Microwave dielectric properties of (1 − x)(Mg0.95Co0.05)TiO3– xCa0.6La0.8/3TiO3 ceramics with V2O5 addition

The microstructures and the microwave dielectric properties of the (1 − x)(Mg0.95Co0.05)TiO3–xCa0.6La0.8/3TiO3 ceramic system were investigated. In order to achieve a temperature-stable material, we studied a method of combining a positive temperature coefficient material with a negative one. Ca0.6La0.8/3TiO3 has dielectric properties of dielectric constant εr ∼ 109, Q × f value ∼ 17,600 GHz and a large positive τf value ∼ 213 ppm/°C. (Mg0.95Co0.05)TiO3 ceramics possesses high dielectric constant (εr ∼ 16.8), high quality factor (Q × f value ∼ 230,000 GHz), and negative τf value (−54 ppm/°C). As the x value varies from 0.1 to 0.8, (1 − x)(Mg0.95Co0.05)TiO3–xCa0.6La0.8/3TiO3 ceramic system has the dielectric properties as follows: 21.55 < εr < 75.44, 21,000 < Q × f < 90,000 and −10 < τf < 140. By appropriately adjusting the x value in the (1 − x)(Mg0.95Co0.05)TiO3–xCa0.6La0.8/3TiO3 ceramic system, zero τf value can be achieved. With x = 0.15, a dielectric constant εr ∼ 25.78, a Q × f value ∼ 84,000 GHz (at 9 GHz), and a τf value ∼ 2 ppm/°C were obtained for 0.85(Mg0.95Co0.05)TiO3–0.15Ca0.6La0.8/3TiO3 ceramics sintered at 1400 °C for 4 h. For practical application in communication systems, it is desirable to be able to sinter at lower temperatures. Therefore, V2O5 was as a sintering aid for lowering the sintering temperature of0.85(Mg0.95Co0.05)TiO3–0.15Ca0.6La0.8/3TiO3 ceramics. At the same time, the 0.85(Mg0.95Co0.05)TiO3–0.15Ca0.6La0.8/3TiO3 ceramic system with 0.5 wt% V2O5 can be obtained good properties at the microwave frequencies for 1200 °C.