Tailoring microwave dielectric properties of MgAl5/4(Li1/3Ti2/3)3/4O4 ceramics for multi-band dielectric resonant antenna

This study introduces a novel microwave dielectric ceramic, MgAl5/4(Li1/3Ti2/3)3/4O4, tailored for modern communication technologies. MgAl5/4(Li1/3Ti2/3)3/4O4 ceramics feature a composite spinel structure (Fd-3m space group) comprising MgAl2O4 and Li4Ti5O12 type phases. By substituting Al3+ of MgAl2O4 ceramic with the composite ion (Li1/3Ti2/3)3+, differences in elemental diffusion induced by sintering temperature (1200–1280 °C) significantly affect the microwave dielectric properties: a low εᵣ (11.83) and enhanced microwave properties (Q×f = 79,381 GHz and τf = −28.5 × 10−6/°C) at 1240 °C. With further optimization of the ceramics, a near-zero τf is realized in 0.93MgAl5/4(Li1/3Ti2/3)3/4O4-0.07CaTiO3 ceramics with excellent comprehensive performance (εr = 14.36, Q×f = 44,144 GHz). Building on this, a multi-band dielectric resonant antenna (DRA) was designed for applications in communication and aeronautical radio navigation, featuring a wide relative bandwidth of 39.37% (5.97–6.49 GHz and 7.19–9.83 GHz). This study presents an optimization strategy for obtaining microwave dielectric ceramics with low εr, high Q×f, excellent frequency-temperature stability, low sintering temperature, and low density.