Studies on chemical stability and electrical properties of proton conducting perovskite-like doped BaCeO₃

The chemical stability and electrical properties of three promising perovskite-related structures BaCe_0.8Gd_0.15Pr _0.05O_3-δ, BaCe_0.85Sm_0.15O ₃-δ, and BaCe_0.85Eu_0.15O _3-δ were tested in air, humidified N² and H ₂, as well as in D₂O+ N₂. Powder X-ray diffraction studies confirmed the formation of a cubic perovskite-like structure. The change in the lattice constant was consistent with B-site substitution in BaCeO₃. All the investigated compounds formed barium carbonate in CO₂ at elevated temperatures and were found to be chemically unstable in boiling H₂ O. The data showed that these three compounds are chemically stable in humidified CH₄ at 800°C; however, at 600°C, the formation of barium carbonate was observed. The electrical conductivity in wet N₂ and/or H₂ was found to be higher than that in the D² O -containing atmosphere, confirming proton conduction in the doped BaCeO₃. The Gd+Pr co-doped BaCeO ₃ showed the highest total conductivity of 2.58× 10 ^-2 S cm_-1 in H₂ +3% H₂ O at 700°C with an activation energy of 0.36 eV in the temperature range of 450-700°C.