Low-temperature sintering and temperature stability improvement of LiAlO₂ microwave dielectric ceramics

Low-dielectric-constant microwave dielectric ceramics can reduce signal transmission delays at high frequencies. LiAlO₂ ceramics are attractive for high-frequency applications due to their low permittivity and loss, but the practical use is limited by their high sintering temperature and large temperature coefficient. In this study, Li-Mg-Zn-B-Si (G6) glass and BaCu(B₂O₅) (BCB) were selected as additives to reduce the sintering temperature of LiAlO₂ ceramics. Excellent microwave dielectric properties were achieved at 950 ℃ by adding 3 wt%G6 and 2 wt%BCB. Additionally, temperature-stable LiAlO₂-Ba₃V₂O₈ composite ceramics were designed and investigated for their phase composition and dielectric properties. The results indicate that with 3 wt%G6 and 2 wt%BCB, the 0.7LiAlO₂-0.3Ba₃V₂O₈ composite ceramics exhibited excellent microwave dielectric properties at 950 ℃ for 4 h: ε_r ∼ 10.49, Q×f ∼ 22,000 GHz (@ f = 9.9 GHz), and a near-zero temperature coefficient (TCF) ∼ + 5.7 ppm/℃. This work presents a practical method for modifying LiAlO₂ ceramics for low-permittivity microwave applications.