Role of synthetic route on the transport properties of BaCe1-xYxO3 proton conductor

In this paper we studied the role of the preparation route on the transport properties of the BaCe1-xYxO3-´ solid solution with x=0, 0.1, 0.15 and 0.2. In particular the samples were synthesised by means of the solid state reaction and by a modified Pechini method. The effect of the grain size on the sintering behaviour of the two samples batches was investigated by means of impedance spectroscopy and electron microscopy. It was found that a good sintering of the pellets can be achieved at 1250°C for the samples prepared through the Pechini method. The ceramic route, even at higher temperatures, does not lead to good density values. The extensive conductivity measurements as a function of doping and gas environment (pure oxygen and argon+5% H2+water) we carried out showed that the optimal Y-doping is around 15% and that a significant proton conductivity can be achieved for T lower than 500°C. Above this temperature, the role of oxygen defects starts becoming relevant. Finally, the presence of a slope change in all the Arrhenius plots, irrespective to the gas environment, at about 450-500°C was observed and qualitatively interpreted as due to a change in the nature of the main charge carriers involved.