Measurement of Microwave Dielectric Properties and Factors Affecting Them

Sebastian, Mailadil Thomas

doi:10.1016/b978-0-08-045330-9.00002-9

Cited by 29 publications

(13 citation statements)

References 76 publications

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“…Symbols are data points and line is fitted polarons tunneling model and correlated barrier hopping model, whereas it is temperature independent in the quantum mechanical tunneling model. [43] As the temperature decreases further the σ dc region shrinks and shifts to lower frequencies until it disappears completely, and the σ (ω) spectrum is characterized mostly by the sublinear JPL regime. This behavior is very common in glassy and crystalline ionic solids along with semiconducting solids.…”

Section: Ac Conductivitymentioning

confidence: 96%

“…Different types of defects show the different frequency and temperature dependences of the dielectric losses. [43] Figure 10 shows the frequency dependence of the imaginary part of dielectric constant ε′′ at selected temperatures. The dielectric loss (ε′′) spectra of the complex for T > 345 K showed negative slopes (log-log scale), indicating that in this temperature and frequency range DC conductivity and/or universal dynamic response of conductivity were dominant.…”

Section: Dielectric Lossmentioning

confidence: 99%

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Spectroscopic, textural, electrical and magnetic properties of antimicrobial nano Fe(III) Schiff base complex

Mousa

Mahmoud

2019

Applied Organom Chemis

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A novel Schiff base ligand (L) was prepared through condensation of 2,6-diaminopyridine and dibenzoyl methane in a 1:1 ratio. This Schiff base ligand was used for complex formation reaction with Fe(III) chloride. The structures of the ligand and its complex were deduced from elemental analyses, mass spectroscopy, 1 H NMR, IR, UV-Vis, electronic spectra, magnetic moment, molar conductivity measurements, thermogravimetric analyses and X-ray diffraction. The molecular and electronic structures of both ligand and complex were optimized theoretically using density function theory (DFT) method.Moreover, the antimicrobial activities of the prepared compounds were studied and proven against some pathogenic bacteria. The Fe(III) complex had higher biological activity than that of the free ligand. Proceeding from the collected information, the properties of the complex were further investigated. The particle size was determined by dynamic light scattering technique to be 92.59 nm.Textural properties of the nano complex were studied by N 2 adsorption to estimate the specific surface area, pore volume and pore size distribution. The pores in the complex were found in the micropore-mesopore range. Differential scanning calorimetric measurements reveal the existence of four endothermic peaks at 243.8, 308, 339.8 and 380.5 K. Dielectric properties and conductivity were scanned at different frequencies and temperatures. The dielectric constant reaches a peak value of 600 at~390 K, 30 Hz. A crossover from the universal dielectric response to the super linear power law of conductivity was reported for this complex at T ≤ 345 K. Finally, the ACmagnetic susceptibility measurements were carried out in the lowtemperature region. The complex showed paramagnetic behavior with a slight change in the magnitude of its magnetic moment at T = 244 K.

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Section: Ac Conductivitymentioning

confidence: 96%

Section: Dielectric Lossmentioning

confidence: 99%

Spectroscopic, textural, electrical and magnetic properties of antimicrobial nano Fe(III) Schiff base complex

Mousa

Mahmoud

2019

Applied Organom Chemis

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“…6. When moving further away from the z-axis, with a In most dielectrics at microwave frequencies, one typically encounters tan δ ≪ 1 (see e.g., [35,36]) while studies in conducting media report tan δ ∼ 1 in the MHz range [37,38].…”

Section: The Effective Current For An Infinite Antennamentioning

confidence: 99%

Alleviating oscillatory approximate-kernel solutions for cylindrical antennas embedded in a conducting medium: a numerical and asymptotic study

et al. 2020

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We alleviate the unnatural oscillations occurring in the current distribution along a linear cylindrical antenna center-driven by a delta-function generator and embedded in a conducting medium. The intensely fluctuating current arises as a small-z0 asymptotic (or numerical) solution of the classical integral equations of antenna theory, for a cylindrical dipole of infinite (or finite) length, where z0 is the discretization length. To alleviate the oscillations, we employ an appropriate effective current further to the recent remedy of oscillations attained for a perfectly conducting linear cylindrical antenna of finite length for the case where the surrounding medium is free space. We derive asymptotic formulas for the infinite antenna, which are then put to numerical test. Furthermore, we point to the physical significance of the effective current whose function transcends a mere computational device.

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“…When a material sample is placed between the two dielectric resonators inside the metallic enclosure that comprises the SPDR fixture, an azimuthal electric field is generated [14]. The Rayleigh-Ritz method [12] is used to determine dielectric parameters of the inserted sample. The real part of permittivity, , in this device is calculated by the iterative function [14]:…”

Section: Introductionmentioning

confidence: 99%

“…The SPDR is capable of measuring the dielectric constant (relative permittivity) and loss tangent of a material in the range of 1 to 20 GHz [12]. Accuracy of the method requires that samples should have a thickness that is uniform and less than the air gap in the SPDR (typically 1 mm) [13].…”

Section: Introductionmentioning

confidence: 99%

Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

Rodríguez

Garcia

Fittipaldi

et al. 2016

AIP Conference Proceedings

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Abstract. The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eightharness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25°C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates.

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Measurement of Microwave Dielectric Properties and Factors Affecting Them

Cited by 29 publications

References 76 publications

Spectroscopic, textural, electrical and magnetic properties of antimicrobial nano Fe(III) Schiff base complex

Spectroscopic, textural, electrical and magnetic properties of antimicrobial nano Fe(III) Schiff base complex

Alleviating oscillatory approximate-kernel solutions for cylindrical antennas embedded in a conducting medium: a numerical and asymptotic study

Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

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