Phase transformation, reaction kinetics and microwave characteristics of Bi2O3–ZnO–Nb2O5 ceramics

Oxide powders of Bi2O3, ZnO and Nb2O5 were used to investigate the phase transformation, reaction kinetics and microwave properties of both Bi2(Zn1/3Nb2/3)2O7 and (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 phases in the Bi2O3–ZnO–Nb2O5 system. Kinetic studies indicate that the formation mechanism of Bi2(Zn1/3Nb2/3)2O7 phase belongs to diffusion controlled reaction with a zero nucleation rate. In contrast, (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 phase was interpreted as diffusion controlled reaction with a constant nucleation rate with either Bi5Nb3O15 or BiNbO4 phases as the nuclei. Furthermore, a lower activation energy and formation temperature were observed in the (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 than Bi2(Zn1/3Nb2/3)2O7 phase. Additionally, the (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 phase exhibits a higher dielectric constant but a lower Q value as compared with Bi2(Zn1/3Nb2/3)2O7 phase.