Determination of oxygen nonstoichiometry and diffusivity in mixed conducting oxides by oxygen Coulometric titration

M.H.R. Lankhorst, Martijn H.R. Lankhorst, Henricus J.M. Bouwmeester

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Abstract

Oxygen coulometric titration has been applied to measure chemical diffusion in La0.8Sr0.2CoO3-δ between 700 and 1000°C. The transient current response to a potentiostatic step has been transformed from the time domain to the frequency domain. The equivalent circuit used to fit the resulting impedance data contains the element that describes the finite-length diffusion of oxygen into the sample specimen. Other elements included are the gas-phase capacitance and the sum of the gas-phase diffusion resistance and that associated with the limited surface exchange kinetics of the sample. The chemical diffusion coefficient of perovskite La0.8Sr0.2CoO3-δ has been determined as a function of temperature and oxygen partial pressure. Its value can be represented by ~D (cm2/s) = 5.91 x exp [(-135 kJ/mol)/RT], and turns out to be practically independent of oxygen partial pressure in the range 10-2 - 0.209 bar.
Original languageUndefined
Pages (from-to)1261-1267
Number of pages7
JournalJournal of the Electrochemical Society
Volume144
Issue number4
DOIs
Publication statusPublished - 1997

Keywords

  • METIS-106487
  • IR-61585

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