Collaborative design of polarization and antiferrodistortion configurations in high energy capacitive relaxor ferroelectrics

Lead-free relaxor ferroelectrics have been regarded as superior candidates for dielectric energy storage applications. Nonetheless, the degradation of energy storage performance resulted from the trade-off between high polarization and low hysteresis in RFEs under superhigh electric fields has become a bottleneck. Here, a chemical framework is established based on NaNbO3-based RFEs, bridging atomic-scale structural control to realize excellent energy storage performance. The framework design leads to unique local lattice distortion with both inhomogeneous polarization and antiferrodistortion configurations, including locally disordered polarization distribution, continuous polarization deflection and the co-existence of ordered and disordered oxygen octahedral tilts, as confirmed by phase-field simulation and scanning transmission electron microscopy. As a result, negligible polarization switching hysteresis as well as the large and delayed saturated polarization simultaneously contribute to the excellent energy storage performance. For instance, two NaNbO3-based RFEs with different compositions show ultrahigh recoverable energy densities of 16.48 and 20.08 J cm-3, respectively, as well as near-zero energy loss (η ~ 90.38% and 95.09%). This work presents new avenues toward designing high-performance lead-free RFEs.