  The kinetics of phase transition processes often governs the resulting
material microstruc-ture. Using optical microscopy, we here investigate the
formation and stabilization of a po-rous crystalline microstructure forming in
low-salt suspensions of charged colloidal spheres containing aggregates
comprising some 5-10 of these colloids. We observe the transformation of an
initially crystalline colloidal solid with homogeneously incorporated
aggregates to indi-vidual, compositionally refined crystallites of perforated
morphology coexisting with an ag-gregate-enriched fluid phase filling the holes
and separating individual crystallites. A prelimi-nary kinetic characterization
suggests that the involved processes follow power laws. We show that this route
to porous materials is neither restricted to nominally single component systems
nor to a particular microstructure to start from. However, it necessitates an
early rapid solidification stage during which the aggregates become trapped in
the bulk of the host-crystals. The thermodynamic stability of the reconstructed
crystalline scaffold against melt-ing under increased salinity was found
comparable to that of pure phase crystallites grown very slowly from a melt.
Future implications of this novel route to porous colloidal crystals are
discussed.
