Microwave dielectric properties of BaWO_4-doped Ba(Mg_(1/3)Nb_(2/3))O_3 ceramics

摘要

In this paper, Ba(Mg_(1/3)Nb_(2/3))O_3 (BMN) ceramics with x (x = 0-9) wt% BaWO_4 were synthesized using the conventional solid-state sintering technique. Effects of BaWO_4 addition on the microstructure and microwave dielectric properties of BMN ceramics were evaluated. X-ray diffraction (XRD) analysis showed that there were three phases: main crystalline phase Ba(Mg_(1/3)Nb_(2/3))O_3 and secondary phases BaWO_4 and Ba_5Nb_4O_(15). Meanwhile, the (100) super-lattice reflection peaks shifted to a higher 29 angle with increasing BaWO_4 content. SEM photographs suggested that BaWO_4 working as a sintering additive promoted the densification and grain growth. The dielectric properties were examined by Vector network analyzer. The dielectric constant (ε_r) was largely determined by the relative density and phase composition. Meanwhile, the addition of BaWO_4 had a positive effect on the Q ×f value, for example the specimen with x = 5 possessed the highest Q ×f value of 111,300 GHz. Optimum microwave dielectric properties (ε_r = 31.7, Q ×f- 111,300 GHz (f= 8 GHz) and τ_f = 0.16 ppm/°C) were obtained for the specimen with x = 5 sintered at 1350 °C for 6 h.