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Analytical electron microscopy of planar faults in SrO-doped CaTiO3

Published online by Cambridge University Press:  31 January 2011

M. Čeh ,
H. Gu ,
H. Müllejans  and
A. Rečnik
M. Čeh
Affiliation:
“J. Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia
H. Gu
Affiliation:
Max-Planck-Institut für Metallforschung, Seestraße 92, 70174 Stuttgart, Germany
H. Müllejans
Affiliation:
Max-Planck-Institut für Metallforschung, Seestraße 92, 70174 Stuttgart, Germany
A. Rečnik
Affiliation:
“J. Stefan” Institute, Jamova 39, 1000 Ljubljana, Slovenia, and Max-Planck-Institut für Metallforschung, Seestraße 92, 70174 Stuttgart, Germany
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Abstract

Oxide-rich planar faults within a perovskite matrix are the prevailing type of extended defects in polycrystalline SrO-doped CaTiO3. These defects form, depending on the temperature of sintering, random networks, or ordered structures. The chemistry of the polytypoid, the isolated planar faults, and the perovskite phase have been studied by spatially resolved electron energy-loss and energy-dispersive x-ray spectroscopies using a dedicated scanning transmission electron microscope. We have found that Sr ions from SrO additions preferably substitute Ca in the CaTiO3 lattice, thus forming a solid solution (Ca1–xSrx)TiO3. The surplus of Ca ions forms single and ordered CaO-rich planar faults in the host (Ca1–xSrx)TiO3 phase. Whereas the excess Ca segregates in a form of single planar faults at lower temperatures, it forms a stable polytypoidic phase at higher temperatures. For materials having up to 25 mol% of SrO additions, this phase has (Ca1–xSrx)4Ti3O10 composition, comprising a sequence of CaO faults followed by three (Ca1–xSrx)TiO3 perovskite layers. Analytical electron microscopy revealed that the composition of the single planar faults, formed at lower temperatures, is identical to that of polytypoids, which are stable at higher sintering temperatures.

Type
Articles
Information
Journal of Materials Research , Volume 12 , Issue 9 , September 1997 , pp. 2438 - 2446
Copyright
Copyright © Materials Research Society 1997

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