| The implementation and advancement of 5G networks are crucial steps for China to empower traditional industries,create more opportunities for digital development in the economy and society,and modernize national governance capacity.The development of 5G network requires a significant number of passive electronic components with exceptional performance.Among these components,microwave dielectric ceramics are a primary raw material.The dielectric properties of these ceramics determine the ultimate performance and size of electronic components.The use of the materials with low dielectric loss and low dielectric constant can significantly reduce signal loss and delay during transmission.Therefore,it is urgent to develop new microwave dielectric ceramics that meets the above requirements.This study focuses on the Na5Ln（MoO4）4 series microwave dielectric ceramics,which were systematically examined to uncover the internal mechanisms that affect their dielectric properties.Through the application of the chemical bond theory of complex crystals,we gained insights into the underlying chemistry of these materials.Additionally,we designed and prepared a patch antenna,which represents an important milestone in the industrialization of materials.The following section provides further details on our research findings.（1）In this paper,using the traditional solid phase method,we successfully prepared Na5Lu（MoO4）4 and Na5Tm（MoO4）4 microwave dielectric ceramics.XRD data and Rietveld finishing results indicate that both ceramics possess a tetragonal scheelite structure with spatial group I41/a（88）.Furthermore,the XRD densities of the two ceramics were determined to be4.233 g/cm3 and 4.171 g/cm3,respectively.The lattice vibration of both ceramics was analyzed using the Raman spectrum,and 13 Raman peaks were obtained through Gauss-Lorentz function fitting.However,the measured number of Raman peaks was smaller than the theoretical number.The strongest Raman peaks of Na5Lu（MoO4）4 and Na5Tm（MoO4）4 ceramics were around 920cm-1,which was caused by the vibration of the Mo–O bond with the shortest bond length in the ceramic.（2）In this paper,the dielectric properties of both ceramics were measured at different sintering temperatures using the Hakki-Coleman method,and the impact of sintering temperature on the dielectric properties was analyzed.The lowest dielectric loss was achieved,when Na5Lu（MoO4）4 and Na5Tm（MoO4）4 ceramics were sintered for 6 hours at 625℃and600℃,respectively.Using the chemical bond theory of complex crystals,we calculated and analyzed the ionic properties,lattice energy,linear expansion coefficient,and bond energy of various chemical bonds present in the two ceramics.Our analysis revealed that the Lu/Tm–O bond plays a dominant role in determining their dielectric constant due to its high ionic property.The Mo–O bond has a larger lattice energy and bond energy compared to other chemical bonds,and its average thermal expansion coefficient is closest to zero.This indicates that the Mo–O bond plays a crucial role in the stability and intrinsic dielectric loss of the ceramic crystal.（3）This paper further investigates the potential application of Na5Lu（MoO4）4 and Na5Tm（MoO4）4 ceramics at high frequencies.Terahertz time-domain spectra were used to measure the dielectric constant and dielectric loss of the two ceramics at about 1 THz.The results show that the dielectric constant of the two ceramics in the THz band is similar to that measured in the microwave frequency band,and the dielectric loss is also in the same order of magnitude.The authors speculate that the polarization mechanism in the terahertz frequency band is also dominated by ion displacement polarization and the dielectric loss is mainly caused by the non-harmonic vibration of the ceramic lattice.These findings suggest that Na5Lu（MoO4）4 and Na5Tm（MoO4）4 ceramics have potential applications in the THz band.（4）Finally,this paper used HFSS software to design and simulate a patch antenna made of Na5Tm（MoO4）4,which has a lower dielectric loss.The designed antenna has a central frequency of 2.40 GHz,which makes it suitable for indoor settings such as WIFI.The simulation results showed that the optimal dimensions for the antenna are 21.05 mm for the length and 29.35 mm for the width of the radiant patch,and 40 mm,40 mm,and 2 mm for the length,width,and height of the ceramic substrate,respectively.The reflection parameter value of the antenna was-22.82 d B,and the bandwidth was 45 MHz.The maximum antenna gain was 3.29,and the working efficiency was 98.38%.When the antenna was measured,the working frequency was 2.36 GHz,the measured reflection parameter was-26.85 d B,and the bandwidth was 35.12 MHz,which confirms the simulation results. |
