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Microwave Dielectrics (microwave + dielectric)
Terms modified by Microwave Dielectrics Selected AbstractsA Novel Temperature-Compensated Microwave Dielectric (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 Ceramics SystemINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2009Chun-Hsu Shen The microstructure and microwave dielectric properties of a (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 ceramics system have been investigated. The system was prepared using a conventional solid-state ceramic route. In order to produce a temperature-stable material, Ca0.6La0.8/3TiO3 was added for a near-zero temperature coefficient (,f). With partial replacement of Mg2+ by Ni2+, the dielectric properties of the (1,x)(Mg0.95Ni0.05)TiO3,xCa0.6La0.8/3TiO3 ceramics can be promoted. The microwave dielectric properties are strongly correlated with the sintering temperature and the composition. An excellent Q × f value of 118,000 GHz can be obtained for the system with x=0.9 at 1325°C. For practical application, a dielectric constant (,r) of 24.61, a Q × f value of 102,000 GHz, and a temperature coefficient of resonant frequency (,f) of ,3.6 ppm/°C for 0.85(Mg0.95Ni0.05)TiO3,0.15Ca0.6La0.8/3TiO3 at 1325°C are proposed. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance. [source] Bi2O3,MoO3 Binary System: An Alternative Ultralow Sintering Temperature Microwave DielectricJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Di Zhou Preparation, phase composition, microwave dielectric properties, and chemical compatibility with silver and aluminum electrodes were investigated on a series of single-phase compounds in the Bi2O3,MoO3 binary system. All materials have ultralow sintering temperatures <820°C. Eight different xBi2O3,(1,x)MoO3 compounds between 0.2,x,0.875 were fabricated and the associated microwave dielectric properties were studied. The ,-Bi2Mo2O9 single phase has a positive temperature coefficient of resonant frequency (TCF) about +31 ppm/°C, with a permittivity ,r=38 and Qf=12 500 GHz at 300 K and at a frequency of 6.3 GHz. The ,-Bi2Mo3O12 and ,-Bi2MoO6 compounds both have negative temperature coefficient values of TCF,,215 and ,,114 ppm/°C, with permittivities of ,r=19 and 31, Qf=21 800 and 16 700 GHz at 300 K measured at resonant frequencies of 7.6 and 6.4 GHz, respectively. Through sintering the Bi2O3,2.2MoO3 at 620°C for 2 h, a composite dielectric containing both , and , phase can be obtained with a near-zero temperature coefficient of frequency TCF=,13 ppm/°C and a relative dielectric constant ,r=35, and a large Qf,12 000 GHz is also observed. Owing to the frequent difficulty of thermochemical interactions between low sintering temperature materials and the electrode materials during the cofiring, preliminary investigations are made to determine any major interactions with possible candidate electrode metals, Ag and Al. From the above results, the low sintering temperature, good microwave dielectric properties, chemical compatibility with Al metal electrode, nontoxicity and price advantage of the Bi2O3,MoO3 binary system, all indicate the potential for a new material system with ultralow temperature cofiring for multilayer devices application. [source] Low-Loss Microwave Dielectrics in the Spinel-Structured (Mg1,xNix)Al2O4 Solid SolutionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Cheng-Liang Huang Solid solutions of (Mg1,xNix)Al2O4 (x=0,1) have been prepared using the solid-state reaction method and their dielectric properties were measured at microwave frequencies. Formation of single-phase spinel-structured solid solutions was confirmed by X-ray diffraction analysis throughout the entire compositional range, and the measured lattice parameters varied linearly from 8.0810 Å at x=0 (MgAl2O4) to 8.0445 Å at x=1 (NiAl2O4) leading to a linear decrease in the unit cell volume from 527.71 to 520.59 Å3. The ionic polarizability obtained, however, increased with the increase of x to a maximum at x=0.25 and decreased thereafter. It shows only a small variance in the ,r with Ni substitution for Mg and a maximum ,r of 8.21 was achieved for (Mg0.75Ni0.25)Al2O4 in response to the highest ionic polarizability and relative density. However, the Q×f value can be significantly promoted up to a maximum value of 130 000 GHz (measured at 15.4 GHz) at x=0.25. In addition, substitution of Mg by Ni also helps to decline the ,f value from ,65 ppm/°C at x=0 to ,53.5 ppm/°C at x=0.25. [source] High-Q Microwave Dielectrics in the (Mg1,xCox)2TiO4 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009Cheng-Liang Huang The microwave dielectric properties and the microstructures of (Mg1,xCox)2TiO4 ceramics prepared by the conventional solid-state route were investigated. Lattice parameters were also measured for specimens with different x. The formation of solid solution (Mg1,xCox)2TiO4 (x=0.02,0.1) was confirmed by the X-ray diffraction patterns, energy dispersive X-ray analysis, and the lattice parameters measured. By increasing x from 0 to 0.05, the Q×f of the specimen can be tremendously boosted from 150 000 GHz to a maximum of 286 000 GHz. A fine combination of microwave dielectric properties (,r,15.7, Q×f,286 000 GHz at 10.4 GHz, ,f,,52.5 ppm/°C) was achieved for (Mg0.95Co0.05)2TiO4 ceramics sintered at 1390°C for 4 h. Ilmenite-structured (Mg0.95Co0.05)TiO3 was detected as a second phase. The presence of the second phase would cause no significant variation in the dielectric properties of the specimen because it possesses compatible properties compared with that of the main phase. In addition, only a small deviation in the dielectric properties was monitored for specimens with x=0.04,0.05 at 1360°,1420°C. It not only provides a wide process window but also ensures an extremely reliable material proposed as a very promising dielectric for low-loss microwave and millimeter wave applications. [source] Low-Loss Microwave Dielectrics in the (Mg1,xZnx)2TiO4 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Cheng-Liang Huang The microwave dielectric properties and the microstructures of (Mg1,xZnx)2TiO4 ceramics prepared by the conventional solid-state route were investigated. Lattice parameters were also measured for samples with different x. As x increased from 0 to 0.05, the Q×f of the specimen can be promoted from 150 000 GHz to a maximum 275 300 GHz. It also showed a remarkable lowering in the sintering temperature (,100°C). Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, is not harmful to the dielectric properties of the specimen because it possesses compatible ones. A fine combination of microwave dielectric properties (,r,15.48, Q×f,275 300 GHz, ,f,,34 ppm/°C) was obtained for (Mg0.95Zn0.05)2TiO4 specimen sintered at 1330°C for 4 h. It is proposed as a very promising dielectric material for low-loss microwave and millimeter wave applications. [source] | ||||||||||