Characterization of microwave dielectric materials NiZrNb2O8 based on the chemical bond theory

Abstract

Wolframite structure NiZrNb2O8 ceramics were prepared by the solid state reaction method. Sintering characteristics and microwave dielectric properties were investigated under various sintering temperatures ranging from 1100 to 1300 °C. The micro-structure, crystal structure and phase composition were studied by the scanning electron microscopy techniques, X-ray diffraction and energy disperse spectroscopy, respectively. Refinement was used to analyze the crystal structure. Based on the cell parameters, the chemical bond theory was used to calculate the lattice energy, bond ionicity and the coefficient of thermal expansion for the characterization of correlations between properties and structures of NiZrNb2O8 ceramics. The microwave dielectric properties of NiZrNb2O8 were strongly dependent on the chemical bond ionicity, lattice energy and coefficient of thermal expansion. The er values could be strongly dependent on the bond ionicity of the Nb–O bonds. The Q·f values were affected by the lattice energy of Nb–O bonds. As for the τf values, it could be mainly affected by the coefficient of thermal expansion of Ni–O bonds. At the sintering temperature of 1250 °C, NiZrNb2O8 ceramics exhibited the excellent microwave properties of er = 18.84, Q·f = 18, 142 GHz and τf = −35.43 ppm/°C.