Ceramic Capacitors Research Articles

Understanding local physical properties of barium titanate ceramics depending on the synthesis conditions assisted by a machine learning algorithm

Barium titanate (BT) is widely used in electronic components, such as multilayer ceramic capacitors, owing to its high dielectric constant and piezoelectricity. The continuously increasing demand for more efficient devices has led to the development of smaller and more efficient BT ceramics by controlling the synthesis conditions. However, despite the decrease in size of BT grains to the nanoscale, the physical properties of BT ceramics have mostly been investigated on a macroscopic scale. In this study, we investigated the effects of synthesis conditions on local physical properties such as surface roughness, leakage current, and domain structure/switching using atomic force microscopy. We further applied machine learning analysis to effectively understand the effects of synthesis conditions on these physical properties; the analysis not only provides local information on BT ceramics but also a comprehensive understanding of their physical properties.

Prominent energy storage density and efficiency of Na0.5Bi0.5TiO3‐based ceramics via multiscale amelioration strategy

AbstractEco‐friendly ceramic capacitors gradually become an important section of pulsed power devices. However, the synchronous realization of ultra‐high energy storage density (Wrec > 6 J/cm3) and efficiency (η > 90%) is difficult. Thus, a novel multiscale amelioration strategy in Na0.5Bi0.5TiO3‐based ceramics is proposed to achieve ultra‐high energy storage density and efficiency. The multiscale amelioration strategy for (Na0.5Bi0.47La0.03)0.94Ba0.06TiO3 (NBLBT) ceramic focuses on grain size, bandgap width, and dielectric relaxor behavior, which can be regulated by introducing Sr(Al0.5Nb0.25Ta0.25)O3 (SANT). On the one hand, the refined grain size and increased bandgap width are conducive to improving the breakdown strength. On the other hand, the optimized dielectric relaxation behavior is beneficial to suppress the remanent polarization. Accordingly, an ultrahigh Wrec = 6.89 J/cm3 and η = 90.1% are simultaneously achieved in 0.84NBLBT‐ 0.16SANT ceramic. In addition, the sample synchronously possesses excellent thermal and frequency stability (a variation within 5% in Wrec and η), transient discharge rate of t0.9 ∼ 78.8 ns and a high‐power density of PD ∼ 114.5 MW/cm3. This study provides an effective strategy to further develop pulsed power devices.

Using highly accelerated life test to study insulation reliability of multi-layer ceramic capacitors sintered at different temperatures

With the developments of the electronic industry, efforts to achieve high DC insulating reliability are underway to improve the mean time to failure (MTTF) of multilayer ceramic capacitors (MLCCs). However, there are few studies on appropriate measuring methods to evaluate their different reliability characteristics quantificationally. This study measured different reliability characteristics of BaTiO3-based multilayer ceramic capacitors sintered at three different temperatures with highly accelerated life tests (HALTs). Kaplan–Meier survival analysis, two-parameter Weibull fitting, and a new method using a stud genetic algorithm were used to calculate their MTTF in HALT conditions, and the comparison among them was carried out to select a proper fitting way. With the appropriate method, their MTTF at the rated condition was predicted and compared. Their conduction modes were also differentiated to explain their aging sensitivities to temperature and voltage. As a result, a proper way to evaluate the sample’s reliability characteristics with a bathtub curve was established, and the best sintering temperature for capacitance that is also the best for reliability at the rated condition was confirmed. Meanwhile, different conducting models of MLCCs were also proved to be related to their insulation stability.

Improvement of high‐temperature energy storage properties of polyimide‐based nanocomposites with sandwich structure

AbstractThe demand for dielectric materials that have high energy and power density properties, and are operational at high temperature has increased with the advancement in new energy technology, high‐end microelectronics, and other industries. Pure ceramic and polymer capacitors are not enough to meet the ever increasing energy requirements in a wide range of applications. In this article, we report a sandwich structure nanocomposite film based on polyimide (PI) with high breakdown strength SiO2/PI as the outer layers and high dielectric constant strontium titanate (SrTiO3)/PI as the sandwich layer. The results showed that the prepared composites can obtain high energy storage density and low dielectric loss at high temperatures. The composites achieved an energy storage density of 5.5 J cm−3 and a dielectric loss of 0.004 at a temperature of 150°C when the filling amount of SrTiO3 was 0.5 vol% and the filling amount of SiO2 was 3 vol%. This work shows that the composites are promising dielectrics for applications at high temperature and provides a new idea for high‐temperature energy storage devices.

Time Dependence of Kinetic Unmixing and Kinetic Decomposition of a Perovskite ABO3 under Applied Voltage—A Case Study for BaTiO3

AbstractIn multinary oxides such as perovskites ABO3, an applied voltage causes charged mobile species (ions, electrons) to move according to their electrochemical mobilities. For different electrochemical mobilities of the cations kinetic unmixing takes place, and after some time even kinetic decomposition may occur. Both kinetic effects are detrimental to the functional application of the oxide, for example, in electrochemical cells or in multilayer ceramic capacitors. Thus far, kinetic unmixing and decomposition are analyzed by treating ABO3 only as a quasi‐binary mixture of AO and BO2, acceptors are not considered, and only the steady state of kinetic unmixing is investigated, allowing no prediction of the lifetime until kinetic decomposition. Here, ABO3 is treated as a really ternary system with defects in all three sublattices and with electronic defects. The complete set of transport equations is derived, and the moving boundary problem with six mobile species is solved numerically to investigate the time‐dependence of kinetic unmixing. As a case study, BaTiO3 is used which has various applications as a functional oxide. The simulations yield the kinetic decomposition voltage of the oxide, below which no kinetic decomposition occurs. For voltages larger than this critical value the lifetime of the oxide until kinetic decomposition is predicted.

The effect of A-site Mg substitution on energy-storage density and efficiency of Bi0.47Na0.47Ba0.06TiO3 ceramics by disordered induction

Lead-free dielectric ceramic capacitors are extensively studied for their environmental protection and excellent electrical properties. In this study, (1-x) Bi0.47Na0.47Ba0.06 TiO3-xMgTiO3 was synthesized by the classical solid-phase method. Perovskite materials usually have a complex structure, and the modification of the A-site and B-site doping can have a wonderful effect on the material. The effect of A-site Mg2+ doping on the phase structure and electrical properties of (1-x)BNBT-xMT was studied. Results showed that a wider optical band gap and a higher grain boundary density can be obtained by doping at the A-site, which greatly improved the breakdown electric field of the ceramics. X-ray diffraction, Raman scattering, transmission electron microscopy, and dielectric constant curves of (1-x)BNBT-xMT ceramics were also performed to characterize the transition between rhombohedral and tetragonal phases. The findings indicated that that doping at the A-site successfully induced the polar nanoregion, and the 0.94Bi0.47Na0.47Ba0.06TiO3-0.06MgTiO3 relaxation ferroelectric ceramics had high Wrec (5.82 J/cm3), stable frequency (Wrec = 2.53 J/cm3±3 %, 1–200 Hz), excellent temperature stability (Wrec≈2.37 ± 3 % J/cm3, 30–100 °C), and fast discharge rate (4μs). This work can provide ideas for the development of green and harmless dielectric capacitors with high charge/discharge rate and high energy-storage density.

Modified (Ba,Sr)(Sn,Ti)O3 via hydrothermal synthesis for electrocaloric application

Electrocaloric cooling systems require components with large entropy change at the desired working temperature, high electric breakdown strength and low dielectric losses. We here report on hydrothermal synthesis (HTS) route for preparation of lead-free electrocaloric (EC) material Ba0.82Sr0.18Sn0.065Ti0.935O3 (BSSnT-18-6.5) with a median particle size of d50 = 150 nm. Influence of molar ratio (Ba,Sr):(Sn,Ti) on the purity and particle size of hydrothermally synthesized powders is investigated. The sintering behavior and the resulting microstructure of bulk ceramic samples prepared with HTS powders as well as their dielectric, ferroelectric, and electrocaloric properties are analyzed and discussed in detail. By using HTS powders we could significantly reduce sintering temperature from 1400 °C to 1275 °C. Samples prepared with a molar ratio (Ba,Sr):(Sn,Ti) of 1.6 show a maximum EC temperature change |ΔTEC| of 0.59 K around 30 °C with a broad peak of |ΔTEC| > 0.3 K in the temperature range from 5 °C to 65 °C under an applied electric field change of 5 V μm−1. Our results show that hydrothermal synthesis is well suited to produce starting powders of lead-free electrocaloric materials for future fabrication of multilayer ceramic (MLC) components.

Improving energy storage performance of BLLMT ceramic by doping BZT combining with defect engineering and film scraping process

The (1-x)(Ba0.94Li0.02La0.04)(Mg0.04Ti0.96)O3-xBi(Zn1/2Ti1/2)O3 ((1-x)BLLMT-xBZT, x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) ceramic thick films were prepared by traditional solid-state sintering method combined with film scraping process. Li+ and La3+ ions doping at A-site, and Mg2+ and Zn2+ ions doping at B-site of the perovskite structure, and adding BZT component enhance charge compensation, enlarge polarization difference, increase breakdown strength, and enhance relaxation degree, leading to the improved pulse charging and discharging energy storage performance of the BaTiO3-based ceramic films. The 0.92BLLMT-0.08BZT ceramic film has high discharge energy density of 4.61 J/cm3, high pulse power density PD = 224.14 MW/cm3, high current density CD = 896.58 A/cm2, high discharge speed of 234 ns, and high pulse discharge density Wd = 4.61 J/cm3 under 500 kV/cm combined with high breakdown strength of 500 kV/cm, relating to charge compensation, multiple ferroelectric phases coexistence, and formation of polar nanoregions. The strategy by equivalent and heterovalent ions doping at A-site and B-site of the perovskite structure and introducing Bi-based component combined with film scraping process strengthens charge compensation, enhances relaxation characteristic, and reduces grain size, providing an efficient route to develop prospect BT-based dielectric ceramic capacitors for potential application in high-power pulse energy storage such as 0.92BLLMT-0.08BZT.

Impact of synthesis route on the microstructure and energy-storage properties of (Bi1/2K1/2)TiO3–SrTiO3 relaxor ferroelectric ceramics: Solid-state and hydrothermal approaches

Bismuth potassium titanate (Bi1/2K1/2)TiO3-based relaxor ferroelectrics are promising materials for high-energy-density ceramic capacitors. Herein, we compare the microstructure and energy-storage properties of (Bi1/2K1/2)0.5Sr0.5TiO3 (BKST50) ceramics fabricated via two different routes: solid-state and hydrothermal reactions. A BKST50 fine powder composed of well-dispersed cubic nanoparticles was obtained via the hydrothermal reaction, whereas the conventional solid-state reaction resulted in the aggregation of primary particles. The grain size of the ceramics prepared from the hydrothermal powder could be controlled between 273 ± 24 and 936 ± 69 nm while maintaining a relative density of over 95% by simply varying the sintering temperature. On the other hand, ceramics prepared via the solid-state reaction could not be fully densified even at 1200°C (the highest tested sintering temperature). The hydrothermally derived ceramics withstood higher electric field owing to dense and fine-grained microstructure, leading to a high recoverable energy-storage density of 2.25 J cm−3 at 240 kV cm−1.

Analysis, Design, and Experimental Assessment of a High Power Density Ceramic DC-Link Capacitor for a 800 V 550 kVA Electric Vehicle Drive Inverter

Analysis, Design, and Experimental Assessment of a High Power Density Ceramic DC-Link Capacitor for a 800 V 550 kVA Electric Vehicle Drive Inverter

Prototyping Na0.5Bi0.5TiO3-based multilayer ceramic capacitors for high-temperature and power electronics

Prototyping Na0.5Bi0.5TiO3-based multilayer ceramic capacitors for high-temperature and power electronics

Loss Characterization and Modeling of Class II Multilayer Ceramic Capacitors: A Synergistic Material-Microstructure-Device Approach

Loss Characterization and Modeling of Class II Multilayer Ceramic Capacitors: A Synergistic Material-Microstructure-Device Approach

Enhanced dielectric properties and improved thermal stability in TiO2-based ceramics by Cu and Nb co-doping

TiO2-based ceramics have application potential in multilayer ceramic capacitors because of its large dielectric constant and low dielectric loss. In this work, Cu2+, Nb5+ co-doped TiO2 ceramics (CNTO) with colossal permittivity and low loss were designed and prepared via an oxide mixed method, and the effect of Cu2+, Nb5+ co-doped amount on dielectric properties were systematically investigated. Remarkably, the compositions of (Cu1/3Nb2/3)0.005Ti0.995O2 and (Cu1/3Nb2/3)0.01Ti0.99O2 exhibit large dielectric permittivity (εr) of ∼27,060 and ∼41,200 accompanied with low dielectric loss (tan δ) of ∼0.011 and ∼0.032 at 1 kHz, respectively. Based on dielectric properties, relaxation behavior assessments and X-ray photoelectron spectroscopy analysis, we confirmed that the high dielectric permittivity of CNTO ceramics mainly originates from the electron-pinned defect-dipole (EPDD) effect. Moreover, the temperature stability value of εr keeps stable of ±7.5% at 1 kHz from −200 to 200 °C for (Cu1/3Nb2/3)0.005Ti0.995O2 and from 10 to 200 °C for (Cu1/3Nb2/3)0.01Ti0.99O2 ceramics, which separately meet the X9F and Z9F capacitor requirements, respectively. The findings presented in this work might have important strategic significance for promoting the miniaturization of electronic components.

Boosting energy storage performance in negative temperature coefficient linear-like dielectrics via composite modulation in the superparaelectric state

Developing dielectric ceramics with both negative temperature coefficient of capacitance (NTCC) and excellent energy storage performance is beneficial to obtain multifunctional dielectric ceramic capacitors. An effective strategy of composite modulation in the superparaelectric (SPE) state is proposed in BaTiO3-BaZrO3-CaTiO3 (BT-BZ-CT) system to achieve the above two points. The simultaneous addition of BZ and CT to BT ferroelectrics can move the SPE state to the normal use temperature zone and the NTCC characteristic with enhanced energy storage performance can be obtained; and the intentional precipitation of CT at grain boundaries can refine the grain size, increase the bandgap, and strengthen the local electric field distribution as well, thus enhancing the breakdown electric field (Eb). Benefiting from these features, EIA class I-R3L code NTCC together with a high Wrec (∼3.46 J/cm3) and η (90.8%) were achieved in 20BT-40BZ-40CT system, providing a paradigm for building NTCC dielectric materials with high energy-storage performance.

Sinterability of sodium bismuth titanate-based electroceramics at low temperatures

The demand for robust multilayer ceramic capacitors with high-temperature and high-power capabilities is surging. Cost-effective production is a key challenge, often linked to precious metal electrodes like Pt, Pd, and Ag in multilayer ceramic capacitors (MLCCs). To address this, cost-efficient base metal electrodes such as Cu and Ni are sought. Promising lead-free options are Na0.5Bi0.5TiO3 (NBT)-based materials. However, their sintering temperatures exceed Cu's melting point (1085 °C), necessitating sintering aids for compatibility. We investigated several low-temperature sintering aids (Li2O, Na2O, Bi2O3, B2O3, ZnO, and V2O5) to lower the sintering temperature of Na0.5Bi0.5TiO3-BaTiO3-CaZrO3-BiAlO3 solid solutions. Results reveal NBT-based materials' sensitivity to acceptor dopant incorporation from sintering aids, impacting electrical properties. Yet, we successfully reduced the sintering temperature to 975 °C, suitable for Cu co-sintering, with minimal adverse effects on capacitor properties using well-tuned sintering aids.

High recoverable energy density of Na0.5Bi0.5TiO3-based ceramics by multi-scale insulation regulation and relaxor optimization strategy

Dielectric ceramic capacitors (DCCs) are highly desired for advanced electronic and electrical power systems owing to their ultrahigh power densities and fast charge-discharge speed. However, the low recoverable energy density (Wrec) of dielectric ceramic resulting from the low Weibull breakdown strength (Eb) has been a long-standing challenge. Here, we fabricated 0.8Na0.5Bi0.5TiO3–0.2Sm1/3Sr1/2(Mg1/3Nb2/3)O3 (0.8NBT–0.2SSMN) relaxor ferroelectric (RFE) ceramics display a greatly improved Eb of 480 kV/cm and largely enhanced Wrec of 7.3 J/cm3, far outperforming pure NBT ceramic. We demonstrate that the proposed multi-scale insulation regulation strategy via introducing SSMN with optimal content can effectively reduce grain sizes, increase the bandgap, and create a highly insulating second phase, leading to a high Eb. Additionally, the introduction of Sm3+ and Mg2+–Nb5+ dopants on the A/B-sites of the Na0.5Bi0.5TiO3 lattice created disruptions in the long-range-ordered ferroelectric domains, leading to excellent RFE property. The high Eb and excellent RFE property led to the substantial improvement of Wrec. Else, an exceptional thermal stability of Wrec and efficiency (η) are obtained at 25–200 °C (Wrec ∼ (1.77 ± 0.08) J/cm3, η ∼ 82.9% ± 4.3%). This work offers a route for designing high energy storage performance relaxor ferroelectric ceramics for high-voltage dielectric ceramic capacitors.

Enhancement of Energy-Storage Properties and Temperature Stability in Complex Perovskite (1−x)NaNbO3−xBi(Li1/3Sn2/3)O3 Lead-Free Ceramics

In general, NaNbO3 (NN) ceramics are considered to be one of the most promising lead-free perovskites (AFE) materials with low cost, low density, and nontoxic advantages. However, the energy storage capability of this material is often greatly hindered by the hysteresis exhibited during the transition from the antiferroelectric to the ferroelectric phase. In this study, lead-free dielectric (1−x)NaNbO3−xBi(Li1/3Sn2/3)O3, x = 0.0 − 0.08, ceramics were synthesized by solid-state reaction method. The XRD data show a structural change from orthorhombic to pseudo-cubic at x = 0.06 composition. With increasing Bi(Li1/3Sn2/3)O3 content, changes in dielectric properties demonstrated that the AFE P phase was successively replaced by the relaxor AFE R phase, resulting in a thin P–E loop characteristic which leads to the improvement of the energy storage density and efficiency of the ceramic capacitors. The optimum recoverable energy storage density (W rec = 0.56 J/cm3) and efficiency (η = 74%) were obtained at x = 0.06 under an electric field of 120 kV/cm. The optimum composition also exhibited temperature stability in the range of 25 °C–100 °C. In addition, an increase in Bi(Li1/3Sn2/3)O3 content can lead to a decrease in leakage current density. This research shows that BLS modified NN ceramics are promising dielectric material candidates for energy storage applications.

Effect of ferrite phase addition on Pb-Free multiferroic composite material for energy storage applications

Bulk composite ceramics exhibit promising potential as energy storage materials due to their strong ferroelectric characteristics. To lessen the use harmful Pb based material, multiferroic composite combining ferrite and perovskite ceramics with piezoelectric and ferroelectric traits, have gained prominence for high-efficiency energy systems such as ceramic capacitor. This study focuses on a dual-phase multiferroic ceramic composite, following the formula (1-x) Ba0.77Ca0.23TiO3 + xNi0.6Zn0.25La0.15Fe2O4 (x = 0.0, 0.1, 0.2, and 0.3), prepared via a solid-state reaction process. XRD analysis confirms the presence of cubic perovskite (BaTiO3) and cubic spinel ferrite (NZLFO) phases. SEM images depict uniform microstructures with sporadic pore formations, which decreased in grain size with ferrite addition. The P-E loops reveal relaxor ferroelectric behavior with near-zero remnant polarization (Pr), indicating its suitability as an energy storage medium. The highest energy density efficiency, approximately 54 %, was achieved at x = 0.1. The addition of more than 10 % ferrite significantly affects both the microstructure and energy storage properties.

Antiferroelectric ceramic capacitors with high energy-storage densities and reduced sintering temperature

Field-driven transition from antiferroelectric (AFE) to ferroelectric (FE) states has gained extensive attention for microelectronics and energy storage applications. High dielectric-breakdown-strength (DBDS) for a given material is a necessity to attain full capacity of electrical energy storage. An approach to increasing energy performances is to modulate the related materials to own a higher phase transition electric field (EFE-AFE) using elemental dopants. In this case, Cd2+ was selected as the dopant at A-site in the Pb0.97La0.02Zr0.50Sn0.45Ti0.05O3 ceramics to tailor this EFE-AFE value due to the ionic difference enhanced antiferroelectricity. Surprisingly, the doped ceramics increased EFE-AFE by half, DBDS by 16 %, and maintained energy storage efficiency η of over 85 %, providing a way to improve energy storage density. It is worth mentioning that while the performance has been improved, the sintering temperature has been reduced by 170 °C. At the same time, the ceramics maintain good temperature stability, extremely fast discharging speed and discharging energy storage density, indicative of a promising choice in pulse power devices.

Microstructure, physical and mechanical properties of dental polychromic multilayer zirconia of uniform composition.

The present study aimed to compare the microstructure, physical, and mechanical properties of three commercially available dental polychromatic multilayer zirconia materials of uniform composition: Dima Mill Zirconia ML, VITA YZ/ST Multicolor, and VITA YZ/XT Multicolor (with 3, 4, and 5mol% Y2 O3 , respectively); thus, the influence of Y2 O3 content on the above properties of the produced materials was experimentally studied. Homogeneous zirconia ceramics with a dense micro- and nanostructure, without pores or defects, were produced after milling the blocks and sintering, which resulted in yttrium-stabilized tetragonal and cubic zirconia. Statistical analysis of the results of measurable magnitudes was performed by the one-way ANOVA test. The increase of Y2 O3 content (from 3 to 5mol%) favored larger grain and crystallite sizes and a decrease of the values of the mechanical properties; yet, the differences were statistically insignificant. Clinically, these differences are expected to have no impact on their function in the oral cavity, both in terms of their fracture propensity and the damage that can be caused to the opposing teeth. Accordingly, the experimental results qualify the polychromic multilayer zirconia ceramics of uniform composition fabricated by milling technology for use in dental restorations.