The role of PbO content on the dielectric and piezoelectric properties of PZN-based ceramics

Stoichiometric and nonstoichiometric (with less and excess PbO) PZN based ceramics with the ABO(3) perovskite structure were prepared by the columbite method. The results show that the content of PbO has a great influence on the structure and the electrical properties of PZN based ceramics. In the compositions with less PbO (A/B < 1), the dielectric constant and piezoelectric coefficients decrease due to the appearing of pyrochlore phase. While in the compositions with excess PbO (A/B > 1), the dielectric constants and the piezoelectric coefficients increase to a maximum at 1-2 mol % excess PbO, then decrease with increasing PbO content. This behavior can be attributed to the grain boundary layer caused by excess PbO. The grain boundary layer can be eliminated by thermal annealing and was examined by transmission electron microscopy. After annealing at 1123 K for 4-8 h, a very strong enhancement in the dielectric and piezoelectric properties was observed in the annealed PZN ceramics. In this work, d(33) = 680 pC/N, k(m) approximate to 27,000, k(p) approximate to 50 % were achieved in annealed PZN ceramics. (C) 2001 Kluwer Academic Publishers.