Improvement Of Bending Strength And Optimization Of Microwave Dielectric Properties Of Li₂ZnTi₃O₈-based Ceramics

The development of wireless communication technology is inseparable from microwave dielectric materials.In recent years,with the stable deployment of 5G communication technology and the research and development of 6G communication technology,microwave dielectric ceramics will have higher requirements and great demand,so it is the focus of current research to explore microwave dielectric ceramics materials with excellent performance in all aspects.In this paper,Li₂ZnTi₃O₈（LZT）microwave dielectric ceramics are studied,and the properties of LZT ceramics are optimized by doping.The effects of doping different substances on the crystal structure,microstructure,bending strength and microwave dielectric properties of LZT ceramics are systematically studied.The specific research contents are as follows:（1）Li₂ZnTi₃O₈+x wt.%Si₃N₄（x=0,0.1,0.3,0.5,0.7）ceramics were prepared by a solid-state reaction method.The effect of different sintering temperatures on the phase structure,microwave dielectric properties and bending strength of ceramics were studied.LZT ceramics doped with Si₃N₄ have cubic spinel structure,which shows that a small amount of Si₃N₄ particles addition have not undergone phase transformation.Compared with the undoped LZT ceramics,the bending resistance of 0.7 wt.%Si₃N₄doped LZT ceramic material is improved from 146 MPa to 202 MPa,andτ_f is adjusted to near zero,while the Q×f value is only reduced by 13840 GHz.LZT ceramics doped with 0.7 wt.%Si₃N₄ sintered at 1025°C show excellent properties with bending strength of 202 MPa,?_r of 21.6,Q×f of 45457 GHz,andτ_f of-4.97 ppm/°C.（2）In order to solve the problem that the microwave dielectric properties of ceramics are deteriorated while the bending strength is improved,Li₂ZnTi₃O₈+x wt.%TiO₂（x=0,0.25,0.5,0.75,1）ceramics sintered at different temperatures were prepared by solid-state reaction method.TiO₂ whisker is an inorganic fiber material,which has the advantages of high mechanical strength and stable chemical properties.The addition of TiO₂ whisker to ceramic materials can achieve the effect of uniform dispersion,which can not only improve the strength of the material,but also adjust other properties.The results show that the doped LZT ceramics have cubic spinel structure without the formation of second phase.The grain size of the sample surface increases and is uniform.The density of LZT ceramics is improved.The bending strength and sintering condition can be improved by doping TiO₂ whisker,besides,the microwave dielectric properties of ceramics can also be optimized.At the same time,with the increase of doping amount,theτ_f value is closer to zero.,the ceramics doped with 0.5 wt.%TiO₂whisker sintered at 1000℃has the highest bending strength and microwave dieletric properties ofσ=192 MPa,?_r=23.8,Q×f=71921 GHz andτ_f=-16.1 ppm/℃.（3）Li₂ZnTi₃O₈+x wt.%Si C（x=0,0.1,0.3,0.5,0.7）ceramics were prepared by solid-state reaction method,and the effects of Si C particles addition on the phase structure,bending strength,microstructure and microwave dielectric properties of LZT ceramics were studied.The results show that the characteristic peaks of Si C particles doped LZT ceramics are slightly passivated and left offset,but no second phase is produced.With increasing the sintering temperature,the bulk density and?_r have the same trend of first decreasing and then increasing.Compared with the undoped LZT ceramics,the ceramics doped 0.5 wt.%Si C have higher Q×f value and the best bending strength withσ=181 MPa,?_r=21.5,Q×f=56310 GHz,andτ_f=-15.7 ppm/℃.