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Materials 2016, 9(3), 154; doi:10.3390/ma9030154

Effect of A-Site Cation Ordering on Chemical Stability, Oxygen Stoichiometry and Electrical Conductivity in Layered LaBaCo2O5+δ Double Perovskite

Department of Material Science and Engineering, NTNU Norwegian University of Science and Technology, Trondheim NO-7491, Norway
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Academic Editor: Lioz Etgar
Received: 22 January 2016 / Revised: 8 February 2016 / Accepted: 23 February 2016 / Published: 3 March 2016
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

The effect of the A-site cation ordering on the chemical stability, oxygen stoichiometry and electrical conductivity in layered LaBaCo2O5+δ double perovskite was studied as a function of temperature and partial pressure of oxygen. Tetragonal A-site cation ordered layered LaBaCo2O5+δ double perovskite was obtained by annealing cubic A-site cation disordered La0.5Ba0.5CoO3-δ perovskite at 1100 °C in N2. High temperature X-ray diffraction between room temperature (RT) and 800 °C revealed that LaBaCo2O5+δ remains tetragonal during heating in oxidizing atmosphere, but goes through two phase transitions in N2 and between 450 °C and 675 °C from tetragonal P4/mmm to orthorhombic Pmmm and back to P4/mmm due to oxygen vacancy ordering followed by disordering of the oxygen vacancies. An anisotropic chemical and thermal expansion of LaBaCo2O5+δ was demonstrated. La0.5Ba0.5CoO3-δ remained cubic at the studied temperature irrespective of partial pressure of oxygen. LaBaCo2O5+δ is metastable with respect to La0.5Ba0.5CoO3-δ at oxidizing conditions inferred from the thermal evolution of the oxygen deficiency and oxidation state of Co in the two materials. The oxidation state of Co is higher in La0.5Ba0.5CoO3-δ resulting in a higher electrical conductivity relative to LaBaCo2O5+δ. The conductivity in both materials was reduced with decreasing partial pressure of oxygen pointing to a p-type semiconducting behavior. View Full-Text
Keywords: layered double perovskite (LDP); cation and anion ordering; chemical expansion; solid oxide fuel cells layered double perovskite (LDP); cation and anion ordering; chemical expansion; solid oxide fuel cells
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Bernuy-Lopez, C.; Høydalsvik, K.; Einarsrud, M.-A.; Grande, T. Effect of A-Site Cation Ordering on Chemical Stability, Oxygen Stoichiometry and Electrical Conductivity in Layered LaBaCo2O5+δ Double Perovskite. Materials 2016, 9, 154.

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