The influence of BBZ glass on phase evolution, sintering behavior and dielectric properties of BaTi₄O₉ ceramics

A low temperature co-fired ceramic (LTCC) material has been fabricated by mixing BaTi₄O₉ ceramic powder with a BaO–B₂O₃–ZnO (BBZ) glass and sintering the mixture at 925 °C/2 h. The influence of the BBZ glass on sintering behavior, phase evolution, microstructure and microwave dielectric properties of the BaTi₄O₉-based LTCC material has been investigated. The results show that the BBZ glass can significantly lower the sintering temperature of the BaTi₄O₉ ceramics from 1350 °C to below 950 °C. The XRD patterns exhibit that remarkable chemical reactions happen between BaTi₄O₉ and the BBZ glass during sintering, forming two new phases BaTi(BO₃)₂ and Ba₄Ti₁₃O₃₀ in the material. As BBZ glass is increased from 5 to 30 wt%, BaTi(BO₃)₂ phase gradually dominates the material and BaTi₄O₉ decreases and almost disappears at the end. At the same time, the dielectric constant decreases from 33 to 25, the temperature coefficient of resonant frequency decreases from +25.44 to −3.19 ppm/°C, and the quality factor firstly increases and then decreases with the peak value of 29500 GHz. The changes of the dielectric properties with the BBZ glass content are correlated with the phase evolution of the material during sintering. Typically, the BaTi₄O₉-based ceramics with 25 wt% BBZ glass sintered at 925 °C for 2 h displays excellent comprehensive properties with a maximum density of 4.33 g/cm³, the dielectric constant of 27.08, quality factor of 29,500 GHz and temperature coefficient of resonant frequency of +3.5 ppm/°C. In addition, the good chemical compatibility of this material with Ag electrode makes it a potential candidate for LTCC technology.