Enhanced mechanical and microwave dielectric performances of Mg(Al0.5Ga0.5Ti0.5Zn0.25Mg0.25)O4 high-entropy ceramic for C-band antenna applications

High-entropy Mg(Mg 0.25 Zn 0.25 Ga 0.5 Ti 0.5 Al 0.5 )O 4 ceramics with disordered spinel structure were prepared at 1420-1500 °C. When sintered at 1480 °C, Mg(Mg 0.25 Zn 0.25 Ga 0.5 Ti 0.5 Al 0.5 )O 4 ceramics exhibited extremely high Q×f of 105,800 ± 300 GHz, improved τ f of –45.3 ± 0.01 ppm/°C, and low ε r of 11.5 ± 0.1, with favorable H v and flexural strength of 11.43 ± 0.01 GPa and 128.1 ± 0.1 MPa, respectively, which were 23.3% and 31.7% higher than those of MgAl 2 O 4 . The measured ε r of Mg(Mg 0.25 Zn 0.25 Ga 0.5 Ti 0.5 Al 0.5 )O 4 ceramics was substantially higher than the calculated εᵣ (C-M) (9.9), due to the underestimated Ti 4+ polarizability and rattling effect. The improved τ f was caused by the decreased τ ε and increased Gibbs free energy. The 1.5 times increase in Q × f stemmed from the increased packing fraction and lattice energy, lowered σ AC , enhanced E a and covalency factor. A cylindrical dielectric resonator antenna was designed with Mg(Mg 0.25 Zn 0.25 Ga 0.5 Ti 0.5 Al 0.5 )O 4 high-entropy ceramic, which can fulfill the communication demands of high-frequency and high-power applications.