Dielectric Properties Research Articles

Borosilicate glasses doped with Er2O3: preparation, physical, optical, dielectric properties and radiation shielding capacity

Borosilicate glasses doped with Er2O3: preparation, physical, optical, dielectric properties and radiation shielding capacity

Dielectric properties of chitosan-based ZnO nanocomposites for high-frequency electronic devices

Dielectric properties of chitosan-based ZnO nanocomposites for high-frequency electronic devices

A Bio-Based Polybenzoxazine Derived from Diphenolic Acid with Intrinsic Flame Retardancy, High Glass Transition Temperature and Dielectric Properties.

A bio-based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME-HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non-isothermal differential scanning calorimetry (DSC). The activation energies of DPME-HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME-HFBz) presented an ultra-high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME-HFBz) was as high as 38%. Poly(DPME-HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME-HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low-dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties.

Ferroelectric, Switchable Dielectric and Nonlinear Optical Properties in Inorganic-Organic Lead-Free 1D Hybrids Based on Bi(III) and Azetidine: (C3NH8)2[BiCl5], (C3NH8)2[BiBr5

This study investigates lead-free organic-inorganic hybrids (C3NH8)2[BiCl5] (ABC) and (C3NH8)2[BiBr5] (ABB), focusing on their structural, dielectric, ferroelectric, and optical properties. Both compounds exhibit paraelectric (I) to ferroelectric (II) phase transitions (PTs) at 230/233 K and 228/229 K, respectively, transitioning from orthorhombic (Pnma) to monoclinic (P21) phases, with distorted [BiX6]3- octahedra forming 1D chains. Quasielastic neutron scattering and solid-state 1H NMR studies reveal the localized motion of azetidinium cations. Dielectric measurements of ABC and ABB show step-like permittivity changes by 11-12 units post-transition I → II, demonstrating reversible switching behavior. Absorption studies reveal band gaps of 3.24 eV for ABC and 2.76 eV for ABB, classifying them as insulators. Luminescence spectra at 77K display 578 nm (ABC) and 708 nm (ABB) emissions, attributed to 3P1,0 → 1S0 transitions. Both compounds demonstrate stable second harmonic generation (SHG) switching of the on-off type. The switching performance is evaluated over multiple thermal cycles using the treq metric, which decreases with increasing temperature change rate and indicates that ABB's SHG switching is approximately 30% faster than that of ABC.

Design and Development of a 3D Network Hybrid Polymeric System for Enhanced Dielectric Properties through Selective γ-Crystal Growth of Poly(PVDF-CTFE) and Reduced High-Frequency Relaxation

Design and Development of a 3D Network Hybrid Polymeric System for Enhanced Dielectric Properties through Selective γ-Crystal Growth of Poly(PVDF-CTFE) and Reduced High-Frequency Relaxation

Investigation of Magnetic and Dielectric Properties of Nanofibric Spinel Oxides ACo2O4 (A = Co, Ni, and Fe) Under Low Magnetic Field

Investigation of Magnetic and Dielectric Properties of Nanofibric Spinel Oxides ACo2O4 (A = Co, Ni, and Fe) Under Low Magnetic Field

Multi-step thermal design of microwave vacuum heating to basaltic regolith simulant towards lunar base construction.

Humanned exploration and extended stay on the Moon are the hottest challenges today. We report highly robust materials by microwave heating under high-vacuum conditions (10- 3 Pa) from a basaltic regolith simulant (FJS-1) to ensure the feasibility of lunar infrastructure construction. The violent degassing dynamics were revealed by monitoring vacuum pressure during heating and analyzing the compounds evolved from basaltic silicate compounds: thermal pyrolysis of silicate compounds became more pronounced above 1000 oC, leading to a catastrophic deformation accompanied by forming countless pores of several hundred µm sizes. The preferential formation of the magnetite phase in vacuum heating dominantly caused the radical change in microwave absorption capacity compared with conventional heating routes using an electrical furnace in atmospheric conditions. Besides, the in-situ measurement of dielectric properties during microwave vacuum heating clarified the increase in one order of magnitude from 100 to 1000 oC. Based on the presumed phenomena during microwave-vacuum heating for basaltic regolith, we propose a new thermal design concept to overcome the practical limitations of microwave technology. The multi-step temperature profile successfully fabricated a highly robust product that demonstrated world-class mechanical performance, equivalent to the compressive strength of 65MPa without any vigorous hydrostatic cold press as a pre-treatment.

Improving computational models of deep brain stimulation through experimental calibration.

Deep brain stimulation has become a well-established clinical tool to treat movement disorders. Nevertheless, the knowledge of processes initiated by the stimulation remains limited. To address this knowledge gap, computational models are developed to gain deeper insight. However, their predictive power remains constrained by model uncertainties and a lack of validation and calibration. Exemplified with rodent microelectrodes, we present a workflow for validating electrode model geometry using microscopy and impedance spectroscopy in vitro before implantation. We address uncertainties in the tissue distribution and dielectric properties and outline a concept for calibrating the computational model based on in vivo impedance spectroscopy measurements. The standard deviation of the volume of tissue activated across the 18 characterized electrodes was approximately 32.93%, underscoring the importance of electrode characterization. Thus, the workflow significantly enhances the model predictions' credibility of neural activation exemplified in a rodent model. Computational models are frequently employed without validation or calibration, relying instead on manufacturers' specifications. Our approach provides an accessible method to obtain a validated and calibrated electrode geometry, which significantly enhances the reliability of the computational model that relies on this electrode. By reducing the uncertainties of the model, the accuracy in predicting neural activation is increased. The entire workflow is realized in open-source software, making it adaptable for other use cases, such as deep brain stimulation in humans. Additionally, the framework allows for the integration of further experiments, enabling live updates and refinements to computational models.

Structural, Optical, Magnetic, and Dielectric Investigations of Pure and Co-Doped La0.67Sr0.33Mn1-x-yZnxCoyO3 Manganites with (0.00 < x + y < 0.20)

Here, we report the structural, optical, magnetic, and dielectric properties of La0.67Sr0.33Mn1-x-yZnxCoyO3 manganite with various x and y values (0.025 < x + y < 0.20). The pure and co-doped samples are called S1, S2, S3, S4, and S5, with (x + y) = 0.00, 0.025, 0.05, 0.10, and 0.20, respectively. The XRD confirmed a monoclinic structure for all the samples, such that the unit cell volume and the size of the crystallite and grain were generally decreased by increasing the co-doping content (x + y). The opposite was true for the behaviors of the porosity, the Debye temperature, and the elastic modulus. The energy gap Eg was 3.85 eV for S1, but it decreased to 3.82, 3.75, and 3.65 eV for S2, S5, and S3. Meanwhile, it increased and went to its maximum value of 3.95 eV for S4. The values of the single and dispersion energies (Eo, Ed) were 9.55 and 41.88 eV for S1, but they were decreased by co-doping. The samples exhibited paramagnetic behaviors at 300 K, but they showed ferromagnetic behaviors at 10 K. For both temperatures, the saturated magnetizations (Ms) were increased by increasing the co-doping content and they reached their maximum values of 1.27 and 15.08 (emu/g) for S4. At 300 K, the co-doping changed the magnetic material from hard to soft, but it changed from soft to hard at 10 K. In field cooling (FC), the samples showed diamagnetic regime behavior (M < 0) below 80 K, but this behavior was completely absent for zero field cooling (ZFC). In parallel, co-doping of up to 0.10 (S4) decreased the dielectric constant, AC conductivity, and effective capacitance, whereas the electric modulus, impedance, and bulk resistance were increased. The analysis of the electric modulus showed the presence of relaxation peaks for all the samples. These outcomes show a good correlation between the different properties and indicate that co-doping of up to 0.10 of Zn and Co in place of Mn in La:113 compounds is beneficial for elastic deformation, optoelectronics, Li-batteries, and spintronic devices.

Thickness-dependent structural and growth evolution in relation to dielectric relaxation behavior and correlated barrier hopping conduction mechanism in Ni0.5Co0.5Fe2O4 ferrite thin films.

Ferrite thin films are explored due to their promising properties, which are essential in various advanced electronic devices. However, depositing a film with pure phase and uniform microstructure is challenging. The Ni0.5Co0.5Fe2O4 ferrite thin films are deposited using pulsed laser deposition (PLD) technique to explore the effect of thickness on structural properties, growth evolution, temperature-dependent dielectric behavior, and conduction mechanisms. Microstructural analysis revealed that the films are uniformly grown, exhibiting surface roughness ranging from  2 to 4 nm. The dielectric response, adhering to a modified Debye model, exhibited multiple relaxation processes, with notable changes in the dielectric constant and loss as film thickness increased. Impedance spectra exhibited both space charge and dipolar relaxation phenomena, corroborated by Cole-Cole and electrical modulus plots. The analysis of the imaginary electric modulus using the Kohlrausch-Williams-Watts (KWW) function revealed non-Debye-type relaxation in all deposited films, characterized by thermally activated broad peaks. Conductivity decreased up to a certain film thickness, and the frequency exponent derived from Jonscher's power law suggested a correlated barrier hopping model for AC conduction. Activation energies improved with film thickness up to 125 nm, consistent with a constant energy barrier for polarons during relaxation and conduction phases. The film with 125 nm thickness exhibited the optimal dielectric properties, with the maximum dielectric constant, minimum dielectric loss, and highest activation energy. These findings highlight the potential of dense, uniformly grown films with high dielectric constants and low dielectric losses for advanced electronic device applications.

Dielectric Hybrid Optimization Model Based on Crack Damage in Semi-Rigid Base Course

To accurately predict the relative permittivity of cement-stabilized base materials, a study on the dielectric mixing model for cracked base materials was conducted. Based on the electromagnetic mixing theory of multiphase composites, a comprehensive dielectric mixing model of cement-stabilized base materials was derived. The volume ratios and relative permittivity values of the specimen constituents in different cracking states of the cement-stabilized base were determined using industrial CT and a Percometer relative permittivity meter, with comprehensive consideration given to the effects of different initial porosities and crack widths on the dielectric properties. Based on the volumetric and dielectric properties of the base material specimens in both intact and cracked states, as well as the error analysis between the predicted and measured values of the relative permittivity constant, the u-optimal solution of the dielectric mixing model for cement-stabilized base material was determined to be 1. Consequently, an optimization dielectric mixing model for semi-rigid base course materials in a cracked state was developed. The optimization model proposed is suitable for predicting the dielectric properties of cement-stabilized base material with crack widths generally greater than 3 mm during the service life of semi-rigid base course in engineering practice.

Focus on synthesis, characterization and applications of low dimensional nanomaterials

Abstract This Editorial summarizes the content of a focus collection on the synthesis, characterization and applications of low dimensional materials. The collection groups original research and review articles providing recent results and prospects in the field, with particular attention on optoelectronic applications, dielectric and magnetic properties, and electrochemical and biological performances.

First-principles study of the structural, electronic, dielectric, and dynamical properties of gallium nitride in the graphite-like hexagonal P63/mmc phase

First-principles study of the structural, electronic, dielectric, and dynamical properties of gallium nitride in the graphite-like hexagonal P63/mmc phase

A high-response-frequency bimodal network polyacrylate elastomer with ultrahigh power density under low electric field.

Dielectric elastomers, used as driver modules, require high power density to enable fast movement and efficient work of soft robots. Polyacrylate elastomers usually suffer from low power density under low electric fields due to limited response frequency. Here, we propose a bimodal network polyacrylate dielectric elastomer which breaks the intrinsic coupling relationship between dielectric and mechanical properties, featuring relatively high dielectric constant, low Young's modulus, and wide driving frequency bandwidth (~200 Hz) like silicones. Therefore, an ultrahigh power density (154 W kg-1@20 MV m-1, 200 Hz) is realized at low electric field and high resonance frequency, 75 times greater than at 10 Hz. Further, a rotary motor is developed, reaching an impressive speed of 1245 rpm at 19.6 MV m-1 and 125 Hz, surpassing previous acrylate-based motors and entering the high-speed domain of silicone-based motors. These findings offer a versatile strategy to fabricate high-power-density dielectric elastomers for low-electric-field soft actuators.

Synthesis, characterization and dielectric properties evaluation of NiO-Co3O4 nanocomposite

AbstractNanosized materials are increasingly being recognized as inherent components in the development of energy storage devices and other state-of-the-art dielectric applications. In this work, nickel oxide (NiO), cobalt oxide (Co3O4) and NiO–Co3O4 nanocomposites in different compositions (10%, 20%, 30% and 40%) were successfully synthesized through hydrothermal method, optimizing concentrations of the precursors, and X-ray diffraction confirmed single-phase polycrystalline NiO and Co3O4. SEM images showed that distinct morphologies for each material and FTIR spectra reveal Ni–O and Co–O. UV–visible analysis shows a plasmon peak at 307 nm for NiO and excition absorption at 282 nm for Co3O4. NiO–Co3O4 nanocomposites displayed band gaps ranging from 2.37 eV to 2.67 eV. Dielectric properties showed a decrease in εʹ with frequency, attributed to Maxwell–Wagner and hopping models. AC conductivity increased with frequency due to Co3O4 content and oxygen vacancies. The study suggests potential applications in supercapacitors, spintronics, high-frequency devices and ultra-high dielectric materials.

Effects of ion irradiation induced phase transformations and oxygen vacancies on the leakage current characteristics of HfO2 thin films deposited on GaAs

Abstract We report on the ion-induced phase transformations, defect dynamics related to oxygen vacancies and the resulting leakage current characteristics of RF sputtered HfO2 thin films grown on GaAs. A systematic growth of HfO2 grains and Ion prompted phase transformations of HfO2 to crystalline phases such as monoclinic and tetragonal/orthorhombic (mixed phase) in otherwise amorphous HfO2 thin films have been observed after irradiation. At lower fluences, Ion induced enhancement in the dielectric properties of HfO2 thin films resulted in a reduction in the leakage current, whereas ion prompted defect formation at higher fluences caused a systematic increase in the leakage current density. Further, the effects of Poole-Frenkel (PF) tunneling and Fowler-Nordheim (FN) tunneling on the leakage current have also been investigated. These mechanisms showed the existence of impurities in the as-grown films. Photoluminescence (PL) study suggests the variation in the defect configuration related to O-vacancies and slight shift in the peak positions due to SHI irradiation are responsible for the observed changes in electrical characteristics. This study offers worthwhile information for considering the effects of electronic excitation prompted defect annealing or defect creation on the performance of HfO2/GaAs based photonic and optoelectronic devices, particularly, when such devices are operated in a radiation harsh environment.

Dielectric and energy storage properties of the g-C3N4/PVDF nanocomposite thick film

Dielectric and energy storage properties of the g-C3N4/PVDF nanocomposite thick film

SUSTAINABLE CONVERSION OF BANANA WASTE INTO ELECTRICAL INSULATION MATERIALS FOR HIGH VOLTAGE APPLICATIONS

<p style="text-align:justify;"><span style="font-family:"Times New Roman","serif";font-size:12.0pt;line-height:150%;text-justify:inter-ideograph;">The study examined the electrical characteristics of epoxy composites that were reinforced with fibers derived from banana leaves and pseudostems. Specifically, the study focused on analysing the dissipation factor, loss factor, and dielectric constant of these composites. The study found that composites containing banana leaf fibers demonstrated enhanced dielectric properties in comparison to pure epoxy composites. This improvement can be attributed to the effective interlocking between the fibers and the matrix, as well as the polarization effects. Enhancing the amount of fibre in the material resulted in greater dielectric constants, reaching a maximum at a critical volume of 17.2%. However, at higher frequencies, the dielectric constants fell due to decreasing polarization. Chemical treatments, such as alkali and peroxide solutions, improved the bonding between the fibers and the matrix, leading to higher resistance to water and greater electrical insulation. The results also showed that banana leaf fibers had superior dielectric performance compared to pseudostem fibers, mostly because of enhanced nanoparticle bonding. Using banana fibers is particularly noteworthy since it contributes to environmental sustainability by recycling agricultural waste, hence mitigating the ecological consequences of synthetic products.</span></p>

Low dielectric properties of alkali-free aluminoborosilicate fiber glasses for PCB applications at 10GHz.

Alkali-free aluminoborosilicate glasses without (GDMC-Si) and with La2O3 addition (GDMC-La) were fabricated with an aim to develop low dielectric glass fibers for use in printed circuit boards (PCBs) as a reinforcing material in high-speed 5G/6G telecommunications application. This study presents the structural, thermo-physical, and dielectric properties of the glasses. The decrease in glass transition temperature (Tg) and the increase in coefficient of thermal expansion (CTE) were found by the addition of SiO2 and La2O3 in the present glass system, which are due to the depolymerization of the glass networks confirmed by the FTIR analysis. The dielectric constants (Dk) and the dissipation factors (Df) of the glasses were investigated at a high frequency of 10GHz. The Dk values of the GDMC-Si and GDMC-La glass systems reached a minimum of 4.50 and 4.75, while their Df values reached a minimum of 2.86 × 10-3 and 3.01 × 10-3, respectively. Notably, the Dk and Df values of the present glasses were lower than the commercial E-glass (Dk: 6.9, Df: 7.0 × 10-3 at 10GHz) and L-glass (Dk: 4.8, Df: 3.0 × 10-3 at 10GHz). Glass fibers with a diameter of 10μm were successfully drawn by the continuous melt-spinning process and their mechanical properties were investigated.

Microwave dielectric properties of Na2O–Ln2O3–MoO3–TiO2 (Ln = Nd, La and Ce) system with low‐sintering temperature

AbstractThis study examines the low‐loss and temperature‐stable Na2O–Ln2O3–MoO3–TiO2 (Ln = Nd, La and Ce) system, synthesized via a solid‐state process at low‐sintering temperatures ranging from 840°C to 900°C The structure, microstructure and microwave properties of the Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce) ceramics as a function of the sintering temperature were studied. The results of XRD patterns and microstructure characterization showed that the main phase in compositions belong to tetragonal scheelite and tetragonal structure. The ceramic composition Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce), sintered at 840°C–900°C for 2 hours, demonstrated excellent microwave dielectric properties, exhibiting relative dielectric constant (εr) of 13.9–14.4, Q × f value of about 31 100 (at 9.66 GHz) – 48 600 GHz (at 9.33 GHz), and temperature coefficient of –8.1 to –1 ppm/°C. Our work designs temperature‐stable microwave dielectric ceramics with low‐sintering temperature for LTCC technology applications.