situ by neutron diffraction under hydrogen flow. Journal of Materials Chemistry A 5: 11078–11085. Available: http://dx.doi.org/10.1039/c7ta01439b.
SponsorsThe authors thank Chris Goodway, Paul McIntyre and Adam Sears of the ISIS User Support Group for technical assistance with the furnace and gas handling equipment during the neutron diffraction experiment and STFC for provision of neutron beam time (RB 1510473). We would like to thank Dr Marek Jura for help on the Rigaku Miniflex 600 X-ray powder diffractometer in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source, and Dr Craig Bull at ISIS for giving us access to pellet-making facilities and a high temperature furnace for on-site sample preparation. MB acknowledges T. Roisnel (UR1) for fruitful advice for the analysis of TOF data. FT thanks the KAUST Academic Excellence Alliance for funding. TEM images were performed at THEMIS facility (ScanMAT, UMS 2001 CNRS- University of Rennes 1) which received a financial support from the European Union.
PublisherRoyal Society of Chemistry (RSC)
JournalJ. Mater. Chem. A