Dielectric properties of low loss (1-x)(Mg_0.95Zn _0.05)TiO₃-xSrTiO₃ ceramic system at microwave frequency

The microstructures and the microwave dielectric properties of the (1-x)(Mg_0.95Zn_0.05)TiO₃-xSrTiO₃ ceramic system were investigated. (Mg_0.95Zn_0.05)TiO ₃ possesses high dielectric constant (ε_r ∼ 17.05), high quality factor (Q × f value ∼ 264 000 at 9 GHz), and negative τ_f value (-40.31 ppm/°C). In order to achieve a temperature-stable material, SrTiO₃, having a large positive τ_f value of 1700 ppm/°C, was added to (Mg _0.95Zn_0.05)TiO₃. Two-phase system was confirmed by the X-ray diffraction patterns and the measured lattice parameters. Evaporation of Zn occurred at temperatures higher than 1300°C and caused an increase in the dielectric loss of the system. As the x value varies from 0 to 0.1, (1-x)(Mg_0.95Zn_0.05)TiO₃-xSrTiO₃ ceramic system has the dielectric properties as follows: 17.05 < ε_r < 26.35, 20 000 < Q × f < 264 000, and -41 <τ_f<140. By appropriately adjusting the x value in the (1-x)(Mg_0.95Zn_0.05)TiO₃-xSrTiO₃ ceramic system, zero τ_f value can be achieved. A new microwave dielectric material, 0.96(Mg_0.95Zn_0.05)TiO ₃-0.04SrTiO₃ applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ε_r ∼ 20.96, a Q × f value ∼ 135 000 GHz (at 9 GHz), and a τ_f value ∼0 ppm/°C. A compact band-pass filter using two open-loop ring resonators with asymmetric tapping feed lines is designed and fabricated using the proposed dielectric to study its performance.