Microwave dielectric properties of BaWO4-doped Ba(Mg1/3Nb2/3)O3 ceramics

In this paper, Ba(Mg1/3Nb2/3)O-3 (BMN) ceramics with x (x = 0-9) wt% BaWO4 were synthesized using the conventional solid-state sintering technique. Effects of BaWO4 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(Mg1/3Nb2/3)O-3 and secondary phases BaWO4 and Ba5Nb4O15. Meanwhile, the (100) super-lattice reflection peaks shifted to a higher 2 theta angle with increasing BaWO4 content. SEM photographs suggested that BaWO4 working as a sintering additive promoted the densification and grain growth. The dielectric properties were examined by Vector network analyzer. The dielectric constant (epsilon(r)) was largely determined by the relative density and phase composition. Meanwhile, the addition of BaWO4 had a positive effect on the Q x f value, for example the specimen with x = 5 possessed the highest Q x f value of 111,300 GHz. Optimum microwave dielectric properties (epsilon(r) = 31.7, Q x f = 111,300 GHz (f = 8 GHz) and tau(f) = 0.16 ppm/degrees C) were obtained for the specimen with x = 5 sintered at 1350 degrees C for 6 h.