Low temperature sintering and microwave dielectric properties of Ba ₃Ti₅Nb₆O₂₈ with B₂O ₃ and CuO additions

The low sintering temperature and the good dielectric properties such as high dielectric constant (ε _r ), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric properties of Ba₃Ti₅Nb ₆O₂₈ ceramics were investigated as a function of B ₂O₃-CuO content. The pure Ba₃Ti ₅Nb₆O₂₈ system showed a high sintering temperature (1250°C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε _r of 37, TCF of -12 ppm/°C. The addition of B₂O₃-CuO was revealed to lower the sintering temperature of Ba₃Ti₅Nb₆O₂₈, 900°C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε _r of 40, TCF of 9 ppm/°C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties.