マイクロ波誘電体BaO-RE2O3-TiO2の誘電特性に及ぼす作製条件の影響

概要

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Recently cordless telephones and mobile telephone systems have been developed rapidly, so that high quality dielectric filter is required. BaO-RE2O3-TiO2system is suitable for microwave dielectrics because of its high dielectric constant and high Q value. The effects of fabrication conditions, such as calcination temperature, press condition, sintering time and sintering temperature on dielectric properties of BaO-Bi2O3-Nd2O3-Sm2O3-TiO2 ceramics were investigated. Spherical grains were observed at sintering temperature 1305°C, and cylindrical grains at 1348°C in these ceramics.It was proved by X-ray analysis that these grains had BaNd2Ti5O14 type crystal structure. Large massive grains of TiO2 rutile type structure were also observed at 1408°C. As these crystal structures change, dielectric properties also change remarkably;the dielectric constant and temperature coefficient increase with Increasing sintering temperature and the Qu factor has a maximum value at about 1360°C. The other fabrication conditions also have a favorable influence upon the properties of this ceramic system
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