Yttrium segregation and intergranular defects in alumina

• Published in: Philosophical magazine (Abingdon, England) Vol. 86; no. 10; pp. 1401 - 1413
• Main Authors: Bouchet, Daniele, Lartigue-Korinek, Sylvie, Molins, Regine, Thibault, Jany
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 01.04.2006; Taylor and Francis; Taylor & Francis
• Subjects: Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Exact sciences and technology; Experimental determination of defects by diffraction and scattering; Humanities and Social Sciences; Impurities: concentration, distribution, and gradients; Physics; Structure of solids and liquids; crystallography; Dislocation motion; Inorganic compounds; Misfit dislocations; Doping; Dislocation structure; Dispersive spectrometry; Defects; Twin boundaries; Electron energy loss spectra; Transmission electron microscopy; Impurities; Transition elements; Yttrium additions; Grain boundary segregation; Aluminium oxides; Physical Sciences
• ISSN: 1478-6435; 1478-6443; 1478-6433
• DOI: 10.1080/14786430500313804

Intergranular segregation of yttrium is investigated in a rhombohedral twin grain boundary of alumina. The deviation from the twin orientation is compensated by a periodic arrangement of intergranular dislocations. TEM tools (CTEM and HREM, EDXS, EFTEM and EELS/ELNES) have been used to characterize changes in chemical and electronic environments along this twin. Within the experimental limits, no Y is detected in the perfect twin parts. On the other hand, Y segregation occurs very locally in the dislocation cores on about four atomic planes perpendicularly to the GB, which in fact corresponds to the step height associated with the interfacial dislocations. By comparison with an undoped bicrystal, both the dislocation distribution and the Y segregation localization confirm the influence of Y on the dislocation mobility. Furthermore, in the Y-rich defects, high spatial resolution analysis of the energy loss near edge structures (ELNES) of the Al-L 23 absorption edge brings some enlightenments about the Al 3+ cation environment, provided the effects of local radiation damage are fully considered and under control.