Characterization of low loss microwave dielectric materials Zn_(0.92)Co_(0.08)ZrNb_2O_8 based on the complex chemical bond theory

摘要

Low loss microwave dielectric ceramics Zn_(0.92) Co_(0.08)ZrNb_2O_8 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-0 bonds. The Q• j values were main affected by the lattice energy and the bond energy of the Nb-0 bonds. As for the τ_fvalues, it could be mainly affected by the coefficient of thermal expansion of Zn/Co-O bonds. At the sintering temperature of 1200℃, Zn_(0.92)Co_(0.08) ZrNb_2O_8 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/℃. These results demonstrated that Zn_(0.92)Co_(0.08)ZrNb_2O_8 ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.