Dielectric Nonlinearity Research Articles

Enhanced crystallinity of (Sr,Ba)Nb2O6 films on sapphire and alumina substrates

Barium-strontium niobate in thin film form can be considered as a prospective ferroelectric material for microwave applications due to high dielectric nonlinearity. Its performance is linked to film structure quality, and one method to achieve high-quality films on microwave substrates goes through the process of annealing. (Sr,Ba)Nb2O6 films of good crystallinity were formed on sapphire and alumina substrates by magnetron sputtering. The processes of recrystallization of films on single- and polycrystalline substrates under the conditions of ex situ annealing at temperatures of 1100–1200 °C were studied. Highly (00l) oriented films on sapphire substrate were obtained by the deposition in oxygen atmosphere at a substrate temperature of 900 °C with post-growth annealing in air at an annealing temperature of 1150 °C.

Contact stress ultrasonic detection method based on contact acoustic resistance model

The size and distribution of the contact stress at the assembly interface will directly affect the connection performance of the mechanical joint. However, the rough assembly interface presents strong dielectric discontinuity and material nonlinearity, which become the bottleneck restricting the development of contact stress detection. How to obtain contact stress by nondestructive testing means has become an urgent problem to be solved. In this paper, a multi-layer interface contact stress detection method based on contact acoustic resistance model is proposed to solve the difficult problem of rough interface contact stress detection. Firstly, based on the formation mechanism of contact acoustic resistance of rough assembly interface, the equivalent contact acoustic resistance expression of contact layer is derived. Secondly, the contact mechanism of rough assembly interface is clarified, and the mapping relationship model between contact acoustic resistance and contact stress is constructed. On this basis, according to the transmission law of ultrasonic wave at different interfaces of multilayer acoustic impedance, the expression of acoustic transmission coefficient at the interface of variable acoustic impedance is obtained. A contact stress detection method based on contact stress-contact acoustic resistance coefficient and acoustic transmission coefficient is proposed. The correctness of the theoretical model is verified by the tensile testing machine, and the maximum error is 15.52 %. This method will provide powerful data support for the evaluation of assembly interface connection state.

Nonlinear topology optimization of flexoelectric soft dielectrics at large deformation

We propose a novel nonlinear topology optimization framework tailored for flexoelectric soft dielectrics undergoing large deformation. A numerical method based on Isogeometric analysis (IGA) is introduced to nonlinear soft dielectrics at finite strain, ensuring the C1-continuity for flexoelectric problems. We outline the process of consistent linearizations and IGA discretizations. Additionally, we introduce an innovative and efficient Strain Density Function (SDF) interpolation scheme for optimizing electromechanical coupling factors (ECFs). In this scheme, the interpolation of electromechanical and hyper-elastic energy terms is grounded in the SIMP model, while a linear material interpolation model is employed for the dielectric energy. Our numerical analysis highlights the remarkable performance of the proposed SDF interpolation scheme in nonlinear electromechanical optimization scenarios. An energy remedy scheme is applied to void regions to eliminate the instability of nonlinear optimization, effectively preventing distortion deformations in low-stiffness elements. Furthermore, we investigate the influence of size effect and larger deformation on the optimization of flexoelectric soft materials. The proposed topology optimization framework adeptly leverages the interplay between size effect and larger deformation, resulting in a notable improvement in ECFs within the optimized structures. Finally, the electromechanical coupling factors (ECFs) of the optimized structures in all the examined cases exhibit enhancements up to 9 times as compared to the reference guess designs.

Effects of Mn doping on the conduction mechanism and dielectric nonlinearity of Na0.5Bi0.5TiO3 thin film

In this work, the conduction mechanism and dielectric nonlinearity of undoped and Mn-doped Na0.5Bi0.5TiO3 (NBT) films were investigated. The potential conduction mechanism in relatively low electric fields should be dominated by hopping conduction rather than typical Ohmic conduction. In the high electric field region, the conduction mechanism is dominated by Poole–Frenkel emission and Schottky emission. The enhancement of electrical insulation of NBT films after Mn doping was shown to result from a decrease in oxygen vacancies and elevation of the conduction energy barrier. Furthermore, significant improvements in the nonlinearity of both the dielectric constant and polarization of Mn-doped NBT films were observed, as indicated by the results of Rayleigh fitting and first-order reversal curve distributions. Such enhancements were attributed to the reduction in domain wall pinning, decreased interference from electrostatic potential and improved leakage characteristics.

Calculation and Measurement of Dielectric Parameters of Ceramic and Ferroelectric Materials in the Microwave Range

Introduction. Determination of the electrophysical parameters of linear and nonlinear dielectric materials for use in microwave technology represents an important direction. Linear dielectrics are used as a basis for the substrates of microwave circuits, as well as volumetric elements for the construction of frequency selective or resonant structures that operate across a wide temperature range. Therefore, the issue of stabilizing the electrical parameters of such structures from temperature influences appears relevant. A possible solution lies in the use of a multilayer combination of dielectrics, both with linear and nonlinear properties. Due to their nonlinear properties, ferroelectrics find application in functional units with an electrical rearrangement of frequency and phase characteristics. Therefore, it is important to determine not only the relative permittivity of the material, but also the control coefficient in the RF– microwave wavelength ranges.Aim. Construction of computational mathematical models for layered bulk and film structures to determine the relative permittivity of linear and nonlinear dielectrics in the ultrahigh frequency range.Materials and methods. The construction of computational mathematical models for the analysis of complex layered structures was carried out on the basis of Maxwell’s equations and the Galerkin method using boundary conditions for electromagnetic field components.Results. An electrodynamic analysis of a two-layer volumetric disk resonator was performed, and numerical results of calculating the resonant frequency were obtained. A numerical analysis of a multielectrode half-wave resonator with a ferroelectric film (FEF) was carried out.Conclusion. The mathematical models created and the experiment performed made it possible to numerically evaluate the properties of linear and nonlinear dielectric bulk and film materials in the microwave range.

High Entropy Nonlinear Dielectrics with Superior Thermally Stable Performance.

A high configurational entropy, achieved through a proper design of compositions, can minimize the Gibbs free energy and stabilize the quasi-equilibrium phases in a solid-solution form. This leads to the development of high-entropy materials with unique structural characteristics and excellent performance, which otherwise couldnot be achieved through conventional pathways. This work develops a high-entropy nonlinear dielectric system, based on the expansion of lead magnesium niobate-lead titanate. A dense and uniform distribution of nano-polar regions isobserved in the samples owing to the addition of Ba, Hf, and Zr ions, which lead to enhanced performance of nonlinear dielectrics. The fact that no structural phase transformation isdetected up to 250°C, and no noticeable change or a steep drop in structural and electrical characteristics isobserved at high temperatures suggests a robust thermal stability of the dielectric systems developed. With these advantages, these materials hold vast potential for applications such as dielectric energy storage, dielectric tunability, and electrocaloric effect. Thus, this work offers a new high-entropy configuration with elemental modulation, with enhanced dielectric material features.

Vortex solitons in large-scale waveguide arrays with adjustable discrete rotational symmetry

We consider vortex solitons in large-scale arrays composed of N elliptical waveguides placed on a ring, which can be fabricated using fs-laser writing technique in transparent nonlinear dielectrics. By introducing variable twist angles between longer axes of neighboring elliptical waveguides on a ring, we create circular arrays with adjustable discrete rotational symmetry ranging from CN to C1, when the number of waveguides N on the ring remains fixed. This allows to consider the impact of discrete rotational symmetry on the properties of available vortex solitons without changing the number of guiding channels in the structure, and to predict how exactly splitting of higher-order phase singularities into sets of charge-1 singularities occurs in vortex states, when they are forbidden by the discrete rotational symmetry of the structure that imposes the restrictions on the maximal possible vortex charge. It is found that separation between split charge-1 phase singularities in such higher-order vortex states increases with increase of the order of solution. We also study linear spectra of such arrays and show how variation of their discrete rotational symmetry affects linear eigenmodes, whose combinations can give rise to vortex modes. We also show that variation of discrete rotational symmetry in arrays with fixed number of guiding channels N has strong impact on stability of vortex solitons. Thus, only higher-charge vortex solitons are stable in such large-scale arrays and the number of stable states typically decreases with decrease of the order of discrete rotational symmetry of the structure at fixed N.

Hybrid Quantum Systems for Higher Temperature Quantum Information Processing

The ability to operate superconducting quantum computers at higher temperatures would greatly expand their utility and range of applications. This could be achieved by increasing resonance frequencies and/or utilizing collective modes that are less noisy and more robust against decoherence. We discuss several nonlinear resonator concepts in which the roles of linear and nonlinear elements are reversed vs. the transmon. The simplest version is a nonlinear <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonator with a linear superconducting inductor and a nonlinear capacitor employing a nonlinear dielectric material. Due to progress in tunable dielectrics for 6G, some ferroelectric composites may enable operation of a nonlinear dielectric – superconductor qubit at hundreds of gigahertz. Other nonlinear dielectric materials include quantum paraelectrics and charge density wave materials. These are of interest due to robust collective modes resulting from macroscopically occupied states. Other proposed nonlinear resonators employing nonlinear dielectrics include quarter- and half-wavelength resonators. Voltage tunability is a potential feature of the proposed concepts.

Electrostatic modulation of the lateral carrier density profile in field effect devices with nonlinear dielectrics

Electrostatic modulation of the lateral carrier density profile in field effect devices with nonlinear dielectrics

Stability of Self-Adaptive Dielectrics Under Various Electrical-Thermal Stress

Nonlinear dielectrics with self-adaptive electrical parameters (SADs) are promising for field grading and stress control in key part of high voltage apparatus. However, the performance of SADs can be considerably affected by various electrical-thermal excitations and their reliability in these complicated working conditions should be further validated. This paper has prepared SADs that consists of EPDM and silicone rubber composites with different ZnO microvaristor filler concentrations. Nonlinear V-I characteristics of the composites are measured under different thermal excitations, including wide temperature range, heat cycles, as well as local hot spot caused by transient overvoltage. The paper has summarized the effect of the electrical-thermal excitations on the nonlinear conducting behavior of the composites and analyzed its mechanism, through which the reliability of SADs under these working conditions is evaluated and the influences of filler and polymer matrix property on the thermal stability of the composites are discussed. Finally, suggestions for field grading as well as material design are proposed.

Nonlinear Dielectric Response of Relaxor Ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 Epitaxial Thin Films

AbstractThin ferroelectric layers are capable of generating large dielectric and electromechanical responses at relatively low voltages, thus can be utilized in various applications including energy storage, energy harvesting, sensors, and actuators. Among ferroelectrics, relaxor ferroelectrics (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 are particularly interesting due to their superior dielectric and piezoelectric properties. However, dielectric and piezoelectric responses of the ferroelectric thin films are significantly suppressed relative to their bulk counterparts. The physical mechanism of the properties degradation still remains elusive, which greatly hinders their technological applications. Herein, this work systematically investigates the dielectric nonlinearity and the relationship between composition and intrinsic/extrinsic contributions of high‐quality (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 epitaxial thin films (x = 0, 0.1, 0.32) fabricated by pulsed laser deposition. Through the Rayleigh analysis, it is found that the suppression of domain wall motion by substrate clamping is the main cause of thin film performance degradation and is further confirmed by continuous application of background dc bias to extract the dielectric response's intrinsic and extrinsic contributions. This work will pave the way for practical applications of (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 thin films in energy storage and electromechanical devices.

Massively Parallel Aligned Poly(vinylidene fluoride) Nanofibrils in All-Organic Dielectric Polymer Composite Films for Electric Energy Storage

It is a formidable challenge to combine the performance advantages of linear and nonlinear polymer dielectrics for developing all-organic film capacitors with high energy density and low loss. In this work, massively parallel aligned poly(vinylidene fluoride) (PVDF) nanofibrils were in situ fabricated for the first time in the polyethylene (PE) matrix via a multistage stretching technology involving hot stretching and solid-state stretching at an elevated temperature. The largely enhanced interfacial area of PVDF nanofibrils could effectively induce interfacial polarization, imparting PE composite films with a high dielectric constant of 4.50. More interestingly, the nanoconfinement effect of PVDF nanofibrils greatly restricted the migration of free electrons and impurity ions, and an impressive breakdown strength of 624 MV m–1 was obtained. As a result, the as-prepared PE/PVDF composite films exhibited an attractive discharged energy density of as high as 6.4 J cm–3, which was more than 10 times of the conventional counterparts, and outperformed the current linear dielectric polymers. The ingenious structure design of in situ nonlinear dielectric nanofibrils provides a promising approach to maximize the advantageous polarizations and minimize the disadvantageous polarizations in the linear and nonlinear polymer dielectric blends, achieving all-organic polymer dielectric composite films with high energy density and low loss.

Dynamic of polar nanoregions and its impact on the pyroelectric and dielectric properties in paraelectric KTN materials

AbstractThe origin of the excellent properties of KTN‐based materials around Curie temperature (TC), which should be originated form the motion of polar nanoregions (PNRs), has attracted considerable research interest. In this paper, the relaxation of a KTa0.63Nb0.37O3 single crystal is discussed with the temperature dependence of permittivity. Moreover, its pyroelectric effect above TC is investigated. In detail, the pyroelectric coefficient decreases from ∼110.0 to ∼13.0 μC/(m2 K), with the temperature increasing from 22 to 33°C, and finally reduces to 0 at 100°C with PNRs disappear. Moreover, the dynamic dielectric nonlinearity for the KTN single crystal is studied in the paraelectric phase. To investigate these mechanisms, the amplitude and phase angle of the first and third harmonics under various electric fields, frequencies, and temperatures are analyzed. As a result, the motions of PNRs induced by electric field, which is pinned and depinned by the defect, are presented to explain the nonlinear dielectric response observed in the paraelectric KTN single crystal.

Microstructural, dielectric, and nonlinear properties of Ca1–xCdxCu3Ti4O12 thin films

The effects of the A-site transition from Ca 2+ to Cd 2+ on the microstructure, morphology, and electrical properties of Ca 1–x Cd x Cu 3 Ti 4 O 12 thin films were studied. The film surfaces are smooth, compact, and without cracks. The CaCu 3 Ti 4 O 12 and CdCu 3 Ti 4 O 12 films had similar morphologies and electrical properties. The grain size initially increased and subsequently decreased with the transition from Ca 2+ to Cd 2+ at the A site. The change in Ca sites has an obvious effect on Cu sites. The film with more copper-rich phases at the grain boundaries had the largest grain size when Ca 2+ and Cd 2+ equally occupied the A sites. The dielectric constant of Ca 1–x Cd x Cu 3 Ti 4 O 12 was closely related to the copper oxide secondary phase. The dielectric loss tangent and nonlinearity coefficient were associated with the compact structure, copper oxide secondary phase, copper vacancies and improved grain boundary response. The simultaneous occupancy of the A sites by Ca 2+ and Cd 2+ improves the dielectric and nonlinear properties of Ca 1–x Cd x Cu 3 Ti 4 O 12 . Optimal dielectric properties (Ɛ r = 5238 and tan δ = 0.009 at 1 kHz) and an enhanced nonlinearity coefficient (∼4.22) were simultaneously obtained for the Ca 0.5 Cd 0.5 Cu 3 Ti 4 O 12 thin film. This study demonstrates that the extrinsic mechanism is the main origin of the high dielectric constant values in Ca 1–x Cd x Cu 3 Ti 4 O 12 films. The resulting films are suitable for applications in capacitors.

Non Linear Dielectric Phenomenon in BaTiO3 - Bi (Ti1-xMgx)O3 . Ceramic Material

The distinguishing characteristic of an insulator is its resistivity. An insulator has a higher resistivity than a semiconductor or conductor and has high dielectric properties. The adjustable dielectric property is characterized by a change in the permittivity of the dielectric under an applied electric field, this phenomenon is called "dielectric nonlinearity" (dielectric tunability properties). With these properties, a new phenomenon will arise adjustable dielectric properties in dielectric ceramic materials. The aim of this research is to observe the non-linear dielectric phenomenon in BaTiO3-Bi(Ti1-xMgx)O3 ceramic material with x= 0.5, 0.6, 0.7, 0.8 and 0.9. Ceramic materials were synthesized using the sol-gel method which produced nano-sized powders. Impedance data was measured using an impedance analyzer (Solartron SI 1260, Solartron Metrology, West Sussex, UK) in a frequency range of 100 Hz to 500 Hz with an ac measuring voltage of 0.1 V. Dielectric tunability properties were measured from 0oC to 250oC using an automatic component analyzer. at 10 kHz. All samples show the phenomenon of dielectric tunability with different maximum permittivity. The highest permittivity was obtained at x= 0.6 but the highest transition temperature where non-linear phenomena occurred was found in the sample with x= 0.5.

Impedance spectroscopy of ferroelectrics: The domain wall pinning element

We introduce an equivalent-circuit element based on the theory of interface pinning in random systems to analyze the contribution of domain wall motion below the coercive field to the impedance of a ferroelectric, as a function of amplitude E0 and frequency f of an applied ac electric field. We demonstrate our model on a bulk PbZrxTi1−xO3 (PZT) reference sample and then investigate capacitor stacks, containing ferroelectric 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3 (BCZT) thin films, epitaxially grown by pulsed laser deposition on Nb-doped SrTiO3 single crystal substrates and covered with Au electrodes. Impedance spectra from f=10 Hz to 1 MHz were collected at different E0. Deconvolution of the spectra is achieved by fitting the measured impedance with an equivalent-circuit model of the capacitor stacks, and we extract for E0=2.5 kV/cm, a frequency-dependent permittivity of εr′(f)=458+7.3ln⁡(1Hz/2πf) for the BCZT films from the obtained fit parameters. From an extended Rayleigh analysis, we obtain a coupling strength of 0.187 cm/kV between dielectric nonlinearity and dielectric dispersion in the BCZT films and identify different domain-wall-motion regimes. Finally, we construct a schematic diagram of the different domain-wall-motion regimes and discuss the corresponding domain-wall dynamics. Our approach can be utilized to replace purely phenomenological constant phase elements (CPEs) in modeling the impedance response of ferroelectrics and extracting material properties.

Structural and Electrical Properties of Glass-Ceramic Ferroelectric Composite Materials

Introduction. Materials exhibiting high dielectric permittivity are relevant for use in modern ultrahigh-frequency electronics. Among them, ferroelectrics with high dielectric nonlinearity present particular interest. The electrical strength of ferroelectric materials can be increased using modern composite structures based on mixing ferroelectries and linear dielectrics - materials exhibiting simultaneously low dielectric permittivity and high electrical strength. This approach provides for the opportunity of creating new multicomponent materials with previously unattainable properties and adjusting their component composition, inclusion size and electrical properties across a wide range. In this work, on the basis of porous potassium-iron-silicate glass (KFS) obtained by ion exchange, glass-ceramic materials containing barium titanate were synthesized for use at ultrahigh frequencies.Aim. Production of glass composites by low-temperature sintering of pre-synthesized BaTiO3 (BTO) and potassium-iron-silicate glass, as well as characterization of their structural and electrical properties at ultrahigh frequencies (microwave).Materials and methods. The crystal structure and phase composition of the obtained films were studied by X-ray diffraction using a DRON-6 diffractometer by the emission spectral line CuKα1 (λ = 1.5406 Å). The dielectric permittivity (ε) of microwave samples was evaluated by the Nicholson-Ross method at room temperature using an Agilent E4980A LCR-meter.Results. According to X-ray diffraction analysis, the synthesized samples are a mixture of KFS glass, ferroelectric BaTiO3 and dielectric barium polytitanates; the ratio of the latter determines the electrical properties of the composites. Depending on the content of barium titanate, the studied samples demonstrate a dielectric constant from 50 to 270 at a dielectric loss level of 0.1...0.02. The samples subjected to annealing in an oxygen medium showed an increase in dielectric permittivity by 10.25 % and an increase in controllability with a decrease in dielectric losses by an average of two times.Conclusion. The composite composition of 70 wt % BTO /30 wt % KFS was found to be the most promising in terms of structural and electrical properties. This composite showed an increase in dielectric permittivity by 25 % and a significant increase in nonlinearity, at the same time as reducing losses by more than two times as a result of annealing in an oxygen medium.

Electrical Energy Storage From First Principles

Dielectric capacitors are particularly suitable to store the electrical energy of a fast-changing nature. Here, we present a review of recent applications of first principles and first-principles-based effective Hamiltonian approaches to the study of energy storage in ferroelectrics, lead-free antiferroelectrics, relaxor ferroelectrics, and nitride semiconductors. Specifically, these approaches are used to investigate the energy density and efficiency in perovskite BaTiO3, PbTiO3, and KNbO3 ferroelectrics; Bi1−xRxFeO3 antiferroelectric solid solutions (where R is a rare-earth ion); Ba(Zr,Ti)O3 relaxor ferroelectrics; and epitaxial AlN/ScN superlattices. Ultrahigh energy densities and efficiencies are predicted in some of these compounds. In addition, phenomenological models are used to analyze and understand these energy storage results. Consequently, the numerical methods and simple models detailed here can be easily employed to design novel nonlinear dielectrics with further enhanced energy storage performance.

Energy Storage Application of All-Organic Polymer Dielectrics: A Review.

With the wide application of energy storage equipment in modern electronic and electrical systems, developing polymer-based dielectric capacitors with high-power density and rapid charge and discharge capabilities has become important. However, there are significant challenges in synergistic optimization of conventional polymer-based composites, specifically in terms of their breakdown and dielectric properties. As the basis of dielectrics, all-organic polymers have become a research hotspot in recent years, showing broad development prospects in the fields of dielectric and energy storage. This paper reviews the research progress of all-organic polymer dielectrics from the perspective of material preparation methods, with emphasis on strategies that enhance both dielectric and energy storage performance. By dividing all-organic polymer dielectrics into linear polymer dielectrics and nonlinear polymer dielectrics, the paper describes the effects of three structures (blending, filling, and multilayer) on the dielectric and energy storage properties of all-organic polymer dielectrics. Based on the above research progress, the energy storage applications of all-organic dielectrics are summarized and their prospects discussed.

Significantly improved energy storage stabilities in nanograined ferroelectric film capacitors with a reduced dielectric nonlinearity

For the development of high energy density ferroelectric film/multilayer capacitors, which have applications in electric power systems and advanced pulsed-discharge devices, a stable energy storage performance in a wide range of temperature, frequency and cycling times has become extremely important. Here, we propose an effective method to boost the energy storage stabilities of ferroelectric film capacitors through the use of a nanoengineered film structure with a reduced dielectric nonlinearity. We show in (Ba0.95,Sr0.05)(Zr0.2,Ti0.8)O3 (BSZT) ferroelectric films that such an approach is facilitated by reducing the size of sputtered columnar nanograins via a synergetic effect between a low temperature deposition process and a buffer-layer technique. In comparison with the BSZT films sputtered at 500 °C which are better ferroelectrics, the 400 °C-sputtered BSZT films not only showed an improved energy storage density and efficiency, but also displayed a reduced dielectric nonlinearity in its polarization response. The latter has led to a significantly improved energy storage stability under a changing temperature (−175 oC ∼ 200 °C) or frequency (1 Hz ∼ 20 kHz), or after a large amount of charge–discharge cycles (up to 2 × 109).