Nucleation and Growth of Nanocrystals in Glass‐Ceramics: An In Situ SANS Perspective

We studied the nucleation and growth of nano‐sized crystals on two glass‐ceramic systems: a conventional lithium‐aluminosilicate ( LAS ) and a ( M g, Z n) spinel. We combined several techniques: in situ Small Angle Neutron Scattering ( SANS ), Differential Scanning Calorimetry ( DSC ), Scanning Electron Microscopy ( SEM ), and laboratory X‐ray diffraction ( XRD ). We observed by SANS , and confirmed by DSC , that during a temperature ramp, transient phenomena occur between the regions of nucleation and growth in the LAS , which do not follow classic kinetic theories. In contrast, the spinel material shows a smooth transition during the temperature ramp between the nucleation and the growth stages, and follows a more conventional growth pattern. In the spinel system the initial phase separation plays a very important role in determining the crystalline phase distribution in the glassy matrix, as crystallites are confined only in one phase.