Design and Fabrication of a Satellite Communication Dielectric Resonator Antenna with Novel Low Loss and Temperature-Stabilized (Sm<sub>1–<i>x</i></sub>Ca<sub><i>x</i></sub>) (Nb<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>)O<sub>4</sub> (<i>x</i> = 0.15–0.7) Microwave Ceramics
Fang-Fang Wu, Di Zhou, Chao Du, Diming Xu, Rui‐Tao Li, Zhongqi Shi, Moustafa A. Darwish, Tao Zhou, Heli Jantunen
Abstract
Phase transition–structure–dielectric properties in microwave band correlations were determined for the (Sm1–xCax) (Nb1–xMox)O4 (SNCMo@x) system. X-ray and Raman analyses along with selected-area electron diffraction indicated that SNCMo@x (0.15 ≤ x < 0.375) ceramics crystallize in the I2/a space group (monoclinic fergusonite), whereas the I41/a space group (tetragonal scheelite) best describes SNCMo@x (0.375 ≤ x ≤ 0.7), suggesting that the increased ionic radius of the A-site effectively contributed to the ferroelastic phase transition and ensures the stability of the scheelite phase. The SNCMo@x ceramic materials exhibit composition-dependent permittivity (εr) with a distribution between 12.0 and 17.7. The distortion and deformation of the [BO] polyhedra should be responsible for the shift from negative to positive temperature coefficient of resonant frequency (TCF) and the irregular behavior of the quality factor (Q × f). An optimum microwave dielectric performance was achieved for [email protected] (εr ∼ 17.1, Q × f ∼ 52, 800 GHz at ∼8.80 GHz, and TCF ∼ −1.4 ppm/°C). This work demonstrates the important role of simultaneous substitution of A/B cations on [BO] polyhedral distortion and deformation in RENbO4 materials and its significant effect on the microwave dielectric properties. Also, the [email protected] ceramic has been designed as a cylindrical dielectric resonator antenna with a high simulated radiation efficiency (97.1%) and gain (5.96 dBi) at the center frequency (7.75 GHz), indicating its promising application in X-band satellite communication (7.62–7.89 GHz) because of its adjustable permittivity, low loss, and good temperature stability.