Effects of CaTiO₃ on Microstructures and Properties of (1-x)ZnAl₂O₄-xMg₂TiO₄(x=0.21) Microwave Dielectric Ceramics

ZnAl2O4-Mg2TiO4-CaTiO3 ceramics were prepared by the solid-state reaction.The effects of CaTiO3 on phase compositions,microstructure and microwave dielectric properties were investigated.It shows that CaTiO3 can effectively improve the sinterability of the ceramics and lower the densification temperature by about 150℃.ZnAl2O4-based spinel,CaTiO3,MgTi2O5 and Zn2Ti3O8 phases are included in the ZnAl2O4-Mg2TiO4-CaTiO3 system,however,Zn2Ti3O8 phase disappears when the sintering temperature is higher than 1400℃.As CaTiO3 content increases,CaTiO3 phase in the sintered body raises while MgTi2O5 phase reduces.Furthermore,CaTiO3 can adjust obviously the temperature coefficient of resonant frequency of the(1-x)ZnAl2O4-xMg2TiO4(x=0.21) ceramics.When 6mol% CaTiO3 is added to the(1-x)ZnAl2O4-xMg2TiO4(x=0.21) system,a temperature-stable microwave dielectric ceramics sintered at 1400℃ with an er of 11.8,a Q·f of 88080GHz and a τf of-7.8×10-6/℃ can be obtained.