In their paper, R. Merkle et al [R. Merkle, J. Maier, K.D. Becker and M. Kreye, Phys.
Chem. Chem. Phys. 6, 3633 (2004)] conducted an experimental study on the chemical diffusion of
oxygen in Fe-doped SrTiO3 single crystals driven by large changes in the oxygen ambient partial
pressure. The stoichiometry dependence of the chemical diffusion coefficient was derived on the
basis of the concept of conservative ensembles for two independent trapping reactions, which then
served for calculating the evolution of vacancy profiles. The theoretical predictions were compared
to the experimental results. In the framework of the same model, in the present communication, the
chemical diffusion of oxygen was analyzed by the concept of a dynamic reaction front [M. Sinder,
J. Pelleg, Phys. Rev. E 61, 4935 (2000); Z. Koza, Phys. Rev. E 66, 011103 (2002)]. We show, that
by using a quasi-chemical reaction rate profile, it is possible to obtain information relating to the
position and width of the zone where the reaction takes place. It is indicated, that the reaction rate
distribution can be directly calculated from measured concentration profiles of the immobile
reactant.
Estimation of the Na Insertion/Extraction Reaction Rate as the Na Chemical Diffusion Coefficient in Low-Temperature-Fired Soft Carbon
