SnO2 doping effects on the phase constitution and microwave dielectric properties of a Co0.5Ti0.5NbO4 system

Abstract

The effects of Sn4+ substitution on the structure–property relationship of Co0.5(Ti1−xSnx)0.5NbO4 ceramics were studied systemically using the dielectric theory of complex crystals, and the intrinsic dielectric properties were examined. A rutile Co0.5(Ti1−xSnx)0.5NbO4 solid solution was formed, and the properties were examined via X-ray diffraction and transmission electron microscopy. According to Rietveld refinement analysis, Sn4+ increased the axis length and unit-cell volume. The dielectric theory of complex crystals showed that the introduction of Sn4+ leads to a consistent variation between the average bond covalency value and dielectric constant, indicating a decline in dielectric polarizability. However, an evaluation of the lattice energy of chemical bonds revealed a decrease in the structural stability, with a concomitant increase in the dielectric loss. Moreover, far-infrared reflectivity analysis, complex dielectric function analysis, and Terahertz time-domain spectroscopy of the intrinsic dielectric properties of Co0.5(Ti1−xSnx)0.5NbO4 (x = 0.2) ceramic revealed similar results between the theoretical fitting and experimental test.