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In this work, the (100-x)Ba(Hf 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 (BHT–xBCT) ferroelectric ceramics were fabricated by a conventional solid-state reaction method. The electrocaloric effect (ECE) of these ceramics was studied by both indirect and direct methods over a wide temperature range with the composition changing from x = 20 to 50. The most excellent direct ECE occurs in the BHT–50BCT with a good direct ΔT EC = 0.27 K (at 92 °C) under the electric field of 10 kV/cm. What's more, the direct EC effect peaks not only locates at near the Curie temperature, but also at the phase-transition temperatures corresponding to the transitions between different ferroelectric phases. In particular, it is found that BHT–50BCT exhibits a direct ECE anomaly ΔT EC = 0.1 K at 30 °C under an electric field of 10 kV/cm, which can be ascribed to the orthorhombic to tetragonal phase transition, proposing that one can achieve a broad temperature window by tuning the temperature gap between ferroelectric (FE) to paraelectric (PE) boundary and FE-FE boundary. In addition, BHT–30BCT shows good stability of indirect ΔT EC,max /ΔE and a broad ECE peak at a higher electric field, indicating that it is possible for electrocaloric temperature ΔT EC to be tuned linearly by electric field. Overall, our results imply that the BHT– xBCT ceramics are promising candidates for lead-free cooling refrigeration applications. [ABSTRACT FROM AUTHOR]

• A W r of 4.6 J/cm3 under 430 kV/cm and η of 62.5% are achieved in Ag 0.97 Nd 0.01 NbO 3. • Ag 0.97 Nd 0.01 NbO 3 ceramics demonstrate excellent temperature stability from 25 ℃ up to 125 ℃. • Outstanding power density of 54.0 MW/cm3 and ultrafast discharge speed (t 0.9) of 59.2 ns were also obtained. Lead-free dielectric capacitors for energy storage device have attracted increasing attention recently because of their high-power density and superior temperature stability. In this work, Nd-doped silver niobate (AgNbO 3 , abbreviated as AN) lead-free antiferroelectric ceramics were prepared by utilizing traditional solid state reaction method. A large energy storage density of 4.6 J/cm3 and an efficiency of 62.5% were simultaneously obtained in the 1% Nd-doped AN sample with an outstanding power density of 54.0 MW/cm3 and an ultrafast discharge speed (t 0.9) of 59.2 ns. Additionally, the 1% Nd-doped AN ceramic demonstrates a good temperature stability from 25 ℃ to 130 ℃. The excellent energy storage properties of the 1% Nd-doped ceramic is ascribed to the enhanced breakdown electric field induced by grain size engineering and the construction of phase structure via heterovalent substitution at the A-site of the lattice structure at room temperature. Our present work suggests that the 1% Nd-doped AN ceramic show promise for energy storage application in miniaturized mobile electronic devices and high-power equipment. [ABSTRACT FROM AUTHOR]

• Large recoverable energy storage density of 2.9 J/cm3 is obtained in BNT-BST-CZ ceramic. • The ceramic shows excellent dielectric permittivity stability at 44-483 °C. • The ceramic owns a fast charge-discharge speed of 110 ns. In the 0.9(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)-0.1CaZrO 3 ceramic, superior energy storage performance and excellent dielectric stability have been achieved, along with a higher discharge rate. Our finding suggests that the ceramic has great potential applications in pulsed power systems and high-temperature capacitors. [Display omitted] Novel (1− x)(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)- x CaZrO 3 (BNT-BST- x CZ, x = 0–0.15) ceramics were manufactured through a solid phase sintering process and their structural and electrical performance have been systematically investigated. By doping CaZrO 3 , a higher recoverable energy storage density of 2.9 J/cm3 and energy storage efficiency of 80% at 330 kV/cm can be simultaneously obtained in BNT-BST-0.1CZ ceramic. Further analysis with the aid of finite element simulation indicates that the improvement of energy storage performance lies in the refined grain size and reduced defects, which are both conductive to improve the dielectric breakdown strength. More importantly, incorporating CaZrO 3 gives slimmer hysteresis loops as well as excellent temperature (20–150 °C) and frequency (5–200 Hz) stability of energy storage properties. Moreover, a stable dielectric permittivity of in an ultra-wide range from 44 °C to 483 °C was achieved in BNT-BST-0.10CZ ceramic. Our findings suggest that the BNT-BST-0.1CZ ceramic has great potential applications in pulsed power systems and high-temperature capacitors. [ABSTRACT FROM AUTHOR]

• BNT-(BCT-BZT) ceramics with large strain and without negative strain were prepared • A large field-induced strain of 0.42% and large d 33 * of 547 pm/V are obtained • Large strain is mainly due to the crossover of relaxor nonpolar state to ferroelectric polar state Piezoelectric ceramics with high strain can convert electrical energy and mechanical energy into each other for a wide range of applications. (1- x)Bi 0.5 Na 0.5 TiO 3 - x (0.5Ba 0.7 Ca 0.3 TiO 3 -0.5BaTi 0.8 Zr 0.2 O 3) (BNT- x (BCT-BZT)) lead-free piezoelectric ceramics were prepared through solid-state reaction methods. The structural, dielectric, field-induced strain and energy storage properties of the ceramics were investigated systematically by various characterization techniques. A large field-induced strain of 0.42% with negligible negative strain and large reverse piezoelectric coefficient of 547 pm/V are obtained in BNT-9(BCT-BZT) ceramics. A large recoverable energy storage of 3.49 J/cm3 under 360 kV/cm and high energy storage efficiency of 64.9% are achieved in the BNT-10(BCT-BZT) ceramics. It believes that the large strain with negligible negative strain is mainly due to the crossover of relaxor nonpolar state to ferroelectric polar state. We believe that the BNT- x (BCT-BZT) ceramics are favorable for the practical applications in the mobile electronic devices. [ABSTRACT FROM AUTHOR]

For several decades, ferroelectrics with enhanced electrocaloric (EC) effect have served as competitive alternatives for solid-state cooling devices. In order to enhance the EC effect, there has been increasing research interest on exploring novel systems of EC materials and efficient cooling cycles. In contrast, optimizing intrinsic properties through doping effect has been relatively ignored. In this work, we introduce the binary compound CuO as an additive into the conventional lead-free BaSn 0·11 Ti 0·89 O 3 (BST) ferroelectric ceramic. This leads to a remarkably large adiabatic temperature change of Δ T = −0.33 °C under a relatively low electric field (10 kV/cm). This is higher than the ΔT of pure BST (Δ T = −0.15 °C, under 10 kV/cm). The largest of Δ T = −0.48 °C was achieved under 20 kV/cm. We assume that the large temperature change was achieved due to the addition of CuO additive, which improves the ferroelectric properties (e.g., a higher polarization and a lower coercive field). In addition, by introducing CuO additives, the breakdown electric field of the ceramics was also enhanced at high temperatures (above the Curie temperature, T C) and the working temperature range was greatly broadened (30 °C–60 °C) under a slightly high electric field. Our findings present a promising approach to enhance the EC effect by tuning the intrinsic properties of EC materials. We expect that our work emphasizes the importance of additives in enhancing the EC properties. • CuO was added into BaSn/TiO 3 as an additive for optimizing ferroelectric and electrocaloric effect (EC) properties. • EC temperature change was increased from −0.15°C to −0.33°C at the electric field of 10kV/cm after adding 2 mol%CuO. • A relatively large EC temperature change of −0.48°C at the electric field of 20kV/cm was achieved. • The relationship between the EC effect and intrinsic properties was explained based on Landau-Devonshire theory. [ABSTRACT FROM AUTHOR]