Dielectric properties of CaTiO₃-Ca(Mg_1/3Nb_2/3)O₃ ceramic system at microwave frequency

The crystal structures and the microwave dielectric properties of the (1 - x)CaTiO₃-xCa(Mg_1/3Nb_2/3)O₃ perovskite ceramic system have been investigated. The (1 - x)CaTiO₃-xCa(Mg_1/3Nb_2/3)O₃ solid solution exhibited orthorhombic crystal structures for all compositions. As the x value increases from 0.2 to 0.8, the dielectric constant ε_r decreases from 109 to 36 and the unloaded quality value Q × f increases from 8600 to 39000 (at 6.7 GHz). The temperature coefficient of the resonant frequency (τ_f) varies from 298 to - 30 ppm/° C as the x value increases from 0.2 to 0.8. A new microwave dielectric material, 0.4CaTiO₃-0.6Ca(Mg_1/3Nb_2/3)O₃, applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ε_r ∼ 54, a Q × f value ∼32000 (at 6.7 GHz) and a τ_f value ∼18 ppm/° C. Further improvement of the τ_f value is expected by adjusting the x value of (1 - x)CaTiO₃-xCa(Mg_1/3Nb_2/3)O₃ ceramics.