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Titel:
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Phase stability and oxygen non-stoichiometry of Sr Co0.8Fe0.3O3-d measured by in situ neutron diffraction
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Auteur(s):
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Gepubliceerd door:
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Publicatie datum:
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ECN
Energie Efficiency in de Industrie
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1-5-2006
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ECN publicatienummer:
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Publicatie type:
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ECN-RX--06-079
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Artikel wetenschap tijdschrift
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Aantal pagina's:
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10
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Gepubliceerd in: Solid State Ionics (Elsevier), , 2006, Vol.177, p.833-842.
Samenvatting:
The phase stability, oxygen stoichiometry and expansion properties of SrCo0.8Fe0.2O3-d (SCF) were determined by in situ neutron diffraction
between 873 and 1173 K and oxygen partial pressures of 5×10-4 to 1 atm. At a pO2 of 1 atm, SCF adopts a cubic perovskite structure, space
group Pm3¯m, across the whole temperature range investigated. At a pO2 of 10-1 atm, a two-phase region exists below 922 K, where the cubic
perovskite phase coexists with a vacancy ordered brownmillerite phase, Sr2Co1.6Fe0.4O5, space group Icmm. A pure brownmillerite phase is
present at pO2 of 10-2 and 5×10-4 atm below 1020 K. Above 1020 K, the brownmillerite phase transforms to cubic perovskite through a twophase
region with no brownmillerite structure observed above 1064 K. Large distortion of the BO6 (B=Co, Fe) octahedra is present in the
brownmillerite structure with apical bond lengths of 2.2974(4)Å and equatorial bond lengths of 1.9737(3) Å at 1021 K and a pO2 of 10-2 atm.
SCF is highly oxygen deficient with a maximum oxygen stoichiometry, 3-d, measured in this study of 2.58(2) at 873 K and a pO2 of 1 atm and a
minimum of 2.33(2) at 1173 K and a pO2 of 5×10-4 atm. Significant differences in lattice volume and expansion behavior between the
brownmillerite and cubic perovskite phases suggest potential difficulties in thermal cycling of SrCo0.8Fe0.2O3-d membranes.
© 2006 Elsevier B.V. All rights reserved.
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