Phase-separated systems

The problem of immiscibility in glasses is reviewed. After defining the sub-liquidus immiscibility and considering the stability regions within a miscibility gap, the dynamics of initial clustering are discussed. The distinction between nucleation and growth, spinodal decomposition and coarsening processes is emphasized. Experimental studies of phase separation corresponding to the above mechanisms are presented and, in particular, the possibility of verifying Cahn's theory is discussed. New results from the supercritical region enable the initial condition after quench to be assessed. Finally, the influence of demixing on crystallization is examined and the possibility of thermodynamical blocking of a stable phase indicated.