Ac Conductivity Values Research Articles

Synthesis of the SWCNTs/TiO2 nanostructure and its effect study on the thermal, optical, and conductivity properties of the CMC/PEO blend

The TiO2 NPs have been successfully synthesized by sol-gel method and the SWCNTs/TiO2 nanostructures have been fabricated by a simple mixing technique. By a solution casting process, pure CMC/PEO and SWCNTs/TiO2 nanohybrid doped CMC/PEO polymer blend films have been prepared. The influence of SWCNTs/TiO2 nanohybrid loading on the thermal, optical, and conductivity properties of the polymer blend has been discussed. The XRD pattern shows that the average crystallite size of the nanoparticles for TiO2 and SWCNTs/TiO2 is 20 nm and 15 nm, respectively, and a change in crystallinity was observed with an increase in doping. The interaction between CMC/PEO chains and SWCNTs/TiO2 nanohybrid is confirmed by FTIR spectra. The optical absorption spectrum shows that the energy gap reduces with the dopant increase. The miscibility between the CMC and PEO was confirmed by DSC thermograms. With an increase in dopant content, the TGA study demonstrates that the system's thermal stability improves. The maximum value of the blend's AC conductivity is 4.77 10−6 S/m, and by increasing the loading of SWCNTs/TiO2 to 3.2 (wt%) increased to 9.23 10−4 S/m. The conduction mechanism changed with SWCNTs/TiO2 loading from the correlated barrier hopping, in the prepared samples. Usage of these nanocomposite films in the semiconductor industry is encouraged by the observed improvements in optical, thermal, and AC conductivity.

Effect of Zn doping on dielectric properties of MgO nanoparticles synthesized by microwave-assisted combustion route

The composite insulating materials are major parts of various electrical devices because of their synergetic effect. The primary aim is to study the dielectric properties of nanoscale MgO and Zn-doped MgO nanoparticles (NPs). MgO and a series of (2, 4 and 6%) Zn-doped MgO NPs were synthesized by microwave-assisted combustion route. The samples were characterized through various techniques and the confirmation of phases and crystallite sizes of MgO and Zn-doped MgO NPs were calculated from XRD pattern. The study of dielectric permittivity, dielctric loss, AC conductivity and impedance were investigated in the frequency range of 1–106 Hz at room temperature. The dielectric permittivity and dielectric loss of the materials increased with increase in the doping of Zn into MgO NPs at lower frequency. The AC conductivity values of doped nanoparticles increased gradually with increase in the frequency range due to the hopping and tunneling mechanism. The real and imaginary impedance were found to decrease with increase in the Zn doping percentage.

Effect of polyaniline on the structural, conductivity, and dielectric properties of chitosan

Polyaniline-chitosan (PANI-Cs) blends were prepared by in situ oxidative polymerization with acetic (CH3COOH) acid and hydrochloric (HCl) acid as dopants. Using Fourier transform infrared (FTIR) spectroscopy, the C N and C C stretching of quinoid and benzenoid of PANI in the PANI-Cs blends was confirmed at ranges 1528cm−1 to 1571cm−1 and 1490cm−1 to 1493cm−1, respectively. PANI emeraldine state was stipulated in all samples and PANI-Cs HCl samples have the highest degree of oxidation which is 48.56±0.23%. The ultraviolet-visible (UV–vis) spectroscopy identified the glucopyranose of Cs (282–308 nm), and π−π* transition of benzenoid (389–437 nm) and quinoid rings (551–554 nm) of PANI. The PANI-Cs blends yielded optical band gap values of 1.968±0.014 to 2.009±0.005 eV due to the presence of PANI. One-way ANOVA was also performed, and results showed the significant effect of using different dopants towards the degree of oxidation of the samples. Frequency dependent behavior was observed to the PANI-Cs samples with AC conductivity values around 1.2–4.1 Scm−1 at 105–107 Hz. The 102 Hz dielectric peak intensity of the samples varied due to influence of dopants on charge polarization. Lastly, PANI-Cs samples showed dominance of DC loss and relaxation at low frequencies 10–103 Hz.

Evaluation of structural, dielectric, magnetic and photocatalytic properties of Nd and Cu co-doped barium hexaferrite

In this study, the micro-emulsion approach was adopted to fabricate rare earth (Nd) and transition metal (Cu) co-doped barium hexaferrite (Ba1-xNdxFe12-yCuyO19) nanoparticles (NPs). The fabricated co-doped and undoped materials were characterized by FTIR, XRD, and SEM techniques for structural and morphological investigation. Structural studies such as XRD and FTIR confirmed Nd and Cu doping at the tetrahedral and octahedral sites of barium hexaferrite, respectively. The SEM analysis made sure that the materials were successfully produced at the nanoscale. Dielectric measurements revealed that the dielectric constant and AC conductivity values of the co-doped sample were higher than those of the undoped sample. The VSM study confirms the improved magnetic properties of the sample after co-doping that facilitates its separation and reuse after photocatalytic experiments. The co-doped and undoped sample's photocatalytic activities (PCA) were explored by comparing their Methyl Green (MG) dye degradation efficiencies. The results revealed that the co-doped barium hexaferrite sample degraded almost 92.6% of the MG dye, while the undoped sample degraded just 37.4%. The higher PCA of the co-doped sample is credited to its structural defects, which adjust the band interval to increase electrical conductivity. In addition, the co-doped sample lost only 2% photocatalytic efficiency after five successive cycles, demonstrating its potential for reuse. Application studies have clearly shown that our Nd-Cu co-doped barium hexaferrite sample has a great potential for practical application to remove toxic dyes from the environment.

Investigation of the effect of in-situ grown PPy on low frequency dielectric properties and other properties of PVA-PVP blend film

Present study is carried out to understand the effect of conducting polymer, polypyrrole (PPy) on structural, morphological, thermal and dielectric properties of bio-compatible polymer blend film of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). The growth of PPy in the matrix of PVA–PVP was analyzed using XRD, FT-IR and SEM studies. The shifting in positions and broadening of XRD diffraction peaks of PVA–PVP-PPy from that of PVA–PVP indicates the structural modification and reduction in the crystallinity of the PVA–PVP due to incorporation of PPy. The SEM studies suggest scattered growth of PPy in PVA–PVP matrix at lower concentration of pyrrole monomer. As the monomer concentration is increased, the uniform and interconnected growth of PPy was observed in SEM micrographs. The TGA thermograms show faster thermal degradation of PVA–PVP- PPy films at lower temperature as compared to PVA–PVP films. The blend films of PVA–PVP- PPy exhibited enhanced values of dielectric constant and ac conductivity as compared to the virgin blend film which are observed to increase with increasing concentration of PPy. The high dielectric constant with high ac conductivity exhibited by PVA–PVP-PPy film suggests its possible application as flexible dielectric material for the development of biosensors, energy storage devices in field of green organic electronics.

Investigation of low temperature dielectric properties of manganese doped-copper oxide nanoparticles by coprecipitation method

Mn-doped CuO nanoparticles were prepared by the co-precipitation method. X-ray diffraction patterns of pristine and Mn-doped CuO (5, 10 and 15%) nanoparticles confirm the formation of monoclinic structure. Scanning electron microscopy revealed that, the change in morphology with increasing Mn content. Dielectric permittivity value increases with increase in Mn concentration. AC conductivity curves depict improvement in conductivity with a low concentration of Mn content. DC conductivity and AC conductivity values are in accordance with Jonscher’s universal power law

Structural, morphological, magnetic hysteresis and dielectric properties of cobalt substituted barium–lead hexagonal ferrites for technological applications

M-type, Ba0.4Pb0.6Fe12-xCoxO19 (x = 0.00, 0.10, 0.20, 0.30, 0.40) hexaferrites, synthesized using citrate gel auto combustion method, and heated at 950 °C, 4 h for lossless applications. XRD analysis shows the development of the M-phase, along with PbM and hematite. The microstructural analysis reveals the stacking clusters of hexagonally shaped platelets. TEM image and SAED pattern of x = 0.3 composition shows polycrystalline nature and formed particles observed to fused with neighbouring particles. M − H loops of all samples reveal hard magnetic behaviour and possess multi-domain structure. The maximum saturation magnetization of 55.427 A m2/kg is observed in x = 0.10 composition and coercivity of prepared hexaferrites was found to vary from 0.058 T to 0.390 T. The cobalt substitution has a strong influence on the dielectric properties of prepared hexaferrites. The value of ac conductivity increases with cobalt substitution from x = 0.00 to x = 0.10, and followed by a reduction from x = 0.10 to x = 0.40. The same trend is observed for the dielectric constant. The low value of loss tangent for all compositions shows apt scope for lossless application.

Effect of Eu3+ ions on electrical and dielectric properties of barium hexaferrites prepared by solution combustion method

This paper reports the electrical conduction behaviour of Eu3+ substituted barium hexaferrites (BaM) prepared via solution combustion method. The structural analysis confirms formation of hexagonal phase of the prepared samples with a space group p63/mmc (No. 194). The SEM micrographs show that the prepared sample has hexagonal plate like structure. Dielectric constant, dielectric loss and AC conductivity of the prepared samples were calculated over a wide frequency range from 102 Hz to 105 Hz at different temperatures. The temperature dependent dielectric studies were also performed over a temperature range of 30°C–200°C. The non –Debye dielectric nature of the prepared samples and presence of electrical relaxation phenomenon were confirmed from the complex impedance spectroscopy. Electrical modulus analysis confirms that there is negligible electrode effect in prepared the samples. From the frequency dependent AC conductivity studies, we find that the AC conductivity values are constant in the lower frequency region and shift towards the higher value in the higher frequency region, which indicates that the prepared samples follow the Almond-West power law. The AC conductivity values decrease gradually with increase in the concentration of Eu3+ ions increases. The dielectric studies show that by doping of Eu3+ ions, the dielectric constant increases. So the prepared materials can be applicable for microwave devices applications.

Dielectric dispersion and relaxations in (PMMA/PVDF)/ZnO nanocomposites

In latest years, the scientific community has shown important interest in nanocomposites as a new generation of materials with elevated dielectric constant and low dielectric loss factor for microelectronics. In this work, the effect of ZnO nanoparticles on PMMA/PVDF blend. Solution-cast technique used to prepare these nanocomposites. FTIR and SEM studies were performed. The effect of ZnO doping on the complex dielectric permittivity, electric modulus properties and ac electrical conductivity of these nanocomposites has been investigated at ambient temperature. Dielectric constant e′, dielectric loss e″, and the loss tangent decreased with increasing frequency and increased with increasing temperature. The dielectric constant values were found almost high (∼24) at (100 Hz) and were referred to the presence of interfacial polarization. The existence of loss peak in e″, tanδ and, M" attributed to α-relaxation existed in the nanocomposites. The temperature-dependent ac conductivity values obeyed Arrhenius behavior. These nanocomposites can be selected for implying capacitors and application of the memory device.

Characterization of nanostructured nickel cobalt oxide-polyvinyl alcohol composite films for supercapacitor application

In the present work, thin films of nickel cobalt oxide and polyvinyl alcohol nanocomposite (NCO-PVA) are prepared by chemical methods. The as-prepared NCO-PVA films have been structurally studied by X-ray diffraction and Fourier transform infrared spectroscopy. The morphology of the NCO-PVA films has been studied by Field emission scanning electron microscopy and High-resolution transmission electron microscopy. X-ray diffraction analysis has been used to study its crystallinity and phase. The optical properties of NCO-PVA nanocomposite films have also been studied. The surface area and pore size measurements have also been done. The UV-Vis spectrum analysis reveals that the films possess two direct band gaps (2.91 eV and 3.48 eV). The red shift of Photoluminescence emission has been observed for nanocomposite films with increasing excitation intensity. The AC electrical conductivity of NCO-PVA films has been studied as the high value of AC conductivity is essential for getting high power and high energy density in supercapacitors. Also, the high value of the dielectric constant of nanocomposite at small frequencies shows its supercapacitive nature. A short relaxation time (~6.37 ≤ 10−7 s) reveals a very small delay in molecular polarization along with changing the electric field, suggesting fewer energy losses. Electrochemical performance is checked by cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy measurements using 1 M Na2SO4neutral aqueous electrolytic solution. Also, the symmetric supercapacitor has been fabricated, using NCO-PVA films as the electrodes, which exhibits the specific capacitance value of50 F g−1and energy density of 18.9 W h kg−1. The results reveal that the prepared nanocomposite films have enough potential for supercapacitor device fabrication, especially the flexible supercapacitors.

Characterization, Structure, Dielectric Permittivity, and AC Conductivity of Co–Ni-Doped Bentonite at Room Temperature

xCo–5%Ni (where x = 0, 1, 3, and 5%) coatings on bentonite were synthesized by insipient wet impregnation method. The phase structures of the coatings, surface analysis, dielectric property of the samples as a function of frequency (at room temperature), were characterized using X-ray diffractometer, energy-dispersive X-ray spectroscopy (EDX) and analytical response analyzer, respectively. The EDX confirmed the presence of Ni and Co in proportions qualitatively consistent with the concentrations of the synthesized composites. X-ray diffraction measurement confirmed the presence of montmorillonite and quartz as the main components in bentonite. Peaks shift has been noticed toward lower diffraction angle in bentonite X-ray diffractogram after insertion of metal ions (Ni and Co ions) which might be due to lattice expansion. The lattice constant was found to be 4.35, 4.42, and 4.41 A for 1%Co–5%Ni/bentonite, 3%Co–5%Ni/bentonite and 5%Co–5%Ni/bentonite, respectively. The diffraction peak at 37.2°, observed for all composites, was ascribed to (111) plane of the NiO cubic phase. The crystallite size has been calculated by Scherer formula and was found to increase from 3.19 to 8.43 nm with increasing the wt% of Co. The dielectric permittivity has decreased with increasing frequency and further decreased by doping. The value of AC conductivity has increased with an increase in frequency. The conduction mechanism for doped samples was hopping, while that for bentonite was due to the localized/reorientation processes.

Dielectric properties of MWCNT dispersed conducting polymer nanocomposites films of PVA-CMC-PPy

The structural, dielectric and electrical properties of multiwall carbon nanotube (MWCNT) dispersed polymer nanocomposite films (PPy) of Polyvinyl alcohol (PVA) blended with Sodium Carboxymethyl cellulose (CMC) and doped with Polypyrrole (PPy) is reported here. Free standing and flexible polymer nanocomposite films (PNC) were prepared by solution cast technique. The XRD study shows that amorphousness of the films increases with blending PPy in PVA-CMC matrix and also by increasing concentration of MWCNT nanopowder in PVA-CMC matrix. Molecular interaction between polymer–polymer and polymer- nanoparticle was studied using FTIR in attenuated total reflection (ATR) mode. Frequency dependent dielectric properties of these PNC films were studied in the frequency range of 100 Hz – 2 MHz. Flexible, biocompatible polymer nanocomposite films of PVA-CMC-PPy having MWCNT (5 wt)% showed appreciable rise in the values of dielectric constant and ac conductivity for measured frequency range.

Structural, dielectric and magnetic properties of double perovskite-La2CoNiO6 ceramics synthesised by wet chemical route

The polycrystalline double perovskite-La2CoNiO6 ceramics were successfully synthesised by facile wet chemical route. The X-ray diffraction pattern has confirmed the formation of rhombohedral phase with R3c symmetry and calculated value of lattice parameters as, a = b = 5.64 A and c =13.25 A, respectively. The presence of La3+ ions, Co2+/Co3+ ions, and Ni2+ ions on the surface of La2CoNiO6 has been exhibited via X-ray photoelectron spectroscopy. The temperature and frequency dependent dielectric and impedance analysis has revealed the effect of grains and grain boundaries in the relaxation process. The observed values of ac conductivity varied from 5.27 × 10−6 S/m to 1.06 × 10−5 S/m with variation of temperature from 300 K to 473 K at frequency of 1 kHz. Further, La2CoNiO6 is a new ferromagnetic semiconductor exhibiting spin glass transition at low temperature of ~50 K. The present first report on structural, dielectric and magnetic study makes La2CoNiO6 a promising material for electronic devices applications.

Enhanced electrical conductivity in Zr-Doped (La0.7Ba0.3)(Mn0.5Fe0.5)O3 solid solutions

The perovskite ([Formula: see text][Formula: see text]([Formula: see text][Formula: see text][Formula: see text]O3, where [Formula: see text] = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be [Formula: see text]118.8 S [Formula: see text] cm[Formula: see text] for [Formula: see text] = 0.3 at 200[Formula: see text]C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent [Formula: see text] versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200[Formula: see text]C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for [Formula: see text] > 1) are supposed to be suitable for cathode materials in SOFCs.

Electrical Properties in Large Frequency and Temperature Ranges of Sr0.6Ca0.4TiO3 Ceramics

Abstract: Lead-free Sr0.6Ca0.4TiO3 (SCT) ceramic was prepared by the solid state reaction route. X-Ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure of the material. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure for the ceramic. The dielectric and conductivity properties of the sample were studied using complex impedance measurement technique in a wide range of frequencies and temperatures: from 100 Hz to 1.8 GHz and from 25°C to 550°C. The ceramic exhibits a stable dielectric permittivity and low dielectric losses in frequency and temperature up to 200°C. This is very interesting in view of developing high-quality lead-free ceramic capacitors for applications requiring high temperatures; for example, in cars. The increase in dielectric permittivity for temperatures higher than 200°C may be related to oxygen vacancies that are heat-activated in the material. Dielectric losses show the existence of a dielectric relaxation at low temperatures and low frequencies. Conductivity measurement investigated at high temperatures show on one hand high AC conductivity values attributed to the high temperature jumping process and on the other hand two electrical conductivity mechanisms above 400° C in the material. Keywords: Strontium calcium titanate, Ceramic, Structure, Dielectric properties, Conductivity.

Influence of UV light intensity on dielectric behaviours of pure and dye-doped cholesteric liquid crystals

This study aims to explore the ultraviolet (UV) light effects on dielectric properties of azo dye methyl red (MR)-doped cholesteric liquid crystal (CLC) composite. The CLC composite formed in the study contains 5CB nematic liquid crystal (LC) and S811 chiral additive. To obtain CLC/MR composite, CLC was dispersed with 2% wt/wt MR azo dye. Dielectric measurements of the CLC and CLC/MR samples were performed using dielectric spectroscopy technique in wide frequency range in the absence of UV light and at various UV light intensities (30, 60 and 90 mW/cm2) for 0 and 40 V. It was observed that the dielectric constant increased with UV light at low-frequency values. Dielectric loss data were utilized to extract relaxation frequency which was observed to increase with UV light exposure. Dielectric anisotropy of CLC sample exhibited typical transition from p-type to n-type, but this behaviour disappears for CLC/MR composite above 60 mW/cm2 UV light intensity. Cole–Cole plots were used for extraction of dielectric relaxation data and obtained results showed that CLC sample shows Debye type relaxation only at 0 V whereas CLC/MR composite exhibits non-Debye type relaxation both at 0 V and 40 V. Moreover, conductivity properties of the samples were also investigated, and dc conductivity values were extracted from experimental ac conductivity values. It was found that MR incorporation increased dc conductivity, also it was significantly increased by UV light exposure and thus similar effect was also observed in current–voltage characteristics of the samples. The results show that azo dye MR molecules are suitable for CLCs since they lead to some enhancements in dielectric and electrical properties.

In-situ polymerization of pyrrole in PVA-PVP matrix: Optimization of oxidant/monomer ratio and its effect on dielectric properties of polymer blend films

Free standing and flexible polymer blend films of PPy (poly pyrrole) doped in PVA (poly vinyl alcohol) – PVP (poly vinyl pyrrolidone) matrix with varying concentrations of PPy have been prepared by solution cast technique at room temperature. In-situ polymerization of pyrrole monomer (Py) in PVA-PVP matrix has been carried out using FeCl3 as oxidant. The effect of monomer amount and monomer to oxidant ratio on the dielectric parameters (such as dielectric constant, dielectric loss, loss tangent, ac conductivity, complex electric modulus, complex impedance) of PPy doped PVA-PVP polymer blend films have been studied in the frequency range of 20 Hz to 2 MHz. Two different molar concentrations (0.15 M and 0.30 M) of oxidants have been taken and for each oxidant concentration, four varying concentrations of monomer have been used to optimize the results. The blend films having oxidant to monomer molar concentration ratio of 0.5 in both the cases (i.e. 0.15 M and 0.30 M) have been found to be smooth, flexible, mechanically strong and easy to process. These films have shown very systematic change and improved values of dielectric parameters within the experimental frequency range. Enhanced dielectric parameters (complex permittivity, ac conductivity and electric modulus) values for films having oxidant to monomer molar ratio of 0.5 suggest the organized growth of PPy chain in the matrix of PVA-PVP.

Effect of carbon-doping on structural and dielectric properties of zinc oxide

In this paper, Carbon-doped Zinc Oxide (C-ZnO) samples were prepared using the solid-state reaction method. The influence of carbon-doping on the structural and dielectric properties of ZnO samples was studied. The shift in the highest peak position (101) in XRD patterns of carbon-doped samples was observed. The Raman peak at 581[Formula: see text]cm[Formula: see text] in undoped ZnO was shifted and broadened in carbon-doped ZnO samples. The ZnO samples doped with carbon show higher values of dielectric constant ([Formula: see text] at 1[Formula: see text]kHz) compared to pure ZnO([Formula: see text] at 1[Formula: see text]kHz) which was due to increase in native point defects in the samples. The ac conductivity ([Formula: see text]) value of the carbon-doped sample was enhanced by 103 times for ((ZnO)[Formula: see text] [Formula: see text]) sample.

Electrical properties of amino acid substituted novel cinnamic acid compounds

Amino acid conjugates are combinations of one or more compounds, at least one of them active in terms of biological, pharmacological or physical. In this work, some novel amino acid conjugates, four different aldehydes (Pyrene, Naphthalene, Phenanthrene and Phenyl benzyl) have been chosen and from these initial materials four different amino acid conjugates were synthesized. The compounds from initial steps to final steps have been characterized by 1H and 13C APT NMR spectroscopy. The dielectric measurements were done by QuadTech 7600 LRC impedance analyzer. The dielectric constant (ε′) dielectric loss (ε’’) and ac conductivity (σ) values of amino acid conjugates in the frequency of 1 kHz and at 25 °C. The results show that the increase in conjugation affect the dielectric constant and conductivity.

Chemical Bonding of Fe3O4 Nanoparticles on the Surface of Poly(acryloyl chloride) Functionalized Multiwalled Carbon Nanotubes

Poly(acryloyl chloride) (PAC) was first reacted with oxidized MWCNT to form oxidized MWCNT-g-PAC. Then, aminated MNP were bonded to the oxidized MWCNT-g-PAC to form oxidized MWCNT-g-PAC-g-aminated MNP. The chemical characterization for primary and the product materials was performed using FT-IR spectroscopy. SEM images and SEM–EDX were used for the surface morphology and elemental characterization, respectively. Vibrating sample magnetometer measurements showed that aminated MNP and oxidized MWCNT-g-PAC-g-aminated MNP have magnetic saturation values of 52.07 emu/g and 20.38 emu/g, respectively. Both of the two samples indicated the superparamagnetic nature. TGA measurements were accomplished to compare the thermal stability of materials. Also, the DSC measurements were performed to compare Tg temperatures. While AC conductivity values of the oxidized MWCNT-g-PAC and oxidized MWCNT-g-PAC-g-aminated MNP increased by increasing frequency, it has not changed with increasing temperature. This result indicates that these materials act as electrical insulators.