Preparation Of Li₂Mg₃ZrO₆, A_0.5Ti_0.5 By High-energy Ball Milling Study On Microwave Dielectric Properties Of BO₄(A=Zn,Mg;B=Nb,Ta) Powder And Ceramics

With the development of wireless communication technology,microwave dielectric ceramics have been paid much more attention,which are basic materials to make microwave components.The research and development of microwave dielectric materials with low sintering temperature and high performance has become the current research hotspot.In order to meet the requirements of microwave devices with miniaturization,integration,high reliability and low cost,microwave dielectric ceramic materials are required to have a suitable dielectric constant(?r),a high quality factor(Q×f>10,000 GHz),a near zero temperature coefficient of resonant frequency(?f)and a low sintering temperature(T<960 ?).In this paper,we take the Li2Mg3ZrO6 and A0.5Ti0.5BO4(A = Zn,Mg;B = Nb,Ta)ceramics as the research object.Firstly,the Li2Mg3ZrO6 ceramics were obtained by high energy ball-milling.The effects of milling time,synthesis temperature and dwell time on the phase formation and sintering behavior,morphology and microwave dielectric properties of Li2Mg3ZrO6 ceramics were investigated systematically.Secondly,LiF was added to lower the sintering temperature of the Li2Mg3ZrO6 ceramics,and the influences of composition on the sintering behavior,phase components,microstructure and microwave dielectric properties of the Li2Mg3ZrO6 ceramics.Finally,the novel A0.5Ti0.5BO4(A = Zn,Mg;B = Nb,Ta)ceramics were prepared by different methods,and the sintering characteristics and microwave dielectric properties were discussed.The specific results are as follows:(1)After researching the effects of milling time,dwell time and synthesis temperature,the phase of Li2Mg3ZrO6 powders milled for 20 h was synthesized at 900? for 2 h derived from high energy ball-milling method.The Li2Mg3ZrO6 ceramics were obtained with a relatively density of 95.3%at 1150 ?,which is 230 ? lower than that required by the conventional ball-milling method.The Li2Mg3ZrO6 ceramics with pore structure exhibited good microwave dielectric properties of?r = 10.1,Q×f= 71870 GHz,?f =-29.32 ppm/?,which suggests the HEBM is a good method to prepare low-firing ceramics.(2)The Li2Mg3ZrO6-xwt%LiF(x= 1.0?2.0?4.0?6.0?8.0)ceramics were prepared by the high energy ball-milling method.With an amount of LiF addition,the sintering temperature of the Li2Mg3ZrO6 ceramics was reduced to 800?950 ?.XRD results showed that all samples sintered at 850 ? exhibit cubic salt rock structure and a minor of secondary ZrO2 phase.It is noted that the(200)peak showed a shift toward higher degrees with increasing LiF addition.The shift of the peak position is associated with the substitution of ions.SEM results showed that the ceramic surface obviously has liquid phase forming the liquid-phase sintering process.The sintering aid LiF effectively reduced the sintering tempertures,which has some reasons:the substitution of ions promoted substance diffusion process;LiF with lower melting point formed liquid phase during the sintering process and lowered densification sintering temperature of ceramic;Low-fired ceramics inhibited the volatilization of Li in sintering process and improved the density due to reducing the porosity.The Li2Mg3ZrO6-6 wt%LiF ceramics sintered at 850 ? possessed fantastic microwave dielectric properties:?r-12.94,Q×f= 131420 GHz,?f=-35.84 ppm/?.The lattice distortion caused by ion substitution tund the temperature coefficient of resonant frequency to negative value.(3)The novel A0.5Ti0.5NbO4(A = Zn,Mg)ceramics with orthorhombic ixiolite structure were fabricated by the high energy ball-milling method.And the A0.5Ti0.5TaO4(A = Zn,Mg)ceramics with tetragonal rutile structure were obtained by a conventional ball-milling route.The pure phase of Zn0.5Ti0.5NbO4 powders was fabricated at 800 ?derived from HEBM,and well-densified Zn0.5Ti0.5NbO4 ceramics exhibited good microwave dielectric properties:?r,37.7,Q×f= 55350 GHz,?f=-78.48 ppm/?.The novel temperature stable Mg0.5Ti0.5NbO4-based ceramics was prepared by using nanopowders(317 nm),and the ceramics sintered at 1140 ? exhibited optimum microwave dielectric properties:?r = 38.8,Q×f= 19710 GHz,?f= +1.28 ppm/?.The novel A0.5Ti0 5TaO4(A = Zn,Mg)phases were obtained at 950 ?,and well densified ceramics sintered at 1200 ? and 1225 ? showed good microwave dielectric properties:?r = 44.6 and 41.6,Q×f = 20330 and 30000 GHz,?f= +103.01 and +103.91 ppm/?,respectively.