Dielectric Dispersion Studies Research Articles

Dielectric dispersion study of binary mixtures of methyl ethers with water at 298.15 K using frequency domain technique

A precision LCR meter along with a liquid dielectric cell have been used to measure the capacitance and resistance of the binary mixtures of methyl ethers with water at 298.15 K in the frequency range of 20 Hz to 2 MHz. The measured values are used to compute the complex dielectric permittivity ε*(ω) . The parameters like complex electrical modulus M*(ω) , complex electrical conductivity σ*(ω) and loss tangent (tan δ ) are obtained from the complex dielectric permittivity values of the samples. The values of excess dielectric permittivity of the samples are calculated using the respective static dielectric permittivity values. The refractive indices of all the samples were measured using Abbe’s refractometer at 298.15 K. All these parameters are used to gain insight into the concentration dependent variation in dielectric and electrical properties of the binary mixtures. A dominance of electrode polarization effect in the lower frequency region is observed for all the samples studied here.

Dielectric dispersion in thin LiNbO3 films

The comparative study of dielectric dispersion in thin LiNbO3 films deposited by radio-frequency (RF) magnetron sputtering and laser ablation on Si substrates was carried out. It was found that the dielectric permittivity of the lithium niobate films prepared by the various methods had the significant dispersion due to the barrier effects arising at the ferroelectric/semiconductor interface. The structure of LiNbO3 films deposited by the laser ablation was more imperfective in a comparison to the LiNbO3 films deposited by the RF magnetron sputtering.

Spectroscopic, dielectric dispersion and dc conductivity studies of Sb2O3doped lithium fluoro borophosphate glasses mixed with small concentrations of NiO

Glasses of the composition(20–x) LiF–10 Sb2O3–10 B2O3–60P2O5: x NiO(0 < x < 0.25) were synthesized by conventional rapid melt quenching method. The non–crystalline nature of the samples was confirmed by XRD analysis and the glass forming abilities were analyzed by DTA studies. The compositional dependence of structural aspects of the glasses was analyzed by FT–IR and Raman studies. The DTA, FT–IR and Raman studies suggested an increasing degree of disorder in the glass network with increasing concentration of NiO up to 0.20 mol %. The reversal trend observed beyond 0.20 mol% is attributed to an increasing polymerization of glass network. The optical absorption (OA) and photoluminescence (PL) studies were also carried on these glasses. The results of OA and PL spectral studies suggested that the gradual increase of octahedral Ni2+ ions with the increase in the concentration of NiO up to 0.20 mol%. Electrical properties viz., dielectric dispersion, DC and AC conductivity of the titled glass samples were also performed on titled glass samples. The observed increase in the values of dielectric constant, dielectric loss and AC conductivity (at any frequency and temperature) with the increase in the concentration of NiO up to 0.20 mol%is ascribed to the increasing space charge polarization in the glass network. The results of conductivity studies indicated that there is a mixed conduction (both ionic and polaronic) and the polaron hopping seems to prevail over ionic conduction in the glasses containing less than 0.20 mol% of NiO.

Dielectric dispersion, relaxation dynamics and thermodynamic studies of Beta-Alanine in aqueous solutions using picoseconds time domain reflectometry

The aqueous solution of beta-alanine characterised and studied by their dispersive dielectric properties and relaxation process in the frequency domain of 10×106Hz to 30×109Hz with varying concentration in mole fractions and temperatures. The molecular interaction and dielectric parameters are discussed in terms of counter-ion concentration theory. The static permittivity (ε0), high frequency dielectric permittivity (ε∞) and excess dielectric parameters are accomplished by frequency depended physical properties and relaxation time (τ). Molecular orientation, ordering and correlation factors are reported as confirmation of intermolecular interactions. Ionic conductivity and thermo dynamical properties are concluded with the behaviour of the mixture constituents. Solute–solvent, solute–solute interaction, structure making and breaking abilities of the solute in aqueous medium are interpreted. Fourier Transform Infrared (FTIR) spectra of beta- alanine single crystal and liquid state have been studied. The 13C Nuclear Magnetic Resonance (NMR) spectral studies give the signature for resonating frequencies and chemical shifts of beta-alanine.

Dielectric dispersion and relaxation studies of melt compounded poly(ethylene oxide)/silicon dioxide nanocomposites

The polymer nanocomposite films consisted of poly(ethylene oxide) (PEO) matrix with different weight percentage concentrations of silicon dioxide (SiO2) as nanofiller have been prepared by melt-pressed technique. The complex dielectric function, ac electrical conductivity, electric modulus and complex impedance spectra of the nanocomposite films have been investigated over the frequency range 20 Hz to 1 MHz, at room temperature. The real part of permittivity increases with decrease of frequency below 10 kHz, whereas these values remain almost constant in the high-frequency region. The high-frequency permittivity of these nanocomposites decreases with increase of SiO2 concentration. The relaxation peaks are observed in dielectric loss, loss tangent and loss modulus spectra of the nanocomposites which are corresponding to the PEO segmental motion (local chain dynamics). It is found that the PEO chain dynamics is much faster in the nanocomposites as compared to that in the pristine PEO film. The real part of electrical conductivity spectra of these materials has linear behaviour of two different slopes in the frequency regions of above 10 kHz and below 1 kHz. The interactions between PEO chain and SiO2 nanoparticles, and their effect on PEO spherulites in these nanocomposites are explored by X-ray diffraction measurements.

Dielectric dispersion studies of some potentised homeopathic medicines reveal structured vehicle

Avogadro's Number gives 12c as the limit beyond which no original substance can be present in a highly diluted and succcussed (potentised) homeopathic medicine, implying that chemically such dilutions consist of nothing but the vehicle. But there is evidence that living systems react to homeopathic medicines diluted even above 12c. To explain how such medicines differ from another I hypothesise that altered structure may cause the difference, such as that between diamond and amorphous carbon. Some scientists have argued that dilution followed by succussion may lead to altered structural arrangement of water molecules. This concept may be termed 'Induced Molecular Structure'. Dielectric dispersion studies were conducted in a broad range with potencies below and above the Avogadro limit by taking 6c and 30c potencies of Graphites and Cuprum Metallicum in liquid form. Measurements were made with an Anomalous Dielectric Dispersion Detector (A3D), an instrument developed by the author. Experiments were carried out in a frequency range of 100kHz to 50MHz. Shifting of resonance frequencies as a function of medicine and potency, with potencies below and above the Avogadro limit, was observed. The range of resonance frequencies suggest that the phenomenon might originate from oscillation of dipoles caused by electric field in variously structured and polarised water. Also, there is reasonable evidence that frequencies change with materials and potency.

Zirconia nanoparticles/ferroelectric liquid crystal composites for ionic impurity-free memory applications

We observed an ionic impurity-free memory effect using a zirconia nanoparticles (ZNPs)/ferroelectric liquid crystal (FLC) composite. The pure and ZNPs doped FLC cells have been analyzed by means of dielectric spectroscopy, polarizing optical microscopy and electrical resistance/conductivity measurements. The memory behavior in ZNPs/FLC composite was confirmed by dielectric dispersion, electrical, and optical studies, whereas dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in FLC materials. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges, whereas the reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of ZNPs. The ZNPs dispersed in FLCs may play a role in trapping the impurity ions (minimize the depolarization fields) under applied voltage and cause a better memory effect in ZNPs doped FLC material. Moreover, the ion adsorption capability of ZNPs is found to be almost independent of temperature as the value of resistance did not change remarkably on increasing the temperature. The reduction of ionic impurities of FLCs by doping ZNPs did not show degradation over time, as we repeated the experiments on the same sample cells after many days and did not find ionic effects in the ZNPs doped FLC materials. These studies would be helpful to provide an idea for designing ionic impurity-free memory devices.

Dielectric Dispersion Studies Indicate Change in Structure of Water by Potentised Homeopathic Medicines

Response of living bodies to different vastly ‘diluted’ homeopathic medicines are different (rejecting the sceptic’s view of ‘placebo’ effect), though they are chemically same. Till now there is no satisfactory answer to how one such medicine differs from another in terms of scientifically measurable parameters. This paper tries to address this basic issue by taking two medicines of the same potency and two different potencies of the same medicine, namely, Arnica Mont 30c, 200c and Anacardium Orient 30c, 200c. These potencies are well above the Avogadro limit. The investigation reported here proceeds with the concept of ‘induced molecular structure’ advanced by a number of scientists. Dielectric dispersion is used as the tool for experimental verification. It is based on the fact that when the exciting frequency of applied electric field equals the characteristic frequency, then macromolecules resonate leading to anomalous dielectric dispersion associated with sharp increase in dielectric loss, the resonance frequencies being different for macromolecules of different structures or dimensions. The results suggest that medicine- and potency-specific attributes are acquired by the vehicle (i.e. water) in the form of macromolecules generated by the potentization process of homeopathy making one medicine structurally different from another.

Structural features of MoO3 doped sodium sulpho borophosphate glasses by means of spectroscopic and dielectric dispersion studies

Na2SO4–B2O3–P2O5 glasses doped with different concentrations of MoO3 (ranging from 0 to 10.0 mol%) were prepared. The valence states of molybdenum ions and their coordination in the glass network have been investigated using optical absorption, ESR, and IR spectroscopy. The analysis of the spectroscopic results has indicated that the molybdenum ions exist in both Mo6+ (occupy octahedral and tetrahedral positions) and Mo5+ (occupy octahedral positions) local coordination sites and the redox ratio increases with the concentration of MoO3. Dielectric properties have been studied over a frequency range (102–105 Hz) and within the temperature range from 30 to 250 °C. The ac conductivity is observed to increase, whereas the activation energy for the conductivity exhibited decreasing trend, with the concentration of MoO3. In the low temperature region, the ac conductivity is nearly temperature independent and is varied linearly with frequency. Such behaviour is explained based on quantum mechanical tunneling (QMT) model. The dispersion of real part of dielectric constant ε′(ω), and loss, tan δ, with temperature have been analyzed on the basis of space charge and orientation polarization models.

Crystal structure, dielectric properties and molecular motions of molecules in thiazolium halometalates(III): (C3H4NS)6M4Br18·2H2O (M=Sb, Bi)

Abstract Two thiazolium analogs, (C3H4NS)6Sb4Br18·2H2O (TBA) and (C3H4NS)6Bi4Br18·2H2O (TBB), have been synthesized and structurally characterized. The compounds appeared to be isomorphous and crystallize in the triclinic symmetry, space group P 1 ¯ (at 100 K). These ionic complexes are built up of thiazolium cations, centrosymmetric [M4Br18]6− anions (M = Sb, Bi) and water molecules. One of three independent thiazolium cations was found to be disordered (two-site model). The cations are hydrogen bonded to [M4Br18]6− moieties and water molecules. The water molecule (Ow) acts as a donor of the O–H⋯Br and an acceptor of the N–H⋯O types of hydrogen bonds. The dielectric dispersion studies disclosed a low frequency relaxation process characterized by a significant slowing down of two independent dielectric relaxators. The dielectric behavior was explained by the motion of thiazolium cations and water molecules The molecular motions of the thiazolium and water molecules were studied by means of the 1H NMR spin–lattice relaxation time (T1) measurements.

NH2(C2H4)2O]MX5: a new family of morpholinium nonlinear optical materials among halogenoantimonate(iii) and halogenobismuthate(iii) compounds. Structural characterization, dielectric and piezoelectric properties

This paper presents the structural features of ionic complexes formed by morpholine and metal ions which belong to group VA, namely Sb(III) and Bi(III). A series of target inorganic-organic hybrid compounds of the general formula [NH(2)(C(2)H(4))(2)O](2)MX(5) (where M = Sb, Bi; X = Cl, Br) has been synthesized by incorporating the organic component (morpholine) into the highly polarizable one-dimensional halogenoantimonate(III)/halogenobismuthate(III) chain network. Among the studied compounds, four were found to crystallize in the room temperature phase in the piezoelectric, orthorhombic space group P2(1)2(1)2(1), Z = 4, the feature being confirmed by the powder second harmonic generation of light and piezoelectric measurements. Dielectric dispersion studies between 200 Hz and 2 MHz disclosed a relaxation process below room temperature well described by the Cole-Cole equation. Based on crystal structures available in Cambridge Structural Database (version 5.32, November 2010) we attempt to show a relationship between the acentric symmetry of compounds and the type of anionic network within the R(2)MX(5)-subgroup (where R denotes organic cation) of halogenoantimonates(III) and halogenobismuthates(III).

Effects of two relaxation processes on the dielectric spectra and conductivity of ultrathin ferroelectric polymer films

Based on the study of dielectric dispersion for 2-nm-thick Langmuir films made of an poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) copolymer, we demonstrated the existence of two simultaneously developing relaxation processes. It was shown that Langmuir-Blodgett films are conducting.

Domain wall contributions in Pb(Zr,Ti)O3 ceramics at morphotropic phase boundary: A study of dielectric dispersion

The dielectric properties of undoped, Nb-, and Fe-doped Pb(Zr,Ti)O3 ceramics with composition near morphotropic phase boundary were investigated in the frequency range from 1 MHz to 20.2 GHz at room temperature. Temperature dependences of dielectric permittivity ε′ and loss ε″ are measured at 100 kHz from 50 to 300 K and around 13.4 GHz from 100 to 300 K. These measurements permit estimation of the upper limit of the intrinsic permittivity and lower limit of the extrinsic contributions to the permittivity as a function of temperature. The extrinsic contributions account for more than 50% of the quasistatic dielectric permittivity in studied samples.

Dielectric relaxation and dispersion studies of mixtures of 1-propanol and benzonitrile in pure liquid state at radio and microwave frequencies

Complex permittivity of 1-propanol, benzonitrile and their binary mixtures over a range of concentrations was obtained in radio and microwave frequency range at various temperatures. Vector network analyzer (VNA) operating in the frequency range 0.3 MHz to 3.0 GHz was used to obtain complex permittivity spectra. Complex permittivity of the liquid samples at two spot frequencies 9.1 GHz and 19.61 GHz were also measured using standard microwave benches. Dielectric constant at optical frequency ( ∈ ∞) was measured using Abbe's refractometer. Measured values of the dielectric loss ( ∈″) have been plotted against dielectric constant ( ∈′) in a complex plane for 1-propanol, benzonitrile and their mixtures. Various dielectric relaxation parameters like relaxation time ( τ), static dielectric constant ( ∈ 0) and high frequency limiting values of dielectric constant ( ∈ ∞1) were obtained from these curves. Dielectric relaxation parameters thus obtained were used to evaluate excess inverse relaxation time (1/ τ) E, excess static permittivity ( ∈ 0 E), Kirkwood correlation factor ( g), angular correlation factor ( g eff) and thermodynamic parameters. Molecular interaction between the molecular species of the liquid mixtures was interpreted in terms of these parameters.

Dielectric dispersion study of Mn-doped PLZT (8/65/35)

Mn-modified Pb0.92La0.08(Zr0.65Ti0.35)O3 (PLZT) was prepared chemically by a coprecipitate method using their respective nitrate salts and isopropoxides. Differential thermal analysis (DTA) and X-ray analysis clearly show the formation of PLZT single rhombohedral phase for samples calcined beyond 750 °C. Uniform grain distribution was observed from scanning electron microscopic (SEM) studies and grain size was found to increase with Mn doping up to x = 0.08 and then decreased. Dielectric measurement shows the decrease in peak transition temperature (TC) with Mn doping up to x = 0.12 and then increase along with a sharp rise in dielectric maxima. A diffuse dielectric dispersion is observed in all the compositions. A detailed dispersion study was carried out using the Vogel–Fulcher empirical relation, a universal relaxation law and the Havriliak–Negami function. The Vogel–Fulcher relation fitting parameters of activation energy and freezing temperature were found to decrease with Mn doping up to x = 0.12, which was expected to be the cause of the variation of TC. The exponent m of the universal relaxation law was found to increase with Mn doping and also with increasing temperature, which suggests an enhanced conducting nature of the composition. In the Havriliak–Negami function, the Cole–Cole fitting parameter α was found to increase and β was found to decrease with Mn doping and also with temperature, which suggests that the dispersion behavior changed from Cole–Cole type to Cole–Davidson type with Mn doping in PLZT. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dielectric critical slowing down in pentakis(imidazolium) undecabromodibismuthate(III):(C3N2H5)5Bi2Br11

Low frequency dielectric dispersion studies have been carried out forthe ferroelectric pentakis(imidazolium) undecabromodibismuthate(III)—(C3N2H5)5Bi2Br11—single crystal in the paraelectric phase in the radio-frequency region(100 Hz–1 MHz). The dielectric dispersion, observed for an electric field along thea-axis(P 21/n space group), is characterized by a polydispersive nature close to the Curie temperature(Tc = 155 K). The dielectric dispersion findings were analyzed accurately with the Cole–Cole formula.In the vicinity of the Curie temperature the process of the dielectric critical slowing down isclearly observed. Such a dynamic dielectric response is characteristic of ferroelectriccrystals classified as ‘order–disorder’ type.

Dielectric dispersion studies of mixtures of aniline and benzonitrile in benzene solutions

Dielectric behavior of aniline, benzonitrile and their binary mixtures of different concentrations were studied in benzene at 293, 303, 313 and 323 K. The complex permittivity ( ∈′, ∈″) at microwave frequencies 7.22, 9.1, 19.61 GHz, static permittivity ∈ 0 at 455 KHz and high frequency limiting dielectric constant ∈ ∞ = n D 2 at optical frequency of these molecules and their binary mixtures were measured. The average relaxation time ( τ 0), distribution parameter ( α) and thermodynamical parameters were determined. The plot of relaxation time ( τ 0) against concentration of benzonitrile in the mixtures is nonlinear indicating complex formation.

Study of Dielectric Dispersion in Non-Layer-Shrinkage Liquid Crystal Compounds

Measurements of dielectric dispersion have been carried out on two liquid crystal compounds 8422[2F3] and 8O23[7F8-], showing non-layer-shrinkage (NLS) behavior through the smectic-A(Sm-A)-smectic-C (Sm-C) transition. The critical exponent γ determined from the data lies 1.5–1.9 for 8422[2F3], and 1.1–1.2 for 8O23[7F8-]. These results indicate that the Sm-A-Sm-C transition with NLS behavior can exhibit quasi two-dimensional Ising critical behavior under a certain condition.

Structural and dielectric properties of thiazolium chlorobismuthate(III) and chloroantimonate(III)

The crystal structures of [C 3H 4NS] 6[ M 4Cl 18]·2H 2O ( M = Sb, Bi) consist of three nonequivalent thiazolium cations and discrete centrosymmetric anions [ M 4Cl 18] 6−. The title compounds appear to be isomorphous and crystallize in the triclinic space group, P 1 ¯ (at 100 K). One of three thiazolium cations was found to be disordered (two-site model). [C 3H 4NS] + cations are hydrogen bonded to [ M 4Cl 18] 6− units and water molecules. The water molecules (O w) via the O–H…Cl hydrogen bonds are involved in the one-dimensional polymeric chains, which extend along the c-axis. The dielectric dispersion studies on two thiazolium analogs in the audio-frequency region disclosed complex relaxation processes. The dielectric response indicates the presence of two independent relaxators, which are characterized by polydispersive nature. The relaxation processes taking place in the both studied crystals are due to the motion of dipolar thiazolium cations.

Dielectric Relaxation in VDF-TeFE Copolymer Near Melting Temperature

The study of dielectric response dispersion in the vicinity of melting temperature lying slightly above the ferroelectric phase transition in copolymer of vinylidene fluoride-tetrafluoroethylene P (VDF 0.88 TeFE 0.12 ) within the frequency range 25-10 6 Hz was carried out. It was found increasing of characteristic relaxation time (τ) as a temperature is approached to a point of phase equilibrium from below. The observed dependence τ (T) can be described in terms of the phenomenological theory of diffused first-order phase transition.