Microwave dielectric property adjustment of CoZrNb2O8 ceramics by CaTiO3 addition
Temperature stable microwave dielectric ceramics CoZrNb 2 O 8 - x CaTiO 3 ( 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 CaTiO 3 addition was benefit to the sintering temperature decrease of CoZrNb 2 O 8 . From x = 1/50 to x = 1/10, unexpected CaNb 2 O 6 and Ti 2 Nb 10 O 29 phases both formed, consequent on the chemical reaction between CoZrNb 2 O 8 and CaTiO 3 . Co-based oxide might separate out in the form of liquid phase and decrease the sintering temperature. Increasing CaTiO 3 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 CaTiO 3 incorporation caused lattice defects and gave noticeable deviation. In current work, CoZrNb 2 O 8 -1/40CaTiO 3 composite displayed a rather small τ f with Q × f = 64,600 GHz at 1225 °C.
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