Dielectric Characteristics Research Articles

Non-linear AC dielectric properties of epoxy composites filled with core–shell SiC particles

Abstract Core–shell structured silicon carbide (SiC)/epoxy (EP) composites exhibit superior non–linear DC conductivity. However, the high voltage alternative current dielectric properties of the composites are rarely reported. In this paper, the time–domain measurement was employed to obtain the basic dielectric characteristics, AC conductivity, and relative permittivity of the SiC/EP and SiC@Al2O3/EP composites under less than the breakdown strength of the SiC/EP (i.e. the amplitude of 1–5 kV mm−1). In addition, in the high AC electric field (i.e. the amplitude of 6–20 kV mm−1), the non–linear AC dielectric properties of the SiC@Al2O3/EP composite are also investigated. The experimental results suggest that the SiC@Al2O3/EP composite shows more obvious non–linear AC dielectric properties than the SiC/EP composite. In the high AC electric field, the AC conductivity of the SiC@Al2O3/EP composite presents the relaxation phenomenon, which is attributed to the excitation field and its derivative. This work lays a foundation for further research on the AC steady–state and transient dielectric properties of the field grading materials, which are widely used to homogenize the nonuniform electric field distribution in many electrical and electronic equipment.

Nonlinear dielectric response and conductivity characteristics of epoxy resin in high voltage AC electric field

Abstract High-voltage dielectric and AC conduction behaviors of epoxy resin (EP) insulation are beneficial for the design and application of solid-state power electronic devices. This study investigates the nonlinear dielectric response and AC conduction characteristics of EP. The dielectric relaxation characteristics, including permittivity and AC conductivity of the EP samples, were investigated using high-voltage dielectric spectroscopy and the ionic polarization model. The results demonstrate a nonlinear increase in the relative permittivity and AC conductivity concerning the AC electric field. The increase in AC conduction under a high-frequency electric field is attributed to the reduction in the threshold field for charge injection caused by elevated temperatures. Considering the dielectric response and carrier hopping, it is evident that the nonlinear dielectric response of EP primarily originates from the ionic process under high electric fields. Ionic polarization, in conjunction with ion-hopping conduction, enhances the dielectric loss at high frequencies and electric fields, thereby facilitating the nonlinear conversion of AC conduction. The equivalent free volume is likely to increase in high-frequency fields. This phenomenon leads to an increase in AC conduction and even dielectric breakdown. This study offers a pivotal theoretical framework for the design and application of high-frequency insulation.

Improved thermal, mechanical, and dielectric properties of thermotropic liquid crystalline poly(ester amide)s containing lactam-derived segmental units

We prepared two different series of thermotropic liquid crystalline poly(ester amide)s (TPEAs) via bulk polycondensation reactions of 4-hydroxybenzoic acid (HBA, 75.0 mol %) and 6-hydroxy-2-naphthoic acid (HNA, 25.0–17.5 mol %) with ε-caprolactam (CL, 0.0–7.5 mol %) or γ-butyrolactam (BL, 0.0–7.5 mol %). Our investigation aimed to explore the impact of lactam-derived aliphatic amide units’ length and content on the liquid crystalline feature, microstructure, thermal transition, thermal stability, mechanical/relaxational/rheological behavior, and dielectric characteristics of TPEAs. The molecular structure and fibrillar formation of TPEAs containing aliphatic amide units were confirmed through FT-IR and SEM analysis. With increasing CL or BL-derived units from 1.0 mol % to 5.0 mol %, we observed an increase in crystallinity, glass transition temperature, melting temperature, complex melt viscosity, and storage modulus of TPEAs, attributed to the enhanced intermolecular hydrogen bonding interactions. However, at 7.5 mol % CL or BL-derived unit content, these properties decreased due to increased chain irregularity as well as lowered crystallinity. Notably, the dielectric constants (3.31–3.04 at 2 MHz) of TPEAs decreased with the increase of lactam-derived aliphatic amide units owing to the restricted chain mobility by intermolecular hydrogen bonding interactions. We believe that the TPEAs synthesized in this study hold significant potential for applications in technical plastics, superfibers, and printed circuit board materials.

Investigation of electrical, dielectric, magnetic and electrochemical characteristics of a BaFe12O19/Co0.5Zn0.5Fe2O4 nanocomposite

BaFe12O19 (barium ferrite, i.e., BaF) nanoparticles, Co0.5Zn0.5Fe2O4 (cobalt zinc ferrite, i.e, CZF) nanoparticles and their nanocomposite were synthesized for the investigation of electrical, magnetic, dielectric, and electrochemical properties. The X-ray diffraction (XRD) pattern revealed the formation of hexagonal structure for BaF nanoparticles and cubic structure for CZF nanoparticles with crystallite size of 32.44 nm and 31.30 nm, respectively. Whereas, for nanocomposite, the crystallite size obtained is 34.21 nm were shifting of peaks revealed the formation of nanocomposite. The Fourier transform Infrared (FTIR) spectra revealed the presence of metal-oxygen vibrational peaks for all the samples. The dielectric data revealed the increase in dielectric constant of nanocomposite as compared to pristine CZF whereas, loss reduced for nanocomposite significantly. Single semicircle in Nyquist plot for all the samples revealed the contribution of grain resistance in impedance. The hysteresis loop showed the increase in specific saturation magnetization from 16.963 emu/g to 21.305 emu/g for nanocomposite when compared with pristine BaF. Whereas specific remnant magnetization increased to 10.305 emu/g for nanocomposites. The electrochemical properties presented by Cyclic voltammetry showed the presence of cathodic and anodic peaks which revealed the presence of redox reaction in all samples. The specific capacitance calculated for all samples at different scan rate revealed that a nanocomposite showed highest Cs value 16.43 F/g at 25 mV, whereas it increased to 27.01 F/g, 35.93 F/g and 38.87 F/g with the increase in scan rate to 50 mV, 75 mV and 100 mV, respectively.

Flexible and Transparent Electrovibration-Based Haptic Display with Low Driving Voltage.

Electrovibration haptic technology, which provides tactile feedback to users by swiping the surface with a finger via electroadhesion, shows promise as a haptic feedback platform for displays owing to its simple structure, ease of integration with existing displays, and simple driving mechanism. However, without electrical grounding on a user's body, the frequent requirement of a high driving voltage near 50 V limits the use of electrovibration haptic technology in practical display applications. This study introduces materials and fabrication strategies that considerably reduce the driving voltage. We used a transparent poly(vinylidene fluoride) (PVDF) thin film deposited on transparent conductive polymers through a simple spin-coating process, thereby enabling easy integration with existing display technologies. The high dielectric constant characteristics of PVDF enabled the production of tactile cues at low voltages (approximately 15 V), which are within the safety limits of common electronics. We verified the feasibility of our electrovibration haptic feedback system on the basis of the absolute threshold voltage through two-alternative forced choice psychological tests. The results revealed that the PVDF dielectric layer exhibited a relatively lower absolute threshold than commonly used polymer films, which possess a relatively lower dielectric constant. To validate the tactile attributes, a Likert five-point scale survey was conducted, considering flat, concave, and convex curvatures. The results indicated that our haptic device can render diverse surface textures, such as "hairy" and "groovy", on the fingertips through the control of applied pulse width modulated voltage signals.

Characterization and properties of solid-state nanocomposite Acacia gum electrolytes with emphasis on diverse applications

A novel, natural, eco-friendly, solid-state Acacia gum nanocomposite electrolyte has been prepared with different weight ratios of nanoparticle ZrO2 introduced to the standard composition of 70% Acacia gum and 30% ZnSO4·7H2O. Sequential examinations, encompassing XRD, and FTIR, were conducted to evaluate the amorphous characteristics, complexation nature, and interaction of dopant nanoparticles within the acacia-salt electrolyte matrix network. The optimum ionic conductivity of nanocomposite electrolytes was found using electrochemical impedance analysis. The remarkable ionic conductivity was achieved for the electrolyte sample consisting of 10% nanoparticle ZrO2 introduced to the standard composition of 70% of Acacia gum and 30% of ZnSO4·7H2O(AZR4) at 100 °C, 6.1×10−3S/cm, at room temperature (RT) the electrolyte sample exhibited conductivity value of 1.13×10−3 S/cm. Additionally, an examination of the dielectric characteristics dependent on frequency demonstrated the existence of space charge polarization in the electrolyte and a notable tail in the low-frequency area. Through the parameters of the dielectric modulus, the research also investigated the hopping mechanism and relaxation time. Furthermore, nano-composite electrolytes were employed in the construction of solar cell devices. The outstanding results were obtained for electrolyte upon (10 wt%) nanoparticle-introduced, overall power conversion efficiency (ƞ) reached 5.38%, short-circuit photocurrent density (Jsc) 10.92 mA/cm2, open-circuit voltage (Voc) at 735 mV, and fill factor (FF) at 0.63.

Tunable annealing temperature for the structural, magnetic, optical, and dielectric characteristics of Mn0.5Zn0.5Ni0.5Fe1.5O4 nano-ferrite

The as-prepared Mn0.5Zn0.5Ni0.5Fe1.5O4 ferrite was prepared by the co-precipitation process and annealed at 300, 500, 900, and 1100 °C. The single-phase cubic spinel structure was confirmed by XRD patterns, Rietveld fitting, TEM imaging and several structural parameters, including crystalline size and lattice constant have been examined. The FTIR spectrum confirmed the main two absorption bands of tetrahedral and octahedral sites in ferrite, where the elastic parameters such as force constants and Debye temperature have been investigated. The saturation magnetization increases with the annealing temperature, while the energy band gap decreases with the annealing temperature, and also the ac conductivity decreases with annealing temperature.

Dielectric and photocatalytic characteristics of novel CaCu3Ti4O12 modified Ba0.5Sr0.5TiO3-based heterojunction synthesized by wet-chemistry method

The study presents a comprehensive investigation into the synthesis, characterization, and application of barium strontium titanate-calcium copper titanate (BST-CCTO) heterojunction, offering insights into their potential for high-energy-density capacitors and photocatalytic applications. It discusses the synthesis methods for BST, CCTO nanoparticles and their heterojunction. It delves into the structural analysis of prepared heterojunctions using techniques like X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance of heterojunctions, particularly in the degradation of organic dyes and pharmaceutical waste under visible light, is explored. Results demonstrate the superior photocatalytic efficiency of BST-CCTO heterojunction, i.e., B2 (99.5 % for RhB) compared to individual BST (78.4 %), suggesting potential applications in environmental remediation. This study also explores the development and properties of dielectric materials, particularly focusing on polyvinylidene fluoride (PVDF) and its composites with high-dielectric ceramics such as BST and CCTO. Various aspects of dielectric behavior, including polarization mechanisms and frequency dependence, are also discussed. Dielectric studies reveal the enhanced dielectric constant (50.93 at 1 kHz for 3 wt% loading of B3) of PBCT-3 composite as compared to pure PVDF composite (10 at 1 kHz), attributed to factors such as interface engineering, complementary electrical properties, and grain boundary effects. The mechanisms underlying the interaction between fillers and PVDF matrix are elucidated, highlighting the role of interface engineering and polarization enhancement in optimizing dielectric performance.

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

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

A Comparative Study of the Linear/Nonlinear Optical, and Dielectric Properties of PVA/CMC/(1−x)ZnWO4−xPbS Blended Polymers for Optoelectronic Applications

An analysis was conducted on the optical, structural, and dielectric characteristics of PVA/CMC/(1−x)ZnWO4/xPbS blends. The structures of the filler samples, undoped, and doped blends were examined using X-ray diffraction. The crystallite sizes of the various phases in the filler samples are affected by the amount of PbS in the nanocomposite. The morphologies of different blends were explored using scanning electron microscopy. The doped blend exhibited superior absorption of Ultraviolet A (UVA) and Ultraviolet B (UVB) types in addition to the visible spectrum. The optical band gaps were minimized to (5.37, 5.56, 4.11) and (4.76, 3.14, 2.92) eV for direct and indirect optical transitions, respectively, when the PVP/CMC doped with nanocomposite had 10% PbS. The highest refractive index, optical dielectric constant,and nonlinear optical parameter values were achieved when the blend was loaded with ZnWO4 only while the highest optical conductivity was obtained as the blend contained 15% PbS. The highest fluorescence intensity was observed when the fillers did not contain PbS, and it decreased as the concentration of PbS in the filler increased.

Structural, optical, and dielectric properties of Mn-doped Ce1-xMnxO2 nanocrystals for frequency-dependent device applications

Cerium oxide (CeO2) is a significant oxide semiconductor known for its advantageous electrical, optical, and dielectric properties. This study investigates the effects of manganese (Mn) doping on the structural, optical, and dielectric characteristics of CeO2. Pure and Mn-doped Ce1-xMnxO2 nanocrystalline powders, with Mn concentrations of 0, 1, 3, 5, and 7 %, were synthesized using a co-precipitation method. Structural analysis confirmed the formation of a cubic crystal structure, while surface morphology revealed agglomerated spherical particles. Notably, the band gap of Ce1-xMnxO2 decreased from 2.80 eV to 2.30 eV with increasing Mn content, indicating enhanced electronic properties due to doping. The dielectric properties exhibited a pronounced frequency dependence, with significant variations in dielectric constant and loss, demonstrating the potential of Mn-doped CeO2 as a diluted magnetic semiconductor. These findings underscore the material's applicability in biosensors and optoelectronic devices, paving the way for advancements in frequency-related technologies.

Low-temperature sintered Li2BaP2O7 ceramic: structural insights, bond characteristics, and microwave dielectric properties

The Li2BaP2O7 ceramics, synthesized through the solid-state reaction method, exhibit a pure monoclinic phase. Upon sintering at 750 °C, the ceramic achieves a high relative density of 97.3%, which is indicative of an optimal microstructure conducive to the superior microwave dielectric properties: a εr of 9.9, a Q × f of 86200 GHz, and a τf of -95.4 ppm/°C. The variation in relative density is identified as the principal driver of changes in both the εr and Q × f values for the Li2BaP2O7 ceramics. The molecular polarizability is pivotal in determining the εr of Li2BaP2O7 ceramics. The P-V-L theory analysis elucidates that the P-O bond significantly surpasses other chemical bonds in contributing to the ionicity, lattice energy, and bond energy, thereby underscoring its dominance over the three principal microwave dielectric characteristics. Furthermore, Raman spectroscopy data demonstrate that the P-O bond vibration predominantly governs the overall vibrational spectrum.

Microwave Frequency Analysis of Dielectric Properties in Biological Tissues: Insights into Dielectric Constant, Conductivity, and Resistivity at 9.4 GHz

This study investigates the dielectric properties of various biological tissues at microwave frequencies, specifically focusing on their dielectric constant, conductivity, resistivity, and loss tangent. Using methods such as Von Hippel’s and Yadav Gandhi’s techniques, the dielectric characteristics of heart, liver, brain, and muscle of chicken tissues were analysed at 9.4 GHz. It is found that tissues with higher water content exhibit greater dielectric constants and conductivities, while those with higher solid content, like liver, display higher resistivity. It has also been observed that tissues with lower dielectric constants and conductivities are those with greater absorption indices, which are typically associated with increased energy dissipation as heat. An increasing amount of energy dissipation may result from tissues with higher absorption rates being less effective at transferring microwave energy, as suggested by this inverse connection, which also emphasizes the complexity of electromagnetic wave interaction within tissues. This work provides critical insights into the interaction of electromagnetic waves with biological tissues, which is essential for applications in medical diagnostics, therapeutic technologies, and electromagnetic exposure safety standards.

The Influence of Cell Thickness and Driving Voltage Shape on the Frequency Dispersions of Dielectric Characteristics of Ferrielectric Liquid Crystal

The Influence of Cell Thickness and Driving Voltage Shape on the Frequency Dispersions of Dielectric Characteristics of Ferrielectric Liquid Crystal

Tailored proton conductive membranes of PVdF-co-HFP: Investigating the synergistic effects of ammonium tetrafluoroborate and phosphoric acid dopants on dielectric characteristics

This study investigates the structural, thermal, and dielectric properties of pure PVdF-co-HFP matrix and its composite electrolytes, PVdF-co-HFP/NH4BF4[x], both before and after PA doping, using FTIR, SEM, TGA, and dielectric analyses. FTIR spectra reveal characteristic vibrational bands, confirming the presence of various functional groups and phases. SEM images display a smooth and homogeneous surface morphology for pure PVdF-co-HFP, while the composite electrolytes exhibit irregular dispersion of NH4BF4 salt and rougher surfaces upon PA doping. TGA analysis shows that the onset of thermal degradation occurs at approximately 370 ℃ for pure PVdF-co-HFP, while PA-doped samples demonstrate higher decomposition temperatures, exceeding 400 ℃ due to hydrogen bonding and ionic complex formation. The presence of NH4BF4 and PA doping also affects the crystallinity of the PVdF-co-HFP matrix, notably shifting the transition temperatures of the alpha and beta phases. Ionic conductivity measurements indicate that PA doping significantly enhances conductivity by increasing charge carrier concentration and facilitating ion transport. PA-doped PVdF-co-HFP/NH4BF4[10] showed the highest conductivity reaching 1.68 × 10−3 S.cm−1 at 1 MHz and 400 K. Dielectric studies reveal frequency-dependent behavior, with dielectric constant (ε') and loss (ε") showing distinct trends influenced by salt concentration and PA doping. The dielectric tangent loss (tanδ) of PA-doped PVdF-co-HFP/NH4BF4 composite membranes exhibits frequency and temperature dependence. At higher temperatures, tanδ increases with frequency, showing a resonance peak that shifts towards higher frequencies. The study elucidates the impact of PA doping on the structural, thermal, and electrochemical performance of PVdF-co-HFP/NH4BF4 composites, providing insights for their potential applications in advanced electrolyte systems.

Study on the Effect of Electron/Hole Injection on the Energy-Storage Properties of Polymer Dielectrics.

As a critical component of electrostatic capacitors, the polymer dielectric directly affects the performance of the capacitor. In this work, Polycarbonate (PC)/Polyvinylidene fluoride (PVDF) asymmetric bilayer polymer dielectrics were prepared, and the influence of different polymer materials' barrier characteristics on various electrical properties of composite dielectrics was studied by changing the direction of applied electric fields. Research has found that the dielectric constant of a composite dielectric is between PVDF and PC (approximately 4.8 at 10 Hz) and is independent of the relative position of PVDF and PC in the dielectric. However, the relative position of PC and PVDF has a significant impact on the energy-storage characteristics of composite dielectrics. When PVDF comes into contact with the negative electrode, even though PC has a higher hole barrier, the composite dielectric can only withstand a maximum electric-field strength of 400 MV/m, which is much lower than the maximum electric-field strength that pure PC can withstand (520 MV/m), and it only achieves an energy-storage density of 3.7 J/cm3. When the PC comes into contact with the negative electrode, the high electron barrier of the PC effectively suppresses the injection of electrons at the electrode. It can withstand the same electric-field strength as PC (520 MV/m), achieving an energy-storage density of 5.48 J/cm3, which is 1.46 times that of pure PC and 1.64 times that of PVDF. This experiment effectively combined the advantages of PC and PVDF by utilizing the electron/hole barrier of polymer materials to obtain a fully organic dielectric with excellent energy-storage performance.

Nickel oxide nanoparticles embedded in polymer-matrix nanocomposite prepared by nanosecond laser ablation method for optoelectronic applications

The polymeric PVA structure embedded with nickel oxide nanoparticles (NiO NPs) was synthesized using nanosecond pulsed laser ablation in liquid media technique for optoelectronic applications. A comprehensive investigation was conducted on the optical and electrical characteristics of the fabricated films to demonstrate the proficiency of the proposed nanocomposite film in that particular domain. Different weights of NiO nanoparticles were generated by embedding them in PVA film using different ablation durations. It was shown that as the concentration of NiO embedded in PVA increased in correlation with the ablation period, the absorption peak changed to a longer wavelength, and the absorption edge of PVA changed towards lower photon energy with a reduction in the band gap density. Followed by the increase in disorder degree through the addition of NiO NPs, while an average value of the dispersion energy is identical, and the nonlinear parameters (χ(3) and n2) increase. Also, the results emphsies that the dielectric characteristics were affected as the concentration of NiO NPs increased due to the rise in the density of states, which resulted in the generation of polarization. Due to the creation of the charge transfer complex, the optical conductivity of the produced nanocomposites rises as the concentration of NiO NPs increases. Therefore, the optical and electrical characteristics of PVA are significantly affected by the incorporation of NiO nanocomposites.

Designing Tb-doped Mn-Ni-Cu ferrite meta-absorbers for a broad frequency range: Magnetodielectric, physical, reflection loss, and absorptivity characteristics

Developing meta-absorbers with exceptional EM wave absorption, shielding capacity, and superior dissipation performance remains worthwhile in the gigahertz (GHz) range. Electromagnetic pollution has a detrimental impact on the health of living organisms due to the emergence of high-frequency waves from communication devices. The challenges were addressed by preparing, designing, and simulating ferrite-based meta-absorbers. The nanoferrites of Tb-doped Mn-Ni-Cu (Mn0.2Ni0.3Cu0.5TbxFe2-xO4) with different levels of Tb (x = 0.00, 0.025, 0.05, 0.075) were prepared utilizing the sol-gel auto combustion technique. The phase, structural, elastic, and magnetic features of the Tb-doped Mn-Ni-Cu ferrites were examined using XRD, FESEM, FTIR, and VSM techniques, respectively. The MAUD software was utilized to obtain refinement and precise structural characteristics. The force constant, phase, and elastic properties were also assessed. The magnetization and coercivity exhibited a reduction. An assessment was conducted on the performance of field switching and high-frequency response. At high frequencies, the dielectric characteristics, such as complex permeability and permittivity, exhibit greater values, while losses diminish. At a frequency of 4.6 GHz, a reflection loss (RL) of −54.21 dB was measured for x = 0.05, whereas a reflection loss of −54.03 dB was measured for x = 0.075. The meta-absorbers of Tb-doped Mn-Ni-Cu ferrites were designed and simulated. The absorptivity of the Tb-doped Mn-Ni-Cu ferrite substrate material is illustrated. The meta-absorber exhibited three distinct absorption peaks at frequencies of 1.5, 2.5, and 4.5–6 GHz, respectively. The absorptivity of the material likewise rises with an increase in the incidence angle; the material's absorptivity also increases. The TM mode exhibited the highest values at an angle of 60 degrees, while the TE mode displayed the highest values at an angle of 0 degrees. Tb-doped Mn-Ni-Cu ferrites are effective for electromagnetic interference (EMI), multilayer ceramic integrated circuits (MLCIs), shielding, and absorbing high-frequency signals in 5 G applications.

Sodium Fluoroborate Glass Loaded with Fixed CoO and Variable La2O3: Fabrication, Physical, FTIR, and Dielectric Characteristics

Sodium Fluoroborate Glass Loaded with Fixed CoO and Variable La2O3: Fabrication, Physical, FTIR, and Dielectric Characteristics

The impact of V2O5 on structure, dielectric, and radiation-shielding characteristics of borate-lead-fluoride glasses

The impact of V2O5 on structure, dielectric, and radiation-shielding characteristics of borate-lead-fluoride glasses