Search for: dielectric
Total 201 records
Correction to: conventional and two step sintering of PZT-PCN ceramics, Article Applied Physics A: Materials Science and Processing ; Volume 124, Issue 2 , February , 2018 , No. 177 ; 09478396 (ISSN) ; Rahmani, H ; Nemati, A ; Hashemi, M ; Sharif University of Technology
Springer Verlag 2018
The original version of this article unfortunately contained a mistake. The presentation of Eq. 1,2, and 3 was incorrect.The correct versions are given below. The original article has been corrected. (Formula Presented.) (1) (Formula Presented.) (2) (Formula Presented.) (3). © 2018, Springer-Verlag GmbH Germany, part of Springer Nature
Variation of the lateral Casimir force between corrugated conductors due to the presence of a dielectric slab, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 86, Issue 2 , 2012 ; 10502947 (ISSN) ; Soltani, M ; Zakeri, P ; Jafari, S. A ; Sharif University of Technology
We investigate the lateral Casimir interaction between two corrugated conductors when they enclose a dielectric slab. The magnitude of the lateral Casimir force can be changed due to the presence of a dielectric slab between them, and it strongly depends on the thickness (d) and dielectric function of the slab and also on the position of the slab with respect to the conductors. In addition, the distance between the conductors (H) and their corrugation wavelengths play important roles in tuning the lateral Casimir interaction. For fixed d and H, quite interestingly, the magnitude of the lateral Casimir force varies when the position of the slab with respect to conductors changes, and it has a...
Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2, Article Materials Letters ; Volume 267 , May , 2020 ; Mahmoudi, P ; Karimi, A ; Sharif University of Technology
Elsevier B. V 2020
In this research, for the first time, the effect of air quenching on the microstructural and electrical properties of (In, Nb) co-doped TiO2 was investigated. The FE-SEM images showed that the air quenching has no effect on microstructure of co-doped TiO2. However, air quenching affected the electrical properties so that the dielectric constant in the frequency of 1 kHz at room temperature sharply enhanced from 21*103 to 26*104 and the dielectric loss surprisingly decreased from 0.6 to 0.1. This incredible improvement in the dielectric properties is attributed to the electron-pined defect dipoles which has been activated through air quenching. © 2020 Elsevier B.V
Optimizing the materials response in humidity capacitive sensors, Article Journal of Nano- and Electronic Physics ; Volume 7, Issue 3 , October , 2015 ; 20776772 (ISSN) ; Golnabi, H ; Gorji, N. E ; Sharif University of Technology
Sumy State University 2015
The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30- 70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to...
Influence of material and geometry of the dielectric on the characteristics of the tank circuit resonators for high-Tc RF-SQUID-based system, Article IEEE Transactions on Applied Superconductivity ; Volume 26, Issue 3 , 2016 ; 10518223 (ISSN) ; Shanehsazzadeh, F ; Sarreshtedari, F ; Fardmanesh, M ; Sharif University of Technology
Characteristics of a lumped element L-C tank circuit resonator of high-Tc rf-SQUIDs, which plays an important role in the device operation, have been experimentally investigated, according to the corresponding simulations obtained by COMSOL Multiphysics. We experimentally investigated the characteristics of the resonators by measuring their scattering parameters, as well as evaluating the rf-SQUID signal. Our SQUIDs are made of sputtered YBCO thin films with 3-mm-diameter washer areas. Different configurations of the resonator are investigated, and it is observed that, by increasing the thickness of the dielectric in a specific range, the reflection coefficient (S11) increases. For the...
Waveguiding characteristics of a metal-clad dielectric grating for terahertz applications, Article Optics Communications ; Volume 476 , 2020 ; Ahmadi Boroujeni, M ; Abbaszadeh, A ; Sharif University of Technology
Elsevier B.V 2020
Dielectric gratings (DGs) have recently been introduced as a new platform for guiding dielectric-based geometrically-induced surface plasmons (SPs) called spoof SPs (SSPs). In this paper, we report on the modal analysis of a metal-clad DG waveguide and compare its performance with other counterparts including the dielectric image guide (IG) and the metal grating (MG) waveguide. The proposed DG waveguide is made up of a periodic array of high-resistivity silicon (HR-Si) pillars on a metal plate with a metal cladding at a proper distance above the structure. By modal analysis of 2D and 3D structures, we show that the presence of the metal cladding enhances the modal field confinement without...
Simultaneous measurements of the resistance and capacitance using a cylindrical sensor system, Article Modern Physics Letters B ; Volume 22, Issue 8 , 2008 , Pages 595-610 ; 02179849 (ISSN) ; Azimi, P ; Sharif University of Technology
In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the...
Thermodynamic complexation of dopamine with magnesium (II) in media with different dielectric constants, Article Main Group Metal Chemistry ; Volume 31, Issue 1-2 , 2008 , Pages 81-91 ; 07921241 (ISSN) ; Boghaei, D. M ; Monajjemi, M ; Sharif University of Technology
Walter de Gruyter GmbH 2008
The solution equilibria of magnesium (II) complex formed with bidentate ligand of dopamine in acidic media (pH=∼4-∼6) have been studied in cosolvent systems at 15, 25, 35 ± 0.1° C and 1=0.2 mol.dm-3 sodium chloride, using phosphate buffer, with spectrophotometric methods. Evidence for the 2:1 complex was not observed for magnesium. The stability constant of the complex was determined KMg(HL)+ = ∼9 and the resulting free-energy changes obtained. The protonation constant of dopamine was determined under the above conditions. The results are discussed in terms of the effect of solvent on protonation and complexation
Modified TMM for waveguides with conducting interfaces, Article Optoelectronics, Materials, and Devices for Communications, Beijing, 12 November 2001 through 15 November 2001 ; Volume 4580 , 2001 , Pages 167-169 ; 0277786X (ISSN) ; Rashidian, B ; SPIE ; Sharif University of Technology
In this article, the transfer matrix method (TMM) is modified for study of optical wave propagation in layered media with conducting interfaces. Both the TE and TM mode transfer matrices are derived and their properties are discussed
Theoretical and experimental broadband tissue-equivalent phantoms at microwave and millimetre-wave frequencies, Article Electronics Letters ; Vol. 50, issue. 8 , April , 2014 , p. 618-620 ; ISSN: 00135194 ; Saviz, M ; Shishegar, A. A ; Sharif University of Technology
Several phantoms have been fabricated for reflection measurements from human tissues in the range of 26.5-40 GHz. For the first time, a novel composition is introduced for fabrication of low-cost simple tissue-equivalent phantoms. The effective medium theory is applied to estimate the dielectric properties of phantoms consisting of polyethylene (PE) powder and the results are verified by dielectric properties measurement on the proposed phantoms. It is shown that mixing theory can estimate the dielectric properties of the PE-based phantoms with minimum error. Therefore, the amount of the ingredients can be estimated theoretically
All-dielectric structure for trapping nanoparticles via light funneling and nanofocusing, Article Journal of the Optical Society of America B: Optical Physics ; Volume 34, Issue 10 , 2017 , Pages 2179-2184 ; 07403224 (ISSN) ; Mehrany, K ; Sharif University of Technology
We propose a dielectric structure which focuses laser light well beyond the diffraction limit and thus considerably enhances the exerted optical trapping force upon dielectric nanoparticles. Although the structure supports a Fabry–Perot resonance, it actually acts as a nanoantenna in that the role of the resonance is to funnel the laser light into the structure. In comparison with the lens illuminating the structure, the proposed structure offers roughly a 10,000-fold enhancement in the trapping force—part of this enhancement comes from an 80-fold enhancement in the field intensity, whereas the remaining comes from a 130-fold enhancement in the normalized gradient of the field intensity...
Analysis of nonuniform nonlinear distributed feedback structures by using nonlinear differential transfer matrix, Article ICONO 2007: Coherent and Nonlinear Optical Phenomena, Minsk, 28 May 2007 through 1 June 2007 ; Volume 6729 , 2007 ; 0277786X (ISSN) ; 081946886X (ISBN); 9780819468864 (ISBN) ; Mehrany, K ; Abediasl, H ; Salehi, J. A ; Rashidian, B ; Sharif University of Technology
Differential transfer matrix method is extended to analyze nonuniform nonlinear distributed feedback structures. The input-intensity dependence of the reflectivity and transmissivity of inhomogeneous nonlinear dielectric slabs is investigated for TE polarized and TM polarized incident waves
Tight-binding analysis of coupled dielectric waveguide structures, Article Fiber and Integrated Optics ; Volume 25, Issue 1 , 2006 , Pages 11-27 ; 01468030 (ISSN) ; Ranjbaran, M ; Mehrany, K ; Rashidian, B ; Fathololoumi, S ; Sharif University of Technology
Based on the mathematical similarity of the Schrödinger and Helmholtz equations, the tight-binding method has been employed for solving optical waveguide problems, in a manner similar to the methods commonly used in solid-state physics. The solutions (TE mode electric field waveforms and propagation constants) of a single dielectric slab waveguide are considered to be known, and tight-binding is used to compute the propagation constants of several multi-waveguide structures. Analytical solutions are derived for linear and circular arrays of adjacent waveguides. The problem of two similar adjacent waveguides is treated in detail for two cases of similar and different propagation constants of...
Simulation of a carbon nanotube field effect transistor with two different gate insulators, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 2332-2340 ; 10263098 (ISSN) ; Faez, R ; Jafari, A. H ; Sharif University of Technology
Sharif University of Technology 2013
In this paper, a novel structure for MOSFET like CNTFETs (MOSCNTs) is proposed, combining the advantages of both high and low dielectrics to improve output characteristics. In this structure, the gate dielectric at the drain side is selected from a material with low dielectric constant to form smaller capacitances, while a material with high dielectric constant is selected at the source side to improve on current and reduce leakage current. The new structure is simulated based on the Schrödinger-Poisson formulation. Obtained results show that the proposed configuration has lower off and higher on current in comparison with low-k MOSCNTs. Also, using a two-dimensional model, a wide range of...
Analysis of terahertz-induced optical phase modulation in a nonlinear dielectric slab, Article Progress In Electromagnetics Research M ; Volume 13 , 2010 , Pages 41-51 ; 19378726 (ISSN) ; Izadi, S. A ; Shahabadi, M ; Sharif University of Technology
Frequency shift of the spectrum of an incident optical pulse by an intense THz pulse inducing cross-phase modulation (XPM) in a nonlinear dielectric slab is analyzed. The effect is predicted with a high degree of accuracy using the well-known transmission line matrix (TLM) technique. In this research, to model the THz-induced temporal and spatial variation of the dielectric permittivity of the nonlinear dielectric slab, the transmission lines of the TLM method are loaded with open shunt stubs. The parameters of the stubs are modified in accordance with the refractive index variation of the dielectric slab, here ZnTe, induced by the strong THz pulse. The obtained numerical results are...
Impact of indium substitution on dielectric and magnetic properties of Cu 0.5 Ni 0.5 Fe 2-x O 4 ferrite materials, Article Ceramics International ; Volume 45, Issue 10 , 2019 , Pages 13431-13437 ; 02728842 (ISSN) ; Khan, M. A ; Akhtar, M. N ; Hussain, A ; Warsi, M. F ; Sharif University of Technology
Elsevier Ltd 2019
Indium substituted Cu[sbnd]Ni nanoferrites with nominal compositions Cu 0.5 Ni 0.5 In x Fe 2-x O 4 (x = 0.00–0.32)were successfully synthesized by sol-gel auto ignition method. X-ray diffraction patterns illustrated the single phase spinel structure for x ≤ 0.24. The lattice parameter ‘a’ increased from 8.3349 to 8.3723 Å and then it decreased for x = 0.32. X-ray density increased from 5.43 to 5.79 g/cm 3 . The average crystallite sizes lie in the range 33.21–17.78 nm. The cell volume was increased from 579.03 to 586.86 Å 3 with the substitution of indium ions into the spinel lattice of copper nickel ferrites. The compositional dependence of tetrahedral and octahedral radii was explained on...
Stable high dielectric properties in (Cr, Nb) co-doped SnO2 ceramics, Article Materials Chemistry and Physics ; Volume 246 , May , 2020 ; Golmohammad, M ; Chermahini, M. D ; Mahmoudi, P ; Moghadam, H. A ; Sharif University of Technology
Elsevier Ltd 2020
In this research, the microstructure, dielectric, and non-Ohmic properties of (Cr, Nb) co-doped SnO2 ceramics, (Cr0.5, Nb0.5)xSn1-xO2 with x% = 0, 0.5, 1.0, 2.0, 5.0, and 10.0, as a colossal dielectric material and a prospective alternative to co-doped TiO2 ceramics were studied. The X-ray diffraction results indicated that in all compositions, the cassiterite phase was achieved without any secondary phases. Moreover, field-emission secondary electron microscopy showed that the microstructure of samples has different morphologies including typical grains, enlarged grains and prism-like grains microstructure for various sintered samples. The maximum dielectric constant (2737) accompanied by...
Fabrication and microwave dielectric characterization of cordierite/BZBS (Bi2O3-ZnO-B2O3-SiO2) glass composites for LTCC applications, Article Journal of Alloys and Compounds ; Volume 882 , 2021 ; 09258388 (ISSN) ; Nemati, A ; Banijamali, S ; Sharif University of Technology
Elsevier Ltd 2021
The present work aims to fabricate cordierite/BZBS glass (Bi2O3-ZnO-B2O3-SiO2) composites through one-step heat treatment. Cordierite was synthesized from a solid-state reaction of aluminum hydroxide, magnesium hydroxide, and silica gel. BZBS glass was obtained through the classic melt quenching technique. Milled cordierite powder was mixed with different volume fractions of glass powders and heat treated at 950 °C. Considering the densification behavior along with the microwave dielectric features, two composites (C70G30 and C60G40) were chosen for further examination. These composites were separately heat treated at different temperatures from 650 up to 900 °C, then characterized due to...
Calculation of effective parameters of high permittivity integrated artificial dielectrics, Article IET Microwaves, Antennas and Propagation ; Volume 9, Issue 12 , September , 2015 , Pages 1287-1296 ; 17518725 (ISSN) ; Rejaei ; Sharif University of Technology
Institution of Engineering and Technology 2015
An analysis is presented of the effective electromagnetic parameters of high-permittivity, anisotropic artificial dielectrics which are built by stacking arrays of metallic elements and conventional dielectric films, with adjacent arrays shifted with respect to each other. The effective parameters of the artificial dielectric are extracted from the scattering coefficients of plane electromagnetic waves which are normally or obliquely incident on a slab of the artificial material with finite thickness. These coefficients are derived from the generalised scattering matrix of a single layer of metallic elements which is computed using the integral equation technique. Both two-dimensional and...
Effects of Ce–Co substitution on structural, magnetic and dielectric properties of M-type barium hexaferrite nanoparticles synthetized by sol–gel auto-combustion route, Article Journal of Materials Science: Materials in Electronics ; Volume 26, Issue 4 , 2015 , Pages 2134-2144 ; 09574522 (ISSN) ; Nemati, A ; Sharif University of Technology
Springer New York LLC 2015
M-type Ce–Co substituted barium hexaferrite nanoparticles were synthesized by sol–gel auto-combustion route. The general formula of ferrites was Ba1−xCexFe12−xCoxO19 in which the x was considered to be: x = 0, 0.1, 0.2, and 0.3. The formed phases in the samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometer. The results indicated that an increase in substitutional ion amount caused to decrease vibration frequencies of Fe–O band in the tetrahedral site due to the substitution of heavier Co2+ ion for Fe3+ ion in the tetrahedral site. Moreover, some of Ce3+ ions was transformed to Ce4+ and...