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Dielectric Characteristics (dielectric + characteristic)
Kinds of Dielectric Characteristics Selected AbstractsDielectric Characteristics for Radio Frequency Waves in a Laboratory Dipole PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2006N. I. Grishanov Abstract Transverse and parallel dielectric permittivity elements have been derived for radio frequency waves in a laboratory dipole magnetic field plasma. Vlasov equation is resolved for both the trapped and untrapped particles as a boundary value problem to define their separate contributions to the dielectric tensor components. To estimate the wave power absorbed in the plasma volume the perturbed electric field and current density components are decomposed in a Fourier series over the poloidal angle. In this case, the dielectric characteristics can be analyzed independently of the solution of the Maxwell's equations. As usual, imaginary part of the parallel permittivity elements is necessary to estimate the electron Landau damping of radio frequency waves, whereas imaginary part of the transverse permittivity elements is important to estimate the wave dissipation by the cyclotron resonances. Computations of the imaginary part of the parallel permittivity elements are carried out in a wide range of the wave frequencies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of A-Site Ionic Radius on the Structure and Microwave Dielectric Characteristics of Sr1+xSm1,xAl1,xTixO4 CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010Min Min Mao SrSmAlO4 microwave dielectric ceramics were modified by Sr/Ti cosubstitution for Sm/Al. The effects of radius difference of A-site ions on the microwave dielectric characteristics were investigated together with the structure. Sr1+xSm1,xAl1,xTixO4 (x=0, 0.05, 0.10, and 0.15) ceramics were prepared by a solid-state reaction approach. X-ray diffraction studies revealed a single-phase K2NiF4 -type solid solution with corresponding peaks shifting to lower 2, as x increased. Minor inhomogeneous grain morphology for x=0.05 and a trace amount of second phases for x=0.10, 0.15 were detected by backscattered-electron microscopy and energy-dispersive X-ray analysis. With increasing Sr/Ti cosubstitution, the dielectric constant ,r increased from 18.4 to 20.4, and the temperature coefficient of resonant frequency ,f was adjusted from ,1.8 to 7.4 ppm/°C almost linearly. However, the Q×f value decreased from 74,500 GHz at x=0,53,000 GHz at x=0.15. The internal stresses caused by the decreased tolerance factor and the large ionic radii difference between Sr2+ and Sm3+ should be the predominant reasons for such a decrease in the Q×f value. The high-resolution transmission electron microscopic results revealed an increase in the lattice distortion with increasing Sr/Ti cosubstitution, and subsequently supported the above conclusion upon the increased internal stresses. [source] Effects of Ca/Ti Cosubstitution upon Microwave Dielectric Characteristics of CaSmAlO4 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009Xie Cheng Fan (Ca1+xSm1,x)(Al1,xTix)O4 (0,x,0.4) ceramics were synthesized by solid-state reaction method and their microstructures and microwave dielectric properties were investigated. X-ray diffraction analysis and energy-dispersive X-ray analysis indicated that the matrix phase was a solid solution with a composition represented by the chemical formula (Ca1+xSm1,x) (Al1,xTix)O4 and minor amount of (Ca,Sm)(Al,Ti)O3 secondary phase was detected. Ca/Ti cosubstitution could significantly improve the microwave dielectric characteristics of CaSmAlO4 ceramics, and the excellent microwave dielectric characteristics were obtained in the modified ceramics as ,r=19,23, Q×f=49 100,118 700 GHz, and ,f=,15,15 ppm/°C. [source] Cation Ordering and Dielectric Characteristics in Barium Zinc NiobateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007Chun-Te Lee Barium zinc niobate (Ba(Zn1/3Nb2/3)O3) (BZN) complex perovskite has been reported to have special microwave dielectric properties with close relation of its ordered structure. This study investigated the effect of calcination on the evolution of ordered structure and on quality factor with Raman spectroscopy, X-ray diffractometry, and transmission electron microscopy. The results revealed that single calcination at a lower temperature inhibited the growth of the ordered domain during sintering. In contrast, the 1:2-ordered domain in double-calcined BZN powder grew significantly with a higher sintering temperature and a longer soaking time. It is attributed that double calcination caused a higher degree of 1:2 ordering and better homogeneity. At the same time, the quality factor of the sintered ceramic body was highly promoted when using double-calcined powder. A close relation of the quality factor with the size of ordered domain, the degree of 1:2 ordering, and the relative density of BZN ceramics was presented. [source] Structural and Dielectric Characteristics of Barium Lanthanum Zinc NiobateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Chun-Te Lee The dielectric properties and microstructural characteristics in solid solutions of Ba1,xLax[Zn(1+x)/3Nb(2,x)/3]O3 (BLZN) are investigated by measuring and observing these properties, respectively, by means of transmission electron microscopy and Raman spectroscopy. The 1:1 ordered structure of BLZN can be explained by the random-site model for the distribution of B-site cations. The decrease in the tolerance factor (t) by lanthanum substitution causes the tilting of oxygen octahedra. It appears that the onset of antiphase and inphase tilting causes the variation in the temperature coefficient of resonant frequency (,f). In the untilted region where t,1.01, the ,f shows a linear increase with decreasing tolerance factor. The region of antiphase tilting, where 0.965,t<1.01, causes a rapid decrease in ,f, including the reverse sign. The ,f slowly increases, where t<0.965, which is due to the presence of inphase tilting of oxygen octahedra. The ,f can be predicted by using the tolerance factor, and the near zero of ,f can be obtained with lanthanum substitution in the solid solution of the BLZN system. [source] Synthesis and Dielectric Characteristics of the Layered Structure Bi4-xLnxTi3O12 (Ln: Pr, Nd, Gd, Dy).CHEMINFORM, Issue 22 2003Jose L. Pineda-Flores Abstract For Abstract see ChemInform Abstract in Full Text. [source] Dielectric Characteristics for Radio Frequency Waves in a Laboratory Dipole PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2006N. I. Grishanov Abstract Transverse and parallel dielectric permittivity elements have been derived for radio frequency waves in a laboratory dipole magnetic field plasma. Vlasov equation is resolved for both the trapped and untrapped particles as a boundary value problem to define their separate contributions to the dielectric tensor components. To estimate the wave power absorbed in the plasma volume the perturbed electric field and current density components are decomposed in a Fourier series over the poloidal angle. In this case, the dielectric characteristics can be analyzed independently of the solution of the Maxwell's equations. As usual, imaginary part of the parallel permittivity elements is necessary to estimate the electron Landau damping of radio frequency waves, whereas imaginary part of the transverse permittivity elements is important to estimate the wave dissipation by the cyclotron resonances. Computations of the imaginary part of the parallel permittivity elements are carried out in a wide range of the wave frequencies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of A-Site Ionic Radius on the Structure and Microwave Dielectric Characteristics of Sr1+xSm1,xAl1,xTixO4 CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010Min Min Mao SrSmAlO4 microwave dielectric ceramics were modified by Sr/Ti cosubstitution for Sm/Al. The effects of radius difference of A-site ions on the microwave dielectric characteristics were investigated together with the structure. Sr1+xSm1,xAl1,xTixO4 (x=0, 0.05, 0.10, and 0.15) ceramics were prepared by a solid-state reaction approach. X-ray diffraction studies revealed a single-phase K2NiF4 -type solid solution with corresponding peaks shifting to lower 2, as x increased. Minor inhomogeneous grain morphology for x=0.05 and a trace amount of second phases for x=0.10, 0.15 were detected by backscattered-electron microscopy and energy-dispersive X-ray analysis. With increasing Sr/Ti cosubstitution, the dielectric constant ,r increased from 18.4 to 20.4, and the temperature coefficient of resonant frequency ,f was adjusted from ,1.8 to 7.4 ppm/°C almost linearly. However, the Q×f value decreased from 74,500 GHz at x=0,53,000 GHz at x=0.15. The internal stresses caused by the decreased tolerance factor and the large ionic radii difference between Sr2+ and Sm3+ should be the predominant reasons for such a decrease in the Q×f value. The high-resolution transmission electron microscopic results revealed an increase in the lattice distortion with increasing Sr/Ti cosubstitution, and subsequently supported the above conclusion upon the increased internal stresses. [source] Fabrication and Tunable Dielectric Properties of (Ba0.7Sr0.3)TiO3 -Glass-Based Thick-Film CapacitorsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009Pulipparambil 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] Effects of Ca/Ti Cosubstitution upon Microwave Dielectric Characteristics of CaSmAlO4 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009Xie Cheng Fan (Ca1+xSm1,x)(Al1,xTix)O4 (0,x,0.4) ceramics were synthesized by solid-state reaction method and their microstructures and microwave dielectric properties were investigated. X-ray diffraction analysis and energy-dispersive X-ray analysis indicated that the matrix phase was a solid solution with a composition represented by the chemical formula (Ca1+xSm1,x) (Al1,xTix)O4 and minor amount of (Ca,Sm)(Al,Ti)O3 secondary phase was detected. Ca/Ti cosubstitution could significantly improve the microwave dielectric characteristics of CaSmAlO4 ceramics, and the excellent microwave dielectric characteristics were obtained in the modified ceramics as ,r=19,23, Q×f=49 100,118 700 GHz, and ,f=,15,15 ppm/°C. [source] Influence of Copper(II) Oxide Additions to Zinc Niobate Microwave Ceramics on Sintering Temperature and Dielectric PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2001Dong-Wan Kim The effect of CuO additions on the firing temperature of ZnNb2O6 ceramics was investigated using dilatometry, transmission electron microscopy, and X-ray diffractometry. A 5 wt% CuO addition to ZnNb2O6 ceramics significantly lowered the firing temperature from 1150° to ,900°C. The presence of a CuO-rich intergranular phase in the specimen was observed and was evidence of the formation of a liquid phase during sintering. The composition of the liquid phase was (ZnCu2)Nb2O8. In particular, the low-fired ZnNb2O6 ceramics had good microwave dielectric characteristics,Q×f= 59 500, ,r= 22.1, ,f=,66 ppm/oC. These properties were correlated with the formation of a second phase, (ZnCu2)Nb2O8. [source] Preparation of Ba6,3xNd8+2xTi18O54 via Ethylenediaminetetraacetic Acid PrecursorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Yebin Xu Ba6,3xNd8+2xTi18O54 ceramic powders were synthesized by the modified Pechini method using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. A purplish red, molecular-level, homogeneously mixed gel was prepared, and transferred into a porous resin intermediate through charring. Single-phase and well-crystallized Ba6,3xNd8+2xTi18O54 powders were obtained from pulverized resin at a temperature of 900°C for 3 h, without formation of any intermediate phases. Meanwhile, the molar ratio of EDTA to total metal cation concentration had a significant influence on the crystallization behavior of Ba6,3xNd8+2xTi18O54. The Ba6,3xNd8+2xTi18O54 (x= 2/3) ceramics prepared via EDTA precursor have excellent microwave dielectric characteristics: ,= 87, Qf= 8710 GHz. [source] Formation of Nanostructures in Multi Component Systems Based on Organic Polymer and Coordination Metal CompoundMACROMOLECULAR SYMPOSIA, Issue 1 2006Nataly Kozak Abstract Structuring of polyurethane (PU) networks is analyzed under influence of transition metal coordination compounds: mono-ionic ,-diketonates and polyheteronuclear metal-organic complexes. Formed in situ nanostructures both organic and inorganic were found in organic polymer modified with coordination metal compound. Influence of coordination junction point spatial symmetry and content of metal ion in modifier on structure and dielectric characteristics of modified PUs is analyzed using X-ray, EPR, SEM and transmission optical microscopy, DRS and DSC methods. [source] Bulk and patch ferrite resonator antennas based on the ceramic matrix composite: GdIGx YIG1- xMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009P. B. A. Fechine Abstract In this study, the dielectric properties of the GdIGXYIG1,X ferrite composite material at radio frequency (RF) and microwave frequency bands were studied. These measurements were carried out in different sample geometries: thick films and cylindrical ceramic bulk ferrite resonator. In the RF range, we observed that the material is rather stable because of its short changes as a function of temperature and frequency range. The temperature capacitance coefficient values for all the samples (thick films and cylindrical ceramic bulk samples) presented short positive values at the RF range. The GdIG0.5YIG0.5 thick film was used as a substrate for the microstrip antenna device, where the upper Ag electrode served as a circular patch antenna and a microstrip line was used as a feed line. The microstrip antenna operates in this configuration at 8.185 GHz. In the study of the dielectric properties of the composites antenna geometry, with the same ferrite composite, a bulk cylindrical geometry was investigated. A numerical study, together with the experimental, was done, and the dielectric characteristics of the composite like ,r, tg,E, and ,r were obtained. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1595,1602, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24395 [source] | ||||||||||