Development of a Predictive Thermo-Chemical Expansion and Stress Model in (Pr,Ce)O2-δ

The non-stoichiometry induced stress developed in the potential cathode material, Pr0.1Ce0.9O2-delta (PCO), upon cooling from high temperature is modeled. Stresses can develop in such mixed ionic electronic materials due to changes in oxygen stoichiometry, resulting in defect induced dilation, or chemical expansion. In this example, a simulated bulk sample of PCO is cooled from 1400 degrees C in air and O-2 at different rates and the resulting diffusion limited concentration gradient is predicted and converted into a stress distribution using the chemical coefficient of expansion. Maximum tensile stresses of similar to 500 MPa are predicted at the sample surface, which can be reduced by cooling in more oxidizing atmospheres and/or at slower rates.