The Effect of Chromium Oxide on the Conductivity of Ce_0.9Gd_0.1O₂, a Solid-Oxide Fuel Cell Electrolyte

To study the effect of chromium oxide on the electric properties of Ce_0.9Gd_0.1O₂, a solid-oxide fuel cell electrolyte, two approaches were used: (a) the studying of electrochemical properties of the Ce_0.9Gd_0.1O₂- electrolyte after the spontaneous adsorption of chromium-containing molecules from a gas phase and (b) the analyzing of transport properties of the Ce_0.9Gd_0.1O₂-based chromium-containing compositions obtained by the mixing of solid-oxide electrolyte with chromium(III) oxide. It was found that the chromium reduction at the electrolyte surface dominates when chromium is adsorbed from gas phase. Both approaches allow concluding that the chromium presence in Ce_0.9Gd_0.1O₂ deteriorates the electrolyte transport properties at temperatures above 735°С. This is caused by the chromium incorporation into the electrolyte’s fluorite structure, as well as surface microheterogeneity induced by the chromium presence at the Ce_0.9Gd_0.1O₂ surface and the cerium and gadolinium cation redistribution between the grains’ bulk and surface. At intermediate temperatures (below 735°С) the electric conductivity of the Ce_0.9Gd_0.1O₂-based chromium-containing composition exceeds that of the initial solid-oxide electrolyte, which can be due to changes in transport properties of the chromium-containing phases formed at the Ce_0.9Gd_0.1O₂ surface and grain boundaries.