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

In this paper, the microstructures and microwave dielectric properties of the (1 − x)(Mg0.95Co0.05)TiO3–xCa0.8Sm0.4/3TiO3 (x = 0.05–0.2) ceramic system were investigated. Ca0.61Sm0.78/3TiO3 increased the dielectric constant (ɛr), reduced the quality factor (Q × f value) and also compensated the temperature coefficient of resonant frequency (τf) of (Mg0.95Co0.05)TiO3. The microstructures of (1 − x)(Mg0.95Co0.05)TiO3–xCa0.8Sm0.4/3TiO3 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 Ca0.8Sm0.4/3TiO3 as minor phase co-existed with (Mg0.95Co0.05)TiO3. The existing Ca0.8Sm0.4/3TiO3 phase can inhibit the grain growth of the main (Mg0.95Co0.05)TiO3 phase. A dielectric constant (ɛr) of 22.5, a Q × f value of 108,000 (at 8 GHz ) and a τf value of −8 ppm/°C were obtained for 0.9(Mg0.95Co0.05)TiO3–0.1Ca0.8Sm0.4/3TiO3 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.