Authors: Dilshod Durdiev, Bai-Xiang Xu

Antiferroelectric ceramics are promising for high-energy-density capacitors, yet improving energy density and efficiency remains difficult. Here, we use an isothermal high-order phase-field model – employing fourth-order gradient terms to represent next-nearest-neighbor interactions rather than flexoelectric or explicit grain boundary energies – to study electromechanical switching in Zr-rich PZT (Pb(Zr(1-x)Ti(x))O3, x<=0.1) across nanoscale grain sizes (51, 30, 17 nm). The simulations show that crystallographic misorientation at grain boundaries generates local fields that act as preferred, non-thermal nucleation sites, lowering switching barriers and enhancing recoverable energy density. In contrast, very fine grains (17 nm) experience strong elastic clamping from dense triple junctions, which suppresses long-range domain order and stabilizes frustrated nanodomain states. As a result, energy-storage performance varies non-monotonically with grain size. Medium-grained microstructures (30 nm) offer the best balance between internal mechanical relaxation and boundary-assisted nucleation, achieving a composition-specific energy efficiency of 77%. By matching experimental length scales, the model reproduces the 1.75–2.2 nm modulations seen in TEM and the sub-micron irregular nanodomains observed in PFM, providing generalizable microstructural design guidelines for optimizing antiferroelectric ceramics.