Dielectric Properties of CaTiO3–Ca(Mg1/3Nb2/3)O3 Ceramic System at Microwave Frequency

Abstract

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.