| With the rapid development of wireless communications technology,high-performance microwave dielectric ceramics have been widely applied to microwave components,such as antennas,resonators and filters,etc.Li3Mg2SbO6 ceramics with low dielectric permittivity,high Q value and near-zero temperature coefficient of resonance frequency are expected to play a significant part in 5G communication equipment.This paper systematically studies the effects of A-site and B-site ion substitution and LBBS glass doping on the phase composition,sintering characteristics and dielectric properties of Li3Mg2SbO6 ceramics.Based on the ceramics studied in this paper,a microstrip antenna with a center frequency of 2.45 GHz was designed through HFSS software.Firstly,Zn2+and Cu2+ions were used to replace the Mg2+ions at the A site ofLi3Mg2SbO6 ceramics respectively in order to improve their dielecties properties.Li3(Mg1-xZnx)2SbO6(x=0.04)ceramics(εr=7.8,Q×f=97 719 GHz,τf=-6 ppm/℃),and Li3Mg2-xCuxSbO6(x=0.02)ceramic(εr=8.97,Q×f=108 607 GHz,τf=-2 ppm/℃)were prepared by solid-statebreaction route.The samples all forme a solid solution without a second phase.The results show that a proper amount of ion substitution can promote the growth of crystal grains so as to ameliorate the microwave dielectric properties of ceramics.The εr value is mainly influenced via the density,and the Q×f value is attributed to the influence of the grain size and full width at half maximum.After that,Mo6+and Ti4+ions were used to replace the Sb5+ions at the B site of Li3Mg2SbO6 ceramics respectively.Excessive Mo6+ions are substituted to form a second phase,and Ti4+ions substitutions form the pure phases.Mo6+ion substitution can promote the growth of crystal grains,but the improvement of the dielectric properties of ceramics is not greatly improved.A proper amount of Ti4+ion substitution can promote the growth of crystal grains,improve the quality factor of ceramics.Li3+xMg2Sb1-xTixO6(x=0.06)ceramics with excellent microwave dielectric properties were prepared:εr=10.02,Q×f=146 834 GHz,τf=8 ppm/℃.Its εr is mainly affected by porosity and ion polarizability.The increase of Q×f value is attributed to the increase of atomic packing fraction,and the τf value is related to SbO6 octahedral distortion.In order to achieve low-temperature sintering and meet LTCC technology,Li3Mg1.92Zn0.08SbO6 ceramic was doped with LBBS glass.When doped with 3 wt%,Li3Mg1.92Zn0.08SbO6 ceramic can reach the best sintering temperature at 950℃,and its microwave dielectric properties:εr=8.57,Q×f=37 660 GHz,τf=-16 ppm/℃.Analysis of its phase composition,sintering characteristics,microwave dielectric properties shows that excessive LBBS glass will cause the appearance of the second phase,and an appropriate amount of LBBS glass can facilitate the densification of the sample and reduce the sintering temperature.Finally,Li3.06Mg2Sb0.94Ti0.06O6 microwave dielectric ceramic material was finally selected as the dielectric substrate of the microstrip antenna.Determine the size of the microstrip antenna by using the relevant formula,and establish and optimize the design of the coaxial-fed rectangular patch microstrip antenna in the HFSS software.A microstrip antenna with a center frequency of 2.45 GHz,a bandwidth of approximately 20 MHz,and a maximum gain of 7.31 dBi was designed.It is verified that the ceramic materials studied in this paper can be used to make antennas and have potential application value. |
