Oxygen coulometric titration has been applied to measure chemical diffusion in La0.8Sr0.2CoO3-δ between 700 and 1000Â°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.
Lankhorst, M. H. R., Lankhorst, M. H. R., & Bouwmeester, H. J. M. (1997). Determination of oxygen nonstoichiometry and diffusivity in mixed conducting oxides by oxygen Coulometric titration. Journal of the Electrochemical Society, 144(4), 1261-1267. https://doi.org/10.1149/1.1837580