The local electronic and atomic structure of (111)-oriented, single crystalline mixed Ce1xPrxO2d (x¼0, 0.1 and 0.6) epitaxial thin films on silicon substrates have been investigated in view of engineering redox properties of complex oxide films. Non-destructive X-ray absorption near edge structure reveals that Pr shows only þ3 valence and Ce shows only nominal þ4 valence in mixed oxides. Extended x-ray absorption fine structure (EXAFS) studies were performed at K edges of Ce and Pr using a specially designed monochromator system for high energy measurements. They demonstrate that the fluorite lattice of ceria (CeO2) is almost not perturbed for x¼0.1 sample, while higher Pr concentration (x¼0.6) not only generates a higher disorder level (thus more disordered oxygen) but also causes a significant reduction of Ce–O interatomic distances. The valence states of the cations were also examined by techniques operating in highly reducing environments: scanning transmission electron microscopy-electron energy loss spectroscopy and X-ray photoemission spectroscopy; in these reducing environments, evidence for the presence of Ce3þ was clearly found for the higher Pr concentration. Thus, the introduction of Pr3þ into CeO2 strongly enhances the oxygen exchange properties of CeO2. This improved oxygen mobility properties of CeO2 are attributed to the lattice disorder induced by Pr mixing in the CeO2 fluorite lattice, as demonstrated by EXAFS measurements. Thus, a comprehensive picture of the modifications of the atomic and electronic structure of Ce1xPrxO2d epitaxial films and their relation is obtained.

On the local electronic and atomic structure of Ce1-xPrxO2-δ epitaxial films on Si

BOSCHERINI, FEDERICO
2014

Abstract

The local electronic and atomic structure of (111)-oriented, single crystalline mixed Ce1xPrxO2d (x¼0, 0.1 and 0.6) epitaxial thin films on silicon substrates have been investigated in view of engineering redox properties of complex oxide films. Non-destructive X-ray absorption near edge structure reveals that Pr shows only þ3 valence and Ce shows only nominal þ4 valence in mixed oxides. Extended x-ray absorption fine structure (EXAFS) studies were performed at K edges of Ce and Pr using a specially designed monochromator system for high energy measurements. They demonstrate that the fluorite lattice of ceria (CeO2) is almost not perturbed for x¼0.1 sample, while higher Pr concentration (x¼0.6) not only generates a higher disorder level (thus more disordered oxygen) but also causes a significant reduction of Ce–O interatomic distances. The valence states of the cations were also examined by techniques operating in highly reducing environments: scanning transmission electron microscopy-electron energy loss spectroscopy and X-ray photoemission spectroscopy; in these reducing environments, evidence for the presence of Ce3þ was clearly found for the higher Pr concentration. Thus, the introduction of Pr3þ into CeO2 strongly enhances the oxygen exchange properties of CeO2. This improved oxygen mobility properties of CeO2 are attributed to the lattice disorder induced by Pr mixing in the CeO2 fluorite lattice, as demonstrated by EXAFS measurements. Thus, a comprehensive picture of the modifications of the atomic and electronic structure of Ce1xPrxO2d epitaxial films and their relation is obtained.
2014
Niu, G.; Schubert, M.A.; D'Acapito, F.; Zoellner, M.H.; Schroeder, T.; Boscherini, F.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/519654
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