Values Of Dielectric Permeability Research Articles

Electrical properties of Ni-doped CaCu3Ti4O12 ceramics

Samples of Ni-doped CaCu3Ti4O12 ceramics with the compositions of CaCu3Ti4-4хNi4хO12-δ and CaCu3-3хNi3хTi4O12 (x ≤ 0.06) were synthesized by the solid phase method. X-ray phase analysis revealed the trace amounts of copper oxide (II) admixture in the samples. Electrical properties of the samples of both compositions were studied in the temperature range of 25–400°С. The minimal dielectric loss tangent 0.07 and the maximal dielectric constant 6.0·103 (at 1 MHz) were exhibited by the CaCu3Ti4-4хNi4хO12-δ (х = 0.03) ceramics at room temperature. The equivalent circuit was created based on the modeling of impedance spectra that well describe the electrical properties of the samples. It was proposed that the ionic charge transfer predominated in the studied samples at room temperature. This mechanism allows to explain the giant values of dielectric permeability and the high values of impedance phase at low frequencies. The electrical properties of Ni-doped CaCu3Ti4O12 ceramics were analyzed and discussed.

Дифференциальная электрохимическая импедансная спектроскопия полимерных протонных электролитов

A method of deriving standard electrochemical impedance spectroscopy (EIS) data such as Bode diagram, Nyquist diagram, and others from frequency dependence of the external impedance using numerical differentiation of the indicated dependence in quadratic coordinates is proposed, the method being named as the differential electrochemical impedance spectroscopy (DEIS). The method was tested experimentally on polyvinyl alcohol-based proton membranes doped with sulphated montmorillonite in granulated or dispersed states as an example. It is shown that DEIS data can be easier and with higher accuracy described by regular semicircles while leaving intact values of ohmic resistance. Very high values of dielectric permeability were obtained in the work enabling to develop condensers with high capacity based on highly conductive polymeric proton electrolytes.

Methods for Substantiating the Electrodynamic and Design Parameters of Absorbing Materials of Waveguide Type

The paper considers the issues related to the microwave diffraction on periodic structures of waveguide type. An approach used for assessing the reflective characteristics of absorbing material is proposed. This approach is based on the assumption that in accordance with the energy conservation law, the entire power of the incident microwave radiation on the absorbing material is distributed into two components. One of them characterizes electromagnetic radiation reflection from material surface and is determined through wave impedance at the interface “medium – absorbing material”, and the other, obeying the law of electromagnetic waves diffraction on nonperfectly conducting closed surfaces of waveguide type, propagates into the lattice, then it is partially absorbed in the bulk of the material and reflected from the object (metal substrate), after which it is summed with the first component at the output. A feature of the proposed technique is the design ratios, allowing to determine rational values of dielectric permeability of material, lattice elements conductivity as well as the period and thickness of the lattice which enable to achieve “a semi-infinite layer” at which the minimum value of material reflection coefficient is observed and its no longer depends on the presence or absence of an object (metal substrate)

Preparation, structure and dielectric studies of solid solutions Pb(Fe1–xInx)2/3W1/3O3

New samples of Pb(Fe1–xInx)2/3W1/3O3 solid solutions were synthesized for the first time by the ceramic technology and detail of X-ray and dielectric studies were carried out. It was established that in the concentration region 0 < x < 0.12 the obtained samples are practically single-phase and represent perovskite solid solutions. The temperature and frequency dependences of the dielectric properties of the obtained solid solutions were firstly studied. It was found that the samples exhibit the characteristics of ferroelectrics-relaxor with pronounced maxima of dielectric permeability at Tm = 175–200 K, the position of which is shifted with increasing frequency towards high temperatures. Substitution of Fe for In in the solid solutions lowers the maximum value of dielectric permeability (from ∼4700 at x = 0 to ∼3700 at x = 0.10) without significantly changing its peak position on the temperature scale.

Dispersion of Water Conductivity in the Frequency Range of 104–106 Hz

The frequency dependence of impedance is studied in a capacitance cell filled with water directly contacting the electrodes. The absolute impedance value is determined by measurement of voltages in the cell and over the known resistance connected in series with it. The impedance dispersion range is found in the range of 104–106 Hz, where it decreases from the maximum to the minimum values. The processing of the impedance data using the corresponding equivalent circuit shows that distilled water has a constant dielectric permeability value (78–80 a.u.) in the whole studied range of 50 Hz to 10 MHz and impedance dispersion is related to dispersion of conductivity of water. An expression is obtained for description of conductivity of water at low, intermediate, and high frequencies (0–100 MHz) analogous to the Debye relationship. The value of τ = 0.6 μs and the value of the limiting high-frequency conductivity of 3 mS/m (at 20–25°C) is found for the additional conductivity dispersion region.

The Influence of Electron Irradiation on the Dielectric Characteristics of Single Crystals of AgGaSe2

The influence of various doses of electron irradiation on the dielectric permeability and specific conductance of ternary nonlinear optical crystals of AgGaSe2 at various frequencies of the measuring field in a range of temperatures of 100–300 K is studied. It is found that the irradiation of single crystals leads to a decrease in the values of dielectric permeability and a significant increase in conductance. It is shown that dielectric permeability and conductance increase with the growth in temperature. It is found that the presence of several types of conductance is characteristic for the crystals of AgGaSe2. Substantial frequency dispersion of the dielectric properties of the studied crystals is found.

Hydrodynamical flows in dielectric liquid in strong inhomogeneous pulsed electric field

We consider a hydrodynamical flow of dielectric liquid near a high voltage needle-shaped electrode in a strong inhomogeneous pulsed electric field. It was shown that under a small rise time, a negative pressure area (pressure is less than critical pressure) appears near the electrode leading to the formation of a cavity in which electric breakdown can develop. A comparison of the dependence of the velocity of fluid near an electrode for two cases (taking into account the dependence of dielectric permeability of the liquid on the electric field and without taking it into account) was made. A field-dependent dielectric coefficient leads to the appearance of two local maximums of the velocities and increases the minimum pressure, thus lowering the possibility of cavitation. While under the constant value of dielectric permeability only one local maximum appears.

RATIONALE FOR CHOOSING THE CHANGE MODEL OF THE DIELECTRIC PROPERTIES OF DISCONTINUOUS SYSTEMS

Purpose. The article deals with the insulation resistance of the track circuit as one of the parameters that affect the operating performance of the railway transport. To reduce the influence of the insulation resistance on the operation modes of the track circuits and the performance indicators of railway transport it is assumed to study the influence of crushed stone treatment on the value of dielectric permeability of the ballast bed. Methodology. The influence of material type for the surface treatment of crushed stone on the value of the dielectric permeability was assessed on the basis of the physical nature determination of the relative dielectric permeability. Determination of the relative dielectric permeability of granular media can only be indirect, as a consequence of incomplete adjoining of crushed stone grains and uncertainty of the pore volume. Thus, the calculations were performed by comparing the measured capacity for a medium with the known with measured medium capacity, for which it is necessary to define. That is, the more the measured capacity is changed, the more changes the dielectric permeability of the medium. Findings. Sleepers and ballast significantly change their electrical conductivity depending on the presence of moisture, ambient temperature changes, the presence of pollutants and other factors. The article analyzes the existing models to describe the dielectric properties of such systems. It has been established that coating the crushed stone ballast with organic substances influences the value of its relative dielectric permeability. The greatest effect of reducing this value is observed for the coatings based on rosin mixture and silicone. Originality. Authors proposed original method of dielectric properties increase of the permanent way by grains’ coating with nonwettable substances, on the surface of which is not formed a water film. Practical value. The article shows the possibility of minimizing the negative influence of reducing the isolation with maximum its elimination. It is proposed the solution of actual problem by eliminating the influence of insulation resistance on the modes of track circuits operation, which will eliminate the part of causes of the failure of signaling devices and reduce the number of cases of «false business».

Adsorption and electrical properties of nanodiamond powders in the presence of water vapor

The adsorption of water vapor on nanodiamond (ND) powders of detonation synthesis with various chemical states of the particle surface is investigated. The specific surface, porosity, and isotherms of water-vapor adsorption by ND powders are determined. It is shown that ND surface chlorination leads to a decrease of concentration of the primary adsorption centers determining the amount of water adsorbed. The data on the influence of the water vapor relative pressure on electrical conductivity G and dielectric permeability ɛ of the powders before and after chemical modification of ND are obtained. The interconnection between the amount of adsorbed water and ND electrical parameters is considered within percolation theory. It is shown that water-vapor adsorption leads to a giant increase in the dielectric permeability value and significant rise of conductivity near percolation threshold.

Comparative study of the electrical and structural properties of woven fabrics

The application of woven fabrics as the substrate materials for electronic products causes the need to examine their electrical properties at various external effects. This paper presents the results of electrical properties of the fabrics of cotton, cotton/polyethyleneterephtalate (PET) and PET. Dielectric loss factor and dielectric permeability were analyzed in a wide range of temperatures and frequencies. Relaxation peak which appears in this measuring region was identified as the secondary β-relaxation. At different frequencies the dielectric permeability has been analyzed at a different relative humidity at room temperature. At the higher values of relative humidity with the increase of frequency leads to greater reduction of the dielectric permeability and this is more prominent in the samples of cotton and cotton/PET blend. The dc volume resistivity has been investigated in the function of relative humidity at room temperature and interpreted by the raw composition and the structural properties. On the basis of the obtained results, it was concluded that on the electrical properties of cotton/PET blend, cotton has greater impact i.e. the component with the higher dielectric permeability value and smaller dc volume resistivity value.

Electronic sensors built on nanostructured cerium oxide films

The influence of the technical parameters of nanostructured CeO x film production on electronic, structural, optical, and photoelectronic characteristics has been studied for their practical application as the active element of various microelectronic sensors—such as high-performance photoresistors, MOS-photodiodes for bioluminescence registration, ion-selective field-effect transistor (ISFETs), and MOS-varactors indicating pH changing as a result of biochemical processes. X-ray photoelectron spectroscopy analysis (XPS) has shown that the ratio of Ce3+ and Ce4+ ions in CeO x films has changed, depending on the technological regime and, first and foremost, on the temperature of the substrate, which results in an changing of the fundamental gap width. The correlation between these alterations and the optical and photoelectric characteristics has been determined. On the basis of highly sensitive photo photoreceivers and living organisms (daphnia and bioluminescence bacteria), a portative electron bioluminescent metric complex has been created to determine the overall water toxicity caused by mycotoxin patulin, biphentrin, and chlorpyrifos. The minimal sensitivity threshold for patulin is 0.1 mg/l after a 2 h experiment and 0.01 mg/l after 6 and 24 h experiments; for biphentrin, it is 0.01 mg/l after a 3 h experiment and 0.0001 mg/l after a 24 h experiment. It is shown that applying nanocrystalline films of cerium oxide CeO x as the dielectric of MOS structures increases the sensitivity and stability of these sensors due to the high density of the surface of sensitive centers of CeO x (to 1020 m−2), the high values of dielectric permeability (ɛ = 26) and the band-gap width (3.6 eV), and low values of leakage currents. The results of ISFET and MOS varactor application with nanocrystalline CeO x film for the creation of immune and enzymatic biosensors have been demonstrated. The sensitivity threshold of an enzymatic sensor based on choline esterase to organophosphorous pesticides is 10−9 M, and for ions of heavy metals it is 10−7 M. The pH sensitivity of ISFET is 58 mV/pH, which is close to the maximal possible sensitivity for the semiconductor-dielectric-solution structure (the so-called Nernst sensitivity is 59 mV/pH).

Role of the Electrostatic Interactions in Pre-orientation of Subunits in the Formation of Protein-protein Complexes

Theoretical estimation of contribution of the electrostatic interactions to pre-orientation of ribonuclease subunits in process of complex formation was carried out. The subunit was considered as a multipole consisting of partial charges of all atoms of the molecule. The object of investigation was a system of two subunits with their centers of gravity fixed at some distance in vacuum. It was proposed that each subunit independently could rotate freely around its fixed center of gravity. The relative orientation states of the sub-units in such system were searched at which the system has electrostatic energy minima (equilibrium states). In first approximation the equilibrium states were found using especially designed approximate method for electrostatic interaction energy calculation, which permitted to calculate and compare the energies of the system in 245 (∼ 8 106) states with different mutual orientation of subunits. The angular coordinates of the found equilibrium states were further specified by calculation with gradient sliding method. Angular coordinates of the equilibrium states and the shapes of energy surface cuts along each coordinate angle were calculated also for the intersubunits distances diminished down to 50 Å. The dispersions of the angular coordinates of equilibrium states caused by heat movement (at T=300°) and their changes with shortening the distance between centers of gravity of subunits were estimated. Mutual orientation of subunits in the equilibrium states of the system under consideration was found to be similar to their mutual orientations in complex. Also it was found that relaxation time of the system, caused by electrostatic interaction of subunits, after removing the system from an equilibrium state, is much less in vacuum than the mean time between their Brownian collisions at room temperature. It follows from these results that in the case of ribonuclease in vacuum the electrostatic interactions of its subunits must be strong enough to realize the effictive pre-orientation of subunits during their Brownian approach from distances of the order 100 Å. Preliminary consideration taking into account the effect of surrounding water molecules on the electrostatic interactions of ribonuclease subunits showed that weakening of the interaction must be much less than in the case when one uses in its calculation the macroscopic dielectric permeability value equal to 80. So the results obtained for vacuum seem to be true for water solution also. More strikt theoretical analysis of this problem will be carried out in the following publication.

The structure of liquids and the nature of anomalies in the scattering and absorption light spectrum

Contour asymmetry of the Rayleigh line C 6 H 6 and CHCl 3 (0–350 sm −1 ) is studied. The nature of anomalies in the spectra is accounted for by the formation of the time and spatial correlation of particles resulting from the collective interaction and diffusion between heterogeneities. This model is used to explain the dependence of the dielectric permeability value on the lager thickness.

Study of dielectric permeability and dielectric loss angle tangent of triglycine selenate depending on the conditions of growing

AbstractTriglycine selenate (TGSe) monocrystals were grown at constant temperature and constant supersaturation. Dielectric permeability and the dielectric loss (angle tangent) of TGSe were studied both in weak and in strong electric fields with growing conditions. It was stated that the Curie temperature is 22,5° ± 0,1°C. The Curie‐Weiss temperature differs by 2–3,5° from the temperature corresponding to the maximum value of dielectric permeability. Nonlinearity of TGSe is determined.