Complex Impedance Diagrams Research Articles

Investigation and Fabrication of Brilliant Green Dye Material-Based Organic Heterojunction: Dielectric Response and Impedance Spectroscopy

Brilliant green (BG) dye material-based heterojunction is fabricated by a spin coating route and characterized by impedance analyzer. Here, we study the impedance spectroscopy of such organic material based thin film onto silicon substrate. The capacitance and conductance versus voltage (C-V), (G-V) characteristics are plotted. So, the dielectric response of BG based heterojunction is studied via the plotting of the dielectric constant, modulus components, complex impedance and Nyquist diagram. Real and imaginary parts of electrical conductivity are also plotted at several frequencies. Real and imaginary parts of electric modulus M’-V and M”-V are investigated for all experimental frequencies. The Z’-V characteristics of our device-based BG organic heterojunction exhibit a peak of 1383 W. It is confirmed that an anomalous peak of Z’ is recorded within 0.5-1 V range. The drastic decay in Z”-V plot occurs for lower 100 and 200 kHz frequency range and Z” values become constant beyond 1V for all frequencies. Ac and Dc conductivity curves demonstrate a growth with frequency and angle phase approaches to 90º within reverse voltage. This result reveals a capacitive conduct of our device.

Photocatalytic activity (dye degradation) of pristine and doped LaFeO3 (dopant Y at a site and Ni at B site) by impedance spectroscopy

Lanthanum iron oxide (LaFeO3) nanoparticles, doped with yttrium (Y) at the A-site and nickel (Ni) at the B-site, were synthesized using a sol-gel method at 600 °C. This study focuses on the synthesis of nanocrystalline La1−xYxFeO3 (Y doped LaFeO3), LaFe1−xNixO3 (Ni doped LaFeO3) and La1−xYxFe1−xNixO3 (Y/Ni doped LaFeO3) materials, where x = 0.01. The Synchrotron-based XRD analysis confirmed the single-phase formation of orthorhombic LaFeO3 (Pbnm space group) in each sample. The characterization through scanning electron microscopy and EDX revealed grains of irregular shape with an average particle size of around 200 nm. Optical properties were explored using UV–Visible spectroscopy, indicating a band gap of 1.7 eV for the pure sample. Additionally, the photocatalytic properties of the synthesized nanoparticles were evaluated for dye degradation. Electrical properties were systematically examined using impedance spectroscopy across a frequency range of 1 Hz–10 MHz at room temperature. The effect of doping on crystal structure and possible implications on dielectric and photocatalytic properties were studied. The complex impedance diagram displayed a depressed semicircle, suggesting non-Debye relaxation processes. A correlation was established between impedance and UV–Vis spectroscopy. However, the current literature lacks a comprehensive investigation for isovalent i.e. +3 substitution at A and B site simultaneously for dye degradation properties of LaFeO3-based materials. This study addresses this research gap by systematically exploring the influence of separate as well as simultaneous Y+3 and Ni+3 doping on the structural, optical, electrical, and photocatalytic characteristics of LaFeO3 nanoparticles, thereby providing valuable insights for the development of advanced functional materials for environmental applications. It was found that Y+3 dopants had a notable impact on the dye degradation properties for Mythlene blue dye at room temperature.

Magnetic and optical properties, electrical behavior and conduction mechanism study by CBH model of Cu(HAsO3).Te(OH)6 compound

The copper hydrogeno-arsenite tellurate material (CuAsTe) was synthesized and its magnetic properties were investigated. Thermal analyses revealed that no mass loss was recorded before 480 K. Additionally, in this current work, electrical properties based on the impedance measurements were determined. The complex impedance diagram at different temperatures demonstrated a single semicircle, implying that the response originated from a single capacitive element corresponding to the grains. The thermal evolution of the conductivity σdc displayed an Arrhenius type behavior and suggested that this material is an ionic protonic conductor at high temperature whereas the σac conductivity was indicative that the conduction mechanism is ensured by the correlated barrier hopping (CBH) model. The variation of M″ versus frequency proved to be a thermally activated dielectric relaxation process. Notably, we specified determined the direct optical band gap Eg = 2.3 eV in order to characterize the optical properties.

Theoretical analysis and operation optimization of eddy current flaw detector sensor interface

The use of input devices of resonance-type in flaw detectors is advisable at frequencies above 100–200 kHz. However, in the practice of non-destructive testing by eddy currents, it is often necessary to use lower frequencies. In this case, one should connect the eddy current probes to devices with a non-resonant interface such as a bridge circuit. The functioning of bridge circuits used in eddy current sensors is significantly different from its functioning when used for components measurement because eddy current sensors operate under linear parametric modulation. In this case, it is advisable to perform the measurements by the self-comparison method, when a pair of closely located identical probes are placed in adjacent arms of the bridge. In this article, we first provide a detailed mathematical analysis of the operation of such a bridge circuit used as a flaw detector interface device. We use impedances of arbitrary finite values as disturbances. It is shown that despite the non-resonant character of the bridge circuit, it exhibits good selectivity for different loading (insertion) impedances. The isolines of the output signal and the probe’s complex impedance diagram (hodograph) in balanced and imbalanced bridge circuits are jointly built. In this way, it is possible, for the first time, to construct hodographs in the complex plane for both selective signal suppression, and maximum sensitivity. Although this method is already used in series flaw detectors designed for aircrafts testing, the theory behind this method is presented here for the first time.

Impedance spectroscopy analysis of an FeNbO4 matrix with different additions of TiO2 and the effects of temperature variation

In this work, investigations of the FeNbO4 ceramic matrix (FNO) and TiO2 additions were carried out in 0, 20, 40, 60, and 80% wt. proportions. The material was synthesized using the solid-state reaction method in an energy mill, and the phases were confirmed by X-ray diffraction and Rietveld refinement. The study of complex electrical impedance was carried out using real and imaginary impedance, with measurements such as permittivity, conductivity, activation energy, and complex impedance diagrams in the range from 1 Hz to 1 MHz and with temperature variation from 100 to 300 oC using a Solartron 1260 impedance analyzer. Furthermore, the temperature coefficients of capacitance for the FNO matrix and its additions were also studied. The complex impedance diagrams showed a non-Debye type relaxation, where the adjustments made showed a good relationship between the experimental and simulated results, and the conduction process was thermally activated, following the Arrhenius relation, where the activation energies calculated were 0.46 and 0.53 eV for the FNO sample, calculated by the displacement of the maximum impedance peak and by the conductivity with temperature variation at 1 Hz. The results showed a greater understanding of the conduction processes of the FNO-TiO2 composite.

One-step spray of Cu2NiSnS4 thin films as absorber materials for photovoltaic applications

A simple one-step «Spray Pyrolysis» technique was developed for preparing Cu2NiSnS4 (CNTS) thin film followed by an annealing treatment process. Originally, the spray technique was successfully used to deposit the thin film onto glass substrate at 250 °C for 60 min spray duration. Again, the deposited thin film was annealed in a sulfur atmosphere at a temperature of 500 °C during 30 min. The sulfured thin film exhibits (111), (220) and (311) orientations correspond well to the cubic CNTS structure and other impurity compounds. The SEM data exhibit a uniform, rough and compact topography of CNTS thin films with an average-thickness of 1.36 µm. The absorption coefficient is found to be higher than 104 cm−1 in the visible region while the direct band energy of 1.62 eV, which is eminently suitable for use as an absorber in the solar cell. The complex impedance diagrams indicate the decrease of resistance by increasing temperature, which attributes to a semiconductor behavior. The close values of activation energies 0.63 and 0.54 eV determined from both angular frequency and DC conductivity indicate that the carrier transport mechanism is thermally activated.

Magnetically tunable electrical transport of multiferroic xLaFeO3- (1−x)PbZr0.58Ti0.42O3 (x = 0.2 and 0.3) nanocomposites

Lanthanum based perovskite type composite materials of xLaFeO3- (1−x)PbZr0.58Ti0.42O3 (x = 0.2 and 0.3) based on ferrite (LaFeO3) and ferroelectric (PbZr0.58Ti0.42O3) phases are synthesized by the ‘solid state route process’. The structural characterization have been done through x-ray diffraction and field emission scanning electron microscope techniques. The complex impedance and modulus diagram illustrate the contribution of grain and grain boundaries effects towards the electrical conductivity attributing the non-Debye type phenomena. The relaxation frequency is changed with an application of magnetic fields ascribing the spin dependent mechanism of the electrical transport at the grain boundaries. The fitting of Nyquist diagram attributes the magnetic domain wall motion across the grain boundaries pinning center of the system. The nature of ac conductivity with an applied magnetic field is decreasing the presence of defect states in the interfaces of LaFeO3 and PbZr0.58Ti0.42O3 grains. It also corresponds to the occurance of strain mediation of piezomagnetic phase of nanocomposites. So, the present study is directed towards the query to know the detailed study of magnetic field dependence electrical transport properties of a system.

Optical and AC conductivity studies on Li2-xRbx MoO4 (x = 0, 0.5, 1) compounds

In this work, we are interested in the new compounds Li1.5Rb0.5MoO4 preparation by the solid state method. Also, we present a comparative study with LiRbMoO4 and Li2MoO4. The X-ray powder diffraction indicates that these compounds crystallize at room temperature in the monoclinic, orthorhombic and trigonal systems with the P21, Pcab and R-3 space groups, respectively. The shapes of the grains for these ceramics were observed by means of scanning electron microscopy (SEM) images. The Tauc model was used to determine the optical gap energy (4, 4.3 and 3.9 ev) and the urbach energies (1.51, 0.35 and 1.14 ev) of our compounds. The electric and dielectric proprieties of Li1.5Rb0.5MoO4 have been studied. We carried out complex impedance spectroscopy in the frequency range 200 Hz-5 MHz at different temperatures (575–723 K). The complex impedance diagram showed a single semicircle, implying that the response originates corresponding to the grains. As a result, an electrical equivalent circuit has been proposed. The spectra follow the Arrhenius law with two energies of activation 1.58 eV for impedance measurements and 1.25 eV for that of modulus. The alternative current (AC) electrical conduction of the three compounds is governed by the overlapping large polaron tunneling (OLPT).

Physical properties of Ag/Ca doped Lantanium manganite

La0.6Ca0.3Ag0.1MnO3 system has been synthesized using the cheap solid–solid process. Structural analysis indicates that the sample exhibits a single phase of intragranular. Electrical and dielectric data, over a wide temperature range and frequencies have been recorded with impedance spectroscopy. We visualize the conductivity, whose activation energy is low, as a successive hopping of electrons as polaron does. Further, the conductivity is governed by the small polaron hopping model at higher temperature region while it fits well with the variable range hopping model at a lower temperature range. Dielectric data has been represented in different alternative complex formalisms, from which complementary information has been extracted. The complex impedance diagram suggests the contribution of only two active microstructures, ruling out the electrode polarization effect. We adopt the spectrum of the imaginary component of the electric modulus M″ to distinguish long range hopping from short range hopping. The relative permittivity spectrum permits to identify the possibility of the existence of electric polarizations. Further, it reveals colossal static dielectric constant, which makes it suitable for multitude potential applications in electronic industrial fields.

Study of the structural, impedance spectroscopy and dielectric properties of Na and Si co-doped NiO ceramics

Sodium and silicon co-doped NiO (NSNO) of the formula NaxSiyNi1 – x−yO (x = 0.05, 0.1 and y = 0.02, 0.05) were prepared by solid state reaction. Structural, electrical conduction and dielectric properties of the NSNO ceramics were investigated. The current NSNO ceramics exhibited giant dielectric constant (ε′ ~ 104 at 1.1 KHz and 300 K) and three dielectric relaxation peaks were found on the curve of the frequency dependence of the imaginary part of electric modulus M″. The complex impedance diagrams showed three electrical responses, which have been attributed to the domain, domain-boundaries and grain-boundaries in the NSNO ceramics. Analysis of the temperature dependence of the conductivity for the current ceramics indicated that the electrical conduction mechanism changes from variable range hoping at low temperatures (T < 220 K) to nearest neighbor hopping mechanism at higher temperatures. The electrically heterogeneous structure, revealed by the complex impedance analysis, combined with considerable polarization due to defect dipoles are thought to be the cause for the giant dielectric response of NSNO ceramics.

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.

Structural, optical properties, impedance spectroscopy studies and electrical conductivity of SnO2 nanoparticles prepared by polyol method

Tin oxide nanoparticles (SnO2) with controlled shapes and sizes were prepared at 160 °C by a simple polyol method. The formation of typical rutilE−type was confirmed by X-ray diffraction studies, and it was found to be a tetragonal structure. X-ray diffraction and transmission electron microscopy show the average diameter of SnO2 nanoparticles about 13 nm obtained after calcination at 700 °C. Moreover, the calcined sample is composed of an aggregated network of almost spherical nanoparticles. The optical property was investigated using an UV–visible Diffuse Reflectance Spectroscopy, the band gap is found to be 3.4 eV. Electrical properties were performed using impedance spectroscopy technique in the frequency range 6 KHz–1 MHz at various temperatures (523–723 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. In fact, AC conductivity is found to follow Jonsche’s s universal power law. As a result, the exponent‘s’ was found to increase with increase in temperature. Further analysis revealed that, the non overlapping small polaron tunneling model mechanism was applicable at the present temperatures.

Optical, electrical properties and OH group adsorption of deposits electrolysis

An electrochemical method, using electrical energy, decompose water into hydrogen and oxygen, which is more important to pH values varying between the intervals {7.9 - 14} and {2-6 - 5}, a degree of salinity lower than 90 g/L and greater than 130 g/L. While the formed film and the resultant powders were characterized by FTIR, UV- Visible and complex impedance. Thus we see that the electrolysis of water causes a change in the stretching vibrations υOH, namely the presence of Cu-O vibration (solid 520-630 cm-1). A spectral shift in the OH absorption band which is a positive indicator of the interaction of the metal particles dispersed in the electrolyte. Comparison of measurements of the value of pH of the electrolyte showed that acid pH values which increase, which is not the case for basic media and which shows a decrease. A peak of UV-visible absorption at 220 nm was recorded for the solution after production, pH = 8, and two bands at 320 and 360 nm due to hydroxyl compounds that are detected. Furthermore, the complex impedance diagrams show capacitive loops at the high frequency domain, and relaxation process of the electrolyte for different pH values.

Electrical conductivity of Ag–Na ion exchanged soda-lime glass

This paper reports on a study of the influence of silver on the electrical conductivity of Ag–Na ion exchanged soda-lime-silica glass. A glass of 22Na2O·8CaO·70SiO2 (mol %) composition was prepared and silver was introduced into its samples by Ag–Na ion exchange at 350°C for 1h. The ion exchanged samples were further subjected to a thermal treatment at 500°C for 24h. Complex impedance diagrams (−Z″ vs. Z′ plots) at several temperatures were obtained to calculate the activation energy for the dc electrical conductivity, Eσ. The electrical conductivity of the ion exchanged sample is close to that of the pristine sample. The complex impedance plots of this sample show a tail in the low frequency range assigned to the non-uniform distribution of silver in the surface layers and stresses produced by the thermal and chemical temperings. The electrical conductivity of the layers was lower than that of the pristine glass. The further thermal treatment reduced the conductivity of the sample due to the formation of metallic silver nanoparticles in the glass matrix and the lower concentration of the mobile Na+ ions. UV–visible optical absorption spectra showed an absorption band at 420nm attributed to the presence of silver nanoparticles in the thermally treated sample.

AC conductivity and dielectric behavior in lithium and sodium diphosphate LiNa3P2O7

• The LiNa 3 P 2 O 7 compound has been synthesized by solid-state reaction technique. • The ac conductivity of this compound is proportional to ω s ( s < 1). • The transport mechanism is explained by hopping of Li + ion in the material. 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 LiNa 3 P 2 O 7, we have carried out complex impedance spectroscopy technique in the frequency range 200 Hz–5 MHz at various temperatures (613–719 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. It can be seen from the experimental data that the ac conductivity of this compound is proportional to ω s ( s < 1), the value of s is to be temperature-dependent, which has a tendency to decrease in temperature. Activation energy values deduced from both dc conductivity and hopping frequency are in the order of E a = 0.95 eV and E a = 0.89 eV respectively. 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 Li + ion in the structure of the investigated material.

A Comparative Study of N-Type ZnO and P-Type NiO Nanostructures for the Detection of Aqueous Ethanol Solution

N-type ZnO nanorod arrays and p-type NiO thin films have been prepared on the ITO substrates by chemical bath deposition (CBD) and sol-gel spin coating method, respectively, then followed by thermal treatment at 400 °C for 1 h. The ZnO nanorod arrays have length of around 1.5 μm and diameter of around 55 nm; the thickness of the NiO film is around 340 nm with average grain size of 22 nm. The sensing properties of the n-type ZnO and the p-type NiO for the detection of aqueous ethanol solutions at room temperature are investigated using electrical impedance spectroscopy (EIS). The EIS results reveal that the series resistance (Rs) is as low as 27 Ω; the charge-transfer resistance (Rct) remarkably contributes to the sensing properties of the ethanol sensor, and decreases with a decreasing concentration (99.5%-1%) from 17.0 kΩ to 2.6 kΩ. An equivalent circuit with capacitors and resistors was developed to investigate the conduction process according to complex impedance (Nyquist) diagrams. In low concentration range, the electron conduction process is dominated by the Rct and a constant phase element (CPE); however, in high concentration ethanol solution, the conduction process is dominated by polarization and decomposition of the absorbed water with larger Rct observed. Moreover, I-V measurements were carried out to evaluate the sensitivity of n-ZnO and p-NiO nanostructures at room temperature.

Physical Essentials of Rotating Complex Impedance Diagram in Some Electrochemical Systems

Physical Essentials of Rotating Complex Impedance Diagram in Some Electrochemical Systems

Investigation of electrical and dielectric properties of antimony oxide (Sb2O4) semiconductor thin films for TCO and optoelectronic applications

This work presents some electrical properties based on the impedance measurements as well as the dielectric constants on thermal evaporated Sb2O4 thin films additional to structural, opto-thermal and optical investigations which are reported previously by Ouni et al. in Journal of Non-Crystalline Solids (vol. 356 (2010) 1294–1299). The electrical conductivity and dielectric properties of Sb2O4 thin film were indeed studied using impedance spectroscopy technique in the frequency range 5Hz–13MHz at various temperatures (325–450°C). 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. It can be seen from the experimental data that the AC conductivity in thin films of Sb2O4 is proportional to ωs (s<1), the value of s is to be temperature-dependent, which has a tendency to decrease in temperature. The temperature dependence of both AC conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. Values of dielectric constants ε1 and ε2 were found to decrease with frequency and increase with temperature. Activation energy values deduced from both DC conductivity and relaxation frequency are of the order of Ea~0.7eV. The analysis of the parameter s leads to the barrier height Wm value which is in agreement with that proposed by the theory of hopping of charge carriers over the potential barrier between the defect states in the band tail as suggested by Elliott.

Dielectric and ac impedance studies of nanostructured CaCu3Ti3.90Ce0.10O12 electro-ceramic synthesized by citrate-gel route

Effect of doping at Ti4+ site by Ce3+ has been examined in CaCu3Ti3.90Ce0.10O12 synthesized by citrate-gel route. DTA/TG analysis of dry powder gives pre-information about formation of final product around 850 °C. X ray diffraction analysis confirmed the formation of CaCu3Ti3.90Ce0.10O12 phase of the ceramic sintered at 950 °C for 12 h. Microstructure has been studied using scanning electron microscopy and confirmed the average grain size found in nano range 200–400 nm in system CaCu3Ti3.90Ce0.10O12.The nature of relaxation behavior of ceramic was also rationalized by using the impedance and modulus spectroscopy. The bulk conductivity indicates an Arrhenius-type thermally activated process. The ac conductivity spectrum obeyed the Jonscher power law. The complex impedance diagrams of the ceramic exhibited a significant contribution from the grains, grain boundaries and electrode. The activation energies calculated from the grain-boundary relaxation time constant was found to be 0.49 eV which confirmed the Maxwell–Wagner type of relaxation present in the ceramic.

Low temperature solution-processed ZnO nanorod arrays with application to liquid ethanol sensors

ZnO nanorod arrays have been prepared by low-temperature chemical bath deposition method. The lengths and diameters of the high-aspect-ratio ZnO nanorods are around 1.5μm and 55nm, respectively. The as-prepared ZnO nanostructures are hexagonal phase with c-axis orientation, and the sensing properties of the ZnO-based sensors against liquid ethanol with different concentrations are investigated using electrical impedance spectroscopy (EIS). The EIS results reveal that the series resistance (Rs) is as low as 27Ω; the charge-transfer resistance (Rct) remarkably contributes to the sensing properties of the ethanol sensor, and decreases with a decreasing concentration (99.5–1%) from 17.0kΩ to 2.6kΩ. An equivalent circuit with capacitors and resistors was developed to investigate the conduction process according to complex impedance (Nyquist) diagrams. In low concentration range, the electron conduction process is dominated by the Rct and a constant phase element (CPE); however, in high concentration ethanol solution, the conduction process is dominated by polarization and decomposition of the absorbed water with larger Rct observed. Also, sensitivity of the ZnO sensor was evaluated from the current–voltage (I–V) characteristics; the results demonstrate that the ZnO nanorod arrays are very promising to fabricate chemical sensors with high sensitivity and low power consumption.