Dielectric properties and applications of low loss (1 - x)(Mg_(0.95)Co_(0.05))TiO_3-xCa_(0.8)Sm_(4/3)TiO_3 ceramic system at microwave frequency

摘要

In this paper, the microstructures and microwave dielectric properties of the (1 - x)(Mg_(0.95)Co_(0.05))TiO_3-xCa_(0.8)Sm_(0.4/3) TiO_3 (x = 0.05-0.2) ceramic system were investigated. Ca_(0.61)Sm_(0.78/3) TiO_3 increased the dielectric constant (epsilon_r), reduced the quality factor (Q X f value) and also compensated the temperature coefficient of resonant frequency (tau_f) of (Mg_(0.95)Co_(0.05))TiO_3. The microstructures of 1 - x)(Mg_(0.95)Co_(0.05))TiO_3-xCa_(0.8)Sm_(0.4/3) TiO_3 ceramics were characterized by X-ray diffraction patterns, scanning electron microscope (SEM). The existing areas of different compositions in the ceramics were observed by means of energy dispersive spectroscopy (EDS), which revealed that Ca_(0.8)Sm_(0.4/3)TiO_3 as minor phase co-existed with (Mg_(0.95)Co_(0.05))TiO_3. The existing Ca_(0.8)Sm_(0.4/3)TiO_3 phase can inhibit the grain growth of the main (Mg_(0.95)Co_(0.05))TiO_3 phase. A dielectric constant (epsilon_r) of 22.5, a Q X f value of 108,000 (at 8 GHz) and a tau_f value of -8 ppm/deg C were obtained for 0.9(Mg_(0.95)Co_(0.05))TiO_3-0. l Ca_(0.8)Sm_(0.4/3) TiO_3 ceramic sintered at 1275 deg C for 4h. Moreover, an ISM band parallel-coupled line band-pass filter with a central frequency of 5.8 GHz was also designed and fabricated using the proposed material as substrate to study its performance. It also showed a substantial reduction in both insertion loss and size in comparison with other dielectrics FR4 and alumina.