Complex Impedance Plane Plots Research Articles

Effect of seasonal variation in dielectric properties of groundwater from Vadodara region

Groundwater samples were collected during different months from the same site from Vadodara district of Gujarat state. The complex permittivity of the water samples were precisely determined over the frequency span 20 Hz to 2 MHz. Complex permittivity spectral data were converted into complex impedance formalism. Obtained results were analysed to get information of seasonal variation in groundwater quality. Dielectric constant for all samples is found to decrease linearly and rapidly with increase in frequency up to about 4 kHz, after which it decreases slowly and achieves static value approximately 78, near 2 MHz for all water samples. Dielectric loss for the water sample collected in monsoon season (August) is the highest, which shows the presence of ions dissolved from the soil in rain water. DC resistance values, determined from the complex impedance plane plot (Z′’ vs. Z″), suggested an increase in the conductivity of the water samples collected near the end of monsoon season, due to the dissolved minerals and salts from soil. The calculated values of ε′’/ε′’ DW and ε″/ε″DW ratio for the water sample of August’18 show a relatively large increase during the post-monsoon month of August’18, above 2 kHz, as compared to other months.

Investigation on electrical transport and dielectric relaxation mechanism in TbCrO3 perovskite orthochromite

Herein, the TbCrO3 (TCO) chromite was synthesized by the sol-gel auto-combustion route and sintered at 900 °C. The Rietveld analysis of the room temperature powder X-ray diffraction profile confirmed the single-phase formation of the material crystallized in the orthorhombic phase of the perovskite structure with Pbnm space group symmetry. The surface morphology, the elemental composition, and the chemical states of the compound were investigated by field emission scanning electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy, respectively. The electronic density of states, band structure, and electron density were analyzed by Density Functional Theory. The electrical transport and dielectric relaxation mechanism were investigated using complex impedance spectroscopy over the experimental frequency and temperature ranging from 40-1.2x106Hz and 138−273 K, respectively. Two semicircular arcs in the impedance complex plane plots were modeled to an equivalent circuit configured by RG∥QG+RGB∥QGB which were attributed to the contributions of the highly resistive grain boundaries and relatively conducting grains in the material. The electrical conductivity as a function of frequency followed Jonscher’s universal power law behavior and an increasing nature of the temperature-dependent frequency exponent suggested small polaron hopping as the electrical conduction mechanism of the material. The least capacitive response of the TCO system was investigated by the complex electrical modulus formalism and the frequency-dependent imaginary modulus spectra were modeled by the Kohlrausch–Williams–Watts function, which resolved the thermally activated peaks of bulk and interface effects to the dielectric relaxation mechanism. The dielectric constant exhibited Maxwell-Wagner interfacial polarization effects and the dielectric loss factor showed frequency dispersion at all temperatures.

Graphene quantum dots (GQDs) decorated Co-Zn ferrite: Structural, morphological, dielectric, and magnetic properties

GQDs/Co0.5Zn0.5Fe2O4 nanocomposite was synthesized using a facile sonication-assisted approach. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental dispersive X-ray spectroscopy (EDX), impedance analyzer and vibrating sample magnetometer (VSM) were employed to characterize the synthesized samples. The XRD data confirmed the formation of GQDs, Co-Zn ferrite and GQDs/Co-Zn ferrite nanocomposite with no detectable impurity peaks. FTIR results identified the presence of GQDs in GQDs/Co-Zn ferrite nanocomposite. The morphological study revealed the decoration of spherical GQDs on the surface of Co-Zn ferrite. Complex impedance plane plots showed the contribution of the relaxation phenomenon associated with grain and grain boundaries in observed dielectric properties of the nanocomposite. The inclusion of GQDs led to the enhancement of the dielectric constant of the nanocomposite at low frequencies. GQDs/Co0.5Zn0.5Fe2O4 showed superparamagnetic properties which makes it a potential material to be used as a contrast agent in magnetic resonance imaging (MRI) applications.

A strategy to improve dielectric permittivity of Mg–Zn ferrite by using silver nanoparticles

In this work, we used silver nanoparticles (Ag NPs) to enhance the dielectric properties of magnesium-zinc ferrite (Mg–ZnFe2O4) by enhancing local electric field with the creation of nano/micro capacitors between conducting metal particles (Ag NPs) and insulating host (Mg–ZnFe2O4). Mg–ZnFe2O4 was synthesized using the sol-gel method and silver NPs were decorated on magnesium zinc ferrite (Ag@Mg–ZnFe2O4) by employing a sonication approach. The effect of Ag NPs concentration was studied on the structural, morphological, optical, dielectric, and magnetic properties of Ag@Mg–ZnFe2O4 nanocomposite. X-ray diffraction (XRD) confirmed the presence of cubic Mg–ZnFe2O4 and face-centred cubic (FCC) Ag NPs in Ag@Mg–ZnFe2O4 nanocomposite. The structural parameters such as lattice strain, crystallite size and microstrain were correlated with Ag NPs concentration. The morphological study of Ag@Mg–ZnFe2O4 showed uniform decoration of silver at low concentrations; higher concentrations of silver led to reduced covering due to the agglomeration tendency of Ag NPs. Diffused reflectance spectroscopy (DRS) was employed to estimate the effect of Ag NPs on the optical bandgap of Mg–ZnFe2O4. The bandgap narrowing was observed due to the overlapping of the Ag conduction band with the valence band of Mg–ZnFe2O4. All Ag@Mg–ZnFe2O4 samples showed superparamagnetic behaviour and the saturation magnetization was decreased with the increase in the non-magnetic Ag nanoparticles in the nanocomposite. Impedance spectroscopy (IS) was employed to comprehensively analyze the dielectric properties of Ag@Mg–ZnFe2O4. Complex impedance plane plots confirmed the involvement of relaxation phenomena related to grains and grain boundaries in the observed dielectric properties. The decoration of silver nanoparticles was associated with the realization of a high dielectric constant (∼104) in all prepared samples at low frequency. Moreover, uniform decoration of silver was found to show a more stable dielectric constant with relatively low dielectric loss.

Structural, morphological, optical and dielectric properties of sodium bismuth titanate ceramics

• The NBT ceramic was prepared by solid state reaction. • Modified Debye theory has been adopted to describe the phenomenon of relaxation. • The temperature dependence of Dc-conductivity of NBT followed the Mott’s Variable Range Hopping (VRH) law. This work focuses on the structural, optical and electrical properties of sodium bismuth titanate Bi 1/2 Na 1/2 TiO 3 (NBT) lead-free ceramic for its possible application in capacitors, batteries and as an electrolyte in SOFC. NBT material was prepared by the solid-state method. X-ray diffraction analysis performed at room temperature revealed a rhombohedral structure with R3c space group. Rietveld refinement confirmed a good agreement between the calculated and the observed pattern. Scanning electron microscopy analysis revealed a polycrystalline nature of the material with a grain size of 29.17 µm. FT-IR analysis showed the presence of different bonds. The band gap energy was extracted through diffuse reflectance spectroscopy and was found to be 2.61eV. Detailed studies of dielectric and impedance properties carried out in the frequency range of 40–10 7 Hz at different temperatures (from 400K-700K) provided many interesting properties. The dielectric loss and dielectric constant with frequency increase. This behavior could be interpreted by the Maxwell–Wagner type of polarization in agreement with Koop's theory. To explain the complex impedance plane plots, an equivalent circuit template was employed, reflecting semiconducting behavior of NBT. The Ac-conductivity spectrum satisfied Jonscher’s power law below 460K and followed Jonscher’s double power law (DPL) above 480K. The correlated barrier hopping (CBH) and small polaron hopping (SPH) models could explain the conduction mechanism at the studied temperature range. The study of the Dc-electrical conductivity confirmed that NBT followed the variable range hopping (VRH) model. The present work could give further insights into this kind of material from a physical point of view and thus enhance its presence in the industrial field.

Effects of partial Li-substitution on structural, electrical and dielectric properties in La1-xLixSrMn2O5+δ(x = 0.05, 0.10 and 0.15) brownmillerite oxides

In this work we have studied the effects of substitution of lanthanum by Li at the A site on the structural, electrical and dielectric properties of the brownmillerite compounds La1-xLixSrMn2O5+δ(x = 0.05, 0.10 and 0.15). The samples prepared by the sol-gel reaction method. Structural investigation by RX diffraction shows that all compounds crystallize in the cubic structure with space group Pm-3 m at room temperature. The morphology and grain size of the compounds were observed using a scanning electron microscope (SEM). Impedance spectroscopy is used to study the AC electrical properties of these materials in the temperature range 100–200 K and in the frequency range 100 Hz to 1 MHz. To study the dielectric behavior of materials and various physical phenomena. Complex impedance plane plots show the grain contribution for the samples. The Nyquist plot Z' as a function of Z" at different temperatures shows semicircular arcs describing an equivalent circuit.Variation of the modulus and electrical conductivity of the compound shows conduction phenomena and a no-debye type relaxation process. The electrical conductivity was determined using Jonscher's law and the activation energies were determined from the conductivity and the imaginary part of the impedance.

Functional Properties of Donor (Al) and Acceptor (Cu) Codoped High Dielectric Constant ZnO Nanoparticles

In this work, we have synthesized donor‐acceptor (Al‐Cu) codoped ZnO nanoparticles with a doping concentration of 0%, 0.25%, 0.5%, and 0.75% by coprecipitation method. The synthesized samples were then annealed at 350°C and 600°C. All the samples showed wurtzite structure of ZnO with no secondary phase. The increase in doping concentration led to deterioration of crystalline quality, while improved crystallinity was observed at higher annealing temperature. The morphological study of these samples showed good grain‐to‐grain contact with less isolated pores. These samples were further characterized by impedance spectroscopy for analyzing dielectric properties. The values of the real part of dielectric constant and tangent loss showed decreasing trend with frequency. The appearance of semicircular arcs in the impedance complex plane plots indicates contribution of grains and grain boundaries and presence of different relaxation processes. 0.5% Al and Cu codoped ZnO showed the best dielectric response with a high value of dielectric constant and low tangent loss.

AC conductivity and dielectric studies in polypyrrole wrapped tungsten disulphide composites

Using in situ chemical polymerization method, polypyrrole/tungsten disulphide (PPy/WS2) composites were synthesized in various compositions viz. 10, 20, 30, and 40 wt% of WS2 in polypyrrole. Composites were structurally and morphologically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectra, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy techniques. AC response studies of the composites at room temperature were carried out in the frequency range 50 Hz–1 MHz. When compared with pristine PPy, the composites have exhibited enhanced conductivity and the same has been reflected in the complex plane impedance plots. This indicates that the conduction mechanism is due to the hopping of charge carriers. The loss tangent curves of the composites have been explained using Rezlescu model.

Enhancing the electrical properties of Bi4Ti3O12 (BiT) matrix by special alloying and sintering

In this work, the electrical properties of Bi4Ti3O12 (BiT) were investigated; those presenting interesting electrical and dielectric properties in the radiofrequency (RF) and microwave (MW) range were analysed. BiT has many applications in telecommunication systems and MW circuits. It was synthesized by the solid-state reaction method, and X-ray diffraction was used for structural characterization of this phase. The properties in the RF range were measured by impedance spectroscopy. An imaginary impedance relaxation peak and high values for real impedance were found. The complex impedance plane plots show the presence of a semicircle that was adjusted by an R-CPE circuit, presenting a thermoactive process for the load carriers. The dielectric properties in the MW range were measured using the Hakki–Coleman method, and the thermal stability was measured using the Silva–Fernandes–Sombra (SFS) technique. BiT was tested as an antenna and distant field parameters were measured and simulated.

Dielectric properties of soil mixed with urea fertilizer over 20 Hz to 2 MHz frequency range

The dielectric properties of sandy soil for various moisture contents of distilled water and Urea-fluid solutions in soil are estimated in the lower frequency range from 20 Hz to 2 MHz using precision LCR meter. The spectra of complex permittivity e*(ω), loss tangent tan δ(ω), electrical conductivity σ*(ω), and complex impedance Z*(ω) plane plots of these soil-fluid system have been investigated for various moisture contents of different concentrations of Urea solution in the soil samples. The dielectric constant and dielectric loss of the soil increase with increase in moisture content of different concentrations of Urea solution in the soil. The dielectric constant and dielectric loss of the soil increases significantly with the decrease in frequency over the given frequency range. The complex impedance plane (Zʹ versus Zʺ) plot separates electrode polarization and bulk material phenomena, which can also be observed in the dielectric loss tangent peaks.

Nanostructured Lead Sulphide Depositions by AACVD Technique Using Bis(Isobutyldithiophosphinato)Lead(II) Complex as Single Source Precursor and Its Impedance Study.

This communication reports the synthesis of bis(diisobutyldithiophosphinato)lead(II) complex and its subsequent application as a single source precursor for the nanostructured deposition of lead sulphide semiconductors and its impedance to explore its scope in the field of electronics. Synthesized complex was characterized by microelemental analysis, nuclear magnetic resonance spectroscopy, infrared spectroscopy and thermogravimetric analysis. This complex was decomposed using the aerosol-assisted chemical vapour deposition technique at different temperatures to grow PbS nanostructures on glass substrates. These nanostructures were analyzed by XRD, SEM, TEM and EDX methods. Impedance spectroscopic measurements were performed for PbS in the frequency range of 40 to 6 MHz at room temperature. In a complex impedance plane plot, two relaxation processes were exhibited due to grains and grain boundaries contribution. A high value of dielectric constant was observed at low frequencies, which was explained on the basis of Koops phenomenological model and Maxwell–Wagner type polarization. Frequency-dependent AC conductivity results were compliant with Jonscher power law, while capacitance–voltage loop had a butterfly shape. These impedance spectroscopic results have corroborated the ferroelectric nature of the resultant PbS nanodeposition.

Effect of Cu-doping on the dielectric properties of [formula omitted][formula omitted] compound

We have presented dielectric and impedance spectroscopic study of the Cu-doped MnV2O6 spin-chain compounds of nominal compositions Mn1-xCuxV2O6 (x = 0.0, 0.125, and 0.25). The studies indicate increase in dielectric permittivity upon Cu-doping without increasing the dielectric loss. Detailed ac conductivity, complex impedance and complex electric modulus analysis indicate that the charge conduction is mediated by small polarons. The analysis also points out that although Cu-doping results in an increase in the charge carrier concentration yet the increase in permittivity is also felicitated by increase in the hopping range of small polarons even in the high temperature region. Finally, the complex plane plots of impedance and electric modulus hints at two simultaneous intrinsic dielectric phases of different permittivity contributions but of similar impedance.

Discussion on Inductive Loop Observed in Complex Plane Plot of Electrochemical Impedance of Mg

Electrochemical impedance spectroscopy (EIS) is able to discriminate several time constants involved in electrode reactions. The time constant regarding adsorption-desorption relaxation may be detected in the plot of impedance spectrum when the adsorption at liquid/solid interface contributes to the kinetics of electrode reaction. For example, the complex plane plots of the electrochemical impedance of Pt electrode, where oxygen reduction occurs, show an apparent inductive loop, indicating the presence of the reaction intermediate adsorbed on the electrode1). The inductive loop is often observed in the cases of metal dissolutions in aqueous solutions2-4), and the origin has been explained by the adsorption of adsorbed intermediate in dissolution reaction. In this presentation, the author derives the theoretical equations of the Faraday impedance involving the contribution of adsorption process during metal dissolution. A current i, which flows across liquid/solid interface, is a function of electrode potential E and surficial coverage θ of adsorbed species as follows. i = f(E, θ) (1)The Faradaic impedance Z F can be represented from the differential calculus of the equation (1), where, a 1 and a 1 are partial differential coefficients.1/Z F = di/dE = a 1 + a 2(dθ/dE) (2)The equation (2) indicates that the Faradaic impedance is a function of (dθ/dE) and describes a semicircle due to an adsorption relaxation on the complex plane. In these cases, the semicircle in the low frequency range is related to the time constant of adsorption and desorption of the reaction intermediate. The conditions that the electrochemical impedance shows the inductive loop in the low frequency range are discussed on the basis of the numerical simulations.References1) M. Itagaki, H. Hasegawa, K. Watanabe, T. Hachiya, J. Electroanal Chem 557 (2003) 59.2 M. Keddam, O. R. Mattos, H. Takenouti, J. Electrochem. Soc, 128 (1981) 257.3) M. Itagaki, M. Tagaki, K. Watanabe, Electrochim.Acta, 41 (1996) 1201.4) G. Baril, G. Galicia, C. Deslouis, N. Pebere, B. Tribollet, V. Vivier, J. Electrochem. Soc, 154 (2007) C108.

Characterisation of batteries by electrochemical impedance spectroscopy

In the pursuit of batteries with higher energy density and lower cost, central to advancement of the technology is the ability to prolong cycle life. Techniques are sought which can elucidate information on battery degradation without significantly disrupting the performance of cells. Electrochemical impedance spectroscopy (EIS) offers a non-destructive route to in-situ analysis of the dynamic processes occurring inside a battery. The technique is relatively easy to use, but meaningful data analysis requires assignment of spectroscopic features to battery impedance components. Three-electrode cell configurations afford a way to potentially disentangle the impedance components. This paper examines a number of three-electrode cell designs reported in the literature, and compares their advantages and limitations. EIS results obtained using a novel in-house, three-electrode pouch cell are reported and the results compared with those obtained from conventional two-terminal impedance complex plane plots. In this way, the separate contributions of anodic and cathodic impedances can be assessed.

Processing of lanthanum doped CaCu3Ti4O12 electroceramics in molten eutectic mixture for low loss high dielectric materials

Giant dielectric material CaCu3Ti4O12 (CCTO) has found widespread applications, but associated high dielectric loss is still a major concern. The decreasing of dielectric tangent loss (tan δ) via rare earth element doping has been proven to be effective strategy, but in most cases it involves complex and time consuming processing. In the present paper, a fast and facile process is reported for the synthesis of lanthanum doped CCTO powders (Ca1-xLaxCu3Ti4O12 where x = 0.0, 0.05 and 0.1) using molten eutectic mixture as the reaction medium. The obtained powders were pressed and finally sintered at 1050°C. La3+ substitution at Ca2+ site results in remarkable reduction in dielectric loss (tan δ < 0.03) at room temperature compared to the parent CCTO. The increased grain boundary resistance (Rgb) estimated from room temperature complex impedance plane plot (Z*) for the doped ceramics is proposed to be the major cause for higher thermal stability of dielectric constant (εr) and remarkable reduction in tan δ at room temperature. Furthermore, the frequency and temperature stability of εr and tan δ over wide ranges make the doped CCTO a promising candidate for high temperature ceramic capacitor application.

Dielectric relaxation of the double perovskite oxide Ba2PrRuO6.

Samples of Ba2PrRuO6 were prepared by the solid state reaction method and the structure was characterized by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and dielectric measurements were performed in order to investigate the morphology and electric properties of the ceramics. X-ray diffraction data reveal that the Ba2PrRuO6 samples are of the cubic crystal structure with the space group Fm3̄m at room temperature. The dielectric properties were studied in the range of 20 Hz to 1 MHz in the temperature range from 10 K to 300 K. Strong dispersion in frequency and a rapid increase in ε′ are observed when T > 150 K. The observed steps of the ε′(T) curves are correlated with the peaks of the tan δ(T) curves, with the peak temperature shifting to higher values as the frequency increases. Impedance spectroscopy studies indicate the presence of grain and grain boundary relaxations in the sample at high temperatures, while at low temperatures only grain relaxation can be observed. Both grain and grain boundary relaxation times follow the Arrhenius law with activation energies of 0.16 eV and 0.17 eV, respectively.

Investigation of concentration dependent electrical and photocatalytic properties of Mn doped SmFeO3

Abstract SmFe1-xMnxO3 (x = 0.1, 0.3, 0.5) is synthesized by the sol-gel method. Rietveld refinement of the X-ray diffraction pattern of the materials show crystallization in the orthorhombic structure with Pbnm space group. The complex impedance and the ac conductivity of SmFe1-xMnxO3 have been studied by the alternating current impedance spectroscopy method. The conductivity analysis implies that the materials behave as a semiconductor in the entire temperature range. It is observed that with the increase of Mn doping, both the dielectric constant and the conductivity increases whereas the value of loss tangent decreases. The conduction mechanism in these materials has been explained by the correlated barrier hopping (CBH) model. The complex impedance plane plot is analyzed using the Cole-Cole model. The photocatalytic activity of the materials is performed by the degradation of organic pollutant under visible light irradiation. The photocatalytic efficiency of these materials show improvement with the increase in Mn concentration.

Enhancement in alternating current conductivity of polypyrrole by multi-walled carbon nanotubes via single electron tunneling

To enhance alternating current (ac) conductivity of polypyrrole (PPy), multi-walled carbon nanotubes (MWCNT) are used to prepare polypyrrole-multi-walled carbon nanotube (PMCN) composites. PPy synthesized by chemical oxidative polymerization and MWCNT prepared by arc discharge were mechanically mixed to prepare two PMCN composites of mass ratios 0.95:0.05 (PMCN-1) and 0.90:0.1 (PMCN-2) respectively. The FTIR studies confirmed strong interaction between PPy and MWCNT in the composites. Highly crystalline nature of PMCN-2 composite in which MWCNT is wrapped around by PPy confirmed from XRD, FESEM and TEM analyses. Significant increase in ac conductivity of PMCN-2 composite by four orders of magnitude due to greater increase in effective degree of electron delocalization in it confirmed. High values of real dielectric constant (ε′) and dielectric loss (tanδ) at low frequency for PPy and the composites due to Maxwell-Wagner polarization, a semicircular complex plane impedance plot for PMCN-2 composite reminiscent of Debye model confirmed. Theoretical interpretation of charge transport mechanism in the composites as due to single electron tunneling as against that in PPy as due to hopping of polarons discussed thoroughly. Composites showing single electron tunneling type of charge transport have potential for production of multi functional semiconductor and superconducting devices.

Tungsten disulfide: an efficient material in enhancement of AC conductivity and dielectric properties of polyaniline

Conducting polyaniline–tungsten disulfide (PANI–WS2) composites with 10, 20, 30, 40 and 50 wt% of WS2 in PANI were synthesized using one step in situ polymerization technique. Room temperature AC conductivity and the dielectric behavior of the aforementioned composites were investigated in the frequency range 50–106 Hz. Apart from obeying the power law above the critical frequency, indicating the universal behavior of disordered media; remarkable increase in conductivity of the composites by one order was observed. Complex plane impedance plots exhibited single semicircle for each composite, indicating the conduction mechanism is by hopping of charge carriers. High dielectric constant of order 106, at the lower frequency for the composites, started decreasing with increase in applied frequencies; this could be attributed to the Maxwell–Wagner polarization. Dielectric tangent loss curves exhibited peculiar peaks due to the relaxation loss at the resonant frequency of the hopping charge carriers and the applied AC field. Higher values of dielectric loss in the lower frequency range, make these materials as suitable candidates to design the medium frequency devices.

AC – Conductivity Study of CdSe Nanorods

The nanorods of cadmium selenide (CdSe) have been synthesized by soft chemical route using mercapto ethanol as a capping agent. The sample forms a rod like shape, confirmed by transmission electron microscope (TEM) measurement. Impedance spectroscopy is applied to investigate the dielectric relaxation of the sample at a various temperature region with varying frequency range. Grain and grain boundary effects both are present in the complex impedance plane plot and is analyzed by an electrical equivalent circuit consisting of a resistance and a constantphase element. Dielectric relaxation mechanism shows peak positions in the imaginary parts of the spectra and that is analyzed by Cole–Cole model. The temperature-dependent relaxation times obeys Arrhenius law having activation energy of 0.391 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The presence of two plateaus in the frequency-dependent conductivity spectra follows double-power law