Dielectric Capacitors Research Articles

Synthesis and functional properties of reduced graphene oxide/bismuth-doped gadolinium ferrite composites

An upsurge in water pollution with developing age leads scientists to exploit new materials and technologies for water purification. Herein, we used a co-precipitation approach to prepare rGO/BixGd1-xFeO3 composites to tackle waste organic dyes in fresh water reservoirs. Bismuth at different concentrations is used to tailor the functionality of gadolinium ferrites deposited on reduced graphene oxide. X-ray diffraction pattern describes the unit cell structure of the composite to be distorted orthorhombic with crystallite sizes in the range of 20-15 nm which are confirmed by scanning electron microscopy. Band gaps are calculated by Tauc plots and are in the range 2.62-2.38 eV and 0.9945-0.2873 eV for direct and indirect calculations making these composites suitable photocatalysts. Textural analysis of the samples is carried by Brunauer-Emmett-Teller surface measurements and the surface area is found to be in the range 62.1 to 29.9 m2g−1. Dielectric studies prove that rGO/Bi0.05Gd0.95FeO3, with the highest dielectric constant and capacitance, is better semiconductor among all six synthesized composites. This result is further supported by impedance analysis. In the presence of ultraviolet-visible light, rGO/Bi0.05Gd0.95FeO3 shows 97.2% degradation of methylene blue dye, a common industrial pollutant, with rate constant 0.006 min−1 while rGO/GdFeO3 only degraded 72.6% of MB. The enhanced photocatalytic ability of rGO/Bi0.05Gd0.95FeO3 is evident through low band gap, small crystallite size, less electron-hole recombination in photoluminescence, large surface area and linear I-V response.

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance

The development of lead-free dielectric capacitors with high recoverable energy storage density and high energy storage efficiency is important for improving the overall performance of electronic and power systems. BaTiO3 (BTO) is one of the most common ferroelectric materials and has attracted much attention for energy storage applications in the past decades due to its excellent dielectric and ferroelectric properties. However, high remnant polarization and low electrical breakdown strength of BTO limit its development in energy storage applications. Many efforts (e.g., elements doping, interface/heterostructure, etc.) have been made to improve the energy storage density of BTO thin films. In this paper, Ba1-xNixTiO3 thin films (x = 0, 0.02, 0.04, 0.06, 0.08; abbreviated as BNxT) were synthesized via sol-gel and spin-coated method. The effect of Ni doping on the structural, dielectric, ferroelectric and energy storage properties of BTO thin films has been studied. The results confirmed that with the increase of Ni doping, a second phase arises and the dielectric constant decreases. While appropriate Ni doping led to the improvement of the breakdown strength, further increase of Ni deteriorated the energy storage because of the high oxygen vacancy. Finally, optimized energy storage performance was obtained for BN0.04T thin film: dielectric constant of 401, dielectric loss of 0.002, recoverable energy density of 20.2 J/cm3 and energy storage efficiency of 83.6% at 965 kV/cm. Meanwhile, the remnant and maximum polarization of the films were 0.06 μC/cm2 and 50 μC/cm2, respectively. BN0.04T thin film has an excellent application prospect and is expected to appear as a component in the future composite energy storage film system.

Constructing local structure heterogeneity in AgNbO3-based antiferroelectrics: Achieving excellent anti-fatigue and energy storage properties

AgNbO3 ceramics are important candidates for developing high-property dielectric capacitors because of their unique field-induced antiferroelectric (AFE)-ferroelectric (FE) phase transformation behavior and good environmental friendliness. However, until now, they have not yet exhibited simultaneously ultrahigh recoverable energy density (Wrec) and efficiency (η), and superior electrical fatigue resistance. Herein, we design a heterovalence-doping-enabled local structure heterogeneity strategy to achieve AgNbO3-based ceramics with excellent anti-fatigue and capacitive characteristics. The replacement of A-site Ag+ with higher valence Sm3+, and the substitution of lower electronegativity Ta5+ for B-site Nb5+ decrease the [Nb/TaO6] octahedral tilting, destroy the long-range ordering of AFE domains and produce low-atom-displacement regions, as confirmed by the atomic-scale electron microscopy. These are in favor of improving AFE features, refining P-E curves, and decreasing electric field-induced strain. Consequently, an ultrahigh Wrec of 8.03 J/cm3, and a large η of 74.77 % are obtained in the (Ag0.94Sm0.02)(Nb0.75Ta0.25)O3 ceramic. More interestingly, the Wrec and η both show excellent anti-fatigue characteristics with less than 2.6 % degradation even after 106 cycles, far superior to those obtained in other AgNbO3 systems with only 104 cycle stability.

Realizing excellent energy-storage performance under low electric fields in lead-free BiFeO3-BaTiO3-based ceramics with ultrahigh polarization difference

Amidst the swift progress of electronic devices, there's an escalating need for capacitors to attain heightened energy storage capabilities (> 5 J/cm3) under low electric fields(< 300 kV/cm), facilitating integration and downsizing. In this research, (0.67-x)BiFeO3–0.33BaTiO3-xLaAlO3 (x = 0–0.07) ceramics with ultrahigh polarization difference (ΔP = Pmax-Pr) were successfully synthesized via the traditional solid-phase method. Initially, the progressive substitution of LaAlO3 was found by XRD Rietveld refinement, PFM, and dielectric spectroscopy analysis to lead to a phase transition from the R3c phase to the Pm3m phase, obtaining ultra-small and highly electric field responsive PNRs, thus facilitating the relaxation behavior and achieving low Pr values. Moreover, the introduction of La3+ enables the 0.67BiFeO3–0.33BaTiO3 ceramics leading to an increased deviation of Bi ions from the centre, which maintains a relatively high Pmax to achieve an ultrahigh ΔP (~52.43 μC/cm2), resulting in excellent energy storage density (Wrec ~ 5.71 J/cm3) under relatively low electric fields (270 kV/cm), along with super temperature stabilities. This study offers an effective pathway to explore the high energy storage capabilities of dielectric capacitors under low fields.

Effect of Rb substitution on dielectric, ferroelectric, mechanical and biocompatibility properties of Na0.2K0.3Bi0.5TiO3 ceramics

This study focuses on the strategically developed Rb-substituted lead-free Na0.2K0.3Bi0.5TiO3 (NKBT) ceramic, highlighting its applications in energy storage, bio-implants, actuators, dielectric capacitors, and various other fields. The significant decrement of average grain size of ∼0.31 μm from ∼0.62 μm has been observed via surface morphology analysis with ultra-high Vickers hardness of ∼8 GPa in Na0.2K0.24Rb0.06Bi0.5TiO3 (RB 6) which is within the range to use bio-implants. The biocompatibility of samples verified cell growth and was monitored using two fluorescence dyes: fluorescein diacetate (FDA for live cell staining) and propidium iodide (PI for dead cell staining) under a fluorescence microscope. Also, the findings reveal that Rb-NKBT exhibits excellent biocompatibility with normal fibroblast cells and possesses impressive mechanical strength. Moreover, The X-ray and Raman inquiry confirms the tetragonal crystal structure of the samples. Frequency-dependent dielectric curve and shifting of Tm reveal the enhanced relaxor property with broadening signifies the increase in thermal stability. It is an important parameter for biological applications, particularly those involving functional temperatures, as the material must remain ferroelectric within the operating temperature range. Furthermore, the higher breakdown strength of ∼110 kV/cm with a recoverable energy storage density of 0.62 J/cm3 was found in the RB 6. The S-ve of the material decreases with the substitution of the Rb, which has been useful for actuator application. This study offers a comprehensive discussion on the utility of NKBT FCs as an active functional material for biomedical applications and dielectric applications with the advantage of non-invasive evaluation for potential failure with their sensing applications.

Ultra-tunable dielectric capacitors enhanced by coupling ferroelectric field effect and semiconductor field effect

Tunable ferroelectric film capacitors play an important role in tunable microwave devices and filter systems due to their high dielectric constant, low loss, and high dielectric tunability. However, there is a trade-off between low loss and high tunability, which limits further enhancement of dielectric performance. Here, we propose an ultra-tunable capacitor by designing a Ba0.7Sr0.3TiO3 (BST)–semiconductor heterostructure. In the tunable capacitor, the BST film is fabricated directly on p-type silicon substrates by magnetron sputtering, and a heterostructure layer is constructed. The coupling effects between the semiconductor depletion layer capacitance and the BST capacitance produce higher capacitance tunability than a traditional sandwich BST capacitor. Based on the coupling effects, a metal–ferroelectric–semiconductor–ferroelectric–metal capacitor is developed, which enables the capacitor to operate under both negative and positive biases, which has an n value (n=Cmax/Cmin) of 90 with 40 V bias voltage and a maximum Q of 1000. The results offer a potential approach to designing high-performance tunable capacitors on silicon with BST film that could build tunable filters for information processing in communication systems.

Tape‐Casting Lead‐Free Dielectrics Permit Superior Capacitive Energy Storage Performance

AbstractDielectric capacitors have garnered significant attention for their promising attributes in advanced pulse power systems of the future, owing to their rapid charge/discharge capabilities, high power density, and remarkable stability. Whereas environmentally friendly lead‐free ceramics are facing serious challenges of low breakdown strength, poor energy storage density, and/or conversion efficiency, which has been an obstacle to developing desirable dielectric capacitors. In this study, high‐quality ultrathin (&lt;20 µm) lead‐free ceramic dielectrics are successfully produced via the tape‐casting method. The local structural characteristics of these ceramics are verified using piezoresponse force microscopy and aberration‐corrected scanning transmission electron microscopy. By introducing Ta5+ ions into Bi0.39Na0.36Sr0.25TiO3 ceramics, the polar clusters tend to decrease together while the maximum applied electric field tends to increase. This phenomenon can be attributed to the decreased grain size and complex polar structure characterized by extremely small polar clusters, enabling the simultaneous achievement of high applied electric field, large polarization, and minimized polarization hysteresis. Notably, the tape‐casted lead‐free ceramics exhibited exceptional comprehensive energy storage performance with a recoverable energy storage density of ≈10.06 J cm−3 and an efficiency of ≈93% under a high electric field of 915 kV cm−1, surpassing the capabilities of most reported lead‐free ceramics. This work offers a viable solution for developing lead‐free ceramic dielectrics with outstanding energy storage capabilities.

Aliovalent doping engineering to synergistically optimize the energy storage properties of Sr0.7Bi0.2TiO3-based linear-like relaxor ferroelectric ceramics

Dielectric capacitors with high energy storage density and power density are essential for the miniaturization and lightweight design of electronic devices. However, current applications are hampered by the challenge of simultaneously achieving high recoverable energy storage density and efficiency, as well as the fact that many dielectric energy storage ceramics contain lead elements. In this study, a multiple optimization strategy is proposed to significantly increase the breakdown strength while maintaining a high polarization strength by forming Bi3+-Li+ defect pairs to disrupt the paraelectric phase, and by introducing aliovalent double ions Li+ and La3+ to increase the cationic disorder. The change of domain structure and the relaxation enhancement mechanism is analyzed by dielectric properties and first-order reversal curve. Band gap, impedance and numerical simulations reveal the breakdown strength enhancement mechanism. As a result, the ceramics achieve a remarkable combination of high Wrec of 4.4 J/cm3 and high ƞ of 90 % at 420 kV/cm. Furthermore, the ceramic exhibits exceptional stability and fatigue resistance. Notably, the ceramic obtains a power density of 99.5 MW/cm3 and a rapid discharge rate of 0.22 µs. These findings demonstrate the excellent potential of Sr0.7Bi0.2TiO3-based ceramics as an alternative to Pb-based ceramics, and provide an effective strategy for developing advanced energy storage materials.

Superior dielectric temperature stability and high energy-storage density of ecologically friendly 0.7(0.94Bi0.5Na0.5TiO3–0.06BaTiO3)-0.3Ba(Mg1/3Ta2/3)O3 ceramics

Recently, much attention has been given to dielectric ceramic capacitors, which have excellent temperature stability and a high energy-storage density. Ecologically friendly ceramics ((1-x)(0.94Bi0.5Na0.5TiO3–0.06BaTiO3)-xBa(Mg1/3Ta2/3)O3, where x = 0, 0.15, 0.2, 0.25, or 0.3) were synthesised using a conventional solid-state method. The ceramic sample with x = 0.3 exhibited a superior dielectric temperature stability, relative permittivity that varied within ±15%, and low dielectric loss of less than 0.02 over a temperature range of −100 to +307 °C, which met the X9R specifications. In addition, a scanning electron microscopy image confirmed that the sample had a dense and uniform microstructure. Furthermore, a high recoverable energy-storage density of 6.75 J/cm3 was obtained for the ceramic sample with x = 0.3 under a moderate applied electric field of 420 kV/cm. These characteristics suggest that it is a promising candidate for an ecologically friendly temperature-insensitive dielectric ceramic for energy-storage capacitors.

Enhanced energy storage performance in polyetherimide composites via oriented one-dimensional BZCT@BT core-shell filler.

The development of dielectric capacitors toward high voltage and high power density requires materials with excellent insulation and energy storage performances. In this work, a polymer dielectric with polyetherimide (PEI) as the matrix and calcium barium zirconate titanate (BZCT) coated by barium titanate fiber (BT) as the filler (BZCT@BT) was constructed. The (0.5%-10% BZCT@BT/PEI) polymer dielectric has an excellent discharge energy density (Ue) of 6.66 J/cm3 and maintains an advanced charge/discharge efficiency (η) of 93.29% when the BT content was 0.5% and the BZCT particle content was 10%. The addition of BZCT endows the polymer dielectric with a higher relative dielectric constant (εr), while BT, maintaining a lower εr than BZCT, could reduce the electric field (E) distortion caused by the dielectric mismatch between PEI and BZCT. Oriented fiber fillers increase the breakdown strength of the polymer dielectric, ultimately increasing the performance of energy storage. A new strategy for the design of energy storage polymer dielectrics was provided by this work.

Room temperature superparaelectric state in 20BaTiO3-60V2O5-20Bi2O3 glass for capacitive energy storage applications

Materials with high dielectric constant exhibit excellent charge storage capacity, making them favorable solutions for next-generation dielectric capacitors. The glass system with the composition of 20BaTiO3-60V2O5-20Bi2O3 was prepared by conventional melt quenching technique. The glassy nature of the sample was confirmed by using DSC and XRD measurement while the existence of nano polar cluster inside the glass matrix was confirmed using HRTEM. The real permittivity (ε\\) value shows two peaks in which the dielectric constant gradually increases up to a maximum value (εm) with the increase in temperature, and then it smoothly decreases, suggesting two phase transitions around 180 and 280 ◦ C. The measurements of the P–E hysteresis loop illustrated energy storage density of 124 mJ/cm3 and energy storage efficiency about 84% at room temperature. The glass sample shows superparaelectric behavior confirmed by the dielectric and P-E loop measurements. For high-energy storage applications, dipolar glasses have more outstanding potential than conventional ceramic dielectrics. Eventually, the glass matrix maintains high breakdown strength and can effectively stabilize nanocluster phases. So, we consider the present glass sample to be a good candidate for capacitive energy storage applications.

Polyimide dielectrics sandwiched by large-bandgap Al2O3 for high-temperature energy storage

High-temperature polymer dielectric capacitors are urgently needed in the new-generation electronic and electrical systems. Whereas, current commercial polymer represented by polyimide (PI) suffer from exponentially growing conduction loss at high temperatures and high electric fields, and hence extremely low discharged energy density and sharply declined charge-discharge efficiency. In this work, we developed superior Al2O3/PI/Al2O3 sandwich films with drastically improved capacitive energy storage performance via atomic layer deposition (ALD) technology. Notably, resultant PI hybrid dielectrics deposited by 130 nm-thickness Al2O3 (Al2O3/PI/Al2O3-130nm) exhibits the highest breakdown strength and the lowest leakage current density compared to pristine PI. Consequently, Al2O3/PI/Al2O3-130nm delivers a discharged energy density of 4.9 J/cm3 at 25 °C and 3.3 J/cm3 at 150 °C, as high as 2.7 times and 3.3 times respectively that of near PI film. Moreover, PI hybrid dielectrics can operate steadily under 200 MV/m and 150 °C during 10,000 cycle measurements. The excellent performance is mainly attributed to the improved barrier height of the electrode/PI interface endowed by deposited large-bandgap Al2O3.This work provides a scalable approach to enable excellent high-temperature energy storage performance of polymer dielectrics and promising to promote the application of PI for capacitive energy storage under harsh conditions.

The electromagnetic field of a circular parallel plate capacitor excited by an AC current and AC voltage supply

Abstract This study investigates the electromagnetic field (EMF) distribution of an ideal circular parallel plate capacitor excited by a time-harmonic power source. Considering the lead wire and capacitor as a charged whole, we formulate the boundary value problems of the Helmholtz equation for the EMF in the lead wire space and capacitor space, respectively. First, we solve for the EMF generated by the total current in the lead wire space of an AC current. Following this, we solve for the EMF boundary value problem of a capacitor filled with linear, uniform, isotropic, and non-magnetic lossy dielectric under an AC current excitation, using the continuity of the total current as a basis. Second, the EMF distributions in the capacitor space and the lead wire space under an AC voltage excitation are provided, following the principles of the generalized Helmholtz theorem. Third, the EMF distribution is discussed when the electromagnetic ‘standing-wave phenomenon’ occurs in the ideal dielectric capacitor, and identify the ‘resonance phenomenon’ and the ‘current-stopping phenomenon’ of the capacitor's EMF when excited by an AC current and AC voltage, respectively. We also present the corresponding ‘resonance frequency’ and ‘current-stopping frequency’. Finally, we explore the quasi-stable solution of the capacitor's EMF under low-frequency condition and the static solutions of the electric and magnetic fields under DC excitation and static voltage excitation. Our findings suggest that the existing formula for the capacitor's EMF approximates our analytical solution under quasi-stable condition.

Structural, Optical, Magnetic, and Dielectric Investigations of Pure and Co-Doped La0.67Sr0.33Mn1-x-yZnxCoyO3 Manganites with (0.00 &lt; x + y &lt; 0.20)

Here, we report the structural, optical, magnetic, and dielectric properties of La0.67Sr0.33Mn1-x-yZnxCoyO3 manganite with various x and y values (0.025 &lt; x + y &lt; 0.20). The pure and co-doped samples are called S1, S2, S3, S4, and S5, with (x + y) = 0.00, 0.025, 0.05, 0.10, and 0.20, respectively. The XRD confirmed a monoclinic structure for all the samples, such that the unit cell volume and the size of the crystallite and grain were generally decreased by increasing the co-doping content (x + y). The opposite was true for the behaviors of the porosity, the Debye temperature, and the elastic modulus. The energy gap Eg was 3.85 eV for S1, but it decreased to 3.82, 3.75, and 3.65 eV for S2, S5, and S3. Meanwhile, it increased and went to its maximum value of 3.95 eV for S4. The values of the single and dispersion energies (Eo, Ed) were 9.55 and 41.88 eV for S1, but they were decreased by co-doping. The samples exhibited paramagnetic behaviors at 300 K, but they showed ferromagnetic behaviors at 10 K. For both temperatures, the saturated magnetizations (Ms) were increased by increasing the co-doping content and they reached their maximum values of 1.27 and 15.08 (emu/g) for S4. At 300 K, the co-doping changed the magnetic material from hard to soft, but it changed from soft to hard at 10 K. In field cooling (FC), the samples showed diamagnetic regime behavior (M &lt; 0) below 80 K, but this behavior was completely absent for zero field cooling (ZFC). In parallel, co-doping of up to 0.10 (S4) decreased the dielectric constant, AC conductivity, and effective capacitance, whereas the electric modulus, impedance, and bulk resistance were increased. The analysis of the electric modulus showed the presence of relaxation peaks for all the samples. These outcomes show a good correlation between the different properties and indicate that co-doping of up to 0.10 of Zn and Co in place of Mn in La:113 compounds is beneficial for elastic deformation, optoelectronics, Li-batteries, and spintronic devices.

Excellent energy storage performance of multi-alternating-layer structured PMMA/PVDF dielectric composite at high-temperature

Polymer dielectric capacitors have high power density and are an integral component of electronic and power device. Currently, the limited energy density restricts their further application. In this research, a novel method was designed to optimize performance of PMMA/PVDF composite via an alternating stacked multi-layer structure. And, the five-alternating-layer of PVDF-PMMA-PVDF-PMMA-PVDF (F-A-F-A-F) composite has excellent dielectric properties, for instance, a better dielectric constant (4.52@1 kHz) and a low dielectric loss (0.034@1 kHz). The discharge energy density (Ue) of it is significantly larger than that of PMMA and PVDF. Particularly, the Ue of F-A-F-A-F composite is increased by 83.0 % (from 4.71 J/cm3 to 8.62 J/cm3) with charging-discharging efficiency of 60 % at 80 °C. Moreover, the F-A-F-A-F composite achieves an excellent stability after 40,000 cycles. This composite has a wide range of potential applications in the field of traditional dielectric capacitor due to its good energy storage performance and cycle stability.

Embedding Plate‐Like Pyrochlore in Perovskite Phase to Enhance Energy Storage Performance of BNT‐Based Ceramic Capacitors

AbstractNext‐generation electrical and electronic systems rely on the development of efficient energy‐storage dielectric ceramic capacitors. However, achieving a synergistic enhancement in the polarization and in the breakdown field strength (Eb) presents a considerable challenge. Herein, a heterogeneous combination strategy involving embedding a high Eb plate‐like pyrochlore phase in a high‐polarization perovskite phase is proposed. The embedded plate‐like pyrochlore increases the breakdown field strength and promotes the dynamic polarization response. Meanwhile, the strong spin–orbit coupling effect of the 5d electrons is conducive to the maintenance of the high polarization value of the perovskite. Consequently, the prepared multilayer ceramic capacitor (MLCC) exhibits an ultrahigh Eb and a high polarization. More specifically, an energy storage density (Wrec) of 14.9 J cm−3 with an efficiency of up to 93.4% is achieved for the optimized pyrochlore/perovskite phase. Furthermore, the MLCCs also exhibits an Wrec of ≈ 7.7 J cm−3 ± 4.5% in the temperature range of −50–180 °C. Therefore, this heterogeneous combination strategy therefore provides a simple and effective method for improving the energy‐storage performances of dielectric ceramic capacitors.

An investigation of the electrochemical characteristics of NiO-Co3O4/graphite/PVDF composites for the development of a supercapacitor with ultrahigh stability

Abstract Supercapacitors are a groundbreaking electrical energy storage technology that falls between batteries and dielectric capacitors which has undergone significant progress in recent years. Among the several elements influencing a supercapacitor’s capacitance, the choice of electrode materials plays a crucial role. Nanomaterials formed from transition metal oxides (TMOs) with incorporated 3D graphite are said to possess high capacitance, conductivity, increased active site area, distinct redox properties and several valence shells, making them an appropriate material for electrode synthesis. Therefore, in this study, three composites of NiO and Co3O4 are prepared in the ratio of 2:8, 3:7 and 4:6 using facile sol–gel method. To the prepared composites, graphite and PVDF are added in equal quantities. The resultant samples are characterized using XRD, SEM, FTIR and UV–vis spectroscopy. The samples are further integrated on an FTO electrode and subjected to CV, GCD and EIS for electrochemical study. The highest specific capacitance is obtained for NiO and Co3O4 composite in the ratio 3:7 and is equal to 156.66 F g−1 at a sweep rate of 10 mV s−1. This material is further subjected to a two-electrode study to check its feasibility to develop a symmetric solid-state device. It demonstrated a specific capacitance of 36 F g−1 with 100% capacitive retention.

Achieving an appropriate polarization-breakdown synergy of multilayer films for dielectric energy storage through temperature gradient annealing

Large polarization and high breakdown strength are the key to achieving an idea energy storage density in dielectric capacitors, but unfortunately the trade-off problem between them is difficult to evade, particularly for those dielectrics with different crystalline degrees. Herein, we propose an appropriate polarization-breakdown synergistic strategy of dielectric multilayer films through temperature gradient annealing. The dielectric properties of a serials of (Pb, La)(Zr, Ti)O3/SrTiO3/(Pb, La)(Zr, Ti)O3 (PLZT/STO/PLZT) structures with different annealing temperature for each layer are compared. The optimum recoverable energy density of 57.9 J/cm3 is achieved at a high breakdown electric field of 5.78 MV/cm and a moderate maximum polarization of 22.5 μC/cm2. In addition to the role of suppressing the carriers transport of interlayer STO, the balance between polarization and breakdown strength in bottom and top PLZT layers with individual dielectric characteristics should be responsible for the enhanced energy storage performance (ESP). The results suggest that it is a feasible way to optimize the ESP of dielectric multilayer films through designing different stacking layer via temperature gradient annealing heat treatment.

Optimized energy storage performance of Bi0.5Na0.5TiO3 ceramic through incorporation of Ca(Nb0.5Al0.5)O3

Dielectric capacitors, because of their rapid charging-discharging capabilities and high power density, are indispensable in advanced cutting-edge pulsed power systems and electronic components. However, they typically exhibit lower energy densities compared to other energy storage systems likely batteries and fuel cells. Herein, we propose a novel approach for optimizing the energy storage performance of Bi0.39Na0.36Sr0.25TiO3 (BNST) ceramic through the modification effects of Ca(Nb0.5Al0.5)O3 (CAN). The incorporation of CAN could concurrently achieve a maximum polarization Pmax and breakdown strength. Consequently, the BNST-0.2CAN ceramic achieves a high recoverable energy density (Wrec) ∼ 6.02 J/cm3 accompany with efficiency (η) close to 90 % at 580 kV/cm. This composition also exhibits exceptional frequency stability from 1 Hz to 200 Hz, robust temperature stability from 25 °C to 200 °C, and outstanding cyclic stability exceeding 104 cycles. This work offers a promising pathway to improve the energy storage performance for application in advanced dielectric capacitors.

Enhanced energy storage performance of temperature-stable X8R ceramics with core-shell microstructure

0.8BaTiO3-0.2(K0.5Bi0.5)TiO3-xNb2O5 (0.8BT-0.2KBT-xNb) lead-free ceramics were fabricated using a solid-state processing method. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) area scanning revealed a core-shell microstructure in the x=0.015 ceramics, featuring a BaTiO3-rich core containing nanodomains (8-30 nm in width) surrounded by a doped BaTiO3-rich shell harboring polar nanoregions (1-2 nm). Optimization of the dielectric temperature stability was achieved via enhanced dielectric relaxation and the presence of a core-shell microstructure with varying polarization levels. Specifically, ceramics with a Nb2O5 content of 0.015 demonstrated the ability to meet the temperature variation requirements of X8R (-55 to 150 °C, △C/C25 °C =±15% or less, as defined by the Electronics Industry Alliance) with a minimal dielectric loss of 0.012, a high dielectric constant of 1794, and a medium sintering temperature of 1150 °C. Additionally, the ultrafine grain size and core-shell microstructure enhanced the breakdown strength. Notably, the 0.8BT-0.2KBT-0.015Nb ceramic exhibited a high recoverable energy density of approximately 2.424 J/cm3 and an exceptional energy storage efficiency of 83.4%. Furthermore, Nb2O5-modified BaTiO3–(K0.5Bi0.5)TiO3 ceramics demonstrated outstanding frequency stability under an electric field of 100 kV/cm. Advanced energy storage properties with fast discharge features (τ0.9=26ns), notable thermal stability across a wide temperature range (20–120 °C) were demonstrated in the 0.8BT-0.2KBT-0.015Nb composite ceramic. This ceramic with a core-shell microstructure could be a potential material for high-efficiency dielectrics in energy-storing pulse-power capacitors.