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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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Low-dielectric-constant aromatic homopolyimide and copolyimide derived from pyromellitic dianhydride, 4,4′-oxydianiline, 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene
摘要： Low-dielectric-constant aromatics, homopolyimide and copolyimide, were introduced. Homopolyimides were prepared by pyromellitic dianhydride (PMDA) as an anhydride monomer and 4,40-oxydianiline (ODA), 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene as an amine monomer. The copolyimides were prepared with PMDA as an anhydride monomer, ODA as an amine monomer with the addition of 2,2-bis[4-(4-aminephenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, or 1,3-bis(4-aminophenoxy)benzene as another amine monomer. The polyimides were well characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, thermomechanical analysis, dielectric measurements, and tensile testing. The homopolyimide and copolyimides showed lower dielectric constants than the homopolyimide formed by ODA and PMDA. The results also indicate that the interchain distance, the quantities of phenyl ether, and the position of the substitute are factors that not only affected the thermal performance of polyimide by improving the molecular ?exibility but also reduced the dielectric constant of polyimide by increasing the free volume of the molecular chain and decreasing the polarization points per unit volume.
关键词： dielectric properties,copolymers,polyimides,films
更新于2025-09-23 15:23:52
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Simultaneous realization of broad temperature stability range and outstanding dielectric performance in (Ag+, Ta5+) co–doped TiO2 ceramics
摘要： Effects of sintering condition on dielectric properties and microstructure were systematically investigated in (Ag1/4Ta3/4)0.005Ti0.995O2 ceramics. A giant dielectric constant of ~9831 (1 kHz) and a relatively low dielectric loss of ~0.041 (1 kHz) were realized at the optimal sintering condition of 1330 °C with a holding time for 10 h. Notably, stable temperature coefficient (within -6.8% to 8.8%) of the dielectric constant at 10 kHz was achieved in a broader temperature range (-200–200 °C), which shows superior temperature stability of our sample than the application requirements (-55~200 °C and ?εr/ε25 °C < ±15%) of commercial X9R capacitor.
关键词： sintering conditions,dielectric properties,ceramics,temperature stability
更新于2025-09-23 15:23:52
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Crystal growth and characterization of γ-glycine grown from AgSO4 for nonlinear optical applications
摘要： In the present work 0.1 M to 0.5 M proportions of silver sulphate (AgSO4) added glycine single crystals were grown by slow solvent evaporation method. The Powder XRD study confirms that the grown crystals have γ-glycine crystal structure and it crystallizes into a hexagonal structure with a non-centrosymmetric space group of P31. The dielectric constant and dielectric loss of grown crystal was carried out as a function of frequency and the results were discussed. The positive photoconducting nature of the grown crystals was studied by the photoconductivity study. Second harmonic generation (SHG) efficiency of the grown γ-glycine crystal was assessed by using Nd: YAG laser. The results confirms that the grown crystals have higher efficiency compared to the reference (KDP) crystal.
关键词： B2. Dielectric Materials,A1. X-ray diffraction,A1. Crystal structure,B2. Nonlinear optic materials
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52
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[Advances in Intelligent Systems and Computing] Information Systems Design and Intelligent Applications Volume 862 (Proceedings of Fifth International Conference INDIA 2018 Volume 1) || Study of Electrical and Magnetic Properties of Multiferroic Composite (BiFeO3)x(Ba5RTi3V7O30)1?x
摘要： Polycrystalline Samples of the composite (BiFeO3)x(Ba5RTi3V2O30)1?x (R––Rare Earth Element) is prepared by high-temperature Solid-State Reaction Technique. The formation of the material has been con?rmed through XRD (X-ray Diffractometer) to ensure the single-phase formation. Dielectric characterization has been done by Impedance Analyser (HIOKI-IM3536) to study the variation of dielectric constant with frequency and temperature in a wide range to see the dielectric anomaly. Magnetization study is also done by Vibration Magnetometer for different values of x in the composite (BiFeO3)x(Ba5RTi3V2O30)1?x.
关键词： Dielectric,XRD,Impedance analyzer,magnetization,Neel temperature
更新于2025-09-23 15:23:52
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Structural, optical, electrical and thermal characteristics of La{CS(NH2)2CO(NH2)2}Cl3 : A novel hybrid complex for optoelectronic applications
摘要： A hybrid complex of lanthanum chloride with urea and thiourea is crystallized at room temperature by conventional solution method. The structural investigations by single crystal X-ray diffraction confirmed the orthorhombic system with cell dimensions a = 7.676 ?, b = 8.564 ?, c = 5.498 ?, α = β = γ = 90°. The optical studies by UV–VIS absorption spectroscopy shows the complex exhibits transmittance about 96%. The complex is characterized as the wide band gap crystals with value greater than 4 eV. The dielectric properties were studied in frequency range 10 kHz–1 MHz in temperature range 303–453 K. The ac conductivity was found to obey the universal power law and suggests the correlated barrier hoping mechanism dominating the conduction process. The thermal stability and the decomposition mechanism were confirmed by thermo gravimetric and differential thermo analytical (TG/DTA) techniques.
关键词： Dielectric analysis,ac conductivity,Hybrid complex,X-ray diffraction,UV–Vis spectrum
更新于2025-09-23 15:23:52
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Excellent thermal-stability and low dielectric loss of BaTiO3-Bi(Sr2/3Nb1/3)O3 solid solution ceramics in a broad temperature range applied in X8R
摘要： (1?x)BaTiO3-xBi(Sr2/3Nb1/3)O3 [(1?x)BT-xBSN, 0.02 ≤ x ≤ 0.1] ceramics were synthesized by a traditional solid state reaction technique. The transition from tetragonal phase to pseudo cubic phase at 0.02 ≤ x ≤ 0.04 was observed in Raman spectra and X-ray di?raction patterns. As the BSN contents increased, the grain size increased. With adding Bi(Sr2/3Nb1/3)O3, the thermal stability of permittivity and dielectric loss of ceramics got a good optimization. Especially, 0.9BT-0.1BSN ceramics have small Δε/ε25°C values (≤ ± 15%) in a wide temperature range of ?75 °C to 153 °C, high relative permittivity (～1505 to 1700) and low dielectric loss (tan δ ≤ 0.02) from ?88 °C to 200 °C, showing that BT-BSN ceramics are suitable for using in MLCCs of X8R. Impedance spectroscopy was analyzed the conduction and relaxation processes. The results showed that the relaxation and the conduction process in the high temperature region are thermally activated, and the oxygen vacancies are charge carriers.
关键词： Thermal stability,Dielectric properties,Impedance,Phase evolution
更新于2025-09-23 15:23:52
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Dielectric property of modified barium titanate/polyamide 11 nanocomposites with different surfactants
摘要： Barium titanate/polyamide 11 (BT/PA11) nanocomposites were prepared by modifying BT nanoparticles with dry surface modification process, which had well dispersion, high dielectric constant, and low dielectric loss. Various methods were reported to improve dispersion and compatibility with complex process and high cost. Herein, three surfactants [γ-aminopropyl triethoxy silane (KH550), sorbitan monostearate (SP60), and octadecyl phosphate ester (OPE)] were chosen to modify BT nanoparticles. Then modified-BT nanoparticles were blended with PA11. The structure was characterized by Fourier transform infrared, scanning electron microscope, and wide angle X-ray diffraction. Dielectric property was studied by broadband dielectric spectroscopy. The frequency dependence and temperature dependence of dielectric constant, dielectric loss, and dielectric modulus were analyzed. In general, dielectric property has strong frequency and temperature dependence. Furthermore, dielectric spectra shows that modified BT/PA11 nanocomposites have higher dielectric constant, lower dielectric loss, fewer interface polarization, and more dipole polarization. In contrast to three surfactants, OPE-BT nanoparticles have better effects, whose dielectric constant increases from 19 to 28 at 1 Hz, and dielectric loss decreases from 0.36 to 0.23. Meanwhile, mechanical property was characterized by universal testing machine. In all, the work improves dispersion of BT nanoparticles and dielectric property with easy process and low cost. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47447.
关键词： BT/PA11 nanocomposites,dielectric property,modification,surfactants
更新于2025-09-23 15:23:52
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Alternative Type 2D-3D Lead Halide Perovskite with Inorganic Sodium Ions as Spacer for High Performance Light Emitting Diodes
摘要： Two-dimensional (2D) lead halide perovskites with long-chain ammonium halides display high photoluminescence quantum yield (PLQY), due to their size and dielectric confinement, which promise a high efficiency and low-cost light emitting diode (LED). However, the presence of insulating organic long-chain spacer cation (L) dramatically deteriorates the charge transport properties along the out-of-plane nanoplatelet direction or adjacent nanocrystals, which would limit the LED device performance. In order to overcome this issue, we successfully incorporate small alkaline ions such as sodium (Na+) to replace long organic molecule. Grazing incident X-ray diffraction (GIXRD) measurements verify the 2D layered formation with preferential crystallite orientation. In addition, the incorporated sodium salt also generates amorphous sodium lead bromide (NaPbBr3) in perovskite as spacers to form nanocrystal-like halide perovskite film. PLQY is dramatically improved in the sodium incorporated film associating with enhanced PL lifetime. With incorporating small concentration of an organic additive, this 2D-3D perovskite can achieve a compact and uniform film. Therefore, a 2D-3D perovskite achieves a high external quantum efficiency (EQE) of 15.9% with good operational stability. Our work develops a type of 2D-3D halide perovskite with various inorganic ions as spacers for high performance of promising optoelectronic devices.
关键词： two-dimensional,alkaline halide,perovskite,dielectric confinement,light-emitting diode
更新于2025-09-23 15:23:52
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Direct Imaging of Isofrequency Contours of Guided Modes in Extremely Anisotropic All-Dielectric Metasurface
摘要： In this work, we investigate an all-dielectric metasurface based on the silicon on insulator platform for manipulating of guided modes in the visible and near-infrared spectral ranges. We use the Fourier modal method to demonstrate numerically, that guided modes excited in the metasurface support both hyperbolic-like and elliptic dispersion regimes. We implement a back focal plane microscope combined with a high refractive index solid immersion lens to directly image the isofrequency contours of the guided modes (surface waves). Reconstruction of dispersion unambiguously reveals the transition between different dispersion regimes.
关键词： Fourier microscopy,All-dielectric metasurface,isofrequency contours,Fourier modal method,dispersion reconstruction,surface waves
更新于2025-09-23 15:23:52