Surface exchange of oxygen in mixed conducting perovskite oxides

Kilner, John A.; Souza, Roger A. De; Fullarton, I. C.

doi:10.1016/0167-2738(96)00153-1

Cited by 234 publications

(240 citation statements)

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“…As early as 1996 Kilner et al [46] showed that there is, for a large number of different oxide materials, a quite obvious correlation 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%

“…This means that Kilner's data compilation [46] comprises only experiments performed in the diffusion controlled regime. The authors' conclusion that their empirical correlation for the activation enthalpies ∆H K (for K O ) and ∆H D (for D O ), which is ∆H K ≈ 0.5 ∆H D [46], has a sound physical basis, would be only true if w O (0) and c O (0), but especially 0 O , were no material specific parameters and if all three of them would not depend on temperature at all-which is not the case.…”

mentioning

confidence: 99%

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

confidence: 99%

mentioning

confidence: 99%

Ceria: Recent Results on Dopant-Induced Surface Phenomena

et al. 2017

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“…Kilner et al [40] have shown that the exchange coefficient k can be correlated to the diffusion coefficient D.…”

Section: Surface Charging/electric Field Effectmentioning

confidence: 99%

Surface oxygen exchange between yttria-stabilised zirconia and a low-temperature oxygen rf-plasma

et al. 2004

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Isotope Exchange/Depth Profiling (IEDP) using Secondary Ion Mass Spectrometry (SIMS) has been used to determine the oxygen tracer diffusion and surface exchange coefficients of (100) oriented 9.5 mol% yttria stabilised zirconia single crystals. Exchange experiments performed with molecular oxygen are compared with the exchange using an oxygen plasma. The surface exchange coefficient for specimens in a plasma is up to 100 times higher compared to measurements with normal molecular oxygen. For the exchange experiments we used an inductively coupled radio frequency (rf) oxygen plasma with a maximum radio frequency power of 250 W. Double probe measurements and optical emission spectrometry are used for the characterisation of the plasma. The measured electron temperatures are within the range of 5 -12 eV. D

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“…Previously, the use of 18 O implants in non-oxide species has been used for two purposes. Oxygen diffusion in either oxide or semiconductor matrices has been observed using an 18 O flood or ion implant (Kilner et al, 1996;Manning et al, 1997). In addition, 18 O implants have been used for quantifying behaviour of sputtered oxygen introduced by either a natural primary beam (Sobers Jr. et al, 2004) or by oxygen flooding .…”

Section: W Magee Jr Et Al: Isotopologue Disequilibrium In Simsmentioning

confidence: 99%

Extreme isotopologue disequilibrium in molecular SIMS species during SHRIMP geochronology

Magee

Danišík

Mernagh

2017

Geosci. Instrum. Method. Data Syst.

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Abstract. The current limitation in the accuracy and precision of inter-element analysis in secondary ion mass spectrometry (SIMS) is the ability to find measurable quantities that allow relative differences in ionization and transmission efficiency of secondary ions to be normalized. In uraniumthorium-lead geochronology, the ability to make these corrections, or "calibrate" the data, results in an accuracy limit of approximately 1 %. This study looks at the ionization of uranium and thorium oxide species, which are traditionally used in U-Pb calibration, to explore the conditions under which isotopologues, or molecular species whose composition differs only in the isotopic composition of one or more atoms in the molecule, remain in or deviate from equilibrium.Isotopologue deficits of up to 0.2 (200 ‰) below ideal mixing are observed in UO + 2 species during SIMS gechronological analyses using the SHRIMP IIe SIMS instrument. These are identified by bombarding natural U-bearing minerals with an 18 O − 2 primary beam. The large anomalies are associated with repeat analyses down a single SIMS sputtering crater (Compston et al., 1984), analysis of high-uranium, radiation-damaged zircon, and analysis of baddeleyite. Analysis of zircon under routine conditions yield UO + 2 isotopologue anomalies generally within a few percent of equilibrium. The conditions under which the isotopologue anomalies are observed are also conditions in which the UO x -based corrections, or calibration, for relative U vs. Pb ionization efficiencies fail. The existence of these isotopologue anomalies suggest that failure of the various UO x species to equilibrate with each other is the reason that none of them will successfully correct the U / Pb ratio. No simple isotopologuebased correction is apparent. However, isotopologue disequilibrium appears to be a more sensitive tool for detecting high-U calibration breakdowns than Raman spectroscopy, which showed sharper peaks for ∼ 37 Ma high-uranium zircons than for reference zircons OG1 and Temora. U-ThSm / He ages were determined for aliquots of reference zircons OG1 (755±71 Ma) and Temora (323±43 Ma), suggesting that the broader Raman lines for the Temora reference zircons may be due to something other than accumulated radiation damage.Isotopologue abundances for UO + and ThO + and their energy spectra are consistent with most or all molecular species being the product of atomic recombination when the primary beam impact energy is greater than 5.7 keV. This, in addition to the large UO + 2 instrumentally generated isotopologue disequilibria, suggests that any attempts to use SIMS to detect naturally occurring isotopologue deviations could be tricky.

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Surface exchange of oxygen in mixed conducting perovskite oxides

Cited by 234 publications

References 2 publications

Ceria: Recent Results on Dopant-Induced Surface Phenomena

Ceria: Recent Results on Dopant-Induced Surface Phenomena

Surface oxygen exchange between yttria-stabilised zirconia and a low-temperature oxygen rf-plasma

Extreme isotopologue disequilibrium in molecular SIMS species during SHRIMP geochronology

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