THESIS
2022
1 online resource (xx, 149 pages) : illustrations (some color)
Abstract
BaFeO
3-δ (BFO)-derived cubic perovskites show promise as air electrodes for intermediate and
low-temperature ceramic fuel cells. Their highly oxygen-deficient structure and their
exceptional mixed ionic-electronic conductivity make them ideal catalysts for the oxygen
reduction reaction. Their electrochemical properties could be further enhanced by the
introduction of crystal defects, such as ionic dopants or deficient stoichiometry, the presence
of secondary phases, and grain-size variations. Nevertheless, the influence of such defects on
the working mechanisms of BFO-derived perovskites is still not completely understood. By
combining first-principle computations and experiments, the proposed work aims at exploring
the matter, focusing on applications of BFO-derived materials in solid...[
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BaFeO
3-δ (BFO)-derived cubic perovskites show promise as air electrodes for intermediate and
low-temperature ceramic fuel cells. Their highly oxygen-deficient structure and their
exceptional mixed ionic-electronic conductivity make them ideal catalysts for the oxygen
reduction reaction. Their electrochemical properties could be further enhanced by the
introduction of crystal defects, such as ionic dopants or deficient stoichiometry, the presence
of secondary phases, and grain-size variations. Nevertheless, the influence of such defects on
the working mechanisms of BFO-derived perovskites is still not completely understood. By
combining first-principle computations and experiments, the proposed work aims at exploring
the matter, focusing on applications of BFO-derived materials in solid oxide fuel cells and
protonic ceramic fuel cells. In particular, the influence of Ag introduction and A-site deficiency
on the properties of BFO are investigated and optimized for intermediate temperature solid
oxide fuel cells by analyzing and characterizing the series of materials Ba
0.9La
0.1Fe
1-xAg
xO
3-δ
and (Ba
0.95La
0.05)
1-xFeO
3-δ. This study subsequently investigates the proton conductive material
Ba
0.9Fe
0.9Zr
0.1O
3-δ as an air electrode for reversible protonic ceramic fuel cells. For its
preparation, the traditional solid-state reaction sintering method is compared with ultrafast
high-temperature sintering (UHS). UHS not only reduces the sintering time from hours to
seconds but also generates an interesting new electrode microstructure. In addition, UHS
enables F substitution generating Ba
0.9Fe
0.9Zr
0.1O
2.9-δF
0.1. The materials are investigated and
compared, producing interesting insights for a better comprehension of the role of defects on
BFO’s working mechanisms.
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