Papers by Keyword: Dielectric Properties

Abstract: Ni_1-2xMg_xCu_xO and Ni_1-2xMg_xRu_xO nanoparticles (x = 0.005, 0.01, 0.02, 0.04, 0.08) were synthesized by the chemical co-precipitation method using salt chloride precursor and EDTA as a capping agent.The present work compares the impact of (Mg, Cu) and (Mg, Ru) co-dopants on the dielectric properties of NiO within a frequency range 0.1 -8 MHz and various dopant concentrations x = 0, 0.005, 0.01, 0.02, 0.04, 0.08. The dielectric properties and phase formation were investigated via an impedance analyser and XRD, respectively. X-ray diffraction patterns confirm the successful synthesis and crystallization of all Ni_1-2xMg_xCu_xO and Ni_1-2xMg_xRu_xO nanoparticles in the fcc structure except for Ni_0.92Mg_0.04Ru_0.04O and Ni_0.84Mg_0.08Ru_0.08O nanoparticles confirming a secondary RuO₂ pahse. Observed and calculated data from the impedance analyzer showed higher dielectric constants, ac conductivity, energy loss, and refractive index values for Ni_1-2xMg_xCu_xO than for Ni_1-2xMg_xRu_xO nanoparticles. However, the impedance values of (Mg, Ru) dual-doped NiO nanoparticles were higher compared with (Mg, Cu) dual-doped NiO nanoparticles. Both samples showed a decrease in dielectric constants, impedance, loss tangent, and refractive index as frequency increased (0.1-7.5MHz), with a vice versa behavior as dopant concentration rose, except for the impedance. Hence, Ni_1-2xMg_xCu_xO and Ni_1-2xMg_xRu_xO nanoparticles are good candidates for electrical and optical applications.

Abstract: Screw pine plant, scientifically know as Pandanus atrocarpus, thrive abundantly across Asia. This study examines the morphology, functional structure, thermal and dielectric properties of fibers extracted from Pandanus atrocarpus leaves. The water-based retting method, facilitated by microbial activity, was utilised to extract the Pandanus atrocarpus fibres from the leaves. Microfibrils vertical alignment was observed on the morphology of leaf fibres with the random measured diameter ranging from 392.2 µm to 406.3 µm. Fourier transform spectroscopy confirmed the existence of cellulose and amorphous constituents. Pandanus atrocarpus leaf retains thermal stability up to 220°C before experiencing degradation of hemicellulose at 296°C, and cellulose at 359°C, as verified by DTG and DSC analyses. The effect of adding Pandanus atrocarpus leaf fibres in epoxy composite improves the dielectric properties across a wide frequency by promoting the interaction of polar molecules and displacement currents, leading to greater orientation polarization, thus well-suited for suitable for polymerization over various high frequency applications.

Abstract: The development of energy storage capacitors with high dielectric constant and good stability has been focused on by researchers due to many issues regarding environmental protection and energy conservation. Barium-Strontium Titanate based ceramic capacitors are widely used for energy storage applications due to their attractive dielectric properties. In this study, (Ba_0.90Sr_0.10) TiO₃ based capacitors were produced, and the influence of additives i.e. CaZrO₃, MnCO₃, CeO₂, ZnO, and Nb₂O₅ was investigated. The parameters of all the fabrication processes have been optimized to get defect-free green and sintered samples. The defect-free green parts were sintered at 1380°C for 2 h and perovskite structure was confirmed by XRD profiles. The grain size was refined from 25 μm to 08 μm analyzed by scanning electron microscopy (SEM). The capacitor was tested at 40 KV successfully and capacitance of 2.0 nF was measured at this high voltage. The results showed that high-voltage capacitors can be fabricated with enhanced energy storage.

Abstract: The heterostructure of composite films filled with conductive fillers can improve the interfacial polarization, which is one of the keywords to enhance the dielectric and ferroelectric properties. In this study, a composite films were created by combining Polyvinylidenefluoride-trifluoroethylenechlorotrifluoroethylene. (PVDF-TrFE-CTFE), Graphene-nanoplatelets (GPN) and Polyvinylidenefluoride-hexafluoropropylene (PVDF-HFP), using the tape casting solution method. The heterostructure of the composite film improved the interfacial polarization, resulting in increased dielectric constant with terpolymer loading and GPN addition. The filled GPN1% film showed a dielectric constant of 21.5 and 13.6 at 100/0 and 70/30, respectively, compared to 17.9 and 11.8 for the 2-phase composite films. Additionally, the terpolymer and GPN loading induced the maximum polarization (Pmax) and changed the PE-loop (hysteresis loop) behavior. The high performance of the PVDF-TrFE-CTFE and GPN composite films in terms of their dielectric constant, dielectric loss, AC conductivity, and polarization performances make them promising materials for electric-capacitor and energy storage applications.

Abstract: Polymer-metal hybrid nanocomposites have garnered significant attention in recent years due to their exceptional electrical and dielectric properties, which find applications in a wide range of industries, including electronics, energy storage, and advanced materials. This review article provides a comprehensive overview of the current state-of-the-art in the field of polymer-metal hybrid nanocomposites, with a particular focus on their electrical and dielectric properties. The first section of the review delves into the synthesis and fabrication techniques employed to create these nanocomposites, highlighting the importance of controlling the dispersion and distribution of metal nanoparticles within the polymer matrix. Various approaches, such as in-situ polymerization, melt mixing, and electrospinning, are discussed in detail, along with their respective advantages and limitations.The subsequent sections explore the influence of metal nanoparticles on the electrical conductivity and dielectric constant of the nanocomposites. The role of factors such as nanoparticle size, shape, and concentration in determining these properties is thoroughly examined. Moreover, the impact of metal surface modifications and the choice of polymer matrix on enhancing electrical and dielectric performance are also addressed. In addition to discussing fundamental aspects, this review highlights practical applications of polymer-metal hybrid nanocomposites in the development of high-performance capacitors, sensors, electromagnetic shielding materials, and flexible electronics. The potential for these materials to revolutionize various technological sectors is discussed, emphasizing their role in advancing miniaturization, energy efficiency, and durability. Furthermore, the review outlines current challenges and future prospects in the field, including the need for a deeper understanding of the underlying mechanisms governing electrical and dielectric behavior in these nanocomposites. Emerging trends such as the incorporation of 2D materials and the development of multifunctional hybrid systems are also explored, hinting at exciting avenues for further research and innovation. In conclusion, polymer-metal hybrid nanocomposites offer a promising platform for tailoring electrical and dielectric properties to meet the demands of modern technology. This review serves as a valuable resource for researchers, engineers, and scientists seeking to explore the potential of these materials and drive advancements in the field of electrical and dielectric engineering.

Abstract: Lead-free ferroelectric materials of sodium-potassium bismuth titanate, (1-x)NBT-xKBT systems were synthesized by a hydrothermal process. In this way, the appropriate conditions for the hydrothermal synthesis of NBT and KBT (i.e., concentrations of synthetic precursors, solution pH and temperature) are given graphically. Ceramics of (1-x)NBT-xKBT with (x(mol.%) = 0; 12; 16; 20; 30 and 100) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The rhombohedral-tetragonal morphotropic phase boundary (MPB) was confirmed to be in the region of 0.12 ≤ x ≤ 0.20 for (1-x)NBT-xKBT at ambient temperature. Scherrer's formula and the Williamson-Hall (W-H) analysis were used to examine the average crystallite size and lattice strain. Raman spectroscopy was effectively applied to study the structural evolution of the (1-x)NBT-xKBT phase. The ceramics exhibited a high temperature of maximum dielectric permittivity at (Tmax = 343 °C at 100 kHz) along with electromechanical coupling factors (kp = 0.34, d33 = 147 pC/N). Based on the composition of all specimens, the results indicate a diffuse phase transition, probably of second order, between ferroelectric and paraelectric phases.

Abstract: Research in improving dielectric materials is rapidly becoming more intense as there are higher demands for novel materials with the ability to store charges. In this work, impedance characterisation and dielectric properties of epoxy composites containing Carbon Black (CB) and a mixture of CB and Carbon Nanotube (CNT), kept at 1:1 wt.% is conducted. For both cases, the total number of fillers are varied from 0.5 wt.% to 6 wt.%. At 20 Hz, the values of dielectric composites, k was recorded to be 2050 for 6 wt.% CB, compared to k = 600, for composites containing dual filler (3 wt.% CB + 3 wt.% CNT). Further analysis revealed that the 6 wt.% sample (CB + CNT) exhibited higher ac conductivity at lower frequency, compared to sample containing only 6 wt.% CB. This could be due to the reason that CNT has more conductivity effects while CB has more storage or capacitive effects. Nyquist plot of impedance for both fillers also revealed the formation of semi-circular shapes for 5 wt.% and 6 wt.%; for both CB and CB + CNT fillers. However, formation of smaller semi-circular shapes is observed for CB + CNT, compared to CB only, indicating formation of conductive network in dual filler composites. This study highlights the potential of CB in enhancing mainly the dielectric properties of epoxy composites.

Abstract: Barium strontium titanate (Ba_0.8Sr_0.2TiO₃) thin films have been prepared by pulsed laser deposition (PLD). The thin film of (Ba_0.8Sr_0.2TiO₃) was deposited on a silicon (Si) substrate with different deposition temperatures. The XRD pattern identifies these specimens as being of the tetragonal phase. As the deposition substrate temperature varied from 200 °C to 400 °C, the average crystal size of BST increased from 34 nm to 68 nm calculated by the XDR pattern. Field (FESEM) images have estimated the particle size of the film. The dielectric constant increased with increasing substrate temperature.

Abstract: Ferrites materials with Spinel structure have been broadly studied in recent years because of numerous technological applications. Lanthanum substituted Co-ferrites nanoparticles (CoLa_0.075Fe_1.925O₄) were synthesized via chemical co-precipitation method. X-ray Diffraction study revealed that prepared nanoparticales are single-phased spinel ferrites. Lattice constant, crystallite size, theoretical densities were estimated from XRD data. Electrical properties have been investigated with frequency ranging from 20Hz to 3MHz at room temperature. Dielectric constant and dielectric loss factor shows decreasing trend with increasing frequency. Ac conductivity exhibit increasing behavior with increasing frequency. The contribution of grains and intergrain boundaries in conduction process was estimated from impedance study. Nyquist plot shows dominant contribution of grain boundary resistance than the grain resistance in conduction mechanism.

Abstract: Bismuth glasses have been prepared from a commercial-grade chemical glass mixture doped with potassium chromate in different contents. They have been melted at 1250 °C for 4 h, quenched in a metal plate, and annealed at 500 °C for 20 min. The surface morphology of glass samples has been examined using scanning electron microscopy (SEM). The dielectric properties have been investigated. UV-Vis-NIR absorption has been analyzed. The results show the growth of microcrystal precipitated in the glass matrix, and colors of glass change from colorless to green and opaque with the increasing content of potassium chromate. The density of glass decreases with the increasing content of potassium chromate. The UV-Vis spectra show strong absorption of UV. The chromium-doped glasses not only absorb the UV but also the violet and/or blue lights which depend on the chromium contents.