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Title: LaFeO₃ as a base material for cathode applications in intermediate temperature solid oxide fuel cells
Author: Taylor, Felicity H.
ISNI:       0000 0004 7964 9303
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Computational techniques have been employed to perform an in-depth study into the defect chemistry of LaFeO₃, a mixed ionic electronic conductor and a promising candidate for intermediate temperature solid oxide fuel cell cathode applications. Initially, a range of isolated point defects and disorder schemes were considered, from which we established the favourable formation of cation and oxygen vacancies, under oxygen rich and oxygen poor conditions respectively. Schottky disorder also plays an important role in the defect chemistry of LaFeO₃ and the defect model we propose was verified through comparison with experimental work on the oxygen non-stoichiometry of LaFeO₃. Work on the activation energy of oxide ion migration through LaFeO₃ considered three pathways, due to two inequivalent oxygen sites being present in orthorhombic LaFeO₃. The pathways between the O1 and O2 and O2 and O2 sites were found to be the most favourable, having low activation energies in line with experimental results. A range of divalent dopants were then considered, for both the A- and B-sites, with strontium, calcium and manganese showing promising results as A-site dopants, due to low solution and binding energies, while cobalt and nickel showed promising results as B-site dopants. We finished by considering two terminations of the (001) surface of LaFeO₃: FeO₂ and LaO. We found that although the LaO terminated surface has the lowest surface energy, the FeO₂ terminated surface is most defective, with cation vacancies and oxygen vacancies having low formation energies. The FeO₂ terminated surface, therefore, is likely to be more catalytically active than the LaO terminated surface. Two techniques have been used throughout this work, interatomic potential-based methods and DFT-based methods, the results from each are compared throughout.
Supervisor: Catlow, C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available