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, MgAl 5/4 (Li 1/3 Ti 2/3 ) 3/4 O 4 , tailored for modern communication technologies. MgAl 5/4 (Li 1/3 Ti 2/3 ) 3/4 O 4 ceramics feature a composite spinel structure ( Fd -3m space group) comprising MgAl 2 O 4 and Li 4 Ti 5 O 12 type phases. By substituting Al 3+ of MgAl 2 O 4 ceramic with the composite ion (Li 1/3 Ti 2/3 ) 3+ , differences in elemental diffusion induced by sintering temperature (1200–1280 °C) significantly affect the microwave dielectric properties: a low ε ᵣ (11.83) and enhanced microwave properties ( Q × f = 79,381 GHz and τ f = −28.5 × 10 −6 /°C) at 1240 °C. With further optimization of the ceramics, a near-zero τ f is realized in 0.93MgAl 5/4 (Li 1/3 Ti 2/3 ) 3/4 O 4 -0.07CaTiO 3 ceramics with excellent comprehensive performance ( ε r = 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 ε r , high Q × f , excellent frequency-temperature stability, low sintering temperature, and low density. • (Li 1/3 Ti 2/3 ) 3+ ion substitution enhanced microwave dielectric properties of MgAl 2 O 4 for MgAl 5/4 (Li 1/3 Ti 2/3 ) 3/4 O 4 ceramics. • ε r = 11.8, Q × f = 79,381 GHz, and τ f = −28.5 × 10 −6 /°C. • Multi-band DRA based on two-phase composite preparation of τ f near-zero ceramics (0.93MALT-0.07CaTiO 3 ). • Multi-band DRA can be used in communication and aviation radio navigation.