Thermodynamics of the movable oxygen and conducting properties of the solid solution YBa2Cu3-xCoxO6+δ at high temperatures

Патракеев, М.В.; Митберг, Э. Б.; Lakhtin, A. A.; Леонидов, И. А.; Кожевников, В. Л.; Poeppelmeier, Kenneth R.

doi:10.1007/bf02375945

Cited by 30 publications

(20 citation statements)

References 22 publications

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“…The average oxidation states of iron cations, estimated from the Mo¨ssbauer spectra of SFA quenched from 1023 K after annealing in air and in H 2 -H 2 O-N 2 mixture, were verified by the coulometric titration method [17]. The Mo¨ssbauer spectroscopy data (table 1) give the total oxygen content of 2.553 and 2.500 per perovskite unit formula for the oxidized and reduced samples, respectively.…”

Section: Resultsmentioning

confidence: 99%

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M�ssbauer Spectra and Catalytic Behaviorof Perovskite-like SrFe0.7Al0.3O3-?

Хартон

Waerenborgh²,

Rojas³

et al. 2005

Catal Lett

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O 3Àd (SFA) exhibits substantial catalytic activity towards partial oxidation of methane and can thus be considered as a component of monolithic ceramic reactors for synthesis gas generation, where the dense membrane and porous catalyst at the permeate-side surface are made of similar compositions. Surface modification of SFA powder and membranes with Pt has no essential effect on the performance of a model reactor, suggesting that the catalytic behavior of SFA is mainly determined by the surface states of iron and oxygen ions in the catalyst. The Mo¨ssbauer spectroscopy shows that reduction of SrFe 0:7 Al 0:3 O 3Àd , having cubic perovskite lattice in air, leads to the co-existence of perovskite-and brownmillerite-like domains, whilst the concentrations of metallic Fe and even Fe 2þ under typical operation conditions are lower than the detection limits. The amount of vacancy-ordered phase increases with decreasing oxygen content, the estimations of which were confirmed by coulometric titration data. The catalytic activity of ferrite-based materials may thus be associated with lattice instability characteristic of morphotropic phase transformations.

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Section: Resultsmentioning

confidence: 99%

“…Distributions of quadruple splittings (QS) or magnetic splittings were fitted according to the histogram method [16]. The coulometric titration technique [17] was used to determine oxygen content as a function of oxygen partial pressure and temperature.…”

Section: Methodsmentioning

confidence: 99%

M�ssbauer Spectra and Catalytic Behaviorof Perovskite-like SrFe0.7Al0.3O3-?

Хартон

Waerenborgh²,

Rojas³

et al. 2005

Catal Lett

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“…Coulometric titration was used to measure the equilibrium oxygen content in the oxide as a function of the temperature and oxygen pressure. The experimental details are reported elsewhere [25]. The absolute value of uncertainty in determination of 8 relative to the reference point (650 ~ air) did not exceed 0.005.…”

Section: Experimental Methodsmentioning

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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“…The oxygen content variations with respect to a reference point were measured as a function of oxygen partial pressure and temperature by means of the coulometric titration technique in the double electrochemical cell, as described elsewhere (19). For La 0.3 Sr 0.7 FeO 2.65+d , the total oxygen content in the reference point (7501C, air) was determined by thermogravimetric analysis (TGA) using a Setaram TG-92 instrument.…”

Section: Methodsmentioning

confidence: 99%