Chemical diffusion of oxygen in perovskites

The role of chemical diffusion is highlighted and discussed for SrTiO3 as a model material and for some important HTSC-cuprates. As experimental techniques, chemical relaxation and electrochemical polarization have been used. In the case of the model material SrTiO3 optical absorption allows the in situ recording of spatially and time resolved profiles; in addition, detailed kinetic considerations lead to the design of a simple and elegant polarization technique. With regard to the HTSC-compounds, special materials peculiarities complicating the systematic evaluation are discussed. In both cases internal redox-reactions are a clue to obtaining a basic understanding of the chemical diffusion coefficients as a function of materials parameters.