Phase transition−structure−dielectric properties in microwave band correlations were determined for the (Sm 1−x Ca x ) (Nb 1−x Mo x )O 4 (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 I4 1 /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 (ε r ) 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 SNCMo@0.18 (ε r ∼ 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 RENbO 4 materials and its significant effect on the microwave dielectric properties. Also, the SNCMo@0.18 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.

In this paper, the medium dielectric constant 0.65CaTiO3‐0.35LaAlO3 (CTLA) composite microwave ceramic is employed to introduce in dielectric patch antennas (DPA). Typical, high‐performance microwave dielectric properties of εr ≈ 44.8, Q × f ≈ 43 950 GHz@3.67 GHz and TCF ≈ 0 ppm °C–1 can be obtained by solid‐state reaction method in CTLA composite microwave ceramics sintered at 1450 °C for 2 h. Then, the CTLA composite ceramic patch fired with silver coating is mounted on the Rogers RO4003C substrate operating as a magnetic wall boundary. A simplified cavity‐like theoretical model is used to analyze the proposed DPA structure and the accuracy of this antenna model is evaluated by the theoretical results from a commercial CST Microwave Studio 2019. Based on this, the CTLA composite ceramic physical property is modified to enhance the radiation efficiency and reduce profile of the DPA. The higher‐order TM121 mode is brought close to the dominant TM101 mode by taking advantage of the multimode characteristics of the dielectric patch resonator and introducing a sintered silver slot in the ceramic dielectric patch. For demonstration, the proposed DPA prototype operating in the multiprobe antenna near the field measurement system is implemented and measured.

Vanadium(V)-substituted cerium niobate [Ce(Nb1–x V x )O4, 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 (εr) 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. εr 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, εr ∼ 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 (|S 11| = −28.8 dB), matching simulations, with >90% radiation efficiency and 3.34–5.93 dB gain.

Array antenna is of great significance in realizing the Sub‐6 GHz fifth‐generation (5G) mobile communication systems, however, its utilization in the base station systems implementation is limited due to high power consumption. In this paper, a high radiation efficiency 4 × 4 cylindrical dielectric resonator antenna (CDRA) array fabricated using the temperature stable 0.8Zn2SiO4‐0.2TiO2 composite ceramic is proposed. TiO2‐doped Zn2SiO4 composite ceramics are synthesized by the conventional solid‐state method. Notably, 0.8Zn2SiO4‐0.2TiO2 composite ceramic sintered at 1250 °C demonstrates excellent microwave dielectric properties with dielectric constant (εr ≈ 8.24), high‐quality factor (Q × f ≈ 35 000@8.08GHz), and the temperature coefficient of resonant frequency (TCF ≈ +4.6 ppm °C−1). Moreover, the composite ceramic CDRA array is designed by exciting fundamental HE11δ mode using the aperture coupling microstrip feeding network. The fabricated composite ceramic based 4 × 4 CDRA array has enhanced measured radiation efficiency of up to 87%, high gain of 17.85 dBi and is a promising candidate for utilization in Sub‐6 GHz 5G Base Station communications systems.