Oxygen nonstoichiometry of La1−xSrxCoO3−δ (0 &lt; x ≤ 0.6)

Петров, А. Н.; Черепанов, В.А.; Kononchuk, O. F.; Gavrilova, L. Ya.

doi:10.1016/0022-4596(90)90066-7

Cited by 86 publications

(37 citation statements)

References 6 publications

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“…Table III. Previous studies 23,24 have shown a power law with the index n Ͻ 0 between oxygen nonstoichiometry ␦ and the oxygen partial pressure p O 2 in the La 1Ϫx Sr x CoO 3Ϫ␦ system at elevated temperatures. One can then expect, from the Wagner equation with ambi Fig.…”

Section: Resultsmentioning

confidence: 95%

Oxygen Permeation Through Cobalt-Containing Perovskites: Surface Oxygen Exchange vs. Lattice Oxygen Diffusion

Huang¹,

Goodenough²

2001

J. Electrochem. Soc.

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The oxygen permeation fluxes from p O 2 Ј to p O 2 Љ (p O 2 Ј Ͼ p O 2 Љ ) across cobalt-containing perovskite ceramic membranes La 1Ϫx Sr x CoO 3Ϫ␦ and SrCo 0.8 Fe 0.2 O 3Ϫ␦ were measured by gas chromatography as functions of oxygen chemical potential gradient, temperature, thickness, and catalytic activity on the surface. Power indexes 0.5 Ͼ n Ͼ 0 for uncatalyzed La 1Ϫx Sr x CoO 3Ϫ␦ and 1 Ͼ n Ͼ 0.5 for SrCo 0.8 Fe 0.2 O 3Ϫ␦ were obtained when J O 2 vs. p O 2 Ј n Ϫ p O 2 Љ n was plotted as a straight line. The results clearly indicate an overall permeation process controlled by both surface oxygen exchange and bulk oxygen diffusion for uncatalyzed La 1Ϫx Sr x CoO 3Ϫ␦ and SrCo 0.8 Fe 0.2 O 3Ϫ␦ . Application of a thin layer of catalytically active SrCo 0.8 Fe 0.2 O 3Ϫ␦ on the feeding-gas surface of La 0.5 Sr 0.5 CoO 3Ϫ␦ under the condition of a fixed p O 2 Ј ϭ0.21 atm and a varied p O 2 Љ not only increases remarkably the overall oxygen flux, but also changes a mixed control to a bulk diffusion control. This enables evaluation of the bulk transport properties of the mixed conductors. A coat of SrCo 0.8 Fe 0.2 O 3Ϫ␦ on the permeate side has little catalytic effect, especially at low p O 2 Љrange, due to the formation of a poorly conducting brownmillerite phase. The results explicitly show a higher activation energy for the surface exchange kinetics than for the ambipolar transport in the mixed conductors. The mechanism of the surface exchange is discussed, and an analytic expression that agrees well with the experimental results is obtained.

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Section: Resultsmentioning

confidence: 95%

Oxygen Permeation Through Cobalt-Containing Perovskites: Surface Oxygen Exchange vs. Lattice Oxygen Diffusion

Huang¹,

Goodenough²

2001

J. Electrochem. Soc.

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“…A considerable body of data concerning oxygen permeability in Lal_xSrxCoO3_~ has been gathered in tests with helium and air as sweep and feed gases, respectively. At these conditions oxygen nonstoichiometry may achieve 8 --x/2 or larger values at the sweep side while it is preserved or kept small at the feed side [7][8][9]. Obviously, the oxygen content across the separating membrane varies significantly in this experimental arrangement, which in turn may result in a variety of oxygen defects including formation of vacancy ordered domains in the membrane material.…”

Section: Introductionmentioning

confidence: 94%

“…This paper aims at elucidating the influence of oxygen content on the oxygen ion conductivity in La0.4Sr0.tCoO3+ This composition was selected as a reliably established single-phase material that sustains large oxygen deficiency [7,8]. To accomplish the goals of this studies, the equilibrium oxygen content was determined in the range 0.12 < 8 < 0.38 as a function of temperature and oxygen partial pressure.…”

Section: Introductionmentioning

confidence: 99%

Oxygen thermodynamics and ion conductivity in the solid solution La1−xSrxCoO3−δ at large strontium content

Патракеев

Леонидов

Митберг

et al. 1999

Ionics

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Abstract. The equilibrium oxygen content was measured in the model system and important oxygen permeable material Lal.xSrxCoO3. 6, where x = 0.6, in the temperature range 650-900 ~ and oxygen partial pressure range between 10 .5 and 1 atm. The data were utilized to obtain changes in the partial entropy and enthalpy of oxygen in the solid as a function of the oxygen content. It is shown that the initially cubic perovskite undergoes to a phase transition to a tetragonal structure at 8 > 0.3. The oxygen permeation of L0.4Sr0.6CoO3_ ~ at 700-900 ~ is found to be controlled by bulk solid state processes. The activation energy equals about 0.8 eV at high oxygen pressure and small oxygen nonstoichiometry. Increasing oxygen deficiency results in a rapid increase in the activation energy. In combination with thermodynamic data, these changes can be explained as resulting from the intrinsic, spatial inhomogeneouty in oxygen vacancy distribution which varies both with temperature and oxygen nonstoichiometry. It is shown that, when the oxygen deficiency increases at constant temperature, the oxygen vacancies form locally ordered microdomains (clusters), which eventually results in a transition of the cubic perovskite structure to the tetragonal structure. The oxygen ion conductivity depends strongly on the development of the ordering.

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“…In general, perovskites such as La~_xSrxCoO3_6 [31][32][33] and La~_xSrxFeO3_6 [34] show a high degree of oxygen nonstoichiometry. The anions are likely to move via a vacancy transport mechanism [28,29 ].…”

Section: Perovskite-type Oxidesmentioning

confidence: 99%

Importance of the surface exchange kinetics as rate limiting step in oxygen permeation through mixed-conducting oxides

1994

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Attention is drawn to the possible involvement of the surface exchange kinetics in limiting the rate of oxygen permeation through mixed-conducting oxide ceramics. A theoretical approach is provided with which it is possible to distinguish between surface exchange-and bulk diffusion controlled kinetics of oxygen permeation. New results on the oxygen permeability of perovskites Lao.aSro.2CoO3_~ and SrCoo.sFeo.203_6 are presented. The importance of the exchange reaction relative to diffusion in limiting overall oxygen transport through (La,Sr) (Co,Fe)O3_6 perovskite-type oxides is emphasized.

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Oxygen nonstoichiometry of La1−xSrxCoO3−δ (0 < x ≤ 0.6)

Cited by 86 publications

References 6 publications

Oxygen Permeation Through Cobalt-Containing Perovskites: Surface Oxygen Exchange vs. Lattice Oxygen Diffusion

Oxygen Permeation Through Cobalt-Containing Perovskites: Surface Oxygen Exchange vs. Lattice Oxygen Diffusion

Oxygen thermodynamics and ion conductivity in the solid solution La1−xSrxCoO3−δ at large strontium content

Importance of the surface exchange kinetics as rate limiting step in oxygen permeation through mixed-conducting oxides

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