Spatially resolved structural correlations at the nanoscale in phase-separated silicate glass revealed by electron total scattering analysis using 4D-STEM

Understanding structural heterogeneity in silicate glasses at the nanometer scale remains challenging because conventional diffraction techniques provide only a spatially averaged structural response and cannot resolve the atomic structure of individual amorphous domains. Here, spatially resolved electron total scattering is used to investigate a phase-separated soda–lime–silicate glass by combining local Selected-Area Electron Diffraction (SAED) and four-dimensional Scanning Transmission Electron Microscopy (4D-STEM). Electron diffraction data were processed using the ePDFMapping software package to obtain electron pair distribution functions (ePDFs). Local SAED measurements reveal two distinct phase-specific structural signatures corresponding to silica-rich droplets and the surrounding modifier-rich matrix. While both phases exhibit similar tetrahedral short-range order, they differ systematically in their medium-range organization, the most prominent feature being a shift of the First Sharp Diffraction Peak (FSDP). Spatially resolved 4D-STEM reproduces this structural contrast and directly maps its spatial distribution across individual amorphous domains at the nanometer scale through Pearson-correlation analysis of both reciprocal-space S ( Q ) and real-space G ( r ) , together with peak position and integrated-area analyses. The close agreement with SAED demonstrates that 4D-STEM provides sufficient sensitivity to resolve these phase-dependent structural signatures while enabling their spatial localization. Conventional bulk X-ray total scattering contains the structural contributions of both amorphous phases only as an averaged response, whereas spatially resolved electron total scattering separates and maps these contributions directly. These results establish spatially resolved electron total scattering as a powerful approach for probing nanoscale variations in medium-range order in heterogeneous glasses and other amorphous materials.