Study On The System Of Li₂MgSiO₄ Low-Loss LTCC Material And Its Application

With the mobile communication technology rapidly expanding everywhere nowadays,the performance of microwave communication devices and basalia materials is increasingly improving.LTCC technology has been widely studied for its high efficiency and high quality on signal transmission.Among these,silicon-based microwave dielectric ceramics of low dielectric constant have become a hot spot because of their low dielectric constant,high quality factor and low sintering temperature(below 961?).In this paper,low-?r Li2MgSiO4 ceramics were used as the base materials,and ion substitution with adding sintering aids were used as the studying methods.The modification mechanism of ion substitution was completed by XRD refinement,calculation of FWHM of diffraction peak,three-dimensional cell diagram and so on,with analyzed thoroughly and comprehensively.Firstly,Mg2+ in Li2MgSiO4 was substituted by Zn2+ gradually,with LBSCA used as the sintering aid.The sintering temperature was reduced from 1250? to 900?,and stable solid solution of Li2(Mg,Zn)SiO4 was formed in the ceramics.When sintered at 900 ?,Li2Mg0.6Zn0.4SiO4+3wt%LBSCA has the best dielectric properties of ?r=5.89,Q×f=44787 GHz,?f=-71.65 ppm/?.Then,Co2+ was used to substitute Mg2+ in Li2Mg0.6Zn0.4SiO4.The similar ionic radius and crystal structure made Li2MgSiO4,Li2ZnSiO4 and Li2CoSiO4 form stable solid solution of Li2(Mg,Zn,Co)SiO4.Proper Co2+ decreased the sintering temperature and further improved the quality factor of the ceramic.The dielectric properties of Li2(Mg0.55Co0.05)Zn0.4SiO4+3wt%LBBS are the best with ?r-5.843,Q×f=47517.9 GHZ,t=-74.8 ppm/?.Then,copper ion improves the temperature coefficient of Li2(Mg0.6-yCuy)Zn0.4SiO4 by changing the distortion of MgO6 octahedron,making if increase positively.When sintering at 925? and y=0.16,the temperature stability was the best:if=-45 ppm/?,Q×f=27,099 GHz,?r=6.311;when y=0.04,Q×f was the highest,reaching 58,742 GHz,with if=-59 ppm/?,?r=5.928.After that,the dielectric properties of Li2Mg0.56Cu0.04Zn0.4SiO4+lwt%LBSCA was proved to be the relatively most optimal among the supplied orthogonal tests,with Q×f=59530 GHz,?f=-56.3 ppm/?.Finally,basing on the developed LTCC material with ?r=5.8,a 3 dB low-pass filter with cut-off frequency of 3.25 GHz was designed.The return loss is less than-25 dB,and the maximum insertion loss of the passband is-0.6 dB,which meets the requirements of relevant performance parameters,realizes the miniaturization and the applicability of the new material.