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.