Phase behavior of binary mixtures of sterically stabilized colloids with large size asymmetry

Experimental phase diagrams of three types of mixtures of sterically stabilized colloids are presented. The size ratios are kept similar, 0.15< or =xi< or =0.17, while the thickness and the chemical nature of the steric layers are varied. For all particles their effective volume fractions are calculated from their hydrodynamic radii. When their phase behavior is expressed in this way, the experimental liquidus curves all lie slightly above recent computer simulation predictions for the fluid-solid binodal of additive hard sphere mixtures. No dramatic shift of the experimental liquidus curves due to nonadditive particle interactions is observed. The dense phase is in all cases solid, with crystallites of the large spheres visible in some samples.