Dielectric Studies Research Articles

Cr-doped Li-based [formula omitted]-(Beta) type hexaferrites: XRD, FTIR, XPS and dielectric evaluations for high-frequency applications

The rapid growth of electronic technology and communications have led to increase demand for high performance microwave absorbing materials. Ferrites are frequently used to absorb microwaves and protect against electromagnetic contamination. In the present study, β-type hexaferrite samples with different chemical compositions of LiFe11-xCrxO17 (x = 0.0, 0.1, 0.3, and 0.5) have been manufactured through the sol-gel auto-combustion technique. The effect of substituting Cr3+ on its structural, electrical and dielectric characteristics was examined. The XRD evaluation helped to develop a single-phase structure for all samples. The substitution of Cr3+ has changed the structural characteristics. FTIR analysis was used to investigate the vibrational properties of Cr-doped β-type hexaferrite. Two absorption bands in the infrared spectroscopy were used to indicate the tetrahedral and octahedral sites. XPS results revealed the incorporation of every metal ion related to their particular electronic states. The dielectric studies were determined in terms of frequency (1–6 GHz) and every sample behavior was described using the Maxwel-Wagner and Koop theories. Impedance analysis was utilized to study the effects of relaxation time and grain boundaries on the electrical features of the produced nanomaterials. Impedance Cole-Cole plots prove that all samples exhibit non-Debye-type multiple relaxation processes. It was observed that among all the synthesized samples, LiFe10.9Cr0.1O17 has a minimum reflection loss of −37.80 dB at 1.22 GHz. Cr-doped β-type hexaferrite results suggested using and designing hexaferrite-based nanocomposite for high-frequency absorbers in the microwave range.

Study on structural, electrical, morphological, thermal and mechanical properties of P(VdC-co-AN)/PEG polymer electrolyte for energy storage applications

Electrochemical devices play pivotal roles in fostering a sustainable future. In modern technologies, the research and development of solid electrolytes are effectively utilized in electrochemical devices. Here in, we report a solid polymer electrolyte as a separator for lithium-ion batteries. Novel synthetic polymers [ Poly (vinylidene chloride- co– acrylonitrile), Poly Ethylene Glycol] are blended with constant weight percentage of salt [lithium perchlorate (LiClO4)] and different concentrations of plasticizer [propylene carbonate (PC)] using solvent casting method. As polymer electrolyte’s ionic conductivity enhanced up to 10-4 S/cm with 4.5 V electrochemical stability at ambient temperature. Furthermore, these polymer electrolytes restrain the growth of lithium dendrites, which were entrenched via temperature-dependent impedance method. The PC influence enhances the tensile strength of polymer electrolyte (upto 56.76 MPa). Dielectric study shows the non-Debye behaviour of the prepared electrolytes. To sum up, PEG and PC incorporated polymer membrane opt-out as a separator in lithium-ion batteries.

Probing the impact of bent-core mesogen on the dielectric relaxations of ferroelectric liquid crystal

The modulation in dielectric relaxations of a conventional ferroelectric liquid crystal (FLC, SCE9) material by doping the bent-core mesogen (BCM) derived from the oxadiazole bisaniline moiety has been greatly investigated using frequency-temperature dependent dielectric spectroscopy. The application of probing ac voltage (i.e., oscillating voltage, 800 mV) has clearly shown the presence of partially unwound helical mode (p-UHM) along with Goldstone mode (GM). However, the temperature-dependent dielectric studies further demonstrate that p-UHM gets merged with GM at higher temperatures and hence becomes difficult to observe it separately. It appears that doping of BCM into FLC leads to the suppression of p-UHM at lower temperature, but with the increase in the concentration of dopant beyond a certain point, p-UHM mode reappears. Moreover, the significant decrement (∼9 °C) in SmC*-SmA* phase transition temperature of FLC with increase in the dopant BCM concentration up to 3 wt%. We believe that such studies would be certainly useful for the understanding of the plausible interaction between two different shaped mesogens (i.e., rod and bent-core) present in the mixture and could pave the way forward to the use of one type of mesogen in the modulation of the dielectric properties of other mesogen.

Molecular interactions of the antioxidant in the coolant oil for energy transformers: Dielectric and simulation studies

This research paper presents experimental and theoretical findings concerning the blending of mineral oil and vegetable oils, both with and without antioxidants. The study analyses a variety of parameters for different blends of mineral and vegetable oils, including breakdown voltage, ageing resistance, dielectric constant, viscosity, dissipation factor, surface tension, flash point, and fire point. The study was further extended to investigate the effects of varying the amount of antioxidants added to mineral oil blends with different vegetable oils. The best transformer insulating solution is found by extensive analyses that include measurements of breakdown voltage, flash point, fire point, and surface tension. This blends’ properties with antioxidant are either better than pure mineral oil or comparable to mineral oil. Density functional theory (DFT) analyses the molecular structure and dipole moment of an antioxidant. Molecular dynamics simulation method (MD) analysis of the average water residual time – periods of an antioxidant will show the stability of H-bond interactions. The primary objective of this experiment is to unveil a novel liquid-insulating material that not only excels in dielectric performance but also aligns with environmentally friendly practices.

Exploration of the structural and electrical characteristics and solar cell applications of an electrolyte membrane derived from acacia gum

The natural and eco-friendly solid-state electrolytes were prepared using varying concentrations (wt%) of ZnSO4.7H2O salt and pure acacia gum through the solution cast method. Multiple analytical methods were employed to characterize the resulting acacia gum electrolyte samples. XRD analysis confirmed the increased presence of the amorphous phase with the introduction of salt. FTIR analysis explored the formation of interlinking bands and their complex nature upon salt incorporation. The ionic conductivity was found from room temperature (RT) to 100 °C range. The optimized high ionic conductivity value was found to be 1.11 × 10−4 S/cm at 100 °C for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O, while at RT it was 1.06 × 10−5 S/cm for the same composition. Activation energy values fell within the 0.6–0.92 eV range for all samples. Complex dielectric (real and imaginary) and complex electric modulus analyses were conducted. Dielectric permittivity and electrical modulus analyses revealed a significant interaction between the segmental movements of acacia gum and salt ions. Ionic relaxation processes were explored in terms of conductivity relaxation time using the electrical modulus. The presence of a long tail in the complex dielectric modulus study indicated that the acacia-based solid electrolyte displayed favorable capacitance properties. Further, the Solar Cell (dye-sensitized solar cell) device was fabricated with (Acacia gum + ZnSO4.7H2O) electrolyte. The current density-voltage (J-V) characteristics of the prepared device were investigated. The outstanding results were optimized in the present work, Voc = 0.81 V, Jsc = 9.56 mA/cm2, Fill Factor of 0.67, and optimum power conversion efficiency ƞ = 5.17 % for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O device.

Insight into properties of sizable glass former from volumetric measurements.

Sizable glass formers feature numerous unique properties and potential applications, but many questions regarding their glass transition dynamics have not been resolved yet. Here, we have analyzed structural relaxation times measured as a function of temperature and pressure in combination with the equation of state obtained from pressure-volume-temperature measurements. Despite evidence from previous dielectric studies indicating a remarkable sensitivity of supercooled dynamics to compression, and contrary to intuition, our results demonstrated the proof for the almost equivalent importance of thermal energy and free volume fluctuations in controlling reorientation dynamics of sizable molecules. The found scaling exponent γ = 3.0 and Ev/Ep ratio of 0.6 were typical for glass-forming materials with relaxation dynamics determined by both effects with a minor advantage of thermal fluctuations involvement. It shows that the high values of key parameters characterizing the sensitivity of the glass transition dynamics to pressure changes, i.e., activation volume ΔV and dTg/dP, are not a valid premise for a remarkable contribution of volume to glass transition dynamics.

Dielectric study of low-cost porous anodic aluminum oxide (AAO) template and AAO template-copper nanowires (Cu/AAO) nanocomposites as a capacitor for energy storage

In this work, we explore the effect of increasing electrodeposition time on the dielectric properties of Cu/AAO nanocomposites. Cu nanowires are electrodeposited within the AAO template pores fabricated using a two-step anodization process. The morphology, composition, and crystalline structure are characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The dielectric properties, including the real part and the imaginary part of the effective complex relative permittivity and the effective AC conductivity of the AAO template and Cu/AAO nanocomposites, are subsequently analyzed. The results demonstrate a clear improvement in effective permittivity and effective AC conductivity of Cu/AAO nanocomposites with increasing electrodeposition time, indicating the potential for tailoring the dielectric properties of AAO templates through the incorporation of metal nanowires for advanced capacitor applications.

Temperature-dependent dielectric relaxation studies of malononitrile from 10 MHz to 30 GHz using time domain reflectometry technique

Dielectric relaxation investigations of malononitrile have been carried out at different temperatures in the frequency range of 10 MHz–30 GHz using a time domain reflectometry technique. The static dielectric constant (ε0) and relaxation time (τ), and asymmetric distribution parameter (β) of liquid malononitrile at different temperatures have been determined using the Least Squares Fit method. The intermolecular hydrogen bonding in malononitrile has also been discussed with the use of the Kirkwood correlation factor and dielectric relaxation parameters.

Dielectric Properties and AC Conductivity Studies in PEDOT-PSS/EG/GO Composites with Ultrahigh Permittivity

Dielectric Properties and AC Conductivity Studies in PEDOT-PSS/EG/GO Composites with Ultrahigh Permittivity

Spontaneous piezoeletric effect as evidence of ferroelastoelectricity in guanidine zinc sulfate crystal

The crystal of [C(NH2)3]2Zn(SO4)2 guanidine zinc sulfate was grown and its structure, dilatometric, dielectric, elastic and piezoelectric properties were studied in a broad temperature range, covering the phase transition point. The crystal undergoes a continuous phase transition at 178 K from the room temperature tetragonal phase with a space group I4¯2d\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{I}\\overline{4}2\ ext{d }$$\\end{document} to the tetragonal low temperature phase with a space group I4¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{I}\\overline{4 }$$\\end{document}. The structural X-ray studies allowed proposing molecular mechanism associated with the rearrangement in the configuration of N–H⋯O hydrogen bonds and reorientation of guanidine cations in the structure, leading to a change in the symmetry of the low temperature phase. Results of thermal expansion and dielectric studies are typical of a structural nonferroelectric continuous transition. Also measurement of piezoelectric and elastic properties revealed small anomalies at 178 K. Below the transition temperature, a new piezoelectric component, that is a ferroelastoelectric macroscopic order parameter, was found.

Ni and La substitution of Cobalt nanoferrites preparation: structural, magnetic, and dielectric studies and photocatalytic activity for waste water treatment

Ni and La substitution of Cobalt nanoferrites preparation: structural, magnetic, and dielectric studies and photocatalytic activity for waste water treatment

Effect of doping on the morphology of cerium molybdate: A mechanistic approach towards efficient energy storage and sustainable environmental mitigation through heterogeneous photocatalysis

In this paper, we describe the synthesis of cerium molybdate (Ce2(MoO4)3) and different compositions of Bi-doped cerium molybdate (Ce2-xBix(MoO4)3) where x = 0.01, 0.03, 0.05, 0.07, and 0.09, through simple co-precipitation method. The synthesized materials were optically, structurally, and morphologically characterized by various sophisticated techniques, including UV–visible, FTIR, Raman, PXRD, BET, and SEM-EDX. Upon addition of bismuth, the optical band gaps are reduced from 3.35 eV (Ce2(MoO4)3) to 2.83 eV Ce1.93Bi0.07(MoO4)3. The charge storage potential and AC conductivity of the synthesized materials were investigated through dielectric studies where the dielectric constant increased by increasing dopant concentration up to 7 %. At 20 Hz, Ce1.93Bi0.07(MoO4)3 showed a significantly greater dielectric constant (3.597 × 106) compared to undoped Ce2(MoO4)3 (3.262 × 105). Similarly, the AC conductivity of Ce1.93Bi0.07(MoO4)3 increased up to 4.758 S m−1 compared to the undoped Ce2(MoO4)3 (2.270 S m−1) at 20 MHz. The photocatalytic efficiency was investigated against diclofenac potassium, which also considerably improved by increasing bismuth content. The maximum photodegradation efficiency of 87.9 % was observed for Ce1.93Bi0.07(MoO4)3 in 180 min under UV light irradiation at optimized conditions (pH = 4, catalyst dosage = 20 mg, and initial concentration of drug = 5 mg L−1). The photocatalytic reaction followed pseudo-first-order kinetics with a rate constant of 0.0108 min−1 with stability up to five successive runs of photocatalytic activity indicating its good recyclability. These findings suggest that Bi-doped cerium molybdate could be used as a promising material for photocatalysis and energy storage devices.

Synthesis and Characterization of High Dielectric Constant Zirconia Nano-Rods for Advanced Sensors and Energy Storage Applications

This study reports the synthesis of high dielectric constant zirconia oxide (ZrO2) nanorods (NRs) via a co-precipitation method followed by calcination at 700 °C for 2 h. X-ray diffraction (XRD) confirms a mixed-phase composition of orthorhombic and monoclinic structures, while transmission electron microscopy (TEM) reveals distinct nanorods. Energy dispersive X-ray analysis (EDAX) verifies the elemental composition. Photoluminescence (PL) spectroscopy indicates band gap energy of 1.9 eV, aligning better with orthorhombic zirconia. UV–vis analysis suggests oxygen vacancy defects potentially influencing the optical properties due to the nanorod morphology. Importantly, dielectric studies show a high dielectric constant of 29 at 1 MHz, which is approximately four times higher than commercially available ZrO2.

Facile sol–gel synthesis of trivalent Al3+-Gd3+ ions co-doped nanoscale cobalt spinel ferrite for magneto-electronic applications

The magnetic spinel ferrites nanomaterials simultaneously doped with multivalent cations have gained a lot of interest from many researchers during the last decade. Also, the doping of trivalent rare-earth ions in spinel ferrites is promising for many technological applications. Considering these facts, in this work we investigated the trivalent Al3+-Gd3+ ions co-doped cobalt ferrite nanoparticles with nominal composition as CoFe2-2xAlxGdxO4 (x = 0.00, 0.03, 0.05, 0.07, 0.10). The sol–gel auto ignition route assisted by citric acid as a chelating agent was utilized to synthesize the series of nanoparticles. The Rietveld refined X-ray diffraction (XRD) patterns were analyzed to ensure the single-phase formation of nanoparticles with spinel cubic structure. The spherical-shaped grain morphology of the nanoparticles was indicated by scanning electron microscopy (SEM) images. The elemental analysis obtained by energy dispersive X-ray analysis (EDAX) revealed stoichiometric formation of the samples along with high purity. The two prominent frequency modes analogous to the spinel ferrite structure were noted in the infrared spectra assuring the successful formation of all the samples. The soft magnetic behaviour with a lower coercivity of the prepared nanoparticles was confirmed by the vibrating sample magnetometer (VSM) technique. The DC electrical resistivity plots indicated that resistivity decreases with an increase in Al3+-Gd3+ co-doping. The dielectric studies of all the samples showed increasing behaviour with an increase in Al3+-Gd3+ co-doping. All the results suggest that the Al3+-Gd3+ co-doped cobalt ferrite nanoparticles can be useful for real-world applications, specifically in nanoelectronics devices.

Second harmonic generation and reverse saturable absorption in electrospun picric Acid-PMMA nanofibers

Picric acid (PA) – polymethyl methacrylate (PMMA) nanofibers were synthesised using electrospinning technique by optimising all the required parameters. The nonlinear optical behaviour of the synthesised nanofibers was investigated along with their preliminary characterisations like morphological, structural, thermal, mechanical, dielectric and linear optical studies. The nanofibers with average diameter around ∼800 nm, were found to crystallise in Pca21 space group under the orthorhombic crystal system. The incorporation of Picric acid nanocrystals inside the PMMA nanofibers enhanced their tensile strength. Second harmonic generation imaging of picric acid embedded PMMA nanofibers was done by nonlinear microscopy and the emission was confirmed by power dependence as well as Kurtz – Perry powder technique. Nonlinear absorption studies by Z – scan technique were conducted with a Q – switched Nd: YAG laser and the nanofibers exhibited reverse saturable absorption nature at all the input intensities (0.616 × 1012 W/m2, 1.23 × 1012 W/m2 and 2.46 × 1012 W/m2) and the value of the nonlinear absorption coefficient increased corresponding to an increase in input intensity (0.98 × 10−10 m/W, 1.39 × 10−10 m/W and 1.61 × 10−10 m/W) owing to a sequential two photon absorption. Using the transmittance data optical limiting properties of the nanofibers were also analysed and the limiting threshold values (1.92 × 1012 W/m2, 1.80 × 1012 W/m2 and 1.54 × 1012 W/m2) at respective intensities were extracted. The low optical limiting threshold obtained in the present case confirms that picric acid – PMMA nanofibers can be an assured contender as optical limiters in laser safety devices.

Enhanced dielectric and electrical properties of Ba(1−x)Nd2x∕3Zr0.1Ti0.9O3 (0.00 ≤ x ≤ 0.04) electroceramics for high temperature-based energy storage devices

The demand for high-temperature endurable dielectric materials with higher thermal stability in electronic systems operating under extreme temperatures sets a significant channel for the electronic industry. This work focuses on the dielectric and impedance behavior for lead-free Ba1−xNd2x∕3Zr0.1Ti0.9O3 (BNZT); (0.00 ≤x≤ 0.04) between 300 ∘C – 400 ∘C and synthesized by conventional solid-state reaction method at optimum temperatures. Structural characterizations confirmed the tetragonal (P4mm symmetry) structure formations for the BNZT ceramics. XPS analysis confirmed the Nd-substitution at the Ba-site in the BNZT ceramics. FE-SEM study showed grain growth reduction with enhanced grain boundaries. The dielectric study showed lower dielectric loss with enhanced dielectric permittivity at high temperatures. Impedance analysis confirmed the negative temperature coefficient of resistance (NTCR) and non-Debye type behavior with higher thermal stability. Singly-ionized oxygen vacancies mainly govern the conduction process in BNZT ceramics. Enhanced dielectric and impedance properties suggest that Nd-substituted BNZT electroceramics are promising materials for applications in high-temperature-based energy storage systems.

Microcube formation and characterization of cobalt and nickel selenite dihydrate: Thermal, spectral, and dielectric insights

This paper outlines the template-free preparation of cobalt and nickel selenite dihydrate microcubes using a simple precipitation method from aqueous solutions at room temperature. Structural analysis revealed the formation of pure, well-crystallized isostructural cobalt and nickel selenite dihydrate, exhibiting monoclinic crystal systems of space group P21/n. Thermal analysis showed distinct decomposition patterns for both compounds, highlighting their thermal stabilities. The intermediate formed after water loss were stable up to ∼550 °C, and crystallized before decomposing into their respective oxides via SeO2 sublimation. Scanning electron microscopy (SEM) images illustrated the presence of irregular-sized well-defined microcubes with smooth surfaces and sharp edges, distributed across the material. The formation of these microstructures is likely driven by self-aggregation and the Ostwald ripening process. Dielectric studies on pelletized materials revealed higher dielectric constants at low frequencies with minimal dielectric loss. CoSeO3⋅2H2O exhibited higher dielectric constants than NiSeO3⋅2H2O due to the larger ionic radius of Co2+ ions, which leads to a greater degree of polarization compared to Ni2+ ions. The considerably higher dielectric constant with an insignificant amount of dielectric loss indicates the materials’ potential for applications in dielectric and microwave technologies.

Structural, optical and dielectric studies of KCl modified TeO2–Bi2O3–B2O3 glasses

Structural, optical and dielectric studies of KCl modified TeO2–Bi2O3–B2O3 glasses

Microstructural study with enhanced dielectric and magnetic properties of Cu1-xCdxFe2O4 nanoparticles prepared at low-temperature green-synthesized technique

The green elaboration tool has taken much consideration due to its consistent and economical ways of producing pure and regular dispersed NPs. The preparation tool is a simple, environmentally friendly, and cost-effective method that does not use toxic chemicals. Therefore, the biological mechanisms themselves act as a reducing agent that prevents, on the surface of nanoparticles, the adsorption of chemical agents. Therefore, we focus in this work on the bio-synthesizes and the characterization (crystallographic, magnetic, transport, and dielectric study) of Cu1-xCdxFe2O4(x = 0.0, 0.3 and x = 0.5) spinel ferrites. X-ray diffraction, transmission electron microscopy (TEM), and photoelectron spectroscopy (XRD and XPS) have been employed to study crystallographic characteristics and chemical bond formation. Surface parameters analysis was conducted using BET isotherms and validated the decreases in specific surface area in the substitution sample. The electrical investigation proves the semiconductor behavior, and the thermal activation are dominated by the small polaron hopping mechanism in the nano-ferrites Cu1-xCdxFe2O4. In addition, the prepared NPS exhibits low dielectric losses. Using the ZFC-FC and M(H) measurement techniques, important modifications in the magnetic behaviors have been detected in the elaborated nanoparticles. Accordingly, the substitution of Cu1-xCdxFe2O4 leads to transitions from ferromagnetic to superparamagnetic behaviors, the increase of the magnetic saturation, and decreased magnetic anisotropy has been shown in Cu0·7Cd0·3Fe2O4 spinel structure.

Molecular interaction and dielectric relaxation study of DMSO-Water binary mixtures using a TDR

Molecular interaction and dielectric relaxation study of DMSO-Water binary mixtures using a TDR