Thermodynamic stabilities of perovskite oxides for electrodes and other electrochemical materials

We report the chemical thermodynamic approach of examining of stabilities of electrodes, interconnections and electrolytes. The stability of conductive complex oxides can be discussed in terms of (1) thelattice stability of particular structures as a function of composition, (2) the valence stability of transition metal ions against oxidative or reductive decompositions, (3) the abilities of the formation of lattice defects, and (4) the chemical stability against reactions with other components and with gaseous substances. Although these properties exhibit complicated variations from oxide to oxide, the fundamental energetics related to these stabilities were found to be relatively simple across the transition metal series. This simplicity will make it possible to gain an insight into the stability issues by using, as a good chemical scale, the ionic radii of transition metal ions. After a chemical thermodynamic representation of these materials, chemical reactions at their interfaces can be thermodynamically analyzed by chemical equilibria calculations and construction of chemical potential diagrams.