Hysteresis in solid-state reactions

Abstract

The problem of the hysteresis that accompanies reversible solid-state redox reactions of oxides has been studied from the point of view of classical thermodynamics. Use is made of the thermodynamic equation of state in its integrated form in order to show that such systems cannot be at equilibrium but must contain some energy of metastability. Data from the literature are used to calculate some of these energies, and it is shown that the energy of interface formation is a likely explanation for the metastability. Thermodynamic equations alone fail to account for the phenomenon of scanning, but a model is developed using thermodynamics plus the nucleation and growth model for solid-phase intergrowth. It is shown that the concept of domains is unnecessary for an explanation of the hysteresis or the scanning. This is in contrast to the hysteresis seen in gas/porous-solid systems for which the domain model works well.