Low temperature sintering and microwave dielectric properties of Ba2Ti9O20 ceramics using glass additions

The effects of glass additions on the microwave dielectric properties and the microstructures of Ba2Ti9O20 ceramics were investigated. The simple glasses B2O3 and SiO2 and the commercial glass PbO–B2O3–SiO2 (PBS) were selected as liquid phase sintering aids to lower the sintering temperature of Ba2Ti9O20 ceramics. With glass additions, the sintering temperatures can be effectively lowered. The dielectric properties of Ba2Ti9O20 ceramics with glass additions are strongly dependent on the densification, the microstructure, and the reaction between glasses and ceramics. Ba2Ti9O20 ceramics without glass addition sintered at 1380°C has a dielectric constant εr = 38.8, a quality factor Q = 7200 at 6.0 GHz, and a temperature coefficient of resonant frequency τf = 4 ppm/°C. Among these glasses, 5 wt% B2O3 added Ba2Ti9O20 can be sintered to achieve theoretical densities of 96 and 95% at 1100 and 1200°C, and gives εr values of 36.5 and 36 together with Q values of 3200 and 6700 (at 6 GHz), respectively. Results of XRD analysis and scanning electron microscopy are also presented.