Effect of CuO-based oxide additives on Bi2O3-ZnO-Nb2O5 microwave ceramics

Abstract

Different kinds of CuO-MO, mixtures were used to investigate their role in the microstructure evolution, sintering densification and microwave properties of Bi-2(Zn1/3Nb2/3)(2)O-7 (BZN) ceramics. Without the addition of CuO-MO, mixtures, pure BZN ceramics have to be sintered above 900 degreesC. However, a comparable bulk density to that of pure BZN ceramics sintered at 950 degreesC can be achieved for 2 wt% 0.29BaCO(3)-0.71 CuO-added at 850 degreesC and 0.15CuO-0,85MoO(3)-added BZN ceramics at 800 degreesC, which was attributed to the liquid-phase sintering. A higher dielectric constant along with a smaller Q factor was obtained in 0.29BaCO(3)-0.71CuO-added BZN ceramics because of the formation of the BaBi2Nb2O9 phase. On the other hand, a larger Q factor of similar to 1500 can be obtained at about 850 degreesC for 1 wt% 0.15CuO-0.85MoO(3)-added BZN ceramics. However, as the 0.2CuO-0.8GCO(2) mixture was used, a partial transformation of pseudo-tetragonal Bi-2(Zn1/3Nb2/3)(2)O-7 to cubic (Bi1.5Zn0.5)(Zn0.5Nb1.5)O-7 phase was induced possibly because both Zn2+ and Ge4+ have similar ion radius and electronegativity. With increasing 0.2CuO-0.8GeO(2) content, a decrease in microwave properties was also obtained due to an inhibition of sintering densification since a eutectic liquid phase was not formed.