Nonstoichiometry and Defect Chemistry in Praseodymium-Cerium Oxide

Stefanik, Todd; Tuller, Harry L.

doi:10.1007/s10832-004-5195-7

Cited by 32 publications

(40 citation statements)

References 3 publications

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“…19. Another study 20 performed at lower temperatures, 600-750°C, at the P O 2 range between 10 −5 and 10 −1 atm suggested ideal behavior. However, the examined powder was nanosized, which significantly alters the reduction properties.…”

Section: Ideal Model: the Reduction Of Pr And Ce Is Treated In An Idementioning

confidence: 93%

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Chatzichristodoulou

Hendriksen

2010

J. Electrochem. Soc.

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The oxygen nonstoichiometry (δ) of Ce0.8Pr0.2normalO2−δ has been measured as a function of PnormalO2 at temperatures between 600 and 900°C by coulometric titration and thermogravimetry. An ideal solution defect model, a regular solution model, and a defect association model, taking into account the association of reduced dopant species and oxygen vacancies, were unable to reproduce the experimental results. However, excellent agreement with the experimentally determined oxygen nonstoichiometry could be achieved when using either a nonideal solution model with an excess enthalpic term linear in δ (ΔHPrexc=anormalHδ) and a completely random distribution of defects (referred to as “δ-linear”), or a “generalized δ-linear” solution model, where the excess Gibbs energy change in the reduction reaction of the dopant linearly varies with δ (ΔGPrexc=anormalGδ) . A comparison of the partial molar enthalpy and entropy of oxidation, estimated from the defect models with those determined directly from the oxygen nonstoichiometry, suggests that the δ-linear solution model is the most appropriate in accounting for the observed nonideal reduction behavior of Pr.

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Section: Ideal Model: the Reduction Of Pr And Ce Is Treated In An Idementioning

confidence: 93%

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Chatzichristodoulou

Hendriksen

2010

J. Electrochem. Soc.

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“…The introduction of more easily reduced cations such as Pr or Tb into ceria allows the material to begin to reduce even under oxidizing conditions. 6,7 In recent publications, the authors of this work reported in detail on the defect, 7-9 transport, 7,9,10 optical, 11 and mechanical [12][13][14] properties of Pr x Ce 1Àx O 2Àd (PCO) with x 5 0.1. Some of the important features of Pr 0.1 Ce 0.9 O 2Àd include the introduction of MIEC behavior under oxidizing conditions; sample coloration, connected with the formation of a Pr-based impurity band; as well as chemical expansion accompanied by a decrease in the energy needed to form oxygen vacancies with reduction.…”

Section: Introductionmentioning

confidence: 99%

Defects and transport in Pr_xCe_1−xO_2−δ: Composition trends

2012

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Nonstoichiometric mixed ionic and electronic conductors (MIECs) find use as oxygen permeation membranes, cathodes in solid oxide fuel cells, oxygen storage materials in three-way catalysts, and chemoresistive gas sensors. Praseodymium-cerium oxide (Pr x Ce 1Àx O 2Àd ) solid solutions exhibit MIEC behavior in a relatively high and readily accessible oxygen partial pressure (P O 2 ) regime and as such serve as model systems for investigating the correlation between thermodynamic and kinetic properties as well as exhibiting high performance figures of merit in the above applications. In this paper, we extend recently published results for Pr 0.1 Ce 0.9 O 2Àd to include values of x 5 0, 0.002, 0.008, 0.1, and 0.20 (in Pr x Ce 1Àx O 2Àd ) to test how both defect and transport parameters depend on Pr fraction. Important observed trends with increasing x include increases in oxygen ion migration energy and MIEC and reductions in vacancy formation and Pr ionization energies. The implications these changes have for potential applications of Pr x Ce 1Àx O 2Àd are discussed.

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“…In the case of x = 0.2 and at 700 • C, t ion was found to be 0.6 under a pO 2 gradient between 1.01 × 10 5 Pa and 0.21 ×10 5 Pa [11]. The mixed conductivity of Ce 1−x Pr x O 2 was also confirmed by the pO 2 dependence of total conductivity by Stefanik and Tuller [10]. For CPO-xMFO, the small decrease in the oxygen permeability in the range of less than 5 vol% MnFe 2 O 4 seems to be attributed to decrease in Pr content in the matrix ceria phase as a result of the formation of PrFeO 3 phase as mentioned above.…”

Section: Resultsmentioning

confidence: 84%

“…Unlike Gd or Sm-doping, Prdoping raises both ionic and electronic conductivities of CeO 2 [10]. This increase in mixed conductivity is favorable for oxygen permeable ceramics.…”

Section: Introductionmentioning

confidence: 99%

Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites

Takamura

Sugai

Watanabe³

et al. 2006

J Electroceram

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The preparation and oxygen permeation properties of the (Ce 0.8 Pr 0.2 )O 2−δ − x vol% MnFe 2 O 4 composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce 0.8 Pr 0.2 O 2−δ , an oxygen flux density of 6 μmol·cm −2 ·s −1 (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000 • C. Unlike composites consisting of Gd-doped CeO 2 and MnFe 2 O 4 , the oxygen permeability of the (Ce 0.8 Pr 0.2 )O 2−δ -x vol% MnFe 2 O 4 composites was almost constant regardless of the volume fraction of MnFe 2 O 4 ; however, the optimum volume fraction of MnFe 2 O 4 was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere. In addition, the surface modification of the (Ce 0.8 Gd 0.2 )O 2−δ -15 vol% MnFe 2 O 4 composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm 2 on the both side of the 0.3 mm-thick (Ce 0.8 Gd 0.2 )O 2−δ -15vol% MnFe 2 O 4 composite increased the oxygen flux density from 0.30 to 0.76 μmol·cm −2 ·s −1 in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by a large pO 2 gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce 0.8 Gd 0.2 )O 2−δ -15vol% MnFe 2 O 4 composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition of the LB film.

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Nonstoichiometry and Defect Chemistry in Praseodymium-Cerium Oxide

Cited by 32 publications

References 3 publications

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Defects and transport in Pr_xCe_1−xO_2−δ: Composition trends

Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites

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Nonstoichiometry and Defect Chemistry in Praseodymium-Cerium Oxide

Cited by 32 publications

References 3 publications

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Oxygen Nonstoichiometry and Defect Chemistry Modeling of Ce[sub 0.8]Pr[sub 0.2]O[sub 2−δ]

Defects and transport in PrxCe1−xO2−δ: Composition trends

Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites

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Defects and transport in Pr_xCe_1−xO_2−δ: Composition trends