Stability of (001) CSL twist boundaries in MgO: a theoretical study

Conference · Fri Jan 01 00:00:00 EST 1982

OSTI ID:6186899

Wolf, D

The energies of (001) coincident-site twist boundries in MgO have been calculated by means of a computer code developed in recent years. Both the empirical interionic potentials of Catlow, Faux, and Norgett as well as the electron gas potentials of Mackrodt and Stewart have been applied. It is concluded that, in contradiction to the MgO bicrystal experiments of Sun and Balluffi, (001) grain boundaries in pure MgO are unstable above room temperature since their main cohesive force arises from rather weak Van-der-Waals attractive interactions between oxygen ions on opposite sides of the interface, while Coulomb interactions do not contribute to the cohesion. A calculation of the binding energy of the isovalent substitutional impurities Fe/sup 2 +/ and Ca/sup 2 +/ to the ..sigma.. = 5 boundary on the one hand and to the free (001) surface on the other yields the interesting result that impurities may contribute to the stabilization of such bicrystals since they may be bound more tightly to the grain boundary than to the free surface. it is therefore concluded that Sun and Balluffi's bicrystals have been stabilized by substantial amounts of impurities having migrated into the grain boundary during the high-temperature pressure-sintering process.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 6186899
• Report Number(s): CONF-8209127-1; ON: DE83010755
• Resource Relation: Conference: Structure and properties of intergranular boundaries meeting, Caen, France, 6 Sep 1982
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MAGNESIUM OXIDES
GRAIN BOUNDARIES
BICRYSTALS
COMPUTER CODES
IMPURITIES
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
MAGNESIUM COMPOUNDS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
POLYCRYSTALS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies