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Dielectric Loss (dielectric + loss)
Kinds of Dielectric Loss Selected AbstractsA New Compound with Ultra Low Dielectric Loss at Microwave FrequenciesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009Ching-Fang Tseng A new ultra low loss microwave dielectric ceramic, Mg(Sn0.05Ti0.95)O3 (MSnT), was found and investigated. The compounds were prepared by the conventional solid-state route, and sintered at 1360°,1480°C for 2,6 h. The investigations show that the MgTi2O5 secondary phase was observed. Moreover, the dielectric properties were correlated with the formation second phase. The excellent microwave dielectric properties of Q×f=322 000 (GHz), ,r=17.4, and ,f=,54 ppm/°C were obtained from the new MSnT ceramics sintered at 1390°C for 4 h. [source] Characterization of gel grown iron-manganese-cobalt ternary levo-tartrate crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2010S. J. Joshi Abstract In the present investigation, iron,manganese,cobalt ternary levo-tartrate crystals of different compositions have been grown by single-diffusion gel growth technique in silica hydrogel medium. The metallic composition in the crystals was estimated by EDAX. The coloration of the crystals changed with composition of metallic content. The powder XRD study suggested the crystalline nature and indicated the presence of some extra phases. The grown crystals were characterized by FT-IR spectroscopy, TGA, dielectric and Vibrating Sample Magnetometer (VSM) studies. The FT-IR study suggested the presence of O-H, C=O, C-O and metal-oxygen bonds. The effect of composition of metallic content was observed in certain absorption regions in FT-IR spectra. The thermal stability of the crystals was studied by thermogravimetry and the kinetic and thermodynamic parameters of dehydration were calculated. The effect of composition of ternary levo-tartrate was observed in dielectric study. The dielectric study was carried out in the frequency range of applied field from 500 Hz to 1 MHz. The variations in dielectric constant, dielectric loss, a.c. resistivity and a.c. conductivity with frequency of applied field were studied. VSM study suggested that all crystals were of paramagnetic nature. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Some biophysical properties of castor oil esterified with some acid anhydridesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 10 2008Mona A. Saied Abstract A series of castor oil adducts were synthesized by esterification of castor oil with acid anhydrides: phthalic, maleic and succinic anhydrides. The chemical structure of castor oil and the prepared adducts were characterized by means of IR and 1H,NMR spectroscopy. The number-average and weight-average molecular weights were measured by gel permeation chromatography. The electrical properties were studied through the permittivity, dielectric loss and conductivity measurements, which are considered to be in the range of electrical insulation. The electrical conductivity, which describes the ionic mobility of the systems, was found to be in the range of 10,9 to 10,12,S/cm. This indicates that castor oil and its esters could be used for antistatic applications. The viscosity,, and the activation energy,E,, obtained from the dependency of viscosity on temperature using the Arrhenius equation, were found to increase with increasing molecular weight of the system. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens R.,solani and S.,rolfsii was studied through the determination of percent germination, average length of hyphal extensions, dry mass yield and the production of sclerotia. The obtained data indicate that the esterification of castor oil with anhydrides improves the antifungal activity. [source] Influence of water absorption on high-frequency characteristics of insulation layers of printed circuit boardsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2007Kaori Fukunaga Member Abstract The influence of water absorption on complex permittivities of various insulating materials used for printed circuit boards was investigated in the frequency range of K-band (18,26 GHz). Experimental results revealed that the influence of water absorption on complex permittivity, the dielectric loss factor tan,, in particular, was considerably high. For example, the dielectric loss of polyimide film at 85°C, 85% RH became 10 times larger than that at room temperature and humidity. Since the complex permittivities, however, retained the initial values when the specimens are dried, the water in the specimen should exist freely at the internal interfaces of the materials. The increase of permittivity directly affects the performance of printed circuit boards at high frequencies, so that it is important to clarify the influence of water on dielectric properties of insulations. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Properties of Porous Si3N4/BN Composites Fabricated by RBSN TechniqueINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010Ji-Xuan Liu Reaction bonding of silicon nitride (RBSN) technique combined with slip-casting shaping process was used to fabricate porous Si3N4/BN ceramic composites. Si/BN slurry with chemical stability, good dispersibility, and viscosity was prepared using glycerol trioleate (GTO) covering on Si surface and poly(acrylic acid) (PAA) as dispersant. The hydrolysis of Si was strongly prevented by GTO coating. The dispersibility of covered Si and BN suspensions were improved by PAA dispersant. Twenty volume percent covered Si/BN slurries with low viscosity were successfully casted. The cast bodies were dried at room temperature, debindered at 750°C and nitrided below 1450°C. The nitrided samples mainly consist of ,-Si3N4, ,-Si3N4, and h-BN. The composites exhibit homogeneous microstructure consisting of faceted particles, ,-Si3N4 nanowires and a large amount of pores. The porosity is 52.64% and the pore size is in the range of 60,300 nm. The composites show compressive strength of 16.6±1.5 MPa. The dielectric constant of the composite is about 3.1 and the dielectric loss is below 0.5% under different frequencies. [source] Zero Shrinkage of LTCC by Self-Constrained SinteringINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2005Torsten Rabe Low shrinkage in x and y direction and low tolerances of shrinkage are an indispensable precondition for high-density component configuration. Therefore, zero shrinkage sintering technologies as pressure-assisted sintering and sacrificial tapes have been introduced in the low-temperature co-fired ceramics (LTCC) production by different manufacturers. Disadvantages of these methods are high costs of sintering equipment and an additional process step to remove the sacrificial tapes. In this article, newly developed self-constrained sintering methods are presented. The new technology, HeraLock®, delivers LTCC modules with a sintering shrinkage in x and y direction of less than 0.2% and with a shrinkage tolerance of ±0.02% without sacrificial layers and external pressure. Each tape is self-constrained by integration of a layer showing no shrinkage in the sintering temperature range of the LTCC. Large area metallization, integration of channels, cavities and passive electronic components are possible without waviness and camber. Self-constrained laminates are an alternative way to produce zero shrinkage LTCC. They consist of tapes sintering at different temperature intervals. Precondition for a successful production of a self-constrained LTCC laminate is the development of well-adapted material and tapes, respectively. This task is very challenging, because sintering range, high-temperature reactivity and thermal expansion coefficient have to be matched and each tape has to fulfill specific functions in the final component, which requires the tailoring of many properties as permittivity, dielectric loss, mechanical strength, and roughness. A self-constrained laminate is introduced in this article. It consists of inner tapes sintering at especially low-temperature range between 650°C and 720°C and outer tapes with an as-fired surface suitable for thin-film processes. [source] Microwave-Induced-Plasma-Assisted Synthesis of Ternary Titanate and Niobate Phases,ADVANCED MATERIALS, Issue 20 2005J. Brooks Microwave-induced plasmas of argon (see Figure) and dioxygen have been used to rapidly prepare ternary niobate and titanate phases directly in the solid state from precursors that do not exhibit microwave heating at room temperature. However, for some reactions heating of the microwave-induced plasma can promote dielectric loss, which allows access to local temperatures greater than the equilibrium plasma temperature. [source] Simultaneously improved toughness and dielectric properties of epoxy/core-shell particle blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Weitao Wan Abstract Epoxy/core-shell particle blends were prepared using a diglycidylether of bisphenol A epoxy and acrylics-type core-shell particles. The impact strength of the blends was tested, and the result showed that the epoxy was greatly toughened with optimum core-shell particle content. Meanwhile, the dielectric properties of both epoxy and its blends were investigated using a broadband dielectric analyzer. It was found that the dielectric constant of the epoxy blends with lower core-shell particle content were less than that of the epoxy in the investigated frequency range, while the dielectric loss was less than that of the neat epoxy over a low frequency range, even for the epoxy blends with the optimum core-shell particle content. The dielectric breakdown strength of the epoxy blends at room and cryogenic temperature were also investigated. To identify the primary relationship of the above properties and structure of the epoxy blends, the microstructure of the core-shell particle and the morphology of the samples were observed by transmission electron microscopy and scanning electron microscopy. It was considered that these epoxy/core-shell particle blends with improved toughness and desirable dielectric properties could have a potential application in the insulation of electronic packaging system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Dielectric properties of thermosetting material nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Newton Luiz Dias Filho Abstract The dieletric relaxation properties of thermosetting material nanocomposites based on spherosilicate nanoplatforms were studied from room temperature to 170°C, varying the frequency from 10 to 1000 KHz. Permittivity (,,), dielectric loss (,,), and activation energy (Ea) were calculated. The results of dielectric relaxation were confirmed by those of the final properties. The dielectric loss amplitude decreases with increasing ODPG content until about 70,73 wt % and slightly increases at higher ODPG content. This means that the increasing of the ODPG content in the composite samples decreases the number of pendants groups and/or increases crosslink density, causing decreased motion of organic tethers, and subsequently decreasing of the dipolar mobility. The results of apparent activation energy, fracture toughness and tensile modulus mechanical properties show the same profile with respect to ODPG content, in the sense that they exhibit maxima around 70 wt % ODPG. For the ODPG/MDA composites, this formulation of 70 wt % ODPG containing excess of amine is not composition where the highest crosslinked density is reached. This implies that the best mechanical properties and Ea are provided by some degree of chain flexibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Efficient oxidative coupling polymerization for synthesis of thermosetting poly(phenylene ether) copolymer with a low dielectric lossJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Jun Nunoshige A novel oxidative coupling polymerization using a water/toluene heterogeneous system for the synthesis of thermosetting Poly(phenylene ether) copolymer (Allyl-PPE) was developed. Allyl-PPE with a narrow molecular weight distribution and a low copper content was obtained in the presence of a Cu/TMEDA catalyst dissolved in water droplets. This method solved the problems during the synthesis of the Allyl-PPE with conventional Cu/pyridine catalysts. The resulting Allyl-PPE exhibited excellent dielectric properties (,, = 2.4, tan , = 0.002 at 10 GHz), and it will be useful for applications to high-speed and high-frequency printed circuit boards. [source] Lift-Off PMN,PT Thick Film for High-Frequency Ultrasonic BiomicroscopyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Benpeng Zhu Piezoelectric 0.65Pb(Mg1/3Nb2/3)O3,0.35PbTiO3 (PMN,35PT) thick film with a thickness of approximately 12 ,m has been deposited on the platinum-buffered Si substrate using a sol,gel composite method. The separation of the film from the substrate was achieved using a wet chemical method. The lifted-off PMN,35PT thick film exhibited good dielectric and ferroelectric properties. At 1 kHz, the dielectric constant and the dielectric loss were 3326 and 0.037, respectively, while the remnant polarization was 30.0 ,C/cm2. A high-frequency single-element acoustic transducer fabricated with this film showed a bandwidth at ,6 dB of 63.6% at 110 MHz. [source] Electric and Dielectric Behaviors of Y-Doped Calcium Copper TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Fengchao Luo Yttrium-doped CaCu3Ti4,xYxO12,x/2 (x=0,0.1) samples were fabricated by using solid-state sintering, and their electric and dielectric properties were investigated. Yttrium addition has shown to reduce the dielectric loss remarkably while maintaining colossal permittivity. At x=0.5, the loss (tan ,) is below 0.1 over the frequency range from 1 to 300 KHz, while that of the pure ceramic is above 0.1 over most measuring frequency range. The current density,electric field curves proved that yttrium doping can effectively enhance the varistor voltage, indicating a rise of the potential barrier height at the grain boudaries. Local measurement of impedance at the grain boundaries was performed by using microcontact probes. The results indicated that yttrium dramatically increases the resistance of the grain boundaries. The differences are attributed to the enhanced Cu segregation at grain boundaries, which is induced by yttrium doping. [source] Improved Dielectric Properties of Bi1.5Zn1.0Nb1.5O7/(111)-Oriented Ba0.6Sr0.4TiO3 Bilayered Films for Tunable Microwave ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010Lihui Yang Bi1.5Zn1.0Nb1.5O7/(111)-oriented Ba0.6Sr0.4TiO3 [BZN/BST (111)] bilayered films (,500-nm-thick) have been prepared on Pt/TiOx/SiO2/Si substrates by RF-magnetron sputtering. Experimental results suggested that the BZN layer has played a positive role in improving the dielectric properties of the films. With the increased thickness of BZN, the dielectric loss was significantly lowered, accompanied with a tolerable reduction of tunability. The thickness effect was discussed with a series connection model of multilayered capacitors, and the calculated permittivity was obtained. At 400 kV/cm, moderate tunability of 50.55%, low dielectric loss of 0.0108, and the largest figure of merit of 46.8 can be achieved for BZN (50 nm)/BST(450 nm) bilayered films. [source] Fabrication and Tunable Dielectric Properties of Magnesium-Doped Lead Barium Zirconate Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Xihong Hao In present work, (Pb0.50Ba0.50)ZrO3 (PBZ) thin films doped by Mg from 0 to 5 mol% were deposited on Pt(111)/TiO2/SiO2/Si substrates by the sol,gel method. The phase structure of the Mg-doped PBZ thin films were characterized by X-ray diffraction. The electric-field and temperature-dependent electrical properties of the Mg-doped PBZ thin films were also investigated in detail. It was found that the Mg content had a strong influence on the dielectric properties of the thin films. The maximum values of dielectric permittivity and dielectric loss were obtained with 1 mol% Mg-doping PBZ thin films. However, the figure of merit (FOM) of the films was improved with increase in the Mg content. [source] Effect of Filler Content on the Dielectric Properties of PTFE/ZnAl2O4,TiO2 CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Sherin Thomas ZnAl2O4,TiO2 (ZAT)/polytetrafluoroethylene (PTFE) composites were prepared by powder processing method. The structure and microstructure of the composites were analyzed using X-ray diffraction and scanning electron microscopic techniques. The effect of different volume fraction of ZAT (0,0.6) on the dielectric properties of the composites was investigated at 1 MHz and at the microwave frequency of 7 GHz. The dielectric properties (relative permittivity and dielectric loss) were found to increase with the ZAT content. The samples with 60 vol.% of ZAT filler showed a relative permittivity of 3.9 and dielectric loss of 0.009, respectively, at 7 GHz. The variation of relative permittivity and dielectric loss showed only a very small variation with temperature in the range 25°,70°C for various ZAT/PTFE composites. The relative permittivity obtained experimentally were compared with that of the theoretical values predicted using modified Lichtenecker, Jayasundere,Smith, and Series mixing formulae. They were found to agree well with the predicted values for low filler content. [source] Dielectric Properties of Electrophoretically Deposited and Isothermally Pressed BaTiO3 Thick FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Ling Zhang Thick BaTiO3 films were prepared on platinum metallic foils by the electrophoretic deposition (EPD) technique using BaTiO3 nanoparticles. In order to increase the density of the thick film, the green film was pressed under an isostatic pressure of 200 MPa before high-temperature sintering. The microstructures of deposited films were examined using X-ray diffraction and scanning electron microscopy techniques. Dielectric properties of the thick films were investigated. As the films grow thicker, the dielectric constant increases gradually and the dielectric loss decreases slightly. The experimental results indicate that isostatic pressing is an effective method to process thick films with dense microstructure and better dielectric properties. [source] Giant Permittivity of a Bismuth Zinc Niobate,Silver CompositeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Sumesh George Bismuth zinc niobate,Silver (BZN,Ag) composites were prepared by the solid-state ceramic route. The sintering temperature of BZN,Ag composites was lowered to 850°C/2 h. The structure and surface morphology of the composites were investigated using X-ray diffraction and optical microscope. The dielectric and conducting properties of the composites were systematically investigated with the volume fraction of silver in the frequency range from 1 KHz to 1 MHz. The dielectric constant of the composite increases with the silver content and is in good agreement with the power law below the percolation limit. Addition of 0.14 volume fraction of silver increases the dielectric constant of BZN+2 wt% B2O3 from 150 to 2350 at 1 MHz. However, 15 volume percentage of silver loading results in a large permittivity of (,r),105 with a low dielectric loss (tan ,,10,2) at 1 MHz. Subsequent increase in silver loading decreases the dielectric constant. The BZN,B2O3,Ag composite with large permittivity may find applications in electromechanical and tunable devices. [source] Microwave Dielectric Ceramics for Resonators and Filters in Mobile Phone NetworksJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006Ian M. Reaney Temperature-stable, medium-permittivity dielectric ceramics have been used as resonators in filters for microwave (MW) communications for several decades. The growth of the mobile phone market in the 1990s led to extensive research and development in this area. The main driving forces were the greater utilization of available bandwidth, that necessitates extremely low dielectric loss (high-quality factor), an increase in permittivity so that smaller components could be fabricated, and, as ever in the commercial world, cost reduction. Over the last decade, a clear picture has emerged of the principal factors, that influence MW properties. This article reviews these basic principles and gives examples of where they have been used to control microwave properties and ultimately develop new materials. [source] LTCC stripline resonator using embedded air cavities for millimeter wave applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2008Young Chul Lee Abstract A stripline T-resonator is designed and implemented in the LTCC substrate for millimeter wave applications. The loss-free air cavities are embedded at both side edges of the conducting strip in order to efficiently reduce the dielectric loss of the stripline structure. The resonator was implemented using 4-layer LTCC dielectrics. The fabricated stripline resonator with air cavities reveals Q-factor of 248 and total loss of 0.035 dB/mm at 34.7 GHz, and that is improved by 108% and 51%, respectively, compared to the conventional one. The proposed LTCC stripline resonator with the embedded air cavities can meet demands for low-loss millimeter-wave system-on-package (SoP) applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 658,661, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23151 [source] 60 GHz multi-chip module based on cost effective hybrid multilayer PWBMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Sung Tae Choi Abstract A novel cost-effective 60-GHz multi-chip module (MCM) is proposed and demonstrated. It is based on a low-cost multilayer printed wiring board (PWB) with a novel vertical transition and a single layer waveguide transition which enables the use of low-cost substrates with high dielectric loss for millimeter wave applications. The proposed MCM technology has been successfully applied to the packaging of a 60-GHz self-heterodyne mixer, and no substantial difference in the RF performance is observed with the packaging. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2303,2305, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22719 [source] Temperature and frequency investigations of the electrical parameters in the TGS ferroelectric transitionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2010Ciceron Berbecaru Abstract Pure and D: alanina doped triglycin sulphate (TGS) crystals were grown from aqueous solutions. Fresh cleaved, polished and silver paste painted samples were temperature and frequency investigated. Pure crystals show nonreproducible values of the permittivity and dielectric loss crossing up and down the Curie point. More stable and much lower values of the permittivity and dielectric loss could be noticed for D: alanina doped crystals. Permittivity and loss values show different frequencies behavior related to polar or nonpolar state of crystals. Frequency dependence of permittivity and loss behavior could be related to the general picture of relaxation of different polarization mechanisms and their contributions to permittivity and loss values for dielectric materials. Much smaller and stable values of permittivity and loss, vs. temperature and frequency, were found for doped crystals. Experimental results point out for a more stable structure with dipoles mobility decreased of doped vs. pure TGS crystals. Thus, higher figure of merit of doped TGS crystals point to a major advantage for technical applications (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3-, filler on the microwave dielectric properties of polyethylene and polystyrene for microelectronic applicationsPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Sumesh George Ceramic reinforced polyethylene and polystyrene composites were prepared by melt mixing and hot molding techniques. Temperature stable low-loss Ca[(Li1/3Nb2/3)0.8Ti0.2]O3-, (CLNT) ceramic was used as the filler to improve the dielectric properties of the polymers. The relative permittivity and dielectric loss in the microwave frequency range were increased with increase in the ceramic loading. As the filler content increased from 0 to 0.50 volume fraction, the relative permittivity increased from 2.3 to 9 and dielectric loss tangent from 0.0006 to 0.005 for polyethylene-CLNT composite. In the case of polystyrene-CLNT composite, the relative permittivity and dielectric loss tangent increased from 2.1 to 10.5 and 0.0005 to 0.0032 respectively with increase in filler content from 0 to 0.50 volume fractions. The thermal stability of the relative permittivity of polymer ceramic composites was also investigated. The experimentally observed relative permittivity was compared with theoretical models. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) compositesPOLYMER INTERNATIONAL, Issue 6 2010Lijie Dong Abstract Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (,) of 165 and a low dielectric loss (tan ,) of 0.03 at 103 Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d33) of PZT/PVDF composites can be up to ca 100 pC N,1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high-efficiency capacitors and as novel piezoelectric materials. Copyright © 2010 Society of Chemical Industry [source] An impedance spectroscopy study in poly(butylene adipate) ionomersANNALEN DER PHYSIK, Issue 10 2004F. Yakuphanoglu Abstract Poly(butylenes adipate) ionomers (PBAi) were synthesized using dimethyl 5-sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. We have investigated electrical and dielectric properties of the ionomers to evaluate alternating current (AC) parameters such as impedance, conductance, dielectric constant, admittance, susceptance, dielectric loss, and resistance by an impedance spectroscopy. It is seen that the ionic conductances of the ionomers increase with increasing content of DMSI. The AC conductance for the ionomers was found to vary as ,s with the index s , 1. A decrease in the relative dielectric constant of the ionomers is observed with the increase in the ionic content. The electrical relaxation in the dielectric spectra of the ionomers was not observed due to the orientation polarization of the dipoles. It is also observed that the tangent loss increases with the increase in the ionic content. [source] Effects of Rare-Earth Dopants on the Ferroelectric and Pyroelectric Properties of Strontium Barium Niobate CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2009Yingbang Yao Effects of various rare-earth (RE) dopants (Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tm3+, Dy3+, Er3+, and Yb3+) on the dielectric, ferroelectric, and pyroelectric properties of Sr0.5Ba0.5Nb2O6 (SBN50) ceramics were investigated. In the present studies, the doping concentrations of all the RE dopants were fixed at 1 mol%. Their potential usefulness in pyroelectric applications was discussed based on their measured pyroelectric detectivity figure of merit (FOM). On the basis of our studies, for RE dopants with atomic numbers smaller than Nd, their dielectric constants were greatly increased, while for RE dopants with atomic numbers larger than Sm, their dielectric constants as well as dielectric losses became smaller. Among various dopants, Eu-doped SBN showed the most improved ferroelectric properties. Its remnant polarization (Pr) was increased to 4.86 ,C/cm2 as compared with 3.23 ,C/cm2 obtained in undoped SBN50. On the other hand, Gd-doped SBN exhibited the largest pyroelectric coefficient of 168 ,C/m2 K, which was over three times of that of the undoped sample (49 ,C/m2 K). The work shows that Gd-doped SBN exhibits the greatest potential for pyro-applications because it bears the largest FOM of 0.45 × 10,5 Pa,0.5 [Correction: After online publication on 11/05/2008, an error was found in this article. The original value, 1.35×10,5 Pa,0.5, was incorrect. The data has been replaced with the correct value.]. [source] Accurate substrate modelling of RF CMOSINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2006M. S. Alam Abstract The losses within the substrate of an RF IC can have significant effect on performance in a mixed signal application. In order to model substrate coupling accurately, it is represented by an RC network to account for both resistive and dielectric losses at high frequency (> 1 GHz). A small-signal equivalent circuit model of an RF IC inclusive of substrate parasitic effect is analysed in terms of its y -parameters and an extraction procedure for substrate parameters has been developed. By coupling the extracted substrate parameters along with extrinsic resistances associated with gate, source and drain, a standard BSIM3 model has been extended for RF applications. The new model exhibits a significant improvement in prediction of output reflection coefficient S22 in the frequency range from 1 to 10 GHz in device mode of operation and for a low noise amplifier (LNA) at 2.4 GHz. Copyright © 2006 John Wiley & Sons, Ltd. [source] Noise in lossless microwave multiportsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2004Q. García-García Abstract This article addresses the noise behaviour (noise temperature and noise figure) of some passive microwave multiport circuits. The analysis method is based on the noise-wave formulation. With the exception of the attenuator case, which is used as a reference, the circuit elements considered are lossless devices, in the sense that neither conductive nor dielectric losses are accounted for. The analysis shows that, when connected to matched loads in some of their ports, these multiports circuits lose their lossless nature and their scattering matrix is not unitary; therefore, they generate thermal noise. The article addresses and formalizes mathematically the noise properties of a number of lossless microwave devices such as N -port power splitters, circulators, and hybrid couplers. While the noise-wave mathematical formulation may be cumbersome in some cases, all the devices and configurations analyzed in this work have been characterized in terms of noise figure and noise temperature, which is a much more practical approach in most situations. Some implications of the use of these devices and configurations in antenna arrays for antenna noise temperature evaluations have been also addressed. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 99,110, 2004. [source] Analysis of Infrared Reflection Spectra of (Mg1,xZnx)Al2O4 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Chang Wei Zheng Infrared reflection spectra of (Mg1,xZnx)Al2O4 ceramics were analyzed by Kramers,Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. According to structure analysis, the losses originating from bend vibration and stretch vibration of the bond between A-site cation and oxygen anion dominated the whole dielectric losses of the spinel ceramics. The coexistence of Mg and Zn deteriorated the intrinsic dielectric properties due to the bond asymmetry thus introduced. The calculated Qf (,105 GHz) was much higher than the measured ones (,104 GHz), suggesting that the extrinsic loss was significant. Therefore, the microwave dielectric properties of MgAl2O4 and ZnAl2O4 could be improved much by microstructure modification, and the little superiority in their solution compared with the end-members was due to microstructure improvement. [source] Electric Field-Dependent Dielectric Properties and High Tunability of Porous Ba0.5Sr0.5TiO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Yuanyuan Zhang Porous Ba0.5Sr0.5TiO3 (BST) ceramics were fabricated by the traditional solid-state reaction process, and their structural, microstructural, dielectric, and tunability properties were systemically investigated. Compared with the fully dense BST samples, porous samples exhibit smaller grain sizes, a more uniform microstructure, and much lower dielectric constants, while at the same time, exhibiting little increase in tunability, which is beneficial to the development of microwave-tunable applications. At a frequency of 10 kHz and a temperature of 18°C, as porosity increased from 0% to 28.8%, the dielectric constant of the BST ceramics (under zero bias field) decreased from ,r(0),1690 to ,r(0),990, while the dielectric losses were still less than 0.2%, and the tunability increased from 17.6% to 19.6% (2.6 kV/mm). [source] Intrinsic Elastic, Dielectric, and Piezoelectric Losses in Lead Zirconate Titanate Ceramics Determined by an Immittance-Fitting MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Takaaki Tsurumi The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ,50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses. [source] | ||||||||||||||||||||||||||||