Interphase structures observed as alumina precipitates in rutile

Abstract

High-resolution electron microscopy of alumina precipitates in a deformed alumina-doped rutile reveals a complex twin interface bisecting the heart-shaped precipitates. This appears to be about 20 Å thick. Small defects within the alumina precipitates are described. The rutile-alumina interface is also complex, containing modulated structures intermediate between rutile and alumina. These appear to act as an efficient elastic and chemical buffer, thus accommodating both the change in stoichiometry as the precipitate grows, and the lattice misfits, which would otherwise lead to plastic deformation and/or brittle fracture of these two ceramics. The observations allow the atomic mechanisms involved to be discussed and the structural principles to be deduced.