Imaginary Part Of Electric Modulus Research Articles

Frequency and voltage dependence of electric and dielectric properties of Au/TiO2/n-4H-SiC (metal-insulator-semiconductor) type Schottky barrier diodes

The main electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) have been investigated as functions of frequency and applied bias voltage. We believe that the use of high dielectric interfacial layer between metal and semiconductor can improve the performance of Schottky diodes. From the experimental data, both electrical and dielectric parameters were found as strong function of frequency and applied bias voltage. The Fermi energy level (EF), the concentration of doping donor atoms (P), barrier height (ΦB) and series resistance (Rs) values were obtained from reverse and forward bias C–V characteristics. The changes in EF and ND with frequency are considerably low. Therefore, their values were taken at about constant. The real and imaginary parts of dielectric constant ( ), tangent loss (tanδ), ac electrical conductivity (σac), and real and imaginary parts of electric modulus (M′ and M″) values were also obtained from reverse and forward bias C–V and G/ω-V characteristics. In addition, the voltage dependent profiles of all these electrical and dielectric parameters were drawn for each frequency. These results confirmed that both electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type SBD are quite sensitive to both the frequency and applied bias voltage due to surface polarization, density distribution of interface traps (Dit), and interfacial layer.

Ionic conductivity and dielectric behavior of PEO-based silver ion conducting nanocomposite polymer electrolytes

Solid nanocomposite polymer electrolytes based on polyethylene oxide (PEO), AgNO3 as salt, and nanosized Fe2O3 (less than 50 nm size) as filler are prepared by hot press method. In (100-x) PEO:xAgNO3 system (where x = 5 ≤ x ≤ 50 wt%), the solid polymer electrolyte 90PEO:10AgNO3 gives highest ionic conductivity. This composition is further used as host matrix and Fe2O3 as filler for the preparation of solid nanocomposite polymer electrolytes (100-x) (90PEO:10AgNO3):xFe2O3 (where x = 5 ≤ x ≤ 30 wt%). The real impedance (Z') and imaginary impedance (Z") of the samples are analysed using LCR meter. The maximum ionic conductivity is observed for 10 wt% of filler Fe2O3. The optimum conducting composition 90(90PEO:10AgNO3):10Fe2O3 is used for further study. The dielectric response of the samples is analysed using dielectric constant (e'), dielectric loss (e"), loss tangent (tanδ), and real and imaginary part of electric modulus (M' and M"). The ionic conductivity and dielectric response of the solid nanocomposite polymer electrolytes are studied within the frequency range of 100 Hz–5 MHz and within the temperature range of 300–323 K. It is observed that the dielectric constant rises sharply towards low frequencies due to electrode polarization effects. The maxima of the loss tangent (tan δ) shift towards higher frequencies with increasing temperature. The enhancement in ionic conductivity is observed when nanosized Fe2O3 filler is added into the solid polymer electrolyte.

DC Conduction and Electric Modulus Formulation of Lithium‐Doped Bismuth Zinc Vanadate Semiconducting Glassy System

The conduction parameters related to dc conductivity and electric modulus formulation in the temperature range 313–533 K for xLi2O (100 − x) (50V2O5.20 Bi2O3. 30 ZnO) glass system have been studied. The temperature‐dependant dc conductivity is analyzed using the Mott's model for transition metals and modified Mott's VRH model. It is observed that Mott's model is in good agreement with the experimental data in high‐ and intermediate‐temperature region as a strong electron–phonon interaction seems to be prevalent. The conduction in these glasses has been attributed to small polaron hopping at the vanadium sites in nonadiabatic regime. The ion‐polaron effect (coupling between ions and polarons) leads to drop of the effective mobility and it can manifest itself as decrease in the dc conductivity with the addition of lithium content. The composition and temperature dependence of imaginary part of electric modulus () collapsed onto a single master curve, confirms the presence of same type of relaxation phenomenon in all the studied glass compositions.

Dielectric properties and electric modulus of Au/PPy/n-Si (MPS) type Schottky barrier diodes (SBDS) as a function of frequency and applied bias voltage

Au/PPy/n-Si Schottky barrier diodes (SBDs) were fabricated by forming polypyrrole (PPy) organic layer on n-Si using the spin coating technique. Frequency-dependent dielectric constant (ε′), dielectric loss (ε″), loss tangent ( tan δ), real and imaginary parts of electrical modulus (M′ and M″) and AC electrical conductivity (σ ac ) parameters of the structure were investigated in the frequency range of 10–500 kHz. It was found that the values of the ε′, ε″ and tan δ, in general, decrease with increasing frequency while an increase is observed in σ ac , M′ and M″. The tan δ and M″ also exhibit a peak at about zero-bias voltage, while peak intensity weakens with increasing frequency. The values of ε′ and M′ decrease with increasing voltage while an increase is observed in ε″, tan δ, σ ac and M″. These changes in ε′, ε″, tan δ, M′, M″ and σ ac values was attributed to surface charge polarization and the particular density distribution of surface states localized at PPy/n-Si interface.

Electrical transport properties of polyvinyl alcohol–selenium nanocomposite films at and above room temperature

Here, we report the DC and AC electrical properties of polyvinyl alcohol (PVA)–selenium (Se) nanocomposite films in the temperature (T) range 298 K ≤ T ≤ 420 K and in the frequency (f) range 120 Hz ≤ f ≤ 1 MHz. The introduction of selenium nanoparticles into the PVA matrix slightly increases the values of DC conductivity whose temperature dependency obeys Vogel–Fulcher–Tammann law. The AC conductivity follows a power law with frequency in which the temperature dependence of the frequency exponent suggests that the correlated barrier hopping is the dominant charge transport mechanism for the nanocomposite films. Comparative discussions with Dyre’s random free-energy barrier model have also been made in this regard. The increase in AC conductivity with increase in nanoparticles concentration was also observed and attributed to the corresponding increase in conducting channels in the PVA matrix. The real part of the dielectric constant increases either with increase in temperature or with increase in selenium nanoparticles loading into the polymer matrix, which may be attributed to the enhancement of interfacial polarization. The frequency dispersion of the dielectric spectra has been modeled according to the modified Cole–Cole equation. Well-defined peaks were appeared in the plotting of imaginary part of electric modulus with frequency above room temperature, which was fitted with suitable equations to account for the deviations from ideal Debye-type behavior. Though the current–voltage characteristics are linear at smaller voltages, it appreciably becomes nonlinear at higher voltages. This nonlinearity has been accounted in light of Werner’s model and back to back Schottky diode model.

Surface and Electrical Properties of Electro-Coagulated Thermal Waste

AbstractThe Electro-Coagulated Thermal Waste (ECTW) sample of the impedance spectroscopy investigation for electrical modulus and conductivity are presented. Electrical properties via temperature and frequency dependent impedance spectroscopy were investigated. Real and imaginary parts of electrical modulus were measured at various frequencies and a related Cole-Cole plot was acquired as well. The surface resistivity of the ECTW was measured by the four-point probe measurement technique, yielding a relatively high surface resistivity. As a result of this study, an effective building shielding material, which is a cost effective alternative, is proposed. The activation energy values were calculated from the Arrhenius plots at different frequencies. The transition region in this plot may be attributed to activation of ionic conductivity at lower temperatures.

On the frequency dependent negative dielectric constant behavior in Al/Co-doped (PVC+TCNQ)/p-Si structures

The dielectric properties, electric modulus and ac electrical conductivity (σac) of Al / Co -doped (PVC+TCNQ)/p- Si structures have been investigated in the wide frequency and voltage range of 0.5 kHz–3 MHz and (-4 V)–(9 V), respectively, using the capacitance-voltage (C–V) and conductance-voltage (G/ω–V) measurements at room temperature. The real and imaginary parts of dielectric constant (ε′, ε″), loss tangent ( tan δ), σac and the real and imaginary parts of electric modulus (M′, M″) were found strongly function of frequency and applied voltage especially at low frequencies. The ε′–V plot shows an anomalous peak in the forward bias region due to the series resistance (Rs), surface states (Nss) and interfacial layer (PVC+TCNQ) effects for each frequency and then it goes to negative values known as negative dielectric constant (NDC) at low frequencies (f ≤ 70 kHz). Such observation of NDC is important result because it implies that an increment of bias voltage produces a decrease in the charge on the electrodes. The amount of negativity ε′ value increases with decreasing frequency and this decrement in the NDC corresponds to the increment in the ε″.

Dielectric properties of BaTiO3 based materials with addition of transition metal ions with variable valence

Dielectric properties of BaTiO3(BT), BaTiO3+0.1wt.%MnO2(BTMn) and BaTiO3+0.1 wt.%Fe2O3 (BTFe) solid solution was investigated. The effects of substitution on the microstructure and on the electric properties of BaTiO3 samples were studied by performing X-ray diffraction and electric measurements. X-ray diffraction analysis of the samples shows the formation of single-phase compound with a tetragonal structure at room temperature. SEM microphotographs exhibit the uniform distribution of grains. The electric properties (a real part of electrical permittivity(□ε') and an imaginary part of electric modulus (M")) were investigated in the temperature range from 150K to 600K and in the frequency range from 0.1 Hz to 10 MHz. It was found that a Fe and Mn ions -doping influence the electric properties of the investigated polycrystalline materials.

Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO6

A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO6 (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the I4/mmm space group with lattice parameters a=b=5.6828(9)Å, c=8.063(2)Å. Structural analysis reveals 1:1 ordered arrangement for the Co2+ and Nb5+ cations over the six-coordinate B-sites of BPCN. The superlattice line (101) at 2θ=19.10° arising from the alternate ordering of Co2+ and Nb5+ sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO6 stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503K and in the frequency range 100Hz to 1MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson–Cole model (DCM). The values of α (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same ~0.4eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures.

Effect of gamma irradiation on opto-structural, dielectric, and thermoluminescence properties of natural phlogopite mica

Gamma ray induced modifications in natural phlogopite mica have been studied in the dose range of 1–2000 kGy. These modifications were monitored using different techniques viz: ultraviolet-visible spectroscopy, Fourier Transform Infrared spectroscopy, dielectric measurements, X-ray diffraction, and thermoluminescence dosimeter. The analysis of the results reveals that the dose of 100 kGy produces significant change in the natural phlogopite mica as compared to pristine and other exposed samples. Ultraviolet-visible analysis provides the value of optical indirect, direct band gap, and Urbach energy. Cody model was used to calculate structural disorder from Urbach energy. Different dielectric parameters such as dielectric constant, dielectric loss, ac conductivity, and real and imaginary parts of electric modulus were calculated for pristine and irradiated samples at room temperature. Williamson Hall analysis was employed to calculate crystallite size and micro-strain of pristine and irradiated sheets. No appreciable changes in characteristic bands were observed after irradiation, indicating that natural phlogopite mica is chemically stable. The natural phlogopite mica may be recommended as a thermoluminescent dosimeter for gamma dose within 1 kGy–300 kGy.

Electrical properties of complex perovskite samarium nickel titanate

The complex perovskite oxide samarium nickel titanate, Sm(Ni1/2Ti1/2)O3 (SNT) is synthesized by solid-state reaction technique. The x-ray diffraction pattern of the sample at room temperature shows monoclinic phase. The microstructure analysis of the sample is performed using scanning electron microscope. Alternating current impedance spectroscopy is used to investigate the electrical properties of SNT in a temperature range from 313 K to 673 K and in a frequency range from 100 Hz to 1 MHz. A peak is observed in the frequency dependence of imaginary part of electric modulus (M″(ω)) indicating a non-Debye type of relaxation. The relaxation peak of M″(ω) moves towards higher frequencies with the increase of temperature showing the thermally activated nature of the relaxation time. The relaxation times for M″(ω) at different temperatures are found to obey Arrhenius law with an activation energy of 0.57 eV. The scaling behaviour of M″(ω) shows that the relaxation describes the same mechanism at various temperatures. The complex impedance plane plots show that the relaxation mechanism in SNT is purely a bulk effect arising from the semiconductive grains of the sample. The frequency dependent conductivity is found to obey the power law.

Enhancement of Dielectric Characteristics of Polyvinyl Alcohol (PVA) Interfacial Layer in Au/PVA/n‐Si Structures by Bi2O3Disperse

Dielectric characteristics such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ) and real and imaginary parts of electrical modulus (Μ′ andΜ″), andacelectrical conductivity (σac) of Au/ Polyvinyl Alcohol (PVA) (Bi2O3‐dispersed)/n‐Si structures have been investigated by using admittance measurements. Results show that the ε′ values of Au/PVA/n‐Si with Bi2O3‐dispersedPVAinterfacial layer are very higher compared with those with pure and other dopant/mixture's ofPVA. Thus,PVAis made very compatible for device applications with the enhanced dielectric properties by Bi2O3disperse and its native very high dielectric strength.

Frequency- and voltage-dependent dielectric properties and electrical conductivity of Au/PVA (Bi-doped)/n-Si Schottky barrier diodes at room temperature

In this study, frequency and voltage dependence of dielectric constant (e′), dielectric loss (e″), loss tangent (tanδ), the real and imaginary parts of electric modulus (M′ and M″) and ac electrical conductivity (σac) of an Au/PVA (Bi-doped)/n-Si Schottky barrier diode have been investigated in detail by using experimental C–V and G–V measurements in the wide frequency range of 5 kHz–10 MHz and the voltage range of ±2 V at room temperature. Experimental results indicate that the values of e′,e″, tanδ and σac are strongly frequency and voltage dependent. It has found that the values of e′,e″ and tanδ decrease while the values of σac, M′ and M″ increase. It is clear that the values of M″ show a distinctive peak with a U-shape and its position shifts towards the positive-bias region with increasing frequency. Such behavior of the peak can be attributed to the particular distribution of interface states located at the Si/PVA interface and interfacial polarization. It can be concluded that the interfacial polarization and the charge at the interface can easily follow the ac signal at low frequencies.

Atypical dielectric behavior in sol–gel derived fine grain PZT/CeO2 nanocomposites

We present here dielectric and electrical modulus studies of sol–gel derived fine grain (100−x)PZT/xCeO2 nanocomposites. Dielectric response shows superimposed local maxima(s) in high frequency regimes, which, in low frequency regions seems to be overshadowed by high conductivity. Observed local maxima(s) were found to be in concurrence with the nadir(s) observed in the imaginary part of electrical modulus plotted on the temperature plane. In addition to this, calculated bulk and grain boundary capacitance exhibit maxima(s) in the measured temperature range displaying the existence of both bulk and grain boundary transition in nanocomposite formation. Therefore, a collective effect of these two processes has been thought to be a plausible mechanism for observed dielectric behavior of nanocomposites. Anomalous increase in bulk transition temperature of 2wt% ceria substituted nanocomposite was also observed. Possibilities of increase in transition temperature have also been discussed taking in to account the extrinsic size effect.

Dielectric Properties of PMMA and its Composites with ZrO2

Abstract The polymer films of PMMA with different thickness and its composites with ZrO2 at various weight percentages but of same thickness have been studied. The determination of its dielectric properties, dielectric loss, a.conductivity and dielectric modulus were carried out using capacitance measurements of the above samples as a function of frequency, over the range 50 Hz – 5 MHz at room temperature. The films of PMMA and its composites have been characterized using X-Ray Diffractometer. The dielectric permittivity of films of PMMA behaves nonlinearly as frequency increases over the range 50-300 Hz, where as above 300 Hz the values of dielectric constant remains constant. But it is observed that the dielectric constant of PMMA increases as thickness of the film increases. In case of composite films of PMMA with ZrO2 the values of dielectric permittivity decreases gradually up to frequency of around 1 KHz and at higher frequencies it remains constant for all the weight percentages of ZrO2. The complex form of dielectric modulus of PMMA is obtained from the experimentally measured data of dielectric constant and dielectric loss values. The relaxation time of the orientation of dipoles is obtained from the peak value of angular frequency through the plots of imaginary part of electrical modulus as function of frequency. The impedance of PMMA polymer increases as thickness of the films increases. The a c conductivity of PMMA film remains constant up to frequency of 1 MHz and above. It shows a nonlinear phenomenon with peak values at frequency 4 MHz. Shape and size of the nanoparticles of composite film of PMMA with ZrO2 was analyzed by Field Emission Scanning Electron Microscope (FESEM).

Dielectric Properties of Au/PVA (Cobalt-Doped)/n-Si Photoconductive Diodes

The voltage (V) and frequency (f) dependence of dielectric parameters such as the dielectric constant (e′), dielectric loss (e″), dielectric loss tangent (tan δ), real and imaginary parts of electrical modulus (M′ and M″), and alternating-current (AC) electrical conductivity (σAC) of Au/PVA (cobalt-doped)/n-Si structures have been investigated by using experimental admittance measurements conducted at room temperature. The values of e′, e″, and tan δ were found to be strong functions of voltage and frequency, especially at low frequencies in the positive voltage region. It was observed that the values of e′ and e″ increase as the frequency decreases. The M′ values increase with increasing frequency due to increasing dielectric relaxation, while M″ values, in general, remain stable as frequency is changed. The σAC values at each bias voltage increase with increasing frequency.

The impedance spectroscopic study and dielectric relaxation in A(Ni1/3Ta2/3)O3 [A=Ba, Ca and Sr

We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni1/3Ta2/3)O3 (BNT), Calcium Nickel Tantalate Ca(Ni1/3Ta2/3)O3 (CNT) and Strontium Nickel Tantalate Sr(Ni1/3Ta2/3)O3 (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 Å and 3.98 Å respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 Å, b=13.45 Å and c=5.47 Å with β=118.3°. The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole–Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan δ/tan δm and M″/M″m versus log ω for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

Activation energy of polarization due to electrical conductivity and dipole rotation in purified ca-bentonite

We determined the activation energy for dipole rotation and electrical conductivity by analyzing the frequency dependent dielectric permittivity measurements of purified Ca-Bentonite. The measurements were performed at four different temperatures between 296K and 353K and at frequencies between 5Hz to 5MHz. We used the Havriliak–Negami (HN) relation to represent the polarization due to dipole orientations and the Maxwell–Wagner–Sillars (MWS) relation with a power law term to represent the interfacial polarization. We obtained expressions for the real and imaginary parts of electric modulus M*(ω).We determined the relaxation times for HN and MWS contributions from a fit of the experimental data. Subsequently, the activation energies for HN and MWS contributions were obtained from an Arrhenius plot. The activation energy for the HN and MWS processes were found to be 22.3kJ/mol and 18.2kJ/mol, respectively.

Morphological, microstructural and electrical examinations on ZnO film on p-Si wafer

This study reports not only main electrical and dielectric characteristics of Ag/ZnO/p-Si heterostructure with the aid of the experimental admittance measurements at room temperature and theoretical approaches but also the microstructure and surface morphology of the heterostructure by means of X-ray diffraction, scanning electron microscopy and atomic force microscopy measurements. The results obtained show that the sample, obtaining Wurtzite structure with the (002) preferred orientation, has a fine crystalline microstructure consisting of micro-sized hexagonal rods growing uniformly in large scale on the film surface. When the diameters of the rods are found to vary from 0.5 μm to 1.5 μm, thickness values are observed to be about 2 μm. Further, series resistance (Rs) and some other electronic parameters of the heterostructure are obtained by the capacitance–voltage (C–V), conductance–voltage (G–V) and C−2–V measurements. Moreover, voltage (V) and frequency (f) dependence of dielectric parameters such as dielectric constant (e′), dielectric loss (e″), dielectric loss tangent (tanδ), real and imaginary parts of electric modulus (Μ′ and Μ″) are determined and discussed. It is found that both electrical and dielectric parameters of the heterostructure prepared in this work depend strongly on the applied bias voltage and frequency.

Characterization of Electrical Behavior of Ba<sub>5</sub>HoTi<sub>3</sub>V<sub>7</sub>O<sub>30</sub> Ceramic Using Impedance Analysis

Polycrystalline sample of Ba5HoTi3V7O30 was prepared using solid-state reaction technique. X-ray structural analysis indicated a single-phase formation with orthorhombic structure. Microstructural study by SEM showed non-uniform distribution of grains over the surface of the sample. Impedance and modulus spectroscopy studies were carried out, as functions of frequency (42 Hz - 5 MHz) and temperature (RT-773K). The Nyquist plots clearly showed the presence of both bulk and grain boundary effect in the compound. Electrical phenomena in the material can appropriately be modeled in terms of an equivalent circuit with R, C and CPE in parallel. The fitting procedure used here allows us to determine the value of R and C with good precision. Here R2 and R3 correspond to the resistance contributed from the grain boundary and bulk, respectively. C1 and C2 correspond to the capacitance contributed from the grain boundary and bulk, respectively. The real part of electrical modulus shows that the material is highly capacitive. The asymmetric peak of the imaginary part of electric modulus M″, predicts a non Debye type relaxation. The activation energy of the compound (calculated both from impedance and modulus spectrum) is same, and hence the relaxation process may be attributed to the same type of charge carriers.