In this paper we present a Raman-scattering study of the phase transitions in the ${\mathrm{PbZr}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_3$ systems around the morphotropic phase boundary over a wide temperature range. The boundary between rhombohedral and monoclinic phases was found to be a quasivertical line between $x=0.46\mathrm{}$ and $x=\mathrm{0.47.}\mathrm{}$ We also studied the monoclinic-tetragonal phase boundary and our spectroscopic results agree very well with those reported by using x-ray diffraction.

• Received 17 February 2002

DOI:https://doi.org/10.1103/PhysRevB.66.132107