Dielectric Compositions Research Articles

A Rational Design of Bio-Derived Disulfide CANs for Wearable Capacitive Pressure Sensor.

Classic approaches to integrate flexible capacitive sensor performance are to on-demand microstructuring dielectric layers and to adjust dielectric material compositions via the introduction of insoluble carbon additives (to increase sensitivity) or dynamic interactions (to achieve self-healing). However, the sensor's enhanced performances often come with increased material complexity, discouraging its circular economy. Herein, a new intrinsic self-healable, closed-loop recyclable dielectric layer material, a fully nature-derived dynamic covalent poly(disulfide) decorated with rich H bonding and metal-catechol complexations is introduced. The polymer network possesses a mechanically ductile character with an Arrhenius-type temperature-dependent viscoelasticity. The assembled capacitive pressure sensor is able to achieve a sensitivity of up to 9.26kPa-1, fast response/recovery time of 32/24ms, and can deliver consistent signals of continuous consecutive cycles even after being self-healed or closed-loop recycled for real-time detection of human motions. This is expected to be of high interest for current capacitive sensing research to move toward a life-like, high performance, and circular economy direction.

Magnetic, magnetoresistive and structural properties of Cox(CoO)100-x thin film composites

The structural, magnetic, and magnetoresistive properties of Cox(CoO)100-x thin film composites synthesized by ion-beam sputtering of a composite target in an argon and mixed atmosphere (argon + oxygen) has been studied. The experimentally determined percolation threshold was significantly lower than that for most of the studied previously nanocomposites: ∼ 12.2 at % Co and ∼8.3 at % Co for films fabricated in inert and mixed atmosphere, respectively. This is explained by the special morphology of the films when small metallic Co nanoparticles are located on the surface of larger CoO particles. A negative tunnel-type magnetoresistance reaching 2.4% in 9 kOe field at room temperature was found for composites with close to the percolation threshold Co content. The magnetoresistance is proportional to the square of magnetization and is characterized by hysteresis, which correlates well with magnetic hysteresis. Magnetic hysteresis with a coercivity of the order of 700 Oe is observed for dielectric compositions up to 4 at. % Co. A possible reason for this behavior, along with the special morphology, is the appearance of thin layers of antiferromagnetic oxide at the interface between Co nanoparticles and CoO particles, which causes a significant increase in magnetic anisotropy.

Fully-Solution-Processed Enhancement-Mode Complementary Metal-Oxide-Semiconductor Carbon Nanotube Thin Film Transistors Based on BiI3 -Doped Crosslinked Poly(4-Vinylphenol) Dielectrics for Ultralow-Power Flexible Electronics.

The threshold voltage (Vth ) adjustment of complementary metal-oxide-semiconductor (CMOS) thin film transistors (TFTs) is one of the research hotspotsdue to its key role in energy consumption control of CMOS circuits. Here, ultralow-power flexible CMOS circuits based on well-matched enhancement-mode (E-mode) CMOS single-walled carbon nanotube (SWCNT) TFTs are successfully achieved through tuning the work function of gate electrodes, electron doping, and printing techniques. E-mode P-type CMOS SWCNT TFTs with the full-solution procedure are first obtained through decreasing the work function ofAg gate electrodes directly caused by the deposition of bismuth iodide(BiI3 )-doped solid-state electrolyte dielectrics. After synthetic optimization of dielectric compositions and semiconductor printing process, the flexible printed E-mode SWCNT TFTs show the high Ion /Ioff ratios of ≈106 , small subthreshold swing (SS) of 70-85mV dec-1 ,lowoperating voltages of ≈0.5 to -1.5V, good stabilityand excellent mechanical flexibility during 10000 bending cycles. E-mode N-type SWCNT TFTs are then selectively achieved via printing the polarity conversion ink (2-Amino-2-methyl-1-propanol (AMP) aselectron dopingagent) in P- type TFT channels. Last, printed SWCNT CMOS invertersare successfully constructed with full rail-to-rail output characteristics and the record unit static power consumption of 6.75 fW µm-1 at VDD of 0.2V.

Negative Dielectric Anisotropy Liquid Crystal with Improved Photo-Stability, Anti-Flicker, and Transmittance for 8K Display Applications.

Video systems such as 8K displays can provide a strong sense of presence and reality due to their extremely high resolution and wide field of view. However, high-resolution displays generally suffer from reduced transmittance, which requires the use of liquid crystals with high transmittance and high stability. In this study, negative dielectric anisotropy liquid crystal compositions with excellent photo-stability, anti-flicker capability, and high transmittance are developed, showing potential for 8K display applications. The stability of different types of negative dielectric anisotropy liquid crystal compounds is assessed under light, and the high photo-stability compounds are obtained. In addition, it is demonstrated that the flicker can be optimized from -17.6 to -47.0 by removing the compounds with a higher ion content and a larger deformation number and adding the compounds with a smaller deformation number in the negative dielectric anisotropy liquid crystal compositions. Combining with the evaluation of the factors affecting the response time, the negative dielectric anisotropy liquid crystal mixed H is designed with improved stability and flicker; thus, the response time was decreased to 9.5 ms, and the optical transmittance was 5.5% higher than that of MAT-09-1284 (for normal) and 3.1% higher than that of BY19-J01A (for 4K).

Challenges and opportunities in microwave-assisted catalytic pyrolysis of biomass: A review

Microwave-assisted catalytic pyrolysis (MACP) is one of the emerging technologies for efficiently converting the solid biomass residues to valuable products, including liquid bio-oil and solid biochar. However, due to the poor dielectric properties, low thermal-conductivity, and complex compositions of biomass feedstock, two major technical challenges of biomass MACP technologies are how to heat biomass efficiently by microwave, and how to tune the pyrolysis process to improve the quality of products by catalysis. In the literature, direct, indirect as well as hybrid (localized and segregated) heating modes have been explored to improve the heating performance of microwave reactors, and in-situ, ex-situ and hybrid (dual, layered and series) catalyst configurations have been applied using different microwave absorbents and catalysts. In this review, those heating and catalysis strategies are systematically and critically reviewed (data from about 80 lab-scale studies and 1 pilot-scale unit) to reveal their differences in terms of heating efficiency and product qualities. For some biomass feedstock with high dielectric properties or under high electromagnetic field, direct heating without the use of microwave absorbent could be used. Indirect heating, on the other hand, can be used for all feedstock in which heat is transferred to the biomass via conduction/convection from high temperature surfaces heated by microwave. Hybrid heating with the use of microwave absorbents can greatly increase the local heating rate, promote the pyrolysis reaction rate and tune the distribution of pyrolytic products. In-situ catalysis shows the capability to tune the quantity and quality of both bio-oil and biochar by promoting direct interaction of catalyst and biomass via the pyrolysis vapour, while ex-situ catalysis exhibits a better potential to adjust the bio-oil yield and selectivity of desired compounds in bio-oil, and extends the catalyst life by avoiding the direct contact between biochar and catalyst. Hybrid catalytic mode combines in-situ and ex-situ catalysis in a more complex setup, but shows a great potential to regulate the yield, composition and properties of multiple products. Techno-economic-environmental assessments were also reported on the benefits of MACP processes with different heating and catalytic strategies, mostly based on the lab and limited pilot scale performance data. Future research and development should be focused on the evaluation of different absorbent-catalyst integration, heating-catalysis synergistic effect, optimization of products yields and properties, and how to scale up the MACP reactor technologies toward commercialization with continuous biomass feeding.

Colossal dielectric constant, electric modulus and electrical conductivity of nanocrystalline SnO2: Role of Zr/Mn, Fe or Co dopants

New dielectric compositions composed of SnO2, Sn0.97Zr0.03O2, Sn0.95Zr0.03Mn0.02O2, Sn0.95Zr0.03Fe0.02O2 and Sn0.95Zr0.03Co0.02O2 nanoparticles were synthesized via coprecipitation method. Single phase of SnO2 tetragonal rutile structure was detected in the XRD patterns and the changes of the lattice parameters suggest the substitution of Sn4+ sites by Zr4+, Mn2+, Fe2+ or Co2+ ions. The TEM images show the formation of nano-sized particle of clear crystalline facets within 15–25 ​nm and the HR-TEM image displays identical fringes with lattice spacing close to 0.32 ​nm which can be assigned to (110) crystallographic plane of SnO2 phase. The EDX pattern of Sn0.95Zr0.03Co0.02O2 sample revealed the existence of Sn, O, Zr and Co elements without any other impurities elements. Nanocrystalline SnO2, Sn0.97Zr0.03O2, Sn0.95Zr0.03Mn0.02O2, Sn0.95Zr0.03Fe0.02O2 and Sn0.95Zr0.03Co0.02O2 compositions exhibit band gap energies of 3.4 ​eV, 3.42 ​eV, 3.4 ​eV, 3.45 ​eV and 3.42 ​eV. Undoped SnO2 exhibits a high dielectric constant value of 4014 ​at 42 ​Hz. Interestingly, the Zr monodoping and Zr based Mn, Fe or Co codoping have the ability to increase the dielectric constant of SnO2 by nearly two, three or four-fold to reach to 14321 for Sn0.95Zr0.03Fe0.02O2. The dielectric properties were explained by means of electric modulus formalism. The electrical conductivity of the synthesized powders exhibited semiconducting behavior with temperature. The electrical conductivity of pure, Zr-monodoped and Zr/Mn, Fe or Co codoped SnO2 was increased with increasing the frequency due to the charge-hopping mechanism.

Development of low-cost planar electrodes and microfluidic channels for applications in capacitively coupled contactless conductivity detection (C4 D).

Electrochemical techniques are commonly applied to micro total analysis system (μTAS) devices mainly due to its high sensitivity and miniaturization capacity. Among many electrochemical techniques, capacitively coupled contactless conductivity detection (C4 D) stands out for not requiring direct electrode-solution contact, avoiding several problems such as electrolysis, bubble formation, and metal degradation. Furthermore, the instrumentation required for C4 D measurements is compact, low cost, and easy to use, allowing in situ measurements to be performed even by nonspecialized personal. Contrarily, the production of metallic electrodes and microchannels adequate for C4 D measurements commonly requires specialized facilities and workers, increasing the costs of applying these methods. We propose alternatives to batch manufacture metallic electrodes and polymeric microchannels for C4 D analysis using more straightforward equipment and lower-cost materials. Three devices with different dielectric layer compositions and electrode sizes were tested and compared regarding their analytical performance. The constructed platforms have shown a reduction of more than 64% in cost when compared to traditional techniques and displayed good linearity (R2 ≥ 0.994), reproducibility (RSD ≤ 4.07%, n = 3), and limits of detection (≤0.26mmol/L) when measuring standard NaCl samples. Therefore, the proposed methods were successfully validated and are available for further C4 D applications such as diagnosis of dry-eye syndrome.

Nanolayers of Tantalum- and Aluminum Oxides and Dielectric Compositions Based on Them

Nanolayers of Tantalum- and Aluminum Oxides and Dielectric Compositions Based on Them

Vibration sensing the mammalian way: an artificial Pacinian corpuscle

A vibration sensor is presented mimicking the structure of the Pacinian corpuscle. A multi-step casting process is used to create a 5 mm diameter sensor with a liquid metal core, elastomer dielectric, and graphite counter electrode creating a spherical capacitive sensing element with sensitivities on the order of 10 Δ pF/mm−1. A model for the capacitance change of the spherical capacitor as it is formed is developed and its findings support the sensitivities observed. Various elastomer dielectric compositions with integrated barium titanate nanoparticles are tested to increase the dielectric constant. The biological acoustic filter within the corpuscle is mimicked using alternating cast layers of oligomers and elastomers around the spherical sensor element. Vibration sensing is characterized over the low frequency range of 10–300 Hz and the minimum detectable sensitivity is found to be 1 µm with a low power requirement of 7 mW. The artificial Pacinian corpuscle has potential applications in tactile sensing and seismic monitoring devices.

Analysis of DC Characteristics in GaN-Based Metal-Insulator-Semiconductor High Electron Mobility Transistor with Variation of Gate Dielectric Layer Composition by Considering Self-Heating Effect

This study investigates metal-insulator-semiconductor high electron mobility transistor DC characteristics with different gate dielectric layer compositions and thicknesses, and lattice temperature effects on gate leakage current by using a two-dimensional simulation. We first compared electrical properties, including threshold voltage, transconductance, and gate leakage current with the self-heating effect, by applying a single Si3N4 dielectric layer. We then employed different Al2O3 dielectric layer thicknesses on top of the Si3N4, and also investigated lattice temperature across a two-dimensional electron gas channel layer with various dielectric layer compositions to verify the thermal effect on gate leakage current. Gate leakage current was significantly reduced as the dielectric layer was added, and further decreased for a 15-nm thick Al2O3 on a 5-nm Si3N4 structure. Although the gate leakage current increased as Al2O3 thickness increased to 35 nm, the breakdown voltage was improved.

Giant dielectric constant and tunable phase‐transition characteristics of ZnF2/BaF2‐modified BaTiO3 thick films

AbstractHigh performance capacitors have been investigated to meet higher integration density with optimized charge‐storing capability. Here, we introduce nonconventional thick film dielectric compositions based on 95BaTiO3–xZnF2–(2−x)BaF2–3glass (x = 0.5, 1.0, and 1.5) where the relative content of ZnF2/BaF2 is critical in controlling dielectric behavior. The thick films were prepared on Cu foils by regular screen‐printing and then firing at 950°C in inert atmosphere. As an optimal example, thick film composition modified with 1.0ZnF2/1.0BaF2 exhibited a dielectric constant of ~1903 and a dielectric loss of ~0.04 at 1 MHz with dispersive dielectric relaxation behavior, which are far better than any reported corresponding values so far. Particularly, it was very interesting to observe that Curie temperature was tunable from −19 to +34°C, depending on the relative content of fluoride additives only within the 2 mol% range. Dependency of the relative contents of the fluorides is primarily investigated with regard to microstructure and dielectric properties.

Optimised phase compositions and improved microwave dielectric properties based on calcium tin silicates

The Ca(1+2y)Sn(1-x)Si(1+y)O(5-2x+4y) low-permittivity microwave dielectric ceramics were prepared through solid-state reaction at 1350–1450 °C for 5 h. The relations between microwave dielectric properties and phase compositions for non-stoichiometric Ca(1+2y)Sn(1-x)Si(1+y)O(5-2x+4y) ceramics have been investigated. A single CaSnSiO5 phase with abnormally positive temperature coefficient of resonant frequency (τf = + 62.5 ppm/°C) was synthesised at 1450 °C. This composition was an effective τf compensator of CaSiO3 and Ca3SnSi2O9 phases with typically negative τf value. The CaSiO3 second phase was related to the Sn deficiency in the CaSn(1-x)SiO(5-2x) (0 <x < 1.0) composition, whereas the Ca3SnSi2O9 second phase was obtained by controlling the Ca:Sn:Si ratios on the basis of the Ca(1+2y)SnSi(1+y)O(5+4y) (0 <y < 1.0) composition. A promising low-permittivity millimetre-wave ceramic with most excellent microwave dielectric properties (εr = 10.2, Q×f = 81,000 GHz and τf = −4.8 ppm/°C) was produced from the Ca(1+2y)SnSi(1+y)O(5+4y) (y = 0.4) ceramic.

Dielectric functions, chemical and atomic compositions of the near surface layers of implanted GaAs by In+ ions

The surfaces of (100) GaAs were irradiated with In+ ions. The implanted samples were isobaric annealed at 800°C and then of dielectric function, the surface atomic concentrations of atoms and also the chemical composition of the near surface layers in these implanted semiconductor samples were obtained. The following investigation methods were used: spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry analyses (RBSA) and X-ray photoelectron spectroscopy (XPS) in the study of the above mentioned quantities, respectively. The change of the shape spectra of the dielectric functions at about 3.0eV phonon energy, diffusion of In+ ions as well as chemical composition changes were observed after ion implantation and the thermal treatment. Due to displacement of Ga ions from GaAs by the In+ ions the new chemical compound InAs was formed. The relative amounts Ga2O3 and As2O3 ratio increase in the native oxide layers with the fluences increase after the thermal treatment of the samples. Additionally, it was noticed that the quantities of InO2 increase with the increasing values of the irradiated ions before thermal treatment.

Open-Innovation in the Electrical and Electronic Industries: Engineered Bio-Fluid Compositions Are Paving the Way, and Testing Therewith

Engineered Biofluids are paving the way to industrialized and specifically produced and tailored functional fluids such as coolant and dielectric, high purity traceable media, for the electrical and electronic industries. Dielectric fluid compositions are commonly used in electrical devices, particularly in transformers. These liquids have the aim to isolate the various conductive elements of the device and to limit the heating of the equipment during its operation; in order to minimize, or maintain at higher power, the size of the device and to increase the lifespan of it. Concomitantly a number of bio and traditional processing advancements are made associated with pioneering process technologies which are outlined within the prime context of this paper. Enzyme Engineering and Cocktailing add “A New Dimension to Softer Greener Chem-Bio Approaches” which are referenced beyond curiosity purpose. Some of them are possibly “revolutionary” more than evolutionary. Testing has to evolve accordingly to appreciate the challenges ahead in semi-extreme conditions which are relevant to climate changes as well. A significant part of this orientation work addresses and exemplifies these necessary testing innovations, likely adaptable to smart and responsive connecting, and further down the line bigger data role and learning machine evolutionary concepts. One other innovative part of this exploratory work, is the influence that such illustrative localized testing, with integrated sensors/induced-tracers, and online interpretation, may have on the smart grid developments; whereby production, transmission, distribution and consumption of energy can be made more reliable, more effective and more predictive and can also have an impact on the performance, reliability and sustainability of the equipment itself. Those technologies and associated testing can support environmental, technological and societal awareness; helping to revert some trends being climate changes, fossil fuel preservation and other planetary challenges to maintain the overall and localized fundamental equilibriums.

HfxAlyO ternary dielectrics for InGaAs based metal-oxide-semiconductor capacitors

The electrical properties of HfxAlyO compound dielectric films and the HfxAlyO/InGaAs interface are reported for various dielectric film compositions. Despite the same trimethylaluminum (TMA) pre-deposition treatment, dispersion in accumulation and capacitance-voltage (C-V) hysteresis increased with hafnium content. Different kinds of border traps were identified as being responsible for the phenomena. After anneal, the density of states in the HfxAlyO/InGaAs interface varied quite weakly with dielectric film composition. The optimal composition for obtaining high inversion charge density in metal oxide semiconductor gate stacks is determined by a tradeoff between leakage and dielectric constant, with the optimum atomic cation ratio ([Hf]/[Al]) of ∼1.

Materials science aspects of dielectric film compositions in the planar technology of Ge-based MIS structures

A new fabrication route for Ge based metal-insulator-semiconductor (MIS) transistors has been developed based on materials research of dielectric layer compositions. Unwanted impurities were encapsulated in the Ge substrate by using the gate-first process and a modified thermal GeO2 layer with increased viscosity at the interface with the Ge substrate. Increasing the density of the oxide layer near germanium interaction with the deposited Si3N4 film hindered diffusion of the impurities adsorbed by the substrate surface into the transistor channel. This increased the electron mobility in the MIS transistor and prevented its decrease at cryogenic temperatures.

Microwave Dielectric Properties, Crystal Structure, and Microstructure of the Bi3Nb1−xTaxO7 Solid Solution

New, commensurate members of the fluorite‐related Bi3Nb1−xTaxO7 family were synthesized and their crystal structures, microstructures, and microwave (MW) dielectric properties were characterized. The incorporation of Ta into the tetragonal Bi3Nb1−xTaxO7 solid solution was found to gradually affect the density and the MW dielectric properties. The materials sintered at 870°C exhibited relative permittivities in the range k′ = 86–72, Q × f values from 793 to 1189 GHz and a positive temperature coefficient of resonant frequency from 88 to 12 ppm/K. The formation of the members of the fluorite‐related solid solution along the Bi3Nb1−xTaxO7 composition depends on a phase transition, and thus their properties are compared within the compositional range. The correlations between their MW dielectric properties, compositions, crystal structures, and processing parameters were discussed in detail. Optimization of MW properties can be achieved by utilizing the ability of the Bi3Nb1−xTaxO7 solid solution that it undergoes a phase transformation from cubic to tetragonal structure which are both characterized by unique properties, under certain synthesis conditions.

Improvement in the Low-Fire Dielectric Compositions with Middle Permittivity for LTCC Applications

Low temperature co-fired ceramics (LTCC) technology becomes crucial in the development of various modules and substrates in electronic packaging, especially in wireless and microwave applications [. self-integrated component has laid basis on flexibility of design, wiring density and dependability for multilayer structures due to LTCC technology. Recently, with the rapid progress in wireless communications,to realize more highly integrated passive components in multilayer LTCC structure, however, it is important to control the matching behavior between component and substrate. The dielectric compositions the permittivity range of which is 20100 are most appropriate for realizing strip or microstrip resonator structures in LTCC multilayer structures due to the RF frequency range which is used in current telecommunication systems (130GHz) and the desirable chip sizes in the current technologies (210 mm)[.

English

The growing importance of the issues for sustainable development requires the consideration of environmental criteria in the development of all new materials and equipment. In the case of dielectric liquid, a better balance must be found between technical performance within the filled equipment and the impact on the environment always possible leaks. In transformers, a stable liquid, inert, with good electrical and thermal properties is necessary; outside, the liquid must be non-toxic to the environment and readily biodegradable. The intrinsic properties of natural vegetable oils in terms of fire resistance, environmental performance and electrical and thermal characteristics of dielectric compositions are particularly useful products in the field of electrical engineering. The objective of our work was to make a comparative study of different vegetable oils: Argan, Rapeseed, Sunflower and analyze the behavior of the electrical resistivity and viscosity as a function of temperature. This study may be useful for a possible application of these oils in technology. Key words: Electrical resistivity, viscosity, vegetable oil, electrotechnical.

Mechanical self-confinement to enhance energy storage density of antiferroelectric capacitors

The energy storage density of electrical capacitors utilizing antiferroelectric compositions Pb0.99Nb0.02[(Zr0.57Sn0.43)1−yTiy]0.98O3 as dielectrics is measured at a series of temperatures in a series of dielectric compositions with and without self-confinement. Under the applied electric field of 70 kV/cm, a maximum energy density of 1.3 J/cm3 is achieved. The mechanical self-confinement was introduced by partially electroding the central portion of the dielectric ceramic disk. A phase-field model was developed and it confirms the presence of compressive stresses ∼30 MPa in the electroded portion of the dielectric disk and the contribution to the increased energy density from the mechanical confinement.