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Due to the demands of miniaturization, weight reduction and green development for electronic devices, development of lead-free dielectric ceramic capacitors with high recoverable energy density (W rec) and energy storage efficiency (η) attracts much attention. To this end, (1- x)[0.75(Na 0.5 Bi 0.5)TiO 3 -0.25SrTiO 3 ]- x NdNbO 4 (abbreviated as: NBST- x NN) ceramics were fabricated through a solid-state reaction method. After adding NN, the non-perovskite phase of Bi 2 Ti 2 O 7 (BTO) with low dielectric constant (ε r) and loss (tan δ) is generated. Finite element software (COMSOL) was used to explore the influence of the BTO phase on breakdown strength (E b). The simulation result indicates that the BTO phase with a low ε r concentrates a larger local electric field (LEF), and thus weakens the LEF loading in the main perovskite phase, which is beneficial for enhancing E b. Moreover, NN doping significantly decreases the oxygen vacancy concentration in NBST ceramics, which plays a key role in improving E b. On the other hand, as NN content increases, the hysteresis of the polarization (P)-electric field (E) loops is substantially suppressed, and the polarization saturation is delayed, which can be ascribed to the appearance of the BTO phase having a linear dielectric characteristic and to the enhanced fluctuations of composition and charge by NN doping. Benefitting from the above factors, the optimal energy storage performance (ESP) with a W rec of 4.14 J/cm3 and an η of 90 % is obtained in NBST-0.08NN ceramics. Meanwhile, the ESP of NBST-0.08NN ceramics shows good charge-discharge properties and thermal stability. In conclusion, these results demonstrate that NBST-0.08NN ceramics are promising candidates as environment-friendly dielectric capacitor materials. [ABSTRACT FROM AUTHOR]

(1- x)(0.75(Na 0.5 Bi 0.5)TiO 3 -0.25SrTiO 3)- x NdGaO 3 ceramics (NBST- x NG, x = 0–0.06) were fabricated through a solid-state reaction method. High-valent Nd3+ ions enter the perovskite A-site to occupy Bi vacancies resulting from the volatilization of Bi, inhibiting the formation of oxygen vacancies and contributing to an enhanced breakdown electric field (E b). Low-valent Ga3+ ions enter the B-site to substitute for Ti4+ ions, resulting in the formation of random electric fields (REFs) at the B-site due to co-occupying hetero-valence ions of Ga3+/Ti4+, which significantly reduces ferroelectric hysteresis. Therefore, a synergic effect of A- and B-sites co-doping was realized in NBST- x NG ceramics. Benefitting from this synergic effect, an enhanced recoverable energy storage density (W rec) of 2.88 J/cm3 and an efficiency (η) of 83% are simultaneously obtained in NBST-0.04NG ceramics under a moderate electric field (E) of 200 kV/cm. Compared with most NBT-based ceramics, the values of (η vs W rec / E 2) for NBST-0.04NG ceramics show an obvious advantage, indicating excellent potential for application as an energy storage material. Moreover, W rec and η of NBST-0.04NG ceramics exhibit excellent temperature stability from 30 °C to 200 °C due to the enhanced correlation strength of polar nanoregions (PNRs) and local structural stability. This work provides a potential strategy to improve the energy storage performance of NBT-based ceramics via the synergic effect of A- and B-site co-doping. [ABSTRACT FROM AUTHOR]

Concerning the practical applications, dielectric capacitors with simultaneously high recoverable energy density (W rec) and large energy storage efficiency (η) under a low electric field is imperative and challenging. Herein, a strategy of complex ions substitution is proposed to achieve the goal. The (1- x)(0.75Na 0.5 Bi 0.5 TiO 3 -0.25SrTiO 3)- x La(Mg 2/3 Ta 1/3)O 3 (NBST- x LMT) ceramics were fabricated through a solid-state reaction method. A significantly enhanced breakdown electric field (E b) of 246.03 kV/cm is obtained in NBST-0.06LMT ceramics due to the refined average grain size (AGS), the enhanced band gap width and the inhibited oxygen vacancies by LMT doping. Furthermore, a high W rec of 3.18 J/cm3and large η of 86% are concurrently achieved in NBST-0.06LMT ceramics under a relatively low electric field of 246 kV/cm. Meanwhile, the variations of (W rec , η) under 170 kV/cm are less than 10% from 30 ℃ to 200 ℃, indicating an excellent thermal stability. Besides, the ceramics show a fast discharge rate of 155 ns by a charge-discharge measuring. In general, our results demonstrate the strategy of complex ions substitution is an effective way to achieve high energy storage performance under a relatively low electric field in NBT-based ceramics. [Display omitted] • Complex ions (La3+, Mg2+ and Ta5+) substitution was proposed to achieve high energy storage performance. • An enhanced Eb (246.03 kV/cm) was realized in NBST ceramics. • A high Wrec of 3.18 J/cm3and large η of 86% were concurrently obtained under 246 kV/cm. • The (Wrec, η) exhibits excellent thermal stability from 30 ℃ to 200 ℃. [ABSTRACT FROM AUTHOR]