Nonstoichiometry of Ce0.9Gd0.1O1.95âx

Wang, Shaorong; Inaba, Hideaki; Tagawa, Hiroaki; Dokiya, Masayuki; Hashimoto, Takuya

doi:10.1016/s0167-2738(97)00519-5

Cited by 140 publications

(77 citation statements)

References 10 publications

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“…Typical values of enthalpy of reduction in the range 410-430 KJ/mol are extracted by using Eq. 10, which are comparable to other results reported in literature (Wang et al, 1997;Wang et al 1998;Kobayashi et al, 1999;Kudo & Obayashi, 1976;Schneider et al, 1997). The simple defect chemistry behaviour can be used to model the theoretical dependence of oxygen loss on oxygen partial pressure (Eq.…”

Section: Determination Of the Oxygen Loss By Coulometric Titrationsupporting

confidence: 88%

“…Deviations from the nearly exponential behaviour are observed at very low values of oxygen partial pressure, mainly for lower temperature. An analogous behaviour was found by other authors (Riess et al, 1987;Panhans et al, 1993;Wang et al, 1998) and could be due to deviations from the simple defect chemistry model, or limitations of the experimental procedure. Though the steady state current I ∞ should account for residual permeability through the YSZ cell components, this may not be the case for deviations from material/gas equilibrium or differences between the measured emf and the true conditions inside the cell.…”

Section: Determination Of the Oxygen Loss By Coulometric Titrationsupporting

confidence: 85%

“…In these cases, reducibility of ceria-based solid electrolytes is a critical limitation, mainly because this implies onset of electronic conductivity (Blumenthal & Hofmaier, 1974;Blumenthal & Sharma, 1975;Tuller & Nowick, 1977;Navarro et al, 1997) and corresponding risks of internal short circuiting and decrease in cell voltage. The reducibility of cerias is affected by trivalent additives and their contents (Wang et al 1997;Wang et al 1998;Kobayashi et al, 1999), altering the mixed transport properties under low values of oxygen pressure according to the defect chemistry models. However some discrepancies are found in literature regarding the level of oxygen losses as well as the electronic conductivity (Mogensen et al, 2000;Zachau-Christiansen et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Pérez-Coll¹,

Núñez²,

Frade³

2011

Advances in Ceramics - Synthesis and Characterization, Processing and Specific Applications

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Section: Determination Of the Oxygen Loss By Coulometric Titrationsupporting

confidence: 88%

Section: Determination Of the Oxygen Loss By Coulometric Titrationsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Pérez-Coll¹,

Núñez²,

Frade³

2011

Advances in Ceramics - Synthesis and Characterization, Processing and Specific Applications

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“…A similar trend was also observed in purely Prdoped ceria 35 and purely Gd-doped ceria. 53 It is also found that the reducibility of Ce 4+ and Pr 4+ in ceria tends to be facilitated by the increasing oxygen nonstoichiometry, leading to a non-ideal reduction behavior. 16 We herein attribute the decreased enthalpy of reduction of Ce to the high oxygen nonstoichiometry in heavily Pr-doped CGO.…”

mentioning

confidence: 95%

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Cheng

Chatzichristodoulou

Søgaard

et al. 2017

J. Electrochem. Soc.

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The oxygen permeation flux of Ce 0.9 Gd 0.1 O 1.95-δ (CGO)-based oxygen transport membranes under oxidizing conditions is limited by the electronic conductivity of the material. This work aims to enhance the bulk ambipolar conductivity of CGO by partial substitution of Ce with the redox active element Pr. A series of compositions of Pr x Gd 0.1 Ce 0.9-x O 1.95-δ (x = 0, 0.02, 0.05, 0.08, 0.15, 0.25, 0.3 and 0.4) was prepared by solid state reaction. X-ray powder diffraction (XPD) indicates that Pr is completely dissolved in the fluorite structure up to 40 at.%. Pronounced nonlinear thermal expansion behavior was observed as a function of temperature, due to the simultaneous contributions of both thermal and chemical expansion. The electronic and ionic conductivities were measured as a function of temperature and oxygen partial pressure. Within the range from 10 to 15 at.% Pr, a drastic drop of the activation energy of the hole mobility and an abrupt increase of the hole conductivity at low temperature was observed. The behavior could be rationalized by a simple percolation model. Oxygen permeation fluxes through disk shaped samples fed with air on one side and N 2 on the other side were also measured. The oxygen flux through Pr 0.05 Gd 0.1 Ce 0.85 O 1.95-δ was higher than that for CGO by one order of magnitude owing to the enhanced electronic conductivity albeit the flux is still limited by the electronic conductivity. In terms of the electronic and ionic conductivity, the estimated maximum oxygen permeation flux of a 10 μm Pr 0.4 Gd 0.1 Ce 0.9 O 1.95-δ -based membrane exceeds 10 Nml cm −2 min −1 at 900 • C under a small oxygen potential gradient (0.21/10 −3 bar) which is promising for use in oxygen production and in oxy-fuel combustion. Also the material may be well applicable to SOFC/SOEC composite electrodes where mixed conductivity is also desirable. Dense ceramic oxygen transport membranes (OTMs) could potentially be applied for production of high purity oxygen for medical purposes, supply of oxygen in the steel industry, oxy-fuel combustion schemes, as well as in the cement and glass industries. Also, importantly, OTMs can beneficially be integrated with a biomass gasifier, allowing production of syngas (CO and H 2 ), which is a precursor for a variety of high value chemicals. 1 Besides being applicable for OTMs, 2 acceptor doped-ceria has been intensively studied for use in a number of other applications e.g. solid oxide fuel cells (SOFCs), 3 solid oxide electrolysis cells (SOECs) 4 and for electrocatalysis. 5 In particular, acceptor doped ceria (e.g. CGO) is interesting owing to high oxide ion conductivity (0.12 Scm −1 for Gd 0.1 Ce 0.9 O 1.95-δ at 900• C 6 ), appreciable electrocatalytic activity, high electronic conductivity under reducing conditions, and excellent chemical stability under harsh reducing and even corrosive gaseous conditions. 3,7 Kaiser et al. 8 reported that the oxygen permeation flux of a 27 μm asymmetric 10 at.% Gd-doped ceria-based membrane exceeds 10 ml cm −2 min −1 under a gradie...

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“…In principle, the best way to determine K r is through thermogravimetric experiments, which are designed to give the weight change of an MIEC sample (and hence the concentration of defects) as a function of P O 2 [42]. However, it is usually very difficult to get accurate and reproducible data from thermogravimetric experiments because of the high sensitivity required to detect very small changes in the mass of the specimen [38].…”

Section: Estimation Of K R From Thermogravimetrymentioning

confidence: 99%

Stable High Conductivity Bilayered Electrolytes for Low Temperature Solid Oxide Fuel Cells

Wachsman¹,

Duncan²

2001

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Nonstoichiometry of Ce0.9Gd0.1O1.95âx

Cited by 140 publications

References 10 publications

Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ

Stable High Conductivity Bilayered Electrolytes for Low Temperature Solid Oxide Fuel Cells

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Nonstoichiometry of Ce0.9Gd0.1O1.95âx

Cited by 140 publications

References 10 publications

Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Reducibility of Ceria-Based Materials Exposed to Fuels and under Fuel/Air Gradients

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria PrxGd0.1Ce0.9-xO1.95-δ

Stable High Conductivity Bilayered Electrolytes for Low Temperature Solid Oxide Fuel Cells

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Nonstoichiometry of Ce0.9Gd0.1O1.95âx

Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria Pr_xGd_0.1Ce_0.9-xO_1.95-δ