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)O-3 (BZN) ceramics have been investigated, BZN has a I : 2 ordered hexagonal structure, and the degree of I : 2 ordering decreased with increasing sintering temperature. Liquid phase was found for the BZN sintered at more than 1350degreesC, 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 1350degreesC 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 1400degreesC for 6h has the maximum Q-value. Since the I : 2 ordering decreased with the sintering temperature, the enhancement of Q-value is not related to the I : 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 1400degreesC and 1300degreesC and the variation of Q-value was explained in terms of the grain size and the relative density.