Synthesis, characterization, and microwave dielectric properties of monoclinal structure ZnZrNb_2O_8 ceramics through the aqueous sol-gel process

摘要

Microwave dielectric ceramics based on mon-oclinic-structure ZnZrNb_2O_8 were prepared by an aqueous sol-gel process. Highly reactive nanosized ZnZrNb_2O_8 powders with particle sizes of 10-30 nm were successfully obtained at 600 ℃ 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 ZnZrNb_2O_8 ceramics were studied depending on sintering temperatures ranging from 1100 to 1250 ℃. The dielectric properties were strongly dependent on the compositions, the densifi-cations and the microstructures of the specimens. With the increase of sintering temperature, density, ε_r and Q·f values increased and saturated at 1200 ℃ with excellent microwave properties: ε_r of 27.38, Q·f value of 66,700 GHz, and τ_f value of -38.4 ppm/℃. The correlations of microstructure and dielectric properties for ZnZrNb_2O_8 ceramics were also investigated.