Solvation Effects on the Dielectric Constant of 1 M LiPF6 in Ethylene Carbonate:Ethyl Methyl Carbonate 3:7

We report the dielectric constant of 1 M LiPF_(6)in EC:EMC 3∶7 w/w(ethylene carbonate/ethyl methyl carbonate)in addition to neat EC:EMC 3∶7 w/w.Using three Debye relaxations,the static permittivity value,or dielectric constant,is extrapolated to 18.5,which is compared to 18.7 for the neat solvent mixture.The EC solvent is found to strongly coordinate with the Li^(+)cations of the salt,which results in a loss of dielectric contribution to the electrolyte.However,the small amplitude and large uncertainty in relaxation frequency for EMC cloud definitive identification of the Li^(+)solvation shell.Importantly,the loss of the free EC permittivity contribution due to Li^(+)solvation is almost completely balanced by the positive contribution of the associated LiPF_(6)salt,demonstrating that a significant quantity of dipolar ion pairs exists in 1 M LiPF_(6)in EC:EMC 3∶7.

Dielectric Relaxation of Adsorbed Water in Wood Cell Wall under Equilibrium and Non-Equilibrium State

This article summarized systematically the previous investigations on t he dielectric relaxation of wood, the main substances and extractives in wood at oven-dry state, and the dielectric relaxation based on the adsorbed water in w o od cell wall under equilibrium and non-equilibrium state. Moreover, some expect a tions for future research were proposed on this basis. The purpose of this artic le is to provide other researchers an overall understanding about the research i n this region, and further to promote the research onto a new and higher level.

Oxygen-vacancy-related dielectric relaxation and conduction mechanisms in Bi5TiNbWO15 ceramics

This paper reports that the intergrowth ceramics Bi5TiNbWO15 （BW-BTN） have been prepared with the conventional solid-state reaction method. The dielectric and conductivity properties of samples were studied by using the dielectric relaxation and AC impedance spectroscopy in detail. Two distinct relaxation mechanisms were detected both in the plots of dielectric loss （tanδ） and the imaginary part （Z″） versus frequency in the frequency range of 10 Hz-13 MHz. We attribute the higher frequency relaxation process to the hopping process of the oxygen vacancies inside the grains, while the other seems to be associated with the space charges bound at the grain boundary layers. The AC impedance spectroscopy indicates that the conductivities at 625 K for bulk and grain boundary are about 1.12 × 10^-2 S/m and 1.43 × 10^-3 S/m respectively. The accumulation of the space charges in the grain boundary layers induces a space charge potential of 0.52 eV.

Dielectric spectroscopy studies of ZnO single crystal

Dielectric relaxation and charge transport induced by electron hopping in ZnO single crystal are measured by using a novocontrol broadband dielectric spectrometer. Typical Debye-like dielectric relaxation originating from electronic hopping between electronic traps and conductive band in surface Schottky barrier region is observed for ZnO single crystal-Au electrode system. However, after insulation of ZnO single crystal by heat treatment in rich oxygen atmosphere, dielectric relaxation and alternating current conductance are observed simultaneously in the dielectric spectra, implying that dielectric relaxation and charge transport can be induced simultaneously by electronic hopping at high temperature in an ordered system. The intrinsic correlation between local dielectric relaxation and long range charge transport offers us a new method to explore complicated dielectrics.

Structure and Dielectric Study of Ce_3NbO_(7+δ)

The structure, phase composition, and migration of oxygen ion in Ce3 NbO7＋δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7＋δ sample was comprised of Ce3 NbO7＋δ phase and CeNbO4.25 phase. In the dielectric study of Ce3 NbO7＋δ sample, two dielectric loss peaks were observed both in temperature spectra and frequency spectra. Both peaks were shifted towards higher temperature with increase in frequency in temperature spectra and towards higher frequency with increase in temperature in frequency spectra, indicating the relaxation essence of these two peaks. It was suggested that the short distance diffusions of oxygen ions in both Ce3 NbO7＋δ phase and CeNbO4.25 phase gave rise to the two dielectric relaxation peaks.

Dielectric properties of Simon poplar wood flour/polypropylene composite at oven-dry state

Interfacial compatibility is a crucial factor to the performance of wood-plastic composites （WPCs）. Yet, so far, the coupling mechanisms of WPC have not been completely understood. In order to further clarify the interfacial coupling mechanism, the dielectric constant and dielectric loss factor of Simon poplar wood flour/polypropylene composites without additives at different wood contents were measured at oven-dry state, and parameters and thermodynamic quantities of the relaxation process were also analyzed and calculated. Consequently, an obvious relaxation process based on the reorientation of methanol groups in amorphous region of wood cell wall was observed exactly that its dielectric loss factor peak decreased with the decreasing wood content within the measured range of 50%-100%. With the trend of dielectric relaxation strength, the two changing trends both revealed that the existence of polypropylene could hinder reorientation of methanol groups. Following the decreasing wood contents, the effect of the hindrance on the dielectric properties turned obvious gradually. It elucidated that introduction of polypropylene caused the quantities of hydrogen bonds formed between each methanol group and the groups around it change. The same conclusion could be drawn from the analysis of thermodynamic quantities during the dielectric relaxation progress.

Conductance and dielectric properties of hydrogen and hydroxyl passivated SiCNWs

Based on the transport theory and the polarization relaxation model,the effects of hydrogen and hydroxyl passivation on the conductivity and dielectric properties of silicon carbide nanowires(SiCNWs)with different sizes are numerically simulated.The results show that the variation trend of conductivity and band gap of passivated SiCNWs are opposite to the scenario of the size effect of bare SiCNWs.Among the influencing factors of conductivity,the carrier concentration plays a leading role.In the dielectric properties,the bare SiCNWs have a strong dielectric response in the blue light region,while passivated SiCNWs show a more obvious dielectric response in the far ultraviolet-light region.In particular,hydroxyl passivation produces a strong dielectric relaxation in the microwave band,indicating that hydroxyl passivated SiCNWs have a wide range of applications in electromagnetic absorption and shielding.

Continuum Model for Electronic Polarization Based on a Novel Dielectric Response Function

A generalized response function based on the use of dielectric spectra for dielectric relaxation process is derived. We apply the general response function to the special case in order to examine how special dielectric relaxation functions developed by other authors for solvent relaxation can be derived based on our formulations. Three typical solvents, water, methanol, and acetonitrile are used to investigate the electronic polarization processes of polar solvents. The solvent electronic polarization process is shown after a linear variation with the external electric field imposed on the solvent. The results show a conclusion that the electronic polarization of the solvents will accompany the electronic transition synchronously, without time lag.

An Investigation of Structure Transition in Sodium Dodecyl Trioxyethylene Sulfate/n-Butanol/n-Octane/Water System by Dielectric Relaxation Spectroscopy Method

The phase diagram of the quaternary system of sodium dodecyl trioxyethylene sulfate(SDES)/n-butanol/n-octane/water was obtained at (30.0±0.1) ℃. There exists a clear, isotropic, and low-viscosity L phase, which can be divided into W/O, bi-continuous(B.C.) and O/W microemulsions by conductivity measurement results. Dielectric Relaxation Spectroscopy(DRS) measurements, including permittivity, conductivity, relaxation strength, characteristic relaxation time, dielectric parameters, phase parameters, etc., were applied to investigating the microstructures of the system mentioned above. For the samples with a fixed SDES/n-butanol mass ratio of 4/6 including 20%(mass fraction) of n-octane, DRS indicated a structure transition from a W/O to an O/W via a B.C. microemulsion with the increase of the water content. For the samples with a fixed (SDES/20%n-octane)/H_2O mass ratio of 5/5, DRS presented that there only exists a onefold structure of a W/O microemulsion as the (n-butanol/20%n-octane) content increases. The results obtained from DRS are in good agreement with those from the phase diagram.

Phase Transition and Oxygen Ion Diffusion in （La1-xLnx）2Mo2O9 （Ln=Nd, Gd, x=0.05-0.25） Using Dielectric Relaxation Method

Dielectric relaxation method was employed to study the properties of oxygen ion diffusion and phase transition in the oxide-ion conductors （Lal-xLnx）2Mo209 （Ln=Nd, Gd, x=0.05-0.25）. Two dielectric loss peaks were observed： peak Pd at about 600 K and peak P5 around 720 K. Peak Pd is a relaxational peak and associated with the short-range diffusion of oxygen ions, while peak P5 hardly changes its position and dramatically decreases in height with increasing frequency, exhibiting non-relaxational nature. With increasing Ln^3＋ concentration, the heights of peak Ph and Pd increase at first and then decrease after passing a maximum at 15% doping. It is suggested that peak P5 is related to the phase transition of a static disordered state to a dynamic disordered state in oxygen ions/vacancies distribution. It is found that the 15%Gd or 15%Nd doped La2Mo209 samples exhibit the highest conductivity in accordance with the highest height of peak Pd at this doping content.

STUDIES ON THE CHAIN STRUCTURAL EFFECT OF PVDF AND VDF (52)/TrFE(48) COPOLYMER BY MEANS OF THE METHOD OF DIELECTRIC RELAXATION

Through improvements on a fully commercial and automatic system measuring frequency andtemperature spectra of the complex elastic, dielectric, and piezoelectric constants of polymerfilms, the precision for measuring complex dielectric constants achieved 2‰ from original 1%.The complex dielectric constants of PVDF, VDF （95 ）/VF （5）, VDF （52）/TrFE （48） and VDF（47. 5）/TrFE（47. 5）/HeFP （5） over a range of-120-140℃, 10-2-10;Hz were measured bythe described system. The diminution of chain regularity due to 5mol% vinyl fluoride in the chainof PVDF led to disappearing of α-relaxation and increase in T;（3℃） of VDF （95）/VF （5）.Because of the spatial impediment of 5mol% HeFP in copolymer chain, the Curie point of VDF（52）/TrFE（48） decreased by 30℃ and T;by 3℃. The behavior of dielectric relaxation indicatedthat 5mol% vinyl fluoride and HeFP made the relaxation strength of noncrystalline regionreduced, the activation energy of local relaxation increased and the relaxation time prolonged respectively.

Dielectric Relaxation in Bi_2BaNb_2O_9 Ceramic

A very strong dielectric relaxation was observed in Bi_2BaNb_2O_9 ceramic.The temperature difference between the maximum dielectric constant temperatures T_m measured at 1 kHz and 100 kHz is 65℃. which is about 2-4 times that of relaxor ferroelectrics.The possible mechanism of the anomalous dielectric relaxation was discussed.

Dielectric Spectra of Aerosol OT/Water Systems at Different Concentrations and Temperatures

The dielectric spectra of aerosol OT[AOT, sodium（bis-2-ethylhexyl）sulfosuccinate]/water systems at different concentrations and temperatures were investigated by the dielectric relaxation spectroscopy（DRS）. Through the dielectric spectra of different concentrations, two dielectric relaxations were observed over a frequency range from 40 Hz to 110 MHz and the mechanisms of the relaxations were also interpreted based on the Grosse’s model. The low-frequency relaxation（around 105 Hz） was attributed to the radial diffusion of counterions along the long-half axis of the rod-like micelle, and the high-frequency relaxation（around 106 Hz） was ascribed to the radial diffusion of counterions along the short-half axis. Furthermore, specific emphasis was placed on studying the effects of temperature on system’s conductivity. It was observed that the low-frequency limit of conductivity（κl） decreased and then increased with the increment of temperature under the measured concentration. On the other hand, the conductivity（κm and κh） in meso- and high-frequency ranges always increased as temperature increased. Both the tendencies of alteration which mentioned above should be related to the phase transition of AOT/water system.

Phases confirmation of cloudy Silwet L-77 aqueous solution by dielectric relaxation spectroscopy

The phase transition of Silwet L-77(a kind of siloxane surfactant) dilute aqueous solution with temperature was investigated by dielectric relaxation spectroscopy.In the initial heating process,a dielectric relaxation was found at about 10~6 Hz,which was considered as the interface polarization ascribed to the interface between water and liquid phases(W and L_1).With the temperature increasing further,a new dielectric relaxation was observed at about 10~4 Hz,which was assigned to the appearance of liquid crystal phase(L_α).According to the dielectric parameters fitted by Cole-Cole equation,the coexistence temperature of W,L_1 and L_αwas determined at about 37.0℃.

Studies on the Phase Properties of Winsor Ⅰ-Ⅲ Type Microemulsions with Dielectric Relaxation Spectroscopy

The dielectric relaxation spectroscopy （DRS） of Winsor I -Ⅲ microemulsions for nonionic surfactant octyl polyglucoside CsG1.46/1-butanol/cyclohexanedwater system was studied. The experiment shows that the permittivity decreases with the increase in the frequency and clear dielectric relaxation phenomena were observed. Permittivity obviously decreases with the change of the microstructure of the microemulsion, W/O, B.C. and O/W can be distinguished by the permittivity.

Dielectric properties of copper-ethanolamine treated Chinese fir (Cunninghamia lanceolata Hook.)

In order to clarify the interaction between copper and wood substances in wood treated with copper containing water-borne wood preservatives, the dielectric constant ε＇ and dielectric loss factor ε＂ of untreated wood and wood treated with four concentration levels of copper-ethanolamine （Cu-EA） solutions were determined within a temperature range from -100 to 40℃ and a frequency range from 100 to 1 MHz. Three dielectric relaxation processes were observed in the ε＂ spectrum; among them R-Ⅰ is based on the reorientation ofmethylol groups in the amorphous region of wood cell walls and R-Ⅱ is related to wood extractives. R-Ⅲ appeared in Cu-EA treated wood, and its magnitude decreases with the concentration of Cu-EA solutions used in this experiment. This relaxation process was considered to be based on the reorientation of copper-ethanolamine-wood complexes in wood cell walls. At low copper retention, the hydrogen in the complex can form hydrogen bonding with adjacent hydroxyl groups, which results in a strong bonding state between copper and wood; at high copper retention, the numerous copper-ethanolamine complexes not only hinder them from forming hydrogen bonding with adjacent wood molecules due to steric hindrance, but also weaken the interaction between wood molecules themselves, which corresponds to reducing ε＂ values of both R-Ⅰ and R-Ⅲ processes. The results explain the fact of increasing copper leaching in wood treated with high concentration copper-based water-borne preservatives.

Pathophysiology of acute graft-versus-host disease from the perspective of hemodynamics determined by dielectric analysis

BACKGROUND Numerous reports have demonstrated that the pathophysiology of graft-versushost disease(GVHD)during hematopoietic stem cell transplantation(HSCT)is closely related to vascular endothelial disorders and coagulation abnormalities.We previously presented the discovery of a principle and the development of a novel instrument for measuring whole blood coagulation.This was achieved by assessing the variations in the dielectric properties of whole blood.AIM To investigate how GVHD affects the changes of dielectric properties of whole blood in patients with HSCT.METHODS We examined the changes of dielectric properties of whole blood and erythrocyte proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis sequentially in patients with HSCT and compared it with clinical symptoms and inflammatory parameters of GVHD.RESULTS During severe GVHD,the dielectric relaxation strength markedly increased and expression of band3 decreased.The dielectric relaxation strength normalized with the improvement of GVHD.In vitro analysis confirmed that the increase of relaxation strength was associated with severe erythrocyte aggregates,but not with decreased expression of band3.CONCLUSION Severe erythrocyte aggregates observed in GVHD may cause coagulation abnormalities and circulatory failure,which,together with the irreversible erythrocyte dysfunction we recently reported,could lead to organ failure.

Electrical and dielectric properties of Na_(1/2)La_(1/2)Cu_3Ti_4O_(12) ceramics prepared by high energy ball-milling and conventional sintering

We report on the measurements of the electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 （NLCTO） ce- ramics prepared by high energy ball-milling and conventional sintering without any calcination steps. The x-ray powder diffraction analysis shows that pure perovskite-like CCTO phase is obtained after sintering at 1025 ℃-1075 ℃. Higher sintering temperatures result in multi-phase ceramics due to thermal decomposition. Scanning electron microscope observations reveal that the grain size is in a range of - 3 μm-5 μm for these ceramics. Impedance spectroscopy measurements performed in a wide frequency range （1 Hz-10 MHz） and at various temperatures （120 K-470 K） are used to study the dielectric and electrical properties of NLCTO ceramics. A good compromise between high ε′ （5.7 ×10^3 and 4.1 × 10^3 at 1.1 kHz and 96 kHz, respectively） and low tan δ （0.161 and 0.126 at 1.1 kHz and 96 kHz, respectively） is obtained for the ceramic sintered at 1050 ℃. The observed high dielectric constant behavior is explained in terms of the internal barrier layer capacitance effect.

Study of Dielectric Relaxation of Insulating Oil from Lagenaria siceraria Seeds

The present work concerns the study of the dielectric relaxation of dielectric oil based on Lagenaria siceraria (calabash) seeds. Dielectric spectroscopy was used to measure the loss angle, the dielectric constant and the electrical modulus. Three relaxation processes in calabash oil were identified. It was also found that the relative permittivity decreases with increasing temperature and frequency. A study of the imaginary part of the electrical modulus was done and revealed a relaxation process at low frequencies. At higher frequencies, the dielectric relaxation is thermally activated. The increase in temperature leads to a decrease in the relaxation rate. The result obtained indicates that relaxation type is not of the Debye type in the high-frequency region. The Cole-Cole model of the imaginary part of the permittivity as a function of its real part in calabash oil for different temperatures was drawn and analyzed. It shows the existence of a negative temperature coefficient of resistance in the fluid and helps identifying a relaxation process in the conductivity of the sample studied. It highlights the presence of Debye relaxation which characterizes the presence of an abnormal dispersion of the dielectric constant over a frequency range. Calabash seed oil exhibits better dielectric constant (relative permittivity) compared to other oils.

Rare earth doped CaCu_3Ti_4O_(12) electronic ceramics for high frequency applications

Ca1-xRxCu3Ti4O12(R=La,Y,Gd;x=0,0.1,0.2,0.3) electronic ceramics were fabricated by conventional solid-state reaction method.The microstructure and dielectric properties as well as impedance behavior were carefully investigated.XRD results showed that the secondary phases with the general formula R2Ti2O7 existed at grain boundaries of rare earth doped ceramics,which inhibited abnormal grain growth.The dielectric constant decreased from 4×105 in pure CaCu3Ti4O12(CCTO) ceramics to 2×103 with rare earth doping....