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Relaxor-ferroelectric ceramics capacitors have been in the front lines of investigations aimed at optimizing energy density due to their high Pmax, suppressed Pr, and high BDS levels, attributed to their highly dynamic polar nano-regions. A set of (1 − x)SrTiO3–x[0.88BaTiO3–0.12Bi(Li0.5Ta0.5)O3] ceramics (x = 0, 20, 40, 60 and 80 mol%), abbreviated as (1 − x)ST–x(BT–BLT), was designed and fabricated via a solid-state reaction route. A striking energy-storage density of 2.24 J cm−3, coupled with a high efficiency of η = 81% at 300 kV cm−1, was measured for these (1 − x)ST–x(BT–BLT) ceramics. The incorporation of BT–BLT ceramics was found to dramatically transform the paraelectric state of strontium titanate into the relaxor-ferroelectric state, by introducing broad relaxor behavior. The energy storage properties of the ceramic with x = 60 mol% showed outstanding stability in frequency (10–100 Hz) and temperature (20–120 °C), with minimal variation of (±≤0.5%), over the course of 105 cycles. Moreover, under various electric fields, rapid charge and discharge (≤1.5 μs) was also observed for this x = 60 mol% ceramic. Most significantly, the outcomes of this study are expected to provide a standard for other emerging lead-free dielectric ceramics displaying very good energy-storage properties and excellent electric field endurance, which are of pragmatic importance for cutting-edge pulsed power technology.

Dielectric capacitors with high energy storage properties are key enablers for potential applications. We report SrTi0.985(Zn1/3Nb2/3)0.015O3–x wt%ZnNb2O6 ceramics with high breakdown strength and energy storage performance by synergy manipulation. The structures, energy storage and dielectric properties of the ceramics are systematically investigated. Introduction of ZnNb2O6 mediates the contradiction between permittivity and breakdown strength. As a result, a high breakdown strength of 422 kV cm−1 and an excellent energy storage density of 2.35 J cm−3 are achieved in x = 4.5 ceramics, which also exhibit fast discharge features (τ0.9 < 1.5 μs), good thermal stability (25–150 °C) and outstanding cyclic characteristics (up to 5 × 105 times). Further results indicate that ZnNb2O6 additives partly dissolve into perovskite lattices to promote the formation of superlattice structures, improving the local polarization, and partly disperse around grain boundary regions to inhibit grain growth and relieve the direct damage from a strong electric field to grains, increasing the breakdown strength. This strategy should be generalizable for designing high performance dielectrics and other novel composite materials that benefit from synergistic effect manipulation.

Pure perovskite Bi(Mg0.5Tix)O3 (abbreviated as BMTx) thin films are successfully fabricated on Pt/Ti/SiO2/Si substrates by a sol–gel method, where the excess TiO2 with an amorphous structure is designed to improve the energy storage performance. The dielectric breakdown strength is found to be abruptly improved for the sample with x ≥ 0.65 due to the synergistic contributions from the fine grain size and amorphous phase structure, which greatly decreases the leakage current. Of particular significance is that BMTx with x = 0.75 exhibits a super high recoverable energy storage density of 126 J cm−3 at 5000 kV cm−1, demonstrating the great potential of environmentally friendly BMTx thin films for energy storage capacitor applications.

For single phase dielectric ceramics prepared using a traditional solid state method, the conflict between high dielectric permittivity and low breakdown strength has always limited the improvement of energy storage density. Here, we design a core–shell structure of Sr0.985Ce0.01TiO3 (SCT)@x wt% SiO2 combining a high dielectric permittivity core with an insulating shell material. The sample of x = 3 wt% sintered at 1300 °C has the largest energy storage density ∼2.23 J cm−3. The effects that different amounts of SiO2 have on phase, microstructure, dielectric and energy storage properties were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectrum (SEM-EDS) and dielectric measurements. As verified by finite element simulations, the energy storage properties are mainly governed by the electric field distribution owing to the introduction of a high dielectric permittivity core (SCT) in a low permittivity shell. The shell material provides an electrical shielding effect around the core, resulting in significant reduction in the field strength within the core material. A comparison of experimental and simulated results is also shown, which is in good agreement with the breakdown properties.

A new energy-storage ceramic system based on (1 − x)(Bi0.5Na0.5TiO3–BaTiO3)–xNaTaO3 ((1 − x)(BNT–BT)–xNT) is reported in this study. XRD refinement indicated a composition induced rhombohedral to tetragonal phase transition. All the samples exhibited a dense microstructure with an average grain size of 1.2–1.9 μm. The introduction of NT greatly improved the temperature stability of the dielectric properties for the BNT–BT system. For compositions x = 0.03–0.15, the working temperature range spanned over 260 °C satisfying TCC150 °C ≤ ±15%. The electric conductivity as a function of frequency followed the double power law. In the temperature region of 325–500 °C, the activation energy of DC conduction ranged from 1.47 eV to 1.71 eV, indicating intrinsic band-type electronic conduction. The optimum energy-storage properties were obtained in 0.90(BNT–BT)–0.10NT with an energy-storage density of 1.2 J cm−3 and energy-storage efficiency of 74.8% at 10 kV mm−1. The results demonstrate that (1 − x)(BNT–BT)–xNT ceramics are promising candidates for high-temperature energy-storage applications.

BaTiO3-based ceramics with a core–double shell structure were fabricated by precipitation and the sol–gel method. Bi(Zn1/2Ti1/2)O3-BaTiO3 (BZT-BT) or Nb oxide was chosen to be the shell-I (inner layer) or shell-II (outer layer) composition. The structure and dielectric properties were investigated by X-ray diffraction (XRD), HRTEM (High Resolution Transmission Electron Microscopy) and electron probe micro analysis (EPMA), with different core to shell ratio (nc/ns). Compared with the designed composition BT–Nb-(0.2BZT-0.8BT), BT-(0.2BZT-0.8BT)–Nb was found to possess improved dielectric temperature stability, where the capacitance variation ΔC/C ≦ ±15% was achieved over a temperature range of −60–155 °C, with the dielectric constant and dielectric loss being in the order of 1860 and 0.011 at room temperature.