Enhancement Of Permittivity Research Articles

Complex Permittivity Spectra of Granular Polymer Composites with Dispersed Ag-Coated Cu Flakes

AbstractConductive particle-containing granular composites with tuneable negative permittivity are being studied to improve the performance of electromagnetic devices, such as shielding materials. In this study, we investigated the relative complex permittivity and electrical conductivity of granular composites of polyphenylene sulfide (PPS) resin and Ag-coated Cu flakes in the radio- to microwave-frequency range and compared them with those of PPS/bare Cu flake composites. Electrical conductivity measurements revealed that the PPS/Ag-coated Cu flake composites have a lower percolation threshold (φc) than the PPS/bare Cu flake composites, whereas the electrical conductivity of the PPS/Ag-coated Cu flake composites in the percolated particle state was higher at the same particle volume fraction. At particle contents above φc, a low-frequency plasmonic state of conduction electrons was achieved in the percolated particle chains in both composites, and negative permittivity spectra were obtained. The percolated PPS/Ag-coated Cu flake composites had a negative permittivity up to a higher frequency than the percolated PPS/bare Cu flake composites. Furthermore, the Drude model was used to analyze the negative permittivity spectra of the composites in the percolated particle state. The plasma frequency of the composites with percolated Ag-coated Cu flakes was higher than that of the composites with percolated bare Cu flakes. Thus, coating Ag on Cu particles improved the conductivity of the composite, leading to negative permittivity up to higher frequencies. This study contributes to the enhancement of the negative permittivity achieved by granular composites, which is useful for microwave technology applications. Graphical Abstract

Preparation of La-doped SrTiO3 ceramics with colossal permittivity and high insulation resistivity via controlling the particle diameters of the powders

Ceramic capacitors are widely studied and applied in the electronic industry. We utilized the sand-milling technique to produce a series of La-doped SrTiO3 powders with varying particle diameters and investigated the effect of particle size on the resulting dielectric properties for the first time. We found that reducing the particle diameter significantly enhances the permittivity from approximately 7000 to 32000 (at 1 kHz, room temperature). Furthermore, a colossal permittivity of ∼32000 (at 1 kHz, room temperature), combined with ultra-high resistivity (>7 × 1011 Ω cm), low loss (0.004), and excellent frequency/temperature stability, were simultaneously achieved in the ceramic. Lastly, the sintering temperature is as low as 1360 °C, making it suitable for industrial production. By analyzing scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results, we discuss the possible mechanism behind the enhancement of permittivity with increased sand-milling time. The low sintering temperature and highly controllable permittivity of the ceramics by adjusting the sand-milling time of the powders offer a new strategy for the scientific study and industrial application of materials with colossal permittivity.

Permittivity enhancement of Al2O3/ZrO2 dielectrics with the incorporation of Pt nanoparticles

Al2O3/ZrO2 (A/Z) layers with embedded Pt nanoparticles (Pt-nps) at the interface of A/Z have been used to create a dielectric film with an enhanced permittivity. The Pt-nps and dielectrics are both grown by the atomic layer deposition process, which is complementary metal–oxide–semiconductor compatible. In order to control the thickness ratio of Pt-nps in the overall dielectrics more easily, the thickness of the ZrO2 layer is changed from 12 to 30 nm with a fixed thickness of 12 nm for Al2O3 and constant growth cycles of 70 for Pt-nps. The results show that the introduction of Pt-nps is beneficial to the enhancement of the dielectric permittivity. As the thickness of ZrO2 is 30 nm, the capacitance density increases from 2.5 to 5.1 fF/μm2 with the addition of Pt-nps, i.e., a doubling of the capacitance density achieved. Additionally, the leakage current at 2 V increases from 1.1 × 10−8 to 1.5 × 10−7 A/cm2. Furthermore, the dielectric breakdown field decreases from 5.4 to 2.7 MV/cm. The electric field distribution simulation and charging–discharging test imply that interfacial polarization is built at the interface of Pt-nps and the dielectric films, which contributes to the dielectric permittivity enhancement, and local electric field increasing in the affinity of Pt-nps gives rise to the deterioration of the leakage current and breakdown electric field.

Dielectric Property Tuning via Electric Field Alignment in Mxene (Ti3C2)-Based Polymer Nanocomposites

Orientation control is crucial for fine-tuning the functional properties of two-dimensional (2D) nanomaterials. MXene (Ti3C2) alignment has drawn significant attention lately as the targeted properties can be controlled by manipulating the structural anisotropy. However, controlled MXene nanosheet orientation inside the polymer matrix is a complex and less understood mechanism. In this study, we applied an in-plane electric field to align the MXene nanosheets vertically inside the semicrystalline polyvinylidene fluoride (PVDF) (Tg⁓ -35°C) matrix in situ, where the amorphous phase assisted the electric field alignment at room temperature. These vertical orientations of the nanosheets were confirmed directly using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Our study reveals a significant correlation between MXene-orientation and dielectric property enhancement. PVDF- 5 wt.% MXene demonstrated the highest dielectric permittivity increase of ⁓500% because of the maximum surface polarization of the nano-capacitors inside the matrix. Interestingly, the loss value shows a sharp jump after the 5 wt. % MXene concentration, demonstrating a percolative network formation. Notably, our nanocomposite exhibited a low loss before (0.07) and after (0.66) applying the electric field, even at a high MXene concentration (20wt.%). Finally, to understand the effect of polymer domain structure on the electric field-induced orientation effect, we conducted a comparative study between non-ferroelectric poly vinyl alcohol (PVA) and ferroelectric (PVDF) polymer-based MXene nanocomposites. Interestingly, we observed a synergistic effect of the polymer chain and MXene orientation on the permittivity enhancement in the ferroelectric polymer-based nanocomposites at both high and low frequencies. This study provides fundamental insights for designing hybrid solid-state dielectric films for next-generation flexible electronics.

Significantly enhanced permittivity and suppressed loss of P(VDF-HFP)-based composites by introducing PPy@BT-OH fillers

Polymer-based composites with high dielectric permittivity (high-k) are extensively utilized in embedded capacitors, pulse power supplies and radio frequency filter, etc. However, the enhancement of permittivity often comes at the price of elevated loss, which greatly diminishes the energy conversion efficiency and stability of the device. Herein, we loaded hydroxylated barium titanate (BT-OH) onto polypyrrole nanowire (PPy) to prepare a kind of PPy@BT-OH fillers and further incorporated them into Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) polymer. Gaining from the stronger interfacial polarization effect and the hindrance to the development of conductive network triggered by PPy@BT-OH fillers, a significantly enhanced permittivity of ∼ 209.2 @ 10 kHz accompanied by a relatively low loss (tan δ ∼ 0.14 @ 10 kHz) was simultaneously realized in PPy@BT-OH/P(VDF-HFP) composite with 8 wt% filler contents.

Enhanced dielectrics, ferroelectric and optical properties of lithium niobate for high temperature applications using potassium oxide (K2O) additive

Dielectrics, Ferroelectric and Optical properties of Lithium Niobate has been examined using Potassium Oxide (K2O) as an additive on the samples prepared by solid state reaction method using high energy ball milling. The crystal structure analysis by Rietveld structure refinement confirms that the LiNbO3 (LN) with K2O additive also exhibit the rhombohedral structure with R3c space group. The SEM characterization of the microstructure reveals that the samples sintered at a temperature of 1050 °C, have regular and uniform grain morphology and better density. The average grain size decreases for the K2O added compositions in the beginning and increases later for higher concentration of additive. Thermal study with TGA suggests that as the activation energy is decreases, the polarization is enhanced and the LN composition with 2.72 wt% K2O additive shows the best thermal stability. The frequency and temperature dependent dielectric properties were investigated in a wide range of frequency and a substantial enhancement in the dielectric constant of LN is obtained by K2O addition. A useful enhancement in permittivity is obtained with increase of temperature. The band gap values for direct and indirect band gaps for the various compositions are also determined. The least direct band gap is discovered to be 2.36 eV for the composition with 2.72 wt% K2O additive. The composition-dependent photoluminescence (PL) emission studies reveal that the emission spectra for both the pure LiNbO3 and K2O added LiNbO3 compositions lies in the UV–visible region. All the investigated compositions exhibit distinct green, yellow, and red emission peaks. The LN with 2.72 wt% K2O additive shows the best dielectric, thermal stability and polarization response with maximum polarization Ps ∼1.16 μC/cm2. The present investigations suggest that properties of LN can be significantly improved by using K2O additive for sustainable, low cost, environmental friendly energy storage material for high temperature applications.

Hollow magnetic Fe3O4 nanospheres for excellent electromagnetic wave absorption

The construction of lightweight magnetic electromagnetic (EM) wave absorption materials is of great significance for the development of EM wave absorption materials. Herein, hollow magnetic Fe3O4 (H–Fe3O4) nanospheres were successfully prepared by hydrothermal method. Analysis of EM parameters indicates that the formation of local conductive and magnetic networks caused by H–Fe3O4 aggregation effects leads to the significantly enhancement of permittivity and permeability. In particular, the H–Fe3O4 composite with a thickness of 2.15 mm achieved the minimum reflection loss of −50.25 dB and the corresponding bandwidth (<−10 dB) was 3.4 GHz. The synergistic effects of ferromagnetic resonance and exchange resonance and polarizations leads to excellent absorption performance. The radar cross section (RCS) simulation indicated that the RCS reduction value of H–Fe3O4 composite can reach 29.8 dB m2 under the incident angle of 20°. Moreover, the metastructure design shows an ultra-wide EM wave absorption bandwidth. This work can provide ideas for the design and application of ultra-light magnetic materials.

Ultrahigh Capacitive Energy Density in Stratified 2D Nanofiller-Based Polymer Dielectric Films.

Dielectric capacitors are critical components in electronics and energy storage devices. The polymer-based dielectric capacitors have the advantages of device flexibility, fast charge-discharge rates, low loss, and graceful failure. Elevating the use of polymeric dielectric capacitors for advanced energy applications such as electric vehicles (EVs), however, requires significant enhancement of their energy densities. Here, we report a polymer thin film heterostructure-based capacitor of poly(vinylidene fluoride)/poly(methyl methacrylate) with stratified 2D nanofillers (Mica or h-BN nanosheets) (PVDF/PMMA-2D fillers/PVDF), that shows enhanced permittivity, high dielectric strength, and an ultrahigh energy density of ≈75 J/cm3 with efficiency over 79%. Density functional theory calculations verify the observed permittivity enhancement. This approach of using oriented 2D nanofillers-based polymer heterostructure composites is expected to be versatile for designing high energy density thin film polymeric dielectric capacitors for myriads of applications.

Wearable Capacitive Tactile Sensor Based on Porous Dielectric Composite of Polyurethane and Silver Nanowire.

In recent years, the implementation of wearable and biocompatible tactile sensing elements with sufficient response into healthcare, medical detection, and electronic skin/amputee prosthetics has been an intriguing but challenging quest. Here, we propose a flexible all-polyurethane capacitive tactile sensor that utilizes a salt crystal-templated porous elastomeric framework filling with silver nanowire as the composite dielectric material, sandwiched by a set of polyurethane films covering silver nanowire networks as electrodes. With the aids of these cubic air pores and conducting nanowires, the fabricated capacitive tactile sensor provides pronounced enhancement of both sensor compressibility and effective relative dielectric permittivity across a broad pressure regime (from a few Pa to tens of thousands of Pa). The fabricated silver nanowire-porous polyurethane sensor presents a sensitivity improvement of up to 4-60 times as compared to a flat polyurethane device. An ultrasmall external stimulus as light as 3 mg, equivalent to an applied pressure of ∼0.3 Pa, can also be clearly recognized. Our all-polyurethane capacitive tactile sensor based on a porous dielectric framework hybrid with conducting nanowire reveals versatile potential applications in physiological activity detection, arterial pulse monitoring, and spatial pressure distribution, paving the way for wearable electronics and artificial skin.

Optimizing electromechanical performance of multilayered multiwalled carbon nanotube/silicone rubber composites via filler content distribution modulation

AbstractDielectric elastomers are widely used as electroactive polymer materials due to their high energy density, high strain, and low loss. However, the practical applications are limited sometimes by their low electromechanical strain ability due to relatively low dielectric permittivity for polymers. Herein, multiwalled carbon nanotube (MWCNT) filled silicone rubber (SR) composites with a five‐layered structure are prepared with the outer two layers of neat SR while the middle three layers are MWCNT filled SR, in which the former functions as insulating layers while the latter acts as the dielectric permittivity enhancement layers. Further, by differing the MWCNT content within the middle three layers, we find that as the concentration distribution increases from 1:1:1 to 1:2:1 and 1:3:1, both Young's modulus and dielectric permittivity gradually improve while dielectric loss remains extremely low even though the total MWCNT content reaches 1.6 wt%. With the combined effects of dielectric permittivity and modulus, the composite with evenly distributed MWCNT content (1:1:1) shows the highest actuation strain under a given electric field strength. Meanwhile, the electric breakdown strength of the composite 1:1:1 is also the highest, leading ultimately to a maximum actuation strain of 10.87% at the breakdown strength of 14.6 kV/mm.

Construction of Nb2CTx/α-MnO2 composites by electrostatic self-assembly for controllable impedance matching and enhanced electromagnetic absorption

Nb2CTx/α-MnO2 composites have been constructed by the deposition of α-MnO2 nanowires on the surface of the layered Nb2CTx matrix through an electrostatic self-assembly strategy. The increase of α-MnO2 content can lead to an improvement of permittivity and a shift of the reflection peak towards low frequency at a fixed thickness. Theory analysis speculates that the synergistic effect of lattice defect and electron hopping of Mn4+-O-Mn3+ chains in α-MnO2 nanowires as well as heterogeneous interfaces between Nb2CTx and α-MnO2 are predominant accounts for the enhancement of permittivity. The effective complementary of impedance matching and microwave attenuation can be responsible for the displacement of the reflection peak towards low frequency and a wide-frequency absorption. Accordingly, Nb2CTx/α-MnO2 composites exhibit an optimal reflection loss of -24.7 dB and an absorption bandwidth of 5 GHz at a thin matching thickness of 1.8 mm, which are better than those of most Nb2CTx-based absorbents.

Synthesis and Characterization of Core-Double-Shell-Structured PVDF-grafted-BaTiO3/P(VDF-co-HFP) Nanocomposite Films.

Core-double-shell-structured nanocomposite films consisting of polyvinylidene fluoride-grafted-barium titanate (PVDF-g-BT) incorporated into a P(VDF-co-hexafluoropropylene (HFP)) copolymer matrix were produced via a solution mixing method for energy storage applications. The resulting films were thoroughly investigated via spectroscopic, thermal, and morphological analyses. Thermogravimetric data provided an enhancement of the thermal stability, while differential scanning calorimetry indicated an increase in the crystallinity of the films after the addition of PVDF-g-BT. Moreover, broadband dielectric spectroscopy revealed three dielectric processes, namely, glass-rubber relaxation (αa), relaxation associated with the polymer crystalline phase (αc), and slower relaxation in the nanocomposites resulting from the accumulation of charge on the interface between the PVDF-g-BT filler and the P(VDF-co-HFP) matrix. The dependence of the dielectric constant from the composition was analyzed, and we found that the highest permittivity enhancement was obtained by the highest concentration filler added to the largest concentration of P(VDF-co-HFP). Mechanical analysis revealed an improvement in Young's modulus for all nanocomposites versus pristine P(VDF-co-HFP), confirming the uniformity of the distribution of the PVDF-g-BT nanocomposite with a strong interaction with the copolymer matrix, as also evidenced via scanning electron microscopy. The suggested system is promising for use in high-energy-density storage devices as supercapacitors.

Development of ultra-thin and high-efficient bi-layer microwave absorbers from Fe3N@C and CoS2 samples

Nowadays, electromagnetic interference (EMI) is one of the pollution that harm human health and electronic devices. Iron nitride (Fe3N) and cobalt sulfide (CoS2) are promising microwave-absorbing materials (MAMs) due to their intriguing properties. In this work, polygonal Fe3[email protected] and flower-like CoS2 were fabricated, and Fe3[email protected] showed pretty good magnetic properties. Microwave absorption properties of as-prepared samples were investigated, where Fe3[email protected] and CoS2 reached minimum reflection loss (RL) of −12 dB and −23 dB, respectively. In addition, Fe3[email protected] mostly had no effective absorption bandwidth (EAB), whereas Co2S was 2.5 GHz. The better microwave absorption properties of CoS2 compared to Fe3[email protected] could be explained through the combination of electrical conductivity, C0 values, loss capacity matching, impedance matching, and attenuation constant. It is worth mentioning that both Fe3[email protected] and CoS2 could not be considered promising MAMs. Therefore, RL curves of bi-layer MAMs made from as-prepared samples were simulated, where CoS2 and Fe3[email protected] acted as absorption and matching layers, respectively. The simulated Fe3[email protected]/CoS2 = 0.6 mm/0.6 mm bi-layer absorber could reach an RL of −45 dB and an EAB of 13 GHz, which was superior to the single-layer ones. The fabricated Fe3[email protected]/CoS2 = 0.6 mm/0.6 mm bi-layer absorber confirmed these excellent properties, which could be a result of the enhancement of complex permittivity, complex permeability, dielectric, and magnetic loss tangents.

Synergistic enhancement in permittivity and energy storage capacity of epoxy dielectrics via constructing continuous 3D BaTiO3 network collaborated with graphene oxide

Three-dimensional (3D) ceramic network has advantages over conventional ceramic nanoparticles in achieving high-performance flexible polymer dielectrics. However, the energy storage capacity cannot be substantially improved due to the relatively large dielectric loss and low breakdown strength. In this study, hierarchical 3DBT/EP-GO (GEBT) dielectric hybrid composites with greatly improved permittivity and energy storage density were obtained by reversely introducing a mixed graphene oxide (GO)/epoxy (EP) solution into three-dimensional BaTiO3 (3DBT) network, which was facilely constructed by sol-gel method using cleanroom wiper as the template. A relatively high dielectric constant (ε′ = 15.6) and breakdown strength (E0 = 239.8 kV mm−1) were simultaneously achieved for the GEBT-4 system with ∼15.4 wt% 3DBT and 0.75 wt% GO (to the epoxy). This system was much superior to the GEBT-1 with only 15 wt% 3DBT (ε′ = 9.2, E0 = 128.8 kV mm−1) and epoxy nanocomposite with 25 wt% BT nanoparticles (ε′ = 6.3, E0 = 121.0 kV mm−1). The continuous 3DBT ceramic network provided an effective polarization pathway within epoxy matrix, in which GO prevented electrical breakdown of the composites, thereby resulting in the significantly enhanced energy storage performance.

Carbon-Dot-Containing Poly(methyl methacrylate) for Highly Dielectric Nanomaterials

In this paper, we report a massive enhancement of the relative permittivity of PMMA-based nanodielectrics in the presence of carbon dots (CDs) and neodymium-doped carbon dots (Nd-CDs). Different weight percentages (0.5, 5, and 10 wt %) of CDs and Nd-CDs were composited with PMMA to form PMMA@CD and PMMA@Nd-CD nanocomposite films, and films were characterized by different techniques. The dielectric response study indicates the significant enhancement of the relative permittivity of PMMA in the presence of CDs (∼15 times), and this value is increased further in the presence of Nd-CDs (∼153 times). The presence of many interfaces inside the PMMA@CD composites due to nanofillers is the cause of this significant enhancement in dielectric permittivity, which is further increased in the presence of Nd-CDs. As the temperature increases, the effective dipolar polarization of the composites increases, which in turn helps enhance relative permittivity. Nevertheless, at 75 °C and 100 Hz, the relative permittivity value for PMMA@Nd-CD composites reaches nearly 1242 (234 times), the highest reported for PMMA composites to date. Moreover, the AC conductivity for PMMA@Nd-CD is higher than that for PMMA@CD, possibly as a result of more charge conduction from the valence band to the conduction band for PMMA@Nd-CD. The conductivity is also increased as a function of temperatures for all composites as a result of the decrement of electronic resistance inside semiconductor nanofillers. In this study, a unique and sensitive change in dielectric and electrical properties of PMMA-based nanodielectrics was observed, which is helpful in the commercial use of PMMA nanodielectrics inside capacitors.

Structure, Microstructure, and Dielectric Response of Polycrystalline Sr1-xZnxTiO3 Thin Films

In a view of the research interest in the high-permittivity materials, continuous enhancement of the dielectric permittivity ε′ with Zn content was reported for conventionally prepared Sr1-xZnxTiO3 ceramics with x up to 0.009, limited by the solubility of Zn on Sr site. Here, we use a sol-gel technique and a relatively low annealing temperature of 750 °C to prepare monophasic Sr1-xZnxTiO3 thin films with higher x of 0.01, 0.05, and 0.10 on Pt/TiO2/SiO2/Si substrates. The incorporation of Zn on the Sr site is confirmed by the decrease of the lattice parameter, while the presence of Zn in the films is proven by energy dispersive spectroscopy. The film thickness is found to be ~330 nm by scanning electron microscopy, while the average grain size of 86–145 nm and roughness of 0.88–2.58 nm are defined using atomic force microscopy. ε′ measured on the films down to 10 K shows a decreasing trend with Zn content in contrast to that for weakly doped Sr1-xZnxTiO3 ceramics. At the same time, the temperature dependence of the dissipation factor tanδ reveals a peak, which intensity and temperature increase with Zn content.

Structural and optical characterization of thin films from bimetallic Au-Sb system as tuneable plasmonic material for UV spectral range

The optical properties of silver and gold based bimetallic alloys make possible to adjust their plasma frequency. The direct alloying and plasmonic activity of thin layers from the Au-Sb system are presented in the present work. The thin films were deposited by thermal co-evaporation of gold and antinomy. The chemical and phase composition of thin films, were analysed by X-ray microanalysis and X-ray diffraction (XRD), respectively. The results of the X-ray microanalysis show that the composition of the thin layers corresponds well to the predetermined. The XRD patterns, depending on the envisaged compositions, show formation of intermetallic compound AuSb2 and binary alloys between the initial elements and the intermediate compound, which is in accordance with the Au-Sb phase diagram.The dispersion of the complex permittivity was determined by spectroscopic ellipsometry. The results show that the increase of the antimony content leads to an increase of the values of the imaginary part of the complex permittivity in the visible spectral region at photon energies greater than 3 eV, and a decrease in the ultraviolet spectral region. Based on the obtained dispersions of the complex permittivity, extinction cross-sections and local field enhancement of spherical Au-Sb nanoparticles were determined and their plasmon activity was evaluated.

Electrical field stimulated modulation of cell fate of pre-osteoblasts on PVDF/BT/MWCNT based electroactive biomaterials.

The present study reports the impact of the interplay between electroactive properties of the biomaterials and electrical stimulation (ES) toward the cell proliferation, migration and maturation of osteoprogenitors (preosteoblasts; MC3T3-E1) on the electroactive poly (vinylidene difluoride) (PVDF)-based composites. The barium titanate (BaTiO3; BT; 30 wt%) and multiwalled carbon nanotubes (MWCNT; 3wt%) were introduced into the PVDF via melt mixing, which led to an enhancement of the dielectric permittivity, electrical conductivity, and surface roughness. We also present the design and development of an in-house customized 12-well plate-based device for providing different types (DC, square, biphasic) of ES to cells in culture in a programmable manner. In the presence of ES of 1V cm-1 , biophysical stimulation experiments performed using 12-well plate-based device revealed that PVDF composite (PVDF/30BT/3MWCNT) can facilitate the enhanced adhesion and proliferation of the MC3T3-E1 in non-osteogenic media, with respect to non-stimulated conditions. Importantly, MC3T3-E1 cells demonstrated significantly better migration and differentiation on the PVDF/30BT/3MWCNT under ES when compared to ES-free culture conditions. Similar enhancement with respect to alkaline phosphatase activity, intracellular Ca2+ concentration, and calcium deposition in MC3T3-E1 cells was recorded, when pre-osteoblasts were grown for 21 days on electroactive substrates. All these observations supported the activation of osteo-differentiation fates, which were further promoted in the osteogenic medium. The present study demonstrates that the synergistic interactions of ES with piezoelectric PVDF-based polymer composite can potentially enhance the proliferation, migration, and osteogenesis of the pre-osteoblast cells, rendering it a promising bioengineering strategy for bone tissue engineering.

Enhancement of permittivity and energy storage efficiency of poly (vinylidene fluoride-chlorotrifluoroethylene) by uniaxial stretching

Dielectric polymer film capacitors with a high-power density as well as efficient charge and discharge rates have great potential for application to fulfill the miniaturized and lightweight requirements of the electronic and stationary power systems. It was reported that the elastic recovery rate and energy storage density of poly (vinylidene fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] polymer film can be enhanced through thermostatic uniaxial stretching. But it is unknown about the relationship between the stretching rate and above properties. In this study, we investigated the effect of different stretching rates on the conformation, elastic recovery, dielectric constant, and energy storage density of stretched P(VDF-CTFE) polymer films. It was found that the stretching rate significantly affected the formation of polar [Formula: see text]-crystal phase, causing different dielectric properties. The degrees of elastic recovery of P(VDF-CTFE) film vary with stretching rates. Among them, the elastic recovery rate of the P(VDF-CTFE) 94/6 film is 46.5% at a stretching rate of 15 mm/min, the dielectric constant is 12.25 at 100 Hz, and the energy density reaches 3.95 J/cm3with the energy loss of 39% at 200 MV/m field.

A high-k Cu-doped ZnO film formed via Ga-ion implantation: The acceptor-donor co-doping approach

Dielectric thin films having high permittivity (high-k) and low dielectric loss is essential for developing high performance capacitive devices like metal oxide field effect transistor or thin film transistor. Ga ion implantation performed on Cu-doped ZnO film fabricated by pulsed laser deposition with optimized doping concentrations and post-implantation annealing yielded film having high permittivity and low dielectric loss (ε = 87 and tan δ = 0.17 at the frequency of 1 kHz). Moreover, the permittivity exhibits good stability over a wide range of frequency from 20 Hz to 10 MHz. The high-k film was characterized by detailed dielectric studies, including frequency dependence of permittivity and dielectric loss, complex electrical modulus analysis, impedance spectroscopy and ac conductivity. The enhancement of the permittivity was attributed to the correlated potential barrier hopping of electrons between the neighboring acceptor-donor defect complex states in the band gap created by the co-doping, thus acting as electric dipoles polarizing the film. This work opens up future possibility for ‘dielectric engineering’. The three-dimensional dielectric spatial profile can be controlled via the selective area ion implantation with the depth controlled by the ion implantation energy. • A high-k Ga-Cu co-doped ZnO film formed via pulsed laser deposition and ion implantation method. • Optimized doping concentrations yielded high permittivity and low dielectric loss (ε=87 and tan δ=0.17 at 1 kHz). • Enhancement of permittivity was attributed to the correlated barrier hopping of electrons between neighboring defect complex.