Design and Fabrication of a C-Band Dielectric Resonator Antenna with Novel Temperature-Stable Ce(Nb1-xVx)NbO4 (X=0-0.4) Microwave Ceramics

Vanadium(V)-substituted cerium niobate [Ce(Nb1-xVx)O-4, CNVx] 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 (TF-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 (epsilon(r)) of similar to 16.81, microwave quality factor (Qf) of similar to 41 300 GHz (at similar to 8.7 GHz), and temperature coefficient of the resonant frequency (TCF) of similar to -3.5 ppm/degrees C. epsilon(r) is dominated by Ce-O phonon absorption in the microwave band; Qf is mainly determined by the porosity, grain size, and proximity of TF-S; and TCF is controlled by the structural distortions associated with TF-S. Terahertz (THz) (0.20-2.00 THz, epsilon(r) similar to 12.52 +/- 0.70, and tan delta similar to 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 (vertical bar S-1(1)vertical bar = -28.8 dB), matching simulations, with >90% radiation efficiency and 3.34-5.93 dB gain.