Synthesis And Microwave Dielectric Properties Of ZnAl₂O₄Ceramic System

In this paper, ZnAl2O4microwave dielectric ceramic was studied. Differentamount of TiO2and SrTiO3was added to adjust the resonance frequency temperaturecoefficient and improve the microwave dielectric properties of the system; Calciningtemperature and secondary milling time was studied to explore the optimal processingparameters for preparing0.79ZnAl2O4-0.21TiO2ceramics; By adding flux(ZBS glassand H3BO3), we studied the low-temperature sintering characteristics and microwavedielectric properties of0.79ZnAl2O4-0.21TiO2microwave dielectric ceramics.Firstly, the (1-x)ZnAl2O4-xTiO2ceramics were prepared by conventional mixedoxide route. The effect of different amounts of TiO2on the sintering behaviors, phasecomposition, micromorphology and microwave dielectric properties were investigatedsystematically, when0.21mol of TiO2was added,0.79ZnAl2O4-0.21TiO2ceramicsystem achieved the best microwave dielectric properties: εr=12.16, Q·f=78954GHz,τf=-2.2ppm/℃.(1-x) ZnAl2O4-xSrTiO3microwave dielectric ceramic was studied inthe same way, the best microwave dielectric properties were achieved by adding0.06mol of SrTiO3.0.94ZnAl2O4-0.06SrTiO3ceramic can be sinterd at1475℃withεr=11.27, Q·f=41487GHz, τf=+7.5ppm/℃.Second, the process parameters of0.79ZnAl2O4-0.21TiO2ceramic were studiedby changing the calcining temperature and secondary milling time, the results showedthat0.79ZnAl2O4-0.21TiO2ceramics with excellent dielectric properties and highdensity can be obtained in the following way: calcining temperature of1050℃,secondary milling time of24h, sintering temperature of1300℃.Finally, in order to reduce the sintering temperature of0.79ZnAl2O4-0.21TiO2ceramics, H3BO3and ZBS glass doping was used and the effects on the sinteringmechanism and dielectric properties of the modified ceramic system were studied.XRD and SEM were employed to interpret the amount of ZBS glass additive on themicrostructure and microwave dielectric properties. It is available to meet the LTCCmicrowave dielectric properties by adding12wt%ZBS glass and sintering at950℃:εr=11.2, Qf=18085GHz, τf=-26ppm/℃. Adding0.5wt%H3BO3, sintering at1250℃, the microwave dielectric properties of0.79ZnAl2O4-0.21TiO2ceramics were: εr=12.02, Q·f=80120GHz, τf=+2.1ppm/℃, Adding2wt%H3BO3, sintering at1200℃, the microwave dielectric properties of0.79ZnAl2O4-0.21TiO2ceramics were:ε=11.75, Q·f=74670GHz, τ=+1.8ppm/℃.