The microstructure and phase transition in relaxor ferroelectric $\mathrm{Pb}\left({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}\right){\mathrm{O}}_3$ (PMN) and its solid solution with ${\mathrm{PbTiO}}_3$ (PT), $\mathrm{PMN}-x\mathrm{PT},$ remain to be some of the most puzzling issues of solid-state science. In the present work we have investigated the evolution of the phase symmetry in $\mathrm{PMN}-x\mathrm{PT}$ ceramics as a function of temperature $(20<T<\mathrm{}500\mathrm{}\mathrm{K})$ and composition $(0\mathrm{}<~x<~0.15)$ by means of high-resolution synchrotron x-ray diffraction. Structural analysis based on the experimental data reveals that the substitution of ${\mathrm{Ti}}^{4+}$ for the complex B-site $({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}{)}^{4+}$ ions results in the development of a clean rhombohedral phase at a PT concentration as low as 5%. The results provide insight into the development of ferroelectric order in PMN-PT, which has been discussed in light of the kinetics of polar nanoregions and the physical models of the relaxor ferroelectrics to illustrate the structural evolution from a relaxor to a ferroelectric state.

• Received 20 August 2002

DOI:https://doi.org/10.1103/PhysRevB.67.104104