Design and Fabrication of a C-Band Dielectric Resonator Antenna with Novel Temperature-Stable Ce(Nb_1–xV_x)NbO₄ (x = 0–0.4) Microwave Ceramics

Vanadium(V)-substituted cerium niobate [Ce(Nb_1–xV_x)O₄, CNV_x] ceramics were prepared to explore their structure–microwave (MW) property relations and application in C-band dielectric resonator antennas (DRAs). X-ray diffraction and Raman spectroscopy revealed that CNVx (0.0 ≤ x ≤ 0.4) ceramics exhibited a ferroelastic phase transition at a critical content of V (x_c = 0.3) from a monoclinic fergusonite structure to a tetragonal scheelite structure (T_F–S), which decreased in temperature as a function of x according to thermal expansion analysis. Optimum microwave dielectric performance was obtained for CNV0.3 with permittivity (ε_r) of ∼16.81, microwave quality factor (Qf) of ∼41 300 GHz (at ∼8.7 GHz), and temperature coefficient of the resonant frequency (TCF) of ∼ –3.5 ppm/°C. ε_r is dominated by Ce–O phonon absorption in the microwave band; Qf is mainly determined by the porosity, grain size, and proximity of T_F–S; and TCF is controlled by the structural distortions associated with T_F–S. Terahertz (THz) (0.20–2.00 THz, ε_r ∼ 12.52 ± 0.70, and tan δ ∼ 0.39 ± 0.17) and infrared measurements are consistent, demonstrating that CNVx (0.0 ≤ x ≤ 0.4) ceramics are effective in the sub-millimeter as well as MW regime. A cylindrical DRA prototype antenna fabricated from CNV0.3 resonated at 7.02 GHz (|S₁₁| = −28.8 dB), matching simulations, with >90% radiation efficiency and 3.34–5.93 dB gain.