Materials synthesis, electrochemical characterization and oxygen permeation properties of Fe-doped BaZrO3

This paper reports the synthesis, materials characterization, electrochemical and transport properties under O2-environments of an iron-doped barium zirconate perovskite (Ba0.90Fe0.10Zr0.90O3 -δ or BZF10), a mixed ionic-electronic conductor (MIEC). BZF10 powder was synthesized by solid-state reaction of the binary oxides and characterized using synchrotron X-ray diffraction (XRD). Analysis of the XRD patterns indicated the presence in the powder of a primary cubic perovskite phase with a lattice parameter 4.19 Å. The actual composition of the powder was measured using proton induced X-ray emission (PIXE). The powder was pressed and sintered into pellets and the fracture cross-section was then investigated by transmission electron microscopy (TEM). TEM analysis indicates a polycrystalline structure and the electron-diffraction pattern confirms the XRD results. The pellets, with attached electrodes, were investigated for electrochemical activity under dry oxidizing atmosphere using a combination of electrical conductivity relaxation (ECR) and electrochemical impedance spectroscopy (EIS) in the range of 600-800 °C and oxygen permeability between 600-900°C. ECR indicates that both the chemical diffusion coefficient DV and the surface kinetic parameter k′ increase with increasing pO2. EIS suggests a primarily p-type semiconduction behavior explaining the dependence of electrical conductivity upon oxygen partial pressure. Separate gas permeation measurements confirm an oxygen permeability of 4.11 × 10- 11 mol/(m·s·Pa). BZF10 materials showed superior stability during the whole study (> 1000 h on stream).