Dielectric capacitors have become a key enabling technology for electronics and electrical systems. Although great strides have been made in the development of ferroelectric ceramic and thin films ...for capacitors, much less attention has been given to preventing polarization fatigue, while improving the energy density, of ferroelectrics. Here superior capacitive properties and outstanding stability are reported over 107 charge/discharge cycles and a wide temperature range of −60 to 200 °C of ferroelectric Aurivillius phase Bi3.25La0.75Ti3O12‐BiFeO3 (BLT‐BFO), which represents one of the best capacitive performances recorded for the ferroelectric materials. The modification of BLT thin films with BFO overcomes the constraints of ferroelectric Aurivillius compounds and presents an unprecedented combination of the ideal features including improved polarization, reduced ferroelectric hysteresis, and lowered leakage current for high‐energy‐density capacitors. Given the lead‐free and fatigue‐free nature of this Aurivillius phase ferroelectric, this work unveils a new approach towards high‐performance eco‐friendly ferroelectric materials for electrical energy storage applications.
Lead‐free ferroelectric Aurivillius thin films are structurally modified to overcome their intrinsic limitations and exhibit improved polarization, reduced ferroelectric hysteresis, lowered conduction loss, and enhanced breakdown strength for superior energy densities and power densities, while retaining their fatigue‐free features and displaying excellent stability over a wide range of temperatures and frequencies.
The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, ...and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge–discharge efficiency at elevated temperatures. At 150 °C and 200 MV m−1, an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge–discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present.
•We reported room temperature chemiresistive gas sensors based on ZnO CQDs synthesized via a simple solution method.•The solution-processed ZnO CQDs could be easily deposited into thin films by ...spin-coating in ambient air at room temperature.•The ZnCl2-treated ZnO CQDs sensors after annealing exhibited fast and selective response toward H2S at room temperature.
Colloidal quantum dots (CQDs), due to the excellent solution processability, low cost and ease of integration, are emerging as promising candidates for gas sensors. Here, colloidal zinc oxide quantum dots were synthesized through a simple colloidal method with oleic acid (OA) as the surface-capping ligand. The well dispersed ZnO CQDs were spin-coated onto ceramic substrates to construct chemiresistive gas sensors. The film-level ligand exchange treatment was applied to remove the long-chain surface-capping which thereby facilitated efficient gas adsorption and carrier transport. The optimal sensor exhibited the best performance with a response of 113.5 upon 50ppm of H2S exposure at room temperature, with a fast response time being 16s. The obtained results suggested that ZnO CQDs are promising materials candidate for high-performance gas sensors.
(Pb
0.87
Ba
0.1
La
0.02
)(Zr
0.68
Sn
0.24
Ti
0.08
)O
3
(
PBLZST
) antiferroelectric (
AFE
) ceramics have been prepared by hot‐press sintering method and conventional solid‐state reaction process, ...and the dependence of microstructure and energy storage properties of the ceramics on sintering approaches has been studied. The results reveal that not only the microstructure, but also the electrical properties of the
PBLZST AFE
ceramics are significantly improved by using the hot‐press sintering method. Samples resulting from the hot‐press sintering process have high breakdown strength of 180 kV/cm which results from the increase of density. Coupled with large polarization, the hot‐pressed
AFE
ceramics are shown to have a high recoverable energy density of 3.2 J/cm
3
. The recoverable energy density of the hot‐pressed
PBLZST AFE
ceramics is 100% greater than the conventional sintered specimens with recoverable energy density of 1.6 J/cm
3
.
(Pb
0.87
La
0.02
Ba
0.1
)(Zr
0.7
Sn
0.3−
x
Ti
x
)O
3
(PLBZST, 0.06≤
x
≤0.09) antiferroelectric ceramics were fabricated by conventional solid state reaction process, and their ferroelectric, ...dielectric, and pyroelectric properties were systemically investigated. PLBZST with different Ti content were all confirmed to be in an antiferroelectric phase at
T
=50°C, which is close to the lowest phase transition temperature. Compared with conventional FE ceramics, PLBZST antiferroelectric ceramics exhibited higher electric field induced pyroelectric coefficient (
p
). As the content of Ti increased from 0.06 to 0.09, the pyroelectric coefficient increased from 1000 to 6500 μC/m
2
K under a 500 V/mm DC bias field. The maximum pyroelectric coefficient of 8400 μC/m
2
K was obtained at
x
=0.09 when an 850 V/mm DC bias field was applied, which is far larger than that of conventional phase transition pyroelectric materials. Large pyroelectric response is beneficial for the development of infrared detectors and thermal imaging sensors.
Metamaterial absorbers, consisting of assembling arrays of optical resonators with subwavelength dimensions and spacing, allow efficiently absorption electromagnetic radiation by leveraging the ...strong electrical and magnetic resonances. Beyond the enhanced absorption, there is a growing interest to realize multi-functional absorbers, for example, absorbers with extended bandwidth, strong polarization extinction ratio, to name a few. Traditionally, designing multi-functional absorbers require complex brute-force optimizations with sizable parameter space, which turn out to be rather inefficient. Here, using the particle swarm optimization algorithm, we design and experimentally demonstrate broadband and highly polarization selective mid-IR metal-insulator-metal absorbers, covering the technologically important 3-5 μm atmospheric transparency band. With spectrally averaged absorption exceeding 70%, a high polarization extinction ratio of 40.6 is concurrently achieved by the algorithm. We also investigate the incident angle dependence of the spectral absorption and clarify the origin of optical losses. By integrating with the growing range of mid-IR detectors and imagers, our devices can enable new applications such as mid-IR full Stokes imaging polarimetry for remote sensing.
As a typical ferroelectric material, the PbZr1−xTix O3 (PZT) thin film with a homogeneous component has drawn extensive attention to the application in self-powered flexible electronics. The design ...of compositionally graded PZT thin films (i.e. artificially control the Zr/Ti ratio in different compositional layers in one film) has shown its immense potentials due to some novel phenomena induced by strain gradient, such as the shifted hysteresis loop, generation of the built-in electric field, enhancement in the motion of domain wall. However, the effect of the compositionally graded heterostructure on the piezoelectric response and its performance on the device level has seldom been investigated. To fill this knowledge gap, we prepare PZT thin films with the compositionally graded structure and based on that, fabricate flexible piezoelectric nanogenerators (PENGs). Furthermore, we explore the 2D mica as the substrate of PENGs and avoid the commonly used costly and troublesome laser-lifting or etching transfer procedure. The PENG prototypes integrated with 1 µm thick PZT films are flexible, translucent, and show high electric responses under different mechanical stimuli. Experiments indicate that up-graded PZT films, of which Zr composition varies from 20% near the bottom to 80% at the top, outperforms the down-graded counterpart. The up-graded PENG achieves a maximum voltage response of 2 V and a current density of 10.0 μA/cm2 when bent by 90°. This work demonstrates that the strain-tuned compositionally graded structure is an effective approach to improve the PENG performance.
Display omitted
•A new method to control the piezoelectric properties via the strain engineering.•The first performance-enhanced compositionally graded PZT thin film at the device level.•The up-graded PZT thin films exhibit a performance comparable to 52/48 multilayer films.
Relaxor ferroelectric poly(vinylidene fluoride) (PVDF) based terpolymers are attracting tremendous interest because of their potential applications in advanced energy harvesting and storage devices. ...Fundamental understanding of the ferroelectric behaviors of poly(vinylidene fluoride) (PVDF) based terpolymers has proved elusive. Current research suggests that the existence of different hysteresis loops results from physical pinning of the ferroelectric domains by the bulky defect monomers and that the size of the defect monomer determines the ferroelectric behavior. In this study, a poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene) random terpolymer is processed using a variety of methods and found to exhibit normal ferroelectric, single hysteresis loop (SHL), and double hysteresis loop (DHL) behaviors depending on the processing method. This indicates that the ferroelectric behavior of the terpolymer is related to not only the size of an individual defect unit but also how they are arranged within the relaxor ferroelectric phase. The results show that DHL behavior is a result of paraelectric domains that are promoted by long crystallization times, while the SHL behavior stems from a more random dispersion of these defects.
(Pb0.87Ba0.1La0.02)(Zr0.68Sn0.24Ti0.08)O3 (PBLZST) antiferroelectric (AFE) ceramics have been prepared by hot‐press sintering method and conventional solid‐state reaction process, and the dependence ...of microstructure and energy storage properties of the ceramics on sintering approaches has been studied. The results reveal that not only the microstructure, but also the electrical properties of the PBLZST AFE ceramics are significantly improved by using the hot‐press sintering method. Samples resulting from the hot‐press sintering process have high breakdown strength of 180 kV/cm which results from the increase of density. Coupled with large polarization, the hot‐pressed AFE ceramics are shown to have a high recoverable energy density of 3.2 J/cm3. The recoverable energy density of the hot‐pressed PBLZST AFE ceramics is 100% greater than the conventional sintered specimens with recoverable energy density of 1.6 J/cm3.
Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher ...breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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