• • LSMO buffer layer stabilizes the ferroelectric O-phase in ZrO2 films, whereas LaMnO3 or SrMnO3 buffers yield non-ferroelectric tetragonal (T) and monoclinic (M) phases, demonstrating a phase-selective effect.
• • Atomic-scale HAADF and EELS with a K3 direct counting detector enable single-atom-column chemical identification, revealing ordered GBs with dimensions of several nanometers and selective segregation of La, Sr, and Mn.
• • iDPC imaging directly visualizes periodic arrangement of La(Sr) and Mn atomic columns along the GB, confirming chemically ordered heterostructures.
• • First-principles calculations show that the ordered eg/t2g orbital arrangement of Mn3+/Mn4+ at GBs regulates Zr–O bond strength to soften phonon modes, stabilizing the ferroelectric phase—a mechanism that can be extended to other ferroelectric systems.