Dielectric Properties of Gelatin Films Determined Using a Simple Set-Up

The dielectric properties of materials when heated at ultrahigh frequencies are determined by methods based on the use of waveguide cavity resonators. However, as the sample is in the closed volume during measurements, the dielectric properties of destructive material thus determined can contain errors attributed filling of the resonator volume and depositing products of the sample decomposition on the internal conducting surfaces of the resonator. We present the results of studying the dielectric properties of destructive materials under heating in waveguide resonator cavity using methods that exclude the impact of destruction products on the accuracy of measurement. To reduce the influence of destructive vapors rising from the surface of the sample during the destruction process, additional thin quartz plates, placed on the sample surface were used. In addition, cuvettes with a lid were also used to prevent destruction products from entering the resonator volume. A method for taking into account the effect of plates and cuvettes in calculating the dielectric constant and dielectric loss tangent of a material sample when heated in a cavity resonator is presented. Changes in the dielectric properties of a composite material consisting of quartz fabric impregnated with an aluminochromophosphate binder and fiberglass laminate made of quartz fabric impregnated with a phenol-formaldehyde binder were studied in a temperature range above the onset of the destruction (up to temperatures at which loss of the structural strength of the material is observed). The developed method can be used in studying the thermophysical properties of destructive materials to assess changes in their dielectric characteristics under operation conditions of high-temperature heating.

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BaBiSb3Ti4O15 is a Bi-based Sb substituted Barium Bismuth Titanate ceramic is processed by mixed oxide process, calcined at 850 °C and subsequently sintered at 875 °C temperature. Room temperature XRD study confirms the formation of single-phase compound. The SEM micrograph shows uniformly distributed grains over the surface of the compound. Dielectric characteristic is studied in a wide frequency (100 Hz–10MHz) and temperature (30 °C–500 °C) range. Phase transition broadening is observed on substitution of antimony ion at bismuth site indicating diffuse phase transition in the material. From the appearance of P ∼ E loop, the existence of ferroelectricity in the material is confirmed. The complex impedance plots inform the impact of the grain and grain interface in the resistive and capacitive behavior of the compound. Negative temperature coefficient of resistance (NTCR) characteristics are noticed from the impedance study confirming the semiconductor-like behavior of the compound.

In the food industry, the interest in dielectric properties of agricultural and food materials has been principally for predicting heating rates when the materials are subjected to high frequency electric fields (Oliveira, 2002). Microwave volumetric heating for food preservation and processing applications has been popular since the early 1970s and products such as rubber, wood, paper and many other agricultural products have been studied extensively (Nelson, 1991). An important application of microwaves in the food industry has been the non-invasive determination of moisture content (Kraszewski, 1998) and its effect on the dielectric properties of materials such as granular solids, meats, vegetables and fruits (Mudgett, 1995). Microwave techniques for drying of food products have also been very popular (Schubert, 2005).

The method suggested for determining the characteristics of dielectrics is not connected with the removal of the samples from the measurement cell, which simplifies the measurement process in comparison with conventional two-electrode methods. The difference between this method and the known three-electrode method resides in the use of a measurement cell with a new spatial arrangement of the additional electrode; this arrangement allows the error with which e is measured to be reduced at frequencies above 100 kHz, while the error in measuring tan δ can be reduced throughout the frequency range. It is also feasible to use this method in temperature investigations of dielectric materials.

We have investigated the electric field and temperature dependence of dielectric, impedance and conduction characteristics of a lead-free complex distorted perovskite (Bi1/2K1/2)(Zn1/2W1/2)O3 ceramic. The material was synthesized by using a standard high-temperature ceramic technology. Analysis of x-ray diffraction data and patterns collected at room temperature has provided the information on the formation of a distorted perovskite with an orthorhombic crystal system. Dielectric and impedance spectroscopy techniques have been utilized to study the effect of frequency and temperature on the dielectric, impedance and transport (conduction) characteristics of the compound. The mechanism of dielectric relaxation phenomenon in the compound has been analyzed using the dielectric and impedance data collected in a wide range of temperature (100–500°C) and frequency (1 kHz–1 MHz). Analysis of temperature-frequency-dependent Nyquist (impedance) plots has shown an important role of grains (bulk) and grain boundaries in the capacitive and resistive characteristics of the material. Based on the frequency-dependent electrical modulus and impedance data of the compound, the dielectric relaxation of non-Debye type has been suggested. The nature of the temperature- and frequency-dependence of ac conductivity of the compound follows Joncher’s power law. The fabricated compound has some important dielectric characteristics which can potentially be used for electronic devices.

A microcontroller-based measuring instrument and a new mathematical model are used to investigate capacitor permittivity and dielectric materials' charge-discharge characteristics. In this study, a prototype capacitive permittivity measurement apparatus for dielectric materials was carefully developed using an Arduino microcontroller, a resistor, and a capacitor. The experimental setup comprises a capacitor-resistor circuit, wherein a 5-volt power supply sourced from the microcontroller interfaces with a computer. During the charging process, a comprehensive evaluation of model-data alignment was performed, yielding values of 0.54252156, 0.9951, and 111.2508701 for the sum of squares error (SSE), the coefficient of determination (R-squared), and the sum of squares total (SST), respectively. Similarly, the analysis extended to the discharging process, unveiling values of 5.10174756, 0.962805684, and 137.1647082 for SSE, R-squared, and SST, respectively. These findings confirm the accuracy of the microcontroller that was programmed by incorporating a model in precisely measuring the relative permittivity of dielectric materials and capacitance values, with an R-squared value above 0.95 following capacitor literature benchmarks. The novelty of this study is that this configuration enabled the precise assessment of both permittivity and the charge-discharge characteristics of the dielectric materials within the capacitor. This methodology made it possible to accurately measure the permittivity and charge-discharge characteristics of dielectric materials within a capacitor. The scientific significance of this research lies in its ability to provide a carefully developed instrument capable of investigating the permittivity of dielectric materials and capacitor capacitance measurements. Scholars, international engineering communities, and academics can use this technological breakthrough to advance research into dielectric material properties and capacitor characteristics.

In this paper is illustrate the dielectric characteristics of a nanocomposite polymer matrix based on polypropylene (PP) with insertion of multi-walled carbon nanotubes (MWCNTs). The dielectric characteristics analyzed are the real and imaginary part of permittivity, dielectric losses and electrical conductivity of the sample based on PP with 5% insertion of MWCNTs. The measurements are done in a range of frequency between 1 MHz to 3 GHz and for a variation of temperature from 30°C to 120 °C, with a step of 5°C. Graphical representation of dielectric characteristics are done in 2D and 3D plans.

Dielectric performance of nanostructured magnesium oxide and effect of cobalt substitution

Dielectric properties, impedance analysis and modulus behavior of CaTiO3 ceramic prepared by solid state reaction

Dielectric properties of materials are used for evaluating their interactions with electromagnetic energy. Dielectric properties of food materials are required for various applications in food industry such as microwave (at 915 or 2450 MHz), radio wave (at 13.56, 27.12 or 40.68 MHz) and magnetic field processing. In order to understand the response of food materials to electromagnetic energy, dielectric parameters must be determined as a function of frequency, temperature, composition and moisture content. In this review, the dielectric properties of different food groups were listed depending on temperature and frequency ranges. In addition to the literature data of dielectric properties, the penetration depths of microwave or radio wave through food groups were calculated. The effects of temperature and composition (mostly moisture content) on dielectric properties depend on the type of the food and sometimes on frequency. However, the effect of frequency is constant; increased frequency decreased dielectric constant, loss factor and penetration depth. The lowest calculated penetration depth belonged to the fish surimi gel as 3.39 mm at microwave frequency whereas they were high generally for fats, oily seeds and flours (max was 372602 mm for corn flour). It appears that dielectric properties of foods should be investigated further depending on the interactions between frequency, temperature and composition. And then, dielectric heating based on the aim of the process can be applied accordingly. Besides, it appears that the moisture content and especially the dipole rotation and the conductivity movements of the molecules in free water content of the food are some of the most critical factors influencing the dielectric properties of food materials.

This work revealed the role of altering vanadium (V) content in Mn–Zn ferrites. We used the traditional solid-state reaction method to prepare the {mathrm{Mn}}_{0.5}{mathrm{Zn}}_{0.5}{mathrm{V}}_{mathrm{x}}{mathrm{Fe}}_{2-mathrm{x}}{mathrm{O}}_{4} (x = 0.0, 0.05, 0.10, 0.15, 0.20) ferrites. Powder X-ray diffraction was used to analyze the samples’ crystal structures, revealing the prepared sample’s spinal cubic crystal structure. With increasing Vanadium concentration, the lattice constant drops proportionately. We used Debye–Scherrer (D–S), Williamson–Hall (W–H) Plot, Halder–Wagner (H–W) Langford, and Size Strain Plot (SSP) methods to compare different structural properties. We also used the impedance analyzer to investigate the samples’ dielectric characteristics and AC conductivity at room temperature over a frequency range of 1 kHz–100 MHz. The magnetic properties, i.e., Saturation magnetization (Ms), Coercive field (Hc), and Remanent magnetization (Mr), were estimated from the ferromagnetic hysteresis behavior of the samples measured using a vibrating sample magnetometer (VSM). The saturation magnetization was observed to decrease with an increase in V content. The Mr and HC vary non-linearly with V contents. The prepared samples’ initial permeability was tested, and a reasonably constant complex permeability (µ') was recorded over a wide frequency range (~ 1000 Hz).

To estimate the dielectric characteristics of an insulating oil for power cables, alkylbenzene oil, an original specimen and specimens aged for 100 and 200 hours at 100/spl deg/C were measured by dielectric characteristics experiments under the conditions of a temperature range from 30[/spl deg/C] to 120[/spl deg/C], a frequency range from 30[Hz] to 1/spl times/10/sup 6/[Hz] and an applied voltage of 2.83 to 19.79[Vpp]. The results of the experiments for the contribution of carrier dynamics to the dielectric characteristics are presented.

Dielectric spectroscopy methods for estimating the state of trees were considered. Dielectric characteristics describe cell membranes and conductivity of plant tissues. A pulsed Fourier transform dielectric spectrometer of an original design was used to measure the values of dielectric characteristics. The spectrometer was connected to a portable computer, which was used to control and power it. The device design allows to expressly (in about 1s) receive information on the dielectric characteristics of the tree trunk tissues in the frequency range from 1 to 100 kHz and to process, visualize and save the results of measurements on a computer in the field conditions. Tree state estimates obtained with the pulsed Fourier transform dielectric spectrometer were compared with the visual tree characteristics and radial growth data. It is shown that there are differences in the values of dielectric characteristics in trees of different state categories and with different values of radial growth. Dielectric spectroscopy data, unlike subjective qualitative visual indicators of tree state, are quantitative and objective. The data can be obtained much faster and with less effort compared to estimates of tree characteristics by radial growth. The described method was used to estimate the state of Siberian pine (Pinus sibirica), Siberian fir (Abies sibirica) and Siberian spruce (Picea obovata) in forest plantations of the Baikal region. Studies were carried out both in control (undamaged) plantations and in those affected by bacterial infection. It is shown that the proposed method can be applied to the express state estimation of trees and the level of their damage.

In a system of dielectric matrix–conducting particles, the dielectric characteristics are analyzed over a wide frequency range (3–37 GHz). Experimental values of the dielectric constant e′ and dielectric loss tangent tanδ are presented for pressureless sintered AlN-based composites with different contents of the conducting particles (Mo, W, and TiN) within the interval from 0% to the percolation threshold. Both the real e′ and imaginary e″ parts of the dielectric constant of the investigated composites monotonically increased, reaching maximum values (e′ = 15 – 26.5, e″ = 0.14–0.28) when the content of the conductive particles approached the percolation threshold. The dielectric loss tangent of the composites, depending on the conducting particle content, reached values of 0.0085 for AlN–16.6%Mo, 0.0095 for AlN–16%W, and 0.0105 for AlN–20.4%TiN. The dielectric losses e″ in the AlN-based composites, as long as they remain nonconductive for the direct current, are low compared to losses of e″ = 0.04 in polycrystalline AlN ceramics and exceed them by only 4–7 times. A relationship between the dielectric losses and the level of microwave absorption has been established. The dielectric characteristics, electrical resistance, and thermal conductivity of the produced AlN-based composites and their achievement of a high absorption of the microwave radiation (L = 23–32 dB/cm) make these materials promising bulk absorbers in microwave devices (TWTs, klystrons).