Effect of borosilicate glasses on the microwave dielectric properties of ZnO-Nb_2O_5-Ta_2O_5 system

摘要

(1 - y)[0.5ZnNb_2O_6-0.5Zn_3Nb_2O_8]-yZnTa_2O_6 with y = 0.91 (ZNT) ceramic have been prepared by conventional solid state ceramic route. The effect of glass additives on the microstructure, densification, and microwave dielectric properties of the ZNT ceramic for low temperature co-fired ceramic applications was investigated. Different weight percentages of quenched glass such as ZnO-B_2O_3-SiO_2, BaO-B_2O_3-SiO_2, LiO-B_2O_3-SiO_2 and MgO-B_2O_3-SiO_2 were added to ZNT powder. The crystal structure of the ceramic-glass composites was studied by X-ray diffraction and microstructure by scanning electron microscopy. The microwave dielectric properties such as relative permittivity (ε_r), quality factor (Q_uxf) and co-efficient of temperature variation of resonant frequency (T_f) of the ceramics have been measured in the frequency range 4-6 GHz. The 5 wt% ZnO-B_2O_3-SiO_2 added ZNT ceramic sintered at 900 ℃ showed: ε_r = 28.1, Q_uxf = 32820 GHz (at 4.92 GHz), and τ_f = -7.7 ppm/℃ respectively.