AC Electrical Measurements Research Articles

Electrochemical and computational evaluation of hydrazide derivative for mild steel corrosion inhibition and anticancer study

In the present study the authors’ main goal is to avoid the corrosive attack of the chloride ions of 3.5% NaCl solution in saline medium on the mild steel (MS), by addition of small amount of a new derivative of the hydrazide called ligand (HL), as a corrosion inhibitor. This study had been achieved by employing different electrochemical measurements such as, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP) methods. The results of the electrochemical test (OCP), showed that, the open circuit potential of the mild steel in saline solution, was guided to more positive direction in presence of the ligand (HL), at its ideal concentration (1 × 10−3 M), compared to the (OCP), of the mild steel in absence of (HL). The results of the electrochemical methods, EIS and PDP presented that, the ligand (HL), was acted as a good corrosion inhibitor for hindering the corrosion process of the mild steel in 3.5% sodium chloride, as it was recorded a good percentage of the inhibition efficiency (77.45%, 53.41%, by EIS and PDP techniques respectively), at its optimum concentration (1 × 10−3 M). Also, the corrosion rate of the mild steel in the saline medium without (HL), was listed about (0.0017 mm/year), while in existence of (HL), was decreased to a value about (0.00061 mm/year). As well, some of electrical properties of (HL), and its derivative [Pd(II), Cr(III), and Ru(III)], complexes were investigated such as; the activation energy (Ea(ac)), which recorded values in the range of 0.02–0.44 (eV) range and electrical conductivity which listed values at room temperature in the range of 10−5–10−8 S.cm−1. The results of the AC and DC electrical conductivity measurements for (HL), and its derivative [Pd(II), Cr(III) and Ru(III)] complexes indicate semiconducting nature which suggests that these compounds could be used in electronic devices. Also, the complexes exhibited higher conductivity values than (HL). Photophysical studies showed good florescence properties of HL that indicated that it can be used to determine most of the drugs with no fluorescence properties by quenching and calculating quantum yield. Moreover, the hydrazide ligand (HL), has shown selectivity as an active anticancer candidate drug for both breast and colon cancer in humans. Density function theory demonstrated that, the frontier molecular orbital HOMOs of the complexes have exhibited similar behavior and the charge density has localized in the metallic region of all the studied complexes. Also, the values of the energy gap of the ligand (HL), and its complexes Pd(II), Cr(III) and Ru(III), had been arranged in this order HL > Cr(III) > Ru(III) > Pd(II). All characterization using different spectroscopic techniques were reported to elucidate the proposed structures such as; thermal analysis, elemental analysis of C, H, and N atoms, spectral analysis using IR, UV, 1H NMR techniques, scanning electron microscopy and energy dispersive X-ray analyses.

Prototype of a Digital Measuring Device Based on Atmega 328P for Measuring Current, Voltage, Electrical Power, and RLC Components

Research on digital measuring device prototypes has developed over the past few years. However, there are still challenges in measuring current, voltage, electrical power, and RLC component parameters accurately. This research aims to design a digital system to measure electrical quantities such as current, voltage, resistance, inductance, and capacitance using Atmega 328P. Data retrieval is done by implementing the system as a whole, namely the AC and DC electrical measurement system and the measurement of RLC components. The results showed that the system can measure and display the result of measuring current, voltage, electric power, and RLC components correctly. The accuracy percentage for the components measuring instrument on the resistor test is 99.35%, the error is 0.65%, and the precision is 99.87%. In the inductor test measurement, the percentage value of accuracy is 94.11%, the error is 5.89%, and the precision is 96.77%. In the capacitor test measurement, the accuracy percentage is 98.03%, the error is 1.97%, and the precision is 98.65%. On the DC voltage sensor, the accuracy percentage is 97.31%, error 2.69%, and precision 99.77%.

A Piezoelectric–Piezoresistive Coupling Electric Field Sensor for Large Dynamic Range AC Electric Field Measurements

We propose a piezoelectric–piezoresistive coupling electric field sensor capable of performing large dynamic range AC electric field measurements. The electric field sensor utilizes direct coupling between piezoelectric (PE) materials and piezoresistive (PR) strain gauges, in conjunction with an external signal conditioning circuit, to measure AC electric fields effectively. We verified the feasibility of the scheme using a finite element simulation, fabricated a prototype of the electric field sensor, and characterized the properties of the prototype. The testing results indicate that the sensor exhibits an ac resolution of 50 V/m and a linear measurable electric field range of 0 to over 200 kV/m, which keeps the linearity at less than 0.94% from 1 Hz to over 5 kHz. Furthermore, the sensor also has advantages, such as a small size and low power consumption. The sensor can enhance the comprehensive observability and measurability of digital power grids.

Synthesis, properties and applications of sulfur doped (CdO)1-x(Mn3O4)x (x = 0.0/0.25/0.50/0.75/1.0) nanocrystals

Studies have been made to understand the effect of anionic doping (with 2.5 wt% sulfur) on the physicochemical properties and photocatalytic, and antimicrobial activity applications of the interesting and useful (CdO)1-x(Mn3O4)x (x = 0.0/0.25/0.50/0.75/1.0) nanocrystals (synthesized by a microwave-assisted solvothermal method, and annealed at 650 °C). X-ray diffraction, electron microscopic (SEM/TEM) and EDX spectral analyses have shown that the synthesized samples are of high phase purity having spherical shaped morphology with crystallite sizes in the range of 11–22 nm. UV–visible spectral (in the wavelength range 200–800 nm) and AC electrical measurements (in the temperature range 40–160 °C and with frequency range 100 Hz–1 MHz) have indicated tuning of optical and electrical properties on doping. Capability in photocatalytic degradation (with Methylene Blue dye under UV–visible light irradiation) and antimicrobial activity (against gram positive Bacillus Subtiles, gram negative Escherichia Coli and fungus Candida Albicans) have also been studied for the 10 samples (including the 5 un-annealed samples) considered.

Fe dopant controlled the ferromagnetic, structural, thermal, optical, and electrical characteristics of CdO nanoparticles

This research paper presents a study on (Fe) doped CdO nanoparticles focusing on their structural (XRD), thermal (TGA and DTA), optical (UV–vis), magnetic (VSM and ESR), and electrical characteristics. The synthesis of Cd1-xFexO with (x = 0.0, 0.01, 0.05, 0.10, 0.15, and 0.20) nanoparticles was carried out using the co– precipitation technique. Fe dopants showed a great impact on the structural parameters and the thermal stabilities of obtained nanomaterials. SEM and TEM imaging techniques are employed to investigate the morphology, size, and distribution of the Cd1-xFexO nanoparticles. UV spectroscopy was employed to better understand the electronic transitions and optical characteristics. Furthermore, magnetization measurements from ESR and VSM showed a weak ferromagnetic order with a high Fe concentration. For instance, the Ac electrical conductivity measurements were used to determine the electrical properties, dielectric losses, and charge transport mechanisms between the Fe-dopants and CdO. The structural, thermal, optical, magnetic, and electrical characteristics data are complemented to better understand for Cd1-xFexO materials for employing them in magnetic storage and sensors, photocatalysis, other future applications.

Preparation and physicochemical properties of pure and O2- doped nanocomposites based on cadmium and manganese sulfides

Pure and O2- (2.5/5.0 wt%) doped (CdS)1−x(MnS2)x nanocomposites (with x = 0.0/0.25/0.50/0.75/1.0) have been (for the first time) prepared by a simple solvothermal method (with pulsed microwave heating) and characterized structurally, chemically and physically (thermally, electrically, optically and magnetically) by adopting the available techniques. The prepared samples (except the pure and doped CdS) are found to be multi-phased nanocomposites, and are paramagnetic in nature. Average crystallite sizes obtained are within 5.6 and 13.9 nm, and the thermal stability has been found to increase in proportion with the amount of CdS present. Bandgap energies obtained are within 1.8 and 2.2 eV, and significant photoluminescence peaks have been observed; DC and AC electrical measurements along with complex impedance analysis have provided useful results. The present study indicates that the prepared nanocomposites (based on CdS and MnS2) are expected to find utility in optoelectronic and energy devices.

Hydrogenation shrinks the colossal permittivity of Sb/Co co-doped TiO2 nanoparticles-structural and optical investigations

Pristine and (Sb/Co)-codoped TiO2 anatase powders were synthesized by hydrothermal method and some of the samples were hydrogenated. The samples were characterized by the traditional techniques: X-rays, optical diffuse reflection spectroscopy (DRS), and ac-electrical measurements. It was observed that the (Sb/Co) codoping induces the growth of the anatase. The optical absorption investigation was clarified by the generation of an intermediate band in the bandgap of TiO2. The catalysis power of the Co2+ ions to the adsorbed H2-dissociation strongly supports the optical absorption strength. The Sb5+/Co2+ codoping could generate weak colossal permittivity, which was lowered by ∼50% with hydrogenation. Such important results was studied and explained.

Temperature dependent dielectric properties of GeTe-rich (GeTe)x(Sb2Te3)1−x glass

The dielectric properties of phase-change materials, which could switch between crystalline and amorphous states, determine the device performances in the electronic and optical applications. Here, we have systematically investigated the dielectric properties of amorphous (a-) Ge8Sb2Te11 thin films with temperature by two complementary methods, i.e., the AC electrical measurement (0.5–186 Hz) and the impedance spectroscopy (9 kHz–3 GHz). The characterization of dielectric behavior of a-Ge8Sb2Te11 at low frequencies approaching DC, as defined by the static dielectric constants (εst), is achieved by the measurement at very low temperature. The resulting εst of a-Ge8Sb2Te11 is much larger than its optical dielectric constant ε∞ at room temperature, which is mainly ascribed to the contribution of infrared active phonons at around tens of meV. The εst increases linearly by 16.5% from 5 to 300 K, due to more optical phonons activated at elevated temperatures. We also notice that εst shows little dependence on the frequency, and the total conductivity of a-Ge8Sb2Te11 extracted from impedance spectroscopies is frequency independent up to 10 MHz. Hence, no obvious dielectric relaxations are observed in a-Ge8Sb2Te11 below 10 MHz close to room temperature. In addition, the bandgap calculated from temperature dependence of the electrical conductivity is larger than that measured from the optical absorption edge by 11.5%.

Exploring the dielectric and conduction characteristics of iodine substituted CaCu3Ti4O12-xIx

AC electrical measurements were carried out on iodine doped, CaCu3Ti4O12-xIx (x = 0, 0.005, 0.05 and 0.2) ceramic specimens sintered at 1100 °C for 12 h in the temperature (300–450 K) and frequency (20 Hz - 1 MHz). The crystalline structure, microstructure, and oxidation state of various ions of pure and iodine-substituted sintered specimens were carried out through XRD, SEM, and XPS, respectively. The dielectric relaxations in grains, grain boundaries, and sample-electrode interfaces for different compositions were investigated through impedance and modulus spectroscopic techniques and were reported in the first part of the investigation. It revealed the involvement of similar types of charge carriers in conduction and relaxation processes in grains and grain boundaries, respectively. This second section emphasizes the dielectric and conduction properties of CaCu3Ti4O12 (CCTO) with iodine doping at the anion site. The XPS study reveals that the concentration [VO••] is reduced, and [VM″] gets increased with increasing concentration of iodine from x = 0.05 to 0.2. This observation also supports the point defect model as reported earlier for charge compensation of impurity defect IO• i.e., with increasing substitutions of iodine, the charge on IO• change from electronic to cationic vacancies, VTi//// or copper VCu// or both to keep electrical charge neutrality. The metal ions get segregated at grain boundaries. This, in turn, will minimize hopping due to electrons between Ti4+ and Ti3+ or Cu2+ and Cu1+. As a result, it increases resistivity and minimizes dielectric losses for the higher concentration of iodine doping. Thus, a high concentration of iodine doping at the oxygen site promotes the formation of a barrier layer capacitor.

Influence of Annealing on the Dielectric Properties of Zn-SiO2/Si Nanocomposites Obtained in "Hot" Implantation Conditions.

This paper presents the results of AC electrical measurements of Zn-SiO2/Si nanocomposites obtained by ion implantation. Implantation of Zn ions was carried out into thermally oxidized p-type silicon substrates with energy of 150 keV and fluence of 7.5 × 1016 ion·cm−2 at a temperature of 773 K, and is thus called implantation in “hot” conditions. The samples were annealed in ambient air for 60 min at 973 K. Electrical measurements of Zn-SiO2/Si nanocomposites were carried out before and after annealing. Measurements were performed in the temperature range from 20 K to 375 K. The measurement parameters were the resistance Rp, the capacitance Cp, the phase shift angle θ and the tangent of loss angle tanδ, as a function of the frequency in the range from 50 Hz to 5 MHz. Based on the characteristics σ(f) and the Jonscher power law before and after sample annealing, the values of the exponent s were calculated depending on the measurement temperature. Based on this, the conductivity models were matched. Additionally, the real and imaginary parts of the dielectric permittivity were determined, and on their basis, the polarization mechanisms in the tested material were also determined.

Impedance Spectroscopy and Structural Characterization of Nanostructured ZnO and Hf-Doped ZnO Ceramics

In this research, nanostructured zinc oxide (ZnO) and hafnium-doped zinc oxide ceramic samples were prepared by the sol-gel technique. ZnO and at%0.5 hafnium-doped ZnO (HZO) nanostructures and their surface morphologies were studied by XRD and FESEM. AC electrical properties (capacitance, conductance, and complex impedance) of ZnO and HZO were studied by impedance analyzer with the frequency range from 20 Hz to 1.5 MHz and temperature range from 300 K to 500 K. General analysis of AC electrical measurements showed that both samples had different equivalent circuit diagrams. The best-fitted equivalent circuit diagram for ZnO was “R(RC)(RC)” at all temperatures. The circuit diagram for HZO was “R(RCPE)” at 300 K, 350 K, and 400 K temperatures and “R(RCPE)(RCPE)” at 450 K, and 500 K temperatures. Negative temperature coefficient of resistance (NTCR), non-Debye behavior, and multiple relaxation times were observed.

Eumelanin-based multisensory platform: A case of study for photolithographic patterning

Eumelanin, the most abundant brown-black pigment found in humans, is an ideal candidate for bioelectronics and eco-design technologies due to its biocompatibility, biodegradability, and hydration-dependent conductivity. Here, we validate the use of standard photolithography for integrating synthetic eumelanin into robust solid-state device platforms without unconventional methodologies. By combining AFM, Raman, and XPS with DC and AC electrical measurements, we have shown that eumelanin's film topography, chemical composition, and charge transport are not affected by the pattern process. Based on these findings, we explore interdigitated electrode structures for pH, humidity, and contact sensing system aiming at miniaturized wearable technologies for human healthcare monitoring.

Successive Phase Transitions and Multiferroicity in Deformed Triangular-Lattice Antiferromagnets Ca3MNb2O9 (M=Co, Ni) with Spatial Anisotropy

We constructed the magnetic field-temperature phase diagrams of new quasi-two-dimensional isosceles triangular lattice antiferromagnets (TLAF) Ca3MNb2O9 (M=Co, Ni) from dc and ac magnetic susceptibilities, specific heat, dielectric constant, and electric polarization measurements on single crystalline samples. Ca3CoNb2O9 with effective spin-1/2 Co2+ ions undergoes a two-step antiferromagnetic phase transition at T N1 = 1.3 K and T N2 = 1.5 K and enters a stripe ordered state at zero magnetic field. With increasing field, successive magnetic phase transitions, reminiscent of the up-up-down (uud) and the oblique phases, are observed. The dielectric constant of Ca3CoNb2O9 shows anomalies related to the magnetic phase transitions, but clear evidence of ferroelectricity is absent. Meanwhile, Ca3NiNb2O9 with spin-1 Ni2+ ions also shows a two-step antiferromagnetic transition at T N1 = 3.8 K and T N2 = 4.2 K at zero field. For Ca3NiNb2O9, the electric polarization in the magnetic ordered phases was clearly observed from the pyroelectric current measurements, which indicates its coexistence of magnetic ordering and ferroelectricity.

Solar Orbiter’s first Venus flyby: Observations from the Radio and Plasma Wave instrument

Context.On December 27, 2020, Solar Orbiter completed its first gravity assist manoeuvre of Venus (VGAM1). While this flyby was performed to provide the spacecraft with sufficient velocity to get closer to the Sun and observe its poles from progressively higher inclinations, the Radio and Plasma Wave (RPW) consortium, along with other operational in situ instruments, had the opportunity to perform high cadence measurements and study the plasma properties in the induced magnetosphere of Venus.Aims.In this paper, we review the main observations of the RPW instrument during VGAM1. They include the identification of a number of magnetospheric plasma wave modes, measurements of the electron number densities computed using the quasi-thermal noise spectroscopy technique and inferred from the probe-to-spacecraft potential, the observation of dust impact signatures, kinetic solitary structures, and localized structures at the bow shock, in addition to the validation of the wave normal analysis on-board from the Low Frequency Receiver.Methods.We used the data products provided by the different subsystems of RPW to study Venus’ induced magnetosphere.Results.The results include the observations of various electromagnetic and electrostatic wave modes in the induced magnetosphere of Venus: strong emissions of ∼100 Hz whistler waves are observed in addition to electrostatic ion acoustic waves, solitary structures and Langmuir waves in the magnetosheath of Venus. Moreover, based on the different levels of the wave amplitudes and the large-scale variations of the electron number densities, we could identify different regions and boundary layers at Venus.Conclusions.The RPW instrument provided unprecedented AC magnetic and electric field measurements in Venus’ induced magnetosphere for continuous frequency ranges and with high time resolution. These data allow for the conclusive identification of various plasma waves at higher frequencies than previously observed and a detailed investigation regarding the structure of the induced magnetosphere of Venus. Furthermore, noting that prior studies were mainly focused on the magnetosheath region and could only reach 10–12 Venus radii (RV) down the tail, the particular orbit geometry of Solar Orbiter’s VGAM1, allowed the first investigation of the nature of the plasma waves continuously from the bow shock to the magnetosheath, extending to ∼70RVin the far distant tail region.

A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

This study intends to reveal the significance of the catalyst to substrate ratio (C/S) on the structural and electrical features of the carbon nanotubes and their polymeric nanocomposites. Here, nitrogen-doped carbon nanotube (N-MWNT) was synthesized via a chemical vapor deposition (CVD) method using three ratios (by weight) of iron (Fe) catalyst to aluminum oxide (Al2O3) substrate, i.e.,1/9, 1/4, and 2/3, by changing the Fe concentration, i.e., 10, 20, and 40 wt.% Fe. Therefore, the synthesized N-MWNT are labelled as (N-MWNTs)10, (N-MWNTs)20, and (N-MWNTs)40. TEM, XPS, Raman spectroscopy, and TGA characterizations revealed that C/S ratio has a significant impact on the physical and chemical properties of the nanotubes. For instance, by increasing the Fe catalyst from 10 to 40 wt.%, carbon purity increased from 60 to 90 wt.% and the length of the nanotubes increased from 1.2 to 2.6 µm. Interestingly, regarding nanotube morphology, at the highest C/S ratio, the N-MWNTs displayed an open-channel structure, while at the lowest catalyst concentration the nanotubes featured a bamboo-like structure. Afterwards, the network characteristics of the N-MWNTs in a polyvinylidene fluoride (PVDF) matrix were studied using imaging techniques, AC electrical conductivity, and linear and nonlinear rheological measurements. The nanocomposites were prepared via a melt-mixing method at various loadings of the synthesized N-MWNTs. The rheological results confirmed that (N-MWNTs)10, at 0.5–2.0 wt.%, did not form any substantial network through the PVDF matrix, thereby exhibiting an electrically insulative behavior, even at a higher concentration of 3.0 wt.%. Although the optical microscopy, TEM, and rheological results confirmed that both (N-MWNTs)20 and (N-MWNTs)40 established a continuous 3D network within the PVDF matrix, (N-MWNTs)40/PVDF nanocomposites exhibited approximately one order of magnitude higher electrical conductivity. The higher electrical conductivity of (N-MWNTs)40/PVDF nanocomposites is attributed to the intrinsic chemical features of (N-MWNTs)40, such as nitrogen content and nitrogen bonding types.

Electron beam radiation induced solid-state synthesis of gold nanoparticles in polyvinyl alcohol films and their Physico-chemical properties

A straightforward strategy is proposed to prepare composites of gold nanoparticles (AuNPs) in polyvinyl alcohol (PVA) films under the effect of electron beam irradiation. The composite films were characterized using UV–Visible spectroscopy, TEM, TGA and AC electrical conductivity measurements. PVA/Au nanocomposites exhibited a surface plasmon peak at about 540 nm assigned to Au nanoparticles. The values of optical energy band gap (Eg, eV) were deeply reduced from 5.8 eV for pure PVA to 3.5 eV for 300 kGy irradiated sample. TEM investigation indicated the formation of more AuNPs as the irradiation dose increases. The AuNPs were found to be in the size range of 10–65 nm, with a mixture of different morphologies. TGA data indicated that the incorporation of Au nanoparticles within PVA matrix and increasing EB irradiation dose decreases the thermal stability of PVA/Au nanocomposite films. AC conductivity at room temperature of PVA/Au samples showed a steady behavior followed by a sharp increase as a function of the applied field frequency for different irradiation doses.

FTIR, DC, and AC electrical measurements of Mg Zn Nano-ferrites and their composites with Polybenzoxazine

FTIR, DC, and AC electrical measurements of Mg Zn Nano-ferrites and their composites with Polybenzoxazine

Ferromagnetism in structurally disordered UFe0.39Ge2

A polycrystalline sample of the uranium ternary germanide UFe0.39Ge2 was examined by means of X-ray powder diffraction, DC magnetization and AC magnetic susceptibility, heat capacity and electrical resistivity measurements performed in wide ranges of temperature and magnetic fields. The experiments confirmed that the compound crystallizes with orthorhombic crystal structure of the CeNiSi2-type that is closely related to that of the ferromagnetic superconductor UGe2 and orders ferromagnetically at 37 K. Moreover, it exhibits some features characteristic of ferromagnetic cluster glasses. The electrical transport in UFe0.39Ge2 is strongly influenced by structural disorder arising from the partly occupied Fe-sites in its crystallographic unit cell.

Fermi level pinning in Co‐doped BaTiO3: Part I. DC and AC electrical conductivities and degradation behavior

AbstractWe explore the synergistic effects of co‐doping BaTiO3 with a judicious combination of acceptors and donors to control the point defect chemistry and electrical properties, with the goal of simultaneously limiting the electronic and ionic conductivities over broad temperature and oxygen partial pressure (pO2) ranges. Specifically, we compare the temperature‐ and pO2‐dependent electrical properties of BaTiO3 ceramics acceptor‐doped with either Mn or Mg and co‐doped with a Y donor. This study, which is the first of a two‐part series, presents the electrical properties as a function of pO2, temperature, and time, focusing on the grain‐interior electrical response. The DC and AC electrical conductivity measurements reveal that co‐doping with Mn and Y can result in (1) increased electrical resistivity over a broad temperature range, (2) pO2‐independent electrical conductivity in oxidizing conditions, and (3) improved time‐dependent dielectric degradation resistance. These behaviors are attributed to a Fermi level pinning effect, as is explained in the companion paper, which presents complementary density functional theory (DFT)‐based grand‐canonical defect chemistry models. The collective experimental and computational studies demonstrate that the pO2‐independent electrical conductivity in the Mn and Y co‐doped BaTiO3 is attributed to a Fermi level pinning mechanism arising from the multivalent Mn dopant, and the background reservoir of positive charge provided by the predominant substitution of Y on the Ba sites. The enhanced degradation resistance is attributed to a reduced oxygen vacancy concentration relative to the other doping chemistries.

Varistor performance of a SnO2-based system doped with low content of SrTiO3

The search and design of new SnO2-ceramics with non-linear current-voltage behavior is quite an important task due to the possibility of their practical application as varistors, devices for the protection of electrical circuits against voltage surges. This work reports the doping impact of the low content of SrTiO3 (0, 0.05, 0.1, 0.2, and 0.4 mol%) on the microstructure and non-ohmic properties of the SnO2-Co3O4-Cr2O3-Nb2O5 system which is frequently used in varistor design. It is found that the SrTiO3-addition results in the increase of activation energy of electrical conduction and the decrease of the leakage current in obtained materials compared with undoped ceramics. The reported materials with SrTiO3-addition possess a smaller average grain size, higher porosity, and their density is lower than that of unmodified SnO2-Co3O4-Cr2O3-Nb2O5 ceramics. The highest non-linear coefficient (α = 17.24) is observed for material with 0.05 mol% SrTiO3 while for undoped ceramics it reaches only 2.68. Energy dispersive spectroscopy (EDS) revealed agglomeration of SrTiO3 which was observed in materials with 0.1–0.4 mol% of SrTiO3. The obtained results are discussed in terms of the known barrier model for varistors based on the information from dc and ac electrical measurements, scanning electron microscopy, X-ray diffraction patterns, and EDS-data.