The demand for high-temperature dielectric materials arises from numerous emerging applications such as electric vehicles, wind generators, solar converters, aerospace power conditioning, and ...downhole oil and gas explorations, in which the power systems and electronic devices have to operate at elevated temperatures. This article presents an overview of recent progress in the field of nanostructured dielectric materials targeted for high-temperature capacitive energy storage applications. Polymers, polymer nanocomposites, and bulk ceramics and thin films are the focus of the materials reviewed. Both commercial products and the latest research results are covered. While general design considerations are briefly discussed, emphasis is placed on material specifications oriented toward the intended high-temperature applications, such as dielectric properties, temperature stability, energy density, and charge-discharge efficiency. The advantages and shortcomings of the existing dielectric materials are identified. Challenges along with future research opportunities are highlighted at the end of this review.
•The composite ceramics have much higher energy storage density than pure anti-ferroelectrics.•SPS process can suppress the diffusion behavior between the tetragonal and orthorhombic phases.•A high ...recoverable energy storage density of 6.40J/cm3 was obtained in the composite ceramics.
Anti-ferroelectric composite ceramics of (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3–(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 (PBLYZST–PLZST) have been fabricated by Spark Plasma Sintering (SPS) method. The effect of SPS process on phase structure, anti-ferroelectric and energy storage properties of the composites has been investigated in detail. The X-ray diffraction, field emission scanning electron microscopy and energy-dispersive spectrometry analysis illustrate that the composites are composed of tetragonal perovskite, orthorhombic perovskite and small amount of non-functional pyrochlore phases. Compared with conventional solid-state sintering (CS) process, SPS process is helpful to suppress the diffusion behavior between the tetragonal PBLYZST and orthorhombic PLZST phases, and thereby improve the contribution of PLZST phase to the FE-to-AFE phase transition electric field (EA) of the composites. As a result, the SPS composite ceramics possess a considerable EA of 162kV/cm and a high recoverable energy storage density valued 6.40J/cm3 which is 1.75J/cm3 higher than that of the CS samples and about 2.3 times as that of the PBLYZST ceramics.
The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies ...that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium strontium titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.
The emerging ferroelectric nematic (N F ) liquid crystal is a novel 3D-ordered liquid exhibiting macroscopic electric polarization. The combination of the ultrahigh dielectric constant, strong ...nonlinear optical signal, and high sensitivity to the electric field makes N F materials promising for the development of advanced liquid crystal electroopic devices. Previously, all studies focused on the rod-shaped small molecules with limited length (l) range and dipole moment (μ) values. Here, through the precision synthesis, we extend the aromatic rod-shaped mesogen to oligomer/polymer (repeat unit up to 12 with monodisperse molecular-weight dispersion) and increase the μ value over 30 Debye (D). The N F phase has a widespread existence far beyond our expectation and could be observed in all the oligomer/polymer length range. Notably, the N F phase experiences a nontrivial evolution pathway with the traditional apolar nematic phase completely suppressed, i.e., the N F phase nucleates directly from the isotropic liquid phase. The discovery of thte ferroelectric packing of oligomer/polymer rods not only offers the concept of extending the N F state to oligomers/polymers but also provides some previously overlooked insights in oxybenzoate-based liquid crystal polymer materials.
Flexible lead‐free ferroelectric ceramic nanowire arrays exhibit a unique combination of features that can contribute to the realization of wearable cooling devices, including an outstanding ...electrocaloric effect at low fields, high efficiency, bendability and stretchability, and robustness against mechanical deformations. Thermodynamic and phase‐field simulations are carried out to validate their superior electrocaloric effect in comparison to thin films.
High energy density is the goal pursued by energy storage dielectric capacitors. Lead-based antiferroelectric ceramics are the most promising material system. Herein, the improved recoverable energy ...storage of 14.5 J/cm3 and efficiency of 77.1 % are obtained at x = 0.02 in Ca2+-modified Pb0.97-xCaxLa0.02(Zr0.93Sn0.05Ti0.02)O3 (PCLZST) antiferroelectric ceramics, which are fabricated by the tape-casting method. It is proved that the partial substitution of Ca2+ to Pb2+ at A-site can effectively strengthen the antiferroelectricity due to the reduced tolerance factor. Besides, the addition of Ca2+ can refine the grains and increase the breakdown strength, up to 448 kV/cm vs 376 kV/cm for PLZST ceramics. In addition, the discharge energy density and time are 11.6 J/cm3 and 5.09 μs, respectively. These characteristics indicate that Pb0.95Ca0.02La0.02(Zr0.93Sn0.05Ti0.02)O3 ceramic is a potential energy storage material for pulsed power systems.
Highly compact and geometrically complex piezoceramics are required by a variety of electromechanical devices owing to their outstanding piezoelectricity, mechanical stability and extended ...application scenarios. 3D printing is currently the mainstream technology for fabricating geometrically complex piezoceramic components. However, it is hard to print piezoceramics in a curve shape while also keeping its compactness due to restrictions on the ceramic loading and the viscosity of feedstocks. Here, we report a gravity-driven sintering (GDS) process to directly fabricate curved and compact piezoceramics by exploiting gravitational force and high-temperature viscous behavior of sintering ceramic specimens. The sintered lead zirconate titanate (PZT) ceramics possess curve geometries that can be facilely tuned via the initial mechanical boundary design, and exhibit high piezoelectric properties comparable to those of conventional-sintered compact PZT (d
= 595 pC/N). In contrast to 3D printing technology, our GDS process is suitable for scale-up production and low-cost production of piezoceramics with diverse curved surfaces. Our GDS strategy is an universal and facile route to fabricate curved piezoceramics and other functional ceramics with no compromise of their functionalities.
Abstract
Pyroelectric energy harvesting has received increasing attention due to its ability to convert low-grade waste heat into electricity. However, the low output energy density driven by ...low-grade temperature limits its practical applications. Here, we show a high-performance hybrid BNT-BZT-
x
GaN thermal energy harvesting system with environmentally friendly lead-free BNT-BZT pyroelectric matrix and high thermal conductivity GaN as dopant. The theoretical analysis of BNT-BZT and BNT-BZT-
x
GaN with
x
= 0.1 wt% suggests that the introduction of GaN facilitates the resonance vibration between Ga and Ti, O atoms, which not only contributes to the enhancement of the lattice heat conduction, but also improves the vibration of TiO
6
octahedra, resulting in simultaneous improvement of thermal conductivity and pyroelectric coefficient. Therefore, a thermoelectric coupling enhanced energy harvesting density of 80 μJ cm
−3
has been achieved in BNT-BZT-
x
GaN ceramics with
x
= 0.1 wt% driven by a temperature variation of 2
o
C, at the optical load resistance of 600 MΩ.
Dielectric materials with excellent energy storage capability at elevated temperatures are critical to meet the increasing demand of electrical energy storage and power conditioning at extreme ...conditions such as hybrid electric vehicles, underground oil industries and aerospace systems. This review study summarises the important aspects and recent advances in the development of nanostructured dielectric materials including ceramics, polymers and polymer composites for high-temperature capacitor applications. The advantages and limitations of current dielectric materials are discussed and analysed. Ongoing research strategies to suppress the conduction loss and optimise the high-temperature capacitive performance of dielectrics have been highlighted. A summary and outlook will conclude this review.
The continuous evolution toward electronics with high power densities and integrated circuits with smaller feature sizes and faster speeds places high demands on a set of material properties, namely, ...the electrical, thermal, and mechanical properties of polymer dielectrics. Herein, a supramolecular approach is described to self‐healable polymer nanocomposites that are mechanically robust and capable of restoring simultaneously structural, electrical, dielectric, and thermal transport properties after multiple fractures. With the incorporation of surface‐functionalized boron nitride nanosheets, the polymer nanocomposites exhibit many desirable features as dielectric materials such as higher breakdown strength, larger electrical resistivity, improved thermal conductivity, greater mechanical strength, and much stabilized dielectric properties when compared to the pristine polymer. It is found that the recovery condition has remained the same during sequential cycles of cutting and healing, therefore suggesting no aging of the polymer nanocomposites with mechanical breakdown. Moreover, moisture has a minimal effect on the healing and dielectric properties of the polymer nanocomposites, which is in stark contrast to what is typically observed in the hydrogen‐bonded supramolecular structures.
Supramolecular polymer nanocomposites can be healed efficiently and repeatedly to fully recover multiple functionalities in addition to structural integrity. The introduction of surface‐modified boron nitride nanosheets leads to the nanocomposites exhibiting superior mechanical strength, improved electrical resistivity, higher breakdown strength, enhanced thermal conductivity, and stabilized dielectric properties compared to the pristine polymer.
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