Invited:
ATOMIC-SCALE ANALYSIS OF CHEMISTRY AT LATTICE DEFECTS

Lattice defects like interfaces, stacking faults and dislocations determine many mechanical, functional, and kinetic properties of materials. Lattice defects do not merely constitute structural imperfections but they are often chemically decorated by solutes. The interplay of structure and chemistry at lattice defects can lead to a wide range of phenomena and manipulation opportunities including Suzuki and Cottrell effects, confined elemental partitioning, complexion formation, linear and planar phase-like states, decomposition and low-dimensional transformations. All these effects alter the defects’ energy, mobility, structure, cohesion and transport properties.

The lecture presents and discusses several aspects in that context:

First, recent progress is presented which allows imaging of both structure and composition features at lattice defects by using correlative imaging through field ion microscopy, atom probe tomography and electron microscopy. Some of these observation methods are enhanced by using quantum mechanical simulations.

Second, atomic-scale experiments on classes of several materials ranging from metals to thermoelectrics are presented which reveal that the interplay between defect structure and chemistry can lead to a much larger variety in compositional – structural states than commonly assumed. Examples are confined phase formation, athermal transformations, spinodal decomposition or inter-defect partitioning at lattice defects to name but a few phenomena.

Third, some thermodynamic considerations are discussed which may guide better understanding and utilization of these phenomena.