Nyquist Plots Research Articles

Improved performance in asymmetric supercapacitors using SnO2–MoS2 composite microspheres

This paper reported the facile synthesis of SnO2, MoS2, and SnO2−MoS2 composite material via sol-gel method with ex-situ hydrothermal method and utilized for supercapacitor applications. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis confirmed the structural and morphological features. At the same time, the electrochemical performance was analyzed by CV, CD, and well-known impedance analysis via a Nyquist plot in three-electrode assembly in KOH solution. The outcomes from the three-electrode assembly demonstrated that the SnO2−MoS2 composite material yields a high capacitance value of 415 F/g than pure SnO2 and MoS2 electrodes with the lowest resistance values, indicating the fast transportation of ions during the electrochemical process. Inspired by the optimized performance of SnO2−MoS2 composite material, an asymmetric supercapacitor was further developed with GO (graphene oxide) severed as the negative electrode and symbolized as “SnO2−MoS2||GO–KOH asymmetric supercapacitor” in aqueous solution as the electrolyte. Remarkably, a high output voltage of 1.6 V was realized coupled with a high capacitance of 102 F/g, which can be attributed to the combined energy storage performance of pseudocapacitive, and double-layer capacitance arises from SnO2−MoS2 and graphene oxide (GO), respectively. Moreover, a high specific energy of 32 Wh/kg at a maximum specific power of 5520 W/kg was achieved at excellent cycling stability of 92.2 % capacitance retention after 5000 cycles at 10 A/g. Therefore, we summarize that metal oxide can composite with metal oxide, and graphene oxide (GO) collectively boosts the overall performance of high-performance supercapacitors.

Structural, dielectric, impedance, and electric modulus characteristics of Y2CaCuO5 high-k dielectric ceramics

With the increasing trends of integrated circuit densification, device miniaturization, and exponential growth of microelectronic components there is a huge responsibility on the part of material researchers to derive, design, and develop new materials. Materials that can overcome the existing limitations in the present compounds available in the market or can expedite the process of material fabrication are of great interest. This feat can be achieved by the fabrication of new materials, and analysis of various characterizations viz. (structural, dielectric, transport behavior, and impedance spectroscopy). With this perspective, in this communication, a high permittivity dielectric material belonging to the Y-Ba-Cu-O ternary systems where barium is replaced by calcium (Y2CaCuO5) is synthesized using solid-state reaction route. X-ray diffraction, scanning electron micrograph, and energy-dispersive X-ray spectroscopic study confirm the phase and microstructure of the sample. The observed higher value of the dielectric constant is understood from Koop’s phenomenological theory and internal barrier layer capacitance model. The dispersive behavior of conductivity is interpreted by Jonscher’s power law. Overlapping large polaron tunneling model for conduction is observed. Impedance spectroscopy analysis reveals non-Debye type of relaxation with variable time constants. According to Nyquist plots; up to 250 °C only grain effect (bulk) is dominantly present; however, at higher temperatures, the contribution from both grain and grain boundary is seen.

A study about the relationships between surface structures and electrical impedance characteristics in single-walled carbon nanotube/polyester composites

The present study aims to understand the relation between impedance characteristics and fractal behaviours. The pure and single-walled carbon nanotube (SWCNT) reinforced unsaturated polyester resin (UPR)-based composite specimens were produced by the hot press process with this aim. The Nyquist variation in the neat sample shows a straight line, which can describe the great resistance in the material and its insulating nature, while the Nyquist plots of the carbon nanotube doped sample show an almost semi-circular shape, indicating the presence of electrical conductivity. In addition, fractal analysis with statistical scaling method is used to determine the relationships between the superficial heteromorphology and electrical properties of samples. The surface particle coverage rates, fractal dimensions, cluster pattern structures, Feret diameters and Feret angles were calculated for samples. Feret angle decreases indicating that the distance between clusters is decreasing as coverage ratio, fractal dimension and Feret diameter increases.

Synthesis and study of rare earth(Dy3+) doped CoCr2O4 ceramics for supercapacitor applications

Rare earth doped Cobalt Chromates are exhibits a significant interest among other materials for supercapacitors Applications. In the present work we reported Dysprosium(Dy3+) doped Cobalt Chromate(CoCr2O4) for possible application in supercapacitors. Samples were prepared by solution combustion method with the general formula CoCr2-xDyxO4 (where x = 0, 0.01, 0.03, and 0.05) using glucose and urea as fuels. As prepared samples were characterized by using “X-ray diffractometer”(XRD), “Transmission electron microscopy”(TEM), and “field emission scanning electron microscopy(FESEM) techniques to study the analytical and morphological structure of the CoCr2-xDyxO4. For the first time, the electrochemical fabrication of CoCr2-xDyxO4 were reported. Using “cyclic voltammetry”(CV), “galvanostatic charge–discharge’(GCD), electrochemical impedance spectroscopy (EIS), and cyclic stability testing, the electrochemical capabilities of CoCr2-xDyxO4 were explored in great detail. The behavior of capacitance was evaluated utilizing CV at a variety of scan speeds, GCD at a selection of constant current densities, and EIS at a selection of frequencies. CV and GCD data for tested electrodes showed their capacitive behavior. The calculated capacitance was 0.29–0.38 F cm−2. It is found increasing with Dy3+ concentration. Based on CV testing results at a scan rate of 1 mV s−1. At a current density of 3 mA cm2, the obtained capacitance was 0.21, 0.22 and 0.23 F cm−2 respectively. The analysis of the compared Nyquist plots of complex impedance revealed that the actual part of the impedance dropped as the Dy3+ content increased. This pointed to an increase in conductivity, which was advantageous for the storage of charge, as also supported by density of states calculations, which demonstrated the remarkable distribution of density of states across the fermi level after Dy3+ doping in CoCr2O4, indicating improved electronic features of CoCr2-xDyxO4.

Advanced Anticorrosive Graphene Oxide-Doped Organic-Inorganic Hybrid Nanocomposite Coating Derived from Leucaena leucocephala Oil.

Metal corrosion poses a substantial economic challenge in a technologically advanced world. In this study, novel environmentally friendly anticorrosive graphene oxide (GO)-doped organic-inorganic hybrid polyurethane (LFAOIH@GO-PU) nanocomposite coatings were developed from Leucaena leucocephala oil (LLO). The formulation was produced by the amidation reaction of LLO to form diol fatty amide followed by the reaction of tetraethoxysilane (TEOS) and a dispersion of GOx (X = 0.25, 0.50, and 0.75 wt%) along with the reaction of isophorane diisocyanate (IPDI) (25-40 wt%) to form LFAOIH@GOx-PU35 nanocomposites. The synthesized materials were characterized by Fourier transform infrared spectroscopy (FTIR); 1H, 13C, and 29Si nuclear magnetic resonance; and X-ray photoelectron spectroscopy. A detailed examination of LFAOIH@GO0.5-PU35 morphology was conducted using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. These studies revealed distinctive surface roughness features along with a contact angle of around 88 G.U preserving their structural integrity at temperatures of up to 235 °C with minimal loading of GO. Additionally, improved mechanical properties, including scratch hardness (3 kg), pencil hardness (5H), impact resistance, bending, gloss value (79), crosshatch adhesion, and thickness were evaluated with the dispersion of GO. Electrochemical corrosion studies, involving Nyquist, Bode, and Tafel plots, provided clear evidence of the outstanding anticorrosion performance of the coatings.

Investigation of the degradation of proton exchange membrane water electrolysis cells using electrochemical impedance spectroscopy with distribution of relaxation times analysis

Reduction of catalyst loading on Proton Exchange Membrane (PEM) Electrolysis Cells (EC) is needed because of scarcity and high price of the catalyst. Monitoring the degradation of these cells is important to be able to allocate the different processes taking place. Electrochemical Impedance Spectroscopy (EIS) might be suitable for this purpose, but in its usual implementation, the system and the contribution of its components to the total resistance must be already known to build a suitable equivalent circuit model (ECM). Furthermore, the overlap of different processes in the Nyquist and Bode plots hinders the identification of single components of the system. The Distribution of Relaxation Times (DRT) analysis converts the EIS data into a distribution of time constants of individual processes. The contribution of each component to the full cell resistance can be identified by varying different operation parameters. In this work, a PEMEC with low iridium loading was analyzed by DRT and the faradaic processes were identified. A long-term test was carried out and the degradation of the cell was investigated by DRT analysis, to determine the components and processes which limit the cell performance.

Power generation using hydrothermally synthesized mesoporous Mg substituted NiO based on-photo catalytic hydroelectric cell

Water-based energy production devices are fast attracting substantial scientific interest due to the ongoing search for future alternate energy supplies. Using a versatile Hydroelectric strategy, here we have demonstrated the fabrication of NiO and Mg-NiO nanoparticle-based hydroelectric cell (HECs) which works on splitting water into H+ and OH−. After the substitution of Mg in NiO BET depicts three times increase in the specific surface area (118 m2/g) of the material which provides more cross section for water splitting to occur. XPS and EPR demonstrate that after Mg substitution oxygen defects in NiO are increased which boosts the physidissociation process of water-splitting. Change in morphology from nanoplate to nanoring has been observed by the FESEM study. A decrease in the band gap from 3.3 eV to 2.2 eV has been observed by Mg substitution in NiO. The Nyquist plot demonstrates the decrease in the internal resistance from 55 Ω of the NiO to 25 Ω by Mg substitution. The Mg-NiO-based HECs deliver a high-power density of about 2.12 times (i.e., 36.5 W/m2) than pure NiO-based HECs. After Mg substitution open circuit voltage generated by HEC increased from 0.7 V to 1.1 V. This study thoroughly reveals the mechanism of magnesium substitution in NiO and proposes a feasible novel technique for meeting current energy demands.

Theoretical benchmark of structure, optical, and transport mechanism of Sm-doped double perovskite cobaltite

Double perovskite cobaltites have attracted more fascination because of their tunable functionality in optoelectronic and electronic devices. In this study, we used the Cambridge Serial Total Energy Package code under equilibrium circumstances, to examine the structural, and optical properties of Bi2Ca2-xSmxCoO6 (x = 0.00, 0.05, and 0.10). In this work, the studied samples have been prepared by co-precipitation method. X-Ray Diffraction reveals a monoclinic structure. Jonscher’s power law was employed to investigate the conduction mechanism in the synthesized samples. Nyquist plots were studied for the investigation of electrical transport properties. The maximum electrical conductivity for the Sm-doped sample was 98.3 S-cm−1.

Improved electrochemical performance of multi-walled carbon nanotube reinforced gelatin biopolymer for transient energy storage applications.

Multi-walled carbon nanotube (MWCNT) incorporated biodegradable gelatin nanocomposites (Gel/MWCNT) have been prepared following a facile solution processing method. The Fourier-transform infrared (FTIR) spectroscopy, field emission scanning electronic microscopy (FESEM), and water contact angle (WCA) measurements revealed improved structural properties and surface morphological features of the nanocomposite films due to the incorporation of MWCNT. A four-fold decrease in the DC resistivity was obtained due to the addition of MWCNTs. The specific capacitance of the nanocomposite increased from 0.12 F/g to 12.7 F/g at a current density of 0.3 μA/cm2 due to the incorporation of 0.05 wt.% MWCNT. EIS analysis and the corresponding Nyquist plots demonstrated the contributions of the different electrical components responsible for the improved electrochemical performance were evaluated using an equivalent AC circuit. The incorporation of MWCNTs was found to reduce the charge-transfer resistance from 127 Ω to 75 Ω and increase the double-layer capacitance from 4 nF to 9 nF. The Gel/MWCNT nanocomposite demonstrated improved cyclic stability with a retention of 95% of the initial capacitance even after 5000 charging/discharging cycles. The biodegradability test showed that the nanocomposite degraded completely after 30 hours of immersion in water. This fully biocompatible nature of the nanocomposites with high specific capacitance and low charge transfer resistance may offer a promising route to fabricate a nature-friendly electrode material for energy storage applications.

Exploration of temperature driven conduction process and ferroelectric properties of Mn doped GdCrO3

This work delivers the research findings of the temperature dependent DC resistivity, AC impedance and ferroelectric polarization of GdCr1−xMnxO3 (x = 0 and 0.3). Mixed valence states of Cr (Cr3+ and Cr4+) are explored using the x-ray photoelectron spectroscopy analysis. The exponential decay of DC resistivity on escalating the temperature advocates the semiconducting-like nature for the probed samples. The DC resistivity data of these samples fit well into small-polaron hopping and variable range hopping models. The impedance attributes of these samples were scrutinized over a broad spectrum of temperatures at selected frequencies. The values of the real and imaginary parts of impedance unveil substantial reduction on raising the temperature, thereby signifying the increase in conductivity of the samples. Pristine sample displays an electrical relaxation peak at 65 °C, which translates towards the lower temperature at higher frequencies. Further, the semicircular behavior of Nyquist plots at higher temperatures indicates the reduction of the charge transfer resistance. The equivalent circuits of Nyquist plots are generated using Z-view software. From these plots, it is perceived that grain boundary resistance upsurges while the grain resistance and capacitance drops upon doping. The ferroelectric measurements reveal that the coercive field (Ec) values decrease whereas the values of maximum polarization (Pm), remnant polarization (Pr) and energy storage increase in 30% doped GdCrO3. These observations establish that electrical and ferroelectric properties of GdCrO3 system can be tuned with appropriate Mn doping.

MICROSTRUCTURAL EVOLUTION AND ANTI-CORROSION CHARACTERISTICS OF AS-CAST AND LPBF PRINTED INCONEL PLATES IN SEAWATER ENVIRONMENT

Inconel 718 (IN 718) belongs to the category of nickel-based superalloys with outstanding mechanical characteristics such as high strength, better corrosion resistance, greater hardness, fatigue and wear resistance. This alloy is mostly implemented in manufacturing the components of aeroengines, nuclear reactors, space shuttles, pressurized boilers and so on. In most cases, the parts made from this alloy work in severe aggressive environments. A prolonged exposure of this alloy in such environments will pave the way for corrosion phenomenon which will minimize the service life of the components. It is reported that the parts made via additive manufacturing will exhibit better mechanical characteristics than the casted and forged parts. This work is aimed to investigate the anti-corrosion characteristics of both as-cast and LPBF printed IN 718 samples at various time intervals in the seawater environment. By means of FESEM micrographs, the microstructural evolution in both as-cast and LPBF printed IN 718 samples was analyzed. The anti-corrosion characteristics of both samples were investigated in the environment containing 3.5 wt.% NaCl (seawater) in terms of EIS and potentiodynamic polarization curves along with the corroded morphology. The results showed that the LPBF printed IN 718 samples exhibit fine cellular and columnar grains decorated with the NbC precipitates along their boundaries, whereas the casted samples have larger and coarser grains with uneven segregation of NbC precipitates. From the Tafel and EIS (Nyquist and Bode) plots, the LPBF IN 718 sample showed greater corrosion resistance in terms of current density and polarization resistance values. In particular, the 15 h LPBF sample has a strong, compact passive film formed on it. This compact passive film paved the way for this sample to exhibit lower current density (3.03 × 10[Formula: see text] A/cm2) and higher polarization resistance (3678 Ω · cm2) when compared with the LPBF and cast samples at other intervals.

Dielectric, electrochemical and magnetic properties of the hydrothermally synthesized double perovskite La2NiMnO6 for energy storage applications

Double perovskite materials are greatly appealing because of their multiferroic properties. Among such materials, double perovskite with rare earth metals are widely studied by researchers. Presently, the double perovskite La2NiMnO6 (LNMO) samples are synthesized using the hydrothermal method by varying the concentration of the solvent (NaOH). The Powder X-ray diffraction analysis confirmed the formation of monoclinic structure with the P21/n space group for prepared LNMO samples. The SEM image of the prepared samples revealed a cube-like structure. The impedance, dielectric, AC conductivity and modulus are studied in a wide frequency range from 100 Hz to 5 MHz to analyse the electrical and microstructure properties of the synthesized LNMO samples. The presence of a non- Debye type of relaxation peak is confirmed by impedance, dielectric and modulus studies. The effect of grains and grain boundaries are analysed by the Nyquist plot and the polarization of the materials are explained by the Maxwell-Wagner interfacial polarization model and Koop's theory. Using a three electrode system, the electrochemical behaviour of prepared LNMO samples are studied in various concentration of electrolyte (KOH) at different scan rates and found to have a pseudocapacitive nature. The highest specific capacitance value for LNMO10 is 44.60 F/g, LNMO20 is 50.14 F/g and LNMO30 is 25.81 F/g at a scan rate of 10 mV/s for 3 M KOH. The room temperature magnetic behaviour of synthesized LNMO samples analysed by Vibrating Sample Magnetometer paves way for magnetic storage applications.

Exploring the structural and electrical trends in Mo2+ substituted Ba0.7Gd0.3MoxF12-xO19 Hexaferrite

The investigation of structural and electrical properties of Ba0.7Gd0.3MoxF12-xO19 for x = 0.02, 0.04, 0.06, and 0.08 were synthesized using a solid-state reaction method. Dielectric study and different impedance parameters were measured at temperature ranging from room temperature (RT) to 500 °C and frequencies ranging from 20Hz to 20 MHz. XRD study confirms the presence of hexagonal P63/mmc phases. Average crystallite size of Ba0.7Gd0.3MoxF12-xO19 for x = 0.02, 0.04, 0.06, and 0.08 were found as 42.177 nm, 42.550 nm, 48.026 nm, and 55.057 nm respectively. Dielectric constant of the sample decreases (at a specific frequency) when the Mo2+ concentration increases. Two transition peaks were observed in the dielectric plot with the temperature variation, indicating multiple electrical transitions in Mo2+ substituted barium hexaferrite. The existence of one semicircle in the Nyquist plot indicates the presence of grain effect in all ceramic samples.

Oxygen diffusion impedance in proton exchange membrane fuel cells – insights into electrochemical impedance spectra and equivalent electrical circuit modeling

In Randles circuit, the oxygen diffusion impedance connects in series with the Oxygen Reduction Reaction charge-transfer resistance, implying that the Cathode Catalyst Layer (CCL) governs oxygen diffusion. The oxygen diffusion impedance can be connected in series with the ORR circuit, implying that Gas Diffusion Layer (GDL) rules oxygen diffusion. The common finite Warburg element and an alternative expression for diffusion through GDL derived by Kulikovsky were tested and compared. For this, experimental data obtained from measurements on various cells geometries, MEA types and operating conditions were used. All cases yield the same trend: the low frequency diffusion impedance in PEMFC mainly relates to the GDL, or both the GDL and the CCL, the latter to a significantly lower extent. EI spectra measured for different cathode Pt-loadings suggest that the ionomer film inside the CCL contributes rather to the high-frequency resistance, increasingly at lower catalyst loading. Hence, the physically most appropriate equivalent electrical circuit is a Kulikovsky diffusion impedance connected in series with the ORR kinetics circuit. Comparing global and local impedance spectra confirmed the significant contribution of perturbation-induced oxygen concentration oscillations to the low frequency loop in Nyquist plots: analyzing local impedance data measured near the oxygen inlet allows to minimize their impact.

Enhancing Antioxidant Activity of Curcumin Using ZnO Nanoparticles Synthesized by Electrodeposition Method

The objective of this study was to fabricate zinc oxide (ZnO) nanoparticles through the utilization of the electrodeposition technique, to employ them as a supportive medium for enhancing the antioxidant properties of curcumin. The study involved the synthesis of ZnO nanoparticles, which were subsequently subjected to characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Additionally, the antioxidant activity of the synthesized nanoparticles was assessed through the use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. In XRD analysis, a notable peak denoted by an asterisk (*) is observed at specific angles of 2θ: 25.84°, 31.63°, 34.21°, and 36.12°, with corresponding index values (h, k, l) of (220), (100), (002), and (101), respectively. This peak is indicative of the degree of crystallinity exhibited by ZnO nanoparticles. The SEM data indicates that the particles generated possess a rod-like morphology, exhibiting a range of sizes. The Nyquist plots exhibit a semicircular arc pattern at low frequencies, as indicated by the findings from the EIS test. The data obtained from antioxidant assays indicated that ZnO-curcumin achieved an inhibition level of 47.09%, while curcumin alone showed a significantly lower inhibition percentage of 4.93%.

Synchronization of theoretical and experimental studies on the enriched optical and dielectric properties of size modulated CoCr2O4 quantum dots

This work focused on the influence of annealing temperature on CoCr2O4 nanoceramics synthesized through a co-precipitation method without the aid of surfactants or templates. The study for the first time correlated the electrical and optical properties of this nanomaterial and investigated the underlying physical concepts through probable theoretical demonstrations. Structural analysis using X-Ray diffractometry, Rietveld Refinement, and FTIR spectroscopy revealed a cubic crystal structure (space group Fd-3m) and the evolution of spinel-type AB2O4 phase. The crystallite size, determined via the Debye-Scherrer method, exhibited growth from 5.2 nm to 23.7 nm due to an increase in annealing temperature from 400 °C to 600 °C. Moreover, FESEM images exhibited an increase in grain size due to nanoparticle agglomeration at elevated annealing temperatures. The direct bandgap decreased from 2.55 eV to 2.40 eV as the annealing temperature escalated. The semi-conducting nature was also verified from Band structure, DOS, and I–V analysis. Crystallinity-mediated behaviour of various optical properties and emission spectra were carefully scrutinized. Frequency and calcination temperature-dependent dielectric properties and Nyquist plot revealed MWS-type polarization and semiconducting arc-like behaviour. The Coats and Redfern model computed activation energy of the system was 24.69 kJ/mol. These findings supported the suitability of this nanomaterial in optoelectronic applications.

Transport of uncharged redox species through an organic thin film analyzed under pseudo-impermeable boundary conditions

The mathematical models that are typically employed for describing the responses of chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) of guest species that diffuse into an impermeable host material have been adapted for the case of an electrode covered with an organic thin film (TF). The mathematical solution has been used for simulating and fitting the electrochemical responses of ferrocene-methanol (FcMeOH) on the surface of a working electrode modified with a TF of highly plasticized polyvinyl chloride. The analysis of chronoamperometric profiles allows us to determine the diffusion coefficient and the concentration of the electroactive species in the TF. Also, from those values is possible to estimate values for the partition coefficient of FcMeOH between an aqueous solution and an organic film, as well as for the film thickness.The EIS responses exhibited remarkable consistency with the CA results. In the high frequency range, the TF system displayed a Warburg-type behavior, while at low frequencies, Nyquist's plot revealed a pronounced capacitive behavior due to the limited insertion of FcMeOH. The fit of CA and EIS responses yielded a set of resistance and capacitance values from which it is possible to infer that the diffusion resistance is significantly larger than the charge transfer resistance and that there are no trapping sites that could be associated with imperfections in the lattice of PVC. To our knowledge, this is the first instance where a model developed for the electrochemistry of insertion has been adapted to elucidate the partitioning of redox species between two immiscible liquids, followed by a charge transfer electrode process.

First-principles and experimental study of structural, electronic, and enhanced dielectric response in Bi2Ca1.95Sm0.05CoO6 nanoparticles

In this study, we synthesized Bi2Ca1.95Sm0.05CoO6 (BCSCO) by the Co-precipitation route. X-ray diffraction was used for structural analysis, which confirmed the monoclinic structure with space group P21/m. Here, we employ the CASTEP (Cambridge Serial Total Energy Package) approach, we conducted a theoretical investigation of the structure, electronic, and optical properties of BCSCO double perovskites. FTIR spectra, BCSCO presents three absorption bands that correspond to the Bi(Ca)-O, O-Co-O, and Co-O. The morphological study showing the agglomeration phenomenon has occurred in the synthesized sample. The AC conductivity and dielectric response have also been studied as a function of frequency (100 Hz-3 MHz) at different temperatures (100 °C-600 °C). Temperature-dependent dielectric relaxation was investigated, and employing the non-linear Debye fitting to determine the spreading factor and relaxation time. The maximum value of the dielectric constant is 2.4 × 106 at 600 °C. AC conductivity is examined at (100 °C-600 °C) using Jonscher’s power law. The model fitting shows the Overlapping Large Polaron Tunneling conduction mechanism for BCSCO. In order to explore the impact of grain barriers and interior, the Nyquist plot was utilized, and the results are inter-connected.

Impedance Spectroscopy and AC Conductivity Analysis of (Ba1−kCak)(Zr0.1Ti0.9)O3, (0.140 ≤ k ≤ 0.160), Ceramics

Ceramic pellets of (Ba1−kCak)(Zr1−zTiz)O3, (k = 0.140–0.160, z = 0.9) were prepared via solid-state reaction technique followed by double sintering. The impedance measurements were carried out at different temperatures and frequencies (12–1000 kHz). The NTCR nature exhibits the semiconducting behavior of the prepared BCZT ceramics in the measured temperature range. The temperature also has a considerable impact on the relaxing process. The characteristics of Nyquist plots show that bulk and grain boundary effects exist in BCZT ceramics. The bulk conductivity indicates an Arrhenius-type thermally activated process. The observed impedance spectra, relaxation behavior, and AC conductivity of the prepared compositions of BCZT ceramics will extend the possibilities for using this compound in various optoelectronic applications.

Surface and bulk contributions to electrical behavior of cesium lead bromide (CsPbBr3) single crystal

Halide perovskite single crystals (SCs) are becoming increasingly popular in the field of optoelectronics due to their superior properties compared to polycrystalline thin films. This is believed to be due to a lower concentration of defects in SCs. Research into the surface and bulk properties of SCs has been a focus area since their discovery. It can be challenging to investigate the surface and bulk properties of perovskite solar cells (PSCs) SCs. This study used impedance spectroscopy (IS) to differentiate between the surface and bulk electrical responses of cesium lead bromide (CsPbBr3) SCs, which is a technique that has been infrequently used in previous reports. This study examined the electrical response of CsPbBr3 solar cells (SCs) by measuring the Nyquist plots and capacitance-frequency responses under different optical excitations. The data collected under blue and red wavelengths were analyzed and compared, revealing that the photocurrent and capacitive response were stronger under blue light (λB) than under red light (λR). This systematic examination of the electrical response under different optical excitations has not been done before. This study observed that the low-frequency capacitance changes less under blue light than under red light. The reason for this difference is thought to be caused by the polarization of the interface between the metal contacts and the surface of the PSCs (SCs) or by the presence of defects in the SCs that affect conductivity. The rapid collection of carriers from the surface under λB means that they do not contribute to the increase in capacitance with temperature. As far as the authors are aware, investigations of the electrical responses of SCs, such as impedance and capacitance, under various illumination wavelengths and temperatures are uncommon in the bibliography.