جستجوی مقالات مرتبط با کلیدواژه « دی الکتریک مایکروویو » در نشریات گروه « مواد و متالورژی »

Microwave dielectric ceramics are irreplaceable components used in devices and systems utilized at microwave frequencies for example mobile and satellite communication systems. In this study the effect of the addition of different amounts of BaZrO3 on the microstructure and microwave dielectric properties of a composition based on Ba (Zn1/3Nb2/3) O3 (BZN) ceramic، i. e. (0. 9-x) Ba ([Zn0. 6Co0. 4] 1/3Nb2/3) O3–0. 1Ba (Ga1/2Ta1/2) O3–xBaZrO3 where x=0-0. 1، has been investigated. Density increased with an increase in BaZrO3 content up to x=0. 08 and then decreased. XRD analysis showed the presence of BZN phase together with a small amount of anunknown second phase for ceramics with x=0، 0. 02 and 0. 04. However، microstructural investigations through optical microscopy showed that ceramics with x=0. 06، 0. 08 and 0. 10 also contained a second phase which could not be detected by X-ray diffraction technique because a small amount of the second phase was present. No super structure peak was observed for ceramics with different BaZrO3 levels. Quality factor for the sample with x=0. 08 was 4366 GHz which was very low. The measurement of quality factor for other samples was not also possible due to their low Q values. As mentioned before? showed that all samples contained a second phase; therefore، the low values of quality factor observed for all samples could be attributed to the presence of the second phase.

Microwave dielectric ceramics are extensively used in systems utilized at microwave frequencies for example mobile telephone and satellite devices. In this study ceramics with 0. 88Ba ([Zn0. 6Co0. 4] 1/3،Nb2/3) O3–0. 1Ba (Ga1/2Ta1/2) O3–0. 02BaZrO3 composition were prepared through the conventional ceramic processing; i. e. mixing and milling of the starting powders، calcination at 1100°C، second milling and sintering of pressed samples at different temperatures. The study showed that increasing sintering temperature resulted in an increase in density so that the highest density was observed at 1500°C. There was also an increase in quality factor (Q´f) when sintering temperature was increased; Q´f was about 16،000 GHz at 1500°C. The increase in quality factor is mainly due to the increase in density. Since superlattice reflections were not observed in XRD spectrum، the increase in quality factor can not be related to an increase in ordering degree. The presence of ordering can also be evaluated by changes in c/a ratio (c and a are lattice parameters of the hexagonal superlattice structure) and changes in lattice distortion. None of these two methods were able to show the existence of ordering.