Glass materials have amorphous structures that do not crystallize upon cooling, resulting in unique physical properties distinct from those of crystalline solids or liquids. These unique properties are widely used in daily life from ornaments to optical fibers. However, the formation process, glass transition, has not been thoroughly understood. The glass transition process, where the material changes from a supercooled liquid to a solid glass, involves a significant increase in viscosity near the glass transition temperature ( T g), while the macroscopic structure of the material shows little change during this transition. To explain this discrepancy, dynamical heterogeneity, in which atomic motion becomes collective and heterogeneous, has attracted much attention because it shows divergent behaviors near T g;[ 1]. Moreover, heterogeneity is also found in the atomic structure. Despite theoretical models suggesting a link between these two phenomena, has not been directly confirmed by experiment due to the difficulty of simultaneous observation of both heterogeneities. To overcome this problem, we developed a five-dimensional scanning transmission electron microscopy (5D-STEM) that can obtain a spatiotemporal distributions of diffraction patterns to directly visualize the dynamical and structural heterogeneities.
STEM observation was performed by JEM ARM-200F (JEOL Ltd.) equipped with a cold field emission gun. Diffraction patterns were recorded by 4DCanvas camera (JEOL Ltd.). Zr 50Cu 40Al 10 metallic glass was selected for the sample. T g and crystallization temperature of this material were 673 K and 750 K, respectively. TEM samples were prepared by focused ion beam milling. The experiment was conducted at several temperatures (from 633 K to 673 K) using an in-situ heating holder to observe how the structure-dynamics relationship evolved with increasing temperature.