Dielectric Spectroscopy Study on Vesicles of CTAB/SDBS System

Amphiphilic molecules can form into different structures, such as micelle, microemulsion, vesicle, liposome, liquid crystals, and so on by self-associating. The Dielectric Spectroscopy (DS) method has been applied to the systems of micelle and microemulsion successfully. For the first time the author put the method to the system of vesicle of CTAB/SDBS. The experiments show clear dielectric relaxation and the results were discussed primarily.

Determination of the oxidative stability of olive oil using an integrated system based on dielectric spectroscopy and computer vision

During storage,olive oil may suffer degradation leading to an inferior quality level when purchased and consumed.Oxidative stability is one of the most important parameters for maintaining the quality of olive oil,which affects its acceptability and market value.The current methods of predicting the oxidative stability of edible oils are costly and time-consuming.The aim of the present research is to demonstrate the use of dielectric spectroscopy integrated with computer vision for determining the oxidative stability index(OSI)of olive oil.The most effective features were selected from the extracted dielectric and visual features for each olive oil sample.Three machine learning techniques were employed to process the raw data to develop an oxidative stability prediction algorithm,including artificial neural network(ANN),support vector machine(SVM)and multiple linear regression(MLR).The predictive models showed a great agreement with the results obtained by the Rancimat instrument that was used as a reference method.The best result for modelling the oxidative stability of olive oil was obtained using SVM technique with the R-value of 0.979.It can be concluded that this new approach may be utilized as a perfect replacement for quicker and cheaper assessment of olive oil oxidation.

Dielectric spectroscopy as a potential technique for prediction of kiwifruit quality indices during storage

Dielectric spectroscopy has been employed as a simple,low cost and a non-destructive way for prediction of some physicochemical indices of kiwifruit during storage.A parallel-plate capacitor was developed and supplied with sinusoidal voltage waves within a frequency range of 40 kHz–20 MHz.Dielectric properties of samples were measured by the dielectric sensor.Additionally,changes associated with fruit ripening properties,including firmness,total soluble solid(TSS)and pH were determined as a function of time at 2
C.The results showed that storage time significantly affected the quality characteristics of kiwifruit.Artificial neural networks(ANNs)were employed to develop models for prediction of quality indices from dielectric properties at the swept frequencies.Dielectric property features were selected as inputs while the quality indices including firmness,TSS and pH were chosen as output for the ANNs.The obtained models were able to predict the firmness,soluble solids content,and pH of kiwifruit non-destructively.Among predictive models,an ANN with a topology of 20-19-1 gave a perfect capability to predict the kiwifruit firmness with R2 value of 0.92.Results of this research show that this technique can be used as an efficient and non-destructive method for kiwifruit quality evaluation and monitoring the ripening.

Piezoresponse force microscopy and dielectric spectroscopy study of Ba_(0.6)Sr_(0.4)TiO_(3)thin films

Research on synthesis,characterization and determination of processing-structure-property relationships of commercially important ferroelectric thin films has been performed.The sol-gel type solution deposition technique was applied to produce good quality thin films of Ba_(0.6)Sr_(0.4)TiO_(3)(BST60/40)chemical composition on the stainless steel substrates.The thin films were characterized in terms of their microstructure,crystal structure,phase composition,piezoelectric and dielectric properties.It was found that the BST60/40 thin film adopted the cubic structure at room temperature with an elementary cell parameter a-3:971e8TÅ.Morphology of the thin film surface was studied with Atomic Force Microscopy(AFM).Average roughness of the thin films surface was found(Sa=0:055μm).Piezoresponse Force Microscopy(PFM)was applied for the thin film characterization.Active piezoelectric regions were found in BST60/40 thin film.Therefore,dielectric response measured at room temperature was studied in assumption of piezoelectric electric equivalent circuit.

Dielectric spectroscopy of solid solutions based on sodium-potassium-cadmium in the temperature range (10 ÷ 900) K

This paper studies the dielectric spectra of solid solutions(SS)of the system(1−x−y)NaNbO_(3)-xKNbO_(3)-yCdNb_(2)O_(6) y=0.075,x=0.05÷0.30 in the temperature range(10÷900)K.The formation of a local maximum was established in the interval(260÷300)K at small x values,which,as KNbO3 increases,is gradually blurred and becomes an inflection point.Detected in SS with x=0.05÷0.10,the shift of the maxima of dependencesε′/ε_(0)(T)andε″/ε_(0)(T),depending on the frequency of the electric field at the temperature ranges(300÷304)K and(258÷271)K,is not related to relaxation.This anomaly may indicate a crystallographic disorder to A and B positions.The conclusion is made about the expediency of using the obtained results for the development of functional ferroactive materials.

Dielectric spectroscopy and structural characterization of nano-filler-loaded epoxy resin

This work outlines the characterization of epoxy resin[Bisphenol A-(epichlorhydrin):epoxy]and hardener[N(3-dimethylaminopropyl)-1,3-propylenediamine]with various inorganic nano-fillers.Dielectric characterizations of epoxy,hardener,neat epoxy(epoxy+hardener)and nano-epoxy(nano-filler+neat epoxy)composites loaded with 1 wt.%of inorganic nano-fillers(SiO_(2),Al_(2)O_(3),TiO_(2)and ZnO)were carried out using precision LCR meter,over the frequency range of 1 kHz-2 MHz at a constant temperature of 300.15 K.The structural information of nano-fillers,neat epoxy and nano-epoxy composites was understood by Fourier transform infrared spectroscopy and by XRD.Moreover,hardness and shear strength(shear punch)were also determined in order to gain additional information about the mechanical properties of epoxy composite.Influence of inorganic nano-fillers on the dielectric properties,structural chemistry and mechanical properties of neat epoxy composite is discussed thoroughly in this study.

Diagnostics of Argon Inductively Coupled Plasma and Dielectric Barrier Discharge Plasma by Optical Emission Spectroscopy

An experimental setup was built up to carry out radio frequency (RF) inductively coupled plasma (ICP) and dielectric barrier discharge (DBD), and to depict the optical emission spectra (OES) of the discharges. OES from argon ICP and DBD plasmas in visible and near ultraviolet region were measured. For argon ICP, the higher RF power input (higher than 500 W for our machine), the higher degree of argon plasma ionization. But that doesn’t mean a higher mean electron energy. With the increase in the power input, the mean electron energy increases slightly, whereas the density of electron increases apparently On the contrary, argon DBD discharge behaves in the manner of a pulsed DC discharge on optical emission spectroscopy and V-I characteristics. DBD current is composed of a series of pulses equally spaced in temporal domain. The Kinetics of DBD emission strength is mainly governed by the frequency of the current pulse.

Dielectric properties of nucleated erythrocytes as simulated by the double spherical-shell model

The dielectric properties of nucleated erythrocytes from bullfrogs were measured in a frequency range of 10 kHz–110 MHz.The complex permittivity(ε*),complex conductivity(κ*),and complex resistivity(ρ*)were analyzed and compared in the 10.63%to 37.58%haematocrit(Hct)range.The relaxation behavior,the passive electrical properties,and the cellular structure parameters,including the cell membrane,the cytoplasm,the nuclear membrane,and the nucleoplasm of the nucleated erythrocyte suspensions were investigated.The method used is based on the binomial Cole–Cole equation and the double spherical-shell physical models.Upon the elimination of the electrode polarization effect,two definite relaxations related to the interfacial polarization are observed on low-and high-frequency dispersions.The permittivity values and the characteristic frequency values differ by one order of magnitude:the low-frequency relaxation increments[?ε1=(5.63±1.43)×103]and the characteristic frequency[fc1=(297.06±14.48)kHz]derived from the cell membrane,the high-frequency relaxation increments[?ε2=(5.21±1.20)×102]and the characteristic frequency[fc2=(3.73±0.06)MHz]derived from the dielectric response to the external electric field of the nuclear membrane,respectively.Moreover,the other core dielectric parameters,such as the relative permittivity of the cell membrane[εm=(7.57±0.38)]and the nuclear envelope[εne=(23.59±4.39)],the conductivity of the cytoplasm(hemoglobin,κHb=(0.50±0.13)S/m]and the nuclear endoplasm[κnp=(2.56±0.75)S/m],and the capacitance of the bilayer membranes[Cm:(0.84±0.04)μF/cm2],and Cne:(0.52±0.10)μF/cm2]were also accurately and reliably measured.This work presents a feasible method to evaluate the dielectric parameters and the cellular structure of the erythrocytes of bullfrogs.Moreover,it paves the way for new studies on the haematology of frogs and the detection of nucleated cells via dielectric impedance spectroscopy.

Dielectric,impedance,modulus spectroscopy and AC conductivity studies on novel organic ferroelectric diisopropylammonium chloride(dipaCl)

Organic molecular ferroelectric diisopropylammonium chloride(dipaCl)was successfully synthesized using diisopropylamine,hydrochloric acid(57%)and methanol solution.Dielectric permittivity,impedance,modulus spectroscopy and conductivity were systematically studied by Capacitance-Conductance(CP-G)measurements in the temperature range of 373-445 K.Dielectric property tests clearly show that the organic molecular ferroelectric dipaCl obeys Curies-Weiss law 1/e=(T-T0)/C.The real(Z′)and imaginary(Z″)parts of the electrical modulus were calculated from the various values of e′and e″.It is shown that AC conductivity satisfies the relation s(w)∞wn,where the power exponent n depends on temperature and frequency.From Arrhenius equation,the activation energies Es and Eh are also calculated which describes the complete conduction mechanism of dipaCl.

Electric field-induced phase transition from the glasslike to paraelectric phase and dielectric spectra hardening in PMN single crystal

One of the key points in the physics of the relaxors is their response to the applied DC field.Many studies of this topic were made,in particular on the influence of the field on the dielectric properties.However,practically,in all the cases,the measurements were performed at a fixed frequency and usually with the change in the temperature at the fixed field strength.In this paper,we report the evolution of the dielectric spectra at low frequencies(0.1 Hz<ω<1 kHz)at fixed temperature 246 K on changing the DC electric field applied in(111)from 1 kV to 7 kV.Cole-Cole function was used to describe the spectra and the field dependences of the mean relaxation timeτ,the oscillation strengthΔεand the width parameterαwere determined.The obtainedτ(E)andΔε(E)provide evidence of the field-induced transition from the nonpolar glass-like phase to the nonpolar paraelectric phase at around 1.5 kV/cm.In the paraelectric phase,very fast hardening of the spectra was observed withτchanging from 10 s to about 10−4 s.The performed analysis demonstrated that the earlier reported positive C-V effect is completely determined by the spectra harden­ing,whileΔεdoes not show any change in the glass-like phase and monotonously decreases with a field increase in the paraelectric state.For complete understanding of the microscopic origin of the observed phenomena,a detailed study on the short-and long-range structures at the same condition is necessary.

Sign of differential reflection and transmission in pump-probe spectroscopy of graphene on dielectric substrate

Pump-probe differential reflection and transmission spectroscopy is a very effective tool to study the nonequilibrium carrier dynamics of graphene. The reported sign of differential reflection from graphene is not explicitly explained and not consistent. Here, we study the differential reflection and transmission signals of graphene on a dielectric substrate. The results reveal the sign of differential reflection changes with the incident direction of the probe beam with respect to the substrate. The obtained theory can be applied to predict the differential signals of other two-dimensional materials placed on various dielectric substrates.

Structure evolution,dielectric,and conductivity behavior of(K_(0.5)Na_(0.5))NbO_(3)-Bi(Zn_(2/3)Nb_(1/3))O_(3) ceramics

(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state method.The crystal structure,microstructure,dielectric,and conductivity behavior of this system were studied.Combined with X-ray diffraction(XRD)patterns,Rietveld refinement,and dielectric spectroscopy,an orthorhombic phase was determined for x=0.010,an orthorhombic-tetragonal mixed phase was identified for x=0.015,and a rhombohedral symmetry appears in 0.020≤x≤0.030.Both 0.98KNN-0.02BZN and 0.975KNN-0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent(tan)in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic.The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly,then drop sharply,and finally decline slowly,which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.

Stable dielectric response of low-loss aromatic polythiourea thin films on Pt/SiO_(2) substrate

We have investigated dielectric properties of aromatic polythiourea(ArPTU,a polar polymer containing high dipolar moments with very low defect levels)thin films that were developed on Pt/SiO_(2) substrate.The detected response is compared to the response of commercially available polymers,such as high density polyethylene(HDPE)and polypropylene(PP),which are at present used in foil capacitors.Stable values of the dielectric constantε'≈5(being twice higher than in HDPE and PP)over broad temperature and frequency ranges and dielectric losses as low as in commercial systems suggest ArPTU as a promising candidate for future use in a variety of applications.

DIELECTRIC RELAXATION IN RELAXOR FERROELECTRICS

In this review the dielectric properties of relaxor ferroelectrics are discussed and compared withthe properties of normal dielectrics and ferroelectrics. We try to draw a general picture ofdielectric relaxation starting from a textbook review of the underlying concepts and pay attentionto common behavior of relaxors rather than to the features observed in specific materials. We hopethat this general approach is beneficial to those physicists, chemists, material scientists and deviceengineers who deal with relaxors. Based on the analysis of dielectric properties, a comprehensivedefinition of relaxors is proposed: relaxors are defined as ferroelectrics in which the maximum inthe temperature dependence of static susceptibility occurs within the temperature range ofdielectric relaxation, but does not coincide with the temperature of singularity of relaxation timeor soft mode frequency.

CH ARACTERIZATION OF LA YERED Na_(2-x-y)LixKyTi_(3)O_(7) CERAMICS BY DIELECTRIC-SPECTROSCOPIC INV ESTIG ATIONS

In this paper,we present detailed investigations on the dielectric properties of Lithium(x=0.10)and Potassium(y=0.01,0.02,0.04,0.05)mixed Sodium trititanate,Na_(2-x-y)LixKyTi_(3)O_(7) poly-crystalline ma terials synthesized by solid-state reaction.The characteristics of the pelletized samples have been studied in the temperature range from 350 to 725 K and on the frequency in the range from 10kHz to 1 MHz.The studies reveal that the chain structured Na_(2-x-y)LixKyTi_(3)O_(7) layered compound posses electronic,ionic,dipolar,and space charge polarization mechanisms over the respective temperature regions in the entire temperature range of study.

Investigation of structural phase evolution and dielectric response of Co-doped BaTiO_(3)

In the present study,we have synthesized polycrystalline samples of BaTi_(1-x)Co_(x)O_(3)(BTCO)(x=0,0.01,0.03,0.05,0.07 and 0.10)with standard solid state reaction technique.The obtained samples are characterized by X-ray diffraction(XRD)and Raman spectroscopy for structural study.The detailed structural analysis has been performed by Rietveld refinement using Fullprof program.We observed an increase in lattice parameters,which results due to substitution of Co2t with large ionic radii(0.9Å)for smaller ionic radii(0.6Å)Ti4t.Moreover,peak at 45.5°shifts to 45°on Co doping,which is due to structure phase transition from tetragonal to cubic.Raman study infers that the intensity of characteristic peaks decreases and line width increases with Co doping.The bands linked with the tetragonal structure(305 cm
1)decreased due to the tetragonal-to-cubic phase transition with Co doping.Our structural study reveals the expansion of BTCO unit cell and tetragonal-to-cubic phase transformation takes place.The results from different characterization techniques are conclusive and show structural evolution with Co doping.The samples are further characterized by dielectric spectroscopy,dielectric measurement reveals the increase of dielectric constant and transition T_(c)-125° is observed for Barium titanate(BaTiO3),whereas transition disappears with Co doping.Both temperature and frequency-dependent tangent loss is also studied.

Dielectric and ferroelectric properties of CoCr_(2)O_(4)nanoceramics

CoCr_(2)O_(4)nanoceramics are prepared by sol-gel auto combustion method.Synchrotron X-ray diffraction analysis affirms the singlephasepristine cubic structure with space group Fd3m.Debye-Scherrer method estimates the crystallite size of main intense peak tobe~27:15 nm.Prominent bands obtained in infrared spectra at 448 and 599 cm^(-1)are due to metal-oxygen stretching bond presentat tetrahedral and octahedral sites.Dielectric parameters decrease as frequency increases from 103 to 106 Hz that can be interpretedby Maxwell-Wagner-type interfacial polarization.Complex impedance spectra(Nyquist plot)reveal arc like behavior,which ismainly due to intergrain(grain boundary)resistance that also exhibits conducting nature of the nanoceramics.Weak ferroelectricityis mainly associated with the partial reversal of the polarization.Leakage current behavior follows the Ohmic and Child square law.Electron conduction process was interpreted by space-charge limited current(SCLC)mechanism.Leakage current behaviorobserved in cobalt chromite nanoceramics is mainly attributed to the oxygen vacancies.

Change in dielectric relaxation with the presence of water in highly filled composites

It is important to determine the dielectric characteristics of semiconductor encapsulation materials based on epoxy resins.We employed the dielectric spectroscopy technique to investigate the dielectric relaxation in the presence of water and how it changes the relaxation.It was observed that the dielectric relaxation of the material was significantly influenced by absorbed water,the local segmental motion(also known as Johari-Goldstein(β)relaxation)was influenced most by the presence of the water,it was modified by the wet sample compared to dry one,and required high activation energy.The relaxation related to the glass transition was contributed by the cooperative motion(the a-relaxation)of the epoxy resin system.The a-relaxation was shifted to a low temperature in the wet sample compared to dry one.The relaxation was modeled with a clear Vogel-Fulcher-Tammann-Hesse(VFTH)behavior;the Vogel temperature of the wet sample was 8 K lower than the dry sample.The presence of water acts as a plasticizer for the molecular relaxation,and speed-up the cooperative process.The measured data were also used to estimate the electrical properties of the resin system by employing an effective-medium model together with a porous media continuum model by taking into account the physical properties of the system.It is already known that the influence of water in semiconductor packaging is important in sensitive applications.The presented measurements and the analysis method would be appreciated within the semiconductor packaging community to improve material selection and performance evaluation efforts.