Unified Phase‐Field Framework for Antiferroelectric, Ferroelectric and Dielectric Phases: Application to HZO Thin Films

Hafnia‐based thin films used in metal–insulator–metal capacitors often exhibit mixed phases: ferroelectric (FE), antiferroelectric (AFE), and dielectric (DE). A theoretical framework linking polycrystalline microstructure to ferroic switching in such mixed‐phase systems remains lacking. Here, we develop a three‐dimensional (3D) phase‐field model that resolves grain topology, and evolves coupled macroscopic and staggered polarization order parameters under self‐consistent electrostatics. In single‐layer films, FE–AFE proximity, rather than long‐range percolation, controls AFE switching. Vertical phase architecture provides a deterministic lever on the coercive field , decomposing it into structural and electrostatic contributions: , arising from interlayer gradient coupling and bound charges, respectively. The saturation electrostatic energy density emerges as the dominant predictor of MV/cm and . This shared dependence creates a trade‐off between and , defining a Pareto frontier that identifies the best‐balanced architecture. These findings establish vertical phase architecture as a design parameter to reduce in such films.