Synthesis mechanism and microwave dielectric properties of Co_0.5Ti_0.5NbO₄ ceramics

Co_0.5Ti_0.5NbO₄ (CTN) microwave dielectric ceramics with low loss were prepared by the conventional solid-state method. The process of phase formation was investigated by X-ray diffraction, it was found that the structure transformed from orthogonal phase to tetragonal phase along with the increasing of temperature from 800 to 1080 °C. Only when temperature was over 1080 °C, the pure CTN phase could be synthesized. However, high calcining temperature would lead to inadequate driving force of sintering. The influences of calcining temperature on the microstructure, densities and microwave dielectric properties were discussed systematically. Calcining at 800 °C for 3 h could achieve optimal microwave dielectric properties in CTN ceramics, permittivity for 64.7, quality factor (Q × f) for 12,141 GHz and the temperature coefficient of resonant frequency (τ_f) for 202 ppm/°C. The lower sintering temperature and excellent microwave dielectric properties would make CTN ceramics become a potential material for microwave applications via tailoring high τ_f.