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Page 8 of 11 Liu et al. Microstructures 2023;3:2023009 https://dx.doi.org/10.20517/microstructures.2022.29

Figure 5. (A) P-E loops and energy storage performance under various electric fields for 0.85NN-0.15CZ ceramics. (B) Comparison of
[6]
energy storage performance among 0.85NN-0.15CZ ceramic and some other systems .
increases, W and W present an almost parabolic growth trend. Eventually, a comprehensive
rec
total
performance of W ~5.4 J/cm and η ~82% can be obtained in 0.85NN-0.15CZ ceramic under an ultrahigh
3
rec
external electric field of 68 kV/mm. It is believed that the excellent energy storage performance is associated
with the following sections: Firstly, the sample with a small grain size of ~2.1 μm has high grain boundary
density, and the grain boundary with large resistance can act as a dissipative layer, effectively hindering the
conduction of space charge and reducing the generation of leakage current. In addition, according to the
relationship of [36] , small grain size is favorable for the enhancement of E . Complex impedance
b
spectroscopy of pure NN and 0.85NN-015CZ ceramics measured at 500 °C are shown in
Supplementary Figure 7. The Z″-Z′ curves of the two exhibited nearly a single semicircle arc with good
fitting results using a series R||CPE equivalent circuit model, and 0.85NN-0.15CZ showed twice as much
resistance as pure NN, which proves the dominant role to the enhanced E of the grain boundary. Secondly,
b
the dense and uniform internal structure with few pores is beneficial to decreasing the possibility of local
breakdown, which can broadly promote E ; Thirdly, the introduction of CZ induces the transition from
[3]
b
antiferroelectric P phase to superparaelectric phase, leading to an enhanced relaxor behavior in ergodic
relaxor region at room temperature. PNRs with fast electric field response characteristics can cause 0.85NN-
0.15CZ ceramic to form the fast and reversible transition between relaxor ferroelectric and ferroelectric
phase under an external electric field, resulting in a small P and a large η. Finally, 0.85NN-0.15CZ ceramic
r
with moderate room-temperature ε can enhance W by inhibiting early polarization saturation under
r
rec
external electric fields.

[37]
Advanced ceramic capacitors are developing toward large energy storage density and high efficiency .
Figure 5B shows the comparison of energy-storage performance among 0.85NN-0.15CZ ceramic and other
relevant dielectric energy storage ceramics (AgNbO (AN), BiFeO (BF), Bi K TiO (BKT), Bi Na TiO 3
3
3
0.5
0.5
0.5
0.5
3
(BNT), BaTiO (BT), K Na NbO (KNN), SrTiO (ST)) [6,12,18,38-46] . Obviously, 0.85NN-0.15CZ ceramic
0.5
3
3
3
0.5
exhibits great performance superiority, making it one of the prospective materials for advanced pulse power
capacitor applications.
CONCLUSIONS
In this work, (1-x)NN-xCZ ceramics are prepared by a conventional solid-state reaction method. With
increasing CZ content to 0.15, the structure of samples changes from antiferroelectric P phase to relaxor
ferroelectric Q phase with superparaelectric state, leading to the destruction of long-range polarization
ordering but reservation of antiferrodistortion ordering, which can be confirmed by the high energy
synchrotron XRD and powder neutron diffraction refinement results as well as TEM images. In this case,