${\text{PbZr}}_{1-x}{\text{Ti}}_x{\text{O}}_3$ (PZT) ceramics made by mixed-oxide and sol-gel routes within the rhombohedral region of the phase diagram have been prepared, and their structures determined by Rietveld refinement using high-resolution time-of-flight neutron diffraction. Different structural models have been used but the best fits have been found using a mixture of rhombohedral $R3c$ $\left(C_{3v}^6\right)$ and monoclinic $Cm$ $\left(C_s^3\right)$ across the whole rhombohedral range with the proportion of monoclinic phase increasing continuously with composition $x$ toward the morphotropic phase boundary. Some differences are found between the ceramics prepared by the two routes, especially with respect to the diffraction peak widths, suggesting that the precise structural arrangements in these materials depend on the method of preparation. The results show that PZT ceramics made in this region always consist of mixed phases and this accounts for the fact that no phase boundary has been discovered in the PZT phase diagram between the monoclinic and rhombohedral phases.

• Received 23 July 2009
• Corrected 25 September 2009

DOI:https://doi.org/10.1103/PhysRevB.80.104109