Analysis Of Ac Conductivity Data Research Articles

Analysis of dielectric and electrical transport properties of NdFeAsO ceramic

The iron-based ceramic NdFeAsO was synthesized by the solid-state reaction method. The tetragonal crystal structure was confirmed at room temperature through the X-ray diffraction technique. The dielectric characteristics i.e. dielectric constant (εr) and loss tangent (tanδ) of the sample were studied at a wide range of temperature and frequencies with an impedance analyzer and revealed that these quantities decreased with an increase in frequency. The dielectric anomalies were observed in the studied sample, which was found to be shifting towards the higher temperature side on increasing the frequency. The analysis of ac conductivity data of the compound obeyed Jonscher’s universal power law as well as the Arrhenius equation. The compound showed a negative temperature coefficient of resistance (NTCR) behavior. The electrical conduction mechanism in the sample can be explained through the correlated barrier hopping (CBH) model.

Characterization and ion transport studies through impedance spectroscopy on (1-x)Pb(NO3)2:xAl2O3 composite solid electrolytes

In this paper, we attribute the conduction mechanism in (1-x)Pb(NO3)2:xCeO2 composite solid electrolytes due to the hopping of polyanion (NO3−). The matrix of composites, nano-alumina (60 nm) dispersed into Pb(NO3)2, was synthesized and characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM) to understand structural, thermal, and morphological properties. XRD and FTIR studies confirm the biphasic nature of composites. FTIR studies reveal the presence of OHˉ and NO3ˉ ions in all the composites. Impedance and modulus spectra were used as tools to study the electrical properties of composites in the temperature range 30 to 330 °C and frequency range 1 Hz to 10 MHz to understand ion transport mechanism. Analysis of AC conductivity data reveals that non-overlapping small polaron tunneling [NSPT] seems to be an appropriate model to understand hopping mechanism of conducting ion species. Maximum enhancement of conductivity was observed in the composite with 10 mol% Al2O3 dispersed system. The distribution of frequency response of imaginary part of modulus response denotes non-Debye behavior at all individual temperatures. The peaks which were obtained from the plots of frequency-dependent imaginary part of modulus, plotted with respect to temperature, had shown an Arrhenius behavior. The values “β” from Kohlrausch-Williams-Watts (KWW) function and n from Johnson power law were found to be temperature-dependent in all these composites.

Signature of magnetoelectric coupling of xNiFe2O4 – (1-x)HoMnO3 (x = 0.1 and 0.3) multiferroic nanocomposites

The magnetoelectric coupling of xNiFe2O4–(1-x)HoMnO3 (x=0.1 and 0.3) multiferroics nanocomposites prepared through low temperature chemical pyrophoric reaction process has been investigated at room temperature. The signature of magnetoelectric coefficient of these nanocomposites is mainly due to the magnetostriction and magnetodielectric properties of the materials. These nanocomposites show the ferroelectric behaviour at room temperature. AC electrical properties of nanocomposites have been studied with applied magnetic fields and temperatures. Nyquist plots at different magnetic fields and temperatures have been fitted using parallel combinations of resistance-capacitor circuits. Moreover, we have estimated activation energy of those composites using Arrhenius relation, which indicates that same kinds of charge carrier are responsible for relaxation process in grain boundaries and grain of the sample. Furthermore, from the analysis of ac conductivity data as a function of frequency is attributed to the large polaronic hopping in the conduction process in the system.

Investigation of electrical and dielectric properties of the new rubidium arsenate tellurate Rb2HAsO4Te(OH)6 compound

This work presents some electrical properties based on the impedance measurements as well as the dielectric constants and electric modulus. In order to through light in the electrical conductivity and dielectric properties of Rb2HAsO4Te(OH)6 (Rb As Te), we have carried out complex impedance spectroscopy technique in the frequency range 200 Hz–5 MHz at various temperatures (304 K–493 K). The complex impedance diagram at different temperatures showed a single semicircle, implying that the response originated from a single capacitive element corresponding to the grains. AC and dc conductivities were studied to explore the mechanisms of conduction. The experimental data shows that the ac conductivity of this compound is proportional to ωs (s < 1), the value of s is temperature-dependent.The conductivity evolution versus temperature reveals the presence of the super-ionic- protonic conduction phase transition. The dielectric properties's dependence on both temperature and frequencies of the compound has been reported. The ionic-protonic conductivity and conductivity relaxation calculated from the impedance and modulus spectra respectively were found to be thermally activated. The conductivity relaxation parameters of some H+ and Rb+ conducting in the RbAsTe material have been determined from an analysis of AC conductivity data measured in a wide temperature range. The near value of activation energies obtained from the hopping frequency and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the motion of the H+ ion in the structure of the investigated material, thus the displacement of the Rb+ cations at the level of the tunnels.

Thermal behavior and dielectric and vibrational studies of Cs2(HAsO4)0.32(SO4)0.68·Te(OH)6

A new compound from the tellurate family was synthesized under a slow evaporation conditions. A crystalline sample of Cs2(HAsO4)0.32(SO4)0.68·Te(OH)6 (CsAsSTe) was calorimetric and spectroscopically characterized. The infrared and Raman spectra of this new compound recorded at room temperature, in the frequency range 500–4,500 and 50–1,500 cm−1, respectively, confirm the presence and the independence of two types of anion HAs/SO4 and TeO6. The thermal analysis of the title compound shows one endothermal and intense peak at 512 K accompanied by a shoulder at 506 K. However, the conductivity evolution versus temperature showed the presence of the protonic super conduction phase transition. The conductivity relaxation parameters of some H+ and Cs+ conducting in the CsAsSTe material have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this compound appear due to H+ ions hopping mechanism.

Synthesis and electrochemical, electrical and gas sensing properties of novel mononuclear metal-free, Zn(II), Ni(II), Co(II), Cu(II), Lu(III) and double-decker Lu(III) phthalocyanines substituted with 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenoxy

A new mono substituted phthalonitrile derivative 3 was prepared by a nucleophilic displacement reaction of 4-nitrophthalonitrile with 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol. Novel metallophthalocyanines 4–8 (M=Zn, Ni, Co, Cu, Lu, respectively), metal free 9 and double decker Lu(III) phthalocyanine 10 with four peripheral 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenoxy groups were synthesized by cyclotetramerisation of the phthalonitrile and characterized by elemental analyses, FTIR, 1H NMR, UV–vis and MALDI-TOF MS spectral data. Cyclic voltammetry, differential pulse voltammetry and in situ spectroelectrochemistry of the phthalocyanine compounds have been studied. This allowed us to identify and compare metal- and phthalocyanine ring-based redox processes of the complexes. Impedance spectroscopy (IS) and dc conductivity measurements were performed as a function of temperature (300–430K) and frequency (40–105Hz.). The sensing properties of the films for toluene were also investigated. The dc results showed an activated conductivity dependence on temperature for all films. While room temperature impedance spectra consist of a curved line, a transformation into a full semicircle with increasing temperature was observed. The analysis of ac conductivity data showed that the CBH model is the dominant conduction mechanism for the electron transport in the films. While exposure to toluene has no effect on the conductivity of the film of 8–10 completely reversible sensor response to toluene only were obtained for compounds 4–7. It was also observed that the operating temperature had a considerable effect on sensing characteristics of the films.

Phase transition and analysis of AC conductivity data of the (Cs)0.26(Rb)0.74H(SO4)0.89(SeO4)0.11 compound

The X-ray diffraction, vibrational and impedance spectroscopy studies of (Cs)0.26(Rb)0.74H(SO4)0.89(SeO4)0.11 (CsRbHSSe) new solid solution are presented. The title compound undergo a superionic phase transition (SPT) at T=395K. This transition was confirmed by an abrupt increase of conductivity. The bulk impedance parameters of CsRbHSSe, RbH(SO4)0.81(SeO4)0.19 (RbHSSe) and CsH(SO4)0.76(SeO4)0.24 (CsHSSe) were determined from an analysis of AC conductivity data measured in a wide temperature range. The charge carriers concentration in the samples investigated has been evaluated using the Almond–West formalism and shown to be independent of temperature.

Conductivity relaxation parameters of some H + and K + conducting in the polycrystalline compound KDyHP 3O 10

Polycrystalline samples of KDyHP 3O 10 was obtained by heating for 12 hour at 553 K a mixture containing K 2CO 3, Dy 2O 3 and H 3PO 4. Samples were characterized through X-ray diffraction, examined by IR vibrational spectroscopy and impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of some H + and K + conducting in this compound have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this material appears as due to H + and K + ions hopping mechanism. The stretched exponential function exp[−( t/ τ σ ) β ] has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the nature of mobile ions. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model.

Analysis of AC Conductivity Data of the Anion Excess Sr1 ? xThxF2 + 2x Solid Solution with Fluorite-Type Structure

Conductivity parameters, number of charge carriers, frequency of hopping, have been determined from an analysis of ac conductivity data of the Sr1 — xThxF2 + 2x (0 ≤ x ≤ 0.225) solid solution with fluorite-type structure. The charge carrier concentration has been estimated: (i) from the frequency dependence of conductivity, in accordance with the Almond-West approach; (ii) from the increment of the dielectric constant due to charge carriers. Similar results have been obtained by both approaches. The fraction of charge carriers per formula unit, evaluated as a function of composition, is in good agreement with the estimations made on the basis of the clustering process model which assumes that the charge carriers at long range in Sr1 — xThxF2 + 2x are interstitial fluoride ions of F′′′ type. For x > 0.05, the results have been interpreted by the additional presence of nn and nnn dipoles, the concentration and reorientation rate parameters of which have been evaluated.

Determination of charge carried concentration in Sr 1 − xBi xF 2 + x solid solution from ac conductivity analysis

The bulk impedance parameters of polycrystalline samples of the Sr 1 − x Bi x F 2 + x (0 ≤ x ≲ 0.50) solid solution with fluorite-type structure were determined from an analysis of ac conductivity data, using a modified Almond-West model. Hopping rates of mobile F − ions were extracted from frequency dependences of conductivity at different temperatures. The fraction of charge carriers (per unit cell) in the samples investigated has been estimated. The nature of charge carriers has been identified on the basis of the clustering process model and neutron diffraction data: the interstitial ions of F′ type appear as responsible for long range motions in Sr 1 − x Bi x F 2 + x .

Use of the modulus formalism in the analysis of ac conductivity data for fast ion conductors

Use of the modulus formalism in the analysis of ac conductivity data for fast ion conductors

Use of the modulus formalism in the analysis of ac conductivity data for ionic glasses

Use of the modulus formalism in the analysis of ac conductivity data for ionic glasses

Determination of the influence of the NaF rate on the charge carriers parameters in some fluoride glasses containing the NaF alkali fluoride

The bulk impedance parameters of various fluoride glasses series containing a large extent in NaF rate have been determined from an analysis of ac conductivity data measured in a wide temperature range. The charge carriers concentration in each glass studied has been evaluated using the Almond-West formalism and shown to be temperature independent. Transport properties in these materials are due to a hopping mechanism of the fraction of F − ions mobile at long range (3–5%). The variation of different conductivity parameters as a function of the NaF content has been determined. When the NaF rate increases, a conductivity decrease is observed, due mainly to a decrease of the charge carriers mobility.

Conductivity relaxation parameters of some Ag + conducting tellurite glasses containing AgI or the (AgI) 0.75 (T1I) 0.25 eutectic mixture

The conductivity relaxation parameters of some Ag + conducting tellurite glasses containing either AgI or the (AgI) 0.75-(T1I) 0.25 eutectic mixture have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in these materials appear as due to an Ag + ion hopping mechanism. The stretched exponential function exp-( t/τ σ) β has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the AgI rate. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model. A correlation has been also established for the glasses investigated between the stretched exponent β of conductivity relaxation function with the decoupling index R τ( T g), proposed by Angell, where R τ( T g) is the τ s/τ σ ratio of the average structural and conductivity relaxation times at the glass transition temperature T g.

Estimation of charge carrier concentration in the fluorite-type Pb 1− x− yIn x− yBi 2 yF 2+ x+ y (fixed x, 0 ⩽ y ⩽ x) solid solution involving two substitutional cations

The bulk impedance parameters of polycrystalline samples of the Pb 1− x− y In x− y Bi 2 y F 2+ x+ y (fixed x, 0 ⩽ y ⩽ x) solid solution with fluorite-type structure were determined from analysis of ac conductivity data measured in a wide temperature range. Hopping rates of mobile F − ions were extracted from frequency dependences of conductivity at different temperatures. The concentration of charge carriers in the samples investigated has been estimated. Independently of y, its value ( log N/ cm 3 = 21.6 ± 0.02) allows to propose, on the basis ofthe clustering model, that charge carriers in these materials are likely the interstitial fluoride ions of F″ type.

Analysis of ac conductivity data for Na 2O·3SiO 2 glass by stretched exponential and Jonscher power-law methods

A comparison is made between two widely used empirical methods of ac conductivity data analysis, namely, the Kohlrausch-Williams-Watts (KWW) approach, which starts from a stretched exponential in the time domain and transforms to the electric modulus functions in the frequency domain, and the Jonscher approach, which deals directly with the ac conductivity and looks for a power-law dependence on frequency. By taking one set of data for the sodium trisilicate glass in the temperature range 300–400 K and analyzing it in both ways, the differences between these two methods can be examined. It is found that the KWW approach does not properly fit the data at the higher frequencies, and thus requires an excessively high constant-loss contribution. It is conncluded that the Jonscher approach is a more meaningful way to explore the high-frequency range of ac conductivity behavior.

Use of the modulus formalism in the analysis of ac conductivity data for ionic glasses

Use of the modulus formalism in the analysis of ac conductivity data for ionic glasses

Ac Conductivity and anionic disorder in the solid solutions Sr 1− xLa xF 2+ x. II. Analysis and discussion of the data

Concentrations of nn-dipoles, nnn-dipoles and charge carriers as well as parameters related to their reorientation and mobility were estimated from an analysis of ac conductivity data. Concentration of nn- and nnn-dipoles have maximal values of 6 × 10 20 and 4 × 10 19 cm −3 respectively at x=0.01. The concentration of charge carriers increases sharply if x>2;0.003 up to the broader limit value 2.0±1.0×10 21 cm −3 or 5.5±2.0 mole% at x=0.01, but does not rise more with x up to x=0.40. A qualitative description of the obtained results in terms of both cluster theory and freezing of anionic disorder model is proposed. The latter is more consistent with the experimental data. Solid solutions such as Sr 1− x La x F 2+ x may be considered as microheterogeneous systems with impurities stabilizing the high-temperature disorder.

A new analysis of ac conductivity data in single crystal β-alumina

The low temperature ac conductivity of single crystal Na β-alumina, in the region of the bulk, intragranular response shows very non Debye-like behaviour. In the Z ∗ plane, a broadened asymmetric arc is observed. Plots of M″ against frequency show broad, asymmetric peaks. Dispersions occur in plots of Y′, Y″, ϵ′ and ϵ″ against frequency. We use a simple equivalent circuit, comprising a frequency dependent admittance in parallel with a Debye-like parallel RC element, which models well the ac response of β-alumina in all four complex formalisms in terms of four independent parameters.