The microwave dielectric properties and the microstructures of La2O3-modified BiNbO4 ceramics

The microwave dielectric properties and the microstructures of La2O3-modifi ed BiNbO4 ceramics were investigated. (Bi1-xLax)NbO4 ceramics combined with orthorhombic and triclinic phases are identified at sintering temperatures of 920-980 degrees C. The density and grain size of (Bi1-xLax)NbO4 ceramic s both increase with increasing sintering temperature while both decrease s lightly with the increase of La2O3 content. The dielectric constant epsilon (r), the quality factor Q and the temperature coefficient of resonant frequ ency tf of the ceramics are affected by the La2O3 content and correlated wi th its microstructure. At a sintering temperature of 920 degrees C and x va lue of 0.01, (Bi1-xLax)NbO4 ceramics exhibit the microwave dielectric prope rties of epsilon(r) similar to 43.36, Q x f similar to 10600 (at 7 GHz), an d tau(f) similar to 2 ppm/degrees C.