The effect of CuO on the sintering and properties of BiNbO4 microwave ceramics

Even if 960°C is used as sintering temperature, the undoped BiNbO4 ceramics are difficult to be densified. The addition of CuO will improve the densification process of BiNbO4 ceramics. As the amount of CuO addition increases from 0.125 to 1.5 wt%, the dielectric constants (εr) of densified BiNbO4 ceramics decrease from 43.9 to 42.8 and the temperature coefficients (τf) change from −4.5 to −31.2 ppm/°C. The quality values (Q) first increase, reach a maximum at 0.5wt% CuO, and then decrease with the increase of CuO amount. In CuO-doped BiNbO4 system, BiNbO4 ceramics with 0.5wt% CuO added and sintered at 920°C have the optimum microwave dielectric properties: (εr=43.6, τf=−20.8 ppm/°C, and Q=1610 (Q×f=10 070)