Dielectric Behavior Research Articles

Exploring dielectric and electrical characteristics in Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 nanocomposites

This study examined the morphological, structural, electrical, and dielectric characteristics of hard-soft (H-S) Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 (x ≤ 0.10) ferrite nanocomposites (NCs), created using one-pot sol-gel combustion route. This study systematically investigated the electrical/dielectric features of H-S Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 NCs where x is within the range of 0.00 ≤ x ≤ 0.10. The examination realizes frequencies that reach 3.0 MHz, conducted within 20 °C–120 °C. A detailed analysis was performed to investigate various conduction mechanisms linked with dielectric constant, dissipation factor, AC/DC conductivity, loss of dielectric capacity, and real/imaginary modulus, which were explored across the entire range of Sn ion substitution ratios. Observations reveal that the conductivity variations adhere to power law dynamics concerning frequency, predominantly influenced by the Sn ion substitution ratios within the NCs. Furthermore, the frequency dependency of the dielectric coefficient across all NCs substantiates the common propagation of dielectric behavior, prominently contingent upon the substitution ratio of "x". Notably, the majority of dielectric parameters observed in H-S Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 (x ≤ 0.10) NCs are attributable to grain-to-grain boundaries, elucidated by conduction mechanisms similar to those observed in most compositional ferrites, explicable through Koop's model.

Investigation of electrical, dielectric and multiferroic properties of 0.7Bi0.95Sm0.05Fe1-xGaxO3-0.3BaTiO3 composite ceramic system for high temperature piezoelectric applications

Lead-free composite ceramics, 0.7Bi0.95Sm0.05Fe1-xGaxO3-0.3BaTiO3 (BSFGx-BT), were made using a solid-state reaction method for x = 2.5, 5, 10, 15, and 20 %. We have investigated the effects of Samarium (Sm) and Gallium (Ga) co-doping on the crystal structure, topography, spectroscopy, electrical and multiferroic characteristics of the 0.7BiFeO3-0.3BaTiO3 (0.7BFO-0.3BTO) system for piezoelectric applications. The structural results indicate that the composite ceramics exhibited rhombohedra R and tetragonal T phases characterized by R3c and P4mm space groups, respectively which was also further confirmed by X-ray Rietveld refinement pattern analysis. In dielectric behaviour study high Curie temperature of 550 °C was obtained with high temperature stability. Furthermore, the study investigated the effects of grain and grain boundaries on capacitive and resistive properties. The ceramics displayed the characteristics of the negative temperature coefficient of resistance (NTCR). It was observed that as the Ga concentration increased, the grain resistance (Rb) also increased, reaching its maximum value for x =10 %. Additionally, at higher temperatures, this composite exhibited lower electrical resistivity. Importantly, the ceramics showed the co-existence of ferromagnetic and ferroelectric behaviour with the enhanced values of remanent magnetization (Mr)= 0.043 emu/g, coercivity (Hc) = 5730 Oe and remanent polarization (Pr) = 6.07 µC/cm2, coercive field (Ec) = 6.78 kV/cm for the composition x =10 %. These findings suggest that Sm & Ga incorporated 0.7BFO-0.3BTO composite ceramics can show promising high-temperature piezoelectric applications.

A comparative study of influence of isovalent and aliovalent A-site substitutions on the structural, magnetic, and dielectric properties of Sr2CrMoO6 double perovskites

We report on a comparative study of the structural, magnetic, and dielectric and properties of isovalent and aliovalent A-site substituted Sr2-xAxCrMoO6 (A = Ca, x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.8, 1.0; A = K, La only x = 0.5) double perovskites, which were synthesized via sol-gel process. X-ray diffraction patterns and Rietveld refinements demonstrated that all the Sr2-xAxCrMoO6 powders crystallized in a cubic crystal structure with space group of Fm3‾m. SEM images revealed that the Sr2-xAxCrMoO6 powders exhibited a spherical morphology. Their chemical compositions were determined by quantitative energy dispersive X-ray spectroscopy, which were close to the nominal values. FTIR spectra analyses verified the presence of (Cr, Mo)O6 octahedra in these powders. XPS spectra validated the existence of Sr2+, K+, Ca2+, La3+, and Cr3+ ions in the powders, and oxygen existed in the forms of lattice oxygen and absorbed oxygen respectively, whereas Mo element had a mixed chemical valence state of Mo4+ and Mo6+. The Sr2CrMoO6 (SCMO) powders had a saturation magnetization (MS) of 0.016 μB/f.u. at 2 K, magnetic Curie temperature (TC) of 337 K, and irreversibility temperature (Tirr) of 329 K where the zero-field cooled (ZFC) and field-cooled (FC) magnetization (MZFC and MFC, respectively) curves became bifurcated. A spin-glass behavior was observed at temperature (TB) of 81 K. Both Tirr and TB shifted towards low temperature with increasing the external magnetic field. In addition, the MZFC and MFC curves became almost overlapped under the external field of 50 kOe, and the spin-glass behavior disappeared. The M-H data demonstrated that both isovalent and aliovalent A-site substitutions could improve the magnetic properties and B-site ordering degree (η) of the SCMO powders. However, isovalent Ca-substitution exhibited more significant enhanced effect on the magnetic properties in comparison with the aliovalent A-site substitutions either by K- or La-substitution. Among the isovalent Ca-substituted Sr2-xCaxCrMoO6 (x = 0.1–1.0) powders, Sr1.2Ca0.8CrMoO6 sample had a maximum MS value of 0.64 μB/f.u. at 2 K, over 30 times enhancement of that of the pristine SCMO powders. The Sr2-xAxCrMoO6 ceramics exhibit a strong frequency dependent dielectric behavior, which can be well interpreted by Maxwell-Wagner relaxation model. The anomalous dielectric relaxor behavior of the SCMO ceramics observed at 260 K was ascribed to the jumping of the electrons trapped in a shallower energy level created by oxygen vacancies. The dielectric constant of the isovalent Ca-substituted Sr1.5Ca0.5CrMoO6 samples was 30 times larger than that of the pristine SCMO samples. Our present results demonstrate that isovalent Ca-substitution at A-site could improve the magnetic and dielectric properties of the sol-gel derived SCMO double perovskite oxides, which have potential applications in the fields of spintronic devices and dielectric devices.

Temperature-induced dielectric and electrical behavior of Cs/HPC-copper vanadate nanocomposites

This study investigates the effects of temperature exposure on the dielectric and electrical properties of Cs/HPC-copper vanadate nanocomposites. The results indicate a direct correlation between the increase in polymer surface roughness and the amount of incorporated copper vanadate nanoparticles. The real dielectric constant and imaginary dielectric constant exhibited a notable increase at lower frequencies, which was attributed to interfacial polarization. At higher frequencies, the decrease was due to space charge polarization. The incorporation of copper vanadate nanoparticles resulted in a significant enhancement of both the real dielectric constant and imaginary dielectric constant highlighting the crucial role of these nanoparticles in the electrical properties of the nanocomposites. The impedance (Z′) and impedance (Z′) measurements indicate a decrease in Z″ with increasing frequency and temperature, suggesting enhanced ionic conductivity and interfacial polarization. The Cole–Cole plots reveal that the dielectric relaxation process in the Cs/HPC-copper vanadate nanoparticles (NPs) follow the non-Debye model. The results provide insights into the charge-transport mechanisms in these nanocomposites and highlight the importance of temperature in controlling their electrical properties.

Langmuir adsorption model to assess the impact of silane coupling on nano-dispersion of silica in SBR

Surface active agents are often used to improve dispersion of nanoparticles. Quantitative correlation between these surface-active molecules and nanoscale dispersion is absent from the literature partly because a quantitative measure of nanoscale dispersion does not exist. Recently, we have developed the Virial-van der Waals method to quantify dispersion in nanocomposites using virial coefficients. In this paper, the Langmuir adsorption model is used to quantify the influence of surface-active agents on nano-scale dispersion in terms of the effective second virial coefficient B2∗. The impact of silane coupling agent on the nano-dispersion and silica aggregate structure in precipitated silica/SBR nanocomposites is demonstrated. It is shown that the higher viscosity SBR matrix led to a greater silica aggregate structural breakup, while lower viscosity matrix improved surface silanization. The isomeric content of the SBR, which impacts the dielectric behavior, impacted whether the system could be modeled through a mean-field or specific interactions. We earlier showed that larger aggregates improve dispersion, and this is reaffirmed in these results. After account is made for aggregate size, nano-scale dispersion improves with the addition of silane coupling agent. The behavior is well modeled using Langmuir monolayer adsorption.

Comprehensive electrical properties and thermal stability of PNT-xPZ-PT ceramics via composition optimization

The structure, electrical properties, and thermal stability of 2 mol% MnO2-doped 0.12Pb(Ni1/3Ta2/3)O3-xPbZrO3-(0.88-x)PbTiO3 (abbreviated as PNT-xPZ-PT-Mn, x = 0.41, 0.42, 0.43, 0.44) ceramics were systematically investigated to analyze the impact of varying PZ content within the range of 0.41–0.44. In addition, the high temperature polarization method was employed to achieve enhanced electrical performance. Notably, optimized electrical properties of d33 = 400 pC/N, Qm = 757, FOM = 3.0×105 pC/N and kp = 0.616 were obtained for the PNT-0.43PZ-PT-Mn ceramics. The enhanced electrical properties observed in this study could be attributed to the presence of dielectric relaxor behavior, and the manifestation of ferroelectric hysteresis effects. In particular, d33 and kp values exhibited a consistent trend from the room temperature to the Curie temperature, thereby indicating the remarkable thermal stability of PNT-0.43PZ-PT-Mn ceramics. This study presented a systematic approach to enhance the properties of PZT-based materials.

Remarkable Dielectric Breakdown Strength of Printable Polyelectrolyte Photopolymer Complexes.

Polymer-based dielectrics are struggling to keep pace with the increasing demands of modern electronics. This lag in dielectric performance has spurred significant interest in the production of advanced dielectrics via novel chemistries and processing techniques. Polyelectrolyte complexes (PECs) have recently shown great promise as dielectric insulation, but processing challenges presented by these ionically bound networks limit their use to conformal thin films. Recent advances have enabled the additive manufacturing of PECs with vat photopolymerization, allowing the creation of a polyelectrolyte complex of arbitrary shape. Herein, multiple polyelectrolyte resin formulations, comprised of polyethylenimine and methacrylic acid (with varying amounts of 2-hydroxyethyl methacrylate and/or N,N-dimethylacrylamide), are investigated for the production of additively manufactured dielectric insulators. These dielectrics not only possess high dielectric breakdown strengths (>300 kV/mm), but their dielectric behavior can also be readily tailored through resin formulation and post-processing conditions. The presented vat photopolymerization of PECs allows for the creation of bulk dielectrics with arbitrary geometry, while the novel chemistry provides a practical route forward to produce dielectrics with precisely tailored properties for specific applications.

A wideband model to evaluate the dielectric properties of biological tissues from magnetic resonance acquisitions

Objective. Aim of this work is to illustrate and experimentally validate a model to evaluate the dielectric properties of biological tissues on a wide frequency band using the magnetic resonance imaging (MRI) technique.Approach. The dielectric behaviour of biological tissues depends on frequency, according to the so-called relaxation mechanisms. The adopted model derives the dielectric properties of biological tissues in the frequency range 10 MHz-20 GHz considering the presence of two relaxation mechanisms whose parameters are determined from quantities derived from MRI acquisitions. In particular, the MRI derived quantities are the water content and the dielectric properties of the tissue under study at the frequency of the MR scanner.Main results.The model was first theoretically validated on muscle and fat using literature data in the frequency range 10 MHz-20 GHz. Results showed capabilities of reconstructing dielectric properties with errors within 16%. Then the model was applied to ex vivo muscle and liver tissues, comparing the MRI-derived properties with data measured by the open probe technique in the frequency range 10 MHz-3 GHz, showing promising results.Significance. The use of medical techniques based on the application of electromagnetic fields (EMFs) is significantly increasing. To provide safe and effective treatments, it is necessary to know how human tissues react to the applied EMF. Since this information is embedded in the dielectric properties of biological tissues, an accurate and precise dielectric characterization is needed. Biological tissues are heterogenous, and their characteristics depend on several factors. Consequently, it is necessary to characterize dielectric propertiesin vivofor each specific patient. While this aim cannot be reached with traditional measurement techniques, through the adopted model these properties can be reconstructedin vivoon a wide frequency band from non-invasive MRI acquisitions.

Uncovering the Possibilities of Ceramic Ba(1−x)CoxTiO3 Nanocrystals: Heightened Electrical and Dielectric Attributes

The hydrothermal synthesis of Ba1−xCoxTiO3 (BCT) ceramic nanocrystals across varied substitution fractions (x = 0, …, 1) is the subject of this study. Hydrothermal synthesis is well known for producing high-purity and well-crystallized nanocrystals. A thorough examination is conducted to examine the effects on the structural and electrical properties of the resultant BCT nanocrystals by altering the cobalt substitution fraction. X-ray diffraction (XRD) is used to analyze the structure, while complex impedance spectroscopy (CIS) is used to analyze the electrical properties. As the cobalt content rises, XRD examination reveals a smooth transition from the ferroelectric BaTiO3 phase to the ferromagnetic CoTiO3 phase, offering extensive insights into the phase composition and crystallographic alterations. This phase shift is important because it creates new opportunities to adjust the properties of the material for particular uses. The electrical activity of BCT nanocrystals is clarified further by CIS measurements. A distribution of relaxation times, frequently linked to complex microstructures or heterogeneous materials, is suggested by the detected non-Debye relaxation. A thermally activated conduction process, in which higher temperatures promote the passage of charge carriers, is suggested by the temperature-dependent increase in conductivity. This behavior is strongly dependent on the cobalt content, suggesting that cobalt enhances electrical conductivity and crystallinity through a catalytic effect. A frequency-dependent dielectric constant that rises with temperature and cobalt content is shown by investigating the dielectric characteristics of BCT nanocrystals. Improved polarization mechanisms inside the material are suggested by this increase in dielectric constant, which may be the result of cobalt ion presence. With a thorough grasp of the dielectric behavior, the examination of the loss angle further validates the non-Debye relaxation process.

Comparative Analysis of Dielectric Behavior under Temperature and UV Radiation Exposure of Insulating Paints for Electrical Equipment Protection—The Necessity of a New Standard?

This paper describes the behavior of some epoxy, acrylic and polyurethane paints used in the protection of electrical equipment under the action of different degradation factors. The degradation factors chosen were temperature and UV radiation. The behavior of the paints under the action of these factors was interpreted by the variation of the tangent of the dielectric loss angle (tg Delta) as well as by FTIR and TG DSC analyses. Tg Delta was considered the reference dielectric characteristic because it best simulates the functionality of the material. The results presented in this paper lead to the conclusion that exposure to thermal cycles and UV radiation is necessary for each paint to give indications about their possibility of use in these conditions. At the same time, the evaluation of thermal stability, even if the exposure is at lower temperatures (than those at which we performed the tests) and/or for shorter periods, is very important for placing the paint in an insulation class. The tests that were the subject of this work provide us with the following information about the three types of paints analyzed: the highest resistance to thermal cycles is presented by S3, followed by S2 and then S1; thermal endurance tests place the polyurethane paint (S3) in insulation class E and the epoxy paint (S1) in insulation class B; and the tests to determine resistance to UV radiation qualify the best paint as acrylic (S2) and the worst as polyurethane (S3). Thus, it can be said that in applications where it is necessary for the protective film to withstand high temperatures, the use of S3 paint (polyurethane) is recommended, and in applications where the films are kept under the influence of UV radiation for a longer time, it is recommended to use coded paint S2 (acrylic). The results presented in this paper lead to the conclusion that the exposure to thermal cycles simulating the use in outdoor conditions and the resilience of paints under UV radiation conditions must be performed for each paint according to its specific use, and the dielectric characteristics must be carefully evaluated because they can reach values under the accepted limit—e.g., thermal stability evaluation—even if the exposure is at lower temperatures and/or for shorter periods. The conclusions of the experimental work must be generalized at different types of electrical insulating paints, and maybe a new standard is necessary to assess the paints’ behavior under usage conditions, with the paints needing to be treated separately from the classical polymeric insulation systems.

Dielectric behavior and breakdown strength of glass fiber reinforced epoxy composites under dynamic mechanical fatigue

Glass fiber reinforced polymer (GFRP), used in insulating components like insulation rods, needs to withstand both high voltage and large dynamic mechanical fatigue during operation. In this paper, the effects of tension–compression fatigue loads on the dielectric properties of GFRP under various fatigue cycles and stress levels are investigated. The results show that DC conductivity has a strong negative correlation with stiffness, while breakdown strength is showing a positive correlation. Fatigue-induced internal damage could cause continuous charge accumulation and enhanced interfacial polarization, leading to the increase of dielectric constant by 46.89% and the reduction of breakdown strength by 15.05%, when the fatigue span ratio reaches 80% under 40% stress level. Understanding the evolution of dielectric properties of GFRP under dynamic mechanical fatigue conditions is helpful for ensuring the safe and stable operation of electrical power equipment subjected to both high voltage and fatigue loads.

Nonlinear Dielectric Behavior of Polythiourea under a High Electric Field

Nonlinear Dielectric Behavior of Polythiourea under a High Electric Field

Image of the solid-state rotary motion encoded in the dielectric response

The future development of advanced molecular systems with controlled rotation requires the development of an effective methodology for assessing the rotational performance of artificial machine components. We identified two patterns of the dielectric behavior for polar rotators in a static non-polar framework of sizable crystal showing relations between the spectral and molecular-level features of solid-state rotary motion. Various functionalization of phenylene rotors with a fluorine atom(s) changed rotational performance from high to low with rotational barriers ranging from 6.06 to 11.84 kcal mol-1. The meta-F-substitution favored rotator-rotator contacts allowing for the implementation of fast rotary motion. Contrary, the presence of rotator-stator contacts inhibited independent rotator dynamics leading to opposite spectral behavior in terms of temperature evolution of loss peak amplitude. Our observations, supported by an analysis based on an asymmetric double well-potential model, show that easily noticeable spectral differences encoded some molecular-level information important for the implementation of rotary motion.

Surface‐Reengineering of BNNs@Hydrocarbon Polymer Composites for Ultra‐Low Dielectric Constant for High‐Frequency Applications

AbstractThis research investigates the synthesis and evaluation of cyclic olefin copolymer (COC) composites with surface‐engineered boron nitride nanosheets (BNNs) at various concentrations. The study focuses on the impact of Cetyltrimethylammonium bromide (CTAB) on BNNs′ surface functionalization to improve their dispersion within the COC matrix, including its dielectric behavior, dielectric breakdown strength, thermal management capabilities, hygroscopic properties, and mechanical robustness. The methodological approach adopted for the fabrication of COC/BNNs hybrid composites commenced with the synthesis of BNNs, surface functionalization of BNNs, in‐situ mixing and hot‐press. This step aimed to enhance compatibility and adhesion between BNNs and the COC matrix, facilitating more homogeneous nanofiller dispersion. The investigative scope of this study encompassed a rigorous evaluation of the resultant composites, with a particular emphasis on their dielectric properties. The dielectric constant (ϵ′) and loss tangent (δ) were measured at a frequency of 10 GHz, revealing an ultra‐low dielectric constant of 1.28, an exceptionally minimal loss tangent of 0.000146, a remarkable 327% (In‐plane) & 129% (axial) increase of thermal conductivity, significant improvement of dielectric breakdown strength up to 88.4 mV/mm, and low water absorptions observed. These results indicate the potential of COC/BNNs composites for high‐frequency electronic packaging applications requiring low dielectric constants.

Niobium Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon ratio was adjusted from 0 to 0.32 while maintaining a constant growth time of 30 min. For the second and third series, the oxygen to argon ratios were fixed at 0.40 and 0.56, respectively, with deposition times ranging from 15 to 60 min. A structural transition from crystalline to amorphous was observed at an oxygen to argon flow rate ratio of 0.32. This transition coincided with a change in appearance, from non-transparent with metallic-like electrical conductivity to transparent with dielectric behavior. The transparent niobium oxide films exhibited thicknesses between 51 nm and 198 nm, with a compact, dense, and featureless morphology, as evidenced by both top-view and cross-sectional images. Films deposited on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates displayed a maximum surface roughness (Sq) of 9 nm and a maximum optical transmission of 83% in the visible range. The electrochromic response of niobium oxide thin films on ITO-coated PET substrates demonstrated a maximum coloration efficiency of 30 cm2 C−1 and a reversibility of 96%. Mechanical performance was assessed through bending tests. The ITO-coated PET substrate exhibited a critical bending radius of 6.5 mm. Upon the addition of the niobium oxide layer, this decreased to 5 mm. Electrical resistance measurements indicated that the niobium oxide film mitigated rapid mechanical degradation of the underlying ITO electrode beyond the critical bending radius.

Structural distortion-induced low-temperature dielectric dispersion in lanthanide titanate pyrochlores

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials.

Preparation and Properties of Nb5+-Doped BCZT-Based Ceramic Thick Films by Scraping Process.

A bottleneck characterized by high strain and low hysteresis has constantly existed in the design process of piezoelectric actuators. In order to solve the problem that actuator materials cannot simultaneously exhibit large strain and low hysteresis under relatively high electric fields, Nb5+-doped 0.975(Ba0.85Ca0.15)[(Zr0.1Ti0.9)0.999Nb0.001]O3-0.025(Bi0.5Na0.5)ZrO3 (BCZTNb0.001-0.025BiNZ) ceramic thick films were prepared by a film scraping process combined with a solid-state twin crystal method, and the influence of sintering temperature was studied systematically. All BCZTNb0.001-0.025BiNZ ceramic thick films sintered at different sintering temperatures have a pure perovskite structure with multiphase coexistence, dense microstructure and typical dielectric relaxation behavior. The conduction mechanism of all samples at high temperatures is dominated by oxygen vacancies confirmed by linear fitting using the Arrhenius law. As the sintering temperature elevates, the grain size increases, inducing the improvement of dielectric, ferroelectric and field-induced strain performance. The 1325 °C sintered BCZTNb0.001-0.025BiNZ ceramic thick film has the lowest hysteresis (1.34%) and relatively large unipolar strain (0.104%) at 60 kV/cm, showing relatively large strain and nearly zero strain hysteresis compared with most previously reported lead-free piezoelectric ceramics and presenting favorable application prospects in the actuator field.

Chitosan/Microcrystalline Cellulose Overlaid rGO/Fe3O4 Films: Broadband Dielectric Spectroscopy Investigations

Hybrid and straightforward inorganic/organic composites that can be used simultaneously for energy storage are reported. Films from chitosan (Cs) with microcrystalline cellulose (MCC) implanted with reduced graphene oxide (rGO) and/or magnetic Fe3O4 nanoparticles were fabricated. The reinforcement of the Cs/MCC films with rGO and /or Fe3O4 was studied through Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy with energy dispersive electron spectroscopy. In addition, their magnetic, conductivity, dielectric constant, and dielectric loss behaviors were studied. The magnetic investigations of the two films loaded with Fe3O4 have supper paramagnetic behavior. The saturation magnetization was decreased with the presence of rGO. At lower frequencies, the contribution of charge transport and interfacial polarization causes a sudden and nearly linear increase in permittivity with decreasing frequency. Unfortunately, no indication of electrode polarization was found, which reduces the ability of the prepared composition to store electrical energy. The electric modulus representation was employed to determine the relaxation time of the interfacial polarization quantitatively and numerically. No indication of electrode polarization was found.

Synthesis and study of structural, electric, and dielectric behavior of La0.5Sm0.2Sr0.3Mn1-xFexO3 perovskite

In this study, the synthesized samples La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) were thoroughly investigated for their crystalline structure, electrical conductivity, and dielectric properties, the samples were prepared using autocombustion method. According to the X-ray diffraction study, the samples crystallized in an orthorhombic symmetry with the Pnma space group. To measure the dielectric characteristics, impedance spectroscopy was conducted over the temperature range of 100–260 K and a frequency range of 100 Hz to 1 MHz. Measurements of AC conductivity are indeed utilized to investigate the transport properties of materials being studied. The results indicated that both temperature and frequency significantly influence the conduction process. Three theoretical hypotheses were proposed to explain the hopping conduction: overlapping large polaron tunneling (OLPT), the non-overlapping small polaron tunneling (NSPT) mechanism, and correlated barrier hopping (CBH). It is also shown that the conductivity diminishes with an increase in Fe content. La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) can be used in electronic applications because of the high permittivity values confirmed by the dielectric measurements. With the aim of evaluating the distinct impacts of electrodes, grain boundaries, and grains on the complex impedance results, an appropriate alternative electrical circuit was utilized. Analysis of the sample's modulus indicated non-Debye characteristics and electrical relaxation phenomena. The materials exhibit good electrical properties, as well as strong chemical and thermal stability.

Communication—Tunable Lorentz-Type Negative Permittivity of PANI/Epoxy Resin Composites in the Frequency Range from 3 kHz to 1 MHz

Negative permittivity in percolation composites garnered significant interest due to its promising implications for practical applications. This study demonstrates that the percolation threshold of the polyaniline(PANI)/epoxy resin composite falls within the range of 40 wt% to 50 wt%. Beyond this percolation threshold, the composites exhibit a corresponding negative dielectric behavior. Notably, at a high PANI content level of 90 wt%, the permittivity exhibits characteristics akin to Lorentz resonance type behavior. This research presents an effective approach to exhibit tunable low-frequency negative permittivity through Lorentz resonance.