Microwave dielectric properties of ZnO-Nb_2O_5-xTiO_2 ceramics prepared by reaction-sintering process

摘要

The ZnO-Nb_2O_5-xTiO_2 (1 ＜ x ＜ 2) ceramics were fabricated by reaction-sintering process, and the effects of TiO_2 content and sintering temperature on the crystal structure and microwave dielectric properties of the ceramics were investigated. The XRD patterns of the ceramics showed that ZnTiNb_2O_8 single phase was formed as x ＜ 1.6 and second phase Zn_(0.17)Nb_(0.33)Ti_(0.5)O_2 appeared at x ＞ 1.8. With the increase of TiO_2 content and sintering temperature, the amount of the second phase Zn_(0.17)-Nb_(0.33)Ti_(0.5)O_2 increased, resulting in the increase of dielectric constant, decrease of Q × f value, and the temperature coefficient of resonant frequency (τ_f) shifted to a positive value. The optimum microwave dielectric properties were obtained for ZnO-Nb_2O_5-2TiO_2 ceramics sintered at 1075 ℃ for 5 h: ε_r = 45.3, Q × f = 23,500 GHz, τ-f = +4.5 ppm/℃.