A synchrotron small-angle X-ray scattering study of order/disorder in colloidal crystals

Abstract

The present work reports results of a detailed x-ray diffraction study of the structure and long-range order of colloidal crystals, self-grown in suspensions of quartz spheres with diameter of about a quarter of a micron. The crystals are found to consist of a randomly-stacked sequence of hexagonal close-packed planes. The results provide a first unambiguous proof that hard sphere colloidal crystals can possess perfect order over distances comparable to the crystal size despite the slight variations in the size of colloidal spheres and the stacking disorder. This conclusion is drawn from a profound evaluation of the size of the reciprocal lattice reflections using a specially-designed high-resolution x-ray diffraction technique with a resolution of one millionth of the wavevector.