Dielectric properties and applications of low loss (1−x)(Mg0.95Co0.05)TiO3–xCa0.8Sm0.4/3TiO3 ceramic system at microwave frequency

Abstract

In this paper, the microstructures and microwave dielectric properties of the (1 − x )(Mg 0.95 Co 0.05 )TiO 3 – x Ca 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 ( ɛ r ), reduced the quality factor ( Q × f value) and also compensated the temperature coefficient of resonant frequency ( τ f ) of (Mg 0.95 Co 0.05 )TiO 3 . The microstructures of (1 − x )(Mg 0.95 Co 0.05 )TiO 3 – x Ca 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 ( ɛ r ) of 22.5, a Q × f value of 108,000 (at 8 GHz ) and a τ f value of −8 ppm/°C were obtained for 0.9(Mg 0.95 Co 0.05 )TiO 3 –0.1Ca 0.8 Sm 0.4/3 TiO 3 ceramic sintered at 1275 °C for 4 h. 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.