Low temperature sintering and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics for LTCC applications

The effects of MnCO3-CuO and Li2O-B2O3-SiO2 (for short LBS) on the sintering behavior, microstructures and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics have been investigated. The pure Ba2Ti3Nb4O18 ceramics sintered at 1220 °C showed microwave dielectric properties: ɛr = 38, Q × f = 23,700 GHz (at 4.8 GHz), and τf = −3 ppm/°C. It was found that a small amount of MnCO3-CuO and LBS glass additives lowered the sintering temperature of Ba2Ti3Nb4O18 ceramics effectively from 1220 °C to 900 °C. The dielectric constant (ɛr) increased and the temperature coefficient of the resonant frequency shifted to a positive value with the addition of MnCO3-CuO and LBS, which were mainly due to the presence of the second phase Ba3Ti4Nb4O21. Ba2Ti3Nb4O18 ceramics with 1.5 wt% MnCO3-CuO and 0.5 wt% LBS sintered at 900 °C for 2 h showed dielectric properties: ɛr = 41, Q × f = 15,000 GHz (at 4.8 GHz), and τf = 4 ppm/°C. It was compatible with Ag electrodes, which made it a promising ceramic for low temperature co-fired ceramics technology application.