Transport properties and in-situ Raman spectroscopy study of BaCe0.9Y0.1O3 − δ as a function of water partial pressures

The total conductivity of BaCe0.9Y0.1O3 − δ material was measured under air, in a large p(H2O) range up to 0.30 bar. The defect concentrations (OHO·, VO· · and h·) and electrical conductivities were calculated on the basis of chemical constants (diffusion coefficients and equilibrium constants reported in the past literature) and compared to the experimental data. Protonic transport number as high as 0.8 was found at 700 °C, under air containing 0.30 bar of water, which allows a possible extension of the protonic temperature range of this material using water rich atmosphere. In-situ Raman spectroscopy under wet and dry air was performed from room temperature up to 700 °C in two wavenumber ranges. At low wavenumber, characteristic of lattice vibrations, this study clearly shows that no significant changes occur upon water insertion while at high wavenumbers, characteristic of OH vibrations, two contributions to the OH vibrations were found. This is discussed in terms of proton environment and transient hydrogen bonds. Moreover, this in situ study confirms that, at moderate p(H2O), water insertion becomes significant at temperature below 650 °C.