Dielectric Properties of Low Loss (1–x)(Mg0.95Zn0.05)TiO3xSrTiO3 Ceramic System at Microwave Frequency

Authors


  • N. Alford—contributing editor

  • This work was sponsored by the National Science Council of the Republic of China under grant NSC 95-2221-E-006-117.

†Author to whom correspondence should be addressed. e-mail: huangcl@mail.ncku.edu.tw

Abstract

The microstructures and the microwave dielectric properties of the (1–x)(Mg0.95Zn0.05)TiO3xSrTiO3 ceramic system were investigated. (Mg0.95Zn0.05)TiO3 possesses high dielectric constant (ɛr∼17.05), high quality factor (Q×f value∼264 000 at 9 GHz), and negative τf value (−40.31 ppm/°C). In order to achieve a temperature-stable material, SrTiO3, having a large positive τf value of 1700 ppm/°C, was added to (Mg0.95Zn0.05)TiO3. Two-phase system was confirmed by the X-ray diffraction patterns and the measured lattice parameters. Evaporation of Zn occurred at temperatures higher than 1300°C and caused an increase in the dielectric loss of the system. As the x value varies from 0 to 0.1, (1–x)(Mg0.95Zn0.05)TiO3xSrTiO3 ceramic system has the dielectric properties as follows: 17.05<ɛr<26.35, 20 000<Q×f<264 000, and −41<τf<140. By appropriately adjusting the x value in the (1–x)(Mg0.95Zn0.05)TiO3xSrTiO3 ceramic system, zero τf value can be achieved. A new microwave dielectric material, 0.96(Mg0.95Zn0.05)TiO3–0.04SrTiO3 applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ɛr∼20.96, a Q×f value∼135 000 GHz (at 9 GHz), and a τf value ∼0 ppm/°C. A compact band-pass filter using two open-loop ring resonators with asymmetric tapping feed lines is designed and fabricated using the proposed dielectric to study its performance.

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