Details

Autor(en) / Beteiligte

• FABRIS, S
• ELSÄSSER, C

Titel

First-principles analysis of cation segregation at grain boundaries in α-Al2O3

Ist Teil von

• Acta materialia, 2003-01, Vol.51 (1), p.71-86

Ort / Verlag

Oxford: Elsevier Science

Erscheinungsjahr

2003

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The modifications in atomistic structure, chemical bonding, and energetics induced by substitutional cation impurities isolated in the bulk volume and segregated at grain boundaries of alpha-Al2O3 were investigated by combining empirical ionic-model and first-principles electronic-structure calculations. The dependency of these modifications on the boundary type, species, and concentration of impurities, was studied by selecting the following variety of systems: three twin boundaries (the prismatic Sigma3 (1 0- 0), the rhombohedral Sigma7 (1 0- 2), and the pyramidal Sigma13 (1 0- 4) twins, three impurities X (X = Sc, Y, and La), and two concentrations for the segregant (approximately 3 and approximately 6 atoms/nm). A partial covalent character is found to be a distinctive feature of the X-O bonds in both bulk and interfacial atomic environments, and to drive the structural distortions of the octahedral XO6 clusters. The energetics of segregation reveals a linear relationship between segregation energy and impurity size. This is interpreted as resulting from a stress field localized at the interface.