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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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Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics
摘要： In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.
关键词： Dielectric properties,Grain size,X-ray diffraction,Optical properties,Sintering
更新于2025-11-21 11:18:25
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Dielectric properties of porous SiC/Si3N4 ceramics by polysilazane immersion-pyrolysis
摘要： The SiC nanotubes were synthesized on porous Si3N4 matrix by polysilazane immersion-pyrolysis. The β-SiC and free C contents increased with the increasing dipping times, which cause some clear vibration and loss peaks of the dielectric constant patterns emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt% and 30 wt% benzoic acid, respectively. The re?ectivity of the obtained ceramics were ?7dB ～ ?10dB from the frequency of 8 GHz–18 GHz, which means that the amount of 80%–90% electromagnetic wave could be attenuated. The ceramics containing 40 wt% benzoic acid showed the high loss, low re?ectivity and a wide absorbing band, indicating the high absorbing e?ciency and good dielectric properties.
关键词： Dielectric properties,Si3N4,Dipping,SiC
更新于2025-11-21 11:18:25
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Investigation of temperature and frequency dependence of electrical conductivity and dielectric behavior in CuS and rGO capped CuS nanocomposites
摘要： In this work, we develop a simple and low-cost strategy toward the one-pot synthesis of reduced graphene oxide (rGO) capped copper sulfide (CuS) nanocomposite through an obvious redox transformation reaction between Cu and graphene oxide (GO) without any additive. The prepared CuS and rGO capped CuS nanocomposite have been characterized by various physicochemical techniques for the observation of shape, morphology, and structure. It reveals the average size of the synthesized samples in the range of 10–30 nm with the hexagonal structure. The UV–vis absorption spectra exposed the strong absorption peak of CuS and rGO capped CuS composites in the range of NIR region was observed. The synthesized samples displayed high dielectric constant and electrical conductivity in a wide range of frequency (102–106 Hz). The effect of temperature on the electrical conductivity of the synthesized rGO capped CuS nanocomposite was also investigated. The excellent electrical conductivity performance is ascribed to the synergistic effect between CuS and rGO. As the temperature increases, the maximum electrical conductivity of rGO capped CuS composite was exponentially increased at high temperature. The synthesized composite with a high dielectric constant and electrical conductivity is a promising material in high capacitance, and further, it is used as electrode materials for supercapacitors and energy storage applications.
关键词： electrical conductivity,temperature effect,CuS nanocomposites,reduced graphene oxide,dielectric constant
更新于2025-11-21 11:18:25
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Temperature-dependent dielectric response of (1-x)PVDF/(x)BaTiO3 nanocomposite films
摘要： The PVDF/BaTiO3 nanocomposite films were prepared by solution casting method by using dimethylformamide as solvent. The dielectric constant and loss tangent of the PVDF and PVDF/BaTiO3 composites have been determined as functions of frequency (20 Hz to 2 MHz) and temperature (80 to 425 K). A significant enhancement in dielectric constant ε' is observed in composite samples. Tangent loss factor (tan δ) is maximum at lower frequencies due to interfacial polarization. In composite samples owing to the synthesis process, there is a phase transition in PVDF from α to β which results in the formation of dipolar relaxation. The dipolar nature of both the PVDF and PVDF/BaTiO3 nanocomposites is arrested below 200 K. The activation energy values (0.43- 0.69 eV) associated with tan δ peak in the region 200 – 270 K are in agreement with the activation energy associated with a dipolar relaxation process. The relaxation time (τ) decreases with increasing BaTiO3 filler content while the number density of dipoles increases from 4.06×1021 cm-3 for pristine PVDF to 6.62×1023 cm-3 for (0.5)PVDF/(0.5)BaTiO3 composite and confirms a significant amount of dipolar relaxation in PVDF/BaTiO3 composites.
关键词： dielectric relaxation,activation energy,dielectric constant,PVDF/BaTiO3 nanocomposites
更新于2025-11-14 17:28:48
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Electric and dielectric characteristics of Al/ZrO2/IL/n-Si MOS capacitors using three-frequency correction method
摘要： In this study, MOS capacitors of Al/ZrO2/IL/n-Si (IL: interface layer) have been fabricated. Bias scan and frequency scan data of measured parallel capacitance (Cm) and parallel resistance (Rm) have been taken in the frequency of ～1 kHz to 2 MHz. To correct external frequency dispersion of parasitic parameters, we have used five-element model (including MOS capacitance C, parallel resistance Rp, IL capacitance Ci, IL resistance Ri, and series resistance Rs) and three-frequency correction method. Extracted capacitance C by the three-frequency correction method has negligible frequency dependence from 0.38 nF to 0.34 nF in the average frequency of ～3.7 kHz to 1.54 MHz. The frequency dispersion of Rp, Ci, Ri, and Rs are explained by some physical mechanisms. Small relative errors ΔC/C, ΔRp/Rp, ΔCi/Ci, ΔRi/Ri and ΔRs/Rs are less than 0.2%, 2%, 3%, 1.2% and 0.4% respectively. We have also used two existing double-frequency methods of three- and four-element models for comparison, and the extracted capacitances show abnormal frequency dependence. Above results indicate the three-frequency method of five-element model is necessary, effective and convenient in providing sufficient list data for bias voltage dependence or frequency dependence. The dielectric parameters, such as relative dielectric constant, conductivity, imaginary part of complex dielectric constant, and dielectric loss tangent have been calculated. The mechanisms of frequency dispersion for the dielectric parameters have been analyzed.
关键词： Three-frequency correction,Parameter extraction,MOS capacitor,Five-element model,Dielectric characteristics,Frequency dispersion
更新于2025-11-14 17:28:48
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Effect of Dielectric Charging on Capacitance Change of an SOI Based CMUT
摘要： Effect of dielectric charging on the performance of SOI based Capacitive Micromachined Ultrasonic Transducers (CMUT) has been investigated. Measurements on an SOI based CMUT show that that the capacitance change as a function of DC bias is considerably higher than analytically calculated values. Investigation shows that this deviation in capacitance from analytically calculated values is due to the combined effects of different dielectric charging phenomena due to a strong electric field, trap charges in the SOI oxide layer, the charge motion associated with the leakage current through the buried oxide layer, and the air in the CMUT cavity. Additionally, this charging effect degrades the transduction efficiency as the induced polarization reduced the effective bias across the CMUT. It is concluded that the buried oxide (BOX) layers in SOI wafers are not suitable for use as dielectric spacers in electrostatic MEMS devices.
关键词： SOI,dielectric charging,Capacitance,microfabrication,MEMS,CMUT,leakage current
更新于2025-11-14 17:28:48
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High dielectric polymer and its application on electro-optical Kerr effect of blue phase liquid crystal
摘要： We present a high-dielectric polymer with a lateral ?uorine group, and its dielectric constant exhibits larger than 20 at 1 kHz. This well-soluble polymer can solely stabilize blue phase liquid crystals (BPLCs) while reducing the operating voltage by 30% and increasing the Kerr constant by nearly 70.6%. The in?uence of the polymer’s dielectric property on the operating voltage is investigated based on the potential distribution. The theoretical result predicts that the operation voltage can be further reduced by 50% when the dielectric constant of the chiral dopant is the same as the high-dielectric polymer. The potential application of high-dielectric materials for the improvement of BPLC devices is foreseeable.
关键词： Kerr constant,blue phase liquid crystals,high-dielectric polymer,electro-optical Kerr effect,operating voltage
更新于2025-11-14 17:28:48
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Enhanced energy storage performance in Sn doped Sr0.6(Na0.5Bi0.5)0.4TiO3 lead-free relaxor ferroelectric ceramics
摘要： SnO2 doped Sr0.6(Na0.5Bi0.5)0.4TiO3 (NBT-ST) ceramics were prepared by a conventional solid-state reaction method. Their phase structures, microstructures and electrical properties were characterized in details. It is found that SnO2 doping could increase the lattice parameters, density and average grain size. A suitable amount of SnO2 can improve dielectric properties, and affect the relaxor behavior of the NBT-ST matrix, thereby it can effectively reduce the energy loss and optimize the energy storage performance. Furthermore, the energy storage properties are improved with SnO2 doping. Especially, the 1 at. % SnO2 doped NBT-ST achieves a high recoverable energy density of 2.35 J/cm3, which is mainly attributed to large maximum polarization of 43.2 μC/cm2, small remnant polarization of 5.83 μC/cm2 and high breakdown strength of 180 kV/cm. Also, relatively good temperature stability for dielectric performance and excellent fatigue resistance are observed in this composition. These properties are attractive for lead-free energy storage applications.
关键词： SnO2,Lead-free,Dielectric,Energy storage,NBT-ST
更新于2025-11-14 17:28:48
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[Lecture Notes in Mechanical Engineering] Advances in Thin Films, Nanostructured Materials, and Coatings (Selected Papers from the 2018 International Conference on “Nanomaterials: Applications & Properties”) || Stain Effect on the Properties of Polar Dielectric Thin Films
摘要： Low cost scalable processing and substrates are critical for optimized polar dielectric performance of functional oxide thin ?lms if they are to achieve commercialization. Here, we present a comprehensive investigation of the role low-cost MgO, Al2O3, SrTiO3 and Si substrates on the structural and electrical properties of sol-gel derived SrTiO3 (ST) and K0.5Na0.5NbO3 (KNN) thin ?lms. The substrate is found to have a strong effect on the stress/stain state and, consequently, on the dielectric and ferroelectric response of the ?lms. A tensile stress induced in-plane by the thermal expansion mismatch between the substrates and the ?lms observed for ST and KNN ?lms deposited on platinized Al2O3 and Si substrates, respectively, lowers the relative permittivity and remanent polarization values in the parallel plate capacitor geometry. In contrast, a compressive stress/strain observed for ST ?lms deposited on MgO/Pt and KNN ?lms on SrTiO3/Pt substrates result in superior polarization and dielectric permittivity, corresponding to enhanced out-of-plane displacement of Ti4+ ions in ST ?lms and Nb5+ ions in KNN ?lms. It is thus demonstrated that for polycrystalline polar dielectric thin ?lms the relative permittivity and polarization may be optimized through an induced compressive stress state.
关键词： Dielectric properties,Sol-gel,Thin ?lms,Stress/strain,Thermal expansion,Ferroelectric hysteresis
更新于2025-11-14 17:28:48
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Highly Efficient and Durable Piezoelectric Nanogenerator and Photo-Power Cell Based on CTAB-Modified-Montmorillonite Incorporated PVDF Film
摘要： Herein, we have successfully designed two eco-friendly, biocompatible and cost-effective devices i.e. a piezoelectric nanogenerator (PENG) and a self-charged photo-power cell (PPC) by developing a multifunctional CTAB modified montmorillonite (MMT) incorporated poly(vinylidene fluoride) (PVDF) thin film with large electroactive β crystallites and dielectric properties. Incorporation of CTAB modified MMT in PVDF leads to nucleation of piezoelectric β crystallite (F(β)) ~ 91% as well as the dielectric constant ~ 48 at 3 mass% doping of CTAB-MMT. The enrichment of the electroactive β phase crystallization and high dielectric constant pilot to a good piezoelectricity ( d33) ~ 62.5 pC/N at 50 Hz of the thin film. Our CTAB-MMT/PVDF based PENG (CMPENG) with superior piezoelectricity shows high output power generation with power density ~ 50.72 mW/cm3 under periodic finger impartation and having ability to charge up a 1μF capacitor up to 2.4 V within 14 seconds under gentle finger impartation. The CMPENG also have the potential to glow up commercially available 26 blue light-emitting diodes (LEDs) connected in series. The self-charged PPC has been designed with the thin film in association with MnO2-MWNT/PVP/H3PO4. Our PPC is able to generate supercilious output voltage ~ 1.38 V and short circuit current ~ 3.7 mA/cm2under light illumination with specific areal capacitance and energy storage efficiency ~ 1501 F/m2 and ~ 93% respectively. The realistic application of our PPC is investigated by lightening up 24 blue LEDs for 7 days with same intensity by charging the device once for 50 seconds.
关键词： MMT,PVDF,power density,piezoelectric,dielectric,energy
更新于2025-11-14 17:28:48