Bulk and grain boundary conductivity of yttria-doped CGO

Different strategies have been proposed to overcome the impact of resistive grain boundaries on overall ionic conductivity of ceria-based electrolytes. The main purpose of this work is to enhance the ionic conductivity of CGO... [ view full abstract ]

Different strategies have been proposed to overcome the impact of resistive grain boundaries on overall ionic conductivity of ceria-based electrolytes. The main purpose of this work is to enhance the ionic conductivity of CGO with designed core-shell composition differences.

Commercial nanocrystalline 5CGO powder (with 5% Gd) was used as the main precursor, with additions of yttria to induce core-shell heterogeneities upon 2-step firing, without previous calcination. These non-conventional sintering cycles allowed flexibility in adjusting the microstructures of resulting ceramics, and their microstructure-related properties. X-ray diffraction was used to characterize structural changes, including bulk changes in lattice parameters induced by dissolution of yttria in the fluorite phase and detection of traces of secondary phase. Electron scanning microscopy and EDS analysis were used for microstructural characterization and to detect induced grain boundary heterogeneities.

Transport properties were evaluated by electrochemical impedance spectroscopy in air and as a function of oxygen partial pressure; this allowed one to de-convolute the bulk and grain boundary contributions to the overall conductivity of ceramics with designed grain boundary heterogeneities, and to analysed space-charge effects ascribed to microstructural changes.