Oxygen Transport Kinetics in La0.5Sro0.5Fe0.8Ga0.2O3−δ Membranes Under Both Small and Large Oxygen Partial Pressure Gradients

1998 ◽  
Vol 548 ◽  
Author(s):  
Sangtae Kim ◽  
Allan J. Jacobson ◽  
Benjamin Abeles
Keyword(s):  
Diffusion Coefficient ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Transport ◽  
Oxygen Flow Rate ◽  
Pressure Gradients ◽  
Exchange Coefficient ◽  
Maximum Enhancement ◽  
Surface Exchange ◽  
Surface Exchange Coefficient

ABSTRACTOxygen permeation through a new perovskite La0.5Sr0.5Fe0.8Ga0.2O3−δ membrane has been measured both under small (air/He) and large (air/CO, CO2) oxygen partial pressure gradients. In both cases oxygen transport is close to surface limited. By modeling the pressure dependence of the oxygen flow rate under small pressure gradient an ambipolar diffusion coefficient 9.65 × 10−7cm2/s and a surface exchange coefficient 7.15 × 10−6 cm/s at 974 °C were determined. With air/CO, CO2 on the permeate side, the permeability increases linearly with the partial pressure of CO. The observed increase is greater than the maximum enhancement predicted by our model.

Oxygen self-diffusion in cerium oxide doped with Nd

2001 ◽  
Vol 16 (1) ◽  
pp. 179-184 ◽  
Author(s):  
Michiyo Kamiya ◽  
Eriko Shimada ◽  
Yasuro Ikuma ◽  
Manabu Komatsu ◽  
Hajime Haneda ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Oxygen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Annealing ◽  
Exchange Coefficient ◽  
Surface Exchange ◽  
Oxygen Diffusion Coefficient ◽  
Self Diffusion ◽  
Surface Exchange Coefficient ◽  
Secondary Ion

Polycrystalline Ce0.77Nd0.23O1.885having a relative density in excess of 98% was prepared. Oxygen diffusion experiments were performed for the temperature range from 750 to 1100 °C, in an oxygen partial pressure of 6.6 kPa. The concentration profile of18O in the specimens following diffusion annealing was measured by secondary ion mass spectroscopy (SIMS). The oxygen self-diffusion coefficient obtained using secondary ion mass spectrometry was expressed by D = 6.31 × 10−9exp(−53 kJ mol−1/RT) m2s−1and was in the extrinsic region. The oxygen diffusion coefficient of Ce0.77Nd0.23O1.885was larger than that of Ce0.8Y0.2O1.90; it was close to those of Ce0.6Y0.4O1.80and Ce0.69Gd0.31O2−δ. The oxygen diffusion coefficient obtained by the tracer method at 700 °C agreed with that calculated from the electrical conductivity in Ce0.77Nd0.23O1.885. The activation energy of the surface exchange coefficient was 94 kJ mol−1, and the values of the surface exchange coefficient were similar to those of stoichiometric CeO2and ThO2.

A Study of the Oxygen Surface Exchange Coefficient on La0.5Sr0.5CoO3−δ Thin Films

1999 ◽  
Vol 606 ◽  
Author(s):  
X. Chen ◽  
S. Wang ◽  
Y.L. Yang ◽  
L. Smith ◽  
N.J. Wu ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Initial Pressure ◽  
Transient Behavior ◽  
Epitaxial Thin Films ◽  
Exchange Coefficient ◽  
Surface Exchange ◽  
Surface Exchange Coefficient ◽  
Pressure Changes ◽  
Oxygen Surface Exchange

AbstractLa0.5Sr0.5CoO3−δ (LSCO) can be used as a cathode material for low temperature solid oxide fuel cell applications. LSCO epitaxial thin films have been deposited on LaAlO3 substrates by pulsed laser deposition (PLD). The transient behavior of the thin film conductivity with the pressure changes was recorded as a function of temperature and partial oxygen pressure. The surface exchange coefficient k of the LSCO thin film was obtained from analysis of the electrical conductivity relaxation data. The measured surface exchange coefficient increases with temperature and with final pressure but is not sensitive to the initial pressure. After prolonged annealing at 900°C, the k value was found to have greatly increased. The mechanism of the dependence of the measured k on pressure is discussed.

scholarly journals Back-exchange: a novel approach to quantifying oxygen diffusion and surface exchange in ambient atmospheres

2017 ◽  
Vol 19 (19) ◽  
pp. 12199-12205 ◽  
Author(s):  
Samuel J. Cooper ◽  
Mathew Niania ◽  
Franca Hoffmann ◽  
John A. Kilner
Keyword(s):  
Isotopic Exchange ◽  
Ambient Air ◽  
Exchange Coefficient ◽  
Effective Surface ◽  
Surface Exchange ◽  
Electronic Conductor ◽  
Novel Approach ◽  
Mixed Ionic Electronic Conductor ◽  
Back Exchange ◽  
Surface Exchange Coefficient

A novel two-step Isotopic Exchange (IE) technique has been developed to investigate the influence of oxygen containing components of ambient air (such as H2O and CO2) on the effective surface exchange coefficient (k*) of a common mixed ionic electronic conductor material.

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