High Q×f and near-zero τf values NaCaGaSi2O7-based ceramics for high-gain dielectric patch antennas

In this work, a series of Na (1- x ) Ca (1+ x ) Ga (1+ x ) Si (2- x ) O 7 (0 ≤ x  ≤ 0.9) ceramics were successfully prepared via the conventional solid-state reaction method, achieved the synergistic substitution of Ca 2+ for Na + and Ga 3+ for Si 4+ in NaCaGaSi 2 O 7 ceramic. The crystal structure evolution, microwave dielectric properties, and structure-performance relationships of the Na (1- x ) Ca (1+ x ) Ga (1+ x ) Si (2- x ) O 7 ceramics were systematically characterized by multiple analytical techniques including XRD Rietveld refinement, XPS, far-infrared spectroscopy, and first-principles calculations. The synergistic dual-ion substitution effectively optimized the microstructure of NaCaGaSi 2 O 7 -based ceramics, suppressed the formation of oxygen vacancy defects, and modulated the chemical bonding characteristics, thereby significantly improving the comprehensive microwave dielectric performances. Notably, the Na (1- x ) Ca (1+ x ) Ga (1+ x ) Si (2- x ) O 7 ( x  = 0.7) ceramic achieved excellent comprehensive properties: ε r  = 9.01, a high Q×f value of 31049 GHz, and a small negative τ f value of −13.36 ppm/°C. Furthermore, a high-gain dielectric patch antenna fabricated using the optimized ceramic substrate achieved a peak gain of 10.66 dBi and a maximum radiation efficiency of 85.68% at 13.63 GHz, verifying the great application potential of Na (1- x ) Ca (1+ x ) Ga (1+ x ) Si (2- x ) O 7 ceramics for Ku-band communication applications.