In situ Neutron Diffraction Study of BaCe0.4Zr0.4Y0.2O3-δ Proton Conducting Perovskite: Insight on phase transition and proton transport mechanism

BASBUS J.F.; ARCE M.D.; ALONSO J.; GONZALEZ M.; CUELLO G; FERNANDEZ DIAZ M; SERQUIS A,; MOGNI L.V

Workshop; Escola Ricardo Rodrigues de Luz Síncrotron (ER2LS); 2021

Ba(Ce,Zr)O3 perovskites with protonic conductivity have potential technological applications as electrolyte for solid oxide fuel and electrolyzer cells, isotopic separation membranes and hydrogen sensors. The understanding of protonic defect transport mechanism in oxides and its proper temperature range of conductivity are fundamentals for materials design and technological applications. Structural features of the material, as well as the lattice distortions and proton mobilities, are key factors defining the protonic conduction. The crystal structure of BaCe0.4Zr0.4Y0.2O3−δ (BCZY) perovskite and its correlation with proton conductivity was studied by X-ray and neutron techniques. The 2nd order phase transition from rhombohedral to cubic symmetry takes place between 400 and 600 °C. Neutron Powder Diffraction (NPD) of deuterated BCZY sample allowed to detect the temperature of the phase transition by dynamic measurements. Crystallographic and microstructural parameters, including deuterium occupancy and anisotropic thermal parameters, were determined from high resolution stationary NPD data. According to the oxygen non stoichiometry, the deuterium occupancy remains its maximum value below 400 °C and the phase transition occurs around 520 °C, when deuterium occupancy starts to decrease. From these results, the protonic transport mechanism depends on deuterium content although it is not intimately related to the phase transition. In addition, the protonic diffusion was calculated and it occurs above the phase transition.