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Tendency and Scale of Chemistry and Bonding Changes at SrTiO3 Grain Boundaries by Fe Segregation

Published online by Cambridge University Press:  10 February 2011

Hui Gu
Hui Gu*
Affiliation:
Japan Science and Technology Corporation, “Ceramics Superplasticity” project, JFCC 2F, 2–4–1, Mutsuno, Atsuta, Nagoya 456, Japan, gu@ngo.jst-c.go.jp
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Abstract

Using a new EELS analysis method the local chemical and structural changes induced by Fe segregation to two types of grain boundaries in SrTiO3 were studied. At Σ5 boundary in bicrystals Fe segregation lowers O/Ti ratio but increases substantially Ti and O concentrations in boundary region. Sr-O bond has been severely changed by the segregation as revealed by ELNES. Grain boundaries in a polycrystalline sample were covered with titania-based amorphous films where Fe content is higher but Ti and O concentrations are both lower than the bulk levels, which are strikingly different from the bicrtysal. More dopants segregated to glass pockets at triple junctions. SiO2 was detected in one of the large pocket but not at the grain boundary films within the detection limit. These observations suggest the equilibrium defect chemistry and the related space charge theory may not be the only explanation for the grain boundary segregation in SrTiO3 Local structure modification at gram boundaries can trigger dramatical change of the chemistry to a degree higher than the segregation level. The existence of titania-based amorphous films at general grain boundaries makes it better to understand Fe segregation from the two phase (SrTiO3-TiO2) equilibrium.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 458: Symposium W – Interfacial Engineering for Optimized Properties , 1996 , 115
Copyright
Copyright © Materials Research Society 1997

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References

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