Structural analysis, phase stability and electrochemical characterization of Nb doped BaCe0.9Y0.1O3−x electrolyte for IT-SOFCs

To improve the chemical stability of high temperature proton conductors based on barium cerate, electrolyte powders doped with different amounts of niobium were synthesized by the citrate–nitrate auto-combustion method. Pure single phases of BaCe0.9−xNbxY0.1O3−x (BCYN, 0.03 ≤ x ≤ 0.12) were obtained by thermal treatment at 1000 °C. Sintering at 1450 °C for 10 h produced dense pellets. X-ray absorption spectroscopy allowed to define the dopant ion insertion site and the co-dopant valency. Treatments in pure CO2 atmosphere at 700 °C for 3 h and subsequent XRD analysis were carried out to probe the chemical stability of the produced electrolytes. The influence of the presence of Nb5+ on conductivity has been investigated by electrochemical impedance spectroscopy (EIS) measurements. Polarization curves were acquired in the 400–750 °C temperature range.

► BaCe0.9−xNbxY0.1O3−x powders with different amounts of niobium were synthesized.
► X-ray absorption and XRD showed that the B site of BCY was co-doped with Nb5+.
► Structural contraction around Nb and local disorder increased with concentration.
► Y and Nb co-doping improved the chemical stability against carbonation.
► Best performance was obtained for BaCe0.84Nb0.06Y0.1.