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

Abstract

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∼17,600GHz and a large positive τf value∼213ppm/°C. (Mg0.95Co0.05)TiO3 ceramics possesses high dielectric constant (εr∼16.8), high quality factor (Q×f value∼230,000GHz), and negative τf value (−54ppm/°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∼84,000GHz (at 9GHz), and a τf value∼2ppm/°C were obtained for 0.85(Mg0.95Co0.05)TiO3–0.15Ca0.6La0.8/3TiO3 ceramics sintered at 1400°C for 4h. 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 0.5wt% V2O5 can be obtained good properties at the microwave frequencies for 1200°C.