2 research outputs found
Strain-Induced Tailoring of Oxygen-Ion Transport in Highly Doped CeO<sub>2</sub> Electrolyte: Effects of Biaxial Extrinsic and Local Lattice Strain
We explored oxygen-ion
transport in highly doped CeO<sub>2</sub> through density-functional
theory calculations. By applying biaxial strain to 18.75 mol % CeO<sub>2</sub>:Gd, we predicted the average migration-barrier energy with
six different pathways, with results in good agreement with those
of experiments. Additionally, we found that the migration-barrier
energy could be lowered by increasing the tetrahedron volume, including
the space occupied by the oxygen vacancy. Our results indicate that
the tetrahedron volume can be expanded by larger codopants, as well
as biaxial tensile strain. Thus, the combination of thin-film structure
and codoping could offer a new approach to accelerate oxygen-ion transport
Identification of an Actual Strain-Induced Effect on Fast Ion Conduction in a Thin-Film Electrolyte
Strain-induced fast
ion conduction has been a research area of
interest for nanoscale energy conversion and storage systems. However,
because of significant discrepancies in the interpretation of strain
effects, there remains a lack of understanding of how fast ionic transport
can be achieved by strain effects and how strain can be controlled
in a nanoscale system. In this study, we investigated strain effects
on the ionic conductivity of Gd<sub>0.2</sub>Ce<sub>0.8</sub>O<sub>1.9−δ</sub> (100) thin films under well controlled experimental
conditions, in which errors due to the external environment could
not intervene during the conductivity measurement. In order to avoid
any interference from perpendicular-to-surface defects, such as grain
boundaries, the ionic conductivity was measured in the out-of-plane
direction by electrochemical impedance spectroscopy analysis. With
varying film thickness, we found that a thicker film has a lower activation
energy of ionic conduction. In addition, careful strain analysis using
both reciprocal space mapping and strain mapping in transmission electron
microscopy shows that a thicker film has a higher tensile strain than
a thinner film. Furthermore, the tensile strain of thicker film was
mostly developed near a grain boundary, which indicates that intrinsic
strain is dominant rather than epitaxial or thermal strain during
thin-film deposition and growth via the Volmer–Weber (island)
growth mode