Nonlinear Dielectric Properties Research Articles

Thermal Stability and Non-Linear Optical and Dielectric Properties of Lead-Free K0.5Bi0.5TiO3 Ceramics.

Lead-free K0.5Bi0.5TiO3 (KBT) ceramics with high density (~5.36 g/cm3, 90% of X-ray density) and compositional purity (up to 90%) were synthesized using a solid-state reaction method. Strongly condensed KBT ceramics revealed homogenous local microstructures. TG/DSC (Thermogravimetry-differential scanning calorimetry) techniques characterized the thermal and structural stability of KBT. High mass stability (>0.4%) has proven no KBT thermal decomposition or other phase precipitation up to 1000 °C except for the co-existing K2Ti6O13 impurity. A strong influence of crystallites size and sintering conditions on improved dielectric and non-linear optical properties was reported. A significant increase (more than twice) in dielectric permittivity (εR), substantial for potential applications, was found in the KBT-24h specimen with extensive milling time. Moreover, it was observed that the second harmonic generation (λSHG = 532 nm) was activated at remarkably low fundamental beam intensity. Finally, spectroscopic experiments (Fourier transform Raman and far-infrared spectroscopy (FT-IR)) were supported by DFT (Density functional theory) calculations with a 2 × 2 × 2 supercell (P42mc symmetry and C4v point group). Moreover, the energy band gap was calculated (Eg = 2.46 eV), and a strong hybridization of the O-2p and Ti-3d orbitals at Eg explained the nature of band-gap transition (Γ → Γ).

Linear and non-linear optical and dielectric properties of transition metals complexes films derived from Azo-Schiff base for photovoltaic applications

A novel azo-Schiff base, which incorporates a heterocyclic triazole nucleus known as 1H-1,2,4-triazol-5-yl)imino)methyl)-5-((2-nitrophenyl)diazenyl)phenol (H2ASB, 1), was formulated and synthesized. Furthermore, a series of Cu2+ complexes, derived from this azo-Schiff base, were prepared by a simple method with a molar ratio of 1 M Cu2+ to 1 M H2ASB. The synthesized compounds were thoroughly characterized using alternative analytical and spectral techniques. The obtained results confirmed that H2ASB bonded with the Cu2+ ions in a uni-negative/neutral bidentate manner, via the phenolic hydroxyl oxygen and azomethine nitrogen atom, thereby resulting in tetrahedral or octahedral geometries. Additionally, theoretical studies employing DFT/B3LYP/LanL2DZ were conducted, which included the assessment of global reactivity descriptors, dipole moment, molecular electrostatic potential image (MEP), optimized geometry, and the LUMO-HOMO energy gap to support the geometrical structure of the synthesized compounds. On the other side, the optical constants of H2ASB and its complexes have been studied over 300–1500 nm spectral range. The optical band gap (Eg) values of the present film's changes from 1.92 eV for H2ASB to 1.45 eV for CuHASB(5) film whereas the static index of refraction (n) takes a different behavior. The obtained values of n and Eg are the same as those recorded for many semiconductor materials. This means that, compared to the cost and ease of preparation, these films under study could replace many other semiconductors, such as CdTe with (Eg = 1.5 eV) which is the same value of CuHASB(4) film. With the help of n and extinction coefficient (k) values, the dielectric and non-linear optical parameters have been estimated and well discussed. Finally, the sheet resistance (Rs) and thermal emissivity (εth) changes due to the incident photon energy have been investigated. It was observed that, the change of Rs and εth with E is opposite to the change of other parameters such as the absorbance and optical conductivity.

Exploring low-temperature dynamics in triple perovskite ruthenates using nonlinear dielectric susceptibility measurements

We report the nonlinear dielectric properties of three triple-perovskite ruthenates: Ba3CoRu2O9, Ba3BiRu2O9, and Sr3CaRu2O9. These compounds exhibit notable correlations among their spin, charge, lattice, and polar degrees of freedom. Ba3CoRu2O9 displays a pronounced frequency-dependent relaxation in χ2,3 just above the magnetoelastic transition, occurring around 100 K, followed by an abrupt loss of polarization within the ordered phase. In Ba3BiRu2O9, we encounter the possibility of multiple coexisting relaxation behaviors, indicating a complex phase strongly influenced by the spin-gap opening at 175 K. Lastly, Sr3CaRu2O9 displays anomalies with strong dispersion effects close to its magnetic transitions, indicating a robust coupling between magnetic and dipolar orders in the system. These measurements highlight the significance of higher-order (hyper-)susceptibilities in providing profound insight into the dynamics of a system, offering information otherwise inaccessible through the linear polarization response alone.

Fe3O4 microplate filled PEI matrix composite with remarkable nonlinear conductive characteristics, dielectric property, and low percolation threshold

As the presence of a percolating network formed by filler is indispensable for field grading composite, particulate fillers often result in high filler content that can be unfavorable in some aspects. The utilization of fillers with high aspect ratio is an effective way of reducing percolation threshold. In this work, Fe3O4 microplate (FMP) was prepared by a PVP-assisted hydrothermal method and it was adopted to fabricate composite films with different filler content by using polyetherimide (PEI) as the matrix. The composite film exhibited a percolation threshold of approximately 8 phr. The nonlinear coefficient measured 6.28 at a filler content of 10 phr. The nonlinearity in the conductive behavior of the composites was attributed to tunneling effect and Schottky emission. The filling of the FMP into PEI resulted in increase in dielectric constant and the dielectric loss maintained low. This study suggests that the FMP is a promising filler of low-filler-content field grading composite.

Dielectric Properties of a Nanocomposite from RbNO3 Incorporated into Pores of Al2O3 Matrix

The present work reports the experimental results of studying linear and nonlinear dielectric properties of a ferroelectric nanocomposite from RbNO3 embedded in pores of an Al2O3 matrix. The dielectric relaxation times were determined above and below the phase transition temperature of pure RbNO3 (436 K). It was shown that for RbNO3 incorporated into nanosized pores of the Al2O3 matrix, a decrease in the phase transition temperature and a change in relaxation times were observed.

Structural Changes and Very-Low-Frequency Nonlinear Dielectric Response of XLPE Cable Insulation under Thermal Aging.

The structural changes and very-low-frequency (VLF) nonlinear dielectric responses are measured to evaluate the aging state of cross-linked polyethylene (XLPE) in power cables under various thermal aging conditions. For this purpose, the accelerated thermal aging experiments were performed on XLPE insulation materials at 90 °C, 120 °C and 150 °C with different durations of 240 h, 480 h and 720 h, respectively. The Fourier transform infrared spectrum (FTIR) characterization and differential scanning calorimeter (DSC) were tested to analyze the influence of different aging on physicochemical properties of XLPE insulation. Besides, the VLF dielectric spectra show that the permittivity and dielectric loss change significantly in the VLF range from 1 mHz to 0.2 Hz. A voltage-current (U-I) hysteresis curve referring to a standard sinusoidal voltage and the response current were introduced to characterize the nonlinear dielectric properties of XLPE insulation caused by thermal aging.

Characterization of PbWO4 thin films formed by the pulsed laser welding technique

Herein thin films of PbWO4 were formed from bilayers of Pb/WO3 by the pulse laser welding technique (PLW) within couple of seconds in an argon atmosphere. Thin films of Pb (100 nm)/WO3 (500 nm) were deposited by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. The films were then exposed to a pulse laser beam of fixed amplitude and variable pulse width (0.1–10 ms). The produced films were characterized by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and optical spectrophotometry techniques. An almost pure phase (∼90%) of tetragonal PbWO4 was achieved after the pulse width exceeds 5.0 ms. PbWO4 thin films produced by the PLW technique exhibited a direct and indirect energy band gaps of 2.27 eV and 3.52 eV, respectively. Energy band tails of widths of 1.35 eV were found dominant in these films. In addition fitting of the dielectric resonance spectra for Pb/WO3 and PbWO4 thin films indicated that the formation of PbWO4 was accompanied with a decrease in the high frequency dielectric constant, a decrease in the free hole concentration and an increase in the electronic friction in the films. The fast method of obtaining PbWO4 thin films and the formation of the direct band gap being 2.27 eV together with the nonlinear dielectric and optical properties make the PbWO4 films obtained by the PLW technique suitable for optoelectronic technology.

Study on Nonlinear Dielectric Properties of Micro Silica

Inorganic insulating powder can potentially be used in nuclear power plant cables, fire-resistant cables, and so on due to its high heat resistance and radiation resistance. It is of great academic and engineering value to study the dielectric properties of inorganic insulating powder. In this paper, we aim to study the nonlinear dielectric properties via the measurement of the time-domain polarization current spectrum under the application of a DC electric field. Three kinds of silica powders are measured by a measurement system with adjustable pressure. The effects of powder shape, particle size, and packing pressure and temperature on the dependence of relaxation polarization and electrical conductivity on the applied electric field are studied. The experimental results show that the relationship between electrical conductivity and the electric field of inorganic insulating powder presents two different characteristics, i.e., field-induced enhancement and field-induced weakening. The relationship between conductance and temperature shows an increase with temperature. That is, the electrical conductivity increases or decreases with the increase in temperature. The inorganic powder insulation can be regarded as a composite, which is composed of inorganic powder particles and air gaps. The interface between the powder particles and air gaps contributes a lot to the polarization of inorganic insulating powder. The phenomena (including the field-induced weakening characteristic between relaxation polarization and electric field and the decrease characteristic of polarization with increasing temperature) can be explained by a simplified interface polarization mechanism.

Nonlinear conductive performance and dielectric properties of MoS2 filled PEI matrix composite

Nonlinear conductive performance and dielectric properties of MoS2 filled PEI matrix composite

Polarization-controlled volatile ferroelectric and capacitive switching in Sn2P2S6

Smart electronic circuits that support neuromorphic computing on the hardware level necessitate materials with memristive, memcapacitive, and neuromorphic- like functional properties; in short, the electronic response must depend on the voltage history, thus enabling learning algorithms. Here we demonstrate volatile ferroelectric switching of Sn2P2S6 at room temperature and see that initial polarization orientation strongly determines the properties of polarization switching. In particular, polarization switching hysteresis is strongly imprinted by the original polarization state, shifting the regions of non-linearity toward zero-bias. As a corollary, polarization switching also enables effective capacitive switching, approaching the sought-after regime of memcapacitance. Landau–Ginzburg–Devonshire simulations demonstrate that one mechanism by which polarization can control the shape of the hysteresis loop is the existence of charged domain walls (DWs) decorating the periphery of the repolarization nucleus. These walls oppose the growth of the switched domain and favor back-switching, thus creating a scenario of controlled volatile ferroelectric switching. Although the measurements were carried out with single crystals, prospectively volatile polarization switching can be tuned by tailoring sample thickness, DW mobility and electric fields, paving way to non-linear dielectric properties for smart electronic circuits.

Excellent permittivity-temperature stability and reliability performance of ultra-thin Ba0.97Ca0.03TiO3-based MLCCs

ABSTRACT High-temperature stability and reliability are in high demand for ultra-thin multilayer ceramic capacitors (MLCCs), which are ubiquitous in electronic industries. Here, two doping matrices of BaTiO3 (BT) and Ba0.97Ca0.03TiO3 (BCT) are chosen to prepare ultra-thin MLCCs, whose effects on the microstructure, nonlinear dielectric properties, temperature stability, and reliability of the capacitors were investigated. Compared with BT-based MLCCs, BCT-based MLCCs possess better core-shell structures, thus, leading to a higher Schottky barrier for inhibiting carrier migration and improving aging performance. For the 1.5 μm-thickness capacitors using the BCT doping matrix rather than BT, the temperature coefficient of capacitance reaches the X7R standard, and the breakdown field increases from 148 to 172 V/μm. Moreover, the ability to resist insulation resistance degradation has been significantly improved. This work demonstrates the great potential of using BCT as the doping matrix to prepare ultra-thin MLCCs with excellent temperature stability and reliability.

Time-domain response model of nonlinear dielectric properties for electrical field grading composites

The electrical field grading materials are expected to well response to arbitrary electrical excitation. In this paper, a modified Voronoi network model is established to simulate the response of electrical field grading materials under arbitrary excitation. The grain-boundary structure of ZnO microvaristors is described by the Voronoi polygons with a distorted hexagonal structure and the nonlinear conductivity is modeled based on the carrier transport mechanism. The network calculations replicate the resistive contacts between fillers and the micro-region breakdown phenomenon of insulating materials during the formation of the conduction path. The accuracy of this model is evaluated using AC and surge measurements for the ZnO/SiR samples. The model can manage the typical nonlinear time-domain responses and well reflect the effect of filler concentrations as well as the relationship between capacitive and resistive components of the responses. This work is helpful to design field grading materials to self-adapt high electrical fields of electronic and electrical devices and increase their stability and durability.

Nonlinear dielectric properties of polyimide in high AC electric field

The nonlinear dielectric properties of polyimide (PI) films, excited by high-intensity, AC electric fields, have been measured. This work highlights that nonlinear DC conduction is a component of the AC conductivity and dielectric loss response when surpassing a certain threshold field strength. An additional Poole–Frenkel polarization, induced by high-intensity, high-frequency fields, also contributes to the nonlinearity. This increases the dielectric losses through a charge de-trapping process, the so-called “jacking-up” effect. A novel expression that captures the large signal behavior of the complex permittivity is introduced using the Cole–Cole format. Finally, it is shown that the dielectric properties and power dissipation density in PI films remain fully linear and frequency-independent up to an AC electric field of EPF ∼100 Vrms/μm and more conservatively below a threshold field of EX ∼ 45 V/μm (i.e., end of the ohmic region). Consequently, polyimide-based insulated electronic devices that are designed to continuously operate below this threshold field (including both uniform and fringe fields) will remain immune to a frequency-dependent electrical aging. Their lifetime should not be affected in any way.

Core-double-shell structured BT@TiO2@PDA and oriented BNNSs doped epoxy nanocomposites with field-dependent nonlinear electrical properties and enhancing breakdown strength

Field-grading polymer nanocomposites have drawn significant attention in high voltage electrical industries due to their excellent nonlinear conductive or dielectric properties. But composites with both nonlinear properties are rarely reported, and desirable nonlinear performance associated with excess fillers in the composite is at the expense of electric breakdown strength. In this work, BaTiO3 nanoparticles were decorated successively using double-shell layers of TiO2 and polydopamine, which are developed as novel nanofillers (BT@TiO2@PDA) for field-grading applications. Subsequently, BNNSs were prepared by liquid phase exfoliation, serving as the inhibitor of breakdown phase growth in the composites. Finally, novel epoxy nanocomposites (EP/BT@TiO2@PDA-OB) with BT@TiO2@PDA and oriented BNNSs were fabricated by a simple hot-pressing method. Results show that the hierarchically designed nanoparticles can make the composites possess not only nonlinear dielectric properties due to high εr of BT and improved interfacial polarization, but also nonlinear conductive properties resulted from the organic semiconductor PDA shell. Nonlinear effective medium theory (EMT) was utilized to explain the nonlinear dielectric properties, and the hopping transport model considering Pool-Frenkel effect was applied to explain the nonlinear conductive properties. In addition, electric breakdown tests reveal that EP/BT@TiO2@PDA-OB has significantly enhanced breakdown strength (45.7 kV/mm) as compared to that of pristine epoxy resin (29.4 kV/mm) and EP/BT@TiO2@PDA-RB (randomly dispersed BNNSs, 36.2 kV/mm). It is expected that these results can open new avenues for the design of novel composites with both nonlinear conductive properties and dielectric properties as well as high breakdown strength.

Dielectric Properties and Phase Transitions of KNO3 Embedded in Porous Aluminum Oxide

Background: The research of nanocomposites based on ferroelectrics has been recently stimulated by the discovery of a number of their unique properties. These properties are of particular interest from both fundamental and applied points of view Objective: This paper presents the results of comparative studies of the linear and nonlinear dielectric properties of potassium nitrate embedded from the solution and from the melt into aluminum oxide films with a pore diameter of 100 nm. Methods: An E7-25 impedance meter with a frequency range of 25 Hz – 1 MHz was used to investigate the linear dielectric properties. The setup for researching nonlinear dielectric properties has a sinusoidal oscillator with an operating frequency of 2 kHz. Results: The temperature dependences of the permittivity ε' and the third harmonic coefficient γ3ω were measured in the heating and cooling mode. It was found that for a nanocomposite obtained from the solution, the ferroelectric phase of KNO3 was formed only upon cooling in the temperature range 397 – 360 K. At the same time, when KNO3 was embedded into the Al2O3 film from the melt, the polar phase occurred both upon heating and cooling in the temperature range of 300 – 432 K and 300 – 421 K, respectively. Conclusion: Thus, the conducted studies of the dielectric properties showed a significant difference in the phase transition temperatures for the KNO3/Al2O3 nanocomposites obtained from the solution and from the melt compared to the bulk sample. The phase transition shifts during heating had a different sign for the nanocomposites obtained from the solution and from the melt. The temperature range of the existence of the ferroelectric phase significantly depends on the method of embedding KNO3 into aluminum oxide films. For the nanocomposite obtained from a solution, the polar phase is formed only upon cooling, whereas when potassium nitrate is embedded from the melt, the polar phase is formed both upon heating and cooling.

Enhancement of Nonlinear Dielectric Properties in BiFeO3-BaTiO3 Ceramics by Nb-Doping.

BiFeO3–BaTiO3 (BF–BT) ceramics exhibit great potential for diverse applications in high temperature piezoelectric transducers, temperature-stable dielectrics and pulsed-power capacitors. Further optimization of functional properties for different types of applications can be achieved by modification of processing parameters or chemical composition. In the present work, the influence of pentavalent niobium substitution for trivalent ferric ions on the structure, microstructure and dielectric properties of 0.7BF–0.3BT ceramics was investigated systematically. Doping with niobium led to incremental reductions in grain size (from 7.0 to 1.3 µm) and suppression of long-range ferroelectric ordering. It was found that core-shell type microstructural features became more prominent as the Nb concentration increased, which were correlated with the formation of distinct peaks in the dielectric permittivity–temperature relationship, at ~470 and 600 °C, which were attributed to the BT-rich shell and BF-rich core regions, respectively. Nb-doping of BF–BT ceramics yielded reduced electronic conductivity and dielectric loss, improved electrical breakdown strength and enhanced dielectric energy storage characteristics. These effects are attributed to the charge compensation of pentavalent Nb donor defects by bismuth vacancies, which suppresses the formation of oxygen vacancies and the associated electron hole conduction mechanism. The relatively high recoverable energy density (Wrec = 2.01 J cm−3) and energy storage efficiency (η = 68%) of the 0.7BiFeO3–0.3BaTiO3 binary system were achieved at 75 °C under an electric field of 15 kV mm−1. This material demonstrates the greatest potential for applications in energy storage capacitors and temperature-stable dielectrics.

Nonlinear Dielectric Properties of the Stator and Transformer Insulation Systems

Composite insulation systems usually exhibit nonlinear phenomena, such as voltage-dependent dielectric response and high-order current harmonics. In this article, a high-voltage system capable of performing both dielectric frequency response (DFR) and polarization/depolarization current (PDC) measurements up to 20 kV is devised. The nonlinear properties of the motor stator and power transformer insulation systems are studied. Experimental results show that the voltage-dependent effect becomes significant as the voltage magnitude approaches the nominal and frequency decreases. The third current harmonic component is found to be dominant over the other components and has a strong correlation with the decrease in the dissipation factor. By taking both the fundamental and third-harmonic components into account, more consistent voltage-dependent characteristics are revealed. These features are important indications of insulation defects that are often neglected in field diagnostic testings. The investigation of the nonlinear properties helps to enhance the condition diagnosis reliability.

Thermally stimuli-responsive materials with transformable double channels of nonlinear optical and dielectric properties.

Organic-inorganic hybrid materials have received extensive attention and in-depth research in the past few decades due to their superior properties and potential applications in storage, sensing, dielectric switches, actuators and other information fields. Based on this scientific background, we developed two organic-inorganic hybrids [TMFEA]2CdI4 (compound 1) and [TMFEA]2ZnI4 (compound 2) (TMFEA = trimethylfluoroethylammonium). Both compounds show transformable double channels of nonlinear optical and dielectric properties induced by structural phase transitions, which was proved by the thermal, nonlinear optical, and dielectric phase changes. In addition, the channels can be switched ON and OFF by temperature regulation. This work will provide inspiration and options for the exploration of opto-electrical dual channel components.

Linear and nonlinear dielectric properties of (CuO)1-x/(BaTiO3)x composites

The temperature dependences of the dielectric constant ε' and the third harmonic coefficient γ3ω for composite ceramics (СuO)1- x /(BaTiO3) x in the temperature range 100–300 K were studied. It is shown that the ε´(T) dependence for СuO has insignificant anomalies at transition temperature ТN 2 = 230 K. The maximum values of the third harmonics fit in the middle of the temperature interval [ТN 1 ; TN 2]. With an increase in the content of barium titanate, an increase in the dielectric constant and a shift of the polar region toward low temperatures are observed.

Harnessing Phase Transitions in Antiferroelectric ZrO2 Using the Size Effect

AbstractThe unique nonlinear dielectric properties of antiferroelectric (AFE) oxides are promising for advancements in solid state supercapacitor, actuator, and memory technologies. AFE behavior in high‐k ZrO2 is of particular technological interest, but the origin of antiferroelectricity in ZrO2 remains questionable. The theory of reversible electric field‐induced phase transitions between the nonpolar P42/nmc tetragonal phase and the polar Pca21 orthorhombic phase is experimentally tested with local structural and electromechanical characterization of AFE ZrO2 thin films. Piezoresponse force microscopy identifies signature evidence of a field‐induced phase transition. A significant size effect in AFE ZrO2 is experimentally observed as film thickness is scaled down from 14.7 to 4.3 nm. The size effect is explained by modifications to the phase transition energy barrier heights ranging from 0.6 to 7.6 meV f.u−1 depending on crystallite size and in‐plane compressive strain with decreasing ZrO2 film thickness. Using the size effect, it is possible to double the energy storage density in ZrO2 from 20 J cm−3 to greater than 40 J cm−3, thus highlighting a feasible route for superior performance in AFE fluorite supercapacitors.