Design and Fabrication of a C-Band Dielectric Resonator Antenna with Novel Temperature-Stable Ce(Nb 1- x V x )NbO 4 ( x = 0-0.4) Microwave Ceramics.

Vanadium(V)-substituted cerium niobate [Ce(Nb 1- x V x )O 4 , 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 CNV x (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 CNV x (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 (| S 11 | = -28.8 dB), matching simulations, with >90% radiation efficiency and 3.34-5.93 dB gain.