Synthesis, characterization, and microwave dielectric properties of monoclinal structure ZnZrNb₂O₈ ceramics through the aqueous sol–gel process

Microwave dielectric ceramics based on monoclinic-structure ZnZrNb₂O₈ were prepared by an aqueous sol–gel process. Highly reactive nanosized ZnZrNb₂O₈ powders with particle sizes of 10–30 nm were successfully obtained at 600 °C as precursors. And the evolution of phase formation was investigated by means of DTA–TG and XRD analysis. Both selected area electronic diffraction patterns and high-resolution crystal lattice image were characterized for the evaluation of crystallinity by mean of transmission electron microscopy. Sintering characteristics and microwave dielectric properties of ZnZrNb₂O₈ ceramics were studied depending on sintering temperatures ranging from 1100 to 1250 °C. The dielectric properties were strongly dependent on the compositions, the densifications and the microstructures of the specimens. With the increase of sintering temperature, density, ε_r and Q·f values increased and saturated at 1200 °C with excellent microwave properties: ɛ _r of 27.38, Q·f value of 66,700 GHz, and τ _f value of −38.4 ppm/°C. The correlations of microstructure and dielectric properties for ZnZrNb₂O₈ ceramics were also investigated.