Microwave Dielectric Properties of CaO-Li₂O-Ln₂O₃-TiO₂ Ceramics

We have investigated the microwave dielectric properties of the Li₂O-Ln₂O₃-TiO₂ system and the CaO-Li₂O-Ln₂O₃-TiO₂ system (Ln: Lanthanide), both of which have a perovskite structure. The relationship between the kind of lanthanide element and dielectric properties at microwave frequencies was confirmed. It was also found that the ionic radius of lanthanide ions has a strong influence on the dielectric properties. Excellent dielectric properties of ε_r=110, f·Q value=4500 GHz and high temperature stability for the resonant frequency at 3 GHz were obtained with a composition of CaO:SrO:Li₂O:Sm₂O₃:TiO₂=15.0:1.0:9.0:12.0:63.0 (molar ratio). Also, band-pass filters made of this material were examined. The filters were greatly miniaturized to the size of about 2×5×4 mm³ (0.04 cm³).