Microwave dielectric property adjustment of CoZrNb₂O₈ ceramics by CaTiO₃ addition

Temperature stable microwave dielectric ceramics CoZrNb₂O₈-xCaTiO₃ (x = 1/60 ~ 1/10) were fabricated by a solid-state technique. The phase formation and sintering behavior were detected for the purpose of structure–property relationship exploration. Appropriate rate of CaTiO₃ addition was benefit to the sintering temperature decrease of CoZrNb₂O₈. From x = 1/50 to x = 1/10, unexpected CaNb₂O₆ and Ti₂Nb₁₀O₂₉ phases both formed, consequent on the chemical reaction between CoZrNb₂O₈ and CaTiO₃. Co-based oxide might separate out in the form of liquid phase and decrease the sintering temperature. Increasing CaTiO₃ ration degraded the quality factor Q × f, but at the same time enhanced the dielectric constant ε_r and temperature coefficient of resonant frequency τ_f. According to the Lichtenecker mixing rule, the estimated microwave dielectric properties basically agreed well with the measured values at first. However, excessive CaTiO₃ incorporation caused lattice defects and gave noticeable deviation. In current work, CoZrNb₂O₈-1/40CaTiO₃ composite displayed a rather small τ_f with Q ×  f= 64,600 GHz at 1225 °C.