Effects of dopant ionic radius on cerium reduction in epitaxial cerium oxide thin films.
Authors/Creators
- 1. School of Physical Science and Technology, Shanghai Tech University, 201210 Shanghai, China
- 2. National Research Council CNR-IOM, TASC National Laboratory, I-34149 Trieste, Italy
- 3. Dept. of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy
- 4. National Research Council CNR-SPIN and Department DICII, University of Roma "Tor Vergata" 00133 Rome, Italy
- 5. f. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, 37831 Oak Ridge, Tennessee, United States
Description
The role of trivalent rare-earth dopants on the cerium oxidation state has been systematically studied by in-situ photoemission spectroscopy with synchrotron radiation for 10mol% rare earth doped epitaxial ceria films. It was found that dopant rare-earths with smaller ionic radius foster the formation of Ce3+ by releasing the stress strength induced by the cation substitution. Decreasing the dopant ionic radius from La3+ to Yb3+ the out-of-plane axis parameter of the crystal lattice decreases without introducing macroscopic defects. The high crystal quality of our films allowed us to comparatively study both the ionic conductivity and surface reactivity ruling out the influence of structural defects. The measured increase in the activation energy of films and their enhanced surface reactivity can be explained in terms of the dopant ionic radius effects on the Ce4+Ce3+ reduction as a result of lattice relaxation. Such findings open new perspectives in designing ceria-based materials with tailored properties by choosing suitable cation substitution.
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paper_XDC_Ge2017.pdf
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