Cerium reduction at the interface between ceria and yttria-stabilised zirconia and implications for interfacial oxygen non-stoichiometry

Abstract

Epitaxial CeO2 films with different thickness were grown on Y2O3 stabilised Zirconia substrates. Reduction of cerium ions at the interface between CeO2 films and yttria stabilised zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce4+ to Ce3+ at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also for understanding ceria catalytic properties.

Quantification of grain boundary defect chemistry in a mixed proton‐electron conducting oxide composite

“…A significant increase of the M 5 to M 4 peak intensities is seen for the Ce 3+ reference as well as the elimination of the right shoulder of each edge which matches other EELS and extended X‐ray absorption near edge structure (XANES) experimental spectra well. To quantify the amount of Ce 3+ within the sample, second derivative analysis of the cerium edges was performed . The second derivative of the right grain in Figure is found in Figure B where the positive part of the spectrum is highlighted in gray.…”

Equilibrium oxygen storage capacity of ultrathin CeO2-δ depends non-monotonically on large biaxial strain

“…However, the ability of 3+ oxidation state of Ce to better accommodate the tetragonal distortion from biaxial strain and the lowering of vibrational free energy favour the creation of oxygen vacancies. The finding that the enhanced reducibility is insensitive to the type of biaxial strain could explain the observation of Song et al 38. about the reduction of Ce in the heterogeneous strain fields surrounding a misfit dislocation.…”

“…To establish a definitive relationship between strain and a functional property, it is desirable to have the oxide film uniformly strained over a wide range of values, both compressive and tensile. This is challenging, because biaxially strained films undergo strain relaxation beyond a critical film thickness, rendering the strain fields inhomogeneous38, or undergo a polymorphic transition due to large local strains39. For instance, in a recent study using electron energy-loss spectroscopy to probe the incoherent CeO 2-δ /YSZ interface, Song et al 38.…”

“…This is challenging, because biaxially strained films undergo strain relaxation beyond a critical film thickness, rendering the strain fields inhomogeneous38, or undergo a polymorphic transition due to large local strains39. For instance, in a recent study using electron energy-loss spectroscopy to probe the incoherent CeO 2-δ /YSZ interface, Song et al 38. found that the Ce atoms are reduced to the 3+ oxidation state near the misfit dislocation, regardless of the sign of the strain.…”

Stabilization of ZrO2 Powders via ALD of CeO2 and ZrO2

“…For example, it has been reported that most Ce ions at the interface of epitaxial ceria films on yttria-stabilized zirconia (YSZ) substrates exist as Ce 3+ and that the average oxidation state is affected several nanometers from that interface [16]. In another report, ceria films on polycrystalline zirconia were shown to be much more reducible than ceria films on alumina [15].…”