Conductivity Relaxation of Proton-Conducting BaCe0.85Y0.15O3−δ Upon Oxidation and Reduction

Abstract

The electrical properties of Y-doped barium cerate (BaCe 0.85 Y 0.15 O 3Àd ; BCY) were studied as a function of both oxygen partial pressure (À3.34 log P O2 /atm À2.72) and water vapor activity (À3.34 log P H2O /atm À2.72) in the temperature range of 700-800 C. The total conductivity slightly increased in reducing atmospheres with increasing water vapor activity but tended to be independent as the atmosphere became oxidized due to the relative contribution to the total conductivity by redox reaction at the given thermodynamic conditions. Due to the sluggish H-unmixing in the oxygen chemical potential gradient and the negligible hydrogen chemical potential gradient developed during oxidation and reduction at a fixed water vapor activity, the chemical diffusivity of oxygen at a fixed water vapor activity,D vO , could only be evaluated from Fick's second law. The chemical diffusivity of oxygen for BCY was an order of magnitude higher than that observed in the Yb-doped SrCeO 3 proton conductor due to the higher proton conductivity of BCY.

Crystal Structure, Hydration, and Two-Fold/Single-Fold Diffusion Kinetics in Proton-Conducting Ba0.9La0.1Zr0.25Sn0.25In0.5O3−a Oxide

“…Consequently, in e.g., the electrical relaxation experiments conducted during change of the water vapor partial pressure in the sample's surrounding atmosphere, the respective relaxation curves should be of a single fold nature. This is in contrast to numerous literature reports showing a two-fold character of the relaxation curves recorded in specific conditions [30][31][32][33][34][35][36].…”

“…Such change implies the presence of the electronic hole conductivity, as can be expected from the discussed characteristics of the EIS data recorded at higher (≥600 °C) temperatures. It should be clarified that, in the case of ECR profiles fitted at 600 °C and above, only R0 component was considered, which is in accordance with the direct current measurements presented in the literature [33,36]. Table 2 values of the proton conductivity are lower [43].…”

“…Interestingly, a coupled and decoupled transport phenomena related to the ionic conductivity were observed. While these effects were previously reported in several studies [34,36], for the presented results, a clear transition occurs as a function of temperature.…”

BaCe0.85Y0.15O2.925 dense layer by wet powder spraying as electrolyte for SOFC/SOEC applications

“…The electrolyte conductivity obtained from the impedance measurements at 650°C in the two-electrode configuration provided a value of 0.053 S cm −1 . Data in literature [28][29][30][31][32] report a conductivity for (a) (b) BCY15 at 650-700°C ranging around 0.02 S cm −1 , rather lower than those here obtained at the lower temperature. These results suggest that the deposition of BCY15 by WPS is a promising procedure, since it is a cheap and up-scalable process for the fabrication of dense electrolyte layers of a refractory material, with very good conductivity and control of the layer thickness.…”

Moving boundary diffusion problem for hydration kinetics evidenced in non-monotonic conductivity relaxations of proton conducting perovskites

“…A series of publications of conductivity relaxation experiments appeared following the reports on the SCYb system [7] and BCYb [8]: BaZr 0.6 Ce 0.25 Y 0.15 O 3 − δ (BZC25Y) [14], BaZr 0.40 Ce 0.45 Y 0.15 O 3 − δ (BZ40CY) [15], BaCe 0.85 Y 0.15 O 3 − δ (BCY) [12,38], and Ba 3 Ca 1.18 Nb 1.82 O 8.73 (BCN18) [13]. The chemical diffusivities upon hydration/dehydration and oxidation/reduction are presented in Figs.…”