Effect of potassium substituted for A-site of SrCe_0.95Y_0.05O₃ on microstructure, conductivity and chemical stability

The chemical stability of potassium substituted for A-site of SrCe_0.95Y_0.05O₃ specimens was examined under CO₂ atmosphere treated at 600 °C and further analyzed by X-ray diffractometer to see their CO₂-resisted capabilities. According to thermodynamic data, the Gibbs free energy of CeO₂ was lower than that of SrCO₃ at the temperature of 600 °C. Thus the formation of CeO₂ might be faster than that of SrCO₃ in SrCeO_3- based materials under CO₂ atmosphere. Unfortunately, the chemical stability of SrCe_0.95Y_0.05O₃ materials in CO₂ atmosphere was reduced with increasing potassium-substituted amount. The microstructures of Sr_1-xK_xCe_0.95Y_0.05O₃ sintered specimens were identified using field emission scanning electron microscope. The conductivity in moisture H₂ atmosphere (RH 30%) was increased with increasing potassium-substituted concentration. The conductivity reached a maximum of 0.0081 Scm^-1 at 900 °C for Sr_0.95K_0.05Ce_0.95Y_0.05O₃ sintered specimens in moisture H₂ atmosphere (RH 30%). Potassium substituted for A-site of SrCe_0.95Y_0.05O₃ could improve the conductivity but not CO₂-resisted capability.