Complex oxides: high temperature defect chemistry vs. low temperature defect chemistry

Abstract

The contribution addresses the bridge between high temperature chemistry at which thermodynamic defect equilibrium with neighbouring phases can be assumed, and low temperature physics in which usually only electronic carriers behave reversibly. An optimised quenching procedure is discussed to obtain profile-free reproducible conditions. The conditioning of multinary compounds, typically complex oxides, exhibiting ionic carriers with distinctly different mobilities, requires a multi-step quenching procedure. The treatment of partial equilibria and the connection between quenched and reversible states allows us to understand a variety of “anomalous” phenomena. In this context, some results on mixed conducting, ion conducting and superconducting ceramics are reviewed.