Journal article
Oxygen incorporation in porous thin films of strontium doped lanthanum ferrite
Electroceramics, Fuel Cells and Solid State Chemistry Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark1
Fuel Cells and Solid State Chemistry Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark2
Risø National Laboratory for Sustainable Energy, Technical University of Denmark3
Swiss Federal Institute of Technology Zurich4
Electrochemistry, Fuel Cells and Solid State Chemistry Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark5
Massachusetts Institute of Technology6
Electrical conductivity relaxation measurements were carried out on thin films of (La0.6Sr0.4)0.99 FeO3 − δ deposited on MgO (100) substrates by pulsed laser deposition in order to determine the surface exchange coefficient, k Ex, of the oxygen incorporation process in the temperature range 550–700°C.
The composition of the films was verified using wavelength dispersive x-ray and Rutherford backscattering spectroscopy. Scanning electron microscopy showed small triangular crystallites with the largest dimension 80 nm and the smallest dimension 10 nm. X-ray diffraction showed a cubic perovskite structure and significant texturing.
At a constant temperature, k Ex was found to be a function only of the final pO2pO2 of the pO2pO2-changes the sample was subjected to during conductivity relaxation experiments, confirming that the magnitude of the exchange coefficient was not influenced by changes in ionic defect concentrations. The k Ex-values determined for these thin films were significantly lower than for bulk samples.
A value of 3.6 × 10 − 6 cm s − 1 was obtained at 702°C and a final pO2pO2 of 0.048 atm, approximately a factor of six lower than that obtained for bulk samples. An activation energy of 282 ± 20 kJ mol − 1 was found for the surface exchange coefficient at pO2pO2 = 0.048 atm. Possible reasons for the reduced magnitude of k Ex are discussed including the role of thermal history in influencing surface morphology and chemistry.
Language: | English |
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Publisher: | Springer US |
Year: | 2011 |
Pages: | 134-142 |
ISSN: | 15738663 and 13853449 |
Types: | Journal article |
DOI: | 10.1007/s10832-011-9658-3 |
ORCIDs: | Hendriksen, Peter Vang and Mogensen, Mogens Bjerg |