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Cation Transport and Surface Reconstruction in Lanthanum Doped Strontium Titanate at High Temperatures

Published online by Cambridge University Press:  11 February 2011

Karsten Gömann ,
Günter Borchardt ,
Anissa Gunhold ,
Wolfgang Maus-Friedrichs ,
Bernard Lesage ,
Odile Kaïtasov  and
Horst Baumann
Karsten Gömann
Affiliation:
Institut für Metallurgie, Technische Universität Clausthal, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld, Germany
Günter Borchardt
Affiliation:
Institut für Metallurgie, Technische Universität Clausthal, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld, Germany
Anissa Gunhold
Affiliation:
Institut für Physik und Physikalische Technologien, Technische Universität Clausthal, Leibnizstr. 4, D-38678 Clausthal-Zellerfeld, Germany
Wolfgang Maus-Friedrichs
Affiliation:
Institut für Physik und Physikalische Technologien, Technische Universität Clausthal, Leibnizstr. 4, D-38678 Clausthal-Zellerfeld, Germany
Bernard Lesage
Affiliation:
Laboratoire d'Etude des Matériaux Hors Equilibre, Université Paris-Sud, F-91405 Orsay Cedex, France
Odile Kaïtasov
Affiliation:
Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Université Paris-Sud, F-91405 Orsay Cedex, France
Horst Baumann
Affiliation:
Institut für Kernphysik, J. W. Goethe-Universität, August-Euler-Str. 6, D-60486 Frankfurt, Germany
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Abstract

Tracer diffusion experiments were carried out in synthetic air at 1573 K in SrTiO3(100) and (110) single crystals, which were either undoped or doped with up to 1 at.% La, respectively. Tracer sources of 139La and 142Nd were applied by ion implantation. The resulting depth profiles were measured by SIMS. The reconstruction of the surface was monitored ex-situ using microscopic and spectroscopic methods including SEM, EPMA, and AFM. The measured tracer diffusivities show no dependency on orientation. The tracer diffusion takes place via cation vacancies. Under oxidizing conditions the dopant is compensated by Sr vacancies. Hence the diffusion is increasing strongly with La concentration. The observed time dependency of the diffusivities may be related to a space charge layer postulated by the current defect chemistry model for donor doped SrTiO3. At high dopant concentrations annealing leads to segregation of bulk La to the surface. La is not significantly incorporated into the secondary crystallites at the surface which consist almost entirely of Sr and O.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 756: Symposia EE/FF – Solid-State Ionics – Materials for Fuel Cells and Fuel Processors , 2002 , EE3.1
Copyright
Copyright © Materials Research Society 2003

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References

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