Search

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]

In this work, Ni-doped SrBi 2 Nb 2 O 9 (Sr 1- x Bi 2+ x Nb 2- x Ni x O 9- x , or SBNN) ceramics were successfully fabricated by using a solid state reaction method, and their band gaps were determined by UV–vis–NIR absorption spectrum. It is found that Ni doping could significantly reduce the band gap of SrBi 2 Nb 2 O 9 . The Sr 0.91 Bi 2.09 Nb 1.91 Ni 0.09 O 8.91 (SBNN9) ceramics show the lowest band gap of 2.25 eV with a relatively high remanent polarization of 2.5 μC/cm 2 . The band-gap reducing effect upon Ni doping might be attributed to the formation of the intermediate gap states generated by the Ni 2+ cations. Despite oxygen vacancies were unavoidably introduced into the systems after Ni doping, the remanent polarizations of the SBNN ceramics remain almost the same or even larger than the pure SrBi 2 Nb 2 O 9 . Our experimental results are also confirmed by the theoretical analysis based on the first-principle calculations. Novel ferroelectric photovoltaic effects were observed in these SBNN compounds. The switchable photovoltaic outputs induced by electric field were detected along different poling directions in the SBNN9 sample. The SBNN ceramics reported in the present work display narrow band gaps and relatively large polarizations, and show promise for ferroelectric photovoltaic device 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]

Dielectric energy-storage capacitors are of great importance for modern electronic technology and pulse power systems. However, the energy storage density (W rec) of dielectric capacitors is much lower than lithium batteries or supercapacitors, limiting the development of dielectric materials in cutting-edge energy storage systems. This study presents a single-phase BaTiO 3 -based high-entropy (BT-H) ceramic, which is synthesized using a conventional solid-state reaction method. It is found that the BT-H ceramic exhibits a remarkable energy storage performance, with a W rec of 5.18 J/cm3 and an ultrahigh η of 93.7% at 640 kV/cm electric field. Moreover, it also features wide temperature stability and excellent frequency stability. It is proposed that the introduction of high entropy enhances the random electric field and stress field, leading to lattice distortion and reduction of nanometer domain size, which in turn reduces remnant polarization and increases electric breakdown strength. This research provides a novel approach to improve the energy storage performance of ceramics through the high-entropy strategy. • High-entropy engineering could enhance the energy storage performance of dielectric capacitors. • An ultrahigh W rec of 5.18 J/cm3 and η of 93.7% at 640 kV/cm electric field were achieved in the BT-H (Mg) ceramics. • The BT-H ceramics exhibit remarkable energy storage performance stability. [ABSTRACT FROM AUTHOR]

Abstract Ferroelectric ceramics possess great application potential in optoelectronic and solar energy devices. However, ferroelectric ceramics normally have large band gaps, strongly inhibiting their photovoltaic performances. In this work, we use a strategy to enhance the visible light absorption of ferroelectric ceramics by incorporating Au nanoparticles into the ferroelectric BaTiO 3 (BT) matrix. The BT-Au nanohybrids are preliminarily synthesized as the "building blocks", which are assembled and then sintered as the 0–3 type composite ceramic. We find that the UV–vis absorption of composite ceramic is improved by localized surface plasmon resonances (LSPRs). While the ferroelectric property of the 0–3 type BT-Au ceramic remains robust. As a result, the composite ceramics show excellent ferroelectric photovoltaic effect with a photocurrent being approximately seven times as that in pure BT ceramics and an open-circuit voltage of 6 V. These findings suggest that interfacial control of ceramic composites may act an effective approach to optimize the photovoltaic responses in ferroelectric ceramics. Graphical abstract Image 1 Highlights • 0–3 type BaTiO 3 -Au ceramics with enhanced visible light absorption were prepared. • 20 nm Au nanoparticles are uniformly dispersed in the ferroelectric matrix. • The 0–3 type composite ceramics show excellent ferroelectric photovoltaic effect. • Photocurrent of composite is 7 times that of pure BaTiO 3. • Open-circuit voltage of 0–3 type BaTiO 3 -Au can reach 6 V. [ABSTRACT FROM AUTHOR]

Abstract Core-shell nanoparticles used as blocks to construct composite ceramics can exhibit high energy storage density, but the effects of original tunable shell thickness on the microstructures and energy storage property of finally sintered bulk ceramics has not been clarified, thus how to achieve the full potential of this technology to improve the energy storage density of ferroelectric-based ceramics remains to be solved. In this study, as precursors to fabricate bulk ceramics, BaTiO 3 @SiO 2 core-shell nanoparticles were successfully synthesized by a wet-chemical method and they were used as models to investigate the effect of the core-shell nanostructured precursors on the energy storage property of the bulk composite ceramics. The original BaTiO 3 nanoparticles coated with various homogenous SiO 2 shells were acquired by controlling the concentration of tetraethyl orthosilicate (TEOS). The surface microstructure of the bulk composite ceramics observed by scanning electron microscope (SEM) revealed that the SiO 2 outer shell of BaTiO 3 @SiO 2 nanoparticles plays an important role in constructing the microstructure of the ceramics. The remodeled microstructure has a great impact on leakage current density and dielectric property, and it makes a leading contribution to the energy storage performance of ceramics. As a result, the optimum SiO 2 loading range was confirmed and the maximum energy storage density obtained from BaTiO 3 @20 wt%SiO 2 was ∼4.799 J/cm3 at 370 kV/cm, demonstrating that nanoscale core-shell architecture is an effective strategy to improve the energy storage performance of ferroelectric-based composite ceramics. Highlights • BaTiO 3 @SiO 2 core-shell nanoparticles are used as blocks to construct composite ceramics for energy storage. • Tunable shell plays an important role in remodeling the microstructure of the ceramics. • The remodeled microstructure has a great impact on leakage current density, dielectric property and energy storage density. • The maximum energy storage density obtained from BaTiO 3 @20 wt%SiO 2 was ∼4.799 J/cm3 at 370 kV/cm. [ABSTRACT FROM AUTHOR]

To meet the booming demands for advanced pulse power systems, developing dielectric ceramics with excellent energy storage performance is extremely urgent. In this work, a composition modulation strategy was adopted for designing Bi 0.5 K 0.5 TiO 3 -based ceramics. That is, incorporating Bi(Mg 0.5 Hf 0.5)O 3 into 0.6Bi 0.5 K 0.5 TiO 3 -0.4Sr 0.7 Bi 0.2 TiO 3 matrix (abbreviated as (1- x)(BKT-SBT)- x BMH, x = 0.00, 0.04 and 0.08). The energy storage performance of the (1- x)(BKT-SBT)- x BMH ceramics was enhanced by increasing the breakdown strength. Ultimately, a recoverable energy density (W rec) of 4.25 J/cm3 together with an efficiency (η) of 87 % was achieved for the x = 0.04 ceramic at 360 kV/cm. Furthermore, excellent energy storage properties (W rec ≥ 2.71 J/cm3, η ≥ 85 %) were obtained over a wide range of temperatures (20–200 ℃), frequencies (0.5–100 Hz) and cycle numbers (105) under 260 kV/cm, indicating good thermal stability, frequency-independent character and fatigue-resistance behavior. Our work would open up a new avenue for preparing BKT-based dielectric ceramics. • Composition modulation was adopted to design Bi 0.5 K 0.5 TiO 3 -based ceramics. • An excellent W rec of 4.25 J/cm3 along with η of 87 % at 360 kV/cm was achieved. • The ceramic displayed good thermal, frequency and cycle stability. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rhombohedral–tetragonal phase coexistence was designed in the ternary system. [•] R–T phase coexistence was identified in the ceramics with 0.03⩽ x <0.05. [•] Enhanced dielectric, ferroelectric, and piezoelectric properties were found in the ceramic with x =0.035. [•] d 33 ∼310pC/N, k p ∼0.45, ɛ r ∼1249, tan δ ∼0.025, and T C ∼338°C were observed in the ceramic with x =0.035. [ABSTRACT FROM AUTHOR]

• Ca2+ and Sr2+ can increase the stability of antiferroelectric phase while Ba2+ decreases it. • An enhanced negative ECE of Δ T around − 10.6 K was obtained in the Pb 0.9 Sr 0.1 ZrO 3 thin film at room temperature. • The modification of antiferroelectric-ferroelectric phase transition is an effective strategy to enhance the negative electrocaloric effect in antiferroelectric thin films. In the Pb 0.9 Sr 0.1 ZrO 3 thin film, an enhanced negative electrocaloric effect (ECE) has been observed based on the Maxwell relation, with Δ T of around − 10.6 K under 450 kV/cm at room temperature, as compared with the pristine PbZrO 3 thin film (with Δ T of around −7.3 K under 300 kV/cm at 361 K), as shown in the figure. Our work demonstrates that modifying antiferroelectric-ferroelectric phase transition is an effective way to enhance the negative ECE in antiferroelectric thin films. [Display omitted] Electrocaloric effect (ECE) in dielectric materials has attracted much attention due to its promising applications in solid-state cooling devices. In this work, alkaline-earth doped PbZrO 3 antiferroelectric thin films (Pb 0.9 A 0.1 ZrO 3 (A=Ca, Sr, and Ba)) were deposited by a sol-gel method and its antiferroelectric-ferroelectric phase competition as well as the negative ECE were studied. It is found that Ca2+ and Sr2+ expand the antiferroelectric phase region while Ba2+ reduces it, due to the different ion radii of these alkaline-earth elements. As a result, the Pb 0.9 Sr 0.1 ZrO 3 thin film exhibits an enhanced negative ECE with Δ T of around − 10.6 K under 450 kV/cm whereas the Pb 0.9 Ba 0.1 ZrO 3 thin film shows a decreased negative ECE with Δ T of around − 2.5 K under 200 kV/cm, as compared with the pristine PbZrO 3 thin films (with Δ T of around −7.3 K under 300 kV/cm). This work provides an effective method to enhance the negative ECE of antiferroelectrics in electrical cooling applications by adjusting their antiferroelectric to ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

• Through modifying Sn4+ content, the breakdown strength is increased by 112.3%. • The recoverable energy density enhanced by 276.2% via incorporation of Sn4+. • The doping of Sn4+ inhibits the migration of grain boundary and refines grains. • The delayed polarization saturation result from Sn4+ with d10 substitutes Ti4+ with d0. [Display omitted] High-performance dielectric ceramic capacitors is a promising candidate in energy storage devices. In this work, the energy storage performance of Ba 0.94 Ca 0.06 Ti 1−x Sn x O 3 (x = 0.04, 0.08, 0.12, 0.16) ceramics was systematically studied. Through modifying Sn4+ doping content, the breakdown strength of the ceramics is enhanced by 112.3% from 133.4 kV/cm (Ba 0.94 Ca 0.06 Ti 0.96 Sn 0.04 O 3) to 283.2 kV/cm (Ba 0.94 Ca 0.06 Ti 0.84 Sn 0.16 O 3). Accordingly, the recoverable energy density is greatly increased by 276.2%, that is, from 0.42 J/cm3 grow to 1.58 J/cm3. The enhanced energy storage properties could be ascribed to the following aspects: (1) the doping of Sn4+ with a larger ionic radius inhibits the migration of grain boundaries and therefore refines grains, resulting in a higher activation energy and a larger E b ; (2) the long range polar order is broke and polar nano-regions are formed, giving rise to lower energy barrier and smaller P r ; (3) the weakened ferroelectricity and delayed polarization saturation lead to higher W rec owing to the fact that Sn4+ with d10 electronic configurations substitutes Ti4+ with d0. Our work provides a novel approach for enhancing energy storage performance in dielectric ceramic capacitors. [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]