A variational approach to surface cation segregation in mixed conducting perovskites

Mebane, David S.

doi:10.1016/j.commatsci.2014.11.025

Cited by 38 publications

(36 citation statements)

References 37 publications

(50 reference statements)

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“…Few techniques offer this combination of possibilities, important for evaluating dynamic processes under in situ conditions. On the other hand, the AC-IS technique (as well as electrical conductivity relaxation) requires metallic current collectors that typically are interfacing with the exact surface of samples being probed, unless they are buried; this means that in theory the current collectors could markedly modify the measured k values, via enhanced catalytic activity, physical blocking of active surfaces, modification of space charge regions [53] and/or poisoning impurities (e.g. current collectors could act as sources or sinks for surface-poisoning species such as Cr, S, Si, Sr), etc.…”

Section: Discussionmentioning

confidence: 99%

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study

Perry

Kim

Tuller

2018

Science and Technology of Advanced Materials

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We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.

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Section: Discussionmentioning

confidence: 99%

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study

Perry

Kim

Tuller

2018

Science and Technology of Advanced Materials

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“…Moreover, oxygen surface exchange processes of the double perovskites are very sensitive to their surface properties [13]. Significant surface composition segregation and morphology reconstruction were observed by T ellez et al [19] and Cox-Galhotra et al [13] for PrBaCo 2 O 5þd , which may be originated from the cation size mismatch and charge interaction [22,23]. The introduction of appropriate Ba deficiencies in PrBaCo 2 O 5þd can reduce the cation size mismatch in the A site and thus tailoring the surface properties of the double perovskites.…”

Section: Introductionmentioning

confidence: 89%

The effect of potassium on the properties of PrBa 1−x Co 2 O 5+δ (x = 0.00–0.10) cathodes for intermediate-temperature solid oxide fuel cells

Pang

Wang

Chen

et al. 2016

International Journal of Hydrogen Energy

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“…To include defect interactions in the description of bulk defect chemistry and bearing in mind the result for the inhomogeneous case (see Refs. and also later), we assume pairwise interactions that are proportional to defect concentrations. Consequently, the electrochemical potential of

{Ce}_{Ce}^{'}

as building units for the homogeneous bulk phase,

{\tilde{μ}}_{n}

, for example, is given by Equation

true {\tilde{μ}}_{n} = μ_{normaln}^{\circ} + f_{normaln normaln} n + f_{normala normaln} a + f_{normalv normaln} v + R T \ln ((), \frac{n}{1 - a - n}) - F ϕ

…”

Section: Figurementioning

confidence: 99%

“…The potential roles of adsorbates, such as CO 3 2− or OH − , in determining the space‐charge potential are ignored here because their inclusion requires more experimental data than is currently available. Second, following previous work, we express the electrochemical potential of

{Ce}_{Ce}^{'}

for a one‐dimensional, inhomogeneous system as Equation

true {\tilde{μ}}_{n} = μ_{normaln}^{\circ} + f_{normaln normaln} n ((), x) + f_{normala normaln} a ((), x) + f_{normalv normaln} v ((), x) + R T l n ((), \frac{n (x)}{1 - a (x) - n (x)}) - F ϕ - β_{n} \frac{\partial^{2} n}{{\partial x}^{2}}

…”

Section: Figurementioning

confidence: 99%

A Space‐Charge Treatment of the Increased Concentration of Reactive Species at the Surface of a Ceria Solid Solution

et al. 2017

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As pace-charge theory applicable to concentrated solid solutions (Poisson-Cahn theory) was applied to describe quantitatively as afunction of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy( XPS) for the concentration of Ce 3+ (the reactive species) at the surface of the oxide catalyst Ce 0.8 Sm 0.2 O 1.9 .I nc ontrast to previous theoretical treatments, these calculations clearly indicate that the surface is positively charged and compensated by an attendant negative spacecharge zone.T he high space-charge potential that develops at the surface (> 0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the spacecharge layer.T his approach emphasizes the need to take into account defect interactions and to allowd eviations from local charge neutrality when considering the surfaces of oxide catalysts.

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A variational approach to surface cation segregation in mixed conducting perovskites

Cited by 38 publications

References 37 publications

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study

The effect of potassium on the properties of PrBa 1−x Co 2 O 5+δ (x = 0.00–0.10) cathodes for intermediate-temperature solid oxide fuel cells

A Space‐Charge Treatment of the Increased Concentration of Reactive Species at the Surface of a Ceria Solid Solution

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A variational approach to surface cation segregation in mixed conducting perovskites

Cited by 38 publications

References 37 publications

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

The effect of potassium on the properties of PrBa 1−x Co 2 O 5+δ (x = 0.00–0.10) cathodes for intermediate-temperature solid oxide fuel cells

A Space‐Charge Treatment of the Increased Concentration of Reactive Species at the Surface of a Ceria Solid Solution

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Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O_3-x thin film case study