Ab initio theoretical tensile test on Y-doped {sigma} = 3 grain boundary in {alpha}-Al{sub 2}O{sub 3}

It has been known for a long time that Y ions segregate to the grain boundaries (GBs) in polycrystalline alumina with the beneficial effects of enhanced mechanical properties and increased creep resistance. No detailed microscopic theory exists to explain this so called 'Y-effect'. We prov...

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Bibliographic Details
Published inActa materialia Vol. 53; no. 2
Main Authors Chen Jun, Xu Yongnian, Rulis, Paul, Ouyang Lizhi, Ching Waiyim
Format Journal Article
LanguageEnglish
Published United States 10.01.2005
Subjects
ALUMINIUM OXIDES
COVALENCE
CREEP
DOPED MATERIALS
GRAIN BOUNDARIES
MATERIALS SCIENCE
POLYCRYSTALS
PRESSURE RANGE GIGA PA
QUANTUM MECHANICS
STRAINS
STRESSES
YTTRIUM IONS
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Summary:It has been known for a long time that Y ions segregate to the grain boundaries (GBs) in polycrystalline alumina with the beneficial effects of enhanced mechanical properties and increased creep resistance. No detailed microscopic theory exists to explain this so called 'Y-effect'. We provide a quantum mechanical explanation for this effect through a series of carefully designed large-scale computations. The results of our theoretical tensile experiments show that the maximum stresses in pure crystalline {alpha}-Al{sub 2}O{sub 3}, undoped {sigma} = 3 GB, and Y-doped {sigma} = 3 GB models are, respectively 55, 31 and 39 GPa at the uni-axial strains of 17%, 14% and 16% in the direction perpendicular to the GB. The participation of the Y-4d and Y-4p orbitals enhances the covalent character of the Y-O bond, making it stronger than the Al-O bond it replaces. This could be the major reason for the improved mechanical properties of Y-doped {alpha}-Al{sub 2}O{sub 3}.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2004.09.035