Dielectric Breakdown Behavior Research Articles

Dielectric breakdown behavior of ferroelectric HfO2 capacitors by constant voltage stress studied by in situ laser-based photoemission electron microscopy

In situ laser-based photoemission electron microscopy observations with time-dependent dielectric breakdown measurements of TiN/Hf0.5Zr0.5O2(HZO)/TiN ferroelectric capacitors were performed to reveal the dielectric breakdown (DB) mechanism. We succeeded in visualizing the hard DB spots through the top electrode. We found that capacitors with short- and long-lifetime distributions were broken down near and far from the edge of the capacitors, respectively. This indicates that the DB is either topography-dependent or film-quality-dependent. This work demonstrates an effective method of detecting DB in a non-destructive manner to provide an insight for achieving higher endurance HfO2-based ferroelectric capacitors.

Electrostriction effects in space charge measurements with the pulsed electroacoustic method for ceramics

The pulsed electroacoustic (PEA) method is an established method for space charge measurements in polymeric dielectrics. In view of the poorly understood impact of space charge on the electrical resistivity and the dielectric breakdown behavior of ceramics, it is desirable to adapt the PEA technique to these materials. However, this adaption is non-trivial due to the constitutive properties of ceramics, which are, at least in part, very different from that of polymers. This contribution addresses a particular effect related to the electrostrictive properties of ceramics on the theoretical level. It is shown that these properties may cause an inversion of the sign of the sound wave generated by electrical voltage pulses when compared to typical polymers, which may in turn result in an incorrect interpretation of the measurement results. Using this finding, a reinterpretation of previous experimental results suggests that homo charge forms at the cathode in sheets of alumina ceramics subjected to high voltages.

The jumping dielectric breakdown behavior induced by crack propagation in ferroelectric materials: A phase field study

Ferroelectric materials often experience fracture and dielectric breakdown under large mechanical and/or electrical loads. These two failure behaviors can affect each other and may lead to new phenomena. This study predicts a new type of jumping dielectric breakdown during crack propagation in ferroelectric materials using a phase field model involving multiple order parameters. The driving forces for the evolution of polarization, fracture, and dielectric breakdown were analysed based on the concept of configurational forces. The jumping dielectric breakdown was attributed to the competition between crack propagation and breakdown initiation at the moving crack tip. The breakdown pattern is related to the polarization domain structure and is significantly influenced by the applied electric field and crack boundary conditions. Furthermore, the jumping breakdown associated with possible mechanical degradation of the material can change the driving and resistance forces for crack propagation. This study introduces a novel dielectric breakdown behavior during crack propagation and provides new insights into the coupling failure of ferroelectric materials.

Enhanced energy storage performance and theoretical understanding of the dielectric breakdown behavior for Ba0.4Sr0.6TiO3/Al2O3 ceramics

Ba0.4Sr0.6TiO3 (BST) ceramics with Al2O3 additives are synthesized by spark plasma sintering (SPS) to enhance the energy storage density. Numerical simulations based on a stochastic model are carried out to further understand the breakdown behaviors in BST/Al2O3 ceramics. Greatly enhanced dielectric breakdown strength from 210 kV/cm to 300 kV/cm is realized in BST-1 %Al2O3 ceramics due to the optimized microstructure and the high insulation of Al2O3 additives. The maximum energy storage density of 1.69 J/cm3 is obtained, which is 1.4 times larger than pure BST ceramics. Based on the simulations, it is found that the discharge channels try to bypass the particles due the high critical breakdown field of Al2O3, which will extend the breakdown path in ceramics and contribute to the improved breakdown strength. However, after exceeding a certain amount of Al2O3 addition, the interface effect will be predominant and lead to the degradation of breakdown strength.

Evaluation of dielectric breakdown of BaTiO3 by novel indentation method

Succinct evaluation of dielectric breakdown strength of dielectric materials has been hampered by extrinsic parameters like size/thickness dependence, electrode configuration, and defect concentration which all mask the materials’ intrinsic value. A novel indentation method to prepare arch-shaped indents on the surface of BaTiO3 green stacks has been developed to overcome this problem. Utilizing this method enables simple and reliable sample preparation for investigation of dielectric breakdown behavior. Theoretical and experimental investigations reveal vanishing electrode edge effects governed by the improved distribution of electric field due to the arch-shaped indents. Thus, the novel indentation method bears advantages compared to measuring DBS of disk-shaped samples and allows for narrowing influences of extrinsic parameters. By obtaining breakdown channels close to the center of the indent, this technique additionally features the possibility of localizing the breakdown event.

Effects of High Magnetic Field on Partial Discharge and Dielectric Breakdown Behavior of Silicone Rubber

In this article, space charge and partial discharge (PD) behavior and the breakdown strength of silicone rubber under ac and dc voltages are tested in high magnetic field. In the case of ac voltage, the effects of high magnetic field on promoting air gap breakdown result in the decrease in PD inception voltage. Polarization of specimens with higher speed and lower air gap breakdown voltage result in the increase in PD frequency and eventually causes the decrease in breakdown strength. In the case of dc voltage, energy level splitting due to Zeeman effects results in lower interface barrier, considering both the increase in electron affinity and the increase in density deference between donor-like and acceptor-like surface traps. The decrease in interface barrier causes more space charge injection. The electric field distortion caused by local space charge accumulation leads to the decrease in breakdown strength in high magnetic field.

Enhanced Energy Storage Performance and Theoretical Understanding of the Dielectric Breakdown Behavior for Ba0.4sr0.6tio3/Al2o3 Ceramics

Enhanced Energy Storage Performance and Theoretical Understanding of the Dielectric Breakdown Behavior for Ba0.4sr0.6tio3/Al2o3 Ceramics

A transport model describing how defect accumulation leads to intrinsic dielectric breakdown and post-breakdown conduction

A charge transport model, originally developed for simulating time-dependent dielectric breakdown (TDDB) behavior at the interconnect level, was modified and extended to also apply to the current-voltage (I-V) behavior in the post-breakdown region. The model allows one to simulate the current-voltage characteristics of the dielectric material from its pristine state, through the wear-out and breakdown phase, and into the post-breakdown region. The systematic transition from the insulator region to the conductor-like region is visualized through the intrinsically generated trap distribution evolution. A percolation starts forming near the anode at a critical trap concentration of 5 × 1026m−3 for the system under study and proceeds directionally, towards the cathode. Soft breakdown occurs when the percolation path front reaches the cathode with a trap volume fraction of 0.15, close to the theoretical value of 0.16. Hard breakdown, at the switching point, is associated with the completion of a vacancy-type percolation path and saturation of the trap concentration. A power law relationship with a power of 2 is found between the system's conductance and the trap concentration near the anode between the critical point and the switching point. A predicted linear post-breakdown region following the breakdown event along with a weak temperature dependence agrees well with experimental observations.

Spectral Measurement of the Breakdown Limit of β−Ga2O3 and Tunnel Ionization of Self-Trapped Excitons and Holes

$\beta-Ga_{2}O_{3}$ is an unusual semiconductor where large electric fields (~1-6 MV/cm) can be applied while still maintaining a dominant excitonic absorption peak below its ultra-wide bandgap. This provides a rare opportunity in the solid-state to examine exciton and carrier self-trapping dynamics in the strong-field limit at steady-state. Under sub-bandgap photon excitation, we observe a field-induced red-shift of the spectral photocurrent peak associated with exciton absorption and threshold-like increase in peak amplitude at high-field associated with self-trapped hole ionization. The field-dependent spectral response is quantitatively fit with an eXciton-modified Franz-Keldysh (XFK) effect model, which includes the electric-field dependent exciton binding energy due to the quadratic Stark effect. A saturation of the spectral red-shift with reverse bias is observed exactly at the onset of dielectric breakdown providing a spectral means to detect and quantify the local electric field and dielectric breakdown behavior. Additionally, the field-dependent responsivity provides insight to the photocurrent production pathway revealing the photocurrent contributions of self-trapped excitons (STXs) and self-trapped holes (STHs). Photocurrent and p-type transport in $\beta-Ga_{2}O_{3}$ are quantitatively explained by field-dependent tunnel ionization of excitons and self-trapped holes. We employ a quantum mechanical model of the field-dependent tunnel ionization of STX and STH to model the non-linear field-dependence of the photocurrent amplitude. Fitting to the data, we estimate an effective mass of valence band holes $(18.8 m_{0})$ and an ultrafast self-trapping time of holes (0.045 fs). This indicates that minority-hole transport in $\beta-Ga_{2}O_{3}$ can only arise through tunnel ionization of STH under strong fields.

Breakdown strength and energy density enhancement in polymer-ceramic nanocomposites: Role of particle size distribution

Polymer-ceramic nanocomposites play a very promising role for energy-storage in high power electronics and advanced pulsed power systems, due to their extremely fast charge-discharge capability. The low energy density is the key factor hindering their application, for which large endeavors have been made in the modulation of the fraction, morphology, size, and dispersion of the particle fillers but small in that of the size distribution, which is critical for energy-storage performance. We first investigated the role of this based on simulated nanocomposites with controlled lognormal distributions via a generation algorithm devised in this work. Dielectric response, breakdown behavior and energy-storage performance were explored for distributions with different standard deviations (SD) and mean values (MV), which were solved with the energy equivalence basis and a phase-field dielectric breakdown model. With the decrease of SD and MV, the effective permittivity declines slightly with enhanced permittivity change, which was related with the enhanced local electric field with intensified fluctuation and should be originated from the major contribution of the polymer matrix from the local energy perspective; whereas improved nominal breakdown strength was achieved owing to the weakened local maximum electric field, which leads to distinctly increased nominal energy density despite the slight decline of the permittivity. Keeping the fillers within a narrow disperse outperforms employing super fine particles. This work demonstrates that enhancement in breakdown strength and energy density can be attained via particle size distribution modulation, paving a new way for the further improvement of the energy-storage performance of polymer-ceramic nanocomposites.

Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

Reactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

Dielectric breakdown behavior of ferroelectric ceramics: The role of pores

Dielectric breakdown is a fundamental issue for ferroelectric ceramics. In this work, a phase-field method is introduced to study the breakdown behavior of ferroelectric ceramics with pores randomly distributed. Effects of the position and the size of pores on the breakdown behavior are analyzed. Results indicate that the position of pores, for example in grains or at grain boundaries, has a significant influence on the breakdown strength of ferroelectric ceramics. The nominal breakdown strength of ferroelectric ceramics with 2 % pores at grain boundaries is almost 50 % higher than 2 % pores in grains. Further, for ferroelectric ceramics with a certain porosity, the smaller the pore size, the higher the breakdown strength. As the nominal pore size decreases from 2.5 to 1, the nominal breakdown strength is enhanced from 0.73 to 1.16. Such results agree well with the widely accepted Gerson-Marshall model and previously published experimental observations.

Effect of LiF addition on sintering behavior and dielectric breakdown mechanism of MgO-based microwave dielectric ceramics

Glass-free MgO-based microwave dielectric ceramics (1-x) wt% (0.98 MgO-0.02 Al2O3)-x wt% LiF (x = 0.5, 1, 2, 3, 4) were synthesized where LiF and Al2O3 were utilized as sintering additive and reinforcement phase in MgO matrix respectively. It was found that ion substitution is apt to occur between LiF and MgO, leading to the formation of oxygen vacancies and MgF2. Nevertheless, different from ordinary liquid-phase sintering, morphologies of ceramics were distinctly altered with grains changing from polyhedron to sphere-like shape and densities underwent obvious decrease when excessive amount of LiF was introduced and we call it excessive liquid-phase sintering. Grain boundary weakening caused by this circumstance would exert an adverse effect on physical properties. Moreover, LiF addition dramatically reduced dielectric breakdown strength and altered the dielectric breakdown behavior of MgO-based ceramics, which is dominated by electrical breakdown mechanism. Combination of good properties were achieved in 1 wt% LiF modified MgO-based ceramics sintered at 950 °C which exhibited superior microwave properties (εr = 9.56, tanδ = 9.2 × 10−5, Qf = 124,600 GHz), high flexural strength (184.5 MPa), high thermal conductivity (21.3 W/(m⋅K)), high coefficient of thermal expansion (∼12 ppm/°C) and moderate electrical properties (Eb = 35.9 kV/mm, ρ = 4.9 × 1012 Ω cm).

Correlation between flash sintering and dielectric breakdown behavior in donor-doped barium titanate ceramics

The present work investigates the influence of donor doping and its concentration on the flash sintering behavior of barium titanate. The characteristic of non-ohimic conductivity during flash event shows that flash sintering is associated with dielectric breakdown due to the similar physical phenomena. The polarization of dielectric particle contributes to the enhancement of local electric field strength. The magnified electric field caused by local charges accumulation gives rise to dielectric breakdown phenomenon during flash sintering. The SEM measurement indicates an obvious breakdown channel through the inside of sample, which provides a convincible evidence for dielectric breakdown. In addition, the impacts of temperature and field on carrier activation and migration are emphasized. Eventually, the non-ohmic conductivity can be explained by the physical phenomenon of dielectric breakdown described by Poole-Frenkel Emission.

Modeling the dielectric breakdown strength and energy storage density of graphite-polymer composites with dielectric damage process

Recent experimental data has demonstrated significant influences of graphite volume concentration on the dielectric breakdown and energy storage behavior of graphite-polymer composites, but no existing homogenization theory has been established to illustrate such dependence in the context of alternating current (AC) loading. In this paper we develop a novel homogenization scheme to connect the microstructural parameters of constituent phases and the AC frequency to the dielectric breakdown strength and energy storage density of the overall composite. The major microstructural features covered are the graphite volume concentration, imperfect bonding effect, graphite aspect ratio, percolation threshold, filler-dependent electron tunneling, Maxwell-Wagner-Sillars polarization, and frequency-dependent electron hopping and dielectric relaxation. A thermodynamic framework is developed to describe the evolution of a dielectric damage parameter with respect to the electric field. We highlight the developed theory with validation through the experimental data of graphite/PVDF composite over a wide range of graphite volume concentration and AC frequency. The results indicate that the dielectric breakdown strength of the graphite-polymer composite decreases with respect to the graphite volume concentration, while the energy storage density increases with it.

Tunable dielectric polarization and breakdown behavior for high energy storage capability in P(VDF-TrFE-CFE)/PVDF polymer blended composite films.

Polymer dielectrics with high dielectric performances and superior discharge energy capability are highly desirable for advanced electrostatic capacitor applications. However, the paradoxical relationship between dielectric polarization and electric breakdown behavior generally hinder their further enhancement in energy storage performances. Herein, polymer blended composite films with high energy storage capability were successfully fabricated by blending together poly(vinylidene fluoride) (PVDF) polymer and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer. The P(VDF-TrFE-CFE) terpolymer has a high dielectric constant to provide a large electric displacement under an applied electric field far below its breakdown field, which is anticipated to modulate the dielectric polarization behavior of PVDF polymer when blended in different proportions. Consequently, the polymer blended composite film consisting of 20 wt% (P(VDF-TrFE-CFE)) terpolymer exhibits a high discharge energy density of 13.63 J cm-3 at an enhanced breakdown strength of 480 MV m-1. This obtained high discharge energy density is 84% higher than the pure PVDF film and 582% higher than a commercialized biaxially oriented polypropylene (BOPP). Large interfacial polarization and strong interaction of polymer chains between the PVDF polymer and P(VDF-TrFE-CFE) terpolymer may contribute to the tunable dielectric constant and electric breakdown strength, thus promoting the energy storage capability. This work establishes a facile, but effective approach to achieve the high energy storage capability of PVDF polymer-based flexible composite films for capacitive energy storage applications.

Investigation on dielectric breakdown behavior of thermally aged cross-linked polyethylene cable insulation

With the rapid development of industry and the increasing demand of power supply, the rated voltage class and current-carrying capacity of power cables become higher and higher, causing the severer service and testing conditions for high voltage (HV) power cables. Therefore, the requirement of the quality of cable insulating materials also becomes increasingly higher. The dielectric breakdown strength is one of the most important indices characterizing the quality and present status of insulating materials, and insulating materials and systems undergo dielectric breakdown tests during development and service. A lot of research results on the dielectric breakdown characterization of polyethylene (PE) and cross-linked polyethylene (XLPE) have been reported up to now, however, few systematic investigations about the dielectric breakdown behaviors of the thermally-aged XLPE cable insulation have been reported in details. Generally, the behaviors of dielectric breakdown for HV insulating materials and structures have been known to obey some statistical distributions, including the Weibull statistical distribution. The changes of the parameters characterizing the Weibull statistical distribution, e.g. the scale and shape parameters may be closely related with those of the physical and chemical properties of the insulating materials considered. This paper aims to investigate the behaviors of the changes of the Weibull statistical parameters for XLPE cable specimens with the different degrees of thermal aging and to elucidate their mechanisms. The investigation results show that the dielectric breakdown characteristics of thermally aged XLPE cable insulating materials also fit well with the Weibull statistical distribution and the changes of their Weibull statistical parameters are very sensitive to the degree of thermal aging, which can be effectively used for the diagnosis of PE or XLPE cable insulation and the analysis of its degradation mechanisms.

Significantly enhanced dielectric breakdown strength and energy density of multilayer ceramic capacitors with high efficiency by electrodes structure design

Multilayer ceramic capacitors (MLCCs) are attracting great interest recently, especially in energy-storage applications due to their high volumetric capacitance, high power density, and fast charge-discharge capability. However, the low dielectric breakdown strength of ferroelectric ceramics always leads to a low discharge energy density, which limits their applications in high-voltage energy-storage systems. In this work, a phase-field electromechanical breakdown model is introduced to give a fundamental understanding of the dielectric breakdown behavior of MLCCs and provide a resource-efficient design strategy for the structure of MLCCs to enhance their dielectric breakdown strength and discharge energy density. Three types of margin lengths of 100 μm, 200 μm, and 400 μm are designed and applied on the MLCCs consisting of ten dielectric layers with the single-layer thickness of 11 μm, to confirm and practice our phase-field breakdown model. A large discharge energy density of 7.8 J cm−3 can be achieved under the applied electric field of 790 kV/cm, together with a high efficiency of 88% in a 400 μm-margin-length MLCC.

Growth of plasma electrolytic oxidation coatings on Nb and corresponding corrosion resistance

Abstract Plasma electrolytic oxidation (PEO) coatings were formed, respectively in three silicate-based, phosphate-based and aluminate-based electrolytes on niobium, with the aim to explore the relationships between electrolyte composition, dielectric breakdown behavior and corresponding corrosion resistance. The initial growth stages of the anodic coatings were studied, and result shows that an impedance falling stage (from about 200 V to 400 V) starts at the emergence of spark discharge accompanied with the surface morphology evolution from compact to porous. The PEO coatings were characterized through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods. Results show the coatings fabricated in (NaPO 3 ) 6 electrolyte provide the best corrosion resistance. It attributes to the effective thickness of the compact inner layer rather than the entire thickness of the coating that decrease diffusion of corrosion medium.

Phase-field modeling of the coupled domain structure and dielectric breakdown evolution in a ferroelectric single crystal.

The study of domain switching and dielectric breakdown behavior of ferroelectrics together with their relations is crucial for understanding the essence of ferroelectric physics and exploring their applications. In this work, a phase-field method is developed to reveal the coupled domain structure and dielectric breakdown evolution in a ferroelectric single crystal (FSC) by employing the Ginzburg-Landau kinetic equation and Griffith type energy criterion. Results show that the domain switching mobility, symbolizing the speed of polarization evolution, has a significant influence on ferroelectric properties, namely coercive field, dielectric breakdown strength (DBS), discharge energy density (DED), and energy storage efficiency (ESE). It is found that FSC with the higher domain switching mobility always displays a lower coercive field and smaller remanent electric displacement (or polarization) together with a higher DBS, accounting for a higher DED and ESE. Such findings can provide effective guidance in understanding and designing high-DBS and high-energy-density ferroelectrics. In addition, the defect concentration has a significant influence on the DBS and the pattern of breakdown paths.