Size-dependent solute segregation and total solubility in ultrafine polycrystals: Ca in TiO[sub 2]

Journal Article · Sun Jan 01 00:00:00 EST 1995 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(95)90288-0· OSTI ID:6806080

Terwilliger, C D; Chiang, Y M ^[1]

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1. Massachusetts Inst. of Technology, Cambridge, MA (United States). Dept. of Materials Science and Engineering

Grain boundary segregation at ultrafine grain sizes has been studied. Using a STEM microanalysis technique to quantify the grain boundary coverage of calcium (0.34 mol%) in TiO[sub 2] ranging in grain size from 50 to 750 nm, it is found that below grain sizes of 150--350 nm, segregation deviates from conventional isotherms, exhibiting a clear size dependence. In this size regime the interfacial area to volume ratio is as important as temperature and composition in determining grain boundary coverage. In the present system, grain boundaries become saturated with calcium when the coverage reaches approximately one half of an equivalent monolayer. The experimental results can be modeled by a statistical thermodynamical treatment of segregation which takes into account the large density of grain boundary sites in this size range. The authors also find direct evidence of enhanced total solubility at very fine grain sizes due to grain boundary segregation.

• DOE Contract Number: FG02-87ER45307
• OSTI ID: 6806080
• Journal Information: Acta Metallurgica et Materialia; (United States), Vol. 43:1; ISSN 0956-7151
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM
SOLUBILITY
TITANIUM OXIDES
GRAIN SIZE
CORRELATIONS
GRAIN BOUNDARIES
SAMPLE PREPARATION
STATISTICAL MODELS
ALKALINE EARTH METALS
CHALCOGENIDES
ELEMENTS
MATHEMATICAL MODELS
METALS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
SIZE
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies