Characterization of BaCe0.4Zr0.4Y0.2O3-δ Protonic Conductor in-operando conditions

BASBUS J.F.; ARCE M.D.; NAPOLITANO F.; SALETA M.; BONANOS N; ALONSO J.; FERNANDEZ DIAZ M; GIEBELER L; CANEIRO A.; SERQUIS A,; MOGNI L.V

Congreso; Materials Science and Engineering-MSE 2018; 2018

Recently, BaCe0.4Zr0.4Y0.2O3-δ (BCZY) perovskite was proposed as PC-SOFC electrolyte due to its high bulk protonic conductivity and good CO2 tolerance. However, the operating temperature range needs to be carefully determined to be used as proton conductor electrolyte. Relationship between the electrochemical and crystallographic properties for barium cerates and zirconates is expected according to bibliography [1]. In addition, different crystal structures for compositions similar to BCZY between room temperature and 800 °C under static air have been reported [2]. In this sense, it is possible that BCZY compound presents rhombohedral or monoclinic instead of cubic symmetry. Therefore, BCZY requires a more detailed characterization as a function of temperature and atmosphere. In this work, BCZY was synthesized by solid state reaction (SSR), calcined and sintered at 1600 °C for 12 hours. Crystallographic and electrical properties were studied simultaneously by performing in-operando synchrotron X-ray diffraction (XRD) and Electrochemical Impedance Spectroscopy (EIS), respectively. These measurements were performed between room temperature and 800 °C under wet synthetic air. Homemade sample holder was designed to study electrical and structural properties under in-operando conditions. A strong correlation between crystallographic and electrochemical properties was observed. Protonic conductivity is the dominant transport mechanism below to 500 °C. Otherwise, oxygen vacancies dominate transport mechanism above 500 °C. Neutron powder diffraction (NPD) was used to determine crystallographic space group and evaluate oxygen non-stoichiometry of BCZY perovskite. XRD and NPD patterns were simultaneously refined indicating that BCZY presents rhombohedral symmetry below to 600 °C, while above this temperature it presents cubic symmetry. The correlation between crystallographic and electrochemical properties is discussed.