Conductivity Relaxation Studies On La0.5Sr0.5Co0.8Ga0.2O3−δ

1998 ◽  
Vol 548 ◽  
Author(s):  
S. Wang ◽  
B. Abeles ◽  
A.J. Jacobson
Keyword(s):  
Relaxation Curve ◽  
Conductivity Measurements ◽  
Conductivity Relaxation ◽  
Exchange Coefficient ◽  
Surface Exchange ◽  
Electrical Conductivity Relaxation ◽  
Diffusion Limited ◽  
Mixed Ionic Electronic Conductor ◽  
Surface Exchange Coefficient ◽  
Plate Geometry

ABSTRACTThe surface exchange coefficient, ki, of the mixed ionic electronic conductor perovskite, La0.5Sr0.5Co0.8Ga0.2O3−δ, was determined in the temperature range 600-900°C by electrical conductivity relaxation on thin plate and long bar samples, using four probe dc conductivity measurements. The normalized conductivity could be fitted by the equation corresponding to surface limited relaxation, (σ(t) − σ1) / (σ2 − σ1) = 1 − exp(−t / Tr), where τ = l1l2 / [(l1 + l2)Γki], σ(t), σ1 and σ2 are the time dependent, initial and final conductivities, Γ is the thermodynamic factor and 21, and 212 are the lateral sides of the bar. Numerical simulation shows that the shape of the relaxation curve for the plate geometry changes only little in going from surface limited to diffusion limited transport, the change is significantly larger for the bar geometry.

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.

Electrical Conductivity Relaxation Study of Solid Oxide Fuel Cell Cathodes using Epitaxial (001)-Oriented Strontium-Doped Lanthanum Manganite Thin Films

2010 ◽  
Vol 1255 ◽  
Author(s):  
Lu Yan ◽  
Balasubramaniam Kavaipatti ◽  
Shanling Wang ◽  
Hui Du ◽  
Paul Salvador
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Elevated Temperatures ◽  
Reduction Process ◽  
Lanthanum Manganite ◽  
Conductivity Relaxation ◽  
Surface Exchange ◽  
Electrical Conductivity Relaxation ◽  
Crystal Films ◽  
Surface Exchange Coefficient

AbstractEpitaxial single-crystal films of La0.7Sr0.3MnO3 (100) having smooth surface morphology were deposited on SrTiO3 (100) substrates by pulsed laser deposition (PLD). Electrical conductivity relaxation (ECR) measurements were carried out at elevated temperatures over a range of absolute oxygen pressures to determine the oxygen surface exchange coefficient. Steady-state conductivity data of the thin films show good agreement with the bulk material's properties. The values of the oxygen exchange coefficients (Kchem) are found to be similar for both oxidation and reduction process between 50 and 500 mTorr O2. The activation energy (Ea) of Kchem is 1.00±0.27 eV at temperatures above 600 °C and Kchem (T=612°C)≈1.2×10-6 cm/s.

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.

Oxygen diffusion and surface exchange in the mixed conducting oxides SrTi1−yFeyO3−δ

2016 ◽  
Vol 18 (42) ◽  
pp. 29495-29505 ◽  
Author(s):  
Veronika Metlenko ◽  
WooChul Jung ◽  
Sean R. Bishop ◽  
Harry L. Tuller ◽  
Roger A. De Souza
Keyword(s):  
Oxygen Diffusion ◽  
Oxygen Exchange ◽  
Exchange Coefficient ◽  
Surface Exchange ◽  
Conducting Oxides ◽  
Single Mechanism ◽  
Surface Exchange Coefficient

Variation of the surface exchange coefficient with Fe concentration suggests single mechanism of oxygen exchange for e−-poor and e−-rich SrTi1−yFeyO3−δ oxides.

scholarly journals Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime

2016 ◽  
Vol 18 (32) ◽  
pp. 22031-22038 ◽  
Author(s):  
Peter Fielitz ◽  
Günter Borchardt
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Oxygen Exchange ◽  
Oxide Surfaces ◽  
Kinetic Regime ◽  
Exchange Coefficient ◽  
Surface Exchange ◽  
Oxide Interfaces ◽  
Surface Exchange Coefficient ◽  
Apparent Activation Energies

The model explains the range of apparent activation energies measured in different kinetic regimes of oxygen exchange at oxide surfaces.

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