Co-doping as a strategy for tailoring the electrolyte properties of BaCe0.9Y0.1O3-δ

The properties of single-doped BaCe0.9Y0.1O3-delta and materials co-doped with 5 mol % of different cations (In3+, Zr4+ and Nb5+) with the general formula BaCe0.85Y0.1M0.05O3-delta were compared to examine the influence of dopants on the electrolyte properties. The samples were synthesized by the citric-nitric autocombustion method. BaCe0.85Y0.1In0.05O3-delta was successfully sintered at 1400 degrees C for 5 h in air, while a complete sintering of the other materials was carried out at 1550 degrees C. This makes the doping with In a preferable method since sintering temperatures below 1500 degrees C can limit BaO evaporation. The total conductivities (sigma) calculated from the electrical measurements at 700 degrees C in wet hydrogen decreased in the following order: BaCe0.9Y0.1O3-delta > BaCe0.85Y0.1Zr0.05O3-delta > BaCe0.85Y0.1Nb0.05O3-delta > BaCe0.85Y0.1In0.05O3-delta. The stability of the ceramics exposed to a 100% CO2 atmosphere at 700 degrees C for 5 h was examined by X-ray analysis. It was observed that only BaCe0.85Y0.1In0.05O3-delta could sustain the aggressive environment containing traces of secondary phases, while the other samples were partially or significantly decomposed. By taking into account the values of the Goldschmidt tolerance factor (t) and dopant electronegativity (chi), it was found that the dopant electronegativity had a decisive role in inhibiting the carbonation of the ceramics.