Effect of structural changes on the microwave dielectric properties of Ba(Zn1/3Nb2/3)O3 ceramics

The microstructure and microwave dielectric properties of Ba(Zn1/3Nb2/3)O3 (BZN) ceramics have been investigated. BZN has a 1 : 2 ordered hexagonal structure, and the degree of 1 : 2 ordering decreased with increasing sintering temperature. Liquid phase was found for the BZN sintered at more than 1350°C, the evaporation of ZnO was responsible for the formation of liquid phase. BaNb6O16 second phase was also found for the specimens sintered at more than 1350°C and the liquid phase is considered to have a composition close to that of BaNb6O16 second phase. The Q-value of BZN was increased with increasing sintering temperature and BZN sintered at 1400°C for 6 h has the maximum Q-value. Since the 1 : 2 ordering decreased with the sintering temperature, the enhancement of Q-value is not related to the 1 : 2 ordering. The increase of the average grain size could be responsible for the increase of the Q-value, and the relative density also influenced the Q-value. BZN ceramics were sintered for various times at 1400°C and 1300°C and the variation of Q-value was explained in terms of the grain size and the relative density.