An accurate way to determine the ionic conductivity of mixed ionic-electronic conducting (MIEC) ceramics

Measuring oxygen transport through dense, mixed ion-electron conducting, ceramic membranes is usually performed in a lab-scale permeation set-up where feed and sweep gas are directly flushed to the membrane surface. Due to concentration gradients, the oxygen partial pressure PO2 measured at the outlet is not the same as on the membrane surface, leading to inaccurate calculations of the oxygen ionic conductivity (σion) of the membrane. A computational fluid dynamics (CFD) model is developed to determine the exact PO2 on the membrane surface. With this model, oxygen ionic conductivity of a model membrane, SrCo0.8Fe0.2O3−δ, is calculated. By comparing σion, based on perfect gas mixing with values based on the CFD model, it is found that the former one is overestimated by ∼50-180% in the temperature and PO2 range regarded. In addition, the influence of parameters, like type and flow rate of the sweep gas, is studied.