Exclusion of impurity particles in charged colloidal crystals.

Uniformly shaped, charged colloidal particles dispersed in water form ordered "crystal" structures when the interaction between the particles is sufficiently strong. Herein, we report the behavior of "impurity" particles, whose sizes and/or charge numbers are different from those of the bulk, on addition to the charged colloidal crystals. These impurities were excluded from the crystals during the homogeneous crystallization, crystal grain growth, and unidirectional crystallization processes. Such systems will be useful as models for studying the refinement of materials and crystal defects.