1. Effects of dopant ionic radius on cerium reduction in epitaxial cerium oxide thin films
- Author
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Piero Torelli, Nan Yang, Giorgio Rossi, Vittorio Foglietti, Sergei V. Kalinin, Giuseppe Balestrino, Carmela Aruta, Silvia Licoccia, Anton V. Ievlev, Elisabetta Di Bartolomeo, and Pasquale Orgiani
- Subjects
Cerium oxide ,Materials science ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Ion ,Settore FIS/03 - Fisica della Materia ,Ionic potential ,Oxidation state ,Ionic conductivity ,Physical and Theoretical Chemistry ,Doped CeO2 ,Ionic radius ,Dopant ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Cerium ,General Energy ,chemistry ,Physical chemistry ,Crystal growth ,0210 nano-technology - Abstract
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 10 mol % 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. With a decrease of 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.
- Published
- 2017