Microwave dielectric properties and co-firing of BiNbO4 ceramics with CuO substitution

The effect of CuO substitution on the sintering behavior and the microwave dielectric properties of BiNbO4 ceramics were studied. The sintering temperatures of (Bi1−2xCu2x)NbO4−x and (Bi1−2xCu3x)NbO4 ceramics decrease from 930 to 850 °C with x value increasing. The size of grains increased with the sintering temperature increasing and decreased with the substitution amount increasing. The dielectric constant ɛr changes between 40 and 45 and the Qf values lie between 4000 and 8000 GHz at about frequency 5.2 GHz. The τf values changes between 0 and −20 ppm °C−1 and decreases with the increasing of x value. Copper electrode was found not to penetrate the ceramic from the SEM and EDS results of the broken surface of co-fired samples.