Grain refinement and partitioning of impurities in the grain boundaries of a colloidal polycrystal

We study the crystallization of a colloidal model system in the presence of secondary nanoparticles which are acting as impurities. Using confocal microscopy, we show that the nanoparticles segregate in the grain boundaries of the colloidal polycrystal. We demonstrate that the texture of the polycrystal can be tuned by independently varying the nanoparticle volume fraction and the crystallization rate, and quantify our findings using standard models for the nucleation and growth of crystalline materials. Remarkably, we find that the segregation efficiency of the nanoparticles in the grain-boundaries is determined solely by the typical size of the crystalline grains. © 2012 The Royal Society of Chemistry.