Specific Dielectric Constant Research Articles

Spinel ferrites having conductive grains, resistive interfacial boundaries and relaxation mechanism for possible supercapacitor applications

Linear increase in crystallite size (16–24 nm) of MnxZn1−xFe2O4 nanostructures and mixed behavior of lattice constant (8.429–8.462 Å) is reported. The system exhibits considerable promise for microwave applications due to its elevated dielectric constants and minimal dispersion losses from 20 Hz to 20 MHz. With x = 0.75, sample is good for energy storage devices like supercapacitors due to large specific surface area (53 m2/g) and dielectric constant. These samples exhibit maximum relaxation times ranging from 1.97 × 10−7 s to 2.43 × 10−4 s, with corresponding relaxation energy values spanning from 159.22 meV to 341 meV for x = 0 and x = 1 samples. The Cole-Cole plots reveal that grains exhibit conductive behavior at lower frequencies, while grain boundaries contribute significantly to the resistive behavior. Additionally, we have introduced Bode diagrams and equivalent electronic circuit models for the first time, offering valuable insights into the electrical behavior of the nanomaterial samples.

Structural phase transition in cobalt oxyfluoride Co3Sb4O6F6 observed by high-resolution synchrotron and neutron diffraction

A structural transition was observed in non-centrosymmetric oxyfluoride Co3Sb4O6F6 at TS ∼180 K from a cubic phase (I4‾3m) to a c > a tetragonal phase (I4‾), through high-resolution neutron and synchrotron powder diffraction. In addition, specific heat, magnetization, and dielectric measurements were performed to investigate this phase transition. Although the specific heat and dielectric constant showed anomalies at TS, no transition to a ferroelectric phase was observed in the polarization hysteresis loop down to 30 K. Moreover, a magnetic structure analysis using neutron powder diffraction data revealed a transition from a paramagnetic phase to a G-type antiferromagnetic phase at TN ∼67 K, at which a peak was also observed in the specific heat measurements. The magnetic moments of Co2+ were aligned along the tetragonal c-axis with a Co2+ moment of 2.80(1) μB at 13 K. The rotation and deformation of the CoO2F4 octahedron due to the large displacement of F atoms were observed at TS from the structural analysis, which play an important role in the structural phase transition in Co3Sb4O6F6.

Kinetic instability of a chitosan – aspartic acid – water system as a method for obtaining nano- and microparticles

The specific electrical conductivity and dielectric constant of aqueous solutions of ionic aminopolysaccharide chitosan in L-aspartic acid were investigated. An increase of the mobility of charge carriers in these solutions was found in comparison with solutions of an individual acid. The evaluation of the kinetic stability revealed that the viscosity, electrical conductivity and dielectric constant of the chitosan – L-aspartic acid – water system decrease, while the pH value increases. It was shown that the time variation of physicochemical and electrochemical parameters is due to the effects of counterionic association with the transition of macromolecules to the ionomeric state and is accompanied by phase segregation of the polymer phase in the form of nano- and microparticles. The conducted studies carried out have shown the fundamental possibility of controlling the metastable state of this system in order to obtain nano- and microparticles.

Formation, structure, properties of chitosan aspartate and metastable state of its solutions for obtaining nanoparticles

Chitosan (200 kDa) dissolution in an aqueous solution of L-aspartic acid, physicochemical properties and features of the resulting chitosan salt were studied by conductometry, potentiometry, viscometry, turbidimetry, IR and NMR spectroscopy, and X-ray diffractometry. Chitosan aspartate is a water-soluble hydrated polymorph exhibiting properties of a cationic polyelectrolyte with an effective macromolecular coil radius 60–75 nm. The specific conductivity, dielectric constant, viscosity and pH of the chitosan – L-aspartic acid – water system change over time after preparation due to counterion-polycation association to form ion pairs, multiplet structures, and their subsequent aggregation. As a result, nanoparticles (40–90 nm) are formed after ~24 h, microparticles (0.6–1.4 μm) are after ~48 h, and precipitation occurs after 72–96 h. The precipitated phase is a water-insoluble chitosan salt with a developed system of H-bonds and high crystallinity degree. Chitosan nanoparticles have high biocompatibility and the ability to accelerate the proliferative activity of epithelial cells. HypothesisIon pairs and multiplets are formed in the chitosan – L-aspartic acid – water system due to counterion association, which leads to phase segregation of the polymer substance at the level of nanoparticles and microparticles.

Design and Performance Assessment of Dielectrically Modulated Nanotube TFET Biosensor

The manuscript proposes a novel charge plasma-based junctionless silicon dual cavity nanotube tunnel field-effect transistor (DC-NT-TFET) based biosensor for the detection of neutral and charged biomolecules. For improved sensing ability, the nanogap cavity is introduced in the inner as well as the outer portion of the NT-TFET. Also, the vertical orientation of the device enhances the even distribution of the biomolecules within the cavity area. The inner cavity provides more space for immobilization of the biomolecules and utilizes the advantages of material solubility. In this manuscript sensitivity of the proposed biosensor is Investigated for four neutral biomolecules of dielectric constant, streptavidin (k =.1), biotin (k = 2.63), 3-aminopropyl-triethoxysilane (APTES) (k = 3.57), and protein (k = 8). Also, charged biomolecule, deoxyribonucleic acid (DNA) with a specific dielectric constant of k = 6 is examined for different positive as well as negative charge density. The sensing capability of the device is analyzed in terms of various DC and RF performance parameters. Also, outer cavity length optimization and on various biomolecules are analyzed in the manuscript.

Effect of substrate material on the performance of planoconcave patch antenna for 5G

In this article the design of a Plano-Concave patch antenna has been explored and reported. The effect of substrate material which include the dielectric with a specific dielectric constant has been analysed. Proposed shape of the patch is designed by subtracting a semi-circular patch from the conventional square patch .To analyse the effect of dielectric material on the performance of antenna, different materials with specific dielectric constant ( εr) like Silicon ( εr=11.7 ), Alumina92_pct( εr=9.2 ), FR4 Epoxy ( εr=4.4 ), RT Duroid ( εr=2.2) have been considered . The performance is considered for 5G LMDS application that includes 26.5 GHz to 29.5 GHz. The analysis has been done by considering the S-Parameter (Return loss <-10 dB), Antenna Gain, Directivity, Radiation Efficiency and surface current distribution. Table 1 provides the comparison of parameters for different substrate material.

Investigations on magnetic characteristics of the soil and their influence on its dielectric response

Abstract Conventionally, soils have been characterized based on their physical, chemical and mineralogical characteristics. However, in order to address various geo-environmental issues that have become a threat for the modern day civilization, soils have also been characterized based on their electrical properties. Furthermore, it has been demonstrated that the electrical properties of the soil mass (i.e., the soil compacted at a certain dry density and water content) are instrumental, primarily, in measuring its volumetric moisture content. In this context, though several efforts have been made by earlier researchers to determine dielectric response of the soil mass, the effect of soil magnetic characteristics on dielectric response and volumetric moisture content has not been established yet. Hence, development of a methodology to determine magnetic characteristics and their relationship with the dielectric response of the soil mass, if any, becomes quite intriguing. With this in view, soils of entirely different characteristics were tested for their magnetic characteristics (viz., remnant magnetization, coercivity and magnetic hysteresis area) by employing a magnetometer. Furthermore, these characteristics have been correlated with the physical, chemical, mineralogical and electrical properties (dielectric dispersion obtained from an impedance analyzer) of the soil. The study demonstrates that the parameter “area of magnetic hysteresis” of the air dried soils has significant influence on soil specific parameters such as specific gravity, iron content and dielectric constant. This preliminary study also proposes a hypothesis to obtain volumetric moisture content of the soil mass based on its magnetic characteristics and dielectric constant, which can be obtained from an impedance analyzer. However, efficiency and utility of the proposed hypothesis should be demonstrated by testing a large number of soils from different parts of the world.

Polar and magnetic order in GaV4Se8

In the present work, we provide results from specific heat, magnetic susceptibility, dielectric constant, ac conductivity, and electrical polarization measurements performed on the lacunar spinel GaV4Se8. With decreasing temperature, we observe a transition from the paraelectric and paramagnetic cubic state into a polar, probably ferroelectric state at 42 K followed by magnetic ordering at 18 K. The polar transition is likely driven by the Jahn-Teller effect due to the degeneracy of the V4 cluster orbitals. The excess polarization arising in the magnetic phase indicates considerable magnetoelectric coupling. Overall, the behavior of GaV4Se8 in many respects is similar to that of the skyrmion host GaV4S8, exhibiting a complex interplay of orbital, spin, lattice, and polar degrees of freedom. However, its dielectric behavior at the polar transition markedly differs from that of the Jahn-Teller driven ferroelectric GeV4S8, which can be ascribed to the dissimilar electronic structure of the Ge compound.

Electrically insulating properties of the 5d double perovskite Sr2YOsO6

A high-pressure-synthesized double perovskite Sr2YOsO6 was investigated by synchrotron X-ray diffraction and measurements of its magnetic susceptibility, specific heat capacity, complex impedance, and complex dielectric constant. It crystallized into a monoclinic double perovskite structure (P21/n) with complete ordering of the Y and Os atoms. Its magnetic behaviors, including the antiferromagnetic transition temperature (∼52 K), Curie-Weiss effective moment [3.48(5) μB/Os], and Weiss temperature [−350.1(7) K], were close to the respective values of Sr2YOsO6 previously synthesized without an applied pressure of 6 GPa. Transport property measurements revealed that the lower limit of the activation energy was 192(1) meV and the charge gap remained open regardless of the presence of magnetic order, conflicting with the electron delocalization predicted by theoretical calculations. Further consideration, including theoretical and experimental investigations of the roles of spin–orbit coupling and U of the 5d electrons of Os 5d-t2g3, may assist in understanding the general magnetic and insulating behaviors of quasi-half-filled 5d-t2g3oxides in the perovskite category toward the use of 5d double perovskite for magnetic applications.

Size-Specific ZnO Quantum Dots as Onsager Cavity in Ooshika–Mataga–Lippert Equation

The influence of the surrounding solvent medium to a solute molecule in solution can be treated within the framework of Onsager reaction field model which is based on the assumption that the solute is reduced to a point dipole at the center of a spherical cavity inside the solvent that can be described as the homogeneous, polarizable medium of specific dielectric constant. When the solute molecules are excited in solution of the polar solvent, the changes in the photophysical properties of the solute are manifested through shifts in the maxima of absorption and fluorescence spectra and the observation can be interpreted in terms of the Ooshika–Mataga–Lippert equation. Over several decades, a wide variety of organic molecules as fluoroprobes have been explored to reveal the polarity of their immediate solvent environment. However, while these molecular probes, with diameters less than 10 A, have been employed so far in the literature as Onsager cavities, the limiting value of their radii has not been restr...

Spin-Driven Multiferroic Properties of PbMn7O12 Perovskite

We synthesize PbMn7O12 perovskite under high-pressure (6 GPa) and high-temperature (1373 K) conditions and investigate its structural, magnetic, dielectric, and ferroelectric properties. We find that PbMn7O12 exhibits rich physical properties from interplay among charge, orbital, and spin degrees of freedom and rich structural properties. PbMn7O12 crystallizes in space group R3̅ near room temperature and shows a structural phase transition at TCO = 397 K to a cubic structure in space group Im3̅; the Im3̅-to-R3̅ transition is associated with charge ordering. Below TOO = 294 K, a structural modulation transition associated with orbital ordering takes place. There are two magnetic transitions with Néel temperatures of TN1 = 83 K and TN2 = 77 K and probably a lock-in transition at TN3 = 43 K (on cooling). There is huge hysteresis on specific heat (between ∼37 and 65 K at 0 Oe), dielectric constant (between ∼20 and 70 K at 0 Oe), and dc and ac magnetic susceptibilities around the lock-in transition. Sharp dielectric constant, dielectric loss, and pyroelectric current anomalies are observed at TN2, indicating that electric polarization is developed at this magnetic transition, and PbMn7O12 perovskite is a spin-driven multiferroic. Polarization of PbMn7O12 is measured to be ∼4 μC/m(2). Field-induced transitions are detected at ∼63 and ∼170 kOe at 1.6-2 K; similar high-magnetic field properties are also found for CdMn7O12, CaMn7O12, and SrMn7O12. PbMn7O12 exhibits a quite small magnetodielectric effect, reaching approximately -1.3 to -1.7% at 10 K and 90 kOe.

RELAÇÃO ENTRE O TEOR DE UMIDADE E A CONSTANTE DIELÉTRICA DE ESPÉCIES DE MADEIRA DA AMAZÔNIA DURANTE O PROCESSO DE SECAGEM1

RESUMO O objetivo deste estudo foi determinar a relação entre constante dielétrica e teor de umidade de seis espécies de madeira, por meio da construção de um capacitor. O material utilizado constituiu-se de madeiras da Amazônia não comercializadas, mas com alta abundância e dominância na Floresta Nacional deAlbizia duckeana (fava-paricá), Brosimumsp. (amapá-doce), Chamaecrista scleroxylon (pau-santo),Qualea dinizii (mandioqueira-rosa), Trattinnickia burserifolia (amescla) e Swartzia laurifolia(gombeira). Os corpos de prova para determinação da constante dielétrica foram confeccionados com as dimensões de 4,5 x 4,5 x 1 cm, definidas por testes preliminares realizados no Laboratório de Produtos Florestais (LPF). Para a coleta dos valores de capacitância, foi também construído um capacitor, utilizando multímetro digital, fios de cobre e placas de alumínio, sendo as medições realizadas em oito ocasiões, com intervalos de 1 h cada, durante o processo de secagem, que se iniciou na condição de massa saturada até atingir massa constante. A partir dos dados, foram ajustadas as curvas de regressão entre os valores de teor de umidade e constante dielétrica da madeira, as quais apresentaram forte correlação com as duas variáveis, mostrando a influência direta e proporcional do teor de umidade sobre a constante dielétrica. Em razão da inexistência de relação direta entre os dados de massa específica e constante dielétrica das espécies estudadas, sugere-se o desenvolvimento de novos estudos para melhor explicar a relação entre essas duas grandezas.

Modeling Proteins and Small Molecules with Inhomogeneous Dielectric Function: Implementation in Delphi

Most implicit solvent models treat bio-molecules as homogeneous dielectric medium inside high dielectric water phase. However, the dielectric distribution inside biological macromolecules is non-homogeneous, which depends on various factors, such as amino acid composition, structure, packing and flexibility. Many approaches have been developed to model the inhomogeneous dielectric distribution in biomolecules, including amino acid specific dielectric constant, using non-typical probe radius in finite-difference algorithm or delivering the dielectric constant from Gaussian distribution of atomic densities. Here, in DelPhi program, we developed an inhomogeneous dielectric method based on Gaussian smooth function. We tested this new method on calculating the solvation energies of 504 small molecules and the results show the method achieves better accuracy of the solvation energy calculation than homogeneous dielectric methods. Other tests on real proteins demonstrate that our inhomogeneous dielectric method is more reliable than homogeneous dielectric method for pKa and electrostatic potential calculations.

Surface Modification of GaN Substrate by Atmospheric Pressure Microplasma

In this study, surface modification of GaN substrates by microplasma was investigated. Microplasma, which is an atmospheric pressure nonthermal plasma and a type of dielectric barrier discharge, was generated with a pair of electrodes that were covered with a dielectric layer and that faced each other at a small discharge gap under 100 µm with a spacer. Owing to small discharge gaps (0–100 µm) and to the assumed specific dielectric constant of εr = 104, a high-intensity electric field (107–108 V/m) could be obtained with a relatively low discharge voltage of only about 1 kV at atmospheric pressure. The GaN surface was treated with atmospheric pressure microplasma using Ar and N2 as process gases and powered by AC and pulse power supplies. Modifications of the surfaces were observed after the treatment and they depend on the gas process, treatment time, and power supply. The surface was analyzed before and after the treatment by X-ray photoelectron spectroscopy (XPS) analysis and Field-emission scanning electron microscopy (FE-SEM).

Multi-channel drop filters using photonic crystal ring resonators

In this paper, we propose a photonic crystal multi-channel drop filter based on ring resonators and investigate its properties numerically by using the finite-difference time-domain (FDTD) method. This structure is constructed in a two-dimensional square lattice. Our multi-channel drop filter is composed of three waveguides and three ring resonators. These ring resonators are located in two different regions (heterostructure) which each region has specific dielectric constant. At resonance of each ring resonator, the power with certain wavelength transferred to one of the three drop waveguides is found to be more than 81%.

Properties of Lead–Free High Refractive Index Barium-Based Glass Doped with TiO2

The effect of varying the TiO2–content on the lead-free high refractive index glass based on 25 wt% barium carbonate added in replacing lead oxide was prepared and its physical, optical, and electrical properties were investigated. Seven glass samples were synthesized and characterized by using an analytical balance, a refractometer, a LCR meter and an X-ray diffractometer. Specific gravity, refractive index, and dielectric constant increased linearly as the increasing of the TiO2-content. The amorphous state of modification of glass structure due to TiO2 addition was confirmed.

Influence of Dye Adsorption Solvent on the Performance of a Mesoporous TiO2 Dye-Sensitized Solar Cell Using Infrared Organic Dye

The influence of a dye adsorption solvent of an infrared organic dye (NK-6037) on solar cell performance was investigated in a mesoporous TiO2 dye-sensitized solar cell (DSC). Various types of alcohols and a mixture of ethanol and tertiary-butanol (t-butanol) were applied as dye adsorption solvents. It was confirmed that the species of dye adsorption solvent significantly influences the performance of a DSC. Decreasing the specific dielectric constant of the dye adsorption solvent caused the amount of dye adsorbed on the TiO2 photoelectrode to increase dramatically. It is suggested that the specific dielectric constant of the dye adsorption solvent influences the solvation state of the NK-6037 dye in the solvent, thus determining, for instance, whether the dye is in the monomer state or the aggregate state. Interestingly, solar cell performance was not linearly proportional to the adsorbed amount of dye but a precise optimum amount of adsorbed dye was required for the best performance of the DSC. The optimum amount of adsorbed dye was approximately 5.0×10−8 mol/cm2 and it was obtained by using solvents having a dielectric constant of approximately 18. This condition was realized by 1-butanol, 2-propanol, and a mixture of ethanol and t-butanol with a volume ratio of 7:3. The best efficiency obtained for the DSC was 1.7%, using the optimum amount of the adsorbed infrared dye NK-6037. It is speculated that an excess of dye on the TiO2 photoelectrode accelerates the formation of H-type dye aggregates, resulting in a decrease in short circuit photocurrent (Jsc) by unfavorable side reactions of electron loss. It is demonstrated that dye adsorption solvent selection is the critical factor in obtaining high performance in a DSC

Purified and porous poly(vinylidene fluoride-trifluoroethylene) thin films for pyroelectricinfrared sensing and energy harvesting

This paper aims at improving the performance of the poly(vinylidene fluoride-trifluoroethylene)[P(VDF-TrFE)] copolymer for pyroelectric infrared detection and direct thermal toelectrical energy conversion. Three different types of samples were prepared and examined:commercial, purified and porous films. Here, full characterization of the thermophysical andelectrical properties relevant to pyroelectric infrared detection and energy conversion ofboth purified and porous P(VDF-TrFE) thin films is presented. Properties measuredinclude (1) density, (2) ferroelectric to paraelectric phase transition temperature, (3)enthalpy of change of phase, (4) electrical resistivity and (5) ferroelectric hysteresis, as wellas (6) specific heat, (7) dielectric constant, (8) loss tangent and (9) pyroelectriccoefficient as a function of temperature. The figures of merit for infrared detectionFV,FI andFD were improved by 47.0, 59.6 and 51.6%, respectively, for the purified filmswhile the porous films with a porosity of 33% showed an improvement of 52.8,66.3 and 62.6%, respectively, when compared to those of dense commercialP(VDF-TrFE) films. In addition, figures of merit for energy harvesting,FE andk2, indicate that the purified and porous films are attractive for thermal to electrical energyconversion as well.

A Universal Model for Nanoporous Carbon Supercapacitors Applicable to Diverse Pore Regimes, Carbon Materials, and Electrolytes

Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model, which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopore regime (2-50 nm), counterions enter mesoporous carbon materials and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (<2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (>50 nm) at which pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, which show the significant effects of pore curvature on the supercapacitor properties of nanoporous carbon materials. It is shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials, including activated carbon materials, template carbon materials, and novel carbide-derived carbon materials, and with diverse electrolytes, including organic electrolytes, such as tetraethylammonium tetrafluoroborate (TEABF(4)) and tetraethylammonium methylsulfonate (TEAMS) in acetonitrile, aqueous H(2)SO(4) and KOH electrolytes, and even an ionic liquid electrolyte, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size It may lend support for the systematic optimization of the properties of carbon supercapacitors through experiments. On the basis of the insight obtained from the new model, we also discuss the effects of the kinetic solvation/desolvation process, multimodal (versus unimodal) pore size distribution, and exohedral (versus endohedral) capacitors on the electrochemical properties of supercapacitors.

Polysilazane Precursor Used for Formation of Oxidized Insulator

ABSTRACTWe report on SiO2 film formation using Polysilazane precursor treated with remote oxygen plasma and high-pressure H2O vapor heating. Polysilazane precursor films with a thickness of 130 nm were formed on silicon substrates by spin coating method. They were annealed at 350°C in remote oxygen plasma at a pressure of 2.0×10−2 Pa and a 13.56×106 Hz radio frequency power of 300 W for 3h followed by 1.3×106-Pa-H2O vapor heating at 260°C for 3 h. Polysilazane precursor films were entirely oxidized by high-pressure H2O vapor heat treatment, and the density of Si-N bonding and Si-H bonding in Polysilazane precursor films were effectively dissociated by the combination of high-pressure H2O vapor heat treatment with remote oxygen plasma treatment. While MOS(Metal-Oxide-semiconductor) capacitors fabricated only by high-pressure H2O vapor heat treatment had a high specific dielectric constant of 6.1, a fixed oxide charge density of 1.3×1012 cm−2 and a density of interface trap of 5.4×1011 cm−2eV−1, the remote oxygen plasma treatment followed by high-pressure H2O vapor heat treatment allowed us to reduce them to 4.1 and 1.6×1011 cm−2, 4.2×1010 cm−2eV−1, respectively.