Characterization of low loss microwave dielectric materials Zn_0.92Co_0.08ZrNb₂O₈ based on the complex chemical bond theory

Low loss microwave dielectric ceramics Zn_0.92Co_0.08ZrNb₂O₈ with wolframite structure were prepared by the solid state method. Sintering characteristics, phase composition and microwave dielectric properties were investigated systematically. X-ray diffraction results showed that all samples exhibited a wolframite structure. Rietveld refinement was used to analyze the crystal structure. Based on the lattice parameters, the bond ionicity, the lattice energy, the bond energy and the coefficient of thermal expansion were calculated to evaluate the structural characteristics. The ε _r values could be strongly dependent on the bond ionicity of the Nb–O bonds. The Q·j values were main affected by the lattice energy and the bond energy of the Nb–O bonds. As for the τ _f values, it could be mainly affected by the coefficient of thermal expansion of Zn/Co–O bonds. At the sintering temperature of 1200 °C, Zn_0.92Co_0.08ZrNb₂O₈ ceramics exhibited the excellent microwave properties of ε _r  = 27.10, Q·f = 61,036 GHz (at 8.54 GHz) and τ _f  = −9.81 ppm/°C. These results demonstrated that Zn_0.92Co_0.08ZrNb₂O₈ ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.