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Lead-free piezoelectric ceramics of (1 − x)K0.5Na0.5NbO3-xCaTiO3 were fabricated, and their crystal structure, microstructure, and electrical properties were systematically studied. Rietveld refinement of the x-ray diffraction data and Raman spectroscopic analyses revealed a composition-dependent structural phase transition: three phase transitions, namely, from a pure orthorhombic phase for x ≤ 0.02 to a mixed phase of orthorhombic and tetragonal phases (0.03 ≤ x ≤ 0.08) and finally another mixed phase of tetragonal + cubic for x = 0.10 and 0.15 at room temperature (RT). The morphological study reveals a decrease in grain size along with a more uniform distribution of grains as the concentration of CaTiO3 (CT) increases; notably, a homogeneous distribution of grains is observed for x = 0.05. The temperature-dependent dielectric properties show two phase transitions, from orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), for unmodified K0.5Na0.5NbO3 (KNN). However, both the phase transition temperatures (TO-T and TC) decrease, and the transition peaks broaden with an increase in CT substitution, and for x > 0.06, the TO-T shifted below RT. The broadening of the transition peak at TO-T may be due to the relaxation behavior. Among the prepared samples, the 5 mol. % CT-modified KNN shows the optimum electrical properties (d33 = 114 pC/N, ɛr = 412, and 2Pr = 15.25 μC/cm2) at RT. The enhanced electrical properties for x = 0.05 are due to the coexistence of orthorhombic and tetragonal phases, facilitating easy polarization rotation and flattening of the free energy profile. A phase diagram has been constructed based on the information gathered from the temperature-dependent dielectric measurements, RT x-ray diffraction, and Raman spectroscopy data and is discussed in detail. [ABSTRACT FROM AUTHOR]

There is no consensus among researchers regarding how phase transitions occur in antiferroelectric (AFE) epitaxial heterostructures, in particular, in heterostructures based on model AFE lead zirconate. The questions about the number of phase transitions in such films and by what mechanism they occur remain controversial. This paper presents a look at the phase transition scenario in two types of epitaxial heterostructures: PbZrO 3 /Ba[La–Sn]O 3 /MgO (001) thin films with thicknesses from 25 to 1000 nm and PbZrO 3 /SrRuO 3 /SrTiO 3 (001) thin film 100 nm thick using the diffuse x-ray scattering in the grazing incidence setup. We register the characteristic butterfly-shaped diffuse scattering (DS) intensity distribution in the H K pseudocubic planes, which corresponds to the anisotropic ferroelectric soft mode. No incommensurate soft mode was observed in the cuts of reciprocal space parallel to the film surface by diffuse scattering. We reproduce the shape of DS distribution at different temperatures by the model based on the dielectric stiffness and the electric polarization correlation tensor in the cubic approximation. Such modeling allows not only to characterize the DS parameters from the challengingly low signal-to-background data set, but also to extract experimentally the sensitivity of the materials with respect to inhomogeneous polarization. While the observed temperature evolution of DS is consistent with the dielectric measurements, the correlation between the DS and the phase transition sequence observed by superstructure reflections is yet to be understood better. [ABSTRACT FROM AUTHOR]

We report the nonlinear dielectric properties of three triple-perovskite ruthenates: Ba 3 CoRu 2 O 9 , Ba 3 BiRu 2 O 9 , and Sr 3 CaRu 2 O 9. These compounds exhibit notable correlations among their spin, charge, lattice, and polar degrees of freedom. Ba 3 CoRu 2 O 9 displays a pronounced frequency-dependent relaxation in χ 2 , 3 just above the magnetoelastic transition, occurring around 100 K, followed by an abrupt loss of polarization within the ordered phase. In Ba 3 BiRu 2 O 9 , we encounter the possibility of multiple coexisting relaxation behaviors, indicating a complex phase strongly influenced by the spin-gap opening at 175 K. Lastly, Sr 3 CaRu 2 O 9 displays anomalies with strong dispersion effects close to its magnetic transitions, indicating a robust coupling between magnetic and dipolar orders in the system. These measurements highlight the significance of higher-order (hyper-)susceptibilities in providing profound insight into the dynamics of a system, offering information otherwise inaccessible through the linear polarization response alone. [ABSTRACT FROM AUTHOR]

The impact of successive replacement of K+ by Na+ on the megahertz–gigahertz polarization response of 0.25[fKSCN + (1 − f)NaSCN] + 0.75CH3CONH2 deep eutectic solvents (DESs) was explored via temperature-dependent (303 ≤ T/K ≤ 343) dielectric relaxation (DR) measurements and computer simulations. Both the DR measurements (0.2 ≤ ν/GHz ≤ 50) and the simulations revealed multi-Debye relaxations accompanied by a decrease in the solution static dielectric constant (ɛs) upon the replacement of K+ by Na+. Accurate measurements of the DR response of DESs below 100 MHz were limited by the well-known one-over-frequency divergence for conducting solutions. This problem was tackled in simulations by removing the zero frequency contributions arising from the ion current to the total simulated DR response. The temperature-dependent measurements revealed a much stronger viscosity decoupling of DR times for Na+-containing DES than for the corresponding K+ system. The differential scanning calorimetry measurements indicated a higher glass transition temperature for Na+-DES (∼220 K) than K+-DES (∼200 K), implying more fragility and cooperativity for the former (Na+-DES) than the latter. The computer simulations revealed a gradual decrease in the average number of H bonds (⟨nHB⟩) per acetamide molecule and increased frustrations in the average orientational order upon the replacement of K+ by Na+. Both the measured and simulated ɛs values were found to decrease linearly with ⟨nHB⟩. Decompositions of the simulated DR spectra revealed that the cation-dependent cross interaction (dipole-ion) term contributes negligibly to ɛs and appears in the terahertz regime. Finally, the simulated collective single-particle reorientational relaxations and the structural H-bond fluctuation dynamics revealed the microscopic origin of the cation identity dependence shown by the measured DR relaxation times. [ABSTRACT FROM AUTHOR]

The electric field dependence of the electrocaloric effect is investigated in BaTiO 3 and Ba(Zr 0.12 Ti 0.88 )O 3 by a direct method with sub-mK temperature resolution. The field dependence of the caloric temperature change Δ T (E) shows a pronounced change within a few Kelvin around the Curie temperature for the first-order phase transition in BaTiO 3. The transition from a linear field dependence in the ferroelectric phase over a butterfly-shaped to a quadratic field dependence in the paraelectric phase is compared to predictions of Landau–Devonshire theory. The simultaneous measurement of caloric and dielectric properties further allows for the investigation of the polarization dependence Δ T (P) of the electrocaloric effect. We find clear deviations from the predicted quadratic polarization dependence for temperatures close to the Curie temperature. Ba(Zr 0.12 Ti 0.88 )O 3 shows in contrast only a slow and gradual change of the field dependence over a broad temperature range as a consequence of its diffuse phase transition. [ABSTRACT FROM AUTHOR]

The slow Arrhenius process (SAP) is a dielectric mode connected to thermally activated equilibration mechanisms, allowing for a fast reduction in free energy in liquids and glasses. The SAP, however, is still poorly understood, and so far, this process has mainly been investigated at temperatures above the glass transition. By employing a combination of methods to analyze dielectric measurements under both isochronal and isothermal conditions, we were able to quantitatively reproduce the dielectric response of the SAP of different polymers and to expand the experimental regime over which this process can be observed down to lower temperatures, up to 70 K below the glass transition. Employing thin films of thicknesses varying between 10 and 800 nm, we further verified that the peak shape and activation energy of the SAP of poly(4-bromostyrene) are not sensitive to temperature, nor do they vary upon confinement at the nanoscale level. These observations confirm the preliminary trends reported for other polymers. We find that one single set of parameters—meaning the activation barrier and the pre-exponential factor, respectively, linked to the enthalpic and entropic components of the process—can describe the dynamics of the SAP in both the supercooled liquid and glassy states, in bulk and thin films. These results are discussed in terms of possible molecular origins of the slow Arrhenius process in polymers. [ABSTRACT FROM AUTHOR]

Glassy films of methyl-m-toluate have been vapor deposited onto a substrate equipped with interdigitated electrodes, facilitating in situ dielectric relaxation measurements during and after deposition. Samples of 200 nm thickness have been deposited at rates of 0.1 nm/s at a variety of deposition temperatures between 40 K and Tg = 170 K. With increasing depth below the surface, the dielectric loss changes gradually from a value reflecting a mobile surface layer to that of the kinetically stable glass. The thickness of this more mobile layer varies from below 1 to beyond 10 nm as the deposition temperature is increased, and its average fictive temperature is near Tg for all deposition temperatures. Judged by the dielectric loss, the liquid-like portion of the surface layer exceeds a thickness of 1 nm only for deposition temperatures above 0.8Tg, where near-equilibrium glassy states are obtained. After deposition, the dielectric loss of the material positioned about 5–30 nm below the surface decreases for thousands of seconds of annealing time, whereas the bulk of the film remains unchanged. [ABSTRACT FROM AUTHOR]

Understanding the nanoscale electrostatic interaction between a conductive atomic force microscopy (AFM) probe and a dielectric film is central to the operation of various nanoscale dielectric microscopies and determination of dielectric properties of the film. There is no simple analytical description of the electrostatic interaction generated in the confined probe-sample geometry for neither static nor dynamic AFM modes used in dielectric measurements. An accurate description of the involved physics is obtained only by means of a finite element analysis modeling of the system. However, the alternative to using the numerical analysis is not very popular due to being slower and requiring relatively high computation resources. In this work, we revised the contributions from different parts of the AFM probe to the probe-sample capacitance by both analytical and numerical methods. We tried to reconciliate the two approaches and observed the differences as a function of geometry and material parameters. Under various noise levels, the efficiency of an analytical model was tested against a finite element analysis that captures in detail the electrostatic interaction in AFM-based dielectric measurements. The investigation was performed in both spectroscopic force-distance curves and constant height scans with measurements for deflection and frequency of the AFM probe. The obtained measurement sensitivities are relevant in selecting the optimal scanning mode and its operational parameters for a given film thicknesses and dielectric constants but also show the critical role of the numerical analysis to the correct interpretation of the measurements. [ABSTRACT FROM AUTHOR]

Fe-based materials exhibiting high dielectric constants have been attracting great attention due to their potential for application in electronic devices. In this work, iron niobate (FeNbO 4) fibres were produced by the Laser Floating Zone technique, applying three different growth speeds: 5, 10 and 25 mm/h. The XRD patterns showed the presence of two phases, being the FeNbO 4 the major one in all the samples. The effect of the growth speed is well perceptible in the morphology of the fibres. The dielectric measurements revealed that all samples have at least one dielectric relaxation phenomenon that is thermally activated, with the activation energy, estimated through the Arrhenius law, presenting values between 0.057 and 0.072 eV. The Nyquist plots showed the presence of a single semicircle for each temperature, that could be modelled by an equivalent electrical circuit consisting of an offset resistance in series with a parallel combination of a grain resistance and a grain constant phase element. The grain resistance increased with the increasing growth speed, from 574 to 64497 Ω, with the constant phase element showing the opposite trend, decreasing from 0.40 to 0.17 nF. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of Zr4+-Co2+ substituted U-type hexaferrites (Ba 4 Zn 2 Fe 36-2x Zr x Co x O 60 (0.0 ≤ x ≤ 1.0, having Δx = 0.25)) were synthesized via sol-gel auto-combustion method. The samples were sintered at 1200 ° C for 6 h. The impact of Zr–Co substitution on phase, structure, morphology, and dielectric behavior were investigated through XRD, FTIR, SEM, XPS and VNA. XRD studies shows that the U-type hexaferrite phase has been developed and the increase in lattice constants (a & c), cell volume, c/a ratio, and percentage porosity was observed. Sample with x = 0.25 exhibited the smallest crystallite size (34.5 nm). The existence of signature metal-oxygen vibrational bands for hexaferrites was observed by FTIR spectra. SEM analysis reflects that the substitution produces a significant effect on morphology and grain size of the samples. X-ray photoelectron spectra (XPS) of sample x = 1.0 confirmed the chemical and elemental composition. The dielectric constant, dielectric loss, and ac conductivity increases with increasing frequency and decreases with Zr–Co substitution. The lowest reflection loss of R L = −64.5 dB (with MW absorption >99.9 %) was observed for the composition x = 0.5 with pellet thickness of 1.73 mm at 1.05 GHz frequency. Due to the improved bandwidth and better absorption, these hexaferrites can be used in microwave and high frequency applications. [ABSTRACT FROM AUTHOR]

In this study, the sol-gel synthesis technique was harnessed to craft nanocomposites of (1-x)La 0.7 Sr 0.3 MnO 3 -(x)BTO with x values of 0.4, 0.6, and 0.8. The attributes of these meticulously engineered materials were exhaustively explored using a diverse suite of characterization methods. X-ray diffraction analysis irrefutably confirmed the phase purity of the perovskite structure, emphasizing the synthesis's precision. Furthermore, Diffuse Reflectance Spectroscopy shed light on the optical properties of the nanocomposites, revealing a significant shift in bandgap energy that correlated directly with the BTO concentration. Specifically, an increment in BTO concentration resulted in a systematic expansion of the bandgap from 1.51 eV to 1.44 eV. For an in-depth analysis of the magnetic characteristics of the composites, Vibrating Sample Magnetometry was utilized. The magnetic analysis identified a conspicuous reduction in saturation magnetization, highlighting the complex interplay between the composite components at the nanoscale. Additionally, the dielectric properties were rigorously investigated through dielectric measurements, which unveiled a notable increase in the dielectric constant, accompanied by the emergence of novel relaxation behaviors. This finding indicates that adjusting the BTO content within the nanocomposites not only modifies their dielectric properties but also provides a method for fine-tuning their functional performance. [ABSTRACT FROM AUTHOR]

This report presents a novel dielectric study of Ba 1-x Y x Ti (1-x/4) O 3 (x = 0, 2 %, 4 %, 6 %, and 8 %) with graphene oxide (GO) via sonication. BaTiO 3 (BT) is a well-known ceramic material with excellent properties, and its temperature stability is crucial for high-temperature applications. However, there is a lack of scientific research exploring this stability at elevated temperatures. This research provides valuable insights into the stability of BaTiO 3 -Yttrium-based ceramics, particularly in conjunction with graphene (BYT@GO), paving the way for potential applications in high-temperature environments. The tetragonality of the structures was identified by powder X-ray diffraction. A uniform grain size was observed for BT@GO, However, BYT@GO (Y% = 2 %, 4 %, 6 %, and 8 %) exhibited a homogeneous morphology and dense microstructure, as observed by scanning electron microscopy. Dielectric measurements were conducted to evaluate the permittivity of the materials as a function of frequency at room temperature. All ceramics demonstrated stable permittivity and low dielectric losses as a function of frequency (<2 × 10−4 for BT@GO, 4 × 10−3 for BYT4%@GO, 6 × 10−3 for BYT6%@GO, and 8 × 10−3 for BYT8%@GO). In addition, BT@GO and BYT 8 %@GO exhibited exceptional dielectric stability at temperatures ranging from 20 to 300 °C. [ABSTRACT FROM AUTHOR]

Synthesis of ternary nanocomposites of BiFeO 3 -Graphene-KNbO 3 through simple solution method has been made at various concentrations of graphene ranging 0.025–0.1 % mole fraction. The obtained nanocomposite powders with varying content of graphitic phase were subjected to different characterization techniques such as XRD, Raman, SEM/EDX/Elemental mapping, HR-TEM, UV–Vis–NIR spectroscopy, dielectric and photodegradation measurements. All above studies have provided the collective impression of the existence of all entities in the prepared ternary composites. Dielectric studies revealed that progressive loading of graphene content led to the increased pathway for the conduction of electrons in the sample. However, the loading of graphene at appropriate concentration has brought out increased dye degradation capacity of BiFeO 3 -Graphene-KNbO 3 ternary nanocomposites towards methylene blue dye. The results obtained from various studies have been discussed in detail. [ABSTRACT FROM AUTHOR]

In this report, I studied the structural, morphological, and dielectric properties of new ferroelectric compounds prepared according to the formula Ba0.95Sr0.05Ti1-ySnyO3. The solid-state reaction method enhanced by a high-efficiency metal ball mill was used in the preparation process. The quantitative and qualitative analysis of the XRD patterns confirmed the crystallization of the samples y = 0.00, 0.05 in the tetragonal crystal system and the presence of the tetragonal and cubic crystal systems together in the samples y = 0.10, 0.14. Formation of BaSnO3 impurities in very low percentages in the doped samples. Their prevalence increases with increasing tin content, reaching 8.7% at the ratio y = 0.14. SEM images of the ceramic samples showed the formation of nano-ceramics with a high degree of condensation at the doping ratio y = 0.05. The dielectric analyses showed high thermal stability in the dielectric properties of the ceramic samples y = 0.05, 0.10, which was shown by the flatness of the dielectric constant curve over the entire temperature range studied, where this stability is attributed to the structure of the nano-grains that resist the ferroelectric-paraelectric phase transition. Furthermore, the dielectric properties were interpreted by accurately linking the dielectric measurements with the nano-structural and polar properties. [ABSTRACT FROM AUTHOR]

The paper presents a synthesis (solid-state. reaction) and characterization of a lead-free double perovskite oxide Ba2(FeMo)O6 ceramic. The initial analysis using X-ray diffraction revealed that the material has a cubic crystal symmetry with a micro-lattice strain of 0.000824 and an average crystallite size of 62 nm. The microstructural features and elemental composition of the prepared polycrystalline sample were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The SEM micrograph, EDX spectrum and elemental mapping show distinctly grown grains with well-defined grain boundaries, purity and distribution pattern of the grains, respectively. Raman scattering spectroscopy is a valuable tool for studying the vibrational modes to get information about structural and chemical properties of materials. The optical properties of the material were investigated using UV–Vis spectroscopy, which provides various parameters including energy bandgap for different technological applications. The electrical behavior of the synthesized double perovskite was examined through frequency- and temperature-dependent dielectric measurements as well as impedance spectroscopy. The electrical conduction in the material followed Jonscher's power law and is supported by a thermally activated conduction mechanism. The analysis of electrical resistance versus temperature confirms negative temperature coefficient of resistance nature and can be used as NTC thermistors. The study of polarization-electric field loop opens up the possibility of the ferroelectric nature of the studied sample and also measures energy storage density, energy loss density and efficiency for searching different potential applications related to sensors. Overall, the results suggest its potential for various technological applications, such as in sensors and devices requiring specific electrical behavior or ferroelectric properties. [ABSTRACT FROM AUTHOR]

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]

We report on temperature-dependent dielectric behavior of disordered ternary A6B2O17 (A = Zr, Hf; B = Nb, Ta)-form oxides in the GHz frequency range. The microwave dielectric properties including relative permittivity, dielectric loss, and temperature-dependent relative permittivity were characterized using cylindrical dielectric resonators using a resonant post measurement technique. Dielectric measurements through the resonant post method approach generally agree with dielectric measurements of A6B2O17 bulk ceramics measured through standard resonant post techniques. Coefficients describing the temperature-dependent relative permittivity for ternary A6B2O17 phases are strongly positive, suggesting contributions to polarizability arising from long-range mechanisms potentially associated with structural disorder. These observations support the working hypothesis that material functionality can be engineered by the chemical diversity and structural disorder possible in high configurational entropy A6B2O17 phases. [ABSTRACT FROM AUTHOR]

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

The self‐assembly and dynamics of amphiphilic diblock copolymers composed of densely grafted poly(oligo ethylene glycol methacrylate) (POEGMA) and poly(lauryl methacrylate) (PLMA) by means of calorimetry, small‐angle X‐ray scattering (SAXS), and dielectric spectroscopy are investigated. It is reported that the inherent immiscibility between the parent homopolymers, combined with the increased molar mass, results in strong segregation, maintained up to elevated temperatures (i.e., T = 423 K). SAXS reveals that well‐separated POEGMA and PLMA domains self‐assemble into spheres with bicontinuous cubic packing and in lamellar nanostructure in copolymers with respective compositions of 16 and 52 wt.% PLMA. This strong segregation enables the weak crystallization/melting of the short ethylene glycol chains. Additionally, molecular dynamics are investigated through isothermal dielectric and calorimetry measurements. The segmental dynamics (i.e., Tg‐related) of POEGMA and PLMA closely resemble that found in respective homopolymers, implying heterogeneous dynamics. In the glassy state, the local motions of the POEGMA side chains predominantly govern the observed secondary processes in the copolymers. The results on the heterogeneous dynamics in the current amphiphilic diblock copolymers with the densely grafted architecture are compared and contrasted with copolymers having a bottle–brush architecture lacking the amphiphilic nature. [ABSTRACT FROM AUTHOR]

Manganese oxides with spinel structure could exhibit abundant physical effects due to the complex sublattice structure, variable valence states and the intricate roles of manganese cations in magnetic interaction. In this work, NiMn 2 O 4 ceramic with space group of Fd 3 ‾ m is synthesized. The low-temperature polarization behavior is investigated accompanied by revealing the multi-stage dielectric relaxation. Moreover, the relaxation mechanism is confirmed through microstructure characterization, multiple-condition pyroelectric measurement and the dielectric tunability properties under electric/magnetic fields. With increasing measuring temperature, different relaxation phenomena are respectively induced by lattice distortion because of the competition among magnetic coupling interactions (below ∼135 K), electron hopping relating to the coexistence of different valence states of manganese ions (∼135–230 K), and the synergistic contribution of oxygen vacancies and domain wall effect (above ∼230 K). These results provide additional evidence for comprehensive understanding the low-temperature polarization in NiMn 2 O 4 , guiding the method design for exploring the physical origin within a wide temperature range. [ABSTRACT FROM AUTHOR]

In this manuscript, a new method for the synthesis of CaCu 3 Ti 4 O 12 (CCTO) perovskite was adopted via co-precipitation followed by calcination processes. The co-precipitation route was employed to synthesize calcium and copper oxalates precipitated on the TiO 2 surfaces and the calcination technique at different temperatures was utilized to follow the single-phase formation. Differential thermal analysis-thermogravimetry (DTA-TG) were used to estimate the proper calcination temperatures and to follow the precursor′s decomposition stages. X-ray diffraction (XRD) revealed the initiation of titanate formation at 700 °C. The complete formation of single-phase was achieved at 1100 °C. In agreement with the XRD measurements, FT-IR spectra confirmed the formation the different phases at different calcination temperatures. The prepared titanate showed giant dielectric properties with values higher than reported in literature. The conductivity measurement indicated semi-conducting properties and revealed a transition agreed well with that obtained in the dielectric properties measurements vs. temperature, attributed to the orientional polarization or change in the entire conduction mechanism from hopping to ionic conduction. The obtained electrical properties enhances the utilization of the entire titanate as capacitors. [ABSTRACT FROM AUTHOR]

Pure anatase TiO 2 nanoparticles and its mono–doped and co–doped derivatives [i.e. (TiN 0.007 O 1.993); (Ti 0.998 Cu 0.002 O 2); (Ti 0.998 Cu 0.002 N 0.007 O 1.993)] were prepared by sol–gel auto–combustion technique. Further, the effects of copper (Cu) and nitrogen (N) dopants have been investigated on structural, optical and dielectric properties of nanostructured TiO 2 using X–ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and dielectric spectroscopy measurement respectively. The Rietveld refinement analysis of XRD data and Raman spectra revealed that all the synthesized samples have pure anatase phase having tetragonal structure with space group of I 4 1 / amd. The pure anatase phase of doped samples illustrate the substitution of Cu ions at Ti4+ sites and N ions at O2− sites in the TiO 2 host lattice. The crystallite size of TiO 2 and its derivatives has been observed in the range of 11–14 nm. The band gap of TiO 2 reduced from 3.2 to 1.9 eV with mono–doping and co–doping of the N and Cu in TiO 2 lattice as confirmed by UV–Vis spectroscopy. This red–shift might be occur due to the possible formation of N–2p and Cu–3d localized levels (mono–doping case), and the creation of isolated intermediate states (co–doping case). The dielectric spectroscopy was carried out to investigate the electrical properties in details and explained in terms of structural and intrinsic ionic behaviour of different dopants. The detected band gap energies in N/Cu mono–doped and co–doped anatase TiO 2 fall within the visible spectrum, rendering them suitable for harnessing solar energy in photocatalysis and photovoltaic applications. [Display omitted] • Synthesis of mono–doped and co–doped TiO 2 by Cu (0.2 mol%)/N (0.7 mol%) ions • Doping was performed using sol–gel method whilst retain anatase phase • Red–shift due to formation of N–2p and Cu–3d localized levels in mono–doping • Red–shift ascribed to isolated intermediate band formation in co–doping • Enhancement in conductivity for co–doping as compared to pure and mono–doping [ABSTRACT FROM AUTHOR]

This article presents the research results of lead-free Ba1−3/2xLax(Fe0.5Nb0.5)O3 (BFNxLa) ceramic materials doped with La (x = 0.00–0.06) obtained via the solid-state reaction method. The tests of the BFNxLa ceramic samples included structural (X-ray), morphological (SEM, EDS, EPMA), DC electrical conductivity, and dielectric measurements. For all BFNxLa ceramic samples, the X-ray tests revealed a perovskite-type cubic structure with the space group Pm 3 ¯ m. In the case of the samples with the highest amount of lanthanum, i.e., for x = 0.04 (BFN4La) and x = 0.06 (BFN6La), the X-ray analysis also showed a small amount of pyrochlore LaNbO4 secondary phase. In the microstructure of BFNxLa ceramic samples, the average grain size decreases with increasing La content, affecting their dielectric properties. The BFN ceramics show relaxation properties, diffusion phase transition, and very high permittivity at room temperature (56,750 for 1 kHz). The admixture of lanthanum diminishes the permittivity values but effectively reduces the dielectric loss and electrical conductivity of the BFNxLa ceramic samples. All BFNxLa samples show a Debye-like relaxation behavior at lower frequencies; the frequency dispersion of the dielectric constant becomes weaker with increasing admixtures of lanthanum. Research has shown that using an appropriate amount of lanthanum introduced to BFN can obtain high permittivity values while decreasing dielectric loss and electrical conductivity, which predisposes them to energy storage applications. [ABSTRACT FROM AUTHOR]

In recent years, environment-friendly lead-free dopants-incorporated Ba-based perovskite oxides have found their potential applications in electronic devices due to their improved performances by modifying the crystal structures. In this study, BCZT [Ba0.9Ca0.1Zr0.1Ti0.9O3], Bi-doped BCZT [(Ba0.9Ca0.1)0.925Bi0.05Zr0.1Ti0.9O3], Cu-doped BCZT [Ba0.9Ca0.1(Zr0.1Ti0.9)0.997Cu0.003O3], and Bi–Cu both doped BCZT [(Ba0.9Ca0.1)0.925Bi0.05(Zr0.1Ti0.9)0.997Cu0.003O3] were prepared by conventional solid-state reaction method to study the effect of doping from microscopic and atomic point of view. XRD and Rietveld techniques are used to identify and quantify the phases, respectively. FTIR study confirmed the modification of the cell parameters due to doping, based on its composition. Raman spectroscopy is used to study the nature of symmetry presence in BCZT ceramics before and after doping. It reveals the presence of trace amount of orthorhombic symmetry with Tetragonal in all samples, as well as little cubic symmetry observed in BCZT-Bi and BCZT-BiCu. FESEM is used to study the surface morphology along with different grains in BCZT with doping. Localized structural distortion originated by dopants was investigated by the Atomic Pair Distribution Function (PDF) method. Aside from average structure, PDF gives information about localized structure within short-range zone, which is significantly modified, whereas long-range structure is almost similar. PDF shows the Raman-predicted orthorhombic phase is not exactly orthorhombic but the distorted tetragonal phase. Ultraviolet–visible (UV–vis) spectra show the bandgap energy increased after doping in BCZT. Dielectric measurement of all samples shows a high dielectric constant (>2000), and it is shown that vacancy in the crystal plays an important role in the dielectric behavior with frequency. The average and atomic–scale structure of Bi/Cu and Bi–Cu doped BCZT helped to understand the dielectric behavior for potential application of the barium titanate complex perovskites. [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]

In this study, we investigated the impact of Chromium substitution on the structural, dielectric and ferroelectric characteristics of Ba 0·90 Sr 0·10 Ti 1-3x/4 Cr x O 3 (x = 0, 0.005, 0.010, 0.015 and 0.020) ceramics fabricated by solid state reaction method. Rietveld refinement of X-ray diffraction pattern confirmed tetragonal perovskite structure for all the samples. Based on the crystal structure and the lattice parameter obtained through XRD measurement, the Madelung energy of each sample was computed. SEM images revealed a reduction in grain size with rising Cr concentration. TEM, HRTEM, SAED and EDS analysis was carried out for BST-Cr3 sample. Diffused rings observed in Selective Area Electron Diffraction (SAED) patterns indicate the crystallinity of the sample. EDS analysis indicated the presence of Ba, Sr, Ti, O and Cr elements. In the temperature range of 30 °C–150 °C, dielectric measurements (dielectric constant 'ε' and tangent loss 'tanδ') have been made at different frequencies (1, 10, 50, 100 and 1000 kHz). The samples displayed a diffused phase transition, with noticeable reduction in Curie temperature 'T c ' and tangent loss 'tanδ' with the substitution of Cr. Polarization versus electric field loops were recorded at different electric fields (5, 10, 15, 20 and 25 kV/cm) and improved values of remnant polarization 'P r ' and coercive field 'E c ' were observed. A lower E c value facilitates easier domain movement within the unit cell, leading to enhanced ferroelectric properties. Temperature dependent P-E loops indicated that as the temperature increased, the material became softer accompanied by simultaneous reduction in P r and E c values. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the dielectric constant of solutions of a polar liquid in a nonpolar solvent: chlorobenzene–benzene, chlorobenzene–hexane. The measurements were carried out at a wavelength λ = 1 2. 8 0 cm in the temperature range from − 8 0 ∘ C to 2 0 ∘ C. The studies were carried out using the dielectric spectroscopy method. This method allows a more detailed study of the dielectric properties of the objects of study due to the large equilibrium ("static") dielectric constant of the object. The temperature dependence of the dielectric relaxation time of molecules in the liquid and solid states of the studied solutions is determined. It has been established that with increasing concentration (0.300, 0.562, 0.794, 1.000 for a chlorobenzene–hexane solution and 0.179, 0.368, 0.567, 0.778, 1.000 for a chlorobenzene–benzene solution) of the halogen substituent, the relaxation time increases. The measurement results of dielectric constant ε ′ and absorption coefficient ε ′ ′ obtained for concentrated solutions chlorobenzene–benzene, chlorobenzene–n–hexane at wavelengths λ = 1 2 , 80 and λ = 3 , 2 6 cm at temperature 2 0 ∘ C are given in the paper. The static dielectric constant is obtained at a frequency of 1 MHz. The obtained experimental values ε ′ , ε ′ ′ and ε 0 of investigated systems in ( ε ′ , ε ′ ′ ) plane locate on the semi-circle the center of which is on ε ′ axis. In this case, the high-frequency limit value of ε ∞ dielectric coefficient exceeds the corresponding n2 refraction index square. The macroscopic and molecular relaxation times are calculated on the base of experimental data. The thermodynamic quantities characterizing the process of dielectric relaxation are calculated for solutions of chlorobenzene–benzene, chlorobenzene–hexane. It has been determined that the height of the potential barrier separating the two equilibrium positions of a polar molecule is greatest in the state of a pure polar liquid and decreases with dilution in a nonpolar solvent. [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]

Microwaves can safely and non-destructively illuminate and penetrate dielectric materials, making them an attractive solution for various medical tasks, including detection, diagnosis, classification, and monitoring. Their inherent electromagnetic properties, portability, cost-effectiveness, and the growth in computing capabilities have encouraged the development of numerous microwave sensing and imaging systems in the medical field, with the potential to complement or even replace current gold-standard methods. This review aims to provide a comprehensive update on the latest advances in medical applications of microwaves, particularly focusing on the near-field ones working within the 1–15 GHz frequency range. It specifically examines significant strides in the development of clinical devices for brain stroke diagnosis and classification, breast cancer screening, and continuous blood glucose monitoring. The technical implementation and algorithmic aspects of prototypes and devices are discussed in detail, including the transceiver systems, radiating elements (such as antennas and sensors), and the imaging algorithms. Additionally, it provides an overview of other promising cutting-edge microwave medical applications, such as knee injuries and colon polyps detection, torso scanning and image-based monitoring of thermal therapy intervention. Finally, the review discusses the challenges of achieving clinical engagement with microwave-based technologies and explores future perspectives. [ABSTRACT FROM AUTHOR]

This paper presents a complete analysis of the electrical and dielectric characteristics of N i C o 2 O 4 (NCO) bulk ceramic synthesized by the co-precipitation process as a future electronic device material. The structural analysis following the synthesis process revealed the formation of cubic-phase spinel NCO in the shape of nanospheres, with an approximate diameter of 25 nm. The present study aimed to examine the relationship between capacitance and conductance for the NCO under investigation, focusing on their frequency and temperature dependencies. The frequency range of interest ranged from 100 Hz to 1.5 MHz, while the temperature range considered was from 300 K to 450 K. The C/f plot has exhibited the phenomenon of negative capacitance, which may be attributed to the augmentation of polarization and the incorporation of additional minority carriers inside the structure. The dielectric parameters, such as permittivity, dielectric loss, alternating current conductance, and electrical modulus, were determined by capacitance and conductance measurements, taking into account their frequency and temperature reliance. All dielectric calculations were influenced by negative capacitance measurements. The negative capacitance feature of N i C o 2 O 4 is attributed to the ferroelectric properties of the Ni and Co elements in its composition. In conclusion, this paper has made a valuable contribution to the existing body of literature by enhancing our comprehension of the negative capacitance behavior and dielectric characteristics of the NCO. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights Epoxy resin (EP) is widely employed in power systems and electronic devices due to its low cost and easy processing along with good insulative and adhesive properties. However, EP insulation properties are compromised at elevated frequencies and temperatures because of its negative temperature coefficient effect (NTC) and poor thermal characteristics. In this context, barium strontium titanate (BST‐60), a positive temperature coefficient (PTC) filler, and hexagonal boron nitride (h‐BN), a thermally conductive filler, both surface‐modified with dopamine, are added in EP to simultaneously improve thermal and dielectric insulation properties at high temperatures and high frequencies. This study finds that below the Curie point of BST, the insulating properties of h‐BN fillers significantly contributes to improving insulation properties. Conversely, above the Curie point, the insulating nature of BST fillers leads to an improvement in the insulation performance of composites. Furthermore, at elevated frequency and temperature, the nano h‐BN enhances thermal conductivity of EP by establishing a thermally conductive network, while micro‐BST suppresses the NTC effect of EP by regulating electrical resistivity above the Curie point. The Heywang model elucidates the PTC effect of BST fillers, while a proposed heat conduction‐dissipation mechanism explains the behavior of incorporated fillers at different temperatures. PDA‐modified Ba0.8Sr0.2TiO3 and h‐BN co‐doped epoxy composites are prepared. Negative temperature coefficient effect of epoxy is mitigated by PTC fillers. The optimal wt.% of filler enhances both dielectric and thermal properties. Dielectric properties are explored at high frequencies and temperatures. Optimized epoxy composites are suitable for high‐frequency applications. [ABSTRACT FROM AUTHOR]

Highlights Bio‐based flexible dielectric substrates have gained tremendous attention for their potential to reduce environmental risks from nonbiodegradable electronic waste. The present study demonstrates the fabrication of facile, nontoxic, and biodegradable chitosan‐based flexible dielectric substrate using graphene nanoplatelet (GNP) as a nanofiller. The detailed impact of different concentrations of GNP (1, 2, and 3 wt%) into the chitosan (CS) matrix was studied on physicochemical, morphological, mechanical, electrical, and thermal properties. The fabricated CS/GNP composites showed improved mechanical strength, thermal stability, and electrical properties compared with unmodified CS film. The composites exhibited excellent thermal stability (200°C) with a promising biodegradation rate (within 6 days). The mechanical strength of the unmodified CS film was increased unequivocally with 2 wt% GNP loading with tensile strength of 23.56 Mpa. Furthermore, the current–voltage (I–V) characteristic curves for CS/GNP (2%) and CS/GNP (3%) showed similar current conduction and ohmic behavior in flat, bending, and flat‐after‐bending modes. The dielectric measurements revealed that the CS/GNP composite with 2 wt% filler exhibited optimal performance having permittivity (έ) of 32.71 (at 102 Hz) with low dielectric loss of 0.04 (at 106 Hz). These results suggest that the dielectric films offer strong prospects as an eco‐friendly alternative for various applications. Biodegradable chitosan‐based flexible dielectric films were prepared. Films were made using a simple solvent casting method with 1–3 wt% GNP filler. Optimum physicochemical and electrical properties were seen at 2 wt% GNP. CS/GNP (2%) film exhibited ohmic behavior in both flat and bending modes. Excellent dielectric properties were achieved at 2 wt% GNP filler. [ABSTRACT FROM AUTHOR]

Complex dielectric measurements were performed in 1-nitropropane (NTP) and DMSO mixtures at various concentrations in the frequency range of 10 MHz to 50 GHz using time domain reflectometry technique. The excess inverse relaxation time values were found to be negative, indicating that the dipoles rotated more slowly. Alenka Luzar's hydrogen-bonded theory is used to calculate theoretical estimates of the static dielectric constant. The variations in dielectric parameters such as dielectric constant, relaxation time, Kirkwood correlation factor and excess properties observed in the study confirm the existence of intermolecular interactions within the NTP-DMSO mixtures. [ABSTRACT FROM AUTHOR]

This paper presents accurate, prompt, and cost‐effective relative permittivity and loss tangent measurements of low‐loss dielectrics such as DuPontTM VESPEL® SP‐1 and VictrexTM polyetherketone (PEEK) 450G, which are commonly used materials in space communication antennas. It is essential for an antenna engineer to have the information regarding the electrical properties, that is, dielectric permittivity, dielectric loss tangent, magnetic permeability, and magnetic loss tangent at the frequency of interest. The test method relies on the accurate measurements of the S‐parameters of the sample under test by means of Through‐Reflect‐Line (TRL) calibration using a Vector Network Analyzer (VNA). Nicholson‐Ross‐Weir (NRW) method is employed to get the conversion from S‐parameters to both complex permittivity and permeability values of the samples. The experimental results are verified with the literature data of Teflon and relative permittivity and loss tangent measurements of VESPEL® SP‐1 (εr=3.119±0.043 ${\varepsilon }_{r}=3.119\pm 0.043$, tanδ=(20.893±4.042)*10−3 $\tan \delta =(20.893\pm 4.042)* {10}^{-3}$) and PEEK 450G (εr=3.119±0.015 ${\varepsilon }_{r}=3.119\pm 0.015$, tanδ=(5.654±1.877)*10−3 $\tan \delta =(5.654\pm 1.877)* {10}^{-3}$) are presented for X‐band (8‐10 GHz) frequencies. [ABSTRACT FROM AUTHOR]

The search for new materials and compositions, in which the phenomena of ferrimagnetism and ferroelectricity are closely coupled, is of great technological interest. In the present study, composite systems of (BaTiO 3) (100- x)% /(CoNb 0 · 02 Fe 1 · 98 O 4) x % where x = 0, 2, 5, 10, 20, and 100% were produced. Initially, BaTiO 3 (BTO) was made by sol-gel combustion approach and CoFe 1 · 98 Nb 0 · 02 O 4 (CoFeNbO) was made by hydrothermal method. Both compounds were then combined via solid-state reaction route to form the composite systems. According to X-ray diffraction, the pristine BTO and CoNbFeO display tetragonal and cubic structures, respectively, and all composite systems consisted of the cubic phase for BTO and spinel phase for CoNbFeO. Scanning electron microscopy showed a decrease in grain size (from 0.552 μm to 0.194 μm) and porosity (from 18.65% to 4.57%) as the CoNbFeO content increases from x = 0 to x = 20%, respectively. The influence of magnetic CoNbFeO content on the magnetic, ferroelectric, magnetoelectric coefficient, electric, and dielectric properties of composite systems has been investigated. The ferromagnetic and ferroelectric natures of diverse composite systems are reflected via the registered M-H and P-E loops at ambient temperature. A steady increase in magnetic parameters such as saturation magnetization and remanent magnetization is observed as the spinel ferrite CoNbFeO content increases. Similarly, the values of the electric coercivity increased from 1.65 kV/cm for x = 0% to 3.99 kV/cm for x = 20%. The frequency-dependent dielectric and electrical measurements were also investigated at various temperatures. By raising the measurement temperature, the dielectric polarization was found to increase for composite systems with x > 2%. Interestingly, the tangent loss was reduced for different composite systems in comparison to pristine BTO and CoNbFeO materials. The lowest tangent loss values were noticed for x = 5% composite system. All composite systems revealed good magnetoelectric coupling with coupling coefficient magnitudes up to a maximum value of ∼22.5 mV/cm.Oe, indicating that they can be potential candidates for use in advanced multifunctional electric devices. [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]

Cell dielectric property measurement holds significant potential for application in cell detection and diagnosis due to its label-free and noninvasive nature. In this study, we developed a biosensor designed to measure the permittivity of liquid samples, particularly cell suspensions at the nanoliter scale, utilizing microwave and millimeter wave coplanar waveguides in conjunction with a microchannel. This biosensor facilitates the measurement of scattering parameters within a frequency domain ranging from 1 GHz to 110 GHz. The obtained scattering parameters are then converted into dielectric constants using specific algorithms. A cell capture structure within the microchannel ensures that cell suspensions remain stable within the measurement zone. The feasibility of this biosensor was confirmed by comparison with a commercial Keysight probe. We measured the dielectric constants of three different cell suspensions (HepG2, A549, MCF-7) using our biosensor. We also counted the number of cells captured in multiple measurements for each cell type and compared the corresponding changes in permittivity. The results indicated that the real part of the permittivity of HepG2 cells is 0.2–0.8 lower than that of the other two cell types. The difference between A549 and MCF-7 was relatively minor, only 0.2–0.4. The fluctuations in the dielectric spectrum caused by changes in cell numbers during measurements were smaller than the differences observed between different cell types. Thus, the sensor is suitable for measuring cell suspensions and can be utilized for label-free, noninvasive studies in identifying biological cell suspensions. [ABSTRACT FROM AUTHOR]

The microwave (MW) dielectric permittivity of gallium oxide (β-Ga2O3) fundamentally determines its interaction with an electromagnetic wave in bulk power. Yet, there is a lack of experimental data due to limitations of high-temperature MW dielectric measurements and the large uncertainty under variable-temperature conditions. Herein, we develop a deep potential (DP) based on density functional theory (DFT) results and apply deep potential molecular dynamics (DPMD) for accurately predicting temperature-dependent MW dielectric permittivity of β-Ga2O3. The predicted energies and forces by DP demonstrate excellent agreement with DFT results, and DPMD successfully simulates systems up to 1280 atoms with quantum precision over nanosecond scales. Overall, the real part of the MW dielectric permittivity decreases with rising frequency, but the dielectric loss increases. The MW dielectric permittivity gradually increases as the temperature increases, which is closely related to the reduced dielectric relaxation time and increased static and high-frequency dielectric constants. Besides, the oxygen vacancy defects significantly reduce the relaxation time; however, augmenting the defect concentration will cause a slight rise in relaxation time. The electron localization function analysis reveals that more free electrons and low localization of electrons produced by high defect concentrations facilitate the increased relaxation time. This study provides an alternative route to investigate the temperature-dependent MW permittivity of β-Ga2O3, which attains prime importance for its potential applications in RF and power electronics. [ABSTRACT FROM AUTHOR]

High permittivity materials are required for efficient organic photovoltaic devices, and the addition of the conjugated polymer composite poly(3,4-ethylenedioxythiophen) polystyrene sulfonate (PEDOT:PSS) to dielectric polymers has been shown to significantly heighten their permittivity. The permittivity of PEDOT:PSS at the optical and microwave frequencies has been investigated, but PEDOT:PSS layers are mainly used for low-frequency device applications, where accurate dielectric property measurements are hindered by their high electrical conductivity and the problems arising from the metal-polymer interfaces. Here, we determine the complex relative permittivity ( ε r * = ε r ′ − j ε r ″ ) of PEDOT:PSS layers perpendicular to the layer plane in the 10−2–106 Hz range by combining data from the reactive energy estimations and electrochemical impedance spectroscopy, and discover that: ε r ′ at <1 Hz is ultra-high (∼106) decreasing with frequency to ∼5 at 106 Hz; the experimental data fit the Cole-Cole dielectric relaxation model by considering multiple relaxation mechanisms; PEDOT:PSS polarizes nonlinearly and ε r ′ increases with the intensity of the applied external field; low frequency ε r ′ increases with both thickness and temperature of the layer, opposite trend of temperature-dependence prevails at >103 Hz; the dielectric properties of PEDOT:PSS are highly anisotropic and the in-plane ε r ′ at 1.0 kHz is three orders of magnitude higher than the vertical ε r ′ ; and that the ε r ′ ′ decreases proportional to the reciprocal of frequency (1/f). The latter finding provides an explanation for the ubiquitous pink noise accompanying signals transmitted through organic conductor links. The described methodology can be adopted for investigations on other conjugated polymers. [ABSTRACT FROM AUTHOR]

Single crystals of Thiourea Cadmium hydrogen borate (TCHB), a hybrid nonlinear optical (NLO) material, are grown from an aqueous solution by slow evaporation solution growth technique at ambient temperature. Characterization studies have been conducted to probe the nonlinear effects of the crystal. The crystalline nature of TCHB is explored using the single crystal X-ray diffraction technique. The chemical composition is resolved by the Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray analysis. UV–Vis spectral studies analyze the transparency of the crystal. Optical studies illustrate the UV cut-off wavelength to be 285 nm with wide window of transparency in the infrared and visible regions. The optical and electrical conductivity studies indicate superior optical response essential for optical computing and photonic applications. The Kurtz powder test has confirmed the NLO capability. The thermal stability is analyzed through a thermogravimetric study. Dielectric and AC conductivity measurements carried out over a wide range of frequencies (100 Hz to 5 MHz) for various temperatures establish the semiconducting and photonic capacity of TCBH crystal to be used as photodiodes, optical fibres and laser lights. [ABSTRACT FROM AUTHOR]

The recent high demand of secondary electron emission yield (SEY) measurements in dielectric materials from space industry has driven SEY laboratories to improve their facilities and measurement techniques. SEY determination by the common capacitive method, also known as pulsed method, is well accepted and has given satisfactory results in most cases. Nevertheless, the samples under study must be prepared according to the experimental limitations of the technique, i.e. they should be manufactured separated from the devices representing faithfully the surface state of the own device and be as thin as possible. A method based on the Kelvin probe (KP) is proposed here to obtain the SEY characteristics of electrically floating Platinum, Kapton and Teflon placed over dielectric spacers with thicknesses ranging from 1.6 to 12.1 mm. The results are compared with those of the capacitive method and indicate that KP SEY curves are less sensitive to spacer thickness. An explanation based on the literature is also given. In all, we have established that KP is better suited for the analysis of dielectric samples thicker than 3 mm. [ABSTRACT FROM AUTHOR]

This paper represents a study of the effect of Al-substitutions on structural, magnetic, and dielectric properties of Sr 0·8 Ce 0·2 Fe 12- x Al x O 19 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) ferrites synthesized in presence of yellow bell leaves extract. All samples were synthesized using the sol-gel combustion technique with the influence of green synthesis by using leaves of Tecomastans (yellow bell) plant. These samples were preheated at 550 °C for 4 h and finally calcinated at 1150 °C for 6h. These samples were characterized using XRD, FTIR spectroscopy, SEM, VSM, LCR measurements, and VNA measurements. XRD analysis confirm the formation of a magnetoplumbite M-phase (hexagonal) with a minor impurity phase of CeO 2 in all samples. Lattice parameters a and c are obtained from rietveld refinement, which are found in the range from 5.859 Å to 5.883 Å, and 22.96 Å to 23.05 Å respectively. FTIR spectra confirm the absence of organic compounds and the presence of an absorption band in the fingerprint region, which are linked to the stretching of the metal-oxygen bond at the octahedral and tetrahedral sites. The surface morphology of these samples is analyzed using SEM images. Grains with hexagonal plate shapes were observed in each sample. The average grain size varies in the range of 0.565 μm–1.455 μm. EDS data confirms the presence of desired elements in the respective sample. VSM analysis shows hard magnetic behavior in all samples. Magnetic parameters were found in the range, M s : 36.281–43.397 emu/g, M r : 12.297–19.841 emu/g, H c : 2.0987–3.814 kOe. In low-frequency (20 Hz-2 MHz) dielectric measurements, the dielectric constant is high at low frequencies, which rapidly falls as frequency increases. Loss tangent curve shows a relaxation peak for each sample above 200 kHz. AC conductivity is very low in the order of 10−5 S/m in plateau region below 2 kHz, which increases as frequency increases. Cole-Cole plot suggests the effect of grain boundary contribution is higher in non-substituted sample compared to Al-substituted samples. In high-frequency (0.2 GHz–20 GHz) measurements, the dielectric constant remains almost constant. These values are found in the range 5–7.5. Low loss tangent of 0–0.16 were observed in every sample in this frequency domain, with AC conductivity of the order of 10−2 S/m. [ABSTRACT FROM AUTHOR]