Supercritical Relaxor Nanograined Ferroelectrics for Ultrahigh‐Energy‐Storage Capacitors

Abstract

Supercritical relaxor nanograined ferroelectrics are demonstrated for high‐performance dielectric capacitors, showing record‐high overall properties of energy density ≈13.1 J cm−3 and field‐insensitive efficiency ≈90% at ≈74 kV mm−1 and superior charge–discharge performances of high power density ≈700 MW cm−3, high discharge energy density ≈6.67 J cm−3, and ultrashort discharge time <40 ns at 55 kV mm−1. Ex/in situ transmission electron microscopy, Raman spectroscopy, and synchrotron X‐ray diffraction provide clear evidence of the supercritical behavior in (Na,K)(Sb,Nb)O3–SrZrO3–(Bi0.5Na0.5)ZrO3 ceramics, being achieved by engineering the coexistence of multiple local symmetries within the ergodic relaxor zone. The vanished difference between the ground relaxor state and the high‐field supercritical state eliminates polarization hysteresis. The supercritical evolution with electric field enables a highly delayed polarization saturation with continuously increased polarization magnitudes. The results demonstrate that such a design strategy of compositionally induced and field‐manipulated supercritical behavior can be generalizable for developing desirable energy‐storage dielectrics for applications in ceramic/film capacitors.

Temperature‐stable Na0.5Bi0.5TiO3‐based ceramics with favorable low‐temperature dielectric and energy storage property

“…Figure 4d,e shows the bright‐field TEM images of the x = 0.30 ceramic grains. A blotchy domain morphology related to the nanodomains can be found, 32 which is distinguished from the complex large‐sized ferroelectric domains observed in the NBT–BT ceramics 33 . The nanodomains are beneficial to improve the ESPs because the small‐sized domains with low switching energy barriers and high dynamics can response to the external electric fields timely and cause a nearly hysteresis‐free polarization response.…”

Superior Capacitive Energy-Storage Performance in Pb-Free Relaxors with a Simple Chemical Composition

“…Further, BBT12 ceramic shows high W rec when η ≥ 90%. Very recently, a superior performance of W rec ≥ 10.1 J/cm 3 and η ∼ 90% was achieved in only two Pb-free systems, KNN-based relaxor, , but both have very complex chemical compositions. As shown in Figure e,f, it appears that enhancing W rec in Pb-free ferroelectric relaxors requires the collaborative introduction of multicomponents. ,,, However, materials with a complex chemical composition are not conducive to large-scale production.…”

“…Relaxors have shown great promise for superior energy-storage performance, due to slim hysteresis with small remnant polarization ( P r ). Designing Pb-free relaxors containing highly polarizable ions with enhanced local polarization is a prevailing idea expected to achieve enhanced energy-storage properties. ,− Importantly, intrinsic polar structures, including the shapes, sizes, dipole patterns, and volume fraction of polar nanoregions substantially affect the properties. Based on rational chemical element substitution/doping and constructing solid solutions, various strategies, such as domain modification, , superparaelectric state, ,, high-entropy, , and phase structure control, − have been proposed.…”

“…Designing Pb-free relaxors containing highly polarizable ions with enhanced local polarization is a prevailing idea expected to achieve enhanced energy-storage properties. ,− Importantly, intrinsic polar structures, including the shapes, sizes, dipole patterns, and volume fraction of polar nanoregions substantially affect the properties. Based on rational chemical element substitution/doping and constructing solid solutions, various strategies, such as domain modification, , superparaelectric state, ,, high-entropy, , and phase structure control, − have been proposed. Furthermore, breakdown strength ( E b ) is also an important parameter, and can be improved through nanostructure construction, , grain refining, electrical microstructure control, , defect engineering, etc.…”

“…Furthermore, breakdown strength ( E b ) is also an important parameter, and can be improved through nanostructure construction, , grain refining, electrical microstructure control, , defect engineering, etc. With synergistic combinations of these strategies, great advances have been achieved, for instance, the realization of W rec ∼ 10 J/cm 3 and η ∼ 90% in only two highly complex KNN-based high-entropy and (Na,K)­(Sb,Nb)­O 3 -SrZrO 3 -(Bi 0.5 Na 0.5 )­ZrO 3 relaxor bulk ceramics. The energy-storage performance in ferroelectric relaxors has progressively improved, yet, it is accompanied by more and more complex chemical compositions.…”