Low Dielectric Loss Research Articles

Liquid Crystal-Engineered Polydimethylsiloxane: Enhancing Intrinsic Thermal Conductivity through High Grafting Density of Mesogens.

The increasing power and integration of electronic devices have intensified serious heat accumulation, driving the demand for higher intrinsic thermal conductivity in thermal interface materials, such as polydimethylsiloxane (PDMS). Grafting mesogens onto PDMS can enhance its intrinsic thermal conductivity. However, the high stability of the PDMS chain limits the grafting density of mesogens, restricting the improvement in thermal conductivity. This work proposes a new strategy to efficiently introduce mesogens onto PDMS through ring-opening copolymerization of liquid crystal cyclosiloxane and octamethylcyclotetrasiloxane, enhancing the grafting density. The relationship between the grafting density and intrinsic thermal conductivity of liquid crystal polydimethylsiloxane (LC-PDMS) is investigated by nonequilibrium molecular dynamics (NEMD) simulations. Based on the simulation results, LC-PDMS with enhanced intrinsic thermal conductivity is synthesized. When the grafting density of mesogens reaches 77.4%, its intrinsic thermal conductivity coefficient (λ) increases to 0.56 W/(m·K), showing a 180.0% improvement over ordinary PDMS (0.20 W/(m·K)). The LC-PDMS also exhibits the low dielectric constant (ε, 2.69), low dielectric loss tangent (tanδ, 0.0027), high insulation performance (volume resistivity, 3.51×1013 Ω·cm), excellent thermal stability (heat resistance index, 217.8℃) and excellent hydrophobicity (water contact angle, 137.4°), fulfilling the comprehensive requirements of advanced thermal interface materials.

Morphotropic Phase Boundary Region 0.7BiFeO3-0.3BaTiO3 Ceramics Exploration Under the Influence of the Incorporated Sn-Ions for Piezo/Ferro Applications

In the field of piezoelectric applications, perovskite-based multifunctional composite ceramics are widely explored. The morphotropic phase boundary (MPB) regions, where dual structural phases coexist, play a crucial role in boosting the ferroelectric and piezoelectric properties significantly. Herein, MPB-region-existent 0.7BiFeO3-0.3BaTiO3 (BFBT) composite ceramic is investigated under the influence of wt%Sn-ion incorporation at the lattice sites of the BFBT. Specifically, the ceramic composition BFBT:0.2Sn has demonstrated excellent remnant polarization (Pr ~ 22.68 µC/cm2), an impressive piezoelectric coefficient (d33 ~ 211 pC/N), stable impedance of 1.07 × 107 Ω, a Curie temperature of 435 °C and low dielectric loss (tanδ) of <0.5. Moreover, the BFBT:0.2Sn ceramic has also maintained a stable d33 of ~150 pC/N and resistivity of ~102 Ω even at a temperature of 400 °C. Such outcomes confirm the ability and potential of the BFBT:0.2Sn ceramic composition for high-temperature piezoelectric applications.

Correlation of Phase Structure, Defect Relaxation, and Microwave Dielectric Properties in Low-Loss Mgn+1TinO3n+1 Ceramic Systems.

Low-loss microwave dielectrics are of significant importance for the miniaturization and integration of microwave devices. In this paper, the ceramics of nominal composition Mgn+1TinO3n+1 (n = 3-6) are synthesized, and the correlations among their phase compositions, defect behaviors, and microwave dielectric properties are systematically investigated. The analyses indicate that the Mgn+1TinO3n+1 ceramics are a biphasic system consisting of hexagonal ilmenite-structured MgTiO3 and cubic spinel-structured Mg2TiO4. The Rietveld refinement results demonstrate that as the n value increases, the content of the MgTiO3 phase gradually increases, while that of the Mg2TiO4 phase decreases. The results of the thermally stimulated depolarization current (TSDC) indicate that the oxygen vacancy-related defects are considered to be the main types of defects in Mgn+1TinO3n+1. As the value of n increases, the increase of the MgTiO3 phases with a more stable crystal structure leads to a gradual decrease in the concentration of oxygen vacancies. The Mgn+1TinO3n+1 ceramics exhibit excellent microwave dielectric properties at n = 6: εr = 17.55, Q × f = 284,600 GHz, and τf = -46.39 ppm/°C. In addition, the relationship between the dielectric constant and the electric field distribution is solved utilizing high-frequency structure simulator (HFSS) software, and the Q × f values are also predicted. The low-frequency dielectric temperature spectra and direct current pulse charge/discharge tests show that the low-loss Mgn+1TinO3n+1 ceramics can be good candidates for microwave capacitors even when operated under high-temperature conditions.

Designing a filler material to reduce dielectric loss in epoxy-based substrates for high-frequency applications.

In response to the demand for epoxy-based dielectric substrates with low dielectric loss in high-frequency and high-speed signal transmission applications, this study presents a surface-engineered filler material. Utilizing ball-milling, surface-modified aluminum flakes containing organic (stearic acid) and inorganic (aluminum oxide) coatings are developed. Incorporation of the filler into the epoxy matrix results in a significant increase in dielectric permittivity, ε r, by nearly 5 times (from 4.3 to 21.2) and nearly an order of magnitude reduction in dielectric loss, tan δ, (from 0.037 to 0.005) across the 1 to 10 GHz frequency range. Extension of this method to glass fabric-reinforced epoxy-based substrates, resembling widely used FR4 in printed circuit boards, exhibits minimal permittivity variation (4.5-5.4) and considerable reductions in dielectric loss (from 0.04 to 0.01) within the same frequency range. These enhancements are attributed to improved filler dispersion and suppression of electron transport facilitated by double-layer coatings on the flake surface under varying electric fields. The findings highlight the potential of surface-modified aluminum flakes as a promising filler material for high-frequency and high-speed substrate applications requiring low-loss.

Enhanced Dielectric Performance in PVDF-Based Composites by Introducing a Transition Interface.

Polymeric dielectrics have garnered significant interest worldwide due to their excellent comprehensive performance. However, developing polymeric dielectric films with high permittivity (εr) and breakdown strength (Eb) and low dielectric loss (tanδ) presents a huge challenge. In this study, amorphous aluminum oxide (Al2O3, AO) transition interfaces with nanoscale thickness were constructed between titanium oxide (TiO2, TO) nanosheets and polyvinylidene fluoride (PVDF) to manufacture composites (PVDF/TO@AO). TO@AO nanosheets showed favorable dispersion in the polymer-based composites. Improved permittivity, suppressed dielectric loss, and enhanced breakdown strength were achieved by introducing AO coating with intermediate permittivity onto TO nanosheets to build a transition interface. The transition interface efficiently depressed the mobility of the charge carrier and electric conduction of the PVDF/TO@AO composites. As a result, the PVDF-based composite with 1 wt% TO@AO showed superior comprehensive performance, including high εr of ~12.7, low tanδ of ~0.017, and exceptional Eb of ~357 kV/mm. This strategy supplies a novel paradigm for the application of fabricating dielectric films with excellent comprehensive performance.

Synthesis, structure, oxygen evolution reaction (OER) and visible-light assisted organic reaction studies on A2M2TeB2O10 (A = Ba and Pb; M = Mg, Zn, Co, Ni, Cu, and Fe).

Compounds with the general formula A2M2TeB2O10 (A = Ba and Pb; M = Mg, Zn, Co, Ni, Cu, and Fe) have been synthesised via solid-state techniques and characterised. The structure exhibits M2B2O10 layers connected by TeO6 octahedra giving rise to a three-dimensional structure with voids, where Ba2+ ions reside. Substitution of Mg by transition elements (M = Co, Ni, and Cu) in Ba2Mg2TeB2O10 and (Ba0.5Pb1.5)Mg2TeB2O10 gives rise to interesting colored compounds. NIR reflectivity studies indicated that white-colored compounds exhibited good NIR reflectivity, which was is comparable to that of TiO2. Dielectric studies indicated reasonable values with low dielectric loss at low frequencies. The cobalt-substituted compounds Ba2(MgCo)TeB2O10 and (Ba0.5Pb1.5)(MgCo)TeB2O10 were explored towards the oxygen evolution reaction (OER) in an alkaline medium. The compound (Ba0.5Pb1.5)(MgCo)TeB2O10 was found to be a good electrocatalyst for the OER with a faradaic efficiency of ∼96%. The Cu-substituted compound Ba2(Mg1.5Cu0.5)TeB2O10 was found to be a good photocatalyst for the formation of α-chloroketones under visible light in the presence of molecular oxygen.

In-plane aligned doping pattern in electrospun PEI/MBene nanocomposites for high-temperature capacitive energy storage

To achieve superior energy storage performance in dielectric polymer film, it is crucial to balance three key properties: high dielectric constant, high breakdown strength, and low dielectric loss. Here, we...

The structure design of poly(ester imide)s with low dielectric loss and high mechanical properties

Combining ester groups and ether bonds balanced the dielectric and mechanical properties of poly(ether-ester imide).

High-performance biodegradable dielectric composite: Towards minimizing electronic waste

Polymer-based dielectric capacitors are crucial in modern electronics due to their wide capacitance range, high operating voltage, lightweight nature, and graceful failure reliability. However, the predominant use of nondegradable dielectric polymers raises environmental concerns. This study addresses this issue by preparing flexible biodegradable dielectric composite films of poly(butylene adipate-co-terephthalate) (PBAT) incorporating varying amounts of nitrogen-doped and non-doped biochar derived from banana peel waste. It was found that the incorporation of biochar in the nanocomposite improved various properties such as dielectric properties, biodegradability, mechanical strength, and thermal stability. The PBAT nanocomposite with 10 wt% N-doped biochar exhibited an 83 % rise in dielectric constant compared to pure PBAT while maintaining a low dielectric loss of 0.071 at 1000 Hz. This approach offers a cost-effective and environmentally sustainable method, showing potential for advancing next-generation disposable electronic materials with enhanced performance attributes.

Extremely low dielectric loss of Mg and Al co-substituted CCTO ceramic with excellent temperature stability

Extremely low dielectric loss of Mg and Al co-substituted CCTO ceramic with excellent temperature stability

Improved dielectric performance of graphene oxide reinforced plasticized starch.

High dielectric constants with less dielectric loss composites is highly demandable for technological advancements across various fields, including energy storage, sensing, and telecommunications. Their significance lies in their ability to enhance the performance and efficiency of a wide range of devices and systems. In this work, the dielectric performance of graphene oxide (GO) reinforced plasticized starch (PS) nanocomposites (PS/GO) for different concentrations of GO nanofiller was studied. The surface morphology, and chemical and structural properties of the PS/GO nanocomposites were investigated by field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectrometry (FTIR), and X-ray diffractometer (XRD). The FESEM study showed a uniform dispersion of the GO nanofiller in the nanocomposites. The XRD analysis showed a reduction in d-space due to the incorporation of GO nanofiller in the nanocomposites. The FTIR data exhibits the formation of hydrogen bonds among PS and GO nanofillers, suggesting the presence of strong interaction between them. The dielectric properties of the nanocomposites were studied at room temperature in the frequency range 100 Hz‒1 MHz. The dielectric constant was found to improve due to the incorporation of GO. This composite nanomaterial also provides low dielectric loss at low frequency. Moreover, an increasing trend is observed for the AC conductivity of the composites. From the complex impedance study, the changes in various impedances with low to high-frequency ranges have been calculated and explained in the equivalent circuit diagram. The complex impedance spectra analysis shows the change in resistance and constant phase element (CPE): grain boundary resistance, R2 decreases from 4.3 KΩ to 1.9 KΩ, and CPE increases from 0.59 μF to 0.72 μF for PS/GO (0.5%) nanocomposite. This study will provide a potential route for the fabrication of biocompatible dielectric device fabrication.

Halbach Array Induced Magnetic Field Alignment in Boron Nitride Nanocomposites

AbstractThermal conductivity enhancement in polymers is vital for advanced applications. This study introduces a novel method to align hexagonal boron nitride (hBN) nanosheets within polydimethylsiloxane (PDMS) matrices using a Halbach array to create a highly uniform magnetic field. This technique achieves significant improvements in thermal conductivity by effectively aligning hBN nanosheets. This research shows that hBN nanosheets, when aligned, can drastically enhance thermal conductivity in PDMS composites. Specifically, 10 wt.% vertically aligned hBN nanosheets in a rotating magnetic field achieve a thermal conductivity of 3.58 W mK−1, an impressive 1950% increase over pure PDMS. Additionally, the study explores the effects of orientation on dielectric properties, finding that the orientation of hBN nanosheets also improves electrical insulation and increases the dielectric constant while maintaining extremely low dielectric losses. For a vertically oriented sample, the dielectric constant reaches ≈14, and dielectric losses are as low as 0.0049 at 100 Hz, highlighting their potential for energy storage capacitors. This approach not only enhances thermal management but also maintains or improves electrical insulation, offering promising advances for polymer composites in various technological applications.

Creating Single-Crystalline β-CaSiO3 for High-Performance Dielectric Packaging Substrate.

β-CaSiO3 based glass-ceramics are among the most reliable materials for electronic packaging. However, developing a CaSiO3 glass-ceramic substrate with both high strength (>230MPa) and low dielectric constant (<5) remains challenging due to its polycrystalline nature. The present work has succeeded in synthesizing single-crystalline β-CaSiO3 for a high-performance glass-ceramic substrate. This is accomplished by introducing Al3+ into the CaO-B2O3-SiO2 glass system, and by optimizing the sintering condition. Al3+ doping facilitates a heterogeneous network structure that energetically favors the precipitation of polycrystalline particles, including nanosized β-CaSiO3 crystals and sub-nanosized α-CaSiO3 crystals. As the sintering temperature increases, the nano α-CaSiO3 crystals (2-10nm) are gradually absorbed by the β-CaSiO3 crystals. Through atomic rearrangement, α-CaSiO3 crystals transform into micrometer-sized single crystal β-CaSiO3 (1-2µm) with layered structure. The low temperature co-fired β-CaSiO3 glass-ceramics exhibit exceptional properties, including a low dielectric constant of 4.04, a low dielectric loss of 3.15 × 10-3 at 15GHz, and a high flexural strength of 256MPa. This work provides a new strategy for fabricating high-performance single-crystalline glass-ceramics for electronic packaging and other applications.

Электрофизические и структурные свойства композитных структур на основе пленок титаната бария стронция и ниобата лития

Ba0.8Sr0.2TiO3 (BST) films were synthesized by high-frequency (HF) sputtering on silicon substrates and silicon substrates with a buffer layer of piezoelectric LiNbO3 (LN) film. Comparative results of electrophysical properties of structures: Ni/BST/SiO2/Si and Ni/BST/LN/SiO2/Si are presented. It is shown that, in contrast to BST/SiO2/Si structures, BST/LN/SiO2/Si objects have a higher breakdown voltage, lower dielectric losses and wider hysteresis loops. Studies using a scanning probe microscope have shown that the effect of the LiNbO3 buffer layer increases the surface roughness of the BST film. The Kelvin probe method has shown that the polarized state in the BST/LN/SiO2/Si structure is stable for several hours.

High-temperature high-k polyolefin by rational molecular design

Polymer film dielectrics are highly favored for capacitive energy storage due to the inherent advantages of high breakdown strength, low dielectric loss, and ease of processing. High-density renewables conversion and harsh-condition electrification further emphasize the need for high-temperature, high-k polymers. A unique design strategy is developed to augment high-temperature polyolefins with improved dielectric constant, via the integration of phenyl pendants hanging off the rigid bicyclic backbone. The impacts of the pendant polarizability and steric positioning on dielectric constant, bandgap, glass-transition temperature (Tg), and high-field, high-temperature dielectric characteristics have been investigated. The orientational polarization of the polar phenyl pendants with rotational degree of freedom imparts cyclic olefins with enhanced dielectric constants, while maintaining the large bandgap, and high glass-transition temperature (Tg > 170 °C). Among these synthesized polymers, m-PNB-BP stands out with a remarkable dielectric constant of 4 at a high sub-Tg temperature of 150 °C, and a high discharged density of 8.6 J/m3 at 660 MV/m. This study unveils a different path for designing high-temperature polymers with enhanced dielectric constants, particularly beneficial for capacitive energy storage.

Enhanced energy storage performance of layered polymer composites with an ultralow loading rate of TNSs@PDA

Polymer-based dielectric nanocomposites have attracted much attention since they have advantages such as high power density and stability. The introduction of inorganic fillers is one of the strategies to enhance the discharge energy density (Ud) of polymer composite dielectrics. However, the negative coupling effect of relative dielectric permittivity (εr) and breakdown strength (Eb) is the key reason for the difficulty in achieving high energy storage density. In this work, polydopamine-modified titania nanosheet (TNSs@PDA) was fabricated, which has been used as fillers for monolayer TNSs@PDA/P(VDF-HFP) composites. The monolayer TNSs@PDA/P(VDF-HFP) composite with 0.2 wt% TNSs@PDA (0.2 wt% 1 L) has a low dielectric loss of 0.038 and its εr increased to 11.94 at 10 kHz, which corresponded to 129 % of that of P(VDF-HFP) (∼ 9.25). Additionally, the monolayer 0.2 wt% 1 L composite film was hot pressed with PEI and P(VDF-HFP) films to form a sandwich structure, which has a high Eb of 599.3 kV/mm, a high Ud of 9.97 J/cm3, a low dielectric loss of 0.025, and an energy storage efficiency of 82 %. This study provides an effective approach for designing polymer composites that combine high Ud with high energy storage efficiency.

Combustion synthesis and spark plasma sintering processing of (1‐x)Ba(Zr₀.₂Ti₀.₈)O₃‐x(Ba₀.₇Ca₀.₃)TiO₃ ceramics

AbstractSolution combustion synthesis (SCS) has proven to be one of the simplest and fastest methods, using inexpensive materials and resulting in homogeneous stoichiometry with nanometric particle sizes. The spark plasma sintering (SPS) method has been used to obtain high‐density ceramic materials with excellent control of microstructure. This work reports the successful combination of these two techniques for the fabrication of the high‐density lead‐free ferroelectric system (1‐x)Ba(Zr₀.₂Ti₀.₈)O₃‐x(Ba₀.₇Ca₀.₃)TiO₃. The X‐ray diffraction of the powder indicates the majority formation of the perovskite structure and other residual reaction products, indicating a reactive powder. The SPS method resulted in highly densified samples, reaching relative density values close to 99% with a single‐phase perovskite structure. Rietveld refinement revealed the presence of at least two perovskite phases, independent of calcium concentration. Dielectric measurements showed anomalies in both the real and imaginary parts of the dielectric permittivity, which are typical of phase transitions and a low dielectric loss for all compositions. This study shows that the combined use of SCS and SPS technique can be a powerful protocol to produce dense, fine‐grained lead‐free ferroelectric ceramics at relatively low temperatures and in short time periods.

A New Synthetic Analogue Of The Burckhardtite Mineral, Pb2TeGa[AlSi3O8]O6: Synthesis, Structure, And Properties.

The mineral, Burckhardtite, Pb2TeFe[AlSi3O8]O6, is synthesized and characterized. A new analogue, Pb2TeGa[AlSi3O8]O6, is successfully prepared for the first time under laboratory conditions. The substitution of Ga3+ by Ti0.5M0.5 (M=Co2+, Ni2+) results in new compounds with the Burckhardtite mineral structure. The transition metal-containing compounds exhibit interesting new colors, partly resulting from d-d transitions and metal-to-metal charge transfer (MMCT) transition. The Ga compound shows a deep UV cut-off (~86 %), which is one of the better known values of deep UV cut-off compounds. The compounds exhibit good dielectric behavior with low dielectric loss. The Eu3+ - substituted samples show deep red emission with a long lifetime of ~0.89 ms. The magnetic behavior of the transition metal containing compounds indicates anti-ferromagnetic interactions. The successful synthesis of the naturally occurring mineral along with newer analogues with interesting properties suggests that it is profitable to investigate compounds of mineral origin.

Effect of temperature and frequency on the dielectric behaviour of cellulose nanocrystals

Nanocellulose is a promising material for advanced applications due to its renewable nature, non-toxicity, eco-friendliness, mechanical strength and other unique properties. This study investigates the dielectric properties of cellulose nanocrystals (CNCs) derived from wastepaper through acid hydrolysis, across a temperature range of 30°C to 100°C and a frequency range of 1 Hz to 10 MHz. Using theoretical models such as the modified Cole-Cole model, Jonscher's universal dielectric response (UDR) model and modified Kohlrausch-Williams-Watts (KWW) model, a detailed analysis is performed. The results indicate that the dielectric properties depend on temperature, with the frequency dispersion of the real (ε′) and imaginary parts (ε″) of the dielectric permittivity fitting the modified Cole-Cole equation. These values show an initial increase up to 70°C (ε′∼ 6000 and dielectric loss <1) followed by a decrease at higher temperatures, which is linked to the hydroxyl groups. A temperature dependence is also observed in space charge conductivity, free charge conductivity and relaxation time. Non-Debye type behaviour is attributed to asymmetrical features in the electric modulus spectra, as explained by the modified KWW model at various temperatures. The frequency variation of AC conductivity adheres to Jonscher’s power law and the temperature variation of the frequency exponent (0≤ s ≤1) indicates a correlated barrier hopping conduction mechanism for charge carriers. Overall, these findings highlight CNCs as excellent candidate for antistatic applications, demonstrating conductivity ranging from 10−5 to10−9 Scm−1. The results also suggest CNCs can be used in energy storage applications due to their outstanding dielectric properties and low dielectric loss (<1).

Low dielectric loss, giant dielectric constant, and high breakdown electric field in (Bi1−Y )2/3Cu3Ti4O12 ceramics

Low dielectric loss, giant dielectric constant, and high breakdown electric field in (Bi1−Y )2/3Cu3Ti4O12 ceramics