Adjusting the electrolyte properties of BaCe0.9Y0.1O3–δ by co-doping

Abstract

Composition of BaCe0.9Y0.1O3-δ was changed by co-doping with 5 mole % of different cations (In3+, Zr4+ and Nb5+) to examine the influence of dopants on the electrolyte properties. The powder samples were synthesized by the citric-nitric autocombustion method. BaCe0.85Y0.1In0.05O3-δ was successfully sintered at 1400 °C for 5 h in air, while a complete sintering of the other materials was carried out at 1550 °C. This makes the doping with In a preferable method since sintering temperatures below 1500 °C can limit BaO evaporation. The presence of In and Nb caused a significant drop in the total conductivity (σ) of the ceramics at 700 °C in wet hydrogen, while the total conductivity of BaCe0.85Y0.1Zr0.05O3-δ was slightly lower than of BaCe0.9Y0.1O3-δ. The stability of the ceramics exposed to a 100 % CO2 atmosphere at 700 °C for 5 h was investigated by X-ray analysis. BaCe0.85Y0.1In0.05O3-δ showed considerable stability under the aggressive conditions containing traces of secondary phases, while the other samples were partially or significantly decomposed. By taking into account the factors that can influence the stability and conductivity, it was found that the dopant electronegativity had a decisive role both in inhibiting the carbonation and in decreasing the total conductivity of the ceramics.