Dielectric Properties (dielectric + property)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Dielectric Properties

  • good microwave dielectric property
  • microwave dielectric property


  • Selected Abstracts


    Dielectric Properties of a Printed Sol,Gel Matrix Composite,

    ADVANCED ENGINEERING MATERIALS, Issue 5 2010
    Tobias Lehnert
    Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol,gel derived network. The exemplary optimization of the properties by varying the sol,gel precursor illustrates the potential of sol,gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response. [source]


    Microwave Dielectric Properties of SrO,2CeO2,nTiO2 (n=4 and 5) Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010
    Ramachandran Satheesh
    SrO,2CeO2,nTiO2 ceramics with n=4 and 5 have been prepared through conventional solid-state ceramic route. Structural and microstructural characterizations of the sintered ceramics were carried out using X-ray diffraction, laser Raman, and scanning electron microscopic studies. Microwave dielectric properties have been measured using postresonator and resonant cavity techniques. SrO,2CeO2,4TiO2 and SrO,2CeO2,5TiO2 ceramics showed dielectric constants of 71.3 and 71.7, respectively, around 4 GHz together with a relatively high unloaded quality factor. [source]


    Synthesis and Dielectric Properties of Niobia Coating on BaTiO3

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2009
    Jia-Jia Gan
    Different from conventional powder mixing, this study demonstrates a method of homogeneous coating for niobia (Nb2O5) on ferroelectric barium titanate (BaTiO3) powders. The precipitation of Nb coating with pH has been determined quantitatively by the inductance-coupled plasma method. Crystalline phases were determined by X-ray diffractometry, and the formation of a "core-shell" structure with a Nb concentration gradient was observed by a transmission electron microscope with X-ray energy-dispersive spectroscopy. The dielectric constant (K) of the samples prepared by the nanocoating method showed a more stable temperature coefficient of capacitance and well satisfied the requirements of X7R. [source]


    The Effect of Dopants on the Dielectric Properties of Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) Microwave Ceramics

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2009
    Lamrat Abdul Khalam
    Low-loss dielectric ceramics based on Ba(B,1/2Ta1/2)O3 (B,=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In) complex perovskites have been prepared by the solid-state ceramic route. The dielectric properties (,r, Qu, and ,f) of the ceramics have been measured in the frequency range 4,6 GHz by the resonance method. The resonators have a relatively high dielectric constant and high quality factor. Most of the compounds have a low coefficient of temperature variation of the resonant frequencies. The microwave dielectric properties have been improved by the addition of dopants and by solid solution formation. The solid solution Ba[(Y1,xPrx)1/2Ta1/2]O3 has x=0.15, with ,r=33.2, Quf=51,500 GHz, and ,f,0. The microwave dielectric properties of Ba(B,1/2Ta1/2)O3 ceramics are found to depend on the tolerance factor (t), ionic radius, and ionization energy. [source]


    Tape Casting and Dielectric Properties of Zn2Te3O8 -Based Ceramics with an Ultra-Low Sintering Temperature

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009
    Johanna Honkamo
    The suitability of dielectric ceramics made of zinc tellurate (Zn2Te3O8) and titanium dioxide (TiO2) with an ultra-low sintering temperature (650C) for tape casting and thus for the multimodule technique with Al electrodes was investigated. The properties of the tape before and after sintering as well as the amount of organic additives for the casting process and a thermal analysis of the tape up to 1000C are reported. In addition, electrodes on a multilayer module made on stacked tapes were prepared using Al paste and postfiring, followed by relative permittivity and loss tangent measurements to verify the electrical performance of the whole structure. The dielectric properties of the stacked module without any electrodes were also measured. The results show that the composition is well suited for the tape process but extra care should be taken especially with the proper sintering temperature for optimized electrical performance. [source]


    Fabrication and Tunable Dielectric Properties of (Ba0.7Sr0.3)TiO3 -Glass-Based Thick-Film Capacitors

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009
    Pulipparambil Vasu Divya
    Ferroelectric glass,ceramics of composition 0.90 (Ba0.7Sr0.3) TiO3,0.10(B2O3:SiO2) (0.90 BST:0.10 BS) synthesized by sol,gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass,ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass,ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm. [source]


    Effect of Bismuth Borate/LiF on the Sintering, Thermal, and Microwave Dielectric Properties of Ba6,3xSm8+2xTi18O54 (x=2/3) Solid Solution

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008
    Narayana Iyer Santha
    Ba6,3xSm8+2xTi18O54 (x=2/3) (BST) was prepared by the solid-state method and the effect of bismuth borate (BB)/LiF on the sinterability, microstructure, and thermal and microwave dielectric properties were studied. BST+3.5 wt% BB+0.5 wt% LiF composite sintered at 1050C has Qf=4500 GHz, ,=52, and ,f=+6 ppm/C. Raman spectrum of the composite was compared with that of BST and the structural changes were investigated. [source]


    Low-Temperature Firing and Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, Ceramics with ZnB2O4 Glass Addition

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008
    Li-Xia Pang
    Low-temperature sintered Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, microwave dielectric ceramics with ZnB2O4 glass (ZBG) addition were prepared by the conventional solid state reaction method. The sintering behavior, microstructure, and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics with ZBG addition were investigated. The ZBG addition lowered the densified temperature of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics from 1150C to 940C. The dielectric constants of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics decreased from 40 to 34 and the temperature coefficient of resonant frequency (,f) changed gradually from +12.7 to ,25.7 ppm/C as ZBG addition increased from 0 to 8 wt%. The Qf values increased greatly from 20,500 GHz of pure Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, to 26,900 GHz when 5 wt% ZBG was added. Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, ceramics with 8 wt% ZBG addition sintered at 940C show good microwave dielectric properties with ,r,32.5, Qf,20,600 GHz, and ,f,,25.7 ppm/C. The relationship between dielectric properties and microstructure was also discussed. [source]


    Effect of Temperature (,5 to 130 C) and Fiber Direction on the Dielectric Properties of Beef Semitendinosus at Radio Frequency and Microwave Frequencies

    JOURNAL OF FOOD SCIENCE, Issue 6 2008
    N. Basaran-Akgul
    ABSTRACT:, The dielectric properties must be defined to design efficient radio frequency (RF) and microwave (MW) processes by the food manufacturers. The objective of this study was to understand how frequency, temperature, and muscle fiber orientation influence the dielectric properties. The eye of round (Semitendinosus) muscle was selected because it contains large, relatively uniform muscle cells with similar muscle fiber orientation and relatively uniform chemical composition throughout the tissue. Dielectric properties were measured using an open-ended coaxial probe technique at 27, 915, and 1800 MHz and temperatures between ,5 and 130 C. Power penetration depth was calculated. Since many commercially prepared, thermally processed, ready-to-eat entrees are made with frozen meat, dielectric property measurements were started from ,5 C. The dielectric constant and dielectric loss factors were often higher for muscle with the muscle fiber measured in a parallel orientation to the probe compared to samples of the same treatment (for example, fresh or frozen) in a perpendicular tissue orientation at the same frequency and temperature. Dielectric constant and loss values for frozen beef tended to be higher than fresh beef at the same temperature and frequency. Tissue orientation appeared to have a greater effect on dielectric loss values at lower frequencies. Penetration depth tended to be greater when the direction of propagation was perpendicular to the muscle fiber. [source]


    Predictive Equations for Dielectric Properties of NaCl, D-sorbitol and Sucrose Solutions and Surimi at 2450 MHz

    JOURNAL OF FOOD SCIENCE, Issue 6 2002
    P. Yaghmaee And
    ABSTRACT: Variation in dielectric properties of aqueous solutions with different concentrations and ratios of NaCl, D-sorbitol, and sucrose were investigated at 21 C using the open-ended coaxial probe technique at 2450 MHz. Several equations to estimate dielectric properties of mixed or pure solutions were formulated. The equations were tested with other concentrations of solutions and surimi as a food sample containing the solutes. The correlation between the new measured dielectric properties and the calculated values were analyzed using a General Linear Model. The resultant prediction equations are suitable for pure and mixed aqueous solutions of (0 to 6%) NaCl, (0 to 18%) D-sorbitol and (0 to 60%) sucrose. For surimi, only loss factor was successfully predicted. [source]


    Microstructure and Microwave Dielectric Properties of xCa(Al0.5Nb0.5)O3+(1,x)SrTiO3 Solid Solutions

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
    Mingzhe Hu
    The crystal structure evolution and microwave (MW) dielectric properties of xCa(Al0.5Nb0.5)O3+(1,x)SrTiO3 (xCAN+(1,x)ST, 0,x,1.0, ) dielectric ceramics were investigated. X-ray diffraction patterns illustrated that a single perovskite solid solution could be formed between the two end members; however, minor amount of pyrochlore phase was also detected in the composition range of 0.5,x,0.9. With the increase of x value, the crystal structure gradually evolved from a simple Pm3m cubic to a monoclinic P21/n space group with the octahedral tilting and the B-site ordering structure transition subsequently developed. The MW dielectric properties of xCAN+(1,x)ST solid solutions were elaborately investigated and correlated to their crystal structures. The microscopic structure-related thermal parameters in the xCAN+(1,x)ST solid solution were analyzed in terms of the Claussius,Mossotti equation to reveal the original contributors in temperature coefficients. Temperature coefficient-compensated ceramic could be obtained in the xCAN+(1,x)ST system in the range of 0.5[source]


    Improved Dielectric Properties of Bi1.5Zn1.0Nb1.5O7/(111)-Oriented Ba0.6Sr0.4TiO3 Bilayered Films for Tunable Microwave Applications

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010
    Lihui 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 Films

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010
    Xihong 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]


    Microwave Dielectric Properties of Ba3(VO4)2,Mg2SiO4 Composite Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010
    Siqin Meng
    Novel Ba3(VO4)2,Mg2SiO4 microwave dielectric composite ceramics with compositions of (1,x)Ba3(VO4)2,xMg2SiO4 (x=0.50,0.65) have been prepared by firing mixtures of Ba3(VO4)2 and Mg2SiO4. X-ray diffraction and scanning electron microscopy analysis revealed that they coexist without forming secondary phases. Because their resonant frequency temperature coefficients (,f) have opposite signs, the ,f of the composite ceramic can be adjusted passing through zero by changing the relative content of the two phases. Dielectric property measurements were performed using the resonator method at around 11 GHz. Ceramics with Mg2SiO4 55 wt% sintered at 1175C exhibited microwave dielectric properties of dielectric constant ,r=9.03, Qf=52 500 GHz, and ,f=0.6 ppm/C at 11.3 GHz. In this composite ceramic, we observed that the formation of the MgSiO3 secondary phase was suppressed. [source]


    Synthesis, Crystal Structure, and Microwave Dielectric Properties of (Mg1,xCox)Ta2O6 Solid Solutions

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010
    Cheng-Liang Huang
    High-dielectric-constant and low-loss ceramics in the (Mg1,xCox)Ta2O6 solid solutions have been prepared using the conventional mixed oxide route and their microwave dielectric properties have been investigated. The X-ray diffraction patterns as well as the measured lattice parameters indicated the (Mg1,xCox)Ta2O6 ceramics tended to form a complete solid solution with a trirutile structure. In comparison with that of simple MgTa2O6, an enhanced grain growth can be achieved by substituting Mg with 0.05 mol% Co. It also leads to an increase in both the ,r and Qf values of the ceramics. The specimen with x=0.05 possessed a combination of microwave dielectric properties: ,r,30.67, the Qf,106 200 GHz, and ,f,42.9 ppm/C. [source]


    Microwave Dielectric Properties of SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
    Sherin Thomas
    The apatite type SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics have been prepared by the conventional solid-state ceramic route. The phase purity and surface morphology of the sintered ceramics were studied using X-ray diffraction and scanning electron microscopy methods. These materials showed poor sinterability and was improved by the addition of a small weight percentage of zinc borosilicate glass. The microwave dielectric properties of these materials were studied for the first time. SrRE4Si3O13 ceramics have a low relative permittivity (,r) in the range 9,16, a Q-factor (Quf) upto 26 000 GHz and a low temperature coefficient of resonant frequency (,f). The SrLa4Si3O13 ceramics possessed a high Quf of nearly 26 000 GHz but with a high negative ,f of ,46 ppm/C. The ,f of SrLa4Si3O13 ceramics was tuned by the addition of suitable amount of TiO2. [source]


    Formation Process and Microwave Dielectric Properties of the R2V2O7 (R=Ba, Sr, and Ca) Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
    Mi-Ri Joung
    Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300,500C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600,700C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000 and 950C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ,r=10.4,12.1, Qf=15 200,19 520 GHz, and ,f=,30.9,34.8 ppm/C. However, the Ba2V2O7 ceramic was well sintered at 900C for 10 h and it showed the good microwave dielectric properties of ,r=10.1, Qf=51 630 GHz, and ,f=,26.5 ppm/C. [source]


    Processing Conditions and Aging Effect on the Morphology of PZT Electrospun Nanofibers, and Dielectric Properties of the Resulting 3,3 PZT/Polymer Composite

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009
    Ebru Mensur Alkoy
    Lead zirconate titanate (PZT) nanofibers are obtained by electrospinning a sol,gel based solution and polyvinyl pyrrolidone (PVP) polymer, and by subsequent sintering of the electrospun precursor fibers. The average diameter of the precursor PZT/PVP green fibers has increased with the aging of the precursor solution along with an increase in the viscosity. Bead-free uniform green PZT/PVP fibers were collected at about an ,230 nm average fiber diameter using a 28 wt% PVP ratio solution with a viscosity of 290 mPa. Shrinkage of 40% was recorded on the fiber diameter after sintering. The X-ray diffraction pattern of the annealed PZT fibers exhibits no preferred orientation and a perovskite phase. Preparation of 3,3 nanocomposites by the infusion of polyvinylester into the nanofiber mat facilitates successful handling of the fragile mats and enables measurements of the dielectric properties. The dielectric constant of the PZT/polyvinylester nanocomposite of about 10% fiber volume fraction was found to be fairly stable and vary from 72 to 62 within the measurement range. The dielectric loss of the composite is below 0.08 at low frequencies and reaches a stable value of 0.04 for most of the measured frequencies. [source]


    Sintering and Microwave Dielectric Properties of the LiNb0.63Ti0.4625O3 Ceramics with the B2O3,SiO2 Liquid-Phase Additives

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009
    Yanping Long
    The effect of B2O3,SiO2 liquid-phase additives on the sintering, microstructure, and microwave dielectric properties of LiNb0.63Ti0.4625O3 ceramics was investigated. It was found that the sintering temperature could be lowered easily, and the densification and dielectric properties of LiNb0.63Ti0.4625O3 ceramics could be greatly improved by adding a small amount of B2O3,SiO2 solution additives. No secondary phase was observed for the ceramics with B2O3,SiO2 additives. With the addition of 0.10 wt% B2O3,SiO2, the ceramics sintered at 900C showed favorable microwave dielectric properties with ,r=71.7, Qf=4950 GHz, and ,f=,2.1 ppm/C. The energy dispersive spectra analysis showed an excellent co-firing interfacial behavior between the LiNb0.63Ti0.4625O3 ceramic and the Ag electrode. It indicated that LiNb0.63Ti0.4625O3 ceramics with B2O3,SiO2 solution additives have a number of potential applications on passive integrated devices based on the low-temperature co-fired ceramics technology. [source]


    Low-Temperature Sintering and Microwave Dielectric Properties of Li2MgSiO4 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2009
    Sumesh George
    Development of a low-temperature sintered dielectric material derived from Li2MgSiO4 (LMS) for low-temperature cofired ceramic (LTCC) application is discussed in this paper. The LMS ceramics were prepared by the solid-state ceramic route. The calcination and sintering temperatures of LMS were optimized at 850C/4 h and 1250C/2 h, respectively, for the best density and dielectric properties. The crystal structure and microstructure of the ceramic were studied by the X-ray diffraction and scanning electron microscopic methods. The microwave dielectric properties of the ceramic were measured by the cavity perturbation method. The LMS sintered at 1250C/2 h had ,r=5.1 and tan ,=5.2 10,4 at 8 GHz. The sintering temperature of LMS is lowered from 1250C/2 h to 850C/2 h by the addition of both lithium borosilicate (LBS) and lithium magnesium zinc borosilicate (LMZBS) glasses. LMS mixed with 1 wt% LBS sintered at 925C/2 h had ,r=5.5 and tan ,=7 10,5 at 8 GHz. Two weight percent LMZBS mixed with LMS sintered at 875C/2 h had ,r=5.9 and tan ,=6.7 10,5 at 8 GHz. [source]


    Synthesis and Microwave Dielectric Properties of Bi4(SiO4)3 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008
    Jin-Seong Kim
    Bi4(SiO4)3 ceramics were synthesized and their microwave dielectric properties were investigated. The Bi12SiO20 second phase was formed at approximately 400C, while the Bi2O2SiO3 and Bi4(SiO4)3 phases started to form at 600C. The amount of the Bi12SiO20 and Bi2O2SiO3 second phases decreased as the firing temperature exceeded 650C. A homogeneous Bi4(SiO4)3 phase was obtained for the specimen fired at 850C. For the specimens sintered at 900C for more than 5 h, high-density Bi4(SiO4)3 ceramics were obtained. In particular, the Bi4(SiO4)3 ceramics sintered at 900C for 8 h exhibited the good microwave dielectric properties of ,r=14.9, Q f=36 101 GHz and ,f=,9.42 ppm/C. [source]


    MgTiO3 and Ba0.60Sr0.40Mg0.15Ti0.85O3 Composite Thin Films with Promising Dielectric Properties for Tunable Applications

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008
    Lina Gao
    Mg2TiO4 -doped Ba0.60Sr0.40Mg0.15Ti0.85O3 (BSTM) thin films with different Mg2TiO4 concentrations were deposited on a polycrystalline alumina substrate via the sol,gel method. With the addition of Mg2TiO4, MgTiO3, MgAl2O4, and BSTM phases were formed in these composite thin films. The dielectric loss of the composite thin films decreased about one order of magnitude and the tunability still remained above 15% at a DC-applied electric field of 80 kV/cm. The dielectric constant decreased from 1040 to 388. The low dielectric constant, high tunability, and figure of merit of these composite thin films can be useful for potential tunable devices. [source]


    Effect of Filler Content on the Dielectric Properties of PTFE/ZnAl2O4,TiO2 Composites

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008
    Sherin 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 25,70C 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 Films

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008
    Ling 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]


    Microwave Dielectric Properties of A-Site Modified Ba(Co0.7Zn0.3)1/3Nb2/3O3 by La3+

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008
    Jian Jiang Bian
    The sintering behavior, ordering state, and microwave dielectric properties of Ba1,xLa2x/3(Zn0.3Co0.7)1/3Nb2/3O3 Ceramics (0,x,0.06) were investigated in this paper. The X-ray diffraction (XRD) results show that all samples exhibit a single perovskite phase except for the sample with x,0.03. The sinterability is slightly improved by La doping. The long range order (LRO) degree on B-site is greatly increased with the increase of x value up to x=0.015 and then slightly decreased with the further increase of x due to the increasing amount of second phases. The dielectric constant at microwave frequency decreases slightly with the increase of x when x<0.015 and increases slightly with further increasing x for the samples sintered at 1375C/10 h. The Qf value increases with x up to x=0.015 and then decreases with further increase of x, which is consistent with the variation trend of LRO degree. The ,f value decreases slightly with the increase of x up to 0.006, then increases greatly with the further increase of x. An optimized dielectric properties of ,r=34, Qf=63 159, GHz and ,f=5.21 ppm/C were obtained for the x=0.01 sample sintered at 1425C/10 h. [source]


    Effect of Oxygen Partial Pressure During Liquid-Phase Sintering on the Dielectric Properties of 0.9MgTiO3,0.1CaTiO3

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008
    Hee-Kyun Shin
    Microstructural evolution and microwave dielectric properties of liquid-phase-sintered 0.9MgTiO3,0.1CaTiO3 dielectric ceramic material have been investigated as a function of oxygen partial pressure () during sintering. Sintering in a weakly reducing atmosphere (=10,14 atm) generally increased the density, permittivity, quality factor (Qf), and the temperature coefficient of resonance frequency (,f), but further reducing atmosphere down toof 10,14 atm generally decreased Qf and ,f. When the 5 wt% lithium borosilicate glass-added specimen was sintered at 950C and=10,14 atm, it demonstrated a permittivity of 18.8, Qf of 19 000 GHz, and ,f of 10 10,6 K,1. [source]


    Nanopowder Preparation and Dielectric Properties of a Bi2O3,Nb2O5 Binary System Prepared by the High-Energy Ball-Milling Method

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008
    Di Zhou
    The high-energy ball-milling (HEM) method was used to synthesize the compositions of BiNbO4, Bi5Nb3O15, and Bi3NbO7 in a Bi2O3,Nb2O5 binary system. Reagent Bi2O3 and Nb2O5 were chosen as the starting materials. The X-ray diffraction patterns of the three compositions milled for different times were studied. Only the cubic Bi3NbO7 phase, Nb2O5, and amorphous matters were observed in powders after being milled for 10 h. After heating at proper temperatures the amorphous matters disappeared and the proleptic phases of BiNbO4 and Bi5Nb3O15 could be obtained. The Scherrer formula was used to calculate the crystal size and the results of nanopowders are between 10 and 20 nm. The scanning electron microscopy photos of Bi3NbO7 powders showed drastic aggregation, and the particle size was about 100 nm. The dielectric properties of ceramics sintered from the nanopowders prepared by HEM at 100,1 MHz and the microwave region were measured. Bi3NbO7 ceramics showed a good microwave permittivity ,r of about 80 and a Qf of about 300 at 5 GHz. The triclinic phase of BiNbO4 ceramics reached its best properties with ,r=24 and Qf=14 000 GHz at about 8 GHz. [source]


    Electric and Dielectric Properties of Nb-Doped CaCu3Ti4O12 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2007
    Seong-Hyeon Hong
    Pure and Nb-substituted CaCu3Ti4,xNbxO12+x/2 (CCTO, x=0, 0.02, 0.1, 0.2, 0.4) ceramics were prepared by a conventional solid-state sintering, and their electric and dielectric properties were investigated using an impedance analyzer. A single-phase CCTO was obtained up to x=0.2 Nb substitution and the lattice parameter increased with Nb substitution concentration. While the grain size decreased with Nb substitution, the resistivity of the grain boundary decreased. The dielectric constant increased with Nb substitution, and the highest value of ,420 000 was observed in the x=0.2 Nb-substituted specimen at 10 kHz. The obtained electric and dielectric properties in Nb-substituted CCTO were discussed in terms of the internal barrier layer capacitor model, particularly focusing on a ratio of thickness of the grain boundary region to grain size. [source]


    Microwave Dielectric Properties of Sintered Alumina Using Nano-Scaled Powders of , Alumina and TiO2

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007
    Cheng-Liang Huang
    The microstructure and the microwave dielectric properties of nano-scaled , alumina (,-Al2O3) ceramics with various added amounts of nano-scaled TiO2 have been investigated. The sintering temperature of nano-scaled , alumina can be effectively lowered by increasing the TiO2 content. The Qf values of nano-scaled , alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Qf values. The phases of TiO2 and Al2TiO5 co-existed at 1350C, and the maximum Qf value appeared right after the eradication of TiO2 phase at 1400C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Qf value of 680 000 GHz (measured at 14 GHz) for nano-scaled , alumina prepared at 1400C for duration of 4 h. In addition, a very low loss tangent (tan ,) of 2 10,5 was also obtained at 14 GHz. The ,f value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, ,f could be adjusted to near zero by adding 8 wt% TiO2 to , alumina ceramics. A dielectric constant (,r) of 10.81, a high Qf value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (,f) of 1.3 ppm/C were obtained for nano-scaled , alumina with 8 wt% TiO2 sintered at 1350C for 4 h. Sintered ceramic samples were also characterized by X-ray diffraction and scanning electron microscopy. [source]


    Electric Field-Dependent Dielectric Properties and High Tunability of Porous Ba0.5Sr0.5TiO3 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007
    Yuanyuan 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 18C, 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]