Loading path effect on the chemical expansion in substoichiometric LSF based perovskite

Permeation induced expansion in substoichiometric perovskites is a key point of their mechanical reliability under oxygen activity gradient. This paper proposes a macroscopic modelling of this phenomenon based on the choice of oxygen activity as state variable. This approach helps to underline the asymmetry of the chemical expansion in its dependence on the difference between the actual surrounding atmosphere and the sintering one. It leads to the development of the notion of loading path in terms of surrounding atmosphere change. The investigations show that the intrinsic chemical expansion behaviour is independent of the sintering atmosphere. The apparent chemical expansion behaviour is driven by the loading path. A study of the sensitivity of each parameters of the model helps to better estimate the possibilities and the limits of the proposed approach.