Imaginary Part Of Electric Modulus Research Articles

Electrical and dielectric characteristics of Al/polyindole Schottky barrier diodes. II. Frequency dependence

AbstractThe dielectric properties and ac electrical conductivity of Al/polyindole (Al/PIN) Schottky barrier diodes (SBDs) were investigated by using admittance spectroscopy (capacitance–voltage [C‐V] and conductance–voltage [G/ω‐V]) method. These C‐V and G/ω‐V characterizations were performed in the frequency range of 1 kHz to 10 MHz by applying a small ac signal of 40 mV amplitude from the external pulse generator, whereas the dc bias voltage was swept from (−10 V) to (+10 V) at room temperature. The values of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), real and imaginary part of electrical modulus (M′ and M″), ac electrical conductivity (σac), and series resistance (Rs) of the Al/PIN SBDs were found to be quite sensitive to frequency and applied bias voltage at relatively low frequencies. Although the values of the ε′, ε″, tanδ, and Rs of the device were observed to decrease with increasing frequencies, the electric modulus and σac increased with increasing frequency for the high forward bias voltages. These results revealed that the interfacial polarization can more easily occur at low frequencies and that the majority of interface states (Nss) between Al and PIN, consequently, contribute to deviation of dielectric properties of the Al/PIN SBDs. Furthermore, the voltage‐dependent profile of both Rs and Nss were obtained from the C‐V and G/ω‐V characteristics of the Al/PIN SBDs at room temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

On the profile of frequency dependent dielectric properties of (Ni/Au)/GaN/Al 0.3Ga 0.7N heterostructures

The voltage ( V) and frequency ( f) dependence of dielectric characteristics such as dielectric constant ( ε′), dielectric loss ( ε ″ ), dielectric loss tangent (tan δ) and real and imaginary part of electrical modulus ( Μ′ and M ″ ) of the (Ni/Au)/GaN/Al 0.3Ga 0.7N heterostructures have been investigated by using experimental admittance spectroscopy (capacitance–voltage ( C– V) and conductance–voltage ( G/w– V)) measurements at room temperature. Experimental results show that the values of the ε′, ε ″ , tan δ and the real and imaginary parts of the electric modulus ( Μ′ and M ″ ) obtained from the C and G/ w measurements were found to be strong function of frequency and applied bias voltage especially in depletion region at low frequencies. These changes in dielectric parameters can be attributed to the interfacial GaN cap layer, interface polarization and a continuous density distribution of interface states and their relaxation time at metal/semiconductor interface. While the values of the ε′ decrease with increasing frequencies, tan δ, Μ′ and M ″ increase with the increasing frequency. Also, the dielectric loss ( ε ″ ) have a local maximum at about frequency of 100 kHz. It can be concluded that the interface polarization can occur more easily at low frequencies with the number of interface states located at the metal/semiconductor interface.

AC conductivity and dielectric relaxation in Ba(Sm 1/2Nb 1/2)O 3 ceramic

The complex perovskite oxide a barium samarium niobate (BSN) synthesized by solid-state reaction technique has single phase with cubic structure. The scanning electron micrograph of the sample shows the average grain size of BSN∼1.22 μm. The field dependence of dielectric response and loss tangent were measured in the temperature range from 323 to 463 K and in the frequency range from 50 Hz to 1 MHz. The complex plane impedance plots show the grain boundary contribution for higher value of dielectric constant in the low frequency region. An analysis of the dielectric constant ( ε′) and loss tangent (tan δ) with frequency was performed assuming a distribution of relaxation times as confirmed by the scaling behaviour of electric modulus spectra. The low frequency dielectric dispersion corresponds to DC conductivity. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with an activation energy of 0.71 eV. The frequency dependence of electrical data is also analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show qualitative similarities in relaxation times. The scaling behaviour of imaginary part of electric modulus M″ and dielectric loss spectra suggest that the relaxation describes the same mechanism at various temperatures in BSN. All the observations indicate the polydispersive relaxation in BSN.

Frequency dependence of ultrahigh dielectric constant of novel synthesized SnO 2 nanoparticles thick films

In this work, the electric and dielectric properties of nanocrystalline SnO 2 thick films were studied using ac impedance spectroscopy under different conditions through capacitance–frequency measurements in frequency range from 1 Hz to 1 MHz and bias voltage range from 0 V to 2 V. Results showed that dielectric constant ( ɛ′), dielectric loss ( ɛ″), loss tangent (tan δ), ac electrical conductivity ( σ) and the electric modulus ( M) are strongly frequency dependent. A decrease in frequency accompanied with an increase in ɛ′ and ɛ″ values. Whereas, ac electrical conductivity ( σ), real ( M /) and imaginary parts of electric modulus ( M //) values are increased with frequency increasing. A comparative study showed that our prepared thick films have greater dielectric value than that of the reported data; hence can be used them as ultrahigh dielectric materials.

Dielectric relaxation of complex perovskite Sm(Ni 1/2Zr 1/2)O 3

Complex perovskite oxide samarium nickel zirconate, Sm(Ni 1/2Zr 1/2)O 3 (SNZ), is synthesized by a solid-state reaction technique. X-ray diffraction of the sample at room temperature shows a monoclinic phase. Impedance spectroscopy is used to study the electrical behaviour of this material in the frequency range 400 Hz–1 MHz and in the temperature range 303–633 K. The frequency dependence of loss peaks is found to obey an Arrhenius law with the activation energy of 0.8 eV. Frequency-dependent conductivity spectra follow a power law. Relaxation mechanism of the sample in the framework of electric modulus formalism is modelled by the Cole–Cole equation. The scaling behaviour of the imaginary part of electric modulus suggests that relaxation describes the same mechanism at various temperatures. Complex impedance plane plot shows two semicircular arcs, indicating the grain and grain-boundary contributions of dielectric relaxation in this material.

Dielectric properties of epoxy/short carbon fiber composites

The dielectric properties of epoxy/short carbon fiber composites at different concentrations 0, 5, 10 and 15% by weight, different thicknesses 2 and 4 mm, and frequency in the range from 20 Hz to 1 MHz were characterized. Scanning electron microscopy and differential scanning calorimetry were utilized. The alternating current (ac) electrical properties (complex impedance, dielectric constant, dielectric loss, real part of electric modulus, imaginary part of electric modulus, electrical conductivity, and relaxation time) were determined. It was found that the applied frequency, filler concentrations, and composite thickness affected the ac electrical properties of the epoxy/carbon fiber composites. The dielectric behaviors of the interfacial polarization between epoxy matrix and carbon fibers could be described by the Maxwell–Wagner–Sillars relaxation. The analysis of the complex electric modulus in the frequency range from 20 Hz to 1 MHz revealed that the interfacial relaxation followed the Cole–Davidson distribution of relaxation times. The universal power-law of ac conductivity was observed in the epoxy/carbon fiber composites. The calculated power exponent (near unity) is physically acceptable within this applied model.

Influence of silver ion reduction on electrical modulus parameters of solid polymer electrolyte based on chitosan-silver triflate electrolyte membrane

The electric modulus properties of solid polymer electrolyte based on chitosan: AgCF3SO3 from 303 to 393 K have been investigated by using impedance spectroscopy. The shift of the M peak spectra with frequeny depends on the dissociation and association of ions. The lowest conductivity relaxation time τσ, was found for the sample with the highest conductivity. 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 distribution of relaxation times was indi- cated by a deformed arc form of Argand plot. The increase of Mand M values above 358 K can be attributed to the trans- formation of silver ions to silver nanoparticles. The complex impedance plots and ultraviolet-visible (UV-vis) absorption spectroscopy indicate the temperature dependent of silver nanoparticles in chitosan-silver triflate solid electrolyte. The for- mation of silver nanoparticles was confirmed by transmission electron microscopy (TEM). The scaling behavior of M spectra shows that the dynamical relaxation processes is temperature independent for aparticular composition. The β expo- nent value indicate that the conductivity relaxation is highly non exponential.

Impedance spectroscopy study of BaMg 1/3Nb 2/3O 3:Frequency and time domain analyses

The complex perovskite oxide barium magnesium niobate, BaMg 1 / 3 Nb 2 / 3 O 3 (BMN) is synthesized by a solid-state reaction technique. The X-ray diffraction of the sample shows the monoclinic structure at room temperature. Impedance spectroscopy is applied to investigate the electrical properties of BMN in a temperature range from 300 to 503 K and in a frequency range from 50 Hz to 1 MHz. An analysis of the real and imaginary parts of dielectric constant with frequency is performed assuming a distribution of relaxation times. The most probable relaxation times are found to obey an Arrhenius law with the activation energy of 0.72 eV. This value of activation energy suggests that the relaxation mechanism in BMN is due to ion hopping between neighbouring sites within the crystalline lattice. The scaling behaviour of imaginary part of electric modulus, M ″ suggests that the relaxation describes the same mechanism at various temperatures in BMN. We have also analysed the conduction mechanism in BMN in time domain. In time domain, the time decay function ϕ ( t ) is obtained from the values of M ″ by using a relaxation function in frequency domain, which is found to be a Cole–Cole distribution function. The Kohlrausch–Williams–Watts (KWW) function is used to analyse the time dependent behaviour of ϕ ( t ) . The conductivity spectra of BMN at various temperatures are investigated considering a power law.

On the profile of temperature dependent electrical and dielectric properties of Au/SiO2/n-GaAs (MOS) structures at various frequencies

Abstract The temperature ( T ) dependence of electrical and dielectric characteristics such as series resistance ( R s ), dielectric constant ( e ′), dielectric loss ( e ″), dielectric loss tangent (tan δ ), and real and imaginary part of electrical modulus ( M ′ and M ″) of the Au/SiO2/ n -GaAs (MOS) structures have been investigated in the temperature range of 80–350 K at various frequencies by using experimental capacitance ( C ) and conductance ( G / w ) measurements. Experimental results show that both C and G / w characteristics were quite sensitive to frequency and temperature at especially high temperatures and low frequencies due to a continuous density distribution of interface states and their relaxation time, and thermal restructuring and reordering of the interface. Series resistance values of this device obtained from Nicollian method decrease with increasing frequency and temperature. The e ′, e ″, tan δ , and M ′ and M ″ were found a strong function of frequency and temperature. While the values of e ′, e ″, and tan δ decrease, M ′ and M ″ increase with increasing frequency. Also, while e ′ and e ″ increase, M ′ and M ″ decrease with increasing temperature. The tan δ and M ′ values are almost independent temperature especially at high frequencies ( f ≥500 kHz).

Dielectric relaxation in complex perovskite oxide In(Ni 1/2Zr 1/2)O 3

The dielectric study of indium nickel zirconate, In(Ni 1/2Zr 1/2)O 3 (INZ) synthesized by solid state reaction technique is performed in a frequency range from 500 Hz to 1 MHz and in a temperature range from 303 to 493 K. The X-ray diffraction analysis shows that the compound is monoclinic. A relaxation is observed in the entire temperature range as a gradual decrease in ɛ′( ω) and as a broad peak in ɛ″( ω) in the frequency dependent real and imaginary parts of dielectric constant, respectively. The frequency dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The frequencies corresponding to the maxima of the imaginary electric modulus at various temperatures are found to obey an Arrhenius law with activation energy of 0.66 eV. The Cole–Cole model is used to study the dielectric relaxation of INZ. The scaling behaviour of imaginary part of electric modulus suggests that the relaxation describes the same mechanism at various temperatures. The frequency dependent conductivity spectra follow the universal power law.

Dielectric relaxation and electronic structure of double perovskite Sr2FeSbO6

The dielectric property and the electronic structure of a double perovskite, Sr2FeSbO6 (SFS) synthesized by solid state reaction technique are investigated. The x-ray diffraction of the sample taken at room temperature shows cubic phase. The scanning electron micrograph of the sample also confirms the formation of the single phase of the material. We have measured the capacitance and conductance of SFS in a frequency range from 50 Hz to 1 MHz and in a temperature range from 163 to 463 K. A relaxation is observed in the entire temperature range as a gradual decrease in ϵ′(ω) and as a broad peak in ϵ″(ω). The frequency dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The frequencies corresponding to the maxima of the imaginary electric modulus at various temperatures are found to obey an Arrhenius law with an activation energy of 0.74 eV. The Cole–Cole model is used to study the dielectric relaxation of SFS. The scaling behavior of imaginary part of electric modulus suggests that the relaxation describes the same mechanism at various temperatures. The frequency dependent conductivity spectra follow the universal power law. The electronic structure of the SFS is studied by x-ray photoemission spectroscopy (XPS). Its valence band consists mainly of the oxygen 2p-states hybridized with the Fe 3d-states. The XPS spectra are investigated by the first principles full potential linearized augmented plane wave method. The angular momentum projected total and partial density of states obtained from first principles calculation are used to analyze the XPS results of the sample. The calculated electronic structures of SFS are qualitatively similar to those of the XPS spectra in terms of spectral features, energy positions, and relative intensities. The electronic structure calculation reveals that the electrical properties of SFS are dominated by the interaction between transition-metal and oxygen ions.

Ac conductivity and dielectric relaxation in ionically conducting soda–lime–silicate glasses

The frequency dependent conductivity and dielectric relaxation of alkali ions in some soda–lime–silicate (Na 2O–CaO–SiO 2) glasses are investigated over a frequency range from 50 Hz to 1 MHz and in a temperature range from room temperature to 603 K by using alternating current impedance spectroscopy. The conductivity isotherms show a transition from frequency independent dc region to dispersive region where the conductivity continuously increases with increasing frequency. The electric modulus representation has been used to provide comparative analysis of the ion transport properties in these glasses. The scaling behavior of imaginary part of electric modulus indicates that all dynamical processes occurring at different frequencies give the same activation energy.

Dielectric relaxation in [formula omitted

The frequency-dependent dielectric dispersion of strontium–magnesium–niobate (SMN), Sr ( Mg 1 / 3 Nb 2 / 3 ) O 3 ceramic synthesized by the solid state reaction technique is investigated in the temperature range from 303 to 613 K. The X-ray diffraction of the sample at room temperature (30 °C) shows monoclinic phase. The scanning electron micrograph of the sample shows the average grain size of SMN ∼ 1 μ m . The frequency-dependent electrical data are also analyzed in the framework of the conductivity formalism. An analysis of the electric modulus and impedance with frequency is performed in the entire temperature range. The frequency-dependent maxima in the imaginary part of electric modulus are found to obey an Arrhenius law with activation energy ∼ 1.8 eV . Such a value of activation energy suggests the existence of a relaxation mechanism (a conductive process), which may be interpreted by an ion hopping between neighbouring sites within the crystalline lattice. Results indicate that the relaxation mechanism of the material is temperature dependent and has dominated bulk contribution in different temperature ranges. The Cole–Cole approach is used to explain the relaxation mechanism in SMN. The scaling behaviour of imaginary part of electric modulus and imaginary impedance suggests that the relaxation describes the same mechanism at various temperatures.

Physico-mechanical and electrical properties of conductive carbon black reinforced chlorosulfonated polyethylene vulcanizates

The present work deals with the effect of conductive carbon black (Ensaco 350G) on the physico-mechanical and electrical properties of chlorosulfonated polyethylene (CSM) rubber vulcanizates. The physico-mechanical properties like tensile strength, tear strength, elongation at break, compression set, hardness and abrasion resistance have been studied before and after heat ageing. Up to 30 parts per hundred rubber (phr) filler loading both tensile and tear strength increases beyond which it shows a decreasing trend whereas modulus gradually increases with the filler loading. Incorporation of car- bon black increases the hysteresis loss of filled vulcanizates compared to gum vulcanizates. Unlike gum vulcanizate, in filled vulcanizates the rate of relaxation shows increasing trend. The bound rubber content is found to increase with increase in filler loading. Dielectric relaxation spectra were used to study the relaxation behavior as a function of frequency (100 to 106 Hz) at room temperature. Variation in real and imaginary parts of electric modulus has been explained on the basis of interfacial polarization of fillers in the polymer medium. The percolation limit of the conductive black as studied by ac conductivity measurements has also been reported.

Frequency and voltage effects on the dielectric properties and electrical conductivity of Al–TiW–Pd2Si/n-Si structures

Different from conventional metal-Si compounds-n-Si structures, the thin film of TiW alloy was deposited on Pd2Si-n-Si to form a diffusion barrier between aluminum (Al) and Pd2Si-n-Si. Dielectric properties and electrical conductivity of TiW-Pd2Si/n-Si structures in the frequency range of 5kHz-10MHz and voltage range of (-4V) to (10V) have been investigated in detail by using experimental C-V and G-V measurements. Experimental results indicate that the values of @e' show a steep decrease with increasing frequency for each voltage. On the other hand, the values of @e'' show a peak, and its intensity increases with decreasing voltage and shifts towards the lower frequency side. The ac electrical conductivity (@sac) and the real part of electric modulus (M') increase with increasing frequency. Also, the imaginary part of electric modulus (M'') shows a peak and the peak position shifts to higher frequency with increasing applied voltage. It can be concluded that the interfacial polarization can be more easily occurred at low frequencies, and the majority of interface states at metal semiconductor interface, consequently contributes to deviation of dielectric properties of TiW-Pd2Si/n-Si structures.

AC conductivity and dielectric relaxation in [formula omitted

The complex perovskite oxide calcium magnesium niobate, CaMg 1 / 3 Nb 2 / 3 O 3 (CMN) is synthesized by a solid-state reaction technique. Dielectric spectroscopy is applied to investigate the electrical properties of CMN in a temperature range from room temperature to 503 K and in a frequency range of 100 Hz–1 MHz. An analysis of the dielectric constant ϵ ′ and loss tangent tan ⁡ δ with frequency is performed assuming a distribution of relaxation times. The low-frequency dielectric dispersion corresponds to the DC electrical conductivity. The frequency dependence of the loss peak is found to obey an Arrhenius law with an activation energy of 1.8 eV. The frequency dependent electrical data are analyzed in the framework of the conductivity and modulus formalisms. Both these formalisms show qualitative similarities in relaxation times. The scaling behaviour of imaginary part of electric modulus M ″ suggests that the relaxation describes the same mechanism at various temperatures in CMN.

Electrical properties of A2.6+xTi1.4−xCd(PO4)3.4−x (A = Li, K; x = 0.0–1.0) phosphate glasses

Electrical properties of A2.6+xTi1.4−xCd(PO4)3.4−x (A=Li, K; x=0.0–1.0) phosphate glasses are investigated over a frequency range from 42Hz to 1MHz at different temperatures. Impedance spectroscopy is used to separate the bulk conductivity from electrode effect of electrical conductivity data. The bulk dc conductivity is Arrhenius activated, with activation energies and pre-exponential factors following the Meyer–Neldel rule. The real part of ac conductivity shows universal power law feature. The variation of dielectric constant with frequency is attributed to ion diffusion and polarization occurring in the phosphate glasses. The frequency dependent imaginary part of electric modulus M″(ω) plot shows non-Debye feature in conductivity relaxation. The Kohlrausch–Williams–Watts stretched exponential function was used to describe the modulus spectra and the stretching exponent β is found to be temperature independent. Scaling in M″(ω) shows that the electrical relaxation mechanisms are independent of temperature for given composition at different temperatures.

‘Window’ effect in the analysis of frequency dependence of ionic conductivity

Usually the frequency dependence of ionic conductivity of solids in analyzed in the form of a power law or as the deviation of imaginary part of electric modulus from ideal Debye peak. The power law formalism is shown to be sensitive to the choice of frequency window employs in the analysis. The results demonstrate the inadequacies of either formalism and a method is suggested of combining the two formalisms for parameterizing non-ideal electric response in the vicinity of the electrical conductivity relaxation time.

Maximum side-aspect target strength of an individual fish

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).

Acoustic imaging in a turbid underwater environment

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).