Structural and electrical properties of BaCe_0.9Ee_0.1O_2.95 electrolyte for IT-SOFCs

Highlights: • BaCe_0.9Ee_0.1O_2.95 (BCE) electrolyte was obtained by the autocombustion method. • Doping with Eu led to an increase in unit cell volume of BaCeO₃. • Eu promotes sintering of BaCeO₃ ceramics at lower temperatures. • Total conductivity of BCE at 600 °C reached 1.21 × 10⁻² S/cm in wet H₂. - Abstract: BaCe_0.9Ee_0.1O_2.95 (BCE) nanopowder was synthesized by citric-nitric autocombustion method. Rietveld refinement analysis showed that unit cell volume was slightly larger compared with the most known BaCe_0.9Y_0.1O_2.95, which might contribute to higher proton mobility. Sinterability of BaCeO₃ is also enhanced by doping with Eu, since dense single-phased BCE electrolyte microstructure comprising of 1–2 μm grains was obtained after sintering at 1450 °C for 5 h. The electrochemical impedance spectroscopy (EIS) analysis revealed separate bulk and grain boundary contributions to the total electrolyte conductivity below 200 °C. The grain boundary conductivity was one to two orders of magnitude lower than the bulk conductivity, indicating blocking effect of the grain boundaries to the mobility of charge carriers. This effect diminished completely above 500 °C and only total conductivities were determined between 500 and 700 °C. Conductivity of BCE in a wet hydrogen atmosphere at 600 °C reached 1.2 × 10⁻² S/cm, which can be considered as one of the highest conductivities among BaCeO₃ based proton conductors