Effects of strontium substitution in Nb-doped PZT ceramics

Nb-doped lead zirconate titanate (PZT) compositions (2.4 mol%) close to the morphotropic phase boundary (MPB) were investigated systematically as a function of Sr doping as well as Zr:Ti ratio. Sr substitution for Pb in PZT shifted compositions away from the MPB toward the tetragonal phase, greatly reducing the Curie temperature and broadening the dielectric constant maximum, but also decreasing the d33. TEM studies revealed intragranular inhomogeneity in the domain structure with widths varying from ∼100 to ∼20 nm. Altering the Zr:Ti ratio back toward the MPB reduced the Curie temperature and increased the d33. The d33 was optimised in a slightly tetragonal phase close to, but not exactly at, the MPB.