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Microwave Dielectric Ceramics (microwave + dielectric_ceramics)
Selected AbstractsHigh Q Microwave Dielectric Ceramics in (Ni1,x Znx)Nb2O6 SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009Sandeep Butee (Ni1,xZnx)Nb2O6, 0,x,1.0, ceramics with >97% density were prepared by a conventional solid-state reaction, followed by sintering at 1200°,1300°C (depending on the value of x). The XRD patterns of the sintered samples (0,x,1.0) revealed single-phase formation with a columbite (Pbcn) structure. The unit cell volume slightly increased with increasing Zn content (x). All the compositions showed high electrical resistivity (,dc=1.6±0.3 × 1011,·cm). The microwave (4,5 GHz) dielectric properties of (Ni1,xZnx)Nb2O6 ceramics exhibited a significant dependence on the Zn content and to some extent on the morphology of the grains. As x was increased from 0 to 1, the average grain size monotonically increased from 7.6 to 21.2 ,m and the microwave dielectric constant (,,r) increased from 23.6 to 26.1, while the quality factors (Qu×f) increased from 18 900 to 103 730 GHz and the temperature coefficient of resonant frequency (,f) increased from ,62 to ,73 ppm/°C. In the present work, we report the highest observed values of Qu×f=103 730 GHz, and ,,r=26.1 for the ZnNb2O6 -sintered ceramics. [source] Cation Ordering and Domain Boundaries in Ca[(Mg1/3Ta2/3)1,xTix]O3 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Mao Sen Fu Cation ordering and domain boundaries in perovskite Ca[(Mg1/3Ta2/3)1,xTix]O3 (x=0.1, 0.2, 0.3) microwave dielectric ceramics were investigated by high-resolution transmission electron microscopy (HRTEM) and Rietveld analysis. The variation of ordering structure with Ti substitution was revealed together with the formation mechanism of ordering domains. When x=0.1, the ceramics were composed of 1:2 and 1:1 ordered domains and a disordered matrix. The 1:2 cation ordering could still exist until x=0.2 but the 1:1 ordering disappeared. Neither 1:2 nor 1:1 cation ordering could exist at x=0.3. The space charge model was used to explain the cation ordering change from 1:2 to 1:1 and then to disorder. A comparison between the space charge model and random layer model was also conducted. HRTEM observations showed an antiphase boundary inclined to the (111)c plane with a projected displacement vector in the ,001,c direction and ferroelastic domain boundaries parallel to the ,100,c direction. [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] 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] Microstrip ring resonator bandpass filters using ceramic substrateMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010Yuan-Bin Chen Abstract The miniaturization of ring bandpass filters by employing high-permittivity ceramic substrates (with respective dielectric constants of 9.7 and 23.5) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high-permittivity ceramics can be used as the substrate for bandpass filters. Moreover, the fundamental characteristics of newly developed compact square-ring resonators have also been described and applied to the design of bandpass filters. In this paper, the designed square-ring resonators structures are simulated using an IE3D simulator. The responses of the fabricated bandpass filters using Al2O3 (,r = 9.7, tan , = 0.000036) and 0.875Mg0.95Zn0.05TiO3 -0.125Ca0.8Sm0.4/3TiO3 (,r = 23.5, tan , = 0.000021) ceramic substrates are designed at the center frequency of 2.4 GHz. This compact size, low loss bandpass filter should be useful in many wireless communication systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 218,220, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24847 [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] Low-Temperature Firing and Microwave Dielectric Properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]O3,, Ceramics with ZnB2O4 Glass AdditionINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008Li-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 1150°C to 940°C. 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 940°C 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] Cation Ordering and Domain Boundaries in Ca[(Mg1/3Ta2/3)1,xTix]O3 Microwave Dielectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Mao Sen Fu Cation ordering and domain boundaries in perovskite Ca[(Mg1/3Ta2/3)1,xTix]O3 (x=0.1, 0.2, 0.3) microwave dielectric ceramics were investigated by high-resolution transmission electron microscopy (HRTEM) and Rietveld analysis. The variation of ordering structure with Ti substitution was revealed together with the formation mechanism of ordering domains. When x=0.1, the ceramics were composed of 1:2 and 1:1 ordered domains and a disordered matrix. The 1:2 cation ordering could still exist until x=0.2 but the 1:1 ordering disappeared. Neither 1:2 nor 1:1 cation ordering could exist at x=0.3. The space charge model was used to explain the cation ordering change from 1:2 to 1:1 and then to disorder. A comparison between the space charge model and random layer model was also conducted. HRTEM observations showed an antiphase boundary inclined to the (111)c plane with a projected displacement vector in the ,001,c direction and ferroelastic domain boundaries parallel to the ,100,c direction. [source] | ||||||||||