5G and forthcoming 6G communication systems require dielectric ceramics with low relative permittivity (εr) and near-zero temperature coefficient of resonant frequency (τf) for the lower part of the microwave (MW) band and at sub-Terahertz. Mg2Al4Si5O18 (MAS) ceramics are promising candidates due to their low εr (~ 6) and high-quality factor (Q×f > 40,000 GHz) but have a large τf. In this study, 5.5 wt% TiO2 (MAS-T5.5) was used to adjust τf of MAS to −2.8 ppm/℃ whilst retaining low εr (5.24) and good Q×f (33,400 GHz), properties consistent with those obtained by infrared reflectance. A demonstrator microstrip patch antenna with gain 4.92 dBi and 76.3% efficiency was fabricated from MAS-T5.5. 

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Low permittivity cordierite-based microwave dielectric ceramics for 5G/6G telecommunications

Herein, a series of microwave dielectric materials in the Na2O-Bi2O3-MoO3 ternary system were studied via phase identification, microstructure characterization, spectral analysis and microwave dielectric properties test, such as Na2MoO4, Na6Mo10O33,...

Ultra-low temperature co-fired ceramics with adjustable microwave dielectric properties in Na2O-Bi2O3-MoO3 ternary system: A comprehensive study

Microwave dielectric ceramics exhibiting a low dielectric constant (εr), high quality factor (Q × f), and thermal stability, specifically in an ultrawide temperature range (from -40 to +120 °C), have attracted much attention. In addition, the development of 5G communication has caused an urgent demand for electronic devices, such as dielectric resonant antennas. Hence, the feasibility of optimizing the dielectric properties of the SmNbO4 (SN) ceramics by substituting Bi3+ ions at the A site was studied. The permittivity principally hinges on the contribution of Sm/Bi-O to phonon absorption in the microwave range, while the reduced sintering temperature results in a smaller grain size and slightly lower Q × f value. The expanded and distorted crystal cell indicates that Bi3+ doping effectively regulates the temperature coefficient of resonant frequency (TCF) by adjusting the strains (causing the distorted monoclinic structure) of monoclinic fergusonite besides correlating with the permittivity. Moreover, a larger A-site radius facilitates the acquisition of near-zero TCF values. Notably, the (Sm0.875Bi0.125)NbO4 (SB0.125N) ceramic with εr ≈ 21.9, Q × f ≈ 38 300 GHz (at ∼8.0 GHz), and two different near-zero TCF values of -9.0 (from -40 to +60 °C) and -6.6 ppm/°C (from +60 to +120 °C), respectively, were obtained in the microwave band. A simultaneous increase in the phase transition temperature (Tc) and coefficients of thermal expansion (CTEs) by A-site substitution provides the possibility for promising thermal barrier coating (TBC) materials. Then, a cylindrical dielectric resonator antenna (CDRA) with a resonance at 4.86 GHz and bandwidth of 870 MHz was fabricated by the SB0.125N specimen. The exceptional performance shows that the SB0.125N material is a possible candidate for the sub-6 GHz antenna owing to the advantages of low loss and stable temperature.

Design of a Sub-6 GHz Dielectric Resonator Antenna with Novel Temperature-Stabilized (Sm1-xBix)NbO4 (x = 0-0.15) Microwave Dielectric Ceramics.

Microwave dielectric ceramics (MWDCs) with low dielectric constant and low dielectric loss are desired in contemporary society, where the communication frequency is developing to high frequency (sub-6G). Herein, Nd2(Zr1−xTix)3(MoO4)9 (NZ1−xTxM, x = 0.02–0.10) ceramics were prepared through a solid-phase process. According to X-ray diffraction (XRD) patterns, the ceramics could form a pure crystal structure with the R<inline-formula> <math display="inline" id="MA1"><mover accent="true"><mn>3</mn><mo>¯</mo></mover></math></inline-formula>c (167) space group. The internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius–Mossotti relationship, Shannon’s rule, and Phillips–van Vechten–Levine (P–V–L) theory. Furthermore, theoretical dielectric loss of the ceramics was measured and analyzed by a Fourier transform infrared (IR) radiation spectrometer. Notably, when x = 0.08 and sintered at 700 ℃, optimal microwave dielectric properties of the ceramics were obtained, including a dielectric constant (εr) = 10.94, Q·f = 82,525 GHz (at 9.62 GHz), and near-zero resonant frequency temperature coefficient (τf) = −12.99 ppm/℃. This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti4+ on the microwave dielectric properties and chemical bond characteristics of Nd2Zr3(MoO4)9 (NZM), which laid a solid foundation for the development of rare-earth molybdate MWDC system.

https://www.sciopen.com/article_pdf/1600045138581311489.pdf

Crystal structure, chemical bond characteristics, infrared reflection spectrum, and microwave dielectric properties of Nd
 2
 (Zr
 
 1−
 x

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.

Fabrication of Wideband Low‐Profile Dielectric Patch Antennas from Temperature Stable 0.65 CaTiO3–0.35 LaAlO3 Microwave Dielectric Ceramic

Herein, the structure and dielectric properties of Sm(Nb1−xVx)O4 (SNV-x) (0.0 ≤ x ≤ 0.9) ceramics were studied by crystal structure refinement, Raman, transmission electron microscope (TEM), far-infrared/THz reflectivity spectroscopy and microwave dielectric tests. Three kinds of ultra-low dielectric loss and temperature-stable Sm(Nb1−xVx)O4 (0.2 ≤ x ≤ 0.4) ceramics with permittivities of 18.01–16.89, Q × f values of 97 800–75 200 GHz (@∼8.6 GHz), and TCF of −5.6 (x = 0.2), to +2.3 ppm °C−1 (x = 0.3), then −6.3 (x = 0.4) ppm °C−1 were synthesized in this system. It was found that V5+ substitution can reliably induce the phase transition of monoclinic fergusonite (M-fergusonite, I2/a) to tetragonal zircon phase (T-zircon, I41/amd) (x ≈ 0.3), while effectively reducing the phase transition temperature. TEM shows that there were two different orientation domain structures in the M-fergusonite phase, and the widths of the two domain structures get closer with an increase in B-site substitution. Moreover, the variations in permittivity (er), quality factor (Q × f), and the temperature coefficient of resonance frequency (TCF) were strongly related to the crystal distortion and phase transition. Notably, a rectangular dielectric resonator antenna (RDRA) was fabricated with an Sm(Nb0.8V0.2)O4 (SNV-0.2) specimen. The antenna resonated at 27.04 GHz and had a bandwidth of ∼820 MHz (S11 < −10 dB). This system is a good candidate for 5G and future millimeter-wave applications.

Temperature stable Sm(Nb1−xVx)O4 (0.0 ≤ x ≤ 0.9) microwave dielectric ceramics with ultra-low dielectric loss for dielectric resonator antenna applications

Fifth-generation mobile communication systems provide a huge market for microwave dielectric materials, especially in the manufacture of dielectric resonators, filters, substrates, and antennas. He...

Temperature-Stable x(Na0.5Bi0.5)MoO4–(1–x)MoO3 Composite Ceramics with Ultralow Sintering Temperatures and Low Dielectric Loss for Dielectric Resonator Antenna Applications

Xiu-Qun Zhang

Papers

Temperature stable Sm(Nb1−xVx)O4 (0.0 ≤ x ≤ 0.9) microwave dielectric ceramics with ultra-low dielectric loss for dielectric resonator antenna applications

Ultra-low temperature co-fired ceramics with adjustable microwave dielectric properties in Na2O-Bi2O3-MoO3 ternary system: A comprehensive study

Design of a Sub-6 GHz Dielectric Resonator Antenna with Novel Temperature-Stabilized (Sm1-xBix)NbO4 (x = 0-0.15) Microwave Dielectric Ceramics.

Temperature-Stable x(Na0.5Bi0.5)MoO4–(1–x)MoO3 Composite Ceramics with Ultralow Sintering Temperatures and Low Dielectric Loss for Dielectric Resonator Antenna Applications