Ultralow Dielectric Loss Research Articles

Plate-barrier architecture of rGO-TiO2 derived from MXene for constructing well-aligned polymer nanocomposites with excellent dielectric performance

Dielectric polymers are playing increasingly important roles in advanced electronics and electric power systems, because of their high dielectric strength, stability, and lightweight. However, the relatively low intrinsic dielectric constant of dielectric polymers hinders their further applications. Herein, dielectric polymer composites were fabricated by blending with plate-barrier architecture fillers, which are comprised of reduced graphene oxide (rGO) and intercalated titanium dioxide (TiO2) cubes. TiO2 cubes are homogeneously and controllably integrated onto rGO nanosheets utilizing 2D transition metal carbides (MXene) by means of shape match. TiO2 cubes could serve as joints to anchor rGO nanosheets for more effective polarization, and as barriers to impede the conductive contact of rGO nanosheets. In the nanocomposites, rGO nanosheets possess high alignment and overlap area resorting to the anchoring effect of TiO2, which increases the micro-capacitors in series that greatly enhance the dielectric constant. Therefore, it is investigated that the nanocomposites exhibit a high dielectric constant (211) and ultralow dielectric loss (0.104). Moreover, the enhancement mechanism of the micro-capacitors was also revealed by the finite element simulation. This contribution provides a novel strategy to fabricate well-aligned nanocomposites that are promising in electronics flexible materials.

Microwave dielectric characteristics of tungsten bronze-type Ba4Nd28/3Ti18-yGa4y/3O54 ceramics with temperature stable and ultra-low loss

A series of high-k Ba4Nd28/3Ti18-yGa4y/3O54 (0≤y≤2, BNTG) ceramics with temperature stable and ultra-low dielectric loss were synthesized via the conventional solid-state reaction. The main phase of all BNTG ceramics demonstrated an orthorhombic tungsten-bronze structure, but the impurity phase (gallium-rich phase) was found in BNTG (y = 2) ceramic. Partial substitution of Ga3+ for Ti4+ in B-site was a valid method to improve the temperature stability and dielectric loss of BNTG ceramics. The variation of εr values of BNTG ceramics was dominated by the ionic polarizability. The ultra-low dielectric loss (ultra-high Q × f values) was associated with grain size, suppression of Ti3+ and impurity phase. The decrease of TCF values was highly dependent on the tilting of Ti-O octahedra and impurity phase. Finally, outstanding combination dielectric characteristics were achieved for BNTG microwave ceramics at y = 1.5 (εr = 72.8, Q × f = 14,600 GHz, TCF=+4.1 ppm/°C) and at y = 2 (εr = 70.3, Q × f = 15,500 GHz, TCF=+3.9 ppm/°C).

Simultaneously ultra-low dielectric loss and rapid discharge time in Ta2O5 doped niobate-based glass–ceramics

Simultaneously ultra-low dielectric loss and rapid discharge time in Ta2O5 doped niobate-based glass–ceramics

Boron nitride whisker @ graphene nanohybrid-filled epoxy composites with high thermal conductivities and low dielectric losses

In this work, we demonstrate boron nitride whisker @ graphene (BN@GE) nanohybrids with a unique morphology as a thermally conductive filler for improving the thermal conductivity of a polymer matrix. In this structure, GE sheets were applied to insulating hexagonal boron nitride (BN) whiskers via a simplified method to ensure the sheets were well separated when used in epoxy composites. The addition of GE to produce the BN@GE hybrids was found to reduce the length of the BN whiskers. In addition, separation of the sheets enhanced the three-dimensional thermally conductive networks within the composite, which improved the thermal conductivity and significantly enhanced the dielectric constant. Furthermore, the implanted insulating network of BN inhibited the charge carrier mobility on the well-separated sheets via GE fixation on the BN whiskers, and resulted in a low dielectric loss. As a result, the epoxy composite containing 40 wt% BN@GE-15 hybrid filler exhibited a thermal conductivity, dielectric constant, and ultra-low dielectric loss of 1.26 W m−1 K−1, 12.7, and 0.0051, respectively. We expect this uniquely structured hybrid filler will be suitable for the fabrication of thermal interface materials with high thermal conductivities and low dielectric losses.

Activating and modulating ferroelectric and optical properties in La/Nd co-doped SrTiO3 ceramics

Defect-dipole and defect-clusters provide a novel paradigm to realize unprecedented dielectric behavior along with ultralow dielectric loss, in any ordinary dielectric material. In the present work, with the help of the La/Nd co-doped SrTiO3 (STO) system, it has been shown that the type, nature, and localization of these defect dipoles and clusters play a significant role in controlling the dielectric behavior. Polycrystalline ceramic samples of La0.1Sr0.9−xNdxTiO3 (x = 0.05, 0.07, 0.09, 0.11) are synthesized by mechanical alloying followed by high temperature solid-state reaction techniques. Investigations of structural and microstructural properties are carried out by using the X-ray diffraction technique and scanning electron microscopy, respectively. The dielectric and electrical parameters are studied in a frequency ranging from 1 kHz to 1 MHz and the temperature ranging from 30 °C to 450 °C. The results demonstrate that all the synthesized samples exhibit single-phase perovskite structure with Pm3̅m space group. Though STO displays quantum paraelectric behavior, intriguingly, all the La/Nd doped STO samples exhibit ferroelectric behavior with the dielectric maximum increasing with the increase in the doping concentration. The superior dielectric behavior in the doped samples is ascribed to the suppression of grain boundary conductivity due to the formation of a double Schottky barrier (due to VSr′′/Vo••) and enhancement of grain conductivity due to localized transport involving defect dipoles/clusters within the grain. Interestingly, the presence of VSr′′andVo•• has been supported by the photoluminescence analysis. Nevertheless, La/Nd doping results in a systematic reduction in the band gap.

Low Dielectric Polyimide/Fluorinated Ethylene Propylene (PI/FEP) Nanocomposite Film for High‐Frequency Flexible Circuit Board Application

AbstractThe low dielectric polymer films have drawn great attention to the application as the dielectric insulating materials in high‐frequency circuit boards, while the weak adhesion to the copper foils and the poor processability resulted from the fluorinated or rigid structures limited their high‐frequency application. In this work, the low dielectric and high adhesive polyimide/fluorinated ethylene propylene (PI/FEP) nanocomposite film for high‐frequency flexible circuit board application is developed. It is indicated that the fluorocarbon surfactants can significantly improve the dispersion of FEP in PI substrate, and thus, the PI/FEP nanocomposite film exhibits excellent mechanical properties, including the tensile strength increases to 46.6 MPa and the elongation at the break increases to 13.7%. Importantly, at the high‐frequency of 10 GHz, the 60 wt% FEP filled PI nanocomposite film displays an ultralow dielectric loss (0.006) and a reduced dielectric constant (2.69). In addition, the high‐frequency flexible circuit board with the PI/FEP film as the dielectric insulating layer has a high peel strength of 0.75 N mm−1, indicating this PI/FEP nanocomposite film can meet the requirements of the high‐frequency flexible circuit board application.

Enhanced dielectric, thermal stability, and energy storage properties in compositionally engineered lead-free ceramics at morphotropic phase boundary

Structural inhomogeneity at morphotropic phase boundary (MPB) offers a novel paradigm to explore and modulate the physical properties of dielectric materials to design next-generation multifunctional devices. In this work, two lead free materials at MPB; Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and (Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNTBT), are combined together to synthesize polycrystalline composite samples of (1-x) BCZT-xBNTBT with x = 0.0, 0.25, 0.50, 0.75, and 1.0. Structural investigations using XRD show the coexistence of double phases for pristine BCZT (tetragonal (P4mm) + rhombohedral (R3m)), and for pristine BNTBT (tetragonal (P4bm) + rhombohedral (R3c)). However, all the doped samples with x = 0.25, 0.5, and 0.75 display a coexistence of triple phases with P4mm, P4bm, and R3c symmetries. Detailed dielectric study reveals a normal ferroelectric to macroscopic ergodic relaxor crossover for samples with x = 0.25 and 0.75. Intriguingly, sample x = 0.25 displays a coexistence of high dielectric constant (4050), ultralow dielectric loss (≤0.02), high temperature thermal stability of permittivity (variation ≤ ±15%) in a temperature range 135 °C–450 °C, large recoverable energy density (Wrec = 423 mJ/cm3) with ultrahigh energy storage efficiency (η = 95.4%) at low applied electric field - 23 kV/cm. Nevertheless, at similar applied field strength, the obtained values of Wrec and η exceed most of the selected lead-free energy storage materials. This work may pave a new path to design superior high-temperature dielectrics, through intermixing of MPBs, for energy storage applications.

A novel poly(p-phenylene benzobisoxazole) (PBO)-based three-phase silk-cocoon network structure nanocomposites with enhanced dielectric properties

Nanocomposites with great thermal stability and excellent dielectric properties play a vital role in the development of high-temperature resistant capacitors. A facile yet effective method to synthesize enhanced dielectric properties of thermostable three-phase poly(p-phenylene benzobisoxazole) (mCCTO@CFGO/PBO) nanocomposite films is demonstrated in this work. The amino-functionalized oxide CaCu3Ti4O12 nanoparticles (mCCTO) are enwrapped by the carboxyl-functionalized ultrathin graphene shells (CFGO), forming the silk-cocoon structure to achieve homogeneous dispersion in the matrix. The final films are fabricated via in situ polymerization by introducing the mCCTO@CFGO nanoparticles into the PBO precursor polymer. The mCCTO@CFGO/PBO nanocomposite films exhibit high thermal stability (the 5% thermal decomposition temperature is 655 °C), while the unique silk-cocoon structure effectively confers the high dielectric constant up to 86.9 and ultra-low dielectric loss (0.063) with the loading of 10 wt% mCCTO@3 wt% CFGO/PBO at 1 kHz and 200 °C. This promising strategy accelerates the development of electronic devices used under high temperatures.

Temperature stable Sm(Nb1−xVx)O4 (0.0 ≤ x ≤ 0.9) microwave dielectric ceramics with ultra-low dielectric loss for dielectric resonator antenna applications

A temperature-stable Sm(Nb0.8V0.2)O4 (SNV-0.2) microwave dielectric ceramic with ultra-low dielectric loss was fabricated, and an RDRA was designed for 5G mm-wave application for the first time, which is a good candidate for 5G and future millimeter-wave MIMO antenna applications.

Low κ Mg2SiO4 ceramic tapes and their role as screen printed microstrip patch antenna substrates

Despite their intolerance to fine machining, certain ceramics possess a unique combination of low dielectric constant and ultra-low dielectric loss, which is ideal for fabricating a patch antenna on them, with increased efficiency. In a candid attempt, we have qualified an ultra-low loss ceramic, magnesium silicate (abbreviated as Mg2SiO4), for microwave antenna applications. Flexible ceramic tapes are prepared through organic solvent-based tape casting method, stalked, isostatically pressed, sintered, and polished. The new substrate possesses excellent microwave dielectric properties on par with commercial polymer composite wafers, while thermal conductivity is two orders better than them. The feasibility of using Mg2SiO4 as microwave substrate was demonstrated by fabricating a microstrip patch antenna for WLAN applications. The radiation characteristics of the antenna show excellent agreement with the simulated ones. The patch antenna fabricated on Mg2SiO4 substrate radiated at 2.44 GHz with a gain of 3.2 dB and a return loss of −20 dB.

Perovskite Bi0.5Na0.5TiO3-based materials for dielectric capacitors with ultrahigh thermal stability

There has been recently a great progress in the development of dielectric capacitors for high temperature electronic applications. The design of lead-free ceramics with high dielectric permittivity, low dielectric loss and a limited variation of these parameters over a wide temperature range is still a big challenge. In this work, lead-free Bi0.35Na0.65–0.5xRb0.5xTi0.7Nb0.3O3 (x = 0–0.05) bulk ceramics were prepared using the solid-state reaction method. Upon Rb substitution, the variation of the dielectric permittivity was reduced substantially, in particular, at high temperature (over 200 °C). In addition, a low temperature coefficient of capacitance (TCC ≤ 10%) together with an ultra-low dielectric loss (tanδ ≤ 0.05) were achieved for the Bi0.35Na0.63Rb0.02Ti0.7Nb0.3O3 sample in the temperature range from −43 °C to 292 °C. The new relaxor-type ferroelectrics also possess the outstanding stability of the dielectric properties under high DC bias voltage, which makes them promising materials for high-performance capacitors of the next generation.

Interface design and dielectric response behavior of SiO2/PB composites with low dielectric constant and ultra-low dielectric loss

The resistance-capacitance time delay, crosstalk interference and poor dimensional stability would damage the signal intact transmission. However, it was still a tough challenge to fabricate an interlayer dielectric material with low dielectric constant and low dielectric loss as well as excellent dimensional stability at the same time. In this work, for the first time, we constructed novel silicon dioxide/polybutadiene (SiO2/PB) composites with different SiO2 morphologies and surface function groups, which showed extremely low dielectric constant and dielectric loss in both low and high frequency bands. The crosslinking reaction between surface surficial vinyl groups of the SiO2 and PB macromolecules tremendously suppressed the interfacial polarization of the SiO2/PB composites. Therefore, the SiO2/PB composites exhibited low dielectric constant of 2.66 and ultralow dielectric loss of 0.0022 at high frequency band (10 GHz), and the coefficient of thermal expansion decreased to 154 × 10−6 /°C, which was three orders of magnitude less than that of the pure PB. The interface polarization response behavior of SiO2/PB composites was also elucidated by double layer theory, and the "resonance" phenomenon was firstly proposed to enhance the interface polarization. This work could provide a robust and simple strategy for the design of composites with ultralow dielectric loss and excellent dimensional stability for high-speed communication in different frequency bands.

Lattice Evolution, Ordering Transformation and Microwave Dielectric Properties of Rock-Salt Li3 +xMg 2-2xNb 1-XTi 2xO6 Solid-Solution System: A Newly Developed Pseudo Ternary Phase Diagram

The new types of multi-component Li3+xMg2-2xNb1-xTi2xO6 (0≤x≤1) solid-solution ceramics were designed based on the Li2TiO3-Li3NbO4-MgO pseudo ternary phase diagram and studied for millimeter-wave applications. The ceramics showed a full range of solid solubility between the Li3Mg2NbO6 and Li2TiO3 endmembers. As the doping content (x) increased, we detected the phase transitions among the orthorhombic, cubic, and monoclinic phase driven by the compositional changes, as well as accompanied with an order-disorder-order transformation. Besides, the smooth orthorhombic-cubic phase transition interfaces were observed in the electron diffraction images for the sample with the low dopant concentration (x=0.2), and the reconstructed superlattices based on the orthorhombic or the cubic structure were both observed nearby the orthorhombic-cubic phase transition interface. The change of Q×f values showed a considerable increase with the emergence of the superlattices, and the enhancement of the Q×f values was related to the very small lattice vibrational anharmonicity in the structures that contain the reconstructed superlattices. Typically, when sintered at 1250 ℃ for 4 h, the ultra-low dielectric loss was achieved in the x=0.2 sample with the properties of er=16.1, Q×f=128,600 GHz (f=9.2 GHz) and τf=-30.4 ppm/℃, and the temperature stable properties were obtained in the x=0.9 sample with er=20.4, Q×f=90,300 GHz (f=7.9 GHz), and τf=2.9 ppm/℃.

Getting self-healing ability and ultra-low dielectric loss for high-k epoxy resin composites through building networks based on Li0.3Ti0.02Ni0.68O grafted carbon nanotube bundles with unique surface architecture

Getting self-healing ability and ultra-low dielectric loss is effective to achieve high service reliability and sustainable development for high dielectric constant (high-k) polymer composites. Herein, new functional fillers with special surface architecture (sLTNO@mAC) were synthesized by grafting Li0.3Ti0.02Ni0.68O particles (sLTNO) on surfaces of carbon nanotube bundles (mAC), which was then embedded in epoxy resin (EP) with disulfide bonds to develop new composites (sLTNO@mAC/EP). Compared with composites based on mAC (mAC/EP) or a blend of sLTNO and mAC (sLTNO/mAC/EP) with the same filler loading, sLTNO@mAC/EP composites have much higher dielectric constant and self-healing efficiency as well as much lower dielectric loss at the same frequency. For the composite based on sLTNO@mAC with 8.2 wt% of sLTNO, coded as sLTNO1@mAC/EP, its dielectric loss is only 0.02, about 1.1 × 10 -3 and 9.4 × 10 -3 times of that of mAC/EP and sLTNO/mAC/EP, respectively; meanwhile its dielectric constant (216.1, 100 Hz) is the highest value among self-healable dielectric composites reported so far, and sLTNO1@mAC/EP has higher self-healing efficiency (97.7%) than mAC/EP and sLTNO/mAC/EP. The mechanism behind these attractive properties reveals that dielectric properties of sLTNO@mAC/EP mainly depend on interface polarization, while those of mAC/EP and sLTNO/mAC/EP are mainly related to the integrity of conductive networks.

Ultralow dielectric loss in Y‐doped SrTiO3 colossal permittivity ceramics via designing defect chemistry

AbstractEffects of doping of Y and sintering atmosphere on the dielectric properties of Sr1‐1.5xYxTiO3 ceramics (SYT, x = 0‐0.014) were systematically investigated. The SYT14 (x = 0.014) ceramic sintered in N2 attains a colossal permittivity (CP, Ɛr = 28 084@ 1kHz, 27 685@ 2MHz) and an ultralow dielectric loss (tanδ = 0.007@ 1kHz, 0.003@ 2MHz) at room temperature. Because of using of the A‐site deficient, there are in SYT ceramics. Through the comprehensive analysis of dielectric responses, X‐ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and complex impedance data, it is proved that doping of Y promotes the formation of (Y3+ are located at Sr2+ site), (Y3+ are located at Ti4+ site), and Ti3+, and sintering in reducing atmosphere of N2 results in more (oxygen vacancy) and (strontium vacancy) generating in SYT ceramics. The defect dipoles, , , , , , and formed by introduced defects make charge carriers localized in SYT ceramics. The combined action of the massive defect dipoles is responsible for the ultralow tanδ and CP in SYT14 ceramics sintered in N2.

High temperature dielectric stable (1-x)[(Na0.5Bi0.5)0.92Ba0.08]0.955La0.03TiO3-xNaNbO3 system with ultra-low dielectric loss range through optimizing the defect chemistry

High permittivity and low dielectric loss are important for the application of high-temperature dielectrics. In present study, high temperature dielectrics based on (1-x) [(Na0.5Bi0.5)0.92Ba0.08]0.955La0.03TiO3-xNaNbO3 compositions were synthesized by a conventional solid-state reaction method. The microstructure, dielectric, ferroelectric and electrical properties were systematically investigated. All the samples show relatively high permittivity and excellent low dielectric loss range from ∼90 °C up to 400 °C. Impressively, the composition x = 0.06 shows a high permittivity of 2436 at 150 °C (1 kHz), (εr−εr150°C)/εr150°C varying no more than 15% in the temperature range of 54 °C–344 °C together with a low loss (tanδ≤0.02) range between 92 °C and 400 °C. By developing highly-localized complex defect-dipoles with La and NaNbO3 dopants to restrain the mobility of oxygen vacancy, as verified by XPS and resistivity-temperature results, the dielectric loss is limited to rather low values. Hence, the current system will be a promising candidate in high temperature ceramic capacitors.

Dielectric and mechanical properties of polyimide fiber reinforced cyanate ester resin composites with varying resin contents

Polyimide (PI)/ bisphenol A dicyanate esters (BADCy) composite laminates with varying resin contents were prepared by filament winding and autoclave molding process. The laminates exhibited ultralow dielectric constant (e of 3.15–3.25) and dielectric loss (tanδ of 0.004–0.006) as well as excellent mechanical properties. When the resin content was 35.6%, the composite achieved outstanding comprehensive properties with tensile strength and modulus equal to 1485.1 MPa and 80.9 GPa, respectively, and the inter-laminar shear strength (ILSS) up to 66.2 MPa. The failure mode of laminates followed an explosive gage middle (XGM) mechanism, which suggested a favorable interface between fiber and resin. According to the mixed law equation, PI fiber at a frequency of 10.2 GHz exhibited dielectric constant of 3.41 ± 0.03 and dielectric loss of about 0.002–0.004. The successful preparation of PI fiber reinforced BADCy composite with low dielectric constant provides new ideas for material design and selection of lightweight high-strength structural-functional integrated composites.

Enhanced dielectric and energy-storage performance of nanocomposites using interface-modified anti-ferroelectric fillers

Abstract Polymer-based 0–3 composites filled with ferroelectric ceramic particles have exhibited prominent dielectric responses and energy-storage performance, and are expected to be promising materials for high-performance, energy-storage capacitors in advanced electric systems. Unfortunately, low discharging efficiency hampers their practical application due to the high remnant polarization and interface related dielectric loss. In the present work, an anti-ferroelectric ceramic (Pb0.97La0.02)[Zr0.63(Sn0.3Ti0.07)O3] (PLZST) was prepared as the filler due to their intrinsic ultra-low dielectric loss and remnant polarization. Meanwhile, 3-aminopropyltriethoxysilane (KH550) was used to modify the surface of PLZST to enhance the interfacial compatibility between the PLZST filler and the polymer matrix. Enhanced dielectric permittivity, lowered loss, increased breakdown strength, and energy density were obtained at a relatively low loading content of the modified fillers (m-PLZST). Specifically, a considerably high energy density of 12.8 J/cm3 was achieved in a thin film with 8.0 wt% m-PLZST fillers. In comparing the properties of the composites filled with surface modified PLZST (m-PLZST) and pristine PLZST, the significant performance enhancement is well addressed with the accompanying reduction in loss, lowered remnant polarization, and depressed interfacial polarization. This result correlates to the anti-ferroelectric characteristics of the filler and enhanced compatibility from the surface modification.

Room-temperature-densified H3BO3 microwave dielectric ceramics with ultra-low permittivity and ultra-high Qf value

With the rapid development of mobile communication technology towards 5G and 6G, the microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are urgently demanded. Here, the excellent microwave dielectric properties are reported in H3BO3 ceramics with the molecular crystal structure, whose permittivity (2.84) and density (1.46 g/cm3) are record-low among the low-loss ceramics. The ultra-high Qf value of 146,000 GHz (or the ultra-low dielectric loss of 1.03 × 10−4 at 15 GHz) is also distinguished. Besides, the H3BO3 ceramics can be densified at room temperature by a simple cold sintering process in a short time of 10 min, and this brings many advantages for the integration with microwave circuits. The large molecule volume originating from the molecular crystal structure and the low dielectric polarizabilities of H+ and B3+ are responsible for the ultra-low permittivity of H3BO3 ceramics, and more microwave dielectric materials with ultra-low permittivity and ultra-high Qf value are expected to be explored in the molecular crystals.

Ultralow dielectric loss of BiScO3-PbTiO3 ceramics by Bi(Mn1/2Zr1/2)O3 modification

BiScO3-PbTiO3 ceramics are attractive for high-temperature piezoelectric applications while their high dielectric loss has to be substantially reduced. In this paper, a ternary perovskite system of xBi(Mn1/2Zr1/2)O3-(1-x-y)BiScO3-yPbTiO3 (abbreviated as xBMZ-BS-yPT) with x = 0.02, 0.04 and y = 0.62–0.67 were fabricated by conventional solid-phase method, and their ceramics were systematically studied with regards to phase structure, microstructure, dielectric and piezoelectric properties. X-ray diffraction results indicate a gradual change from rhombohedral to tetragonal phase with increasing PT composition. Morphotropic phase boundary (MPB) is revealed for the system with x = 0.02, y = 0.64, at which ultralow dielectric loss factor (0.58 %), almost unchanged Curie temperature (449 °C), high electromechanical properties (d33 = 360 pC/N, kp = 0.53), and stable strain output below 200 °C are observed. With such excellent piezoelectric properties and high-temperature stability, BMZ modified BS-PT ceramics are promising candidates for power electromechanical devices, especially operating in high-temperature environments.