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Solid-state Route (solid-state + route)
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] 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] Synthesis of Ba(Mg1/3Ta2/3)O3 Microwave Ceramics through a Sol,Gel Route Using Acetate SaltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004Chien-Cheng Tsai A sol,gel process to unsophisticatedly synthesize Ba(Mg1/3Ta2/3)O3 (BMT) ceramics at low cost has been developed in the present work. This process involves the reaction of TaCl5 with acetates of Ba and Mg in the presence of citric acid. Pure BMT polycrystalline powders can be obtained by calcining the synthesized products at 1000°C. The BMT powders were found to have a primary particle size as small as 100 nm. BMT ceramics with favorable structural characteristics can be obtained from sintering of the sol,gel BMT at temperatures much lower than that for the conventional solid-state BMT. Sintering the sol,gel BMT in pellet form at 1300°C resulted in an ordering parameter of 0.72 for the pellet, and a relative density of >95% was achieved with sintering at 1500°C. The grain size of the sintered sol,gel BMT was large and uniform in comparison with the products from the solid-state method. Using the sol,gel route, sintering at temperatures as low as 1400°C gave ceramics with acceptable microwave dielectric properties (a dielectric constant of 16 and Qf factor of 14 400 GHz), while higher temperatures (>1600°C) are needed for the solid-state route to give similar properties. [source] Positive Temperature Coefficient of Resistivity in Donor-Doped BaTiO3 Ceramics derived from Nanocrystals synthesized at Low Temperature,ADVANCED MATERIALS, Issue 5 2008L. Brutchey Small, donor-doped Ba1- xLaxTiO3nanocrystals are successfully prepared for the first time. These nanocrystals are suitable precursors for small-grain Ba1- xLaxTiO3 ceramics with a sizeable positive temperature coefficient of resistivity (PTCR) that is comparable to that of traditional large-grain ceramics derived from solid-state routes. [source] | ||||||||||