Synthesis And Ions Substitution Of Li₂MgTi₃O₈Microwave Dielectric Ceramics

A spinel structure microwave dielectric ceramic material, Li2MgTi3O8ceramics,have been widely used in microwave communication systems for its optimal dielectricperformance, low sintering temperature ang low cost of raw materials. In this paper,the effects of synthesis and ions substitution on the phase composition, themicrostructure and dielectric properties of Li2MgTi3O8ceramics were investigated.The details are as follow.Firstly, in this paper, Li2MgTi3O8ceramics have been prepared by the conventionalsolid-state ceramic route, the effects of synthesis on dielectric properties ofLi2MgTi3O8ceramics were investigated. When calcined at900℃for4h, secondaryball milled for4h, the Li2MgTi3O8ceramics sintered at1080℃for4h exhibited goodmicrowave dielectric properties: r=26.9，Q×=43,200GHz，τ=-1.72ppm/℃.Further improvement of the microwave dielectric properties can be achieved by A-site and B-site substitution in Li2MgTi3O8ceramics. It’s found the effects of the Mn2+,Ni2+and Co2+substitution on the phase composition, the microstructure and dielectricproperties of Li2MgTi3O8ceramics were different. Compared with Mn2+, Ni2+andCo2+substitution, Mn2+ion doping was good for the improvement of quality factor ofLi2MgTi3O8ceramics. The dielectric constants were respectively brought to28.1and28.3by the appropriate amount of Ni2+and Co2+substitution.The effect of the substitution of B-site ions (Sn4+, Mn4+) on the phase composition,the microstructure and dielectric properties of Li2MgTi3O8ceramics were investigated.As the Sn4+content increased, the ceramics included a single spinel phaseLi2MgTi3O8. The Q×increased to52,400GHz with the increase of Sn concentration,while the rand τ decreased. Moreover, the effects of excessive Sn4+on the phasecomposition, the microstructure and dielectric properties of Li2MgTi3O8ceramicswere investigated. It’s also found that the addition of SnO2is beneficial to the growthof grains, which improved the quality factor markedly. At1100℃, theLi2Mg(Ti1-xSnx)3O8(x=0.15) ceramics possesses excellent microwave dielectricproperties:εr=26.0, Q×=74,700GHz and τ=-5.2ppm/℃. However, themicrostructures of Li2MgTi3O8ceramics were changed significantly by B-site Mn4+ion substitution. As the Mn4+content increased, the dielectric properties ofLi2MgTi3O8ceramics deteriorated.