Study On Microwave Low Permittivity Dielectric Ceramic

Hexagonal titanioferrite structure and microwave dielectric properties of microwave low-permittivity ZnTiO3 system are studied in this paper. The XRD and DTA demonstrate that the additive MgO stabilizes the hexagonal titanioferrite structure, avoiding the ZnTiO3 decomposes into Zn2TiO4 and rutile above 945℃. (Zn1-xMgx)TiO3(x=0.1~0.4)solid solution is formed after adding different amount of MgO. The solid solution has higher sintering temperature than ZnTiO3 because of the high sintering temperature 1450℃ of MgTiO3. The round slices possess excellent dielectric properties in 1 MHz and the cylindrical microwave dielectric resonators represent perfect microwave dielectric properties at the same time. The effect of Co2O3 on dielectric properties is also studied in this paper.Heat treatment performs dramatic effect on microscopic pattern structure and microwave dielectric properties which lead to ceramic densification, grain boundary purification and Q value enhancement.The change of microwave dielectric properties such as resonant frequency and Q0* f0 value is resulted from the different resonator shape. The relationship and rule can be used in resonator design.After systematic studies, we achieve microwave dielectric material(Zn1-xMgx)TiO3 possessing excellent properties which can be sintered during medium- low-temperatue 1040℃~1080℃. The dielectric properties of round slice are indicated as below:Dielectric loss: tanδ< 0.6×10-4,Insulation resistance: ρv >1×1014Ω·CM,Dielectric constant: ε= 21.43~22.23,Temperature-coefficient of the capacitivity: αc = -13.67ppm/℃= ±30 ppm/℃。The dielectric properties of cylindrical microwave dielectric resonators are indicated as below:Dielectric constant: ε=18.38~20.90, Max resonant frequency f0: f0max =11.297,Q0*f0 value: Q0*f0 =133748~161203 (Resonant frequency f0 =6~7GHz), Temperature coefficient of resonant frequency: τf =1.839 ppm/℃= ±10 ppm/℃.