Flattening the polarization energy landscape in BiFeO3-based dielectrics via nanoscale phase coexistence for superior electrostatic energy storage

Abstract

The advancement of pulsed power electronics requires electrostatic capacitors combining high energy density with fast discharge capabilities. Although lead-free BiFeO₃ holds tremendous promise, its long-range polar order induces a steep energy landscape, severely restricting its capacitive performance. Here, a structural engineering approach is employed to flatten the polarization energy landscape via nanoscale phase coexistence in BiFeO₃-based dielectrics. Atomic-resolution microscopy confirms the presence of finely dispersed, weakly polar tetragonal domains within a strongly polar rhombohedral matrix. This hierarchical polar heterogeneity disrupts long-range ferroelectric coupling and minimizes domain switching barriers, yielding pronounced relaxor behavior with low hysteresis. Concurrently, local lattice distortion and grain-size refinement enhance electron scattering, doubling the breakdown strength to 660 kV cm⁻¹. As a result, the optimized dielectrics achieve a superior recoverable energy density of 8.12 J cm⁻³ alongside an efficiency of 88.2%. Exhibiting an ultrafast energy release (∼32 ns) and sustained stability over 10⁴ cycles, this work demonstrates that manipulating nanoscale structural heterogeneity is an effective avenue for advancing electrostatic energy storage technologies.