Microwave dielectric properties and low-temperature sintering of Ba3Ti4Nb4O21 ceramics with B2O3 and CuO additions

The low sintering temperature and the good dielectric properties such as high dielectric constant (ɛr), high quality factor (Q × f) and small temperature coefficient of resonant frequency (τf) are required for the application of chip passive components in the wireless communication technologies. In the present study, the sintering behaviors and dielectric properties of Ba3Ti4Nb4O21 ceramics were investigated as a function of B2O3–CuO content. Ba3Ti4Nb4O21 ceramics with B2O3 or CuO addition could be sintered above 1100 °C. However, the additions of both B2O3 and CuO successfully reduced the sintering temperature of Ba3Ti4Nb4O21 ceramics from 1350 to 900 °C without detriment to the microwave dielectric properties. From the X-ray diffraction (XRD) studies, the sintering behaviors and the microwave dielectric properties of low-fired Ba3Ti4Nb4O21 ceramics were examined and discussed in the formation of the secondary phases. The Ba3Ti4Nb4O21 sample with 1 wt% B2O3 and 3 wt% CuO addition, sintered at 900 °C for 2 h, had the good dielectric properties: ɛr = 65, Q × f = 16,000 GHz and τf = 101 ppm/°C.