Interfacial segregation in perovskites. Part 1; Theory

Journal Article · Wed Oct 31 23:00:00 EST 1990 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1990.tb06466.x· OSTI ID:5160829

Desu, S B ^[1]; Payne, D A ^[2]

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1. Dept. of Materials Engineering, Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (US)
2. Dept. of Materials Science and Engineering, and Materials Research Lab., Univ. of Illinois at Urbana-Champaign, Urbana, IL (US)

Based on thermodynamic principles a theory for equilibrium interfacial segregation is proposed for perovskite materials, and this theory is applied to BaTiO{sub 3}. An approach developed by Frenkel and refined by Kliewer and Koehler is extended to undoped ternary oxide materials such as BaTiO{sub 3}. The approach uses regular solution approximations and considers space charge effects as the major driving force for segregation. The analysis based on this model indicates the presence of a negative space charge potential (-0.1 V at 800{degrees}C) at the surface of pure BaTiO{sub 3}. The model also predicts cation enrichment at the interface. The thickness of the space charge layer decreases with increasing temperature, and calculated values agree well with experimental results. Since both elastic and electrostatic driving forces are important for dopant/impurity segregation, an approach where the grain boundary is considered to be a two-dimensional phase, in equilibrium with the three-dimensional phase of the grain, proves useful. Solving for the impurity/dopant segregation ratio is case specific and requires knowledge of the charge neutrality conditions as well as the strain energy contribution.

• DOE Contract Number: AC02-76ER01198
• OSTI ID: 5160829
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 73:11; ISSN JACTA; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
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& Refractories-- Physical Properties
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CRYSTAL STRUCTURE
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GRAIN BOUNDARIES
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MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
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