The Microwave Dielectric Properties and the Microstructures of La₂O₃-Modified BiNbO₄ Ceramics

Abstract

The microwave dielectric properties and the microstructures of La 2 O 3 -modified BiNbO 4 ceramics were investigated. (Bi 1- x La x )NbO 4 ceramics combined with orthorhombic and triclinic phases are identified at sintering temperatures of 920–980°C. The density and grain size of (Bi 1- x La x )NbO 4 ceramics both increase with increasing sintering temperature while both decrease slightly with the increase of La 2 O 3 content. The dielectric constant ε r , the quality factor Q and the temperature coefficient of resonant frequency τ f of the ceramics are affected by the La 2 O 3 content and correlated with its microstructure. At a sintering temperature of 920°C and x value of 0.01, (Bi 1- x La x )NbO 4 ceramics exhibit the microwave dielectric properties of ε r ∼43.36, Q × f ∼10600 (at 7 GHz), and τ f ∼-2 ppm/°C.