Microwave dielectric properties and co-firing of BiNbO4 ceramics with CuO–WO3 substitution

The effect of CuO and WO3 substitution on the sintering behavior, morphology, the microwave dielectric properties and the co-firing with copper electrode of BiNbO4 ceramics and were studied. With x-value increasing from 0.001 to 0.01, the densified temperatures of Bi(CuxW3xNb1−4x)O4 ceramics decreased from 1010 to 930 °C and the grain size decreased as well. The dielectric constant ɛr was between 38.5 and 43.5 and the Qf values lied between 15,000 and 2000 GHz at about 3.9 GHz. Temperature coefficient of resonant frequencies τf values were between +5.06 and −9.76 ppm/°C and decreased with x-value increasing. The CuO and WO3 substitution can adjust the τf values to near zero with proper substitution amount but deteriorate the dielectric properties when substitution amount increased. Copper electrode was found not to penetrate into the ceramic from the SEM and EDS results of the co-fired samples.