Determination of Oxygen Vacancy Concentration in a Thin Film of La[sub 0.6]Sr[sub 0.4]CoO[sub 3−δ] by an Electrochemical Method

Abstract

Equivalent circuit analysis was undertaken on a mixed conductor electrode/solid oxide electrolyte system. In a limited case where surface reaction is the predominant rate-controlling process, the equivalent circuit was simplified to parallel connection of a resistor (surface reaction resistance) and a capacitor (chemical capacitance due to oxygen nonstoichiometry). Equilibrium oxygen vacancy concentration was correlated with the chemical capacitance. The model was applied to a dense film of La0.6Sr0.4CoO3−δ deposited on a sintered plate of Ce0.9Gd0.1O1.95 by a laser ablation method. Frequency response of the electrochemical impedance was measured under dc bias at 873-1073 K in O2­normalAr gas mixtures. The observed capacitance was extremely large, e.g., around 0.1 to 1 Fcm−2 for the 1.5 μm thick film. The oxygen vacancy concentration in the film was calculated from the capacitance and compared with the literature data measured by thermogravimetry. The film was found to show smaller oxygen nonstoichiometry. The enthalpy for oxygen vacancy formation in the film was about 40 kJ mol −1 larger than the bulk. © 2002 The Electrochemical Society. All rights reserved.

Model for Solid Electrolyte Gas Electrode Reaction Kinetics; Key Concepts, Basic Model Construction, Extension of Models, New Experimental Techniques for Model Confirmation, and Future Prospects

“…However, some important results are published only in proceedings papers. [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] Most of these proceedings papers are in preliminary forms but a few of them turned to be the final ones because they were published in volumes of monographs or commercialized books. [60][61][62][73][74][75][76] Some of the proceedings papers are comprehensive ones.…”

Nonlinear coupled equations for electrochemical cells as developed by the general equation for nonequilibrium reversible-irreversible coupling

“…21,23 This applies also to the two-dimensional system, the surface, when it is defined with Gibbs excess variables. In electrochemistry the assumptions of local thermodynamic equilibrium and electroneutrality are commonly used, see, e.g., Ref.…”

“…In electrochemistry the assumptions of local thermodynamic equilibrium and electroneutrality are commonly used, see, e.g., Ref. 21.…”

“…Equations like (21) express that the pressure gradient balances the gradient in the electric potential at steady state. We return to these issues in Sec.…”

Oxygen permeation flux through 10Sc1YSZ-MnCo 2 O 4 asymmetric membranes prepared by two-step sintering

“…In contrast, ionic conductors like doped zirconia ((ZrO2)1-x(Y2O3)x (YSZ), (ZrO2)1-x(Y2O3)x(Sc2O3)y (ScYSZ)) or doped ceria (Ce1-xGdxO2-δ (CGO), Ce1-xSrxO2-δ (CSO), Ce1-xPrxO2-δ (CPO)) have high chemical stability in CO2 and at low oxygen partial pressure. Fluxes in membranes constructed from such materials is strongly limited by electronic conductivity [18] [19].…”