Low temperature sintering and microwave dielectric properties of Ba ₂Ti ₉O ₂₀ ceramics using glass additions

The effects of glass additions on the microwave dielectric properties and the microstructures of Ba ₂Ti ₉O ₂₀ ceramics were investigated. The simple glasses B ₂O ₃ and SiO ₂ and the commercial glass PbO-B ₂O ₃-SiO ₂ (PBS) were selected as liquid phase sintering aids to lower the sintering temperature of Ba ₂Ti ₉O ₂₀ ceramics. With glass additions, the sintering temperatures can be effectively lowered. The dielectric properties of Ba ₂Ti ₉O ₂₀ ceramics with glass additions are strongly dependent on the densification, the microstructure, and the reaction between glasses and ceramics. Ba ₂Ti ₉O ₂₀ ceramics without glass addition sintered at 1380°C has a dielectric constant ε _r = 38.8, a quality factor Q = 7200 at 6.0 GHz, and a temperature coefficient of resonant frequency τ _f = 4 ppm/°C. Among these glasses, 5 wt% B ₂O ₃ added Ba ₂Ti ₉O ₂₀ can be sintered to achieve theoretical densities of 96 and 95% at 1100 and 1200°C, and gives ε _r 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.