Polymorphic Localized Heterostructure Design for High‐Performance Amorphous/Nanocrystalline Composite Film

Abstract Analogous to linear dielectric, amorphous perovskite dielectrics characterized of high breakdown strength and low remanent polarization possess in‐depth application in the sea, land, and air fields. Amorphous engineering is a common approach to balance the inverse relationship between polarization and breakdown strength in dielectric ceramic capacitor, however, the low polarization is the major barrier limiting the improvement of energy storage density. To address this concern, the polymorphic localized heterostructure confirmed by high‐resolution transmission electron microscope (HR‐TEM) and HADDF images is constructed in BaTiO 3 ‐Bi(Ni 0.5 Zr 0.5 )O 3 amorphous/nanocrystalline composite film with SiO 2 addition (BT‐BNZ‐xS, x = 3, 5, 7, 10 mol%). The stability of nanocrystalline region achieved by Si‐rich transition region and the enhancive ultra‐short‐range ordering in the amorphous region synergistically result in large breakdown strength and nonhysteretic polarized response. This polymorphic localized heterostructure optimizes the thermal stability in a wide temperature range and contributes ultrahigh energy storage density of 149.9 J cm −3 with markedly enhanced efficiency of 79.0%. This study provides a universal strategy to design the polarization behavior in other amorphous perovskite‐based dielectrics.