IMF2017

Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) is one of the most widely studied relaxor ferroelectric materials with perovskite structure due to its outstanding physical properties. In the present study, the temperature, electric field, and angular dependences of Raman scattering were performed to clarify the physical origin of local structures in PMN-17PT single crystals. Upon cooling, the Raman active modes within the range between 500-900 cm^-1 show significant changes at around 343 K, suggesting the change of paraelectric cubic to ferroelectric rhombohedral phase (T_C-R). The intensity variations of Raman active modes with the rotation angle in a paraelectric cubic phase at fixed temperature were observed clearly. Periodic functions, representing these intensity variations, were calculated theoretically by considering the local Fm-3m and R3m symmetries, respectively. Theoretical calculations were then compared with the experimental data and a discussion was provided. Under the electric field along the [100] direction just above the T_C-R, the sudden changes in the intensities of the Raman peaks at around 740 and 780 cm^-1 indicated the field induced phase transition from cubic to tetragonal structure. The applied electric field in a paraelectric cubic phase suppressed the random fields (RFs) and therefore, the change of Raman tensor ratio and phase differential were observed compared with the zero field results. In addition, at sufficiently higher electric field, the RFs were diminished and the angular variation changes perfectly from its zero field behavior.