Thermodynamic prediction of the effect of CO2 to the stability of (La0.8Sr0.2)0.98MnO3±δ system

Abstract

Thermodynamic predictions regarding the formation of secondary phases in CO2 containing atmosphere on the (La0.8Sr0.2)0.98MnO3±δ (LSM-20) surface and at the LSM-20 (cathode)/8YSZ (electrolyte) interface have been studied using the CALculation of Phase Diagram (CALPHAD) approach. The effects of temperature, CO2 partial pressure, O2 partial pressure and the cathode composition on formation of secondary phases have been investigated and correlated with the available experimental results found in the literature. Our study predicts that the SrCO3 has the possibility to form on the surface and at triple phase boundaries (TPBs) as a result of CO2 exposure to the system. In addition, our study also indicates that the CO2 exposure does not change the electronic/ionic carriers' concentration in perovskite phase. The observed electrical conductivity drop is predicted to occur due to the formation of secondary phases such as LaZr2O7, SrZrO3 or SrCO3, at the LSM-20/8YSZ interface, resulting in the blocking of the electron/ion transfer paths.