Effects of aqueous gelcasting and dry pressing on the sinterability and microwave dielectric properties of ZnAl2O4-based ceramics

The effects of aqueous gelcasting and dry pressing on the sinterability and microwave dielectric properties of 90 wt.% (0.75ZnAl2O4–0.25TiO2)–10 wt.% MgTiO3(ZTM) ceramics have been investigated. It is found that aqueous gelcasting could effectively decrease the sintering temperature of ZTM ceramics by 100 °C and acquire more excellent microwave dielectric properties of ZTM ceramics compared with conventional dry pressing. X-ray diffraction (XRD), environment scanning electron microscope (ESEM) and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the phase compositions and microstructures of ZTM ceramics. The results illustrate that the phase compositions are completely uniform no matter what sintering temperature and forming method are adopted. However, the densities, ɛr and Q × f values are greatly affected by different forming methods, whereas there are few effects on the τf values. It is observed that ZTM ceramics prepared by aqueous gelcasting exhibit greater densities, more excellent and stable microwave dielectric properties compared with that prepared by dry pressing at the relative low sintering temperatures. However, when the sintering temperature becomes higher, the opposite phenomenon would gradually appear.