Effects of Mg2+ substitution on microstructure and microwave dielectric properties of (Zn1−xMgx)Nb2O6 ceramics

The sintering behavior, microstructure and microwave dielectric properties of (Zn1−xMgx)Nb2O6 (0<x<1.0) solid solution were investigated systematically by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and a network analyzer. The sintering temperature of (Zn1−xMgx)Nb2O6 ceramics increased from 1150 to 1350 °C with increasing Mg content from x=0 to x=1.0. The crystal structure exhibited a columbite structure for all x values. The changes of grain shape from equiaixed to rectangle were observed in sintered samples as x varied from 0 to 0.5. The dielectric properties of (Zn1−xMgx)Nb2O6 solid solution exhibited a significantly dependence on the sintering condition, microstructure and compositions of ceramics. The dielectric constants (er) of sintered samples decreased from 23.66 to 19.17 with increasing Mg content from x=0 to x=1.0. All quality factors (Q×f) of (Zn1−xMgx)Nb2O6 ceramics were lower than those of ZnNb2O6 and MgNb2O6 and ranged from 82 220 to 31 218 GHz for sintered samples. However, the τf values were lower than those of ZnNb2O6 and MgNb2O6, the minimum τf value can be obtained at x=0.5 and were −29.46 ppm/°C.