| Cold sintering process?CSP?is a brand new ceramic sintering technology.Compared with traditional high-temperature sintering?900?-1500??,CSP can achieve ceramic densification at a temperature close to room temperature?<300??by introducing a liquid phase.In recent two years,it has been widely concerned in the world.In this paper,microwave composite ceramics were prepared by cold sintering process.The relationship between the microstructure of composite ceramics and the three parameters of microwave dielectric properties?dielectric constant?r,quality factor Q×f,resonance frequency temperature coefficient?f?was studied.Finally,high-quality composite ceramics were preferred for making 5G prototype ceramic antennas.Test the electromagnetic performance of the prototype antenna.The main contents of this paper are as follows:?1??1-x?Li2MoO4?LMO?-xMg2SiO4?MSO??x=0,5,10,15,20,25,30,50,90wt%?composite ceramics was successfully cold-sintered at 200?for 60 min with a uniaxial pressure of 500MPa.The relative density was in the range of 85%-100%.XRD,EDS and Raman confirmed that there were only LMO and MSO phases in?1-x?LMO-x MSO composite ceramics,but no other phases.SEM showed that the composite ceramics have dense microstructure.The range of?r was 5.05?5.3,and the range of Q×f was 9450?24320 GHz.?2??1-x?Li WVO6?LWVO?-xK2MoO4?KMO??x=60,65,70,75,80,90wt%?composite ceramics with>92%theoretical density were densified by cold sintering at160?and 300MPa for 60 min.XRD?Raman not only indicated the coxistence of LWVO and KMO phases in all composites but also the absence of other phases.?1-x?LWVO-x KMO composite ceramics had?r ranging from 6.8 to 8.5,Q×f ranging from 2050GHz to 7182GHz,and?f ranging from-49ppm/?to+25ppm/?.Near-zero?f was obtained for 30wt%LWVO-70wt%KMO with?r?7.8,Q×f?4514GHz,?f?1.3ppm/?.?3??1-x?CaSnSiO5?CSSO?-xK2MoO4?KMO??x=20,30,35,40,50,60,70,80,90,100wt%?composite ceramics with?98%theoretical were densified by cold sintering at 180?and 400 MPa for 60 min.XRD,EDS and Raman confirmed that?1-x?CSSO-x KMO composite ceramics only have two phases of CSSO and KMO,and no other phases.SEM indicated that the composite ceramics have a dense microstructure.As KMO oncentration increased,the?rand?fdecreased,whereas Q×f increased,with increasing weight of KMO.A near-zero?f was obtained for65wt%CSSO-35wt%KMO with?r?9.168,Q×f?6240 GHz,?f??0.5ppm/?.65wt%CSSO-35wt%KMO composite ceramics co-fired with silver by cold sintering process.SEM and EDS confirmed that there was no chemical reaction among CSSO-KMO-Ag.A 5G prototype ceramic microstrip patch antenna with a center operating frequency of 5.2 GHz was designed and fabricated using cold sintered65wt%CSSO-35wt%KMO composite ceramic material as the substrate.A S11 of-10d B had a bandwidth of 144 MHz.An antenna gain of 5.7 d Bi and a total efficiency of 88.4%at 5.2GHz.The antenna can be used in the 5 GHz industrial,scientific and medical?ISM?spectrum. |
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