Kenichi Ezaki

Dielectric Characteristics of (A1/21+·A1/23+)TiO3 Ceramics at Microwave Frequencies

We have investigated the dielectric characteristics at microwave frequencies of perovskites with the formula (A1/21+A1/23+)TiO3, (where A1+ represents an alkali metal from the lithium to potassium series and A3+ represents a member of the lanthanide series from lanthanum to lutetium). It was found for the first time that in the case of Li1+ substitution at the A1+ site, the larger the ionic radius of the element which substituted at the A3+ site, the higher the dielectric constant was and the greater the negative shift of the temperature coefficient of resonant frequency was. For the (1-x)(Li1/21+Sm1/23+)TiO3-x(Na1/21+Sm1/23+)TiO3 system at 3 GHz, high dielectric properties of er=81, Q=2050 and τf=+17ppm/ °C were obtained when x=0.4.

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 er=110, fQ 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).