| With the worldwide popularity of mobile communication in recent years,as the critical material in microwave communication systems,microwave dielectric ceramics become an indispensable component of the whole systems in the form of microwave components such as resonator,filter,microwave oscillator,dielectric diplexer and microwave antenna.Microwave dielectric ceramic materials,as a decisive role in the development of 5G and 6G in the future,especially in the application of communication systems,should possess high dielectric constant??r?,low dielectric loss?low tan?,or high Q value?,and stable resonant frequency?near-zero temperature coefficient?f?.Therefore,the research and development of microwave dielectric ceramic materials with excellent properties is vital for national information development.Traditional solid-state reaction method was adopted for preparing the microwave dielectric ceramic samples in this paper.Based on Li3Mg2NbO6 microwave dielectric ceramics low melting point glass and second phases,were introduced,aiming at obtaining a promising material system with low-temperature sintering,high Q×f value,and near-zero?f value.The microstructure and dielectric propertieswere analyzed by means of X-ray diffraction?XRD?,energy disperse spectroscopy?EDS?,scanning electron microscope?SEM?and network analyzer.Main research conclusionsare as follows:1.In order to lower the sintering temperature of the Li3Mg2NbO6 ceramics to meet the requirements of low-temperature co-firing ceramics?LTCC?technology,Li2O-B2O3-SiO2-CaO-Al2O3?LBSCA?glass was introduced as the sintering aid.The experimental results illustrated that the LBSCA glass with low melting point can effectively reduce the sintering temperature to below 960? without any secondary phase.When the introduce amount of the LBSCA glass was 0.5 wt.%,excellent microwave dielectric performance was obtained at the sintering temperature of 925?:er=15.16,Q×f=90557 GHz,tf=-16.22 ppm/?.2.In order to obtain high temperature stability,that is,tune the?f value to near-zero,Li3Mg2NbO6-Ba3?VO4?2 and Li3Mg2NbO6-CaTiO3 composite ceramics were synthesized via a solid-state route.?1?For Li3Mg2NbO6-xBa3?VO4?2?x=0.2-0.5?,when the x value increased from 0.2to 0.5,from-3.16 ppm/? increase to+11.8 ppm/? of the resonant frequency temperature coefficient.When x=0.3,Li3Mg2NbO6-xBa3?VO4?2 ceramics sintered at1025? for 4 h possessed optimal properties:?r=15.36,Q×f=64830 GHz,tf=+1.55ppm/?.?2?For Li3Mg2NbO6-xCaTiO3?x=0.04-0.1?,when the x value increased from 0.04to 0.1,from-8.7 ppm/? increase to+5.83 ppm/? of the resonant frequency temperature coefficient.When x=0.08,Li3Mg2NbO6-xCaTiO3 ceramics sintered at1125? had excellent microwave dielectric properties:er=16.45,Q×f=131711 GHz,tf=-2.2 ppm/?.3.In order to tune the temperature coefficient to near zero while maintaining lower sintering temperature,the Li2O-MgO-B2O3?LMB?glass was introduced into the Li3Mg2NbO6-0.1CaTiO3 matrix as the sintering aid.With the increase of the LMB glass content,thetf value decreased gradually.For the sample with 2 wt.%of the LMB glass sintered at 925?,excellent microwave dielectric properties were obtained:er=13.54,Q×f=58120 GHz,tf=+1.2 ppm/?. |
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