Order-disorder transition, microstructures and microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics

Bi2(Zn1/3Nb2/3)2O7 ceramics were synthesized using conventional solid-state reaction. The effect of densification annealing treatments on microstructures and microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics have been investigated. The ordered of B-site zirconolite structures were obtained after a long-time annealing. The order-disorder transition contributes to enhance the microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics. The ceramics sintered at 980 °C exhibit a large permittivity of 75 and a Qf value of 3000 GHz. The most efficient annealing treatment which induced a≈100% improvement of Qf value was obtained in the samples annealed at 890 °C for 24 h, while the permittivity remain stable. As the annealing temperature increased to 930 °C, the Qf value abruptly decreased. The microwave dielectric properties of Bi2(Zn1/3Nb2/3)2O7 ceramics are affected by the enhancement of cation order and the reduction of crystal defect. An excellent microwave dielectric properties Qf ≈ 6300 GHz, ε ≈ 76 and τf ≈ 189 ppm/°C was obtained when the ceramic was annealed at 890 °C for 24 h.