Dielectric Loss Measurements Research Articles

Optical, thermal, and electrical characteristics of cashew gum/Polypyrrole/zinc oxide nanocomposites for next‐gen optoelectronics

AbstractIn this electronic era, there is a demand to switch from conventional polymers to conducting biopolymers. We developed conducting biopolymer nanocomposites of cashew gum (CG) and polypyrrole (PPy) with zinc oxide (ZnO) nanofillers [CG/PPy/ZnO] via in‐situ oxidative polymerization using a sustainable solvent. These nanocomposites were characterized using Fourier‐transform infrared spectroscopy (FTIR), UV–visible spectroscopy, field emission scanning electron microscope (FE‐SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The FTIR signal at 855 cm−1 confirms the successful inclusion of ZnO nanofillers into the biopolymer. UV–vis absorption of the blend nanocomposite increases with the nanoparticle doses. Among the various blend nanocomposites, the least bandgap energy was observed for 7 wt% ZnO loading. FE‐SEM revealed homogeneous dispersion of ZnO nanofillers in the CG/PPy blend at 7 wt% ZnO. TGA and DSC demonstrated that the CG/PPy/ZnO nanocomposites have better thermal stability and glass transition temperature than the pure polymer blend, indicating enhanced thermal properties. The CG/PPy/7 wt% ZnO showed the highest conductivity, 4.62 times greater than the pristine blend at 100 Hz. Dielectric constant, activation energy, AC conductivity and dielectric loss measurements demonstrated that the nanocomposites outperformed the pure polymer blend. Complex impedance analysis revealed increased impedance with rising temperature. Overall, CG/PPy/ZnO nanocomposites exhibit superior optical, morphological, thermal, electrical, and dielectric properties, making them promising for energy storage and optoelectronic applications.Highlights Ecofriendly synthesis of CG/PPy/ZnO nanocomposites Enhancement in optical, structural, and thermal properties of CG/PPy/ZnO Dielectric properties and temperature‐dependent AC conductivity are summarized. Blend nanocomposite shows higher AC conductivity and dielectric constant CG/PPy/ZnO nanocomposites are suitable for energy storage applications

Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films

In this study, the DBD plasma reactor has been constructed, characterized, and tested to be employed in material treatment for use in different applications. A neon power source with an output of 10 kV, 30 mA, with a frequency of 20 kHz is used to drive the DBD reactor in an atmospheric-pressure environment. The investigation covered the analysis of many parameters of the dielectric barrier discharge (DBD) reactor, including its discharge voltage, current, capacitance, consumption energy, and the light emission of the produced plasma. Also, to examine the generated DBD plasma effect, the photoemission, optical, and electrical characteristics of untreated/treated polycarbonate films were investigated using photoluminescence spectroscopy, UV/Vis spectroscopy, and electrical spectroscopy. The results demonstrated the appearance of two modes in the DBD discharge: filamentary and homogeneous. Moreover, the DBD reactor's power consumption has been measured to be 20 mW at a supplied voltage of 6.5 kV peak-to-peak, operated in atmospheric–pressure. The photoluminescence emission results emphasized that the treated films are modified particularly with increasing DBD treatment time. The UV–Vis spectra demonstrated a notable displacement of the absorption edge towards higher wavelengths as the duration of DBD exposure increased. This is indicative of the reduction of the band gap energy, thus improving the electric conductivities. The optical parameters of the treated polycarbonate films were enhanced in comparison to the untreated sample. Through the used frequency range, measurements of dielectric loss, dielectric constant, as well as AC electrical conductivity, are sensitive parameters to the modifications in electrical behaviors due to DBD plasma treatment.

Exploring the possibilities of lead-free 0.98NaNbO3-0.02BiSmKZrO3 for electrical and optical applications using solid-state method

A new lead-free ceramic materials 0.98NaNbO3 - 0.02 (Bi(1-x)Smx)0.5K0·5ZrO3, are developed with varying levels of x (mole) (x = 0.01, 0.02, 0.03, and 0.04). The conventional sintering process involves adjusting the ratio of the constituent elements to optimize the material's properties. This results enhanced electrical conductivity and improved optical properties. Our findings show that the material exhibits an orthorhombic phase at x (mole) levels between 0.01 and 0.04. The FESEM and TEM analysis provided detailed information about the surface morphology and internal structure of the NaNbO3 ceramic materials. Additionally, the UV–Vis absorption spectra indicated that the band-gap range of 3.3 eV (± 0.04) (at x = 0.01–0.04) makes these materials suitable for various optoelectronic applications Furthermore, the luminescence behaviors of Sm3+ doped NaNbO3 materials were found to be influenced by the co-doping of Bi3+. Additionally, the dielectric constant (εr) and dielectric loss (tan δ) measurements indicated that the material undergoes two phase transitions from antiferroelectric to paraelectric within a temperature range of 120–250 °C. The investigation also compared the material's electric features, such as piezoelectricity and ferroelectricity, with its leakage current. The results showed that the co-doping of Bi3+ not only influenced the luminescence behaviors but also had an impact on the material's electrical properties. The synthesized proposed system 0.98 NaNbO3 - 0.02BiSmKZrO3 material also demonstrates excellent optical properties, with a high color purity of 80–81 % at x-0.02 under a 407 nm excitation wavelength. Additionally, the estimated color coordinates of the material fall within the reddish-orange domain, further enhancing its visual appeal.

Dielectric and thermodynamic investigation of heterocyclic compound Indole-3-Carbinol (I3C) using time domain reflectometry

The present work aims at the study of dielectric relaxation spectroscopy, which involves the measurement of dielectric loss and dielectric permittivity of Indole-3-carbinol in (Dimethyl Sulfoxide) DMSO over the frequency range of 10 MHz to 50 GHz. Two relaxation modes were observed for the studied system. Low-frequency relaxation mode is observed at the frequency of about 80–100 MHz, which is attributed to Indole-3 Carbinol (I3C) molecules, and high-frequency relaxation is observed at about 6–7 GHz, which is due to DMSO molecules. The structural properties of I3C have been studied through dielectric parameters such as dielectric constant (εi), relaxation time (τi), distribution parameters, dipole moment, Kirkwood correlation factor (g), and number of DMSO molecules irrotationally bound to I3C molecules (Zib), and the results have been expressed in terms of molecular interaction between solute–solute and solute solvent (I3C and DMSO) molecules. The results obtained using dielectric spectroscopy are corroborated by the thermodynamic parameters.

Measurement of Dielectric Loss in Silicon Nitride at Centimeter and Millimeter Wavelengths

This work presents a suite of measurement techniques for characterizing the dielectric loss tangent across a wide frequency range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 1 GHz to 150 GHz using the same test chip. In the first method, we fit data from a microwave resonator at different temperatures to a model that captures the two-level system (TLS) response to extract and characterize both the real and imaginary components of the dielectric loss. The inverse of the internal quality factor is a second measure of the overall loss of the resonator, where TLS loss through the dielectric material is typically the dominant source. The third technique is a differential optical measurement at 150 GHz. The same antenna feeds two microstrip lines with different lengths that terminate in two microwave kinetic inductance detectors (MKIDs). The difference in the detector response is used to estimate the loss per unit length of the microstrip line. Our results suggest a larger loss for SiN <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{x}$</tex-math></inline-formula> at 150 GHz of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\mathrm{\tan \delta \sim 4\times 10^{-3}}}$</tex-math></inline-formula> compared to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathrm{2.0\times 10^{-3}}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathrm{\gtrsim 1\times 10^{-3}}$</tex-math></inline-formula> measured at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 1 GHz using the other two methods. These measurement techniques can be applied to other dielectrics by adjusting the microstrip lengths to provide enough optical efficiency contrast and other mm/sub-mm frequency ranges by tuning the antenna and feedhorn accordingly.

Computationally driven design of low dielectric-loss epoxy resin for medium-frequency transformers

The design of low dielectric-loss epoxy resin (EP) systems plays an important role in the insulation optimization of medium-frequency transformers (MFTs). Due to the diversity of EP and curing agents, the traditional design method inspired by dielectric-loss measurements cannot complete low dielectric-loss EP systems design in plentiful candidate EP systems. In this study, molecular dynamics (MD) computation was introduced to drive the design of a low dielectric-loss EP system for MFTs. By analyzing the relationship between the dielectric loss and molecular motion of the EP systems, two MD results were selected as descriptors to indicate the dielectric loss of EP systems, including mean square displacement and α-transition temperature. Eventually, the low dielectric-loss EP system blending EP, methyl tetrahydrophthalic anhydride, and dodecenyl succinic anhydride was effectively designed according to the descriptors. The rationality of the computationally driven design was verified by broadband dielectric spectroscopy measurement and the finite element method. Compared with previous EP systems, MFT insulated with the designed EP system had not only a 40% lower dielectric loss (9.79 W) but a higher overload capacity. This study provides an effective method for the design of low dielectric-loss EP systems.

Precision Measurement of the Microwave Dielectric Loss of Sapphire in the Quantum Regime with Parts-per-Billion Sensitivity

To better understand decoherence in superconducting qubits, the authors develop a technique to measure the loss tangent of dielectric substrates and predict the impact of dielectric loss on qubit lifetimes. This is done with no need to fabricate planar devices; the technique is independent of material platform. Measurements of sapphire in a demonstration of the approach suggest that coherence of superconducting qubits on a common form of sapphire is limited significantly by bulk dielectric loss. The same technique also shows that another form of sapphire would substantially mitigate this bulk dielectric loss and prolong qubit coherence.

Effect of Gamma Irradiation on Dielectric and AC Conductivity Studies of Bismuth Borate Glasses Doped with V2O5

Objectives: To study gamma ray irradiation effect on dielectric and AC conductivity of V2O5 doped bismuth borate glasses designed with the compositions 50B2O3-(50-X)Bi2O3-XV2O5 where, X = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and establishing the conduction mechanism. Methods: Glasses were synthesized by traditional melt quenching technique at 1323K. The prepared samples were subjected to annealing at 623K, which helps to remove strain in the samples. Absence of crystalline phases in the samples was confirmed by X-ray diffraction studies. An independent measurement of dielectric constant, dielectric loss and AC conductivity was carried out for temperature range from 300Kto 493K by impedance analyzer. Findings: The physical properties of glass were achieved by studying the density and the molar volume. Dielectric constant (e ’) and dielectric loss (e ”) were measured as a function of temperatures in the range from 300K to 493K, over the frequencies 102 Hz – 106 Hz before and after gamma ray irradiation. AC conductivity (s AC) of the glasses was measured as a function of frequency for different temperatures before and after gamma ray irradiation. Novelty: For the first time, it was attempted that the effect of gamma ray irradiation on dielectric and AC conductivity properties of bismuth-borate glasses doped with vanadium oxide has been investigated. Here we have observed the change in the variation of dielectric constant, dielectric loss and AC conductivity with frequency and temperature before and after gamma ray irradiation. The borate network becomes more compact after being exposed to gamma rays, and the energy band gap may even narrow. Furthermore, it has been found that the composition of the glass influences how radiation impacts conductivity. Keywords: Oxide Glasses; XRD; Gamma Ray Irradiation; Dielectric Properties; AC Conductivity

Effective Electrical Properties and Fault Diagnosis of Insulating Oil Using the 2D Cell Method and NSGA-II Genetic Algorithm.

In this paper, an experimental analysis of the quality of electrical insulating oils is performed using a combination of dielectric loss and capacitance measurement tests. The transformer oil corresponds to a fresh oil sample. The paper follows the ASTM D 924-15 standard (standard test method for dissipation factor and relative permittivity of electrical insulating liquids). Effective electrical parameters, including the tan δ of the oil, were obtained in this non-destructive test. Subsequently, a numerical method is proposed to accurately determine the effective electrical resistivity, σ, and effective electrical permittivity, ε, of an insulating mineral oil from the data obtained in the experimental analysis. These two parameters are not obtained in the ASTM standard. We used the cell method and the multi-objective non-dominated sorting in genetic algorithm II (NSGA-II) for this purpose. In this paper, a new numerical tool to accurately obtain the effective electrical parameters of transformer insulating oils is therefore provided for fault detection and diagnosis. The results show improved accuracy compared to the existing analytical equations. In addition, as the experimental data are collected in a high-voltage domain, wireless sensors are used to measure, transmit, and monitor the electrical and thermal quantities.

Comparison of Methods to Detect Thermomechanical Ageing of the Insulation System for Rotating High-Voltage Machines

Increased dynamic operation of long rotating high-voltage machines as well as elevated operating temperatures lead to intensified thermomechanical stress in the insulation system of global vacuum-pressureimpregnated machines. Meanwhile, the requirements regarding reliability of the machine and the electric insulation system remain high. Consequences of thermomechanical stress include delaminations and abrasion. To satisfy the high standards of longevity, reliable diagnosis of thermomechanical ageing is essential to allow manufacturers to develop and improve countermeasures. This work identifies diagnostic tools, which investigate the effects of thermomechanical ageing on model replicates of machine insulation systems. The longitudinal thermal expansion of the conductor during dynamic operation is replicated by applying mechanical force to the conductor of specimens, thus inducing mechanical stress in the insulation system. Recurring measurements of partial discharges, dielectric losses and capacitance are evaluated regarding their sensitivity in detecting resulting ageing phenomena. The study reveals that partial discharge measurements detect preliminary damages before insulation rupture caused by mechanicalstress occurs. Knowledge of these capabilites enables future-oriented development of insulation systems for dynamically-operated long rotating machines.

Multi-stress Cyclic Testing of Roebel Stator Bars for Hydropower

A multi-stress test rig was built to investigate the effect of many start-stops (load cycling) on hydropower generator insulation. To emulate real-life start-stops, stator bars were subjected to accelerated temperature cycling by circulating a 3.5 kA current and then cooling down with fans while high voltage (service voltage) was applied simultaneously to the insulation. A total of 250 load cycles were applied. Partial discharges (PD) were recorded on-line during load cycling, and after every 50 cycles, off-line dielectric loss and PD measurements were conducted. There was an apparent increase in dielectric losses after they had been subjected to a total of 250 load cycles. During load cycling, the PD level generally decreased with temperature, but there was a temporary increase in the PD activity during temperature rise and fall. This trend can be explained by different thermal expansion in copper and insulating material (epoxymica), suggesting that a stator bar that is load-cycled will be exposed to substantially higher PD levels than a stator bar under a uniform load and temperature, leading to further deterioration of the insulation quality.

Identification of saline landscapes from an integrated SVM approach from a novel 3-D classification schema using Sentinel-1 dual-polarized SAR data

This study presented an integrated SVM classification method that investigated the relationship between intrinsic scattering attributes of the surface features and the conductivity characteristics of the soil in the newly proposed two- and three-dimensional classification (2D and 3D) schema to classify the saline landscape. The study was conducted in the Vellore district, Tamil Nadu, which is composed of heterogeneous saline landforms due to the active geological processes and anthropogenic activities. The intensity products of Sentinel-1 data (VV + VH) of C-band frequency were employed in the present study. The SVM with linear kernel has outperformed the other models, namely random forest (RF), naive Bayes (NB), and K-Nearest Neighbour (k−NN), in performing the broad level of classification from the 2D classification schema (SVMOA = 84.2%, RFOA = 80.4%, k-NNOA = 78.8%, NBOA = 68.4%). The soil EC values derived from the dielectric loss measurements (R2 = 0.79, ρ = 0.018, and α=95%) were used to introduce the integrated SVM approach in the 3D schema to further breakdown the mapped classes into non-saline (NS) (soil EC ≤ 2 ds/cm), slightly saline (SS) (soil EC = 2.1 to 4 ds/cm) and moderately saline (MS) (soil EC = 4.1 to 8 ds/cm) categories. The overall performance of the integrated SVM approach implemented for the 3D classification schema (F1 = 0.80) was found to be satisfactory, but with an associated uncertainty majorly from MS (Precision = 0.52, F1 = 0.69), SS (Recall = 0.09, F1 = 0.15), and NS waterbodies (Recall = 0.18, F1 = 0.29) as shown in the Precision-Recall graph (AUCPR3D = 0.62). However, with the promising performance level demonstrated for the other nine classes such as NS, SS, and MS wet soil (F1 = 0.92, 0.92, 0.96), healthy plants (F1 = 0.83), salt-tolerant plants under SS and MS conditions (F1 = 0.83, 0.88), and waterlogged vegetation under NS, SS, and MS conditions (F1 = 0.82, 0.83, 0.83), the proposed classification scheme becomes an effective method to map saline and non-saline features from dual-polarimetric SAR data.

Medium and Low Voltage Cable Measurements - TD, PD, LIRA

Elmont d.o.o. Krško – We have spread our main scope of the services from electrical maintenance, modifications implementations and quality control to cable testing area. The main reason for expanding our scope was to support Nuclear Power Plant Krško Cable Aging Management program and the world trend of LTE (Life Time Extension) in power plants. Scope of work – We are identifying potential downgraded conditions for safety and operational important cables in special areas (heat, water, radiation). Our main scope is visual control, and testing with analysis. For low voltage cables the main testing method is Line Resonance Analysis (LIRA). LIRA technology is based on the transmission line theory, through the estimation and analysis of the complex line impedance as a function of the applied signal frequency. We can monitor the global, progressive degradation of the cable insulation due to harsh environment conditions (high temperature, humidity, radiation) and detect local degradation of the insulation material due to mechanical impacts or local abnormal environmental conditions. For medium voltage cables we are using new methods with a power generator that uses Very Low Frequency – 0,1Hz (VLF). The main reason for this is that the measurement unit needs 500 times less energy than the unit which uses 50Hz frequency (50/0,1=500). With this power source we are performing dielectric loss measurements – Tan delta (TD) and Partial discharge measurements (PD). TD measurements show the severity of Water treeing in the measured cable. Water trees mainly come from moisture and are therefore present in cables that lie in manholes filled with water or they submerged in any other way. PD measurements show the severity of voids or other types of defects in cable insulation. These defects can arise during the manufacturing of the cable or they can arise during the installation of the cable or from an accident with the cable during the operational time.

A method for locating and diagnosing cable abrasion based on broadband impedance spectroscopy

Modern power systems contain different types of cables and that makes it important to diagnose defects before they result in faults. Existing cable inspection methods, such as dielectric loss measurement and partial discharge, still fail to detect and locate weak cable defects. This paper presents a novel non-destructive method for detecting wear and aging defects based on broadband impedance spectroscopy (BIS) is proposed. A digital model of the cable distribution parameters is developed in this paper. The effects of different angular wear defects on the impedance spectroscopy were compared, and the degree of defects was successfully distinguished by discrete Fourier transform (DFT). The severity of the defect can be determined from the difference in peak height at the defect location after normalization. By using DFT and the Chebyshev Window it was also possible to identify two defects in the cable within 0.47% deviation of the defect position.

Dielectric properties of PVDF-PZT composite films and their thermal dependence

Piezoelectric polymer-ceramic composite materials are promising candidate for transducer application because of their inherent capability of combining the favourable properties of both ceramic and polymer materials. Present work discusses the dielectric properties of such composite films developed from two piezoelectric materials viz. Poly(vinylidene fluoride) (PVDF) as a matrix and Lead Zirconate Titanate (PZT) as filler in PVDF. PVDF-PZT composite films were prepared by solvent casting method followed by hot pressing for better packing and connectivity of ceramic phase in the composite and hence improved piezoelectric properties in the material. The dielectric parameters of these films are evaluated by the measurement of dielectric constants (ε¢ and ε¢¢), intrinsic impedance, capacitance and dielectric loss, etc. as function of frequency at room temperature. The temperature dependence of the dielectric properties is studied as well from 40˚C to 75˚C. It was found that dielectric properties like permittivity and capacitance were quite stable in the frequency range 100 Hz-100 kHz. A variation of 20 to 50% in dielectric properties was observed, for increase in temperature with respect to room temperature, which may be accounted to pyroelectric behaviour of material.

Structural and tunable dielectric properties of cobalt ferrite-based nanocomposites

Nanocomposites C:S-1:4 comprising cobalt ferrite (CoFe2O4), strontium ferrite (SrFe12O19) and C:B-1:4 containing cobalt ferrite (CoFe2O4), barium ferrite (BaFe12O19) were synthesized in weight ratios of 1:4 by chemical co-precipitation route with higher content corresponding to SrFe12O19 and BaFe12O19. Rietveld refinement was employed to confirm the presence of independent CoFe2O4, SrFe12O19 and BaFe12O19 phases. The average crystallite size of CoFe2O4 and SrFe12O19 in C:S-1:4 was observed as 20 nm and 56 nm which depicts an increase as compared to individual components. The observed lattice strain in C:S-1:4 was 0.05% and 0.03% for CoFe2O4 and SrFe12O19. In C:B-1:4, the value of strain was 0.06% and 0.04% for CoFe2O4 and BaFe12O19. Increased lattice strain was observed in the prepared composites. Increase in impedance for the prepared composites was observed from measurements performed in the frequency range 20 –106 Hz. Conduction mechanism was explained by overlapping large polaron tunneling model. Dielectric loss measurements for the prepared composites were observed to decrease establishing their usage in microwave applications.

Dielectric responses and stimulative optical shuttering action of self-assembly supramolecular hydrogen bond liquid crystalline formation via x- and y-types benzoic acids

Investigations of a single hydrogen bonded liquid crystals are made between alkyloxy benzoic acids (x-BOA) and alkyloxy benzoic acids (y-BOA) and are discussed in the present investigation. Type of mesogenic phases exhibited are visualized and recorded with the help of a Polarizing Optical Microscopy (POM). Conventional phases such as ‘Nematic’ (Nematic droplets, ‘Schlieren’ or threaded textures, four brush textures), ‘Smectic C’ (Schlieren and broken focal conical texture), ‘Smectic F’ (chequered board texture) and ‘Smectic G’ (multi colored smooth mosaic texture) are observed. Newly investigated textural phases viz., ‘Smectic X’ (‘worm’ like texture) is also characterized to elucidate their structure. Phase diagrams are constructed to study in detail the thermal stability, occurrence and thermal span of the phases as a function of the chemical constitution of hydrogen bonded (HB) complexes. Thermal analysis include analysis of Differential Scanning Calorimetry (DSC) thermograms, study of the order of the transition by Navard & Cox parameter and construction of the relevant phase diagrams. Electrical attempts include measurement of permittvity and dielectric loss with respect to the electrical stimulus applied and light intensity profile analysis.

Development of three-in-one equipment for withstand voltage, partial discharge and dielectric loss

Many major accidents in domestic and foreign power grids were caused by cable defects, causing huge economic losses and adverse social impacts. At present, the three main tests for cable testing are withstand voltage test, dielectric loss measurement and partial discharge measurement, which require different equipment for testing, which is low in efficiency and time-consuming. Among them, the very-low frequency method is suitable for the withstand voltage test, and the damped oscillatory wave method is suitable for the measurement of dielectric loss and partial discharge. This paper is based on very-low frequency cosine square wave and damped oscillatory wave technology, implements technology integration, and realizes the three-in-one detection of withstand voltage, dielectric loss, and partial discharge for cable.

Non-stoichiometric zinc ferrite nanostructures: Dielectric, magnetic, optical and photoelectrochemical properties

Spinel zinc ferrite nanostructures possess incredible dielectric and magnetic properties due to the presence of oxygen vacancies, cation distribution and surface spin disorder. However, the mechanism behind the photoelectrochemical properties is seldomly investigated. Herein, we report the influence of zinc non-stoichiometry on the optical, dielectric, magnetic and photoelectrochemical properties of zinc ferrite by preparing polyvinylpyrrolidone (PVP) coated and uncoated ZnxFe2O4±δ (x = 1, 0.98 and 1.02) nanostructures synthesized via the hydrothermal method. X-ray diffraction showed the formation of a single-phase spinel structure of all the samples. FTIR spectroscopy confirmed the formation of the metal oxide with two of its fingerprint vibrational bands detected near 550 cm−1 and 400 cm−1. Moreover, a decrease in bandgap (Eg) and the saturation magnetization values were observed for Zn-deficient samples. The dielectric constant and dielectric tangent loss measurement showed similar dielectric behavior for all the ZnFe2O4 samples. The variation in dielectric permittivity and dielectric tangent loss, with the concentration of zinc, were found to be in good agreement with Koop’s phenomenological theory of dielectric dispersion. The photoelectrochemical (PEC) characterization of the prepared samples was investigated for hydrogen production under visible light irradiation. It was found that the 2% Zn-deficient electrode (higher photocurrent density, −0.336 V flat-band potential and 1575 Ohm charge transfer resistance) increased PEC water oxidation activity compared to pure and excess ZnFe2O4 electrodes. The deficiency of Zn increased the majority carrier concentration and surface defects, which in turn improved the surface charge separation efficiencies. The results give a new perspective on the importance of zinc ferrite as a catalyst to synthesize photoelectrodes for efficient solar energy conversion devices.

Bulk growth of Iminodiacetic acid single crystal and its characterization for nonlinear optical applications

A bulk size transparent nonlinear organic single crystal of Iminodiacetic acid was harvested using slow evaporation solution growth technique in controlled atmosphere with a span of 4 weeks. The structural properties of titled crystal were examined by single-crystal X-ray diffraction. The quality of the ingot was determined by high-resolution X-ray diffraction and found that the sample is free from grain boundaries. From UV–Vis analysis, one can understand that there is less absorption in the entire wavelength range of visible region and observed cut-off wavelength is 242 nm. From photoluminescence analysis, the emission of wavelength is identified at 421 nm. Mechanical strength and various parameters like work-hardening coefficient and stiffness constant of ingot was measured using Vickers microhardness test and corresponding experimental data had been explained using distinct theoretical models. The variation measurement of dielectric constant and dielectric loss in respect of frequency was carried out to compute the electronic polarizability of titled compound using Penn model. The detailed analysis of third-harmonic generation was executed using Z-scan method. The values of nonlinear refractive index (n2) and two photon absorption coefficient (β) were obtained to be 2.19 × 10−17 cm2 W−1 and 4.25 × 10−12 cm W−1, respectively. The higher value of coupling factor suggests nonlinear absorption is more dominant and the crystal is suitable for optical limiting application.