Effects of Al_2O_3 addition on the microstructure and microwave dielectric properties of Ba_4Nd_(9.33)Ti_(18)O_(54) ceramics

摘要

Ba_4Nd_(9.33)Ti_(18)O_(54) . x wt%Al_2O_3 (BNT-A) ceramics (x=0, 0.5, 1.0, 1.5, 2.0, 2.5) were prepared by the conventional solid state reaction. The effects of A1203 on the microstructure and microwave dielectric properties of Ba_4Nd_(9.33)Ti_(18)O_(54) (BNT) ceramics were investigated. X-ray diffraction and backscatter electronic images showed that the Al_2O_3 additive gave rise to a second phase BaAl_2Ti_5O_(14) (BAT). The formation mechanism and grain growth of the BAT phase were first discussed. Dielectric property test revealed that the Al_2O_3 additive had improved the dielectric properties of the BNT ceramics: increased the Q x f value from 8270 to 12,180 GHz and decreased the τ_f value from 53.4 to 11.2 ppm/°C. A BNT-A ceramic with excellent dielectric properties: ε_r=70.2, Q x f= 12,180 GHz, τ_f=20 ppm/°C was obtained with 2.0 wt% Al_2O_3 added after sintering at 1320 °C for 4 h.