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- impedance spectroscopy
- molten-salt
- conductivity
- Ba0.97La0.02Ti1-xNb4x/5O3
- EIS spectrum
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- liquid crystals
- electric conductivity
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- South Ural State University
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Compositional dependence of properties in calcium substituted sodium borophosphate glasses containing $${\hbox {VO}}^{2+}$$ VO 2 + ions
摘要： Synthesis of calcium-substituted sodium borophosphate glasses with compositions xCaO ? (30 ? x)Na2O ? 35B2O3 ? 35P2O5 (x = 0, 2, 5, 7 and 10 mol%, abbreviated as CNVx) containing additional 1.0 mol% of V2O5 following a melt-quench method has been carried out. Different analytical techniques viz. wide angle X-ray diffraction (to con?rm non-crystalline nature), ultraviolet–visible spectroscopy (for optical band gap analysis), infrared absorption spectroscopy (for structural analysis) and differential thermal analysis (to evaluate characteristic temperatures) were employed to characterize the synthesized compositions. The optical band gap is calculated for both indirect allowed and indirect forbidden transitions. The values of the band gap decrease with increasing concentration of CaO (from 5 to 10 mol%) at the cost of Na2O. The cut-off wavelength and Urbach’s energy are determined from the optical absorption spectra and were related to the structural changes occurring in these glasses with an increase in CaO content. The results obtained from Fourier-transform infrared studies con?rm that V2O5 and CaO play the role of network modi?er oxides. Also, the signi?cant shifting in IR bands with an increase in CaO content in the glass matrix suggests the formation of a new boron–oxygen ring. From differential scanning calorimetry measurements it is observed that substitution leads to the increase in natural bond orbitals, high degree cross-linking and thus strengthens the glass network. Glass transition temperature (Tg) is found to increase from 483 to 522?C. Electrical and dielectric properties are analysed using dc conductivity and impedance spectroscopy. Using impedance spectroscopy, different dielectric parameters i.e. dielectric loss (ε(cid:4)), electrical modulus (M ?) and ac conductivity (σac) etc. are evaluated as a function of frequency, temperature and composition. The frequency dependence of impedance exhibits the non-Debye relaxation behaviour and the total conductivity obeys Jonscher’s power law.
关键词： Jonscher’s power law,impedance spectroscopy,Band gap,differential thermal analysis
更新于2025-11-14 14:48:53
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A Facile Film-Nanoctahedron Assembly Route to Plasmonic Metamaterial Absorbers at Visible Frequencies
摘要： Plasmonic metamaterial absorbers (MAs) with broadband and near-perfect absorption properties in the visible region were successfully fabricated via a facile film-colloidal nanoparticle (NP) assembly method. In this approach, colloidal octahedral Au NPs were employed as the surface meta-atoms of MAs, while the nanoscale-thick SiO2 and Al films were used as the dielectric spacer and reflector respectively. It is worth noting that the Au nanoctahedron were randomly assembled onto the Al-SiO2 films, and no effort was made to precisely control their spatial arrangements. The optical characterization showed that the as-prepared MAs exhibited broadband high absorption (average absorptivity above 85%) within the whole visible spectrum for a broad range of incident angles (0°–60°). In particular, two polarization-independent near-perfect absorption peaks (absorptance above 99%) were recorded near 540 nm and 727 nm respectively. Moreover, the absorption properties of the MAs can be effectively controlled and tailored by varying the geometry (the thickness of the dielectric spacer and the surface coverages of the Au nanoctahedron). Electromagnetic simulations further demonstrated that enhanced Mie resonances and strong plasmonic coupling effects were critical for the designed MAs. This work here may provide an efficient and alternative route for the design of scalable visible light absorbers for applications such as solar cells, photothermalvoltaics, and biochemical sensors.
关键词： metamaterial absorbers,broadband and near-perfect absorption,aperiodic nanostructures,optical impedance matching,self-assembly
更新于2025-10-22 19:40:53
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Monopole Design for Superdirectivity with Pattern Radiation Reconfigurable
摘要： This paper presents a global study for superdirectivity of an array of 2 monopoles antennas. It is principally based on Uzkov’s theory, who define the possibility to obtain a high directivity in order of N 2 in a desired direction by linearly associating a large number N of radiators closely spaced. A first study is made by exciting monopoles by specific currents excitation in magnitude and phase to obtain a superdirectivity reconfigurable in a desired direction. Secondly, to reduce until eliminate mutual coupling between monopoles, we excite one of monopole by a unit current and loaded the other one by an impedance Zload determined from uzkov’s theory. Simulator Ansys HFSS is used to calculated impedance matrix Hmn of monopoles antennas array and then currents excitation coefficients a0n used after to determine impedance Zload. Simulations show approximately similar results in the 2 cases with a reconfigurable directivity a least in around of 8.5dB in a desired direction.
关键词： impedance active,end-fire,Superdirectivity,impedance-matched
更新于2025-09-23 15:23:52
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Influence of thermal oxidation temperature on the microstructure and photoelectrochemical properties of ZnO nanostructures fabricated on the zinc scraps
摘要： In this paper, zinc oxide (ZnO) nanowires were synthesized by thermal oxidation method of zinc scrap at various temperatures ranging between 400 °C and 900 °C under air atmosphere. The influence of different temperature on the phase structures, surface morphologies and photoelectrochemical (PEC) properties of ZnO nanowires were investigated. The characterizations were carried out via X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results showed that annealing temperature played a significant role on surface morphology and phase structure. The band gap energy of the ZnO nanowires changed between 3.12 and 3.194 eV. The photoelectrochemical (PEC) study of the ZnO nanowires was investigated in 0.1 M Na2SO4 aqueous solution. The PEC findings represented that the ZnO nanowire annealed at 600 °C had 252.2 mA/cm2 net photocurrent density which was the best efficiency and at least 10 times higher than that of the lowest one at 1.25 V (vs. VRHE). Mott-Schottky analysis showed that the ZnO nanowires behaved as n-type semiconductor. ZnO nanowire annealed at 600 °C had the highest carrier density value (Nd = 9.03 × 10^23). Moreover, the charge transfer behavior of the ZnO nanowires was determined by means of electrochemical impedance spectroscopy (EIS) measurements. As a result, this work recommends that the ZnO nanowires could be good candidate on PEC applications. Also, thermal oxidation method is an efficient method for fabrication of ZnO nanowires.
关键词： Thermal oxidation,Zn scrap,Electrochemical impedance spectroscopy (EIS),ZnO nanowires,Photoelectrochemical (PEC)
更新于2025-09-23 15:23:52
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Synthesis, Conductivity and Impedance Studies on across adjacent ring formed new metallo phthalocyanines
摘要： The synthesis and characterization of Co(II), Zn(II) and Ni(II) phthalocyanines (Pcs) 4, 5 and 6, respectively containing two Bis[2-(4-hydroxyphenyl)-2-propyl]benzene across adjacent ring formed at the peripheral positions are described. The Pcs were synthesized by cyclotetramerization of the previously prepared precursor 4,4’-bis[1,3-propylbenzene-2-p-phenoxy]phthalonitrile (3) with the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. Elemental analysis, UV-Vis, FT-IR, MALDI-TOF mass and 1H-NMR spectrometry techniques were used for characterization of 4. DC and ac conductivity and impedance spectra (IS) measurements were performed on the films 5, and 6 between the temperatures 293 - 523 K and frequencies 40-100 kHz. The dc conductivity values were calculated as 2.11x10-10 S/cm, 3.48x10-10 S/cm, and 1.90x10-10 S/cm for the films of 4, 5, and 6 at room temperature. Activation energy values of the films were also calculated. ac conductivity results suggest that dominant charge transport mechanisms can be explained by hopping model depending on temperature and frequency range. From impedance spectra, Cole-Cole plots, the relaxation time in Debye dispersion relation is considered as a distribution of relaxation time values, rather than as a single relaxation time. To elucidate the structural, spectroscopic and bonding properties of the obtained compounds, DFT/TD-DFT calculations were performed.
关键词： Density functional theory,Conductivity,Electrical characterization,Impedance spectra,Metallophthalocyanine,Hopping
更新于2025-09-23 15:23:52
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Design of a high-gain wideband antenna using double-layer metasurface
摘要： A wideband antenna is studied in this paper using a multi-layer metasurface structure and implementing a periodic array for enhancing the gain. The performance of the multilayer antenna is improved by using a sub-wavelength Fabry-Perot cavity (FPC). The feeding and main radiation patches of the microstrip antenna are placed separately on two substrates, which are stacked on top of each other without an air-gap in between. Two other substrates are placed within an optimized distance on top of the microstrip antenna. This structure, which has a double-sided periodic array configuration, includes a capacitive artificial impedance surface (AIS) on one side, and an inductive partially reflective surface (PRS) on the other side of the substrates. Making use of this configuration increases the gain up to 18 dBi and widens the frequency bandwidth. Moreover, measurement results indicate a frequency range from 10.8 GHz to 15 GHz with an S11 less than ?10 dB.
关键词： Fabry-Perot cavity,microstrip antenna,artificial impedance surface,partially reflective surface,metasurface
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Miramar Beach, FL (2018.8.22-2018.8.24)] 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - On using Micron-Sized Silver Coated Particles to Control the Electromagnetic Response of a Metamaterial with Complementary Split Ring Resonators and Wires in a Host Dielectric
摘要： Micron-sized conducting particles that columnize along the magneto-static field lines are used to implement the wires in a traditional split ring resonator/wire metamaterial unit-cell configuration. It is shown that the impedance of the metamaterial can be effectively changed from 1GHz-20GHz by controlling the particle columns.
关键词： CSRR,wave impedance,Metamaterials
更新于2025-09-23 15:23:52
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Variation in Structural, Electrical and Optical Properties of Selenium Nanowires After Irradiation with Ni6+ Ions
摘要： The effect of Ni ion irradiation on selenium nanowires of 80 nm diameter is studied in the present work. Se nanowires were prepared by using electrodeposition technique in polycarbonate membrane. Changes in the structural, optical and electrical properties are studied using XRD, UV/Vis spectroscopy and current–voltage characteristics, of the pristine and irradiated samples. X-ray diffraction study confirms the variation in peak intensity without any shifting in peak position. Variation in texture coefficient and grain size was clearly observed which is a consequence of changing plane orientation, irradiation induced grain growth and grain fragmentation. A decrease in the optical band gap takes place due to interstitial energy band states in the vicinity of conduction and valence band. IVC also shows variation in the conductivity which is due to the generation of current carriers with the passage of energetic ions.
关键词： Ion irradiation,Optical analysis,Selenium nanowires,Impedance,Electrical properties,Structural analysis
更新于2025-09-23 15:23:52
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Chemical Sensing Performance of Flower-Like ZnO/PSi Nanostructures via Electrochemical Impedance Spectroscopy Technique
摘要： ZnO nanostructures were synthesized on porous Si (PSi) structures using a method developed by this study known as electric field-assisted aqueous solution technique. The detailed characterization of this nanostructure was performed using atomic force microscopy, field emission scanning electron microscopy, x-ray diffraction, room-temperature photoluminescence and Raman spectroscopy. Electrochemical impedance spectroscopy (EIS) technique was used to detect two classifications of chemical solvents, namely polar and non-polar solvents. Nyquist plots in EIS were utilized to detect chemical solvents (ethanol, acetone, toluene and benzene) exposed to ZnO/PSi nanostructure arrays. The results showed that the grown flower-like ZnO nanostructure arrays served as good chemical sensors with high sensitivity and low power consumption. Meanwhile, the ZnO/PSi nanoflowers exposed to ethanol showed the highest sensitivity (94.6% response) compared to other chemical solutions with the least response exhibited by benzene (68.4% response). It was postulated that the interaction between the solution and oxygen species of ZnO/PSi nanostructure surface induced a resistance change resulting in the release of free electrons that migrated to the conduction band of ZnO/PSi nanoflower structures and reduced the number of surface-adsorbed oxygen species. Subsequently, the changes observed in the Nyquist semicircle diameter and Warburg impedance led to the chemical sensing response.
关键词： ZnO/PSi nanoflower,electric field-assisted aqueous solution technique,Chemical sensors,electrochemical impedance spectroscopy,Nyquist plot
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE PES/IAS PowerAfrica - Cape Town (2018.6.28-2018.6.29)] 2018 IEEE PES/IAS PowerAfrica - Estimation of Inverter-Based Solar PV Penetration on Medium Voltage Networks Using Grid Impedance
摘要： Installation and control of connecting inverter-based generation to medium voltage networks are constrained by network grid structure and by technical regulations that limits its penetration into the network. Medium voltage networks form the backbone to which low-voltage inverter-based generation such as solar PV systems are connect to. However, these networks generally have inconsistent impedances that vary with line lengths, conductor types and load distribution and therefore make them not as flexible and cost effective to efficiently allow adequate penetration of solar PV type distributed generation (capacity in kW) to be integrated. A generic model that mimics a medium voltage network is analyzed in this paper to determine how inverter-based generation can be maximized on the network in terms of its location by focusing on line impedance ratios to achieve voltage regulation.
关键词： voltage regulation,Inverter-based generation,line impedance ratio,conductor type,medium voltage,line lengths
更新于2025-09-23 15:23:52