The (1− x )BaTiO 3 – x Bi(Zn 2/3 Nb 1/3 )O 3 ( x = 0.01–0.30) ceramics were synthesized by solid-state reactions. The solubility limit was determined to be x = 0.20. A systematic structural transition from a tetragonal phase ( x ≤ 0.034), to a mixture of tetragonal and rhombohedral phases (0.038 ≤ x ≤ 0.20), and finally to a pseudocubic phase ( x ≥ 0.22) at room temperature was identified. Dielectric measurement revealed a ferroelectric ( x ≤ 0.04) to relaxor ( x ≥ 0.06) transition with permittivity peak broadening and flattening, which was further verified by Raman spectroscopy and differential scanning calorimetry (DSC). Activation energies obtained from the Vogel–Fulcher model displayed an increasing trend from ~0.03 eV for x ~ 0.05, to unusually high values (>0.20 eV) for the compositions with x ≥ 0.15. With the increase in Bi(Zn 2/3 Nb 1/3 )O 3 content, the polarization hysteresis demonstrated a tendency from high nonlinearity to sublinearity coupled with the reduction in remnant polarization and coervice field. The deconvolution of the irreversible/reversible polarization contribution was enabled by first-order reversal curve distributions, which indicates that the decreasing polarization nonlinearity with the increase in Bi(Zn 2/3 Nb 1/3 )O 3 concentration could be related with the change from the ferroelectric domain and domain wall contributions to the weakly coupled relaxor behaviors.
The significant polarization hysteresis under external fields can be stimulated by long-range ordered distortions, including cation displacements and oxygen octahedral tilts, deteriorating the energy storage performance and reliable operation of dielectric capacitors. Here, we propose a strategy of localized distortion to craft a disordered nanostructure landscape, manifested as strongly polar orthorhombic rocks dissociated in the transition region of polymorphic nanoclusters and strong oxygen-tilted blocks embedded in the weak oxygen distortion region, resulting in a smooth polarization response trajectory with large polarization fluctuations, small hysteresis, and delayed polarization saturation. Through localizing distortion, an ultrahigh recoverable energy density of 12.5 J cm–3 can be realized with an inspiring efficiency of 87%, alongside ultrawide capacitance temperature stability (from −100 to 432 °C) far exceeding X9R criteria, showing breakthrough progress in the overall performance for NaNbO3-based lead-free bulk ceramics. This work unveils an effective avenue of localized distortion to develop dielectrics with excellent energy storage performance and the potential to be extended to other functionalities.
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