Multilayer Capacitors Research Articles

Dimensioning and Realization of an LTCC Multilayer Capacitor for Energy Conversion

In this paper, we present the dimensioning as well as the thermal and electrostatic modelling of a multilayer capacitor low-temperature co-fired ceramic (LTCC) to insert it in a Buck converter. We also present the different stages of the realization of the LTCC capacitor. Our aims are volume and weight reduction, good frequency behaviour, low values of the series inductance and series resistance, and small ripples of the output voltage. The results obtained after the realization are satisfactory and encouraging, with a 92% reduction in volume and 99% in the surface area. To validate the correct operation of the capacitor, we used the PSIM simulation software to compare the voltage and current waveforms of the outputs of the Buck converter with a perfect capacitor and others with LTCC capacitor. COMSOL multiphysics simulation software allowed us to determine the operating temperature of the LTCC capacitor and to validate its electrostatic behaviour (distribution of electrical potential, of electrical field and electrical current density). The multilayer capacitor is manufactured in the LAPLACE laboratory at Paul Sabatier University.

Enhanced Energy Storage Performance of Lead-Free Capacitors in an Ultrawide Temperature Range via Engineering Paraferroelectric and Relaxor Ferroelectric Multilayer Films.

Industry has been seeking a thin-film capacitor that can work at high temperature in a harsh environment, where cooling systems are not desired. Up to now, the working temperature of the thin-film capacitor is still limited up to 200 °C. Herein, we design a multilayer structure with layers of paraferroelectric (Ba0.3Sr0.7TiO3, BST) and relaxor ferroelectric (0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3, BT-BMZ) to realize optimum properties with a flat platform of dielectric constant and high breakdown strength for excellent energy storage performance at high temperature. Through optimizing the multilayer structure, a highly stable relaxor ferroelectric state is obtained for the BST/BT-BMZ multilayer thin-film capacitor with a total thickness of 230 nm, a period number N = 8, and a layer thickness ratio of BST/BT-BMZ = 3/7. The optimized multilayer film shows significantly improved energy storage density (up to 30.64 J/cm3) and energy storage efficiency (over 70.93%) in an ultrawide temperature range from room temperature to 250 °C. Moreover, the multilayer system also exhibits excellent thermal stability in such an ultrawide temperature range with a change of 5.15 and 12.75% for the recoverable energy density and energy storage efficiency, respectively. Our results demonstrate that the designed thin-film capacitor is promising for the application in a harsh environment and open a way to tailor a thin-film capacitor toward higher working temperature with enhanced energy storage performance.

Impacts of density of deposited dielectric films on temperature dependence of interface dipole layer strength in multilayered dielectric capacitors for energy harvesting

We have proposed and successfully demonstrated the operation principle of the energy harvesting method with multi-dielectric layer capacitors in a temperature fluctuating environment, and showed that the temperature coefficient of the flat-band voltage (VFB) is one of the important factors to enhance its efficiency. Next, we investigated the impact of densities of both SiO2 and Al2O3 deposited films on measurement temperature dependence of the Al2O3/SiO2 interface dipole layer strength. A positive temperature coefficient of dipole layer strength was pronounced only when SiO2 was grown at a high temperature and Al2O3 was annealed at low temperature. It was suggested that both oxides were required to have a lower density for the positive temperature coefficient. These results indicate a guideline to control the temperature coefficient of dipole layer strength of a Al2O3/SiO2/Al2O3/SiO2··· multilayer stack, which is one of the important factors to determine the efficiency of the proposed energy harvesting method.

Heat flow in electrocaloric multilayer capacitors

Abstract Multilayer capacitors (MLCs) represent promising electrocaloric (EC) cooling elements because they operate at low voltages, they possess large breakdown fields, they contain inner electrodes that facilitate heat transfer, and they exhibit a macroscopic volume of active EC material. However, almost ten years after they were first suggested as EC elements, the internal heat flow has not been well studied. In this paper, we use an infrared camera to investigate heat flow within representative MLCs of Pb(Mg,Nb)O3, and we achieve good agreement with the results of finite element modelling (FEM) by identifying for the inner electrodes an effective thermal conductivity that represents the limiting factor for heat flow. Increasing the inner electrode thickness by a factor of five would increase heat flow by a factor of 2.6. Our work therefore shows that FEM can play an important role in MLC design for EC applications.

Boosted energy-storage efficiency by controlling conduction loss of multilayered polymeric capacitors

Among the organic dielectrics, polyvinylidene fluoride PVDF-based polymers present the highest level of polarizability with permittivity >35. Nonetheless, their applications in advanced electronics and industrial uses are limited by significant leakage current under high voltage, which is considered the principal cause of device energy consumption and short lifetime. Therefore, the main objective of this paper was to focus on alternative capacitor structure-based polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (PVDF-TrFE-CTFE) terpolymers to efficiently limit the leakage current and lead to enhanced electrical breakdown with negligible degradation of polarization level. The novel bilayer capacitor was constructed by depositing a thin barrier layer of high polar PVDF-HFP copolymer on the terpolymer via a rapid solution-casting technique. The relationship between leakage current, dielectric strength and conduction mechanisms was investigated. Implementation of such a barrier layer led to a significant reduction (70%) in leakage current and ferroelectric losses (approximately 90%), thus boosting the performance of multilayered material up to 50% of enhanced energy-storage efficiency. Experimental results are very promising, allowing to confirm that combining both terpolymer and copolymer in a hybrid multilayer design makes a possibility to achieve the best compromise in terms of energy efficiency, dielectric properties, and breakdown strength.

Relaxation dynamics, conductivity and electrical study of a lead free perovskite

The present investigation is detailed study of structural, dielectric and transport properties of revived lead free perovskite family. The structural analysis reveals material is single phase belonging to orthorhombic crystal system. Dielectric and impedance spectroscopy material confirms material has high dielectric constant with relatively low loss which can be useful for multi-layer capacitor and other energy storage devices. The transport properties of the material reveals conductions in the material are due to localized hopping of charge carriers as well as other defects or vacancies present in the sample.

Radiation resistance of nanolayered silicon nitride capacitors

Single-layered and multi-layered 20–60 nm thick silicon nitride (Si3N4) dielectric nanofilms were fabricated using a low-pressure chemical vapour deposition (LPCVD) method. The X-ray photoelectron spectroscopy (XPS) confirmed less oxygen content in the multi-layered nanofilms. The capacitors with Si3N4 multilayer demonstrated a tendency to a higher breakdown voltage compared to the capacitors with Si3N4 single layer. Si3N4 nanofilms and capacitors with Si3N4 dielectric were exposed to 1 kGy dose of gamma photons. Fourier transform infrared (FTIR) spectroscopy analysis showed that no modifications of the chemical bonds of Si3N4 were present after irradiation. Also, gamma irradiation did not influence the breakdown voltage of the capacitors but decreased their capacitance measured at 1 MHz frequency. However, the multi-layered capacitors were not affected by radiation more than the single-layered capacitors. These findings suggest a promising process to fabricate nano-scaled multi-layered Si3N4 capacitors with improved breakdown voltage characteristics and resistance to ionizing radiation.

CONDENSER STRUCTURES BASED ON BARIUM TITANATE FILMS FORMED BY SOL-GEL METHOD

The objective of the work is investigation the dielectric permittivity and dielectric loss tangent of BaTiO3 films in a capacitor structure formed by sol – gel method on a Si/TiOx/Pt substrate. The basis of this capacitor is a four-layer film of barium titanate xerogel with a thickness of about 200 nm. The film was synthesized by sol-gel method at a final annealing temperature 750 °C. The problems related to the development of method of forming multilayer capacitor structures, the analysis of the morphology and phase composition of BaTiO3 film, and also the measurement of the capacitance-voltage characteristics in the frequency range 10 kHz – 2 MHz have been solved. Morphology of the films was analyzed using a Hitachi S-4800 scanning electron microscope. X-ray diffraction spectra was recorded using a DRON-3 automated diffractometer, using monochromatic CuKα radiation. Capacitance-voltage characteristics were obtained using a B1500A semiconductor analyzer. Dielectric constant and dielectric loss tangent, calculated for capacitance measurements, are changed as follows: for a bias voltage of U = 0 V, the change in ε is 232–214, and tanδ 0.022–0.16, and for a bias voltage of U = 10 V, ε occurs in the range 135–124 and tanδ from 0.02 to 0.1. The obtained frequency dependences of the dielectric constant of BaTiO3 films show a decrease in the dielectric constant in the range of 10 kHz – 2 MHz. It was found that, with a BaTiO3 film thickness of less than 100 nm, a thin-film capacitor with a lower platinum electrode is not always formed, which is probably caused by shunting of the structure.

Energy-storage properties of low-temperature Co-fired BNT-ST/AgPd multilayer lead-free ceramic capacitors

A lead-free 0.6Bi0.5Na0.5TiO3-0.4SrTiO3 ceramic doped with Nb2O5, CuO and MnO2 additives (BNSr0.4TNbxCu0.8Mn0.15) was synthesized at a relatively low firing temperature of 1050 °C. Using this composition, multilayer ceramic capacitors with AgPd inner electrodes were successfully prepared by a tape-casting method for energy storage applications. Due to the high polarization Pmax and low hysteresis, the largest recoverable energy storage density Wrec value of 1.9 J/cc and high efficiency η of 89% were obtained in the BNSr0.4TNb2.5Cu0.8Mn0.15 composition under a low electric field of 170 kV/cm. The multilayer BNSr0.4TNb2.5Cu0.8Mn0.15/Ag75Pd25 capacitors contain 30 active layers, in which the thickness of a single ceramic layer was approximately 27 μm. Under a low electric field of 270 kV/cm, excellent energy storage performance was observed in multilayer capacitors, with a Wrec of 2.83 J/cc and η of 85%. The capacitors demonstrate the temperature insensitive properties that the variation in Wrec was less than 5% between 25 °C and 100 °C. These results indicate that this ceramic capacitor is a promising candidate for lead-free energy storage applications.

Multifunctional character of revived double perovskite for device applications

The materials having multifunctional behavior are in the form of single crystal or poly crystalline. The present reports belong to polycrystalline samples of lead reducing double perovskite vanadates of Pb2-xSrxBiVO6 (0.5 ≤ x ≤ 1.5) oxide ceramics. To synthesize the present samples cost effective solid solution casting technique has been adopted. Their formation, density, phase identification as well as purity were verified through X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Fourier transmission Infra-red (FTIR) and RAMAN spectroscopy. The optical properties of the materials have been investigated by utilizing room temperature UV–Vis and photo luminescence (PL) spectroscopic analysis. It is observed the band gap of the materials were found to be in the range of 2.68–2.23eV from UV–Vis study which suggest materials can be useful for photo catalytic devices whereas PL emission spectra confirms they are may be useful as blue white LED devices. Presence of ferroelectricity in the materials was confirmed from dielectric as well as polarization study which allows their utility for multi-layer capacitor and memory devices. Transport and leakage characteristics of the materials were studied from loss tangent, impedance spectroscopy as well as modulus spectroscopy recorded at different conditions of frequency and temperature which may be useful for microelectronics.

A review on the development of lead-free ferroelectric energy-storage ceramics and multilayer capacitors

Typical lead-free energy storage systems and their performances for dielectric and multilayer capacitors over the last decade.

Fatigue resistant lead-free multilayer ceramic capacitors with ultrahigh energy density

Electrical homogeneity is vital in optimising energy storage performance in BiFeO3–BaTiO3–xBi(Li0.5Nb0.5)O3 ceramic multilayer capacitors, giving rise to high recoverable energy density ∼13.8 J cm−3 under electric field ∼950 kV cm−1 and fatigue resistance behaviour.

Interface modulation in multi-layered BaTiO3 nanofibers/PVDF using the PVP linker layer as an adhesive for high energy density capacitor applications

In this work, we have studied the role of a linker across the interface in a multi-layered polymer nanocomposite-based capacitor using barium titanate (BT) nanofibers (NFs) as nanofillers and polyvinylidene fluoride (PVDF) as the polymer matrix.

Una nueva topología de bajo costo para microinversores

In recent years, the implementation of solar energy facilities has grown, as it is considered an environmentally friendly way to produce electricity. Solar energy can be exploited under different configurations or connection schemes. The most useful connection schemes are the string connection, the power optimizers and the microinverters. Microinverters have a wide advantage compared to the other schemes due to their ability to take advantage of solar energy under different environmental conditions, such as partial shading, temperature and irradiation. The implementation of microinverters has been slowed down because of its high cost and reduced lifetime. In general, the design of microinverters commonly includes elements such as transistors, electrolytic capacitors, sensors and a microcontroller. Electrolytic capacitors are commonly used as decoupling stages, even though they present a lower lifetime due to high frequencies of operation and current rises. In this paper, a new microinverter topology is presented, it uses a low-cost array of multilayer capacitors to filter high frequencies and get a low-cost topology.

Preparation of Barium Titanate from Barite Ore of Andhra Pradesh

Barium titanate (BaTiO3) is an attractive material in the field of electro ceramics and microelectronics due to its better characteristics. It is having high dielectric constant and low loss characteristics and hence barium titanate is an excellent choice for many applications, such as capacitors, multilayer capacitors (MLCs) and energy storage devices. In the present study an attempt is made to prepare barium titanate from ore using reduction ,leaching ,precipitation and calcinations techniques. The material is giving higher dielectric constant compared to the synthetically prepared materials.

Electrocalorics hit the top.

A first-order ferroelectric phase transition is driven supercritically in multilayer capacitors of PbSc0.5Ta0.5O3, enabling an electrocaloric response of 5.5 K near room temperature.

High fidelity direct measurement of local electrocaloric effect by scanning thermal microscopy

Electrocaloric effect (ECE) has great potential in solid-state cooling. However, the lack of reliable measurement method, especially at the local scale, hinders its materials optimization and structure design. In this paper, a high fidelity local measurement of ECE response with temperature sensitivity as high as ~8 mK has been developed based on scanning thermal microscopy (SThM) experiment and finite element model based quantitative analysis. With such high sensitivity, we have probed a multilayer capacitors (MLC) made of doped barium titanate, demonstrating significant effect of Joule heating that interferes the ECE measurement. An approach to correct the Joule heating has been proposed, with which we have identified the intrinsic ECE response, showing peak response near ferroelectric phase transition. Local mapping in ECE temperature response has also been acquired, revealing substantial spatial variation due to different heat exchange with exterior environment, leading to smaller temperature change experimentally measured in comparison to intrinsic ECE response. This demonstrates the importance of localized ECE measurement under direct method. The developed direct measurement method points to an alternative, reliable and high fidelity pathway for investigating ECE at local scale.

Synthesis of single phase MgTiO3 and influence of Sn4+ substitution on its structural, dielectric and electrical properties

In this work, synthesis of single-phase MgTiO3 and Mg(Ti0.95Sn0.05)O3 ceramics through conventional solid state mixed oxide route using Mg(OH)2 or MgO as raw material was investigated. The phase purity of prepared specimens was examined using X-ray diffraction; bond characteristics were determined via Raman spectroscopy, dielectric properties at low frequency were measured by Impedance spectroscopy and dielectric properties at microwave frequency were measured by vector network analyzer. The properties of Mg(OH)2 based ceramics were also compared to that of MgO based ceramics in frequency range of 10 kHz-3 MHz and temperature range of 298–468 K. It was observed that Mg(OH)2 based materials exhibited not only low losses (tan δ) and low relative permittivity (ϵr) but also possessed smaller value of temperature coefficient of resonant frequency (τf) in comparison to that of MgO based materials. Dielectric and electrical properties of MgTiO3 were further improved by partial replacement of tetravalent cations Ti4+ with Sn4+. The mechanism of electrical conduction for the synthesized specimens was also studied using Jonscher power law and activation energy was evaluated using Arrhenius equation. Best dielectric properties at room temperature in 10 kHz-3 MHz frequency range were displayed by Mg(OH)2 based Mg(Ti0.95Sn0.05)O3 compound having tan δ of 2.32 × 10−4, ϵr of 14.61 and τf of −39.7 ppm/K at 100 kHz frequency. At 15 GHz Mg(OH)2 based Mg(Ti0.95Sn0.05)O3 exhibited tan δ of 2.73 × 10−2 and ϵr of 14.12. This material could be utilized for fabrication of multilayer capacitors, dielectric resonators, filters, antennas, buffer layers and protective coatings.

Large electrocaloric effects in oxide multilayer capacitors over a wide temperature range.

Heat pumps based on magnetocaloric and electrocaloric working bodies-in which entropic phase transitions are driven by changes of magnetic and electric field, respectively-use displaceable fluids to establish relatively large temperature spans between loads to be cooled and heat sinks1,2. However, the performance of prototypes is limited because practical magnetocaloric working bodies driven by permanent magnets3-5 and electrocaloric working bodies driven by voltage6-16 display temperature changes of less than 3kelvin. Here we show that high-quality multilayer capacitors of PbSc0.5Ta0.5O3 display large electrocaloric effects over a wide range of starting temperatures when the first-order ferroelectric phase transition is driven supercritically (as verified by Landau theory) above the Curie temperature of 290kelvin by electric fields of 29.0volts per micrometre. Changes of temperature in the large central area of the capacitor peak at 5.5kelvin near room temperature and exceed 3kelvin for starting temperatures that span 176kelvin (complete thermalization would reduce these values from 5.5 to 3.3kelvin and from 176 to 73kelvin). If magnetocaloric working bodies were to be replacedwith multilayer capacitors of PbSc0.5Ta0.5O3,then the established design principles behind magnetocaloric heat pumps could be repurposed for better performance without bulky and expensive permanent magnets.

Low-Temperature Sintering and Enhanced Dielectric Properties of BaZr0.2Ti0.8O3-Based Y5V Ceramics with Li2CO3 to Reduce the Sintering Temperature

We synthesized BaTi0.8Zr0.2O3 (BZT)-based powders using the sol–gel method, and introduced Li2CO3 with a low melting point (723°C) as a source of the liquid phase to reduce the sintering temperature (Ts) and improve the dielectric properties of the BZT-based ceramics. The x-ray powder diffractometer patterns exhibited a perovskite structure in all samples. The scanning electron microscope images revealed that the sinterability of the BZT-based ceramics was improved by adding an appropriate amount (3.0 wt.%) of Li2CO3; Ts decreased from 1280°C to 1100°C. The BZT-based ceramics sintered at 1100°C with 3.0 wt.% Li2CO3 met the Y5V requirements, with good electrical properties: emax = 17987, er = 15950, and tan δ = 0.02. The results indicated that Li2CO3 can improve the dielectric properties and reduce the Ts of BZT-based ceramics. Our method therefore represents a less expensive approach for developing materials suitable for use in multilayer capacitors.