Part Of Dielectric Permittivity Research Articles

Facile Synthesis and Structural, Microstructural, and Dielectric Characteristics of SnO2-CeO2 Semiconducting Binary Nanocomposite

Polycrystalline (1-x)SnO2-xCeO2 nanocomposites, where x = 0, 0.05, and 0.10, were synthesized using conventional co-precipitation method without any traces of impurities. Structural characterization revealed that the composition with x = 0 exhibited single-phase tetragonal rutile symmetry, whereas for x = 0.05 and 0.10 compositions showed both tetragonal and cubic phase coexistence as confirmed by Rietveld refinement studies. HRTEM micrographs showed nanoscale formation of nanocomposites and also displayed fringes depicting d spacing (110) = 0.34 nm belonging to SnO2 crystal matrix and d spacing (111) = 0.31 nm for cubic CeO2 crystal lattice. Dielectric properties of host SnO2 nanoparticles were improved by CeO2 addition in the SnO2. The increment in the real part of dielectric permittivity was observed for CeO2 modification of SnO2 matrix.

Study of the effect of capping agent variation on P3HT:CdSe hybrid solar cells

We present here a new study on the incorporation of cadmium selenide (CdSe) nanoparticles (NPs) in Poly-3-hexylthiophene (P3HT) polymer matrix. Our aim is to improve the performance of the hybrid solar devices by varying capping agents on top of CdSe NPs for each active layer sample. We investigated the optical properties of differently capped Bulk Heterojunction (BHJ) P3HT:CdSe cells. We extracted the optical constants (refractive index n, extinction coefficient k, real ε′ and imaginary ε′′ parts of dielectric permittivity) from fitted Transmittance T and Reflectance R spectra. Then, we were able to determine the static refractive index ns and permittivity εs, the plasma frequency ωp, the carrier density to effective mass ratio N = me, the optical conductivity roc, the optical band gap Eg and the oscillation and dispersion energies E0 and Ed, using equations proposed by the theoretical models such as Cauchy model, Drude-Lorentz, Tauc model, and Wemple-DiDomenico.

Investigation on Electrical Properties of Solid Polymer Sheets (HDPE AND LDPE) at Audio Frequency Range

Two different groups of solid polymer sheets: low density polyethylene (LDPE) sample of thickness 0.006 cm and 0.007 cm along with high density polyethylene (HDPE) sample of the thickness of 0.009 cm, 0.010 cm were taken in this work. The measurement of electrical properties such as dielectric constant, ε' and dielectric loss, ε'' for LDPE and HDPE polymer sheets have been measured using a dielectric cell. The dielectric cell has been fabricated which consists of two circular parallel plates of pure stainless steel each of 5 cm diameter and 2 mm thickness. An impedance bridge (GRA 650A) was used for measurement of capacitance, C, and dissipation factor, D in the audio frequency (AF) range, 100 Hz to 10 kHz. Different samples were loaded in between the two plates of the cell and the capacitance as well as the dissipation factor were estimated from the dial readings of the bridge. Effect of frequency variation on ε', ε'', relaxation time, τ , dissipation factor, tanδ and ac conductivity, σ were also discussed at audio frequency range. The complex permittivity, ε*, related to free dipole oscillating in an alternating field and loss tangent, tanδ were calculated. The frequency-dependent conductivity, dielectric behavior, and electrical modulus, both real (M') and imaginary (M") parts of LDPE and HDPE have been studied in this work. The values of the real part of the electrical modulus (M') did not equal to zero at low frequencies and it is expected that the electrode polarization may develop in both sheets. These findings reveal an increased coupling among the local dipolar motions in a short-range order localized motion. The analysis of real (ε') and imaginary (ε'') parts of dielectric permittivity and that electrical modulus real (M') and imaginary (M") parts signify poly dispersive nature of relaxation time as observed in Cole-Cole plots.

Effect of fullerenes C60 on dielectric relaxation, electric conductivity, and electro-optic properties of 4-cyano-4′-pentylbiphenyl

Effect of fullerenes C60 on dielectric relaxation, electric conductivity, and electro-optic properties of nematic liquid crystal 4-cyano-4′-pentylbiphenyl is investigated. It is shown that the inclusion of fullerenes into liquid crystal leads to decreasing of the clearing temperature and the order parameter. In this case, the transverse component of the real part of dielectric permittivity increases while the longitudinal component decreases. A maximum of dielectric absorption shifts to the low-frequency region. The capture of moving ions by fullerenes leads to a decrease of electric conductivity. The elastic constant, rotational viscosity and switching times decrease while the threshold voltage of Freedericksz effect increases.

Development and characterization of multifunctional yttrium iron garnet/epoxy nanodielectrics

In the present work, a series of yttrium iron garnet/epoxy nanocomposite systems were fabricated, and the morphology of nanocomposites were tested by Scanning Electron Microscopy. The thermal stability of the developed systems was assessed by Thermogravimetric Analysis; their thermal properties were further investigated via Differential Scanning Calorimetry (DSC) and their viscoelastic response via Dynamic Mechanical Analysis (DMA). Finally, the dielectric characterization was carried out by means of Broadband Dielectric Spectroscopy. DSC curves revealed an endothermic step-like transition of all systems, attributed to the glass to rubber transition of the polymer matrix. All nanocomposites exhibit a two stages degradation profile. The presence of nanoinclusions enhances the thermal stability of the systems shifting the onset of the first degradation process to higher temperatures. Through the DSC and DMA techniques, the transition from glassy to rubbery state of the polymer matrix was observed and the characteristic Tg temperature was determined. The addition of the ceramic inclusions enhances the thermomechanical properties, as well as the dielectric response of the nanocomposites, as implied by the augmenting values of the real part of dielectric permittivity along with the storage modulus with the reinforcing phase loading. Three dielectric relaxation processes were identified: interfacial polarization, glass to rubber transition of the polymer matrix and reorientation of the small polar side groups of the polymer chain at low, intermediate and high frequencies, respectively. Furthermore, the ability of the systems to store energy was examined via the dielectric reinforcing function.

The threshold voltage, dielectric and conductivity properties of C60-doped smectic A liquid crystal

Influence of fullerenes C60 on the threshold voltage, dielectric and conductivity properties of smectic A liquid crystal 4-hexyloxyphenyl ether 4′-hexyloxy 3′-nitrobenzoic acid is investigated. It is shown that the transverse component of the real part of dielectric permittivity increases at the additive of fullerenes while the longitudinal component decreases. In this case, a maximum of dielectric absorption shifts to the high-frequency region. Conductivity increases at low frequencies and decreases at the high ones. Experimental results are explained by location of fullerenes between liquid crystal molecules reducing their interaction. As a result, the order parameter and viscosity of the matrix decrease.

Effect of fullerenes C60 on dielectric properties and the threshold voltage of smectic A liquid crystal

Influence of fullerenes C60 on the threshold voltage, dielectric, and conductivity properties of smectic A liquid crystal 4-nitrophenyl-4′-decyloxybenzoic acid is investigated. It is shown that the transverse component of the real part of dielectric permittivity increases at the additive of fullerenes while the longitudinal component decreases. At this case, a maximum of dielectric absorption shifts to the high-frequency region. Conductivity increases at low frequencies and decreases at the high ones. Experimental results are explained on the base of the Maier-Meier theory for anisotropic liquids and also participation of fullerenes in ionic conductivity of liquid crystal.

Negative refraction of plane electromagnetic waves in non-uniform double-negative media.

We propose a new model of a plane-layered medium with a fixed positive refractive index, but variable non-vanishing dielectric permittivity and magnetic permeability. An analytical solution of the problem of plane electromagnetic wave propagation through the medium has been found. It is shown that the negative-refraction effect occurs in this type of medium; in particular, an explicit expression for the field has been first obtained in the region of its formation. This result suggests that the necessary condition for the occurrence of this effect in quite complex media is not the negativity of their refractive indices, but only the requirement of simultaneous negativity of the real parts of dielectric permittivity and magnetic permeability. We also demonstrate that the medium is passive (absorbing) if a plane E-polarized wave propagates in it, and active (amplifying) in the case of H-polarized wave propagation.

Dielectric properties of Al/PVA/p-Si (MPS) Structure as a function of frequency and voltage

Abstract Metal-Polymer-Semiconductor (MPS) structure Al/PVA/p-Si was fabricated using polyvinyl alcohol (PVA) as an organic interfacial layer on a p-type silicon wafer by spin coating method. Frequency dependent dielectric properties like real and imaginary part of dielectric permittivity (dielectric constant e′ and dielectric loss e″), dissipation factor or loss tangent (tan δ), real and imaginary parts of the electric modulus (M′, M′′) of the fabricated MPS structure were investigated for various frequencies from 50 KHz to 1 MHz. Frequency dispersion has been found for all dielectric parameters. Simultaneously these were found to be a function of voltage. It was found that e′ and e″ decrease with the increase in frequency. M′ increases with frequency while M′′ shows a peak behaviour that shifts towards lower frequency with increasing applied voltage. All these changes in dielectric parameters may be attributed to surface states distribution at PVA/p-Si interface and interfacial polarization.

Investigation of thermal and electrical properties of As–Se glasses modified with Cu using DSC and AC impedance spectroscopy

Investigations of thermal properties of CuxAs50Se50 − x chalcogenides were carried out using a differential scanning calorimeter. It was established that copper introduction significantly affects the complexity of structural network. This was indicated by double-stage crystallization process in the compound Cu15As50Se35. Besides α relaxation, all the glasses during heating show β relaxation. The complexity of the network influences the conductivity values and transport properties in a way of higher DC and AC conductivity for the compound with the highest Cu share. Impedance spectra show two semicircles, indicating the existence of two polarization processes in different frequency ranges. The presence of kinetic and as well as diffusion processes in polarization of the samples with x = 10 and 15 at% of Cu strongly affects the unusually high values of the real part of dielectric permittivity in low- and medium-frequency range.

Optical and structural properties enhancement of hybrid nanocomposites thin films based on polyaniline doped with Zinc Oxide embedded in bimodal mesoporous silica (ZnO@SiOX) nanoparticles

Hybrid thin films of doped polyaniline (PANI) with Zinc Oxide (ZnO) nanoparticles (NPs) embedded in bimodal mesoporous silica-forming (ZnO@SiOx) NPs were prepared. The preparation was done by spin coating techniques of the solution of a protonated PANI with TFA acid with sequential weight ratios of ZnO@SiOx NPs in the range from 15% to 60%. The prepared thin film morphologies were investigated using Scanning Electron Microscopy (SEM). The aggregation or the clustering of ZnO@SiOx) NPs in the polymer network matrix is very limited due to the silicone oxide (SiOx) which is known to limit the growth of aggregation clusters. The optical properties of hybrid thin films were studied through reflectance and transmission spectroscopy in the UV–Vis range. The optical constants such as the refractive index (n), extinction coefficient (k), real (ɛ') and imaginary (ɛ'') parts of dielectric permittivity and the absorption coefficient were deduced via analysis of the transmittance spectra using ‘CODE’ software. Increase of the ZnO@SiOx NPs content gives rise to a decrease of the values of these constants: The refractive index n showed a significant decrease for the highest ratio. The static dielectric permittivity constant, the gap energy Eg and the Urbach energy were determined by using common optical models. Eg decreases with increasing ZnO@SiOx NPs content. For the nanocomposites corresponding to an amount of 45%, the value of Eg reached 2.4eV. The bonding of the ZnO@SiOx NPs to the protonated PANI by TFA doping was investigated thoroughly by FTIR spectroscopy. Based on its optical and electrical properties the novel PANI/ZnO@SiOx hybrid nanocomposite is a promising candidate for optoelectronic and photovoltaic applications.

Microwave Interferometry Based On Open-ended Coaxial Technique for High Sensitivity Liquid Sensing

This paper describes a modified open-ended coaxial technique for microwave dielectric characterization in liquid media. A calibration model is developed to relate the measured transmission coefficient to the local properties of the sample under test. As a demonstration, the permittivity of different sodium chloride solutions is experimentally determined. Accuracies of 0.17% and 0.19% are obtained respectively for the real and imaginary parts of dielectric permittivity at 5.9 GHz.

Low dielectric permittivity and low loss of low temperature co-fired Li2ZnxMg0.98−xCo0.02SiO4 ceramics with LiF–Bi2O3 additives

In present study, low temperature co-fired Li2ZnxMg0.98−xCo0.02SiO4 ceramics with LiF–Bi2O3 additives were prepared by solid state reaction method. The LiF and Bi2O3 additives were not only reducing the sintering temperature of Li2ZnxMg1 − xCo0.02SiO4 ceramics, but also enhancing the dielectric properties. The effects of LiF–Bi2O3 on structure and dielectric properties were investigated. Under the additive action, all XRD patterns showed the single phase and the grain size increased gradually. Additional, the ratio of Zn2+ and Mg2+ ions affected the structure and properties of Li2ZnxMg0.98−xCo0.02SiO4 ceramics. When x = 0.6, the real part of dielectric permittivity was about 6.12 at 1 MHz–1.5 GHz, while the dielectric loss was about 1.2 × 10−3, which was fairly potential application for antenna substrate.

Electrical properties of PMN-33PT thin film at MPB

ABSTRACTThis paper presents a systematic investigation of the electric properties of epitaxial PMN-33PT thin film as a function of temperature and frequency. Complex impedance measurements were performed over the temperature range of 30 – 500 K and frequency range 20 Hz – 1 MHz. Obtained results were corrected for the SRO series resistance. Ferroelectric hysteresis loops and electric field tunability of the real part of dielectric permittivity were measured in the 300 K – 450 K temperature range and at a frequency of 1 kHz. The results of electrical field tunability of complex dielectric permittivity were approximated by Landau-Ginsburg-Devonshire theory frame by the Johnson relation. Meanwhile, ferroelectric hysteresis loop measurements of epitaxial PMN-33PT thin film shows a good hysteresis property with a remnant polarization of 2Pr 10 µC/cm2 and coercive field of 2Ec 12 kV/cm at temperature range from 300 K to 380 K.

Effect of Gd3+- Cr3+ ion substitution on the structural, electrical and magnetic properties of Ni - Zn ferrite nanoparticles

Gd3+ doped nickel zinc nanoceramics with general formula Ni0.4Zn0.6Cr0.5GdxFe1.5 - xO4 (where x=0.00, 0.02, 0.04, 0.06) were synthesized by solution combustion method using oxylyldehydrazine as a fuel. The obtained powder was sintered at 1000°C for 2h. The detailed structural, electrical and magnetic studies were carried out through X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), impedance spectroscopy and vibrating sample magnetometer (VSM). The XRD pattern of as prepared sample confirms the formation of single phase with cubic spinel structure. The average crystallite size was found to be 34 to 19 nm and decreases with increasing Gd3+ ion concentration. The IR spectra exhibited two expected absorption bands between 600 to 300 cm-1 corresponding to the stretching vibrations of tetrahedral (A) and octahedral (B) metal oxygen vibrations. The variation of room temperature real (ε') and imaginary (ε") part of dielectric permittivity as a function of frequency and composition have been studied in the frequency range from 40Hz to 10MHz. The real and imaginary dielectric permittivity decreases with increase in frequency as well as Gd3+ concentration, which is normal behaviour of ferrite material and results have been explained on the basis of Maxwell - Wagner's two layer model. The VSM results showed that the Gd3+ concentration had significant impact on the saturation magnetization and coercivity, x = 0.02 shows the highest value of dielectric constant and saturation magnetization, thus the material is becoming low loss dielectric and highly resistive and soft magnetic material due to Gd-Cr doping.

Investigation of dielectric relaxation in ferroelectric composite nanocrystalline cellulose – triglycine sulfate

ABSTRACTDielectric relaxation in ferroelectric composite nanocrystalline cellulose – triglycine sulfate in the frequency range from 103 to 106 Hz in a weak measuring field (1 V·cm−1) from room temperature to the phase transition temperature of these composites (+54°C) has been investigated. Two series of nanocomposites were used: the first one with the perpendicular directions of nanochannels with respect to the sample surface and the second one – with parallel. The typical for single-crystal triglycine sulfate maximum of the imaginary part of dielectric permittivity at frequencies (105 Hz – 106 Hz) in the case of composites nanocrystalline cellulose – triglycine sulfate is shifted to the range of lower frequencies (104 Hz – 105 Hz).

Dielectric behaviour of BaTi1-xZrxO3 ceramics obtained by means of a solid state and mechanochemical synthesis

ABSTRACTIn this study the comparison of dielectric behaviour of BaTi1-xZrxO3 (BTZx) ceramic samples prepared by means of a solid state and mechanochemical synthesis was presented. A single phase of perovskite structure was identified in the samples at room temperature. No significant impurities were detected in an EDS spectrum and the samples had a good stoichiometric ratio. The morphology of the investigated samples was characterized by a scanning electron microscopy (SEM). The investigation of dielectric properties of the BTZx samples within the temperature range from 140 K to 600 K was performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The temperature dependences of real part of dielectric permittivity showed the changes of the character of the paraelectric–ferroelectric (PE–FE) phase transition for the ceramic samples obtained by means of both methods.

Experimental and theoretical studies of structural phase transition in a novel polar perovskite-like [C2H5NH3][Na0.5Fe0.5(HCOO)3] formate.

We report the synthesis, single crystal X-ray diffraction, and thermal, dielectric, Raman and infrared studies of a novel heterometallic formate [C2H5NH3][Na0.5Fe0.5(HCOO)3] (EtANaFe). The thermal studies show that EtANaFe undergoes a second-order phase transition at about 360 K. X-ray diffraction data revealed that the high-temperature structure is monoclinic, space group P2(1)/n, with dynamically disordered ethylammonium (EtA(+)) cations. EtANaFe possesses a polar low-temperature structure with the space group Pn and, in principle, is ferroelectric below 360 K. Dielectric data show that the reciprocal of the real part of dielectric permittivity above and below the phase transition temperature follows the Curie-Weiss, as expected for a ferroelectric phase transition. Based on theoretical calculations, we estimated the polarization as (0.2, 0, 0.8) μC cm(-2), i.e., lying within the ac plane. The obtained data also indicate that the driving force of the phase transition is ordering of EtA(+) cations. However, this ordering is accompanied by significant distortion of the metal formate framework.

Enhanced magnetic and dielectric properties of Bi0.7Y0.2Ba0.1Fe0.98−xCoxO3 ceramic with Co3+ substitution

In this paper, we prepared the Co substituted Bi0.7Y0.2Ba0.1Fe0.98−xCoxO3 (x = 0.00, 0.02, 0.04, 0.06) ceramic materials by conventional solid-state reaction method. In order to further enhance the magnetic properties, we chose Co3+ ions to substitute Fe3+ ions in Bi0.7Y0.2Ba0.1Fe0.98O3 ceramic materials. Phase formation, dielectric and magnetic properties of the samples were investigated by X-ray diffractometer, scanning electron microscope, impedance analysis and vibrating sample magnetometer. The results indicated that Co3+ ion substitution could cause the lattice distortion, but did not change the phase formation of samples. With Co3+ increasing from 0.00 to 0.06, the saturation magnetization (M s) increased by 24 % (from 7.81 to 9.68 emu/g), the coercivity (H c) increased by 50 % (from 110.56 to 166.68 Oe). With the increasing of Co substitute amount, the real part of dielectric permittivity (e′) firstly increased by 71 % to reach 58.56 and then decreased by 4 % to reach 56.26, and kept stable value in a wild frequency range of 10 MHz–1 GHz.

Dielectric Behaviour of (Ba1-xNax)(Ti1-xNbx)O3 Ceramics Obtained by a Conventional and Mechanochemical Syntheses

The (Ba1-xNax)(Ti1-xNbx)O3 (BNTNx) ferroelectric ceramics have been prepared by a solid state reaction with the use of a conventional method. A mechanochemical treatment based on the high-energy planetary ball milling has been used as an alternative method of synthesizing of the ceramics. The morphology of the investigated samples was characterized by a scanning electron microscopy (SEM). The characterization of electrical properties of the BNTNx samples within the temperature range from 130 K to 600 K were performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The temperature and frequency dependences of real part of dielectric permittivity showed the changes of the character of the paraelectric–ferroelectric (PE–FE) phase transition for the ceramic samples obtained by both methods. These functional materials turned out to be either classical or relaxor ferroelectrics.