Postsintering annealing induced extrinsic dielectric and piezoelectric responses in lead–zinc–niobate-based ferroelectric ceramics

The effect of postsintering annealing on the dielectric and piezoelectric responses in lead–zinc–niobate (PZN)-based ferroelectric ceramics was systematically studied in this work. Sintered PZN ceramics with the same composition were annealed at temperatures from 700 to 900 °C from 30 min to 24 h in various atmospheres. As a result, significant improvements in the dielectric and piezoelectric responses were observed in this system. After annealing, there was a huge increase of up to 130% in the dielectric constants, especially near the temperature of maximum dielectric constant. While the dielectric peaks became sharper and less diffuse, there was almost no change in frequency dispersion. Similar large improvements in the piezoelectric properties such as the coupling factor and piezoelectric constant were also observed. Optimized parameters, such as d₃₃=642 pC/N, d₃₁=-256 pC/N, k_p=48% and Є_m=28 000, were achieved by annealing at 850 °C in an O₂-rich atmosphere for 4–8 h. The observed improvement in the electrical properties can be attributed to an extrinsic contribution induced by domain wall motion. After annealing, the pinning effects caused by oxygen vacancies and internal stress on domain wall motion were largely reduced or eliminated, therefore a significantly reduced coercive field, an increased polarization level, and a greatly increased dielectric constant were observed in the PZN-based ferroelectric ceramics. © 2002 American Institute of Physics.