Limits to the rate of oxygen transport in mixed-conducting oxides

2017 ◽  
Vol 5 (38) ◽  
pp. 20334-20350 ◽  
Author(s):  
Roger A. De Souza
Keyword(s):  
Oxygen Transport ◽  
Tracer Diffusion ◽  
Surface Exchange ◽  
Conducting Oxides ◽  
Oxygen Surface Exchange ◽  
Oxygen Tracer ◽  
Oxygen Surface

Chemically reasonable limits to the rates of oxygen tracer diffusion and oxygen surface exchange in acceptor-doped oxides are examined.

Influence of ionic conductivity of the nano-particulate coating phase on oxygen surface exchange of La0.58Sr0.4Co0.2Fe0.8O3−δ

2017 ◽  
Vol 5 (10) ◽  
pp. 4991-4999 ◽  
Author(s):  
Saim Saher ◽  
Sahir Naqash ◽  
Bernard A. Boukamp ◽  
Bobing Hu ◽  
Changrong Xia ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Surface Exchange ◽  
Conducting Oxides ◽  
Surface Decoration ◽  
Exchange Kinetics ◽  
Kinetics Of ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface ◽  
Particulate Coating

Surface decoration with nano-particulate oxides is one of the options to improve the surface exchange kinetics of mixed ionic-electronic conducting oxides.

Oxygen Surface Exchange and Tracer Diffusion in Differently Oriented Thin Films of Gd-Doped CeO2

2020 ◽  
Vol 12 (32) ◽  
pp. 36768-36777
Author(s):  
Stephan P. Waldow ◽  
Benjamin J. Statham ◽  
Hans F. Wardenga ◽  
Thomas E. Weirich ◽  
Andreas Klein ◽  
...  
Keyword(s):  
Thin Films ◽  
Tracer Diffusion ◽  
Surface Exchange ◽  
Doped Ceo2 ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface

Oxygen Isotope Exchange in Proton-Conducting Oxides Based on Lanthanum Scandates

2018 ◽  
pp. 70-87
Author(s):  
A. S. Farlenkov ◽  
A. V. Khodimchuk ◽  
N. A. Shevyrev ◽  
A. Yu. Stroeva ◽  
A. V. Fetisov ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Diffusion Coefficients ◽  
Isotope Exchange ◽  
Dissociative Adsorption ◽  
Surface Exchange ◽  
Oxygen Isotope Exchange ◽  
Conducting Oxides ◽  
Reducing Atmosphere ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface

The method of oxygen isotope exchange with the gas phase equilibration have been used to obtain the temperature dependences of the oxygen surface exchange and diffusion coefficients with proton-conducting oxides La1–xSrxScO3–δ (x = 0; 0.04; 0.09) in the temperature range of 600−900°C at oxygen pressure 1.01 kPa. The paper determines that the diffusion and oxygen surface exchange coefficients increase with the increasing of the strontium content in the oxides. We have found out the rates of the individual stages of the oxygen exchange process on the surface of the oxides. It is shown that oxygen incorporation is rate-determining stage of the oxygen exchange on the surface of the undoped oxide, whereas for the strontium-doped oxides La1–xSrxScO3–δ (x = 0; 0.04; 0.09) with increasing of strontium concentration, the difference between the rates of dissociative adsorption and oxygen incorporation decreases so that for the oxide La0,91Sr0,09ScO3–δ the stage of dissociative adsorption of oxygen becomes rate-determining stage. The paper analyzes the possible reasons of these differences in oxygen surface exchange kinetics. Moreover, the paper using the obtained oxygen diffusion coefficients that have been recalculated in the oxygen-ionic conductivities according to the Nernst-Einstein equation performs the contributions of the oxygen-ion and proton components of the total conductivity of oxides La1–xSrxScO3–δ (x = 0; 0.04; 0.09) in the wet reducing atmosphere (pH2O = 2.35 kPa, pO2 = 10−15 Pa). Proton transference numbers are shown to be close to unit in the temperature range of 500–600 °С at the wet hydrogen-containing reducing atmosphere.

scholarly journals Influence of Heterointerfaces on the Kinetics of Oxygen Surface Exchange on Epitaxial La1.85Sr0.15CuO4 Thin Films

2021 ◽  
Vol 11 (9) ◽  
pp. 3778
Author(s):  
Gene Yang ◽  
So-Yeun Kim ◽  
Changhee Sohn ◽  
Jong K. Keum ◽  
Dongkyu Lee
Keyword(s):  
Thin Films ◽  
Oxygen Vacancies ◽  
Elevated Temperatures ◽  
Surface Exchange ◽  
Electrical Conductivity Relaxation ◽  
Exchange Kinetics ◽  
Relaxation Curves ◽  
Kinetics Of ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface

Considerable attention has been directed to understanding the influence of heterointerfaces between Ruddlesden–Popper (RP) phases and ABO3 perovskites on the kinetics of oxygen electrocatalysis at elevated temperatures. Here, we report the effect of heterointerfaces on the oxygen surface exchange kinetics by employing heteroepitaxial oxide thin films formed by decorating LaNiO3 (LNO) on La1.85Sr0.15CuO4 (LSCO) thin films. Regardless of LNO decoration, tensile in-plane strain on LSCO films does not change. The oxygen surface exchange coefficients (kchem) of LSCO films extracted from electrical conductivity relaxation curves significantly increase with partial decorations of LNO, whereas full LNO coverage leads to the reduction in the kchem of LSCO films. The activation energy for oxygen exchange in LSCO films significantly decreases with partial LNO decorations in contrast with the full coverage of LNO. Optical spectroscopy reveals the increased oxygen vacancies in the partially covered LSCO films relative to the undecorated LSCO film. We attribute the enhanced oxygen surface exchange kinetics of LSCO to the increased oxygen vacancies by creating the heterointerface between LSCO and LNO.

Surface potentials and oxygen surface exchange coefficients of acceptor and donor-doped CeO2 thin films

2021 ◽  
Author(s):  
Hans F. Wardenga ◽  
Katharina N.S. Schuldt ◽  
Stephan Peter Waldow ◽  
Roger A De Souza ◽  
Andreas Klein
Keyword(s):  
Thin Films ◽  
Work Function ◽  
Surface Electron ◽  
Surface Exchange ◽  
Surface Potentials ◽  
Doped Ceo2 ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface

In order to evaluate the influence of work function and surface electron concentrations on oxygen surface exchange coefficients, the surface potentials of acceptor-, donor-, and nominally un-doped CeO2 films are...

Using Mechano-Electro-Chemical Coupling to Measure the Thin Film Elastic Constants, Thermo-Chemical Expansion Coefficients, and Oxygen Surface Exchange Coefficients of Praseodymium Doped Ceria Presentation Format: Oral Preferred

2018 ◽  
Vol MA2018-01 (32) ◽  
pp. 1942-1942
Author(s):  
Yuxi Ma ◽  
Jason D. Nicholas
Keyword(s):  
Film Stress ◽  
Doped Ceria ◽  
Surface Exchange ◽  
Chemical Expansion ◽  
Young’S Moduli ◽  
Curvature Measurements ◽  
Expansion Coefficients ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface

A Multi-beam Optical Stress Sensor (MOSS) is a curvature measurement platform which is commonly used to measure the film stress in bilayer samples. It has been widely used as an in-situ technique to measure the film stress during deposition.1 However, when combined with the dual substrate method proposed by Zhao et al,2 in situ curvature measurements can be used to measure Young’s moduli and thermo-chemical expansion coefficients simultaneously as a function of temperature. Using the curvature relaxation (κR) technique developed recently,3-5 oxygen surface exchange coefficients (kchem) can also be measured as a function of temperature using in situ curvature measurements. In this work, the Young’s moduli, thermo-chemical expansion coefficients and kchem values of praseodymium doped ceria (PCO) were measured as a function of temperature using a MOSS. First, phase pure Pr0.1Ce0.9O1.95 (PCO) powder was prepared through glycine nitrate combustion and subsequent calcination at 1100oC in air. This powder was then pressed in a stainless-steel die and fired to 1450oC to produce a pulsed laser deposition (PLD) target. In preparation for PLD, (001) oriented 9.5% yttria doped zirconia (YSZ) and (001) oriented magnesium oxide (MgO) substrates (Crystec, GmbH) were pre-annealed at 1450oC for 20 hours to remove residual stress within them. PCO PLD was then conducted at 680oC for 20 min, with a 10-2 torr oxygen partial pressure and 350 mJ power density. After deposition, the PCO bilayers were re-equilibrated with air by firing them in air at 1000oC for 1 hour. For dual substrates measurements, stress vs. temperature data for PCO|YSZ and PCO|MgO were collected with a 1oC/min heating rate and a 0.2oC/min cooling rate. The slopes of the stress vs. temperature curves can be expressed by: dσPCO|YSZ/dT = MPCO(αYSZ-αPCO) (1) dσPCO|MgO/dT = MPCO(αMgO-αPCO) (2) where is the stress of bilayer sample, T is the temperature, M is the biaxial modulus of the film, is the thermo-chemical expansion coefficient. With two unknowns and two equations, and were then extracted as a function of temperature. The Young’s moduli were then calculated from assuming a Poisson’s ratio of 0.33 as has been done previously for 6. For κR measurements, relaxation data were recorded at 650~725oC with 25oC increments. The oxygen partial pressure was switched between synthetic air (20%O2-80%Ar) and 10% diluted synthetic air (10% synthetic air-90%Ar). Figure 1 shows the Young’s modulus and thermo-chemical expansion coefficients measured here compared to other literature studies.6-8 In contrast to other studies the present study produced PCO Young’s moduli over a complete range of temperatures. In addition, the PCO Young’s moduli started to decrease significantly once the PCO started to become nonstoichiometric (as indicated by an uptick in chemical expansion in Figure 1b). The PCO kchem values (not shown) were in good agreement with the kchem values measured by other electrode-free techniques, such as optical relaxation.9 Figure 1

Accelerating oxygen surface exchange

2020 ◽  
Vol 3 (11) ◽  
pp. 863-864
Author(s):  
Sossina M. Haile
Keyword(s):  
Surface Exchange ◽  
Oxygen Surface Exchange ◽  
Oxygen Surface
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