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Nanoscale structure of Ti1−xNbyO2 mixed-phase thin films: Distribution of crystal phase and dopants

Published online by Cambridge University Press:  23 January 2012

Paul A. DeSario
Affiliation:
Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208
Jinsong Wu
Affiliation:
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
Michael E. Grahm
Affiliation:
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
Kimberly A. Gray*
Affiliation:
Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208
*
a)Address all correspondence to this author. e-mail: k-gray@northwestern.edu
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Abstract

Transmission electron microscopy (polycrystalline electron diffraction, nanoelectron diffraction, and energy dispersive x-ray spectroscopy) was used to determine the dispersion of crystal phase and Nb dopants in mixed-phase (anatase and rutile) Ti1−xNbyO2 thin films prepared by reactive sputtering. When co-sputtering mixed-phase TiO2 with a dopant, it is unclear how the crystal phases are distributed within thin film structures, what the dominant interfaces are, and how the dopant is distributed within the crystal phases. In the Ti1−xNbyO2 films, anatase and rutile grains were found to be homogeneously dispersed indicating that anatase/rutile interfaces are the dominant interfaces. Anatase/rutile interfaces are a critical feature of mixed-phase materials which impart high reactivity to the composite. Nb homogeneously dispersed at low concentrations, but at high concentrations, Nb segregated in the rutile phase. There is an apparent threshold beyond which Nb segregates according to its higher solubility in rutile due to a better lattice fit.

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Articles
Copyright
Copyright © Materials Research Society 2012

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