| Abstract Scope |
Traditional electron microscopy resolves nanoscale features of complex oxides but struggles to capture field-dependent behavior and three-dimensional (3D) correlations among atomic and polar structures. Four-dimensional scanning transmission electron microscopy (4D STEM) now overcomes many of these limits, linking local structure, chemistry, and strain, while operando 4D STEM connects structural change to functionality. I will show how 4D STEM, through multislice electron ptychography, reveals polar domain structures in relaxor ferroelectrics and reconstructs the 3D domain architecture, including high-angle domain walls and polar nanodomains, in quantitative agreement with molecular dynamics simulations. These results connect local energetics, 3D polar topology, and field-driven responses. I will also present operando 4D STEM studies of the antiferroelectric-to-ferroelectric transition in PbZrO₃ thin films, using nanobeam diffraction for strain mapping alongside atomic-resolution imaging to track intermediate states and domain reconfiguration. Together, these approaches constrain phase-field and first-principles modeling, suggesting design rules for transducers, nonvolatile memories, and energy-storage technologies. |