Variation Of Dielectric Constant Research Articles

The Multi-parameter on Line Monitoring of Hydraulic Oil Through a Tuning Fork Sensor

Based on a tuning fork sensor, a multi-parameter online monitoring system for oil was constructed. The influence factors on the dielectric constant, viscosity and density of hydraulic oil were studied. The experimental results show that the variation of dielectric constant, viscosity and density is directly related to the temperature, and that these parameters can reflect the changes of the moisture content and acid value in the hydraulic oil. Thus, the multi-parameters of dielectric constant, viscosity and density can be applied to assess the quality of hydraulic oil and realize it’s on line monitoring.

Growth, vibrational, optical, dielectric, thermal and third order NLO single crystal of manganese(II) hydrogen maleate tetrahydrate

ABSTRACTA nonlinear optical crystal of manganese(II) hydrogen maleate tetrahydrate (MHMT) is grown by slow evaporation technique at room temperature. The unit cell parameters of MHMT are confirmed by single crystal X-ray diffraction. A comprehensive FTIR and Raman spectral data of MHMT single crystal is presented. The UV-Vis-NIR spectrum is recorded from which the energy gap is evaluated confirms the possibility of charge transfer within the molecule. The gradual decomposition of the grown crystal by applying heat and hence the thermal stability is studied by means of TGA. The variation of dielectric constant (εr) and dielectric loss (tanδ) with frequency for temperatures 40–120 °C are studied. The electrical conductivity of MHMT crystal indicates the presence of mobile charge carriers in the crystal. Third-order nonlinear response is obtained using Z-scan technique with a He–Ne laser (632.8 nm). NLO parameters such as nonlinear absorption coefficient and third-order susceptibility are determined, which confirm that the crystal is a prospective candidate for applications in non-linear optics.

SST Dependence of Ku- and C-Band Backscatter Measurements

The normalized radar cross section (NRCS) measured by satellite ocean radar systems is representative of the sea surface roughness at the scale of gravity-capillary waves, which are not only dominated by winds, but also modulated by some secondary factors such as sea surface temperature (SST) and sea surface salinity (SSS). In this paper, the variations of NRCS due to SST changes, depending on scatterometer radar frequency, polarization, and incidence angle, are investigated on the basis of a physics-based radar backscatter model and a dataset of collocated ASCAT C-band and RapidScat Ku-band scatterometer measurements. The study shows that the SST effects are substantial at Ku-band, but rather negligible for C-band NRCS measurements. Furthermore, the SST effects are wind speed dependent and more pronounced in VV polarization and at higher incidence angles. SSS effects, due to dielectric constant, surface tension, and dynamic viscosity variations, on scatterometer winds are limited (within 1%). This study concludes that it is necessary to take SST into account in scatterometer wind retrieval for radar wavelengths smaller than C-band.

Crystal growth, structural, spectral, thermal, linear and nonlinear optical characterization of a new organic nonlinear chiral compound: l-tryptophan-fumaric acid-water (1/1/1) suitable for laser frequency conversion

A new organic active nonlinear optical crystal l-tryptophan fumaric acid water (1/1/1), (C15H17N2 O7. H2O)(LTFAW), consisting of zwitterion tryptophan molecule in conjunction with a fumaric acid molecule and a water molecule was grown by slow solvent evaporation technique from aqueous solution. The organic chromophore crystallizes from water in its zwitterions exhibiting tabular habit in monoclinic system with acentric space group C2 (Z = 4). The sharp peaks observed in Powder X-ray diffractogram depicts the crystalline nature. The presence of functional groups in the grown crystal was analyzed using FT-IR spectrum. The carbon and hydrogen environment in molecular structure was investigated using FT-NMR technique using deuterated DMSO solution. Ultraviolet–visible spectral analysis reveal that the crystal possess lower cut-off wavelength down to 275 nm, is a key factor to exhibit Second Harmonic Generation (SHG) signal. The direct optical band gap is evaluated to be 5.28 eV from the UV absorption profile. The evaluation of optical constants by employing UV–visible absorbance data such as, extinction coefficient, reflectance, refractive index, optical conductivity are supportive towards good performance as NLO devices. Temperature of decomposition was investigated using thermogravimetric analysis/differential thermal analysis techniques (TG/DTA). The luminescence profile exhibited two peaks (362 nm, 683 nm) due to the donation of protons from carboxylic group to amino group. The nonlinear optical behavior from the noncentrosymmetric crystal was observed by the generation of frequency doubled (2ω) optical radiation when subjected to pulsed Nd:YAG laser (1064 nm, 10 ns, 10 Hz) using Kurtz-Perry method. The variation of dielectric constant (εʹ) and dielectric loss (εʹʹ) vs. Log f for the title compound was analysed at a few selected temperatures and frequencies.

Influence of La3+ on structural, magnetic, dielectric, electrical and modulus spectroscopic characteristics of single phase CoFe2−xLaxO4 nanoparticles

In this work, we have studied the influence of La3+ substitution on structural, magnetic, dielectric, electrical and modulus spectroscopic characteristics of cobalt ferrite nanoparticles synthesized by starch-assisted sol–gel combustion method. The powder X-ray diffraction analysis confirms the formation of single-phase CoFe2−xLaxO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20) spinel ferrite nanoparticles. Raman spectroscopy study also reveals the formation of single phase spinel ferrite crystal structure. The morphological feature of synthesized ferrite nanoparticle was observed by scanning electron microscopy that demonstrate formation of spherical nanoparticles with grain size 10–50 nm. The presence of constituent’s, i.e., Co, Fe and La were authenticated by energy dispersive X-ray analysis. The magnetic parameters are measured by employing vibrating sample magnetometer. The saturation magnetization decreases with La3+ substitution, whereas coercivity shows anomalous behaviour. Cation redistribution in spinel ferrite nanoparticles are confirmed by X-ray photoelectron spectroscopy. The variation of dielectric constant (ϵ′, ϵʺ), loss tangent (tanδ), ac conductivity (σ), electric modulus (M′, Mʺ) and impedance (Z′, Zʺ) as a function of La3+ ion concentration and frequency has been investigated. The dielectric constant and ac conductivity increases with increase of La3+ substitution, whereas dielectric loss tangent exhibits anomalous behaviour. The modulus spectra reveal two semicircles associated with grain and grain boundary effects. The cole–cole plots in modulus formalism show that the electrical characteristics contribute from both the grains and grain boundaries. Modulus spectra suggest that the distribution of relaxation times and conduction mechanism are influenced by La3+ ion substitution in cobalt ferrite nanoparticles.

Influence of cerium dopant on magnetic and dielectric properties of ZnO nanoparticles

Ce-doped ZnO nanoparticles (NPs) with different Ce doping concentrations (0, 0.96, 1.96, 2.52 and 3.12 at.% of Ce) were prepared by the chemical co-precipitation method. Energy-dispersive analysis of X-rays confirms the presence of Ce in Ce-doped ZnO nanoparticles. Raman spectra revealed the hexagonal wurtzite structure of pure and Ce-doped ZnO nanoparticles and presence of various defects. The photoluminescence spectra exhibited enhanced violet and blue emission peak intensities for 0.96 at.% of Ce, while broad band green emissions decreased with Ce content. Electron paramagnetic resonance (EPR) studies revealed the presence of oxygen vacancies (V O), zinc vacancies (V Zn) and Ce3+ ions in the prepared ZnO nanoparticles. VSM studies showed room temperature ferromagnetism (RTFM) in the Ce-doped ZnO NPs. The substituted Ce3+ions found to induce RTFM along with V O, V Zn in correlation with the results obtained from the EPR, PL and Raman studies. The variation of dielectric constants (e r), dielectric loss (e″) and ac conductivity (σ ac) as a function of frequency and Ce concentration is studied using ‘Maxwell–Wagner Model.’

Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm3-have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively

Depth Estimates of Buried Utility Systems Using the GPR Method: Studies at the IAG/USP Geophysics Test Site

Identifying underground utilities and predicting their depth are fundamental when it comes to civil engineering excavations, for example, to install or repair water, sewer, gas, electric systems and others. The accidental rupture of these systems can lead to unplanned repair costs, delays in completing the service, and risk injury or death of workers. One way to detect underground utilities is using the GPR-Ground Penetrating Radar geophysical method. To estimate depth, the travel time (two-way travel time) information provided by a radargram is used in conjunction with ground wave velocity, which depends on the dielectric constant of materials, where it is usually assumed to be constant for the area under investigation. This procedure provides satisfactory results in most cases. However, wrong depth estimates can result in damage to public utilities, rupturing pipes, cutting lines and so on. These cases occur mainly in areas that have a marked variation of water content and/or soil lithology, thus greater care is required to determine the depth of the targets. The present work demonstrates how the interval velocity of Dix (1955) can be applied in radargram to estimate the depth of underground utilities compared to the conventional technique of constant velocity applied to the same data set. To accomplish this, synthetic and real GPR data were used to verify the applicability of the interval velocity technique and to determine the accuracy of the depth estimates obtained. The studies were carried out at the IAG/USP test site, a controlled environment, where metallic drums are buried in known positions and depths allowing the comparison of real to estimated depths. Numerical studies were also carried out aiming to simulate the real environment with variation of dielectric constant in depth and to validate the results with real data. The results showed that the depths of the targets were estimated more accurately by means of the interval velocity technique in contrast to the constant velocity technique, minimizing the risks of accidents during excavation.

Structural and electrical studies of Mn-Ni mixed nanoferrites

Mn-Ni mixed spinel nanoferrites with varying nickel concentration (0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by co-precipitation method. The spinel phase formation was confirmed by XRD and FTIR. Microstructure and compositional analysis were done by SEM and EDX respectively. Room temperature dielectric properties, resistivity and AC-conductivity were studied. The nanoferrites possess a very high dielectric constant. Dielectric loss tangent decreases with increase in nickel concentration and a broad peak appears for higher nickel concentration (0.2, 0.3, 0.4 and 0.5). Variation in DC-resistivity with nickel concentration goes in agreement with the variation of dielectric constant. Frequency variation of AC-conductivity for different nickel concentration shows dispersion at higher frequencies for different Ni concentration. Conduction mechanism has been explained on the basis of hopping electron model of ferrites.

A Charge-Plasma-Based Dielectric-Modulated Junctionless TFET for Biosensor Label-Free Detection

To reduce the fabrication complexity and cost of the nanoscale devices, a charge-plasma concept is introduced for the first time to implement a dielectric-modulated junctionless tunnel field-effect transistor (DM-JLTFET) for biosensor label-free detection. The formation of p+ source and n+ drain regions in DM-JLTFET is done by the deposition of platinum (work function = 5.93 eV) and hafnium (work function = 3.9 eV) materials, respectively, over the silicon body. Furthermore, a nanogap cavity embedded within the gate dielectric is created by etching the portion of gate oxide layer toward the source end for sensing biomolecules. For this, the sensing capability of DM-JLTFET has been investigated in terms of variation in dielectric constant, charge density, length, and thickness of the cavity at different bias conditions. Finally, a comparative study between DM-JLTFET and MOSFET biosensor is investigated. The implementation of proposed device and all the simulations have been performed by using ATLAS device simulator.

Impact of Dielectric Constant and Frequency Variation on the Conductance of A Rectangular Microstrip Patch Antenna

Impact of Dielectric Constant and Frequency Variation on the Conductance of A Rectangular Microstrip Patch Antenna

Conformal Coating of a Phase Change Material on Ordered Plasmonic Nanorod Arrays for Broadband All-Optical Switching.

Actively tunable optical transmission through artificial metamaterials holds great promise for next-generation nanophotonic devices and metasurfaces. Plasmonic nanostructures and phase change materials have been extensively studied to this end due to their respective strong interactions with light and tunable dielectric constants under external stimuli. Seamlessly integrating plasmonic components with phase change materials, as demonstrated in the present work, can facilitate phase change by plasmonically enabled light confinement and meanwhile make use of the high sensitivity of plasmon resonances to the variation of dielectric constant associated with the phase change. The hybrid platform here is composed of plasmonic indium-tin-oxide nanorod arrays (ITO-NRAs) conformally coated with an ultrathin layer of a prototypical phase change material, vanadium dioxide (VO2), which enables all-optical modulation of the infrared as well as the visible spectral ranges. The interplay between the intrinsic plasmonic nonlinearity of ITO-NRAs and the phase transition induced permittivity change of VO2 gives rise to spectral and temporal responses that cannot be achieved with individual material components alone.

Magnetic, dielectric and magnetoelectric properties of BiFeO3-CoFe2O4 nanocomposites

Nanocomposites (NCs) comprising BiFeO3 (BFO) and CoFe2O4 (CFO) with nominal composition, x CoFe2O4 - (1-x) BiFeO3 (x = 0.2, 0.3 and 0.4) have been synthesized adopting a sol-gel route. XRD patterns of the prepared samples exhibit presence of both BFO and CFO crystalline phases. TEM images of the NCs show that particles are mostly spherical with size in the range 15–25 nm. Room temperature Mössbauer spectra of the pristine samples and NCs reveal presence of Fe3+ ions at different inequivalent sites of BFO and CFO. Room temperature dc magnetization measurements show significant enhancement in magnetization of the NCs compared to that of the pristine BFO. Variation of dielectric constant of the NCs with frequency shows a dispersive behavior in low frequency region which is attributed to grain boundary relaxation in the NCs. εr – T curves of all samples exhibit an anomaly near the antiferromagnetic transition temperature of BFO indicating presence of magnetoelectric (ME) coupling. Variation of capacitance of the NCs in presence of external magnetic field confirms an improvement of ME coupling in BFO after formation of the NCs.

Multi-ferroic and optical spectroscopy properties of (Bi0.5Sr0.5) (Fe0.5Ti0.5) O3 solid solution

Solid solution of (Bi0.5Sr0.5) (Fe0.5Ti0.5) O3 (BFST) ceramic is explored here to obtain multiferroic and optical properties of the sample. The polycrystalline sample BFST was prepared by a standard solid state reaction route. Room temperature XRD, Raman and FTIR spectra of the compound exhibit an appreciable change in its crystal structure of SrTiO3 on addition of BiFeO3 in equal ratio. The surface morphology of the gold-plated sintered pellet sample recorded by SEM and EDX exhibits a uniform distribution of small grains with well defined grain boundaries. Detailed studies on nature of polarization, magnetization and variation of dielectric constant, tangent loss with temperature as well as frequency indicate the existence of multiferroicity in the studied compound. The optical property of the sample has been studied by using UV–vis spectroscopy technique. Using diffuse reflectance and absorbance data, the optical band gap of the studied sample has been estimated as 2.87 eV which is useful for photo catalytic application.

Active switching and tuning of sharp Fano resonances in the mid-infrared spectral region.

We propose and analyze a scheme for active switching and spectral tuning of mid-infrared Fano resonances. We consider dielectric resonators made of semiconductor cylinder arrays and block pairs, and theoretically investigate their optical response change due to carrier generation. Owing to sharp optical resonances in these structures and large dielectric constant variations with carrier densities, the significant spectral tuning of Fano resonances is achievable. Furthermore, selective optical pumping in coupled semiconductor structures can even enable dynamic switching of Fano resonances. This leads to a drastic change in the scattering spectra as well as in the near-field intensity. We also observe a stark difference between Fano resonances in cylinder arrays and block pairs. To understand this unusual behavior, we adopt the two coupled oscillator model, and extract the relevant Fano resonance parameters that explain this difference. Our findings and in-depth analyses can be useful for molecular sensors and switching devices in the technologically important mid-infrared spectral region.

The effect of solvent dependent local field factor in the optical properties of CdTe quantum dots

CdTe quantum dots (QDs) are synthesized at room temperature in aqueous solvents of different dielectric constants and characterized using optical spectroscopy. Absorption spectra of the QDs obtained is used to calculate the size dependent dielectric function of the QDs using Kramers–Kronig relation and iterative matrix inversion method. Effect of solvent dielectric constant on optical properties of QDs is studied theoretically using Maxwell–Garnett effective medium theory. Direct correlation between absorption intensity and solvent dielectric constant is explained on the basis of decreasing local field factor of the solvents. Emission rates of QDs is also found to have dependence on the dielectric constant of the solvent. Spontaneous emission rates of QDs in Ionic liquid environment is studied theoretically using Maxwell–Garnett effective medium theory. Our results show that variation in dielectric constant of Ionic liquids have a significant impact on spontaneous emission properties of the QDs.

Magnetic field effect on exciplex-forming organic acceptor/donor system: a powerful tool for understanding the preferential solvation

Many acceptor/donor systems can form excited-state charge-transfer complexes (exciplexes) in photo-induced electron transfer reactions. Exciplex can be detected by their luminescence. In addition, the exciplex luminescence is magneto-sensitive. Here, we employ an approach based on the magnetic field effect on the exciplex of 9,10- dimethylanthracene/N,N-dimethylaniline pair in micro-homogeneous and micro-heterogeneous binary solvents to investigate the effects of the preferential solvation processes on solute molecules in solutions. Micro-homogeneous solvent mixtures of propyl acetate (PA)/butyronitrile (BN) allow for a systematic variation of the static dielectric constants, s , in the range from 6.0 to 24.6. The mixtures of toluene (TO)/dimethylsulfoxide (DMSO) with varying the s values in the range from 4.3 to 15.5 are used as micro-heterogeneous binary solvents. In micro-heterogeneous environment, DMSO molecules get preferentially favoured in the solvation shell, forming micro-clusters surrounding the solute molecules. This solvation effect is reflected in the altered magnetic field effects, lifetimes and dissociation rate constants of the exciplexes.

Low dielectric constant of polymer based composites induced by the restricted polarizability in the interface

Polyimide (PI) based composites filled by modified-TiO2 particles were fabricated by in-situ dispersive polymerization. The results show that there are lots of interface regions between organic-inorganic. With TiO2 content increasing, the dielectric constant of the composites firstly varies from 3.35 to 3.16 (0–3wt%), then increases to 3.46 (3–7wt%) at 0.1Hz. The restricted orientation and electronic distortion polarizabilities in the interface are responsible for the reduced dielectric constant. The restricted effect along with the enhanced interfacial polarization determines the variation of dielectric constant of PI/TiO2 composites. The present work provides a promising route to the design and fabrication of low-K polymer composites.

A hybrid dielectric resonator antenna for spectrum sensing and ultra‐wideband applications

ABSTRACTA new type of dielectric resonator antenna with consistent monopole‐shape radiation pattern across an ultra‐wideband operating spectrum of at least 15 GHz is presented. A hybrid resonator configuration along with three different matching enhancement methods including, composite dielectric, dielectric shaping, and step matching technique, is used to obtain this radiation performance. A radially dielectric constant variation structure is proposed to create the composite dielectric material. Deemed to be appropriate for spectrum sensing and UWB applications, the frequency domain responses of this antenna are experimentally presented and discussed. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2609–2611, 2016

Simulation of dielectric behavior in RFeO $$_{3}$$ 3 orthoferrite ceramics (R = rare earth metals)

Due to their colossal dielectric constant (CDC), $$\hbox {RFeO}_{3}$$RFeO3, orthoferrite ceramics (R = rare earth metal) have recently attracted much attention. In the present research, the dielectric constants of $$\hbox {RFeO}_{3}$$RFeO3 orthoferrite ceramics, whether with or without CDC, have been simulated. The type of synthesis method, the type of R material, temperature, and frequency as the effective parameters on the dielectric behavior are introduced to the model. Another input parameter is the ratio of $$\hbox {Fe}^{+2}/\hbox {Fe}^{+3}$$Fe+2/Fe+3 peak area (in the XPS diagram), which is the most important parameter that affects the CDC behavior. Initially, a colossal database is formed by means of WebPlotDigitizer software and 2930 experimental data, and then the simulation is carried out through gene expression programming. Two case studies are also performed on $$\hbox {PrFeO}_{3}$$PrFeO3 and $$\hbox {NdFeO}_{3}$$NdFeO3 orthoferrite ceramics to validate the accuracy of the presented model. $$\hbox {PrFeO}_{3}$$PrFeO3 exhibits significant CDC behavior whereas the $$\hbox {NdFeO}_{3}$$NdFeO3 ceramic samples possess little CDC property, both of which were precisely simulated by the model. Two-dimensional tenth-degree equations resulting from the model predict the dielectric constant variations accurately.