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BiFeO3-BaTiO3 is a promising high-temperature lead-free piezo-ceramics due to its high Curie temperature (TC > 500 °C) and excellent piezoelectric properties. However, a high leakage current was often detected in this system, which severely affects its applications. In this work, the 0.7BiFe(1−x)GaxO3-0.3BaTiO3 (BFGax-BT, 0.00 ≤ x ≤ 0.10) system was designed to reveal the reason of leakage-current density decreased by their leakage mechanism. Because of the suppression of generation of Fe2+ and oxygen vacancy ( V O ∙ ∙ ), the leakage mechanism from space charge limited conduction mechanism found in Ga-free BF-BT ceramics turns into Ohmic conduction and Schottky emission mechanism as Fe3+ was replaced with Ga3+. A good combination of piezoelectric properties (d33 = 174 pC N−1 and kp = 29%) and high Curie temperature (TC = 497 °C) was achieved in the BFGa0.06-BT ceramic owning the lowest leakage-current density. This work will provide the clues for preparing the high insulation and high piezoelectric performance BF-BT-based ceramics by suppressing the valence change of Fe3+ and V O ∙ ∙ appearance. [ABSTRACT FROM AUTHOR]

Environmentally friendly BiFeO3 capacitors have great potential for applications in pulsed-discharge and power conditioning electronic systems because of their excellent intensity of spontaneous polarization (Ps). Herein, (0.7−x)BiFeO3-0.3BaTiO3-xNaTaO3 + 0.3 wt% MnO2 (abbreviated as BF-BT-xNT) multilayer ceramic capacitors (MLCCs) were designed and prepared to improve the energy storage performance via enhancing ion bonding and dielectric relaxation. The BDS of BF-BT-xNT MLCCs from 500 kV cm−1 at x = 0.05 increases greatly to 800 kV cm−1 at x = 0.15 due to the increase of the band gap and resistance, and the decrease of dielectric permittivity. An excellent energy storage density Urec = 9.1 J cm−3 and efficiency η > 80% were obtained since ultrahigh BDS (780 kV cm−1) and low Pr value (2.1 μC cm−2 at measured electric field 780 kV cm−1) were achieved simultaneously in BF-BT-xNT multilayer capacitors at x = 0.12. This work provides a strategy for improving energy storage properties of BiFeO3, which is via enhancing ionic bonding and relaxor behavior to achieve high BDS, low Pr and large Pmax, simultaneously. [ABSTRACT FROM AUTHOR]

Environmentally friendly NaNbO3 capacitors have a great potential for applications in pulsed-discharge and power conditioning electronic systems because of their AFE-like hysteresis behavior, high saturation polarization and low mass. Here, we demonstrate (0.96 − x)NaNbO3–0.04CaZrO3–xBi0.5Na0.5TiO3 (abbreviated as NN-CZ-xBNT) capacitors with high energy storage density (Wrec) and efficiency (η). The performances of capacitors were tuned by the composition induced relaxor behavior and grain refinement which resulted in reduction of hysteresis and increase in the breakdown strength (BDS). Two-step sintering is found to be effective for reducing the grain size of MLCCs to 3 μm, which is 86% smaller as compared to grain size obtained by conventional solid-state sintering (22 μm). Small grain size significantly reduces the leakage current and losses and increases the BDS, yielding excellent Wrec = 3.7 J cm−3 and η = 82.1% in the NN-0.04CZ-0.16BNT multilayered capacitors. Results provide a systematic strategy for enhancing the energy storage density and efficiency of dielectric capacitors through the combination of dielectric relaxation and grain size refinement. [ABSTRACT FROM AUTHOR]

Antiferroelectric (AFE) materials owing to their double-loop-shaped electric-field (E) dependent polarization (P) are considered quite promising for energy-storage capacitors. Among the large family of AFE materials, the AgNbO3 composition is attractive not only because it is environmentally friendly, but also because it has high recoverable energy storage density (Wrec). However, the reported values of Wrec < 4 J cm−3 in Ag(Nb0.85Ta0.15)O3 multilayer capacitors are lower than that of the corresponding monolithic ceramic. This is attributed to high leakage current density (J) and inferior breakdown strength (BDS) in multilayer structures. Here we demonstrate that MnO2 doping not only effectively reduces the J value and results in slim P–E loops, but also enhances the breakdown strength (BDS). Multilayer capacitors with composition Ag(Nb0.85Ta0.15)O3 + 0.25 wt% MnO2 (ANT + Mn) demonstrated an excellent Wrec = 7.9 J cm−3 and efficiency η = 71%. Extensive investigations were conducted on ANT + Mn multilayer capacitors to demonstrate the role of strain engineering in enhancing the maximum polarization (Pmax) and ΔP values. Results reveal the effect of built-in stress in the active layers of multilayer capacitors on the magnitude of Pmax, remanent polarization (Pr) and Wrec, and provide guidance towards the development of high energy storage density in multilayer capacitors. [ABSTRACT FROM AUTHOR]

0.7Bi1-xLaxFeO3–0.3BaTiO3 (abbreviated as BLxF-0.3BT at 0.00 ≤ x ≤ 0.05) system was designed to explore the relationship between the morphotropic phase boundary (MPB) separating with rhombohedral (R) phase and pseudocubic (PC) one, and piezoelectric property. X-ray diffraction and Rietveld refinement results of XRD data reveal that the phase structure of samples evolved from R-PC two-phase coexistence at 0.00 ≤ x ≤ 0.03 to PC-symmetry at x = 0.05. Due to coexisting R-PC two phases near MPB region and the improvement of polarization property, excellent d33 = 170 pC/N and kp = 28.74% were achieved in BLxF-0.3BT system at x = 0.01. This research revealed the potential of BLxF-0.3BT system as promising lead-free piezoelectric ceramics with relatively high Curie temperature TC = 477 °C. [ABSTRACT FROM AUTHOR]