Lattice vibration characteristics and dielectric response mechanisms in low-temperature sintered SrSn(BO3)2−x wt% LiF microwave ceramics for 5G microstrip antenna applications

Abstract

In this study, SrSn(BO₃)₂–x wt% LiF microwave ceramics were successfully prepared at 950 °C via conventional solid-state sintering. Phase composition and microstructure were characterized by XRD and SEM, respectively. XRD confirmed the absence of secondary phases, while SEM revealed that the x = 3.0 wt% sample exhibited the most uniform grain size and highest density. Lattice vibrational characteristics were analyzed using Raman and FTIR spectroscopy. With increasing LiF content, the A_g mode shifted to higher wavenumbers, indicating shortened B–O bond lengths and reduced polarizability, leading to a decrease in the dielectric constant. The FWHM of the v₂ mode reflected structural ordering and showed a negative correlation with Q × f. Seven FTIR vibrational modes were identified, and intrinsic dielectric properties were evaluated using the four-parameter semiquantum model to elucidate dielectric response mechanisms. Among them, mode 2 contributed most significantly to both the dielectric constant (33.33%) and dielectric loss (53.84%). Results indicate that SrSn(BO₃)₂–3 wt% LiF ceramics exhibited excellent microwave dielectric properties: ε_r = 5.17, Q × f = 42 211 GHz (15.72 GHz) and τ_f = −42.31 ppm °C⁻¹. A microstrip patch antenna simulated using this ceramic as a substrate showed a center frequency of 12.0 GHz, return loss (S₁₁) of −40.0 dB, and peak gain of 6.86 dBi, demonstrating strong application potential in microwave communication systems.