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- 2018
- arbitrary coupling coefficients
- Dielectric resonator
- filtering
- coupler
- filtering balun
- dual-band
- dual-mode dielectric resonator (DR)
- Electronic Science and Technology
- Nantong University
- Sun Yat-Sen University
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AlGaN/GaN MIS-HEMT with PECVD SiNx, SiON, SiO2 as Gate Dielectric and Passivation Layer
摘要： Three different insulator layers SiNx, SiON, and SiO2 were used as a gate dielectric and passivation layer in AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMT). The SiNx, SiON, and SiO2 were deposited by a plasma-enhanced chemical vapor deposition (PECVD) system. Great differences in the gate leakage current, breakdown voltage, interface traps, and current collapse were observed. The SiON MIS-HEMT exhibited the highest breakdown voltage and Ion/Ioff ratio. The SiNx MIS-HEMT performed well in current collapse but exhibited the highest gate leakage current density. The SiO2 MIS-HEMT possessed the lowest gate leakage current density but suffered from the early breakdown of the metal–insulator–semiconductor (MIS) diode. As for interface traps, the SiNx MIS-HEMT has the largest shallow trap density and the lowest deep trap density. The SiO2 MIS-HEMT has the largest deep trap density. The factors causing current collapse were confirmed by Photoluminescence (PL) spectra. Based on the direct current (DC) characteristics, SiNx and SiON both have advantages and disadvantages.
关键词： interface traps,MISHEMT,gallium nitride,PECVD,current collapse,dielectric layer
更新于2025-09-23 15:22:29
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Significance of Micro and Nano PZT Particles on Dielectric and Piezoelectric Properties of PZT-PVDF Composites
摘要： PZT-PVDF composites were prepared using different particle size of PZT and a hot press apparatus has been used for making samples. The structural and compositional analysis of the composite sample was done by using Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX) respectively. The grain size of the ball milled PZT powder was analyzed using powder X-Ray Diffraction (XRD). The samples were poled at a fixed temperature for about an hour under different poling fields. The dielectric constant (εr) and the piezoelectric properties like piezoelectric strain coefficient (d33) and voltage coefficient (g33) of composite have been analyzed.
关键词： composite,ferroelectric materials,dielectric constant,strain coefficient,voltage coefficient,particle size,lead zirconate titanate
更新于2025-09-23 15:22:29
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Peculiarities of the dielectric properties of ternary 0.5(Y0.1Zr0.9O2) – 0.5(0.6SrTiO3 – 0.4BiScO3) ceramic system
摘要： Ceramic samples of ternary 0.5(Y0.1Zr0.9O2) – 0.5(0.6SrTiO3 – 0.4BiScO3) system consisting of individual Y0.1Zr0.9O2 and 0.6SrTiO3 – 0.4BiScO3 subsystems were synthesized via solid-state processing techniques. By XRD analysis, a coexistence of tetragonal P42/nmc phase related to the Y0.1Zr0.9O2 subsystem, and cubic Pm m3? and tetragonal P4mm phases associated with the 0.6SrTiO3 – 0.4BiScO3 subsystem was found. A deviation of real composition from nominal one for both Y0.1Zr0.9O2 and SrTiO3 – BiScO3 subsystems due to Sc substituting for Zr in the Y0.1Zr0.9O2 subsystem and, vice versa, Zr substituting for Sc in the SrTiO3 – BiScO3 subsystem was also observed. Peculiarities of the dielectric properties related to both di?use ferroelectric phase transition and dielectric relaxation processes were found and analyzed in comparison with the dielectric properties of two-component 0.6SrTiO3 – 0.4BiScO3 system. It was found that the di?use phase transition in ternary system, ?rstly, shifts to lower temperatures and, secondly, has a less degree of di?useness as compared to two-component system. Such kind of behavior could be attributed to a di?erence of ionic radii of ions Zr4+ and Sc3+. Dielectric relaxation processes associated with the O2- ions migration were observed within temperature 500–800 K for both ternary and two-component systems. Two dielectric relaxation processes related to the Y0.1Zr0.9O2 and 0.6SrTiO3 – 0.4BiScO3 subsystems were found in ternary system, whereas one dielectric relaxation process was observed in two-component system. The activation energies for the dielectric relaxation processes were estimated as ~ 1.3 eV and ~ 0.9 eV for Y0.1Zr0.9O2 and 0.6SrTiO3 – 0.4BiScO3 subsystems, respectively, for ternary system, and ~ 0.75 eV for two-component system.
关键词： Dielectric relaxation process,Two-component ceramic system,Y0.1Zr0.9O2 and 0.6SrTiO3 – 0.4BiScO3 subsystems,Ternary ceramic system,Di?use phase transition
更新于2025-09-23 15:22:29
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High dielectric and breakdown properties achieved in ternary BaTiO3/MXene/PVDF nanocomposites with low-concentration fillers from enhanced interface polarization
摘要： Although high permittivity is achieved in barium titanate (BT) filled polymer nanocomposites, severely reduced insulation and breakdown properties are frequently found due to overload and agglomeration of BT nanoparticles with ultrahigh specific area. To simultaneously realize high permittivity and breakdown strength, in this work, unfunctionalized 2D Ti3C2 MXene nanosheets with 2 wt % weight concentration were introduced to prepare ternary BT/MXene/polymer nanocomposites by solution cast process. Employing low-concentration conductive MXene instead of high-concentration ferroelectric BT could lead to significant improvement of permittivity of ternary composites, ascribed to remarkably increased interface types and enhanced interface polarization. In comparison to binary BT/polymer composites, ternary composites could have slightly improved dielectric loss and conductivity as well as gracefully reduced breakdown strength, attributed to finely retained high interface compatibility and filler dispersion. Ternary composite containing 8 wt % BT and 2 wt % MXene had a permittivity of 77, loss of 0.15 at 100 Hz and breakdown strength of 220 MV m-1. This work might open the door to large-scale fabrication of promising composites with high permittivity and breakdown strength under low filler loading (~ 10 wt %).
关键词： B. Composites,A. Films,C. Dielectric properties,D. Carbides
更新于2025-09-23 15:22:29
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Enhanced dielectric permittivity in surface-modified graphene/PVDF composites prepared by an electrospinning-hot pressing method
摘要： In the present work, the surface-modified graphene (SMG)/poly(vinylidene fluoride) (PVDF) fibrous membranes obtained from the electrospinning were treated by the hot pressing in the laminating mode to form the SMG/PVDF composites. The SMG was prepared by subjecting the graphene oxide to silane modification, NaBH4 reduction, and PVDF grafting in sequence. The successful surface modification of graphene was confirmed by TEM, XPS, Raman spectroscopy, FTIR, WAXD, and TGA. Furthermore, the structures of SMG/PVDF composites fabricated by the electrospinning-hot pressing method were studied by SEM, FTIR, and WAXD, which exhibited the well dispersion of SMG in the PVDF matrix. Finally, the investigation showed that the dielectric permittivities of SMG/PVDF composites increased with the SMG content, which were significantly higher than that of pristine PVDF. The dielectric permittivity of SMG (16 wt.%)/PVDF composite (83.8) at 1000 Hz was found to be ten-fold that of the corresponding value of pristine PVDF (8.3) with a relatively low dielectric loss factor (0.34) and a relatively high thermal conductivity (0.679 W/mK).
关键词： surface-modified graphene/PVDF composite,thermal conductivity.,electrospinning-hot pressing method,dielectric performance
更新于2025-09-23 15:22:29
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Growth behavior and thermally stable electrical properties of TiNbO5 nanosheet thin films grown using the electrophoretic method
摘要： TiNbO5 (TNO) thin films were deposited by electrophoresis at room temperature by using TNO nanosheets. These TNO films exhibited a large (001) interplanar distance (1.18 nm) owing to the presence of TBA+ between the TNO layers. The TBA+, which were used to synthesize the TNO nanosheets, were removed from the TNO film after annealing at 600 °C. Two types of structures were developed in the film annealed at 600 °C: type-1 and type-2, which revealed (001) interplanar distances of 0.52 and 0.71 nm, respectively. The TNO film annealed at 600 °C showed a dielectric constant of 48.5, low dielectric loss (0.02), and small leakage current density of 4.16 × 10^-7 A/cm^2 at 0.6 MV/cm. The dielectric properties were stable with respect to the film thickness and the applied electric field; the dielectric and insulation properties were maintained up to 300 °C. Therefore, TNO films are good candidates for high-temperature capacitors.
关键词： Electrophoresis,Robust dielectric,Inorganic nanosheets,TiNbO5 film,High temperature capacitor
更新于2025-09-23 15:22:29
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An evaluation study of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights in building energy simulation
摘要： The potential of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights for daylighting control has drawn a considerable research attention in the recent years, owing to its feature of variable transmittance according to the sun position, but the viability of using it as skylights in buildings has not been explored yet comprehensively. This paper aims to study the feasibility of utilizing miniature dCCPC panel as skylight in different locations under various climates in terms of energy saving potential besides its daylighting control function. The transmittance of dCCPC panel varies at every moment according to the sky condition and sun position. Due to this specific property, this study novelly implemented a polynomial formula of the dCCPC transmittance in the Grasshopper platform, from which EnergyPlus weather data can be called to calculate the hourly transmittance data of dCCPC skylight panel throughout the whole year. An hourly schedule of transmittance is generated according to the hourly sky condition determined by the daylight simulation through Radiance and Daysim, and is then input to EnergyPlus simulation to predict the energy consumption of a building with dCCPC skylight. Fourteen locations around the world are therefore compared to find the most appropriate place for using miniature dCCPC panel as skylights. The energy saving in cooling, heating and lighting with use of dCCPC skylight panel are investigated and compared with low-E and normal double glazing. The results show that the dCCPC skylight panel can reduce cooling load by mitigating solar heat gain effectively although its performance is affected by several criteria such as sky conditions and local climates. It is generally more suitable for the locations with longer hot seasons, e.g., Los Angeles, Miami, Bangkok and Manila, in which dCCPC could provide up to 13% reduction in annual energy consumption of building. For the locations having temperate and continental climates like Beijing, Rome, Istanbul and Hong Kong, a small annual energy saving from 1% to 5% could be obtained by using dCCPC skylight panel.
关键词： Grasshopper,Dielectric crossed compound parabolic concentrator (dCCPC),Daylighting control,Energy saving
更新于2025-09-23 15:22:29
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Effect of Zinc Oxide nanorods on the structural, thermal, dielectric and electrical Properties of Polyvinyl alcohol /Carboxymethyle Cellulose composites
摘要： ZnO nanorods were prepared by chemical vapor deposition (CVD) have lengths ranging between 104.12 and 307.64 nm and diameters ranging between 21.17 and 55.88nm determined by transmission electron microscopy (TEM). Polyvinyl alcohol/carboxymethyl cellulose nanocomposites and Zinc oxide (ZnO) were prepared by casting method. The prepared samples were characterized by various methods. The results of XRD analysis depict the amorphous nature of these polymer samples and the degree of amorphousity is increased due to the addition process. The interaction of the ZnO NRs with the PVA/CMC blend was identified by Fourier transforms infrared spectroscopy (FTIR). The dispersion of dopant within the polymer matrix was supported by scanning electron microscopy (SEM). DSC and TGA was utilized to study the thermal behavior of the films and the highest conducting polymer material is lower the glass transition temperature. The conductivity and dielectric behaviors were analyzed by complex impedance spectroscopy as a frequency function at different temperature. The ac conductivity is found to obey Jonscher’s law, whereas dc conductivity is seen to exhibit Arrhenius behavior and increases with temperatures and the activation energy of the films with an increasing of ZnO NRs content was decreased. The dielectric properties of pure blend and nanocomposites have been enhanced due to the addition of ZnO NRs and are found to be highly temperature dependent. The frequency exponent (s) have been well fitted with the proposed correlation equation of the barrier hopping model. Significant increase in dc and ac conductivities in these nanocomposites samples makes them a potential candidate for electrochemical device applications.
关键词： AC and Dielectric parameters.,TEM,FT-IR,ZnO nanorods,SEM
更新于2025-09-23 15:22:29
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Fabrication, electrical and magnetic properties of 0.7(BiGd <sub/>x</sub> Fe <sub/>1?x</sub> O <sub/>3</sub> )?0.3(PbTiO <sub/>3</sub> ) composites
摘要： The polycrystalline samples having chemical formula 0.7(BiGdxFe1?xO3)?0.3(PbTiO3) (x = 0.0, 0.05, 0.10, 0.15 and 0.20) were fabricated by using high temperature mixed oxide route. The X-ray diffraction spectra suggested rhombohedral (major) symmetry with small impurity phases. The surface microstructure showed a highly dense packing of grains throughout the wider area for all samples. The dielectric permittivity and loss factor of all samples were studied with the help of temperature-dependent dielectric parameters. The relaxation mechanism was suggested from the dielectric and impedance spectroscopy. The conduction mechanism of all samples was investigated. The P–E and M–H loops of all the samples were taken at room temperature showing the multiferroic properties.
关键词： Dielectric,conductivity,magnetic properties,ferroelectric,impedance
更新于2025-09-23 15:22:29
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Tissue-mimicking materials for breast phantoms up to 50 GHz
摘要： Millimeter (mm)-wave imaging has been recently proposed as a new technique for breast cancer detection, based on the significant dielectric contrast between healthy and tumor tissues. Here we propose a procedure to fabricate, electromagnetically characterize and preserve realistic breast tissue-mimicking phantoms for testing mm-wave imaging prototypes. Low-cost, non-toxic and easy-to-produce mixtures made of sunflower oil, water and gelatin were prepared and their dielectric properties were for the first time measured in the [0.5-50] GHz frequency range using a coaxial probe kit. Different oil and gelatin percentages were tested. An alternative recipe based on a waste-oil hardener was also proposed. Finally, water and sunflower oil were investigated as preservation media. The mixtures electromagnetic properties were in good agreement with those of human breast ex vivo samples. By changing the ingredient concentrations or using different solidifying agents it was possible to mimic different tissue types. Besides, we show that sunflower oil represents an effective preservation medium for the developed materials. The first breast phantom mimicking a tumor mass into healthy tissues up to 50 GHz was also successfully fabricated. Results demonstrated the potential of the designed recipes to mimic breast tissues with different biological characteristics.
关键词： microwave imaging,breast phantoms,breast cancer,dielectric properties,millimeter waves,cancer screening
更新于2025-09-23 15:22:29