Microwave dielectric properties of (1−x)ZnAl2O4–xCaTiO3 compound ceramic with controlled temperature coefficient

In this study, microwave dielectric properties of (1−x)ZnAl2O4−xCaTiO3 samples with controlled temperature coefficient feature are analyzed. The crystal structures of all the compositions were refined by X-ray diffraction. A homogeneous distribution of cations within instrument sensitivity in all the samples was observed using scanning electron microscopy, coupled with energy dispersive X-ray analysis. ZnAl2O4 and CaTiO3 could coexist when the x content was less than 0.1, whereas Al2O3 and Ca3Al2O6 phases were observed in composite ceramics. As expected, the dielectric constant (εr) of the composite ceramics increased with the increasing x content, and the quality factor (Qf) generally decreased with increasing x-content because of the low Qf of the CaTiO3 phases. The temperature coefficient of resonant frequency (τf) could be controlled by varying the CaTiO3 content and could lead to zero τf value. The 0.92ZnAl2O4−0.08CaTiO3 ceramic exhibited εr of 10.8, Qf of 32,300 GHz, and τf of 0 ppm/°C.