Development of ferroelectric order in relaxor (1-x) Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (0≤x≤0.15)

The microstructure and phase transition in relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃ (PMN) and its solid solution with PbTiO₃ (PT), PMN-xPT, 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 PMN-xPT ceramics as a function of temperature (20<T<500 K) and composition (0≤x≤0.15) by means of high-resolution synchrotron x-ray diffraction. Structural analysis based on the experimental data reveals that the substitution of Ti4+ for the complex B-site (Mg_1/3Nb_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.