Superior Capacitive Energy Storage of NaNbO₃‐Based MLCCs Enabled by Heterogeneous Short‐Range Ferroic Orders

Achieving simultaneously high energy density and efficiency in lead‐free dielectric capacitors for pulse power applications remains challenging. To address this, a NaNbO 3 ‐based relaxor ferroelectric (FE) is designed by incorporating FE‐active (Bi 0.5 K 0.5 )TiO 3 and non‐polar SrZrO 3 , achieving exceptional energy storage performance driven by heterogeneous short‐range ferroic orders. Atomic‐scale structural characterization reveals coexisting polymorphic polar nanoregions with complex superlattice structures, confirming local diversity of FE symmetries and antiferrodistortive (AFD) modes. The short‐range ordering of both FE and AFD distortions effectively reduces polarization switching barriers and suppresses the formation of long‐range FE ordering under high electric fields, as evidenced by in situ piezoresponse force microscopy analysis of field‐induced domain evolution dynamics. Consequently, polarization hysteresis is minimized and polarization saturation is delayed, enabling an ultrahigh recoverable energy density of ≈19.1 J cm −3 coupled with an outstanding efficiency of ≈89.2% in NaNbO 3 ‐(Bi 0.5 K 0.5 )TiO 3 ‐SrZrO 3 multilayer ceramic capacitors. This work establishes a promising materials design strategy for optimizing energy storage in ferroic dielectrics.