Nature 320, 340 - 342 (27 March 1986); doi:10.1038/320340a0

Phase behaviour of concentrated suspensions of nearly hard colloidal spheres

P. N. Pusey & W. van Megen^*

Royal Signals and Radar Establishment, St Andrews Road, Malvern WR14 3PS, UK
^*Permanent address: Department of Applied Physics, Royal Melbourne Institute of Technology, Melbourne, Australia

Suspensions of spherical colloidal particles in a liquid show a fascinating variety of phase behaviour which can mimic that of simple atomic liquids and solids. 'Colloidal fluids'¹⁻⁴, in which there are significant short-range correlations between the positions of neighbouring particles, and 'colloidal crystals'⁵⁻⁷, which have long-range spatial order, have been investigated extensively. We report here a detailed study of the phase diagram of suspensions of colloidal spheres which interact through a steep repulsive potential. With increasing particle concentration we observed a progression from colloidal fluid, to fluid and crystal phases in coexistence, to fully crystallized samples. At the highest concentrations we obtained very viscous samples in which full crystallization had not occurred after several months and in which the particles appeared to be arranged as an amorphous 'colloidal glass'. The empirical phase diagram can be reproduced reasonably well by an effective hard-sphere model. The observation of the colloidal glass phase is interesting both in itself and because of possible relevance to the manufacture of high-strength ceramics⁸.

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