Low Permittivity Ba(Al_0.98Co_0.02)₂Si₂O₈-Ba₅Si₈O₂₁-Based Microwave Dielectric Ceramics for LTCCs

0.7Ba(Al_0.98Co_0.02)₂Si₂O₈-0.3Ba₅Si₈O₂₁(BACS-BS)-based microwave dielectric ceramic was prepared by traditional solid-state reaction method. The effects of Li₂O-B₂O₃(1wt%)(L-B) sintering aids on the microstructure, phase composition and microwave dielectric properties were investigated. Deviation between theoretical and experimental permittivity of 0.7BACS-0.3BS+1wt%(L-B) ceramic was discussed. The results show that adding 1wt%(L-B) sintering aids could decrease the sintering temperature of BACS-BS-based to 950 ℃. However, it apparently degrades the microwave dielectric properties. 0.7Ba(Al_0.98Co_0.02)₂Si₂O₈−0.3Ba₅Si₈O₂₁+1wt%(Li₂O-B₂O₃) ceramic could be well-sintered at 950 ℃ and show good microwave dielectric properties: ε_r=7.56, Q×f=13 976 GHz, τ_f=−6.32 ppm/℃. The good chemical compatibility between the ceramic and Ag electrodes was exhibited, which made it be a promising candidate for the practical applications of LTCC materials.