Factors controlling the oxide ion conductivity of fluorite and perovskite structured oxides

Mogensen, Mogens Bjerg; Lybye, Dorthe; Bonanos, Nikolaos; Hendriksen, Peter Vang; Poulsen, F.W.

doi:10.1016/j.ssi.2004.07.036

Cited by 224 publications

(130 citation statements)

References 23 publications

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“…where F is the Faraday constant in [C/mol], V m the molar volume in [cm 3 /mol] and µ p , µ n and µ V the mobilities in [cm 2 /V · s] of p-type (holes), n-type (electrons) and ionic (oxygen vacancies) charge carriers, respectively. The solid lines in Fig.…”

Section: Electrical Conductivity and Carrier Mobilitymentioning

confidence: 99%

Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta

Lohne

Phung

Grande

et al. 2013

J. Electrochem. Soc.

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The oxygen non-stoichiometry was determined by coulometric titration for the perovskite oxides La 0.2 Sr 0.8 FeO 3−δ and La 0.2 Sr 0.8 Fe 0.8 B 0.2 O 3−δ (B = Al 3+ , Ti 4+ and Ta 5+ ) in the temperature range 600• C and the oxygen partial pressure range: 1 · 10 −15 ≤ p O 2 ≤ 0.209 atm. The non-stoichiometry (δ) is observed to decrease with B-site substitution of Fe. The data can be well fitted with simple defect chemistry models. At low oxygen non-stoichiometry all compositions show a deviation from a localized electrons defect model. The standard and partial molar thermodynamic quantities were obtained and a gradual transition from localized to itinerant electrons with decreasing non-stoichiometry is proposed from the δ-dependency of the configurational entropy. The absolute value of the enthalpy of oxidation decreases upon B-site substitution of Fe proposing a decreased thermodynamic stability for the substituted materials. The electrical conductivity was measured at T = 900• C in the oxygen partial pressure range: 1 · 10 −17 ≤ p O 2 ≤ 0.209 atm. The electrical conductivity and charge carrier mobility decrease upon 20% substitution of Fe roughly by a factor of 2, but do not show a significant dependence on the nature of the B-site dopant.

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Section: Electrical Conductivity and Carrier Mobilitymentioning

confidence: 99%

Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta

Lohne

Phung

Grande

et al. 2013

J. Electrochem. Soc.

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“…Examples of features related to the type of cation substitutes are: 1) the crystal lattice shrinks if a fluorite like CeO 2 is doped with a 2 or 3-valent cation of approximately the same size as Ce 4+ ; 2) mechanical failure due to stress gradients caused by volume change gradients during reduction of substituted CeO 2 ; and 3) the oxide ion conductivity reaches its maximum as a function of dopant radius for a dopant radius -the matching radius -that does not change the lattice parameter of the host crystalline compound, i.e. the highest conductivity occurs if Vegard's slope is zero or the conductivity-for a given dopant concentrationis highest in the stress free lattice [1][2][3][4]. Thus, knowledge on volumetric aspects of the crystal defects may help us in optimizing devices that utilize such materials, e.g.…”

mentioning

confidence: 99%

Size of oxide vacancies in fluorite and perovskite structured oxides

et al. 2014

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An analysis of the effective radii of vacancies and the stoichiometric expansion coefficient is performed on metal oxides with fluorite and perovskite structures. Using the hard sphere model with Shannon ion radii we find that the effective radius of the oxide vacancy in fluorites increases with increasing ion radius of the host cation and that it is significantly smaller than the radius of the oxide ion in all cases, from 37 % smaller for HfO 2 to 13 % smaller for ThO 2 . The perovskite structured LaGaO 3 doped with Sr or Mg or both is analyzed in some detail. The results show that the effective radius of an oxide vacancy in doped LaGaO 3 is only about 6 % smaller than the oxide ion. In spite of this the stoichiometric expansion coefficient (a kind of chemical expansion coefficient) of the similar perovskite, LaCrO 3 , is significantly smaller than the stoichiometric expansion coefficient of the fluorite structured CeO 2 . Our analysis results indicate that the smaller stoichiometric expansion coefficient of the perovskites is associated with the restraining action of the A-O sub-lattice to dimensional changes in the B-O sub-lattice and vice versa.

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“…2,3 As an example, the high ionic conductivity SOFC electrolyte and anode material, Gd x Ce 1Àx O 2Àx/2Àd , is known to become highly oxygen decient ($4% at 800 C) under anode conditions with isothermal chemical expansion on the order of 1-2%. [4][5][6] In order to avoid mechanical failure, such behavior places constraints on the operational range and design of SOFCs.…”

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confidence: 99%

Reducing the chemical expansion coefficient in ceria by addition of zirconia

Bishop

Marrocchelli

Fang

et al. 2013

Energy Environ. Sci.

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Factors controlling the oxide ion conductivity of fluorite and perovskite structured oxides

Cited by 224 publications

References 23 publications

Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta

Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta

Size of oxide vacancies in fluorite and perovskite structured oxides

Reducing the chemical expansion coefficient in ceria by addition of zirconia

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Factors controlling the oxide ion conductivity of fluorite and perovskite structured oxides

Cited by 224 publications

References 23 publications

Oxygen Non-Stoichiometry and Electrical Conductivity of La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Fe, Ti, Ta

Oxygen Non-Stoichiometry and Electrical Conductivity of La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Fe, Ti, Ta

Size of oxide vacancies in fluorite and perovskite structured oxides

Reducing the chemical expansion coefficient in ceria by addition of zirconia

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Product

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Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta

Oxygen Non-Stoichiometry and Electrical Conductivity of La_0.2Sr_0.8Fe_0.8B_0.2O_{3 − δ}, B = Fe, Ti, Ta