Structural characteristics and microwave dielectric properties of low-loss spinel type Li2M2Ga2Ti3O12 (M = Mg, Zn) ceramics for dielectric resonant antenna applications

Two novel ceramics, Li 2 Mg 2 Ga 2 Ti 3 O 12 (LMGT) and Li 2 Zn 2 Ga 2 Ti 3 O 12 (LZGT), featuring a spinel structure, were synthesized utilizing the solid-state method. Comprehensive characterization confirms that LZGT ( P 4 3 32) forms a B-site 1:3 ordered spinel, while LMGT ( Fd -3 m ) adopts a disordered spinel structure. The ceramics exhibit outstanding microwave dielectric properties, characterized by low ε r of 14.92 and 19.11, high Q×f of 120,000 and 93,800 GHz, and negative τ f of −40.21 and −32.83 ppm/°C for LMGT and LZGT, respectively. The observed ε r values significantly exceed theoretical values due to underestimated Ti 4+ polarizability along with the rattling effect of Ti 4+ and Ga 3+ . Q×f values correlate with packing fraction, lattice energy, and electrical properties. The negative τ f values stem from dominant positive τ ε and τ αm contributions. Utilizing LMGT with ultra-low loss, a dielectric resonator antenna was designed, achieving a radiation efficiency of 93.01 % and a gain of 6.12 dBi at 6.60 GHz, highlighting significant potential for C-band communication satellite applications.