Search

Manganese mercury thiocyanate (MMTC), a nonlinear optical organometallic single-crystal material, was successfully grown by the Sankaranarayanan-Ramasamy (SR) method. The as-grown MMTC crystals were subjected to 50 shock pulses and designated as MMTC50S. The lattice parameters were measured by single-crystal x-ray diffraction (XRD) with values of a, b, and c of 11.3150 Å, 11.3150 Å, and 4.2720 Å with a tetragonal system for the pure MMTC, and values of 11.3180 Å, 11.3180 Å, and 4.2737 Å for MMTC50S, respectively. Fourier transform infrared (FTIR) spectroscopy was used to identify the functional groups present in the MMTC50S crystal. Scanning electron microscopy (SEM) was used to assess the surface morphology, which revealed a pattern of minor defects and minor dislocations in the MMTC50S crystal in contrast to the pure form because of the shock pulses on the MMTC crystal to create the MMTC50S specimen. The UV-visible spectrum showed increased absorption for the MMTC50S crystal. Fluorescence (FL) studies revealed blue fluorescence emission for MMTC50S. Dielectric measurements were carried out and the dielectric constant was calculated for the grown sample. The piezoelectric coefficients and sensor response at room temperature were also determined for MMTC and MMTC50S. The maximum sensitivity for the MMTC50S with a red light-emitting diode (LED) was 8.88%, whereas the blue LED achieved 9% sensitivity. [ABSTRACT FROM AUTHOR]

Owing to sensitivity to external perturbations such as temperature, electric field, and magnetic field, the dielectric and electro-optical properties of liquid crystals (LCs) can be easily tuned. In recent years, the dispersion of nanomaterials into LCs has proven to be an important tool for the fabrication of various devices with improved characteristics. In the present study, we have synthesized a nanocomposite of vanadium-doped titanium oxide (VTO) with the integration of molybdenum diselenide (MoSe2) and molybdenum trioxide (MoO3), designated as VTO-MSE (V-TiO2/MoSe2/MoO3), through a hydrothermal procedure and measured the dielectric features of 4′-octyl-4-biphenylcarbonitrile (also known as 8CB) LC material doped with the VTO-MSE nanocomposite at different concentrations (0.1 wt.%, 0.25 wt.%, 0.5 wt.% and 1 wt.%) in smectic A (SmA) and nematic (N) phases of 8CB at 28 °C and 36 °C, respectively. The uniform dispersion of VTO-MSE in 8CB was confirmed using polarizing optical microscopy, and the dielectric measurements were performed using frequency-dependent dielectric spectroscopy in the frequency range of 20 Hz–2 MHz. The dielectric parameters (ɛ′ and ɛ″) decreased on the dispersion of the nanocomposite in 8CB LC in the low-frequency region due to the reduction of mobile ions. The peak of the dielectric loss factor (tan δ) also shifted towards the low-frequency side because of the decrease in the mobile ion density. The threshold voltage was found to decrease for the VTO-MSE-mixed 8CB samples and dielectric anisotropy was also obtained, which shows an increase in its value for the nanocomposite dispersed systems. These results can be beneficial for the manufacture of display devices. [ABSTRACT FROM AUTHOR]

Magnesium-doped nickel ferrite nanoparticles with the chemical composition (Ni1−xMgxFe2O4, x = 0.00, 0.20, and 0.40) have been prepared by a modified sol–gel citrate method. Structural analysis was carried out through x-ray diffractograms (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The spherical-shaped morphology of the prepared nanoparticles has been confirmed by field-emission scanning electron microscopy (FESEM). The energy dispersive x-ray (EDX) analysis confirmed the presence of elements (Ni, Mg, Fe, and O) in the prepared compositions. The distribution of cations over tetrahedral and octahedral sites has been confirmed by Rietveld refinement using FullProf software. The phenomena of Maxwell–Wagner polarization is exhibited in the dielectric measurements. Cole–Cole plots showed that the net grain (Rg) and grain boundary resistance (Rgb) values are decreasing for the maximum concentration of Mg2+ ions in the nickel ferrites. Almost 96% deductions in the tangent loss values have been observed at high temperatures with the increasing concentration of Mg2+ ions in the nickel ferrites. Fitting of AC conductivity was carried out using the Jonscher Power Law function. The net magnetization saturation values also decreased from 27.7 emu/g to 16.7 emu/g upon the doping of Mg2+ ions in the pure nickel ferrites. These properties are all desired for materials working under high-frequency applications. [ABSTRACT FROM AUTHOR]

Non-linear optical materials have greatly impacted science and technology in recent years. In the present work, crystals of amino acid derivative l-histidinium acetate dihydrate (L-HA) were grown using the gradual evaporation method. The powder-crystal X-ray diffraction (PXRD) technique was applied to examine the phase composition of the crystal sample. The XRD analysis showed that the L-HA was crystallized into the triclinic system. Microstructural parameters were evaluated, including dislocation density and micro-strain induced in the samples. The vibrational modes of the L-HA crystal were found using confocal Raman spectrum analysis. UV–Vis spectral analysis was applied to ascertain the crystal's optical absorbance and transmittance. The bandgap and Urbach edge of L-HA were explored in the UV–Vis spectrum. The second harmonic generation potency of L-HA was examined using Kurtz–Perry analysis, and it was found that L-HA exhibited significant SHG efficiency. The dielectric and impedance characteristics of the L-HA were assessed in the 100 Hz‒5 MHz range at different temperatures. Dielectric measurements show that at frequencies higher than 10 kHz, the dielectric constant and dielectric loss are saturated at minimum levels. The Nyquist graph displays the negative temperature coefficient of resistance in the compound. Vickers microhardness analysis demonstrates the normal indentation size effect and hard nature of the L-HA sample. Thus, the L-HA crystals are suitable for optoelectronic applications due to their excellent optical characteristics, considerable SHG efficiency, and appropriate dielectric, impedance, and microhardness features. [ABSTRACT FROM AUTHOR]

The tetragonal tungsten bronze structural type (TTB) is one of the interesting family where the structure is compatible with a wide variety of cationic substitution that permits tailoring physical properties including ferroelectricity, piezoelectricity, nonlinear optics, and energy storage properties. Over the past years, major consideration was devoted to niobate based- tetragonal tungsten bronze, as promising materials for electronic components. In the present work, the conventional solid-state method was used to prepare samples within the NaNbO3−BaNb2O6−MoO3 system. The structural refinement performed by the Rietveld method and using GSAS-II software, showed that this sample is constituted by two crystalline phases namely Ba2Mo0.80NaNb4.20O15 and Ba2Mo0.40NaNb4.60O15. The first one crystallizes in the P4bm- tetragonal structure with cell parameters of a = b = 12.3762Å and c = 3.98587Å. However, the second was found to crystallize in the orthorhombic symmetry with Pba2 as space group and a = 12.5260 Å, b = 12.42936 Å, and c = 3.97861 Å. Raman spectroscopy was used to get complementary comments on the structure of the BNMO ceramic. The dielectric measurements were carried out from 25 °C to 550 °C and in a frequency range of (10 Hz–1 MHz). [ABSTRACT FROM AUTHOR]

In this study, we used the solution casting process to produce polyvinyl chloride (PVC) polymer nanocomposites incorporated with ZnMn2O4/CuCo2O4 (ZMCC) and different tetramethylammonium iodide (TMAI) quantities. The PVC/ZMCC/x wt% TMAI polymers were characterized with several analytical techniques; x-ray diffraction, transmission electron microscope, UV–vis diffuse reflectance, photoluminescence (PL), and dielectric measurements. The results obtained from these techniques demonstrated an excellent interaction between the different fillers and the PVC matrix. The reflectance (R), transmittance (T), extinction coefficient (k), refractive index (n), optical dielectric constants, optical conductivity, energy loss functions and nonlinear optical parameters were analyzed. Upon composing with the fillers, T is reduced while A is enhanced for all composition ratios with minimum T and maximum A for the blend with 6 wt% TMAI. The optical energy gap declined from (4.29, 5.17) eV and (4.02, 4.79) eV to (3.04, 3.93, 5.01) eV and (2.43, 3.57, 4.22) eV for direct and indirect transition as the content of TMAI became 6 wt% in loaded polymer. Under varying excitation wavelengths, a blue-violet emission was observed in all the polymers. The effect of fillers on the dielectric constants, dielectric moduli, energy density, and AC conductivity were examined. The polymer with 6 wt% TMAI produced the highest AC conductivity, while the polymer with ZMCC has the highest capacitance. The Cole–Cole plot, obtained using a non-Debye technique, exhibited a semicircular shape. Hence, the improved optical and dielectric properties of the PVC/ZMCC/x wt% TMAI polymers nanocomposites suggest that these materials are suitable for smart electronic devices. [ABSTRACT FROM AUTHOR]

The present work explores a systematic investigation of the microstructural, optical, and dielectric properties of W1−xNixO3 (x = 0, 0.02, 0.04, and 0.06) samples and their application in supercapacitors. The sol–gel auto-combustion process was used to synthesize these samples, and a number of analytical techniques such as x-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman, Scanning Electron Microscopy (SEM), UV–visible spectroscopy, dielectric measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize them. The Rietveld refined XRD patterns confirm the monoclinic phase with space group P21/n in a single phase. FTIR spectroscopy confirms the functional groups associated with stretching and bending vibrational modes at various wavenumbers. Raman spectroscopy ensures the phase purity of the materials and shows a blue shift with Ni doping. SEM microscopy reveals a uniform surface morphology as well as particle agglomeration at the surface. UV–visible studies reveal a significant decrease in the bandgap (2.13–1.81 eV) as the Ni concentration is increased. Dielectric studies show that as the frequency rises, the dielectric constant decreases and becomes saturated at higher frequencies. The highest value of the dielectric constant (ε') is observed for the 4% Ni-doped WO3 sample. The electrochemical and capacitive properties have been characterized and studied using CV and EIS analysis. Cyclic voltammetry tests were carried out in the range of − 0.2 to 0.8 V with varying scan rates (5–100 mVs−1), exhibiting a significantly large area under the CV curve, hence higher values of specific capacitance. The maximum specific capacitance at a scan rate of 5 mVs−1 for each sample of W1−xNixO3 (x = 0, 0.02, 0.04, and 0.06) is found to be 126.671, 192.31, 278.52, and 128.58 Fg−1, respectively, in 2M KOH electrolyte. Thus, the synthesized samples exhibit potential for application as electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Soil salinity at the crops' root zone is a significant environmental issue as it considerably affects agricultural productivity. This study was carried out to demonstrate the combined potential of microwave and multispectral remote sensing data products in identifying the accumulation of soil salinity both on the surface and in the root zone. The research was performed in the Vellore district, Tamil Nadu. The Landsat-8 imageries were employed to assess the soil salinity and moisture at the surface level in the dry and wet seasons using the Diagonal Soil Salinity Index and Modified Diagonal Soil Moisture Stress Index. Further, the soil moisture for the wet season was retrieved from the dielectric measurements of the Sentinel-1 data using Modified Dubois and Topp's Model. In the present study, Salinity Accumulation Index was proposed by integrating the resultant products of soil moisture and salinity retrieved from multispectral and microwave models. The results revealed that the lower (0.25–0.5) and higher range (0.5–1) of values of the proposed Salinity Accumulation Index were shown adequate statistical significance with in-situ salinity accumulation at the root zone (R2 = − 0.7) and surface level (R2 = 0.8), respectively. The trend analysis of the Normalized Differential Vegetation Index (2000–2019) with the results of Salinity Accumulation Index has demonstrated that a considerable proportion of the total agricultural area in the north-eastern part of the study region was majorly affected by the root zone salinity, while the southwestern part was detected with surface accumulated salinity. [ABSTRACT FROM AUTHOR]

A thorough understanding of the interplay between polarization mechanisms is pivotal for the interpretation of electrical measurements, since sub-megahertz electrical measurements in sedimentary rocks are dominated by interfacial polarization mechanisms. Nonetheless, rock-physics models oversimplify pore-network geometry and the interaction of electric double layers relating to adjacent grains. Numerical algorithms present the best possible framework in which to characterize the electrical response of sedimentary rocks, avoiding the constraints intrinsic to rock-physics models. Recently, an algorithm was introduced that can simulate the interactions of electric fields with the ions in solution. The sub-kilohertz permittivity enhancement in sedimentary rocks is dominated by Stern-layer polarization, but a model for the polarization mechanism associated with the Stern layer has not been developed. Hence, the aim of this paper is to develop and test a numerical simulation framework to quantify the influence of Stern- and diffuse-layer polarization, temperature, ion concentration, and pore-network geometry on multi-frequency complex electrical measurements. The algorithm numerically solves the Poisson–Nernst–Planck equations in the time domain and a mineral-dependent electrochemical adsorption/desorption equilibrium model to determine surface charge distribution. Then, the numerical simulator is utilized to perform a sensitivity analysis to quantify the influence of electrolyte and interfacial properties on the permittivity of pore-scale samples at different frequencies. [ABSTRACT FROM AUTHOR]

We report high-resolution calorimetric, optical and dielectric studies on two Schiff's based liquid crystalline materials, 4O.5 and 5O.5, which exhibit multiple phase transitions. The study goes beyond the commonly studied isotropic-to-nematic (I–N) and nematic-to-smectic A (N–SmA) phase transitions and explores higher-order smectic phase transitions. The critical exponent, α values, for different phase transitions has been explored. For the I–N, N–SmA, SmA–SmC, SmC–SmF, SmF–CrG and SmB–CrG transitions, α values close to 0.5 and amplitude ratios A−/A+ ~ 1.6 and D−/D+ ~ 1 indicate a first-order nature. Notably, for the SmA–SmB transition, although α (≈ 0.64) is larger than the tricritical value of 0.5, A−/A+ ~ 1.2 and D−/D+ ~ 1, and the study reports an order parameter critical exponent (β) of 0.26 ± 0.002, which supports a tricritical nature for this transition. Importantly, the ratios of A−/A+ and D−/D+ are found to have similar values across all three-measurement methods, indicating consistency and agreement among these methods. [ABSTRACT FROM AUTHOR]

The polycrystalline (1-x)BiFeO3-xNa0.5Bi0.5TiO3, x = 0.00, 0.05, 0.10 and 0.15, ceramics were prepared using conventional solid-state route. The structural studies using X-ray diffraction and Raman measurements confirmed the rhombohedral R3c structure of the compounds. The scanning electron micrographs showed that grain size decreased, and the density of the compounds increased with the higher Na0.5Bi0.5TiO3 content. The weak ferromagnetism was induced in the solid solution of antiferromagnetic BiFeO3 compound with Na0.5Bi0.5TiO3 content. The structural distortions were increased with the increase of x, which favours the increase of weak ferromagnetism in the antiferromagnetic compound. The electric polarisation measurements indicated that leakage character decreased with the increase in Na0.5Bi0.5TiO3 fraction. The temperature and frequency-dependent dielectric measurements showed that the dielectric constant was improved and loss tangent was decreased in Na0.5Bi0.5TiO3 rich compounds. The temperature dependence of dielectric constant data showed a dielectric anomaly near the magnetic transition of BiFeO3, which shifted towards the lower temperature side with the increase of x. The UV-VIS-NIR spectroscopy measurements evidenced an increase in band gap energy for higher Na0.5Bi0.5TiO3 concentration.. [ABSTRACT FROM AUTHOR]

The quality 2-amino-5-chloropyridinium 4-aminobenzoate (2A5ClP4AB) single crystals were grown in methanol solvent by employing the solvent evaporation technique. The stoichiometry ratio of 2A5ClP4AB was confirmed by microanalysis. The melting point, decomposition, crystalline phase, purity, and specific heat capacity of 2A5ClP4AB crystal were explored by thermogravimetric-differential thermal analyses (TG–DTA), differential scanning calorimetry (DSC), and modulated scanning calorimetry (MDSC) methods. The various dielectric properties of 2A5ClP4AB single crystal concerning temperature and frequency were examined by dielectric measurements. The nonlinear optical (NLO) parameters such as dipole moment, polarizability, first-order hyperpolarizability, and second-order hyperpolarizabilities of the 2A5ClP4AB molecule were computed using density functional theory (DFT) by utilizing the Gaussian 09 program. The figured HOMO–LUMO energies of 2A5ClP4AB demonstrate the occurrence of a charge transfer mechanism, whereas the MESP map illustrates how various molecular interactions took place in it. Hirshfeld surface analyses helped to decode the nature of the interactions and packing structure of the crystals. The above studies were intended to explore the structural, thermal, electrical and NLO properties of 2A5ClP4AB and also to strengthen its effectiveness for optoelectronic and frequency conversion applications. [ABSTRACT FROM AUTHOR]

Polymer nanocomposites (PNCs), exhibiting enhanced physical properties, are emerging as innovative functional materials due to their versatile characteristics suitable for various technological applications. Composite films comprising 0.1% copper (Cu) doped Nickel oxide (NiO) [CNO1 (350)] nanoflakes calcined at 350 °C embedded in Poly (vinylidene fluoride) (PVDF) polymer were prepared using the solution casting method. The influence of CNO1 (350) filler incorporation on the structure and morphology of the composite films was scrutinized through X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM). Results unveiled a direct correlation between CNO1 (350) filler concentration and the crystallinity, β-phase content, and morphology of the composite films, attributed to heterogeneous nucleation. Room temperature electrical measurements indicated dielectric constants reaching more than six times at 40 Hz and a conductivity increase exceeding two orders of magnitude, with a percolation threshold identified around 25wt% of CNO1 (350) filler content. The observed outcomes are elucidated through Maxwell–Wagner–Sillars interfacial polarization occurring at the interface of CNO1 (350) and the insulating polymer matrix. This elucidation involves the development of a conductive network and the establishment of a micro-capacitive structure within the PVDF thin films modified with CNO1 (350). [ABSTRACT FROM AUTHOR]

The root dielectric response was measured on a minute scale to assess its efficiency for monitoring short-term cadmium (Cd) toxicity non-destructively. Electrical capacitance (CR), dissipation factor (DR) and electrical conductance (GR) were detected during the 24 to 168 h after Cd treatment (0, 20, 50 mg Cd2+ kg–1 substrate) in potted maize, cucumber and pea. Stress was also evaluated by measuring leaf chlorophyll content, Fv/Fm and stomatal conductance (gs) in situ, and shoot and root mass and total root length after harvest. CR showed a clear diurnal pattern, reflecting the water uptake rate, and decreased significantly in response to excessive Cd due to impeded root growth, the reduced tissue permittivity caused by accelerated lignification, and root ageing. Cd exposure markedly increased DR, indicating greater conductive energy loss due to oxidative membrane damage and enhanced electrolyte leakage. GR, which was coupled with root hydraulic conductance and varied diurnally, was increased transiently by Cd toxicity due to enhanced membrane permeability, but declined thereafter owing to stress-induced leaf senescence and transpiration loss. The time series of impedance components indicated the comparatively high Cd tolerance of the applied maize and the sensitivity of pea cultivar, which was confirmed by visible shoot symptoms, repeated physiological investigations and biomass measurements. The results demonstrated the potential of single-frequency dielectric measurements to follow certain aspects of the stress response of different species on a fine timescale without plant injury. The approach can be combined with widely used plant physiological methods and could contribute to breeding crop genotypes with improved stress tolerance. [ABSTRACT FROM AUTHOR]

The orthophosphates materials are one of the most important groups in the field technologically advanced materials that are accessible, inexpensive, and environmentally friendly. This materials are of great demand due to their various optoelectronic applications in recent years. In this study, a solid-state method was employed to synthesize the AgCoPO4 orthophosphate sample. Analyzing the XRD pattern, of the studied compound, confirms the triclinic phase with the P 1 ¯ space group. The examination of SEM analysis and energy dispersive spectroscopy (EDS) revealed the same morphology and different particle sizes. As for the EDX analysis, all chemical elements were detected and found in their appropriate ratio. Besides, the impedance spectroscopy measurements conducted at 100 Hz to 5 MHz and 473–673 K are used to investigate the electrical and dielectric properties of the AgCoPO4 compound. The frequency dependence of the conductivity of alternating current is explained using Jonscher's law. The calculated activation energy is in accordance with Arrhenius's behavior based on DC conductivity, which was determined to be 0.93 (2) eV. The primary transport mechanism is governed by the correlated barrier hopping model. A comparative study of impedance and modulus responses versus frequency suggests Cole–Cole behavior. deep investigation of the electric and dielectric performances demonstrated a significant dielectric constant (ε′ ∼ 104) at low frequencies and low dielectric loss at high frequencies. Thus, it highlights its exceptional dielectric potential, particularly in applications related to electronic capacitors. [ABSTRACT FROM AUTHOR]

In this paper, optical and transport properties of Polyvinyl Alcohol/Silver incorporated Zinc Oxide (PVA/Ag–ZnO) nanocomposites of varying Ag–ZnO nanoparticles content prepared by solution casting method are studied to explore their multifunctional applications. The nanocomposites are characterized using X-ray diffraction, Scanning electron microscope, Energy-dispersive X-ray analysis, UV–Visible spectroscopy and Fourier transform infra-red spectroscopy. The UV–visible spectra showed zero transmittance in the UV region with increasing Ag–ZnO nanoparticles content in the PVA matrix suggesting that the nanocomposites could be used as a potential UV shielding material. The optical band gap energy decreases from 5.77 to 1.54 eV with increasing Ag–ZnO nanoparticles content in the PVA matrix. Frequency- and temperature-dependent dielectric measurement of the samples reveals maximum dielectric constant at PVA/15 wt% Ag–ZnO nanocomposite. Dielectric loss results showed a lossless behaviour at higher frequencies (< 0.2), suggesting that the prepared samples are suitable for use in high-frequency applications. The AC conductivity studies reveal that electrical conduction mechanism in the nanocomposites is governed by the correlated barrier hopping mechanism. Activation energy calculation indicates the involvement of two different types of conduction mechanism in the samples. The Nyquist plot for all the samples is fitted using the equivalent circuit model. The studied results show that the PVA/Ag–ZnO nanocomposites can serve as potential candidates for optoelectronic and electronic device application. [ABSTRACT FROM AUTHOR]

This study aims to contribute to the investigation of the electrical and dielectric behavior of the well-known brownmillerites Ca2Fe2O5 compound. The compound was produced using a solid-state reaction process and examined using X-ray powder diffraction and Rietveld refinement to confirm its orthorhombic crystal structure, as well as its cell characteristics. A thorough dielectric and electrical examination was carried out across a wide range of temperature and frequency, from 30 to 400 °C and 10 Hz to 1 MHz. Remarkably, at a relatively temperature of approximately 170 °C, the dielectric measurements revealed a complex behavior, indicative of diffuse phase transition. Similar distinctive changes were also observed in impedance spectroscopy and conductivity studies, suggesting a temperature like phase transition phenomenon. This observation was further substantiated through a differential scanning calorimetry analysis, which identified an endothermic dip at around 170 °C, signifying a structural disturbance at these temperatures. These findings contribute significantly to our comprehensive understanding of the material's behavior across a wide temperature range, providing valuable insights into the polarization mechanisms, relaxation dynamics, and electrical conduction properties. [ABSTRACT FROM AUTHOR]

This study aims to contribute to the investigation of the electrical and dielectric behavior of the well-known brownmillerites Ca2Fe2O5 compound. The compound was produced using a solid-state reaction process and examined using X-ray powder diffraction and Rietveld refinement to confirm its orthorhombic crystal structure, as well as its cell characteristics. A thorough dielectric and electrical examination was carried out across a wide range of temperature and frequency, from 30 to 400 °C and 10 Hz to 1 MHz. Remarkably, at a relatively temperature of approximately 170 °C, the dielectric measurements revealed a complex behavior, indicative of diffuse phase transition. Similar distinctive changes were also observed in impedance spectroscopy and conductivity studies, suggesting a temperature like phase transition phenomenon. This observation was further substantiated through a differential scanning calorimetry analysis, which identified an endothermic dip at around 170 °C, signifying a structural disturbance at these temperatures. These findings contribute significantly to our comprehensive understanding of the material's behavior across a wide temperature range, providing valuable insights into the polarization mechanisms, relaxation dynamics, and electrical conduction properties. [ABSTRACT FROM AUTHOR]

In this study, we addressed the synthesis of spinel-structured nano-scaled materials involving Ni2+ and Mg2+ substitutions in (NixMgxCo1−2xFe2O4 with 0 ≤ x ≤ 0.25) through the citric acid-catalyzed sol–gel combustion method. The investigation was motivated by the need to understand the synthesized materials' structural, electrical, and magnetic properties. We identified the problem of the non-uniformly shaped grains and their varying sizes, impacting the overall structure. Our method involved powder X-ray diffraction (XRD) for structural studies, revealing the formation of pure single-phased nanoparticles. The unit cell parameters fell within the range of 8.3782–8.4325 Å, validating the successful synthesis. Morphological analysis further uncovered randomly distributed, non-uniformly shaped grains with varying sizes, influencing the electrical and magnetic properties. Fourier transform infrared spectroscopy (FTIR) confirmed the spinel structure synthesis. The DC electrical resistivity, dielectric, and AC measurements displayed a non-monotonic pattern concerning dopant concentration, highlighting the complexity of the electrical behavior. Dielectric measurements suggested lower frequency dispersion effects attributed to high polarization at grain boundaries. Room temperature magnetic measurements, conducted using a vibrating sample magnetometer (VSM), demonstrated tuned variations in magnetic parameters. In conclusion, our comprehensive analysis provides valuable insights into the synthesis, structure, and properties of spinel-structured materials, contributing to understanding their potential applications. [ABSTRACT FROM AUTHOR]

Dielectric measurements performed on vinyl resin (VR) matrix and its composites reinforced with microcrystalline cellulose (MCC) and multi-wall carbon nanotubes (MWCNT) focus on the effect of the reinforcement weight fraction variation on its electrical properties in the frequency and temperature ranges 0.1 Hz–1 MHz and 30–130 °C, respectively. The relative volume fraction ratio of the MCC/MWCNT multi-scale reinforcement is of 9:1. In this analytical study, three reinforcement weight fractions of 2%, 4% and 6% are undertaken. The dielectric analysis reveals the presence of two dielectric relaxations for the VR matrix at temperatures above the glass transition temperature. The first one appearing at lower temperatures and higher frequencies is associated with the α relaxation originating from the glass rubbery transition of the terpolymer. Whereas the second one appearing at higher temperatures and lower frequencies is attributed to α′ relaxation due to more repeat units compared to α relaxation. An additional dielectric phenomenon originating from the interfacial polarization effect occurred at the reinforcement/matrix interfaces is identified for the composites. All these dielectric features are taken into account in the complex impedance analysis in order to probe their effects on the improvement of AC conductivity. Furthermore, the AC conductivity analysis using the developed Jonscher law allows determining the associated conduction mechanisms. Hence, changes of the electrical properties may be related to different reinforcement/matrix interactions and to the semi-crystalline character variation of the terpolymer shown by the thermal and structural analyses based on the differential scanning calorimeter and X-ray diffraction, respectively. [ABSTRACT FROM AUTHOR]

Ceramic materials of the composition Pb1 − xCuxTiO3 with x = 0.00, 0.04, 0.06 and 0.08 were synthesized using the sol–gel process. An analysis of their structural, dielectric, and non-ohmic characteristics was investigated. X-ray diffraction data and Rietveld refinement indicate the crystallization of the PbTiO3 ceramic in a pure perovskite structure of tetragonal symmetry, with a phase transition to the pseudo-cubic structure following the incorporation of copper into the PT matrix. The texture, morphology, and microstructure of Pb1 − xCuxTiO3 ceramics were observed using a scanning electron microscope. An impedance spectroscopy study of the dielectric measurements was carried out and revealed that the phase transition temperature decreases proportionally with increasing copper concentration, confirming the incorporation of copper and highlighting its influence on the Curie temperature (Tc), the value of the permittivity (εr), and the dielectric losses (tg δ). The electrical characteristics of PCuxT ceramics reveal that variations in grain size clearly influence the non-ohmic properties. This observation can be attributed to the barrier behavior inherent in the Schottky-type model, as well as to the grain size limitation characteristics of the Internal Barrier Layer Capacitor model. [ABSTRACT FROM AUTHOR]

Gadolinium-substituted W-type hexaferrites BaCo2Fe16-xGdxO27 (0.00 ≤ x ≤ 0.20) nanomaterials were fabricated using the sol–gel method. Structural, spectral, and dielectric characteristics of all the prepared hexagonal ferrites were evaluated. XRD analysis demonstrated that these nanoparticles had a pure phase W-type structure. With increasing the gadolinium substitutions, the crystallite size values show a decreasing trend ranging from 33.63 to 36.58 nm. Lattice constant and volume (Vcell) vary because the substituted and Fe3+ ions have different ionic radii. The behavior of local symmetry in manufactured crystals and the ordering procedure in nano-crystalline ferrites were studied using FTIR spectroscopy. W-type hexagonal ferrite structure was validated by FTIR analysis, which detected waves with a range of 400–3500 cm−1. Raman spectra were used to study the vibrational and rotational energy states. The Raman spectra revealed the distinctions between the substituted and unsubstituted samples. XPS spectra were employed to confirm the elemental composition. The XPS survey displayed that the hexagonal structure had fully developed because its results resembled the XRD patterns and FTIR spectra in every way. The dielectric measurements have been determined as a function of frequency (1–6 GHz), and the Maxwell–Wagner and Koop theories described each sample's performance. Gd-doped BaCo W-type hexagonal ferrites with x = 0.20 and x = 0.15 depicted RL values of − 42 dB, − 39 dB at 1.25 GHz and 1.12 GHz, respectively. The results demonstrated that samples could be utilized for MLCIs and microwave absorption applications in the GHz region. [ABSTRACT FROM AUTHOR]

This study centers on the environmentally benign synthesis of zinc oxide nanoparticles (ZnO NPs) derived from Zn (CH3COO)2·2H2O and Moringa seeds. The synthesized nanostructures underwent comprehensive characterization utilizing diverse analytical techniques, encompassing X-ray diffraction (XRD), UV–VIS spectroscopy, field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. XRD measurements coupled with W–H plot transformation unequivocally confirmed the formation of ZnO nanostructures, characterized by an average size of 24.9 nm. UV–VIS spectroscopy, complemented by Kubelka Munk curve analysis, elucidated the direct conduction and determined a bandgap of 3.265 eV. FESEM analysis revealed minimal particle aggregation, showcasing well-defined grain boundaries spanning sizes from 20.4 to 87.7 nm. XPS analysis substantiated the presence of Zn (2p), Zn (3p), Zn (3d), and O (1s). Raman spectroscopy identified E2H as the predominant mode, followed by E1(TO) and (E2H-E2L). ZnO thin films, fabricated via pulsed laser deposition (PLD) and deposited onto silicon (100) substrates, exhibited exemplary morphology and discernible topography, characterized by a normal grain size distribution. Zeta potential tests yielded a value of approximately (z ~ − 43.8 mV), indicative of the commendable stability of the colloidal suspension, likely attributable to low particle aggregation. Dielectric measurements conducted on sintered pellets at 900 °C unveiled elevated capacitance and dielectric constant at low frequencies across the temperature range of 289.935–310 K. These findings affirm the potential utility of environmentally synthesized ZnO for a spectrum of applications, including energy devices and nanofluids. [ABSTRACT FROM AUTHOR]

In the current study, an organic compound, l-histidine maleate-(1.5)-hydrate (LHM1.5H), was created by a slow evaporation approach. The structural, spectral, optical, dielectric, and electrical conductivity measurements were performed on the synthesized LHM1.5H crystals to describe their characterizations. The LHM1.5H compound exhibits a positive temperature coefficient of solubility, as indicated by the gravimetrical analysis. According to the crystallographic studies, the LHM1.5H revealed a monoclinic crystal system with a P21 space group. The chemical contents of LHM1.5H were identified using EDX microanalysis. The FT-IR and FT-Raman analyses were applied to detect the compound's functional groups and molecular vibrations. According to the UV–Vis study, the maximum optical transmittance of the LHM1.5H is found in the 270–1200 nm range. It is found that LHM1.5H has a bandgap of 4.57 eV. The optical parameters, like refractive index (n) and extinction coefficient (k), were obtained from the optical measurements. The SHG ability of the LHM1.5H crystal is 0.65 times that of potassium dihydrogen phosphate (reference). The dielectric measurements display that the dielectric constant and loss factor decrease with the rise in frequency, attaining the smallest values at higher frequency ranges. Temperature-dependent fluctuations in the loss factor and dielectric constant have been investigated. The AC and DC electrical conductance studies were conducted for the LHM1.5H sample. The Jonscher universal power law has been employed to investigate the electrical conduction process. The activation energy values for the AC and DC conduction mechanisms were calculated, and they were discovered to be 2.068 eV and 0.85 eV, respectively. The experimental outcomes show that the LHM1.5H crystal is helpful for optoelectronic applications. [ABSTRACT FROM AUTHOR]

A hydrothermal process is applied to fabricate copper-doped dilute magnetic semiconductor nanorods Zn1 − xCuxO (x = 3%). The influence of reaction pH value and synthesis temperature was evaluated on their physical properties' anti-bacterial and photocatalytic activities. XRD denouements imply that the material is crystalline and exhibits hexagonal wurtzite geometry whose crystallinity reduces from 29.86 to 26.1 nm and enhances from 29.86 to 34.83 nm with increasing pH value and synthesis temperature, respectively. The material morphology was switched from nanorods to nanowires, and a blue shift from 3.14 to 3.28 eV was noticed in the optical bandgap along with shifting in various vibrations. The dielectric and electrical measurements showed similar behavior, whereas the relative permeability and saturation magnetization were knocked off by increasing pH value and temperature. The photocatalytic activity results showed the maximum degradation of MO dye (95%) under sunlight using the Cu-doped ZnO synthesized at pH 13 and 130 °C. All the samples were found active to inhibit the growth of bacterial strains. [ABSTRACT FROM AUTHOR]

This paper presents microwave head imaging for the detection of tumours and experimental verification using a semi-solid complex multilayer head phantom. Phantoms are an inevitable part of medical diagnosis for obtaining an optimum design before trials in humans. Simple chemical compositions are used to create a material with electrical characteristics that are identical to those of sensitive human brain tissues. The artificially fabricated soft tissues are housed in a man-made substance that has a human skull-like form. This paper describes advancements in the development and measurement of a head phantom, devoted to the testing of a microwave-based head imaging in a realistic laboratory-controlled configuration for brain tumour detection. Dielectric property measurements are performed using a vector network analyser (VNA) with a dielectric probe arrangement and an antipodal Vivaldi antenna (48 mm × 21 mm) with a resonance frequency of 4 GHz. A total of 201 measurements were taken at room temperature (25°C), and a frequency range of 1–6 GHz was used for electrical characterization of the phantom. Measurements were taken multiple times per day, and the average value of the dielectric properties of the phantom components mimicked actual head tissues. The measured reflection coefficient (S11) value with the tumour was −28 dB and that without the tumour was −33 dB for a tumour radius of 10 mm. These measured parameters were used to construct an image in MATLAB using different confocal imaging algorithms. The experimental results for the final phantom product emulated the properties of the required tissues and the location of the tumour. [ABSTRACT FROM AUTHOR]

A dielectric model based on the refractive dielectric model of the mixture of thawed and frozen forest organic soils in the root zone for a frequency of 435 MHz has been developed. The model is created on the basis of dielectric measurements of four soils whose organic matter content varies in the range from 15 to 31%. The dielectric measurements are carried out in the range of the gravimetric moisture from 0 to 0.6 g/g and temperature range from –30 to 25°C. The coefficient of determination (R2) between values calculated by the model and measured values of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity is 0.97. The normalized root-mean-square error is 16 and 21% for the real and imaginary parts of the complex dielectric permittivity, respectively. This dielectric model may be applied in remote sensing algorithms when retrieving the value of forest soil moisture in the root zone from radar and radiometric data. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on the synthesis, characterization, and analysis of the structural, optical, dielectric, and electrical properties of barium-doped lead titanate PbTiO3 (PT) ceramics. The hydrothermal synthesis method was employed to fabricate the Ba-doped PbTiO3 ceramics, followed by sintering at 1000 °C for 4 h. X-ray diffraction analysis reveals a transition from a tetragonal to pseudo-cubic crystal structure with increasing barium concentration, accompanied by changes in lattice parameters. Raman spectroscopy confirms characteristic phonon modes of the tetragonal phase, with broadening and intensity changes indicating the presence of defects induced by barium doping. UV–Vis–NIR spectroscopy shows increased absorption in the ultraviolet region, suggesting modified optical properties. The band gap energy values also increase with barium content. Dielectric measurements demonstrate the impact of barium doping on the dielectric behavior, with higher dielectric constants observed for higher barium concentrations. The modified Uchino plots reveal parameters γ and δ, providing insights into the electrical properties and dielectric response. Overall, this study highlights the structural modifications, optical changes, and dielectric behavior induced by barium doping in PbTiO3 ceramics. [ABSTRACT FROM AUTHOR]

In this study, the optical and electrical characteristics of a PVP/CMC blend have been improved by doping with hydrogen titanate nanotubes (HTNT) and tetramethylammonium iodide (TMAI) for adaptable eco-friendly applications. Undoped and doped PVP/CMC/HTNT/x wt% TMAI blends were formed using casting procedure, x = 0.0, 0.05, 0.1, 0.15, 0.2. HRTEM micrographs of HTNT manifested a tubular structure. XRD measurements manifested a clear modification in the structure of the PVP/CMC blend owing to HTNT/TMAI doping. Diffuse reflectance and transmittance measurements revealed a big enhancement in absorption, in the range 250–400 nm, with a clear reduction in transmittance of PVP/CMC blend upon loading HTNT/TMAI, especially for x = 0.1. The direct and indirect bandgaps (4.86, 4.36 eV) for PVP/CMC were reduced attaining minimum values (2.87, 3.46) and 2.99 eV for x = 0.15 and 0.1 wt% TMAI, respectively. Also, the refractive index of the blend increased especially for the Vis/IR region (~ 1.35) getting a maximum value (2.85) for x = 0.1. The influence of HTNT/TMAI doping on the different optical parameters: absorption coefficient, optical density, dielectric constant, optical conductivity, optical surface resistance, thermal emissivity and nonlinear optical parameters has been explored. The fluorescence intensities and CIE chromaticity coordinates of doped blends are affected by the excitation wavelength and the kind of fillers. From dielectric measurements, blends doped with 0.15 and 0.2 wt% TMAI have a higher capacitive nature than the undoped blend. Except for the blend containing 0.1 wt% TMAI, which possesses the highest energy density, all doped blends were found to have the lowest energy density compared to the undoped blend. The AC conductivity reached its highest value as the amount of TMAI doping became 0.15 wt%. [ABSTRACT FROM AUTHOR]

An array of water-soluble polymer blends composed of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) have been synthesized by the solution casting technique. The prepared blends were tested using X-ray diffraction (XRD), differential scanning calorimetry, mechanical, optical, and dielectric measurements. According to the XRD studies, PEG has a significant plasticizing impact on PVA, as evidenced by the drop in crystallinity (Xc) values from 31.24 to 25.45%. The thermal study reveals the reduction in the glass transition temperature Tg from 89.2 to 60.6 °C. The outcomes showed that adding PEG affects the mechanical characteristics of PVA/PEG blends, and the ideal blend was one with 25 wt% of PEG loading, where the value of the percentage elongation at break (78%), Toughness (0.44) and surface energy (0.076) reached the highest values at this blend. Meanwhile, Young's modulus declined from 20.34 MPa for pure PVA to 7.07 MPa at 25 wt% PEG. According to the optical studies, the absorption edge shifted from 5.24 to 4.26 eV while the optical band gap ( E g ind , E g d ) decreased from 4.81, 5.46 eV (pure PVA) to 3.77, 5.04 eV (PVA/PEG30%) respectively, which indicates that forming charge transfer complexes between PVA and PEG polymer. The EU values enhanced from 0.238 to 1.296 eV and the refractive index improved from 1.38 to 2.97 when PEG content increased. The dielectric and conduction properties were studied from 100 Hz to 1 MHz. It was demonstrated that the dielectric constant ( ε ′ ) and dielectric loss ( ε ′ ′ ) are highly frequency-dependent. In addition to that, (ε ′ , ε ′ ′) values improved from (30, 2) for PVA to (44.46 and 5.39) for PVA/30 wt% PEG blend at 100 Hz, respectively. At the same time, the AC electrical conductivity is improved by increasing the PEG content. These results will likely have far-reaching consequences across a variety of fields, the possible applications due to the increased flexibility of PVA film are flexible packaging, biomedical materials, and other industries that need adaptive and flexible materials. Furthermore, the improved refractive index of the PVA/PEG combination demonstrates its appropriateness for certain applications such as optoelectronic equipment, waveguides, anti-reflective coats, and LEDs. This blend has uses in charge storage devices, such as embedded capacitors due to the enhancement of dielectric constant. Finally, one can say that the research samples have multifunctional applications. [ABSTRACT FROM AUTHOR]

The article develops the possibility of forming silicon oxide structures with tapered walls using dry etching methods, including a two-stage process involving the formation of a tapered photoresist mask and plasma etching of the silicon oxide. A study of the process of tapered resist etching was carried out. The influence of plasma parameters and composition on the etching process was studied, plasma diagnostics were carried out using Langmuir probe and optical emission actinometry methods, and the mechanisms of tapered resist etching were suggested. The etching process was optimized and structures with a resist thickness of 400 nm and a sidewall angle of up to 61° were obtained. A subsequent SiO2 etching process allowed the slope of the resist to be transferred. The slope of the SiO2 wall was 57°. The resulting structures with tapered SiO2 walls make it possible to produce capacitors for studying the characteristics of dielectrics, as well as the structure of microelectromechanics and microfluidics. [ABSTRACT FROM AUTHOR]

The article presents a study into the measurement of dielectric parameters of materials. The study aims to examine promising high-precision methods for measuring the complex permittivity of low-loss materials within the decimeter wavelength range and a non-resonant method for measuring the dielectric parameters of materials characterized by increased dielectric losses. For measuring the complex permittivity of low-loss materials within the decimeter wavelength range, a resonance method of measurement in a coaxial resonator with an adjustable capacitive gap and a method of measurement in a dielectric-filled H011 cavity resonator were developed. In order to measure increased dielectric losses of 10−2–10−1, a transmission line technique was developed using a non-resonant measuring transducer on the basis of a shielded dielectric waveguide, the specimen to be analyzed. The developed methods are applied in GET 110-2023 State Primary Standard for the units of complex permittivity within the frequency range of 0.1–178.4 GHz. The frequency range of the standard is 0.1–178.4 GHz; the reproduction range of relative permittivity is 1.2–500; and the reproduction range of dielectric loss tangent is 10−8–10−1. GET 110-2023 can be used to provide metrological support for dielectric control in the production of radio frequency cables, telecommunication equipment, electronic components, etc. [ABSTRACT FROM AUTHOR]

The measurement of dielectric properties of foods is essential in the design and control of microwave drying systems as they describe the capability of a material to absorb, transmit and reflect electromagnetic energy. The dielectric properties of selected low-moisture products (corn starch, curry, paprika, rice grain and wheat grain) were evaluated by open-ended coaxial probe (OECP) and cavity perturbation techniques. Semi-skimmed milk powder was heated at 50 and 60 °C, to determine the change in dielectric properties at higher temperatures. The increase in moisture content (from 7.19 to 13.08%, wet basis, w.b.) and its influence on the relative complex permittivity was verified for semi-skimmed milk powder. The results showed that the dielectric constant tends to increase with temperature and moisture content, and with the decrease in frequency from 2450 to 915 MHz. Values ranged from 1 for corn starch (OECP at 2450 MHz) to 4.36 for rice grain (cavity perturbation at 915 MHz). The loss factor ranged from 0.02 for curry to 0.48 for rice grain, both at 2450 MHz. It was possible to obtain a comparison between the two techniques and to have a general idea of the range of values for dielectric properties of foods with low moisture. The OECP technique requires good contact between product and probe, which was possible with the compression system developed in this study. The cavity perturbation technique has been proven to be reliable for many foods, especially at low moisture contents, requiring a specific microwave applicator to be designed for each frequency range. [ABSTRACT FROM AUTHOR]

A near-morphotropic phase boundary (MPB) composition of ternary 0.49BiFeO3-0.20Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 (BF-PMN-PT) ceramic was synthesized for various dielectric, ferroelectric and piezoelectric applications using the conventional solid-state reaction method via a two-step columbite precursor technique. Powder x-ray diffraction (XRD) confirms the perovskite phase of the synthesized ceramic with a monoclinic crystal structure belonging to the P1m1 space group. The dielectric properties and the relaxation mechanisms of this ternary ceramic were studied using dielectric spectroscopy measurements for the frequency range of 10 Hz to 1 MHz over a wide range of temperature from 50°C to 400°C. A good dielectric response was observed with a high dielectric constant value (~ 800) that decreases with increasing frequency. A phase transition temperature (Tc = 275°C) and a low dielectric loss were also observed. The dielectric exhibits a clear and distinct Debye-type relaxation in the ferroelectric phase. The measured dielectric data fit quite well with the modified Debye model. Various Debye fitting parameters were obtained which show a temperature-dependent nature. The value of Debye broadening parameter α exhibits a decreasing trend from 0.136 to 0.003 as temperature increases from 50°C to 200°C, after which it increases and attains a maximum value of 0.566 at 350°C. The Cole–Cole plot obtained from the measured data reveals the distributive nature of the sample's dielectric relaxation. [ABSTRACT FROM AUTHOR]

In this work, xMWCNT/chitosan composite films with multi-walled carbon nanotubes (MWCNT) as filler and chitosan as matrix were prepared via a solution blending method. Varied content of MWCNT of 0, 0.5 wt.%, 1 wt.% and 1.5 wt.% was investigated. The dielectric properties of the films were investigated in the temperature range of −60°C to 60°C and frequency range of 102–106 Hz. The experimental results show that the incorporation of MWCNT can effectively improve the dielectric properties of the film, with optimal results when the content of MWCNT is close to the percolation threshold. A giant dielectric constant (GDC) was found in all the samples and was studied by dielectric and impedance measurements. Maxwell Wagner relaxation was observed in all samples, which is caused by space charges at different interfaces. The GDC is thought to be related to a Maxwell–Wagner relaxation caused by sample–electrode contact. The addition of MWCNT can enhance the Maxwell–Wagner relaxation. The largest enhancement was found in the sample with 1 wt.% MWCNT. [ABSTRACT FROM AUTHOR]

Synthesis of tellurite borate (35-x) TeO2 + 35 B2O3 + 20 Bi2O3 + 10 Li2O + x CeO2 and x = 0, 0.5, 1.5, 3 mol% glasses have been achieved by using the melt quenching technique. Density, X-ray diffraction (XRD), Raman spectroscopy measurements and UV–Vis analysis were measured. Dielectric measurements were recorded in the frequency range of 100 Hz–100 kHz at room temperature. XRD patterns of all the investigated glass samples doped with CeO2 are completely amorphous. Densities of the prepared glasses increased from 4.80 to 4.89 g/cm3 and molar volumes decreased from 36.74 to 36.14 cm3/mole. Raman spectroscopy reveals that the Raman intensity increases with increasing substitution of CeO2 by TeO2. UV–Vis analysis reveals that a higher CeO2 substitution ratio increased the absorbance and optical properties of produced glass samples. The CeO2 content of tellurium borate glass samples were found to affect all of the optical characteristics. With increasing CeO2 concentration, the optical energy gap decreases (E g opt ) from 2.77 to 1.96 eV for direct allowed transitions and from 2.45 to 1.82 eV for indirect allowed transitions. It has also been studied how electrical conductivity and dielectric properties change with frequency and composition. Values ε′, ε″ and σac of sample with x = 0 are greater than those values of with x = 3. The variation of the imaginary part of the electric modulus (M″) versus frequency (F) plot curve is asymmetric of non-Lorentzian type. A shift of the frequency peak towards the higher frequency region was observed by increasing CeO2 mol%. [ABSTRACT FROM AUTHOR]

Recent research aims to study the structural, optical, mechanical, and dielectric characteristics of polyvinyl alcohol (PVA) filled with Cu2+/Zn2+ doped-PVA polymeric composite films. Cu2+/ Zn2+/PVA films were prepared by the solution casting method and examined by different techniques such as XRD, UV–Vis, tensile testing, and dielectric measurements. PVA's crystallinity is affected by the interaction of the PVA's main chain and metal ions doping. The Cu2+-ions codoped Zn/PVA composite films reveal the absorbance spectrums in the visible region due to the surface plasmonic resonance (SPR) phenomenon for Cu-particles. It is found that the mechanical characteristics were improved, where the strength, Young's modulus, and ductility were increased through the increase of Cu2+-ions content in Zn/PVA composite films. The dielectric measurement of the as-prepared polymeric composite films has investigated and demonstrated a highly attractive dielectric constant for the polymeric dielectric media. The obtained dielectric behaviors, alternating-current conductivity, and dielectric modulus depended on the Cu2+-ions content. The power output is reduced by increasing Cu2+-ions content, and therefore, the optical limiting of polymeric films becomes better. Finally, Cu2+-ions doped Zn/PVA composite films showed unique properties to be used as flexible electronic and optoelectronic devices, especially in dielectric media, CUT-OFF laser filters for biomedical laser applications. [ABSTRACT FROM AUTHOR]

The polycrystalline powder of CoMnP2O7 has been prepared via the conventional solid-state reaction route. The X-ray diffraction analysis revealed the formation of a single-phase monoclinic lattice system. The atomic positions as well as the characteristic interatomic distances and angles have been deduced through the Rietveld refinement. The SEM images indicate the polycrystalline nature of the material with grain size anisotropy. The CoMnP2O7 is identified as a wide direct band-gap material, further highlighting its potential use across a range of industries, including electronic and optical device manufacturing. Dielectric measurements have been performed in the temperature range of 298–800 K at different frequencies, and versus frequency under various temperatures. This material demonstrates promising characteristics for potential capacitor applications, as evidenced by its high dielectric constant and low losses. The CoMnP2O7 pyrophosphate presents high permittivity at low frequencies owing to Maxwell–Wagner polarization arising from the inter-grain boundaries, as confirmed through impedance spectroscopy. An equivalent circuit has been provided to model the electrical response. The ac-conductivity increases as the temperature increases, and oxygen vacancies dominate at high temperatures. The obtained results also suggest the possibility of using this material for capacitors as well as both NTC and PTC thermistors. [ABSTRACT FROM AUTHOR]

In this study, effect of Cr doping on the dielectric, ferroelectric, and magnetic properties of doped Ba0.80Ca0.20TiO3 (BCT) ceramics has been investigated in correlation with structural changes. Polycrystalline ceramics with a chemical formula Ba0.80Ca0.20Ti1–3x/4CrxO3 (x = 0.000, 0.005, 0.010, 0.015, and 0.020) have been prepared by solid-state reaction method. The Cr-doped BCT ceramics exhibited a single-phase tetragonal perovskite structure without any secondary phases. Tolerance factor, lattice parameters (a and c), unit cell volume (a2c), c/a ratio, and grain size have decreased with increase in Cr dopant concentration. The crystallite size also reduced with increasing Cr doping, as confirmed by both Debye–Scherrer and Williamson-Hall (W–H) plot methods. Dielectric measurements of the prepared BCT ceramics showed a dielectric anomaly "hump" at around 447 K at low frequencies in the paraelectric region, caused by acceptor-induced defect dipoles. The temperature-dependent dielectric measurements of prepared BCT ceramics possess diffused phase transition (DPT) and an increase in the width of DPT has been observed with Cr doping. % Temperature coefficient of capacitance (%Tcc) has been obtained between ± 15% in the temperature range 303 K to 523 K. In addition, feeble ferromagnetism was observed at room temperature under low magnetic fields in the prepared ceramic compositions, which was dominated by diamagnetism at higher fields. [ABSTRACT FROM AUTHOR]

In this paper, the molecular dynamics at different thermodynamic conditions of hydrogen-bonded (H-bonded) active pharmaceutical ingredient—ticagrelor (TICA) have been investigated. Extensive high-pressure (HP) dielectric studies revealed surprising high sensitivity of the structural (α)-relaxation to compression. They also showed that unexpectedly the shape of the α-peak remains invariable at various temperature (T) and pressure (p) conditions at constant α-relaxation time. Further infrared measurements on the ordinary and pressure densified glasses of the examined compound indicated that the hydrogen-bonding pattern in TICA is unchanged by the applied experimental conditions. Such behavior was in contrast to that observed recently for ritonavir (where the organization of hydrogen bonds varied at high p) and explained the lack of changes in the width of α-dispersion with compression. Moreover, HP dielectric measurements performed in the glassy state of TICA revealed the high sensitivity of the slow secondary (β)-relaxation (Johari–Goldstein type) to pressure and fulfillment of the isochronal superpositioning of α- and JG-β-relaxation times. Additionally, it was found that the activation entropy for the β-process, estimated from the Eyring equation (a high positive value at 0.1 MPa) slightly increases with compression. We suggested that the reason for that are probably small conformational variations of TICA molecules at elevated p. [ABSTRACT FROM AUTHOR]

Nanocomposite of polyvinyl alcohol (PVA)/polyvinylpyrrolidone filled with different mass fraction of multi-walled carbon nanotubes was prepared via traditional casting route. Mechanical properties including hardness, ultimate strength, toughness, Young modulus, and elongation at break show an obvious enhancement with increasing MWCNTs content up to a certain concentration (~ 1%). Aggregations of MWCNTs in the higher filling levels may cause reduction in mechanical properties. The DC electrical conductivity was observed to be increased with increasing temperature and MWCNTs concentration. DC electrical conductivity measurements also show an abrupt increase in conductivity with the increase in MWCNTs concentration from 0.5 to 1.0% by weight, suggesting occurring of the percolation phenomenon. Dielectric measurements for the present samples were examined in a wide range of frequencies from 10−1 to 107 Hz at various fixed temperatures (from 303 to 343 K). A decrease in dielectric loss and dielectric constant measurements was observed with increasing frequency and temperature. At 3% MWCNTs content, the dielectric loss and dielectric constant values obtained are maximum, reaching 2.4 × 107 for dielectric loss and 3.5 × 107 for dielectric constant. While dielectric loss and dielectric constant increase with increasing MWCNTs content, it was observed that the higher MWCNT present low dielectric loss and dielectric constant values due to MWCNTs aggregations. [ABSTRACT FROM AUTHOR]

Controlling the dielectric properties is desirable for monitoring the efficiency of materials, which are newly applicable in electronic devices. In this work, the simple and well-known Rother-Lichtenecker equation has been modified to predict the real part of the dielectric permittivity of polymer nanocomposites. In the proposed model, the real part of dielectric permittivity is a function of interphase properties (thickness, volume fraction, and dielectric permittivity) and nanoparticle characteristics (shape, size, and volume fraction). The model results agree well with the experimental data for polymer nanocomposites containing different spherical, cylindrical, and plate-like nanoparticles. In addition, the predicted interphase properties cope very well with the experimental observations of interfacial interactions from valid literature. The high interphase properties and the small size of the nanoparticles are desired requirements of a nanocomposite with high dielectric permittivity. However, the dielectric permittivity of the nanoparticles barely affects that of the nanocomposite. The proposed model can accurately estimate the interphase properties of any available polymer nanocomposite considering the dielectric permittivity measurements. [ABSTRACT FROM AUTHOR]

Bismuth ferrite with manganese doping (BiFe0.95Mn0.05O3 or BFMO) and bismuth ferrite with cobalt and manganese doping (Bi0.95Co0.05Fe0.95Mn0.05O3 or BCoFMO) were both synthesized as nanocrystalline powders by the sol–gel autocombustion technique. X-ray diffraction examination of the powders indicates a rhombohedral distortion in the perovskite phase in both samples. The calcined powders were examined for their microstructure and elemental composition with high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDAX), respectively. Scanning electron microscopy (SEM) was used to examine the microstructures of sintered BMFO and BCoFMO specimens at room temperature. Dielectric characteristics were studied at various frequencies and temperatures and found to follow space charge polarization. At ambient temperature, a vibrating sample magnetometer was used to analyse the materials' magnetic behaviour (M–H loops). Saturation magnetization is significantly increased with increased coercivity in the BCoFMO sample compared to the other sample. Improved structural, dielectric, and magnetic values in these doped systems, however, suggest they'd be an excellent fit for spintronic, multifunctional memories, sensors, and actuators. [ABSTRACT FROM AUTHOR]

By coating the inside of an overmoded, smooth wall metallic waveguide with a thin dielectric layer, one can obtain similar boundary conditions to corrugated waveguides and achieve extremely low transmission loss propagating the HE11 mode. A theoretical model provides an analytic method for computing attenuation. The propagation mode of a prototype dielectric lined waveguide is characterized using low power transmission measurements to analyze the beam radiated from the waveguide aperture. Results indicate HE11 mode purity of approximately 98%. Furthermore, we quantified attenuation with low power Fabry-Pérot measurements, verifying low loss performance of the experimental prototype. These results demonstrate that dielectric lined waveguides could have applications in many fields demanding low attenuation millimeter and terahertz transmission, such as radar, high-frequency communication systems, THz dynamic nuclear polarization, and electron cyclotron heating in magnetically confined fusion experiments. [ABSTRACT FROM AUTHOR]

La0.6Sr0.4FeO3 ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been investigated according to dielectric measurements in the frequency range 10–1 - 106 Hz and the temperature range 93 - 313 K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model. This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects attributed to the heterogeneous structure of La0.6Sr0.4FeO3 grain boundary according to the morphological analysis. Such characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures. [ABSTRACT FROM AUTHOR]

This study explored the structural, optical, and dielectric properties of Pure and Mn+2 doped ZnO nano-particles (Zn1−xMnxO) with x ≥ 20%, synthesized by co-precipitation method followed by annealing at 4500C. Different characterization techniques were conducted to characterize the as-prepared nano-particles. X-ray Diffraction analysis of the pure and Mn+2 doped presented a hexagonal wurtzite structure and a decreased crystallite size with increasing doping concentration. Morphological analysis from SEM revealed finely dispersed spherical nanoparticles with particle size of 40–50 nm. Compositional analysis from EDX confirmed the incorporation of Mn+2ions in ZnO structure. The Results of UV spectroscopy showed that changing the doping concentration affects the band gap, and a red shift is observed as the doping concentration is increased. The band gap changes from 3.3 to 2.75 eV. Dielectric measurements exhibited decrease in the relative permittivity, dielectric loss factor and ac conductivity by increasing Mn concentration. [ABSTRACT FROM AUTHOR]

The collective intermolecular dynamics of protein and water molecules, which overlap in the sub-terahertz (THz) frequency region, are relevant for expressing protein functions but remain largely unknown. This study used dielectric relaxation (DR) measurements to investigate how externally applied sub-THz electromagnetic fields perturb the rapid collective dynamics and influence the considerably slower chemical processes in protein–water systems. We analyzed an aqueous lysozyme solution, whose hydration is not thermally equilibrated. By detecting time-lapse differences in microwave DR, we demonstrated that sub-THz irradiation gradually decreases the dielectric permittivity of the lysozyme solution by reducing the orientational polarization of water molecules. Comprehensive analysis combining THz and nuclear magnetic resonance spectroscopies suggested that the gradual decrease in the dielectric permittivity is not induced by heating but is due to a slow shift toward the hydrophobic hydration structure in lysozyme. Our findings can be used to investigate hydration-mediated protein functions based on sub-THz irradiation. The collective intermolecular dynamics of protein and water molecules, which overlap in subterahertz frequencies, are relevant for protein function expressions. Here the authors develop highly sensitive dielectric measurements, revealing that protein hydration is nonthermally accelerated by sub-terahertz irradiation. [ABSTRACT FROM AUTHOR]

Electrical property tomography (EPT) is a noninvasive method that uses magnetic resonance imaging (MRI) to estimate the conductivity and permittivity of tissues, and hence, can be used as a biomarker. One branch of EPT is based on the correlation of water and relaxation time T1 with the conductivity and permittivity of tissues. This correlation was applied to a curve-fitting function to estimate electrical properties, it was found to have a high correlation between permittivity and T1 however the computation of conductivity based on T1 requires to estimate the water content. In this study, we developed multiple phantoms with several ingredients that modify the conductivity and permittivity and explored the use of machine learning algorithms to have a direct estimation of conductivity and permittivity based on MR images and the relaxation time T1. To train the algorithms, each phantom was measured using a dielectric measurement device to acquire the true conductivity and permittivity. MR images were taken for each phantom, and the T1 values were measured. Then, the acquired data were tested using curve fitting, regression learning, and neural fit models to estimate the conductivity and permittivity values based on the T1 values. In particular, the regression learning algorithm based on Gaussian process regression showed high accuracy with a coefficient of determination R2 of 0.96 and 0.99 for permittivity and conductivity, respectively. The estimation of permittivity using regression learning demonstrated a lower mean error of 0.66% compared to the curve fitting method, which resulted in a mean error of 3.6%. The estimation of conductivity also showed that the regression learning approach had a lower mean error of 0.49%, whereas the curve fitting method resulted in a mean error of 6%. The findings suggest that utilizing regression learning models, specifically Gaussian process regression, can result in more accurate estimations for both permittivity and conductivity compared to other methods. [ABSTRACT FROM AUTHOR]

Dielectric spectroscopy methods revealed the existence of two types of relaxation processes in the semiconductor phase of VO2:Fe films. The characteristic relaxation times are denoted by τ1 and τ2. It is shown that the temperature dependences of τ1 and τ2 have hysteresis, the position of the loops of which coincides with the points of the semiconductor-metal phase transition in VO2:Fe films. τ1 corresponds to undoped, and τ2 corresponds to Fe-doped nanocrystallites of the VO2 film. It is shown that the physical mechanism of the relaxation process is due to the establishment of equilibrium after the action of an electric field on conduction electrons. The numerical values of the parameters of the distribution of relaxers over relaxation times are determined. [ABSTRACT FROM AUTHOR]

0.42Pb(Mg0.335Nb0.665)O3–0.26Pb(In0.5Nb0.5)O3–0.32PbTiO3 (PMINT): x % Eu2O3 (x = 0, 1, 1.5, 2 and 2.5) ternary ceramics were prepared using solid-state reaction technique. The powder X-ray diffraction analysis confirmed the diffusion of Eu3+ ions in the PMINT lattice and tetragonal structure in the P4mm space group. The temperature and frequency dependence of dielectric measurement revealed the relaxor such as behaviour and high Curie temperature (Tc ~ 180 °C) achieved for PMINT: 1% Eu ceramic. High remnant polarization (Pr ~ 28.09 µC/cm2) and coercive field (Ec ~ 13.36 kV/cm) were attained for PMINT: 1% Eu and PMINT: 2% Eu samples, respectively. An improved piezoelectric charge coefficient d33 ~ 462 pC/N was found for PMINT: 1.5% Eu. The unipolar strain vs electric field (S–E) hysteresis loops were investigated and the maximum strain Smax = 0.11% for PMINT: 2.5% Eu and the piezoelectric strain coefficient d33* = 387 pm/V for PMINT: 1.5% Eu. This work provides a new way to fabricate Eu-doped PMINT ternary ceramics, both piezoelectric and induced strain properties can be enhanced simultaneously. [ABSTRACT FROM AUTHOR]