Defect-Transport-Induced Stress in Mixed Ionic-Electronic Conducting (MIEC) Ceramic Membranes

Abstract

An extension of the Nernst–Planck–Poisson (NPP) formulation is developed to include the effects of stress in modeling mixed ionic-electronic conducting (MIEC) ceramics. In addition to diffusion and migration contributions, the Nernst–Planck flux includes the effects of hydrostatic stress gradients on the transport of charged defects. The model uses a thin-plate formulation to determine hydrostatic stress profiles, which depend on the defect-concentration profiles. With oxygen-separation membranes in mind, the model is illustrated using a combination of measured and estimated material properties for La0.6Sr0.4Co0.8Fe0.2O3 − δ (LSCF6482). Under transient conditions, where the oxygen partial pressure on one side of a membrane is suddenly changed, the model predicts concentration and stress profiles. The predicted maximum tensile stress can be very high, suggesting the possibility for membrane damage or failure.