Effect of B2O3 on the microstructure and microwave dielectric properties of Ba(Mg1/3Nb2/3)O3 ceramics

The influences of different doping contents of additive B2O3 on the sintering behavior, microstructure and microwave properties of Ba(Mg1/3Nb2/3)O-3 (BMN) microwave ceramics were studied. The main phase in the sintered ceramics was crystallized as Ba(Mg1/3Nb2/3)O-3 (BMN). Ba2B2O5 as the secondary phase was observed with x >= 10. Scanning electron microscopy (SEM) analysis revealed that the photograph of optimally nonstoichiometric ceramics sintered at 900 degrees C for 5 h displayed a dense microstructure. The dielectric properties and microstructures of BMN ceramics were very sensitive to the nonstoichiometry. The addition of B2O3 had a positive influence on the Q x f value, for example the sample with x = 7 showed the highest Q x f value of 89,800 GHz. Finally, excellent microwave dielectric properties (epsilon(r) = 31.6, Q x f = 89,800 GHz and tau(f) = 3.6 ppm/degrees C) were achieved for the sample with x = 7 sintered at 900 degrees C for 5 h.