(Ni_1/3Nb_2/3)⁴⁺-Improved High-K Ba₃Ti₄Nb₄O₂₁ Microwave Dielectric Ceramics for Miniaturized All-Ceramic Radomes with...

With the rapid development of 5G communication technology, microwave dielectric ceramics with high dielectric constants are very conducive to the miniaturization of passive devices. Here, Ba₃Ti_4-(Ni_1/3Nb_2/3)Nb₄O₂₁ (BTN ∼ NN, 0.03 ≤ x ≤ 0.15) ceramics with hexagonal phases are synthesized via the solid-phase route. The composite (Ni_1/3Nb_2/3)⁴⁺ ion substitution strategy can substantially improve the microwave dielectric properties of the Ba₃Ti₄Nb₄O₂₁ (BTN) ceramic. The ε_r and Q × f values depend on the ionicity (Nb-O bonds) and lattice energies (Nb(1)-O3 and Nb(1)-O2(1) bonds). The microwave dielectric properties of the BTN ∼ NN (x = 0.09) ceramic sintered at 1250 °C are ε_r = 60.3, Q × f = 22073 GHz, and τ_f = 78.1 ppm/°C. A miniaturized all-ceramic radome (@400 mm × 400 mm × 8 mm) for 5G beam-splitting function is designed and demonstrated using this ceramic. Compared to other radomes designed for other work utilizing low ε_r, the size of this radome has been reduced by 3/7. The reflection coefficients of the beam splitting function are all 0.73, and the phase shifts are all 360°. This work contributes to the development of miniaturized passive devices from a materials point of view.