New Features of the Morphotropic Phase Boundary in the PbZr(1-x)TixO3 System

Recently a new monoclinic phase in the PbZr(1-x)TixO3 ceramic system has been reported by Noheda et al. for the composition x= 0.48. In the present work, samples with Ti contents of x= 0.47 and 0.50, which are both tetragonal below their Curie points, have been investigated. In the sample with x= 0.50, the tetragonal phase was found to transform to a monoclinic phase at about 200 K as the temperature was lowered. The sample with x= 0.47 showed a complicated region of phase coexistence between 440-320 K, becoming rhombohedral at around 300 K. No further symmetry change was found down to 20 K. Dielectric measurements for these two samples are also reported. On the basis of these results, a preliminary phase diagram is presented. Optimum compositional homogeneity is needed to properly characterize the new monoclinic region.