High Dielectric Permittivity Research Articles

A SIMPLE LABORATORY CALIBRATION METHOD FOR MITIGATING SEAWATER EFFECTS ON SOIL MOISTURE SENSORS

The importance of moisture content for sediment dynamics in coastal environments is well documented, particularly in reference to aeolian sediment transport (Davidson-Arnott, 2005). Tidally-induced changes in moisture content in partially saturated environments, such as beaches, cause significant changes in surface shear strength through the development of suction stresses, which can affect erodibility (Sassa and Watabe, 2007). Thus, the accurate measurement of moisture content in these environments is important for determination of strength properties and for predicting sediment transport. Most moisture sensors work by measuring dielectric permittivity, the ability to carry electric charge, of the substrate, which is proportional to the moisture content. However, most moisture sensors are not calibrated for seawater, which has a higher dielectric permittivity than freshwater, causing overestimation of the moisture content. Therefore, the goal of this study is to develop and demonstrate a laboratory calibration scheme to account for this overestimation, and thus to allow for more accurate measurements of moisture content in coastal environments.

Facile synthesis of samarium and cerium doped double perovskite cobaltite with enhanced dielectric response

The investigation of Sm–Ce doping on structure, conduction, and dielectric response of Bi2Ca2–2xSmxCexCoO6 (x = 0.000, 0.025, 0.050, 0.075) (BCSCCO) are presented. All the specimens were synthesized by a facile synthesis technique named the co-precipitation route. X-ray diffraction (XRD) reveals that BCSCCO crystallizes into one phase with space group P21/m. The crystallite size, dislocation density, lattice parameters, lattice strain, unit cell volume, and bulk density were determined using XRD data. The structural properties of Bi2Ca2CoO6 were examined using calculations based on the density functional theory. Theoretical and experimental values discrepancy is less than 1%. A scanning electron microscope was used for performing a microstructural analysis. The SEM images demonstrate the homogeneous distribution of grains with a range of sizes (0.054–0.090 μm). The alternating current (ac) conductivity, dielectric permittivity, and tangent loss were also studied as a function of frequency (20 Hz–3 MHz) at different temperatures (100–500 °C). All synthesized samples were examined using non-linear Debye's function to determine their spreading factor and relaxation time. The specimen with the lowest crystallite size (∼23 nm) exhibits a high dielectric permittivity (∼3.80 × 106). The conduction mechanism was examined in the studied samples with the use of Jonscher's power law. The power law indicates that the BCSCCO (x = 0.000, 0.025) follows correlated barrier hopping, whereas the x = 0.050 and 0.075 compositions follow non-overlapping polaron tunneling. The studied specimen Bi2Ca1.90Sm0.050Ce0.050CoO6 with the highest density (∼5.65 g/cm3) displays a high electrical conductivity (∼46.1 S/cm). These findings correspond to those published for ceramics made from calcium cobaltite using solid–state reactions (5.0–26.0 S/cm).

Structure analysis, ferroelectric and ferromagnetic properties in nanostructured Bi2O3 –Fe2O3 –PbTiO3 for magnetoelectric applications

The ternary 0.52Bi2O3 – 0.18Fe2O3 – 0.30PbTiO3 (BFPT) system was prepared by mechanosynthesis in a high-energy planetary mill. The mixed powder was milled for 1, 2, 5, and 10 h. After 5 h of milling, the partially crystalline phase was achieved, as investigated by the XRD analysis. HRTEM verified the nanoparticle formation, and the mean size of the particles is estimated to be ⁓ 2.95 nm. Dielectric permittivity, loss tangent, electric modulus, and ac conductivity were measured for the milled system for 5 h as a function of frequency and temperature. The nanostructured BFPT sample shows a high dielectric permittivity (ε′ ⁓ 1388 at 500 Hz) obtained at Tc ⁓ 633 K (Curie temperature), which corresponds to the structural phase transition. The experimental results of σac are acceptable with the CBH model. The measurements of the P–E hysteresis loop illustrated recoverable energy density (Wrec=4.33 mJ/cm3) and energy storage efficiency (η=60.56%) at room temperature. The M-H data represent remnant magnetization (Mr) of 12.41 × 10−3 emu/g and coercive field (Hc) of 497.23 Oe. These remarks suggest that the nanostructured BFPT sample might be a promising option for magnetoelectric applications.

Epoxy-based high-k composite vitrimer: With low dielectric loss, high breakdown strength and surface electrical damage repairability

High dielectric constant/permittivity (high-k) polymer-matrix composites (PMCs) are widely used in the electronics and electrical industries since their high energy density, ease of processing and light weight. However, the high dielectric permittivity (εr) usually leads to a significant increase in dielectric loss (tanδ) and an obvious decrease in breakdown strength (Eb), which is still a major problem that restricts the development of high-k PMCs. In addition, to extend the service life, the next generation electrical/electronic components also demand materials have electrical damage repairability. In this study, a new epoxy-based high-k composite vitrimer was constructed. The dynamic disulfide bonds were introduced into the cross-linked network to provide the high-k composite vitrimer with excellent repairability, while the nanoparticle (NPs) fillers surfaces were modified by grafting disulfides to improve the dynamic rearrangement ability of the composite network and enhance the electrical properties of the high-k composite vitrimer. The results show that this high-k composite vitrimer has low tanδ and high Eb, which is about 0.025 (at 0.1 Hz and room temperature) and 26.0 kV/mm (under 50 Hz AC voltage of 1 mm samples), respectively. Moreover, it has excellent mechanical damages and electrical damages repairability. For mechanical damages, it can repair mechanical scratches by heating at 180 °C for 10 min. For surface electrical damages, it can also eliminate the residual carbons, regain the surface organic structure, and restore more than 94% insulation strength by thoil treatment under 80 °C for 60 min. This study provides a new reference method for the preparation of low tanδ, high Eb and repairable high-k PMCs.

Composition controllable multifunctionality of PVDF/PMMA/BaTiO3/OMMT based ternary and quaternary hybrid polymer nanocomposites

State-of-the-art engineered multifunctional nanocomposites composed of different polymer matrices and functional nanomaterials are in high industrial demand for advances in all-solid-state flexible device technologies. Within this framework, the host matrices of poly(vinylidene fluoride) (PVDF) and its blend with poly(methyl methacrylate) (PMMA), and the barium titanate (BaTiO3) and organo-modified montmorillonite (OMMT) clay mixed nanomaterial dispersed ternary PVDF/x wt% (BaTiO3+OMMT) and quaternary (PVDF+PMMA)/x wt% (BaTiO3+OMMT) hybrid polymer nanocomposites (HPNCs) are prepared through ultrasonicated homogenized solution casting method. The XRD patterns and FTIR transmittance spectra confirmed the composition dependent crystal phases of the PVDF and the heterogeneous polymer-polymer and polymer-nanomaterial interactions in these HPNC materials. The DSC measurements explained a huge alteration in the PVDF crystallite melting temperatures and also the degree of crystallinity of different HPNC materials. The UV–Vis absorbance of these hybrid materials depends strongly on their composition design and demonstrated dual energy band gaps attributed to host polymer matrices and the nanofillers. The dielectric permittivity dispersion in the broadband frequency range of 20 Hz − 1 GHz explains the contribution of several polarizations and relaxation processes in these complex composites, at 27 °C. Appreciably high dielectric permittivity (4 to 7) in the 20 Hz − 1 MHz range and low permittivity at the ultra high radio frequencies confirmed the promising nanodielectric characteristics of these hybrid materials. The interesting structure-property relationship, tunable energy band gaps, a wide range of composition controllable dielectric permittivity, and frequency dependent electrical conductivity revealed the usefulness of these HPNCs in making flexible-type innovative optoelectronic, capacitive energy storage, and microelectronic devices.

Preparation of xerogel based on syndiotactic polystyrene (sPS)/MWCNTs hybrid polymer gel for application as a dielectric material with high dielectric permittivity

MWCNTs were dispersed in sPS gel in both pristine as well as functionalized form to observe its effect on structure, morphology, thermal as well as dielectric properties of the resulting hybrid polymer gel. Since, the ortho-xylene induces clathration in pure sPS polymer in α-phase leading to thermoreversible gelation resulting in the δ-crystalline phase (sPS gel). Therefore, the removal of solvent from solvated δ-crystalline phase gives non-solvated δe-crystalline phase (sPS xerogel). The three dimensional fibrillar networks, as observed with scanning electron microscopy (SEM) and atomic force microscopy (AFM), have the polymer chains with s(2/1)2 helical conformation which makes the gel elastic. Fourier transform infra red spectroscopy (FTIR) shows the conformation change from trans planar to s(2/1)2 helical as indicated by the disappearance of peak at 541 cm−1 and appearance of peak at 537 cm−1 and 571 cm−1. The peak at 7.9° confirms the δ-crystalline phase presence whereas the absence of solvent is indicated by peak absence at 10°. Differential scanning calorimetry (DSC) thermogram confirms the δ to γ phase transition in the 100–150 °C temperature range. As we get an intermingled structure of gel fibers and MWCNTs, therefore, the dielectric behavior showed the percolative nature of the hybrid sPS xerogel. The pure sPS xerogel displayed no response to the frequency change whereas due to interfacial polarization, hybrid sPS xerogel responded to frequency change.

Structure and electrical properties of cold-sintered strontium-doped potassium sodium niobate

Cold sintering is an attractive method for sintering ferroelectric ceramics at temperatures at or below 300 °C. While we can practically obtain bulk samples by introducing a transient liquid and applied pressure, the mechanisms of sintering and final functional properties of cold-sintered ceramics are far from being understood. Here, we investigate the influence of grain size and sintering parameters on the microstructure and ferroelectric properties of 0.5 % Sr-doped K0.5Na0.5NbO3 ceramics. By comparing with the conventionally-sintered samples, we find that cold-sintered ceramics have higher dielectric permittivity and lower dielectric losses, which we attribute to smaller grains and higher relative density. Using atomic-scale analysis, we point out the presence of numerous lattice dislocations that likely act as pinning sites and thus inhibit any significant polarization-switching behaviour. Due to the slim P–E loop and high dielectric breakdown fields of the cold-sintered ceramics we consider its potential for energy storage applications.

Clamping of ferroelectric PVDF to enhance the electromechanical performance of a 1–3 PMN-PT/PVDF piezoelectric composite

A group of 1–3 type piezoelectric Pb (Mg1/3Nb2/3)O3-PbTiO3/polyvinylidene fluoride (PMN-PT/PVDF) composite sheets are prepared using a complex two-step hot-pressing method. Then the molecular structure model of piezoelectric materials and an inverse piezoelectric simulation of the composites are performed to express the horizontal compression, indicating the clamping activity of ferroelectric PVDF on PMN-PT. As such, this composite sheet possesses a high dielectric permittivity (εr) of 560 at 100 Hz for its compacted connecting of two phases. After polarization, a very large piezoelectric coefficient (d33) of 1125 pC/N and a considerable electromechanical coupling factor (kt) of 0.43 is obtained in PMN-PT/PVDF sheet with a proper aspect ratio of 1.4 and a thickness of 2.1 mm, further indicating that promoting effect of PVDF matrix on the strain in Z-direction of PMN-PT. The result shows that ferroelectric PVDF serving as polymer matrix favors the electromechanical coupling effect, and may provide a prospect of the potential application of PMN-PT/PVDF composite in sensor or transistor for matrix ultrasonic probes.

Mechanical treatment of aluminum plate surfaces for improvements of capacitance and dielectric permittivity

The surface mechanical alloying (SMA) technique achieved high capacitances, improved capacitance (C) and dielectric permittivity (ε′) of mixed Aluminum/fiber-glass ‘Al/F-glass’ formed on aluminum plates. The radiofrequency RF range 0.1–106 Hz was applied on the Al/F-glass on Al plates, acting as parallel electrodes sandwiching the mixed ceramic Al/F-glass as dielectric. Capacitance increase observed after surface alloying on treated Al with small 1.5 balls than 6 mm balls on Al-plate & 1 A l-plate 2 respectively, giving twice the permittivity constant of the annealed Al. Deformation micro-scale cavities in Al surfaces played important role in raising capacitance and permittivity values; Interpreted as condensers inside a condenser caused capacitance increase according Maxwell-Wagner-Sillars effect. Dielectric relaxation model Havriliak-Negami Model was used to examine the occurrence of the Maxwell-Wagner-Sillars effect in alloyed Al/F-glass surfaces on Al plates, which confirms micro-cavities important role due to pre-treatment of Al surfaces.

Enhanced magnetic properties and leakage current mechanism in bismuth lanthanum ferrite thin films coupled with impedance and magnetic studies

A highly crystalline and pure phase Bi0.993La0.007FeO3 (BLFO) thin films have been grown using a pulsed laser deposition technique. The structural analysis confirmed the thin film is well crystallized with a rhombohedral crystal structure with an R3c space group. The BLFO phase and composition are also confirmed by transmission electron microscopy and EDAX analysis. The surface chemistry of thin films, analysed by X-ray photon spectroscopy, reveals Fe's presence in Fe3+ and Fe2+ states. At RT, the deposited film exhibited high dielectric permittivity (∼4 × 102) and low dielectric loss (∼10−1). The isothermal magnetization on highly oriented (001)-MgO and LaAlO3 (LAO) substrates is investigated. The response is compared to the randomly oriented polycrystalline films on low-cost substrates (Pt/TiO2/SiO2/Si and n-type Si substrate). The enhanced saturation magnetization of 57 emu/cm3 and 36 emu/cm3 at 10 K and 300 K are observed at 2.5 kOe applied field for the film grown on the LAO substrate. Additionally, the low leakage current density of the film is obtained around ∼1 × 10−7 A/cm2 at a field of 100 kV/cm. Acquiring single-phase BLFO thin films with enhanced electrical and magnetic properties can be relevant in designing multiferroic materials for multiple-state memories, magnetic field sensors, and spintronics applications.

Enhancement in the electromagnetic shielding properties of doped [formula omitted] magnetite nanoparticles [formula omitted

Fe3O4 nanoparticles (NPs) are one of the most investigated materials in the field of microwave absorbers. To further optimize the electromagnetic interference (EMI) shielding effectiveness, doped M0.01Fe2.99O4(M=Mn,Ni,Cu,Zn) NPs were synthesized through co-precipitation method. All samples were subjected to X-ray diffraction analysis to determine their crystal structure. Transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were performed to confirm the morphologies, distribution of elements, and valence of iron in the prepared nanoparticles, respectively. The dielectric and magnetic characteristics displayed a considerable improvement for the doped Fe3O4 samples, except Zn0.01Fe2.99O4 where the obtained values were found to be comparable to those of pure Fe3O4. These variations are described in terms of the homogeneously distributed microstructure, mixed spinel cationic distribution in the doped samples, and Fe2+/Fe3+ ratios at the octahedral interstitial sites. Moreover, the EMI shielding efficiency was measured in the X-band frequency range (8.2 – 12.4 GHz) using a wave guide approach. The total shielding effectiveness of Cu0.01Fe2.99O4 and Ni0.01Fe2.99O4 samples was found to be much higher than that of pure Fe3O4 with absorption being the dominant mechanism. This is most likely owing to their high dielectric permittivity, enhanced conductivity, and high magnetic permeability, which results in improved impedance matching and stronger microwave absorption. This suggests that these doped nanoparticles may be utilized as efficient electromagnetic absorbers.

Simultaneous enhancement of dielectric properties and temperature stability in BaTiO3‐based ceramics enabling X8R multilayer ceramic capacitor

AbstractModified BaTiO3 ceramics that possess high dielectric permittivity and acceptable temperature stability have been widely utilized as multilayer ceramic capacitors (MLCCs) for high‐frequency bypass and power filtering in automotive applications. However, since the increasing demand for high‐capacity and small‐size, high‐permittivity materials that can serve as dielectric layers in MLCCs are urgently required. In this work, we design and fabricate a special BaTiO3‐0.03Mg‐0.02Y‐0.02CaZrO3 ceramic with a high dielectric permittivity of 3000 and the dielectric variation below ±13% in the temperature range of ‐55–150°C, fulfilling the requirements of X8R capacitors. To achieve these results, we employed grain size engineering and cation doping, using BaTiO3 precursors with a particle size of 240 nm to prepare the BaTiO3‐based ceramics with fine grains, while Mg and Y co‐doping was used for improving the temperature stability due to dielectric dispersion. Utilizing these high‐permittivity BaTiO3‐based materials, we fabricated MLCCs that satisfy the X8R criterion, possessing a high dielectric constant of 2950 and a high breakdown field (410 kV/cm).

Effect of nanodispersed zinc oxide concentrations on the structural, optical, dielectric, viscous, and acoustic properties of ethylene glycol– glycerol mixture based nanofluids

Nanofluids (NFs) are green-formulated innovative soft materials, enormously used for thermal management medium in energy harvesting/ storage and heat transport, as high breakdown voltage insulators/ nanodielectrics in electrical and energy storage systems, and in the advances of soft condensed matter device technologies. In this study, NFs consisting of ethylene glycol (EG) and glycerol (Gly) mixture in equal volumes as the base fluid and semiconductive zinc oxide (ZnO) nanoparticles with increasing concentrations from 0.005 to 1.00 wt% are prepared and characterized by employing different advanced techniques. X-ray diffraction (XRD) patterns recorded directly on these NFs confirmed the homogeneity and nanosuspension stability of ZnO particles in the hydrogen-bonded supramolecular 3D structure of viscous EG–Gly base fluid. The UV-Vis absorbance spectra explained the ZnO concentration tunable photo sensing and UV blocking properties of these semiconductive nanofluids. The 20 Hz to 1 MHz range dielectric spectra revealed high static dielectric permittivity of these NFs, at 298.15 K, confirming them as promising nanodielectric for electric energy storage devices. The dielectric dissipation factor, electric modulus, and impedance spectra confirmed that these EG–Gly/ZnO NFs have electrode polarization and conductivity relaxation processes around 200 Hz and 20 kHz, respectively. The electrical conductivity is observed in the range of 0.32– 0.65 μS/cm with a noticeable increase at the higher ZnO concentration which infers appreciable insulation performance of these NFs. The rheological measurements demonstrated Newtonian behavior of these NFs with a dynamic viscosity of about 69 mPa.s, at 298.15 K. Ultrasound velocity and various acoustic parameters of these NF materials are marginally altered with varying the ZnO concentration and revealed appreciable thermal conductivity of 0.31 W·m–1·K–1, at ambient temperature. The temperature dependent viscosity measurements of EG–Gly/1.00 wt% ZnO sample demonstrated its Arrhenius behavior with high activation energies for both the viscous and relaxation processes. These experimental results establish the EG–Gly/ZnO nanofluids as multifunctional materials for highlighting current applications and also in futuristic soft condensed matter technologies.

Cold Sintering Process for a BaTiO3/Poly(vinylidene difluoride) Ceramic-Polymer Composite: Evaluation of the Structural and Microwave Dielectric Properties.

The sintering process is essential to transforming particular material into dense ceramics. Although several sintering techniques have emerged over the past few years, the process is still performed at high temperatures. The alternative cold sintering process (CSP) is a potential strategy for producing an advance high dielectric permittivity and enables densification at low temperature. In this process, the CSP technique has been applied to successfully prepare the BaTiO3/poly(vinylidene difluoride) (PVDF) nanocomposite. The inorganic material of the BaTiO3/PVDF nanocomposite was confirmed by various physical characterizations, and the densification studies were performed using a semiautomated press, indicating a dissolution-precipitation mechanism. When a uniaxial pressure of 350 MPa was applied, with transient liquid could be sintered at 190 °C, and a relative density of 94.8%. The nanocomposite exhibits an excellent dielectric properties like εr = 71.1 and tan δ = 0.04 with frequency range at 1 GHz for various dwelling times and maximize the electrical resistivity. The BaTiO3/PVDF composite indicating a breakthrough opportunity toward an increase of the high dielectric constant will be significantly impacted by cold sintering. It enables innovative materials design and integrated devices to advance modern electronic industry applications.

Homogeneous Two-Layer Structures for Broadband and Wide-Angle RCS Reduction

A two-layer stacked resonance absorber is proposed to achieve broadband and wide-angle radar cross section reduction. The most prominent structure feature is its simple geometry, which comprises two homogeneous dielectric slabs only. The two slab heights are chosen as one-sixth of a guided wavelength to form a three-way cancellation mode via interface reflections while a high permittivity dielectric is used to achieve low profile. The total thickness is less than 0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda_{L}$</tex-math></inline-formula> . Because it involves no periodic structure, both monostatic and bistatic scattering levels can be suppressed in a broad frequency band and a wide angular region. A bouncing ray-based high frequency method was developed to perform parametric studies and design optimization in a timely fashion. Measured and simulated results are compared in spectral and angular domains. An 83% 10 dB RCS reduction band is observed. More than 10 dB back scattering suppression is achieved up to ±75° from the surface's normal.

Evolution of High Dielectric Permittivity in Low-Temperature Solution Combustion-Processed Phase-Pure High Entropy Oxide (CoMnNiFeCr)O for Thin Film Transistors

An investigation of dielectric permittivity on the sintered high entropy oxide (HEO) capacitor composed of Co, Cr, Fe, Mn, and Ni (i.e., (CoCrFeMnNi)O) developed using solution combustion synthesis is performed. Stabilization of the phase in HEO is extremely important as it has a direct influence on the properties. In order to explore phase stabilization, in-depth studies of thermal, structural, morphological, and compositional analyses are carried out. The optimized processing parameters are further implemented on depositing (CoCrFeMnNi)O dielectric thin films followed by a thin film transistor. Irrespective of the reaction medium, the precursors undergo combustion at a low temperature below 250 °C, resulting in amorphous HEO. Upon crystallization at 500 °C, no secondary impurity oxides were detected and phase-stabilized to a spinel structure (Fd3m). A homogeneous distribution of all five cations without any segregation and a completely disordered occupancy of the cations were displayed by the bulk and thin films of HEOs. The spinel (CoCrFeMnNi)O exhibited high permittivity, with values approximately 7.3 × 102 (in bulk) and 3 × 101 (in a thin film), measured at 1 kHz owing to the entropy stabilization effect of HEO. Due to their high permittivity and low leakage current density (∼10–8 A/cm2), the (CoMnNiFeCr)O thin film was integrated into thin film transistors (TFTs) with molybdenum disulfide-channel. TFTs showed a field effect mobility of 8.8 cm2 V–1 s–1, an on–off ratio of approximately 105, a threshold voltage of −1.5 V, and a subthreshold swing of 0.38 V/dec. The low voltage operation (<5 V) of these TFTs makes solution combustion-derived HEO (CoMnNiFeCr)O a potential candidate in microelectronics and optoelectronics applications.

Pb, Bi, and rare earth free X6R barium titanate–sodium niobate ceramics for high voltage capacitor applications

0.9Ba(Ti1−xMgx)O3−x-0.1NaNbO3 (BTNN-100xMg) solid solutions are investigated with a view to developing Bi, Pb, and rare earth free, high voltage multilayer ceramic capacitors. Mg doping on the B-site significantly reduced the electronic conductivity and resulted in ceramics that could withstand a pulsed unipolar field of &amp;gt;300 kV/cm (Emax) to give a recoverable energy density of 3.4 J/cm3 at 82.6% efficiency for x = 0.01. The high Emax is accompanied by a high dielectric permittivity (ε′ ∼ 1700 at room temperature) with temperature-stable dielectric permittivity of Δε/ε298K ≤ ±15% and loss tangent tan δ &amp;lt; 0.02 from 116 to 378 K, corresponding to an X6R designation in the Electronic Industry Alliance codes.

Computational and experimental investigations of the giant dielectric property of Na1/2Y1/2Cu3Ti4O12 ceramics

A modified sol-gel method was used to successfully produce Na1/2Y1/2Cu3Ti4O12 ceramics with high dielectric permittivity. The dielectric permittivity of Na1/2Y1/2Cu3Ti4O12 ceramics reaches values larger than 104 at room temperature and 1 kHz. Moreover, these ceramics exhibit two distinct thermally induced dielectric relaxations over a broad temperature range. The loss tangent is indeed small, ~0.032–0.035. At low temperatures, dielectric relaxation was attributed to the oxygen vacancy effect, while at high temperatures, it was attributed to grain boundary and sample-electrode contact effects. Our calculations revealed that Y and Na ions are likely to occupy Ca and Cu sites, respectively. As a result, other Cu related phases, especially CuO, were observed at the grain boundaries. Based on our analysis, there is a charge compensation between Na and Y ions in Na1/2Y1/2Cu3Ti4O12. Additionally, the Cu+ and Ti3+ states observed in our XPS study originate from the presence of an oxygen vacancy in the lattice. Last, the primary cause of the enormous dielectric permittivity of Na1/2Y1/2Cu3Ti4O12 ceramics primarily comes from the internal barrier layer capacitor effect.

Improved dielectric and mechanical properties in Ti3C2Tx MXene-MoS2/Methyl vinyl silicone rubber composites as flexible dielectric materials

Flexible dielectric composites have gained extensive attention in the field of electronics. However, its application is limited by the low dielectric permittivity. Here, we report a way for fabricating Ti3C2Tx MXene-MoS2 hybrid fillers/Methyl vinyl silicone rubber (MVQ) composites with high dielectric permittivity. The properties of the composites were investigated systematically. The Ti3C2Tx MXene-MoS2 hybrid fillers were distributed uniformly in the MVQ matrix. The composite with 2.2 wt% Ti3C2Tx MXene-MoS2 hybrid fillers showed a high dielectric permittivity of 7.35 at 103 Hz, while the loss tangent was only 0.00133. The enhanced dielectric properties can be due to the improved specific surface area and enhanced conductivity of the Ti3C2Tx MXene-MoS2 hybrid fillers, resulting in stronger interfacial polarization. Besides, the composites displayed excellent mechanical properties, with high tensile strength of 0.496 MPa and elongation at break of 342%, while the elastic module was lower than 0.456 MPa. Thus, by adding a small amount of Ti3C2Tx MXene-MoS2 hybrid fillers, the uniqueness and practicability of the Ti3C2Tx MXene-MoS2/MVQ composites used in electronic equipment were proved. This work provides a way for the excellent properties of MVQ composites which can be applied to the field of dielectric elastomer.

Polyvinyl chloride-based dielectric elastomer with high permittivity and low viscoelasticity for actuation and sensing

Dielectric elastomers (DEs) are widely used in soft actuation and sensing. Current DE actuators require high driving electrical fields because of their low permittivity. Most of DE actuators and sensors suffer from high viscoelastic effects, leading to high mechanical loss and large shifts of signals. This study demonstrates a valuable strategy to produce polyvinyl chloride (PVC)-based elastomers with high permittivity and low viscoelasticity. The introduction of cyanoethyl cellulose (CEC) into plasticized PVC gel (PVCg) not only confers a high dielectric permittivity (18.9@1 kHz) but also significantly mitigates their viscoelastic effects with a low mechanical loss (0.04@1 Hz). The CEC/PVCg actuators demonstrate higher actuation performances over the existing DE actuators under low electrical fields and show marginal displacement shifts (7.78%) compared to VHB 4910 (136.09%). The CEC/PVCg sensors display high sensitivity, fast response, and limited signal drifts, enabling their faithful monitoring of multiple human motions.