Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

Søgaard, Martin; Hendriksen, Peter Vang; Mogensen, Mogens Bjerg

doi:10.1016/j.jssc.2007.02.012

Cited by 200 publications

(242 citation statements)

References 27 publications

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“…A more thorough discussion on ionic conductivity and diffusion coefficients for the materials in this study can be found elsewhere [31]. Also the values found here is close to the value reported for La 0.6 Sr 0.4 FeO 3−δ in [14]. Table 6.…”

Section: Electrical Conductivity and Carrier Mobilitysupporting

confidence: 85%

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 Mobilitysupporting

confidence: 85%

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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“…This value seems to be unusually large in comparison with the data in [19] and our results for PrBaCo 2 O 5+δ . It also seems to be overestimated in comparison with the redox enthalpy in the cubic perovskite-like cobaltite La 0.5 Sr 0.5 CoO 3-δ where it achieves only about 100 kJ mol -1 [20] and with the similar value in La 0.6 Sr 0.4 CoO 3-δ [29]. Our estimation in Table 1 appears to be in a more favorable comparison with the data for La 1 À x Sr x CoO 3 À δ because smaller absolute value for oxidation enthalpy of PrBaCo 2 O 5+δ in reaction (2) can naturally be explained as due to crystalline structure less dense in the double perovskite -than in the simple perovskie-like cobaltites.…”

Section: Defect Equilibrium Modelmentioning

confidence: 86%

“…Our estimation in Table 1 appears to be in a more favorable comparison with the data for La 1 À x Sr x CoO 3 À δ because smaller absolute value for oxidation enthalpy of PrBaCo 2 O 5+δ in reaction (2) can naturally be explained as due to crystalline structure less dense in the double perovskite -than in the simple perovskie-like cobaltites. For instance, the room temperature volume of the reduced elementary unit in PrBaCo 2 O 5.5 equals 58.6 Å 3 [25] while the elementary unit volume in La 0.6 Sr 0.4 CoO 3-δ is 56.4 Å 3 [29]. The difference reflects shorter and stronger bonds Со-О and, therefore, oxidation enthalpy larger in La 0.6 Sr 0.4 CoO 3-δ than in LnBaCo 2 O 5+δ .…”

Section: Defect Equilibrium Modelmentioning

confidence: 98%

Defect equilibrium in PrBaCo2O5 at elevated temperatures

Suntsov

Леонидов

Патракеев

et al. 2013

Journal of Solid State Chemistry

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a b s t r a c t A defect equilibrium model for PrBaCo 2 O 5+δ is suggested based on oxygen non-stoichiometry data. The model includes reactions of oxygen exchange and charge disproportionation of Co 3+ cations. The respective equilibrium constants, enthalpies and entropies for the reactions entering the model are obtained from the fitting of the experimental data for oxygen non-stoichiometry. The enthalpies of oxidation Co 2+ -Co 3+ and Co 3+ -Co 4+ are found to be equal to 115 7 9 kJ mol -1 and 45 74 kJ mol -1 , respectively. The obtained equilibrium constants were used in order to calculate variations in concentration of cobalt species with non-stoichiometry, temperature and oxygen pressure.

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“…Thermodynamic functions of oxygen, ΔH O and ΔS O , are known to be very sensitive to changes of oxygen content in the structure and, therefore, can provide rather detailed information on defect equilibria in non-stoichiometric oxides [21][22][23][24]. Hence, the present work was aimed at calculation of partial molar thermodynamic functions of oxygen in CаMnO 3−δ from the earlier obtained experimental data [17] with the use of defect formation reactions (1) and (2).…”

Section: +mentioning

confidence: 99%

Thermodynamics of oxygen in CaMnO3 − δ

Goldyreva

Леонидов

Патракеев

et al. 2013

J Solid State Electrochem

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The experimental data for equilibrium oxygen content were used in order to extract increments of partial molar thermodynamic functions of oxygen with changes of oxygen stoichiometry in calcium manganite CaMnO 3−δ . It is shown that along with the oxygen exchange reaction, thermal excitation of Mn 4+ cations plays an important role in equilibration of charged manganese species that appear in response to the loss of oxygen at heating. The interrelation of partial molar enthalpy and entropy of oxygen with electron and ion defect formation parameters is obtained in approximation of the point defect model. The nearly linear changes of oxygen partial molar enthalpy are shown to directly reflect thermally driven changes in concentration of Mn 3+ cations.

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Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

Cited by 200 publications

References 27 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

Defect equilibrium in PrBaCo2O5 at elevated temperatures

Thermodynamics of oxygen in CaMnO3 − δ

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Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

Cited by 200 publications

References 27 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

Defect equilibrium in PrBaCo2O5 at elevated temperatures

Thermodynamics of oxygen in CaMnO3 − δ

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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