Oxygen isotope exchange in La<sub>2</sub>NiO<sub>4±δ</sub>

Ananyev, M.V.; Tropin, E. S.; Еремин, В. А.; Фарленков, А. С.; Smirnov, Andrey S.; Kolchugin, A.А.; Поротникова, Н. М.; Khodimchuk, Anna V.; Berenov, A.; Курумчин, Э. Х.

doi:10.1039/c5cp05984d

Cited by 76 publications

(49 citation statements)

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“…[23][24][25] In these materials, the oxygen molecules have to complete four different steps before diffusing through the volume: (i) adsorption/ionization, (ii) surface diffusion to find a vacancy, (iii) dissociation and (iv) migration of the second ion to find another vacancy. [26][27][28] Among these steps, the slowest one limits the overall rate of the surface reaction and, for this reason, it is known as the rate determining step (rds). The rds can vary depending on the particular case that is being considered.…”

Section: Introductionmentioning

confidence: 99%

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

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Sánchez-Valdés

Stangl

et al. 2017

Phys. Chem. Chem. Phys.

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The kinetics of oxygen incorporation (in-diffusion process) and excorporation (out-diffusion process), in YBaCuO (YBCO) epitaxial thin films prepared using the chemical solution deposition (CSD) methodology by the trifluoroacetate route, was investigated by electrical conductivity relaxation measurements. We show that the oxygenation kinetics of YBCO films is limited by the surface exchange process of oxygen molecules prior to bulk diffusion into the films. The analysis of the temperature and oxygen partial pressure influence on the oxygenation kinetics has drawn a consistent picture of the oxygen surface exchange process enabling us to define the most likely rate determining step. We have also established a strategy to accelerate the oxygenation kinetics at low temperatures based on the catalytic influence of Ag coatings thus allowing us to decrease the oxygenation temperature in the YBCO thin films.

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Section: Introductionmentioning

confidence: 99%

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Cayado

Sánchez-Valdés

Stangl

et al. 2017

Phys. Chem. Chem. Phys.

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“…orders of magnitude for D * O ) for a number of perovskite compositions (with predominant electronic conductivity). Despite this empirical evidence it is assumed until to date [47][48][49], however, that K O and D O are independent parameters, each of which reflecting an independent microscopic mechanism. In Appendix A we show that this intuitive approach is not generally correct.…”

Section: Revision Of the Standard Picture Of The Oxygen Exchange Kinementioning

confidence: 99%

Ceria: Recent Results on Dopant-Induced Surface Phenomena

et al. 2017

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Abstract:Redox studies on dense zirconia-doped ceria pellets were carried out by thermogravimetric investigations and dilatometry. Up to 1600 K reduction parameters determined by both methods correspond to each other. At higher temperatures, however, thermogravimetry overestimates the degree of reduction since mass loss is not only due to oxygen exsolution but also to selective evaporation of CeO 2 whose vapour pressure is considerably higher than that of ZrO 2 . As a consequence surface segregation of zirconia occurs in (Ce,Zr)O 2−δ pellets leading to a porous surface zone of Ce 2 Zr 2 O 7 pyrochlore which gradually grows in thickness. Surface enrichment of zirconia is detrimental for splitting CO 2 or H 2 O since re-oxidation temperatures of (Ce,Zr)O 2−δ are known to be shifted towards lower temperatures with increasing ZrO 2 content. Thus, very harsh reduction conditions should be avoided for the (Ce,Zr)O 2−δ redox system. The kinetics investigations comprised the high temperature reduction step (T ∼ = 1600 K) and the "low" temperature oxidation reaction with a carbon dioxide atmosphere (T ∼ = 1000 K). The reduction kinetics (at around 1600 K and an oxygen activity of 7 × 10 −4 in the gas phase) directly yield the (reduction) equilibrium exchange rate of oxygen in the order of 10 −7 mol·O/(cm 3 ·s) as the kinetics are surface controlled. The oxidation step at around 1000 K, however, occurs in the mixed control or in the diffusion control regime, respectively. From oxygen isotope exchange in combination with SIMS depth profiling oxygen exchange coefficients, K, and oxygen diffusivities, D, were determined for so-called equilibrium experiments as well as for non-equilibrium measurements. From the obtained values for K and D the (oxidation) equilibrium exchange rates for differently doped ceria samples were determined. Their dependency on the oxygen activity and the nature and the concentrations of a tetravalent dopant (Zr) and trivalent dopants (La, Y, Sm) could be semi-quantitatively rationalised on the basis of a master equation for the equilibrium surface exchange rate.

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“…Figs. 9, 10 illustrate the temperature dependencies of oxygen exchange coefficient and oxygen diffusion coefficient, respectively, in comparison with literary data for different oxides [22,[26][27][28][29]. The values of activation energy for the exchange and diffusion processes are listed in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Oxygen diffusion and surface exchange kinetics for the mixed-conducting oxide La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ

et al. 2018

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Studies of oxygen surface exchange kinetics for La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ oxide were performed using the technique of isotopic exchange of molecular oxygen with analysis of gas phase isotopic composition in a static circulation system at the temperatures of 600-800 °С in the oxygen pressure range of 0.27-2.13 kPa. The values of interphase exchange rate and oxygen diffusion coefficient were determined. The effective activation energies for oxygen exchange and diffusion processes as well as the exponents in the dependence of these values versus oxygen pressure in the double logarithmic coordinates were calculated. The process of oxygen dissociative adsorption at the surface of La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ oxide was found to be the rate-determining stage.

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Oxygen isotope exchange in La₂NiO_4±δ

Cited by 76 publications

References 20 publications

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Ceria: Recent Results on Dopant-Induced Surface Phenomena

Oxygen diffusion and surface exchange kinetics for the mixed-conducting oxide La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ

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Oxygen isotope exchange in La2NiO4±δ

Cited by 76 publications

References 20 publications

Untangling surface oxygen exchange effects in YBa2Cu3O6+xthin films by electrical conductivity relaxation

Untangling surface oxygen exchange effects in YBa2Cu3O6+xthin films by electrical conductivity relaxation

Ceria: Recent Results on Dopant-Induced Surface Phenomena

Oxygen diffusion and surface exchange kinetics for the mixed-conducting oxide La0.6Sr0.4Co0.8Fe0.2O3-δ

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Oxygen isotope exchange in La₂NiO_4±δ

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Untangling surface oxygen exchange effects in YBa₂Cu₃O_6+xthin films by electrical conductivity relaxation

Oxygen diffusion and surface exchange kinetics for the mixed-conducting oxide La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ