Ultrahigh energy-storage performance
of dielectric ceramic capacitors
is generally achieved under high electric fields (HEFs). However,
the HEFs strongly limit the miniaturization, integration, and lifetime
of the dielectric energy-storage capacitors. Thus, it is necessary
to develop new energy-storage materials with excellent energy-storage
densities under moderate electric fields (MEFs). Herein, the antiferroelectric
material Ag0.9Ca0.05NbO3 (ACN) was
used to modify the relaxor ferroelectric material 0.6Na0.5Bi0.5TiO3–0.4Sr0.7Bi0.2TiO3 (NBT-SBT). The introduction of ACN results
in high polarization strength, regulated composition of rhombohedral
(R3c) and tetragonal (P4bm), nanodomains, and refined grain size. An outstanding
recoverable energy density (W
rec = 4.6
J/cm3) and high efficiency (η = 82%) were realized
under an MEF of 260 kV/cm in 4 mol % ACN-modified NBT-SBT ceramic.
The first-principles calculation reveals that the interaction between
Bi and O is the intrinsic mechanism of the increased polarization.
A new parameter ΔP/E
b was proposed to be used as the figure of merit to measure the energy-storage
performance under MEFs (∼200–300 kV/cm). This work paves
a new way to explore energy-storage materials with excellent-performance
MEFs.